• Title/Summary/Keyword: Gap Controlling

Search Result 141, Processing Time 0.036 seconds

Characterization of Band Gaps of Silicon Quantum Dots Synthesized by Etching Silicon Nanopowder with Aqueous Hydrofluoric Acid and Nitric Acid

  • Le, Thu-Huong;Jeong, Hyun-Dam
    • Bulletin of the Korean Chemical Society
    • /
    • v.35 no.5
    • /
    • pp.1523-1528
    • /
    • 2014
  • Silicon quantum dots (Si QDs) were synthesized by etching silicon nanopowder with aqueous hydrofluoric acid (HF) and nitric acid ($HNO_3$). Then, the hydride-terminated Si QDs (H-Si QDs) were functionalized by 1- octadecene (ODE). By only controlling the etching time, the maximum luminescence peak of octadecylterminated Si QDs (ODE-Si QDs) was tuned from 404 nm to 507 nm. The average optical gap was increased from 2.60 eV (ODE-Si QDs-5 min) for 5 min of etching to 3.20 eV (ODE-Si QDs-15 min) for 15 min of etching, and to 3.40 eV (ODE-Si QDs-30 min) for 30 min of etching. The electron affinities (EA), ionization potentials (IP), and quasi-particle gap (${\varepsilon}^{qp}_{gap}$) of the Si QDs were determined by cyclic voltammetry (CV). The quasi-particle gaps obtained from the CV were in good agreement with the average optical gap values from UV-vis absorption. In the case of the ODE-Si QDs-30 min sample, the difference between the quasi-particle gap and the average optical gap gives the electron-hole Coulombic interaction energy. The additional electronic levels of the ODE-Si QDs-30 min and ODE-Si QDs-15 min samples determined by the CV results are interpreted to have originated from the Si=O bond terminating Si QD.

Controlling of detonation strength through inserted gaps in multi-material shock physics simulation (화약내 Gap을 통한 폭발력 제어 가능성에 대한 수치해석적 연구)

  • Lee, Jinwook;Yoh, Jai-ick
    • 한국연소학회:학술대회논문집
    • /
    • 2012.04a
    • /
    • pp.275-278
    • /
    • 2012
  • We investigate the interaction between the propagation of detonation and inserted gaps in the high explosive. The Eulerian-based multi-material simulation code validated through comparison with experimental results was used. A series of gap materials is used to understand the detonation propagation characteristic in the presence of multiple gaps.

  • PDF

A Study on the Back Bead control by Using Short Circuit Frequency in GMA Welding of Sheet Metal (박판 GMA 용접에서 단락 주파수를 이용한 이면비드의 제어에 관한 연구)

  • 안재현;김재웅
    • Journal of Welding and Joining
    • /
    • v.13 no.4
    • /
    • pp.75-84
    • /
    • 1995
  • In GMA welding of sheet metal, the short circuit metal transfer mdoe is preferred because of its low heat input and capability of bridging the root gap. The molten electrode is transferred to the workpiece during repectitive short circuit in the model. The waveform of welding current or voltage and the frequency of short circuiting are affected by a number of factors including: magnitude of welding current and voltage, root gap, electrode extension, power supply characteristics, and so on. In this study experimental models were proposed, which are able to determine the relationship between the root gap and short circuit frequency and the relationship between the root gap and appropriate welding speed that produces the good quality of back bead without burn through. Using the experimental models, the root gap can be obtained from measuring the short circuit frequency, and then the appropriate weldig speed to the root gap can be determined. Thus a back bead control system was constructed by controlling the welding speed for maintaining the quality of back bead. The developed system has shown the successful capability of back bead control.

  • PDF

Fabrication of Electrostatically Actuated Nano Tweezers Using FIB(Focused Ion Beam) (집속이온빔 장치를 이용한 정전기 구동 나노트위저의 제작)

  • Chang Ji-Young;Kim Jong-Baeg;Min B.K.;Lee S.J.
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2006.05a
    • /
    • pp.495-496
    • /
    • 2006
  • Electrostatically actuated nanoscale tweezers are fabricated on micro processed electrodes using FIB-CVD. Heavily doped electrode works as interconnection platform for controlling nanoscale devices. Short bent pillars are deposited to control the gap distance of main tweezers fabricated on bent ones. Two types of tweezers which have different gap distances are fabricated and tweezing motion was successfully demonstrated. The threshold voltages at snap-down of the pillars are dependent on the initial gap distance of the unactuated pillars, and the measured values were 93V for 3.6um and 30V for 2.2um. The dimension of nano tweezers and initial gap distances are controllable as demonstrated and we expect more complicated 3-dimensional shapes are also possible.

  • PDF

Air Gap Change of a Maglev Vehicle at the Moment a Linear Induction Motor Runs (자기부상열차 고가 선로 구조특성에 따른 부상공극 응답)

  • Shin, Hyeon-Jae;Han, Hyung-Suk;Lee, Jong-Min;Rho, Kyu-Sok
    • Proceedings of the KSR Conference
    • /
    • 2009.05a
    • /
    • pp.1213-1217
    • /
    • 2009
  • The air gap between electromagnet and guiderail in an EMS-type Maglev vehicle must be maintained within an allowable deviation by controlling the voltage on the magnet. In this type of vehicle, the air gap response is strongly dependent on the structural characteristics of the elevated guideway, such as stiffness, damping and mass. For this reason, the dynamic interaction between the vehicle with electromagnets and the elevated guideway must be understood to ensure safe running. The response of the air gap to guideway characteristics such as mass, stiffness, and damping are analyzed through vehicle tests over different guideways. Through such tests, the design requirements for Maglev vehicles and elevated guideways can be established, improving levitation stability.

  • PDF

A Study on Development of an Electromagnetic Inductive Sensor for Automatic Weld Seam Tracking (용접선 자동추적용 전자기유도센서의 개발에 관한 연구)

  • Bae Kang-Yul
    • Journal of Welding and Joining
    • /
    • v.23 no.4
    • /
    • pp.66-72
    • /
    • 2005
  • An electromagnetic inductive sensor consisted of one exciter and three separated (triple) detectors has been developed for both tracking the weld seam of a workpiece and controlling the sensor-to-workpiece distance (height) simultaneously. The left and right detectors are used to track the seam, while the fore and the other two detectors allow the sensor to determine the height and the gap width by being coupled their outputs together. A series of experiments with the proposed sensor located above a mild steel plate containing a weld seam of gap are carried out to examine the feasibility of the sensor. The results revealed that the proposed sensor could fairly well track the desired seam and also well control the height to be constant even when the gap width of the seam varied. The gap width can be also determined during the seam tracking by using the sensor outputs. As a consequence, these can provide the developed sensor with substantial improvement for industrial uses with respect to the previous electromagnetic sensors being used for the weld seam tracking.

Design of Direct-Shear Mode MR Damper (전단 모드형 자성유체댐퍼의 설계)

  • Kim, Hae-Lan;Lee, Young-Shin;Lee, Eun-Yup;Lee, Gyu-Seop;Oh, Boo-Jin
    • Proceedings of the KSME Conference
    • /
    • 2007.05a
    • /
    • pp.626-631
    • /
    • 2007
  • MR(Magneto-rheological) fluid is smart material that can be changed viscosity by controlling the magnetic field. MR damper with MR fluid can control damping force. It can be used extensively many engineering structures for reducing the effect of dynamic external disturbances. There are three kinds of MR dampers, such as valve mode, direct-shear mode and squeeze mode. In this study, design process of direct-shear mode MR damper with the MR fluid gap was developed. The parameters that used in the direct-shear mode MR damper Informed from the experiment of valve mode MR damper of Lord company. Magnetic analysis with finite element method was performed to find the optimal annular gap.

  • PDF

Embodiment of Low Operating Voltage in Positive Column AC-PDPs

  • Kim, Hyun;Tae, Heung-Sik;Chien, Sung-Il
    • 한국정보디스플레이학회:학술대회논문집
    • /
    • 2003.07a
    • /
    • pp.95-98
    • /
    • 2003
  • The positive column discharge characteristics in the long gap (440 ${\mu}m$) are investigated based on the voltage distribution among three electrodes. In particular, the effects of the amplitude and width of the short pulse applied to the address electrode on the positive column discharge characteristics are examined intensively. By proper controlling of the amplitude and width of the address short pulse, it is found that the positive column discharge in the long gap is well constructed. As a result, under the stable static voltage margin condition, the firing and sustaining voltages are as low as those of conventional short gap(60 ${\mu}m$) discharge($V _f=220V$, $V_s=150V$) and the color purity is improved. Moreover, the luminous efficiency increases up to 60% in comparison with the conventional case.

  • PDF

Dynamic Analysis of Tip-actuators for Controlling Tip-media Gap in Cantilever Type Optical Data Storage (캔틸레버형 광 정보저장에서의 빠른 팁/매체 간극제어를 위한 팁/구동기의 동역학적 분석)

  • 이성규;송기봉;김준호;김은경;박강호;남효진;이선영;김영식
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2003.05a
    • /
    • pp.1004-1008
    • /
    • 2003
  • Near-filed optical storage using cantilever aperture tip is a promising way fer next generation optical data storage. To enhance the speed of reading and writing data, gap between tip and media should be controlled fast and precisely within near field region. In this paper, several PZT actuators are analyzed far constructing dual servo control algorithm: coarse actuators(stact. PZT, bimorph PZI) for media surface inclination and One actuator(film PZT) for media surface roughness. Dynamic analysis of stack PZT, bimorph PZT, and film PZT are performed through the frequency response. Based on the frequency response and mathematical model, fast analog controller is designed.

  • PDF

A Damped Sinusoidal Electromagnetic Pulse Generator using a Charged Line (충전선로를 이용한 Damped Sinusoidal 전자기펄스 발생장치)

  • Ryu, Ji-Heon
    • Journal of the Korea Institute of Military Science and Technology
    • /
    • v.9 no.2 s.25
    • /
    • pp.136-142
    • /
    • 2006
  • A damped sinusoidal electromagnetic pulse generator was designed, fabricated and tested. The pulse generator consisted of an oscillator(a spark gap switch and an initially charged low impedance line) and a high impedance antenna. This generator was capable of producing damped sinusoidal pulses at closure of the spark gap switch. A Marx generator was employed to supply the Pulse generator with high voltage pulses. While the pulse generator was provided with the high voltage pulses of 200kV from the Marx generator, its output power was maximized by controlling the pressure of the gas contained in the spark gap switch. The output power of the damped sinusoidal electromagnetic pulse oscillator was 1.3GW and the amplitude of electric field radiated from the pulse generator was 4kV/m at the range of 25m.