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.

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.

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

Sensitive and selective electrochemical detection of dopamine using an electrode modified with carboxylated carbonaceous spheres

Guo, Zheng,Seol, Myeong-Lok,Kim, Moon-Seok,Ahn, Jae-Hyuk,Choi, Yang-Kyu,Liu, Jin-Huai,Huang, Xing-Jiu The Royal Society of Chemistry 2013 The Analyst Vol.138 No.9

<P>A highly sensitive and selective electrochemical sensor of dopamine (DA) has been developed by employing carboxylated carbonaceous spheres to modify glassy carbon electrodes (GCEs). Scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy were used to characterize as-prepared carbonaceous spheres. The results show that the diameter of carboxylated carbonaceous spheres is uniformly 500 nm and that their surfaces mainly expose carboxyl groups with negative charges. Electrochemical measurements demonstrate that carboxylated carbonaceous spheres greatly improve the accumulation of positively charged dopamine, leading to good sensing performance on a modified GCE. Through applying the differential pulse voltammetric approach, linear calibration curves were obtained in a range of about 0.1 to 40 μM with a detection limit down to 30 nM. Furthermore, depending on the charge-based discrimination, the modified electrode displays good selective detection of DA and reliable anti-interference to UA and glucose besides a weak and negligible response to AA. Therefore, the carboxylated carbonaceous sphere introduced here is a good candidate to develop electrochemical sensors for the sensitive and selective detection of DA.</P> <P>Graphic Abstract</P><P>Carboxylated carbonaceous spheres (CCSs) reproducibly supported as advanced electrode coating for the determination of dopamine with high sensitivity, good selectivity and response stability. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3an36669c'> </P>

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>

Influence of random road excitation on DCT vehicle dynamic characteristics during starting and shifting

Zheng Guo,Datong Qin,Antai Li,Jihao Feng,Yonggang Liu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9

Road excitation is the basic input of vehicle vibration, which greatly impacts on vehicle ride comfort. In addition, it can cause vertical vibration of the vehicle, leading to deformation of the powertrain mount. Similarly, the longitudinal movement of the powertrain can also cause deformation of the powertrain mount. Due to the effect of the powertrain mount, there is a mutual coupling between the vehicle in the longitudinal and vertical directions, which has a great influence on the smoothness and comfort of the vehicle. In order to reveal the impact of random road excitation on the vehicle dynamic characteristics of a dual clutch transmission (DCT) vehicle under starting and shifting conditions, a longitudinal-vertical coupled dynamic model of the DCT vehicle considering the powertrain mount was established. This model includes dynamic torque model of the engine, powertrain mount model, transmission system model, tire model and road excitation model. The influence of random road excitation on the vehicle’s dynamic characteristics is analyzed under starting, shifting, and different starting and shifting intentions. The simulation results of the longitudinal-vertical coupling dynamic DCT vehicle model considering road excitation are compared with vehicle test results, the model is found to accurately reflect the influence of road excitation on the dynamic performance of DCT vehicles under starting and shifting conditions, thus verifying the correctness of the model.

Wide input/output control strategy for multiphase series capacitor bidirectional DC-DC converters

Guo, Zheng,Wang, Yubin,Wang, Fan,Tian, Xinna,Dong, Yuxiang The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.5

The series capacitor converter is one kind of high-gain bidirectional DC-DC converter based on interleaved and switched capacitor techniques. For the n-phase series capacitor converter, n times voltage gain when compared with the traditional boost converter under a specific duty cycle, as well as automatic current sharing among phases can be achieved. The specific duty cycle is (n - 1)/n to 1 in the boost mode and 0 to 1/n in the buck mode, which means that it is not suitable for wide input and/or wide output applications. To solve this issue, an 180° interleaved switching strategy is proposed in this paper. The proposed strategy is more suitable for converters to widen the working duty cycle range. The working principle, voltage gain and current distribution/sharing characteristics with the duty cycle ranging from 0 to 1 are analyzed and calculated in greater detail. In addition, as one of the n-phase series capacitor converters, a small signal model of a three-phase series capacitor converter is built, and a dual closed-loop controller is studied and designed. Finally, an experimental prototype with an input voltage that varies from 10 to 30 V and an output voltage of 100 V is built and tested. Results obtained with the prototype verify the correctness of the proposed switching strategy.

Naphthazarin Derivative (V) : Formation of Glutathione Conjugate and Cytotoxic Activity of 2-or 6-Substituted 5,8-Dimethoxy-1,4-napthoquinones in the Presence of Glutathione-S-transferase, in Rat Liver S-9 Fraction and Mouse Liver Perfusate

Zheng, Xiang-Guo,Kang, Jong-Seong,Kim, Hwan-Mook,Jin, Guang-Zhu,Ahn, Byung-Zun The Pharmaceutical Society of Korea 2000 Archives of Pharmacal Research Vol.23 No.1

Formation of glutathione (GSH) conjugates with 2- or 6-(1-hydroxymethyl)- and 2-(1-hydroxyethyl)-DMNQ derivatives (DMNQ, 5,8-dimethoxy-1,4-naphthoquone was carried out in phosphate buffer (pH 7.4), in the presence of glutathione-S-transferase (GST), in rat liver S-9 fraction and by perfusion, and the rates of conjugates formation were compared and correlated to cytotoxicity. The GSH conjugates of 6-(1-hydroxyalkyl)-DMNQ derivatives were formed faster than 2-(1-hydroxyalkyl)-DMNQ derivatives under all of the media, implying that steric hindrance was the cause of lowering the rate of conjugate formation of 2-substituted derivatives. For both isomers, addition of GST did not improve the reaction rate, compared with that in buffer, while the reaction in the S-9 fraction and the perfusate was accelerated to a great extent. The catalytic effect of the S-9 fraction and the perfusate contain an effective system relaxing the steric hindrance of 2-(1-hydroxyalkyl)-DMNQ derivatives. Furthermore, a good correlation between the formation of the GSH conjugates and the cytotoxic activity of both naphthazarin isomers suggests that the steric hindrance is a cause of lowering the cytotoxicity of 2-isomers.

Modelling of the Hot Flow Behaviors for Ti-13Nb-13Zr Alloy by BP-ANN Model and Its Application

Guo-zheng Quan,Shi-ao Pu,Zong-yang Zhan,Zhen-yu Zou,Ying-ying Liu,Yu-feng Xia 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

The plastic deformation mechanisms and the constitutive model of flow behaviors at different deformation conditions in biomedical titanium alloy are an essential step to optimize the design of any forging process for implant productions. A series of isothermal compressions tests on Ti-13Nb-13Zr alloy in a wide range of true strain, temperature and strain rate were conducted on a thermomechanical simulator. The hot flow behaviors with different softening mechanisms, including dynamic recrystallization and dynamic recovery, were characterized based on true strain-stress curves. A back-propagational artificial neural network (BP-ANN) method was conducted to evaluate and predict this non-linear problem by self-training to be adaptable to the material characteristics. The flow stress of this material a wide deformation condition range can be predicted accurately by the BP-ANN model obtained in this study. The prediction ability of this BP-ANN Model was evaluated by three accuracy indexes, Absolute error, Relative error and Average absolute relative error. Sequently, the developed BP-ANN model was programed and implanted into the finite element (FE) analysis platform, Msc.Marc software. The results have sufficiently articulated that the well-trained ANN model has excellent capability to deal with the complex flow behaviors and has great application potentiality in hot deformation processes.