Distributed controller design and performance optimization for discrete‐time linear systems

This article addresses the problem of distributed controller design for linear discrete‐time systems. The problem is posed using the classical framework of state feedback gain optimization over an infinite‐horizon quadratic cost, with an additional sparsity constraint on the gain matrix to model the distributed nature of the controller. An equivalent formulation is derived that consists in the optimization of the steady‐state solution of a matrix difference equation, and two algorithms for distributed gain computation are proposed based on it. The first method consists in a step‐by‐step optimization of said difference matrix equation, and allows for fast computation of stabilizing state feedback gains. The second algorithm optimizes the same matrix equation over a finite time window to approximate asymptotic behavior and thus minimize the infinite‐horizon quadratic cost. To assess the performance of the proposed solutions, simulation results are presented for the problem of distributed control of a quadruple‐tank process, as well as a version of that problem scaled up to 40 interconnected tanks.     

基于小波能量谱的先天或风湿性心脏病异常心音分类算法研究

目的为解决先天性心脏病或风湿性心脏病异常心音分辨问题,应用离散小波频带能量对异常心音分类算法进行研究。方法采集22人的正常心音和116人的异常心音,对心音信号做离散小波变换,根据病理性心杂音在频域内的分布范围划分5层频带,计算得到各层频带的能量占比,根据单因素方差分析方法,提出了基于小波能量谱的心音分类指标。结果对正常心音和异常心音的4个听诊区域进行了分类,最优分类准确率为92%。区分动脉导管未闭和其余异常心音的最优分类准确率为81.9%。结论基于小波能量谱的心音分类算法无需对心音信号进行分割,提取特征值少,可准确有效地对心音信号进行分类,相较于传统的心音听诊,算法的引入能够在异常心音临床诊断中提供参考数据。     

Localized lesions of arcopallium intermedium of the lateral forebrain caused a handling-cost aversion in the domestic chick performing a binary choice task

Behavioral effects of handling cost (time and/or energetic cost for food consumption) on choice were examined using domestic chicks trained in operant task reinforced by delayed food rewards. When scattered sesame was delivered in more demanding conditions, a colored cue bead associated with six grains ('large' and 'costly' reward) was chosen progressively less frequently against another bead associated with one grain ('small' and 'not costly' reward). The choice thus proved to be highly sensitive to the anticipated handling cost. Excitotoxic lesion of the bilateral arcopallium intermedium also selectively reduced the choice of the six grains, while leaving actual cost investment (number of pecks and handling time) unaltered. No significant changes occurred in choices between one grain of sesame ('small' and 'not costly' reward) and one grain of barley (or a ball composed of six sesame grains glued by starch; 'large' and 'not costly' reward), indicating that choice based on anticipated food amount was not impaired. On the other hand, lesion of the ventral striatum did not change the choice ratio in any trial types. Operant peck latencies somewhat depended on food rewards, but were not affected by lesions of the arcopallium or the ventral striatum. The arcopallium could contribute to foraging behaviors by enabling chicks to overcome the handling cost, thus gaining more beneficial food. Furthermore, the present results indicate doubly dissociated functional roles of the ventral striatum and the arcopallium, the former in the cost of traveling for food and the latter in the cost of handling food, respectively.     

Online identifier–actor–critic algorithm for optimal control of nonlinear systems

In this paper, a novel identifier–actor–critic optimal control scheme is developed for discrete‐time affine nonlinear systems with uncertainties. In contrast to traditional adaptive dynamic programming methodology, which requires at least partial knowledge of the system dynamics, a neural‐network identifier is employed to learn the unknown control coefficient matrix working together with actor–critic‐based scheme to solve the optimal control online. The critic network learns the approximate value function at each step. The actor network attempts to improve the current policy based on the approximate value function. The weights of all neural networks are updated at each sampling instant. Lyapunov theory is utilized to prove the stability of closed‐loop system. It shows that system states and neural network weights are uniformly ultimately bounded. Finally, simulations are provided to illustrate the effectiveness of the developed method. Copyright © 2016 John Wiley & Sons, Ltd.     

Optimal linear quadratic Gaussian control for discrete time-varying system with simultaneous input delay and state/control-dependent noises

This article focuses on the problem of linear quadratic Gaussian (LQG) control for discrete time-varying system with input delay and state/control-dependent noises. When the state variables can be exactly observed, first, we obtain the maximum principle by applying the method of variation. Second, a nonhomogeneous relationship between the state and the costate is developed in virtue of the obtained maximum principle and the mathematical induction. It is noted that the nonhomogeneous relationship is the solution to the forward and backward stochastic difference equations (FBSDEs). Finally, based on the solution to the FBSDEs, a necessary and sufficient condition for the optimal LQG control is derived in terms of coupled Riccati equations. Moreover, the analytical expression of the optimal controller is presented. The derived results are applied in networked control systems with packet dropout. Numerical examples are shown to illustrate the effectiveness of the proposed algorithm.     

Patients' preferences and trade-offs for the treatment of early stage hepatocellular carcinoma

Background

Radio frequency ablation (RFA) and hepatic resection (HR) provide similar survival for early stage hepatocellular carcinoma (ES-HCC). Although RFA has a higher recurrence rate, HR is associated with an increased risk of complications and death. When multiple treatments are available, patients should be enabled to direct their preferred therapy. Yet there is lack of knowledge on patients' preferences for the treatment of ES-HCC. The objective of this study was to assess treatment preferences between HR and RFA for ES-HCC.

Methods

A cohort of 75 cirrhotic adults was educated about the natural history of HCC, treatment options, and the risks and the benefits of HR and RFA. Probability trade-off interviews were used to elicit participants' preferences between the two treatments and strength of their decisions.

Results

RFA was preferred by 70% of participants (P = 0.001) who identified the risk of perioperative morbidity and mortality of HR as the main reasons for their decision. Participants changed their minds if HR could provide better 5 (≥15%) and 3-y disease-free survival (≥10%) when compared with RFA. Their preference also changed when RFA had a median ≥8% risk for complications, ≥5% for mortality, ≥8% for nonradical therapy, and ≥5% for tumor seeding.

Conclusions

Informed cirrhotic patients prefer RFA for the treatment of ES-HCC. Participants who preferred RFA were more concerned about the risks of perioperative morbidity and mortality of HR than long-term cancer outcomes. Patients' values and attitudes toward risks and benefits for the treatment of ES-HCC should be explicitly elicited and included in multidisciplinary treatment decisions.     

Patterns of Compartment Involvement in End‐stage Knee Osteoarthritis in a Chinese Orthopedic Center: Implications for Implant Choice

Objectives

Knee osteoarthritis (OA) is a prevalent disease in the elderly, causing pain and contributing to poor quality of life. Surgical intervention, such as knee arthroplasty, can be used in those with end‐stage knee OA. Total knee arthroplasty (TKA) is one of the most common surgical procedures for end‐stage knee OA, with promising clinical outcomes. However, a large proportion of patients with isolated compartment OA can be treated with unicompartmental knee arthroplasty (UKA) instead. UKA has shown better patient‐reported functional outcomes, and lower mortality and major complication rates than TKA. The percentage of UKA in knee arthroplasty varied in different orthopedic centers, and we believed that the requirement for UKA was underestimated in many centers. A retrospective study was carried out on our Chinese patient population presenting for knee arthroplasty; it aimed to identify the proportion of patients that might be suitable for UKA.

Methods

A retrospective cross‐sectional study of 155 consecutive patients (168 knees) awaiting TKA for end‐stage primary OA was performed. The pattern and grade of OA was recorded from preoperative weight‐bearing anteroposterior and non‐weight‐bearing lateral radiographs. The medial, lateral, patellofemoral compartment was given an individual Kellgren–Lawrence grade on the radiographs, and those grade ≥3 were defined as end‐stage OA. The compartments involvement was established then. The integrity of the anterior cruciate ligament (ACL) was determined by the modified Keyes classification on lateral radiographs. The applicability for total or partial knee arthroplasty was determined according to the compartments involvement.

Results

Medial compartment involvement was found in 154 (91.7%) knees, while the involvement of the lateral compartment and patellofemoral joint was found in 54 (32.1%) and 57 (33.9%) knees, respectively. Eighty‐one (48.2%) of the knees showed medial compartment OA with or without patellofemoral joint involvement, and modified Keyes classification grade 1, indicating an intact ACL, and, hence, potential suitability for medial UKA. Isolated lateral OA indicating possible suitability for lateral UKA was identified in 11 knees (6.5%). No patients showed isolated patellofemoral joint OA. The other 76 (45.2%) knees could be treated by TKA.

Conclusions

The medial compartment was the most commonly affected in our Chinese patients indicated for knee arthroplasty. More than half of the patients in this group could be treated by either medial or lateral UKA.

     

Genetic screening in maternity care: preventive aims and voluntary choices

This paper analyses a prenatal genetic screening programme for three gene defects, conducted at maternity care centres in Eastern Finland in 1995 and 1996. What is special in this case is that the screening ended sooner than was planned. This paper investigates how the genetic screening programme was launched, the problems it encountered and the circumstances of its closure. The present analysis focuses on the co‐existence of, and tensions between, the two major objectives of the project: preventing disability and increasing mothers' choices. The tensions between these two objectives were highlighted at maternity care centres. The public health nurses working at these centres were confused about whether or not they should offer autonomous consumer choice or guidance to mothers to behave in responsible and health‐conscious ways. The nurses' confusion was intensified because the goal of prevention was identified with financial savings for the municipality, which the nurses thought was an inappropriate reason for abortions.     

四川省中医药企业发展战略案例研究

目的:为四川省中医药企业建立一个基于未来、以价值创造为导向的持续发展战略模型。方法:基于战略管理理论,运用实证研究、理论研究和模型研究3种方法对四川扁鹊药业股份有限公司进行定量、定性分析。结果:扁鹊药业股份有限公司的战略选择是实行专业化发展战略、差异化竞争战略和横向一体化战略。结论:四川省同类型中医药企业可以此为鉴,突出现有核心业务,横向整合扩展经营规模,在多个目标细分市场做大做强,以取得良好效益。