• Proceedings of the KIEE Conference
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• summer
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• pp.1193-1195
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• 2004

Ozone gas is one of the strongest oxidizing and bleaching agents which leave no residues harmful to the global environment. In recent years, the ozone generator has been widely utilized, However, it has been known that a broader application of ozone is hindered primarily because of its low efficiency of generation. Thus, it is more indispensable to improve actual system efficiency of the silent discharge type ozonizer using high frequency inverter. This paper presents a multi level resonant ozone power regulation by association of high frequency transformers and full bridge invert. And proposed resonant inverter system can generate continuous output voltage. can control linearly quantity of ozone gas. This invert that add PWM forms within square forms of output voltage about one level range. The power regulation characteristics and operating performances of silent discharge (SD)type ozone generating tube load driven by this load proposed inverter using FET modules are illustrated from a practical point of view, which can operate under stable conditions of basic level and PWM hybrid control strategy implemented DSP(2406). The effectoveness of propsed invert type ozonizer is proved by experiment results.

• Journal of Power Electronics
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• v.16 no.1
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• pp.153-162
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• 2016

Given their structural arrangement, photovoltaic (PV) modules exhibit parasitic capacitance, which creates a path for high-frequency current during zero-state switching of the converter in transformerless systems. This current has to be limited to ensure safety and electromagnetic compatibility. Many solutions that can minimize or completely avoid this phenomenon, are available. However, most of these solutions are patented because they rely on specific and often complex converter topologies. This study aims to solve this problem by introducing a solution based on a classic converter topology with an appropriate modulation technique and passive filtering. A 5.5 kW single-phase residential PV system that consists of DC-DC boost stage and DC-AC H-bridge converter is considered. Control schemes for both converter stages are presented. An overview of existing modulation techniques for H-bridge converter is provided, and a modification of hybrid modulation is proposed. A system prototype is built for the experimental verification. As shown in the study, with simple filtering and proper selection of switching states, achieving low leakage current level is possible while maintaining high converter efficiency and required energy quality.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.488-490
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• 2003

This paprer presents the evlauation method for transmission marginal loss factors(MLFs) considering the electrical distance. Generally, MLFs are represented as the sensitivity of transmission losses, which is computed from the change of generation by the change of the load. MLFs are classified as load-focused MLFs and generator-focused MLFs. The existing evaluation method for generator focused MLFs has the limit not reflecting the characteristic of power systems since the method has been introduced the assumption which the output of a generator is supplied to all of the load buses on the power system. Therefore, to overcome the limit of evaluation method for generator-focused MLFs, we have applied the process, which it approximately can find the load buses that supplied a generator to the method. We have applied the proposed method to the simple 5-bus system because the proposed method is not analytic but the hybrid method incorporated the Kirschen and Bialek's algorithm to the existing analytic method to find the load buses supplied by a generator.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.450-453
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• 2017

In this abstract, the FPGA system using solar tracking is introduced. Solar tracking system combined with sensor tracking and solar altitude programming is utilized. The sensor tracking system consists of image sensor, light sensor, and the programs for sun altitude received by the computer. The sun altitude is received from the national weather database by wireless communication. The goal is to have maximum energy generation efficiency using bi-directional tracking and mixed tracking with FPGAs that are relatively inexpensive in terms of developing and programming the system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.2
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• pp.132-136
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• 2009

SiOC thin film of hybrid-type that is the limelight as low dielectric material of next generation were deposited by plasma enhanced chemical vapor deposition (PECVD) method with bistrimethylsilylmethane (BTMSM) precursor increased by 2 sccms from 24 sccms to 32 sccm. Manufactured samples are analyzed components by measuring FT/IR absorption lines. It is a tendency that seems to be growing of Si-O-Si(C) bonding group and narrowing of Si-O-$CH_3$ bonding group relative to the increasing flow-rate BTMSM. The chemical shift in the XPS analysis was shown in the specimens between the BTMSM=26 sccm and BTMSM = 28 sccm. The binding energy of Si 2p, C 1s and O 1s electron orbit spectra was the low-est at the specimen of the BTMSM=26 sccm. From the results of electrical Properties using the 1 MHz C - V measurements, the dielectric constant was 2.32 at the specimen with the BTMSM = 26 sccm.

• International Journal of Industrial Entomology and Biomaterials
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• v.32 no.2
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• pp.54-59
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• 2016

All of silkworm varieties reared in farmhouses are first generation hybrids, for the production of these hybrid silkworms precise and labor-saving sex discrimination is necessary. The new variety "Hanbyeolnue" is biparental sex-limited larval marking yellow cocoon variety which was bred from biparental sex-limited strain of Japanese originated Jam 319 and Chinese originated Jam 320. Productivity test of Hanbyeolnue in 2015 showed high healthiness and short larval period. The Hanbyeolnue was evaluated as an excellent variety which can be utilized for special purpose silkworm such as male pupae or Cordyceps production.

• Laser Solutions
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• v.14 no.4
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• pp.14-20
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• 2011

The advantage of using lasers for through silicon via (TSV) drilling is that they allow higher flexibility during manufacturing because vacuums, lithography, and masks are not required; furthermore, the lasers can be applied to metal and dielectric layers other than silicon. However, conventional nanosecond lasers have disadvantages including that they can cause heat affection around the target area. In contrast, the use of a picosecond laser enables the precise generation of TSVs with a smaller heat affected zone. In this study, a comparison of the thermal and crystallographic defect around laser-drilled holes when using a picosecond laser beam with varing a fluence and repetition rate was conducted. Notably, the higher fluence and repetition rate picosecond laser process increased the experimentally recast layer, surface debris, and dislocation around the hole better than the high fluence and repetition rate. These findings suggest that even the picosecond laser has a heat accumulation effect under high fluence and short pulse interval conditions. To eliminate these defects under the high speed process, the CDE (chemical downstream etching) process was employed and it can prove the possibility to applicate to the TSV industry.

• Journal of Institute of Convergence Technology
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• v.1 no.1
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• pp.34-40
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• 2011

In this paper, a hybrid design tool combining one-dimensional(1D) lumped model and three-dimensional computational fluid dynamics(CFD) approach has been developed in order to evaluate the performance of inkjet print head and droplet control process are studied to reduce the deviations between nozzles which affect the size of the printed line for the industrial application of direct writing on printed circuit boards(PCB). 1D lumped model analysis shows that it is useful tool for evaluating performance of an inkjet head by varying the design parameters. The differences in ejected volume and droplet velocity between analytical and experimental result are within 12%. Time sequence of droplet generation is verified by the comparison between 3D analysis result and photographic images acquired by stroboscopic technique. In addition, by applying DPN process, velocity and volume uniformity between nozzles is dramatically improved that the tolerance achieved by the piezoelectric inkjet printhead across the 64 nozzles is 5 to 8%. A printed line pattern is successfully obtained using the fabricated inkjet print head and droplet calibration system.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.11-11
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• 2018

본 연구에서는 1시간부터 1년 단위의 강우 특성들을 잘 모의하는 혼합 추계 강우 생성 모형을 개발하였다. 본 모형의 가상 강우 생성 과정은 4단계로 이루어진다. 첫 단계에서 Seasonal ARIMA 모형을 통하여 시계열 특성을 반영한 월 강우를 생성한다. 두 번째 단계는 생성된 월 강우에 해당하는 일 단위 이하의 강우 통계치 세트를 생성하는 것이며, 통계치간 상관관계를 통해 평균, 표준편차, 자기상관 계수, 무강우 확률을 생성한다. 생성된 통계치 세트는 세 번째 단계에서 Modified Bartlett-Lewis Rectangular Pulse (MBLRP) 모형의 6개의 매개변수를 보정하는데 사용되며, 마지막으로 MBLRP 매개변수 세트를 통해 가상 강우 시계열을 생성한다. 위 모형을 통해 미국 동부 지역 29개 강우 관측소에 대하여 200년 길이의 가상 강우를 생성하였으며, 그 결과 시 단위부터 연 단위까지 강우의 1차, 2차 통계치 및 무강우 확률을 성공적으로 재현하였다. 또한 기존 MBLRP 모형에 비하여 극한 강우 사상을 재현하는 능력이 향상되었다. 빈도분석 결과를 통하여 MBLRP 모형이 재현기간에 따라 10%에서부터 40%까지 극한 사상을 과소 추정한 반면, 본 모형에서는 20% 이내의 값을 나타내었다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.10
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• pp.819-825
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• 2006

In a SOFC/GT (solid oxide fuel cell/gas turbine) hybrid power generation system, the recuperator is an indispensible component to enhance system performance. Since the expansion ratio to the recuperator core is very large, generally, the effective header design to distribute the flow uniformly before entering the core is crucial to guarantee the required performance. In the present study, we focus on the design of a diffuser type recuperator header with a 90 degree turn inlet port. To reduce the flow separation and recirculation flows, multiple horizontal vanes are used. The number of horizontal vanes is varied from 0 to 24. The air flow velocity is measured at 40 points just behind the core outlet by using a hot wire anemometer. Then, the flow non-uniformity is evaluated from the measured flow velocity. The experimental results showed that inlet air velocity did not effect on relative flow non-uniformity. According to increasing the number of horizontal vanes, flow non-uniformity reduced about $40{\sim}50%$ than without using horizontal vanes.