• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.478-481
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• 2006

Energy is vital to global prosperity, yet dependence on fossil fuels as our primary energy source contributes to global climate change environmental degradation, and health problems. Hydrogen $(H_2)$ offers tremendous potential as a clean renewable energy currency. Hydrogen has the highest gravimetric energy density of any known fuel and is compatible with electrochemical and combustion processes for energy conversion without producing carbon-based emission that contribute to environmental pollution and climate change. Numerous methodologies have been developed for effective hydrogen production. Among them, the biological hydrogen production has gained attention, because hydrogen can be produced by cellular metabolismunder the presence of water and sunlight. The green alga Chlamydomonas reinhardtii is capable of sustained $H_2$ photoproduction when grown under sulfur deprived condition. Under sulfur deprived conditions, PSII and photosynthetic $O_2$ evolution are inactivated, resulting in shift from aerobic to anaerobic condition in the culture. After anaerobiosis, sulfur deprived algal cells induce a reversible hydrogenase and start to evolve $H_2$ gas in the light. According to above principle, we investigated the effect of induction parameters such as cell age, cell density. light intensity, and sulfate concentration under sulfur deprived condition We also developed continuous hydrogen production system by sulfate re-addition under sulfur deprived condition.

• Structural Engineering and Mechanics
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• v.50 no.3
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• pp.365-382
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• 2014

In this article, the force method and Charged System Search (CSS) algorithm are used for the analysis and optimal design of truss structures. The CSS algorithm is employed as the optimization tool and the force method is utilized for analysis. In this paper in addition to member's cross sections, redundant forces, geometry and topology variables are considered as the optimization variables. Minimum complementary energy principle is used directly to analyze the structure. In the presented method, redundant forces are calculated by the CSS in order to minimize the energy function. Combination of the CSS and force method leads to an efficient algorithm in comparison to some of the optimization algorithms.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.231-232
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• 2011

It is very important thing to efficiently utilize the solar power. The conventional solar power system has no energy storage device. So the conventional system cannot cut the peak load. In this paper, the solar power system with the energy storage device and the operation algorithm of peak cut function was proposed to cut the peak load. The algorithm principle is proposed based on the insolation curve and load curve. The simulation and experiment was performed to demonstrate the validity of the peak cut algorithm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1698-1708
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• 2002

The main topic covered in this paper is that of the impact process, that is, where two bodies come into contact and rebound or stick together. This paper presents how to determine the rebound velocities of a microparticle that approaches a surface with arbitrary initial velocities and relate the impact process to the physical properties of the materials and to the adhesion force. Actual adhesion forces demonstrate a significant amount of energy dissipation in the form of hysteresis, and act generally in a normal to the contact surfaces. Microparticles must also contend with forces tangent to the contact surfaces, namely Coulomb dry friction. The developed model has an algebraic form based on the principle of impulse and momentum and hypothesis of energy dissipation. Finally, several analyses are carried out in order to estimate impact parameters and the developed analytical model is validated using experimental results.

• Environmental Engineering Research
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• v.16 no.1
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• pp.35-39
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• 2011

An integrated gasification combined cycle (IGCC) system has been attracting attention due to its increased energy conversion efficiency and ability to treat various carbonaceous materials. IGCC is also expected to play an important role in the future supply of hydrogen energy. The use of a palladium-based membrane to separate the hydrogen from the synthesis gas stream has been intensively studied due to its exceptional hydrogen-separating capability. However, theoretical research on hydrogen separation is still an unfamiliar area in Korea. First-principle density functional theory was applied in this study to investigate the dissociative adsorption of hydrogen onto a palladium surface. The stability of hydrogen on the surface was theoretically evaluated with various adsorption configurations, partial pressures and temperatures. Further theoretical and experimental studies were also suggested to find a more hydrogen-selective material.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.446-450
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• 2004

The amount of electric energy used in a vehicle will be increased continuously. The increment of electric power demand causes interest on new higher power system such as 42V Power Net. Furthermore, the necessity for development of energy storage device is highlighted recently. Bidirectional nm Converter is one of the important parts in 42V power system. Therefore, this paper proposes bidirectional Cascade Buck-Boost DC/DC Converter which can satisfies required specifications in 42V power system The operation principle is described along with simple control method, and experimental results on a 500W prototype are provided.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.544-546
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• 2008

An improved dual-path energy recovery circuit (ERC) using a current source and a voltage source for plasma display panel (PDP) is proposed. The proposed ERC uses the voltage source to charge a panel and the current source to discharge the panel. Thus, the proposed circuit can make the panel charge to $V_S$ and discharge to 0V, fully and it is possible to achieve zero voltage switching (ZVS) of all switches in H-bridge inverter and zero current switching (ZCS) of all switches in the ERC. Moreover, it has less conduction and switching loss in ERC devices by the dual energy recovery paths for charging and discharging the panel. Furthermore, it has features of canceling the gas discharge current, high performance and the low cost ERC components. The operation principle and features of the proposed ERC are presented in detail and verified with 42-inch SD PDP.

• Journal of the Korean Wood Science and Technology
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• v.22 no.3
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• pp.51-58
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• 1994

Environmental conservation has become one of the greatest concerns of all the people in the world. This issue is related to wood utilization in two major view points such as carbon dioxide emitted by the use of manufacturing energy and absorbed during the growth of trees. Wood construction materials require less manufacturing energy, which, in turn, means less carbon dioxide emission. In addition, wood keeps absorbed carbon in itself as far as it is not burnt. Therefore, wood is environmentally superior to other materials in terms of potential effects on atmospheric carbon dioxide. As examples of the environmental effect of wood utilization, the following two results were obtained: 1) If wood construction becomes popular in Korea as in Japan, more than 24% of carbon dioxide emission during construction of residential housings can be reduced: and 2) If aluminum windows are substituted by wood windows, more than 19% of carbon dioxide emission can be reduced. If the principle of "cut and plant" is kept well, wood is the best construction material for environmental protection as well as human residence.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.250-255
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• 1993

In this paper, for detection and isolation of instrument and process faults related with steam generator(S/G) in nuclear power plant, two types of observers are designed based on the linearized dynamic model of S/G : a bank of Dedicated Observers (DOS) for instrument faults detection and a bank of Unknown Input Observers(UIO) for process faults detection. And then, they are combined to decide which one between the above two faults occurs. In principle, the failure in ith instrument(process) can be isolated by monitoring the error between the ith output and its estimation obtained from the ith DOS(UIO). It is shown via computer simulations that the present scheme is feasible in finding out the source of a fault.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.169-176
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• 1999

An improved formulation for spatial stability md free vibration of thin-walled curved beams with variable curvature and non-symmetric cross sections are presented based on the displacement field considering the second order terms of finite semitangential rotations. By introducing Vlasov's assumptions, the total potential energy is derived from the principle of linearized virtual work for a continuum. In this formulation, all displacement parameters and the warping function are defined at the centroid axis so that the coupled terms of bending and torsion are added to the elastic strain energy. Also, the potential energy due to initial stress resultants is consistently derived corresponding to the semitangential rotation and moment. The cubic Hermitian polynomials are utilized as shape functions for development of the curved thin-walled beam element having eight degrees of freedom. In order to illustrate the accuracy and practical usefulness of this study, . numerical solutions for free vibration of arches are presented and compared with resells of other researchers and solutions analyzed by the ABAQUS's shell element.