pwc-archive/papers-with-abstracts huggingface dataset:
A Mathematical Framework Exhibiting the Emergence of Dynamic Expansion of Task Repertoire in \emph{Pheidole dentata}
Date: 2016-04-14 00:00:00

The division of labor (DOL) and task allocation among groups of ants living
in a colony is thought to be highly efficient, and key to the robust survival
of a colony. A great deal of experimental and theoretical work has been done
toward gaining a clear understanding of the evolution of, and underlying
mechanisms of these phenomena. Much of this research has utilized mathematical
modeling. Here we continue this tradition by developing a mathematical model
for a particular aspect of task allocation, known as age-related repertoire
expansion, that has been observed in the minor workers of the ant species
\emph{Pheidole dentata}. In fact, we present a relatively broad mathematical
modeling framework based on the dynamics of the frequency with which members of
specific age groups carry out distinct tasks. We apply our modeling approach to
a specific task allocation scenario, and compare our theoretical results with
experimental data. It is observed that the model predicts perceived behavior,
and provides a possible explanation for the aforementioned experimental
results.
Learning Discriminative Representations for Semantic Cross Media Retrieval
Authors: Jiang Aiwen, Li Hanxi, Li Yi, Wang Mingwen
Date: 2015-11-18 00:00:00
Tasks: Representation Learning, Retrieval

Heterogeneous gap among different modalities emerges as one of the critical
issues in modern AI problems. Unlike traditional uni-modal cases, where raw
features are extracted and directly measured, the heterogeneous nature of cross
modal tasks requires the intrinsic semantic representation to be compared in a
unified framework. This paper studies the learning of different representations
that can be retrieved across different modality contents. A novel approach for
mining cross-modal representations is proposed by incorporating explicit linear
semantic projecting in Hilbert space. The insight is that the discriminative
structures of different modality data can be linearly represented in
appropriate high dimension Hilbert spaces, where linear operations can be used
to approximate nonlinear decisions in the original spaces. As a result, an
efficient linear semantic down mapping is jointly learned for multimodal data,
leading to a common space where they can be compared. The mechanism of "feature
up-lifting and down-projecting" works seamlessly as a whole, which accomplishes
crossmodal retrieval tasks very well. The proposed method, named as shared
discriminative semantic representation learning (\textbf{SDSRL}), is tested on
two public multimodal dataset for both within- and inter- modal retrieval. The
experiments demonstrate that it outperforms several state-of-the-art methods in
most scenarios.
Comparison of the analytical approximation formula and Newton's method for solving a class of nonlinear Black-Scholes parabolic equations
Date: 2015-11-24 00:00:00

Market illiquidity, feedback effects, presence of transaction costs, risk
from unprotected portfolio and other nonlinear effects in PDE based option
pricing models can be described by solutions to the generalized Black-Scholes
parabolic equation with a diffusion term nonlinearly depending on the option
price itself. Different linearization techniques such as Newton's method and
analytic asymptotic approximation formula are adopted and compared for a wide
class of nonlinear Black-Scholes equations including, in particular, the market
illiquidity model and the risk-adjusted pricing model. Accuracy and time
complexity of both numerical methods are compared. Furthermore, market quotes
data was used to calibrate model parameters.
Problems with the use of Web search engines to find results in foreign languages
Authors: Lewandowski Dirk
Date: 2015-11-18 00:00:00

Purpose - To test the ability of major search engines, Google, Yahoo, MSN,
and Ask, to distinguish between German and English-language documents
  Design/methodology/approach - 50 queries, using words common in German and in
English, were posed to the engines. The advanced search option of language
restriction was used, once in German and once in English. The first 20 results
per engine in each language were investigated.
  Findings - While none of the search engines faces problems in providing
results in the language of the interface that is used, both Google and MSN face
problems when the results are restricted to a foreign language.
  Research limitations/implications - Search engines were only tested in German
and in English. We have only anecdotal evidence that the problems are the same
with other languages.
  Practical implications - Searchers should not use the language restriction in
Google and MSN when searching for foreign-language documents. Instead,
searchers should use Yahoo or Ask. If searching for foreign language documents
in Google or MSN, the interface in the target language/country should be used.
  Value of paper - Demonstrates a problem with search engines that has not been
previously investigated.
The Retrieval Effectiveness of Web Search Engines: Considering Results Descriptions
Authors: Lewandowski Dirk
Date: 2015-11-18 00:00:00
Tasks: Retrieval

Purpose: To compare five major Web search engines (Google, Yahoo, MSN,
Ask.com, and Seekport) for their retrieval effectiveness, taking into account
not only the results but also the results descriptions.
  Design/Methodology/Approach: The study uses real-life queries. Results are
made anonymous and are randomised. Results are judged by the persons posing the
original queries.
  Findings: The two major search engines, Google and Yahoo, perform best, and
there are no significant differences between them. Google delivers
significantly more relevant result descriptions than any other search engine.
This could be one reason for users perceiving this engine as superior.
  Research Limitations: The study is based on a user model where the user takes
into account a certain amount of results rather systematically. This may not be
the case in real life.
  Practical Implications: Implies that search engines should focus on relevant
descriptions. Searchers are advised to use other search engines in addition to
Google.
  Originality/Value: This is the first major study comparing results and
descriptions systematically and proposes new retrieval measures to take into
account results descriptions
What Users See - Structures in Search Engine Results Pages
Authors: Hoechstoetter Nadine, Lewandowski Dirk
Date: 2015-11-18 00:00:00
Tasks: valid

This paper investigates the composition of search engine results pages. We
define what elements the most popular web search engines use on their results
pages (e.g., organic results, advertisements, shortcuts) and to which degree
they are used for popular vs. rare queries. Therefore, we send 500 queries of
both types to the major search engines Google, Yahoo, Live.com and Ask. We
count how often the different elements are used by the individual engines. In
total, our study is based on 42,758 elements. Findings include that search
engines use quite different approaches to results pages composition and
therefore, the user gets to see quite different results sets depending on the
search engine and search query used. Organic results still play the major role
in the results pages, but different shortcuts are of some importance, too.
Regarding the frequency of certain host within the results sets, we find that
all search engines show Wikipedia results quite often, while other hosts shown
depend on the search engine used. Both Google and Yahoo prefer results from
their own offerings (such as YouTube or Yahoo Answers). Since we used the .com
interfaces of the search engines, results may not be valid for other
country-specific interfaces.
Ranking library materials
Authors: Lewandowski Dirk
Date: 2015-11-18 00:00:00

Purpose: This paper discusses ranking factors suitable for library materials
and shows that ranking in general is a complex process and that ranking for
library materials requires a variety of techniques.
Design/methodology/approach: The relevant literature is reviewed to provide a
systematic overview of suitable ranking factors. The discussion is based on an
overview of ranking factors used in Web search engines. Findings: While there
are a wide variety of ranking factors applicable to library materials, todays
library systems use only some of them. When designing a ranking component for
the library catalogue, an individual weighting of applicable factors is
necessary. Research limitations/applications: While this article discusses
different factors, no particular ranking formula is given. However, this
article presents the argument that such a formula must always be individual to
a certain use case. Practical implications: The factors presented can be
considered when designing a ranking component for a librarys search system or
when discussing such a project with an ILS vendor. Originality/value: This
paper is original in that it is the first to systematically discuss ranking of
library materials based on the main factors used by Web search engines.
The Influence of Commercial Intent of Search Results on Their Perceived Relevance
Authors: Lewandowski Dirk
Date: 2015-11-18 00:00:00
Tasks: Retrieval

We carried out a retrieval effectiveness test on the three major web search
engines (i.e., Google, Microsoft and Yahoo). In addition to relevance
judgments, we classified the results according to their commercial intent and
whether or not they carried any advertising. We found that all search engines
provide a large number of results with a commercial intent. Google provides
significantly more commercial results than the other search engines do.
However, the commercial intent of a result did not influence jurors in their
relevance judgments.
The retrieval effectiveness of search engines on navigational queries
Authors: Lewandowski Dirk
Date: 2015-11-18 00:00:00
Tasks: Retrieval, valid

Purpose - To test major Web search engines on their performance on
navigational queries, i.e. searches for homepages. Design/methodology/approach
- 100 real user queries are posed to six search engines (Google, Yahoo, MSN,
Ask, Seekport, and Exalead). Users described the desired pages, and the results
position of these is recorded. Measured success N and mean reciprocal rank are
calculated. Findings - Performance of the major search engines Google, Yahoo,
and MSN is best, with around 90 percent of queries answered correctly. Ask and
Exalead perform worse but receive good scores as well. Research
limitations/implications - All queries were in German, and the German-language
interfaces of the search engines were used. Therefore, the results are only
valid for German queries. Practical implications - When designing a search
engine to compete with the major search engines, care should be taken on the
performance on navigational queries. Users can be influenced easily in their
quality ratings of search engines based on this performance. Originality/value
- This study systematically compares the major search engines on navigational
queries and compares the findings with studies on the retrieval effectiveness
of the engines on informational queries. Paper type - research paper
A Framework for Evaluating the Retrieval Effectiveness of Search Engines
Authors: Lewandowski Dirk
Date: 2015-11-18 00:00:00
Tasks: Retrieval

This chapter presents a theoretical framework for evaluating next generation
search engines. We focus on search engines whose results presentation is
enriched with additional information and does not merely present the usual list
of 10 blue links, that is, of ten links to results, accompanied by a short
description. While Web search is used as an example here, the framework can
easily be applied to search engines in any other area. The framework not only
addresses the results presentation, but also takes into account an extension of
the general design of retrieval effectiveness tests. The chapter examines the
ways in which this design might influence the results of such studies and how a
reliable test is best designed.
The relationship between internet user type and user performance when carrying out simple vs. complex search tasks
Authors: Singer Georg, Pruulmann-Vengerfeldt Pille, Norbisrath Ulrich, Lewandowski Dirk
Date: 2015-11-18 00:00:00
Tasks: Articles

It is widely known that people become better at an activity if they perform
this activity long and often. Yet, the question is whether being active in
related areas like communicating online, writing blog articles or commenting on
community forums have an impact on a persons ability to perform Web searches,
is still unanswered. Web searching has become a key task conducted online; in
this paper we present our findings on whether the user type, which categorises
a persons online activities, has an impact on her or his search capabilities.
We show (1) the characteristics of different user types when carrying out
simple search tasks; (2) their characteristics when carrying out complex search
tasks; and, (3) the significantly different user type characteristics between
simple and complex search tasks. The results are based on an experiment with 56
ordinary Web users in a laboratory environment. The Search-Logger study
framework was used to analyze and measure user behavior when carrying out a set
of 12 predefined search tasks. Our findings include the fact that depending on
task type (simple or complex) significant differences can be observed between
users of different types.
The Entropic Measure Transform
Date: 2019-02-21 00:00:00
Tasks: Math

We introduce the entropic measure transform (EMT) problem for a general
process and prove the existence of a unique optimal measure characterizing the
solution. The density process of the optimal measure is characterized using a
semimartingale BSDE under general conditions. The EMT is used to reinterpret
the conditional entropic risk-measure and to obtain a convenient formula for
the conditional expectation of a process which admits an affine representation
under a related measure. The entropic measure transform is then used provide a
new characterization of defaultable bond prices, forward prices, and futures
prices when the asset is driven by a jump diffusion. The characterization of
these pricing problems in terms of the EMT provides economic interpretations as
a maximization of returns subject to a penalty for removing financial risk as
expressed through the aggregate relative entropy. The EMT is shown to extend
the optimal stochastic control characterization of default-free bond prices of
Gombani and Runggaldier (Math. Financ. 23(4):659-686, 2013). These methods are
illustrated numerically with an example in the defaultable bond setting.
Network-based recommendation algorithms: A review
Authors: Yu Fei, Zeng An, Gillard Sebastien, Medo Matus
Date: 2015-11-19 00:00:00
Tasks: Recommendation Systems

Recommender systems are a vital tool that helps us to overcome the
information overload problem. They are being used by most e-commerce web sites
and attract the interest of a broad scientific community. A recommender system
uses data on users' past preferences to choose new items that might be
appreciated by a given individual user. While many approaches to recommendation
exist, the approach based on a network representation of the input data has
gained considerable attention in the past. We review here a broad range of
network-based recommendation algorithms and for the first time compare their
performance on three distinct real datasets. We present recommendation topics
that go beyond the mere question of which algorithm to use - such as the
possible influence of recommendation on the evolution of systems that use it -
and finally discuss open research directions and challenges.
Predicting and controlling the Ebola infection
Date: 2015-11-19 00:00:00

We present a comparison between two different mathematical models used in the
description of the Ebola virus propagation currently occurring in West Africa.
In order to improve the prediction and the control of the propagation of the
virus, numerical simulations and optimal control of the two models for Ebola
are investigated. In particular, we study when the two models generate similar
results.
Dynamic fluctuations coincide with periods of high and low modularity in resting-state functional brain networks
Date: 2015-11-19 00:00:00
Tasks: Functional Connectivity

We investigate the relationship of resting-state fMRI functional connectivity
estimated over long periods of time with time-varying functional connectivity
estimated over shorter time intervals. We show that using Pearson's correlation
to estimate functional connectivity implies that the range of fluctuations of
functional connections over short time scales is subject to statistical
constraints imposed by their connectivity strength over longer scales. We
present a method for estimating time-varying functional connectivity that is
designed to mitigate this issue and allows us to identify episodes where
functional connections are unexpectedly strong or weak. We apply this method to
data recorded from $N=80$ participants, and show that the number of
unexpectedly strong/weak connections fluctuates over time, and that these
variations coincide with intermittent periods of high and low modularity in
time-varying functional connectivity. We also find that during periods of
relative quiescence regions associated with default mode network tend to join
communities with attentional, control, and primary sensory systems. In
contrast, during periods where many connections are unexpectedly strong/weak,
default mode regions dissociate and form distinct modules. Finally, we go on to
show that, while all functional connections can at times manifest stronger
(more positively correlated) or weaker (more negatively correlated) than
expected, a small number of connections, mostly within the visual and
somatomotor networks, do so a disproportional number of times. Our statistical
approach allows the detection of functional connections that fluctuate more or
less than expected based on their long-time averages and may be of use in
future studies characterizing the spatio-temporal patterns of time-varying
functional connectivity
Evolution of public cooperation in a monitored society with implicated punishment and within-group enforcement
Date: 2015-11-19 00:00:00

Monitoring with implicated punishment is common in human societies to avert
freeriding on common goods. But is it effective in promoting public
cooperation? We show that the introduction of monitoring and implicated
punishment is indeed effective, as it transforms the public goods game to a
coordination game, thus rendering cooperation viable in infinite and finite
well-mixed populations. We also show that the addition of within-group
enforcement further promotes the evolution of public cooperation. However,
although the group size in this context has nonlinear effects on collective
action, an intermediate group size is least conductive to cooperative
behaviour. This contradicts recent field observations, where an intermediate
group size was declared optimal with the conjecture that group-size effects and
within-group enforcement are responsible. Our theoretical research thus
clarifies key aspects of monitoring with implicated punishment in human
societies, and additionally, it reveals fundamental group-size effects that
facilitate prosocial collective action.
Fluctuations between high- and low-modularity topology in time-resolved functional connectivity
Date: 2017-08-22 00:00:00
Tasks: Attribute, Functional Connectivity

Modularity is an important topological attribute for functional brain
networks. Recent studies have reported that modularity of functional networks
varies not only across individuals being related to demographics and cognitive
performance, but also within individuals co-occurring with fluctuations in
network properties of functional connectivity, estimated over short time
intervals. However, characteristics of these time-resolved functional networks
during periods of high and low modularity have remained largely unexplored. In
this study we investigate spatiotemporal properties of time-resolved networks
in the high and low modularity periods during rest, with a particular focus on
their spatial connectivity patterns, temporal homogeneity and test-retest
reliability. We show that spatial connectivity patterns of time-resolved
networks in the high and low modularity periods are represented by increased
and decreased dissociation of the default mode network module from
task-positive network modules, respectively. We also find that the instances of
time-resolved functional connectivity sampled from within the high (low)
modularity period are relatively homogeneous (heterogeneous) over time,
indicating that during the low modularity period the default mode network
interacts with other networks in a variable manner. We confirmed that the
occurrence of the high and low modularity periods varies across individuals
with moderate inter-session test-retest reliability and that it is correlated
with previously-reported individual differences in the modularity of functional
connectivity estimated over longer timescales. Our findings illustrate how
time-resolved functional networks are spatiotemporally organized during periods
of high and low modularity, allowing one to trace individual differences in
long-timescale modularity to the variable occurrence of network configurations
at shorter timescales.
An ISA-Tab specification for protein titration data exchange
Date: 2016-02-15 00:00:00

Data curation presents a challenge to all scientific disciplines to ensure
public availability and reproducibility of experimental data. Standards for
data preservation and exchange are central to addressing this challenge: the
Investigation-Study-Assay Tabular (ISA-Tab) project has developed a widely used
template for such standards in biological research. This paper describes the
application of ISA-Tab to protein titration data. Despite the importance of
titration experiments for understanding protein structure, stability, and
function and for testing computational approaches to protein electrostatics, no
such mechanism currently exists for sharing and preserving biomolecular
titration data. We have adapted the ISA-Tab template to provide a structured
means of supporting experimental structural chemistry data with a particular
emphasis on the calculation and measurement of pKa values. This activity has
been performed as part of the broader pKa Cooperative effort, leveraging data
that has been collected and curated by the Cooperative members. In this
article, we present the details of this specification and its application to a
broad range of pKa and electrostatics data obtained for multiple protein
systems. The resulting curated data is publicly available at
http://pkacoop.org.
A simple framework for the axiomatization of exponential and quasi-hyperbolic discounting
Date: 2015-11-19 00:00:00

The main goal of this paper is to investigate which normative requirements,
or axioms, lead to exponential and quasi-hyperbolic forms of discounting.
Exponential discounting has a well-established axiomatic foundation originally
developed by Koopmans (1960, 1972) and Koopmans et al. (1964) with subsequent
contributions by several other authors, including Bleichrodt et al. (2008). The
papers by Hayashi (2003) and Olea and Strzalecki (2014) axiomatize
quasi-hyperbolic discounting. The main contribution of this paper is to provide
an alternative foundation for exponential and quasi-hyperbolic discounting,
with simple, transparent axioms and relatively straightforward proofs. Using
techniques by Fishburn (1982) and Harvey (1986), we show that Anscombe and
Aumann's (1963) version of Subjective Expected Utility theory can be readily
adapted to axiomatize the aforementioned types of discounting, in both finite
and infinite horizon settings.