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A Hybrid Traffic Flow Model for Real Time Freeway Traffic Simulation
Liguo Zhang,Yong Ma,Liang Shi 대한토목학회 2014 KSCE JOURNAL OF CIVIL ENGINEERING Vol.18 No.4
Macroscopic traffic flow models play a significant role in the Intelligent Transportation Systems (ITS), especially for the urbantraffic control and the dynamic traffic assignment, in which the traffic dynamics usually described by the nonlinear equations aredifficult to be solved and limit the practice application. This paper presents a hybrid macroscopic and microscopic (macromicroscopic)traffic model by extending Daganzo’s Cell Transmission Model (CTM) with the real time speed dynamic. A simplesupplying and demanding function is defined to represent the traffic propagation between the adjacent cell boundaries, and the carfollowingmodel is integrated to specify the dynamics of average speed in each cell. Simulation results with data set collected from a4-kilometre long urban freeway show the performance of the model compared to the METANET model.
( Liguo Zhang ),( Qiaoying Ban ),( Jianzheng Li ),( Ajay Kumar Jha ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.8
The effect of pH on propionate degradation in an upflow anaerobic sludge blanket (UASB) reactor containing propionate as a sole carbon source was studied. Under influent propionate of 2,000 mg/l and 35ºC, propionate removal at pH 7.5-6.8 was above 93.6%. Propionate conversion was significantly inhibited with stepwise pH decrease from pH 6.8 to 6.5, 6.0, 5.5, 5.0, 4.5, and then to 4.0. After long-term operation, the propionate removal at pH 6.5-4.5 maintained an efficiency of 88.5%-70.1%, whereas propionate was hardly decomposed at pH 4.0. Microbial composition analysis showed that propionate-oxidizing bacteria from the genera Pelotomaculum and Smithella likely existed in this system. They were significantly reduced at pH ≤5.5. The methanogens in this UASB reactor belonged to four genera: Methanobacterium, Methanospirillum, Methanofollis, and Methanosaeta. Most detectable hydrogenotrophic methanogens were able to grow at low pH conditions (pH 6.0-4.0), but the acetotrophic methanogens were reduced as pH decreased. These results indicated that propionate-oxidizing bacteria and acetotrophic methanogens were more sensitive to low pH (5.5-4.0) than hydrogenotrophic methanogens.
The Cement Content Measurement of Cement Mixing Piles with EDTA Titration Method
Fuhai Zhang,Lei Zhang,Liguo Yang,Tugen Feng,Lei Chen,Xiaochun Zhong 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.11
The uniformity of cement mixing piles is visually tested on the drilled core samples, significantly relying on experience and extremely inaccurate. The cement content of core samples is an important parameter to quantify the uniformity of cement mixing piles. However, there were no well-accepted methods of testing the cement content of core samples. EDTA titration method is widely used as an effective way to test the cement content of cement-stabilized soil in highway subgrade. However, the cement mixing piles cannot be drilled until 28 days after construction, which causes remarkable change of water content and cement hydration during this period. In addition, factors affecting the EDTA titration results should be investigated before standard EDTA titration curves are constructed. In this paper, effects of different factors including curing method, curing period, soil type, content of water glass, and cement type, on EDTA titration testing results were investigated. It is found that cement type and soil type will significantly affect the test result. It is critical to keep the curing environment and soil unsieved before testing. Water glass will reduce the EDTA solution consumptions at early stages of curing. The EDTA titration results are verified by the proposed density estimation method.
Integrated fault location method for distribution networks based on IACO‑PS
Shuqing Zhang,Xiaowen Zhang,Anqi Jiang,Liguo Zhang,Mingliang Li 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.1
This paper develops a new hybrid method based on an improved ant colony optimization algorithm that incorporates pattern search (IACO-PS) for determining the location of faults in a distribution network. The performance of the conventional ant colony optimization (ACO) algorithm is improved using the opposite-based learning strategy to generate the initial population and adding a weight coefficient into the pheromone update mechanism to dynamically adjust the pheromone volatilization factor. The hybrid IACO-PS algorithm combines the individual strengths of ACO and PS. In addition, the fitness function is constructed by counting the false and missing fault information into the fault variable. In optimizing benchmark function experiments, the proposed hybrid IACO-PS presents a superior performance when compared to other improved versions of ACO. The effectiveness of the proposed approach is corroborated by tests performed on an IEEE 134-bus network. Simulation results show that the proposed hybrid IACO-PS method can determine the location of a fault even in the presence of fault distortion. In addition, it is immune to noise and data loss errors. Finally, the method proposed in this paper significantly outperforms other published fault location methods, and it can accurately locate faults and identify the type of distortion.
An improved unified description of charge-carrier mobilities in disordered organic semiconductors
Liguo Wang,Huaiwu Zhang,Xiaoli Tang,Chunhong Mu,Jun Li 한국물리학회 2010 Current Applied Physics Vol.10 No.4
An improved unified description of the dependence of the charge-carrier mobility on temperature, carrier density, and electric field in disordered organic semiconductors is proposed based on the Arrhenius temperature dependence ln(μ) ∝ / 1=T and non-Arrhenius temperature dependence ln(μ) ∝ / 1=T2. The improved description of the mobility can quite well fit the numerical solution of the master equation at both the low densities and high densities, the latter of which cannot be accurately described using the model introduced by Pasveer et al. [6]. Experimental current–voltage characteristics in devices based on organic semiconductors are also excellently reproduced with this improved description. Finally, we calculate and analyze the distribution of the charge-carrier density and electric field with position in polymer layer for two organic semiconductors in detail by using the improved description.
Liguo Wang,Qingyue Jiang,Chaoyu Zhang,Dongxin Jin,Hui Deng 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3
In order to satisfy the urgent requirements for the overheating protection of induction motors, an approach that can be used to identify motor temperature has been proposed based on the rotor slots harmonic (RSH) in this paper. One method to accomplish this is to improve the calculation efficiency of the RSH by predicting the stator winding distribution harmonic order by analyzing the harmonics spectrum. Another approach is to increase the identification accuracy of the RSH by suppressing the influence of voltage flashes or current surges during temperature estimation based on model predictive control (MPC). First, an analytical expression of the stator inductance is extracted from a steady-state positive sequence motor equivalent circuit model developed from the rotor flux field orientation. Then a procedure that applies MPC for reducing the identification error of the rotor temperature caused by voltage sag or swell of the power system is given. Due to this work, the efficiency and accuracy of the RSH have been significantly improved and validated our experiments. This work can serves as a reference for the on-line temperature monitoring and overheating protection of an induction motor.
Wang, Liguo,Jiang, Qingyue,Zhang, Chaoyu,Jin, Dongxin,Deng, Hui The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3
In order to satisfy the urgent requirements for the overheating protection of induction motors, an approach that can be used to identify motor temperature has been proposed based on the rotor slots harmonic (RSH) in this paper. One method to accomplish this is to improve the calculation efficiency of the RSH by predicting the stator winding distribution harmonic order by analyzing the harmonics spectrum. Another approach is to increase the identification accuracy of the RSH by suppressing the influence of voltage flashes or current surges during temperature estimation based on model predictive control (MPC). First, an analytical expression of the stator inductance is extracted from a steady-state positive sequence motor equivalent circuit model developed from the rotor flux field orientation. Then a procedure that applies MPC for reducing the identification error of the rotor temperature caused by voltage sag or swell of the power system is given. Due to this work, the efficiency and accuracy of the RSH have been significantly improved and validated our experiments. This work can serves as a reference for the on-line temperature monitoring and overheating protection of an induction motor.
Haicong Zhang,Jianxiong Yu,Qingyue Jiang,Liguo Wang,Dianguo Xu 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper proposes a sensor-less temperature identification and an intelligent power supply method for Electric Submersible Motor (ESM) in oil wells. With measurements obtained from the proposed identification, a thermodynamics module is established for the temperature and the fault detection. Besides, the relationship between the rotor temperature and the load can be calculated. Then based on different loads, suitable ratios of voltage to frequency in different conditions can be captured. Finally, the control of the ratio enables power supply to match the oil pump output automatically. The experimental results from an ESM (12kW) in lab are shown to validate the proposed method. The whole scheme is effective and reliable and is therefore suitable to reduce the maintenance frequency of oil pumps and the power consumption of oil wells.