Using Task-Induced Pupil Diameter and Blink Rate to Infer Cognitive Load

Minimizing user cognitive load is suggested as an integral part of human-centered design, where a more intuitive, easy to learn, and adaptive interface is desired. In this context, it is difficult to develop optimal strategies to improve the design without first knowing how user cognitive load fluctuates during interaction. In this study, we investigate how cognitive load measurement is affected by different task types from the perspective of the load theory of attention, using pupil diameter and blink measures. We induced five levels of cognitive load during low and high perceptual load tasks and found that although pupil diameter showed significant effects on cognitive load when the perceptual load was low, neither blink rate nor pupil diameter showed significant effects on cognitive load when the perceptual load was high. The results indicate that pupil diameter can index cognitive load only in the situation of low perceptual load and are the first to provide empirical support for the cognitive control aspect of the load theory of attention, in the context of cognitive load measurement. Meanwhile, blink is a better indicator of perceptual load than cognitive load. This study also implies that perceptual load should be considered in cognitive load measurement using pupil diameter and blink measures. Automatic detection of the type and level of load in this manner helps pave the way for better reasoning about user internal processes for human-centered interface design.     

基于有限元的太阳翼驱动机构结构强度分析验证

为研究空间驱动机构在力学和热学环境下的结构强度,提出一种强度分析验证方法。以太阳翼驱动机构为例,在随机振动载荷和热载荷作用下,研究机构强度设计是否满足要求。利用HyperWorks和Abaqus构建有限元模型,借助振动扫频试验数据完成模型的有效性验证,开展随机振动分析和热学分析,并对分析结果进行合理性判断。结果表明：应力强度最大值均在安全设计裕度内,太阳翼驱动机构结构强度满足设计要求。该验证方法可有效指导产品设计、降低研制费用和缩短研制周期。     

Bolt–plate contact assemblies with prestress and external loads: Solved with super element technique

In dynamically loaded bolted assemblies fatigue is the designing factor. The primary quantity that controls the fatigue is the part of the external load that is transferred to the bolt, as described by the ratio between transferred load to external load. In an idealized setting this ratio can be expressed by a stiffness ratio between the plate members and the bolt. The ratio of transferred load is, however, highly dependent on the size and position of the external loading.The bolt–plate/member connection is modelled using the finite element technique. The modelling includes contact between bolt and members and between the clamped member plates. The modelling includes the prestress that is described by a single scalar value. This prestressed state is followed by an arbitrary external load case.In this paper a finite element technique with super elements is applied to solve the contact problem of the combined prestress and external load in an overall non-iterative way. The conclusions are that it is difficult to make general design rules but in most cases the standard calculation methods will underestimate the strength of the connections. However for some specific loading situations this might not be the case.     

Effects of automation and task load on task switching during human supervision of multiple semi-autonomous robots in a dynamic environment

The present study assessed the impact of task load and level of automation (LOA) on task switching in participants supervising a team of four or eight semi-autonomous robots in a simulated ‘capture the flag’ game. Participants were faster to perform the same task than when they chose to switch between different task actions. They also took longer to switch between different tasks when supervising the robots at a high compared to a low LOA. Task load, as manipulated by the number of robots to be supervised, did not influence switch costs. The results suggest that the design of future unmanned vehicle (UV) systems should take into account not simply how many UVs an operator can supervise, but also the impact of LOA and task operations on task switching during supervision of multiple UVs.

The findings of this study are relevant for the ergonomics practice of UV systems. This research extends the cognitive theory of task switching to inform the design of UV systems and results show that switching between UVs is an important factor to consider.     

Web系统负载测试的实现

本文结合作者工作中参与的测试项目,对Web系统的负载测试进行研究;根据软件测试理论和负载测试原理,采用负载测试工具HP LoadRunner对Web系统进行负载测试;通过分析被测系统的测试需求,设计相应的测试案例.文中引入了自动化测试流程,采用专业的负载测试工具,描述整个Web系统的负载测试设计与测试实施过程.     

From Cognitive Load Theory to Collaborative Cognitive Load Theory

Cognitive load theory has traditionally been associated with individual learning. Based on evolutionary educational psychology and our knowledge of human cognition, particularly the relations between working memory and long-term memory, the theory has been used to generate a variety of instructional effects. Though these instructional effects also influence the efficiency and effectiveness of collaborative learning, be it computer supported or face-to-face, they are often not considered either when designing collaborative learning situations/environments or researching collaborative learning. One reason for this omission is that cognitive load theory has only sporadically concerned itself with certain particulars of collaborative learning such as the concept of a collective working memory when collaborating along with issues associated with transactive activities and their concomitant costs which are inherent to collaboration. We illustrate how and why cognitive load theory, by adding these concepts, can throw light on collaborative learning and generate principles specific to the design and study of collaborative learning.     

人字齿轮啮合刚度计算与齿面载荷分布研究

为了精确地进行人字齿轮的强度计算和动态特性分析,首先建立了渐开线真实齿廓的人字齿轮三维模型,提出了一种基于有限元方法和齿轮啮合原理的准确计算人字齿轮啮合刚度和齿面载荷分布的有效方法.方法利用有限元方法计算齿面柔度系数,考虑了齿轮的动态啮合过程.运用该方法计算了一对人字齿轮模型,最后分析了斜齿轮和人字齿轮啮合刚度的关系,得出了斜齿轮和人字齿轮啮合刚度近似相等的结论,为后续的动力学分析提供了准确的刚度激励.     

基于多信道无线传输的旋翼载荷测试技术研究

直升机旋翼系统载荷和强度飞行试验是对真实大气环境中旋翼系统应力载荷谱的研究,它提供的真实数据是理论计算所不能提供的;因此旋翼系统载荷试飞是直升机设计定型试飞中极其重要的项目;针对直升机旋翼系统载荷测试技术需求,采用模块化、冗余度和高集成的设计理念,通过多信道无线传输设计等技术,将采集的动态载荷数据调制、发射与解调,实现了多通道、高带宽和精同步的旋翼系统载荷数据采集与监控;该技术对于直升机旋翼系统载荷试飞中遇到的类似问题具有一定的借鉴意义。     

Optimum design with imperfection sensitivity coefficients for limit point loads

A computational method is presented for finding a sequence of optimum designs of a discrete system which exhibits limit point behaviour. Optimality conditions are derived in terms of the theory of imperfection sensitivity coefficients for the limit point load factor. Only those designs of the structures which exhibit limit point behaviour are considered as feasible designs, and the design change is conceived as generating a kind of imperfection. The efficiency of the proposed algorithm will be appreciated particularly for large structures, because incremental nonlinear analysis to find the limit point load factor needs to be carried out only once for the structure of trivial initial optimum design. The sequence of optimum designs is described by piecewise Taylor series expansions with respect to the specified limit point load factor. It is shown in the examples that the proposed method is efficient and of good accuracy for a large space truss.     

Limit load and shakedown analysis of plastic structures under stochastic uncertainty

Problems from plastic analysis are based on the convex, linear or linearised yield/strength condition and the linear equilibrium equation for the stress (state) vector. In practice one has to take into account stochastic variations of several model parameters. Hence, in order to get robust maximum load factors, the structural analysis problem with random parameters must be replaced by an appropriate deterministic substitute problem. A direct approach is proposed based on the primary costs for missing carrying capacity and the recourse costs (e.g. costs for repair, compensation for weakness within the structure, damage, failure, etc.). Based on the mechanical survival conditions of plasticity theory, a quadratic error/loss criterion is developed. The minimum recourse costs can be determined then by solving an optimisation problem having a quadratic objective function and linear constraints. For each vector a(·) of model parameters and each design vector x, one obtains then an explicit representation of the “best” internal load distribution F^∗. Moreover, also the expected recourse costs can be determined explicitly. Consequently, an explicit stochastic nonlinear program results for finding a robust maximal load factor μ^∗. The analytical properties and possible solution procedures are discussed.     

无人机集群编队自组网可靠性评估

针对无人机集群编队自组网的可靠性评估问题,考虑无人机集群编队在执行任务时对信息交互的时效性需求,提出一种自组网可靠性评估方案.首先,分析消息传输的可用时间;其次,通过排队论建立消息传输延迟模型以计算消息传输所需时间;然后,以消息传输所需时间小于可用时间的概率作为评估指标建立消息传输可靠性计算模型,进而为无人机集群编队提供一个动态可靠性评估框架以适应集群编队体系配置和环境变化的随机性与时变特性;最后,仿真分析在不同传输任务需求下,编队构型、无人机数量、编队缩放因子、传输速率、信息交互强度以及环境干扰对消息传输可靠性的影响.仿真结果可以为集群编队的队形设计以及集群编队的体系配置提供一定参考依据.     

依赖关系模型的建立及应用

依赖关系是项目系统中广泛存在的一种关系，通过建立依赖关系模型，可以提高系统效率。利用线性代数知识以及多线程等软件知识，建立依赖关系模型。并通过细化系统任务，降低事件之间的依赖性，增加任务量，提高资源利用率等方法，可以提高系统效率。依赖关系模型特别是在仪器开发领域具有广阔的应用前景。     

高速列车车体数值模拟和优化设计

针对高速列车车体的强度和疲劳损伤问题,对高速动车组车体结构进行有限元分析和强度校核.结果表明,头车和中间车的最大应力均发生在车钩载荷施加附近的极小区域内,且应力值大于许用应力值,此处结构可能产生局部破坏,在车体试验时需要重点关注.为增强车钩强度,采用灵敏度分析方法优化头车车钩载荷施加区域、更改圆孔弧度,在很大程度上降低局部应力峰值,优化设计后的车体满足强度要求.     

产品性能因素描述构架的建立

产品性能作为产品设计的核心，贯穿产品设计的整个过程，抓住产品设计的共性，无疑是产品设计的关键。采用知识工程中的因素空间理论作为理论支撑，基于三层调和功能基础的统一功能分类表达，构建了以统一功能表达分类为维名称的产品性能因素描述构架，并对此构架空间的属性进行了理论分析。为了更好地理解构架空间的概念，描述了具体产品按照性能因素纳入构架空间的5个主要步骤。产品性能因素描述构架的建立，不仅使产品在性能级抽象层次上获得了表面的空间，更重要的是它为产品性能的量化提供了坐标参考，也为分布式资源环境下基于性能驱动的产品检索提供了知识获取依据，从而使CAD技术有望在性能驱动的产品概念设计阶段得到应用。     

基于粗糙集理论的面向个性化知识发现算法

在基于粗糙集理论的数据处理与决策分析的基础上,从实际应用的角度出发,提出了面向个性化知识发现的启发式算法。从理论上证明了算法的正确性,给出了面向个性化的知识获取算法的描述,分析了算法的性能。算法的关键在于规则合成的方法和可信度、覆盖度和规则强度计算的方法。通过例子说明了算法的有效性和实用性。     

以项目为中心的设计课程管理

以项目为中心的课程可以让设计专业的学生建立起自己的知识结构,有效的提高学生的设计技能。此类课程的管理有两个关键因素;一个是围绕着项目进行课堂教学环节设计,可以使用案例分析、以项目为中心的教学进程、客座教师指导等模式;另一个是有效的课程项目的管理,方法有项目进程的互动式管理、加强学生团队管理等。     

Stability and load-carrying capacity of three-dimensional long-span steel arch bridges

The behavior of several models of three-dimensional long-span steel arch bridges is investigated for evaluating the effects of various design parameters on both the strength and stability of these special structures. The major concerns in the design of a long-span steel arch bridge, from the structural safety point of view, are the yield and buckling failures. Different design parameters may affect the failure load for either type of failure in various ways. This study investigates how changes in certain design parameters would affect the behavior of steel arch bridges, which could lead to an optimum design of this type of bridge structures. The effects of the plate girder stiffness and arch bracing stiffness as well as the rise-to-span ratio and inclination of the arches towards each other are examined in this study. Both critical buckling load and the load-carrying capacity of each design alternative are investigated using the finite element method. All design alternatives are based on the latest AASHTO code for highway bridge design. It is concluded from this study that the inclined arch bridge using the maximum practical rise-to-span ratio (which is about 0.25) is the most favorable design. In addition, the increase in the stiffness of the plate girder does not reduce the bending moments in the arch ribs. However, providing a lateral bracing system with sufficient stiffness greatly reduces the out-of-plane bending moments and increases the load-carrying capacity and the critical buckling load of a long-span arch bridge.     

Effect of load/unload process on friction/stiction and durability of head-disk interface

 Effect of various operating parameters viz. load/unload speed, disk speed, ramp height, and disk dynamics on load/unload performance, friction/stiction and durability of a head-disk interface (HDI) were studied. Load/unload performance was evaluated using acoustic emission signals and friction force measurements. The load/unload performance was found to be better for higher load/unload durations, lower disk speeds and higher ramp heights. The effect of ramp height was studied for two different slider suspension designs. A slider suspension with `A' type suspension design performed well for higher ramp heights. The slider with `B' suspension design was not affected by a change in ramp height. Disk dynamics studies indicated how strongly HDI can be affected by disk vibrations and supported the effect seen by varying ramp heights. Durability tests revealed that the HDI deteriorated faster for lower ramp heights for a slider with `A' type suspension design than for the slider with `B' type suspension design. Received: 22 February 2002/Accepted: 20 June 2002     

兆瓦级风力发电机组轮毂强度数值分析

基于GL规范,采用有限元法对某兆瓦级风力发电机组轮毂进行极限强度分析.对轮毂S N曲线进行修正,分析疲劳计算需要考虑的载荷工况,使用GH Bladed软件仿真得到疲劳计算所需的载荷时间序列.使用ANSYS/nCode软件对轮毂进行疲劳寿命分析,结果表明轮毂的极限强度和疲劳强度均满足设计规范的要求.分析结果可以为兆瓦级风力发电机组轮毂的结构设计提供参考.     

材料非线性对钢筋混凝土高墩稳定性的影响

由于采用传统的以弹性理论为基础的设计计算方法求算高墩的内力和变形会引起较大偏差,因此考虑箍筋对核芯混凝土强度的提高作用,使用ANSYS软件分析高墩的稳定性.选用MAN-DER本构模型模拟约束混凝土的应力-应变关系,对墩高、约束指标及混凝土强度3个敏感参数进行分析,得出非线性钢筋混凝土本构关系对高墩承载力的影响规律.结果表明,考虑箍筋对混凝土的约束作用后,高墩的承载力最大可提高约50%.