• 한국세라믹학회지
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• 제55권1호
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• pp.55-60
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• 2018

In this study, quantum dots composed of $Mn^{2+}$ doped ZnS core and ZnS shell were synthesized using MPA precursor at room temperature. The ZnS: Mn/ZnS quantum dots were prepared by varying the content of MPA in the synthesis of ZnS shells. XRD, Photo-Luminescence (PL), XPS and TEM were used to characterize the properties of the ZnS: Mn/ZnS quantum dots. As a result of PL measurement using UV excitation light at 365 nm, the PL intensity was found to greatly increase when MPA was added at 15 ml, compared to the case with no MPA; the PL peaks shifted from 603 nm to 598 nm. A UV sensor was fabricated by using a sputtering process to form a Pt pattern and placing a QD on the Pt pattern. To verify the characteristics of the sensor, we measured the electrical properties via irradiation with UV, Red, Green, and Blue light. As a result, there were no reactions for the R, G, and B light, but an energy of 3.39 eV was produced with UV light irradiation. For the sensor using ZnS: Mn/ZnS quantum dots, the maximum current (A) value decreased from $4.00{\times}10^{-11}$ A to $2.62{\times}10^{-12}$ A with increasing of the MPA content. As the MPA content increases, the PL intensity improves but the electrical current value dropped because of the electron confinement effect of the core-shell.

• 조명전기설비학회논문지
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• 제14권4호
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• pp.23-30
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• 2000

열병합발전 시스템은 환경 친화적인 동시에 상대적으로 고 효율의 에너지 시스템으로서 분산 방전설비의 혁신 기술중 하나이다, 아울러 열병합발전 시스템운 열과 전기의 분산공급에 적절한 발전 시스템이다. 그러나, 열병합발전 시스템의 계통 연계는 전압 소정, 전압변동, 보호협조, 안전등의 제반 연제문제를 수반한다. 특히, 이러한 연계문제 중 열병합발전 시스템의 배전계통 연계.분리 운전은 배전계통의 전압조정 및 변동에 영향을 미칠 것이 예상된다. 최근 수용가 소유의 컴퓨터 및 민감한 전자소자의 사용 증가로 인하여 전력품질온 중요한 고려사항이 되고 있다. 따라서 열병합발전 시스템과 관련한 전압품질은 반드시 분석되어야만 한다. 왜냐하면 전압품질은 전력 품질의 중요한 요소이기 때문이다. 본 논문에서는 열병합발전 시스템의 배전계통 연계 운전에 따른 순서전압변통 에 대하여 컴퓨터 시물레이션을 롱하여 분석하였고、 또한 이의 억제 대책을 제시하였다. 아울러 순시전압변동 측면에서 본 피더 당 열병합발전시스템의 단위 도입 용량을 평가하였다. 본 논문의 결과는 열병합발전 시스템 또는 분산형 전원의 계통 연계 표준. 가이드라인에 유용한 자료가 되리라 믿는다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.131-131
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• 2008

Silicon carbide (SiC) has attracted significant attention for high frequency, high temperature and high power devices due to its superior properties such as the large band gap, high breakdown electric field, high saturation velocity and high thermal conductivity. We performed Al ion implantation processes on n-type 4H-SiC substrate using a SILVACO ATHENA numerical simulator. The ion implantation model used a Monte-Carlo method. We studied the effect of channeling by Al implantation simulation in both 0 off-axis and 8 off-axis n-type 4H-SiC substrate. We have investigated the Al distribution in 4H-SiC through the variation of the implantation energies and the corresponding ratio of the doses. The implantation energies controlled 40, 60, 80, 100 and 120 keV and the implantation doses varied from $2\times10^{14}$ to $1\times10^{15}cm^{-2}$. In the simulation results, the Al ion distribution was deeper as increasing implantation energy and the doping level increased as increasing implantation doses. After the post-implantation annealing, the electrical properties of Al-implanted p-n junction diode were investigated by SILV ACO ATLAS numerical simulator.

• 한국통신학회논문지
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• 제34권7B호
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• pp.677-685
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• 2009

무선 센서네트워크에서 에너지 절약을 위해 필요한 송선전력을 제어하는 기법들이 많이 연구 되었다. 그러나 기존 연구들은 송신전력제어 과정에서 최적화된 송신전력 단계를 계산하기 위해 많은 패킷이 필요하다. 본 논문에서는 추가척인 제어 패킷을 발생시키지 않고 최단경로를 고려하는 송신전력제어 기법을 제안한다. 그 기법은 네트워크 구성에 필요한 광고 메시지를 최대한 활용하여 제어 패킷을 사용하지 않으며 네트워크 구성 초기에 최대 송선전력 단계로 광고 메시지를 전달하여 구성된 최단경로를 기준으로 한다. 제안한 기법의 평가를 위해 TinyOS 에서 제안한 기법을 적용하였다. 그리고 21개의 노드를 이용하여 네트워크를 구성하고 형균 전류 소요량, 평균 네트워크 깊이 등을 측정하였다. 측정한 결과 제안한 기법을 척용한 네트워크가 이전보다 송신 시 명균 전류량이 약 24.7% 만큼 적으며 네트워크의 흡 수가 일반 네트워크 홉 수보다 약 41% 적였다.

• Steel and Composite Structures
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• 제24권4호
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• pp.399-408
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• 2017

Of high strength bolts, the torque shear type bolt is known to be clamped normally when pin-tails are broken. Sometimes the clamping loads on slip critical connections considerably fluctuate from the required tension due to variation of torque coefficient. This is why the viscosity of lubricant affects the torque coefficient by temperature. In this study, the clamping tests of high strength bolts were performed independently at laboratory conditions and at outdoor environment. The temperatures of outdoor environment candidates were ranged from $-11^{\circ}C$ to $34^{\circ}C$ for six years. The temperature at laboratory condition was composed from $-10^{\circ}C$ to $50^{\circ}C$ at each $10^{\circ}C$ interval. At outdoor environment conditions, the clamping load of high strength bolt was varied from 159 to 210 kN and the torque value was varied from 405 to 556 Nm. The torque coefficients at outdoor environment were calculated from 0.126 to 0.158 when tensions were measured from 179 to 192 kN by using tension meter. The torque coefficients at outdoor environment conditions were analyzed as the range from 0.118 to 0.152. From these tests, the diverse equations of torque coefficient, tension dependent to temperature can be acquired by statistic regressive analysis. The variable of torque coefficient at laboratory conditions is 0.13% per each $1^{\circ}C$ when it reaches 2.73% per each $1^{\circ}C$ at outdoor environment conditions. When the results at laboratory conditions and at outdoor environment were combined to get the revised equations, the change in torque coefficient was modified as 0.2% per each $1^{\circ}C$ and the increment of tension was adjusted as 1.89 % per each $1^{\circ}C$.

• ETRI Journal
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• 제21권1호
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• pp.1-27
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• 1999

We present a new description of envelope-function equation of the superlattice (SL). The SL wave function and corresponding effective-mass equation are formulated in terms of a linear combination of Bloch states of the constituent material with smaller band gap. In this envelope-function formalism, we review the fundamental concept on the motion of a wave packet in the SL structure subjected to steady and uniform electric fields F. The review confirms that the average of SL crystal momentums K = ($k_x,k_y,q$), where ($K_x,k_y$) are bulk inplane wave vectors and q SL wave vector, included in a wave packet satisfies the equation of motion = $_0+Ft/h$; and that the velocity and acceleration theorems provide the same type of group velocity and definition of the effective mass tensor, respectively, as in the Bulk. Finally, Schlosser and Marcus's method for the band theory of metals has been by Altarelli to include the interface-matching condition in the variational calculation for the SL structure in the multi-band envelope-function approximation. We re-examine this procedure more thoroughly and present variational equations in both general and reduced forms for SLs, which agrees in form with the proposed envelope-function formalism. As an illustration of the application of the present work and also for a brief investigation of effects of band-parameter difference on the subband energy structure, we calculate by the proposed variational method energies of non-strained $GaAs/Al_{0.32}Ga_{0.68}As$ and strained $In_{0.63}Ga_{0.37}As/In_{0.73}Ga_{0.27}As_{0.58}P_{0.42}SLs$ with well/barrier widths of $60{\AA}/500{\AA}$ and 30${\AA}/30{\AA}$, respectively.

• 전기전자학회논문지
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• 제15권4호
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• pp.324-329
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• 2011

휴대 기기가 고기능화, 다기능화 됨에 따라 다양한 멀티미디어 기능이 요구되면서 배터리를 보다 장시간 이용하면서 더 높은 전력과 에너지가 요구되고 있다. 이에 따라 여러 개의 리튬이온 cell을 연결한 배터리팩이 많이 사용되고 있다. 2개 이상의 cell로 구성된 리튬이온 배터리를 안전하게 사용하기 위해서는 과전압 및 과전류, 고온으로 부터 보호해야 됨은 물론, 수명을 연장하기 위해서 각 cell의 전압을 같게 유지시켜주는 balancing 기능이 반드시 요구된다. 본 논문에서 제안한 IC는 모바일 기기뿐만 아니라 E-bike, 하이브리드 자동차, 전기 자동차 분야에도 적용 가능할 것으로 예상되며, 국내 PMIC 발전에 기여할 것으로 기대된다.

• 대한화학회지
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• 제23권1호
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• pp.37-41
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• 1979

Benzyl m-nitrobenzenesulfonate와 N,N-dimethylaniline類와의 反應速度를 아세톤 溶媒에서 電氣傳導度法으로 測定하였다. N,N-디메틸아닐린의 反應性에 關한 置換基效果와 直線 自由에너지 關係를 考察하였다. 反應速度常數 k는 2.55∼487 $10^{-4}l{\cdot}mol^{-l}{\cdot}sec^{-1} (35^{\circ}C)$였으며 置換基가 電子를 주는 能力이 클수록 反應은 빨랐다. Hammett 도시에서 置換基常數 ${\sigma}$와 ${\sigma}p$-MeO = -0.35의 새로운 값을 使用했을때 ${\rho}$ = -1.37의 좋은 直線이 얻어졌다. 本反應의 경우 r값은 브롬화벤질에 比해 큰 값을 가졌다. Bronsted 圖示에서 溶媒效果에 基因된 p-MeO基를 除外하고는 좋은 直線이 얻어졌으며 C${\cdot}{\cdot}{\cdot}$O 結合의 쪼개짐이 結合 形成보다 優先的인 $S_N2$ 轉移狀態를 갖는다고 推定된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.262-270
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• 2004

Basic experiments were carried out using the THT-IV low-power Hall thruster to examine the influences of magnetic field shape and strength, and acceleration channel length on thruster performance and to establish guidelines for design of high-performance Hall thrusters. Thrusts were measured with varying magnetic field and channel structure. Exhaust plasma diagnostic measurement was also made to evaluate plume divergent angles and voltage utilization efficiencies. Ion current spatial profiles were measured with a Faraday cup, and ion energy distribution functions were estimated from data with a retarding potential analyzer. The thruster was stably operated with a highest performance under an optimum acceleration channel length of 20 mm and an optimum magnetic field with a maximum strength of about 150 Gauss near the channel exit and with some shape considering ion acceleration directions. Accordingly, an optimum magnetic field and channel structure is considered to exist under an operational condition, related to inner physical phenomena of plasma production, ion acceleration and exhaust plasma feature. A new Hall thruster was designed with basic research data of the THT-IV thruster. With the thruster with many considerations, long stable operations were achieved. In all experiments at 200-400 V with 1.5-3 mg/s, the thrust and the specific impulse ranged from 15 to 70 mN and from 1100 to 2300 see, respectively, in a low electric power range of 300~1300 W. The thrust efficiency reached 55 %. Hence, a large map of the thruster performance was successfully made. The thermal characteristics were also examined with data of both measured and calculated temperatures in the thruster body. Thermally safe conditions were achieved with all input powers.

• 설비공학논문집
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• 제27권10호
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• pp.544-551
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• 2015

This study was conducted to determine the LCC of apartment complexes with district heating and a cogeneration system. For the purpose of analyzing LCC according to the size of the apartment complex, 500, 1,500, and 4,000-unit model apartments were selected. Analysis was performed on the design of the heating system and the life cycle cost including total construction cost, maintenance and operation cost for the duration of the project period (15 years). According to the calculated results, 1) The initial cost of the cogeneration system for 500, 1,500, and 4,000-unit apartments is higher than that of the district heating system by 20%, 13%, and 12%, respectively. 2) In the case of the cogeneration system, the payback period by electric generation was found to be 5.21, 4.92 and 4.47 years, and saving cost was calculated to be 29 billion won, 94 billion won and 262 billion won after the payback period for 500, 1,500, and 4,000-unit apartments, respectively. 3) The LCC values of the cogeneration system were 1.12, 1.07 and 1.06 times larger than those of the district system according to the size of the apartment complex. In this study, the district heating system was found to be more efficient than the cogeneration system in terms of LCC reduction. 4) District heating is affected by fuel bills, so energy efficiency should be improved through recovering waste heat (incineration heat, etc.). Also, district cooling should be provided according to heat use to keep the temperature high in winter and low in summer.