• Geomechanics and Engineering
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• v.35 no.4
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• pp.425-436
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• 2023

An effective tool for researching actual problems in geotechnical and mining engineering is to conduct physical modeling tests using similar materials. A reliable geometric scaled model test requires selecting similar materials and conducting tests to determine physical properties such as the mixing ratio of the mixed materials. In this paper, a method is proposed to determine similar materials that can reproduce target properties using a polynomial model based on experimental results on modeling materials using a gypsum-sand mixture (GSM) to simulate rocks. To that end, a database is prepared using the unconfined compressive strength, elastic modulus, and density of 459 GSM samples as output parameters and the weight ratio of the mixing materials as input parameters. Further, a model that can predict the physical properties of the GSM using this database and a polynomial approach is proposed. The performance of the developed method is evaluated by comparing the predicted and observed values; the results demonstrate that the proposed polynomial model can predict the physical properties of the GSM with high accuracy. Sensitivity analysis results indicated that the gypsum-water ratio significantly affects the prediction of the physical properties of the GSM. The proposed polynomial model is used as a powerful tool to simplify the process of determining similar materials for rocks and conduct highly reliable experiments in a physical modeling test.

• The Journal of Korean Physical Therapy
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• v.12 no.1
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• pp.41-47
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• 2000

BACKGROUND AND PURPOSE. The purpose of this study is to investigate the effect of the disturbed vision on the gait distance parameters on the healthy young population. SUBJECTS. Twenty four healthy college aged individuals are randomly assigned to both a condition with a strobe light and the other condition without a strobe light. METHODS. The instrumentation used for gait analysis is the GaitRite electronic walkway system with a personal IBM computer. The examiner naked all the subjects to walk 6 times on the gait mat without the strobe light and. 6 times on the mat with the strobe light. The first 4 trials were practice and the last two trials were recorded in both conditions. The gait parameters analyzed were as follows : velocity, cadence, step length, and heel to heel base of support. RESULTS. Paired samples t-test used for this study did not found any significant differences between the two conditions because the p-values that were analyzed on the experiment were Utter than 0.05. The gait parameters that were analyzed included cadence, velocity, left and right heel to heel base of support, and left and right step length. DISCUSSION AND CONCLUSION. Based on this population, the condition of disturbed vision via the effect of the strobe light was not significantly challenging to compromise the body's sensory systems. However, in the elderly population, these systems can undergo age related changes. Visual changes rapidly decline in people 60 to 80 years of age and changes in the vestibular system include $20-40\%$ reduction in hair cells.

• Journal of the Korean GEO-environmental Society
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• v.11 no.12
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• pp.63-74
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• 2010

Normally consolidated and slightly overconsolidated soft clay layer is widely distributed in the south coast of Korea. To ensure the efficient and economical construction design of any structure to be built on this soft soil, exhaustive studies related to geotechnical and physical engineering properties are required. In this study, the relationship of the physical properties of southern Gwangyang marine clay in the Korea Peninsula were examined, including natural water content, specific gravity, total unit weight, initial void ratio, liquid limit, plastic limit, and physical properties of activity and soil parameters. For the parameter relationship analysis, the latest relatively reliable data on the large harbor construction work were used, optimum values were deducted with linear regression and non-linear regression between soil parameters, water content or initial void ratio appears to be very large. Moreover, in the linear and involution pattern regression, equal coefficient of determination appeared. The relationship of the different parameters was shown to be excellent in the non-linear regression of involution equation and exponential equation pattern compared with the findings of linear regression analysis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.9
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• pp.892-899
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• 2013

This paper discusses difficulties in precise measurements of the scattering parameters in (sub-)millimeter-wave range and tips for more accurate measurements, and provides measurement examples in the G-band(140~220 GHz). First, one investigates the differences in operating principles of scattering parameters measurement systems used in microwave and (sub-)millimeter-wave ranges and describes tips for better operation of the (sub-)millimeter-wave scattering parameters measurement system. In addition, one describes tips for better transmission properties and connection repeatability of waveguides and a precise measurement method for devices with small reflection coefficients.

• Nuclear Engineering and Technology
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• v.41 no.5
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• pp.677-690
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• 2009

A previous study demonstrated that the two-row fuel assembly has much more favorable neutron-physical and thermal-hydraulic behavior than the conventional one-row fuel assemblies. Based on the newly developed two-row fuel assembly, an SCWR core is proposed and analyzed. The performance of the proposed core is investigated with 3-D coupled neutron-physical and thermal-hydraulic calculations. During the coupling procedure, the thermal-hydraulic behavior is analyzed using a sub-channel analysis code and the neutron-physical performance is computed with a 3-D diffusion code. This paper presents the main results achieved thus far related to the distribution of some neutronic and thermal-hydraulic parameters. It shows that with adjustment of the coolant and moderator mass flow in different assemblies, promising neutron-physical and thermal-hydraulic behavior of the SCWR core is achieved. A sensitivity study of the heat transfer correlation is also performed. Since the pin power in fuel assemblies can be non-uniform, a sub-channel analysis is necessary in order to investigate the detailed distribution of thermal-hydraulic parameters in the hottest fuel assembly. The sub-channel analysis is performed based on the bundle averaged parameters obtained with the core analysis. With the sub-channel analysis approach, more precise evaluation of the hot channel factor and maximum cladding surface temperature can be achieved. The difference in the results obtained with both the sub-channel analysis and the fuel assembly homogenized method confirms the importance of the sub-channel analysis.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.498-508
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• 2015

In the simulation of photovoltaic (PV) power conditioning systems, PSIM is a widely accepted circuit simulation platform because of its fast speed and C-code support. PSIM provides two kinds of generic PV panel models: functional model and physical model. Whereas the functional model simulates PV in the standard test condition (STC) only, the physical model can emulate changing PV characteristics under varying temperatures and irradiation conditions and is thus more suitable for system simulation. However, the physical model requires complicated parameters from users, and thus it is prone to errors and is difficult to use. In this study, a new PSIM model for PV is presented to solve these problems. The proposed model utilizes manufacturers' datasheet values specified under STC only and excludes user-defined information from input parameters. To achieve good accuracy even in varying environmental conditions, single-diode model parameters are successively tuned to a time-varying virtual datasheet. Comparison with a conventional physical model shows that the proposed model provides more accurate simulation according to error analysis based on the EN50530 standard.

• Physical Therapy Rehabilitation Science
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• v.10 no.3
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• pp.270-277
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• 2021

Objective: The purpose of this study is to compare the effect of static balance, lower extremity function, and gait ability between a lower extremity restrain robot gait training and a general robot gait training in subacute stroke subjects. Design: Two-group pretest-posttest design. Methods: A total of 12 subacute stroke patients were randomly divided into an Experimental group (n=6) and a control group (n=6). Both groups were performed for four weeks, three times a week, for 20 minutes. To compare the Static balance function, the center of pressure (COP) path-length and COP velocity were measured. The Fugl-Meyer assessment lower extremity (FMA-LE) were evaluated to compare the Lower Extremity function. 2D Dartfish Program and 10 Meter Walking Test (10 MWT) on Gait ability were evaluated to compare the gait function. Results: In the intra-group comparison, Experimental groups showed significant improvement in COP path-length, velocity, Lower Extremity Function, 10 MWT, Cadence, by comparing the parameters before and after the intervention (p<0.05). Comparison of the amount of change between groups revealed significant improvement for parameters in the COP path-length, velocity, Lower extremity function, 10 MWT by comparing the parameters before and after the intervention (p<0.01). Conclusions: The Experimental group showed enhanced efficacy for variables such as COP path-length, velocity, Lower extremity function, 10 MWT as compared to the control group.

• PNF and Movement
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• v.22 no.1
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• pp.91-99
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• 2024

Purpose: Backward walking has shown positive effects on gait recovery in rehabilitation patients. It is increasingly used as an aerobic training method in rehabilitation populations, inducing more sensory and motor stimulation than forward walking. Therefore, the purpose of this study is to investigate the effects of visual stimulation during backward walking. Methods: Twenty-seven healthy adults with a visual acuity of 0.8 or higher participated in the study. To compare the effects of visual stimulation during various walking conditions among healthy individuals, the participants randomly selected cards numbered one to six and walked a distance of 10 meters. Walking ability was measured using Optogait. Results: Statistically significant differences were observed in speed, stride, and percentages of single support and contact phase during backward walking. Within eyes-closed conditions during backward walking, significant differences were found in percentages of single support, terminal stance, and contact phase. Moreover, the percentage of terminal swing significantly differed during backward walking with head turn conditions. Conclusion: Gait parameters such as speed, stride, and percentages of single support and contact phase were higher during backward walking than forward walking. These results indicate that backward walking involves multiple sensory systems and varying conditions.

• Journal of the Korean Society of Physical Medicine
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• v.2 no.1
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• pp.73-84
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• 2007

Purpose : The purpose of this study was to determine risk factors and methods in balance assessment associated with fall in older adults. Methods : This article describes many of the tools that can be used to evaluate the physical parameters associated with fall risk in older adults. Results : Composite ratings of performance(Tinetti balance assessment, Guralnik test battery, Berg balance scale, modified-physical performance test) measures the score compounding the balance measure to determine fall risk. Static balance instruments are composed of FICSIT-4 that measures the ability of maintaining foot positions and CTSIB that measures postural stability. Dynamic balance instrument is composed of functional reach test. To measure walking velocity and mobility, 8-foot up-and-go test and walking around two cones are used. We can use 1-RM and to measure muscular strength, isokinetic dynamometery, and 30-second chair stand to measure lower extremity muscle strength. Conclusion : The described instruments are easy to use and widespread. To select and use these tool kits carefully is considered to be helpful in identifying those who are most likely to fall. The final part of the article includes a brief discussion of the potential role of exercise training interventions to improve these physical parameters and prevent falls.

• The Journal of Korean Physical Therapy
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• v.18 no.4
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• pp.27-40
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• 2006

Purpose: This study was to investigate the effect of an arm sling on gait with hemiparesis. Methods: Fifteen patients(8 male, 7 female) with hemiparesis participated in this study and walked self-selected speed over 10m walkway, randomly without arm sling, with Single strap hemisling and Rolyan humeral cuff sling. It were filmed by 5 video camera and used with 3-dimensional motion analyzer system. The following gait variables were analyzed: temporo-spatial parameters, kinematic parameters. Results: In the comparison of temporo-spatial parameters each trial, walking velocity and single support time on affected side was significantly increased and step length on affected side, step length asymmetry ratio, single support time asymmetry ratio was significantly decreased in the Single strap hemisling and Rolyan humeral cuff sling. In the comparison of kinematic parameters each trial, maximal angle of the hip flexion on affected side was significantly increased in the Single strap hemisling and Rolyan humeral cuff sling and maximal angle of the knee flexion on affected side was significantly increased in the Rolyan humeral cuff sling and maximal angle of the ankle dorsiflexion on affected side was significantly increased in the Single strap hemisling. Conclusion: An arm sling improved walking velocity and decreased asymmetry and increased maximal angle of hip, knee, ankle flexion on affected side with hemiparesis caused by stroke.