• 전기학회논문지
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• 제64권12호
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• pp.1686-1694
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• 2015

Stator tooth segmentation and back-iron segmentation is key solution to easing the burden of manufacturing process of permanent magnet synchronous motor. The purpose of this paper is the design and characteristic analysis of permanent magnet synchronous motor having the segmented phase modular stators. Using by two-dimensional finite element method, the static/no-load characteristic analysis of the permanent magnet synchronous motor is performed. The analysis has been performed considering the additional air gaps between stator modules. The analysis results were experimentally verified, and the validity of the proposed analysis method and feasibility of the machine was confirmed.

• 한국광학회지
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• 제4권3호
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• pp.317-322
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• 1993

본 논문에서는 특성행렬을 사용하여 비선형 집적거울 etalon의 입출력 특성을 해석하는 방법을 제시한다. 빛의 세기에 따른 매질의 굴절률 및 흡수율의 변화 특성을 알면, 관계식과 특성행렬식을 결합하여 집적거울 etalon의 비선형 특성을 해석할 수 있다. 이 방법은 파장에 따른 각 거울의 반사율(크기와 위상)을 일일이 구하지 않고, etalon의 구조가 주어지면 바로 임의의 파장에서의 etalon의 입출력 특성을 해석할 수 있다. 또한, 특성행렬식을 이용하여 비선형 집적거울 etalon에서의 쌍안정성을 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.3-5
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• 1994

It is shown that the power flow considering the voltage characteristic of the composite load has some difference comparing with conventional load flow in this paper. When the load flow is used in a study of the static voltage stability, it is necessary to consider the voltage characteristic of load, since the composite load of a typical power system bas constant power, constant current, and constant impedance characteristic. The load is modeled to a polynomial form in here, and used in solving the load flow problem. In this way, the effect which the voltage characteristic of the load has on several voltage collapse proximity indicator based on sensitivities is compared with the conventional load flow, or with another load model having a different voltage characteristic. In this paper, the voltage collapse proximity indicator using the sensitivity of real power for transmission loss is also proposed, and compared with other indicators.

• 한국통신학회논문지
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• 제37A권10호
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• pp.895-902
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• 2012

본 논문에서는 비선형 전력증폭기(PA:power amplifier)의 AM/PM 비선형 왜곡특성을 포함하는 군 지연을 보상하는 새로운 등화기를 제안한다. 군 지연 특성은 각 주파수 성분에 따라 서로 다르게 나타나는 상수가 아닌 비선형 시간지연이다. 전력증폭기에서 발생되는 AM/PM 특성으로 인한 위상 왜곡 현상은 군 지연을 증가시키는 주요한 요인이다. 이러한 군 지연 왜곡으로 신호 성상도에서 신호는 퍼지면서 회전하게 된다. 위와 같은 문제점을 고려하여 각 주파수 성분에 따라 다르게 나타나는 비선형 시간지연을 정적인 군지연으로 구분하고, PA의 AM/PM 특성인 입력신호 크기에 따라서 위상 천이가 다르게 발생하는 것을 동적인 군 지연으로 구분한다. 정적인 군 지연은 주파수 영역에서 Type-Based 방법으로 위상 왜곡을 추정 및 보상하고 동적인 군 지연은 시간영역에서 위상회전을 보상한다. 제안된 군 지연 보상기법으로 전력증폭기의 AM/PM 특성을 포함한 군 지연 특성을 충분히 보상할 수 있음을 확인하였다.

• The Journal of Advanced Prosthodontics
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• 제7권2호
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• pp.146-150
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• 2015

PURPOSE. This in vitro study aimed to compare the failure load and failure characteristics of two different zirconia framework designs of premolar crowns when subjected to static loading. MATERIALS AND METHODS. Two types of zirconia frameworks, conventional 0.5 mm even thickness framework design (EV) and 0.8 mm cutback of full contour crown anatomy design (CB), were made for 10 samples each. The veneer porcelain was added on under polycarbonate shell crown made by vacuum of full contour crown to obtain the same total thickness of the experiment crowns. The crowns were cemented onto the Cobalt-Chromium die. The dies were tilted 45 degrees from the vertical plane to obtain the shear force to the cusp when loading. All crowns were loaded at the lingual incline of the buccal cusp until fracture using a universal testing machine with cross-head speed 0.5 mm/min. The load to fracture values (N) was recorded and statistically analyzed by independent sample t-test. RESULTS. The mean and standard deviations of the failure load were $1,170.1{\pm}90.9$ N for EV design and $1,450.4{\pm}175.7$ N for CB design. A significant difference in the compressive failure load was found (P<.05). For the failure characteristic, the EV design was found only cohesive failures within veneering porcelain, while the CB design found more failures through the zirconia framework (8 from 10 samples). CONCLUSION. There was a significant difference in the failure load between two designs, and the design of the framework influences failure characteristic of zirconia crown.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1532-1536
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• 2020

For ensuring nuclear safeguards, we report the analytical signal-detection performance of thermal ionization mass spectrometry (TIMS) with continuous heating for the measurement of isotopic ratios in samples containing ultra-trace amounts of uranium. As methods for detecting uranium signals, peak-jumping mode using a single detector and static mode using multiple detectors were examined with U100 (10% ²³⁵U-enriched) uranium standard samples in the femtogram-to-picogram range. Uranium isotope ratios, n(²³⁵U)/n(²³⁸U), were measured down to levels of 1 fg and 3 fg in static and peak-jumping modes, respectively, while n(²³⁴U)/n(²³⁸U) and n(²³⁶U)/n(²³⁸U) values were measured down to levels of 100 fg in both modes. In addition, the dependency of the ²³⁸U signal intensity on sample quantity exhibited similar tendencies in both modes. The precisions of the isotope ratios obtained in the static mode over all sample ranges used in this study were overall slightly higher than those obtained in peak-jumping mode. These results indicate that isotope ratio measurements by TIMS with continuous heating are almost independent of the detection method, i.e., peak-jumping mode or static mode, which is characteristic of isotope-ratio measurements using the TIMS method with continuous heating. TIMS with continuous heating is advantageous as it exhibits the properties of multiple detectors within a single detector, and is expected to be used in various fields in addition to ensuring nuclear safeguards.

• 열처리공학회지
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• 제14권4호
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• pp.220-227
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• 2001

The static creep behaviors of dispersion strengthened copper GlidCop were investigated over the temperature range of $650{\sim}690^{\circ}C$ (0.7Tm) and the stress range of 40~55 MPa (4.077~5.61 $kg/mm^2$). The stress exponents for the static creep deformation of this alloy was 8.42, 9.01, 9.25, 9.66 at the temperature of 690, 677, 663, and $650^{\circ}C$, respectively. The stress exponent, (n) increased with decreasing the temperature and became dose to 10. The apparent activation energy for the static creep deformation, (Q) was 374.79, 368.06, 361.83, and 357.61 kg/mole for the stress of 40, 45, 50, and 55 MPa, respectively. The activation energy (Q) decreased with increasing the stress and was higher than that of self diffusion of Cu in the dispersion strengthened copper. In results, it can be concluded that the static creep deformation for dispersion strengthened copper was controlled by the dislocation climb over the ranges of the experimental conditions. Larson-Miller parameter (P) for the crept specimens for dispersion strengthened copper under the static creep conditions was obtained as P=(T+460)(logtr+23). The failure plane observed for SEM slightly showed up transgranular at that experimental range, however, universally it was dominated by characteristic of the intergranular fracture.

• 한국추진공학회지
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• 제24권3호
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• pp.1-11
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• 2020

본 연구에서는 lab-scale 젤로켓모터를 이용하여 액상 케로신 연료와 이를 젤화 시킨 젤 케로신 연료의 연소시험을 수행함으로써, 각 연료별 연소실 정압특성 및 동압특성에 대해 분석하였다. 액상 케로신과 젤 케로신의 정압, 특성속도 및 특성속도 효율은 예상외로 큰 차이를 보이지 않음을 확인하였다. 그러나 액상 케로신과 젤 케로신의 동압 특성을 비교한 결과, 특정 고주파수 영역에서 젤 케로신의 압력 진폭이 액상 케로신 대비 증가하는 것을 확인하였다. 이는 젤 추진제의 고유 연소 메커니즘에 기인한 특성으로 여겨지며, 이들 압력 섭동 진폭이 추후 젤로켓모터의 고주파 연소불안정에 영향을 미치는 주요 인자로 적용될 가능성이 클 것으로 판단되었다.

• 대한기계학회논문집B
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• 제37권3호
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• pp.213-219
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• 2013

본 논문의 목적은 스풀 랜드(spool land)와 슬리브(sleeve) 사이의 정특성 방정식으로부터 스풀 밸브의 압력 특성과 유동특성을 구하는 것이다. 이러한 목적을 달성하기 위하여, 스풀 랜드와 슬리브 사이의 유동을 환상간극 유동과 오리피스 유동, 그 중간의 천이 영역으로 나누고, 천이 영역의 유량계수를 길이에 따른 두 영역으로 나눈 선형 일차방정식으로 가정하였다. 스풀 밸브의 압력특성방정식을 구하기 위해 스풀의 중립지점에서부터의 변위에 따른 유동을 $q_a=q_b=0$의 조건으로부터 구하였으며, 스풀 밸브의 유량특성방정식을 구하기 위하여 스풀의 중립지점에서부터의 변위에 따른 유동을 $q_a=q_b$, $p_a=p_b$의 조건으로부터 구하였다. 구해진 수식의 타당성은 수치해석을 통해 실험식 및 기존논문과의 비교를 통해 확인하였다.

• Design & Manufacturing
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• 제7권1호
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• pp.55-59
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• 2013

A Light Emitting Diode(LED) is a semiconductor device which converts electricity into light. LEDs are widely used in a field of illumination, LCD(Liquid Crystal Display) backlight, mobile signals because they have several merits, such as low power consumption, long lifetime, high brightness, fast response, environment friendly. In general, LEDs production does die bonding and wire bonding on board, and do silicon and phosphor dispensing to protect LED chip and improve brightness. Then lens molding process is performed using mixed liquid silicon rubber(LSR) by resin and hardener. A mixture of resin and hardener affect the optical characteristics of the LED lens. In this paper, computational design of static mixer was performed for mixing of liquid silicon. To evaluate characteristic of mixing efficiency, finite element model of static mixer was generated, and fluidic analysis was performed according to length of mixing element. Finally, optimal condition of length of mixing element was applied to static mixer from result of fluidic analysis.