基于水质模拟的水质在线监测站点布设研究

随着水质监测连续化的需求增加,河流水质在线监测站布设成为不可忽视的问题。本文采用水文模拟模型HSPF对台湾淡水河流域进行水量水质联合模拟。水文模拟以9个测站比对,纳什效率系数多数大于0.7;相关系数r皆大于0.7。水质模拟以27个测站比对,生化需氧量、氨氮、悬浮固体、溶氧的修正平均百分误差多数小于25%。基于水质变化率和水质超标率提出水质敏感河段概念,并以此确定为补充布设水质在线监测站点的优先河段。研究指出,淡水河流域水质在线监测站目前仍缺乏且位置不尽合理,应优先补充三峡河的三峡大桥、景美溪的宝桥、基隆河的江北桥水质在线监测站。     

EFFECT OF A PROPELLER AND GAS DIFFUSION ON BUBBLE NUCLEI DISTRIBUTION IN A LIQUID

A multi-bubble dynamics code accounting for gas diffusion in the liquid and through the bubble wall was developed and used to study the modification of a bubble nuclei population dynamics by a propeller.The propeller flow field was obtained using a Reynolds-Averaged Navier-Stokes(RANS) solver and bubble nuclei populations were propagated in this field.The numerical pro-cedure enabled establishment of the possibility of production behind the propeller of relatively large visible bubbles starting from typical ocean nuclei size distributions.The resulting larger bubbles are seen to cluster in the blade wakes and tip vortices.Parametric investigations of the initial nuclei size distribution,the dissolved gas concentration,and the cavitation number were conducted to ide-ntify their effects on bubble entrainment and the resultant void fractions and bubble distribution modifications downstream from the propeller.Imposed synthetic turbulence-like fluctuations unto the average RANS flow field were also used to study the effect avera-ging in the RANS procedure has on the results.     

A state-space approach to Walsh series solution of linear systems

A state-space procedure for solving linear dynamic systems by the Walsh series is developed. A new operational matrix plays the main role and a new Kronecker product formula is established. The laborious use of Corrington'B tables is eliminated. Several examples illustrate the process and demonstrate the power of the approach.     

Stabilization of large structural systems under mode truncation,parameter perturbations and actuator saturations

The stabilization of large structural systems (LSS) under (i) mode truncation and linear parametric perturbations, or (ii) mode truncation and actuator saturations is considered. A new robust stability condition for the perturbed LSS controlled by observer-based compensators is derived. A stability criterion is also given for the stabilization of LSS by observer-based constrained controls. Finally, a simply supported beam problem is provided for illustration.     

Model matching systems: necessary and sufficient conditions for stability under plant perturbations

Necessary and sufficient conditions of robust stability are derived for multivariate perfect model matching systems under external disturbances and plant perturbations (non-linear, linear feedback perturbations and fractional perturbations). The derived results also provide an intuitive insight into controller effects on robustness. A general parametrized 2-D controller is introduced to stabilize the nominal plant.     

Robustness optimization in LQG multivariable systems with time-varying non-linear perturbations

This paper presents an algorithm to synthesize a controller in order to treat the problem of robustness optimization in LQG (linear-quadratic-gaussian) multi-variable systems subjected to time-varying non-linear perturbations. The controller not only minimizes the cost functional in LQG problems but also maximizes the excess robustness with respect to the Hardy H^∞-norm criterion by selecting two frequency-dependent weighting matrices Q(s) and R(s). Our approach is based on the Wiener-Hopf technique (frequency domain approach) and two weighting matrices in the cost functional are shaped by the inverse LQG method to achieve the robustness optimization. Furthermore, the plant of the system has no stable, proper, square, and minimum phase constraints. An example is given to illustrate our result.     

为下一代作准备:林后四林平地森林园区规划

林后四林平地森林园区是一处集平地造林、在地文化、栖地营造、资源利用与环境教育为一体的学习园区.在其不断的发展下,现成为大武山低海拔自然森林园区,作为生态栖地修复、区域文化体验及休闲游憩的场域.从环境修复的角度保有农垦地和草生地生态环境,并营造大武山低海拔森林的栖地环境,提供猛禽、鸟类及两栖类动物栖息繁衍之地.重视生态保育意义的同时,发挥环境教育和生态旅游的价值.因气候环境变迁,以分散排水、贮流、自然人渗及自然过滤方式为主,同时进行土壤地利改良,达到环境保全修复的功效.以现地环境保育及生态演变历史延续对自然环境的关怀,营造合宜的生态栖地、掌握水资源的保存与再利用,为下一代的自然生态环境作准备.     

Fractal Dimensions of Hydrogen Induced Brittle Fracture of Titanium Aluminide

The relationship between the stress intensity factor K_1~* required for brittle crack initiation and propa-gation and the fractal dimension D_F of the fracture surface was derived,i.e,InK_1~*=(1/2)In2γE'+(1/2)In(d_f/L_0)(1-D_F)The real surface energy can be calculated based on the measured linear relation of the InK_1~* vs D_F,The equation is not only suitable for the overload fracture but also for the delayed fracture,e.g.hydrogen induced cracking (HIC) and stress corrosion cracking (SCC).The experiment resultsshowed that the hydrogen induced delayed cracking occurred in the Ti-24AI-11 Nb alloy during dy-namic charging,and the threshold stress intensity factor was very low,i.e..K_(IH)/K_(IC)= 0.43.The ex-perimental relationship between the stress intensity factor K_1~* and D_F was consistent with the theo-retical equation.     

Multipurpose controller design using parametric optimization with dynamic constraints

A systematic and effective design procedure for a class of linear multivariable feedback control systems is proposed For simultaneously achieving robust tracking of the prescribed input signal via the Q-parametrization approach and internal model principle, the prescribed transient specifications by choosing an appropriate performance criterion, robust stabilization, and sensitivity minimization. The problem can best be cast in the form of an optimization problem with dynamic constraints. A numerical method is formulated to solve the optimization problem with dynamic constraints using a non-linear programming method. A numerical example is provided to illustrate the main results of the paper.