Accuracy assessment and waveform analysis of CryoSat-2 SARIn mode data over Antarctica

ABSTRACT

The new synthetic aperture radar interferometric (SARIn) measurement mode of CryoSat-2 provides better performance on the rough topography of the ice sheet margins than that of conventional radar altimetry. We assess the accuracy of CryoSat-2 SARIn mode data from Baseline C product of the European Space Agency (ESA), through comparison with two airborne laser altimeters on NASA IceBridge missions. The time difference between two compared data was limited to 30 days resulting in a reduction in the random error of ~0.3 m. We also assess the sensitivity of ESA retracker to surface slope, roughness and firn density using the mean waveform and retracked bin derived from CryoSat-2 Level 1B and Level 2i product. The ESA retracker appears to be sensitive to the surface slope and roughness according to the different leading edge shape and the retracked bin locations, however, not sensitive to the different firn density over four ice shelves. The modelled echo waveforms as SARIn are also used to analyse the impacts of surface characteristics (slope, roughness, and penetration depth) on echo waveform shape. It illustrates that the processes for ESA product fail to differentiate the changes in near-surface dielectric properties and determine radar-signal-penetration depth.     

基于WCF的综合自动化系统联动控制模式

结合综合自动化在煤矿企业的实际应用,对联动控制模式的类型和特点进行了归纳和分类,提出了基于WCF的综合自动化系统联动控制模式,并实现了联动控制接口的规范。该模式将WCF服务寄宿于采集模块中,为平台终端提供联动控制服务,由采集模块实现平台终端和被控制子系统之间交互信息的传递和转换,遵循了原有平台架构,充分利用了采集模块的专职职能。     

主观题自动阅卷技术研究

为了实现考试系统中主观题型的自动阅卷,提出了基于语句相似度的计算方法对主观题进行自动批改.通过对语句相似度的定义和计算模型的建立以及汉语的特殊性分析,同时借鉴自动问答、自动文摘、信息检索等领域内关于语句相似度的研究,建立了对主观题的自动阅卷模型.通过对语句的词形、词序、词义3个层次计算相似度的融合,使句子的相似度计算更加准确.实验结果表明,主观题自动阅卷技术的正确率达到81.5%.     

Field study of subjective assessment of negative pressure half-masks. Influence of the work conditions on comfort and efficiency

The aim of this study was to assess the effects of work conditions on the acceptability and efficiency of respiratory protective devices (RPD). The subjective evaluation of comfort, protection, respiratory and visual constraint, and the acceptable duration of wear of six RPDs against dust was achieved by 30 workers during their actual work. Metabolic rate was evaluated for each worker, and dry and wet air temperatures measured in the work area. RPDs objective protection factor was measured during each of the 180 test periods.

In the conditions of this study, the acceptable duration of wear was about 1 h. This duration and the comfort parameters were reduced when the air temperature increased. The younger workers and/or smokers were less sensitive to mask discomfort. Objective protection factors of the RPDs are reduced under wanner conditions, and when the metabolic rate is low. Finally, the results of this study also show the poor capacity of standardized leakage tests to assess the objective respiratory protection of workers in the field. Some hypotheses which can explain this fact are discussed.     

Location selection by multi-criteria decision-making methods based on objective and subjective weightings

Knowledge and Information Systems - The location selection is a strategic decision that significantly influences revenue, level of competition, and success of companies and countries. This study...     

Design of automation for telerobots and the effect on performance,operator situation awareness,and subjective workload

In this article we review and assess human‐centered level of automation (LOA), an alternate approach to traditional, technology‐centered design of automation in dynamic‐control systems. The objective of human‐controlled LOA is to improve human‐machine performance by taking into account both operator and technological capabilities. Automation literature has shown that traditional automation can lead to problems in operator situation awareness (SA) due to the out‐of‐the (control) loop performance problem, which may lead to a negative impact on overall systems performance. Herein we address a standing paucity of research into LOA to deal with these problems. Various schemes of generic control system function allocations were developed to establish a LOA taxonomy. The functions allocated to a human operator, a computer, or both, included monitoring system variables, generating process plans, selecting an “optimal” plan and implementing the plan. Five different function allocation schemes, or LOAs, were empirically investigated as to their usefulness for enhancing telerobot system performance and operator SA, as well as reducing workload. Human participants participated in experimental trials involving a high fidelity, interactive simulation of a telerobot performing nuclear materials handling at the various LOAs. Automation failures were attributed to various simulated system deficiencies necessitating operator detection and correction to return to functioning at an automated mode. Operator performance at each LOA, and during the failure periods, was evaluated. Operator SA was measured using the Situation Awareness Global Assessment Technique, and perceived workload was measured using the NASA‐Task Load Index. Results demonstrated improvements in human‐machine system performance at higher LOAs (levels involving greater computer control of system functions) along with lower operator subjective workload. However, under the same conditions, operator SA was reduced for certain types of system problems and reaction time to, and performance during, automation failures was substantially lower. Performance during automation failure was best when participants had been functioning at lower, intermediate LOAs (levels involving greater human control of system functions). © 2000 John Wiley & Sons, Inc.     

Discrete time sliding mode,continuous time sliding mode and vector control of induction motors

Three control strategies are implemented and compared in this paper: vector control, continuous time sliding mode control and discrete time sliding mode control of an induction motor. The induction motor model used for control takes into account magnetizing inductance saturation and rotor resistance variation. While the magnetizing inductance is mapped to the operating conditions, the rotor resistance is estimated on-line. The motor is controlled with optimal efficiency flux. Flux weakening is employed above rated speed. Experimental results are drawn to show the advantages and disadvantages of the control methods.     

Metabolic cost and subjective assessment of palletizing and subsequent recovery

Twenty-one male blue collar workers repeatedly lifted (palletized) a box weighing 22 kg six times min(-1) for 5 min to a shelf of fixed height. The experimental conditions included two planes of lifting (symmetries), two shelf clearances, and three headrooms. The metabolic (heart rate, caloric cost and ventilation volume) and psychophysical variables (rate of perceived exertion, RPE; visual analogue score, VAS; and body part discomfort ratings, BPDR) were measured during resting, palletization, and recovery phases. In palletization the heart rate and metabolic cost ranged between 25 to 35% of the maximal aerobic capacity. Of the three factors only headroom had a significant effect on metabolic cost (p<0.02) and the BPDR for low back (p<0.05). In the recovery phase only headroom had significantly effect (p<0.001) on metabolic cost. The metabolic recovery took 10 min; however, recovery measured through psychophysical indices appeared to continue for 20 min.     

Metabolic cost and subjective assessment of palletizing and subsequent recovery

Twenty-one male blue collar workers repeatedly lifted (palletized) a box weighing 22 kg six times min^-1 for 5 min to a shelf of fixed height. The experimental conditions included two planes of lifting (symmetries), two shelf clearances, and three headrooms. The metabolic (heart rate, caloric cost and ventilation volume) and psychophysical variables (rate of perceived exertion, RPE; visual analogue score, VAS; and body part discomfort ratings, BPDR) were measured during resting, palletization, and recovery phases. In palletization the heart rate and metabolic cost ranged between 25 to 35% of the maximal aerobic capacity. Of the three factors only headroom had a significant effect on metabolic cost (p < 0.02) and the BPDR for low back (p < 0.05). In the recovery phase only headroom had significantly effect (p < 0.001) on metabolic cost. The metabolic recovery took 10 min; however, recovery measured through psychophysical indices appeared to continue for 20 min.     

基于下推自动机的XML数据流递归查询研究

针对具有子孙轴(//)和谓词([])结构特征的XPath对具有不同递归深度的XML数据流进行递归查询处理问题,提出了基于下推自动机技术的处理方法,通过将XPath各类置步转化成相对应的处理模块,由算法将各类处理模块组合起来,建立了自上而下的树状查询模型.由于查询过程中将会发生多重匹配,从而会产生大量的匹配模式,该模型通过有效的匹配策略和缓存操作,对匹配模式进行保存及检验,成功地实现XML数据流递归查询.实验结果表明,该算法在性能上要优于传统方法.     

Paired comparison-based subjective quality assessment of stereoscopic images

As 3D image and video content has gained significant popularity, subjective 3D quality assessment has become an important issue for the creation, processing, and distribution of high quality 3D content. Reliable subjective quality assessment of 3D content is often difficult due to the subjects’ limited 3D experience, the interaction of multiple quality factors, minor quality differences between stimuli, etc. Among subjective evaluation methodologies, paired comparison has the advantage of improved simplicity and reliability, which can be useful to tackle the aforementioned difficulties. In this paper, we propose a new method to analyze the results of paired comparison-based subjective tests. We assume that ties convey information about the significance of quality score differences between two stimuli. Then, a maximum likelihood estimation is performed to obtain confidence intervals providing intuitive measures of significance of the quality differences. We describe the complete test procedure using the proposed method, from subjective experiment design to outlier detection and score analysis for 3D image quality assessment. Especially, we design the test procedure in a way that quality comparison across different contents is enabled while the number of pair-wise comparisons is minimized. Experimental results on a stereoscopic image database with varying camera distances demonstrate the usefulness of the proposed method and enhanced quality discriminability of paired comparison in comparison to the conventional single stimulus methodology.     

基于语句结构及语义相似度计算主观题评分算法的研究

文字类主观题的自动评分是实现远程教育中在线考试系统的一个关键技术,由于其自动评判具有相当难度,使自动评分系统中在对语句结构、关键字匹配、词性、词义以及语义方面的判断还存在很多问题.通过对已有的算法分析,提出了一种方法,采用浅层次句法结构分析和深层次语义分析相结合的算法计算相似度,该方法可以提高主观题自动评分的效率和准确度,具有一定的实用价值.     

一种基于HEVC帧内预测模式快速选择算法

在保证编码性能前提下减少帧内编码复杂度是当前研究的热点。因此一种帧内预测模式快速选择算法被提出。首先基于边缘方向强度,将帧内预测模式按照基本方向进行初筛,然后结合累积梯度和最终确定帧内预测模式,从而降低了率失真优化所带来的计算复杂度。实验结果表明,整体编码时间相对于参考算法减少大约20%~25%。     

Scheduling parallel operations in automation for minimum execution time based on pert

The use of parallel operations in automation, such as part fabrication and assembly, computation and control of industrial robots, etc., may yield a minimum production time and thereby increase productivity. However, the coupling between consecutive phases of operations results in series-parallel precedence constraints that may create unavoidable idle time intervals during the operations. To solve the problem, idle time intervals must be broken down and reduced. An algorithm that determines a minimum time-ordered schedule for the parallel operaitons is developed based on the Program Evaluation and Review Technique using the method of “variable” branch and bound.     

Coefficient of friction and subjective assessment of slippery work surfaces.

Research was conducted to determine how well subjects could distinguish between surfaces with different coefficient of friction (COF) values and to evaluate how well subjective ratings of slipperiness correlated with the actual COF values. Thirty-three ironworkers experienced in working and walking on steel surfaces and 23 university students inexperienced with these tasks participated in the study. Subjective slipperiness ratings for a variety of climbing and walking conditions were obtained from the subjects. It was found that subjects could identify differences in the slipperiness of four types of steel coatings tested in the study. There was a high correlation between the subjective ratings and the measured COF values. Subjects did not slip at a COF of 0.41 but did lose footing at a COF of 0.20.     

Platform for real-time subjective assessment of interactive multimedia applications

With the advent of cloud computing and remote execution of interactive applications, there is a need for evaluating the Quality of Experience (QoE) and the influence on this QoE of network condition variations, media encoding parameter settings and related optimization algorithms. However, current QoE assessment focuses mainly on audiovisual quality in non-interactive applications, such as video-on-demand services. On the other hand, where experiments aim to quantify interactive quality, the focus is typically targeted at games, using an ad-hoc test setup to assess the impact of network variations on the playing experience. In this paper, we present a novel platform enabling the assessment of a broad range of interactive applications (e.g., thin client remote desktop systems, remotely rendered engineering applications, games). Dynamic reconfiguration of media encoding and decoding is built into the system, to allow dynamic adaptation of the media encoding to the network conditions and the application characteristics. Evaluating the influence of these automatic adaptations is a key asset of our approach. A range of possible use cases is discussed, as well as a performance study of our implementation, showing that the platform we built is capable of highly controllable subjective user assessment. Furthermore, we present results obtained by applying the platform for a subjective evaluation of an interactive multimedia application. Specifically, the influence of visual quality and frame rate on interactive QoE has been assessed for a remotely executed race game.     

A decision support tool based on QFD and FMEA for the selection of manufacturing automation technologies

With the advent of the new challenge to design a more lean and responsive computer-integrated manufacturing system, firms have been striving to achieve a coherent interaction between technology, organisation, and people to meet this challenge. This paper describes an integrated approach developed for supporting management in addressing technology, organisation, and people at the earliest stages of manufacturing automation decision-making. The approach uses both the quality function deployment (QFD) technique and the failure mode and effects analysis (FMEA) technique. The principal concepts of both applications are merged together to form a decision tool; QFD in its ability to identify the most suitable manufacturing automation alternative and FMEA in its ability to identify the associated risk with that option to be addressed in the manufacturing system design and implementation phases. In addition, this paper presents the results of a practical evaluation conducted in industry.     

Maintaining AUC and H-measure over time

Machine Learning - Measuring the performance of a classifier is a vital task in machine learning. The running time of an algorithm that computes the measure plays a very small role in an offline...