Analytic design of adaptive sampling control law in sampled-data systems

A unified analytic approach is presented for the design of adaptive sampling control law in sampled-data systems. This is accomplished by introducing an objective function which measures the performance of the sampler over each sampling interval, and then minimize it to obtain the sampling control law. A total of six different control laws, which are functions of the sampled function, are derived from the generalized objective function by selecting different weighting coefficients. More than half of these control laws are identical to existing results. Similar control laws as functions of the system output can be derived as well. Also included are some experimental results on the performances of four representative control laws in a second-order system subject to step disturbance.     

Effects of X-ray irradiation on GIDL in MOSFETs

The effect of X-ray irradiation on the gate-induced drain leakage (GIDL) is shown to be mostly due to the electrostatic effect of the trapped positive charge in n-channel MOSFETs. In p-channel MOSFETs, in addition, irradiation increases the interface-state-assisted tunneling component of the GIDL. In both n- and p-channel MOSFETs, a forming gas anneal at 400°C completely removes all effects of irradiation on the GIDL     

On an inverse problem in optimal control

The problem of optimizing linear-stationary control systems subject to quadratic performance indices and bounded control effort constraints is studied. This problem was first proposed by Letov [1]. His solution, however, has been found to be valid only in some special cases [3]. In this paper, necessary and sufficient conditions for the existence of the optimal control laws of the saturation type are developed. It is shown that the weighting factors in the performance index have to be chosen in a particular manner, and the plants have to satisfy certain conditions to yield an optimal saturation type control law. As the weighting on the control effort in the performance index is decreased, the optimal solution approaches a bang-bang type singular control.     

An Automated System for ST Segment and Arrhythmia Analysis in Exercise Radionuclide Ventriculography

A computer-based system for interpretation of the electrocardiogram (ECG) in the diagnosis of arrhythmia and ST segment abnormality in an exercise system is presented. The system was designed for inclusion in a gamma camera so that ECG diagnosis could be combined with the diagnostic capability of radionuclide ventriculography. Digitized data are analyzed in a beat-by-beat mode and a contextual diagnosis of underlying rhythm is provided. Each beat is assigned a beat code based on a combination of waveform analysis and RR interval measurement. The waveform analysis employs a new correlation coefficient formula which corrects for baseline wander. Selective signal averaging, in which only normal beats are included, is done for an improved signal-to-noise ratio prior to ST segment analysis. Template generation, R wave detection, QRS window size, baseline correction, and continuous updating of heart rate have all been automated. ST level and slope measurements are computed on signal-averaged data. Arrhythmia analysis of 13 passages of abnormal rhythm by computer was found to be correct in 98.4 percent of all beats. 25 passages of exercise data, 1-5 min in length, were evaluated by the cardiologist and found to be in agreement in 95.8 percent in measurements of ST level and 91.7 percent in measurements of ST slope.     

Joint trajectory generation for redundant robots in an environment with obstacles

Collision avoidance is an absolutely essential requirement for a robot to complete a task in an environment with obstacles. For kinematically redundant robots, collision avoidance can be achieved by making full use of the redundancy. In this article, the problem of determining collision-free joint space trajectories for redundant robots in an environment with multiple obstacles is considered, and the “command generator” approach is employed to generate such trajectories. In this approach, a nondifferentiable distance objective function is defined and is guaranteed to increase wherever possible along the trajectory through a vector in N(J), the null space of Jacobian matrix J. Algorithms that implement this nondifferentiable optimization problem are fully developed. It is shown that the proposed collision-free trajectory generation scheme is efficient and practical. Extensive simulation results of a four-link robot example are presented and analyzed.     

On sampled data approach to parameter identification of continuous linear systems

It is generally preferable to estimate unknown parameters in analog transfer functions by sampled data techniques. This approach calls for the derivation of an appropriate discrete modelD(z)for a given analog systemH(s)with undetermined parameters, and then the fitting of the sampled input-output data byD(z)to estimate these parameters. This correspondence presents a method for obtaining such discrete models. It also provides a more effective procedure for calculating the parameter estimates from the identified discrete transfer functionhat{D}(z).     

Partial nitrification of ammonium-rich wastewater as pretreatment for anaerobic ammonium oxidation (Anammox) using membrane aeration bioreactor

A lab-scale membrane aeration bioreactor (MBR) system was developed for treating synthetic ammonium-rich wastewater to yield an appropriate NO(2)(-)/NH(4)(+) mixture as a pretreatment for anaerobic ammonium oxidation (Anammox). The effluent with a suitable NO(2)(-)/NH(4)(+) ratio (1:1 to 1:1.3) was obtained in 24 h using the developed MBR system under suitable conditions. Additionally, the control of bulk dissolved oxygen (DO) level under a desired condition (anoxic condition) was easier and more economical than traditional aeration systems. An optimal initial alkalinity of 1500 mg CaCO(3)l(-1) was necessary for achieving 50% partial nitrification of wastewater with an initial ammonium concentration of 510 mg NH(4)-N l(-1) within 24 h. Furthermore, there is no need for pH adjustment by adding a base or an acid throughout the reaction if the initial alkalinity is appropriately controlled. Both the appropriate NO(2)(-)/NH(4)(+) ratio and the low DO level make this MBR system an ideal system for Anammox.     

High-performance adaptive group-of-picture rate control for H.264/AVC

In this paper, an adaptive group-of-picture (AGOP) control is proposed to improve the coding performance for the H.264/AVC system. The efficient algorithm is developed to find the quantized parameter with temporal correlation between inter-frames. According to the estimated parameters, the GOP coding type can be adaptively selected as AGOP or BGOP (basic GOP). The rate control with some decision functions is proposed to modify the quantization parameter (QP). The coding rate can accurately meet the target rate with adjusting QP value dynamically, while keeping low computational overhead. Simulation results show that the proposed algorithm can improve PSNR by about 1 dB in average compared with the original H.264/AVC reference software (JM12.4), from various sequences testing.