ppxscal/embedding_network huggingface dataset:
Optimal placement and channel assignment of relay stations in heterogeneous wireless mesh networks by modified Bender's decomposition
Authors: Aaron So, Ben Liang
Venue: Ad Hoc Networks (2009)

Fixed Broadband Wireless Access (FBWA) technology is designed to serve as a wireless DSL replacement to provide broadband Internet access in underserved areas where no other access technology exists. Due to the enormousness of the target service area, relay equipment play an important role in such networks, and the installation and maintenance cost of the network is directly proportional to the cost of the relay equipment. To minimize the network operational cost, an optimization framework which computes the minimum number of relay stations and their corresponding placements and channel assignments in the network is desired. Because the problem is NP-hard, we propose an efficient optimization algorithm based on a modified version of Bender's decomposition to iteratively compute converging bounds to the problem solution. Our numerical results show that by using a few relay stations in a rural community, broadband Internet access can be established in a cost effective manner.
How to extract continuum materials properties for (lead-free) solders from tensile tests and nanoindentation experiments
Authors: W. H. M&#x00fc;ller, H. Worrack, J. Sterthaus, J. Villain, J. Wilden, A. Juritza
Venue: Microsystem Technologies (2008)

Fabrication of modern microelectronic components requires miscellaneous solder materials for joining. In order to guarantee the quality of the manufacturing process and the reliability of the resulting solder joint it is necessary to know the material properties of the joining parts and of the solder materials. In particular Young&#x2019;s modulus, yield stress, and the hardness are of great interest. Moreover, a complete stress-strain curve is important for a detailed material characterization and simulation of a component, e.g., by Finite Elements (FE). The miniaturization of modern electronic products with small solder joints allows only fabrication of very small-sized specimens. Because of this miniature tests are used for measuring the mechanical properties of the solders in the experimental investigations of this paper. More specifically two miniature tests are presented and discussed, a mini-uniaxial-tension-test and a nanoindenter experiment. In the tensile test the axial loading is prescribed, the corresponding extension of the specimen length is recorded, both of which determines the stress-strain- curve directly. The stress-strain curves are then mathematically analyzed by assuming a non-linear relationship between stress and strain of the Ramberg-Osgood type and fitting the corresponding parameters to the experimental data by means of an optimization routine. For a detailed analysis of very local mechanical properties nanoindentation is used, resulting primarily in load vs. indentation-depth data. According to the procedure of Pharr and Oliver this data can be used to obtain hardness and Young&#x2019;s modulus but not a complete stress-strain curve, at least not directly. In order to obtain such a stress-strain-curve, the nanoindentation experiment is combined with FE and the coefficients involved in the corresponding constitutive equation for stress and strain are obtained by means of the inverse method. Finally in this paper, the stress-strain curves from nanoindentation and tensile tests are compared for two materials, namely aluminum and steel and differences are explained in terms of the locality of the measured properties.
Segment-based multiple sequence alignment
Authors: Tobias Rausch, Anne-Katrin Emde, David Weese, Andreas Döring, Cedric Notredame, Knut Reinert
Venue: Bioinformatics (2008)

Motivation: Many multiple sequence alignment tools have been developed in the past, progressing either in speed or alignment accuracy. Given the importance and wide-spread use of alignment tools, progress in both categories is a contribution to the community and has driven research in the field so far. Results: We introduce a graph-based extension to the consistency-based, progressive alignment strategy. We apply the consistency notion to segments instead of single characters. The main problem we solve in this context is to define segments of the sequences in such a way that a graph-based alignment is possible. We implemented the algorithm using the SeqAn library and report results on amino acid and DNA sequences. The benefit of our approach is threefold: (1) sequences with conserved blocks can be rapidly aligned, (2) the implementation is conceptually easy, generic and fast and (3) the consistency idea can be extended to align multiple genomic sequences. Availability: The segment-based multiple sequence alignment tool can be downloaded from http://www.seqan.de/projects/msa.html. A novel version of T-Coffee interfaced with the tool is available from http://www.tcoffee.org. The usage of the tool is described in both documentations. Contact: rausch@inf.fu-berlin.de
A practical scalable distributed B-tree
Authors: Marcos K. Aguilera, Wojciech Golab, Mehul A. Shah
Venue: Proceedings of the VLDB Endowment (2008)

Internet applications increasingly rely on scalable data structures that must support high throughput and store huge amounts of data. These data structures can be hard to implement efficiently. Recent proposals have overcome this problem by giving up on generality and implementing specialized interfaces and functionality (e.g., Dynamo [4]). We present the design of a more general and flexible solution: a fault-tolerant and scalable distributed B-tree. In addition to the usual B-tree operations, our B-tree provides some important practical features: transactions for atomically executing several operations in one or more B-trees, online migration of B-tree nodes between servers for load-balancing, and dynamic addition and removal of servers for supporting incremental growth of the system. Our design is conceptually simple. Rather than using complex concurrency and locking protocols, we use distributed transactions to make changes to B-tree nodes. We show how to extend the B-tree and keep additional information so that these transactions execute quickly and efficiently. Our design relies on an underlying distributed data sharing service, Sinfonia [1], which provides fault tolerance and a light-weight distributed atomic primitive. We use this primitive to commit our transactions. We implemented our B-tree and show that it performs comparably to an existing open-source B-tree and that it scales to hundreds of machines. We believe that our approach is general and can be used to implement other distributed data structures easily.
Perceived improvements in nitrogen fertilizer efficiency from cotton precision farming
Authors: J. Colby Torbett, Roland K. Roberts, James A. Larson, Burton C. English
Venue: Computers and Electronics in Agriculture (2008)

Site-specific information technologies help cotton farmers make decisions to improve nitrogen (N) fertilizer efficiency. Various information technologies, as well as farm and farmer characteristics, could affect fertilizer decisions differently. Knowing these differences could assist the targeting of specific groups of farmers for the adoption of various site-specific information technologies to improve N fertilizer efficiency and reduce negative environmental impacts. Ordered logit analysis was used to identify the information technologies and farm and farmer characteristics that influence the importance farmers place on precision farming (PF) technologies in improving the efficiency of N fertilization of cotton (Gossypium hirsutum L.). Data were obtained from a 2001 mail survey of cotton farmers in six southeastern states in the United States of America. Results indicated that yield monitoring, management zone and grid soil sampling, and on-the-go sensing increased farmers' perceptions of the importance of PF in improving N fertilizer efficiency. Farmers who used geospatial mapping were more likely than other farmers to find PF unimportant. Older cotton farmers who rented a larger portion of the land they farmed were more likely to place greater importance on PF for improving N efficiency.
Partially ordered distributed computations on asynchronous point-to-point networks
Authors: Ricardo C. Corrêa, Valmir C. Barbosa
Venue: Parallel Computing (2009)

Asynchronous executions of a distributed algorithm differ from each other due to the nondeterminism in the order in which the messages exchanged are handled. In many situations of interest, the asynchronous executions induced by restricting nondeterminism are more efficient, in an application-specific sense, than the others. In this work, we define partially ordered executions of a distributed algorithm as the executions satisfying some restricted orders of their actions in two different frameworks, those of the so-called event- and pulse-driven computations. The aim of these restrictions is to characterize asynchronous executions that are likely to be more efficient for some important classes of applications. Also, an asynchronous algorithm that ensures the occurrence of partially ordered executions is given for each case. Two of the applications that we believe may benefit from the restricted nondeterminism are backtrack search, in the event-driven case, and iterative algorithms for systems of linear equations, in the pulse-driven case. We provide some experimental evidence in these two cases.
Optimization of an eMule-like modifier strategy
Authors: Luca Caviglione, Cristiano Cervellera, Franco Davoli, Filippo Aldo Grassia
Venue: Computer Communications (2008)

One of the main issues in peer-to-peer file-sharing services is to ensure balanced transfers of data among peers. For instance, the popular eMule file-sharing client interface implements techniques based on a credit system and time modifiers, in order to guarantee a fair degree of contribution/reward, e.g., to prevent leeching. However, fixed heuristic modifiers may not be able to guarantee a fair treatment for every peer participating in the service. This paper introduces an optimized strategy to compute modifiers in order to promote cooperation among peers, while guaranteeing a suitable degree of fairness. Simulations are provided to compare the proposed mechanism to the standard one adopted by the popular eMule client interface.
Analysis of segmental duplications via duplication distance
Authors: Crystal L. Kahn, Benjamin J. Raphael
Venue: Bioinformatics (2008)

Motivation: Segmental duplications are common in mammalian genomes, but their evolutionary origins remain mysterious. A major dif.culty in analyzing segmental duplications is that many duplications are complex mosaics of fragments of numerous other segmental duplications. Results: We introduce a novel measure called duplication distance that describes the minimum number of duplications necessary to create a target string by repeated insertions of fragments of a source string.We derive an ef.cient algorithm to compute duplication distance, and we use the algorithm to analyze segmental duplications in the human genome. Our analysis reveals possible ancestral relationships between segmental duplications including numerous examples of duplications that contain multiple, nested insertions of fragments from one or more other duplications. Using duplication distance, we also identify a small number of segmental duplications that appear to have seeded many other duplications in the genome, lending support to a two-step model of segmental duplication in the genome. Availability: Software for computing duplication distance is available upon request. Contact:clkahn@cs.brown.edu; braphael@cs.brown.edu.
Embodied conversational agents for voice-biometric interfaces
Authors: Álvaro Hernández-Trapote, Beatriz López-Mencía, David Díaz, Rubén Fernández-Pozo, Javier Caminero
Venue: Proceedings of the 10th international conference on Multimodal interfaces (2008)

In this article we present a research scheme which aims to analyze the use of Embodied Conversational Agent (ECA) technology to improve the robustness and acceptability of speaker enrolment and verification dialogues designed to provide secure access through natural and intuitive speaker recognition. In order to find out the possible effects of the visual information channel provided by the ECA, tests were carried out in which users were divided into two groups, each interacting with a different interface (metaphor): an ECA Metaphor group -with an ECA-, and a VOICE Metaphor group -without an ECA-. Our evaluation methodology is based on the ITU-T P.851 recommendation for spoken dialogue system evaluation, which we have complemented to cover particular aspects with regard to the two major extra elements we have incorporated: secure access and an ECA. Our results suggest that likeability-type factors and system capabilities are perceived more positively by the ECA metaphor users than by the VOICE metaphor users. However, the ECA's presence seems to intensify users' privacy concerns.
On efficiently searching trajectories and archival data for historical similarities
Authors: Reza Sherkat, Davood Rafiei
Venue: Proceedings of the VLDB Endowment (2008)

We study the problem of efficiently evaluating similarity queries on histories, where a history is a d-dimensional time series for d &ge; 1. While there are some solutions for time-series and spatio-temporal trajectories where typically d &le; 3, we are not aware of any work that examines the problem for larger values of d. In this paper, we address the problem in its general case and propose a class of summaries for histories with a few interesting properties. First, for commonly used distance functions such as the Lp-norm, LCSS, and DTW, the summaries can be used to efficiently prune some of the histories that cannot be in the answer set of the queries. Second, histories can be indexed based on their summaries, hence the qualifying candidates can be efficiently retrieved. To further reduce the number of unnecessary distance computations for false positives, we propose a finer level approximation of histories, and an algorithm to find an approximation with the least maximum distance estimation error. Experimental results confirm that the combination of our feature extraction approaches and the indexability of our summaries can improve upon existing methods and scales up for larger values of d and database sizes, based on our experiments on real and synthetic datasets of 17-dimensional histories.
Three-dimensional reconstruction of the Carrara Syncline (Apuane Alps, Italy): An approach to reconstruct and control a geological model using only field survey data
Authors: Andrea Tonini, Enrico Guastaldi, Marco Meccheri
Venue: Computers Geosciences (2009)

This paper presents an approach to reconstruct geological structures in three dimensions using and honouring field survey geological data. The methodology was developed to reconstruct the poly-deformed Carrara Syncline (Apuane Alps, Italy) in order to better understand the relationships regarding the structural geology of the area and the hydrogeological fluxes. In the first step, all the geological data (observed, measured and interpreted) of the study area were organized in a database using a geographical information system. The standard tools of a computer-aided design (CAD) environment were used to build geological profiles using the observed data (outcropping contact lines) extracted from the database, as well as, to create the contact surfaces via interpolation using non-uniformal rational B-spline surfaces. The intersection lines between each of these surfaces and the digital elevation model yield the model contact lines (MCLs). Discrepancies between the MCLs and the corresponding outcropping contact lines were analysed to further constrain the surfaces of the model. Starting from these surfaces, a voxel-based solid model was built, for storing and displaying each rock formation.
LAST: locality-aware sector translation for NAND flash memory-based storage systems
Authors: Sungjin Lee, Dongkun Shin, Young-Jin Kim, Jihong Kim
Venue: ACM SIGOPS Operating Systems Review (2008)

As flash memory technologies quickly improve, NAND flash memory-based storage devices are becoming a viable alternative as a secondary storage solution for general-purpose computing systems such as personal computers and enterprise server systems. Most existing flash translation layer (FTL) schemes are, however, ill-suited for such systems because they were optimized for storage write patterns of embedded systems only. In this paper, we propose a new flash management technique called LAST which is optimized for access characteristics of general-purpose computing systems. By exploiting the locality of storage access patterns, LAST reduces the garbage collection overhead significantly, thus increasing the I/O performance of flash-based storage devices. Our experimental results show that the proposed technique reduces the garbage collection overhead by 54% over the existing flash memory management techniques.
Analysis and Hardware Architecture Design of Global Motion Estimation
Authors: Yi-Hau Chen, Shao-Yi Chien, Ching-Yeh Chen, Yu-Wen Huang, Liang-Gee Chen
Venue: Journal of Signal Processing Systems (2008)

Global motion estimation and compensation (GME/GMC) is an important video processing technique and has been applied to many applications including video segmentation, sprite/mosaic generation, and video coding. In MPEG-4 Advanced Simple Profile (ASP), GME/GMC is adopted to compensate camera motions. Since GME is important, many GME algorithms have been proposed. These algorithms have two common characteristics, huge computation complexity and ultra large memory bandwidth. Hence for realtime applications, a hardware accelerator of GME is required. However, there are many hardware design challenges of GME like irregular memory access and huge memory bandwidth, and only few hardware architectures have been proposed. In this paper, we first analyzed three typical algorithms of GME, and a fast GME algorithm is proposed. By using temporal prediction and skipping the redundant computation, 91% memory bandwidth and 80% iterations are saved, while the performance is kept, compared to Gradient Descent in MPEG-4 Verification Model. Based on our proposed algorithm, a hardware architecture of GME is also presented. A new scheduling, Reference-Based Scheduling, is developed to solve the irregular memory access problem. An interleaved memory arrangement is applied to satisfy the memory access requirement of interpolation. The total gate count of hardware implementation is 131 K with Artisan 0.18 um cell library, and the internal memory size is about 7.9 Kb. Its processing ability is MPEG-4 ASP@L3, which is 352×288 with 30 fps, at 30 MHz.
ContentPlace: social-aware data dissemination in opportunistic networks
Authors: Chiara Boldrini, Marco Conti, Andrea Passarella
Venue: Proceedings of the 11th international symposium on Modeling, analysis and simulation of wireless and mobile systems (2008)

This paper deals with data dissemination in resource-constrained opportunistic networks, i.e., multi-hop ad hoc networks in which simultaneous paths between endpoints are not available, in general, for end-to-end communication. One of the main challenges is to make content available in those regions of the network where interested users are present, without overusing available resources (e.g., by avoiding flooding). These regions should be identified dynamically, only by exploiting local information exchanged by nodes upon encountering other peers. To this end, exploiting information about social users' behaviour turns out to be very efficient. In this paper we propose and evaluate ContentPlace, a system that exploits dynamically learnt information about users' social relationships to decide where to place data objects in order to optimise content availability. We define a number of social-oriented policies in the general ContentPlace framework, and compare them also with other reference policies proposed in the literature.
Knowledge Assessment Based on Evaluation of 3D Graphics Annotation in Lesson Context
Authors: Dorian Gorgan, Teodor Stefanut, Madalina Veres, Istvan Gabos
Venue: Proceedings of the 4th Symposium of the Workgroup Human-Computer Interaction and Usability Engineering of the Austrian Computer Society on HCI and Usability for Education and Work (2008)

Instead of classical user interfaces based on forms, the graphics annotation proposes another type of user interaction providing support for free expressions, creativity, manual ability, and artistic imagination. Moreover the graphics annotation directly on the surface of 3D eLearning objects requires the development of new graphics algorithms, annotation models, and interaction techniques. This paper reports the experiments developed through the eTrace eLearning Environment concerning with possibility of using the 3D graphics annotation in the context of eLearning lessons. The research addresses a few subjects such as the appropriate model of the 3D graphics annotation that support the automatic evaluation, lesson context based annotation model and processing, interaction techniques for annotation description, drawing and visualization. The work concerns with practical solutions for all the steps through which the teacher defines the annotation related constraints, the system records the annotation specifications within the lesson structure, the user carries out the graphics annotation based answer, the system processes the annotation, quantifies the answer and computes the final mark. This paper highlights mainly the first step of the 3D graphics annotation model description. The research opens new opportunities for graphics annotation based knowledge assessment in eLearning applications against the well known and limited multiple choice questions.
Robot task planning using semantic maps
Authors: Cipriano Galindo, Juan-Antonio Fernández-Madrigal, Javier González, Alessandro Saffiotti
Venue: Robotics and Autonomous Systems (2008)

Task planning for mobile robots usually relies solely on spatial information and on shallow domain knowledge, such as labels attached to objects and places. Although spatial information is necessary for performing basic robot operations (navigation and localization), the use of deeper domain knowledge is pivotal to endow a robot with higher degrees of autonomy and intelligence. In this paper, we focus on semantic knowledge, and show how this type of knowledge can be profitably used for robot task planning. We start by defining a specific type of semantic maps, which integrates hierarchical spatial information and semantic knowledge. We then proceed to describe how these semantic maps can improve task planning in two ways: extending the capabilities of the planner by reasoning about semantic information, and improving the planning efficiency in large domains. We show several experiments that demonstrate the effectiveness of our solutions in a domain involving robot navigation in a domestic environment.