• 한국정밀공학회지
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• 제29권4호
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• pp.455-460
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• 2012

The Electrostatic Inkjet system has many applications in cost and time effective manufacturing of printed electronics like RFIDs, OLEDs and flexible displays etc. This paper presents pneumatic ink supply system for an electrohydrodynamic deposition (EHD) setup for the precise pressure control to produce a small amount of discharge at the end of the capillary. The meniscus shape depends upon the applied pneumatic pressure to the ink supply system. Furthermore, this paper also compares meniscus shapes at different applied pneumatic pressures. It is concluded that patterning of constant line-width can be achieved better by controlling the meniscus shape using this technique.

• 한국진공학회지
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• 제15권6호
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• pp.594-604
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• 2006

일정한 기체 공급 압력에서 정해진 만큼 밸브를 개방하는 방식과 밸브를 조절하여 일정한 유량을 흐르도록 하는 두 가지 기체 주입 방식의 작동특성에 대한 시뮬레이션을 통해 공급 압력, 밸브 컨덕턴스, 유량 등 시스템 조건 및 기체 수송관의 길이와 굵기에 따라 기체흐름의 유형이 어떻게 바뀌는지 조사했다.

• 대한기계학회논문집B
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• 제35권3호
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• pp.245-253
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• 2011

속도 제어형 트림을 구성하는 기본 유로 요소로서 $90^{\circ}$의. 굴곡을 갖는 유로를 선택하여 폭과 길이가 상사성을 가지도록 설정하고 0, 4, 8 회의 굴곡을 갖는 총 48개의 단위 유로 요소에 대해 유동 해석을 수행하였다. 먼저, 동일 요소에 대한 실험과 수치해석 결과를 비교하여 수치해석 접근방법의 타당성을 검증하였다. 일정한 차압에 대해 굴곡횟수에 따른 유량을 계산한 결과, 굴곡이 없으면 유로의 길이가 증가함에 따라 유량이 감소하였다. 굴곡이 있는 경우, 유로가 길어지면 유량이 증가하다가 감소하였다. 케비테이션의 억제의 관점에서 압력장을 분석하였고, 이로부터 동일한 굴곡횟수를 가질 경우 유로가 길수록 유로를 따라 발생하는 압력 강하 특성이 우수함을 알았다. 또한, 유로의 길이가 같은 경우에는 굴곡횟수가 많을수록 압력이 완만히 감소하는 특성을 가짐을 알 수 있었다.

• International Journal of Control, Automation, and Systems
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• 제5권2호
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• pp.161-169
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• 2007

The PLL equivalent augmented system incorporated with state feedback is proposed in this paper. The optimal value of filter time constant of loop filter in the phase-locked loop control system and the optimal state feedback gain designed by using linear quadratic regulator approach are derived. This approach allows the PLL control system to employ the large value of the phase-frequency gain $K_d$ and voltage control oscillator gain $K_o$. In designing, the structure of phase-locked loop control system will be rearranged to be a phase-locked loop equivalent augmented system by including the structure of loop filter into the process and by considering the voltage control oscillator as an additional integrator. The designed controller consisting of state feedback gain matrix K and integral gain $k_1$ is an optimal controller. The integral gain $k_1$ related to weighting matrices q and R will be an optimal value for assigning the filter time constant of loop filter. The experimental results in controlling the second-order lag pressure process using two types of loop filters show that the system response is fast without steady-state error, the output disturbance effect rejection is fast and the tracking to step changes is good.

• 한국수소및신에너지학회논문집
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• 제19권5호
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• pp.403-409
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• 2008

Polymer electrolyte membrane fuel cell (PEMFC) is very interesting power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, improvement of performance, effect of temperature and initial start at low temperature. These problems can be approached to be solved by using experiment and mathematical method which are general principles for analysis and optimization of control system for heat and hydrogen detecting management. In this paper, insulation vessel and control system for stable operation of fuel cell at low temperature were developed for experiment. The constant temperature capability and the heating time at sub-zero temperatures with insulation control system were studied by using a heating bar of 60W class. PEMFC stack which was made by 4 cells with $50\;mc^2$ active area in each cell is a thermal source. Times which take to reach constant temperature by the state of insulation vacuum were measured at variable environment temperatures. The test was performed at two conditions: heating mode and cooling mode. Constant temperature capability was better at lower environment temperature and vacuum pressure. The results of this experiment could be used as basis data about stable operation of fuel cell stack in low temperature zone.

• 한국산업융합학회 논문집
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• 제25권2_1호
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• pp.149-159
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• 2022

Biomass is material that is comprehensive of carbonaceous materials from plants, crops, animals, and algae. It has been used as one of heating fuel since the beginning the emergence of human beings. Since biomass is regarded as carbon-neutral energy source, it has recently been attracting attention as an energy source that can replace fossil fuels. The most widely applied field is distributed power generation, and a method of generating electric power by driving an internal combustion engine with syngas produced by gasifier is chosen. While the composition of the syngas produced in gasifiers changes depending on the air flowing into the reactor, commercialized gasifiers so far do not control the air flowing into the reactor. When the inner pressure in reactor increases, the air sucked into the reactor is reduced. That change of amount of air makes the composition of syngas varied. Those variations of composition of syngas cause the incomplete combustion hence the power output of engine drops, which is a critical weakness of the gasification technology. In this paper, to produce the uniformly composed syngas, PID control is applied. The result was shown when the amount of air into the reactor is supplied with the constant amount using PID control, the standard deviation of caloric values of syngas is around 2[%] of its average value. Meanwhile the gasifier without PID control has the standard deviation of caloric values is around 7[%]. Therefore, Adopting PID control to supply constant air to the gasifier is highly desirable.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1991년도 추계학술발표회논문집
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• pp.5-10
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• 1991

There are many articles about the HID lamps about it's characteristics and simulation methods for lamps design or ballast design. For the eletronic ballasts of HID lamps, There are some problems caused by acoustic resonance which destabilizes the arc of HID lamps. So, some studies suggest the methods to avoid it. For example, the methods to avoid it. For example, the methods suggested are high frequency driving over 100kHz, and mixed frequency driving which alternates high frequency and low frequency, and square wave driving etc. This study suggests the electronic ballast of HID lamps which solves the problems of acoustic resonance, and which can control the luminance by constant current boosted chopper of which frequency is 30kHz and by the sqarewave driving of which frequency is 55.5Hz. As follows, we have the good eletronic ballast for HID lamps which has the characteristics of a light weight, and a function of luminance control and a high quality luminosity and which saves electrical energy.

• 연구논문집
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• 통권29호
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• pp.123-130
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• 1999

Flow divider valve는 한 개의 공급라인에서 두 개 이상의 출력라인으로 유압유를 일정비율로 분배하는 유압제어밸브로서 하중압력이나 공급압력 등에 관계없이 항상 일정비율의 유량분배가 가능해야 한다. 현재 상용제품의 유량분할 정확도는 90~95% 수준이며, 이러한 유량분할오차(Flow dividing error)는 유압시스템에 누적오차로 작용하여 많은 문제점을 야기시키고 있어 보다 고정밀 유량제어가 가능한 Flow divider valve 개발이 요구된다. 본 연구에서는 외력을 고려한 스푸울의 거동을 수치적으로 정확하게 조사하여 Flow divider valve의 동특성을 규명함과 동시에 유량분할 오차를 감소시키는 최적설계방안을 제시하고자 한다. 동특성 해석은 일정한 하중저항을 입력신호로 작용하는 경우에 대해서 제시하였으며, 이때의 고정오리피스와 가변오리피스의 단면적 및 스푸울의 단면적 변화에 따른 동특성의 변화를 조사하였다.

• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2395-2406
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• 2023

To study the influence of parameter uncertainty in small pressurized water reactor (SPWR) once-through steam generator (OTSG), the nonlinear mathematical model of the SPWR is firstly established. Including the reactor core model, the OTSG model and the pressurizer model. Secondly, a control strategy that both the reactor core coolant average temperature and the secondary-side outlet pressure of the OTSG are constant is adopted. Then, the uncertainty quantification method is established based on Latin hypercube sampling and statistical method. On this basis, the quantitative platform for parameter uncertainty of the OTSG is developed. Finally, taking the uncertainty in primary-side flowrate of the OTSG as an example, the platform application work is carried out under the variable load in SPWR and step disturbance of secondary-side flowrate of the OTSG. The results show that the maximum uncertainty in the critical output parameters is acceptable for SPWR.

• 한국산학기술학회논문지
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• 제13권7호
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• pp.3132-3139
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• 2012

본 연구는 회전근개건염 환자에게 체외충격파 치료를 실시하여 통증과 기능에 어떠한 영향을 미치는지 알아보고자 하였다. 2011년 9월부터 2012년 2월까지 초음파를 통해 회전근개건염 진단을 받은 환자 32명(치료군 16명, 대조군 16명)을 대상으로 치료군에게 4주 동안 체외충격파 치료를 실시하였다. 통증은 visual analog scale(VAS)와 pressure pain threshold(PPT)를 사용하여 평가하였고 기능평가는 위해 Constant and Murley Scale(CMS)와 Simple Shoulder Test(SST)를 통해 평가 하였다. 연구 결과 체외충격파 중재 후 치료군에서는 대조군에 비해 통증과 관절가동 범위, 근력, 기능 등 모든 부분에서 유의한 변화를 보였다. 이 결과는 회전근개건염 환자에게 체외충격파 치료가 어깨의 통증과 기능에 영향을 미칠 수 있는 가능성을 시사하고 효과적인 치료방법이라 할 수 있다.