• Proceedings of the KSME Conference
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• 2001.11b
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• pp.118-123
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• 2001

The linear compressor have been widely used for pressure wave generation in the Stirling cryocooler and Stirling type pulse tube cryocooler for tactical purpose. The linear compressor has small and compact structure, and long life due to having non-contact sealing mechanism. and the pressure drop through regenerator was ver important role in the motion of displacer in the expander of the Stirling cryocooler. In this study, the characteristic of the linear compressor and the pressure drop through regenerator in the expander was experimentally investigated. The results show the resonance of the compressor is very important to get maximum performance. and the gas spring force in the compression space of the compressor has effect on the characteristic of reonance. and the results show the pressure drop through regenerator is very small than operating pressure change.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.3
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• pp.276-282
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• 2013

This paper proposes an ultrasonic method for measurement of linear and hysteretic interfacial stiffness of contacting surfaces between two steel plates subjected to nominal compression pressure. Interfacial stiffness was evaluated by the reflection and transmission coefficients obtained from three consecutive reflection waves from solid-solid surface using the shear wave. A nonlinear hysteretic spring model was proposed and used to define the quantitative interfacial stiffness of interface with the reflection and transmission coefficients. Acoustic model for 1-D wave propagation across interfaces is developed to formulate the reflection and transmission waves and to determine the linear and nonlinear hysteretic interfacial stiffness. Two identical plates are put together to form a contacting surface and pressed by bolt-fastening to measure interfacial stiffness at different states of contact pressure. It is found from experiment that the linear and hysteretic interfacial stiffness are successfully determined by the reflection and transmission coefficient at the contact surfaces through ultrasonic pulse-echo measurement.

• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.464-469
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• 2016

All-optical non-return-to-zero (NRZ) -to- return-to-zero (RZ) data-format conversion has been successfully demonstrated using a semiconductor optical amplifier in a fiber-loop mirror (so-called SOA-loop mirror) with a continuous-wave (CW) holding beam. The converted RZ signal after pulse compression has been used to create a 40 Gb/s OTDM (Optical Time Division Multiplexing) signal. Here is proposed an NRZ-to-RZ conversion method without any additional optical clocks, unlike conventional methods based on optical AND logic. In addition, it has the merit of operating at various bit-rate speeds without any controlling device. Moreover, it has a simple structure, and it can be used for all-optical bit-rate-flexible clock recovery.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.229-231
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• 1988

In this paper, we design adaptive DPCM by the two dimensional linear prediction using the covariance method and propose adaptive algorithm which determines analysis frame size by the compassion of the local standard deviation and the global standard deviation of images.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1984.04a
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• pp.9-12
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• 1984

A digital TV CODEC has been implemented. This CODEC uses a pulse code modulation with a resolution of 9 bits per sample and generates digital ouput at the rate of 90.194Mb/s. In this system, we aadopted a horizontal blanking control scheme to meet the contraint of 90.194Mb/s transmission rete, conswequently ontaining data compression of 9.4%, our system's performances have been measured. Its SNR

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.238-239
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• 2001

sub-30fs 펄스폭의 상용 Ti：sapphire 레이저시스템에 대한 펄스압축기 및 2차 조화파 발생기를 제작하여 특성을 평가하였다. 그림la에서 82MHz의 주파수로 모드록되는 상용 Ti：sapphire 레이저 (Spectra-Physics Millennia/Tsunami laser)의 출력이 반사경 Ml, M2를 거쳐 펄스압축기에 입사되고 압축되어 나온 펄스가 다시 M6, M7를 거쳐 2차 조화파발생기로 입사되는 2단구조로 설계되었다. 압축기에 입사되기전 평균파워는 파장 800nm에서 520mW로 측정되었으며, 측정된 스펙트럼 반치폭 47nm에 (그림 2a)에 대해 chirp-free sech$^2$t 펄스로 가정할 경우 본 레이저시스템의 변환한계 펄스폭은 14.5fs로 계산된다. (중략)

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1463-1464
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• 2006

이 논문에서는 코일의 구조가 변압기형태인 나선형 자속압축 발전기, 켄칭매질인 $SiO_2$ 분말과 동선으로 제작한 퓨즈개방스위치, 두 개의 전극으로 간단하게 만든 스파크 갭 스위치 그리고 수저항 모의부하로 이루어진 대전류 고전압 펄스발생 시스템을 제작하고 출력특성을 분석하였다. 실험결과, 축전기로부터 공급한 364J의 초기에너지를 나선형 자속압축발전기로 증폭을 하고 최대 출력전류에서 퓨즈개방스위치가 동작하여 $120{\Omega}$의 수저항에 펄스상승시간이 56ns이고, 펄스폭이 $0.1{\mu}s$인 180kV의 고전압펄스를 인가하였다.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.4
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• pp.482-490
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• 2017

The radar signal processing procedure is divided into the pre-processing such as frequency down converting, down sampling, pulse compression, and etc, and the post-processing such as doppler filtering, extracting target information, detecting, tracking, and etc. The former is generally designed using FPGA because the procedure is relatively simple even though there are large amounts of ADC data to organize very quickly. On the other hand, in general, the latter is parallel processed by multiple DSPs because of complexity, flexibility and real-time processing. This paper presents the radar signal processor design using FPGA which includes not only the pre-processing but also the post-processing such as doppler filtering, bore-sight error, NCI(Non-Coherent Integration), CFAR(Constant False Alarm Rate) and etc.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.5
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• pp.646-654
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• 2020

This paper is to develop an electromagnetic wave-based sensor that can measure the spatial distribution of precipitation, and to a electromagnetic wave rain gauge (hereinafter, "EWRG") capable of simultaneously measuring rainfall, snowfall, and wind field, which are the core of heavy rain observation. Through this study, the LFM transmission and reception signals were theoretically analyzed. In addition, In order to develop a radar transceiver, LFM transceiver design and simulation were conducted. In this paper, we developed a K-BAND pulse-driven 6W SSPA(Solid State Power Amplifiers) transceiver using a small HMIC(Hybrid Microwave Integrated Circuit). It has more than 6W of output power and less than 5dB of receiving NF(Noise Figure) with short duty of 1% in high temperature environment of 65 degrees. The manufactured module emits LFM and Square Pulse waveform with the built-in waveform generator, and the receiver has more than 40dB of gain. The transceiver developed in this paper can be applied to the other small weather radar.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.381-388
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• 2017

The CPR guidelines emphasize the delivery of effective chest compressions but do not address the effects of chest compressions on CPR providers. This study determined the effects of chest compressions on healthy adult firefighters' symptoms, hemodynamics, and electrocardiography after performing multiple cycles of CPR. Healthy adult firefighters were trained in CPR and performed CPR on mannequins. The provider vital signs, electrocardiography, and fatigue scores were determined immediately before CPR, after 5cycles of CPR, and after 10 cycles of CPR. In addition, the presence of clinical symptoms among the providers was determined after CPR; 39 firefighters participated in the study. Their mean age was $35.54{\pm}10.26years$. Many providers developed fatigue, shortness of breath, and dizziness. Significant changes in heart rate (p=0.000), respiratory rate (p=0.010), end-tidal CO2(p=0.000), O2 saturation(p=0.000), and pulse pressure (p=0.000) were observed after both 5 and 10 cycles of CPR. One participant developed sinus dysrhythmia and premature ventricular contractions after 10 cycles of CPR. The delivery of chest compression results in fatigue and hemodynamic alterations in many young healthy adults after performing 5 or 10 cycles of CPR. The CPR guidelines and education should take into consideration the effects of chest compressions on CPR providers.