• Title, Summary, Keyword: Conversion rate

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Effects of ortho-para hydrogen conversion on hydrogen liquefaction performance (Ortho-para 수소변환이 수소액화성능에 미치는 영향)

  • 최항집;강병하;최영돈
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.2
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    • pp.131-139
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    • 2000
  • A direct hydrogen liquefaction equipment has been developed and tested, which consists of a GM refrigerator, a liquefaction vessel, a radiation shield, a cryostat, and an ortho-para converter with catalyst. The effect of ortho-para hydrogen conversion on the performance of hydrogen liquefaction has been investigated. The time needed for the hydrogen liquefaction process with hydrogen pressure charge of 4 atm was delayed to around 75 minutes, and the liquefied mass flow rate of the hydrogen was about 0.0150∼ 0.0205 g/s when the hydrogen was liquefied with the direct hydrogen liquefaction system considering ortho-para conversion. With ortho-para conversion, the liquefied mass flow rate decreased up to 20%. Considering ortho-para conversion, there were up to 30% increase in the work input per unit liquefied mass flow rate. When the ortho-para conversion was considered, FOM decreased to be about 0.031∼0.045.

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Developement of a 3 channel digital CVSD bit-rate converter using a general purpose DSP (범용 DSP를 이용한 3 채널 디지탈 CVSD 전송율 변환기 개발)

  • 최용수;강홍구;김성윤;박영철;윤대희
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.22 no.2
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    • pp.306-317
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    • 1997
  • This ppaer presents a bit-rate conversion system for efficient communications between 3 channel CVSD systems with different bit-rates. The proposed conversion system is implemented in the digital domain and specially, the conversion problem between 32 Kbps and 16 Kbps CVSD systems is studied. The conventional conversion system implemented in the analog domain allows signals to be easily degraded by external noises. To overcome this problem, a digital CVSD bit-rate conversion system robust to external noises is developed. the new systemdecodes CVSD bit sequences and converts sampling rates of decoded signals, then encodes signals at target bit-rates. Since linear phase property does not matter in this application, instead of FIR filters a IIR filter is employed to reduce the system complexity. Therefore, a 3 channel digital CVSD bit-rate conversion system was successfully real-time implemented using a general purpose DSP. In addition, conversion problems with unkown time constants were experimented and good experimental results were obtained.

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Design of Audio Sampling Rate Conversion Block (Audio Sampling Rate Conversion Block의 설계)

  • 정혜진;심윤정;이승준
    • Proceedings of the IEEK Conference
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    • pp.827-830
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    • 2003
  • This paper proposes an area-efficient FIR filter architecture for sampling rate conversion of hi-fi audio data. Sampling rate conversion(SRC) block converts audio data sampled at 96KHz down to 48KHz sampled data and vice versa. 63-tap FIR filter coefficients have been synthesized that gives 100dB stop band attenuation and 5.2KHz transition bandwidth. Time-shared filter architecture requires only one multiplier and accumulator for 63-tap filter operation. This results in huge hardware saving of up to 10~19 times smaller compared with traditional FIR structure.

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Region based Scan Rate Up-Conversion Technique (영역 기반 Scan Rate Up-Conversion 기법)

  • Kim, Young-Ro;Hong, Byoung-Ki
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • pp.173-176
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    • 2005
  • 본 논문에서 영역 분할을 기반으로 하는 새로운 scan rate of-conversion 기법을 제안한다. 제안하는 공간적 보간 방법과 기존의 시간적 보간 방법을 이용하여 시공간 보간을 한다. 제안된 방법에서는 먼저 분수령 알고리즘을 이용한 영역 분할하고, 분할된 영역을 기반으로 하여 영역간의 에지 방향성을 결정한다. 기존 알고리즘과 같이 화소간 값 차이를 이용하여 에지의 방향을 구하지 않고 분할된 영역에서 영역구분에 따른 방향에 따라 보간을 함으로써 에지를 유지하면서 scan rate up-conversion을 할 수 있다.

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Proposed One-Minute Rain Rate Conversion Method for Microwave Applications in Korea

  • Shrestha, Sujan;Choi, Dong-You
    • Journal of information and communication convergence engineering
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    • v.14 no.3
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    • pp.153-162
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    • 2016
  • Microwave and millimeter waves are considered suitable frequency ranges for diverse applications. The prediction of rain attenuation required the 1-min rainfall rate distribution, particularly for data obtained locally from experimental measurement campaigns over a given location. Rainfall rate data acquired from Korea Meteorological Administration (KMA) for nine major sites are analyzed to investigate the statistical stability of the cumulative distribution of rainfall rate, as obtained from a 10-year measurement. In this study, we use the following rain rate conversion techniques: Segal, Burgueno et al., Chebil and Rahman, exponential, and proposed global coefficient methods. The performance of the proposed technique is tested against that of the existing rain rate conversion techniques. The nine sites considered for the average 1-min rain rate derivation are Gwangju, Daegu, Daejeon, Busan, Seogwipo, Seoul, Ulsan, Incheon, and Chuncheon. In this paper, we propose a conversion technique for a suitable estimation of the 1-min rainfall rate distribution.

Characterization of SCR System for NOx Reduction of Diesel Engine (II) (디젤엔진의 질소산화물 저감을 위한 Urea SCR 시스템 특성 분석 (II))

  • Lee, Joon-Seong;Kim, Nam-Yong
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.11
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    • pp.83-89
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    • 2008
  • The Effect of Space Velocity(SV) on NOx conversion rate was performed to develop NOx reduction after-treatment system. SV is calculated from engine exhaust gas volume and SCR catalyst volume. Found the Urea injection duty of maximum efficiency for NOx conversion if increase SV, NOx Conversion rate is down. Especially, when SV is more than $110,000h^{-1}$, NOx conversion rate decrease suddenly. Same case, if SV is lower than $40,000h^{-1}$, NOx conversion rate is down. Also, the characterization of Urea-SCR system was performed. Three candidate injectors for injecting Urea were tested in terms of 속 injection rate and NOx reduction rate. The performances of SCR catalytic converter on temperature were investigated. The performance of Urea-SCR system was estimated in the NEDC test cycle with and without EGR. It was found that nozzle type injector had high NOx conversion rate. SCR catalytic converter had the highest efficiency at the temperature of $350^{\circ}C$. EGR+Urea-SCR system achieved NOx reduction efficiency of 73% through the NEDC test cycle.

A Theoretical Study on Conversion Rate of Jeonse Price to Monthly Rent for Housing - Focused on Rental Supply Costs - (주택 전월세 전환율에 관한 이론 연구 - 임대 공급원가를 중심으로 -)

  • Kim, Won-Hee;Jeong, Dae-Seok
    • The Journal of the Korea Contents Association
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    • v.20 no.3
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    • pp.245-253
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    • 2020
  • If the conversion rate of jeonse price to monthly rent is the market interest rate or the landlord's expected return, then the conversion rate of jeonse price to monthly rent in the country should be the same. However, the conversion rate of jeonse price to monthly rent has always been higher than the market interest rate. This study identifies the supply cost components of rental housing as a risk premium in the presence of current housing prices, market interest rates, depreciation costs, holding taxes, and leases, and identifies the relationship between the current housing prices and each factor. Housing rent is expressed as the current price. This overcomes the shortcomings that implicitly assume fluctuations in housing prices or do not include current housing prices in the conversion rate of jeonse price to monthly rent. This study found that the conversion rate of jeonse price to monthly rent is the required rate of return or required rate of renter, not market interest rate, by expressing the supply cost of rental housing as a combination of components. This not only explained the fact that the conversion rate of jeonse price to monthly rent was always higher than the market interest rate, but also explained the regional differences. It also explained why the conversion rate of jeonse price to monthly rent varies by type of housing.

Catalytic Oxidation of Ammonia over Metal Supported on Alumina at Low Temperature (금속담지 활성알루미나 촉매의 암모니아 저온연소반응)

  • Lim, Yun-Hui;Lee, Ji-Yeol;Park, Byung-Hyun
    • Journal of the Korean Applied Science and Technology
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    • v.30 no.3
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    • pp.371-379
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    • 2013
  • In order to improve the selective oxidation reaction of gaseous ammonia at a low temperature, various types of metal-impregnated activated alumina were prepared, and also physical and chemical properties of the conversion of ammonia were determined. Both types of metal (Cu, Ag) impregnated activated alumina show high conversion rate of ammonia at high temperature (over $300^{\circ}C$). However, at lower temperature ($200^{\circ}C$), Ag-impregnated catalyst shows the highest conversion rate (93%). In addition, the effects of lattice oxygen of the developed catalyst was studied. Ce-impregnated catalyst showed higher conversion rate than commercial alumina, but also showed lower conversion rate than Ag-impregnated sample. Moreover, 5 vol.% of Ag activation under hydrogen shows the highest conversion rate result. Finally, through high conversion at low temperature, it was considered that the production of NO and $NO_2$, toxic by-products, were effectively inhibited.

Empirical Prediction Models of 1-min Rain Rate Distribution for Various Integration Time

  • Jung, Myoung-Won;Han, Il-Tak;Choi, Moon-Young;Lee, Joo-Hwan;Pack, Jeong-Ki
    • Journal of electromagnetic engineering and science
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    • v.8 no.2
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    • pp.84-89
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    • 2008
  • In a wireless channel above microwave frequency, rain attenuation is very important. In order to predict rain attenuation, 1-min. rain rate distribution is required. This paper discusses appropriate conversion methods to estimate 1-minute rain rate from that of other integration time. Based on the measurement data filed in ITU-R WP3J including ETRI data for 6 consecutive years, distributions of rain rate with 1-, 5-, 10-, 20-, 30-minute integration time were analyzed, both on the global and regional basis, and the parametric relationship between the statistical characteristics of 1-minute and other measurement data were investigated to deduce the conversion methods. It is shown that the global model works good with good accuracy for 5-, 10-, 20-min integration time, and the global model is also applicable globally with good accuracy for 5-, 10-, 20-min integration time. The global conversion model was adopted last year as an ITU-R document for new recommendation. The regional conversion model would also be very useful for locations of similar climatic zone.

Effect of Polyvinylpyrrolidone on the Copolymerization of Acrylonitrile and Methylacrylate Initiated by Azobisisobutyronitrile in Dimethylformamide Solution System (Acrylonitrile과 Methylacrylate의 Dimethylformamide(DMF) 용액중합에 있어 Polyvinylpyrrolidone의 영향)

  • Lee, Shin-Hee;Kim, Sung-Hong;Park, Soo-Min
    • Textile Science and Engineering
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    • v.34 no.9
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    • pp.591-597
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    • 1997
  • The mechanism of the solution copolymerization of acrylonitrile and methylacrylate in DMF at 7$0^{\circ}C$ initiated by azobisisobutyronitrile (AIBN) has been investigated in the presence of polyvinylpyrrolidone (PVP) as an additive. Data of fractional conversion of the copolymers, fractional polymerization rate, instantaneous and cumulative composition of the copolymer and instantaneous monomer feed composition as a function of the reaction time or conversion are presented. The monomer reactivity ratio determined by the Finemann-Ross method in the presence and absence of PVP (3 wt%) were $r_1=1.122,\;r_2=0.858\;and\;r_1=0.995,\;r_2=0.744$, respectively. The PVP was found to affect the polymerization rate, conversion, and degree of polymerization of polyacrylonitrile copolymer. The PVP in the polymerization solution was found to increase the initial polymerization rate and limiting conversion. The conversion and degree of polymerization at limiting conversion time increased.

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