Output feedback performance recovery in the presence of uncertainties

We propose an output-feedback tracking controller for uncertain, nonaffine, nonlinear systems. The output feedback controller results in a closed-loop system with a three-time-scale structure; an extended high-gain observer estimates unmeasured states and uncertainties in the fastest time scale and dynamic inversion is used to deal with nonaffine inputs and input uncertainties in the intermediate time scale while the plant dynamics evolves in the slowest time scale. The dynamic inversion algorithm is based on sector conditions and results in exponential convergence of the inputs. Together with the extended high-gain observer, dynamic inversion results in performance recovery of a target system. The singular perturbation method is used to analyze the stability and performance of the system and numerical simulations are used to demonstrate the effectiveness of the control design.     

嵌入式系统中大素数的快速生成

在公钥密码应用中，RSA算法现在仍处于主流地位，RSA算法在受限环境，嵌入式环境中最慢的操作是生成密钥对，即寻找两个大素数，该文在Robin-Miller概率 素性判别算法之前，采用适合于嵌入环境实现的方法，先对随机数进行过滤，可以使素数生成的整体效率提高50％。     

Visual and auditory attention in patient monitoring: a formative analysis

We investigate the effectiveness of sonification (continuous auditory display) for supporting patient monitoring while reducing visual attentional workload in the operating theatre. Non-anaesthetist participants performed a simple continuous arithmetic task while monitoring the status of a simulated anaesthetised patient, reporting the status of vital signs when asked. Patient data were available either on a monitoring screen behind the participant, or were partially or completely sonified. Video captured when, how often and for how long participants turned to look at the screen. Participants gave the most accurate responses with visual displays, the fastest responses with sonification and the slowest responses when sonification was added to visual displays. A formative analysis identifying the constraints under which participants timeshare the arithmetic and monitoring tasks provided a context for interpreting the video data. It is evident from the pattern of their visual attention that participants are sensitive to events with different but overlapping temporal rhythms.     

Accelerating the SVD Block-Jacobi Method

The paper discusses how to improve performance of the one-sided block-Jacobi algorithm for computing the singular value decomposition of rectangular matrices. In particular, it is shown how cosine-sine decomposition of orthogonal matrices can be used to accelerate the slowest part of the algorithm – updating the block-columns.     

Experiences with optimizing two stream-based applications for cluster execution

We explore optimization strategies and resulting performance of two stream-based video applications, video texture and color tracker, on a cluster of SMPs. The two applications are representative of a class of emerging applications, which we call “stream-based applications”, that are sensitive to both latency of individual results and overall throughput. Such applications require non-trivial parallelization techniques in order to improve both latency and throughput, given that the stream data emanates from a limited set of sources (exactly one in the two applications studied) and that the distribution of the data cannot be done a priori.We suggest techniques that address in a coordinated fashion the problems of data distribution and work partitioning. We believe the two problems are related and need to be addressed together. We have parallelized two applications using the Stampede cluster programming system that provides abstractions for implementing time- and throughput-sensitive applications elegantly and efficiently. For the Video Textures application we show that we can achieve a speedup of 24.26 on a 112 processor cluster. For the Color Tracker application, where latency is more crucial, we identify the extent of data parallelism that ensures that the slowest member of the pipeline is no longer the bottleneck for achieving a decent frame rate.     

多屏显示的并行绘制同步控制算法

为改善现今大规模场景并行绘制中的由于网络潜在的不稳定性所导致的各个绘制节点所出现的帧数据丢失以及帧绘制延缓等状况,提出了一种新的处理多屏显示的并行绘制同步控制方法。该方法利用一种新的基于缓冲机制和插值的思想,在少量牺牲几个绘制节点的绘制同步的前提下,使得整个绘制系统的绘制效率不受制于最慢绘制节点,并可以容忍各种网络延迟、仿真数据包丢失等网络不稳定情况。实验结果表明,该方法在一定程度上缩短了整个并行绘制系统平均每帧的绘制时间,画面显示的平滑性也有所改善,画面停滞现象相对减少。     

A biomechanical evaluation of lifting speed using work- and moment-related measures.

A biomechanical evaluation of lifting speed was conducted in the laboratory. The study investigated the effects of lifting speed on several predetermined biomechanical cost functions. The lifting tasks consisted of five lifting speeds labelled as the slowest, slow, normal, fast and fastest, and three weights, 50, 65 and 80% of their maximum acceptable weight of lift. The speed at each level was determined individually by each subject according to their capability. The study found that work-related measures, including the total net muscle work, total absolute net muscle work and work done to the load, decreased significantly as the lifting speed increased (p < 0.05, < 0.001 and < 0.001, respectively). The time integral of sum of squared ratio of joint moment and strength also decreased significantly (p < 0.001). This indicates that lifting at a faster speed tends to reduce the work the body has to do. The peak speed of load occurred at 70% of total lifting time for the slowest lifts, but at 30% of total lifting time for other lifting speeds. Performing lifts at the minimum speeds changed the usual speed coordination technique the subjects used.     

Coherency based decomposition and aggregation

The relationship between coherency, area decomposition and aggregation is investigated for a class of models of electromechanical networks, including power system models. It is established that coherency conditions and a physically meaningful area-aggregate, reproducing a prescribed set of system modes, depend on external connections only. Coherency with respect to a set of slowest modes (‘slow coherency’) and an earlier developed grouping algorithm are used to identify weakly coupled areas, as demonstrated on a 48-machine model of the United States North-East power system.     

Improvements on dynamic adjustment mechanism in co-allocation data grid environments

Several co-allocation strategies have been coupled and used to exploit rate differences among various client-server links and to address dynamic rate fluctuations by dividing files into multiple blocks of equal sizes. However, a major obstacle, the idle time of faster servers having to wait for the slowest server to deliver the final block, makes it important to reduce differences in finishing time among replica servers. In this paper, we propose a dynamic co-allocation scheme, namely Recursive-Adjustment Co-Allocation scheme, to improve the performance of data transfer in Data Grids. Our approach reduces the idle time spent waiting for the slowest server and decreases data transfer completion time.

运动估计快速半象素级搜索方法的实验研究

提出了３种运动估计快速半象素级搜索方法。实验分析表明这３种方法具有较好的ＭＳＥ性能和解码图象质量；３种快速方法中最慢的可以节省约２９．１７％运算次数，最快的可节省近５８．３３％运算次数。本文所提出的快速方法可作为运动估计单元中半象素级搜索实时实现的候选算法。     

Fourier Analysis of Correlated Monte Carlo Importance Sampling

Fourier analysis is gaining popularity in image synthesis as a tool for the analysis of error in Monte Carlo (MC) integration. Still, existing tools are only able to analyse convergence under simplifying assumptions (such as randomized shifts) which are not applied in practice during rendering. We reformulate the expressions for bias and variance of sampling-based integrators to unify non-uniform sample distributions [importance sampling (IS)] as well as correlations between samples while respecting finite sampling domains. Our unified formulation hints at fundamental limitations of Fourier-based tools in performing variance analysis for MC integration. At the same time, it reveals that, when combined with correlated sampling, IS can impact convergence rate by introducing or inhibiting discontinuities in the integrand. We demonstrate that the convergence of multiple importance sampling (MIS) is determined by the strategy which converges slowest and propose several simple approaches to overcome this limitation. We show that smoothing light boundaries (as commonly done in production to reduce variance) can improve (M)IS convergence (at a cost of introducing a small amount of bias) since it removes C₀ discontinuities within the integration domain. We also propose practical integrand- and sample-mirroring approaches which cancel the impact of boundary discontinuities on the convergence rate of estimators.     

A biomechanical evaluation of lifting speed using work- and moment-related measures

A biomechanical evaluation of lifting speed was conducted in the laboratory. The study investigated the effects of lifting speed on several predetermined biomechanical cost functions. The lifting tasks consisted of five lifting speeds labelled as the slowest, slow, normal, fast and fastest, and three weights, 50, 65 and 80% of their maximum acceptable weight of lift. The speed at each level was determined individually by each subject according to their capability. The study found that work-related measures, including the total net muscle work, total absolute net muscle work and work done to the load, decreased significantly as the lifting speed increased (p&lt;0.05, &lt;0.001 and &lt;0.001, respectively). The time integral of sum of squared ratio of joint moment and strength also decreased significantly (p&lt;0.001). This indicates that lifting at a faster speed tends to reduce the work the body has to do. The peak speed of load occurred at 70% of total lifting time for the slowest lifts, but at 30% of total lifting time for other lifting speeds. Performing lifts at the minimum speeds changed the usual speed coordination technique the subjects used.     

Maintenance of infinite-server service systems subjected to random shocks

Motivated by the need to study traffic incident management, we consider a Markovian infinite server queue that is subjected to randomly occurring shocks. These shocks affect the service of all servers to deteriorate, i.e., increase the service time of all servers, and might also cause other shocks, thus causing further service deterioration. There are a finite number of service levels, zero corresponding to the normal service with the highest service rate and the last level corresponding to the slowest service rate which could even be equal to zero, implying the complete service breakdown. The repair process is performed only at the last level. These types of queues also represent an approximation of multi-server call-centers with deteriorating service. We derive the mean and variance of the stationary number in the system, and show that the mean is convex with respect to the repair rate. Furthermore, we study the optimal repair rate that minimizes the expected long-run average cost incurred due to delay and repairs. We show that the expected total cost per unit time as a function of repair rate is unimodal. We derive conditions under which the cost function is in one of three simple forms, so that the optimum repair rate can easily be obtained. Numerical examples are also provided.     

Slow and steady wins the race? Three-year-old children and pointing device use

While adult performance with different pointing devices has received extensive study in the human-computer interaction literature, there is little data on the performance of young children using any input devices at all. In the present study, 64 three-year-old children used a joystick, mouse, or trackball to perform a simple cursor placement task. Two substantive results were obtained. First, trackball users were the slowest, but also the most accurate in their cursor control. Second, characteristics of the children's performance suggest that adult standards for an optimal interface, which stress speed and efficiency, may not be appropriate when children are the intended users.     

Completely synchronous manufacturing for automotive assembly — some lessons learned

The concepts of synchronous manufacturing look deceptively simple on paper. It appears obvious on the surface that when manufacturing operations are dependent upon one another, then the slowest operation will determine the pace of the combined operations.

Theory is one thing. Learning to really get a complex manufacturing and assembly system to work smoothly takes real patience.

One of the teaching tools was computer simulation with animation to demonstrate the concepts of synchronous manufacturing.

This paper focuses on 3 models developed using this simulation/animation tool.     

Dynamical analysis of bursting oscillations in the Chay-Keizer model with three time scales

Based on the Chay-Keizer model with three time scales, we investigate the role of the slowest variable in generating bursting oscillations in pancreaticcells. It is shown that both of the two slow processes can interact to drive fast, medium and slow bursting oscillations typically observed in pancreaticcells. Moreover, diverse patterns of electrical bursting are presented, including the fold/fold bursting, fold/homoclinic bursting, fold/Hopf bursting via fold/fold hysteresis loop, and the fold/fold burstin...     

Emergence of autocatalytic reaction in a meme propagation model based on particle motion

Meme refers to a unit of human cultural transmission, analogous to biological evolution. Meme propagation has an autocatalytic property in the sense that it increases its reproductive rate by duplicating the source of propagation. The purpose of this study is to gain general knowledge about the dynamics of meme propagation. This paper presents a minimal model based on the physical movement of particles for investigating the relationship between the behavior of the hosts (velocity of particles) and the autocatalytic property of the meme. It is demonstrated that two extreme memes, the fastest and the slowest ones, have a strong tendency to survive by autocatalytic properties at individual and aggregate levels, respectively, although all memes seem neutral in terms of fitness in the model definition.     

SENSORI-MOTOR PERFORMANCE UNDER VARYING NOISE CONDITIONS

A group of subjects performed a task in quiet and noisy environments. The noise was intermittent, within the frequency range of 75 to 9600 cycles and at sound levels of 70, 80, 90, and 100 db. The study was experimental, but simulated an occupational situation.

There was a tendency for more errors and less precision when working in the noisy environment. Response times were slower and the number of errors greater than when noise levels and frequencies were highest. The frequency range of 2400-4800 cycles was associated with the slowest response time and largest number of errors, both at 90 and 100 db.

It appears that intermittent noise may have a reducing effect on the individual's capacity for quick and precise execution of coordinated movements. The implications for safety and certain production tasks seem obvious.     

Deterministic annealing with Potts neurons for multi-robot routing

A deterministic annealing (DA) method is presented for solving the multi-robot routing problem with min–max objective. This is an NP-hard problem belonging to the multi-robot task allocation set of problems where robots are assigned to a group of sequentially ordered tasks such that the cost of the slowest robot is minimized. The problem is first formulated in a matrix form where the optimal solution of the problem is the minimum-cost permutation matrix without any loops. The solution matrix is then found using the DA method is based on mean field theory applied to a Potts spin model which has been proven to yield near-optimal results for NP-hard problems. Our method is bench-marked against simulated annealing and a heuristic search method. The results show that the proposed method is promising for small-medium sized problems in terms of computation time and solution quality compared to the other two methods.

     

A stochastic algorithm for makespan minimized multi-agent path planning in discrete space

Makespan minimized multi-agent path planning (MAPP) requires the minimization of the time taken by the slowest agents to reach its destination. The resulting minimax objective function is non-smooth and the search for an optimal solution in MAPP can be intractable. In this work, a maximum entropy function is adopted to approximate the minimax objective function. An iterative algorithm named probabilistic iterative makespan minimization (PIMM) is then proposed to approximate a makespan minimized MAPP solution by solving a sequence of computationally hard MAPP minimization problems with a linear objective function. At each iteration, a novel local search algorithm called probabilistic iterative path coordination (PIPC) is used to find a sufficiently good solution for each MAPP minimization problem. Experimental results from comparative studies with existing MAPP algorithms show that the proposed algorithm strikes a good tradeoff between the quality of the makespan minimized solution and the computational cost incurred.