• 대한인간공학회지
• /
• 제32권4호
• /
• pp.389-396
• /
• 2013

Objective: The ride qualities of the six passenger cars were evaluated in 4 subjects on the highway and uneven road. The relation between vibration with driving velocity and driving posture were also investigated separately. Background: Ride comfort plays an important role in the vehicle design. Vibration is the one of the principal components associated with ride comfort. Method: The acceleration of the foot, hip and back were measured using B&K accelerometers in this study. The velocity of the passenger cars was maintained at a constant speed of 80km/h on the highway and 40km/h on the uneven road. For evaluating the effects of driving velocity and driving posture on vehicle's vibration level, separate experiments were performed on the highway with 5 different vehicle speeds and 5 different backrest angles, respectively. Results: The overall ride value of the luxury car showed the best result while the smaller car showed the worst value on the highway. On the uneven road the overall ride value level was increased 75~98%. All the vehicles had the SEAT value less than 1. Faster the velocity lowers the SEAT value. The ride quality in terms of vibration gets worst when the backrest angle increased. Conclusion: The smaller car had a first mode at the higher frequency and showed higher vibration level. SEAT value was mostly affected by the seat property not by vehicle. We ranked the luxury car seat had a best vibration reduction quality than others based on SEAT values. When the driving velocity increased, the overall ride values were increased proportionally and the SEAT values were somewhat decreased. Application: Evaluation of whole-body vibration in the passenger car.

• The Korean Journal of Ecology
• /
• 제9권1호
• /
• pp.41-50
• /
• 1986

The net primary production in the Korean peninsula was estimated by Miami model, Montreal model and Kira's model, based on 148 meteorological data. The modes in frequency distribution of the values calculated by Montreal and Miami model were found at 1,500g/m2/yr. class and at one step high class in 100g. interval, while by Kira's madel at 1,700g/m2/yr. class. The relationships between values by Miami model(X) and those by Motreal model (Ym) and Kira's model(Yk) can be expressed as follows: Ym=0.365X+944.7, Yk=0.462 X+1006.9 and Yk=1.282Ym-211.5. The total amount of the net primary production in 218,583.4km2, 98.9% of the whole area(220,951 km2) of the Korean Peninsula, was estimated as 290,691,407 tons/yr. by Miami model, 310,751,566 tons/yr by Montreal model and 352,071,901 tons/yr by Kira's model. Therefore, it is reasonable that the organic substance over 300 million-tons is added yearly in the Korean Peninsula, because only 1.1% of the whole area no calculated. In additiion, the net primary production amount of Han-river basin was estimated as ca. 38 million-tons, whether calculated with the meteorological data in level of the Korean Peninsula or with more detail data.

• 전자공학회논문지D
• /
• 제35D권6호
• /
• pp.15-20
• /
• 1998

Fiber dispersion을 이용한 소신호 응답특성으로부터 1.55㎛ strained MQW DFB 레이저의 linewidth enhancement factor α 및 fiber 분산을 측정하였다. 측정된 fiber 분산값은 16.766∼16.786ps/nm/km로 일반적인 단일모드 fiber의 분산값을 잘 나타내었다. 레이저의 실제 동작조건에서 α의 변화를 관찰하기 위하여 광출력의 변화에 따른 α의 변화를 측정하였는데 광출력 증가에 따라 α값도 선형적으로 증가함을 알 수 있었다. 이 결과로부터 아직까지의 어떤 측정보다도 정확히 non-linear gain에 의한 α의 변화를 설명할 수 있었다.

• 한국안전학회지
• /
• 제27권3호
• /
• pp.1-8
• /
• 2012

Characteristics of smoke emission in light duty diesel vehicles was investigated according to the year of production, engine displacement volume, and mileage. The smoke emission was measured using light extinction smoke measurement method under free acceleration test mode. Total number of the tested vehicles was 180. The year of production of the tested vehicles distributed from 2002 to 2007. The displacement volumes of the tested vehicles were categorized as 2-liter, 2.5-liter, 2.7-liter, and 3-liter. The mileage of the tested vehicles distributed from 20,000 km to 400,000 km. The more recent in the year of production of the tested vehicles did not show clearly lower in smoke emissions. Smoke emission showed different values according to driver's pedal pushing pattern. Also, smoke emission peak for each free acceleration test initially increased and reach a maximum of the peak values. Afterwards, the smoke peak gradually decreased as number of test increased. A new guide line was proposed to determine the smoke value from the light duty diesel vehicles based on smoke emission peak patterns which were obtained with several repeated free acceleration tests.

• Bulletin of the Korean Chemical Society
• /
• 제35권4호
• /
• pp.1043-1049
• /
• 2014

Density functional theory (DFT) calculations at the B3LYP/6-31G(d,p) theoretical level were performed for two novel explosives (compounds B and C) based on the guanidine-fused bicyclic skeleton $C_4N_6H_8$ (A). The heats of formation (HOFs) were calculated via isodesmic reaction. The detonation properties were evaluated by using the Kamlet-Jacobs equations. The bond dissociation energies (BDEs) for the thermolysis initiation bond were also analyzed to investigate the thermal stability. The results show that the compounds have high positive HOF values (B, 1064.68 $kJ{\cdot}mol^{-1}$; C, 724.02 $kJ{\cdot}mol^{-1}$), high detonation properties (${\rho}$, D and P values of 2.04 $g{\cdot}cm^{-3}$ and 2.21 $g{\cdot}cm^{-3}$, 9.98 $km{\cdot}s^{-1}$ and 10.99 $km{\cdot}s^{-1}$, 46.44 GPa and 59.91 Gpa, respectively) and meet the basic stability requirement. Additionally, feasible synthetic routes of the these high energy density compounds (HEDCs) were also proposed via retrosynthetic analysis.

• Nuclear Engineering and Technology
• /
• 제42권4호
• /
• pp.468-473
• /
• 2010

We confirmed that the dismantling of two research reactors with thermal power of $2MW_{th}$ and $100kW_{th}$, respectively, reveals no significant difference between the radiation levels of the research reactor site and the surrounding environment far away from it, from the radiation level aspect. Radiation dose and radioactivity were measured at monitoring points around the research reactor site of the Korea Atomic Energy Research Institute (KAERI) in Seoul and comparison points 0.5 km to 3.3 km from the site. To grasp trends in the radiation levels during dismantling from the end of 2002 to the end of 2007, the gamma radiation dose rate, the accumulated dose, and the radioactivity of the strontium, tritium, and gamma isotopes were statistically treated and estimated. The averages of these items between the two groups, the research reactor site and comparison points, were assessed by applying a T-test with a significance level of 0.05. P-values found by using the T-test were from 0.12 to 0.83 where the values were much higher than the significance level. As a result, no difference was observed between the radiation levels at the research reactor site and at the comparison points by this T-test. This study showed that dismantling activity of the Korea Research Reactor of the Seoul site did not expose the public or the environment to harmful levels of radiation.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
• /
• pp.241-245
• /
• 2009

High speed train system generates much EMI (electromagnetic interference) by arc between the pantograph and the trolley line during the running time. EMI from the tilted EMU train system which is similar to HEMU-400X system for 400 km/h speed and with the distributed engines was measured following EN50121-2, 'Railway applications. - Electromagnetic compatibility (Emission of the whole railway system to the outside world)'. Measured EMI values exceed the limiting values of EN50121-2 in high frequency band ($30\;MHz{\sim}1,000\;MHz$), but exceeding frequencies were identified that they are used for mobile communications. Measured EMI values did not exceed the limiting values in other low frequency band between 9 kHz and 30 MHz.

• 대한기계학회논문집A
• /
• 제39권3호
• /
• pp.303-309
• /
• 2015

본 연구에서는 무현가 복합소재 대차프레임의 철도차량 적용 가능성을 검토하기 위해 동특성 해석과 시험을 수행하였다. 복합소재 대차에서 윤축의 가이드 역할을 하는 고무부싱의 강성을 10MN/m에서 100MN/m까지 10MN/m 단위로 변화시키면서 차량 동특성을 해석적으로 평가하였다. 평가 결과 고무부싱의 강성이 40MN/m 이상에서는 성능요구조건을 만족하고 있음을 알 수 있었다. 또한, 81MN/m의 강성을 갖는 고무부싱을 제작하여 대차에 설치하고 주행 동특성 시험을 수행하였다. 시험결과 임계속도는 약 363km/h로 나타났으며, 주행 해석에서 얻은 330km/h와 약 10%의 오차를 보였다.

• 한국자동차공학회논문집
• /
• 제24권3호
• /
• pp.265-272
• /
• 2016

The objective of vehicle aerodynamic design is on the fuel economy, reduction of the harmful emission, minimizing the vibration and noise and the driving stability of the vehicle. Especially for a sedan, the driving stability of the vehicle is the main concern of the aerodynamic design of the vehicle indeed. In this theoretical study, an evaluation algorithm of aerodynamic driving stability of a vehicle was made to estimate the dynamic stability of a vehicle at the given driving condition on a road. For the stability evaluation of a driving vehicle, CFD simulation was conducted to have the rolling, pitching and yawing moments of a model vehicle and compared the values of the moments to the resistance moments. From the case study, it is found that a model sedan running at 100 km/h in speed on a straight level road is stable under the side wind with 45 m/s in speed. But the different results may be obtained on the buses and trucks because those vehicles have the wide side area. From the case study of the model vehicle moving on 100 km/h speed with 15 m/s side wind is evaluated using the numerical algorithm drawn from the study, the value of yawing moment is $608.6N{\cdot}m$, rolling moment $-641N{\cdot}m$ and pitching moment $3.9N{\cdot}m$. These values are smaller than each value of rotational resistance moment the model vehicle has, and therefore, the model vehicle's driving stability is guaranteed when driving 100 km/h with 15 m/s side wind.

• 한국대기환경학회지
• /
• 제12권1호
• /
• pp.15-21
• /
• 1996

Daily measutements of visibility on 09 LST have been made at a rural site in Chong-won, Chong-book since 1991 to find out a possible influence of emissions of anthropogenic pollutants and water vapout in urban and rural environments. Daily visibility data collected over four-year period were compared with the available visibility and air quality data obtainde from other stations. Detailed examinations of our data showed that the frequency of fog occurrence (visibility .leq. 1 km) at a rural site (KNUE) was at least three times higher (77 days per year) than the frequency of fog both in Chong-ju city (19 days) and at the Air Force Base(AFB) in the rural area. We interpret that the higher frequency of fog at KNUE was due to abundant water vapour in the Mieho River (upstream of the Keum River) area. In Chong-ju city, fog usually continued for a relatively long duration, while it dissipated simewhat faster in the rural environment due to higher solar radiation in the countryside area. The number of misty (.leg. 6 km) days (including foggy days) at KNUE were 235 days as compared with 135 days at the AFB and 67 days in Chong-ju city. In turn the number of days with low visibility (less than 6 km) at KNUE was about 64% per year. Since the moisture alone in a calm morning does not produce a visibility impairment, there must had abundant condensation nuclei including anthropogenic air pollutants. Air pollution was examined, for instance, average values of TSP for November and December 1993 were 115 and 116.mu.g/m$^{3}$, respectively. We conclude that the above mentioned environmental conditions with moisture are favourable for the formation of fog and mist in the rural sampling site at KNUE. Additionally, we found at least 10 days of acid fog at KNUE in September 1994 alone. Measured pH values in the acid for water were in the range of 4.36 .sim. 5.01 with the mean value of 4.51 Our observations suggested that strikingly acid fog do occur occasionally even in the rural environment.