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.

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.

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.

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.

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.

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>

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

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.