• Journal of Periodontal and Implant Science
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• 제42권4호
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• pp.127-135
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• 2012

Purpose: The aim of this study was to compare the clinical outcome of open flap debridement (OFD) with a biphasic calcium phosphate (BCP) graft to that of OFD without BCP graft for the treatment of intrabony periodontal defects (IBDs). Methods: The study included 25 subjects that had at least one intrabony defect of 2- or 3-wall morphology and an intrabony component ${\geq}4$ mm as detected radiographically. Subjects were randomly assigned to treatment with (BCP group, n=14) or without BCP (OFD group, n=11). Clinical parameters were recorded at baseline and 6 months after surgery and included the plaque index, gingival index, probing depth (PD), clinical attachment level (CAL), and gingival recession (REC). A stringent plaque control regimen was enforced for all of the patients during the 6-month observation period. Results: In all of the treatment groups, significant PD reductions and CAL gains occurred during the study period (P<0.01). At 6 months, patients in the BCP group exhibited a mean PD reduction of $3.7{\pm}1.2$ mm and a mean CAL gain of $3.0{\pm}1.1$ mm compared to the baseline. Corresponding values for the patients treated with OFD were $2.5{\pm}0.8$ mm and $1.4{\pm}1.0$ mm, respectively. Compared to OFD group, the additional CAL gain was significantly greater in the patients in BCP group (P=0.028). The additional PD reduction was significant for the BCP group (P=0.048). The REC showed a significant increase in both groups, and the amount of recession was significantly smaller in the BCP group than OFD group (P=0.023). In radiographic evaluation, the height of the bone fill in the BCP group was significantly greater than OFD group. Conclusions: The clinical benefits of BCP found in this study indicate that BCP may be an appropriate alternative to conventional graft materials.

• 한국통신학회논문지
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• 제31권6B호
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• pp.495-507
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• 2006

무선 LAN에서 스케줄링 알고리즘은 실시간 멀티미디어 서비스가 요구하는 엄격한 QoS(Quality of Service) 요구사항을 보장하는데 있어 가장 중요한 요소 중 하나이다. 본 논문에서는 MPEG 스트림과 같은 멀티미디어 트래픽의 지연을 보장하기 위한 다중폴링 기반의 동적 스케줄링 알고리즘을 제안한다. 제안된 알고리즘은 MPEG 스트림의 특성을 이용한다. 채널할당 요청 정보를 갖고 있는 동적 파라미터를 AP(Access Point)에서 동작하는 PC(Point Coordinator)로 전달하기 위해 미니 프레임이라는 피드백(Feedback) 제어 프레임을 이용한다. 하나의 수퍼프레임 동안에 각 단말에 할당될 채널시간은 MPEG 프레임 종류와 트래픽 양, MPEG 프레임의 지연한도(Delay bound) 등에 따라 동적으로 변한다. 시뮬레이션을 통하여 제안된 방법의 성능을 다른 방법과 비교 분석한다. 비교 분석결과, 제안된 방법이 지연한도를 보장하면서 높은 성능을 보임을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.136-139
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• 2004

The requirement of planarity, such as with-in-wafer nonuniformity, post thickness range, have become increasingly stringent as critical dimensions of devices are decreased and a better control of a planarity become important. The key factors influencing the planarity capability of the CMP process have been well understood through numerous related experiments. These usually include parameters such as process pressures, relative velocities, slurry temperature, polishing pad materials and polishing head structure. Many study have been done about polishing pad and its groove structure because it's considered as one of the key factors which can decide wafer uniformity directly. But, not many study have been done about polisher head structure, especially about polisher head plate design. The purpose of this paper is to know how the plate structure can affect wafer uniformity and how to deteriorate wafer yield. Furthermore, we studied several new designed plate to improve wafer uniformity and also improve wafer yield.

• 대한전자공학회논문지TC
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• 제42권11호
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• pp.1-12
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• 2005

무선 PAN에서 채널시간할당(Channel time allocation) 알고리즘은 실시간 멀티미디어 서비스가 요구하는 엄격한 QoS (Quality of Service) 요구사항을 보장하는데 있어 가장 중요한 요소 중 하나이다. 본 논문에서는 IEEE 802.15.3 고속율 무선 PAN에서 MPEG 스트림과 같은 멀티미디어 트래픽의 지연을 보장하기 위한 동적 채널시간할당 알고리즘을 제안한다. 제안된 알고리즘은 MPEG 스트림의 특성을 이용하고 DEV(Device)는 채널시간할당을 수퍼프레임(Superframe) 끝에서 PNC(Piconet coordinator)로 요청한다. 채널시간할당 요청 정보를 갖고 있는 동적 파라미터를 PNC로 전달하기 위해 미니 패킷이라는 피드 백(Feedback) 제어 패킷을 이용한다. 하나의 수퍼프레임 동안에 각 DEV에 할당될 채널시간은 MPEG 프레임 종류와 트래픽양, MPEG 프레임의 지연한도(Delay bound) 등에 따라 동적으로 변한다. 시뮬레이션을 통하여 제안된 방법의 성능을 다른 방법과 비교 분석한다. 비교 분석결과, 제안된 방법이 지연한도를 보장하면서 높은 성능을 보임을 확인하였다.

• 한국대기환경학회지
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• 제18권6호
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• pp.539-546
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• 2002

The physicochemical properties of solid wastes generated from seven highway service areas, four branch offices, and one construction site were analyzed in concert with air pollutants including heavy metals emitted from near-by small-scale incinerators. The amount of solid wastes generated from highway areas has been increasing with recent increases in the number of highways and passengers. Twelve incinerators examined in this study generally had capacity smaller than 100 kg/hr, most of which were equipped with cyclone for dust removal. It was seen that the concentrations of the gas-phase air pollutants (e.g., SO$_2$, NO$_{x}$, HCl and H$_2$S) were above the acceptable emission standards except one or two sites. CO concentrations at all incinerators were also higher due to incomplete combustion. In addition, particulate matters showed concentration six times higher at their maximum. The results of heavy metal analysis showed that the concentrations of Cu, Cd, and Ni satisfied the emission standards. whereas Pb at one site and Zn at five sites exceeded the standards. Cr measurement results indicated that 9 of 12 incinerators had higher values than the standard; especially one branch office showed nine times higher than normal concentration. In order to satisfy more stringent emission standards in the near future, it is necessary to install air pollution control system and to develop an intensified management plan.n.

• 한국전자파학회논문지
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• 제22권4호
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• pp.440-446
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• 2011

본 논문에서는 레이더 시스템에 적용이 가능한 50 W 출력을 가지는 X-대역 pulsed SSPA(Solid State Power Amplifier)를 설계 및 제작하였다. SSPA를 펄스 모드로 동작시키는 방법으로 펄스 변조 방법과 전원 스위칭 방법을 혼용한 방법을 제안하였다. SSPA는 구동 증폭기, 고출력 증폭기, 펄스 변조기로 구성되며, 충분한 이득과 출력 크기를 얻기 위해 25 W GaAs FET 4개를 병렬 구조로 구성하였다. 측정 결과 1.12 GHz 대역폭에서 출력 50 W, 이득 44.2 dB의 성능을 가졌다. 또한, pulse droop은 1 dB 이하로 설계 목표를 만족하였으며, 12.45 ns 이하의 상승/하강 시간을 가졌다. 제작된 X-대역 pulsed SSPA 크기는 $150{\times}105{\times}30\;mm^3$로 매우 작은 크기를 가졌다.

• Journal of Power Electronics
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• 제11권3호
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• pp.360-368
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• 2011

This paper proposes an active frequency with a positive feedback in the d-q frame anti-islanding method suitable for a robust phase-locked loop (PLL) algorithm using the FFT concept. In general, PLL algorithms for grid-connected PV PCS use d-q transformation and controllers to make zero an imaginary part of the transformed voltage vector. In a real grid system, the grid voltage is not ideal. It may be unbalanced, noisy and have many harmonics. For these reasons, the d-q transformed components do not have a pure DC component. The controller tuning of a PLL algorithm is difficult. The proposed PLL algorithm using the FFT concept can use the strong noise cancelation characteristics of a FFT algorithm without a PI controller. Therefore, the proposed PLL algorithm has no gain-tuning of a PI controller, and it is hardly influenced by voltage drops, phase step changes and harmonics. Islanding prediction is a necessary feature of inverter-based photovoltaic (PV) systems in order to meet the stringent standard requirements for interconnection with an electrical grid. Both passive and active anti-islanding methods exist. Typically, active methods modify a given parameter, which also affects the shape and quality of the grid injected current. In this paper, the active anti-islanding algorithm for a grid-connected PV PCS uses positive feedback control in the d-q frame. The proposed PLL and anti-islanding algorithm are implemented for a 250kW PV PCS. This system has four DC/DC converters each with a 25kW power rating. This is only one-third of the total system power. The experimental results show that the proposed PLL, anti-islanding method and topology demonstrate good performance in a 250kW PV PCS.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.292-295
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• 2004

The SIT was introduced by Nishizawa. in 1972. When compared with high-voltage, power bipolar junction transistors, SITs have several advantages as power switching devices. They have a higher input impedance than do bipolar transistors and a negative temperature coefficient for the drain current that prevents thermal runaway, thus allowing the coupling of many devices in parallel to increase the current handling capability. Furthermore, the SIT is majority carrier device with a higher inherent switching speed because of the absence of minority carrier recombination, which limits the speed of bipolar transistors. This also eliminates the stringent lifetime control requirements that are essential during the fabrication of high-speed bipolar transistors. This results in a much larger safe operating area(SOA) in comparison to bipolar transistors. In this paper, vertical SIT structures are proposed to improve their electrical characteristics including the blocking voltage. Besides, the two dimensional numerical simulations were carried out using ISE-TCAD to verify the validity of the device and examine the electrical characteristics. A trench gate region oxide power SIT device is proposed to improve forward blocking characteristics. The proposed devices have superior electrical characteristics when compared to conventional device. Consequently, the fabrication of trench oxide power SIT with superior stability and electrical characteristics is simplified.

• 한방안이비인후피부과학회지
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• 제30권4호
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• pp.62-74
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• 2017

Objectives : The purpose of this study is to investigate the effect of laser therapy for diabetic ulcer by using methods of systematic review. Methods : In this review, PubMed, Cochrane library, Web of Science, CNKI, CiNii, J-STAGE, NDSL and OASIS were used as the search engines. The search period is from the start date of the search engine to October 3, 2016. Randomized controlled trials(RCTs) using laser therapy for diabetic ulcer were searched and extracted by two independent researchers. Risk of bias(RoB) of Cochrane was used to assess methodological quality of studies. Results : Finally, five RCTs were selected. The follow-up period ranged from 15 days to 20 weeks. InGaAlP laser, GaAlAs laser and light emitting diode(LED) were used to treat diabetic ulcer. The clinical trials used sham laser irradiation or standard treatment as control in comparison to laser therapy. The endpoints included ulcer size, rate of healing and time to healing with follow-up period. The RCTs demonstrated therapeutic outcomes with no adverse effect. Most items of RoB were unclear and methodological quality was low. Conclusions : Our analysis suggests that laser therapy has therapeutic effects for diabetic ulcer. However, more systematic and stringent clinical trials will be required.

• 보건행정학회지
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• 제25권3호
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• pp.149-151
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• 2015

United Nations (UN) adopted 17 global sustainable development agenda to the year 2030 in the 68th general assembly on september, 2015. The global agendas and goals are important for 3 reasons: (1) to adopt the international standard for determining the health status; (2) to identify areas in need of attention; and (3) to advance international cooperation regarding health issues. In the area of infectious diseases, our goals include the eradication of human immunodeficiency virus infection and acquired immune deficiency syndrome, tuberculosis, and malaria as well as a substantial reduction of hepatitis by the year 2030. In the area of non-communicable diseases, our goal is to reduce premature mortality (${\leq}70years$) at least 30% by the year 2030. Preventive activities such as smoking cessation, alcohol abstinence, nutritional measures, and physical activities, should also be promoted intensively nationwide. It is also necessary to establish stringent policies for control hypertension, diabetes, obesity, and hypercholesterolemia. Additionally, environmental health, injury by traffic accident, mental health, and drug and alcohol abuse are important health policies. Furthermore, in the area of international health and cooperation, maternal and child health remain important areas of support for underdeveloped countries. Education and training towards the empowerment of health professionals in underdeveloped countries is also an important issue. The global agenda prioritize resources(manpower and budget) allocation of international organizations such as UN, World Health Organization, United Nations Development Programme, and World Bank. The global agenda also sets the contribution levels of Official Developmental Assistance donor countries. Health professionals such as professors and researchers will have to turn their attention to areas of vital international importance, and play an important role in implementation strategies and futhermore guiding global agenda.