The effect of keypad angle of a table keyphone on keying performance

Two keypad angle experiments, one numeral legibility experiment and one button-tapping rate experiment are described. The effects of keypad angle on keyphone positioning, keying time, keying errors and on a keying performance measure are discussed. A geometrical method for estimating optimum keypad angle is introduced.

It is concluded that the optimum angle for a keypad depends on its height above the desk surface. The geometrical method can be used to estimate the best anglein the absence of experimental evidence. For the experimental keyphone (keypad height about 90 mm) the best keypad angle was found to be about 25° to the horizontal, but the effect of a 10° deviation either way from this angle was quite small.     

The effect of a database feedback system on user performance

Abstract

There are two main approaches to improving the effectiveness of database interfaces. One is to raise the level of abstraction for the content of the user-database interaction. The relational model belonging to the logical level has replaced the hierarchical and network models that belong to the lower physical level. It is likely that the relational model will eventually be replaced by models belonging to the even higher conceptual level, such as entity relationship models and object-oriented models. The second approach is to enhance the actual interaction process. This can be done by providing better feedback to the user. Feedback can be in the form of more comprehensible error messages, and the provision of a natural language interpretation of user's query. Such a feedback system was developed, and its effectiveness tested in an experiment. The results showed that the feedback system enhanced user performance greatly. Specifically, users who used the feedback system were 12.9% more accurate than those without the feedback system. They were also 41.2% more confident of their answers, and they took 29.0% less time than those without the feedback system.     

The effect of a database feedback system on user performance

There are two main approaches to improving the effectiveness of database interfaces. One is to raise the level of abstraction for the content of the user-database interaction. The relational model belonging to the logical level has replaced the hierarchical and network models that belong to the lower physical level. It is likely that the relational model will eventually be replaced by models belonging to the even higher conceptual level, such as entity relationship models and object-oriented models. The second approach is to enhance the actual interaction process. This can be done by providing better feedback to the user. Feedback can be in the form of more comprehensible error messages, and the provision of a natural language interpretation of user's query. Such a feedback system was developed, and its effectiveness tested in an experiment. The results showed that the feedback system enhanced user performance greatly. Specifically, users who used the feedback system were 12.9% more accurate than those without the feedback system. They were also 41.2% more confident of their answers, and they took 29.0% less time than those without the feedback system.     

Ergonomic aspects of aircraft keyboard design: the effects of gloves and sensory feedback on keying performance

Increasing requirements for aircraft keyboards have indicated inadequacies in ergonomic standards for airborne environments, in particular for tasks involving unskilled, discontinuous data entry, with emphasis on accuracy rather than speed. Four experiments are reported from a programme of research aimed at the development and application of methodologies for assessing factors relevant to keyboard design. Experiment 1 demonstrated that the effects of various aircrew gloves on a representative aircraft data entry task are highly situation specific. Experiment 2 showed that gloves impaired performance on a high compatibility continuous keying task, with relatively high keying rates, and that this impairment was not reduced by additional auditory feedback. Experiment 3 demonstrated that the high compatibility keying task provided a successful methodology for investigating the effects of key displacement and resistance on speed and accuracy. Experiment 4 indicated the relative contributions of reduced tactility and mobility to the effects on keying and manipulative performance caused by aircrew gloves. Together, these experiments suggest that kinaesthetic and tactile feedback associated with keying are relatively unaffected by aircrew gloves, and that restrictions on mobility caused by gloves may be more important for continuous data entry involving relatively high keying rates     

The effect of feedback on linear multivariable systems

This paper describes effective algebraic procedures for performing certain operations on matrix transfer functions, the most important being the calculation of the effect of feedback. Such operations are required, for example, in designing, sequentially, controllers for linear multivariable systems. Previous papers have described algorithms for performing these operations numerically at specific frequencies to obtain, for example, the closed-loop matrix frequency response, in numerical form. However, if algebraic solutions, which are matrix transfer functions whose elements are rational functions, are required, naive use of standard formulae must be avoided, since they result in rational functions of needlessly high degree. This paper shows how this needless increase in the degree of the rational functions may be avoided, thus yielding effective algebraic procedures for the operations considered. Although the results are of interest in their own right, a brief resume of a specific procedure, the sequential return difference method, for designing linear multivariable control systems which utilises these results, is given.     

The effect of sampling on linear equivalence and feedback linearization

We investigate the effect of sampling on linearization for continuous time systems. It is shown that the discretized system is linearizable by state coordinate change for an open set of sampling times if and only if the continuous time system is linearizable by state coordinate change. Also, it is shown that linearizability via digital feedback imposes highly nongeneric constraints on the structure of the plant, even if this is known to be linearizable with continuous-time feedback. For n = 2, we show, under the assumption of completeness of ad_FG, that if the discretized system is lineariable by state coordinate change and feedback, then the continuous time affine complete analytic system is linearizable by state coordinate change only. Also, we suggest a method of proof when n ≥ 3.     

The impact of online video lecture recordings and automated feedback on student performance

To what extent a blended learning configuration of face-to-face lectures, online on-demand video recordings of the face-to-face lectures and the offering of online quizzes with appropriate feedback has an additional positive impact on the performance of these students compared to the traditional face-to-face course approach? In a between-subjects design in which students were randomly assigned to a group having access to the online lectures including multiple choice quizzes and appropriate feedback or to a group having access to the online lectures only, 474 students (161 men and 313 women) of a course on European Law agreed to participate in the experiment. By using regression analysis we found that the course grade of the students was predicted by their grade point average, their study discipline, their grade goal for the course, the expected difficulty-level of the course, the number of online lectures they viewed, the number of lectures the students attended in person and the interaction between the lectures they viewed online and attended in person. Students who attended few lectures had more benefit from viewing online lectures than students who attended many lectures. In contrast to our expectations, the regression analysis did not show a significant effect of automated feedback on student performance. Offering recordings of face-to-face lectures is an easy extension of a traditional course and is of practical importance, because it enables students who are often absent from the regular face-to-face lectures to be able to improve their course grade by viewing the lectures online.     

移频键控信号测量系统设计

为了提高铁路机车中移频键控信号的测量精度,给出了一种利用FPGA和ARM处理器测量频率的方法。该方法在FPGA中利用量化时钟实时测量一组FSK信号周期长度,并将测量数据存储在FPGA内部设计的双口RAM中。FPGA通过设计的串口模块将测量数据送给ARM处理器,ARM处理器对产生测量误差的主要原因进行分析,并对上、下边频切换时产生的畸变数据进行处理,给出了时间间隔测量误差的分析和补偿方法。实验表明,该系统具有较好的抗扰动能力,能够满足一般工业现场测试速率和精度的要求。     

The best keying protocol for sensor networks

Many sensor networks (especially networks of mobile sensors or networks that are deployed to monitor crisis situations) are deployed in an arbitrary and unplanned fashion. Thus, any sensor in such a network can end up being adjacent to any other sensor in the network. To secure the communications between every pair of adjacent sensors in such a network, each sensor $x$ in the network needs to store $n?1$ symmetric keys that sensor $x$ shares with all the other sensors, where $n$ is an upper bound on the number of sensors in the network. This storage requirement of the keying protocol is rather severe, especially when $n$ is large and the available storage in each sensor is modest. Earlier efforts to redesign this keying protocol and reduce the number of keys to be stored in each sensor have produced protocols that are vulnerable to impersonation, eavesdropping, and collusion attacks. In this paper, we present a fully secure keying protocol where each sensor needs to store $(n+1)/2$ keys, which is much less than the $n?1$ keys that need to be stored in each sensor in the original keying protocol. We also show that in any fully secure keying protocol, each sensor needs to store at least $(n?1)/2$ keys.     

The effect of passive smoking on vigilance performance

The present experiment was designed to test for effects of passive smoking on vigilance performance as well as to determine whether smokers and non-smokers are differentially affected by exposure to passive smoking. Four groups of subjects were used--smokers and non-smokers working in either clean or smoky air--and measures of decision time, movement time, correct detections, d' and beta, were obtained together with ratings of mood. The results show that sensitivity and accuracy of both smokers and non-smokers was detrimentally affected by passive smoking, and that the onset of the effect was earlier for the non-smoking subjects than for the smoking subjects. In addition, passive smoking significantly reduced decision time for the non-smoking subjects although movement time and beta were not significantly affected by exposure to the smoky environment. The findings indicate that both smokers and non-smokers may be adversely affected by passive smoking although effects may not appear until some time has elapsed. Data obtained from the mood scale show that feelings of anger and annoyance are increased by exposure to smoke and it is suggested that these feelings may contribute to the observed performance deficits.     

The effect of passive smoking on vigilance performance

Abstract

The present experiment was designed to test for effects of passive smoking on vigilance performance as well as to determine whether smokers and non-smokers are differentially affected by exposure to passive smoking. Four groups of subjects were used-smokers and non-smokers working in either clean or smoky air-and measures of decision time, movement time, correct detections, d' and β, were obtained together with ratings of mood. The results show that sensitivity and accuracy of both smokers and non-smokers was detrimentally affected by passive smoking, and that the onset of the effect was earlier for the non-smoking subjects than for the smoking subjects. In addition, passive smoking significantly reduced decision time for the non-smoking subjects although movement time and β were not significantly affected by exposure to the smoky environment. The findings indicate that both smokers and non-smokers may be adversely affected by passive smoking although effects may not appear until some time has elapsed. Data obtained from the mood scale show that feelings of anger and annoyance are increased by exposure to smoke and it is suggested that these feelings may contribute to the observed performance deficits.     

The effect of video feedback delay on frustration and emotion communication accuracy

Previous research has demonstrated that for unacquainted dyads and groups interacting over video, feedback delay can interfere with the impression-formation process and increase cognitive load, in turn leading to incorrect interpersonal judgments. In this study, 35 dyads participated in two 10-min conversation periods over video monitors. In one period there was a 1-s delay in the audio/video signal and in the other there was no delay. In period 1 the presence of feedback delay was associated with decreased frustration and increased ability to accurately judge a partner’s emotions. In period 2, however, feedback delay was associated with increased frustration and had no effect on emotion communication accuracy, which was decreased in both conditions by inaccurate assumed similarity. Results supported and expanded the relation-alignment perspective, which states that individuals will consciously attempt to manage their impressions over technological channels, but that they can also be unconsciously influenced by technological distortion.     

The effect of feedback training on lumbosacral compression during simulated occupational lifting

This study measured the effect of a feedback training program on lumbar compression during simulated occupational lifting. Two distinct types of feedback were compared: real-time electromyographic feedback, vs. an acceleration index delivered verbally post-lift. Kinematic data were collected from 28 subjects during symmetrical sagittal plane lifts. Following a baseline session, two feedback training sessions were provided, with a 1-week interval between each session. A control group followed the same protocols, but without receiving feedback training. A post-training session, using protocols identical to the baseline session, was used to assess pre-to-post changes in the dependent variable: peak lumbosacral compression computed using a dynamic linked-segment model. All three groups showed reductions in peak compression from pre-to-post: on average the control group improved by 11.2%, the EMG group by 16.7%, and the acceleration group by 25.3%. The results revealed an interaction between the improvement and the group (p?=?0.023), and a difference between the improvement in the control group and that in the verbal acceleration feedback group (p?<?0.01). These reductions in lumbosacral compression persisted after a 7-day interval without feedback training, suggesting that this approach could provide sustained risk-reduction during manual materials handling.     

The effect of system feedback and decision context on value-based decision-making behavior

Relatively few studies in MIS research have examined systems to support value-based decision-making behavior. The increasing complexity of the decision environment necessitates more reliance on personal values by decision-makers, thus making it an important component to study when considering the design of systems to aid decision-making. This paper describes an exploratory experiment that was conducted to determine how individual value-based decision-making behavior can be influenced by an information system through the use of value specific feedback. It also examines the role of decision context on value-based decisions. The results indicate that value-based decision-making behavior can be influenced and discusses operant theory and reactance theory as useful predictors of decision-maker response to feedback in different decision contexts.     

The effect of feedback training on lumbosacral compression during simulated occupational lifting

This study measured the effect of a feedback training program on lumbar compression during simulated occupational lifting. Two distinct types of feedback were compared: real-time electromyographic feedback, vs. an acceleration index delivered verbally post-lift. Kinematic data were collected from 28 subjects during symmetrical sagittal plane lifts. Following a baseline session, two feedback training sessions were provided, with a 1-week interval between each session. A control group followed the same protocols, but without receiving feedback training. A post-training session, using protocols identical to the baseline session, was used to assess pre-to-post changes in the dependent variable: peak lumbosacral compression computed using a dynamic linked-segment model. All three groups showed reductions in peak compression from pre-to-post: on average the control group improved by 11.2%, the EMG group by 16.7%, and the acceleration group by 25.3%. The results revealed an interaction between the improvement and the group (p=0.023), and a difference between the improvement in the control group and that in the verbal acceleration feedback group (p<0.01). These reductions in lumbosacral compression persisted after a 7-day interval without feedback training, suggesting that this approach could provide sustained risk-reduction during manual materials handling.     

The effects of static and adaptive performance feedback in game-based training

Training in virtual environments (VEs) has the potential to establish mental models and task mastery while providing a safe environment in which to practice. Performance feedback is known to contribute to this learning; however, the most effective ways to provide feedback in VEs have not been established. The present study examined the effects of differing feedback content, focusing on adaptive feedback. Participants learned search procedures during multiple missions in a VE. A control group received only a performance score after each mission. Two groups additionally received either detailed or general feedback after each mission, while two other groups received feedback that adapted based on their performance (either detailed-to-general, or general-to-detailed). Groups that received detailed feedback from the start of training had faster performance improvement than all other groups; however, all feedback groups showed improved performance and by the fourth mission performed at levels above the control group. Results suggest that detailed feedback early in the training cycle is the most beneficial for the fastest learning of new task skills in VEs.     

Robust performance assessment of feedback control systems

The proper measure of closed-loop performance variation in the presence of model-plant mismatch is discussed in this paper. A generalized closed-loop error transfer function, which is a special representation of the dual Youla parameter and has a close relationship with the pointwise ν-gap metric, is proposed as the suitable means of representing closed-loop performance variation in case of plant perturbation, and the closed-loop performance variation measure is accordingly defined as its maximum singular value frequency by frequency. It is shown that this measure is essential and informative in characterizing closed-loop performance variation. This measure is also shown to be readily applicable to on-line closed-loop performance assessment or monitoring, even without the explicit model of the plant. Its variant, defined as the η-function, which features the relative performance variation as well as generalized stability margin variation with respect to the nominal plant, is also discussed.     

The effect of buffering on the performance of R-trees

Past R-tree studies have focused on the number of nodes visited as a metric of query performance. Since database systems usually include a buffering mechanism, we propose that the number of disk accesses is a more realistic measure of performance. We develop a buffer model to analyze the number of disk accesses required for spatial queries using R-trees. The model can be used to evaluate the quality of R-tree update operations, such as various node splitting and tree restructuring policies, as measured by query performance on the resulting tree. We use our model to study the performance of three well-known R-tree loading algorithms. We show that ignoring buffer behavior and using number of nodes accessed as a performance metric can lead to incorrect conclusions, not only quantitatively, but also qualitatively. In addition, we consider the problem of how many levels of the R-tree should be pinned in the buffer     

The effects of feedback on performance and retention of skill for a natural language interface

This study investigated the effectiveness of different types of on-line feedback following user errors for informing users of the information and functions available in a system with a natural language interface. Twenty-four individuals performed a task based on an industry cost savings program, in which they were given general goals to pursue with regard to the task. Three feedback levels which differed according to the type and amount of feedback provided, along with two levels of system complexity, were examined. In addition, subjects performed the task again after one week to determine the effects of feedback on retention. Results indicated that the subjects in the second level of feedback generally performed better with respect to accessing system functions and information than those in the first level. Although there was some performance improvement from the second to third level, it was not significant. However, the third level of feedback did significantly improve the efficiency with which subjects used information to complete the task during the return condition. Overall, feedback did not affect the errors made, though at certain more limited stages of the tasks this effect was observed.     

The effect of handgrip span on isometric exercise performance

Fourteen male and eight female volunteers served as subjects in these experiments lo determine the effect of hand tool dimensions on isometric strength, endurance, the surface EMG above the active muscle, and the cardiovascular responses to isometric exercise. As reported by others, we found that for each individual, there existed one handgrip size at which he or she could exert the greatest isometric strength. Endurance was the same at any work load relative to the maximum strength for a given grip dimension. The EMG and blood pressure responses to isometric exercise were the same at any given grip span: however, the heart rate response was lowest when subjects worked with their muscles at the optimal grip span.