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2021 ◽  
Vol 5 (OOPSLA) ◽  
pp. 1-30
Author(s):  
Truc Lam Bui ◽  
Krishnendu Chatterjee ◽  
Tushar Gautam ◽  
Andreas Pavlogiannis ◽  
Viktor Toman

The verification of concurrent programs remains an open challenge due to the non-determinism in inter-process communication. One recurring algorithmic problem in this challenge is the consistency verification of concurrent executions. In particular, consistency verification under a reads-from map allows to compute the reads-from (RF) equivalence between concurrent traces, with direct applications to areas such as Stateless Model Checking (SMC). Importantly, the RF equivalence was recently shown to be coarser than the standard Mazurkiewicz equivalence, leading to impressive scalability improvements for SMC under SC (sequential consistency). However, for the relaxed memory models of TSO and PSO (total/partial store order), the algorithmic problem of deciding the RF equivalence, as well as its impact on SMC, has been elusive. In this work we solve the algorithmic problem of consistency verification for the TSO and PSO memory models given a reads-from map, denoted VTSO-rf and VPSO-rf, respectively. For an execution of n events over k threads and d variables, we establish novel bounds that scale as n k +1 for TSO and as n k +1 · min( n k 2 , 2 k · d ) for PSO. Moreover, based on our solution to these problems, we develop an SMC algorithm under TSO and PSO that uses the RF equivalence. The algorithm is exploration-optimal , in the sense that it is guaranteed to explore each class of the RF partitioning exactly once, and spends polynomial time per class when k is bounded. Finally, we implement all our algorithms in the SMC tool Nidhugg, and perform a large number of experiments over benchmarks from existing literature. Our experimental results show that our algorithms for VTSO-rf and VPSO-rf provide significant scalability improvements over standard alternatives. Moreover, when used for SMC, the RF partitioning is often much coarser than the standard Shasha-Snir partitioning for TSO/PSO, which yields a significant speedup in the model checking task.


2021 ◽  
Vol 5 (OOPSLA) ◽  
pp. 1-29
Author(s):  
Zhe Zhou ◽  
Robert Dickerson ◽  
Benjamin Delaware ◽  
Suresh Jagannathan

Programmers often leverage data structure libraries that provide useful and reusable abstractions. Modular verification of programs that make use of these libraries naturally rely on specifications that capture important properties about how the library expects these data structures to be accessed and manipulated. However, these specifications are often missing or incomplete, making it hard for clients to be confident they are using the library safely. When library source code is also unavailable, as is often the case, the challenge to infer meaningful specifications is further exacerbated. In this paper, we present a novel data-driven abductive inference mechanism that infers specifications for library methods sufficient to enable verification of the library's clients. Our technique combines a data-driven learning-based framework to postulate candidate specifications, along with SMT-provided counterexamples to refine these candidates, taking special care to prevent generating specifications that overfit to sampled tests. The resulting specifications form a minimal set of requirements on the behavior of library implementations that ensures safety of a particular client program. Our solution thus provides a new multi-abduction procedure for precise specification inference of data structure libraries guided by client-side verification tasks. Experimental results on a wide range of realistic OCaml data structure programs demonstrate the effectiveness of the approach.


2021 ◽  
Vol 10 (2) ◽  
pp. 83-89
Author(s):  
Ehsan Maani Miandoab ◽  
Amir Hossein Jafari ◽  
Aref Valipour

The generation of electricity by renewable energies is an important need of today's society. Piezoelectric energy harvesting is one of these useful technologies which can generate electricity by applying external force on piezoelectric material. This study illustrates more power generation from piezoelectric tile by changing the situation of piezo discs and connect to proportional electrical circuit. Two different designs of piezoelectric tile are presented by performing experimental analyses. The experimental results showed that placing piezoelectric elements in a bending position leads to higher power generation in comparison with traditional flat positioning, which was approximately 78 times far superior. It is also revealed that by design of an electrical circuit, the tile can be advantageous for lighting in crowded sidewalks with required lighting time. The results of this paper can be beneficial in the design and fabrication of these tiles for different applications.


2022 ◽  
Vol 12 (1) ◽  
pp. 0-0

The traditional frequency based approach to creating multi-document extractive summary ranks sentences based on scores computed by summing up TF*IDF weights of words contained in the sentences. In this approach, TF or term frequency is calculated based on how frequently a term (word) occurs in the input and TF calculated in this way does not take into account the semantic relations among terms. In this paper, we propose methods that exploits semantic term relations for improving sentence ranking and redundancy removal steps of a summarization system. Our proposed summarization system has been tested on DUC 2003 and DUC 2004 benchmark multi-document summarization datasets. The experimental results reveal that performance of our multi-document text summarizer is significantly improved when the distributional term similarity measure is used for finding semantic term relations. Our multi-document text summarizer also outperforms some well known summarization baselines to which it is compared.


2022 ◽  
Vol 12 (1) ◽  
pp. 0-0

The WWW contains huge amount of information from different areas. This information may be present virtually in the form of web pages, media, articles (research journals / magazine), blogs etc. A major portion of the information is present in web databases that can be retrieved by raising queries at the interface offered by the specific database and is thus called the Hidden Web. An important issue is to efficiently retrieve and provide access to this enormous amount of information through crawling. In this paper, we present the architecture of a parallel crawler for the Hidden Web that avoids download overlaps by following a domain-specific approach. The experimental results further show that the proposed parallel Hidden web crawler (PSHWC), not only effectively but also efficiently extracts and download the contents in the Hidden web databases


Author(s):  
Christian Alvin Setiabudi ◽  
◽  
Gede Putra Kusuma

Indoor Positioning System has been one of the most attractive research after Bluetooth Low Energy (BLE) was introduced. This technology mainly used because of the reduction of material and energy cost over time that has huge impact compared to other technologies, which are more costly. Most recent research resolve around improving the accuracy of calculated position of the user by implementing different method to enable an indoor positioning system, and to remove any noises in the dataset. This paper objective is to compare some of the available methods that are used to enable Indoor Positioning System such as Fingerprinting, Multilateration, Trilateration, and Heron Bilateration. Since the performance of Fingerprinting is better compared to other methods, we combine Fingerprinting’s offline phase with the other methods to create a hybrid method and compare the accuracy of predicted user’s position. The experimental results show that the Fingerprinting and WKNN method outperform all other methods by resulting on 271.76 cm mean of error.


Author(s):  
Qichen Zhang ◽  
Xiaodong Kang ◽  
Huiqing Liu ◽  
Xiaohu Dong ◽  
Jian Wang

AbstractCurrently, the reservoir heterogeneity is a serious challenge for developing oil sands with SAGD method. Nexen’s Long Lake SAGD project reported that breccia interlayer was widely distributed in lower and middle part of reservoir, impeding the steam chamber expansion and heated oil drainage. In this paper, two physical experiments were conducted to study the impact of breccia interlayer on development of steam chamber and production performance. Then, a laboratory scale numerical simulation model was established and a history match was conducted based on the 3D experimental results. Finally, the sensitivity analysis of thickness and permeability of breccia layer was performed. The influence mechanism of breccia layer on SAGD performance was analyzed by comparing the temperature profile of steam chamber and production dynamics. The experimental results indicate that the existence of breccia interlayer causes a thinner steam chamber profile and longer time to reach the peak oil rate. And, the ultimate oil recovery reduced 15.8% due to much oil stuck in breccia interlayer areas. The numerical simulation results show that a lower permeability in breccia layer area has a serious adverse impact on oil recovery if the thickness of breccia layer is larger, whereas the effect of permeability on SAGD performance is limited when the breccia layer is thinner. Besides, a thicker breccia layer can increase the time required to reach the peak oil rate, but has a little impact on the ultimate oil recovery.


2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Jianfeng Guan ◽  
Xuetao Li ◽  
Ying Zhang

Most of the current authentication mechanisms adopt the “one-time authentication,” which authenticate users for initial access. Once users have been authenticated, they can access network services without further verifications. In this case, after an illegal user completes authentication through identity forgery or a malicious user completes authentication by hijacking a legitimate user, his or her behaviour will become uncontrollable and may result in unknown risks to the network. These kinds of insider attacks have been increasingly threatening lots of organizations, and have boosted the emergence of zero trust architecture. In this paper, we propose a Multimodal Fusion-based Continuous Authentication (MFCA) scheme, which collects multidimensional behaviour characteristics during the online process, verifies their identities continuously, and locks out the users once abnormal behaviours are detected to protect data privacy and prevent the risk of potential attack. More specifically, MFCA integrates the behaviours of keystroke, mouse movement, and application usage and presents a multimodal fusion mechanism and trust model to effectively figure out user behaviours. To evaluate the performance of the MFCA, we designed and implemented the MFCA system and the experimental results show that the MFCA can detect illegal users in quick time with high accuracy.


2021 ◽  
Vol 67 (6 Nov-Dec) ◽  
Author(s):  
N. Aouail ◽  
M. Noureddine Belkaid ◽  
A. Oukebdane ◽  
M. Hocine Tedjini

In this paper, the fundamental semiconductor properties of Hg1-xCdxTe and Hg1-xZnxTe are investigated by ab initio calculations based on the FP-LAPW method.   Structural properties have been calculated using LDA and GGA approximations. The electronic properties are studied using the LDA and GGA approximations, and the potential TB-mBJLDA coupled with the lattice parameters aLDA and aGGA. The optical properties are determined from the optimal gap energies based on the TB-mBJLDA potential. Lattice parameters aLDA obtained by the LDA calculations predict values that are in good agreement with the experimental results and are better than those results obtained by the GGA calculations.  The use of TB-mBJLDA potential coupled with the lattice parameter aGGA gives gap energy values in good agreement with the experimental results for all alloys except  Hg1-xZnxTe (x=0.5, 0.75) where the (TB-mBJ LDA+aLDA) is more suitable. Optical constants are calculated from the dielectric function in the energy range (0-30 eV).  The spectrum of real and imaginary parts of the dielectric function, the energy loss function, the refractive index, the extinction coefficient, the absorption coefficient, and the reflectivity show that optical properties of Hg1-xCdxTe are comparable to those of  Hg1-xZnxTe. Our results are found to be in reasonable agreement with existing data reported in the literature.


Author(s):  
Navneet Kaur ◽  
Jagtar Singh Sivia ◽  
Rajni

Abstract In this paper, the design of frequency reconfigurable planar antenna by incorporation of metasurface superstrate (FRPA-MSS) is presented using an artificial neural network. The dual-layer radiating structure is created on a 1.524 mm thick Rogers RO4350B substrate board (εr = 3.48, tan δ = 0.0037). The candidate antenna is designed and analyzed using a high-frequency structure simulator (HFSS) tool. The transfer matrix method is employed for the successful retrieval of electromagnetic properties of the metamaterial. Frequency reconfiguration is achieved by placing the metasurface superstrate onto the rectangular patch antenna. A simplified ANN approach has been employed for the design of metasurface incorporated proposed antenna. Presented prototypes are characterized through experimental measurements. It is found from the practical observations that the proposed antenna effectively reconfigures the tuning range from 5.03 to 6.13 GHz. Moreover, the presented antenna operates efficiently with agreeable gain, good impedance matching, and stable pattern characteristics across the entire operational bandwidth. The experimental results obtained validate the simulated performance.


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