Coverage Metrics Research Articles

SNPitty: An Intuitive Web Application for Interactive B-Allele Frequency and Copy Number Visualization of Next-Generation Sequencing Data

Exploration and visualization of next-generation sequencing data are crucial for clinical diagnostics. Software allowing simultaneous visualization of multiple regions of interest coupled with dynamic heuristic filtering of genetic aberrations is, however, lacking. Therefore, the authors developed the web application SNPitty that allows interactive visualization and interrogation of variant call format files by using B-allele frequencies of single-nucleotide polymorphisms and single-nucleotide variants, coverage metrics, and copy numbers analysis results. SNPitty displays variant alleles and allelic imbalances with a focus on loss of heterozygosity and copy number variation using genome-wide heterozygous markers and somatic mutations. In addition, SNPitty is capable of generating predefined reports that summarize and highlight disease-specific targets of interest. SNPitty was validated for diagnostic interpretation of somatic events by showcasing a serial dilution series of glioma tissue. Additionally, SNPitty is demonstrated in four cancer-related scenarios encountered in daily clinical practice and on whole-exome sequencing data of peripheral blood from a Down syndrome patient. SNPitty allows detection of loss of heterozygosity, chromosomal and gene amplifications, homozygous or heterozygous deletions, somatic mutations, or any combination thereof in regions or genes of interest. Furthermore, SNPitty can be used to distinguish molecular relationships between multiple tumors from a single patient. On the basis of these data, the authors demonstrate that SNPitty is robust and user friendly in a wide range of diagnostic scenarios.

Temporal Coverage Analysis for Dynamic Verification

Dynamic verification is widely used to ensure the logical correctness of system design. Verification progress is usually gauged by coverage metrics. Most coverage metrics measure the sub-structures of design under verification that are exercised. More importantly, the probability of a bug being detected is approximated by probabilistic coverage analysis. However, existing analysis methods do not consider the temporal nature of digital systems, i.e., it only applies to combinational circuit but not sequential circuit. In this brief, we propose a probabilistic analysis framework which takes into account the temporal behavior of system design. We propose an effective analysis algorithm which can estimate the probability of a bug being detected for sequential circuit. Experimental results on 17489 random instances show that our method is both efficient and accurate. The analysis has time complexity quadratic to the number of coverage bins and linear to the number of simulation cycles. The analysis result has an average relative error of about 7.38%. In practice, our analysis result can be used to measure the completeness of verification.

Understanding and measuring uptake and coverage of oral pre-exposure prophylaxis delivery among adolescent girls and young women in sub-Saharan Africa.

In response to World Health Organization (WHO) guidance recommending oral pre-exposure prophylaxis (PrEP) for all individuals at substantial risk for HIV infection, significant investments are being made to expand access to oral PrEP globally, particularly in sub-Saharan Africa. Some have interpreted early monitoring reports from new programs delivering oral PrEP to adolescent girls and young women (AGYW) as suggestive of low uptake. However, a lack of common definitions complicates interpretation of oral PrEP uptake and coverage measures, because various indicators with different meanings and uses are used interchangeably. Furthermore, operationalising these measures in real-world settings is challenged by the difficulties in defining the denominator for measuring uptake and coverage among AGYW, due to the lack of data and experience required to identify the subset of AGYW at substantial risk of HIV infection. This paper proposes an intervention-centric cascade as a framework for developing a common lexicon of metrics for uptake and coverage of oral PrEP among AGYW. In codifying these indicators, approaches to clearly define metrics for uptake and coverage are outlined, and the discussion on ‘low’ uptake is reframed to focus on achieving the highest possible proportion of AGYW using oral PrEP when they need and want it Recommendations are also provided for making increased investments in implementation research to better quantify the sub-group of AGYW in potential need of oral PrEP.and for improving monitoring systems to more efficiently address bottlenecks in the service delivery of oral PrEP to AGYW so that implementation can be taken to scale.

Stereotactic radiosurgery for multiple brain metastases: Results of multicenter benchmark planning studies

PurposeStereotactic radiosurgery is indicated for treatment of multiple brain metastases. Various treatment platforms are available, but most comparisons are limited to single-center studies. As part of a national commissioning program, benchmark planning cases were completed by 21 clinical centers, providing a unique dataset of current practice across a large number of providers and equipment platforms. Methods and materialsTwo brain metastases cases were provided, with images and structures predrawn, involving 3 and 7 lesions. Centers produced plans according to their local practice, which were reviewed centrally using metrics for target coverage, selectivity, gradient fall-off, and normal tissue sparing. ResultsFifty plans were submitted, using 24 treatment platforms. Eleven plans were revised following feedback, including 2 centers that acquired a new platform; 1 other center accepted a restriction of service. All centers prioritized coverage, with the prescription isodose covering ≥95% of 233 of 235 target volumes. Selectivity was much more variable, especially for smaller lesions, and when combined with poor gradient indices resulted in large volumes of normal tissue being irradiated. Tomotherapy submissions were outliers for either selectivity or gradient index, but other platforms could produce plans with relatively low gradient indices for larger lesion volumes. There was more variation among Varian and Elekta LINAC plans than for Gamma Knife and CyberKnife, and larger differences for smaller targets, both inter- and intratreatment platform. Doses to normal brain and brainstem were highest when margins were applied, but improvements were possible by replanning alone. ConclusionsMulticenter benchmarking exercises have highlighted some variation in clinical practice and priorities, with a few outliers. Most platforms are able to achieve comparable plans, except for the smallest volumes and when larger planning margins are used. The data will be used to advance standardization and quality improvement of national services and can provide useful guidance for centers worldwide.

Agile deployment and code coverage testing metrics of the boot software on-board Solar Orbiter's Energetic Particle Detector

In this day and age, successful embedded critical software needs agile and continuous development and testing procedures. This paper presents the overall testing and code coverage metrics obtained during the unit testing procedure carried out to verify the correctness of the boot software that will run in the Instrument Control Unit (ICU) of the Energetic Particle Detector (EPD) on-board Solar Orbiter. The ICU boot software is a critical part of the project so its verification should be addressed at an early development stage, so any test case missed in this process may affect the quality of the overall on-board software. According to the European Cooperation for Space Standardization ESA standards, testing this kind of critical software must cover 100% of the source code statement and decision paths. This leads to the complete testing of fault tolerance and recovery mechanisms that have to resolve every possible memory corruption or communication error brought about by the space environment. The introduced procedure enables fault injection from the beginning of the development process and enables to fulfill the exigent code coverage demands on the boot software.

Direction modulated brachytherapy (DMBT) for treatment of cervical cancer: A planning study with 192 Ir, 60 Co, and 169 Yb HDR sources.

To evaluate plan quality of a novel MRI-compatible direction modulated brachytherapy (DMBT) tandem applicator using 192 Ir, 60 Co, and 169 Yb HDR brachytherapy sources, for various cervical cancer high-risk clinical target volumes (CTVHR ). The novel DMBT tandem applicator has six peripheral grooves of 1.3-mm diameter along a 5.4-mm thick nonmagnetic tungsten alloy rod. Monte Carlo (MC) simulations were used to benchmark the dosimetric parameters of the 192 Ir, 60 Co, and 169 Yb HDR sources in a water phantom against the literature data. 45 clinical cases that were treated using conventional tandem-and-ring applicators with 192 Ir source (192 Ir-T&R) were selected consecutively from intErnational MRI-guided BRAchytherapy in CErvical cancer (EMBRACE) trial. Then, for each clinical case, 3D dose distribution of each source inside the DMBT and conventional applicators were calculated and imported onto an in-house developed inverse planning optimization code to generate optimal plans. All plans generated by the DMBT tandem-and-ring (DMBT T&R) from all three sources were compared to the respective 192 Ir-T&R plans. For consistency, all plans were normalized to the same CTVHR D90 achieved in clinical plans. The D2cm3 for organs at risk (OAR) such as bladder, rectum, and sigmoid, and D90, D98, D10, V100, and V200 for CTVHR were calculated. In general, plan quality significantly improved when a conventional tandem (Con.T) is replaced with the DMBT tandem. The target coverage metrics were similar across 192 Ir-T&R and DMBT T&R plans with all three sources (P>0.093). 60 Co-DMBT T&R generated greater hot spots and less dose homogeneity in the target volumes compared with the 192 Ir- and 169 Yb-DMBT T&R plans. Mean OAR doses in the DMBT T&R plans were significantly smaller (P<0.0084) than the 192 Ir-T&R plans. Mean bladder D2cm3 was reduced by 4.07%, 4.15%, and 5.13%, for the 192 Ir-, 60 Co-, and 169 Yb-DMBT T&R plans respectively. Mean rectum (sigmoid) D2cm3 was reduced by 3.17% (3.63%), 2.57% (3.96%), and 4.65% (4.34%) for the 192 Ir-, 60 Co-, and 169 Yb-DMBT T&R plans respectively. The DMBT T&R plans with the 169 Yb source generally resulted in the greatest OAR sparing when the CTVHR were larger and irregular in shape, while for smaller and regularly shaped CTVHR (<30cm3 ), OAR sparing between the sources were comparable. The DMBT tandem provides a promising alternative to the Con.T design with significant improvement in the plan quality for various target volumes. The DMBT T&R plans generated with the three sources of varying energies generated superior plans compared to the conventional T&R applicators. Plans generated with the 169 Yb-DMBT T&R produced best results for larger and irregularly shaped CTVHR in terms of OAR sparing. Thus, this study suggests that the combination of the DMBT tandem applicator with varying energy sources can work synergistically to generate improved plans for cervical cancer brachytherapy.

Non-Autonomous Coverage Control With Diffusive Evolving Density

We consider nonuniform coverage optimization with respect to a non-autonomous coverage metric by spatially deploying a platoon of mobile agents in a planar region. Conventional coverage metrics usually encode a density field that weights points in the workspace. We consider a time-varying diffusive density that evolves according to a conservation law, and the induced time-varying coverage. Boundary conditions can model a time-varying flux across the boundary, and/or a time varying boundary density. We propose a decentralized state-feedback control law that maximizes the generalized non-autonomous coverage metric. The current approach of nonuniform deployment of autonomous agents applies to environmental monitoring and intervention, with deployment of mobile sensors in areas affected by penetration of substances governed by diffusion mechanisms, as for example oil in a marine environment, that pose immediate or long-term threats. We establish asymptotic convergence results illustrated by simulations.

Technical Note: Using k-means clustering to determine the number and position of isocenters in MLC-based multiple target intracranial radiosurgery.

PurposeTo present the k‐means clustering algorithm as a tool to address treatment planning considerations characteristic of stereotactic radiosurgery using a single isocenter for multiple targets.MethodsFor 30 patients treated with stereotactic radiosurgery for multiple brain metastases, the geometric centroids and radii of each met were determined from the treatment planning system. In‐house software used this as well as weighted and unweighted versions of the k‐means clustering algorithm to group the targets to be treated with a single isocenter, and to position each isocenter. The algorithm results were evaluated using within‐cluster sum of squares as well as a minimum target coverage metric that considered the effect of target size. Both versions of the algorithm were applied to an example patient to demonstrate the prospective determination of the appropriate number and location of isocenters.ResultsBoth weighted and unweighted versions of the k‐means algorithm were applied successfully to determine the number and position of isocenters. Comparing the two, both the within‐cluster sum of squares metric and the minimum target coverage metric resulting from the unweighted version were less than those from the weighted version. The average magnitudes of the differences were small (−0.2 cm2 and 0.1% for the within cluster sum of squares and minimum target coverage, respectively) but statistically significant (Wilcoxon signed‐rank test, P < 0.01).ConclusionsThe differences between the versions of the k‐means clustering algorithm represented an advantage of the unweighted version for the within‐cluster sum of squares metric, and an advantage of the weighted version for the minimum target coverage metric. While additional treatment planning considerations have a large influence on the final treatment plan quality, both versions of the k‐means algorithm provide automatic, consistent, quantitative, and objective solutions to the tasks associated with SRS treatment planning using a single isocenter for multiple targets.

Abstract 5352: Optimization of library and enrichment procedures for RNASeq using RNA from formalin fixed paraffin embedded tissue

Abstract Large repositories of diagnostic formalin-fixed, paraffin-embedded (FFPE) tissue remain underutilized for transcriptome sequence analysis due to degradation of the RNA from the fixation process, which makes the samples unsuitable for traditional mRNA sequencing (mRNASeq). The use of random primers to generate cDNA, and biotinylated exon baits to enrich for coding regions allows for the generation of RNASeq data, but still yields data of variable quality, in part due to differences in FFPE sample processing. We performed a systematic analysis to determine which aspects of library construction and the enrichment process can be optimized to provide the best RNASeq data from FFPE samples. The TruSeq RNA Access Library Prep Kit (Illumina) protocol was selected to evaluate optimization procedures for RNASeq from FFPE material. RNA was isolated from FFPE tissue using the Maxwell automated system (Promega). RNA libraries were also prepared with RNA extracted from frozen tissue of the matching samples using the TruSeq V2 mRNASeq Library Prep Kit (Illumina) for a comparison of exon coverage metrics. Samples derived from different types of pediatric cancer were selected for evaluation, including 2 low-grade gliomas, 2 ependymomas, 9 melanomas and 1 Ewing sarcoma. All of the FF tumor samples selected contained oncogenic gene fusions, previously identified by analysis of mRNASeq data. The parameters investigated included the initial amount of RNA input (10ng-400ng), library amplification PCR cycle number (9 cycles-15 cycles), and the duration of time for exon probe hybridization (1.5 hours vs 16 hours). The quality of the data was based on the overall library complexity and exon coverage. The complexity of the sequencing was measured using duplication rate (DupRate) defined as a library inserts from different sequence reads mapping to the same location in the reference genome; while the coverage was measured using the percentage of coding bases with coverage &amp;gt;=20x (PCB20x). Using the RNA Access protocol, we found that the PCB20x metrics were comparable between the FFPE samples and matched FF mRNASeq controls under the non-optimized conditions of 20ng of RNA input, 1.6 hour hybridization, and 15 cycles of PCR for library amplification. However, optimizing the protocol by increasing the input of RNA to 400ng, reducing the PCR to between 9-11 cycles, and extending the hybridization time to 16 hours increased library diversity, reduced the DupRate from greater than 80% to less than 44%, and increased coding region coverage PCB20x by at least 10%. All expected gene fusions identified in the RNASEQ data from the FF samples were also detected in the FFPE samples. We have shown that increasing RNA input, reducing PCR cycles and extending the length of hybridization can significantly improve data quality and maximize library diversity, allowing for greater utilization of archival FFPE material for RNASeq. Citation Format: Ji Wen, Ying Shao, Ruth Tatevossian, Yongjin Li, David W. Ellison, Gang Wu, Jinghui Zhang, John B. Easton. Optimization of library and enrichment procedures for RNASeq using RNA from formalin fixed paraffin embedded tissue [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5352. doi:10.1158/1538-7445.AM2017-5352

An Automatic Functional Coverage for Digital Systems Through a Binary Particle Swarm Optimization Algorithm with a Reinitialization Mechanism

At present, functional verification represents the most expensive part of the digital systems design. Moreover, different problems such as: clock synchronization, code compatibility, simulation automation, new design methodologies, proper use of coverage metrics, among others represent challenges in this area. The automated test vector generation is involved in these problems. In this work, an automated functional test sequences generation for digital systems based on the use of coverage models and a binary Particle Swarm Optimization algorithm with a reinitialization mechanism (BPSOr) is described. Also, a comparison with other meta-heuristic algorithms such as: Genetic algorithms (GA) and pseudo-random generation is presented using different fitness functions, coverage models and devices under verification. The main strategy is based on the combination of the simulation and meta-heuristic algorithms to test the device behavior through the generation of test vector sequences. According to the results, the proposed test generation method represents a good alternative to increase the functional coverage during the automated functional verification of block-level digital systems verification.

Evaluating user search trails in exploratory search tasks

Exploratory search is characterized by a user’s uncertainty towards a complex information seeking task. A user conducting such a search in an information retrieval (IR) system may need help and recommendations that are beyond mere query suggestions. In this paper we propose a new method for recommending search trails to struggling users. We first use a search process prediction model from the literature to predict whether a user is likely to under-perform in an exploratory search task, and given that case, recommend a search trail based on other users’ search behaviors in a similar context. We then present a method to evaluate the effectiveness of these recommendations that involves two different evaluation criteria. First, we use Open Directory Project (ODP)-based categorization of user-traversed Web pages to evaluate each user’s information coverage. Next, we evaluate the order of users’ search trails while simultaneously incorporating a novel set of metrics that use adjacency of queries issued and Web pages traversed. To evaluate search trails, we incorporated proposed metrics with transactional log data from multiple user studies in which more than 300 users conducted exploratory search tasks on different topics.We demonstrate the effectiveness of the proposed evaluation criteria by measuring how the recommended search trails lead to improvements in both information space coverage and search performance metrics for users across multiple user search datasets. Based on the analysis results, we demonstrate that the order of the recommended search trails plays a significant role and it outperforms the random order of search trails thus being beneficial for the struggling users in improving their overall search effectiveness. We also show that by providing search trail recommendations, users are able to discover more information across multiple facets (in breadth) as well as investigate certain facets in more detail (in depth). These findings provide substantial evidence across multiple datasets to confirm that recommended search trails improve users’ information seeking coverage and overall knowledge acquisition throughout their search processes.

A Time-Optimized Scheme Towards Analysis of Channel-Shorts in on-Chip Networks

With the continuous growth in technology, the role of nano-electronic systems is rapidly expanding in every facet of modern life. Subsequently, the demand of high performance computations and communications by many applications in order to interact with environment and users has become a compulsion. Traditional integrated circuit-based systems, e.g., bus-based systems-on-chip (SoCs), as a consequence are turned into networks- on-chips (NoCs) because of the communication bottleneck by the SoCs. Though, the NoCs visibly move the concern and meet the requirements by the applications but fabricating such NoCs without any defect in channels or logics has eventually evolved into a major challenge. Indeed, one of the major demand nowadays for such systems is to design a time-efficient mechanism for the pre- and post-manufacturing testing of NoC functional components, in order to guarantee outgoing quality while not sacrificing yield and reliability. This paper presents a cost effective and distributed on-line test mechanism that addresses channel-shorts in NoC-based systems. The proposed mechanism detects and diagnoses both intra- and inter-channel short faults. The test mechanism additionally targets transient and stuck-at faults in channels. A convenient test scheduling and energy model are presented. The scheduling scheme offers constant test time with little hardware area and performance overheads on the NoCs irrespective of their topologies and sizes. The proposed test solution is evaluated with fault injection campaign in channels of a set of NoC architectures. Fault simulation detects all modeled faults in channels resulting 100% test and fault coverage metrics. On-line evaluation of the proposed solution reveals insights of the effect of channel-shorts on various performance metrics at large amount of traffic. Furthermore, the proposed solution improves various quality metrics on the set of NoCs, for instance, the test area overhead is reduced up to 28% while the proposed model becomes 16 × faster. Also, improvement on the performance overhead is noticed. The packet latency for instance, is improved by 14.98---50.67% while packet flit energy consumption is reduced by 6.83---43.89%. Such improvements are found to grow with NoC size.

Generalized non-autonomous metric optimization for area coverage problems with mobile autonomous agents

Motivated by area coverage optimization problems with time-varying risk densities, in this paper we propose a decentralized control law for a team of autonomous mobile agents in a 2-D area such that their asymptotic configurations optimize a generalized non-autonomous coverage metric. We emphasize that the generalized non-autonomous coverage metric explicitly depends on a nonuniform time-varying measurable scalar field that is defined by the trajectories of a set of mobile targets (distinct from the agents). The time-varying density that we consider here is not directly controllable by agents. We show that under certain conditions on the density defined on a closed bounded region of operation, the agents configure themselves asymptotically to optimize a related generalized non-autonomous coverage metric. A set of simulations illustrates the proposed control.

Hepatitis B vaccination timing: results from demographic health surveys in47 countries.

ObjectiveTo examine the impact of hepatitis B vaccination schedules and types of vaccines on hepatitis B vaccination timing.MethodsWe used data for 211 643 children from demographic and health surveys in 47 low- and middle-income countries (median study year 2012). Data were from vaccination cards and maternal interviews. We grouped countries according to the vaccination schedule and type of vaccine used (monovalent or combination). For each country, we calculated hepatitis B vaccination coverage and timely receipt of vaccine doses. We used multivariable logistic regression models to study the effect of vaccination schedules and types on vaccination delay.FindingsSubstantial delays in vaccination were observed even in countries with fairly high coverage of all doses. Median delay was 1.0 week (interquartile range, IQR: 0.3 to 3.6) for the first dose (n = 108 626 children) and 3.7 weeks (IQR: 1.4 to 9.3) for the third dose (n = 101 542). We observed a tendency of lower odds of delays in vaccination schedules starting at 6 and at 9 weeks of age. For the first vaccine dose, we recorded lower odds of delays for combination vaccines than for monovalent vaccines (adjusted odds ratio, aOR: 0.76, 95% confidence interval, CI: 0.71 to 0.81).ConclusionWide variations in hepatitis B vaccination coverage and adherence to vaccination schedules across countries underscore the continued need to strengthen national immunization systems. Timely initiation of the vaccination process might lead to timely receipt of successive doses and improved overall coverage. We suggest incorporating vaccination timing as a performance indicator of vaccination programmes to complement coverage metrics.

Green DRCT

Being a good software testing engineer, one should have the responsibility towards environment sustainability. By using green principles and regulations, we can perform Green Software Testing. In this paper, we present a new approach to enhance Branch Coverage and Modified Condition/Decision Coverage uses concolic testing. We have proposed a novel transformation technique to improve these code coverage metrics. We have named this new transformation method Double Refined Code Transformer (DRCT). Then, using JoulMeter, we compute the power consumption and energy consumption in this testing process. We have developed a tool named Green-DRCT to measure energy consumption while performing the testing process.

Статическая верификация конфигураций ядра Linux

The Linux kernel is often used as a real world case study to demonstrate novel software product line engineering research methods. It is one of the most sophisticated programs nowadays. To provide the most safe experience of building of Linux product line variants it is necessary to analyse Kconfig file as well as source code. Ten of thousands of variable statements and options even by the standards of modern software development. Verification researchers offered lots of solutions for this problem. Standard procedures of code verification are not acceptable here due to time of execution and coverage of all configurations. We offer to check the operating system with special wrapper for tools analyzing built code and configuration file connected with coverage metric. Such a bundle is able to provide efficient tool for calculating all valid configurations for predetermined set of code and Kconfig. Metric can be used for improving existing analysis tools as well as decision of choice the right configuration. Our main goal is to contribute to a better understanding of possible defects and offer fast and safe solution to improve the validity of evaluations based on Linux. This solution will be described as a program with instruction for inner architecture implementation.

Simulation environment based on the Universal Verification Methodology

Universal Verification Methodology (UVM) is a standardized approach of verifying integrated circuit designs, targeting a Coverage-Driven Verification (CDV). It combines automatic test generation, self-checking testbenches, and coverage metrics to indicate progress in the design verification. The flow of the CDV differs from the traditional directed-testing approach. With the CDV, a testbench developer, by setting the verification goals, starts with an structured plan. Those goals are targeted further by a developed testbench, which generates legal stimuli and sends them to a device under test (DUT). The progress is measured by coverage monitors added to the simulation environment. In this way, the non-exercised functionality can be identified. Moreover, the additional scoreboards indicate undesired DUT behaviour. Such verification environments were developed for three recent ASIC and FPGA projects which have successfully implemented the new work-flow: (1) the CLICpix2 65 nm CMOS hybrid pixel readout ASIC design; (2) the C3PD 180 nm HV-CMOS active sensor ASIC design; (3) the FPGA-based DAQ system of the CLICpix chip. This paper, based on the experience from the above projects, introduces briefly UVM and presents a set of tips and advices applicable at different stages of the verification process-cycle.

Geometrical Characterization of Offloading through Wireless LANs

The offloading of cellular traffic through WLAN APs (wireless local area network access points) distributed in a homogeneous Poisson process (HPP) is theoretically evaluated. The probability $P_w$ that a user can use WLAN and the expected number of vertical handovers $N_h$ are evaluated as the basic performance metrics of WLAN AP coverage. Explicit formulas are derived for the metrics, and the fundamental relationships between the metrics and many parameters such as the shape of each WLAN coverage region $D_1,D_2,\ldots$ are described. These metrics depend on the size and perimeter length of $D_i$ but do not depend on their other shape parameters for a convex $D_i$ . In addition, it is proven that a disk-shaped $D_i$ minimizes $N_h$ for a fixed WLAN coverage size and that $P_w$ is often insensitive to the perimeter length of $D_i$ . It is also proven that the $P_w$ of a user at a random location is equal to that moving along a random straight line or a random bounded curve. One hundred empirical location data sets of WLAN APs in Japan, Korea, and the US were used to confirm the theoretical results. Although these locations do not follow an HPP, many theoretical results are shown to be valid. For example, $N_h$ is minimized by a disk-shaped $D_i$ . Simultaneously, we find that $P_w$ slightly increases when a slender $D_i$ is used for highly clustered AP locations.

Pricing of Internet Companies: Financial and Non-financial Value Drivers

In this paper we explore the importance of financial statements and non-financial value(volatility, media coverage and web metrics) drivers on the pricing of Internet companies,using the relative valuation method and, more specifically, price/sales ratio. Multipleregression analyses were run to determine which value drivers the data supported. Ourresults show that financial statements could not explain about two-thirds of variation inthe price/sales ratio. Moreover, our results suggest that the market values of profitable andunprofitable Internet companies are inherently different. In addition, we find evidence tosupport payout ratio as a value driver for profitable Internet companies reflecting maturation in the Internet industry. At the same time, we also find evidence that Media Mentionsis an explanatory factor in general for unprofitable Internet companies, and not only afteran IPO. We also find sufficient evidence to support number of visits and recent revenuegrowth as important value drivers.

Energy-efficient Custom Topology Generation for Link-failure-aware Network-on-chip in Voltage-frequency Island Regime

The voltage-frequency island (VFI) design paradigm has strong potential for achieving high energy efficiency in communication centric manycore system-on-chip (SoC) design called network-on-chip (NoC). However, because of the diminished scaling of wire-dimension and supply voltage as well as threshold voltage in modern CMOS technology, the vulnerability to link failure in VFI NoC is becoming a crucial challenge. In this paper, we propose an energy-optimized topology generation technique for VFI NoC to cope with permanent link failures. Based on the energy consumption model, we exploit the on-chip communication traffic patterns and characteristics of link failures in the early design stage to accommodate diverse applications and architectures. Experimental results using a number of multimedia application benchmarks show the effectiveness of the proposed three-step custom topology generation method in terms of energy consumption and latency without any degradation in the fault coverage metric.