• 한국정보통신학회논문지
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• 제10권7호
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• pp.1326-1331
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• 2006

일반적으로 용접 Root 캡은 여러 가지 용접 결함들 중에 용접 품질을 저하시키는 중요한 요인 중의 하나이다. Gas metal arc welding (GMAW)에서 root 갭은 용접 전류, 아크 전압, 용적률 등과 같은 여러 가지 용접 파라미터들에 영향을 미친다. 그러나 용접 공정의 비선형성 때문에 root 갭과 많은 용접 파라미터들 사이의 관계를 분석하기가 힘들다. 그리고 아크센서를 사용하였을 경우, 감지된 신호에 대한 신호처리가 어렵지만 가격이 저렴하고 자동화하기가 쉬우므로 현재의 산업공정에서 대부분 아크센서가 사용되고 있다. 지금까지 언급된 여러 가지 어려운 문제점과 아크센서의 특정 때문에 본 논문에서는 GMAW에서 root 갭을 검출할 수 있는 적당한 용접 파라미터들을 선정하고, root 캡과 선정된 파라미터들의 관계를 인식할 수 있는 신경회로망을 이용하여 root 갭 검출 시스템을 설계하였다. 또한, 용접 품질의 검사에 용접 비드형상이 중요한 요인이다. 따라서 본 논문에서는 신경회로망으로 용접 파라미터와 용접 비드형상과의 관계를 인식하여, 용접 품질을 추정하고 용접 파라미터들의 효과를 분석할 수 있는 용접 비드 형상의 실시간 모니터링 시스템을 제안하여 여러 실험 데이터들을 기반으로 한 시뮬레이션을 통해 제안된 시스템이 root 갭을 검출하고 또한 용접 비드 형상을 실시간으로 모니터링이 가능함 보여준다.

• 한국진공학회지
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• 제20권5호
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• pp.322-326
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• 2011

상부 전극에 RF power 가 직접 인가되는 capacitively coupled plasma source를 이용한 oxide layer etching 공정은 현재 반도체 제조 공정에서 매우 유용하게 사용되고 있는 방식이다. 그러나 디바이스의 사이즈가 점점 작아지면서 공정을 진행하기 위한 RF power도 커지고, plasma ignition 되는 electrode 사이의 간격도 점점 좁아지는 기술적 변화가 이루어지고 있다. 이러한 H/W의 변화에 따라 예상치 못한 문제들로 공정을 적용하는데 많은 문제점이 발생하고 있는데, 공정 진행 시에 plasma의 영향으로 인한 electrode의 온도 변화도 그 중 하나이다. 이러한 온도 변화로 인해 wafer to wafer의 공정 진행 결과가 서로 다르게 나타나게 하는 문제가 야기되고 있다. 아래의 내용에서는 상부 electrode의 온도 변화에 따른 etch 특성을 연구하고, 이를 개선할 수 있는 방법에 대해 논하고자 한다.

• 대한건축학회논문집:구조계
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• 제35권10호
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• pp.207-215
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• 2019

The aim of the research is analyzing the simple adiabatic temperature rising properties and the heat of hydration based on different placing timing of the mass concrete depending on various replacing ratios of blast furnace slag to comparative analyze the thermal cracking index and cracking possibility. As a result from the experiment, a suggested adiabatic temperature rising equation based on various blast furnace slag replacing ratios can be provide favorable correlation with over 0.99 of $R^2$ value by applying the initial induction period. With this relationship, more accurate prediction of the amount of the hydration heat rising and heating timing, and it is known that there is an approximately $13.1^{\circ}C$ of gap between plain concrete without blast furnace slag and concrete with 80 % of replacing blast furnace slag. To control the setting time and heat rising gap, the mix designs between top and bottom concrete casts were changed 15 cases, and D, E, H, I, and L models of controlling the heat of hydration showed 41.23 to $46.88^{\circ}C$ of core temperature and 0.98 to 1.27 of thermal cracking index. Therefore the cracking possibility was 15 to 52 % of favorable results of possibly controlling both the cracking due to the internal and external retainment and concrete temperature at early age.

• 한국전기전자재료학회논문지
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• 제37권3호
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• pp.292-296
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• 2024

In this study, Iron (III) oxide-hydroxide (δ-FeOOH) was successfully synthesized using hydrogen peroxide (H₂O₂) as an oxidizing agent. The synthesis of δ-FeOOH was carried out by controlling the amount of H₂O₂, and pure δ-FeOOH was successfully synthesized in ranges from 0.2 mL to 0.6 mL of H₂O₂. The size of the synthesized δ-FeOOH particles was compared by controlling the amount of oxidant H₂O₂. The average particle size of the synthesized pure δ-FeOOH particles increased from 875.1 nm to 897.2 nm as the amount of H₂O₂ was increased. The optical properties of δ-FeOOH synthesized under these specific conditions were investigated. All δ-FeOOH showed a similar trend of increasing and decreasing light absorption from 800 nm to 400 nm, although there was a slight difference in the amount of light absorption, with the largest amount of light absorption at 410 nm. The band gap energy of δ-FeOOH through the Tauc plot method was about 2.1~2.2 eV when H₂O₂ was 0.2~1.4mL. With a sufficient small particle size, simple control of that particle size, and a small band gap energy enough to absorb light in the visible spectrum, δ-FeOOH could be useful in a variety of applications, including photoelectrochemistry and battery electrodes.

• 한국항공우주학회지
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• 제46권6호
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• pp.487-495
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• 2018

환형 갭과 핀틀갭의 면적을 동시에 제어할 수 있는 가변 슬리브 인젝터의 분무특성을 실험적으로 분석하고, 넓은 추력범위에서 일정한 성능으로 제어할 수 있는 방안을 연구하였다. 슬리브의 개도에 관계없이 일정한 차압을 설정한 경우 설계유량을 만족하지 못하는 것을 확인하였다. 이를 개선하기 위해 개도에 따라 환형 갭과 핀틀 갭에서의 차압을 개도에 따라 다르게 적용하였다. 운용범위 내에서 설계 유량을 만족하였고, 선형적인 슬리브 면적으로 25%에서 100%까지 선형적으로 추력제어가 가능한 것을 확인하였다.

• 전기의세계
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• 제22권2호
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• pp.57-69
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• 1973

The aim of this study was to investigate the behaviors of plasma jet under coaxial magnetic field in paralled with it for controlling optical characteristics and input power of plasma jet without impurity and instability of arc plasma column. Because the discharge characteristics of plasma jet were so distinctively different according to the existence or non-existence of magnetic field, the input power, luminous intensity of plasma jet and thermal efficiency were comparatively studied in respect of such variables as arc current, gap of electrode, quantity of argon flow, magnetic flux density, diameter and length of nozzle, with the use of several materials which were different in diameter and length of nozzel. The results were as follows; 1) The voltage tends to show a drooping characteristic at law current and then rises gradually. The luminous intensity of plasma jet increases exponentially with arc current. 2) Arc voltage increases and luminous intensity tends to decrease gradually as gap of electrode increases. 3) Arc voltage and luminous intensity tends to decrease gradually as gap of electrode increases. 3) Arc voltage and luminous intensity increase in accordance with the quantity of argon flow. 4) At first step, arc voltage increases to maximum value with the growth of flux density and then tends to show a gradual decrease. Luminous intensity decreases with the growth flux density. 5) Arc voltage decreases as the constriction length of nozzle increases, maximum decrease is shown at the constriction length of 20(mm) and it increases beyond that value. The luminous intensity decreases as the constriction length grows. 6) Arc voltage and luminous in tensity increase with the growth of diameters of nozzle. 7) Thermal efficiency has values between 50% and 75%, being influenced by arc current, the quantity of argon flow, flux density, the length of electrode gap and the constriction length of nozzle.

• 조명전기설비학회논문지
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• 제25권1호
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• pp.93-100
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• 2011

This paper presents a technical study for the first short stroke lightning current generator using a crowbar device. The so-called crowbar-technology is most common to make 10/350[${\mu}s$] impulse currents with high amplitude, and the lightning current generator with crowbar device has an economic advantage than the nominal RLC current generator. But both the operating efficiency and the operating reliability of crowbar spark gap are very important to design the current generator. So, the peaking circuit which consists of small capacitors and a spark gap is applied. And the multi-step coil for controlling the circuit constant at the different test conditions is used. The presented test facility is designed to perform impulse tests with amplitudes up to 50[kA] of 10/350[${\mu}s$].

• The Journal of the Acoustical Society of Korea
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• 제21권2E호
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• pp.81-90
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• 2002

Single absorbing materials and Helmholtz resonators have limited absorption characteristics over limited frequency ranges due to their structures and properties. Porous materials are highly absorptive for mid and high frequency ranges, while they have little sound absorption for low frequency sounds. Helmholtz resonators are generally used to absorb sound energy for a specified frequency range. Hence they have limited capability in controlling the overall acoustic properties of a space. Not much has been known about useful finishing materials which have enough rigidity and absorption over broad frequency range, in spite of wide demands from acoustic designers and consultants. The present work measured and analyzed absorption characteristics of a slit absorber by varying surface materials, depths of air gap, dimensions of slat and slit widths. It was found that the narrower the slit width, the larger the absorptions over the wide frequency ranges and the pattern was dependent on the presence of porous material. Narrower slat's width tend to increase the slit absorber's absorption more or less. Absorption coefficients at low frequency ranges were dramatically improved (from 0.23 to 0.56) by increasing air gap when porous materials were present.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권8호
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• pp.473-480
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• 2000

A fuzzy PID controller is proposed for the posture control of a two DOF robot vehicle inspecting the defects of the inner wall of sewage pipes. The main difficulty in controlling these kinds of vehicles lies in that the center of two mobile shafts does not coincide with the weight center of the vehicle due to its long and wide shape. In this case the previous controller, based on the assumption that the gap between these centers are small, can not guarantee satisfactory transient response characteristics. In this paper, this gap is included in the mathematical modelling of the robot kinematics, and in order to compensate the unsatisfactory transient response characteristics, the fuzzy PID controller is proposed. This controller tunes the PID control gains with respect to the current state of the errors between the reference and the current postures. A series of simulations has been performed to investigate the tracking performance of the proposed controller for the lane changing path and the robustness to the external disturbance. The simulation results show that the proposed controller has a satisfactory tracking performance in the transient state as compared with that of the backstepping control given in reference.

• 한국정밀공학회지
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• 제27권7호
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• pp.109-116
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• 2010

The magnet wheel which generates on its interfacing conductive part a repulsive force and a traction torque by rotation of permanent magnets is used to manipulate the conductive plate without mechanical contact. Here, the air-gap magnetic field of the magnet wheel is shielded partially to convert the traction torque into a linear thrust force. Although a magnitude of the thrust force is constant under the fixed open region, we can change the direction of force by varying a position of the shield sheet. So, the spatial position of conductive plate is controlled by not the force magnitude from each magnet wheel but the open position of shield sheet. This paper discusses non-contact conveyance system of the conductive plate using electromagnetic forces from multiple magnet wheels.