• 한국전기전자재료학회논문지
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• 제14권4호
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• pp.289-296
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• 2001

The piezoelectric transformers of 2.0x10x48 ㎣ size were fabricated with PSN-PMN-PZT(T10 and PNW-PMN-PZT(T2) composition ceramics. Effects of micro structural and piezoelectric properties on the electrical characteristics of the piezoelectric transformers were investigated. Under the fixed output power of 6 W, temperature rise of T1 transformer at the optimum load was smaller than T2 one because of fine grain size effect. Voltage step-up ratio of T1 transformer showed higher value than T2 one T1 transformer showed an excellent properties with voltage step-up ratio of 12.41, efficiency of 95.23% and temperature rise of 7.2$^{\circ}C$ at 200㏀ load resistance. And also, T2 transformer showed an excellent properties with voltage step up ratio of 9.81, efficiency of 95.51% and temperature rise of 9$^{\circ}C$ at 150㏀ load resistance.

• PNF and Movement
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• 제8권2호
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• pp.9-15
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• 2010

Purpose : This study aimed to investigate the effect of differing ground contact conditions on the eletromyographic(EMG) activity in rectus femoris, biceps femoris, tibialis anterior, gastrocnemius medialis during step-up activity in patients with hemiparesis. Methods : 10 hemiparetic patients performed step-up activity on three different ground contact conditions: entire ground contact, 2/3 ground contact, 1/3 groud contact. Result : The EMG activities of gastrocnemius medialis significantly changed on 1/3 ground contact(p<.05). However, no significant changed rectus femoris, biceps femoris, tibialis anterior between three differing ground contact conditions (p>.05). Conclusion : This study provides that EMG activities of gastrocnemius medialis significantly changed on different ground contacts. Therefore, this method can be used to strengthen the gastrocnemius medialis.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.813-816
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• 2004

Unipoled piezoelectric transformers were designed with different input and output area ratios. The voltage step-up ratio increased proportionally with increasing the input area. The piezoelectric transformers operated in each transformer's resonance vibration mode. In this paper, ANSYS(FEM program) was used for analysing piezoelectric transformers. We compared with analysis and experimental results. The voltage step-up ratio showed maximum value in output area of small size. Output characteristics of piezoelectric transformers with various size were simulated. The result of analysis showed $2\sim7$ times higher voltage step-up ratio than a experiment result.

• Journal of Power Electronics
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• 제19권5호
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• pp.1069-1073
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• 2019

In this paper, an alternative non-isolated DC-DC converter with a high voltage boosting capability is proposed. Two inductors are used and one of them has its flux linkage increases during its charging period to achieve a high step-up voltage gain. Among the three integrated capacitors, one portrays the partial characteristic of the switched-capacitor technique, while the other two are connected in series across the load. With the two switches controlled using the same duty cycle, the proposed topology demonstrates the merits of a higher and wider range of step-up voltage gain when compared with recent topologies. In addition, a reduction in loss is induced and a higher efficiency is ensured with all the voltage stresses constrained within the output voltage. Operation of the proposed converter is analyzed and validated through experimental results obtained with a prototype.

• Journal of Power Electronics
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• 제19권1호
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• pp.134-145
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• 2019

A single-phase step-up five-level inverter topology with a new phase-shifted pulse width modulation (PS-PWM) strategy is proposed in this paper. When compared with conventional single-phase five-level inverter topologies, the proposed topology can realize multilevel inversion with a double step-up ratio, a reduced number of switching devices and self-balanced capacitor voltages. When compared with the conventional PS-PWM strategy, the new PS-PWM strategy can be implemented with one carrier reduced, which makes it much easier to implement in a digital signal processor (DSP) system. Experimental results have been presented to verify the effectiveness of the proposed inverter and the PS-PWM strategy.

• 전력전자학회논문지
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• 제28권1호
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• pp.8-14
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• 2023

This paper proposes a PFC converter with a double step-up function using an asymmetrical PWM scheme. For the conventional PWM scheme, the input voltage range, which maintains a double step-up function, is limited because the proposed converter has different voltage gains and characteristics when the duty ratio(D) is less than 0.5. The proposed converter has a constant voltage gain regardless of the magnitude of the input voltage and can achieve output voltage balancing by using the asymmetrical PWM scheme. A 1.6-kW prototype of the proposed converter was built and tested to verify the performance.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.152-153
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• 2010

This paper presents the design of a low-input-voltage step-up converter. Such circuits can be useful for single fuel cell to generate less than 0.7V. Important issues to design it are physical volume, efficiency and start-up method. In this paper, we propose a step-up converter with a simple start-up circuit. The operation of proposed circuit is presented and the experimental results are provided to verify the feasibility of the proposed technique.

• 한국공간구조학회논문집
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• 제10권4호
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• pp.67-74
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• 2010

대공간 구조형식을 갖는 단층 래티스 돔은 역학성, 가능성, 심미성 등을 갖는 구조물로서 그 용도가 점점 확대되고 있다. 단층 래티스 돔의 골조 격자 패턴은 무수히 존재하며, 그 대표적인 패턴에는 삼각형, 사각형, 육각형, 라멜라형, 리브형 등이 있다. 대공간 구조물의 경우, 일반구조물과 달리 재래적인 공법으로 지붕 골조를 시공할 경우 많은 가설재가 소요됨으로 시공비 증가가 예상된다. 따라서 대공간 구조물의 지붕 골조 설치는 특수 Erection 공법에 의하는 것이 일반적이며, 그 중 지상에서 지붕골조를 설치 후 jack-up 서포트에 의해 골조를 인양하는 Step-Up 공법을 적용할 경우 공기와 공비의 대폭적인 절감이 예상된다. 따라서 본 논문의 목적은 Step-Up 공법에 의해 단층라멜라 돔의 지붕골조를 시공할 경우, 인양 중 가설 서포트 개수와 위치에 따른 좌굴특성을 검토하는 것이다. 연구 결과 서포트 개수 및 위치에 따른 단층라멜라 돔의 다양한 좌굴 특성에 관한 실무자를 위한 기초적인 자료를 얻을 수 있었다.

• Journal of Power Electronics
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• 제18권1호
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• pp.266-276
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• 2018

This paper presents a new step-up and step-down multi-pulse auto-transformer rectifier unit (ATRU) topology. This structure can achieve a wide range of output voltages, which solves the problem of auto-transformer output voltage being difficult to regulate. Adding middle taps to the primary winding and reasonably setting the number of auto-transformer windings, constituted two groups of three-phase output voltages with a $30^{\circ}$ phase difference. Multi-pulse output DC voltage is obtained after a three-phase output voltage across two rectifier bridges and inter-phase reactor. Thus, the output DC voltage is related to the number and configuration of the auto-transformer winding. In this paper, the relationship between the voltage ratio of the auto-transformer and the ratio of winding, input current and auto-transformer kilovoltampere rating are deduced and validated by simulations. On this basis, the output voltage range is optimized. An experiment on two different voltage ratio principle prototypes was carried out to verify the correctness of the analysis design.

• 복식
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• 제58권5호
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• pp.13-34
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• 2008

In Headgear and Ornaments for Diadem in the Period of the Three States there was Conical Cap(or Pointed Cap), Feathered Cap(Trim), and Crown[Tree-typed Diadem and Tree and Antler-typed Diadem] was excavated from the tombs. Feathered Trim is 5 types, Feathered Trim I-A, Feathered Trim I-B, Feathered Trim II-A, Feathered Trim II-B, Feathered Trim II-C in according to upper part of central insert plate style. Feathered Trim I-A, I-B, II-B type was general style that was found in most of the old tombs in ancient Silla, Gaya. Feathered Trim II-A type was excavated from the only Silla tombs and II-C type was excavated from Gaya tombs. The Ornaments for Diadem in Baekje was excavated from the tombs is adorned with a arranged leaf-stems on either sides and the flower-shaped. They were distinguished with the original mode of Goguryeo and ancient Silla at the time. Tree-typed Diadem is five part in according to the Mountain(;山)-typed piled up. Only one Mountain(;山)-typed one in three stand-up ornament(I-1 type), and three step one in three stand-up one(I-2 type), modification one (I-3 type), three step one of four and five stand-up ones(I-4 type), and four step one of four and five stand-up ones (I-5 type). Tree and Antler-typed Diadem is three part in according to the step of Mountain(; 山)-typed and cross-shaped of the upper part. Three one of three step one of Mountain(;山)-typed and two Antler- typed (II-1 type), cross-shaped one(II-2 type), four step one(II-3 type).