• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1993-2001
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• 2006

The piezoelectric bimorph film, which, as an actuator, can generate more effective displacement than the usual PVDF film, is used to control the turbulent boundary-layer flow. The change of wall pressures inside the turbulent boundary layer is observed by using the multi-channel microphone array flush-mounted on the surface when actuation at the non-dimensional frequency $f_b^+$:=0.008 and 0.028 is applied to the turbulent boundary layer. The wall pressure characteristics by the actuation to produce local displacement are more dominantly influenced by the size of the actuator module than the actuation frequency. The movement of large-scale turbulent structures to the upper layer is found to be the main mechanism of the reduction in the wall- pressure energy spectrum when the 700$700{\nu}/u_{\tau}$-long bimorph film is periodically actuated at the non- dimensional frequency $f_b^+$:=0.008 and 0.028. The biomorph actuator is triggered with the time delay for the active forcing at a single frequency when a 1/8' pressure-type, pin-holed microphone sensor detects the large-amplitude pressure event by the turbulent spot. The wall-pressure energy in the late-transitional boundary layer is partially reduced near the convection wavenumber by the open-loop control based on the large amplitude event.

• Transactions of Materials Processing
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• v.4 no.4
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• pp.398-409
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• 1995

The wear properties of the alumina short fiber reinforced tin-bronze matrix composites manufactured by hot pressing was studied at the room temperature and $350^{\circ}C.$ The wear loss of various specimens having different constituent and different density was examined by a pin-on-disc type wear testing machine. The results were discussed by the observation of the worn surface morphology and the analysis of the composition on the worn surfaces. Since the reinforced effect of the alumina fiber on the wear resistance was dependent on the strength of alloy matrix, the pressureless sintered composites having a lower matrix strength showed a marked increase in wear resistance by the fiber reinforcement. As the wear condition became severe, the fiber reinforcement was more effective. The delamination on the wear surface was observed in the pressureless sintered specimens having pores which are related to the initiation and the propagation of cracks. However, the wear mechanism acting on a big failure area was not found on the wear surfaces of the hot pressed specimens having a few pores.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.971-973
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• 1993

Deflection Yoke(the following, DY) is the important electric device of CRT which deflects R, G, B beans influencing magnetic field produced by yoke coils. Recently, DY is designed to the saddle/saddle type of coils, being proposed for high-definite and high-efficient CRT. This paper presents the optimization of pin-sectioned saddle coil's shape for minimizing gap between desired and practical deflections of electron beams by using Genetic Algorithm. Evolution Startegy is utilized in this paper, since evolution strategy is a kind of genetic algorithms finding the optimized values by choicing the better generation with comparing the parents and their children. Here, the children are generated by only mutations from the normal random variables. Evolution strategy has shown better powerful converge rate than the other genetic algorithms becuase of using only the mutation-operator.

• Tribology and Lubricants
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• v.34 no.6
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• pp.313-317
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• 2018

Carbon-based coatings, including carbon nanotubes (CNTs), graphene, and buckyball ($C_{60}$), receive much interest because of their outstanding mechanical and electrical properties for a wide range of electromechanical component-based applications. Previous experimental results demonstrate that these carbon-based coatings are promising solid lubricants because of their superior tribological properties, and thus help prolong the lifetime of silicon-based applications. In this study, CNT coatings are deposited on a bare silicon (100) substrate by electrodynamic spraying under different deposition conditions. During the coating deposition, the applied voltage, CNT concentration of the solution, distance between the injecting nozzle and the substrate and diameter of the injecting nozzle are optimized to control the thickness and surface roughness of the CNT coatings. The surface morphology and thickness of the coatings are characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. The friction and wear properties of the coatings are investigated by using a pin-on-reciprocating-type tribotester under various experimental conditions. The friction coefficient of the CNT coating is as low as 0.15 under high normal loads. The overall results reveal that CNT coatings deposited by electrodynamic spraying provide relatively uniform with superior lubrication performance.

• Korean Journal of Optics and Photonics
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• v.24 no.1
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• pp.1-8
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• 2013

In this paper, we report design, fabrication and characterization of the WBRM (Wide Band Receiver Module) for LADAR (LAser Detection And Ranging) application. The WBRM has been designed and fabricated using self-made APD (Avalanche Photodiode) and TIA (Trans-impedance Amplifier). The APD and TIA chips have been integrated on 12-pin TO8 header using self-made ceramic submount and circuit. The WBRM module showed 450 ps of rise time, and corresponding 780 MHz bandwidth. Furthermore, it showed very low output noise less than 0.8 mV, and higher SNR than 15 for 150 nW of MDS(Minimum Detectable Signal). To the author's knowledge, this is the best performance of an optical receiver module for LIDAR fabricated by 200 um InGaAs APD.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.5
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• pp.559-575
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• 2014

In this paper, we propose a horizontal/vertical calibration kit for calibrating a vector network analyzer(VNA) to measure the vertical connector pin. If the conventional calibration kit is used, we should change the arm for a probe or need an assistant device and it takes a long time. In addition there is a risk of precision degradation caused by the position change of the probe tip sensitive to the surroundings. We suggest a 4-port vertical calibration kit to make up for the aforementioned shortcomings. The calibration kit was manufactured for the SOLT calibration method. 'Short', 'Open', and 'Load' are available in the horizontal plane, 'Thru' is available not only in the horizontal plane on the two planes of a PCB, but in the vertical plane between the two planes according to the positions of the probes. We complemented the conventional calibration kit to make a vertical calibration kit to be used for the vertical measurement method. We compared and analysed their reflection/transfer characteristics of the SOLT calibration standards of the proposed calibration kit and conventional one, we get a ${\pm}0.1$ dB differences of transfer characteristics in the range from 300 kHz to 8.5 GHz. In order to demonstrate usefulness, and we performed a case study for horizontal and vertical cases, and compared the results of the proposed calibration kit and conventional one.

• Korean Journal of Environment and Ecology
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• v.19 no.3
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• pp.312-326
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• 2005

The purpose of this study is to provide data for conservation and ecological management of Pinus densiflora forest by analyzing ecological characteristics and the change of Pin us densiflora community structure for fifteen years in Namsan(Mt.). The actual vegetation of Pinus densiflora forest was divided into total six types and fifteen detail types. According to the results of TWINSPAN analysis of Pinus densiflora forest, there were fourty-four plots(unit: 400 m') and it was classified into five community types. The dominant species were Pinus densiflora in canopy layer, Styrax japonica in the understory layer and Stephanandra incisa with Rhododendron mucronujatum in the shrub layer. The index of shannon's diversity was from 1.5980 to 1.1485 per $400m^2$and the range of species number was from seventeen to twenty-two. As a result of the change of Pin us densinora forest structure, the importance percentage(1.p.) of Pinus densi. nora$(I.P.:\;77.9\%\rightarrow50.6\%) was decreased, Styraxjaponica$(I.P.:\;5.3\%\rightarrow22.6\%), Prunus sargen $(I.P.:\;1.5\%\rightarrow9.2\%) and Stephanandra incisa$(I.P.:\;3.5\%\rightarrow7.7\%) were increased for fifteen years. Based on standard of $2,000m^2$unit area, shannon's diversity changed 1.1719 into 0.8829 and species number changed thirty-four into twenty-one.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.9 s.112
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• pp.900-912
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• 2006

A GPS receiving antenna installed in the missile's warhead is designed and fabricated at a center frequency 1.575 GHz. The circular shaped antenna is installed in the middle of the warhead where the antenna's patch and the ground plane are connected with a hollow cylindrical shaped short pin. Using the dual feeding and phase difference method, an omni-directional radiation pattern which direction is normal to the missile's axis(H-plane) is obtained. The optimized diameters of the circular patch and the cylindrical ring typed shorting pin of the GPS receiving antenna which use the FR4.material(dielectric constant $\varepsilon_r=4.6$) are 59.5 mm and 14 mm, respectively. The cylindrical body with diameter 100 mm and height 500 mm is attached to the lower part of the warhead in order to complete the missile figure. The radiation patterns are measured by changing the angle and phase between the dual feeding points. When the phase difference of dual feeding is $100^{\circ}$ and the angle between the dual feeding points is $100^{\circ}$, the nearly omni-directional radiation pattern in the H-plane is obtained. In this case, the antenna gain is -5.55 dBd and the relative level difference between the maximum and the minimum radiation intensity is 3.98 dB.

• Korean Journal of Plant Tissue Culture
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• v.22 no.6
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• pp.329-334
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• 1995

Transformation system of rolC gene, dwarf gene in Lycium chinenese Mill. established by using system. Pin-punctured leaves induced numerous adventious buds in abaxial side when cultured on 3/2 MS medium containing 2.0 mg/L zeatin. Survival rate and shoot regeneration frequency of leaf explants decreased as kanamycin sulfate level increased. Shoot buds were not regenerated on 3/2 MS medium containing 10 mg/L kanamycin sulfate and 2.0 mg/L zeaein. Of the level tested, 10 mg/L of kanamycin sulfate was optimum in selection of kanamycin sulfate resistant plant. Co-culture time of bacteria and leaf explants was affected at the frequency of shoot regeneration and survival of leaf explants. Leaf explants co-cultivated during above 48hr severely decreased survival rate and shooting rate. Best result on survival rate and shooting rate were obtained when exposed for 24 h. 80 explants of 105 leaf explants survived on 3/2 MS medium containing 2.0 mg/L zeatin and 10 mg/L kanamycin sulfate, and 15 shoots was regenerated on the same medium. To select kanamycin sulfate resistant plant, regenerate as cultured on 3/2 MS medium containing 10 mg/L kanamycin sulfate, and obtained 5 kanamycin resistant plants. Southern blot analysis conformed that the rolC gene was incorporated into the genomic DNA of kanamycin resistant plants.

• Applied Science and Convergence Technology
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• v.26 no.5
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• pp.118-128
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• 2017

The scope of this work is to determine and compare the effect of electron temperature ($T_e$) and number density ($N_e$) on the yield rate and concentration of reactive chemical species ($^{\bullet}OH$, $H_2O_2$ and $O_3$) in an argon, air and oxygen injected negative DC (0-4 kV) capillary discharge with water flow(0.1 L/min). The discharge was created between tungsten pin-to pin electrodes (${\Phi}=0.5mm$) separated by a variable distance (1-2 mm) in a quartz capillary tube (2 mm inner diameter, 4 mm outer diameter), with various gas injection rates (100-800 sccm). Optical emission spectroscopy (OES) of the hydrogen Balmer lines was carried out to investigate the line shapes and intensities as functions of the discharge parameters such as the type of gas, gas injection rate and inter electrode gap distances. The intensity ratio method was used to calculate $T_e$ and Stark broadening of Balmer ${\beta}$ lines was adopted to determine $N_e$. The effects of $T_e$ and $N_e$ on the reactive chemical species formation were evaluated and presented. The enhancement in yield rate of reactive chemical species was revealed at the higher electron temperature, higher gas injection rates, higher discharge power and larger inter-electrode gap. The discharge with oxygen injection was the most effective one for increasing the reactive chemical species concentration. The formation of reactive chemical species was shown more directly related to $T_e$ than $N_e$ in a flowing water gas injected negative DC capillary discharge.