센서구동 방식에 의한 태양추적 시스템

박정국,최연옥,조금배,최창주 조선대학교 에너지.자원신기술연구소 2004 에너지·자원신기술연구소 논문지 Vol.26 No.2

Nowaday, almost of practical energy comes from the fossil fuel, such as coal, oil and gas. But those methode causes the environmental pollution. Photovoltaic systems are considered as a alternative energy source to overcome the shortage of electricity in the future. Photovoltaic system is easier to operate and maintain than the other power generating system since it generally contains no moving parts, operate silently and require very little maintenance. In this paper, it is proposed 150[W] solar tracking system, the system designed as the normal line of the solar cell always runs parallel the ray of the sun. This design can minimize the cosign loss of the system.

Dirichlet 경계조건하에서의 비선형 타원형 방정식

한춘호,김정국 江原大學校 産業技術硏究所 1998 産業技術硏究 Vol.18 No.-

이 논문에서는 Diruchlet 경계 조건을 갖는 비선형 타원형 방정식 -△u+g(u)=f(x)의 해의 존재에 대한 연구를 하였다.존재하는 해의 다중성을 증명하기 위하여 임계점 이론과 롤의 정리를 사용하였으며, 대응되는 범함수에 따라서 방정식의 해와 임계점이 동시에 나타난다는 정리를 이용하였다. 이 때 g(u)=bu?-au?으로 나타날때 외력항 (방정식의 우변)의 상수로 주어지는 경우 적어도 두 개의 해가 존재한다는 것을 증명하였다.만약 우변(외력항)의 상수가 음수이거나 0인 경우이 방정식의 해가 존재하지 않거나 자명한 해만 존재하기 때문에 상수는 양수인 것으로 가정하였다.

Hollow CuO nanospheres uniformly anchored on porous Si nanowires: preparation and their potential use as electrochemical sensors.

Guo, Zheng,Seol, Myeong-Lok,Kim, Moon-Seok,Ahn, Jae-Hyuk,Choi, Yang-Kyu,Liu, Jin-Huai,Huang, Xing-Jiu RSC Pub 2012 Nanoscale Vol.4 No.23

<P>Hollow CuO nanospheres have been prepared via a reduction reaction of copper ions on porous Si nanowires combined with calcination in air and uniformly anchored on their surfaces. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize and analyze as-synthesized samples. The results reveal that Si nanowires fabricated from heavily doped Si wafer are formed with a meso-porous structure by an Ag-assisted etching approach, and Cu nanoparticles are formed and uniformly decorated on the Si nanowires through a reaction of copper ions reduced by silicon. After annealing in air, Cu nanoparticles are in situ oxidized and transformed into CuO, leading to the formation of hollow nanospheres because of the Kirkendall effect. The diameter size of as-prepared CuO hollow spheres anchored on porous Si nanowires is mainly around 30 nm. Finally, in order to illuminate the advantages of this novel hybrid nanostructure of nanosized hollow spheres supported on porous nanowires, its electrochemical sensing performance to hydrazine as an example has been further investigated. The results confirm that it is a good potential application to detect hydrazine.</P>

A Research of High Frequency Isolated Photovoltaic Inverter

( Zheng Guo Piao ),( Teng Zhang ) 조선대학교 공학기술연구원 2014 공학기술논문지 Vol.7 No.2

In recent years, high frequency inverter technology has become a research focus for renewable energy power generation system. High frequency isolated inverter has electrical isolation, light weight, small volume etc. In this paper, we research on the control technology of high frequency isolation inverter, and introduce the soft switching technology of the high frequency isolation photovoltaic grid connected inverter. Using the LCL resonant circuit, reduce the switching loss of the switching devices. Finally, its feasibility is validated by simulation.

Glutathione Conjugates of 2- or 6-Substituted 5,8-Dimethoxy-1,4-Naphthoquinone Derivatives : Formation and Structure

Zheng, Xiang-Guo,Kang, Jong-Seong,Kim, Yong,You, Young-Jae,Jin, Guang-Zhu,Ahn, Byung-Zun The Pharmaceutical Society of Korea 1999 Archives of Pharmacal Research Vol.22 No.4

Thirty-four glutathione conjugates of 5,8-dimethoxy-1,4-naphthoquinones (DMNQ) were synthesized and their structure was determined. The yield of GSH conjugate was dependent on size of alkyl group; the longer the size of alkyl group was, the lower was the yield. It was also found that the length of alkyl side chain influenced the chemical shift of quinonoid protons; the quinonoid protons of 2-glutathionyl DMNQ derivatives with R=H to propyl, 6.51-6.59 ppm vs. other ones with R=butyl to heptyl, 6.64-6.68 ppm. this was explained to be due to a folding effect of longer alkyl group. Glutathione (GSH) reacted with DMNQ derivative first to form a 1,4-adduct (2- or 3-glutathionyl-1,4-dihydroxy-5,8-dimethoxynaphthalenes) and then the adduct was autooxidized to 2- or 3-glutathionyl-DMNQ derivatives. Moreover, GSH reduced DMNQ derivatives to their hydrogenated products. It was suggested that such an organic reaction might play an important role for a study of metabolism or toxicity of DMNQ derivative sin the living cells.

Influence factors of non-uniform phase transformation in hot stamping process of ultra-high-strength steel sheet

Guo-zheng Quan,Chao An,Hui-min Qiu,Le Zhang,Xuan Wang 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.7

In the hot stamping process of ultra-high-strength steel sheets, it is a significant issue to reveal the nonuniformity of cooling rate in space–time domain by finite element method and even uncover the inner cause, which contributes to the further adjustment of the phase transformation. In this work, a series of heat transfer experiments between dies and sheets were conducted on the self-developed experimental apparatus. The temperature evolution curves of die and BR1500HS ultra-high-strength steel sheets under different pressures and holding time were obtained. Moreover, the transient heat transfer coefficients (HTC) under different mean interface temperatures and pressures were calculated by the inverse heat transfer algorithm. Subsequently, based on the HTC curves, a thermal–mechanical-phase dynamic coupling finite element model was developed for modeling the hot stamping process, and a series of simulations for analyzing the non-uniform microstructures distribution in hot stamping parts were implemented. Finally, the simulation results were validated by actual hot stamping experiments. Two significant influence factors on the nonuniform distribution of microstructures were summarized as follows: the existence of incomplete contact between steel sheets and dies due to the sheet thickness reduction in sidewall and circular bead regions, and the temperature differences between dies and steel sheets.

Construction of Processing Maps based on Expanded Data by BP-ANN and Identification of Optimal Deforming Parameters for Ti-6Al-4V Alloy

Guo-zheng Quan,Hai-rong Wen,Jia-Pan,Zhen-yu Zou 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.2

The intrinsic relationships between deforming parameters and microstructural mechanisms for Ti-6Al-4V alloy were analyzed by processing maps. A series of thermal compression tests were carried out in the temperatures range of 1023~1323 K (across β-transus) and strain rates range of 0.01~10 s-1 on a Gleeble-3500 thermo-mechanical simulator. Based on the stress-strain data collected from compression tests, a back-propagation artificial neural network (BP-ANN) model was developed, which presents reliable performance in tracking and predicting strain-stress data. By utilizing this model, the volume of stress-strain data was expanded. According to the intensive stress-strain data, the apparent activation energy was calculated to be 564.05 kJ mol-1 and 300.20 kJ mol-1 for α+β-phase field and single β-phase field, respectively. Moreover, the processing maps were constructed at finer intervals of temperature, from which, the stable regions with higher power dissipation efficiency (η > 0.3) and unstable regions with negative instability parameter (ξ < 0) were clarified clearly. By combining processing map with microstructure observations, two main stable softening mechanisms, i.e., globularization and dynamic recovery (DRV) were identified, and globularization-predominant (0.3 < η < 0.55) parameter domain ( < 0.1 s-1) in α+β-phase field and DRV-predominant (0.25 < η < 0.41) parameter domain (0.032 s-1< <1 s-1) in β- phase field were recommended. Manuscript

Multi-Variable and Bi-Objective Optimization of Electric Upsetting Process for Grain Refinement and Its Uniform Distribution

Guo-zheng Quan,Le Zhang,Chao An,Zhen-yu Zou 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.6

It is significant to adjust the microstructures of preforms in pursuit of high-quality exhaust valves. This work is a novel attempt to identify the optimum process parameters in electric upsetting of 3Cr20Ni10W2 high-alloy to achieve grain refinement and uniform distribution by multi-objective genetic algorithm (MOGA) optimization. A finite element (FE) model on basis of electric-thermalmechanical and macro-micro sequential multi-physics analysis methods was developed in software MSC. Mar. And different schedules of four independent process variables (heating current (I), clamping length (L), upsetting pressure (Pset) and velocity of the anvil cylinder (v)) were performed aiming to achieve two objective indicators (average grain size (dav) and inhomogeneous degree of grain distribution (σd)). Then, two objective response surfaces were constructed as the functions between the two indicators and the four independent process variables. As per the criterion that simultaneously minimize dav and σd, the processing parameters (Pset, L, v, I) were optimized by MOGA, and corresponding numerical simulation were performed. The results show that both dav and σd are improved significantly at the optimal process condition as verified by the trial-manufacture experiments, which validated the optimal design and corresponding simulation based on grain refinement and uniform distribution by MOGA was credible and effective.

Improvement of Formability for Multi-point Bending Process of AZ31B Sheet Material Using Elastic Cushion

Guo-Zheng Quan,구태완,강범수 한국정밀공학회 2011 International Journal of Precision Engineering and Vol.12 No.6

On multi-point forming process, one of the most obvious limitations is the need for a pliable interpolating material such as elastic cushion between punch element tips and sheet metal to prevent the formation of dimples on the surface of final part. In this study, numerical simulations of multi-point bending process in case of different thicknesses of elastic cushion are performed to obtain a specified final shape as a cylindrical surface with curvature radius of 434.65mm and centre angle parameter of 52.73° by using initial blank with length of 800mm, width of 600mm, and thickness of 2mm, respectively. To find the suitable thickness of the elastic cushion, four evaluating indicators including plastic dissipation energy, stress components, shape error and maximum ductile damage are introduced and analyzed. As the results, each value of four evaluating indicators is decreased, and their distributions become more uniform on the deformed blank by adopting the elastic cushion. Resultantly, it is summarized that the formability of AZ31B magnesium alloy can be improved by using the elastic cushion, and the most proper thickness of the elastic cushion is 4 mm for the multi-point bending process of AZ31B sheet with thickness of 2mm.

평판형 및 아치형 태양광발전 시스템의 성능평가 분석

Zheng-Guo Piao,최연옥(Youn-Ok Choi) 대한전기학회 2015 전기학회논문지 Vol.64 No.7

The studies on the operating performance analysis or design about the fixed tilt angle flat-plate photovoltaic (PV) system are still lively going off. However the operating property analysis about the arch type PV system which means PV array were designed as round type is dissatisfied. In this paper, we theoretically established the factors which are cause of the deterioration in performance of arch type PV system. In addition, we use the Solar Pro simulation tools to design both flat-plate type and arch type 30kW PV systems. The simulations about arch type PV system applied two ways such as central inverter and string inverter were conducted. The performance ratio (PR) of the PV system with flat-plate type shows the highest value 74[%] when the tilt angle is 30°. In case of arch type, when applying central inverter method, PR value shows approximately 73[%] and no more difference with arch type of the PV array. This value shows 1[%] decrease compare with the flat-plate type. However when applying string inverter methods, the average PR value shows 80 % and 6% improved than the central inverter method.