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关键词： Routing   Costs   Blockchains   Contracts   Stochastic processes   Scalability   Computer science   Blockchain   payment channel   game theory   Shapley value  

摘要： Scaling blockchain efficiency is crucial to its widespread usage in which the payment channel is one of the most prominent approaches. With payment channels and the network they construct, two users can move some transactions off-chain to avoid expensive and time-consuming on-chain settlements. Existing works are devoted to designing high-throughput payment channel networks (PCNs) or efficient PCN routing policies to reduce the fee charged by intermediate nodes. In this paper, we investigate the PCN routing from a different perspective by answering whether the routing fee of transactions can be saved through being a bit more patient. The key idea is to reorder the processing sequence of atomic transactions, other than to handle each of them separately and immediately. We present two mechanisms, one is periodic transaction processing and the other is purely strategic waiting. In the former, the incoming transactions in a short time interval are processed collectively. We formulate an optimization model to minimize their total routing fee and derive the optimal permutation of processing transactions as well as the routing policy for each of them. A Shapley value based scheme is presented to redistribute the benefit of reordering among the transactions efficiently and fairly. In the latter, we model the waiting time of a strategic transaction on a single payment channel as the first passage time problem in queuing theory when the transaction value is higher than the channel balance upon its arrival. By capturing the balance dynamics, we are able to calculate the recursive expression of waiting time distribution that is useful to gauge a user's cost of patience. Experimental results manifest that our cost redistribution mechanism can effectively save routing fees for all the transactions, and the waiting time distribution coincides with the model well.

关键词： Sociology   Statistics   Evolutionary computation   Optimization   Heuristic algorithms   Search problems   Computer science   Evolutionary algorithm (EA)   irregular Pareto front   multiobjective optimization   projection  

摘要： This article proposes a simple yet effective multiobjective evolutionary algorithm (EA) for dealing with problems with irregular Pareto front. The proposed algorithm does not need to deal with the issues of predefining weight vectors and calculating indicators in the search process. It is mainly based on the thought of adaptively selecting multiple promising search directions according to crowdedness information in local objective spaces. Concretely, the proposed algorithm attempts to dynamically delete an individual of poor quality until enough individuals survive into the next generation. In this environmental selection process, the proposed algorithm considers two or three individuals in the most crowded area, which is determined by the local information in objective space, according to a probability selection mechanism, and deletes the worst of them from the current population. Thus, these surviving individuals are representative of promising search directions. The performance of the proposed algorithm is verified and compared with seven state-of-the-art algorithms [including four general multi/many-objective EAs and three algorithms specially designed for dealing with problems with irregular Pareto-optimal front (PF)] on a variety of complicated problems with different numbers of objectives ranging from 2 to 15. Empirical results demonstrate that the proposed algorithm has a strong competitiveness power in terms of both the performance and the algorithm compactness, and it can well deal with different types of problems with irregular PF and problems with different numbers of objectives.

关键词： Machine learning   Informatics   Critical infrastructure   Privacy   Medical services   Wireless communication   Computer science   Critical Infrastructure   Security   Federated Learning   Cyber incident  

摘要： Critical energy infrastructure (CEI) is specific engineering information about proposed or existing critical infrastructure. Modern critical infrastructures are increasingly turning into distributed, complex cyber-physical systems that need proactive protection and fast restoration to mitigate physical or cyber incidents or attacks. Most importantly, combined cyber-physical attacks are much more challenging and are expected to become the most intrusive attack. This is particularly true for the CEIs. During 2015, the Industrial Control Systems Cyber Emergency Response Team in the Unites States responded to more than 245 incidents; the energy sector tops the list with 32% incidents. Considering the importance of energy in our daily lives and its influence on other critical infrastructures, CEI requires significant attention comparatively. For example, the wind-turbine system is considered one of the most complex cyber-physical infrastructures, causing huge cascading effects to other CEIs, such as electrical power and energy systems and transportation, healthcare sector, communications, industry, and finance. Wind turbines are mainly composed of condition monitoring and operational data (i.e., supervisory command and data acquisition), including air temperature, air pressure, voltage, and power with multiple parameters and periodic characteristics.

关键词： Computer science education   Computational thinking   Programming   Systematic review   K-12  

摘要： This systematic review examined how computer science (CS) education was implemented in schools and its efficacy for developing students' computational thinking (CT). Sixty-six papers were selected for this systematic review and analyzed for patterns in relation to the implementation of CS education in K-12 schools and its impact on the development of students' CT skills. Although educational interventions have not always been successful in CS education, this review provides strong evidence that overall, CS education promotes the development of students' CT in the K-12 setting while improving their creative and critical thinking skills. We recommend early access to CS education, various innovative instructional approaches to CS education and appropriate support and guidance for student learning.

关键词： capital punishment   clothing   executions   gender   resistance   subversion  

摘要： In this paper we examine the dress of execution victims. Executions provide both the convict and the state with an opportunity to claim honor and respectability. Drawing on newspaper accounts of executions conducted between 1840 and 1940, we demonstrate that convict attire reveals an important tension between the convicts' gendered character claims and the efforts by execution managers to arrange a credible execution. But whereas displays of masculinity reinforce more than challenge the propriety of executions, women's femininity displays challenge not only the propriety of executions, but also the respectability of those tasked with their killing. We conclude that the subversive potential of clothing is found not only in the garments themselves, nor only on the wearers' intentions, but also on the institutional settings in which they are presented.

关键词： Computer science   Online teaching and learning   Instructional strategies   Assessment   Design   Facilitation  

摘要： Current research surrounding online computer science education emphasizes the need for high-quality professional development opportunities. However, there is a gap in research in the inclusion of online computer science educators to identify needs and strategies that make the online computer science courses effective. Through a Research-to-Practice Partnership (RPP), this paper examines the instructional strategies and recommendations from online Computer Science teachers. This study seeks to better understand (1) What design, facilitation, and assessment strategies do teachers use to teach programming online? and (2) What recommendations do teachers have for those interested in teaching programming online? The feedback teachers provided during the study assisted in identifying the current needs in online AP Computer Science. The participants suggested additional ways the RPP could support teachers in strengthening their practice, which has assisted in the production of high-quality professional development to support novice teachers entering the field of Computer Science.

关键词： Early childhood education   Preservice teachers   Computer science   Coding   Gender stereotypes  

摘要： The purpose of this exploratory study was to investigate early childhood preservice teachers' perceptions of computer science and gender stereotypes in computer science, and perceptions of coding in early childhood education. Quantitative and qualitative data were collected from early childhood preservice teachers enrolled in a teaching methods course at a large southeastern university in the U.S. Findings showed that participants had misconceptions about what CS is and what computer scientists do. They were also neutral about coding and its integration in early childhood education. Both qualitative and quantitative data supported that the participants did not hold gender stereotypes in CS.

关键词： Computer science education   Culturally responsive computing   Research-practice partnership   Elementary education  

摘要： Implementing computer science education in an elementary classroom is at the forefront of computing education. Nevertheless, the literature on K-12 Computer Science (CS) education offers limited guidance for developing elementary CS curricula that lead to multiple career paths through project-based learning. Particularly, more research is needed on culturally responsive elementary school computing that leverages students' cultural references to create a more equitable CS education that acknowledges one's identity, culture, or background in the curriculum planning. This paper offers an approach for designing culturally responsive computing for upper elementary students from a highly diverse, low socio-economic school district using a research-practice approach. The approach can be adapted for other schools that face unique diversity and curricular challenges.

关键词： Learning systems   Neural networks   Computer science   Feature extraction   Zinc   Cybernetics   Gallium nitride   Broad learning system (BLS)   classification   incremental learning   weighted generalized cross-validation (WGCV)  

摘要： The broad learning system (BLS) is an emerging flat network, which has demonstrated its outstanding performance in classification and regression problems. The regularization plays an important role in the performance of the BLS. In real applications, since the BLS network is usually expanded dynamically, a predetermined regularization parameter may reduce the performance of the network. Using a fixed regularization in some cases, the classification accuracy of the BLS decreases dramatically when we expand the network. To alleviate this problem, we propose a method that automatically finds appropriate regularization parameters for different datasets, which is based on the weighted generalized cross-validation (WGCV). The experimental results indicate that the WGCV method improves the performance of the BLS, and alleviates the accuracy decrease of the incremental learning algorithm.

关键词： Encryption   Databases   Computer science   Faces   Two dimensional displays   Encrypted database   data privacy   order-preserving encryption   order-revealing encryption  

摘要： Order-preserving encryption (OPE) is a cryptographic primitive that preserves the order of plaintexts. In the past few years, many OPE schemes were proposed to solve the problem of executing range queries in encrypted databases. However, OPE leaks some certain information (for example, the order of ciphertext), so it is vulnerable to many attacks. Subsequently, order-revealing encryption (ORE) was proposed by Boneh et al. (Eurocrypt 2015) as a generalization of order-preserving encryption. It breaks through the limitation of the numeric order of OPE plaintext. It implements ciphertext comparison for any specific form of plaintext through a publicly computable comparison function. In this article, we aim to design a new ORE scheme which reduces the leakages and preserves the practicality in terms of ciphertext length and encryption time. We first propose the hybrid model named HybridORE. Then, we propose an improved scheme named EncodeORE which achieves acceptable security and appropriate ciphertext length. They both explore the encode strategy of encoding plaintext into different parts and apply suitable ORE algorithms to each part according to its security characteristics to reduce leakages. Compared with the typical CLWW scheme (FSE 2016) and Lewi-Wu (CCS 2016) in large domain, they have fewer leakages. The experiment shows that the proposed EncodeORE is very practical.