• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.4
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• pp.1337-1358
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• 2015

In this paper, we present an analytical and simulated study on the performance of adaptive vehicular ad hoc networks (VANET) priority based on Transmission Distance Reliability Range (TDRR) and data type. VANET topology changes rapidly due to its inherent nature of high mobility nodes and unpredictable environments. Therefore, nodes in VANET must be able to adapt to the ever changing environment and optimize parameters to enhance performance. However, there is a lack of adaptability in the current VANET scheme. Existing VANET IEEE802.11p's Enhanced Distributed Channel Access; EDCA assigns priority solely based on data type. In this paper, we propose a new priority scheme which utilizes Markov model to perform TDRR prediction and assign priorities based on the proposed Markov TDRR Prediction with Enhanced Priority VANET Scheme (MarPVS). Subsequently, we performed an analytical study on MarPVS performance modeling. In particular, considering five different priority levels defined in MarPVS, we derived the probability of successful transmission, the number of low priority messages in back off process and concurrent low priority transmission. Finally, the results are used to derive the average transmission delay for data types defined in MarPVS. Numerical results are provided along with simulation results which confirm the accuracy of the proposed analysis. Simulation results demonstrate that the proposed MarPVS results in lower transmission latency and higher packet success rate in comparison with the default IEEE802.11p scheme and greedy scheduler scheme.

• Geomechanics and Engineering
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• v.12 no.1
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• pp.139-160
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• 2017

The bearing mechanism of tunnel-type anchorage (TTA) for suspension bridges is studied. Model tests are conducted using different shapes of plug bodies, which are circular column shape and circular truncated cone shape. The results show that the plug body of the latter shape possesses much larger bearing capacity, namely 4.48 times at elastic deformation stage and 4.54 times at failure stage compared to the former shape. Numerical simulation is then conducted to understand the mechanical and structural responses of plug body and surrounding rock mass. The mechanical parameters of the surrounding rock mass are firstly back-analyzed based on the monitoring data. The calculation laws of deformation and equivalent plastic strain show that the numerical simulation results are rational and provide subsequent mechanism analysis with an established basis. Afterwards, the bearing mechanism of TTA is studied. It is concluded that the plug body of circular truncated cone shape is able to take advantage of the material strength of the surrounding rock mass, which greatly enhances its bearing capacity. The ultimate bearing capacity of TTA, therefore, is concluded to be determined by the material strength of surrounding rock mass. Finally, recommendations for TTA design are proposed and discussed.

• Journal of the Korean Magnetic Resonance Society
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• v.6 no.1
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• pp.20-37
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• 2002

MnAPSO-34 and Mn-impregnated SAPO-34(Mn-SAPO-34) sample were prepared with various manganese contents and studied by electron spin resonance(ESR) and electron spin echo modulation(ESEM). Electron spin echo modulation analysis of 0.07mo1 ％ Mn(relative to p) in MnAPSO-34 with adsorbed D$_{2}$O shows two deuteriums at 0.26 nm and two at 0.36 nm from Mn. This suggests that two waters hydrate an MnO$_{4}$ configuration with a D-O bond orientation for the waters as expect for a negatively charged site at low manganese content (0.1 mol％), the ESR spectra of MnAPSO-34 and MnH-SAPO-34 exhibit the same parameters(g 2.01 and A 89 G), but the spectra obtained from MnAPSO-34 samples are better resolved. The decomposition temperature of as-synthesized MnAPSO-34 were in the range of 200-600 $^{\circ}C$ of the morpholine which is 12 $^{\circ}C$ higher than that in as-synthesized MnH-SAPO-34. Infrared spectra showed that the position of a band at 3450 $cm^{-1}$ / shifted about 15 $cm^{-1}$ / toward higher energy in MnAPSO-34 versus MnH-SAPO-34. The modulation depth of the two-pulse ESE of MnAPSO-34 with adsorbed D$_{2}$O is deeper than that of MnH-SAPO-34 with adsorbed D$_{2}$O. Three-pulse ESEM of MnAPSO-34 and MnH-SAPO-34 with adsorbed deuterium oxide shows that the local environments of manganese in the hydrated samples are different, suggesting that Mn(II) is framework substituted in MnAPSO-34 since it obviously occupies an extraframework position in MnH-SAPO-34.

• Journal of the Korean Solar Energy Society
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• v.36 no.2
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• pp.65-72
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• 2016

PV module is installed in various outdoor conditions such as solar irradiation, ambient temperature, wind speed and etc. Increase in solar cell temperature within PV module aggravates the behaviour and durability of PV module. It is difficult to measure temperature among respective PV module components during PV module operating, because the temperature within PV module depends on thermal characteristics of PV module components materials as well as operating conditions such as irradiation, outdoor temperature, wind etc. In this paper, simulation by using finite element method is conducted to predict the temperature of each components within PV module installed to outdoor circumstance. PV module structure based on conventional crystalline Si module is designed and the measured values of thickness and thermal parameters of component materials are used. The validation of simulation model is confirmed by comparing the calculated results with the measured temperatures data of PV module. The simulation model is also applied to estimate the thermal radiation of PV module by front glass and back sheet.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.254-260
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• 2013

This paper deals with electromagnetic characteristics of IPMSM (Interior Permanent Magnet Synchronous motor) caused by field weakening current control. In order to extend operation speed, field weakening current control is generally used in IPMSM operation. During field weakening, distorted linkage fluxes are resulted by saturation of core material. Therefore, distorted input voltage waveform is required for sinusoidal current input. As the current vector angle increases for field weakening, distortion of linkage flux and back-emf becomes significant. This situation is analyzed by 2-dimensional finite element analysis and verified by experiment. With the results, it is concluded that motor parameters, such as linkage flux by permanent magnet, phase resistance, d-q axis inductance, are insufficient for estimating required voltage for given speed especially in field weakening and additional considerations for increased harmonics of voltage are required.

• Physical Therapy Korea
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• v.24 no.4
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• pp.1-10
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• 2017

Background: Flexion-relaxation phenomenon (FRP) was a term which refers to a sudden onset of myoelectric silence in the erector spinae muscles of the back during standing full forward flexion. Hamstring muscle length may be related to specific pelvic and trunk movements. Many studies have been done on the FRP of the erector spinae muscles. However, no studies have yet investigated the influence of hamstring muscle flexibility on the FRP of the hamstring muscle and lumbopelvic kinematics during forward bending. Objects: The purpose of this study was to examine the flexion-relaxation ratio (FRR) of the hamstring muscles and lumbopelvic kinematics and compare them during forward bending in subjects with different hamstring muscle flexibility. Methods: The subjects of two different groups were recruited using the active knee extension test. Group 1-consisted of 13 subjects who had a popliteal angle under $30^{\circ}$; Group 2-consisted of 13 subjects who had a popliteal angel above $50^{\circ}$. The kinematic parameters during the trunk bending task were recorded using a motion analysis system and the FRRs of the hamstring muscles were calculated. Differences between the groups were identified with an independent t-test. Results: The subjects with greater hamstring length had significantly less lumbar spine flexion movement and more pelvic flexion movement. The subjects with greater pelvic flexion movement had a higher rate of flexion relaxation during full trunk bending (p<.05). Conclusion: The results of this study suggest that differences in hamstring muscle flexibility might cause changes in people's hamstring muscle activity and lumbopelvic kinematics.

• KCI Concrete Journal
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• v.12 no.2
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• pp.85-93
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• 2000

Potentially significant mechanical improvements in tension can be achieved by the incorporation of randomly distributed, short discrete fibers in concrete. The improvements due to the incorporation fibers significantly influence the composite stress - strain ($\sigma$-$\varepsilon$) characteristics. In general incorporating fibers in a plain concrete has relatively small effect on its precracking behavior. It, however, alters its post-cracking behavior quite significantly, resulting in greatly improved ductility, crack controls, and energy absorption capacity (or toughness). Therefore, a thorough understanding the complete tensile stress - strain ($\sigma$-$\varepsilon$) response of fiber reinforced concrete is necessary for proper analysis while using structural components made with fiber reinforced concrete. Direct tensile stress applied to a specimen is in principle the simplest configuration for determining the tensile response of concrete. However, problems associated with testing brittle materials in tension include (i) the problem related to gripping of the specimen and (ii) the problem of ensuring centric loading. Routinely, indirect tension tests for plain concrete, flexural and split-cylinder tests, have been used as simpler alternatives to direct uniaxial tension test. They are assumed to suitable for fiber reinforced concrete since typically such composites comprise 98% by volume of plain concrete. Clearly since the post-cracking characteristics are significantly influenced by the reinforcing parameters and interface characteristics, it would be fundamentally incorrect to use indirect tensile tests for determining the tensile properties of fiber reinforced concrete. The present investigation represents a systematic look at the failure and toughening mechanisms and macroscopic stress - strain ($\sigma$-$\varepsilon$) characteristics of fiber reinforced concrete in the uniaxial tension test. Results from an experimental parametric study involving used fiber quantity, type, and mechanical properties in the uniaxial tension test are presented and discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1131-1142
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• 2013

This study aims to verify the applicability of TRANSIMS (TRansportion ANalysis SIMulation System) in interrupted traffic flow through calibration and validation process based on observation data; such as headway, traffic volume, speed, and travel time from Dalguberl Boulevard in Dae-gu metropolitan city. On this study, several micro-simulation parameters are derived from the calibration and validation process through performing a headway comparison and applying an ID back tracking methodology. As a result, it is figured out that actual circumstances of Korean roadway; for example, traffic volume per lane, speed, and travel time, can be applied on the TRANSIMS. Especially, it was possible to find out the influence of cell size parameter to traffic flow characteristic of simulation. However, it is hard to conclude that TRANSIMS is applicable to Korean roadway environment with studying particular target area. Therefore, additional studies; such as more case studies with various types of road, signal, and land use, will be required to localize TRANSIMS to Korea.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.6
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• pp.407-420
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• 2003

Purpose : The purpose of this study was to analyse the facial changes and factors contributing to then after bilateral sagittal split ramus osteotomy of mandibular prognathism. Materials and Methods : Forty patients with Class III dental and skeletal malocclusion who were treated with bilateral sagittal split ramus osteotomy were reviewed. Frontal and lateral cephalometric radiographs were taken preoperatively, immediate postoperatively and more than six months postoperatively in each patient. After tracing the cephalometric radiographs, various parameters were measured. Results : 1. Gonial angle at postoperative two days was decreased about $10.4^{\circ}$ than preoperatively and gonial angle at postoperative six months was increased about $6.8^{\circ}$ than postoperative two days. So, gonial angle at postoperative six months was decreased about $3.6^{\circ}$ than preoperative gonial angle. 2. Facial height postoperative two days was decreased about 0.8mm than preoperatively and facial height at postoperative six months was decreased about 0.7mm than postoperative two days. So, facial height at postoperative six months was decreased about 1.5mm than preoperative facial height. 3. Mandibular width postoperative two days was decreased about 1.0mm than preoperatively and mandibular width at postoperative six months was increased about 1.8mm than postoperative two days. So, mandibular width at postoperative six months was decreased about 2.8mm than preoperative mandibular width. 4. Amount of set back and mandibular plane angle were not influencing on relapse degree. Conclusion : It is thought that bilateral sagittal split ramus osteotomy in mandibular prognathic patients is effective to improve long face and steep gonial angle. More prudent operation and careful postoperative management is required to maintain stable face postoperatively. Further research for soft tissue changes and factors which are related with relapse is needed.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.1-10
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• 2006

The purpose of this study was to identify critical parameters of a putting performance using jerk cost function. Jerk is the time rate of change of acceleration and it has been suggested that a skilled performance is characterized by decreased jerk magnitude. Four elite golfers($handicap{\leq}2$) and 4 novice golfers participated in this study for the comparison. The 3D kinematic data were collected for each subject performing 5 trials of putts for each of these distances (random order): 1m, 3m, 5m The putting stroke was divided into 3 phases such as back swing. down swing and follow-through. In this study, it was assumed that there exist smoothness difference between elite and novice golfers during putting. The distance and jerk-cost function of Putting stroke for each phase were analyzed Results showed that there was a significant difference in jerk cost function at putter toe (at media-lateral direction) and at the center of mass between two groups by increasing putting distance. From these it could be concluded that jerk can be used as a kinematic parameter for distinguishing elite and novice golfers.