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조형문(Hyung-mun Cho),조성남(Sungnam Cho),김병국(Byeong-guk Kim),최영하(Youngha Choi),윤석주(Suckju Yoon),한종규(Jongkyu Han) 한국자동차공학회 2007 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
This paper presents the effects of equivalence ratio on the performance of a small spark-ignited gasoline engine. The engine used in this test was a single cylinder, two-stroke, air-cooled 26CC engine for lawn mower. The rpm, torque, power, and fuel consumption were measured under the four different equivalence ratio conditions and the engine loads respectively. In addition, the difference of the rpm on the dynamometer and the engine was confirmed to verify the effect of clutch by using for transfer the engine power. The results showed that the maximum power and minimum fuel consumption could be obtained at =0.9 and 9% load of dynamometer and clutch effect such as the slip on the λ surface was not concerned.
Frequency and Quadrature-Amplitude Modulation for Downlink Cellular OFDMA Networks
Hong, Sungnam,Sagong, Min,Lim, Chiwoo,Cho, Sunghye,Cheun, Kyungwhoon,Yang, Kyeongcheol IEEE 2014 IEEE journal on selected areas in communications Vol.32 No.6
<P>The distribution of the intercell interference (ICI) in conventional cellular networks employing orthogonal frequency-division multiple-access (OFDMA) with quadrature-amplitude modulation (QAM) tends to approach a Gaussian distribution when all available subcarriers in each cell are fully loaded. Recently, it has been also shown that the worst-case distribution of the ICI as additive noise in wireless networks with respect to the channel capacity is Gaussian. Thus, the channel capacity in cellular networks is expected to be further enhanced when the ICI could be designed properly so that it has a non-Gaussian distribution. This observation motivates us to propose, in this paper, a downlink cellular OFDMA network employing a modulation scheme called frequency and QAM (FQAM). We also derive maximum-likelihood metrics for the binary or non-binary error-correcting codes employed in the proposed network and propose their practical sub-optimal versions. Numerical results demonstrate that the distribution of the ICI in the proposed network deviates far from the Gaussian distribution. As a result, the transmission rates for the cell-edge users in the proposed network are significantly improved. In addition, the measurement results using practically implemented FQAM-based OFDMA systems verify that the transmission rates for the cell-edge users can dramatically increase, compared with the conventional QAM-based OFDMA network.</P>
Hong, Sungnam,Cheun, Kyungwhoon,Lim, Hyuntack,Cho, Sunghye The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.6
The performance of M-ary turbo coded synchronous, fast frequency-hopping spread spectrum multiple-access (FHSS-MA) networks with M-ary frequency shift keying (MFSK) and noncoherent detection is analyzed under Rayleigh fading. Results indicate that M-ary turbo codes dramatically enhance the performance of FHSS-MA networks using MFSK compared to binary turbo codes.
신귀수(Gwisu Shin),조성남(Sungnam Cho),류신열(Shinyeol Ryu),김근주(Keunjoo Kim) 한국자동차공학회 2004 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
The high-voltage discharging filter was designed for the purification of the exhaust gases in automobile. The filter was located on the exhaust line after catalyst and front of a muffler. The electric power 3.6 W with the voltage of 12 V and the current of 300 mA was applied and the voltage was transformed to 5 KV. The experimental measurement of smoke density was performed by the implement of the truck named. "Galloper". a product of Hyundai Motor Co at the engine speed of 2000 rpm. The smoke opacity in optical absorption measurement was reduced from 4 to 3% by the operation of the discharge filter.<br/> <br/>
최영하(Youngha Choi),조성남(Sungnam Cho),김병국(Byeongguk Kim),조형문(Hyungmun Cho),윤석주(Suckju Yoon),한종규(Jongkyu Han) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This paper presents the effects of equivalence ratios and throttle open degrees on the emission and performance of a small spark-ignition gasoline engine. The engine used in this paper was a single cylinder, diaphragm carburetor, two-stroke, air-cooled 26㏄ engine for brush cutter. The rpm, torque, fuel consumption and CO emission were measured under the four different equivalence ratio and three different throttle degree conditions on the engine loads respectively. In addition, the difference of the rpm on the dynamometer and the engine was confirmed to verify the effect of clutch by using for transfer the engine power. The results showed that the maximum power and minimum fuel consumption could be obtained at λ=0.9 and 9% load of dynamometer, and also the leaner mixture tuning develops the lower CO emission.
Rotational dynamics of thiocyanate ions in highly concentrated aqueous solutions
Kim, Heejae,Park, Sungnam,Cho, Minhaeng The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.18
<P>The thiocyanate (SCN<SUP>−</SUP>) anion is known as one of the best denaturants, which is also capable of breaking the hydrogen-bond network of water and destabilizing native structures of proteins. Despite prolonged efforts to understand the underlying mechanism of such Hofmeister effects, detailed dynamics of the ions in a highly concentrated solution have not been fully elucidated yet. Here, we used a dispersive IR pump–probe spectroscopic method to study the dependence of vibrational lifetimes and rotational relaxation times of thiocyanate ions on KSCN concentration in D<SUB>2</SUB>O. The nitrile stretch mode is used as a vibrational probe for dispersed IR pump–probe and FTIR measurements. To avoid possible self-attenuation of the IR pump–probe signal by highly concentrated SCN<SUP>−</SUP> ions, we added a small amount of <SUP>13</SUP>C-isotope-labeled thiocyanate ions (S<SUP>13</SUP>CN<SUP>−</SUP>) and focused on the excited-state absorption contribution to the IR pump–probe signal of the <SUP>13</SUP>C-isotope-labeled nitrile stretch mode. Quite unexpectedly, the vibrational lifetime of S<SUP>13</SUP>CN<SUP>−</SUP> ions is independent of the total KSCN concentration in the range from 0.46 m (molality) to 11.8 m while the rotational relaxation time of S<SUP>13</SUP>CN<SUP>−</SUP> ions is linearly dependent on the total KSCN concentration. By combining the present experimental findings with the fact that the dissolved ions of KSCN salt have a strong tendency to form a large ion cluster in a highly concentrated aqueous solution, we believe that the ion clusters consisting of potassium and thiocyanate ion pairs in D<SUB>2</SUB>O behave like ionic liquids and the ions inside ion clusters are weakly bound by electrostatic Coulombic interactions. The ability of SCN<SUP>−</SUP> ions to form ion clusters in aqueous protein solutions seems to be a key to understand the Hofmeister ion effect. We anticipate that the present experimental results provide a clue for further elucidating the underlying mechanism of the Hofmeister ion effects on protein stability in the future.</P> <P>Graphic Abstract</P><P>Rotational dynamics of <I>chaotropic</I> thiocyanate ions in highly concentrated aqueous solutions studied by IR pump–probe spectroscopy. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp23749k'> </P>