• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.846-853
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• 2009

This paper presents the design of a high efficiency frequency multiplier with load-pull simulation and analyses the nonlinear distortion of the frequency multiplier. The frequency multiplier shows serious distortion of multiplying signal bandwidth because of nonlinearity when modulated signal is applied, so a digital predistortion with look up table (LUT) is applied to compensate for the distortion of the frequency multiplier. The frequency multiplier is designed to produce 5.8GHz output by doubling the input frequency to be operating at IEEE 802.11a standard wireless LAN. The output spectrum shows 12dB ACPR improvement both at +11MHz, +20MHz offset from center frequency after linearization.

• Journal of the Korean Vacuum Society
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• v.12 no.2
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• pp.79-85
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• 2003

Experimental investigations are performed for the rarefied gas flows in a multi-stage disk-type drag pump. The pump considered in the present study consists of grooved rotors and stators. The flow-meter method is adopted to calculate the pumping speed. Compression ratios and pumping speeds for the nitrogen gas are measured under the outlet pressure range of 0.13∼533 Pa. The present experimental data show the leak-limited value of the compression ratio in the molecular transition region. The rotational speed of the pump is 24,000rpm, and nitrogen is used as a test gas. The pumping characteristics of various drag pumps are performed. The inlet pressures are measured for various outlet pressures of the test pump. The ultimate pressures for zero throughput are measured for three-stage, two-stage and single-stage disk-type, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.93-93
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• 2011

고진공 펌프 국산화의 일환으로 터보분자 펌프와 크라이오 펌프 개발이 진행 중이다. 크라이오 펌프 개발은 기계연구원, 우성진공(주), 국민대학교가 연합해서 수행하고 있다. 올해 9월말에 끝나는 1단계 마지막 3차 년도에는 두 고진공 펌프 모두 시제품을 완성하고 성능을 입증해야 한다. 이를 위해 고진공 펌프 개발과 별도로 진공 펌프 종합특성평가 시스템 개발도 표준과학연구원 주도로 진행되고 있는데 크라이오 펌프 평가 시스템은 원자력연구원이 담당하고 있다. 완성된 크라이오 펌프 성능평가 장치는 상온 기준 5${\times}$10-11 mbar의 기저압력을 보이고 있어서 초고진공 영역에서 크라이오 펌프 운전성능을 평가할 수 있는 준비를 마쳤다. 현재 크라이오 펌프 냉동기는 전반적으로 목표 설계치에 근접한 냉각성능을 나타내고 있는데 예를 들면 2차 냉각단 냉각능력이 10 K, 10 W로 대형 크라이오 펌프를 제작하기에도 충분하다. 활성탄 어레이도 여러 모델들을 자작하여 배기성능을 시험해 보았으므로, 최종적으로 3,600 L/s 급에 적합한 어레이를 만들고 이를 개발된 냉동기에 얹고 열차폐와 몸통을 씌워 펌프로서의 운전성능을 평가하는 일이 남아있다. 시제품은 상용품과 달리 기기가 차지하는 공간이 크고 부대설비가 복잡해서 운전성능 평가 장치에 부착해서 실험하기 어려울 수도 있으므로 기계연구원 현장에서 진공 게이지와 기체도입구만 부착한 마구리 플랜지를 펌프 흡기구 위에 달고 간이로 배기속도를 측정하는 것도 고려하고 있다. 이 경우는 표준용기를 사용할 때보다 배기속도가 과대평가되므로 이를 보정해 주는 방안을 마련해 놓아야 한다.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.889-894
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• 2008

Exhaust system used in toilet and cooking place of high riser public house is roof fan of two basic types : natural roof ventilator and natural/forced roof ventilator. Natural/forced roof ventilator has a motor in the rotary shaft. There are many high riser public house in Korea. These buildings were not viewed as being major contributors to exhaust pollutants producted in indoor. It was because many engineers thought that exhaust in high riser building depend on stack effect. This study investigates on stack pressure determined by exterior pressure and the difference pressure control in exhaust stack used in high riser public house. This paper focuses mainly on the effect of the time interval for power supply of motor installed in roof fan with function of natural wind velocity and of exhaust air volume of toilet. It is observed there are higher exhaust efficiency than the existing natural roof ventilator.

• Fire Science and Engineering
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• v.17 no.4
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• pp.105-110
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• 2003

In Part II, the temperature and smoke particle distributions of the extraction system, which yielded the best smoke removal performance among the three smoke control systems in Part I, for extraction flowrates of 0.6∼2.4 ㎥/s and two fire sizes of 200 ㎾ and 2 ㎿ were presented. The same numerical method was utilized to the same computational domain and configurations as Part I. It was shown that the extraction flowrate affects the smoke control performance significantly, and that a similar trend in improving the smoke removal performance with the increasing extraction flowrate between the two fire sizes. An extraction flowrate of 2.4 ㎥/s or higher was required for the temperature in the escape route less than $^{\circ}C$ for the given situations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.10
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• pp.971-978
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• 2013

This work presents a W band frequency synthesizer which is composed of 26 GHz VCO, Phase Locked Loop and frequency tripler using 65 nm RF CMOS process. Frequency tuning range of 26 GHz VCO covers the band from 22.8~26.8 GHz and final output frequency of the tripler is from 74 to 75.6 GHz. The fabricated frequency synthesizer consumes 75.6 mW and its phase noise is -75 dBc/Hz at 1 MHz offset, -101 dBc/Hz 10 MHz offset respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.446-452
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• 2013

Interest in the energy efficiency and carbon reduction technology is increasing. Many studies have done on the technologies of heat recovery systems, because over 30% of the total energy is released into the atmosphere with the exhaust gas flow. In this study, the Rankine cycle is analyzed in the optimum conditions given through the previous work. The result shows that the exergy efficiency is 0.53 and the output is 1.43 kW at the condition of the pressure ratio of 0.6 and the mass flow rate of 0.7.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12A
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• pp.1019-1024
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• 2003

In the thesis, we propose a new type of the predistortion linearizer using frequency multiplier The linearizer utilizing the 2nd and 3th harmonic used the individual control of the 3rd and 5th order intermodulation distortion(IMD) component. This structure is composed of wilkinson power combiner for combine and isolation of output signal, 3rd order IMD product controller using doubler and 5th order IMD product controller using tripler. The proposed predistortion linearizer controlled by individual order is obtained for about -16 dBc and 18 dBc of 3rd order and 5th order IMD components, respectively, over the frequency band 870 MHz to 880 MHz at the output power of 34 dBm/tone.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.7
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• pp.90-97
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• 2014

The effects of high pressure and low pressure exhaust gas recirculation (HP/LP EGR) portion on diesel engine combustion and emissions characteristics were investigated in a 2.2 L passenger-car diesel engine. The po3rtion of HP/LP EGR was varied from 0 to 1 while fixing the mass flow rate of fresh air. The intake manifold temperature was lowered with the increasing of the portion of LP EGR, which led to the retardation of heat release by pilot injection. The lowered intake manifold temperature also resulted in low nitrogen oxide (NOx) emissions due to decreased in-cylinder temperature and prolonged ignition delay, however, the carbon monoxide (CO) emission showed opposite trend to NOx emissions. The brake specific fuel consumption (BSFC) was decreased as the portion of LP EGR increased due to lowered exhaust manifold pressure by wider open of turbocharger vane. Consequently, the trade-off relationship between NOx and BSFC could be improved by increasing the LP EGR portion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4111-4116
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• 2013

The progressive die producing continuously while transferring in order a multiple process is processing law that it is efficient and quality is excellent. In this study the position of precision secured that it occurred when be welded exhaust efficiency of gas boiler combustion exhaust pipe and the exhaust pipe which is cause of incomplete combustion for the purpose of productivity increase. it add burring to a product form and progressive die make die don't disassemble and it be able to exchange burring punch the position of precision and productivity by progressive die is able to improve.