Critique of "distance estimation with night vision goggles: a little feedback goes a long way"

The authors addressed a topic that has practical importance and that deserves further study. They raised interesting questions about distance estimates, and extended results obtained with unaided vision to performance with NVGs. In this critique, several issues were raised in an attempt to foster an informative scholarly exchange.     

Guidelines for distance education: a case study in Taiwan

Abstract  Through a questionnaire survey and in-depth interviews with the teachers, students and staff involved, this paper presents a case study which describes the current status of telecommunications distance education via real-time interactive videoconferencing in Taiwan. Participants' views were analysed and showed that instructional development components, such as learner characteristics, instructional resources, support services and rehearsal, are quite different from the traditional mode especially with regard to neglected factors such as educational administration and policy. The paper summarises the findings as an itemised list of guidelines for operating instructional development for a telecommunications distance education. These guidelines can contribute not only to improving the quality of distance education, but also to faculty development, staff training, elaboration of theory and professional practice in the field.     

On feedback identification of unknown characteristics: a bioreactor case study

The problem of dynamical identification of unknown characteristics (states/parameters) in a biochemical model of a fed-batch bioreactor system given observations of some states is considered. An algorithm that solves this simultaneous state and parameter estimation problem and that is stable with respect to bounded informational noises and computational errors is presented. The algorithm is based on the principle of auxiliary models with adaptive controls. Convergence of the algorithm is proven and a convergence rate is derived. The performance of the algorithm is illustrated to a typical single-species bioreactor example.     

Adaptive feedback generation to support teachers in web-based distance education

This work examines the application of user-adapted technologies to address problems experienced in web-based distance education. We have proposed an approach to support distance learning instructors by offering advice that points at problems faced by students and suggests possible activities to address these problems. The paper describes an original feedback generation framework which utilises student, group and class models derived from tracking data in web course management systems, and follows a taxonomy of feedback categories to recognise situations that are brought to the instructors’ attention. The results of an empirical study in an online learning course point at benefits of the generated feedback to both instructors and students. Teachers can get a better understanding of their students by knowing what problems they may be facing, when they are behind or ahead of their peers, who can help them and how, and what roles can be assigned in discussion forums. This, in turn, can have a positive effect on students who can receive feedback tailored to their needs and problems. The evaluation study points at issues that can be related in general to planning empirical evaluations of user-adapted systems in realistic web-based learning settings.     

Optimal periodic output feedback control: a continuous-time approach and a case study

This article deals with the problem of optimal static output feedback control of linear periodic systems in continuous time, for which a continuous-time approach, which allows to deal with both stable and unstable open loop systems, is presented. The proposed approach is tested on the problem of designing attitude control laws for a Low-Earth Orbit (LEO) satellite on the basis of feedback from a triaxial magnetometer and a set of high-precision gyros. Simulation results are used to demonstrate the feasibility of the proposed strategy and to evaluate its performance.     

Skeleton-guided 3D shape distance field metamorphosis

We introduce an automatic 3D shape morphing method without the need of manually placing anchor correspondence points. Given a source and a target shape, we extract their skeletons and automatically estimate the meaningful anchor points based on their skeleton node correspondences. Based on the anchors, dense correspondences between the interior of source and target shape can be established using earth mover’s distance (EMD) optimization. Skeleton node correspondence, estimated with a voting-based method, leads to part correspondence which can be used to confine the dense correspondence within matched part pairs. This produces smooth and plausible morphing sequence based on distance field interpolation (DFI). We demonstrate the effectiveness of our algorithm over shapes with large geometric variation and structural difference.     

Constrained distance based clustering for time-series: a comparative and experimental study

Constrained clustering is becoming an increasingly popular approach in data mining. It offers a balance between the complexity of producing a formal definition of thematic classes—required by supervised methods—and unsupervised approaches, which ignore expert knowledge and intuition. Nevertheless, the application of constrained clustering to time-series analysis is relatively unknown. This is partly due to the unsuitability of the Euclidean distance metric, which is typically used in data mining, to time-series data. This article addresses this divide by presenting an exhaustive review of constrained clustering algorithms and by modifying publicly available implementations to use a more appropriate distance measure—dynamic time warping. It presents a comparative study, in which their performance is evaluated when applied to time-series. It is found that k-means based algorithms become computationally expensive and unstable under these modifications. Spectral approaches are easily applied and offer state-of-the-art performance, whereas declarative approaches are also easily applied and guarantee constraint satisfaction. An analysis of the results raises several influencing factors to an algorithm’s performance when constraints are introduced.     

Nonlinear feedback control of flexible joint manipulators: a singlelink case study

A nonlinear feedback control for a flexible joint manipulator is investigated. It is shown that if the elastic (parasitic) modes are weakly observable from the output of the system, a state-space coordinate transformation and a static state feedback and control space transformation will turn the flexible system into a linear controllable and observable system. In contrast, if the parasitics are strongly observable, a dynamic state feedback is required for input-output linearization. Numerical simulations for a single link flexible joint manipulator are reported, illustrating the application of the methodology     

The effect of a feedback signal in a computer mouse on hovering behaviour, productivity, comfort and usability in a field study

The aim of this study was to determine the effect of a tactile feedback signal on hovering behaviour, productivity, usability and comfort after 1 week of using an experimental mouse. In a randomized controlled trial, a regular computer mouse was compared to a new developed mouse with a tactile, vibrating feedback signal to prevent unnecessary hovering above the computer mouse. According to this study, participants do decrease their hovering behaviour when using a mouse with tactile feedback. Furthermore, the mouse with tactile feedback did not influence productivity. Usability was rated somewhat mixed. The use of a mouse with a tactile vibrating feedback signal seems promising for preventing neck, shoulder and arm complaints. Further research is needed to study long-term effects on (prevention of) neck, shoulder and arm complaints and development of learning effects.     

CAVE and HMD: distance perception comparative study

Virtual Reality - This paper proposes to analyse user experience using two different immersive device categories: a cave automatic virtual environment (CAVE) and a head-mounted display (HMD). While...     

Remote ultrasound using cooperative video: a field study

In this ultrasound field study, patients were examined by a technologist in a separate room from the radiologist. Two-way audio and the NTSC video signal from the ultrasound probe were provided to the remote radiologist. Data were collected using observation, surveys, and interviews. Of particular interest was how often the radiologists felt it clinically necessary to walk to the examination room and interact directly with the patient, indicating a failure of the technology. The system was judged viable with no cases requiring hands-on viewing during the last 3 weeks of the 5- week study. Based on this experience, such video technology has been purchased and is currently in use in the clinic. Similar pilot studies are recommended during introduction of remote consultation facilities to improve technology interaction, develop new organizational procedures, and insure minimal interpersonal conflicts.     

Robust constrained predictive feedback linearization controller in a solar desalination plant collector field

This paper proposes a feedback linearization strategy for a solar collector field, which is a constrained non-linear processes. The benefits of input–output feedback linearization are improved by a filtered Smith predictor-based model predictive control algorithm with embedded variable constraint mapping to take advantage of: (i) linear control without losing the intrinsic non-linearities typical of thermal power plants; (ii) including input amplitude constraint handling capabilities due to control signal saturations induced, for example, by strong irradiance disturbances or plant start-up; and (iii) avoiding unstable or highly oscillatory responses caused by plant-model mismatch. Simulation studies are first presented to analyze robustness and constraint-mapping features, and real experimental tests of this technique in the AQUASOL desalination plant solar field have been included to demonstrate the advantages of its implementation, especially for reference tracking despite disturbances.     

Firefighter learning at a distance – a longitudinal study

This article presents a summary analysis of a 5‐year study on the implementation of a technology‐supported distance firefighter training programme in Sweden, focused on the firefighter students' learning processes regarding challenges, contradictions and changes that occurred during the implementation period. With activity theory as the theoretical basis, three data collections were carried out. The analysis, based on interviews with firefighter students and instructors as well as observation logbooks and educational documents, identified two phases, an implementation phase and a dissemination phase. The implementation phase is characterized by the distance students developing a self‐directed and goal‐oriented learning, supported by the revised and technology‐supported training design. During the dissemination phase, when many technology‐inexperienced instructors become involved in the distance programme, a number of challenges and contradictions are identified, which, however, turn out to be a driving force for the students to develop alternative learning strategies. Finally, vocational distance training is discussed in terms of potential opportunities for developing vocational students' learning processes.     

基于差异距离反馈的多执行体裁决算法与调度算法

针对现有多执行体裁决算法和调度算法主要将执行体受攻击的次数作为可信度的参考依据,难以区分每次攻击行为的恶意程度,也难以应对执行体输出为数值且允许存在误差的应用场景的问题,以电力系统状态估计异常检测作为应用场景,提出根据归一化的执行体输出差异距离调整其可信度的裁决算法,以及基于运行时长、可信度和切换开销等构造收益函数的调度算法。仿真实验结果表明,相比同等权重的裁决算法和随机切换的调度算法,所提算法在系统执行开销基本相同的情况下,可以将系统平均失效率降低43.8%,能够有效地提升工业网络防护设备的防御能力。     

Crossing the line: a field study of inhabited television

This paper reports on an ethnographic field study of 'Out Of This World' (OOTW, Benford et al. 1999) an experiment in 'inhabited television' combining broadcast technologies with a collaborative virtual environment in a live show. The study focuses on the work of producing OOTW and how personnel managed the manifold contingencies of working with complex technology. The use of a specially developed virtual camera control application is discussed together with the methods the director used for live editing views from cameras into a 'broadcast from virtual reality'. The challenges faced by the multiple professions involved (TV personnel, research scientists, actors) are documented and the viability of inhabited TV as a 'new medium' is assessed. Future technological refinements are briefly discussed along with some general implications for CSCW and 'media studies' of the work reported.     

Changing the speed of shift rotation: a field study

Abstract

A group of 33 controllers of an emergency service were studied before and after a change in shift roster. The original roster was the traditional weekly rotating type of three shifts, morning, afternoon and night in that direction, in which controllers worked seven consecutive shifts of the same type. This was changed to a rapidly rotating roster of shifts with no more than three consecutive night shifts. The direction of shift change remained the same. Sleep and meal diaries were kept by all controllers for 2 weeks before the roster change. Self-report measures were taken of health, social drug consumption and work variables, an anxiety inventory, the State-Train Anxiety Inventory and the Work Environment Scale were administered both before and 5 months after the roster change. Significant improvements were found after the shift roster change on almost all measures with the exception of self-reported nervousness and loss of appetite and a number of items in the Work Environment Scale. This finding provides some evidence from the field for the argument that rapidly rotating shifts may be the optimal form of shift system.     

Population coding and decoding in a neural field: a computational study

This study uses a neural field model to investigate computational aspects of population coding and decoding when the stimulus is a single variable. A general prototype model for the encoding process is proposed, in which neural responses are correlated, with strength specified by a gaussian function of their difference in preferred stimuli. Based on the model, we study the effect of correlation on the Fisher information, compare the performances of three decoding methods that differ in the amount of encoding information being used, and investigate the implementation of the three methods by using a recurrent network. This study not only rediscovers main results in existing literatures in a unified way, but also reveals important new features, especially when the neural correlation is strong. As the neural correlation of firing becomes larger, the Fisher information decreases drastically. We confirm that as the width of correlation increases, the Fisher information saturates and no longer increases in proportion to the number of neurons. However, we prove that as the width increases further--wider than (sqrt)2 times the effective width of the turning function--the Fisher information increases again, and it increases without limit in proportion to the number of neurons. Furthermore, we clarify the asymptotic efficiency of the maximum likelihood inference (MLI) type of decoding methods for correlated neural signals. It shows that when the correlation covers a nonlocal range of population (excepting the uniform correlation and when the noise is extremely small), the MLI type of method, whose decoding error satisfies the Cauchy-type distribution, is not asymptotically efficient. This implies that the variance is no longer adequate to measure decoding accuracy.