Measuring the risk of sustaining injury in sport a novel approach to aid the re-design of personal protective equipment

Despite the possibilities offered by new approaches in design and advances in materials and manufacturing methods, few items of Personal Protective Equipment (PPE) used in sport have seen significant change for many decades. A major reason for this is the tradition and conservative attitudes associated with many sports, although the absence of appropriate tools and techniques to assist the design and development process has also played a large part. The aim of this study was to develop the first stage of a method of identifying specific regions of the human anatomy that are at the greatest risk of sustaining injury during participation in sports in which the player is subjected to multiple ballistic impacts. It is proposed that the findings could be used to confirm future designs of sports PPE. Previous studies have identified the amount and the location of the protection provided by current commercially available products but, until now, no evidence has been reported to determine what protection is required based on an understanding of the likely impact and the anatomy of the athlete.     

Patterns as a paradigm for theory in community-based learning

Learning about information technology is typically not a first-order goal for community-based volunteer organizations. Nonetheless, information technology is vital to such groups for member recruiting and management, communication and visibility to the community, and for primary group activities. During the past 12 years, we have worked with community groups in Centre County, Pennsylvania, and Montgomery County, Virginia. We have built partnerships with these groups to better understand and address their learning challenges with respect to information technology. In this paper, we suggest that patterns, standard solution schemata for recurring problems (as used in architecture and software engineering, among other design domains), can be a paradigm for codifying and developing an understanding of learning in and by community organizations. Patterns are middle-level abstractions; they capture regularities of practices in ways that are potentially intelligible, verifiable, and perhaps useful to the practitioners themselves. We present two example patterns and discuss issues and directions for developing patterns as a theoretical foundation for community-based learning.     

可编程控制器逻辑控制类程序经验法编程思路的探讨

从梯形图的基本结构及计算机程序表达的基本特征出发,介绍了可编程控制器“经验法”编程的思维方法及编程步骤,给出了示例程序。     

Relatively quantified constraint satisfaction

The constraint satisfaction problem (CSP) is a convenient framework for modelling search problems; the CSP involves deciding, given a set of constraints on variables, whether or not there is an assignment to the variables satisfying all of the constraints. This paper is concerned with the more general framework of quantified constraint satisfaction, in which variables can be quantified both universally and existentially. We study the relatively quantified constraint satisfaction problem (RQCSP), in which the values for each individual variable can be arbitrarily restricted. We give a complete complexity classification of the cases of the RQCSP where the types of constraints that may appear are specified by a constraint language.     

Shape sensitivity analysis and design studies for CAD flume sections

This paper presents shape design sensitivity analysis (DSA) and design studies for recreational waterslides represented in computer-aided design (CAD) environment. The mathematical representations of a number of commonly used flume sections that serve as the building blocks for waterslide configurations are created in CAD tools. Geometric dimensions of the individual sections that affect not only their geometric shape but also the overall configurations are identified as design variables. These design variables can be varied to search for better design alternatives, for example, safer waterslides. A set of coupled differential equations based on Lagrange’s equations of motion that describe the motion of the riding object are derived. The equations of motion incorporate friction forces between the riding object and the surface of the flume sections. These second-order differential equations are then solved using Mathematica. Based on the equations of motion and design variables identified, a set of differential equations are derived for calculating shape DSA coefficients. These equations are solved numerically again using Mathematica. The major contribution of the paper are (1) extending waterslide design parameterization and shape DSA computation to true CAD-based flume sections, which greatly alleviates the design for manufacturing issues previously encountered, (2) incorporating friction forces into shape DSA computation, and (3) developing a design scenario that includes sensitivity display and what-if studies for a compromised design that is safer and with a larger acceleration, therefore, higher excitement levels. Incorporating friction forces into the computation supports design for rider’s excitement levels, which are related to accelerations. Waterslide design will not be realistic without including friction forces.     

Designing information artefacts for knowledge workers

This paper describes the characteristics of technology to support the knowledge worker through an analysis of the model of knowledge which they embody. The disparity between this model and the post-industrial model of knowledge, coupled with examples of technologies that are designed more sympathetically towards the post-industrial model, provides insights that motivate a design approach explicity focused on addressing the requirements and circumstances of the knowledge worker.     

Mediating roles of self-presentation desire in online game community commitment and trust behavior of Massive Multiplayer Online Role-Playing Games

Massive Multiplayer Online Role-Playing Games (MMORPGs), which allow simultaneous participation of several gamers, have attracted a great deal of attention recently. Since MMORPGs can be categorized as a type of online community, the behavior of MMORPGs users needs to be considered as the general behavior in online communities. However, previous studies of online communities did not pay enough attention to MMORPGs, in which users can express themselves by interacting actively through games and game avatars. Understanding the characteristics of MMORPGs as online game communities where users communicate and interact will allow games to be vitalized and users to be immersed in games in a more positive way. Hence, using self-presentation theory and social identity theory, this study examined the factors influencing self-presentation desire and the mediating role of self-presentation desire examined in terms of trust of and commitments to online game communities. The results showed that the interactivity in the spaces of MMORPGs had the biggest impacts on self-presentation desire; personal innovativeness and game design quality also was influential. The results also indicated that self-presentation desire caused trust of online games and eventually led to even stronger commitments to gamers.     

Encouraging serendipity in research: Designing technologies to support connection-making

Mobile applications have the ability to present information to users that is influenced by their surroundings, activities and interests. Such applications have the potential to influence the likelihood of individuals experiencing ‘serendipity’, through a combination of information, context, insight and activity. This study reports the deployment of a system that sends push text suggestions to users throughout the day, where the content of those messages is informed by users’ experience and interests. We investigated the responses to and interactions with messages that varied in format and relevance, and which were received at different times throughout the day. Sixteen participants were asked to use a mobile diary application to record their experiences and thoughts regarding information that was received over a period of five consecutive days. Results suggest that participants’ perception of the received suggestions was influenced by the relevance of the suggestion to their interests, but that there were also positive attitudes towards seemingly irrelevant information. Qualitative data indicates that participants, if in an appropriate time and place, are willing to accept and act upon push suggestions as long as the number of suggestions that they receive is not overwhelming. This study contributes towards an understanding of how mobile users make connections with new information, furthering our understanding of how serendipitous connections and insightful thinking could be accommodated using technology.     

Low-level dichotomy for quantified constraint satisfaction problems

Building on a result of Larose and Tesson for constraint satisfaction problems (CSPs), we uncover a dichotomy for the quantified constraint satisfaction problem QCSP(B), where B is a finite structure that is a core. Specifically, such problems are either in ALogtime or are L-hard. This involves demonstrating that if CSP(B) is first-order expressible, and B is a core, then QCSP(B) is in ALogtime.We show that the class of B such that CSP(B) is first-order expressible (indeed trivial) is a microcosm for all QCSPs. Specifically, for any B there exists a C — generally not a core — such that CSP(C) is trivial, yet QCSP(B) and QCSP(C) are equivalent under logspace reductions.     

Value ordering for quantified CSPs

We investigate the use of value ordering in backtracking search for Quantified Constraint Satisfaction problems (QCSPs). We consider two approaches for ordering heuristics. The first approach is solution-focused and is inspired by adversarial search: on existential variables we prefer values that maximise the chances of leading to a solution, while on universal variables we prefer values that minimise those chances. The second approach is verification-focused, where we prefer values that are easier to verify whether or not they lead to a solution. In particular, we give instantiations of this approach using QCSP-Solve’s pure-value rule Gent et al. (QCSP-solve: A solver for quantified constraint satisfaction problems. In Proceedings of IJCAI, pp. 138–143, 2005). We show that on dense 3-block problems, using QCSP-Solve, the solution-focused adversarial heuristics are up to 50% faster than lexicographic ordering, while on sparse loose interleaved problems, the verification-focused pure-value heuristics are up to 50% faster. Both types are up to 50% faster on dense interleaved problems, with one pure-value heuristic approaching an order of magnitude improvement. This work was supported in part by Microsoft Research through the European PhD Scholarship Programme, and by the Embark Initiative of the Irish Research Council for Science, Engineering and Technology (IRCSET).     

Bounded-width QBF is PSPACE-complete

Tree-width and path-width are two well-studied parameters of structures that measure their similarity to a tree and a path, respectively. We show that QBF on instances with constant path-width, and hence constant tree-width, remains PSPACE-complete. This answers a question by Vardi. We also show that on instances with constant path-width and a very slow-growing number of quantifier alternations (roughly inverse-Ackermann many in the number of variables), the problem remains NP-hard. Additionally, we introduce a family of formulas with bounded tree-width that do have short refutations in Q-resolution, the natural generalization of resolution for quantified Boolean formulas.     

A Replicated Empirical Study of the Impact of the Methods in the PSP on Individual Engineers

The Personal Software Process (PSP) has during the last couple ofyears gained attention as a way to individual improvements insoftware development. The PSP is introduced to students and engineersthrough a course, which introduces a personal software developmentprocess. The personal software development process is improvedin steps during the course and a collection of methods is introducedto support the personal development process. The question is,however, how do these methods influence the performance of anindividual engineer? This question has been studied in a studymade at the Software Engineering Institute, and the study hasshown that the methods in the PSP have a positive effect on theperformance of the individuals. There is however a need to replicatethis study to confirm the findings in other settings and withother individuals. This paper describes a replicationof the study made at the Software Engineering Institute. Boththe original study and this replication are made on data reportedfrom the students taking the PSP course. The differences betweenthe two studies are the programming languages used, which heldthe courses, the class sizes, and the experiences of the students.In summary, the results from this replication confirm the resultsin the original study: Size estimation accuracy gets better,the defect density gets lower, the defects are found earlierand that the pre-compile yield gets better during the PSP course.Basically, the two studies show that the methods in the PSP helpengineers to improve their performance.     

数字信号量化处理极值方法解析

信号非均匀量化最优化处理过程,是解析数字信号最大信噪比的关键,本文根据数字信号量化具体约束条件要求,利用线性空间泛函极值、变分等方法验证其求解过程。