bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acoustic wave propagation and permeability in sandstones with systems of aligned cracks
Authors: King M. S. , Shakeel A. , Chaudhry N. A. 
Published: September 2007

Abstract

A polyaxial (true triaxial) stress-loading system has been developed for testing cubic specimens of rock, with the capability of varying each of the principal stresses independently. Facilities are incorporated for measuring all nine components of P and polarized S-wave velocities and attenuation in the principal directions, and for fluid permeability in the 1-direction. Tests have been performed on specimens of five sandstones, in which systems of aligned cracks have been introduced by increasing
σ
1
and
σ
2
together to near failure, while maintaining
σ
3
constant at some low level. Results indicate that there are excellent correlations between permeability in the plane of the aligned cracks as they are closed under hydrostatic stress and both velocities and attenuation of (1) P and S waves propagating in a direction normal to the plane of the cracks, and (2) S waves propagating in the plane of the cracks and polarized normal to the plane.
A simple but powerful model for simulating elastic wave velocities in clastic Silicate rocks
Authors: Xu Shiyu , Doorenbos Just , Raikes Sue , White Roy 
Published: September 2007

Abstract
We describe a practical velocity model for clastic silicate rocks developed from the Kuster and Toksöz, differential effective medium and Gassmann theories. The model divides the total pore space into two parts, one associated with sand grains and the other associated with clays (including bound water). The difference in pore geometry makes the clay fraction more compliant with increasing porosity than the sand fraction. The model accurately simulates the combined effect of lithology, porosity, clay content, water saturation and fluid type on laboratory and logging P- and S-wave velocities. Velocity dispersion is modelled by considering the relaxed and unrelaxed extremes of fluid flow. Of three possible schemes for predicting S-wave logs from other logs, prediction from the P-wave sonic and porosity logs is generally the most accurate; comparisons of blind test predictions and S-wave logs at two Norwegian North Sea wells demonstrate the accuracy and robustness of the method. The predictions were further improved once geological information was provided on the formations encountered in the well. Examples of application to the prediction of velocity dispersion and dry frame moduli, the detection of hydrocarbons from crossplotting the P-wave and S-wave sonic velocities, and sonic log editing confirm the flexibility, accuracy and reliability of the model. The model has proved invaluable in constructing accurate models of the seismic reflection response in the vicinity of wells.
Petrophysical estimation from downhole Mineralogy logs
Authors: Harvey P. K. , Lovell M. A. , Lofts J. C. , Pezard P. A. , Bristow J. F. 
Published: September 2007

Abstract
A number of physical and chemical properties of rocks, many of which are important in petrophysics are simple, usually linear functions, of a rock’s mineralogy. Examples include matrix density, porosity, magnetic susceptibility and cation exchange capacity. Mineralogy logs can be obtained directly from geochemical logs through an inversion process and, in turn, estimates of petrophysical properties such as those noted above can be obtained. The accuracy of such estimates is directly dependent on the quality of both the inversion and the geochemical measurements. Examples from producing oil fields and from deep-sea environments are used to show that accurate estimates of derived parameters can be obtained provided that appropriate inversion procedures are adopted, and that these estimates are generally better than those obtained by conventional log analysis. Logs of some parameters, such as cation exchange capacity, cannot be obtained except through the mineral inversion.
Fractal Geometry, porosity and complex resistivity: from rough pore interfaces to hand specimens
Authors: Da Rocha Brígida Ramati P. , Habashy Tarek M. 
Published: September 2007

Abstract
We propose a new model to interpret the electrical behavior of rocks containing metallic or clay particles. This new model encompasses some of the other commonly used models as special cases.

This model is a generalization of two models, one developed by Dias (Journal of Geophysical Research 77, 4945–4956, 1972) and another by Pelton
et al.
(
Geophysics
Geophysics
, 589–609, 1978). Its circuit analog includes an impedance
K
(
iω
)
−η
which simulates the effects of the fractal rough pore interfaces between the conductive grains (metallic or clay minerals which are blocking the pore paths) and the electrolyte. This generalized Warburg impedance is in series with the resistance of the blocking grains and both are shunted by the double layer capacitance. This combination is in series with the resistance of the electrolyte in the blocked pore passages. The unblocked pore paths are represented by a resistance which corresponds to the normal DC resistivity of the rock. The parallel combination of this resistance with the ‘bulk’ sample capacitance is finally connected in parallel to the rest of the above-mentioned circuit.

The model was tested over a wide range of frequencies against experimental data obtained for amplitude and phase of resistivity or conductivity as well as for the complex dielectric constant. The samples studied are those of sedimentary, metamorphic and igneous rocks.
Feature recognition and the interpretation of images acquired from horizontal wellbores
Authors: Lofts J. C. , Bedford J. , Boulton H. , van Doorn J. A. , Jeffreys P. 
Published: September 2007

Abstract
The acquisition of borehole resistivity and acoustic images has become increasingly common in horizontal wells drilled for hydrocarbons. The appearance, and later interpretation of these images is somewhat different to that of conventional vertical wellbore images. Shallow-dipping bedding planes appear as long drawn-out sinusoids in unrolled workstation images whilst sub-vertical fractures appear as low-amplitude sinusoids, the opposite to what geologists are used to in vertical wells. Due to the sub-parallel orientation of the wellbore with respect to the bedding, such intersections will produce unusual features that can be misleading and difficult to interpret. The mechanics of drilling, and of acquiring image data in a horizontal plane also leads to the creation of certain artefacts or noise in images which must be identified correctly. The most common sedimentary and tectonic features imaged in horizontal wellbores are described and discussed here as a reference for geoscientists.
Approximation via cost sharing
Authors: Gupta Anupam , Kumar Amit , P´al Martin , Roughgarden Tim 
Published: September 2007

We present constant-factor approximation algorithms for several widely-studied NP-hard optimization problems in network design, including the multicommodity rent-or-buy, virtual private network design, and single-sink buy-at-bulk problems. Our algorithms are simple and their approximation ratios improve over those previously known, in some cases by orders of magnitude.
We develop a general analysis framework to bound the approximation ratios of our algorithms. This framework is based on a novel connection between random sampling and game-theoretic cost sharing.
Efficient power modeling and software thermal sensing for runtime temperature monitoring
Authors: Wu Wei , Jin Lingling , Yang Jun , Liu Pu , Tan Sheldon X.-D. 
Published: September 2007

The evolution of microprocessors has been hindered by increasing power consumption and heat dissipation on die. An excessive amount of heat creates reliability problems, reduces the lifetime of a processor, and elevates the cost of cooling and packaging considerably. It is therefore imperative to be able to monitor the temperature variations across the die in a timely and accurate manner.
Most current techniques rely on on-chip thermal sensors to report the temperature of the processor. Unfortunately, significant variation in chip temperature both spatially and temporally exposes the limitation of the sensors. We present a compensating approach to tracking chip temperature through an OS resident software module that generates live power and thermal profiles of the processor. We developed such a software thermal sensor (STS) in a Linux system with a Pentium 4 Northwood core. We employed highly efficient numerical methods in our model to minimize the overhead of temperature calculation. We also developed an efficient algorithm for functional unit power modeling. Our power and thermal models are calibrated and validated against on-chip sensor readings, thermal images of the Northwood heat spreader, and the thermometer measurements on the package. The resulting STS offers detailed power and temperature breakdowns of each functional unit at runtime, enabling more efficient online power and thermal monitoring and management at a higher level, such as the operating system.
Managing energy-performance tradeoffs for multithreaded applications on multiprocessor architectures
Authors: Park Soyeon , Jiang Weihang , Zhou Yuanyuan , Adve Sarita 
Published: September 2007

In modern computers, non-performance metrics such as energy consumption have become increasingly important, requiring tradeoff with performance. A recent work has proposed performance-guaranteed energy management, but it is designed specifically for sequential applications and cannot be used to a large class of multithreaded applications running on high end computers and data servers.
To address the above problem, this paper makes the first attempt to provide performance-guaranteed energy management for multithreaded applications on multiprocessor architectures. We first conduct a comprehensive study on the effects of energy adaptation on thread synchronizations and show that a multithreaded application suffers from not only local slowdowns due to energy adaptation, but also significant slowdowns propagated from other threads because of synchronization. Based on these findings, we design three Synchronization-Aware (SA) algorithms, LWT (Lock Waiting Time-based), CSL (Critical Section Length-based) and ODP (Operation Delay Propagation-based) algorithms, to estimate the energy adaptation-induced slowdowns on each thread. The local slowdowns are then combined across multiple threads via three aggregation methods (MAX, AVG and SUM) to estimate the overall application slowdown.
We evaluate our methods using a large multithreaded commercial application, IBM DB2 with industrial-strength online transaction processing (OLTP) workloads, and six SPLASH parallel scientific applications. Our experimental results show that LWT combined with the MAX aggregation method not only controls the performance slow down within the specified limits but also conserves the most energy.
Highly interactive online study skills course
Authors: Halstensen Maths , Haug Frode 
Published: September 2007

This poster describes the most important aspects concerning design and development of an highly interactive web based study skills course called
"Unstuck"
which is a work in progress to be finished June 2008.
"Unstuck"
is a project started by both teachers and students from Gjøvik University College and Telemark University College in Norway.

This project started in 2006 as a result of experience from more than 10 years of teaching students with insufficient study skills. In this course we aim to present the theory and practice of "How to study" in an exiting interactive multimedia environment.
Telemark University College has since 2002 educated students starting with only a certificate of completed apprenticeship. In 2007, approximately 70% of all the students studying electrical engineering have this type of background, and insufficient study skills are a challenge.

"Unstuck"
will be used by students in secondary High school and University Colleges in Telemark, and Gjøvik in Norway from August 2008.

What makes Unstuck different from other study skills courses? The content of Unstuck is similar to other courses; the difference is the way the content is presented for the students. Unstuck will contain intensive use of interaction with the student, which involves various active actions such as pressing buttons, placing objects to specific locations on the screen, marking key words etc. Videos are used to demonstrate how to study in practice and to illustrate class room and other study related situations.

At the end of the course the student will have a short test (quiz). If the student don't pass, it is possible to immediately repeat relevant sections, and subsequently repeat the test.
"Unstuck"
will be an easy to use interactive multimedia study skills course on the weB.
An account of the use of synoptic assessment for students in the area of databases at level 2
Authors: Gorra Andrea , Lazarevski Sanela , Campbell Jackie 
Published: September 2007

The purpose of this poster is to share innovative teaching methods at Leeds Metropolitan University in the Innovation North Faculty of Information and Technology (INN Faculty). An explorative study has been undertaken to provide an initial evaluation of the use of synoptic assessments within the subject area of Computing.
Synoptic assessments, also known as integrated assessments, help to enable students to make connections between modules, to increase the level of student engagement and to provide teaching staff with the opportunity to adopt a holistic approach to delivering modules. This type of assessment pulls together independent assessments from a number of modules into a single assessment exercise.
Synoptic assessment is driven by providing an environment for synoptic learning via a supporting course structure. For this reason, the course structures of the Innovation North Faculty are described for all three undergraduate levels. See Table 1 for an example of the course structure for Level 2.
A series of semi-structured interviews were conducted to learn about staff and students' perspectives on integrated assessments and their views of the learning environment in general. Twenty computing students were approached to talk about their experience with and opinions of integrated assessments. In addition to the student interviews, ten members of academic teaching staff were interviewed.
The findings are the result of an exploratory study and should be taken as indicative. The use of synoptic assessments within the INN Faculty is currently evaluated in depth as part of the CETL ALiC project [1, 2] and results will be published in the near future. The analysis of the interviews indicates that students perceive the delivery pattern of block teaching and pairing of modules as beneficial. The main reason for this is that it enables students to concentrate on two subject areas at a time in comparison to the traditional semester structure of four modules. Potential areas for concern are the nature of modules that are paired and a fair marking scheme. Teaching staff feel that the synoptic assessment enabled by a case study has worked well for the students. However, issues with timetabling need to be considered, and dependencies between the paired modules need to be avoided.
'But i don't read text printed in braille font'...
Authors: Dickinson Anne 
Published: September 2007

The author works in Coventry University and has been engaged in tutoring a student with disabilities who had enrolled for a degree in Business and IT at Coventry University. To do this, the author drew upon previous experiences in the Further Education (FE) sector at a College in the Midlands, where she taught Information Technology (IT) to diverse groups of students who had varied abilities. The ages of the FE students ranged from pre-16, visiting the College from a local special school to attend "taster" sessions, to adults, some of whom were seniors, attending a day centre for disabled adults that had a special arrangement for College tutors to give classes.
The degree student was a white cane user, read Braille and navigated the computer with screen reader software. During her time at University, she took on an ambassadorial role: she gave guided tours to prospective students around the University campus during open days! From time to time she would recount stories that she described as amusing but which clearly showed ignorance on the part of her tutors. The title of this presentation is taken from one of her anecdotes.
The Degree course in Business and IT had several workshops in Computing including statistics where spreadsheets and specialist software were used. The author was asked to tutor the student for the IT workshops of a year-long module. This included translating the instructional handouts from mouse-based to keyboard-based, being aware of potential problems with specialist software and the quirks of the online learning system (WebCT) [1] and finding ways of working around them all. This poster shows some of the issues related to the student's stories, the creating and translating of instructions for keyboard use and navigating the keyboard using JAWS.
Comparing the performance of web server architectures
Authors: Pariag David , Brecht Tim , Harji Ashif , Buhr Peter , Shukla Amol , Cheriton David R. 
Published: September 2007

In this paper, we extensively tune and then compare the performance of web servers based on three different server architectures. The μserver utilizes an event-driven architecture, Knot uses the highly-efficient Capriccio thread library to implement a thread-per-connection model, and WatPipe uses a hybrid of events and threads to implement a pipeline-based server that is similar in spirit to a staged event-driven architecture (SEDA) server like Haboob.
We describe modifications made to the Capriccio thread library to use Linux's zero-copy sendfile interface. We then introduce the SY mmetric Multi-Processor Event Driven (SYMPED) architecture in which relatively minor modifications are made to a single process event-driven (SPED) server (the μserver) to allow it to continue processing requests in the presence of blocking due to disk accesses. Finally, we describe our C++ implementation of WatPipe, which although utilizing a pipeline-based architecture, excludes the dynamic controls over event queues and thread pools used in SEDA. When comparing the performance of these three server architectures on the workload used in our study, we arrive at different conclusions than previous studies. In spite of recent improvements to threading libraries and our further improvements to Capriccio and Knot, both the event-based μserver and pipeline-based Wat-Pipe server provide better throughput (by about 18%). We also observe that when using blocking sockets to send data to clients, the performance obtained with some architectures is quite good and in one case is noticeably better than when using non-blocking sockets.
Ginger
Authors: Hilton Andrew D. , Roth Amir 
Published: September 2007

The negative performance impact of branch mis-predictions can be reduced by exploiting control independence (CI). When a branch mis-predicts, the wrong-path instructions up to the point where control converges with the correct path are selectively squashed and replaced with correct-path instructions. Instructions beyond the convergence-point-the branch's control-independent (CI) instructions-are spared from squashing. Exploiting CI requires updating the input data dependences of CI instructions to reflect the selective removal and insertion of logically older instructions and transitively re-dispatching those CI instructions whose inputs have changed. This capability is generally called out-of-order renaming. Previously proposed CI designs use out-of-order renaming schemes that either consume excessive rename/dispatch bandwidth, can only be applied in limited cases, or incur a cost even when the branch would be correctly predicted.
Ginger is a CI design that is both general and bandwidth efficient. Ginger implements out-of-order renaming using tag rewriting, re-linking the input dependences of CI instructions as they sit in the window. To do this, Ginger halts the pipeline uses the idle map table read and write ports and the issue queue match lines and write lines to perform a register-tag "search-and-replace" operation. After a few cycles, the pipeline restarts and execution resumes with correct data dependences. Cycle-level simulation shows that Ginger out-performs previous CI designs, yielding geometric mean speedups over an aggressive non-CI processor of 5%, 12%, and 11%-on SPECint2000, MediaBench, and Comm-Bench-with speedups of 15% or greater on 11 of 46 programs.
External memory page remapping for embedded multimedia systems
Authors: Ning Ke , Kaeli David 
Published: September 2007

As memory speeds and bus capacitances continue to rise, external memory bus power will make up an increasing portion of the total system power budget for system-on-a-chip embedded systems. Both hardware and software approaches can be explored to balance the power/performance tradeoff associated with the external memory.
In this paper we present a hardware-based, programmable external memory page remapping mechanism which can significantly improve performance and decrease the power budget due to external memory bus accesses. Our approach was developed by studying common data access patterns present in embedded multimedia applications. In the paper, we evaluate a mechanism that can perform page remapping of external memory. We also develop an efficient algorithm to map application data and instruction memory into external memory pages. We employ graph-coloring techniques to guide the page mapping procedure. The objective is to avoid page misses by remapping conflicting pages to different memory banks (i.e., by assigning them different colors). Our algorithm can significantly reduce the memory page miss rate by 70-80% on average. For a 4-bank SDRAM memory system, we reduced external memory access time by 12.6%. The proposed algorithm can reduce power consumption in majority of the benchmarks, averaged by 13.2% of power reduction. Combining the effects of both power and delay, our algorithm can benefit significantly to the total energy cost.
Scratchpad allocation for data aggregates in superperfect graphs
Authors: Li Lian , Nguyen Quan Hoang , Xue Jingling 
Published: September 2007

Existing methods place data or code in scratchpad memory, i.e., SPM by either relying on heuristics or resorting to integer programming or mapping it to a graph coloring problem.
In this work, the SPM allocation problem is formulated as an interval coloring problem. The key observation is that in many embedded applications, arrays (including structs as a special case) are often related in the following way: For any two arrays, their live ranges are often such that one is either disjoint from or contains the other. As a result, array interference graphs are often superperfect graphs and optimal interval colorings for such array interference graphs are possible. This has led to the development of two new SPM allocation algorithms. While differing in whether live range splits and spills are done sequentially or together, both algorithms place arrays in SPM based on examining the cliques in an interference graph. In both cases, we guarantee optimally that all arrays in an interference graph can be placed in SPM if its size is no smaller than the clique number of the graph. In the case that the SPM is not large enough, we rely on heuristics to split or spill a live range until the graph is colorable. Our experiment results using embedded benchmarks show that our algorithms can outperform graph coloring when their interference graphs are superperfect or nearly so although graph coloring is admittedly more general and may also be effective to applications with arbitrary interference graphs.