• The Transactions of the Korean Institute of Power Electronics
• /
• v.11 no.4
• /
• pp.385-394
• /
• 2006

The application areas of traditional push-pull converters are limited because the voltage stress of switches is high (twice of the input voltage). But the push - pull converter topology is suitable for unregulated low-voltage to high-voltage power conversion such as the fuel cell. This paper presents a novel power converter structure that is very suitable for the DC/DC converter in fuel cell systems. Based on this structure, a ZVS- ZCS push-pull converter is proposed. The switches of the proposed push-pull converter can operate under ZVS or ZCS condition with the help of a new passive clamping circuit. The passive clamping techniques solves the voltage overshoot problem. Because the buck converter circuit operates at twice the synchronous switching frequency of the push-pull converter, the peak current in the current-fed inductor and transformer is reduced. The operation principle of the proposed converter is analyzed and verified by simulations and experimental results. A 1 kW DC/DC converter was implemented with DSP TMS320F2812, from which experimental results have shown that efficiency improvement and surge suppression can be achieved effectively.

• The KIPS Transactions:PartA
• /
• v.11A no.3
• /
• pp.207-212
• /
• 2004

This paper provides the higher user QoS(Quality of Service) by analyzing media service model between server and client in single VoD(Video on Demand) environment and applying it to parallel VoD environment. Media service model is divided into the Client Pull, Server Push, and IPP(Interleaving Pull & Push) model. A server sends data based on client's request in the Client Pull Model. A server one-sidedly sends data without client's request in the Server Pull model. And the WP model unites above two models. For a parallel VoD environment, We built the PMSS system which provides the parallel media streaming services that one client is simultaneously served by several servers. In the single and parallel VoD environment, We compare and analyze the performance of service models with respect to network delay and data size in buffer. In this experiment, we found that IPP service model keeps the least network delay and stable client buffer in the parallel VoD environment. This result shows that PMSS can provide the more quality of service.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.1
• /
• pp.593-601
• /
• 2014

In this study, we investigated the methods of improving the capturing ability of acid fume by assessing the performance of slot-type external hood installed on both sides of an open surface tank for acid washing process. A field survey and the results of computational fluid dynamics revealed that capturing performance of existing hoods is very poor. To solve such problem, 'push-pull hood' that pushes from one side of an open surface tank and pulls on the other side was suggested. The initial prediction was that if a push-pull hood is used, the acid fume of an acid-washing tank surface could be moved towards the hood through the push flow. However, this study has confirmed that if the push flow velocity becomes too high, it could spread to other areas due to flooding from the hood. Therefore, if the push air supply is maintained at around 25 $m^3/min$(push 10 m/s), proper control flow is formed on the surface of a tank and acid fume that stayed at the upper part of the tank is smoothly captured toward the hood, significantly enhancing the capturing performance.

• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.373-376
• /
• 2000

기존의 Push-Pull 트랜스듀서보다 간단한 구조를 가지며 출력을 한층 더 높이기 위해서 실린더 중앙에 구동부를 둔 새로운 구조의 Push-Pull 트랜스듀서를 설계하고자 한다. 유한 요소 상용 Package인 ANSYS를 이용하여 트랜스듀서의 모델을 구성한 후, 분석 시 고려되어 지는 길이, 반경, Endcap Edge 형상에 대해 변수로 설정, 변수들의 변화에 대한 음압의 변화 경향을 조사하여 최대 음압을 구현하기 위한 최적 길이, 반경, Endcap Edge 형상을 설정하였다. Endcap의 형상이 수직, 삼각형 형태의 트랜스듀서에서 나타난 결과에서 힘의 전달이 Edge형상이 수직일 때보다는 삼각형일 때가 더 좋은 것을 볼 수가 있었다. 또한 기존의 트랜스듀서를 유한 요소로 설계를 하여서 분석을 하였고, 기존의 트랜스듀서와 비교해 본 결과, 최적 설계한 트랜스듀서가 구조적으로 더 단순한 구조임에도 불구하고 더 큰 음압을 구현할 수 있는 고출력 트랜스듀서라는 것을 입증하였다.

• Journal of the Korean Chemical Society
• /
• v.66 no.6
• /
• pp.521-525
• /
• 2022

• Korean journal of applied entomology
• /
• v.58 no.3
• /
• pp.209-218
• /
• 2019

This study was conducted to develop a technology for environmentally friendly control of sweet-potato whitefly, Bemisia tabaci, by controlling their behavior using a push-pull strategy in a tomato greenhouse. B. tabaci was attracted the most by yellow color, light source of 520 nm, whereas it avoided the complex light treatment of 450 + 660 nm. The two natural enemies of B. tabaci, Cyrtopeltis tenuis and Orius laevigatus, were attracted the most by 520 nm light source. B. tabaci was repelled by the volatile organic compounds ocimene and carvacrol and was the most attracted by methyl isonicotinate. When buckwheat was added into the tomato greenhouse, the density of C. tenuis was maintained at about 16 times higher than when untreated for 15 days. As a result of the combined treatment of push-pull strategy, the density per trap of B. tabaci was three times lower than when no treatment was applied, and the control of this pest increased with time and reached up to 68.7%.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.18 no.3
• /
• pp.247-255
• /
• 2013

In this paper, a soft switching DC-DC converter for AC module type photovoltaic (PV) module integrated converter is proposed. A push-pull converter is suitable for a low voltage PV AC module system because the step-up ratio of a high frequency transformer is high and the number of primary side switches is relatively small. However, the conventional push-pull converters do not have high efficiency because of high switching losses by hard switching and transformer losses (copper and iron losses) by high turns-ratio of the transformer. In the proposed converter, primary side switches are turned on at zero voltage switching (ZCS) condition and turned off at zero current switching (ZVS) condition through parallel resonance between secondary leakage inductance of the transformer and a resonant capacitor. Therefore the proposed push-pull converter decreases the switching loss using soft switching of the primary switches. Also, the turns-ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. The theoretical analysis of the proposed converter is verified by simulation and experimental results.

• The Journal of Asian Finance, Economics and Business
• /
• v.7 no.12
• /
• pp.501-508
• /
• 2020

The focus of this research was on Bali, Indonesia as an international tourist destination. The survey strategy involved self-administered questionnaires distributed to collect data and information supporting this research. The sampling method was non-probability convenience purposive sampling, which means that only those respondents who had visited Bali as a destination for more than two times for their holiday by the time the research was conducted were eligible to fill in the questionnaires. There were 300 questionnaires distributed, only 254 of which were valid. Interview was also conducted for data collection in this research. The structural equation modelling approach was used to analyze the data obtained from respondents, who had visited Bali at least two times. The outcomes of this research reveal a positive influence of push and pull motivational factors on tourist satisfaction. Moreover, a positive, significant correlation between satisfaction and destination loyalty can be seen in this research. With the aim to sustain and enhance destination competitiveness, the results of this research will be beneficial for stakeholders of Bali as a destination. This study helps stakeholders identify push and pull motivational factors in order to better prepare marketing strategies and utilize indicators of push and pull motivation that affect tourists' experience during their stay.

• Journal of Agricultural Extension & Community Development
• /
• v.22 no.2
• /
• pp.101-116
• /
• 2015

This study aims to identify the decision-making factors of people who have returned to rural areas for farming and residence according to personal characteristics and regions. The survey was conducted on 420 return farmers of six cities and counties in Gyeongsangbuk-Do from September 1st to October 11th 2013. For data analysis, researchers used 280 answered sheets and utilized two-way ANOVA and multinomial logistic regression analysis. Research results indicate three factors of returning to farm which are pull to rural area, push from city, and policy factor. The highest scores of factor is pull to rural area (2.93), the second one is push from city (2.31), and the lowest score is politic factor (2.18). In addition, these three factors of returning to farm are elucidated by environmental variable, economic variable, and information and opportunity provided by government. In other words, the factor of pull to rural area is related environmental variable and the factor of push from city is affected by economic variable. Lastly, politic factor pertains to information and opportunity provided by government.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.41 no.4
• /
• pp.51-58
• /
• 2004

Push-pull structure with balun transformer is presented for load modulation technique which improves the overall efficiency of power amplifier Under the assumption that output impedance of fumed-off amplifier is high, conventional Doherty amplifier is composed of impedance inverter and peaking amplifier, of which operation is controlled by the input power level. In many case, however, impedance of 'off'amplifier is very low due to matching network or parasitic output capacitance. This paper introduces novel load modulation technique which uses low output impedance of 'off'amplifier. Experimental results show that good linearity and efficient!'enhancement of the proposed push-pull structure