福建省岩土与基础工程现状与展望

1 岩土与基础工程的现状 福建省地处我国东南沿海主要分布有软土地基区域和山区坡残积土、风化岩地基，地基工程特性极不稳定地层，结构复杂，因此给广大岩土与基础工程技术人员提出了许多新的课题，也因此带动我省岩土与基础工程领域不断向前发展。20多年来，特别是近十年来我省岩土与基础工程技术发展迅猛，从岩土的勘探与测试，天然地基利用和山地地基的开发利用，桩基技术，地基处理技术，基坑与边坡支护技术、检测与监测技术等方面，取得了显著的成绩和突破性的进展，具体表现在：     

树立科学发展观 建立城市综合防灾减灾体系

近年来，随着城市规模的不断扩大，城市的综合防灾减灾能力逐渐体现出许多不适应，一些城市在一次灾害下就导致城市的部分功能瘫痪、生命财产损失．生产生活受挫等等，目前，城市防灾减灾已成为世界性的难题。2005年10月2日福州百年一遇的台风龙王引发的特大暴雨，造成市区内涝，市区及城郊的部分交通、供水、供电系统瘫痪，给人民生活带来了很大的影响。造成这次洪涝灾害的主要原因有：预警信息系统不够健全，不够畅通；防涝排涝运行系统尚不健全、标准不高；防灾减灾规划不够完善；整体应急体系欠完备等。随着城市建设的发展，经济越发展，灾害所造成的损失越大。     

Continuous-time optimal robust servo-controller design with internal model principle

The linear quadratic design of an optimal robust servo–controller for a continuous–time control system is described. It introduces a servo–control performance measure which accommodates the internal model principle. The measure selectively discounts penalties on control effort of desirable frequencies and provides complete flexibility in the selection of weighting matrices. The proposed servo–controller uses plant state feedback, signal state feedforward and a servo–compensator for ensuring robust asymptotic command tracking and disturbance rejection. An informal alternate proof of the internal model principle in the state variable domain is presented using an operator-transformation technique. Where necessary, observers are used to complement the servo-controller. The proposed optimal robust servo–controller yields the expected superior performance in terms of response and error minimization. An illustrative example is given.     

Linear optimal control problem of a system with circuit-free graph structure

We solve a linear optimal control problem with state and control restrictions by the method of region analysis, where the state equations describe the flow in a directed graph without a circuit. The results are used for the optimal control of a system of hydroelectric power plants.     

THE INFLUENCE OF RECYCLE ON MULTI-PASS LAMINAR COUNTERFLOW HEATERS OR COOLERS

A multi-pass laminar counterflow cooler or heater is an open duct divided into four subchannels with uniform wall temperature by inserting three impermeable sheets. Only the temperature of the flow stream varies along the subchannels. Improvements in heat transfer efficiency were investigated analytically with the use of eigenfunction expansions in the power series. The enhancement results in heat-transfer efficiency for two multi-pass devices (flow pattern A and flow pattern B) are represented graphically and compared with those in a single-pass device (without three impermeable sheets inserted) and those in a double-pass device (only one impermeable sheet inserted). Analytical results show that suitable impermeable-sheet position adjustments can effectively enhance heat transfer efficiencies for two multi-pass devices (flow pattern A and flow pattern B) compared with the efficiencies of single and double-pass devices.     

Rate-dependent premature beats in man

Ventricular premature beats (VPBs) appeared in a patient after pacemaker insertion for complete heart block secondary to acute myocardial infarction. Contrary to expectations, the frequency of VPBs was directly related to the basic pacemaker rate. The VPBs are either reentrant beats or represent VPBs arising from pacemaker cells with "slow-response" characteristics, which have been shown to become more automatic with increasing rates of electrical stimulation. This case documents the phenomenon of rate dependency of VPBs in man and discusses its practical importance.