選擇卷期
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Thermal performance improvement for a two-phase loop thermosyphon (TPLT) with non-condensable gas (NCG) was attempted by fitting twin spiky ribbed twisted tapes (SRTTs) in the evaporator. The startup process and the steady-state boiling flow structures, boiling heat transfer rates, thermal resistance networks at various heater powers, and condenser thermal resistances were examined with 40% molar fraction of air in the TPLT. With treated water as the working fluid at an evaporator volumetric filling ratio of 50%, all tests were performed at sub-atmospheric pressures. The thermal performance improvement achieved by using SRTTs in the evaporator was determined by comparing the test results measured from the TPLT of the plain evaporator without NCG and the TPLT with NCG and SRTTs in the evaporator. Axial swirls generated in the evaporator suppressed the oscillatory interfacial structures caused by shooting intermittent vapor slugs, which led to improved boiling stability and reduced the overall thermal resistance. Correlations for evaluating the boiling Nusselt numbers over pool boiling, intermittent, and vapor regions as well as the dimensionless overall thermal resistance were devised for the present enhanced TPLT with NCG to represent all generated data.
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This paper proposes a passive fuzzy controller design methodology for stabilization of the nonlinear lift feedback fin stabilizer system of a ship. The proposed design approach is developed based on multiplicative noised Takagi-Sugeno fuzzy model and parallel distributed compensation control technique. Applying the Itô's formula and the sense of mean square, the sufficient conditions are developed to analyze the stability and to design the controller for stochastic nonlinear systems. The sufficient conditions derived in this paper belong to the linear matrix inequality forms which can be solved efficiently by convex optimal programming algorithm. Besides, the passivity theory is applied to discuss the effect of external disturbance on the system. Finally, the proposed systematic design method is applied to the fuzzy controller design of lift-feedback-fin stabilizer systems of a ship. The simulation results of lift-feedback-fin stabilizer control system of a ship show that the proposed passive fuzzy controller design method is effective.
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Chen (2013) extended the exiting SBM approaches and developed a joint model (J-SBM) that can (1) simultaneously compute SBM scores for inefficient DMUs and super-efficiency for efficient DMUs, (2) guarantee the reference points generated by the J-SBM are Pareto-efficient, and (3) the J-SBM scores of a DMU are continuous in the input and output space. In this note, we provide a counter example which shows that the reference point generated by the J-SBM might not be Pareto-efficient, and the current study has also revised the model (8) proposed by Chen (2013).
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An improved ant colony optimization (ACO) algorithm is proposed in this paper for improving the accuracy of path planning. The main idea of this paper is to avoid local minima by continuously tuning a setting parameter and the establishment of novel mechanisms by means of partial pheromone updating and opposite pheromone updating. As a result, the global search of the proposed ACO algorithm can be significantly enhanced to derive an optimal path compared to the conventional ACO algorithm. The simulation results of the proposed approach perform better in terms of the short distance, mean distance, and success rate towards optimal paths. To further reduce the computation time, the proposed ACO algorithm for path planning is realized on a FPGA chip to verify its practicalities. Experimental results indicate that the efficiency of the path planning is considerably improved by the hardware design for embedded applications.
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This paper explores the properties of the efficiency measures of the variant of radial measure (VRM) which is capable of dealing with negative data in DEA. We found that the input-oriented efficiency measure for VRM might be negative and the range of the output-oriented efficiency measure for VRM might be limited to [0.5, 1]. To circumvent these two situations, we propose the new efficiency measures which prevent the input-oriented efficiency from becoming negative and the output-oriented efficiency from being limited to [0.5, 1].
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International container ports are critical hubs for global logistics, and high efficiency is a particularly important requirement for managing these ports. International container ports in Taiwan and surrounding areas have to deal with increasingly larger amounts of cargo in recent years. As a result, it has become more difficult to measure these ports' efficiency. This study offers a new approach for measuring the efficiency of international ports. Twelve international container ports in Taiwan and surrounding areas were chosen as the samples, and their six inputs (application service process, service personnel ability, service personnel attitude, advisory services, harbor rates and stevedoring rates), and seven outputs (tug boat operation, rope untwisting operation, pilot operation, stevedoring efficiency, low damage rate for goods, awaiting unloading and working, and service flexibility) are analyzed herein with fuzzy data envelopment analysis (DEA). This approach allows objective and easy measurement of international container port efficiency.
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This study examined the flame behavior and thermal structure of non-premixed transversely oscillating plane jet flames. A V-shaped fluidic oscillator was installed with deflection plates to merge alternately issued pulsating jets, and induce transverse oscillations of the merged jet. Co-flowing air streams were supplied with two planar air jets arranged next to the burner. Isothermal jet frequencies were detected using single hot-wire anemometry. Flame behaviors were studied using photographic techniques. Flame temperatures were measured using a fine-wire type-R thermocouple, and combustion concentrations of products were measured using a gas analyzer. The Strouhal number for the transversely oscillating jet shows an asymptotic value of 0.188. Three flame modes exist in the domain of the jet Reynolds number Re and the co-flow air Reynolds number Re_a: attached flame, transitional flame, and lifted flame. At Re ＜ 1204, the axial location of the maximum flame width decreases as Re_a increases, while at Re ＞ 1204, the axial location of the maximum flame width increases as Re_a increases. As Re_a increases, the flames become thinner, the maximum flame width decreases, and the maximum flame temperature increases. Co-flow air Re_a of 846 produces higher flame temperatures by approximately 100°C compared with the co-flow air Re_a of 445. The analysis reveals that high velocity co-flow air results in better combustion performance when compared to low velocity co-flowing air. The combustion characteristics of the transversely oscillating plane jet flames improved significantly, especially with high velocity co-flow air due to the enhanced jet turbulence, entrainment, and mixing.
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In this study, quality function deployment (QFD) and gray relational analysis (GRA) were combined to develop a gray QFD approach to determine the techniques for improving the Chinese guanxi quality (CGQ) of ocean freight forwarders in Taiwan. The first step was to identify the consignors' needs and technical requirements of improving the CGQ. Then, a relationship matrix was constructed to link technical requirements and consignor's CGQ needs based on cross-functional expertise. Finally, the grey relational analysis was employed to determine the execution priority of technical requirements. The results revealed that the top five technical requirements to improve the CGQ with consignors are as follows: find a common topic, listen to customers' needs, greet each other regularly, meet for pleasurable meals, and participate in customers' social and business events. Furthermore, recommendations regarding the top five technique solutions are presented in this paper.
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In a steel plant, waste heat recovery systems of hot-blast furnace are characterized by high-temperature exhaust gas from a hot stove that flows through heat pipe heat exchangers. By heating gas in a hot stove and combustion air in a blast furnace, stable and balanced heat exchange efficiency is achieved in this system. The thermosyphon, which is also known as a gravitational heat pipe, uses latent heat to transfer the heat. In this article, heat pipe performance limits, including entrainment and boiling limits, are experimentally and theoretically investigated. Heat pipe tube lengths of 130 mm, 200 mm, and 300 mm were used in the experiment, and the operating temperature and heat transfer rates obtained were compared in a MATLAB prediction program to determine when boiling and entrainment limits occur. The precision comparisons of the theoretical and experimental results were 8.7% and 6.7%, respectively. Therefore, a standard test method and prediction program for boiling and entrainment limits are presented in this study, and the heat transfer phenomena in heat pipes of any scale are explained when these limits occur. Additionally, according to data from the China Steel Corporation, the capacity limit of the heat transfer rate for the heat pipe in this study is calculated at 8,370 W.
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This paper proposes the design of an Intelligent Damping Controller (IDC) for a Static Synchronous Compensator (STATCOM), linking to a high voltage direct current (HVDC) transmission line, where a permanent magnet synchronous generator (PMSG)- based offshore wind farm (OWF) is connected. This IDC consists of a critic network with the proposed Functional Link based Recurrent Fuzzy Neural Network (FLRFNN) and Genetic Algorithm Hybrid Time Varying Particle Swarm Optimization (GAHTVPSO) algorithm. A single-machine infinite-bus and a multi-machine hybrid power system were used for test the system stability. GAHTVPSO approach is developed to adjust the learning rates to improve the learning capability. Analysis of the performance shows that it can achieve better damping characteristics.