Effects of retained dry material on the impact,overflow and landing dynamics

During long-term operation,the performance of obstacles would be changed due to the material accumulating upslope the obstacle.However,the effects of retained material on impact,overflow and landing dynamics of granular flow have not yet been elucidated.To address this gap,physical flume tests and discrete element simulations are conducted considering a range of normalized deposition height h0/H from 0 to 1,where h0 and H represent the deposition height and obstacle height,respectively.An analytical model is modified to evaluate the flow velocity and flow depth after interacting with the retained materials,which further serve to calculate the peak impact force on the obstacle.Notably,the computed impact forces successfully predict the experimental results when a≥25°.In addition,the results indicate that a higher h0/H leads to a lower dynamic impact force,a greater landing distance L,and a larger landing coefficient Cr,where Cr is the ratio of slope-parallel component of landing velocity to flow velocity just before landing.Compared to the existing overflow model,the measured landing distance L is underestimated by up to 30%,and therefore it is insufficient for obstacle design when there is retained material.Moreover,the recommended Cr in current design practice is found to be nonconservative for estimating the landing velocity of geophysical flow.This study provides insightful scientific basis for designing obstacles with deposition.

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.

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.

RICB： Integer Overflow Vulnerability Dynamic Analysis via Buffer Overflow

Integer overflow vulnerability will cause buffer overflow. The research on the relationship between them will help us to detect integer overflow vulnerability. We present a dynamic analysis methods RICB （Run-time Integer Checking via Buffer overflow）. Our approach includes decompile execute file to assembly language; debug the execute file step into and step out; locate the overflow points and checking buffer overflow caused by integer overflow. We have implemented our approach in three buffer overflow types： format string overflow, stack overflow and heap overflow. Experiments results show that our approach is effective and efficient. We have detected more than 5 known integer overflow vulnerabilities via buffer overflow.

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.

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。

CRITICAL HYDROLOGIC CONDITIONS FOR OVERFLOW BURST OF MORAINE LAKE

Floodwater and debris flow caused by glacial lake burst is an important land process and a serious mountain disaster in glacial area of Xizang (Tibet) Autonomous Region, and the overflow burst is mainly caused by glacial landslide falling into moraine lake. On the premise that moraine lake is full, instantaneous burst in part of the lake bank happens, as flow velocity at burst mouth caused by overflow head is higher than threshold flow velocity of glacial till. Under some supposes, d(90) and d(10) of the glacial till in the hank were used as the threshold sizes of coarse and fine grains respectively. Thus, the formula of calculating threshold flow velocity of uniform sand was simplified, and threshold flow velocity of glacial till was calculated with the formula. Then, with synthesis formula calculating flow velocity of instantaneous part burst, flow velocity at overflow burst mouth was calculated, and calculation formula of critical height (H(0)) of overflow head was derived. Overflow head was caused by volume and surge of glacial landslide falling into moraine lake, calculation formulas of ascendant height (H(1)) of lake water surface and surge height (H(2)) on burst mouth caused by glacial landslide falling into moraine lake were derived. To sum up, critical hydrologic conditions of moraine lake burst with overflow form are: the burst is inevitable as H(1) > H(0); the burst is possible as H(1) < H(0) and (H(1)+H(2)) > H(0); the burst is impossible as (H(1)+H(2)) < H(0). In the factors influencing the burst critical conditions, it is advantageous for the burst that scale of the lake is 10(5)m(2) range; terminal glacial till is more fine and is even more uniform; the width of overflow mouth is even smaller than the length of the bank; the landslide has large scale and steep slip surface; and glacial end is close to the lake. With burst of Guangxiecuo Lake in Midui Valley of the Polongzangbu River in Xizang as an example, the burst critical conditions were tested.

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。

Stack Overflow的缺陷代码特征分析与相似缺陷检测

目前在软件代码缺陷审查以及缺陷预测中,研究人员对源代码进行分析研究却忽略了代码的缺陷信息.本文通过对缺陷信息进行分析,发现缺陷信息对于相似缺陷的检测有着重要的参考价值.基于这一思想,本文分析软件缺陷社区Stack Overflow中关于缺陷代码的信息,提出一种基于缺陷代码特征分析的相似缺陷检测方法.该方法首先对缺陷报告进行LDA主题分析并将缺陷报告分类到不同的主题(类别)中,统计得到高频缺陷类别;其次对于高频缺陷类别的缺陷代码提取特征;最后根据缺陷代码特征构建相似缺陷检测模型.为了验证相似缺陷检测模型的有效性,针对数据操作缺陷数据构建诊断模型并对该模型进行实证,实验结果表明该方法对检测其他代码中相似缺陷有较好的效果.

基于CBOW-LDA主题模型的Stack Overflow编程网站热点主题发现研究

Stack Overflow是一个热门的国外编程问答网站,通过对该网站编程提问帖的问题文本进行文本语义挖掘,能获析用户关注的编程热点。由于研究对象所代表的短文本信息具有高维性及分布不均的特点,易导致主题获取不明晰。文中提出一种基于LDA(Latent Dirichlet Allocation)主题模型的CBOW-LDA建模方法,该方法对目标语料进行相似词聚类后再完成主题建模,能有效降低文本输入维度,使主题分布更明确。采集Stack Overflow网站上2010-2015年的问题帖数据集POST,并对其进行实验,同等主题数下采用文本建模中衡量模型性能的评价指标困惑度(Perplexity)来度量算法在不同数据集容量维度下的性能。结果表明,与现有的基于词频权重的词量化主题建模TFLDA方法相比,CBOW-LDA方法的困惑度更低,在实验语料下的困惑度降低约4.87%,证明了所提算法的性能更好。采用CBOW-LDA方法对Stack Overflow进行热点挖掘,同时使用TF-LDA方法进行对比实验,建立手工标注的标准评测集对两种方法获取的热门主题和热搜词汇进行查全率、查准率及F1值的判定,结果证实CBOW-LDA表现更佳,其热点挖掘效果较好。由实验结果可知,Java为该编程网站提问帖中最热门的主题,而C和Javascript则为该网站用户提问中被提及得最频繁的词汇。

中外技术问答社区的实证对比研究与启示——以CSDN和Stack Overflow为例

社会化问答社区是当前网络用户进行知识交流的重要平台,而技术问答社区则是专注于技术知识交流的问答社区。本文选取国内外最具有代表性的两大技术问答社区进行对比研究,旨在指出国内技术问答社区的优势与不足,并为国内技术问答社区的进一步发展与优化提出针对性建议。本文分别从社区活跃度、社区主题、社区问题质量、用户体验和社交属性5个维度开展了对比分析,并利用相关性分析,分析并比较了在两个问答社区中影响问题被回答情况的相关因素。本文发现两大技术问答社区在活跃度、用户提问与回答情况等方面存在显著差异,并从优化问题质量评价机制、提高用户回答积极性、优化激励机制以及强化社交属性等方面为我国技术问答社区的进一步发展与完善给出了建议。

Stack Overflow系统的特征融合答案推荐策略

针对Stack Overflow系统中用户寻找问题答案效率低的问题,提出一种基于标题相似度、描述相似度、标签相似度、语义相似度的特征融合答案推荐策略(FIARS)。从Stack Overflow网站中抽取“问题与答案”语料集,对答案进行去重处理,建立问题索引和问题对应的答案集索引;采用余弦相似度计算新问题与语料库中问题在标题、标签、问题描述等维度上的相似度,并构建语义模型计算语义相似度;基于这些相似度筛选出最佳的“问题与答案”候选集并把答案推荐给用户。为了验证策略的可行性和有效性,使用Stack Overflow真实数据集进行分析实验,实验结果表明该策略能够较大地提高答案推荐的准确率。

A fresh look at the deepwater overflow in the Luzon Strait

On the basis of the latest version of a U.S. Navy generalized digital environment model （GDEM-V3.0） and World Ocean Atlas （WOA13）, the hydraulic theory is revisited and applied to the Luzon Strait, providing a fresh look at the deepwater overflow there. The result reveals that： （1） the persistent density difference between two sides of the Luzon Strait sustains an all year round deepwater overflow from the western Pacific to the South China Sea （SCS）; （2） the seasonal variability of the deepwater overflow is influenced not only by changes in the density difference between two sides of the Luzon Strait, but also by changes in its upstream layer thickness; （3） the deepwater overflow in the Luzon Strait shows a weak semiannual variability; （4） the seasonal mean circulation pattern in the SCS deep basin does not synchronously respond to the seasonality of the deepwater overflow in the Luzon Strait. Moreover, the deepwater overflow reaches its seasonal maximum in December （based on GDEM-V3.0） or in fall （October-December, based on the WOA13）, accompanied by the lowest temperature of the year on the Pacific side of the Luzon Strait. The seasonal variability of the deepwater overflow is consistent with the existing longest （3.5 a） continuous observation along the major deepwater passage of the Luzon Strait.

Buffer Overflow Detection on Binary Code

Most solutions for detecting buffer overflow are based on source code. But the requirement tor source code is not always practical especially for business software. A new approach was presented to detect statically the potential buffer overflow vulnerabilities in the binary code of software. The binary code was translated into assembly code without the lose of the information of string operation functions. The feature code abstract graph was constructed to generate more accurate constraint statements, and analyze the assembly code using the method of integer range constraint. After getting the elementary report on suspicious code where buffer overflows possibly happen, the control flow sensitive analysis using program dependence graph was done to decrease the rate of false positive. A prototype was implemented which demonstrates the feasibility and efficiency of the new approach.

Influence of two inlets of the Luzon overflow on the deep circulation in the northern South China Sea

An inverse reduced-gravity model is used to simulate the deep South China Sea(SCS)circulation.A set of experiments are conducted using this model to study the influence of the Luzon overflow through the two inlets on the deep circulation in the northern SCS.Model results suggest that the relative contribution of these inlets largely depends on the magnitude of the input transport of the overflow,but the northern inlet is more efficient than the southern inlet in driving the deep circulation in the northern SCS.When all of the Luzon overflow occurs through the northern inlet the deep circulation in the northern SCS is enhanced.Conversely,when all of the Luzon overflow occurs through the southern inlet the circulation in the northern SCS is weakened.A Lagrangian trajectory model is also developed and applied to these cases.The Lagrangian results indicate that the location of the Luzon overflow likely has impacts upon the sediment transport into the northern SCS.

OverflowDungeon:一种新颖的溢出攻击防护系统

溢出攻击是网络上威胁最大的一种攻击方式,现有的防护技术存在不同的缺陷。本文提出并实现了一种新颖的防护机制,它从阻止溢出攻击产生破环性效果入手,抑制攻击行为,该方式不需要修改编译器,或修改操作系统,具有很高的实用性,它采用了统计方式,可有效防护 Dummy return 攻击技术。试验结果表明,系统不仅能有效地阻止溢出攻击,在效率方面相对于其他方式也有显著优势。

Poisson Process and Its Application to the Storm Water Overflows

The homogenous Poisson process is often used to describe the event arrivals. Such Poisson process has been applied in various areas. This study focuses on the arrival pattern of storm water overflows. A set of overflow data was obtained from the storm water pipeline of a municipality. The aim is to verify the overflow arrival pattern and check whether the Poisson process can be applied. The adopted method is the analysis over the inter-arrival times. The exponential distribution test is conducted on the annual data set as well as the entire data set. The results show that all data sets follow the exponential distribution. With the verification of Poisson process, specific examples are also given to show how the Poisson process properties can be used in the management of storm water pipeline management. For other data that are featured with various heterogeneities, the homogenous Poisson process might not be able to be verified and used. Under such circumstances, non-homogenous survival model can be used to simulate the arrival process.

Why do they ask? An exploratory study of crowd discussions about Android application programming interface in stack overflow

Nowadays,more and more Android developers prefer to seek help from Q&A website like Stack Overflow,despite the rich official documentation.Several researches have studied the limitations of the official application programming interface(API)documentations and proposed approaches to improve them.However,few of them digged into the requirements of the third-party developers to study this.In this work,we gain insight into this question from multidimensional perspectives of API developers and API users by a kind of cross-validation.We propose a hybrid approach,which combines manual inspection on artifacts and online survey on corresponding developers,to explore the different focus between these two types of stakeholders.In our work,we manually inspect 1000 posts and receive 319 questionnaires in total.Through the mutual verification of the inspection and survey process,we found that the users are more concerned with the usage of API,while the official documentation mainly provides functional description.Furthermore,we identified 9 flaws of the official documentation and summarized 12 aspects(from the content to the representation)for promotion to improve the official API documentations.