• 한국산림과학회지
• /
• 제94권2호통권159호
• /
• pp.108-111
• /
• 2005

This study was conducted to identify the road effect on small rodent populations within fragmented forest areas around the road from June to September 2002, in 9 study sites of Baekdugdaegan mountains, Korea. Two species of small rodents, Korean field mouse Apodemus peninsulae and striped field mouse Apodemus agrarius, were captured in this study. Korean field mouse preferred forest area, and striped field mouse generally has been found edge area around road. Mean body weight of Korean field mouse was significantly different, but that of striped field mouse was not between both distance from road. Korean field mouse is forest-dwelling species and their distribution is limited in forest area. In contrast, striped field mouse has wide distributional range around road. The effects of road is different in each small rodent species and their habitat preferences.

• 대한방사선치료학회지
• /
• 제25권2호
• /
• pp.175-180
• /
• 2013

목 적: 방사선치료에 있어 환자자세 설정(Set-up) 오차를 줄이기 위하여 많은 장비들이 개발되어 왔다. CBCT 촬영은 Set-up 오차를 줄이고, 정확한 치료를 수행하는 최신 방법 중 하나이다. CBCT의 조사야를 조절하여 영상의질(Image quality) 향상과 피폭선량을 측정하고 분석함으로써 임상에서 최적화하여 사용할 수 있는 치료조사야(Field size)를 제시하고자 한다. 대상 및 방법: Catphan phantom을 이용하여 Half fan, Full fan mode로 조사야를 2~16 cm까지 2 cm 간격으로 촬영하였다. Small field size (2 cm, 4 cm), Medium field size (8 cm, 10 cm), Large field size (14 cm 이상)으로 구분하여 Image quality를 평가하였다. CTDi는 CTDi phantom과 Ion chamber를 이용하여 측정 및 분석하였다. 결 과: CT값 일치도(CT number linearity)는 Small, Large field size에서 촬영한 값이 Medium field size보다 크게 나타났다. 공간분해능(Spatial resolution)은 Full fan에서 Small field size촬영을 제외하고 나머지 Field size에서 크게 차이가 나지 않았다. Half fan에서는 많은 차이를 보였다. CT 값 균일도(HU uniformity)는 Full fan에서는 Medium size를 제외하고는 제조사에서 권고하는 값을 초과하였으며, Half fan에서는 모든 Field size가 Full fan에서는 Medium field size에서는 안정된 값으로 분석되었다. CT 피폭선량(CTDi)는 Medium field size에서 증가 할수록 루트함수의 그래프의 형태로 나타났다. 결 론:Small field size에서는 Image quality와 실용성의 측면에서도 적절하지 않은 것으로 사료된다. Medium field size는 Large field size에서 보다 Image quality도 우수하고 환자의 피폭선량을 줄일 수 있으므로 본 논문에서는 CBCT 촬영 시 Field size 8~10 cm 촬영이 유용하다고 사료된다.

• 한국유체기계학회 논문집
• /
• 제14권6호
• /
• pp.5-10
• /
• 2011

Recently, small hydropower attracts attention because of its renewable, clean and abundant energy resources to develop. Therefore, a tubular type hydro turbine is proposed for small hydropower in this study because the turbine has relatively simple structure and high possibility of applying to small hydropower. The purpose of this study is to investigate the performance characteristics of the turbine by field test. Field test iss conducted using one tubular turbine system as well as serial arrangement system by two tubular turbines taking into consideration of actual operation conditions. The results show that efficiency of test turbine changes considerably by the runner vane angle. Best efficiency of one turbine arrangement is higher than that of two turbine serial arrangement.

• 천문학회지
• /
• 제29권spc1호
• /
• pp.155-158
• /
• 1996

Magnetic fields correlated on several kiloparsec scales are seen in spiral galaxies. Their origin could be due to the winding up of a primordial cosmological field or due to amplification of a small seed field by a turbulent galactic dynamo. Both options have difficulties: There is no known battery mechanism for producing the required primordial field. Equally the turbulent dynamo may self destruct before being able to produce the large scale field, due to excess generation of small scale power. The current status of these difficulties is discussed. The resolution could depend on the nature of the saturated field produced by the small scale dynamo. We argue that the small scale fields do not fill most of the volume of the fluid and instead concentrate into intermittent ropes, with their peak value of order equipartition fields, and radii much smaller than their lengths. In this case these fields neither drain significant energy from the turbulence nor convert eddy motion of the turbulence on the outer scale to wave like motion. This preserves the diffusive effects needed for the large scale dynamo operation.

• 한국환경농학회지
• /
• 제30권1호
• /
• pp.37-42
• /
• 2011

본 연구의 목적은 논의 중간 낙수 기간 동안 미꾸라지의 이동 특성을 살펴보는 것이다. 실험 결과, 미꾸라지는 중간 낙수 초기에는 배수로 쪽으로 수로가 형성되어 둠벙보다는 배수로 쪽으로 이동하는 경향이 있었다. 전체 표지한 미꾸라지 중 약 3.0%가 배수초기에 배수로를 통해 농업용 배수로로 이동한 것으로 나타났다. 중간 낙수가 완료되어 논에 물이 없는 시기에는 전체 표지 미꾸라지 중 5.0%의 미꾸라지가 둠벙으로 이동하여, 중간 낙수기간 동안 둠벙을 피난처로 이용한다는 것을 알 수 있었다. 실험기간동안 표식한 미꾸라지 중 논 바닥을 파고들어 가는 것은 채집되지 않았다. 둠벙이 있는 논에서는 바닥을 파고 들어가기보다는 둠벙으로 이동하는 것을 선호한 것인지 아니면 표식에 의한 스트레스로 바닥을 파고들어갈 힘이 부족했던 것인지에 대해서는 추가적인 연구가 필요하다. 둠벙과 논에서 채집한 미꾸라지의 소화관 내용물을 분석한 결과, 둠벙에서는 동물성 먹이가 86.1%, 식물성 먹이가 13.9%를 차지하여 동물성 먹이가 매우 우세하였다. 둠벙에서 채집된 미꾸라지 중 90% 이상이 먹이를 섭식하고 있었으며 10% 정도가 공복상태를 보이고 있어 표식 후 방류한 미꾸라지가 둠벙에서 정상적인 섭식 활동을 한 것으로 사료된다. 반면 논에서 채집된 미꾸라지는 모든 개체가 공복 상태를 보이고 있어 섭식활동에 장애를 받은 것으로 나타났다.

• Journal of Biosystems Engineering
• /
• 제24권2호
• /
• pp.135-144
• /
• 1999

An yield monitoring system plays a key role in precision farming. An yield monitoring system and a DGPS were implemented to a widely used domestic combine for yield mapping of a small sized paddy field, and yield mapping algorithms were investigated in this study. The yield variation in the 0.1ha rice paddy field was measured by installing a yield flow sensor and a grain moisture sensor at the end of the clean grain elevator discharging grains into a grain tank. Yield map of the test filed was drawn in a point map and a linear interpolated map based on the result of the field test. The size of a unit yield grid in yield mapping was determined based on the combine traveling speed, effective harvesting width and data storing period. It was possible to construct the yield map of a small sized paddy field.

• 한국전자파학회논문지
• /
• 제28권11호
• /
• pp.916-919
• /
• 2017

본 논문에서는 모바일 기기용 소형 금속 캔으로부터 발생하는 전자기장의 누설 경로를 시뮬레이션을 통해 확인하고, IC-stripline 방법을 이용하여 전기장 및 자기장에 대한 근접장 결합(coupling) 현상을 분석하였다. 금속 캔의 윗면 개구부에 의한 전자기장 누설은 주로 자기장이 우세하고, 측면을 통한 누설은 전기장이 우세함을 확인하였다.

• Coupled systems mechanics
• /
• 제12권2호
• /
• pp.167-181
• /
• 2023

The determination of the blast protection level and the corresponding minimum load-bearing capacity for a laminated glass (LG) window is of crucial importance for safety and security design purposes. In this paper, the focus is given to the window response under near-field blast loading, i.e., where relatively small explosives would be activated close to the target, representative of attack scenarios using small commercial drones. In general, the assessment of the load-bearing capacity of a window is based on complex and expensive experiments, which can be conducted for a small number of configurations. On the other hand, nowadays, validated numerical simulations tools based on the Finite Element Method (FEM) are available to partially substitute the physical tests for the assessment of the performance of various LG systems, especially for the far-field blast loading. However, very little literature is available on the LG window performance under near-field blast loads, which differs from far-field situations in two points: i) the duration of the load is very short, since the blast wavelength tends to increase with the distance and ii) the load distribution is not uniform over the window surface, as opposed to the almost plane wave configuration for far-field configurations. Therefore, the current study focuses on the performance assessment and structural behaviour of LG windows under near-field blasts. Typical behavioural trends are investigated, by taking into account possible relevant damage mechanisms in the LG window components, while size effects for target LG windows are also addressed under a multitude of blast loading configurations.

• ETRI Journal
• /
• 제29권2호
• /
• pp.135-142
• /
• 2007

The small anechoic chambers built by many small-/medium-sized companies and universities present difficulties in testing electrically large antennas because the chamber size cannot satisfy the far-field criterion of large antennas. In this paper, a method for Fresnel-region measurement on a cylindrical surface with variation of the measurement height is proposed and verified by both calculations and experiments. We implement the proposed method using a direct far-field measurement system by adding a few supporting structures. The results show good accuracy.

• 한국농공학회논문집
• /
• 제46권3호
• /
• pp.3-14
• /
• 2004

A two-dimensional numerical model based on a finite volume method was formulated to solve the shallow water equations and applied for evaluating drainage characteristics at large-sized paddy fields. Manning roughness coefficient was calibrated using the observed inundating depths at drainage tests, and used for validating the model with the results from another drainage test. The simulated results were in good agreement with the observed inundating depths. The result of surface drainage showed that the longer width of the outlet was or the more the number of drainage outlet was, the shorter the drainage time was taken, and the larger the size of the field become, the longer the drainage time was taken, and the field shape had little effect on drainage time. To reduce the drainage time to 24 hours, the outlet is located lower than the elevation of the basin and small drainage ditch is constructed at the field. The results showed that the drainage time was taken short as the small drainage ditch was constructed. The comparison of drainage time as to the size of field constructed small drainage ditch showed the field, 100m ${\times}$ 200 m, can be drained in 24 hours.