• Journal of Power Electronics
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• 제15권4호
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• pp.964-973
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• 2015

This paper presents a simple approach for the selective harmonic elimination (SHE) of multilevel inverter based on the transistor-clamped H-bridge (TCHB) family. The SHE modulation is derived from the sinusoidal voltage-angle equal criteria corresponding to the optimized switching angles. The switching angles are computed offline by solving transcendental non-linear equations characterizing the harmonic contents using the Newton-Raphson method to produce an optimum stepped output. Simulation and experimental tests are conducted for verification of the analytical solutions. An Altera DE2 field-programmable gate array (FPGA) board is used as the digital controller device in order to verify the proposed SHE modulation in real-time applications. An analysis of the voltage total harmonic distortion (THD) has been obtained for multiple output voltage cases. In terms of the THD, the results showed that the higher the number of output levels, the lower the THD due to an increase number of harmonic orders being eliminated.

• 한국광학회지
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• 제2권3호
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• pp.127-132
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• 1991

축소 배율$(\times5)$을 갖고, Seidel 3차 수차중 구면수차(spherical aberration), 코마(coma), 비점수차(astimatism) 및 왜곡수차(distortion)가 제거된 4-구면 반사경계를 해석적인 방법으로 구하고, 설계변수에 따른 광학계의 구조적 특성, vignetting 그리고 Petzval 상면만곡수차에 대한 수치적인 해석을 하였다. 이렇게 구한 4개의 수차가 보정된 유한 물체점을 갖는 4-구면 반사경계의 N.A와 half field angled은 각각 $0.2, 1.5^{\circ}$이다.

• Journal of Welding and Joining
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• 제29권6호
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• pp.82-87
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• 2011

In this study, we conducted laser welding by using remote scanner that is 5J32 aluminum alloy to observe the mechanical properties and optimize welding process parameters. As the control factors, laser incident angle, laser power and welding speed were set and as the result of weldablility, tensile shear tests were performed. ANOVA (Analysis of Variation) was also carried out to identify the influence of process variables on tensile shear strength. Strength estimation models were suggested using regression alnalysis and 2nd order polynomial model had the best estimation performance. In addition optimal welding condition was determined in terms with wedalility and productivity using objective function and fitness function. Final optimized welding condition was laser power was 4 kW, and welding speed was 4.6 m/min.

• Journal of the Optical Society of Korea
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• 제19권3호
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• pp.303-310
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• 2015

An image-space telecentric lens for an intra-oral 3D scanner was designed and fabricated for dental application. Since a telecentric function can provide the same results regardless of image plane position, it helps to realize a more accurate image for an intra-oral scanner. The performance of the designed lens meets the required properties for HD resolution. In particular, lateral color is corrected within 1 pixel. This system achieves depth of focus of more than 3 mm. For user convenience, the developed system consists of a prism part and an imaging part. Both parts are optimized to reduce the front size and weight of the system. In order to make the parallax sights, parallax angle was determined to be 8 degrees between two optical systems.

• 전기학회논문지
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• 제68권1호
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• pp.129-139
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• 2019

In order for a gun-launched guided projectile to glide to the maximum range, when to deploy the fin and start flight with guidance and control should be considered in range optimization process. This study suggests a solution to the optimal guidance problem for flight range maximization of the flight model of a guided projectile in vertical plane considering the aerodynamic properties. After converting the nonlinear Multi-Phase Optimal Control Problem to Two-Point Boundary Value Problem, the optimized guidance command and the best fin deployment timing are calculated by the proposed numerical method. The optimization results of the multiple flight rounds with various initial velocity and launch angle indicate that determining specific launch condition incorporated with the guidance scheme is of importance in terms of mechanical energy consumption.

• 한국전기전자재료학회논문지
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• 제32권2호
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• pp.141-146
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• 2019

Non-emissive LCDs need a backlight, and have difficulty implementing wide viewing angles due to differences in phase retardation depending on the behavior of the liquid crystals. Although wide viewing angles are good characteristics for devices such as TVs, they are not good for mobile devices. In this paper, we propose ways to design diffusers with ELC lenses to achieve wide and narrow viewing angles depending on the circumstances. A study was conducted on optimizing the design of a liquid lens diffuser with the same light as that for an OLED, by extracting design factors that affect the performance of the diffuser and applying the Taguchi method to them.

• International Journal of Advanced Culture Technology
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• 제10권4호
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• pp.470-477
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• 2022

EOTS for drones is showing another aspect of market expansion in detection and recognition areas previously occupied by artificial satellites. The two-axis EOTS for drones controls the vibration or disturbance caused by the drone during the mission so that EOTS can accurately recognize the goal. Vibration generated by drones is transmitted to EOTS. Therefore, it is essential to develop a stabilization controller that attenuates vibrations transmitted from drones so that EOTS can maintain the viewing angle. Therefore, it is necessary to standardize drone disturbance and secure the performance of EOTS disturbance attenuation controller optimized for disturbance level through this. In this paper, a method of standardizing drone disturbance applied to EOTS is studied, through which EOTS controller simulation is performed and stabilization controller shape is selected and designed.

• International Journal of Advanced Culture Technology
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• 제11권2호
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• pp.323-329
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• 2023

In this study, Proline pentamer model was used to investigate change in the dihedral angle, intramolecular hydrogen bonding and formation energies during structural optimization. L-Proline (LP, as an imino acid residue) pentamers having four conformation types [β: φ/ψ=t−/t+, α: φ/ψ=g−/g−, PP_II: φ/ψ=g−/t+ and Plike: φ/ψ= g−/g+] were carried out by QCC [B3LYP/6-31G(d,p)]. The optimized structure and formation energy were examined for designated structure. In LP, P-like and PP_II types did not change by optimization, and β types were transformed into PP_II having no H-bond independently of the designated ψ values. PP_II was more stable than P-like by about 2.2 kcal/mol/mu. The hydrogen bond distances of d2(4-6) type H-bonds were 1.94 - 2.00Å. In order to understand the processes of the transformations, the changes of φ/ψ, distances of NH-OC (d_NH/CO) and formation energies (ΔE, kcal/mol/mu) were examined.

• 한국광학회지
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• 제18권4호
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• pp.264-269
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• 2007

기존 필라멘트 방식의 루미나리에용 조명의 단점을 극복하기 위해 필라멘트를 LED로 바꾸기 위한 연구가 활발하게 진행 중이다. 본 연구는 루미나리에용에 적합한 LED패키지 구조를 만들기 위해 ray tracing simulator를 이용해 다양한 구조를 모델링하고 시뮬레이션을 통해 각 구조에서의 배광분포를 측정하였다. 시뮬레이션 결과, LED 패키지의 내부 반사경의 각을 증가시킬수록 배광분포가 두 개의 피크로 갈라지면서 피크간의 각이 점점 커졌다. 또한 외부 반사경 각이 증가함에 따라 양쪽 피크간의 각이 점점 줄어들다가 $50^{\circ}$를 기준으로 다시 증가하였다. 이러한 결과는 LED에서 발생한 빛이 두 개의 반사경에 의하여 반사되는 각도가 달라짐에 의하여 발생함을 알 수 있었다. Ray tracing simulator를 이용하여 구한 LED 패키지 구조의 조건을 적용하여 루미나리에용 LED패키지를 제작하였고 배광분포 측정기를 이용해 광 특성을 측정하였으며 시뮬레이션의 결과와 유사한 특성을 얻었다.

• 한국전자파학회논문지
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• 제17권11호
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• pp.1040-1049
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• 2006

본 논문에서는 광대역 동축-마이크로스트립 선로에서 전송 손실을 최소화하는 수직 트랜지션(transition)의 설계 기법을 제안하였다. 동축-마이크로스트립 선로의 수직 트랜지션은 동축 선로와 인쇄 회로 기판이 수직으로 연결되는 구조로서 인쇄형 안테나 혹은 마이크로스트립 기판을 사용하는 마이크로파 송수신 장치 등에 널리 사용된다. 제안한 설계 방법은 넓은 대역폭을 가지면서 전송 손실을 최소화하는 방법으로, 접지 개구면(ground aperture)의 지름, 프로브(probe)의 지름, 접지 개구면의 오프셋과 스텁(stub) 길이를 설계 변수로 설정하여, 시뮬레이션을 통하여 설계 값을 구하였다. 동축 선로와 마이크로스트립 기판은 일반적으로 널리 사용되는 SMA 커넥터와 PTFE 재질의 두께 0.254, 0.508 및 0.787 mm 기판을 사용하였다. 시뮬레이션 결과로부터 구한 설계 변수 값들을 입증하기 위하여 SMA 동축 커넥터와 0.787 mm 두께의 기판을 사용하여 수직 트랜지션 시험 블록을 제작하였다. 이 트랜지션의 특성을 측정한 결과 $0.05{\sim}20GHz$주파수 범위에서 반사 계수가 -22 dB 이하이고, 전송 손실이 0.45 dB 이하인 만족할만한 결과를 얻었다.