• Journal of IKEEE
• /
• v.15 no.4
• /
• pp.319-323
• /
• 2011

In this paper presents a new model of dual-mode synchronous buck converter with dynamic control for mobile applications was proposed. The proposed circuit can operate at 2.5MHz with supply voltage 2.5V to 5V for low ripple and minimum inductor and capacitor size, which is suitable for single-cell lithium-ion battery supply mobile applications. For high efficiency, the proposed circuit adopts synchronous type and dynamic control. The proposed circuit is designed by using the device parameter of TSMC 0.18um BCD process and the performance is evaluated by Cadence spectre. Experimental board level results show the maximum conversion efficiency is 96% at 100mA load current.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.4
• /
• pp.347-352
• /
• 2007

This paper describes the design and implementation of PFM(Proto Flight Model, PFM) of DRE(Data Receiving Equipment, DRE) for Science and Technology Satellite 2(STSAT-2) and the results of integration performance test. DRE components are X-band receiver, DCE(Data Combine Equipment, DCE) and RAC(Receiving and Archiving Computer, RAC). DCE consists of I&Q data combiner and ECL signal distributor. RAC consists of DRC(Data Receiving Card) and ST2RAS(STSAT-2 Receiving and Archinving Software). X-band receiver receives 10Mbps QPSK I, Q satellite data and sends the data to DCE. DRC stores the I&Q combine data from DCE to RAID. The pre-processing program sorts and stores to satellite status data and payload data. The performance of DRE in the functional and space environments test satisfies the requirements of STSAT-2.

• Journal of the Korean Academy of Esthetic Dentistry
• /
• v.22 no.1
• /
• pp.30-46
• /
• 2013

Porcelain fused to metal crown has been used mostly over the last 50 years for restorations in dentistry. However, the patients' awareness of aesthetic aspect, biocompatibility and the problems such as an allergy to metals led to the growing interest in the 'metal free restoration'. In particular, the price of the precious metals that have been mainly used to date has risen drastically, which made them impossible to play their role as oral restorative materials anymore, and in addition, the PFM restoration has intrinsic problems of chipping and fracture. Therefore, the CAD/CAM has been drawing more attention than ever due to the popular needs for the material that is more aesthetic and stronger for restoration of the molar implant. Considerations in carrying out the full zirconia restoration are as follows: 1) strength, 2) combination work, 3) light penetrability, 4) treatment of cracks, 5) the color reproducibility of the block, 6) the abrasivity of antagonistic tooth, 7) low temperature degradation. In this presentation, the color reproducibility of the block will be discussed. One of the biggest reasons for avoiding the full zirconia restoration is that it is difficult to reproduce the natural color compared to the conventional PFM restoration. Thus, many clinicians show reluctance due to the exposure of the ugly block when the coloring on the surface is removed after occlusal adjustment. From the experience of using blocks by Zirkonzahn for more than 4 years, it is considered that these problems can be addressed to some degrees. Accordingly, how to make restorations that are well in harmony with surrounding prosthesis or natural teeth will be discussed.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.6
• /
• pp.1-9
• /
• 2008

This paper suggests the triple-mode CMOS DC-DC converter that has temperature/voltage variation compensation techniques. The proposed triple-mode CMOS DC-DC converter is used to generate constant or variable voltages of 0.6-2.2V within battery source range of 3.3-5.5V. Also, it supports triple modes, which include Pulse Width Modulator (PWM) mode, Pulse Frequency Modulator (PFM) mode and Low Drop-Out (LDO) mode. Moreover, it uses 1MHz low-power CMOS ring oscillator that will compensate malfunction of chip in temperature/voltage variation condition. The proposed triple-mode CMOS DC-DC converter, which generates output voltages of 0.6-2.2V with an input voltage sources of 3.3-5.5V, exhibits the maximum output ripple voltage of below 10mV at PWM mode, 15mV at PFM mode and 4mV at LDO mode. And the proposed converter has maximum efficiency of 93% at PWM mode. Even at $-25{\sim}80^{\circ}C$ temperature variations, it has kept the output voltage level within 0.8% at PWM/PFM/LDO modes. For the verification of proposed triple-mode CMOS DC-DC converter, the simulations are carried out with $0.35{\mu}m$ CMOS technology and chip test is carried out.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.52 no.3
• /
• pp.296-302
• /
• 2007

This study was conducted to evaluate the effect of slow release fertilizers (SRF), crotonylidene diurea (CDU) and latex coated urea (LCU), on nitrogen (N) use efficiency (NUE) and nitrate-N leaching in a silty clay loam soil under polyethylene film mulching (PFM) for sesame cultivation. In PFM plot, concentrations of $NO_3-N$ and $NH_4-N$ in SRF applied soils were less than that in the urea plot during the whole growing period. However, $NO_3-N$ and $NH_4-N$ in all the non-mulched plots (NM) were not significantly different. Urea-N in soil treated with SRF was higher than urea plot until 50 days after application and was comparable in all the treatments after 50 days. $NO_3-N$ concentrations in leached solution in 21 days after urea fertilization in PFM and NM were 26 mg $L^{-1}$ and 83 mg $L^{-1}$, respectively. However, $NO_3-N$ in leached solution at applied CDU and LCU was less than that of urea similar to nitrate concentration in soil. $NO_3-N$ in leached solution in applied CDU and LCU in 44 days after application was about 25% lower than that urea plot and PFM, while the $NO_3-N$ concentration of CDU and LCU treatment in NM did not changed. Application of SRF increased the yield of sesame and N recovery compared to urea and there was a little difference between SRF and N levels. In conclusion, application of 80% N level with SRF increased N recovery and reduced nitrate leaching without reduction of yields compared with urea application.

• Bulletin of the Korean Space Science Society
• /
• 2006.04a
• /
• pp.88-88
• /
• 2006

• Proceedings of the Korean Vacuum Society Conference
• /
• 2006.02a
• /
• pp.200-200
• /
• 2006

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.401-401
• /
• 2009

Recently, demands for the development of compact, lightweight power supplies with higher power density and higher efficiency have been increased. Since Piezoelectric Transformer (PT) was emerged in device and material industry, it has been suggested as a viable alternative to the magnetic transformer in some applications. PT has some advantages such as low profile and mechanical energy transfer with little electromagnetic interface (EMI). Also, PT can provide high voltage stepping ratio with good isolation and requires no copper windings saving copper usage especially for large voltage conversion differences. Conventional control of PT converter has mainly two-way. One is the pulse frequency modulation (PFM) control method and the other is the pulse width modulation (PWM) control with frequency fixed method. It is known that the maximum PT efficiency can be obtained when it operates near the resonant frequency of the PT. And, also PT's resonant frequency moves according to the load condition. Therefore, selection of PT converter control method is very difficult. This paper analyzes general piezo-electric converter modeling and proposes a guide-line to selection of control method and stabilization control.

• Proceedings of the KIPE Conference
• /
• 2008.06a
• /
• pp.397-399
• /
• 2008

본 논문은 대용량에 적합한 새로운 DC/DC 컨버터에 관한 것으로써, PFM-SBC(Series-Boost Capacitor) 풀 브리지 컨버터를 제안한다. 제안된 회로는 스위칭 주파수에 따라 직렬 부스트 캐패시터의 전압을 증감하여 출력전압을 제어하는 방식이며, 50% 고정 시비율로 구동하기 때문에 기존 위상천이 풀 브리지 회로에 존재하는 환류 구간이 발생하지 않는다. 또한 넓은 부하 영역에 대해 영전압-스위칭이 보장되므로 효율 및 발열 특성이 우수하며, 출력 인덕터 전류 리플이 작은 장점이 있다. 본 논문에서는 기존 컨버터들의 특성을 분석하고, 제안된 회로의 이론적 해석 및 PSIM 모의실험을 수행하며, 이를 실제로 1.2KW급 서버용 전원장치 프로토 타입 제작을 통하여 제안된 SBC 풀 브리지 컨버터의 타당성을 검증한다.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.19 no.4
• /
• pp.317-323
• /
• 2003

When making crown and bridges on anterior regions, many practitioners consider the esthetics the most. For this reason functional aspect are not considered as much as the esthetics. If the occlusion on the anterior region are not formed correctly, movement of the temporomandibular joint can be disturbed and excessive stress can be occur that pathologic condition can be under lied. On this case presentation will show the importance of the anterior guidance and suggest the appropriate protocol of using customized anterior guide table. A 45years old male had to remake both of the upper central and lateral PFM because of the porcelain fracture. The new PFM crowns were made conventional methods without considering the anterior guidance. After the temporary setting, the patient complained of discomfort and short looking upper anteriors. To solve these problems we had to restore the palatal contour and length of the new crowns by making customized anterior guide table using temporary crowns that contains patient's old anterior guidance. This procedure which is copying the pt's comfortable anterior guidance to the final prosthesis made them to be esthetic and patients to feel comfortable.