Overflowing phenomenon during ultrasonic treatment in Al-Si alloys

At the late stage of solidification with ultrasonic treatment （UST） in Al-Si alloys, a part of semisolid overflows and climbs along the probe. The interesting phenomenon and its influence on the solidification microstructure were investigated in order to better study the mechanism of UST. It is considered that the overflowing phenomenon occurs due to the changes of vibration and flow in the remaining semisolid. Because the overflowed portion comes from the region with intense UST effect and vibrates with the probe during solidification, great modification of primary and euteetic Si （about 10 pm in length） and refinement of primary a（Al） （about 70 μm in size） are observed in this portion.

一种结合代码片段和混合主题模型的软件数据聚类方法

使用主题模型进行文档聚类是众多文本挖掘任务中一种常见的做法。许多研究针对软件问答网站的数据,利用主题模型进行聚类来分析不同领域在社区的发展情况。然而,这些软件相关数据往往包含代码片段且文本长度分布不均,使用传统单一的主题模型对文本数据建模,易得到不稳定的聚类结果。文中提出了一种结合代码片段和混合主题模型的聚类方法,并使用Stack Overflow作为数据源,构造了在该平台上被提问数量排名前60的Python第三方库数据集,经过建模,该数据集最终划分为以下6个不同的领域:网络安全、数据分析、人工智能、文本处理、软件开发和系统终端。实验结果表明,在自动评估和人工评估的指标上,使用代码片段结合文本进行主题建模,在聚类结果划分的质量上表现良好,而联合多个模型进行实验,一定程度上提高了聚类结果的稳定性和准确性。

Pre-emptive Channel Borrowing and Traffic Overflowing Channel Allocation Scheme for Multimedia Overlay Networks

This paper proposes a channel allocation scheme for multimedia wireless networks,in which a twolayer macro-cell or micro-cell architecture is considered.Macro-cells are used to access high-mobility services;while micro-cells,which are overlaid by the macro-cells,are used to cater low-mobility services.To analyze the scheme,a multidimensional Markov traffic model is firstly developed,in which traffic characteristic of two special periods of time is considered.And then,a pre-emptive channel-borrowing scheme combined with trafficoverflowing strategy for multimedia(voice,video or data) networks is proposed,in which handoff requests can not only borrow channels from adjacent homogenous cells,but also be overflowed to heterogeneous cells.Priority strategies are also dedicated to high-mobility services for they can pre-empt channels being used by low-mobility services in macro-cells.To meet the high quality of service(QoS) requirements of video services and increase the channel utilization ratio,video services can be transformed between real-time services and non-real-time services as necessary.Simulation results show that our schemes can decrease the blocking probabilities and improve the channel utilization.

Chinese lanterns overflowing with lights, colors in Europe

In the winter of 2017,southern France was hit by the most severe freeze in a decade,and yet the southern city of Gaiaque,with a population of just 10,000,had 250,000 visitors in town.What attracted them to brave the cold and rain to visit the small city?A Chinese lantern festival,the first kind of it in France.The lantern festival,jointly

基于问答语义匹配的知识社区新问题专家推荐方法

传统的知识社区专家推荐方法采用文本相似度匹配机理,并基于问题或专家描述来构建专家特征.这些方法没有利用问题与答案的语义匹配关系,因此难以充分挖掘专家回答问题的能力特征,影响推荐性能.提出一种基于综合历史和当前问答语义匹配的知识社区新问题的专家推荐方法(History-Now Semantics Expert RECommendation model,HNS-EREC).首先,采用反馈评价和负采样技术来处理数据集中的两类不平衡现象;其次,基于问答语义来提取专家回答问题能力特征;最后,提出一种基于问答语义匹配的History-Now联合专家推荐模型,该模型能够实现面向专家的历史问答和当前问答的语义联合学习.实验结果表明,相对于其他方法,本文所提出的HNS-EREC方法在新问题专家推荐方面具有显著的优势.

Water hammer protection for diversion systems in front of pumps in long-distance water supply projects

For a water supply system with long-distance diversion pipelines, in addition to the water hammer problems that occur beyond pumps, the safety of the water diversion pipeline in front of pumps also deserves attention. In this study, a water hammer protection scheme combined with an overflow surge tank and a regulating valve was developed. A mathematical model of the overflow surge tank was developed, and an analytical formula for the height of the overflow surge tank was derived. Furthermore, a practical water supply project was used to evaluate the feasibility of the combined protection scheme and analyze the sensitivity of valve regulation rules. The results showed that the combined protection scheme effectively reduced the height of the surge tank, lessened the difficulties related to construction, and reduced the necessary financial investment for the project. The two-stage closing rule articulated as fast first and then slow could minimize the overflow volume of the surge tank when the power failure occurred, while the two-stage opening rule articulated as slow first and then fast could be more conducive to the safety of the water supply system when the pump started up.

An Integrated Load Balancing Scheme Based on SDN ASR Algorithm

At present,the flow table of the SDN switch is stored in the costly Ternary Content Addressable Memory(TCAM)cache.Due to the cost problem,the number of flow tables that the SDN switch can store is extremely limited,which is far less than the number of traffic,so it is prone to overflow problem,and leads to network paralysis.That has become a bottleneck in restricting the processing capacity of the data center,and will become a weak point focused by attackers.In this paper,we propose an algorithm for the Alarm Switch Remove(ASR)that fully loads the flow table space in SDN,and further put forward an integrated load balancing scheme in SDN.Finally,we use Mininet to verify that the scheme can ease the SDN switch flow table overflow problem and increase network throughput.

面向专家示例的Stack Overflow本体构造和推理研究

Stack Overflow是一个计算机领域的IT技术问答网站,为了获取问答网站中的专家示例并将其应用于API挖掘中。首先采用Scrapy爬虫框架技术获取Stack Overflow问答网站中的结构化数据,并存储在关系模式中;再使用本体建模工具Protégé构建本体,然后使用D2RQ工具实现对关系数据库的知识抽取,将关系模式转换为三元组形式的本体模型;同时,提出了一个面向专家示例的子本体抽取算法,用于从原本体中抽取出专家示例推理相关的子本体,并提出了若干条专家示例推理规则,能推导出专家所编写的代码示例。实验结果证明,从Stack Overflow本体模型中抽取的专家示例能提高API调用序列挖掘的准确率。

Detection of Buffer Overflow Attacks with Memoization-based Rule Set

Different abnormalities are commonly encountered in computer network systems.These types of abnormalities can lead to critical data losses or unauthorized access in the systems.Buffer overflow anomaly is a prominent issue among these abnormalities,posing a serious threat to network security.The primary objective of this study is to identify the potential risks of buffer overflow that can be caused by functions frequently used in the PHP programming language and to provide solutions to minimize these risks.Static code analyzers are used to detect security vulnerabilities,among which SonarQube stands out with its extensive library,flexible customization options,and reliability in the industry.In this context,a customized rule set aimed at automatically detecting buffer overflows has been developed on the SonarQube platform.The memoization optimization technique used while creating the customized rule set enhances the speed and efficiency of the code analysis process.As a result,the code analysis process is not repeatedly run for code snippets that have been analyzed before,significantly reducing processing time and resource utilization.In this study,a memoization-based rule set was utilized to detect critical security vulnerabilities that could lead to buffer overflow in source codes written in the PHP programming language.Thus,the analysis process is not repeatedly run for code snippets that have been analyzed before,leading to a significant reduction in processing time and resource utilization.In a case study conducted to assess the effectiveness of this method,a significant decrease in the source code analysis time was observed.

台山核电厂淡水水源工程水库溢流坝消能试验研究

以台山核电厂淡水水源工程为例,通过水力模型试验研究,推荐溢流坝采用宽尾墩+坝面削角阶梯+底流消力池的联合消能方案。试验结果表明,该方案消能效果较显著、工程量小,优化了溢流坝工程布置和体型。

Experimental study on inner slope failure mechanism of seawall by coupling effect of storm surge and wave

In the context of global climate change,the impact of group-occurring ocean dynamic disasters on China's offshore areas is becoming more and more intense.The study of the effect of existing ocean dynamic disasters on offshore hazard-bearing bodies mostly focuses on the effect of single disaster-causing factors,and it is still insufficient to study storm surge and dynamic wave coupling&reinforcement effects as well as the process of the dynamic response of such hazard-bearing bodies as seawalls.This study firstly realized the synchronous process of water level and wave through continuous tide generation and wave generation by the wave maker and tide generating device,so as to realize the dynamic coupling simulation of storm surge and wave in the laboratory.Then the physical model test of the typical seawall section was carried out under the dynamic coupling of storm surge and wave as well as at a conventional fixed water level respectively.In the process of test wave overtopping discharge and the damage process of the levee crown and backwall of seawalls were observed and compared,and their damage mechanism was also studied.

Numerical Study of Storm Surge Inundation in the Southwestern Hangzhou Bay Region During Typhoon Chan-Hom in 2015

Storm surge inundation is a major concern in marine hazard risk assessment during extreme weather conditions.In this study,a high-resolution coupled model(the ADVanced CIRCulation model+the Simulating WAves Nearshore model)was used to investigate the storm surge inundation in the southwestern Hangzhou Bay region during Typhoon Chan-hom in 2015.The simulated hydrodynamic processes(sea surface wave and storm tide)were validated with measured data from wave buoys and tide gauges,indicating that the overall performance of the model was satisfactory.The storm surge inundation in the coastal area was simulated for several idealized control experiments,including different wave effects(wave-enhanced wind stress,wave-enhanced bottom stress,and wave radiation stress).Dike overflowing cases with different dike heights and dike breaking cases with different dike breach lengths were considered in the simulation.The results highlight the necessity of incorporating wave effects in the accurate simulation of storm surge inundation.Dike height significantly influences the magnitude and phase of the maximum inundation area in the dike overflowing cases,and dike breach length is an important factor impacting the magnitude of the maximum inundation area in the dike breaking cases.This study may serve as a useful reference for accurate coastal inundation simulation and risk assessment.

An improvement to the simulation of phase-change heat-transfer during soil freezing and thawing

A new variable time step method,which is called the backwards calculating time step method,is presented in this paper.It allows numerical simulation of soil freezing and thawing while avoiding "phase change missing and overflowing".A sensitive heat capacity model is introduced through which the calculation errors are analyzed.Then the equation using the self-adjusted time step is presented and solved using finite differences.Through this equation,the time needed for a space cell to reach the phase change point temperature is calculated.Using this time allows the time step to be adjusted so that errors caused by "phase change missing and overflowing" are successfully eliminated.Above all,the obvious features of this method are an accelerated rate for adjusting the time step and simplifing the computations.An actual example proves that this method can accurately calculate the temperature fields during soil freezing and thawing.It is an improvement over traditional methods and can be widely used on complicated multi-dimensional phase change problems.

基于数据挖掘的专业可信回答者个性化推荐——以Stack Overflow问答社区为例

针对问答社区中问题不能得到及时、有效解答的现状,文章以Stack Overflow问答社区为例,首先介绍了问答社区数据的采集与预处理情况;然后,通过挖掘学习者信息,得到专业可信回答者、高信誉回答者和徽章回答者三种潜在回答者;最后,实施了三种回答者推荐并对比了推荐性能。实验结果表明,与高信誉回答者推荐和徽章回答者推荐相比,考虑回答质量和专业相关性的专业可信回答者推荐具有更高的准确率和召回率,其推荐性能更优。实施基于数据挖掘的专业可信回答者个性化推荐,能有效缓解问答社区的信息过载问题,有助于建设更高效的网络学习社区环境。

Numerical simulation of cup hydrodynamic deep drawing

The simulation of hydrodynamic deep drawing by means of FEM is an efficient method that can relieve experimental burden and find the optimum process parameters. Some problems such as mathematical description of cavity liquid flow pressure must be solved firstly. A math formula about hydrodynamic flow pressure that can be applied in general FEM software was proposed, and good results were gained. It was proved that the theoretical results keep coincident with experimental results.[

A New Channel Allocation Scheme for Hierarchical Wireless Networks

A channel allocation scheme for hierarchical wireless networks was proposed in terms of the connection-level quality of service. The channel allocation scheme was analyzed using both horizontal channel borrowing and vertical traffic overflowing. Pre-emptive priority strategies are used to classify real-time services and non-real-time services, real-time service is given higher priority for it is allowed to pre-empt channels used by non-real-time service. Some channel borrowing thresholds and acceptance ratios are used to avoid channel locking or dynamic power control, which can also be dynamically adjusted according to network load. Simulation results show that the proposed schemes can improve the system performance.

Method of integer overflow detection to avoid buffer overflow

A simplified integer overflow detection method based on path relaxation is described for avoiding buffer overflow triggered by integer overflow. When the integer overflow refers to the size of the buffer allocated dynamically, this kind of integer overflow is most likely to trigger buffer overflow. Based on this discovery, through lightly static program analysis, the solution traces the key variables referring to the size of a buffer allocated dynamically and it maintains the upper bound and lower bound of these variables. After the constraint information of these traced variables is inserted into the original program, this method tests the program with test cases through path relaxation, which means that it not only reports the errors revealed by the current runtime value of traced variables contained in the test case, but it also examines the errors possibly occurring under the same execution path with all the possible values of the traced variables. The effectiveness of this method is demonstrated in a case study. Compared with the traditional buffer overflow detection methods, this method reduces the burden of detection and improves efficiency.

Lossless Mapping from Semi-Structured Data to Structured Data

Most semi-structured data are of certain structure regularity. Having beenstored as structured data in relational database (RDB), they can be effectively managed by databasemanagement system (DBMS). Some semi-structured data are difficult to transform due to theirirregular structures. We design an efficient algorithm and data structure for ensuring losslesstransformation. We bring forward an approach of schema extraction through data mining, in whichdifferent kinds of elements are transformed respectively and lossless mapping from semi-structureddata to structured data can be achieved.

Stack Overflow上机器学习相关问题的大规模实证研究

为了调查机器学习相关主题分布和发展趋势,从在线问答网站Stack Overflow上,利用过滤标签,从4 178多万帖子中提取出60 028个与机器学习相关的问题帖.通过分析问题帖,统计各个机器学习平台的讨论量,发现Scikit-learn、TensorFlow、Keras是前3位频繁被讨论的机器学习平台,占总讨论量的58%.为了进一步分析机器学习相关讨论主题,进行潜在狄利克雷分布(LDA)主题模型训练,提出自适应LDA中的主题数渐进搜索方法,采用主题一致性系数评估输出结果,获得主题最佳数量,从而发现9个讨论主题,分属3个类别:代码相关、模型相关、理论相关.基于主题中问题帖的浏览数、评论数,分析不同主题的流行度和回答困难程度.

基于Stack Overflow的数据库相关主题分析

数据库管理系统虽是一种较为成熟的软件系统,但开发人员在应用数据库系统进行数据管理以及数据分析时还是会遇到各种问题,因此会在Stack Overflow之类的问答论坛上寻求解决方法。文中获取了Stack Overflow上94473条与数据库相关的问题,应用LDA主题模型将这些问题归为25个主题,结果显示开发者的问题可归为"表""SQL""SELECT"等主题。通过研究与数据库相关的不同主题的流行度和困难程度发现,"SQL"主题相关的问题较为流行。除此以外,文中还分别研究了3种不同的数据库,即MySQL,Oracle和MongoDB,分析了与不同数据库系统相关的问题的主题分布。文中的研究成果有助于了解数据库开发者所面临的挑战,从而为数据库系统版本更新、数据库课程教学内容的设置,甚至是数据库领域的研究问题提供参考。