• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.7
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• pp.1095-1099
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• 2002

We experimentally investigate the evolution of nanosecond Stokes pulses in a single-pass Raman laser pumped by a Q-switched Nd:YAG laser at 1064 na As a Raman medium, a GeO2-doped graded-index multimode fiber ot 220 m long Is used. We demonstrate that efficient generation of several Stokes components with 1.5∼2.7 nanosecond pulsewidth is obtained by varying the input pump energy.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.164-165
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• 2001

An IGBT driver for serially connected pulse switching IGBTS was contructed and tested. The IGBT driver has ten output pulses with 1 ${\mu}ysec$ pulse width Its pulse repetition-rate can adjusted from 0 to 20 kHz. The output pulses was insulated from 10 kV high voltage by a pulse transformer. Their voltage amplitude are 18 V, voltage rising time 250 nsec., and voltage falling time 200 nsec when IGBT gates with 12 nF input capacitance are connected.

• Journal of the Korean Society of Safety
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• v.14 no.4
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• pp.100-107
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• 1999

The purpose of the study is to investigate the effect of H$_2$ pressure on partial discharge (PD) activity and aging rate in turbine generator winding insulations. A series of field tests and laboratory tests were peformed to investigate the effect of $H_2$ pressure on PD activity. Field tests were conducted at two unit turbine generators in two conditions, in $H_2$ pressure and in air atmosphere. Obtained results are as follows ; 1) ${\Delta}tan{\delta}$ and maximum partial discharge are reduced with increase of $H_2$ pressure and partial discharge inception voltage. 2) The reduction ratio of ${\Delta}tan{\delta}$ due to $H_2$ pressure is higher than one of PD magnitude. 3) Partial discharge pulses suffer from attenuation and distortion when transmitted along windings, because of the complex L-C network between windings. From the result, partial discharge pulses are subjected to resonance phenomena in a generator winding.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.4
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• pp.45-49
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• 2007

When drilling using electrical-discharge machining (EDM), severe electrode wear makes in-process measurements of the depth of the drilled hole and the volume of material removed impossible. To estimate the volume of material removed a reliable real-time discharge pulse counting method is proposed by assuming that the volume removed in EDM is proportional to the number of discharge pulses from an iso-energy pulse generator. The geometry of machined holes, including depths and cross-sectional profiles, is estimated using geometric analysis. A proportional relationship between the volume of material removed and the number of discharge pulses was developed and verified by experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.204-209
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• 2002

A PDP(Plasma Display Panel) module consists of a discharge panel, a SMPS(Switched Mode Power Supply) for power supply, driving boards for panel control, and a logic board. Driving boards supply high voltage pulses to induce glow discharge in the PDP panel. The electrical pulses excite the circuit elements and subsequently generate acoustic noises. The main sources of the noise in the circuit are the transformer of SMPS and the power MOSFET(Metal Oxide Semiconductor Field Effect Transistor) of driving boards, and the heat sinks often amplify the noise level. The reduction of the acoustic noises was achieved by modifying both the structural and circuit elements. The structural method was executed by the improvement of heat sinks. The optimization of SMPS and condensers was carried out for the circuit elements.

• International Journal of Industrial Entomology and Biomaterials
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• v.4 no.1
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• pp.69-76
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• 2002

Mustard aphid, Lipaphis erysimi(Kalt.) plays a key role in determining the productivity of rapeseed-mustard. This pest alone attributes 30-70% losses in yield potential in different agro climatic zones with a mean loss of 54.2% in India. Considering the extent of damage caused by the pest, the present experiment was conducted at Pulses and Oilseeds Research Station during 1992-93 to 1994-95 to study the migratory nature of mustard aphid by trapping them in yellow colour pan tray and their simultaneous growth and development on three different genotypes. The temperature during noon hours is the predominant factor to govern the appearance of alate mustard aphid in rapeseed-mustard field. Stepwise regression analysis revealed that temperature and relative humidity played an important role for its development. The variety RW white flower glossy stem harboured minimum number of aphid in comparison to other two varieties B 9 and T6342. The population reached a peak of 61.28 aphids/10 cm central twig during $6^{th}$ standard week irrespective of varieties.

• Journal of Institute of Convergence Technology
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• v.2 no.2
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• pp.25-29
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• 2012

Micro machining technologies have been required to satisfy various conditions in a high-technology industry. Micro electrochemical process is one of the most precision machining methods. Micro electrochemical process has been divided into electrochemical etching through protective layer and electrochemical machining using ultrashort voltage pulses. Micro shaft can be fabricated by electrochemical etching. The various protective layers such as photo-resist, oxide layer and oxidized recast layer have been used to protect metal surface during electrochemical etching. Micro patterning on metal surface can be machined by electrochemical etching through protective layer. Micro hole, groove and structures can be easily machined by electrochemical machining using ultrashort voltage pulses. Recently, the groove with subnanometer was machined using AFM.

• The Korean Journal of Pharmacology
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• v.4 no.1 s.5
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• pp.37-39
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• 1968

A method for presenting the heart rate of intact animals as a kymographic record is described. A transistorized impulse generator with a dry battery power supply is used to produce pulses. The pulses are integrated and make a pen motor drived. The ability of the instrument to follow a wide range of heart rate change is demonstrated. The instrument is especially usefull to observe an acute and transitory heart rate change. A method for changing the heart beat to sound and a method for counting the heart rate of intact animal and isolated preparations by employing post office counter were also described.

• Proceedings of the KOSOMBE Conference
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• v.1992 no.05
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• pp.92-97
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• 1992

The pulsatile nature of blood flow makes artefacts in 2D Fourier transform image. Spatial presaturation is known to be effective in eliminating flow artefacts when the spin echo acquisition is employed. However. this method requires additional RF pulse and spoiling gradient for presaturation. In this paper a new flow saturation technique which does not require additional saturation-RF and gradient is proposed. The proposed technique is equivalent to the existing saturation technique but the elimination of the flow component is achieved by a pair of tailored $90^{\circ}-180^{\circ}$ RF pulses in tile spin echo sequence. By use of two tailored RF pulses with opposite phase polarity, a linear phase gradient is generated for those moving materials and consequently all the spins of moving materials become dephased thereby no signal is observable. Computer simulations and experimental results obtained using both a phantom and a human volunteer with a 2.0 T whole body system are also presented.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.471-474
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• 1997

Several selective excitation pulses are used in MRI. Because of the nonlinearity of the Block equation, the pulse problem is nonlinear generally. Recently, Shinnar & Le Roux have proposed a direct solution of this problem. In this paper, we introduce the SLR algorithm and design pulses using SLR algorithm. This SLR pulse produces a specified slice profile. For example, we demonstrate the sinc function pulse with piece wise constant duration ${\Delta}t$. Further, we will design $\pi/2$ pulse and slice profile.