• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.5
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• pp.442-446
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• 2001

Purpose : This study evaluated clinical and radiographic results after open reduction and lag-screw fixation of mandibular condyle fractures. Patients and Methods : 26 patients had been treated by lag-screw fixation for madibular condyle fracures via submandibular approach and follow up for over 6 months. The lag-screw used in this study was designed by Eckelt. Results : Radiographically, resorption of the condyle head found in 4 cases (15%) and minimal displacement of the condyle head was found in 3 cases (12%). Post-operative infection were not found in all cases. Clinically, All patiens had a stable occlusion and normal mouth opening (over 40mm). TMD problems with crepitus or some discomfort encountered in 4 patients but tolerable to the patients. Conclusion : Lag screw fixation can be a good option especially high level condylar fractures, however this procedure must be used in cautiously because of slipping of the fragments and possible to resorption of the fragments.

• Korean Journal of Applied Biomechanics
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• v.33 no.1
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• pp.1-9
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• 2023

Objective: This study identifies the difference among the heights of a chair's backrest (High, Mid, No), the biomechanical changes chair users undergo over time, and the variables that can measure musculoskeletal disorders, eventually providing information on the appropriate type of backrest. Method: Eleven healthy subjects in their 20s and 30s who had no experience with musculoskeletal disorders or surgical operations within the last 6 months participated in this study. Computer typing tasks were randomly designated and performed according to the type of chair backrest, and evaluation was performed for Flexion-Relaxation Ratio (FRR) analysis after the computer typing tasks. This study used eight infrared cameras (sampling rate: 100 Hz) and nine-channel electromyography (sampling rate: 1,000 Hz). ANOVA with repeated measures was conducted to verify the results, with the statistical significance level being α = .05. Results: Although there was no significant difference in craniovertebral angle (CVA), this study showed time and interaction effects depending on the height of the backrest (p<.05). When working without the backrest, the head-spine angle was lower compared to the chairs with backrest, based on the computer work. As for the head angle, the higher the back of the chair was, the less the head flexion and the body angle became, whereas the body flexion became less when there was a backrest. In addition, the body flexion increased over time in all types of backrests (p<.05). The muscle activity of the upper body tended to be high in the high backrest chair. On the other hand, a lower muscle activity was found with a low backrest. Conclusion: These results show that a chair is more ergonomic when the body angle is correctly set without bending and when it is supported by a low backrest. Accordingly, this study determines that the backrest affects shoulder and neck musculoskeletal disorders during typing and that medium-height backrest chairs can help prevent musculoskeletal disorders, contrary to the expectation that high-backrest chairs are preferable.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8B
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• pp.699-706
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• 2008

This paper compares throughput performance of TCP and SCTP in a variety of network environments. For experiments, we construct a Linux-based testbed and consider a set of performance metrics such as MSS(Maximum Segment Size), transmission delay, and packet loss rate. In addition, we analyze the effect of SCTP multi-streaming on throughput. From the experimental results, we can see that SCTP provides throughput gain of approximately $20%{\sim}50%$ over TCP. This performance gain comes from the distinctive features of SCTP such as chunk bundling, initial congestion window of 2 MTU and SACK(Selective ACK) based error control. In the lossy networks, we can see that SCTP multi-streaming transmissions can effectively overcome the so-called HoLB(Head-of-Line Blocking) phenomenon of TCP.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.1
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• pp.1-6
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• 2011

In this study, we investigated the effect of the simplification for high frequency region in Head-Related Transfer Function(HRTF) on the sound localization. For this purpose, HRTF was measured and analyzed. The result in the HRTF frequency characteristic of the back sound source showed that the decrease revel of high frequency was smaller than that of low frequency region, which means the possibility of simplification in the high frequency region. Simplification was performed by flattening of the high frequency amplitude characteristics with the insertion of the low-pass filter, whose cutoff frequency is given by boundary frequency. Auditory experiments were performed to evaluate the simplified HRTF. The result showed that direction perception was not influenced by the simplification of the frequency characteristics of HRTF for the error of sound localization. The rate of confusion for the front and back was not affected by the simplification of the frequency characteristics over 8kHz of HRTF. Finally, we made it clear that the sound localization was not affected by the simplification of frequency characteristics of HRTF over 8kHz.

• Journal of the Korean Geotechnical Society
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• v.22 no.8
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• pp.25-31
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• 2006

Over the years the investigation of behaviour of piles in groups connected to a cap in consolidating soil has attracted far less attention than the study of isolated piles in groups. In this paper, a series of three-dimensional numerical simulations have been performed to study the behaviour of pile groups connected to a cap in consolidating ground. Both elastic no-slip and elasto-plastic slip analyses were considered. Based on the analysis results, when piles were connected to a cap, tensile forces were developed near the pile head at the outer piles. Elastic solution and no-slip analysis over-predicted the tensile force near the pile head for outer piles. Relatively speaking, the number of piles in a group is more important than the pile spacing in terms of the influence of negative skin friction on the pile behaviour. The issue on the development of tensile forces on the pile head at the outer piles is perhaps needed to be carefully considered in the pile design to prevent the damages of the pile-cap connection.

• The Journal of the Acoustical Society of Korea
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• v.33 no.5
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• pp.341-350
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• 2014

In this paper, an energy efficient clustering scheme using self organization method is proposed. The proposed scheme selects a cluster head considering not only the number of neighbor nodes but also the residual battery amount. In addition, the network life time is extended by re-selecting the cluster heads only in case the current cluster head's residual energy falls down below a certain threshold level. Accordingly, the energy consumption is evenly distributed over the entire network nodes. The cluster head delivers the collected data from member nodes to a Sink node in a way of multi-hop relaying. In order to evaluate the proposed scheme, we run computer simulation in terms of the total residual amount of battery, the number of alive nodes after a certain amount of time, the accumulated energy cost for network configuration, and the deviation of energy consumption of all nodes, comparing with LEACH which is one of the most popular network clustering schemes. Numerical results show that the proposed scheme has twice network life-time of LEACH scheme and has much more evenly distributed energy consumption over the entire network.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1555-1557
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• 1998

In order to investigate the core material for over-head transmission line with non-magnetic and high strength nitrogen steel, microstructure and several basic properties of Fe-Mn-Cr-Ni-N steel have been studied. It is necessary that core material have a $\gamma$ phase to have a non-magnetic characteristics. To acquire a $\gamma$ phase, Mn, Ni and C are added as a alloying element. It was found that Fe-25Mn-16Cr-1Ni-N alloy have a stable $\gamma$ phase. The precipitate from this alloy system was $(Cr, Fe)_7C_3$. High Mn and N steel satisfies Sievert's relation that solubility of nitrogen increases with the square root of partial pressure of gas in metal-gas system and the hardness have proportional relation with nitrogen concentration.

• Research in Community and Public Health Nursing
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• v.19 no.1
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• pp.36-45
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• 2008

Purpose: This study was to estimate the prevalence of dementia in order to estimate the associations of dementia with its risk factors in the community elderly. Methods: The multistage random cluster sampling method was used to select the subjects. The response rate was 94.3%. For the 1st stage screening survey, the Korean-version Mini-Mental State Examination (K-MMSE) and the Bathel Index of activities of daily living (ADL) and instrumental activities of daily living (IADL) were used as primary screening tools. At the 2nd stage. diagnoses were confirmed according to the Clinical Dementia Rating Scale (CBR) and Computer Tomogram (CT). Results: Age-sex adjusted prevalence (%) [95% CI] of dementia was 6.25% [4.47-7.83] (male 4.21% [2.40-6.02]; female 8.28% [5.71-10.85]). Four statistically significant risk factors of the dementia were identified: age 70-74 (OR=1.367), age 75-79 (OR=1.712), age 80-84 (OR=2.465), age 85 over (OR=7.363) illiteracy (OR=3.827); unconsciousness after head injury (OR=3.383), and no exercise (OR=2.188). Hosmer and Lemeshow goodness-of-fit index of dementia risk model was E (legit of dementia)= -4.337+$0.312^*Age(70{\sim}74)+0.538^*Age(75{\sim}79)+0.902^*Age(80{\sim}84)+1.996^*Age$(85over)+$1.342^*$Illiteracy+$1.219^*$Unconsciousness after head trauma+$0.783^*$No exercise. We confirmed that the overall prevalence of dementia in adults aged 65 and older was 94.3%. The risk factors of dementia were explained by age, illiteracy unconsciousness after head trauma and no exercise. Conclusion: These data have been used to estimate the incidence of dementia in elderly community population and to manage the possible role of risk factors as predictors of dementia.

• Journal of International Academy of Physical Therapy Research
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• v.11 no.3
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• pp.2119-2125
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• 2020

Background: Adults with forward head posture (FHP) often suffer from thoracic hyperkyphosis and thoracic dysfunction, and including reduction of the craniovertebral angle (CV angle) and tightening of the superficial neck muscles. In order to treat thoracic dysfunction, interventions aimed at improving thoracic mobility are necessary. Objectives: To examine the effects of maitland manual mobilization therapy on the thoracic spine in adults with FHP. Design: Single-blind randomized controlled trial. Methods: Thirty adults with FHP who met the selection criteria were randomized to the thoracic multiple joint mobilization (TMJM; n=15) group and the thoracic general joint mobilization (TGJM; n=15) group. Joint mobilizations were performed for 23 minutes a day for 4 weeks continuously, two times per week. Outcome measures were ImageJ, BTS FREE EMG 1000, neck disability Index (NDI). Results: Although changes in the left sternocleidomastoid muscle activity and NDI scores over time between the two groups differed, other variables were noted only changes observed over time. Muscle activity in the right sternocleidomastoid increased again in the TGJM group post-intervention and 2 weeks after the end of the experiment, but changes in other variables were retained or improved, confirming the lasting effects of thoracic joint mobilization. Conclusion: Thoracic multiple joint mobilization may be recommended as a more effective intervention for adults with FHP.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1901-1903
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• 1999

To investigate invar alloy as a core material for increased capacity over-head transmission line which have high strength and low thermal expansion coefficient, hardness and thermal expansion coefficient of Fe-Ni-Co alloy have been studied. It is necessary that invar alloy have low thermal expansion coefficient and high strength for increased capacity over-head transmission line. In this paper. we tried to find out the effect of Ni and Co which has ferromagnetic properties and high saturation magnetization. It was found that Ni decrease thermal expansion coefficient and hardness, Co decrease thermal expansion coefficient but increase hardness in Fe-xNi-Co system. In Fe-(29-x)Ni-Co system, the material has no low thermal expansion properties substituting Co instead of Ni in concentration range of $1\sim7$%Co.