• Geomechanics and Engineering
• /
• 제38권1호
• /
• pp.93-106
• /
• 2024

The present paper investigates the spatial variability effect of soil property on the three-dimensional probabilistic characteristics of the bearing capacity factor (i.e., mean and coefficient of variation) of a circular footing resting on clayey soil where both mean and standard deviation of undrained shear strength increases with depth, keeping the coefficient of variation constant. The mean trend of undrained shear strength is defined by introducing the dimensionless strength gradient parameter. The finite difference method along with the random field and Monte Carlo simulation technique, is used to execute the numerical analyses. The lognormal distribution is chosen to generate random fields of the undrained shear strength. In the study, the potential failure of the structure is represented through the failure probability. The influences of different vertical scales of fluctuation, dimensionless strength gradient parameters, and coefficient of variation of undrained shear strength on the probabilistic characteristics of the bearing capacity factor and failure probability of the footing, along with the probability and cumulative density functions, are explored in this study. The variations of failure probability for different factors of safety corresponding to different parameters are also illustrated. The results are presented in non-dimensional form as they might be helpful to the practicing engineers dealing with this type of problem.

• 제어로봇시스템학회논문지
• /
• 제8권9호
• /
• pp.812-817
• /
• 2002

This paper presents a development of high accuracy aligner and describes a method to find the orientation of a substantially circular disk shaped wafer with at least one flat region on an edge thereof. In the developed system, the wafer is spun one 360 degree turn on a chuck and the edge position is measured by a linear array to obtain a set of data points at various wafer orientation. The rotation axis may differ from wafer center by an unknown eccentricity. The flat angle is found by fitting a cosine curve to the actual data to obtain a deviation. The maximum deviation is then corrected for errors due to a finite number of data points and wafer eccentricity by calculating an adjustment angle from data points on the wafer fiat. After determining the flat angle the wafer is spun to the desired orientation. The wafer eccentricity can be calculated from four of the data points located away from the flat edge region. and the wafer is then centered.

• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
• /
• pp.192-197
• /
• 2003

It can be said that rock mass properties are characterized not by a mean value but by values with variation due to its characteristic uncertainty. This characteristic is one of the most important parts for the design of underground structures, but yet to be fully examined. Stochastic finite element method (SFEM) has been developed in order to take the randomness of structural systems into account. Using SFEM, the response variability of structural system can be obtained and it leads probabilistic stability of structure to be analyzed. In this study, displacements response variability of circular opening with hydrostatic stress field are analyzed in terms of rock mass properties having a certain mean and a standard deviation using the SFEM. The analyzed response variability shows that the necessity of probabilistic stability analysis of underground structures using reliable mean value and standard deviation of deformation modulus.

• 한국분무공학회지
• /
• 제28권2호
• /
• pp.97-104
• /
• 2023

A sprinkler is a fire suppression system that extinguishes combustible materials in the early stages of a fire, creating a spray. However, spray formation method of the sprinkler can result in an uneven distribution of water spray on the surface of combustible materials. It is necessary to ensure a consistent water flux density regardless of the spray direction and angle. In this study, the water flux distribution was analyzed for the various types of sprinkler head: circular, flush, pendent, and upright types. All sprinkler heads have a K-factor of 80 LPM/(0.1MPa)^0.5. In this study, water collection cubes were used to examine the water flux distribution. The upright type sprinkler head showed a low standard deviation in total sprayed area, indicating a high level of uniformity. The upright type head showed the lowest standard deviation in the radial direction, and also showed the lowest standard deviation in the azimuthal direction. Upright sprinkler head has no obstructing structure along the path of droplets after they are generated. For this reason, upright sprinkler head showed the most uniform water flux distribution on the floor.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 1997년도 가을 학술발표회 논문집
• /
• pp.203-210
• /
• 1997

• 대한의용생체공학회:의공학회지
• /
• 제38권4호
• /
• pp.197-204
• /
• 2017

The aim of this study was to evaluate driving performance of normal subjects for controlling the steering wheel by using foot operated steering devices in the driving simulator. Many people with complete bilateral loss or loss of use of upper limbs but with normal lower limbs are frequently left without use and/ or control of their hands, arms, or the upper extremities of their bodies. As a result, persons disabled in this manner have problems in operation an automobile because they cannot grasp and manipulate a conventional steering wheel. Therefore, if foot operated steering devices are used for controlling the vehicle on in people with disabilities, the disabled people could improve their community mobility by driving a car safely. Ten normal subjects were involved in this research to evaluate steering performance by using three types of steering devices(conventional steering wheel, pedal type foot steering, circular type foot steering) in driving simulator. STISim Drive 3 program was used for testing the driving performance in two road scenarios: straight road and curved road at low and high speed of vehicle (40 km/h and 80 km/h). This study used two-way ANOVA to compare the influences of two factors(type of foot steering device and road scenario) in the three dependent variables of steering performance(standard deviation of lateral position, the lateral position of vehicle and the number of line crossing). The average values of the three dependent variables(standard deviation of lateral position, lateral position and the number of line crossing) of driving performance were significantly smaller for conventional steering wheel or pedal type foot steering than circular type foot steering.

• 대한기계학회논문집
• /
• 제10권6호
• /
• pp.823-829
• /
• 1986

본 연구에서는 와동의 대류속도를 H.H. Brunn의 방법과 달리 측정하였으며, 또 이를 이용하여 와동의 중심들 사이의 간격을 구하고자 한다. 이를 위하여 먼저 포텐셜코어영역(potential core region)과 혼합층영역(mixing layer region)의 경계 및 천이영역(transition region)과 난류영역(turbulent region)경계를 구하여야 한다. 각 영역들의 대체적인 구분은 Fig.1과 같다.

• 대한기계학회논문집
• /
• 제18권12호
• /
• pp.3386-3394
• /
• 1994

An experimental study has been performed on the flow over a rotating disk, where the diameter of the disk is 500 mm and the maximum vertical deviation of the upper surface is $50 \mu{m}$ for the whole range of the angular velocity up to 3400 rpm. The flow visualization experiment for the wall jet flow induced by impinging circular jet is carried out using schlieren system and measurements are made by 3-hole and 5-hole pitot tubes. Schlieren photographs show that as the rotating speed increases the wall jet flow becomes more stable and the size of the largest eddies becomes smaller. Measurements for impinging jet flow on the stationary disk verify the accuracy of the present experiment, and those for free rotating disk flow display the existence of transition region from laminar to turbulent flows. Measurements for impinging jet flow on the rotating disk exhibit the interaction between the wall jet and the viscous pumping effect, which explains the decay in size of turbulent eddies illustrated by the schlieren photographs.

• 한국정밀공학회지
• /
• 제30권11호
• /
• pp.1171-1177
• /
• 2013

In this study, the torque transmitting capability of a flexible disk coupling was investigated. Flexible disc coupling is used to transmit power between two axes, and there exist mis-alignments such as angle of deviation and end play between two shafts. A disk is an important part in the flexible disk coupling because the disk has to transmit power between two mis-aligned shafts. To investigate the effect of mis-alignment on load carrying capacity, finite element analyses were carried out. Analyses were carried out for two types of disk; i.e., circular and square disks. The rotational and bending stiffness of disk plates was predicted to investigate the effect of mis-alignment on stress. As a result, it was shown that the mis-alignment can cause severe decrease in load-carrying capacity. And, the square disk showed better performance than the circular disk.

• Radiation Oncology Journal
• /
• 제7권2호
• /
• pp.299-303
• /
• 1989

Authors have developed highly reproducible calibration method for the Micro-Selectron HDR Ir-192 system (Nucletron, Motherland). The new jig has a 10cm radius circular hole in the $30cm{\times}30cm{\times}0.2cm$ acrylic plate, and 5F flexible bronchial tubes are attached around the hole. The source moves along the circle in the tubes and the ionization chamber is placed verticaly at the center of the circular hole (center of the jig). Dose distribution near the center was derived theoretically, and measured with the film dosimetry system. Theoretical calculation and measurement show the error margin below $0.1\%$ for 1mm or 2mm position deviation. We have measured at 12 and 24 points of circle with 1, 6, 11 and 21 second dwell time of source in order to calculate the activity of the source. Measurements have been repeated daily for 50 days. The accuracy and the reproducibility are below $1\%$ error margin. The half life of the source from our measurement is estimated $73.4\pm0.4$ days.