대형천연가스차량의 공연비제어기 설계를 위한 엔진모델

심한섭,이태연 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.5

Air partial pressure ratio and inlet air mass flow are influenced by water vapor and gaseous fuel in mixture on Compressed Natural Gas (CNG) engines. In this paper, the effects of the water vapor and the gaseous fuel that change the air mass flow and the air-fuel ratio are studied. Effective air mass ratio is defined as the air mass flow divided by mixture mass flow, and also it is applied to the estimation of the det air mass flow and the air-fuel ratio. The presence of the gaseous fuel and the water vapor in the mixture reduces the air partial pressure and the effective air mass ratio of the CNG engines. The experimental results for the CNG engine show that estimation of the air-fuel ratio based upon the effective air mass ratio is more accurate than that of a normal mode.

2 상 유동 및 물질전달 특성에 미치는 오리피스 노즐형상과 소요동력의 영향

양희천(Hei Cheon Yang) 대한기계학회 2016 大韓機械學會論文集B Vol.40 No.4

호기성 수처리 과정의 폭기에 소요되는 에너지의 이용효율을 높이기 위해서는 물질전달 특성뿐만 아니라 소요동력에 대한 연구가 필요하다. 본 논문은 수직 2 상 유동 및 물질전달 특성에 미치는 오리피스 노즐형상과 소요동력의 영향에 대한 실험적 연구를 목적으로 한다. 측정 변수들을 이용하여 유량비, 소요동력, 물질전달 계수 그리고 물질전달 효율을 산출하였다. 소요동력이 커지면 물질전달 계수는 증가하는 반면에 유량비와 물질전달 효율은 감소하였다. 무차원 면적비가 작은 오리피스 노즐의 유량비, 물질전달 계수 및 효율이 높게 나타났다. 물질전달 특성에 미치는 유량비, 소요동력 그리고 프라우드 수의영향을 평가하기 위한 실험식을 제시하였다. It is necessary to investigate the input power as well as the mass transfer characteristics of the aeration process in order to improve the energy efficiency of an aerobic water treatment. The objective of this study is to experimentally investigate the effect of orifice nozzle design and input power on the flow and mass transfer characteristics of a vertical two-phase flow. The mass ratio, input power, volumetric mass transfer coefficient, and mass transfer efficiency were calculated using the measured data. It was found that as the input power increases the volumetric mass transfer coefficient increases, while the mass ratio and mass transfer efficiency decrease. The mass ratio, volumetric mass transfer coefficient, and mass transfer efficiency were higher for the orifice configuration with a smaller orifice nozzle area ratio. An empirical correlation was proposed to estimate the effect of mass ratio, input power, and Froude number on the volumetric mass transfer coefficient.

중앙구동 이젝터의 설계변수에 따른 유동특성

박상규(Sang Kyoo Park),양희천(Hei Cheon Yang) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.8

본 논문은 중앙구동 이젝터의 유량비에 미치는 설계변수의 영향에 대한 연구를 목적으로 한다. 중앙구동 이젝터의 설계변수는 구동노즐 출구 단면적 및 거리비, 디퓨저 출구 단면적비로 설정하였다. 실험장치는 가변노즐 이젝터, 전동 모터-펌프, 구동유체 저장수조, 제어판넬 그리고 고속 카메라 시스템으로 구성하였다. 유량비는 실험변수에 따라 측정되는 유입 공기량과 구동유체인 물의 유량을 이용하여 도출하였다. 유량비는 구동노즐 거리비와 혼합관 길이비가 커지면 증가하는 반면에, 구동노즐 면적비와 디퓨저 출구 면적비가 커지면 감소하였다. The objective of this study is to experimentally investigate the effect of design parameter on the mass ratio of a central-driven ejector. The design parameters are the primary nozzle area and distance ratios, diffuser exit-area ratio and mixing-tube length ratio. The experimental setup was an open-loop continuous circulation system which has a movable nozzle ejector, an electric motor-pump, a water tank, a control panel and high-speed camera unit. We calculated the mass ratio using the measured primary and suction-flow rates with the experimental parameter of primary water-flow rate or pressure. The results showed that the mass ratio increased with the primary nozzle distance ratio and mixing tube length ratio, while the mass ratio decreased with the primary nozzle-area ratio and diffuser exitarea ratio.

Comparison of Neutrophil/Lymphocyte and Platelet/Lymphocyte Ratios for Predicting Malignant Potential of Suspicious Ovarian Masses in Gynecology Practice

Topcu, Hasan Onur,Guzel, Ali Irfan,Ozer, Irfan,Kokanali, Mahmut Kuntay,Gokturk, Umut,Muftuoglu, Kamil Hakan,Doganay, Melike Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.15

Purpose: To compare the diagnostic accuracy of the neutrophil/lymphocyte ratio (NLR) with the platelet/lymphocyte ratio (PLR) in predicting malignancy of pelvic masses which are pre-operatively malignant suspicious. Materials and Methods: In this retrospective study we evaluated the clinical features of patients with ovarian masses which had pre-operatively been considered suspicious for malignancy. The patients whose intraoperative frozen sections were malign were classified as the study group, while those who had benign masses were the control group. Data recorded were age of the patient, diameter of the mass, pre-operative serum Ca 125 levels, platelet count, neutrophil/lymphocyte ratio and platelet/lymphocyte ratio. Results: There was statistically significantly difference between the groups in terms of age, diameter of the mass, serum Ca 125 levels, platelet number and platelet/lymphocyte ratio. Mean neutrophil/lymphocyte ratios showed no difference between the groups. ROC curve analysis showed that age, serum Ca 125 levels, platelet number and PLR were discriminative markers in predicting malignancy in adnexal masses. Conclusions: According to the current study, serum Ca 125 levels, pre-operative platelet number and PLR may be good prognostic factors, while NLR is an ineffective marker in predicting the malignant characteristics of a pelvic mass.

다중 검출 유도결합 플라즈마 질량분석기를 이용한 납 및 카드뮴안정동위원소비 분석의 질량 편향 보정방법 비교

김지영 ( Jee Young Kim ),김명진 ( Myung Jin Kim ),유은진 ( Eun Jin Yoo ),이강현 ( Kang Hyun Lee ),이경석 ( Kyoung Seok Lee ),이원석 ( Won Seok Lee ),최종우 ( Jong Woo Choi ),권오상 ( Oh Sang Kwan ) 한국환경분석학회 2014 환경분석과 독성보건 Vol.17 No.3

To obtain precise and accurate isotope ratios with a multi-collector ICP-MS, three methods such as interelementalinternal calibration, sample-standard bracketing (SSB), and log-log linear regression correction model were applied to isotope ratio measurement of lead (Pb) and cadmium (Cd) for the correction of instrumental mass discrimination. Certified reference materials including NIST SRM 981 (Pb), NIST SRM 3108(Cd), and BAM I012 (Cd) were used as reference materials for the isotope ratios of lead and cadmium to compare the corrected results obtained from the respective correction models. The accuracies of lead isotope ratio measurements were in the range of -0.002 (207/206Pb) to -0.035 (208/204Pb) % when the inter-elemental internal calibration applied. The same range of -0.002 (207/206Pb) to -0.035 (208/204Pb) % was also found with the SSB method. The log-log linear regression correction model, on the other hand, showed a different range of -2.160 (207/206Pb) to 0.219 (208/204Pb) %. The precisions of lead isotope ratios with these three correction methods ranged from 0.027 (206/204Pb) to 0.127 (208/204Pb), 0.025 (206/204Pb) to 0.124 (208/204Pb), and1.265 (207/204Pb) to 1.367 (207/206Pb), respectively. Therefore, both of the inter-elemental internal calibration and the SSB method were selected as good methods for mass bias correction of lead isotope ratios. Theε114/110Cd values obtained from the application of the three different correction models were -14.5±0.7 (Agas an internal standard), -13.0±2.1 (SSB), and -15.2±1.8 (log-log linear regression correction model), respectively. For ε114/110Cd values, the inter-elemental internal calibration showed the best precision among the three correction methods. Isobaric interferences with cadmium were also corrected when correction coefficients were applied to each isotope of cadmium. The difference of correction coefficients between the isotope ratios with natural abundances and the empirical ratios in the isobaric interferences reached up to 11%. The heavier isobaric interferences (106, 108, 110Pd vs. 105Pd) were underestimated in the application of the natural ratios, while the lighter isobaric interferences (112,114,116Sn vs. 118Sn and113In vs. 115In) were overestimated. In conclusion, the inter-elemental internal calibration and the SSB method can properly correct the isotope ratios of interest in the isotope ratio measurement using the MC-ICP-MS. Further research on the isotope ratio analysis of environmental samples should follow to improve precision and accuracy.

공기-물 혼합분류의 유량비에 따른 물질전달 특성

양희천(Hei Cheon Yang) 대한기계학회 2022 大韓機械學會論文集B Vol.46 No.5

본 연구는 중심노즐 이젝터를 이용한 공기-물 혼합분류의 물질전달 특성에 대한 실험적 연구를 목적으로 한다. 유량비에 따라 수조에 분출되는 혼합분류의 거동과 물질전달 계수 및 효율에 대해 정량적으로 분석하였다. 구동유량이 증가하면 유량비는 감소하고, 유량비가 증가하면 비 소요동력은 감소하였다. 유량비가 커지면 수평분류에서 부력분류로 천이되는 길이와 분류선단 도달길이가 감소하였다. 유량비가 커지면 총괄 물질전달 계수는 감소하며, 물질전달 효율은 약간 증가한 후에 감소하였다. The aim of this study was to experimentally investigate the mass transfer characteristics of air-water mixed jet with central nozzle ejector. Using the mass ratio, the mixed jet behavior discharged in a water tank, the mass transfer coefficient, and efficiency were analysed qualitatively. The mass ratio decreased with the primary flowrate, and the specific input power decreased with the mass ratio. Additionally, as the mass ratio increased, the transient length from horizontal jet to buoyancy jet, and the total penetration length of mixed jet decreased. Furthermore, with the increase in the mass ratio, the volumetric mass transfer coefficient decreased, while the mass transfer efficiency increased slightly and then decreased.

가상 질량 동조기에 의한 구조물의 감쇠비 추정

황재승 한국풍공학회 2016 한국풍공학회지 Vol.20 No.1

본 연구는 가상 질량 동조기(VMT)를 이용하여 구조물의 응답으로부터 구조물의 감쇠비를 구하는 기법을 다룬다. 백색잡음뿐만아니라, 특정 진동수 가진, 충격하중 가진 등 다양한 하중종류 및 특성에 의하여 발생한 구조물의 계측응답에 대하여 VMT를 적용하였을 때 구조물의 감쇠비를 추정하는 기법에 대해서 다루고, VMT의 동적특성이 구조물 감쇠비 추정에 미치는 영향을 수치적으로 분석하였다. 수치해석결과에 의하면, VMT에 의하여 구조물 감쇠비 추정이 충분한 신뢰성을 가지고 예측되는 것을 확인 할 수 있었다. 충격하중을 받는 응답을 이용하는 경우 VMT에 의하여 가장 안정적으로 구조물 감쇠비 추정이 가능한 것을 알 수 있었으며, 백색잡음, 협소대역 하중에 대해서도 VMT의 지정 감쇠비를 너무 작게 산정하지 않으면 감쇠비 추정이 가능한 것으로 나타났다. 정현파의 경우에는 가진 진동수의 VMT 비율을 이용하여 감쇠비 추정이 가능한데 고유진동수와 인접할수록 정밀도가 높아지는 것을 알 수 있었다. This study outlines a technique to obtain a structural damping ratio from measured responses of the structure using the virtual mass tuner(VMT). For the structural responses induced by the different load types such as white noise, narrow band load, impact load and sine wave load, numerical analyses are performed to verify the applicability of VMT in the estimation of the damping ratio, and to consider the effect of the characteristics of loads and VMT on the accuracy of the damping ratio. From the numerical results, it is found that VMT is able to precisely estimate the damping ratio with a sufficient reliability regardless of the load type. When using a response by the impact load, the damping ratio is much more stably estimated. In addition, if the damping ratio of VMT is designated not too small, the damping ratio can be accurately estimated for the response induced by the white noise and narrow band load. In the case of the sine wave, it is possible to estimate the structural damping ratio using a variance ratio of the VMT at the different excitation frequencies.

감쇠진동계에 부착된 복합동흡진기의 효과에 관한 연구

안찬우,최석창,김동영 한국소음진동공학회 1997 소음 진동 Vol.7 No.6

This paper describes the effects of dual dynamic vibration absorbers attached to a primary vibration system with damping. The efficiency of dual dynamic vibration absorbers was investigated with the height of amplitude ratio at the resonance frequency ratio of the damped vibration system according to mass ratio, natural frequency ratio and damping ratio. The variation of amplitude ratio related to frequency ratio of primary vibration system is verified experimentally and theoretically according to dual dynamic vibration systems using computer program designed to find mutual relationship between two absorbers.

브루나이 열대우림 내 주요 3개 수종 고사목의 초기 질량 감소율과 탄질율 변화

노유진,장민주,손요환,Roh, Yujin,Jang, Minju,Son, Yowhan 한국환경생물학회 2021 환경생물 : 환경생물학회지 Vol.39 No.2

본 연구에서는 열대우림인 브루나이 MDF와 PSF의 주요 수종(D. aromatic, D. rappa, C. arborescens)을 대상으로 초기 분해 단계의 수종별 질량 감소율과 탄질율의 변화를 파악하였다. 2019년 5월에 총 48개의 고사목 시료(15 cm ×4.8 cm ×5 cm)를 산림 지표면에 배치하고 16개월 후 수거하였다. 분해 전 수종별 고사목의 밀도(g cm^-3)는 0.64±0.01 (D. aromatic), 0.60±0.00 (D. rappa), 0.44±0.02 (C. arborescens) 등이었으며, 16개월 동안 수종별 연간 질량 감소율(%)은 6.37 (D. aromatic), 8.17 (D. rappa), 18.53 (C. arborescens) 등으로 나타났다. 부후등급은 C. arborescens에서 III등급이 약 25%로 높았으며 흰개미의 분해 흔적이 나타났다. 한편, 16개월 후 탄질율은 D. aromatic과 D. rappa에서 통계적으로 유의하게 감소하였으나, C. arborescens에서는 감소하는 경향이 유의하지 않았다. 이러한 연구 결과는 열대우림 내 고사목의 초기 분해는 밀도와 같은 수종의 물리적 특성에 따라 차이가 나타날 수 있으며, 주요 분해자의 유형에 따라 탄질율의 변화에도 상대적으로 차이가 있을 수 있음을 시사하는 것이다. This study was conducted to determine the mass-loss rates and the changes in carbon/nitrogen (C/N) ratio of dead woods, which were of following species: Dryobalanops aromatic, D. rappa, and Cratoxylum arborescens. These were dominant tree species in mixed Dipterocarp forests (MDF) and peat swamp forests (PSF) in Brunei Darussalam. In May, 2019, 48 dead wood samples (15 cm×4.8 cm×5 cm) were placed in MDF and PSF sites, and all the samples were collected after 16 months. The effects of species on mass loss were statistically significant (p<0.05); however, no difference was observed in the mass loss obtained from the two forest types (p>0.05). The initial density (g·cm^-3) of the dead woods D. aromatic, D. rappa, and C. arborescens, was 0.64±0.02, 0.60±0.00, and 0.44±0.01, respectively. Also the annual mass loss rate (%) was estimated to be 6.37, 8.17, and 18.53 for D. aromatic, D. rappa, and C. arborescens, respectively. The proportion of dead woods in decay class III was only 25% of C. arborescens samples, which were attacked by wood-feeding invertebrates, such as termites. The C/N ratio decreased significantly in D. aromatic and D. rappa, but the decreasing trend of C/N ratio was not statistically significant in C. arborescens. The results indicate that physical traits of dead woods, such as density, could be one of the main factors causing the decomposition of dead woods initially, as invertebrates such as termites are one of the key decomposers of dead wood in tropical rainforests. In the samples of C. arborescens, which was attacked by invertebrates, nitrogen immobilization occurred to lesser extent as compared to that observed in D. aromatic and D. rappa.

Ratio of PM2.5 to PM10 Mass Concentrations in Beijing and Relationships with Pollution from the North China Plain

Zhigang Li,Xin Yang,Chuanfeng Zhao,Tianyi Fan 한국기상학회 2021 Asia-Pacific Journal of Atmospheric Sciences Vol.57 No.3

Five years of PM2.5/PM10 ratios and their potential relationships with wind and relative humidity (RH) were analyzed for three areas in Beijing (northwestern mountainous area, urban area and southern suburbs), and these values were compared with those of five other cities, including Tianjin, Dalian, Hangzhou, Shanghai and Guangzhou. In the past five years, both PM2.5 and PM10 mass concentrations have decreased over the three Beijing regions, particularly during winters. The PM2.5/PM10 ratios have distinct seasonal characteristics, with more frequent high ratios in winter than in other seasons. The high ratio frequency decrease is most evident in winter and in the southern Beijing suburbs. This fine particle proportion decrease is related to air pollution control policies, including the national project ‘Coal to Gas’. HighPM2.5/PM10 ratios are linked to heavy pollution levels and low wind speeds, indicating the importance of PM2.5 accumulation during pollution events in Beijing. The higher PM2.5/PM10 ratios in Beijing are also closely related to southerly winds and high humidity, indicating the contribution of anthropogenic pollution transported from the south. Due to similar geographic environments, Tianjin is similar to Beijing in terms of the frequency distribution characteristics of the PM2.5/PM10 ratios. The coastal city of Dalian is further north and not similar to Beijing or Tianjin, owing to a sea breeze influence. Different from Beijing and Tianjin, the southern cities of Hangzhou, Shanghai and Guangzhou show almost no change in the PM2.5/PM10 ratio frequency distribution with increases in wind speed and relative humidity.