A proposed synthesis method for Application-Specific Instruction Set Processors Due to the rapid technology advancement in integrated circuit era, the need for the high computation performance together with increasing complexity and manufacturing costs has raised the demand for high-performance configurable designs; therefore, the Application-Specific Instruction Set Processors (ASIPs) are widely used in SoC design. The automated generation of software tools for ASIPs is a commonly used technique, but the automated hardware model generation is less frequently applied in terms of final RTL implementations. Contrary to this, the final register-transfer level models are usually created, at least partly, manually. This paper presents a novel approach for automated hardware model generation for ASIPs. The new solution is based on a novel abstract ASIP model and a modeling language (Algorithmic Microarchitecture Description Language, AMDL) optimized for this architecture model. The proposed AMDL-based pre-synthesis method is based on a set of pre-defined VHDL implementation schemes, which ensure the qualities of the automatically generated register-transfer level models in terms of resource requirement and operation frequency. The design framework implementing the algorithms required by the synthesis method is also presented. Today's increasingly developing manufacturing technology makes it possible to build complete data processing systems on a single chip including digital and analog building blocks with on-chip memories and communication. These complex systems called System on Chips (SoCs) comprise various computational submodules called ApplicationSpecific Integrated Circuits (ASICs) with a well-defined functionality, which cannot be modified after manufacturing. ASICs provide favorable energy-efficiency and high computation performance since they are optimized for a specific function. However, besides the high computation capacity, the reusability and flexibility as design constraints have gained significant importance because of the extremely high manufacturing costs.. There are two major ways to ensure flexibility in SoCs. The first approach is based on embedded reconfigurable logic devices, such as Field Programmable Gate Arrays (FPGAs) and Complex Programmable Logic Devices (CPLDs), which make it possible to implement arbitrary digital functionality and can be reconfigured "on the field" after manufacturing. The other solution is the usage of general purpose devices operating according to a stored program. These devices are the well-known microprocessors whose functionality can be changed with a simple software update.. Both solutions provide flexibility on the cost of limited computation capacity. In case of general purpose microprocessors, the additional memory accesses and other administrative operations necessitated by the programmable nature cause a significant penalty in computation performance. In case of programmable logic devices the reconfigurability is achieved by generic logic cells and a high amount of programmable interconnection and wiring resources, which cause high path delays that result in a relatively low operation frequency and high power consumption.. The concept of Application-Specific Instruction Set Processors (ASIPs) is a promising result of the trade-off exploration between flexibility and computation performance [1] . ASIPs are microprocessors with a unique instruction set optimized for a specific application domain. Since they execute a program, they can quickly adapt to the varying functional requirements. At the same time they have instructions and hardware resources optimized for the target application; therefore, they provide a higher computational performance than the general purpose microprocessors [2, 3] .. Due to the rigorous time-to-market requirements, reducing the time-consumption of ASIP design is essential. The primary design tools of ASIPs are the Architecture Description Languages (ADLs), which are specific modeling tools for instruction sets and microarchitecture. The design frameworks based on these formal language models mainly concentrate on the software parts of the microprocessor systems, namely the instruction set simulator, assembler, compiler, and debugger generation. The automated hardware synthesis plays a secondary role since the complex datapaths including internal data storage subsystems and interdependent pipeline stages characteristic to the instruction set processors require a high level of optimization, which cannot be achieved by contemporary ComputerAided Design (CAD) tools. Therefore, the ADL-based design frameworks, even if they are able to generate a hardware model, often compromise or neglect the quality of the final register-transfer level (RTL) implementation [4] . This paper presents a novel approach for ASIP modeling with great emphasis on automated hardware generation. The main idea of our solution is similar to High-Level Synthesis (HLS) [5] [6] [7] , where the design is described as an algorithm, then a High-Level Synthesis procedure generates an RTL model. With lowering the abstraction of the formal specification while keeping the readable algorithmic design style, our approach makes it possible to achieve a high level of optimization and a reduced development time.. The basis of the presented approach is a new abstract model of ASIP architectures and a mixed algorithm and RTL description language called Algorithmic Microarchitecture Description Language (AMDL) optimized for the proposed abstract architecture model. The algorithmic language environment of AMDL combined with the detailed description style characteristic to RTL ensures the rapid architecture implementation and the comprehensive control over the microarchitectural details as well. The initial formal language model comprises a lot of structural information, which makes it possible to generate an optimized, technologyindependent RTL output, which can be transformed into a gate level model using the existing logic synthesis tools. This paper is organized as follows: Section 2 provides a brief overview of SoC implementation solutions, ASIP modeling methodologies, and their drawbacks in terms of hardware generation. Section 3 presents a proposed novel architecture model of ASIPs and Section 4 describes a proposed synthesis approach and modeling language for this architecture model. Section 5 gives an overview of the design framework implementing the proposed synthesis method. Section 6 presents experimental results and Section 7 draws conclusions.

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Content-based video copy detection based on motion vectors estimated using a lower frame rate We propose a motion vector-based video contentbased copy detection method. One of the signatures of a given video is motion vectors extracted from image sequences. However, when consecutive image frames are used, the resulting motion vectors are not descriptive enough because most vectors are either too small or they appear to scatter in all directions. We calculate motion vectors in a lower frame rate than the actual frame rate of the video to overcome this problem. As a result, we obtain large vectors and they represent a given video in a robust manner. We carry out experiments for various parameters and present the results. In this article, we experimentally show that motion vectors are substantial signatures of videos as long as they are extracted in lower frame rates. Therefore, motion vectors can be used in CBCD algorithms. Primary aim of this article is to show that the motion vectors are good feature candidates (if n = 7) for CBVCD algorithms rather than providing a complete CBVCD algorithm. A complete CBVCD algorithm would consist of database search algorithm. However, we manually align two videos before comparison. Videos that have higher motion content give more reliable results and the videos having intensive motion activity are easier to distinguish when the neighboring image frames are used. However, videos containing slow-moving objects have very little motion vectors, and the vectors may appear to be random when the current and the next frame are used for motion vector computation.. In order to obtain reliable signature vectors for all videos motion vectors of the current, the next nth frame (n > 1) is used in motion vector estimation algorithms. Resulting motion vectors provide a reliable representation for all types of videos. Magnitude and phase angles of motion vectors are used separately as feature parameters of a given video. It is experimentally shown that both the magnitude and the phase of vectors can be considered as unique signatures of the video. The proposed motion-based feature parameters are resistant to illumination and color changes in video.. Motion vectors do not change significantly up to a level of resizing, croppingm, and blurring of the video. Most video copy detection methods are not robust to cropping. The MPMV feature is a robust feature in action videos because the moving objects are cropped in video as they are the information bearing part of a typical video and the direction of the object is the same in both the original and the cropped copy. If the recorded video is in low quality, then phase information is less affected than the magnitude information of the frames. However, MPMV is not rotation invariant but MMMV is rotation invariant. Therefore, it is better to use both MMMV and MPMV at the same time.. Another important comparison criterion of the CBCD algorithms in terms of the practical results is the size of the feature set in a database. The MMMV and the MPMV information do not occupy much space in the database as other methods. They both occupy one byte (one feature) per frame in the database.

O B I I O O B I O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Bison:

bisulfite

alignment

on

nodes

of

a

cluster

Background:

DNA

methylation

changes

are

associated

with

a

wide

array

of

biological

processes.

Bisulfite

conversion

of

DNA

followed

by

high-throughput

sequencing

is

increasingly

being

used

to

assess

genome-wide

methylation

at

single-base

resolution.

The

relative

slowness

of

most

commonly

used

aligners

for

processing

such

data

introduces

an

unnecessarily

long

delay

between

receipt

of

raw

data

and

statistical

analysis.

While

this

process

can

be

sped-up

by

using

computer

clusters,

current

tools

are

not

designed

with

them

in

mind

and

end-users

must

create

such

implementations

themselves.Results:

Here,

we

present

a

novel

BS-seq

aligner,

Bison,

which

exploits

multiple

nodes

of

a

computer

cluster

to

speed

up

this

process

and

also

has

increased

accuracy.

Bison

is

accompanied

by

a

variety

of

helper

programs

and

scripts

to

ease,

as

much

as

possible,

the

process

of

quality

control

and

preparing

results

for

statistical

analysis

by

a

variety

of

popular

R

packages.

Bison

is

also

accompanied

by

a

variant

of

Bison

with

the

same

output

but

that

can

scale

to

a

semi-arbitrary

number

of

nodes,

with

concomitant

increased

demands

on

the

underlying

message

passing

interface

implementation.Conclusions:

Bison

is

a

new

bisulfite-converted

short-read

aligner

providing

end

users

easier

scalability

for

performance

gains,

more

accurate

alignments,

and

a

convenient

pathway

for

quality

controlling

alignments

and

converting

methylation

calls

into

a

form

appropriate

for

statistical

analysis.

Bison

and

the

more

scalable

are

natively

able

to

utilize

multiple

nodes

of

a

computer

cluster

simultaneously

and

serve

to

simplify

to

the

process

of

creating

analysis

pipelines.

Bison

and

enable

rapid

and

accurate

alignment

of

BS-seq

reads,

such

as

those

produced

by

the

Illumina

HiSeq.

Both

have

equivalent

to

superior

accuracy

when

compared

to

many

previously

published

aligners.

These

programs

also

make

performing

quality

control

of

the

resulting

mapped

reads

simple.

As

computer

clusters

are

becoming

increasingly

prevalent

in

research

settings,

the

speed

of

these

tools

removes

the

time-burden

of

alignment

and

simplifies

the

process

of

creating

alignment

pipelines,

allowing

the

researcher

to

begin

statistically

analyzing

experiments

in

a

fraction

of

the

time

previously

required.

The

open

source

nature

of

these

programs

and

their

usage

of

standard

formats

enable

further

adaptation

and

extension

by

end-users..

(See

figure

on

previous

page.)

Figure

Methylation

percentage

and

coverage

comparison

using

the

RRBS

dataset.

The

Pearson's

correlation

coefficients

of

the

per-CpG

estimated

methylation

percentages

produced

by

each

aligner

are

generally

high,

A,

upper

triangle.

The

correspondence

between

GNUMAP-bs

and

and

the

other

aligners,

however,

is

notably

lower,

possibly

due

to

their

lower

alignment

rate.

The

Pearson's

correlation

coefficients

of

the

per-CpG

coverage,

A,

lower

triangle,

is

also

generally

high.

The

number

of

CpGs

with

a

given

coverage

decreases

rapidly

as

a

function

of

coverage

regardless

of

aligner,

B.

Note

that

CpGs

with

or

greater

methylation

calls

are

binned

together.

This

binning

produces

the

large

spike

at

coverage,

which

is

likely

due

to

PCR

duplication.

DNA

methylation

involves

the

covalent

modification

of

cytosine

bases

and

serves

to

epigenetically

regulate

a

large

variety

of

biological

properties,

from

imprinting

to

development

and

its

dysregulation

is

associated

with

diseases

such

as

cancer

While

there

are

a

number

of

methods

currently

available

to

probe

DNA

methylation

(e.g.

MeDIP-seq

and

MRE-seq),

the

gold-standard

for

single-base

resolution

is

bisulfite

sequencing,

sometimes

referred

to

as

BS-seq.

Here,

DNA

is

treated

with

bisulfite,

which

results

in

the

conversion

of

unmethylated

Cytosine

(C)

to

Uracil

(read

by

the

sequencer

as

Thymine

(T)),

leaving

methylated

Cs

unconverted..

Mapping

of

bisulfite-converted

short

reads,

such

as

those

commonly

produced

by

the

Illumina

HiSeq,

creates

a

number

of

difficulties.

Firstly,

if

both

Cs

and

Ts

in

reads

can

map

to

Cs

in

the

genome,

then

methylation

metrics

will

be

systematically

skewed,

as

methylated

reads

will

map

preferentially,

given

that

they

contain

more

information.

The

alternative

is

to

in

silico

convert

both

the

reads

and

the

genome

prior

to

alignment,

thereby

producing

unbiased,

but

less

efficiently

mapped,

alignments.

This

creates

a

second

difficulty

in

that

the

two

DNA

strands

are

no

longer

complementary,

requiring

them

to

be

treated

separately.

Finally,

PCR

amplification

during

library

preparation

results

in

the

creation

of

an

additional

two

DNA

strands,

complementary

to

the

original

bisulfite

converted

strands.

The

presence

of

multiple

non-complementary

strands

is

a

situation

for

which

standard

short-read

aligners

are

generally

unequipped..

For

these

reasons,

a

number

of

bisulfite

aligners

have

recently

been

created,

the

most

popular

of

which

is

Bismark

(see

for

a

general

comparison

of

BS-seq

aligners).

Bismark,

like

BSmooth

and

exploits

the

short-read

aligners

bowtie

or

to

perform

alignments.

While

these

aligners

generally

produce

good

results,

they

are

quite

slow,

due

to

running

up

to

instances

of

bowtie

simultaneously

on

the

same

computer

as

well

as

other

implementation

issues.

Bismark

and

in

particular,

have

a

higher

than

necessary

false-positive

rate

due

to

not

producing

alignments

with

associated

mapping

qualities

(MAPQ

scores),

which

could

otherwise

be

used

to

filter

out

methylation

calls

from

alignments

with

too

high

a

probability

of

being

wrong,

and

how

they

decide

which

alignment

to

report.

Similarly,

while

BSmooth

produces

alignments

with

MAPQ

scores,

they

are

based

only

on

alignment

to

a

single

strand,

so

a

read

aligning

equally

well

to

multiple

strands

will

have

an

aberrantly

high

MAPQ

score.

As

an

example,

given

a

read

that

aligns

with

a

MAPQ

score

of

to

one

strand

and

to

another,

BSmooth

will

output

the

alignment

with

a

MAPQ

score

of

and

leave

that

MAPQ

score

unchanged.

Had

this

MAPQ

score

instead

been

calculated

in

a

context

within

which

the

alternative

(MAPQ

score

of

alignment

was

known,

the

resulting

MAPQ

score

would

have

appropriately

been

much

lower.

BSMAP

an

older

aligner,

has

previously

been

reported

to

require

a

similar

amount

of

time

as

bismark

to

run

but,

because

it

uses

its

own

aligner,

produces

somewhat

better

coverage

Other

recent

bisulfite

aligners,

e.g.

GNUMAP-bs

purport

to

have

higher

speed

and

accuracy

at

the

expense

of

significantly

increased

memory

requirements.

In

practice,

though,

the

speed

increase

is

marginal

and

accuracy

increases

are

nonexistent.

As

the

alignment

step

is

simply

an

intermediate

between

receiving

raw

data

and

actual

statistical

analysis,

this

creates

an

unnecessary

experimental

impediment..

To

combat

these

issues,

we

have

developed

a

novel

bisulfite

aligner,

Bison

(BISulfite

alignment

On

Nodes

of

a

cluster),

written

in

C

that

exploits

the

increasing

prevalence

of

computer-clusters

to

rapidly

align

BS-seq

reads.

Bison

can

utilize

either

or

nodes,

a

master

node

to

process

alignments

and

one

worker

node

per

DNA

strand

for

aligning

reads.

We

also

provide

a

second

version,

which

scales

to

run

on

a

semiarbitrary

number

of

cluster

nodes,

rather

than

being

limited

to

nodes,

depending

on

library

type.

Like

Bismark,

BSmooth

and

Bison

utilizes

to

perform

actual

alignments,

but

produces

alignments

with

recalculated

MAPQ

scores

(a

more

general

feature

comparison

is

shown

in

Table

Because

Bison

can

simultaneously

use

multiple

nodes

it

requires

less

memory

per-node.

Furthermore,

as

the

algorithm

used

by

Bison

to

judge

the

best

alignment

is

different

from

that

used

by

the

other

aligners,

its

false-positive

rate

is

decreased

to

that

of

Even

when

using

identical

resources,

Bison

performs

its

alignments

in

a

fraction

of

the

time

required

by

all

of

the

other

compared

aligners,

except

BSMAP.

Bison

produces

more

accurate

results

than

all

of

the

other

compared

aligners

on

simulated

datasets.

Unlike

most

other

BS-seq

aligners,

does

not

create

temporary

files,

decreasing

both

I/O

and

space

requirements.

To

easily

facilitate

statistical

analysis,

Bison

comes

with

methylation

extraction

and

conversion

programs.

Bison

also

provides

the

facility

for

easy

quality

control

of

aligned

data

and

it

can

compute

methylation

metrics

dependent

upon

these

quality

control

results..

Finally,

bison

is

accompanied

by

a

helper

program

that,

unlike

similar

programs,

uses

both

alignment

position

and

methylation

calls

to

mark

likely

PCR

duplicates,

which

are

then

ignored

during

the

methylation

extraction

and

quality

control

process.

Figure

Bison

produces

more

accurate

results

than

BSmooth

or

GNUMAP-bs.

The

MAPQ

density

of

correctly

(red)

and

incorrectly

(blue)

aligned

reads

from

the

test

dataset

for

alignments

performed

by

Bison,

BSmooth,

and

GNUMAP-bs.

Bismark,

BSMAP

and

are

not

shown

as

they

do

not

produce

alignments

with

MAPQ

scores.

Scaling

of

the

correct

and

incorrect

metrics

is

performed

separately,

as

the

incorrect

density

would

otherwise

not

be

visible.

The

general

workflow

is

depicted

in

Figure

with

recommended

steps

external

to

noted.

As

with

other

aligners,

an

index

of

the

genome

is

created

to

facilitate

faster

mapping.

This

step

needs

to

be

performed

only

once.

Two

temporary

copies

of

the

genome

are

created,

one

C->

T

and

the

other

G->

A

in

silico

converted.

Prior

to

alignment,

low

quality

bases

and

incorporated

adapter

sequences

should

be

removed,

as

previously

recommended

We

recommend

Trim

Galore!

as

it

is

tailored

toward

bisulfite-converted

reads

and

supports

paired-end

reads.

An

alternative

to

trimming

is

using

local

alignment.

While

Bison

is

capable

of

producing

local

alignments,

the

likelihood

of

incorrect

methylation

calls

due

to

partial

adapter

alignment

has

caused

us

to

default

to

producing

end-to-end

alignments.

For

the

same

reason,

the

comparisons

included

below

contain

only

trimmed

datasets.

Both

Bison

and

accept

the

resulting

trimmed

fastq

files,

which

may

also

be

compressed

to

save

space.

can

also

process

a

list

of

single

or

paired-end

files,

writing

results

to

individual

files.

This

is

particularly

convenient

when

processing

multiple

samples,

as

the

genome

and

its

indices

only

need

to

be

read

from

disk

and

loaded

into

memory

once.

Bison

in

silico

converts

these

reads

on

the

master

node

as

appropriate

and

writes

the

results

to

a

file

or

files.

The

number

and

nature

of

the

conversion

is

dependent

upon

whether

the

libraries

were

directional

or

non-directional

and

run

single

or

paired-end.

These

converted

reads

are

then

aligned

as

appropriate

by

on

the

worker

nodes.

In

the

process

is

similar,

except

reads

are

sent

unconverted

via

MPI

from

the

master

node

to

the

worker

nodes,

where

they

are

converted

prior

to

being

given

via

named-pipes

to

As

each

worker

node

creates

alignments,

they

are

sent

via

MPI

to

the

master

node.

There,

the

alignments

are

collated

and

a

best

alignment

is

selected

(process

described

below).

Subsequently,

the

methylation

state

of

each

base

in

each

read

is

determined.

If

a

read

contains

a

mismatch,

the

methylation

state

of

that

base

is

set

to

to

denote

"not

applicable".

The

results

are

then

written

to

a

BAM

file

using

the

samtools

C

API

Unmapped

reads

may

optionally

be

written

to

fastq

files..

After

performing

quality

control

(see

below),

methylation

metrics

are

normally

extracted

and

written

in

bedGraph

format.

For

paired-end

reads,

overlapping

portions

of

each

pair

are

processed

as

a

unit

so

to

not

double-count

methylation

calls.

It

sometimes

occurs

that

reads

in

a

pair

disagree

on

a

methylation

call,

either

because

one

read

contains

an

N

at

a

given

position,

or

because

both

reads

simply

contain

different

high

quality

base

calls.

In

the

former

case,

Bison

will

always

use

the

methylation

call

of

the

read

not

containing

an

N

at

the

position

in

question.

In

the

latter

case,

neither

methylation

call

is

used.

The

resulting

methylation

metrics

are

written

for

every

C

in

a

CpG,

CHG,

or

CHH

context

to

separate

bed-Graph

files.

A

helper

program

is

also

included

to

merge

metrics

from

both

C's

in

a

CpG

context.

Other

auxiliary

scripts

are

provided

to

produce

various

metrics

(e.g.

per-CpG

coverage),

merge

bedGraph

files

from

technical

replicates,

and

convert

files

for

easy

input

into

R

for

processing

by

methylKit

BSseq

BiSeq

BEAT

and

MethylSeekR

O O B O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Performance Analysis of Markov Modulated 1-Persistent CSMA/CA Protocols with Exponential Backoff Scheduling Abstract. This paper proposes a Markovian model of 1-persistent CSMA/CA protocols with K-Exponential Backoff scheduling algorithms. The input buffer of each access node is modeled as a Geo/G/1 queue, and the service time distribution of each individual head-of-line packet is derived from the Markov chain of the underlying scheduling algorithm. From the queuing model, we derive the characteristic equation of network throughput and obtain the stable throughput and bounded delay regions with respect to the retransmission factor. Our results show that the stable throughput region of the exponential backoff scheme exists even for an infinite population. Moreover, we find that the bounded delay region of exponential backoff is only a sub-set of its stable throughput region due to the large variance of the service time of input packets caused by the capture effect. All analytical results presented in this paper are verified by simulations. Carrier Sense Multiple Access (CSMA) is a standardized Media Access Control (MAC) protocol for the transmission of network stations over a commonly shared medium, such as 802.11 wireless LANs or Ethernet networks. It is a set of rules for resolving collisions when two or more nodes attempt to use a transmission channel simultaneously. The network stations governed by CSMA with collision avoidance (CSMA/CA) check the busy/idle status of the transmission channel before attempting to transmit. If the channel is detected busy, the packets involved in the collision attempt to retransmit after a random time interval. With exponential backoff scheduling, this random waiting time interval for retransmission geometrically increases with the number of collisions encountered by the packet.. The p-persistent CSMA protocols try to maximize the channel utilization by continuously monitoring the transmission medium. An active node with a packet ready to transmit constantly checks the channel status. If the channel is sensed idle, the node transmits the packet with a probability p. Otherwise, the node will persistently monitor the channel until it becomes idle, and then transmits again with the same probability p. This process repeats until the packet is dispatched.. Collisions may still occur when two or more packets are simultaneously transmitted. The 1-Persistent Carrier-Sense Multiple Access (1P-CSMA) protocol is a special case of the p-persistent CSMA protocol with p = 1. We have analyzed the stability conditions in terms of stable throughput and bounded delay for slotted 1-persistent CSMA/CA networks. The queuing model of input buffer with the K-Exponential Backoff collision resolution algorithm is proposed to conduct the throughput analysis of the entire system and the performance of each individual input buffer.. Based on this model, the exponential backoff scheduling algorithm has been used to establish the stable throughput region and bounded delay region with respect to aggregate input rate and retransmission factor q. It is shown that the network throughput of the exponential backoff scheme can always be stabilized with the proper selection of q; while the region shrinks remarkably subject to the bounded delay requirement. Consequently, the maximum achievable throughput of the network within the bounded delay region is slightly smaller than the absolute maximum throughput. The proposed methodology can also be applied to other CSMA-based networks, such as IEEE 802.11, in the future.. List of Figure Fig. 1 . The renewal process of 1P-CSMA with two types of transmission periods.

B I O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Helping business schools engage with real problems: The contribution of critical realism and systems thinking The world faces major problems, not least climate change and the financial crisis, and business schools have been criticised for their failure to help address these issues and, in the case of the financial meltdown, for being causally implicated in it. In this paper we begin by describing the extent of what has been called the rigour/relevance debate. We then diagnose the nature of the problem in terms of historical, structural and contextual mechanisms that initiated and now sustain an inability of business schools to engage with real-world issues. We then propose a combination of measures, which mutually reinforce each other, that are necessary to break into this vicious circlecritical realism as an underpinning philosophy that supports and embodies the next points; holism and transdisciplinarity; multimethodology (mixed-methods research); and a critical and ethical-committed stance. OR and management science have much to contribute in terms of both powerful analytical methods and problem structuring methods. Abstract The world faces major problems, not least climate change and the financial crisis, and business schools have been criticised for their failure to help address these issues and, in the case of the financial meltdown, for being causally implicated in it. In this paper we begin by describing the extent of what has been called the rigour/relevance debate. We then diagnose the nature of the problem in terms of historical, structural and contextual mechanisms that initiated and now sustain an inability of business schools to engage with real-world issues. We then propose a combination of measures, which mutually reinforce each other, that are necessary to break into this vicious circlecritical realism as an underpinning philosophy that supports and embodies the next points; holism and transdisciplinarity; multimethodology (mixed-methods research); and a critical and ethical-committed stance. OR and management science have much to contribute in terms of both powerful analytical methods and problem structuring methods.Keywords In the introduction, we identified a range of problems that are seen to be besetting business schools at this time -lack of engagement with external organisations, irrelevance of research, inappropriate teaching curricula, little concern for pressing social issues and questionable ethical commitments. In the second section we analysed a range of historical and structural mechanisms which generated this situation initially, and now sustain it, making change difficult to bring about. The main purpose of the paper, however, it to propose a combination of approaches that mutually reinforce one another and that, taken together, could break into the current vicious cycle and perhaps begin to turn it round towards more practical, relevant and engaged activity. The philosophical approach of critical realism forms the scaffolding for this proposal..  CR works as an underpinning philosophy that allows us to accept the strengths of both empiricism and constructionism without having to accept their limitations in terms of realworld problem solving. It asserts the existence of a causally efficacious real world while accepting the inevitably limited nature of our access to that world. It thereby directs our attention to go beyond simply describing what we experience, whether in terms of empirical observations or personal values and beliefs, towards trying to explain the causality behind these experiences and thus towards being able to change them. Where desired  Critical realism naturally leads into a holistic and systemic worldview which itself necessitates transdisciplinarity -an overcoming of the current disciplinary silos. This is necessary because the serious problems that we face are inevitably complex, inter-woven and multi-dimensional and resist reductionist or partial approaches..  The pluralist character of critical realism and the need for holism and transdisciplinarity in turn mean that we need mixed-method research to employ together a range of research methodologies, empirical, interpretive and oriented towards practical action (action research)..  Finally, critical realism destroys the illusion that research can be value-free research and that we can turn a blind eye to the effects of our research activities, or indeed to our lack of activity. Instead, it argues that social science is committed towards trying to achieve a better society for all.. Nor is all this an idle pipe-dream -there are real signs that we have reached a cusp in which both internal and external pressures for change could lead to business schools becoming meaningfully engaged in helping society face its real problems.

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O


Partial Derivative Guidance for Weak Classifier Mining in Pedestrian Detection Boosting over weak classifiers is widely used in pedestrian detection. As the number of weak classifiers is large, researchers always use a sampling method over weak classifiers before training. The sampling makes the boosting process harder to reach the fixed target. In this paper, we propose a partial derivative guidance for weak classifier mining method which can be used in conjunction with a boosting algorithm. Using weak classifier mining method makes the sampling less degraded in the performance. It has the same effect as testing more weak classifiers while using acceptable time. Experiments demonstrate that our algorithm can process quicker than [1] algorithm in both training and testing, without any performance decrease. The proposed algorithms is easily extending to any other boosting algorithms using a window-scanning style and HOG-like features. Pedestrian detection is important for many applications in fields of computer vision such as visual surveillance, image retrieval and driver assistance system. But at the same time, pedestrian detection is still a challenging task because of the variations in appearance, articulation, posture and illumination condition.. Among various algorithms of pedestrian detection, the boosting-from-weak-classifier ones are probably the most popular scheme. These algorithms combine local image features into a strong classifier, which is then applied to all possible sub-windows in the input images to detect pedestrians. Viola et al. [2] proposed an algorithm using Haar wavelet features with the Adaboost and cascade training framework [3] . Dalal and Triggs [4] presented a new feature called Histogram of Oriented Gradient (HOG), which is notably more effective than Haar wavelet in pedestrian detection. Zhu et al. [5] combined HOG feature with the cascade structure, thereby reduced scanning detection time significantly. Sabzmeydani and Mori [6] described a midlevel feature set called shapelet, trained by two levels of Adaboost. Tuzel et al. suggested utilizing covariance matrices as object descriptors and a learning algorithm on Riemannian manifolds. Lin et al. [7] feature to mitigate feature misalignment problem. Meanwhile, some researchers have attempted to improve the time efficiency of pedestrian detection algorithms. The combination of boosting and cascade structure is a widely used approach. Most efficient works [2] , [3] , [5] - [7] depend on this structure.. However, in every stage of cascade training, the evaluation of each weak classifier is very time consuming. Considering the training time efficiency, researchers always adopt certain sampling on the feature pool in practical. In comparison with using all features in feature pool, using sampling will result in a little worse performance. [5] The researchers took into account the unacceptable long training time and tolerate the disparity. However, it is practical to search better weak-classifier and make the disparity smaller under the acceptable training time. There are already some successful works in feature selection of online boosting [8] , in which a gradient-based feature selection approach is proposed in pedestrian tracking.. We propose a weak classifier mining algorithm in picking weak classifiers which comes out with better result than traditional sampling method. Since diamond search algorithm [9] is useful in finding the minimum residual in the neighborhood and is widely used in video coding, we use it in finding the minimum false alarm rate in the neighborhood of feature space. The proposed weak classifier mining is steered by partial derivatives in feature space. We also propose a practical computing method for these partial derivatives which will notably reduce time consumption in efficient mining of the weak classifiers and can be easily extended to any other boosting algorithm that has a windowscanning style and HOG-like features. Corresponding experiments confirmed that the result after using weak classifier mining is close to the ideal result of evaluating every block in each stage. In this paper, we propose a partial derivative guidance for weak classifier mining method which can be used together with boosting algorithm. We make the sampling less degraded in the performance by weak classifier mining method. And fewer classifiers involved in the detector make the time consumption less in training and detection. Experiments demonstrate that the performance of our algorithm keeps the same with fewer weak classifiers. To evaluate the performance of the proposed algorithm, we implemented it with the support of the Intel OpenCV library and a PC running on a 2.33 GHz Intel CPU. Except for our original weak classifier mining algorithm, other components of training and detection algorithm are implemented according to Pang's work [1] in order to demonstrate the improvement of our algorithm over fundamental methods.. We used the INRIA dataset [4] as our training and testing samples, which includes 2416 positive training samples. For negative samples, we bootstrapped new training samples from the negative training images in the INRIA dataset at the beginning of training each cascade stage. The test dataset contains 1126 calibrated positive samples and 453 negative images. As in Pang's work [1] , we chose HOG as feature, linear SVM as the weak classifier, and Adaboost + cascade as the training framework. We sampled 5% features from the feature pool in every training process. Figure 3 compares the weak classifier number involved in every stage of our algorithm with the number of basic algorithm. It can be noticed that the number of weak classifier has about 25% in decrease. In training section, we use the same goal in each level. Thus, we can prove that our algorithm use less weak classifiers to get the same performance. This will speed up the training and detection process about 15% and 10%. Table 1 summarizes the training and detection time comparison. The comparison demonstrates the advance in boosting results of our algorithm, since weak classifier mining method make the boosting process cover much more HOG features. Figure 4 provides the ROC curve of proposed algorithm together with algorithm in [1] . Theoretically, our new algorithm only reorganizes the computation structure, without any simplification or approximation. Therefore, in the terminal case, it will not make any difference in performance compared to the reference algorithm. But in limited stage, the performance is different by using the weak classifier mining. Our weak classifier mining method should be easily extended to any other boosting algorithms using a window-scanning style and HOG-like features.

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On the free resolution induced by a Pommaret basis We combine the theory of Pommaret bases with a (slight generalisation of a) recent construction by Sköldberg based on discrete Morse theory. This combination allows us the explicit determination of a (generally non-minimal) free resolution for a graded polynomial module with the computation of only one Pommaret basis. If only the Betti numbers are needed, one can considerably simplify the computations by determining only the constant part of the differential. For the special case of a quasi-stable monomial ideal, we show that the induced resolution is a mapping cone resolution. We present an implementation within the CoCoALib and test it with some common benchmark ideals. Free resolutions are of fundamental importance in commutative algebra and algebraic geometry. In particular, the minimal free resolution of a homogeneous polynomial ideal encodes much relevant information about the ideal and is related to many important invariants like the Betti numbers. However, the explicit determination of the minimal free resolution (or in fact of any free resolution) is a computationally demanding task and only for certain special cases closed-form expressions for a resolution are known. Most algorithms presented in the literature follow either a vertical or a horizontal strategy, i. e. they construct the resolution either one homological degree after the other or they proceed according to the symmetric degree. Discussions can be found in (Kreuzer and Robbiano, 2005) or (La Scala and Stillman, 1998) . Seiler (2009b) showed that the (revlex) Pommaret basis of a polynomial ideal or submodule induces a free resolution. More precisely, via the involutive form of the Schreyer theorem, one can read off the Pommaret basis without any further computations the shape of a free resolution (leading to sharp upper bounds for the Betti numbers). However, a closed form of the differential could be derived by Seiler (2009b) only for quasi-stable monomial ideals. In general, the induced resolution is not minimal. One obtains a minimal resolution (in generic coordinates), if and only if the module is componentwise linear.. The free resolution induced by the Pommaret basis is highly structured consisting of "linear layers." Despite the fact that it is generally not minimal, this structure allowed Seiler (2009b) to obtain important homological invariants like the Castelnuovo-Mumford regularity or the projective dimension from the Pommaret basis without further computations. This article presents some new results from our ongoing analysis of this resolution with emphasis on "topological" methods for its construction. Sköldberg (2006) and independently Jöllenbeck and Welker (2009) developed an algebraic version of the discrete Morse theory of Forman (1998) and started to apply it to the construction of resolutions. More recently, Sköldberg (2011) derived the minimal free resolution for modules with initially linear (minimal) syzygies from a two-sided Koszul complex. His definition of initially linear syzygies contains a minimality condition which restricts the applicability of his results to componentwise linear modules, but which is only needed for ensuring that the final resolution is the minimal one. Our first main result is that, after dropping this condition, one can apply his construction to the Pommaret basis of a submodule of a free module and obtains then a resolution isomorphic to the one presented in (Seiler, 2009b) . In particular, we show that his construction yields then a Pommaret basis of each syzygy module. Thus combining Sköldberg's work with Pommaret bases makes it fully effective and applicable to arbitrary finitely presented polynomial modules, as the Pommaret bases lead automatically to initially linear syzygies whereas in Sköldberg's work even the existence of such a presentation remains an open question.. In algebraic geometry it often suffices to obtain the (bigraded) Betti numbers; the whole resolution is not really needed. Our second main result consists of showing that it is possible to extract directly the constant part of Sköldberg's differential without determining the remainder of the resolution. Then the determination of the Betti numbers is reduced to linear algebra over the ground field. This approach yields an algorithm which seems to be faster than any other proposed in the literature so far.. For arbitrary monomial ideals, a free resolution in closed form was e. g. provided by Taylor (1960) . However, the problem of giving a closed form minimal resolution for arbitrary monomial ideals is wide open and different approaches to it have produced many interesting results, see e. g. (Miller and Sturmfels, 2004) . One line of research in this area studies the minimal free resolution of particular families of monomial ideals. A seminal result in this respect is the minimal resolution of stable ideals found by Eliahou and Kervaire (1990) .. Pommaret bases only exist in generic coordinates. For polynomial ideals, this is not a fundamental problem. However, in the case of monomial ideals, the required coordinate transformations generally destroy the monomiality. This observation leads to the class of quasi-stable ideals as those monomial ideals possessing a monomial Pommaret basis. In the literature, these ideals have been called ideals of nested type by Bermejo and Gimenez (2006) , ideals of Borel type by Herzog et al. (2003) or weakly stable ideals by Caviglia and Sbarra (2005) . Stable ideals are now those monomial ideals where already the minimal basis is the Pommaret basis (Mall, 1998) . In this case, the resolution induced by the Pommaret basis is the Eliahou-Kervaire resolution, i. e. the minimal one. For arbitrary quasi-stable ideals, the induced resolution is very similar to the Eliahou-Kervaire resolution, but no longer minimal.. Another approach to the construction of-generally non-minimal-resolutions that can be used for any monomial ideal consists of iterated mapping cones and has been studied by various authors like Charalambous and Evans (1995) or Herzog and Takayama (2002) . In particular, it was shown that both the Eliahou-Kervaire and the Taylor resolution can be obtained this way. Our third main result is that this is also the case for the resolutions of quasi-stable ideals induced by their Pommaret bases. The proof is based on the recent observation (Hashemi et al., 2012) that the notion of linear quotients introduced by Herzog and Takayama (2002) is closely related to Pommaret bases and the construction of a contracting homotopy for polynomial resolutions via Gröbner bases (Seiler, 2002) .. Section 2 briefly reviews Pommaret bases and describes the free resolution induced by them. The following section gives a brief survey over algebraic discrete Morse theory and presents Sköldberg's construction of a resolution for modules with initially linear syzygies. In Section 4, we combine this construction with the theory of Pommaret bases and show that the two resolutions are isomorphic. The next section discusses a special case where the differential becomes much simpler and which includes in particular monomial ideals.. Section 6 describes our implementation in CoCoA and discusses the efficient determination of Betti numbers. In Section 7, we specialise to quasi-stable monomial ideals and show that here the Pommaret basis induces an iterated mapping cone resolution. Finally, some conclusions are given. In the first part, we combined the construction of a free resolution for polynomial modules due to Sköldberg (2011) with the theory of Pommaret bases as given in (Seiler, 2009b) . This combination makes Sköldberg's approach via algebraic discrete Morse theory fully algorithmic, as Pommaret bases provide us with a systematic method for generating presentations with initially linear syzygies: the existence of such presentations can be seen as one of the core ideas underlying the theory of Pommaret bases.. A distinctive feature of our algorithm compared to other approaches for constructing resolutions is the fact that only one Pommaret basis (namely for the given submodule U) is needed whereas usually several Gröbner bases (typically the number is given by pd U) have to be computed. Although the evaluation of the closed formula for the differential might appear very complicated, it requires mainly very cheap operations. The only polynomial operations are some involutive normal forms of products x µ h α for generators h α in the Pommaret basis of U. As we observed that the same product often appears many times, significant savings could be achieved by simply storing these.. The main reasons for the not yet satisfactory timings are our currently still very naive implementation of the minimisation process and the sometimes extreme difference in the sizes of the non-minimal and the minimal resolution, respectively. Here one can expect on one side substantial improvements just by optimisations of the code. On the other hand, it is obvious that a decisive factor is simply the size of the complex G • . While this size is completely determined by the Pommaret basis of U, it can be affected by linear coordinate transformations. In a forthcoming work, we will present a deterministic approach to construct generally fairly sparse coordinate transformations such that the leading module lt U is not only quasi-stable but stable (or even strongly stable). Then the complex G • should be considerably smaller; more precisely, it will have the same size as the minimal resolution of lt U. Finally, our current approach first determines the full complex G • and then minimises it. Probably very significant gains in efficiency are possible by interweaving the construction of this complex with the minimisation process (as it is done by classical algorithms to compute minimal resolutions).. The full power of our approach becomes already now apparent, if one does not need the whole resolution but only the Betti numbers. To our knowledge we presented here the first method to compute them which does not require the minimal resolution. As Table 2 demonstrates, for all examples save one our implementation was the fastest to compute the Betti numbers, often even by orders of magnitude. The main reasons are of course that, due to the knowledge of a closed form of the differential, we can construct directly only the constant part of the resolution and the subsequent "minimisations" require only linear algebra over the base field k and not over the polynomial ring P. Obviously, similar techniques should exist for tackling other questions where only certain parts of the minimal resolution are relevant like an analysis of the linear part of the resolution or its linear strand.. In the second part of this work, we specialised to a particular class of monomial ideals, the quasi-stable ideals. We proved that the resolution induced by the Pommaret basis is also obtainable via iterated mapping cones. Thus we showed that this interesting property of the Eliahou-Kervaire resolution remains valid for our generalisation of it to quasi-stable ideals. An interesting question here is whether further nice properties of the Eliahou-Kervaire resolution like the fact that it is a cellular resolution (Mermin, 2010 ) also extend to the resolution induced by a Pommaret basis.

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Metric learning for sequences in relational LVQ Metric learning constitutes a well-investigated field for vectorial data with successful applications, e.g. in computer vision, information retrieval, or bioinformatics. One particularly promising approach is offered by lowrank metric adaptation integrated into modern variants of learning vector quantization (LVQ). This technique is scalable with respect to both, data dimensionality and the number of data points, and it can be accompanied by strong guarantees of learning theory. Recent extensions of LVQ to general (dis-)similarity data have paved the way towards LVQ classifiers for non-vectorial, possibly discrete, structured objects such as sequences, which are addressed by classical alignment in bioinformatics applications. In this context, the choice of metric parameters plays a crucial role for the result, just as it does in the vectorial setting. In this contribution, we propose a metric learning scheme which allows for an autonomous learning of parameters (such as the underlying scoring matrix in sequence alignments) according to a given discriminative task in relational LVQ. Besides facilitating the often crucial and problematic choice of the scoring parameters in applications, this extension offers an increased interpretability of the results by pointing out structural invariances for the given task. * Init. we compare the classification performance of RGLVQ with and without metric adaptation, as before. In the latter case, RGLVQ training uses fixed dissimilarities based on the respective initial costs λ. The choice of meta-parameters was optimized w.r.t. the data in a 5-fold cross-validation with 10 repeats, setting crispness β = 20, and learning rate η = 0.45/N to adapt λ. In order to minimize the computational effort, we chose k = 1, which prove to be sufficient. First, we consider the initialization of λ according to the weighting scheme from [15] . The results are displayed in Figure 6 , and Table 1 (the two top rows). With fixed metric parameters, the final classification accuracies are rather low with 73% average test accuracy, see the baseline in Figure 6a . This is expectable, since the number of prototypes for RGLVQ was deliberately chosen to be only one per class, which implies minimal complexity of the classification boundary. Using more prototypes yields some improvements: with 3, 5, and 7 prototypes per class, 79%, 79%, and 81% average test accuracy is achieved, respectively.. However, metric adaptation with only one prototype enables a nearly perfect average accuracy of 97% for training and test sets. This demonstrates how a problem-adapted metric can alleviate the given classification task, even without a complex classifier model. (We observed no considerable benefit, when more prototypes are used.) Interestingly, this major improvement was achieved by subtle changes in λ from the initial scoring (see Figure 6b) to the final state after training (see Figure 6c , taken from the last cross-validation run). The adaptation mainly changes the replacement costs for neighboring scales of difference: many values on the first off-diagonals become nearly zero, signifying that these symbols are interchangeable within classes. At the same time, the gap costs for the symbol "=" become lower, which can be attributed to the fact that it is the most frequent symbol in the set (see Table 6 in the Appendix 7.2).. Comparing the class-separation in the fixed vs. the adapted dissimilarities, we observe that the separation ratio drops and the 5-NN accuracy improves, as reported in Table 1 . Also, the average number of support vectors used in the trained SVM classifiers decreases drastically, which indicates a less complex classification boundary. This underlines our hypothesis, that metric learning can greatly facilitate class-discrimination, especially when the parameterization of the underlying dissimilarity measure is complex.. In the next step, we consider the case of initializing λ with equal costs (metaparameters set to β = 7, η = 0.45/N , k = 1). Surprisingly, this very simple setting of λ yields higher accuracies than the cost pattern proposed in [15] , see the bottom two rows in Table 1 . Without any adaptation of the alignment costs, RGLVQ achieves 89% average test accuracy for one prototype per class. This can be improved by increasing the model complexity: 93%, 95%, and 95% average test accuracy are achieved with 3, 5, and 7 prototypes per class, respectively. Learning the metric parameters provides the same level of improvement to 95%, however, with only one prototype, since the underlying data representation is tuned according to the classification task. Thereby, the resulting model is very sparse, and it offers the possibility to inspect and interpret the adapted metric parameterization. In this case, increasing the number of prototypes also results in a slightly better classification performance: for example, 5 prototypes per class yield 96% average test accuracy. Although the 5-NN accuracy is not increased, the separation ratio is improved by the metric adaptation, and the average number of support vectors for SVM drops, again supporting our claim.

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Receiver design for the uplink of base station cooperation systems employing SC-FDE modulations The presented paper considers the uplink transmission in base station (BS) cooperation schemes where mobile terminals (MTs) in adjacent cells share the same physical channel. We consider single-carrier with frequency-domain equalization (SC-FDE) combined with iterative frequency-domain receivers based on the iterative block decision feedback equalization (IB-DFE). We study the quantization requirements when sending the received signals, from different MTs, at different BSs to a central unit that performs the separation of different MTs using iterative frequency-domain receivers. Our performance results show that a relatively coarse quantization, with only 4 bits in the in-phase and quadrature components of the complex envelope already allows close-to-optimum macro-diversity gains, as well as an efficient separation of the transmitted signals associated with each MT. It is expected that the demand for wireless services will continue to increase in the near and medium term, calling for more capacity and putting more and more pressure on the usage of radio resources. Future spectral efficiency improvements will be focused on interferencereducing techniques that require the cooperation of network elements [1] , since the point-to-point link capacities are already close to the fundamental Shannon limit [2] . Conventional cellular systems adopt different frequencies at different cells, with frequency reuse factors of 3, or even more. Clearly, the overall system's spectral efficiency and capacity are conditioned by the frequency reuse factor, typically decreasing linearly with it. Since the spectrum is a scarce and expensive resource in wireless systems, it would be desirable to design systems operating in universal frequency reuse (i.e., with frequency reuse factor 1). Multicell cooperation is a promising solution to mitigate interference between different cells, to improve the system's fairness and to increase capacity [3] [4] [5] [6] [7] . For these reasons, it is already under study in LTE Full list of author information is available at the end of the article [8] , namely, under the so-called coordinated multi-point concept which although not included in current releases, will probably be specified for future ones.. In conventional cellular architectures, different cells are regarded as separate entities and each mobile terminal (MT) is assigned to a given cell and, consequently, a given base station (BS). The MT transmits its signals to the corresponding BS, and when this signal is received by another BS, it is regarded as interference. In BS cooperation architectures [9] , the signals between different MTs and BSs are collected and processed by a central processing unit (CPU), so as to perform the user separation and/or interference mitigation. In fact, BS cooperation allows not only universal frequency reuse but also substantial macro-diversity effects, significantly improving the overall performance of wireless systems, as well as the coverage and power requirements associated with each individual link. The signal separation in the downlink transmission (i.e., the link from the BSs to the MTs) of BS cooperation schemes is usually achieved by appropriate pre-processing schemes [10] [11] [12] . In the uplink transmission (i.e., the link from the MTs to the BSs), the overall signals received by different BSs (with contributions from all MTs) are sent to the CPU that performs the signal separation, to extract the data blocks transmitted by each MT, before sending them to the corresponding BS [3] . These BS cooperation schemes involve interference mitigation, allowing the use of the same physical channel by MTs in adjacent cells, which means that the overall system capacity can be significantly improved.. It is well known that block transmission techniques, combined with frequency-domain processing, are choice candidates for broadband wireless systems. These techniques include orthogonal frequency division multiplexing (OFDM) [13] and single-carrier with frequency domain equalization (SC-FDE) [14] , which have similar overall signal processing requirements and achievable performance. However, the receiver complexity is higher for SC-FDE, and the transmitter complexity is higher for OFDM. If we also take into account that the envelope fluctuations of single-carrier signals are much lower than the envelope fluctuations of OFDM signals with the same constellations, SC-FDE is clearly preferable for the uplink transmission while OFDM is interesting mainly for the downlink transmission [15, 16] .. In this paper, we consider the uplink of broadband wireless systems with BS cooperation architectures with the employment of SC-FDE modulation schemes. MTs in adjacent cells can share the same physical channel and the signals received by a given BS are digitalized, through appropriate sampling and quantization procedures. The corresponding bits are sent to the central unit. The separation of the signals associated with different MTs is performed using iterative frequency-domain receivers based on the iterative block decision feedback equalization (IB-DFE) concept [17] [18] [19] . Due to its processing nature, the IB-DFE can be considered as a frequency-domain low complexity turbo equalizer [20] [21] [22] . Hence, the IB-DFE does not need the channel decoder output at the feedback loop. Nevertheless, turbo equalizers based on IB-DFE schemes can be conceived [23] . The quantization requirements for the signals received at a given BS are studied in detail.. This paper is organized as follows: in Section 2, we describe the BS cooperation scenario considered in this paper and Section 3 is concerned with the receiver design. A set of performance results is presented in Section 4, and Section 5 concludes the paper.. Throughout the paper, we will adopt the following notations: bold letters denote vectors and matrices; x * , x T , and x H denote complex conjugate, transpose, and Hermitian (complex conjugate transpose) of x, respectively. I N denotes a N × N identity matrix, and e p is an appropriate column vector with 0 in all positions except the pth position that is 1. The expectation of x is denoted by E[ x]. In this paper, we considered the receiver design for the uplink transmission in BS cooperation schemes employing SC-FDE signals. Here, the received signals at a certain BS are sampled and have the option of being quantized, with the corresponding bits being transmitted to a central unit that performs the user detection and/or separation using iterative frequency-domain receivers. Also, in this paper, we developed and presented an analytical approach for obtaining the performance of the proposed receivers.. The presented performance results demonstrated that the proposed receivers allow significant macro-diversity gains, as well as an efficient user separation. It is shown that we can have excellent performances using only 4 bits to quantize the real and imaginary parts of the complex envelope of the received signal at the BS, with a performance close to the MFB, and although relatively simple, our analytical approach was shown to be quite accurate. Hence, these techniques are presented as an excellent approach for future broadband wireless systems employing BS cooperation schemes.

O O O O O O O O O O O B O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O


Conceptualising health information seeking behaviours and exploratory search: result of a qualitative study The Internet has become an important source of health information for many people, including nonmedical experts. While much health information is provided through the Internet, such information is often spread across multiple websites and providers. With the decentralised nature of the Internet, people are often unable to access health information at a single point, and thus extra efforts are needed for seeking information with search engines. The information seeking process is a crucial step for obtaining the needed health information. According to prior research, seekers apply an exploratory approach in the information seeking process of health-related topics. Although information seeking behaviours have been studied extensively in past research, few details specifically about information seeking in the health context can be found. This paper reports on a qualitative study that investigates the information needs and behaviours of health information seekers. Based on the results of the study, we present a model conceptualising health information seeking behaviours as well as the characteristics of the exploratory search approach observed in the health information seeking process.Keywords: search approach, exploratory search, consumer health information, information seeking behaviour The final publication is available at Springer via http://dx The Internet is a source of a range of different health information resources for non-medical experts, from official health websites, private health service providers, personal blogs, to discussion forums. Past studies have demonstrated that the use of online resources for obtaining health information is increasing [1, 2] . As the demand for online health information grows, it is crucial to understand the motivations underlying these information seeking behaviours, the information needs of the seekers, the strategies for seeking information chosen by the seekers.. The World Wide Web is designed as a decentralised network. Health information, even on the same general topic, is available from many different websites and providers. For example, descriptions about Hepatitis B can be obtained from government websites, the website of medical centres, or even Wikipedia. Without a single source of information, this decentralised nature makes search engines the primary mechanism for accessing online information -i.e., people choose to search for the information in the first instance. Shown in a study, 77% of health information seekers in fact use search engines [2] .. Getting health information from the Internet is like finding a needle in the haystack. Especially when dealing with unfamiliar and unknown problems [3] , as is often the case for health-related concerns [4] , the search approach employed becomes more exploratory [5] . In contrast to simply submitting a search query, exploratory search involves a series of cognitive learning and query reformulation processes. With exploratory search, a more complete picture of the knowledge domain is being built during the search, which implies the existence of both learning and investigating activities. Although exploratory search can be found in different search tasks, there is only limited understanding of exploratory search in the health context.. In order to have a more complete understanding about online information seeking and search approaches taken in the consumer health context, we conducted a qualitative study to observe participants' behaviours. We discover that in many cases people take an exploratory approach to find relevant information. In addition, based on the activity logs recorded in the study, we summarise the patterns of participant behaviours into a model with four categories. Information seekers in these categories have different levels of research tactics and reading engagement. The model aims to provide a perspective from the angle of behavioural outcomes, so that health website owners and information retrieval (IR) specialists can improve their products in terms of user needs. Some design implications are identified as well at the end of this paper. This paper is structured as follows: it firstly summarises the current research and trends in obtaining online health information, followed by a report on the result of our qualitative study. Drawn from the results of the study, we propose a model for conceptualising online health information seeking behaviours, as well as the characteristics of the exploratory search approach observed in the health information seeking process. While not every instance of health information seeking is exploratory, with this research, we have found that people take an exploratory search approach for seeking online health information in various scenarios. Exploratory seekers are found to be more engaged in the search process and potentially gain more understandings of health problems through the search. Even with these benefits, currently the support for exploratory health search is limited, thus we proposed to address this issue in two design directions: namely assisting the discovery of new information and adapting to reading needs.. Based on the information seeking activities in our qualitative study, we proposed a model to conceptualise health information seeking behaviours. During the information seeking process, we argue that seekers may adapt either basic or extensive research tactics, reflecting their eagerness to investigate the problem. At the same time, seekers may choose to engage in reading online information or just skim through. The combinations of research tactics and reading engagement reflect different information seeking behaviours while searching for online health information.. As with other qualitative studies, ours is subject to limitations. Participants were invited to a lab environment and performed artificial search tasks. Depending on the environment and the understanding of the tasks, the study may not truly reflect the real behaviours in their daily lives. Secondly, the time constraint of our lab study may force the participants to complete the experiment at an unusual pace. To minimize the problem, we included an interview to learn more about the daily search experience. In addition, health information seeking behaviours may vary depending on factors such as the type of diseases (i.e., acute vs. chronic) or stage of the illness. While we have presented an outcome that applies to a general group of health information seekers, it would also be valuable to extend the research to more specific groups of seekers or patients.. The findings of this paper have revealed a deeper understanding of health information needs and relevant information seeking behaviours. As a health information provider or a health website designer, more accurate and better tailor-made information can be delivered to the consumers after understanding their different information needs and information seeking behaviours. This understanding can lead to a more effective design of health websites, which provide a more pleasant experience for accessing online health information. In the future, our plan is to build a test health website with the goal of assisting the discovery of new information and enhancing reading engagement. A large scale of user study will be launched to gather feedback and evaluate the new design elements in this new website. Based on the results of our qualitative study, we further discuss the phenomenon of exploratory search approaches taken during health information seeking processes. We propose a model to conceptualise the health information seeking behaviours and derive design implications for health websites to provide better support for seekers' needs. This section reports on the data gathered in the qualitative study. Firstly we present the observation of the lab experiment and list the themes that emerged after the analysis of interview transcripts. Then, we present the behavioural patterns of our participants. These patterns were observed from the navigation graphs produced from the activity logs.. During the review of the data collected in our study, we segmented the dataset into age groups and by gender. The analysis of the partitioned data shows no significant themes and patterns across different groups of participants. Therefore, the results and discussions in this paper apply to general health information seekers, regardless of their age and gender.

O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B I B I B I I B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O B I O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O