117 research outputs found
Local Search For SMT On Linear and Multilinear Real Arithmetic
Satisfiability Modulo Theories (SMT) has significant application in various
domains. In this paper, we focus on quantifier-free Satisfiablity Modulo Real
Arithmetic, referred to as SMT(RA), including both linear and non-linear real
arithmetic theories. As for non-linear real arithmetic theory, we focus on one
of its important fragments where the atomic constraints are multi-linear. We
propose the first local search algorithm for SMT(RA), called LocalSMT(RA),
based on two novel ideas. First, an interval-based operator is proposed to
cooperate with the traditional local search operator by considering the
interval information. Moreover, we propose a tie-breaking mechanism to further
evaluate the operations when the operations are indistinguishable according to
the score function. Experiments are conducted to evaluate LocalSMT(RA) on
benchmarks from SMT-LIB. The results show that LocalSMT(RA) is competitive with
the state-of-the-art SMT solvers, and performs particularly well on
multi-linear instances
Trabalhadores chineses em Portugal: desafios e sugestões, tendo como base uma experiência de estágio
Relatório de estágio de mestrado em Estudos Interculturais Português/Chinês: Tradução, Formação e Comunicação EmpresarialAtualmente, a China e a globalização são tópicos mais frequentes da nossa vida do dia-a-dia. O impacto da economia chinesa está a ser fortemente sentido, por tudo o mundo, e os seus negócios estão a expandir e crescer pelos quatro cantos do planeta, incluindo Portugal. Com o lançamento do “Programa dos Vistos Gold”, com as mais próximas relações diplomáticas entre a China e Portugal, cada vez mais chineses fazem negócios e investimentos em Portugal e, ao mesmo tempo, cada vez mais empresas portuguesas têm mais oportunidades de cooperar com empresas chinesas. No entanto, no processo de fazer negócios transnacionais, ambos os lados enfrentam uma enorme diversidade em termos de comunicação empresarial, o que de alguma forma criará mal-entendidos e trará complicações, assim como interferirá na produtividade do trabalho. Portanto, a primeira parte deste relatório centra-se na explicação das origens e das razões para a emigração de cidadãos chineses para Portugal, na identificação de diferenças entre portugueses e chineses em contexto de trabalho e na apresentação de alguns casos relacionados com problemas e desafios na comunicação empresarial. A segunda parte deste relatório apresentará brevemente a Câmara de Comércio e Indústria Luso-Chinesa, a sua missão, os seus órgãos sociais, os seus serviços, a sua história e os seus eventos representativos. A última parte deste relatório descreverá mais especificamente sobre os meus objetos, as minhas tarefas e o meu trabalho durante os meus quatro meses de estágio, além de mencionar alguns dos eventos importantes que eu participei.Nowadays, China and globalization are more and more common topics of our daily life. The impact of China’s economy is being strongly felt by the world, and its businesses are going to expand and grow in every corner of the world, Portugal is no exception. With the launch of “Golden Visa Scheme”, with the closer diplomatic relationships between China and Portugal, more and more Chinese people are doing business and investment in Portugal, and at the same time, more and more Portuguese companies have more opportunities to cooperate with Chinese companies. However, in the process of doing transnational business, both sides of the companies are facing a huge diversity in terms of business communication, which somehow will create misunderstandings and bring complications, as well as interfere with the working productivity. Therefore, the first part of this report focuses on the explanation of the origins and reasons for the emigration of Chinese citizens to Portugal, the identification of differences between Portuguese and Chinese in the workplace, and the presentation of some cases related to problems and challenges in business communication. The second part of this report will briefly introduce the Portuguese- Chinese Chamber of Commerce and Industry, its mission, social bodies, services, history and its representative events. The last part of this report will describe more specifically my objects, my tasks and work during my four months of internship, also mention some of the important events that I have participated.现今,中国与全球化对大家来说都不陌生,全世界都在强烈地感受着中国经济带来的影响。中国的业务发展正在扩展到全世界的各个角落,葡萄牙也不例外。随着“黄金签证计划” 的实施以及中葡外交关系的日益密切,越来越多的中国人在葡萄牙开展业务和投资。同时,也有越来越多的葡萄牙公司拥有更多的机会与中国公司进行合作。然而,在发展跨国业务的过程中,中葡公司在业务沟通方面却面临着巨大的差异,而这些差异有时会使双方产生误解,或使问题越来越复杂,或影响工作效率。因此,本报告的第一部分将重点分析中国人向葡萄牙移民的起源和原因,中国人和葡萄牙人的工作差异,以及介绍一些在商业交流中出现的问题和挑战的相关案例。 本报告的第二部分将简要介绍葡中工商会,其使命、机构组成、服务、历史及其代表性活动。 本报告的最后一部分将具体地描述本人的实习目标以及为期四个月的实习任务和工作,并简要描述实习期间所参与的一些重要活动
Improving Local Search for Minimum Weighted Connected Dominating Set Problem by Inner-Layer Local Search
The minimum weighted connected dominating set (MWCDS) problem is an important variant of connected dominating set problems with wide applications, especially in heterogenous networks and gene regulatory networks. In the paper, we develop a nested local search algorithm called NestedLS for solving MWCDS on classic benchmarks and massive graphs. In this local search framework, we propose two novel ideas to make it effective by utilizing previous search information. First, we design the restart based smoothing mechanism as a diversification method to escape from local optimal. Second, we propose a novel inner-layer local search method to enlarge the candidate removal set, which can be modelled as an optimized version of spanning tree problem. Moreover, inner-layer local search method is a general method for maintaining the connectivity constraint when dealing with massive graphs. Experimental results show that NestedLS outperforms state-of-the-art meta-heuristic algorithms on most instances
New Characterizations and Efficient Local Search for General Integer Linear Programming
Integer linear programming (ILP) models a wide range of practical
combinatorial optimization problems and has significant impacts in industry and
management sectors. This work proposes new characterizations of ILP with the
concept of boundary solutions. Motivated by the new characterizations, we
develop an efficient local search solver, which is the first local search
solver for general ILP validated on a large heterogeneous problem dataset. We
propose a new local search framework that switches between three modes, namely
Search, Improve, and Restore modes. We design tailored operators adapted to
different modes, thus improving the quality of the current solution according
to different situations. For the Search and Restore modes, we propose an
operator named tight move, which adaptively modifies variables' values, trying
to make some constraint tight. For the Improve mode, an efficient operator lift
move is proposed to improve the quality of the objective function while
maintaining feasibility. Putting these together, we develop a local search
solver for integer linear programming called Local-ILP. Experiments conducted
on the MIPLIB dataset show the effectiveness of our solver in solving
large-scale hard integer linear programming problems within a reasonably short
time. Local-ILP is competitive and complementary to the state-of-the-art
commercial solver Gurobi and significantly outperforms the state-of-the-art
non-commercial solver SCIP. Moreover, our solver establishes new records for 6
MIPLIB open instances. The theoretical analysis of our algorithm is also
presented, which shows our algorithm could avoid visiting unnecessary regions
and also maintain good connectivity of targeted solutions.Comment: 36 pages, 2 figures, 7 table
Improving Local Search for Structured SAT Formulas via Unit Propagation Based Construct and Cut Initialization (Short Paper)
This work is dedicated to improving local search solvers for the Boolean satisfiability (SAT) problem on structured instances. We propose a construct-and-cut (CnC) algorithm based on unit propagation, which is used to produce initial assignments for local search. We integrate our CnC initialization procedure within several state-of-the-art local search SAT solvers, and obtain the improved solvers. Experiments are carried out with a benchmark encoded from a spectrum repacking project as well as benchmarks encoded from two important mathematical problems namely Boolean Pythagorean Triple and Schur Number Five. The experiments show that the CnC initialization improves the local search solvers, leading to better performance than state-of-the-art SAT solvers based on Conflict Driven Clause Learning (CDCL) solvers
Real-Time Marker Localization Learning for GelStereo Tactile Sensing
Visuotactile sensing technology is becoming more popular in tactile sensing,
but the effectiveness of the existing marker detection localization methods
remains to be further explored. Instead of contour-based blob detection, this
paper presents a learning-based marker localization network for GelStereo
visuotactile sensing called Marknet. Specifically, the Marknet presents a grid
regression architecture to incorporate the distribution of the GelStereo
markers. Furthermore, a marker rationality evaluator (MRE) is modelled to
screen suitable prediction results. The experimental results show that the
Marknet combined with MRE achieves 93.90% precision for irregular markers in
contact areas, which outperforms the traditional contour-based blob detection
method by a large margin of 42.32%. Meanwhile, the proposed learning-based
marker localization method can achieve better real-time performance beyond the
blob detection interface provided by the OpenCV library through GPU
acceleration, which we believe will lead to considerable perceptual sensitivity
gains in various robotic manipulation tasks
A facile approach to fabricate highly sensitive, flexible strain sensor based on elastomeric/graphene platelet composite film
This work developed a facile approach to fabricate highly sensitive and flexible polyurethane/graphene platelets composite film for wearable strain sensor. The composite film was fabricated via layer-by-layer laminating method which is simple and cost-effective; it exhibited outstanding electrical conductivity of 1430 ± 50 S/cm and high sensitivity to strain (the gauge factor is up to 150). In the sensor application test, the flexible strain sensor achieves real-time monitoring accurately for five bio-signals such as pulse movement, finger movement, and cheek movement giving a great potential as wearable-sensing device. In addition, the developed strain sensor shows response to pressure and temperature in a certain region. A multifaceted comparison between reported flexible strain sensors and our strain sensor was made highlighting the advantages of the current work in terms of (1) high sensitivity (gauge factor) and flexibility, (2) facile approach of fabrication, and (3) accurate monitoring for body motions
BAGEL: Backdoor Attacks against Federated Contrastive Learning
Federated Contrastive Learning (FCL) is an emerging privacy-preserving
paradigm in distributed learning for unlabeled data. In FCL, distributed
parties collaboratively learn a global encoder with unlabeled data, and the
global encoder could be widely used as a feature extractor to build models for
many downstream tasks. However, FCL is also vulnerable to many security threats
(e.g., backdoor attacks) due to its distributed nature, which are seldom
investigated in existing solutions. In this paper, we study the backdoor attack
against FCL as a pioneer research, to illustrate how backdoor attacks on
distributed local clients act on downstream tasks. Specifically, in our system,
malicious clients can successfully inject a backdoor into the global encoder by
uploading poisoned local updates, thus downstream models built with this global
encoder will also inherit the backdoor. We also investigate how to inject
backdoors into multiple downstream models, in terms of two different backdoor
attacks, namely the \textit{centralized attack} and the \textit{decentralized
attack}. Experiment results show that both the centralized and the
decentralized attacks can inject backdoors into downstream models effectively
with high attack success rates. Finally, we evaluate two defense methods
against our proposed backdoor attacks in FCL, which indicates that the
decentralized backdoor attack is more stealthy and harder to defend
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