• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.471-491
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• 2016

Traditional limit equilibrium method needs an assumption of the failure surface to calculate the bearing capapcity of the shallow foundation. From the viewpoint of the mechanics of granular materials, however, the failure of the soil mass is initated by the local buckling of the contact force chains. In this study we observed the directional distribution of the contact force chains in the granular assembly stacked by model particles subjected to the model shallow foundation during loading. Two sets of the assemblies with a regular structure and initially local imperfection were prepared for tests. Existence of the initial local imperfection has a significant effect on the directional distribution of the contact force chains. The bearing capacity of the assembly with local imperfection is only 67% the capacity of the assembly with the regular structure.

• Journal of Korean Society of Steel Construction
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• v.13 no.2
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• pp.201-210
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• 2001

A numerical analysis and experimental study were performed to investigate the behavior and strength of tube-gusset connection subjected to axial and lateral forces. To investigate the behavior of the connections, experiment was conducted by applying three directional loads. Local buckling and local plastic bending deformation of the connection were observed from the test. Analytical results were compared with test results for the limited cases. Primary interests here are the effect of eccentricity on the strength of the connection. To suggest a formula for the strength of tube-gusset connection, lateral forces were replaced with equivalent wall moment and eccenrtric vertical component force of lateral force. Ultimate strength formula for the each force was proposed. Finally, nondimensionalized ultimate strength interaction relationships between the wall moment of tube($M_w$), vertical axial force($P_v$), and eccentric vertical component of lateral force($P_e$) were formulated through parametric study.

• Journal of Mechanical Science and Technology
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• v.18 no.1
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• pp.132-144
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• 2004

This paper presents a new method driving multiple robots to their goal position without collision. To consider the movement of the robots in a work area, we adopt the concept of avoidability measure. The avoidability measure figures the degree of how easily a robot can avoid other robots considering the velocity of the robots. To implement the concept to avoid collision among multiple robots, relative distance between the robots is proposed. The relative distance is a virtual distance between robots indicating the threat of collision between the robots. Based on the relative distance, the method calculates repulsive force against a robot from the other robots. Also, attractive force toward the goal position is calculated in terms of the relative distance. These repulsive force and attractive force are added to form the driving force for robot motion. The proposed method is simulated for several cases. The results show that the proposed method steers robots to open space anticipating the approach of other robots. In contrast, since the usual potential field method initiates avoidance motion later than the proposed method, it sometimes fails preventing collision or causes hasty motion to avoid other robots. The proposed method works as a local collision-free motion coordination method in conjunction with higher level of task planning and path planning method for multiple robots to do a collaborative job.

• Journal of the Korean Society of Physical Medicine
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• v.3 no.3
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• pp.145-149
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• 2008

Purpose : The purpose of this study was evaluate the effects of vibration on joint position sense. Methods : The subjects were divided into vibration group(n=20) and control group(n=20). Vibration group was given local vibration on elbow joint for 15 minutes and control group was given resting 15 minutes by resting position. All subjects of each group were tested pre-post on maximal grip force and joint position sense. Results : Maximal grip force test and joint position sense test of vibration group was showed a significant difference between pre and post(p<0.05). Conclusion : There was a different change on maximal grip force and joint position sense.

• Journal of Korean Society of Steel Construction
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• v.23 no.2
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• pp.179-188
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• 2011

The performance-based design is highlighted as an alternative for the current design method, which cannot definitely specify the performance level that a building requires. Research on it is already in progress, however, in developed countries like the United States and Japan, to establish the basis for a performance-based design. Many studies on such design are also being conducted in South Korea, but South Korea still lags behind other countries in all-around technology. On the other hand, the column members, especially the lower external column, are affected by the variation of the axial force by overturning the moments in the case of lateral loads by earthquake. Varying the axial force can affect the time of local buckling and the ultimate behavior. Thus, in this study, the structural performance, such as the time of local buckling and the ultimate behavior, was analyzed through an experimental study on column members under varying axial force. The feasibility of a domestic study proposing a performance level with a story drift angle formed about a structural-performance-based steel structure design was also verified.

• Computers and Concrete
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• v.33 no.2
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• pp.195-204
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• 2024

Floor inertial forces are transferred to lateral force resisting systems through a diaphragm action during earthquakes. The diaphragm action requires floor slabs to carry in-plane forces. In precast concrete diaphragms, these forces must be carried across the joints between precast floor units as they represent planes of weakness. Therefore, diaphragm reinforcement with sufficient strength and deformability is necessary to ensure the diaphragm action for the floor inertial force transfer. In a shake table test for a three-story precast concrete structure, an unexpected local failure in the diaphragm flexural reinforcement occurred. This failure caused loss of the diaphragm action but did not trigger collapse of the structure due to a possible alternative path for the floor inertial force transfer. This paper investigates this failure event and its impact on structural seismic responses based on the shake table test and simulation results. The simulations were conducted on a structural model with discrete diaphragm elements. The structural model was also validated from the test results. The investigation indicates that additional floor inertial force will be transferred into the gravity columns after loss of the diaphragm action which can further result in the increase of seismic demands in the gravity column and diaphragms in adjacent floors.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.10
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• pp.919-926
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• 2011

The fin of high speed air vehicle is composed of skins and strong skeletons. In the flutter analysis, the eigenmodes of a fin are used for evaluating the unsteady aerodynamic force and the modal approach is applied for solving the flutter equation in both time and frequency domain. Therefore, the proper eigenmodes used for a modal flutter analysis should be chosen. For the appropriate choice of eigenmodes, when there exist local modes of a skin in the high modes, the effects of those modes on the unsteady aerodynamic force and flutter characteristics are anlalyzed.

• Journal of agricultural medicine and community health
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• v.41 no.4
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• pp.183-194
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• 2016

Objectives: The purpose of this study was to investigate the differences of capacity of local health organization to regional characteristics and the influence of organizational capacity on organizational performance. Methods: The study used the secondary data for 160 local public health organizations from $5^{th}$ Community Health Plans and 2009 Community Health Survey. The collected data were analyzed using one-way ANOVA and multiple regression analysis. Results: Work force and budget showed differences in regional size and elderly population rate. And consumer satisfaction and health care utilization showed differenced in work force and budget. The regression model with total number of employee, number of registered nurses, number of doctors and budget against consumer satisfaction was statistically significant (F=14.70, p=<.001), and number of registered nurses was identified as a factor influencing consumer satisfaction. This model also explained 20.5% of service satisfaction. The regression model for consumer satisfaction was statistically significant (F=45.98, p=<.001), and total number of employee nurses was identified as a factor influencing health care utilization. This model also explained 53.1% of utilization. Conclusions: The findings of this study imply that organizational capacity as work force and budget should be increased to improve the organizational performance as consumer satisfaction and health care utilization.

• Wind and Structures
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• v.32 no.4
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• pp.371-391
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• 2021

Tornadoes are the most devastating meteorological natural hazards. Many empirical and theoretical numerical models of tornado vortex have been proposed, because it is difficult to carry out direct measurements of tornado velocity components. However, most of existing numerical models fail to explain the physical structure of tornado vortices. The present paper proposes a new empirical numerical model for a tornado vortex, and its load effects on a low-rise and a tall building are calculated and compared with those for existing numerical models. The velocity components of the proposed model show clear variations with radius and height, showing good agreement with the results of field measurements, wind tunnel experiments and computational fluid dynamics. Normal stresses in the columns of a low-rise building obtained from the proposed model show intermediate values when compared with those obtained from existing numerical models. Local forces on a tall building show clear variation with height and the largest local forces show similar values to most existing numerical models. Local forces increase with increasing turbulence intensity and are found to depend mainly on reference velocity Uref and moving velocity Umov. However, they collapse to one curve for the same normalized velocity Uref / Umov. The effects of reference radius and reference height are found to be small. Resultant fluctuating force of generalized forces obtained from the modified Rankine model is considered to be larger than those obtained from the proposed model. Fluctuating force increases as the integral length scale increases for the modified Rankine model, while they remain almost constant regardless of the integral length scale for the proposed model.

• Asia-Pacific Journal of Business
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• v.13 no.3
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• pp.329-341
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• 2022

Purpose - The purpose of this study was to investigate consistency in estimating the number of vacant jobs using the two business labor force survey with two different time points of survey. Design/methodology/approach - We studied the cause of the differences in estimating the number of vacant jobs between the monthly sample and the new sample in business labor force survey. Findings - To summarize our findings, As the size of the company increases, the number of vacant jobs in the company also increases, and the probability that the number of vacant jobs in the company is zero decreases. The monthly sample was assessed to have a higher likelihood that the number of vacant jobs in the company was zero and the number of vacant jobs was considerable compared to the local sample. Research implications or Originality - Because local survey sample companies tend to minimize the number of vacant jobs even when they reply under the same conditions, the estimation result of the number of vacant jobs in the current monthly survey differs significantly from the estimation result of the local survey. Divergent "degrees of knowledge of question items," survey methodologies, or investigators could be the causes of the various response trends.