• 대한기계학회논문집B
• /
• 제36권1호
• /
• pp.61-66
• /
• 2012

본 연구에서는 NACA0014 천음속 익형 유동에 있어서 비평형 응축이 Terminating shock 의 진동에 미치는 영향을 TVD 수치해석을 통하여 연구하였다. 주류 마하수 0.81-0.87 에 대해 정체점 상대습도가 유동 특성에 미치는 영향이 구명되었다. 받음각 ${\alpha}=0^{\circ}$ 정체점 온도(288K) 및 주류 마하수가 동일한 경우, 정체점 상대습도의 증가는 Terminating shock 의 충격파 강도를 약화시키고 충격파의 진동수도 감소시킨다. 정체점 상대습도가 동일한 경우는 주류 마하수가 클수록 충격파의 진동수는 증가한다. 정체점 상대습도가 동일한 경우, 충격파의 이동거리는 주류 마하수가 클수록 증가하는 것으로 나타났다. 특히, 충격파가 동일한 x/c 에 위치하는 경우, Terminating shock 의 충격파 강도는 충격파가 상류로 이동할 때가 하류로 이동할 때보다 강하게 된다.

• 한국작물학회:학술대회논문집
• /
• 한국작물학회 2017년도 9th Asian Crop Science Association conference
• /
• pp.250-250
• /
• 2017

Studies were conducted to select the optimum sowing date and planting density of sesame in the middle area of Korea. To select the optimum sowing date, sesame seeds sowed from 20 April to 7 July with 15-day intervals. To select the optimum planting density, sesame seeds investigated under four different planting distances ($30{\times}10,\;30{\times}15,\;30{\times}20$, and $30{\times}25cm$)respectively in the experimental field. As seeding date was delayed, days to emergence were shortened flowering and maturing date were delayed. Delayed sowing date resulted in decreased length, capsule setting stem length and number of capsules, and branchs per plant. Number of Capsules was high sowing date on 5 May in the range of 90~95ea/plant in sesame. Also yield of sesame seeds was most high on 5 May in the range of 142kg/10a by sowing date. Sowing date up to 5 May showed no effect on grain yield, but from 5 June to 5 July decreased 27%, 68% and 86%, respectively. For all planting distances, weight of 1,000 grain was not significantly different. However, number of branches and capsules tended to increase. Number of Capsules was high planting distance of $30{\times}20cm$ and $30{\times}25cm$ in the range of 146.7~165.7ea/plant in the Geonbaekkae. Areumkkae also showed the same tendency on planting distance of $30{\times}20cm$ and $30{\times}25cm$ in the range of 122.0~147.5ea/plant, respectively. Yield of Geonbaekkae and Areumkkae seeds was most high 116kg/10a, 117kg/10a, respectively on planting distance $30{\times}20cm$. Decreased in the planting distance of sesame has increased the incidence of disease and lodging. Based on the results, we suggest a planting distance of $30{\times}20cm$ maximal growth and yield of sesame in the middle area of Korea. Considering growth characteristics, sesame yield ability, the optimum sowing date was 5 May and optimum planting pattern was founded to be two rows planting in one ridge and planting densities was $30{\times}20cm$.

• Wind and Structures
• /
• 제30권2호
• /
• pp.181-198
• /
• 2020

In the traditional buffeting response analysis method, the spanwise incomplete correlation of buffeting forces is always assumed to be same as that of the incident wind turbulence and the action of the signature turbulence is ignored. In this paper, three typical bridge decks usually adopted in the real bridge engineering, a single flat box deck, a central slotted box deck and a two-separated paralleled box deck, were employed as the investigated objects. The wind induced pressure on these bridge decks were measured via a series of wind tunnel pressure tests of the sectional models. The influences of the wind speed in the tests, the angle of attack, the turbulence intensity and the characteristic distance were taken into account and discussed. The spanwise root coherence of buffeting forces was also compared with that of the incidence turbulence. The signature turbulence effect on the spanwise root coherence function was decomposed and explained by a new empirical method with a double-variable model. Finally, the formula of a sum of rational fractions that accounted for the signature turbulence effect was proposed in order to fit the results of the spanwise root coherence function. The results show that, the spanwise root coherence of the drag force agrees with that of incidence turbulence in some range of the reduced frequency but disagree in the mostly reduced frequency. The spanwise root coherence of the lift force and the torsional moment is much larger than that of the incidence turbulence. The influences of the wind speed and the angle of attack are slight, and they can be ignored in the wind tunnel test. The spanwise coherence function often involves several narrow peaks due to the signature turbulence effect in the high reduced frequency zone. The spanwise coherence function is related to the spanwise separation distance and the spanwise integral length scales, and the signature turbulence effect is related to the deck-width-related reduced frequency.

• 한국정보통신설비학회:학술대회논문집
• /
• 한국정보통신설비학회 2009년도 정보통신설비 학술대회
• /
• pp.104-107
• /
• 2009

In this paper, we analyze the effect of interference between DTV system and IEEE 802.11n. We set DTV as a victim receiver and IEEE 802.11n as an interfering system. When they exist in the same area, they can make an interference effect. Therefore, we calculate a minimum coupling loss (MCL) and compare the resulting value with a path loss for determining whether there exists a potential interference or not. The minimum separation distance is determined when the path loss is larger than the MCL.

• Journal of Advanced Marine Engineering and Technology
• /
• 제28권3호
• /
• pp.413-422
• /
• 2004

The flow characteristic in the wake around a circular cylinder with tripping wires, which was set in constant distance, was experimentally investigated in the uniform flow, Re=2.92$\times10^4$. The measurement of velocity vector and pressure distribution are carried out various angles of tripping wires in the range of $50^(\circ)$ to $80^(\circ)$ with $10^(\circ)$ interval. The results show that velocity profiles and pressure distributions are different with angles of tripping wires. The drag of the circular cylinder was decreased about 60% maximum when tripping wires' angle was $50^(\circ)$. The lowest reduction of the velocity and wake width was occurred by coanda effect when the angle was $60^(\circ)$, and the vortex shedding periodicity become rare at the same time.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
• /
• pp.267-271
• /
• 1987

The test cell for preventing the edge effect reducing the intrinsic breakdown strength of polypropylene film and measuring the intrinsic breakdown strength of the film was developed. The new approach was to develope an electrode system with an edge region which is carefully graded over an extended distance. The new test arrangement employed a central circular electrode at high voltage and a set of nine concentric surrounding rings each controlled in potential by external grading resistors to be at decreasing potentials from that at the center in 10% increments. Two different size structures using the same basic principle were tried and were both found to be successful. The test electrodes were manufactured using standard printed circuit technology and were chosen to be copper on high dielectric constant GIO board.

• 한국콘텐츠학회논문지
• /
• 제10권1호
• /
• pp.192-201
• /
• 2010

본 연구에서는 영상 콘텐츠의 표현밀도를 화면의 해상도와 피사체와의 거리감으로 정의하고, 표현밀도가 보는 이에게 미치는 감정의 변화를 살펴보고자 하였다. 부산지역 대학교에 재학 중인 학생 61명에게 HDTV방송화면에서 캡처한 영상이미지를 제시하고, 즐거움, 흥분, 통제 3가지 차원의 감정측정을 위해 SAM평가를 실시하였다. 서로 다른 해상도에 대한 비교결과 저해상도보다 고해상도의 콘텐츠 이미지를 볼 때 즐거운, 흥분되는, 통제되지 않는 방향으로 나타났다. 또한 해상도가 연속해서 동일할 때보다 변화가 있을 때 감정 변화 폭이 크게 나타났는데, 고해상도를 보다가 저해상도 이미지를 볼 때 감정이 유쾌하지 않은, 차분해지는 경향을 볼 수 있었다. 그러나 통제 감정에 대해서는 유의미한 결과가 나타나지 않았다. 또한 피사체와의 거리감에 대해 근거리, 중거리, 원거리를 사후다중비교 결과 근거리의 경우 다른 경우들 보다 즐거운, 흥분되는, 통제되지 않는 감정의 값이 더 높아졌다. 다변량 검증결과 해상도와 거리감에 대한 즐거움과 흥분 감정차원은 정의 상관관계를 가지고 있는 것으로 나타났다.

• 동력기계공학회지
• /
• 제21권4호
• /
• pp.57-61
• /
• 2017

The vehicle label fuel economy is used as an energy management indicator nationwide. It induces technology development of automobile manufacturers and plays a role of providing information when purchasing a consumer vehicle. However, consumers who purchase a new vehicle continued to complain that the label fuel economy is different from the mandatory fuel economy rate. The domestic fuel economy measurement method is the same as the North American measurement method. The results of the two test modes (urban (FTP-75 mode), highway (HWFET mode)) are calculated in five test modes reflecting various environmental conditions and driving patterns 5-cycle correction formula is used which is equivalent to the fuel efficiency value. In this study, to solve the consumers' curiosity about the fuel economy of new vehicle, we use domestic fuel economy measurement method to measure the new car condition within 150 km of driving distance and the cumulative driving distance condition of domestic label fuel economy test vehicle. A comparative evaluation of fuel economy was carried out for a durability vehicle of $6,500{\pm}1,000km$. A result, mean value of the fuel economy of the four gasoline vehicles increased by 2.7 % in the city center mode and by 2.5 % in the highway mode in the durable vehicle compared new vehicle. And in the case of the diesel vehicle it increased by 2.5 % and 3.9 % respectively. The harmful exhaust gas emitted from the vehicle also resulted in more emissions of both gasoline and diesel vehicles in new vehicles. It is considered that the increase of the frictional force of the vehicle driving system and the lubricating oil system would have an effect on the reduction of the fuel economy of the new vehicle, and it was found that the fuel economy and the exhaust gas were improved by proper cumulative distance (domesticate) to the new vehicle.

• 대한조선학회논문집
• /
• 제54권3호
• /
• pp.250-257
• /
• 2017

It is desirable to have a way to predict the pressure drag due to various appendages attached to stern. As a mathematical model for these, a sphere and a singularity behind it, both in the uniform flow can be considered. We may use the Butler's sphere theorem to find the Stokes' stream function when the resulting flow is axisymmetric, and then the extended Lagally's theorem to get the force upon the sphere due to the singularity. Assuming the separation distance between the sphere and the singularity is small, the leading order approximation for the force is obtained and it is found out that if the separation distance and the square root of the strength of the dipole are of the same order, the effect of the image of the dipole with respect to the sphere is the most important.

• 한국임상수의학회지
• /
• 제16권1호
• /
• pp.182-188
• /
• 1999

This study was performed to determine the causes of the bursting casualties such as death of sows and piglets, abortion, still birth and infertility in a pig farm after consecutive detonation for three months to construct 345 KV in Kimje area. 1. Temperatures in Kimje district, management condition, microorganism in the feed, inbreeding, hematological conditions, and viral agent causing abortion were not proved as the factors of acute occurrence of abortion and infertility in the pig farm. 2. The amount of explosive was increased from 250 kg to 1,100 kg from 23 Dec. 1996 to 28 Jan. 1997 and at the same time the distance between the spot of detonation and the pig farm got closer, from 200 m at the begining to 100 m at the last detonation. 3. Theoretical concussion and sound values were 0.66 kine and 89.39 ㏈, respectively, in the case of 100 m distance between the detonation spot and the pig farm. In conclusion, death of 675 piglets and 11 sows and infertility of 69 sows in the pig farm were assumed to be caused by the concussion or sound stress after detonation.