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.

Thermal Deformation Isolation for Satellite Platforms via Flexible Connections

Zheng-Chun Du,Hong-Fu Hou,Zhi-Guo Wang,Jian-Guo Yang 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.12

Thermal deformation is a serious issue for many space structures when travelling around Earth. This paper presents a method to achieve extremely low thermal deformation in satellite platforms with prototype applications. In addition to using the traditional nearzero coefficient of thermal expansion (CTE) material, the platform succeeded in comparison to the traditional energy-consuming methods mainly due to the unique isolation of the residual thermal expansion by flexible connections. First, the design of the composite with near-zero CTE is briefly introduced and used to develop the precision satellite platform. Next, the isolation mechanism to minimize the thermal deformation is presented. Then, the deformation isolation is detailed through the “flexible connecting” method. The effectiveness of this method is demonstrated by finite element (FE) analyses and further verified with a prototype. The experimental results from the prototype recorded a 90% reduction in comparison to the traditional platforms in the wrapping deformation of the payload panel, which was measured by projection moiré methods. The thermal wrapping deformation decreased from 1.013 mm using the rigid connection to 0.104 mm using the flexible connection. This result proves that the proposed method is effective for a high-precision satellite structure and has considerable potential in engineering applications.

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.

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.

Theoretical Studies on Nitramine Explosives with -NH2 and -F Groups

Guo Zheng Zhao,Ming Lu 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.6

The nitramine explosives with -NH2 and -F groups were optimized to obtain their molecular geometries and electronic structures at DFT–B3LYP/6-31+G(d) level. The theoretical molecular density (ρ), heat of formation (HOF), detonation velocity (D) and detonation pressure (P), estimated using Kamlet-Jacobs equations, showed that the detonation properties of these compounds were excellent. Based on the frequencies scaled by 0.96 and the principle of statistic thermodynamics, the thermodynamic properties were evaluated, which were respectively related with the temperature. The simulation results reveal that 1,3,5,7-tetranitro-1,3,5,7-tetrazocan-2- amine (molecule B1) performs similarly to the famous explosive HMX, and 2-fluoro-1,3,5-trinitro-1,3,5- triazinane (molecule C1) and 2-fluoro-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (molecule D1) outperform HMX. According to the quantitative standard of energetics and stability as an HEDC (high energy density compound), molecules C1 and D1 essentially satisfy this requirement. These results provide basic information for molecular design of novel high energetic density compounds.

Research of NCS Algorithm in Cloud Demand System

Guo Zheng-Hong,Ma Xinhua 보안공학연구지원센터 2015 International Journal of u- and e- Service, Scienc Vol.8 No.6

In order to reduce the bandwidth overhead and the node request rejection rate of the cloud video-on-demand server, this paper builds the cloud auxiliary framework and proposes the neighbors and chunks selection algorithm, which contains the node selection sub-algorithm and the block download sub-algorithm. The buffer-based node selection algorithm treats the download point as the benchmark to effectively find the neighbor nodes that can provide the video data, and the buffer-based block download algorithm calculates the required minimum buffer values of the two different kinds of block download strategies under the framework, which provides the theoretical basis for the download method of the video block. The experimental results show that the algorithm in this paper achieves good effects in the aspects of the bandwidth overhead of the server, the request rejection rate and the download rate.

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>

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.

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.