分布式发电中燃料电池的建模与控制

合适的燃料电池(fuel cell,FC)动态模型对分布式发电技术的研究起着很重要的作用。提出了非线性质子交换膜燃料电池和固体氧化物燃料电池的动态模型,该模型考虑了燃料利用率的影响和各种反应物随时间变化的压力。并在该模型的基础上,应用电池效率和发电经济性分析得出了燃料利用率一般控制在0.7～0.9范围内比较好。详细阐述了FC在并网运行时的控制策略,以及在含FC发电系统的潮流计算中,将FC的并网节点当作PV节点来处理。

控制输入受限的准全控制利用率有限时间稳定控制

针对控制输入受限的非线性系统,分6种情况证明有限时间稳定控制器(finite time stable controller,FTSC)作用下的系统状态收敛速度在论域空间中每一点必快于非有限时间稳定控制器(non-FTSC,NFTSC)作用下的系统状态收敛速度,并给出每一类情况下设计参数应满足的充分性约束条件,同时证明这些条件的存在性.在此基础上,提出全控制利用率控制器(CCUC)的定义,证明CCUC必然引起抖振,进而提出准全控制利用率控制器(QCCUC)设计的思想,并证明控制输入受限条件下,FTSC的控制利用率必优于任意快速FTSC(FFTSC),即具有更优的控制性能,从而得到一系列关于参数优化的结论.理论证明的结论通过图表、数例和仿真得到了验证.所得结论对终端滑模控制、加幂积分控制、有限时间稳定backstepping控制等多种FTSC均广泛适用.

谈如何控制煤化验数据的准确性

作为我国经济发展重要支撑性资源,煤炭在冶金、化工等方面的生产当中皆是不可或缺的重要原材料,同时,人们日常生活也对煤有着极大依赖性,例如楼房供暖等方面,而煤化实验与煤自身质量有着最为直接的关联,并且对于煤使用效率有着决定性作用。基于此,本文将主要针对如何对煤化实验数据准确性进行有效控制展开探讨。

Data-driven nonlinear control of a solid oxide fuel cell system

Solid oxide fuel cells (SOFCs) are considered to be one of the most important clean,distributed resources. However,SOFCs present a challenging control problem owing to their slow dynamics,nonlinearity and tight operating constraints. A novel data-driven nonlinear control strategy was proposed to solve the SOFC control problem by combining a virtual reference feedback tuning (VRFT) method and support vector machine. In order to fulfill the requirement for fuel utilization and control constraints,a dynamic constraints unit and an anti-windup scheme were adopted. In addition,a feedforward loop was designed to deal with the current disturbance. Detailed simulations demonstrate that the fast response of fuel flow for the current demand disturbance and zero steady error of the output voltage are both achieved. Meanwhile,fuel utilization is kept almost within the safe region.

Fair Data Collection Scheme in Wireless Sensor Networks

To solve the slow congestion detection and rate convergence problems in the existing rate control based fair data collection schemes, a new fair data collection scheme is proposed, which is named the improved scheme with fairness or ISWF for short. In ISWF, a quick congestion detection method, which combines the queue length with traffic changes of a node, is used to solve the slow congestion detection problem, and a new solution, which adjusts the rate of sending data of a node by monitoring the channel utilization rate, is used to solve the slow convergence problem. At the same time, the probability selection method is used in ISWF to achieve the fairness of channel bandwidth utilization. Experiment and simulation results show that ISWF can effectively reduce the reaction time in detecting congestion and shorten the rate convergence process. Compared with the existing tree-based fair data collection schemes, ISWF can achieve better fairness in data collection and reduce the transmission delay effectively, and at the same time, it can increase the average network throughput by 9.1% or more.

Utilization of Fungi for the Biological Control of Insect Pests and Ganoderma Disease in the Indonesian Oil Palm Industry

Biological control is usually the first choice of control and prevention method for integrated pest management （IPM） strategies and has now been widely implemented by Indonesian oil palm plantations. Entomopathogenic fungus, i.e., Metarhizium anisopliae, Cordyceps militaris and Beauveria bassiana have been demonstrated to control renowned pests of oil palm. Metarhizium has been used to control Oryctes larvae and the mortality has ranged from 91.67% to 100% in laboratory and 7.4% to 88.75% in the field. Metarhizium has been applied in combination with a termite baiting system （TBS） to control termites in the field for preventive and curative action as well. In many oil palm plantations in Indonesia, Cordyceps has been used to reduce the field moth population ofSetothosea asigna. Application of Cordyceps within the oil palm circle was able to infect S. asigna pupae up to 80%. Meanwhile, Beauveria in an effervescent formulation was demonstrated to have better efficacy on Darna trima larvae. A significant finding on the biological control of basal stem rot disease （Ganoderma） was the isolation of Trichoderma sp. and Gliocladium sp.. The efficacy was conducted with promising result and techniques on the application of Triehoderma have been developed, i.e., hole-in-hole system, surgery and a mounding method. However, as the roots developed, Trichoderma was no longer able to protect the palm from Ganoderma. In spite of that, the use of Trichoderma still prolonged the life ofoil palms by up to 2-3 years. Another fungi belonging to vesicular arbuscular mychorrhiza （VAM） has been developed to control Ganoderma. The efficacy in the nursery showed promising results and the Ganoderma incidence remained low compared to the untreated control. Large scale field trials are ongoing. Challenges on the implementation of biological control in oil palm plantations are because of application and availability of biopesticides/natural enemies. Therefore, advances in research on the formulation of biological control agents are still needed.

Rate-aware optimal transmission power analysis in wireless ad hoc networks

The problem of transmission power control in a rate-aware way is investigated to improve the throughput of wireless ad hoc network. The behavior of basic IEEE 802.11 DCF is approximated by the p-persistent CSMA through a Markov chain model. The throughput model takes hidden terminals, muhi-hop flow and concurrent interference into account. Numerical results show that the optimal transmission power derived from this model could balance the tradeoff between spatial reuse and data rate and hence yield maximum throughput.

Effects of Sodium Butyrate on Nutrient Availability of Broilers

A metabolism trial was conducted to investigate the effects of graded dietary supplement of Sodium Butyrate （SB）, either powder （uncoated） or coated on nutrient utilization in broilers. Seventy-two 42-day-old AA broilers were randomly divided into nine treatments, each treatment consisted of four replicate cages of two chickens each. Broilers were fed the following diets： A） CTR： control diet （without any SB and antibiotics）; B） Antibiotic： supply antibiotics （Zinc Bacitracin 40 mg/kg ＋ Colistin Sulfate 8 rng/kg） into the basal diet; C） PSB-100： control diet ＋ 100 mg/kg PSB （powder Sodium Butyrate）; D） PSB-200： control diet ＋ 200 mg/kg PSB; E） PSB-300： control diet ＋ 300 mg/kg PSB; F） CSB-100： control diet ＋ 100 mg/kg CSB （coated Sodium Butyrate）; G） CSB-200： control diet ＋ 200 mg/kg CSB; H） CSB-300： control diet ＋ 300 mg/kg CSB. The birds were housed in 36 wire cages in an environmentally controlled room, fed for ad libitum intake and had free access to water. Feed and excreta samples were collected to determine DM （dry matter）, CP （crude protein）, EE （ether extract）, GE （gross energy） and NDF （neutral detergent fibre）. Results in- dicated that compared with control diet, SB could improve the AMR （apparent metabolic rate） and TMR （true metabolic rate） ofDM, CP, EE, GE and NDF on broilers, and it could replace antibiotics partly, and the effect of CSB was better than that of powder （uncoated） ones.