Energy and Exergy Analysis, and Thermoeconomic Performance of a BCHP System

Building cooling, heating and power (BCHP) systems should play an important role in achieving the goals of energy efficient use and environment protection in China. It will make big sense when this type of system shows a good performance energetically and economically. An on-site BCHP system being the first in the country was installed and put to use five years ago. As the first step to evaluate the project, com~tations were made based on thermodynamic and themoeconomic theories to evaluate the system on full load and off-design conditions in summer. Discussion and analyses are made mainly in terms of exergetic efficiency and costs of unit amount of useful exergy produced in this paper.     

Adaptive Excitation Control with L2 Disturbance Attenuation for Multi-Machine Power Systems

Generator excitation control plays an important role in improving the dynamic performance and stability of power systems. This paper is concerned with nonlinear decentralized adaptive excitation control for multi-machine power systems. Based on a recursive design method, an adaptive excitation control law with L2 disturbance attenuation is constructed. Furthermore, it is verified that the proposed control scheme possesses the property of decentralization and the robustness in the sense of L2-gain. As a consequence, transient stability of a multi-machine power system is guaranteed, regardless of system parameters variation and faults.     

ClustNails:Visual Analysis of Subspace Clusters

Subspace clustering addresses an important problem in clustering multi-dimensional data.In sparse multi-dimensional data,many dimensions are irrelevant and obscure the cluster boundaries.Subspace clustering helps by mining the clusters present in only locally relevant subsets of dimensions.However,understanding the result of subspace clustering by analysts is not trivial.In addition to the grouping information,relevant sets of dimensions and overlaps between groups,both in terms of dimensions and records,need to be analyzed.We introduce a visual subspace cluster analysis system called ClustNails.It integrates several novel visualization techniques with various user interaction facilities to support navigating and interpreting the result of subspace clustering.We demonstrate the effectiveness of the proposed system by applying it to the analysis of real world data and comparing it with existing visual subspace cluster analysis systems.     

Participation of large-scale wind power generation in power system frequency regulation

The initiative participation of wind power generators in power system frequency regulation is an inevitable demand to ensure power system safe operation with large-scale wind power integration. However, it is principally difficult for conventional wind turbines to participate in power system frequency regulation. For this reason, solution to this problem is becoming a hot topic in the current studies. This paper systematically reviews the relevant research progresses in the control strategies and the capability assessment of using wind power generators in the power system frequency regulation, including the comparing among the emu- lating inertia control, the droop control, the rotor speed control, the pitch angle control and the coordinated control. Also, future research in this area is pointed out in the paper.     

Using Agents in Web-Based Constructivist Collaborative Learning System

Web-based learning systems are one of the most interesting topics in the area of the application of computers to education. Collaborative learning, as an important principle in constructivist learning theory, is an important instruction mode for open and distance learning systems. Through collaborative learning, students can greatly improve their creativity, exploration capability, and social cooperation. This paper used an agent-based coordination mechanism to respond to the requirements of an efficient and motivating learning process. This coordination mechanism is based on a Web-based constructivist collaborative learning system, in which students can learn in groups and interact with each other by several kinds of communication modes to achieve their learning objectives efficiently and actively. In this learning system, artificial agents represent an active part in the collaborative learning process; they can partially replace human instructors during the multi-mode interaction of the students.     

Vital basic research on modern power systems geared to 21st century

Through analysis of the demand on national modern power systems, a proposal is made to establish and develop basic theories for collapse prevention and optimal operation of large power systems in the 21st century, including three main parts: large system stability theory, nonlinear control theory, and real time simulation and strategic decision systems. The basic features of large power systems are first discussed. Then, by summarizing the research results in this field, the main framework of the above basic theories and the related important scientific problems are systematically described. Their current development conditions and possible research directions are also discussed.     

Design of Optimal Weight for a Gear Transmission System Using Hybrid Taguchi-Genetic Algorithm

The gear transmission system has been widely applied in mechanical systems, and many high-performance applications of these systems require low weight. With the aid of establishing the optimization model of the gear transmission system that consists of an objective function and some constraints (for example, the bending stress, the contact stress, the torsional strength, etc.), the optimal weight design of the gear transmission system can be transformed into the optimization problem for the objective function under the constraints. Moreover, both the shaft and the gear of the gear transmission system are considered simultaneously in our design. The hybrid Taguchi-genetic algorithm (HTGA) is employed to find the optimal design variables and the optimal weight of the system. An illustrated example for the single spur gear reducer is given to show that the optimal weight design problem can be successfully solved using the proposed design scheme. It also proves the high efficiency and feasibility of the algorithm in the gear design.     

Reliability Study on the Risk Precontrol Management System of Coal Mines Safety

Risk precontrol management system of coal mines safety（ RPMSCS） provides a set of preventive safety management strategy for high-risk coal industries, which has captured extensive attentions. Fundamentally,there are several membership systems with subsystems in the management system, and the subsystem reliability has an important influence on the management system performance. Through analyzing the structure characteristics of the management system,the phase type distribution was employed to analyze its subsystem reliability by considering repair process and three states including working,fail-abnormal,and fail-emergency states. The reliability indices of the subsystem were derived respectively,including the probabilities that the subsystem in three states,mean time to the first failure, mean time to first failemergency,mean working time to first fail-emergency,and mean maintenance time to the first fail-emergency, are derived respectively. The probabilities of the membership systems and the management system in three states were also derived. Some numerical examples were used to show the procedures. The result is important for better understanding the management system operation and improving its operational performance from the respect of system reliability.     

A novel lignite pre-drying system with low-grade heat integration for modern lignite power plants

The lignite pre-drying process plays an important role in modern lignite power plants and the fluidized bed dryer with internal heat utilization is a promising drying method which has both high efficiency and cost-effectiveness. After conducting an in-depth analysis of a typical lignite pre-drying power plant, this work proposed a novel lignite pre-drying system with low-grade heat integration. Through system integration, the low-temperature evaporation of the lignite was recovered to heat the combustion air, while the residual heat from the flue gases was used to heat the feed or condensed water, thereby saving a portion of heat from the steam bleeds of the high and intermediate pressure turbines. The results for a 1,000 MW lignite-fired power plant showed that, the proposed pre-drying system could yield an increase in net plant efficiency of approximately 3.6 % points and a reduction in the cost of electricity of $1.83/（MW h）. The thermodynamic and economic performances were each superior to those of the existing pre-drying system, convincingly demonstrating that the research of this paper may provide a promising integrated lignite pre-drying method for the next-generation of lignite-fired power plants.     

Identification of Markovian open system dynamics for qubit systems

We discuss the problem of identification of the dynamical generators for open two-level quantum systems in a Markovian environment.Based on Bloch sphere representation,the identification problem is converted to the estimation of a 3-dimensional real process matrix A and an inhomogeneous term c.The parameter identifiability and sufficient conditions for completely identification of A and c are obtained.Further discussion shows that the obtained sufficient conditions are not always necessary.The approach can be generalized to finite-level open quantum systems in an arbitary Markovian environment.     

Leaching of a copper flotation concentrate with ammonium persulfate in an autoclave system

The leaching behavior of a copper flotation concentrate was investigated using ammonium persulfate (APS) in an autoclave system. The decomposition products of APS, active oxygen, and acidic medium were used to extract metals from the concentrate. Leaching experiments were performed to compare the availability of APS as an oxidizing agent for leaching of the concentrate under atmospheric conditions and in an autoclave system. Leaching temperature and APS concentration were found to be important parameters in both leaching systems. Atmospheric leaching studies showed that the metal extractions increased with the increase in APS concentration and temperature (up to 333 K). A similar tendency was determined in the autoclave studies up to 423 K. It was also determined that the metal extractions decreased at temperatures above 423 K due to the passivation of the particle surface by molten elemental sulfur. The results showed that higher copper extractions could be achieved using an autoclave system.     

Hamilton-Jacobi-Bellman equations and dynamic programming for power-optimization of a multistage heat engine system with generalized convective heat transfer law

A multistage endoreversible Carnot heat engine system operating between a finite thermal capacity high-temperature fluid reservoir and an infinite thermal capacity low-temperature environment with generalized convective heat transfer law [q∝(ΔT) m ] is investigated in this paper.Optimal control theory is applied to derive the continuous Hamilton-Jacobi-Bellman (HJB) equations,which determine the optimal fluid temperature configurations for maximum power output under the conditions of fixed initial time and fixed initial temperature of the driving fluid.Based on the universal optimization results,the analytical solution for the Newtonian heat transfer law (m=1) is also obtained.Since there are no analytical solutions for the other heat transfer laws (m≠1),the continuous HJB equations are discretized and dynamic programming algorithm is performed to obtain the complete numerical solutions of the optimization problem.The relationships among the maximum power output of the system,the process period and the fluid temperature are discussed in detail.The results obtained provide some theoretical guidelines for the optimal design and operation of practical energy conversion systems.     

电化学阻抗技术在高容量锂离子电池中的研究进展

The world’s energy system is changing dramatically. Li-ion battery, as a powerful and highly effective energy storage technique, is crucial to the new energy revolution for its continuously expanding application in electric vehicles and grids. Over the entire lifetime of these power batteries, it is essential to monitor their state of health not only for the predicted mileage and safety management of the running electric vehicles, but also for an “end-of-life” evaluation for their repurpose. Electrochemical impedance spectroscopy (EIS) has been widely used to diagnose the health state of batteries quickly and nondestructively. In this review, we have outlined the working principles of several electrochemical impedance techniques and further evaluated their application prospects to achieve the goal of nondestructive testing of battery health. EIS can scientifically and reasonably perform real-time monitoring and evaluation of electric vehicle power batteries in the future and play an important role in vehicle safety and battery gradient utilization.     

On-line Tool Wear Classification in Unmanned-machining Environments

One of the most important features of the modern ma ch ining system in an “unmanned“ factory is to change tools that have been subjec ted to wear and damage. An integrated tool condition monitoring system composed of multi-sensors, signal processing devices and intelligent decision making pla ns is a necessary requirement for automatic manufacturing processes. An intellig ent tool wear monitoring system will be introduced in this paper. The system is equipped with power consumption, vibration, AE and cutt...     

CFSBC： Clustering in High-Dimensional Space Based on Closed Frequent Item Set

Clustering in high-dimensional space is an important domain in data mining. It is the process of discovering groups in a high-dimensional dataset, in such way, that the similarity between the elements of the same cluster is maximum and between different clusters is minimal. Many clustering algorithms are not applicable to high dimensional space for its sparseness and decline properties. Dimensionality reduction is an effective method to solve this problem. The paper proposes a novel clustering algorithm CFSBC based onclosed frequent hemsets derived from association rule mining. which can get the clustering attributes with high efficiency. The algorithm has several advantages. First, it deals effectively with the problem of dimensionality reduction. Second, it is applicable to different kinds of attributes, Third, it is suitable for very large data sets. Experiment shows that the proposed algorithm is effective and efficient     

The optimal power distribution in cooperative communication relay system

In order to optimize power utilization of relay nodes in cooperative communication,a power allocation algorithm with objective function to maximize system capacity is proposed.Based on the convex optimization theory,an ellipsoid algorithm is used to solve this problem,which could simplify the subgradient choosing steps and improve convergence stability,so that an optimized power allocation algorithm is presented.Theoretical analysis and simulation results show that the algorithm can effectively distribute the power of each node with lower complexity,and ensure the transmission capability of relay nodes in cooperative communication.     

High-voltage transmission tower-line system subjected to disaster loads

The high-voltage power transmission system is an important lifeline structure. It is significant for wide researches on the features and ability of the system subjected to earthquake and environmental loads. The promising prosperity of the system has been demonstrated around the world. The corresponding advances of the system with respect to the mechanism of loading action, analytical methods, experimental research measurements, structural vibration control, fatigue damage, lifetime prediction, and design methods are comprehensively discussed herein. Finally, further research work on dynamic response characteristics of high-voltage transmission tower-line system in the near future is predicted.     

Development of Oxide Ceramics for Application in Solid Oxide Fuel Cells

1 Results Solid oxide fuel cells (SOFC) are ceramic fuel cells that convert chemical into electrical energy in a temperature region between 650 ℃ and 1 000 ℃.Systems are currently under development for a variety of applications e.g. for both small and large scale stationary combined heat and power systems but also for the supply of electrical energy in the automotive area. The current objectives in the development of SOFCs is to lower the operating temperature from 850 ℃ down to below 750 ℃ in order to improve durability and reduce costs of the SOFC stack.     

Distributed Estimation for Sensor Networks with Channel Estimation Errors

This paper describes the effect of channel estimation error (CEE) on the performance of distributed estimations of an unknown parameter in a wireless sensor network. Both the classical and Bayesian estimators are derived to mitigate the adverse effects caused by the CEE. Power scheduling among sensors and the power ratio between the training and data transmission at each individual node are optimized by directly minimizing the final average mean squared error to compensate for the CEE. A closed-form power scheduling policy is given for a homogeneous environment, which shows that more than 50% of the power should be allocated to sensor observation transmissions. For an inhomogeneous environment, a multilevel waterfilling type solution is developed for the power scheduling among sensors for only the sum power constraint with a "cave" waterfilling solution for both the sum and individual power constraints. Simulations show that the proposed power scheduling schemes achieve better performance than the equal power scheduling scheme.