• 조명전기설비학회논문지
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• 제29권3호
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• pp.22-29
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• 2015

The AC-LED driving system which is connected directly to alternative current source is suitable for commercialization because of it's simple structure and low cost. However, it requires additional circuits compensating for current differences between the parallel connected LED strings. In this paper, we proposed the circuit compensating for current error of the three LED strings using the Y type balancing transformer. The proposed Half-bridge AC Chopper LED driving system used the ferrite material's balancing transformer. at the same time, it is able to dimming control. The proposed system is applied to 80W AC-LED module consist of three parallel strings. Experiment results present that Power factor and THD measured with power analyzer are 0.958 and 26.473% respectively satisfied with IEC61000-3-2 harmonics standard.

• 한국조경학회지
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• 제19권3호
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• pp.55-71
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• 1991

The purpose of this thesis is to suggest objective basic data for the environmental design through the quantitative analysis of the visual quality included in the physical environment of Basemsagol valley sequence landscape. For this, visual volumes of physical elements have been evaluated by using the mesh analysis, spatial images structure of physical elements have been analyzed by factor analysis algorithm, and degree of visual quality have been measured mainly by questionnaires. Also, this study aims to understand semiotics and to grope the possibility of application to the sequence landscape assessment. A semiological approach suggests a new dimension in sequence landscape assessment, which is a contrast to the existing scientific evaluation methods. Result of this thesis can be summarized as follows. Visual volumes of the immediate vegetation, rock, bridge, road and distant vegetation are found to be the main factor determining the visual quality. Factors covering the spatial image of natural park sequence landscape have been found to be the overall synthetic evaluation, potentiality, natural quality, spatial, appeal and dignity. By using the control method for the number of factors, T.V. has been obtained as 40.22%. The characteristics of the semiological approach is qualitative, open, holistic, and experiential, whereas that of the scientific approach is quantitative, closed, reductive, and experimental.

• Journal of Power Electronics
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• 제14권2호
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• pp.292-301
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• 2014

This paper presents a new configuration for a three-phase multilevel voltage source inverter. The main bridge is built from a classical three-phase two-level inverter and three bidirectional switches. A variable DC-link employing two unequal DC voltage supplies and four switches is connected to the main circuit in such a way that the proposed inverter produces four levels in the output voltage waveform. In order to obtain the desired switching gate signals, the fundamental frequency staircase modulation technique is successfully implemented. Furthermore, the proposed structure is extended and compared with other types of multilevel inverter topologies. The comparison shows that the proposed inverter requires a smaller number of power components. For a given number of voltage steps N, the proposed inverter requires N/2 DC voltage supplies and N+12 switches connected with N+7 gate driver circuits, while diode clamped or flying capacitor inverters require N-1 DC voltage supplies and 6(N-1) switches connected with 6(N-1) gate driver circuits. A prototype of the introduced configuration has been manufactured and the obtained simulation and experimental results ensure the feasibility of the proposed topology and the validity of the implemented modulation technique.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.429-430
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• 2011

This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multi-phase interleaved half-bridge topology with coupled inductors. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is made up of three sub-interval operating modes; pre-charging mode, constant-current mode, and constant-voltage mode. The pre-charging mode employs the staircase shaped current profile to accomplish shorter charging time while maintaining the reliable operation of the battery. The proposed system is able to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 67A. The optimal discharging algorithm for Vehicle to the Grid (V2G) operation has been adopted to maintain the discharging current of 1C. Owing to the simple and compact power conversion scheme, the proposed solution has superior module-friendly mechanical structure which is absolutely required to realize flexible power expansion capability in a very high-current rapid charging system.

• 대한기계학회논문집A
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• 제20권7호
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• pp.2213-2222
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• 1996

This paper presents the design process and evaluaation results of a two-axis force transducer for measuring flange reaction forces. A double-cantilever beam structure is used as a sensing element, and its optimal configuration is determined based on the derived strain equations to maximize the sensitivity and minimize the regid body displacements. To reduce the coupling errors between two-axis forces, strain distributions by finite elemetns analysis are utilized and the Wheaststone bridge cricuits composed of strain gages are built such that the output voltage should be zero, although strains of four strain gages are not zero. Calibration test shows that the two-azxis force transducer developed in this paper is useful in measuring flange reaction forces within the coupling error of 5.53%.

• Journal of Electrical Engineering and Technology
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• 제3권1호
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• pp.88-93
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• 2008

The electromagnetic parameters of a permanent magnet synchronous motor (PMSM) such as the open load permanent magnet flux, d axis reactance $X_d$, and q axis reactance $X_q$, are most essential to the performance analysis and optimization design of the motor. Based on the numerical analysis of the 3D electromagnetic field, the three electromagnetic parameters of permanent magnet synchronous motors with U form interior rotor structures are calculated by FEA. The rules of the leakage coefficient and reactance parameters changing with the air gap length, permanent magnet magnetism length, and isolation magnetic bridge dimensions in the rotor are given. The calculated values agree well with the measured values. The FEA results are integrated with the self compiled electromagnetic design program to optimize the prototype motor. The tested performances of the prototype motor prove that the method is suitable for the optimization of motor structure.

• 한국실내디자인학회논문집
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• 제14권5호
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• pp.26-34
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• 2005

The systematic way of the boundary thought in Buddhism, when applied to the principles of building, determines certain forms to certain temples, and organizes their topological boundary concept structure - the continuous experience of the visitor from his/her entry bridge(connecting), through the main temple gate(neighbourhood), pavilion gate(including), stairs(continuance), to the arrival at the pavilion of the god of a mountain(spiral), which reconstitutes the Buddhist boundary symbolism and philosophy. The topological boundary spaces of temples are an architectural manifestation of Buddhism's Mahayana boundary concept aspects, whose object is to play a productive and active role in the enlightenment of people, serving the very basic end of the religion. The disciplined topological boundary spaces of the temple, as a reification of the boundary symbolisms of Buddhist topological cosmology, corresponds to Buddha-Ksetra, the highest state of existence in the universe. Visitors to the temple are invited to participate in the world of abundant Buddhist boundary concept symbols, and through this process, is enabled to elevate oneself to the transcendent topological boundary world and have a simulated experience of liberation.

• 한국안전학회지
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• 제25권3호
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• pp.91-99
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• 2010

In this study, the advanced numerical algorithm is developed which can performed the static and dynamic stochastic finite element analysis by considering the effect of uncertainties included in the member stiffness of steel cable-stayed bridges and seismic load. After conducting the linear and nonlinear initial shape analysis, the advanced numerical algorithm is the assessment tool which can performed structural the response analysis considering the static linearity and non-linearity of before or after induced intial tensile force, and examined the reliability assessment more efficiently. The verification of the developed numerical algorithm is evaluated by analyzing the regression analysis and coefficient of correlation using the direct monte carlo simulation. Also, the dynamic response characteristic and coefficient of variation of the steel cable-stayed bridge is calculated by considering the uncertainty of random variables using the developed numerical algorithm. In addition, the quantitative structural safety of the steel cable-stayed bridges is evaluated by conducting the reliability assessment based upon the dynamic stochastic finite element analysis result.

• Steel and Composite Structures
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• 제11권5호
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• pp.375-390
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• 2011

Composite beam, which combined the material characteristic of the steel and concrete, has been widely used in the construction of various building and bridge system. For the effective application of the composite beam, the composite action on the composite interface between the concrete element and the steel element should be achieved by shear connectors. The behavioral characteristics of composite beam are related with the degree of interaction and the degree of shear connection according to the shear strength and shear stiffness of the stud shear connectors. These two concepts are also affected by the number of installed shear connector and the strength of composite materials. In this study, experimental and analytical evaluations of the degree of shear connection affected by stud diameter were conducted, and the relationship between structural behavior and the degree of shear connection was verified. The very small difference among the ultimate loads of the specimens depending on the change of the degree of connection was possibly because of the dependence of the ultimate load on the characteristic of plastic moment of the composite beam.

• Journal of Microbiology and Biotechnology
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• 제17권6호
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• pp.1002-1009
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• 2007

A rapid, convenient homogeneous competitive enzyme immunoassay for estimating the amount of fenthion is described. The assay utilizes glucose-6-phosphate dehydrogenase-hapten conjugates that are inhibited in solution by antibodies obtained from bovine serum albumin-hapten conjugates. In order to investigate the effects of bridging group recognition on the sensitivity of dose response characteristics, the bridging groups of varying alkyl chain length were attached at the phosphate position of fenthion. Among the antibodies used, the one obtained from the use of hapten (fenthion analog) with the same bridging group structure that was used in preparing the enzyme-fenthion conjugates showed maximum inhibition (up to 51.8%) in the absence of fenthion. In the presence of fenthion, the activity of the enzyme-hapten conjugate is regained in an amount proportional to the fenthion concentration. Under the optimized condition, the $ED_{50}$ value for fenthion was $0.809{\mu}g/ml$. The assay developed in this study is a rapid effective screening method for fenthion prior to precise analysis.