• 한국정밀공학회지
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• 제17권1호
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• pp.76-82
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• 2000

An arc sensor system to compensate positional errors was developed on the foundation of sensor interface system to make use of the on-line shift function of industrial welding robot. Investigating the on-line shift function, we examine the quantitative relationship between the deviation from programmed path and the correction data transferred from personal computer to robot controller. The number of input parameters for weld seam tracking can be reduced by making the relationship between the deviation and the correction data during half weaving be the function of only cross time. With the results of weld seam tracking for the butt joint with V-groove and fillet joint of sheet metal, good performance was implemented. By developing the sensor interface system to compensate the positional errors, industrial welding robot can be expected to contribute to the promotion of welding automation.

• 한국생산제조학회지
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• 제6권1호
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• pp.27-33
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• 1997

A neural network approach has been developed to determine the depth of a surface breaking crack in a steel plate from ultrasonic backscattering data. The network is trained by the use of feedforward three-layered network together with a back-scattering algorithm for error correction. The signal used for crack insonification is a mode converted 70$^{\circ}$transverse wave. A numerical analysis of back scattered field is carried out based on elastic wave theory, by the use of the boundary element method. The numerical data are calibrated by comparison with experimental data. The numerical analysis provides synthetic data for the training of the network. The training data have been calculated for cracks with specified increments of the crack depth. The performance of the network has been tested on other synthetic data and experimental data which are different from the training data.

• 한국전문물리치료학회지
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• 제16권2호
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• pp.67-76
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• 2009

In order to prevent upper extremity musculoskeletal disorders, effective keyboard selection is an important consideration. The aim of this study was to compare upper extremity muscle activity according to transverse plane angle changes during vertical keyboard typing. Sixteen healthy men were recruited. All subjects had a similar typing ability (rate of more than 300 keystrokes per minute) and biacromion and forearm-fingertip lengths. Four different types of keyboard (vertical keyboard with a transverse plane angle of $60^{\circ}$, $96^{\circ}$, or $120^{\circ}$, and a standard keyboard) were used with a wrist support. The test order was selected randomly for each subject. Surface electromyography (EMG) was used to measure upper extremity muscle activity during a keyboard typing task. The collected EMG data were normalized using the reference contraction and expressed as a percentage of the reference voluntary contraction (%RVC). In order to analyze the differences in EMG data, a repeated one-way analysis of variance, with a significance level of .05, was used. Bonferroni correction was used for multiple comparisons. There were significant differences in the EMG amplitude of all seven muscles (upper trapezius, middle deltoid, anterior deltoid, extensor carpi radialis, extensor carpi ulnaris, flexor carpi radialis, and flexor carpi ulnaris) assessed during the keyboard typing task. The mean activity of each muscle had a tendency to increase as the transverse plane angle increased. The mean activity recorded during all vertical keyboard typing was lower than that recorded during standard keyboard typing. There was no significant difference in accuracy and error scores; however, there was a significant difference between transverse plane angles of $60^{\circ}$ and $120^{\circ}$ with regard to comfort. In conclusion, a vertical keyboard with a transverse plane angle of $60^{\circ}$ would be effective in reducing muscle activity compared with vertical keyboards with other transverse plane angles.

• The Journal of Korean Physical Therapy
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• 제31권5호
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• pp.298-303
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• 2019

Purpose: This study examined the effects of slashpipe exercise on reducing the thickness of the left and right external oblique, internal oblique, transverse abdominis, erector spinae, and multifidus muscles. Methods: A total of 29 healthy adult men and women were included in the study. They performed trunk flexion in the supine position and trunk extension in the prone position with a slashpipe and weight bar. The external oblique, internal oblique, and transverse abdominis muscles were measured in the supine position, while the erector spinae and multifidus muscles were measured in the prone position. The data were analyzed using the SPSS ver 21.0 statistical program. The difference in thickness between the right and left sides of the trunk muscle was analyzed by repeated measures analysis. The statistical significance level was set to p<0.05. Results: The results showed that the slashpipe exercise reduced significantly the difference in thickness of the oblique internus and erector spinae muscles compared to the weight bar exercise. Conclusion: The chaotic fluidity of the fluid filled inside the slashpipe could be used as sensory feedback information on body mal-alignment, which would have positively affected the symmetrical contraction of the trunk muscles as a trigger for self-correction. Therefore, it will have a useful effect not only on the health of the general public, but also on low back patients and athletes with muscle asymmetry.

• 한국전산구조공학회논문집
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• 제19권4호
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• pp.407-418
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• 2006

본 논문에서는 일차전단변형이론(FSDT)을 이용한 복합재료 적층평판의 고정밀 해석기법을 소개한다. 전단수정계수가 자동적으로 포함되도록 횡방향 전단 변형에너지를 혼합변분이론(mixed variational theorem)을 이용하여 개선하였다. 혼합변분이론에서는 변분을 횡방향 응력들에 대해서만 취하였다. 가정된 횡방향 전단응력은 효율적인 고차이론(Cho and Parmerter, 1993)으로부터 구하였다 횡방향 수직응력은 3차 다항식으로 가정하였고, 무전단 응력조건과 평판의 윗면과 아랫면에서의 응력을 만족하는 조건을 부과함으로써 얻었다. 한편, 변위들에 대해서는 일차전단변형이론의 변위장을 사용하였다. 이렇게 해서 얻어진 변형 에너지를 본 논문에서는 EFSDTM3D이라고 명명 하였다. 본 논문에서 개발된 EFSDTM3D는 변위와 응력의 계산에서 고전적인 FSDT와 같은 정도의 계산 효율을 가지면서, 동시에 변위와 응력의 두께방향의 정확도를 면내 방향 응력들에 대한 최소오차자승법에 기초하여 응력 회복 과정을 적용함으로써 개선하였다. 계산된 결과는 고전적인 FSDT, 3차원 탄성해, 그리고 참고문헌 중에서 이용 가능한 결과들과 비교하여 검증하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.475-480
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• 2001

The flowfield of transverse jet in a supersonic air stream subjected to shock wave turbulent boundary layer interactions is simulated numerically by Generalized Taylor Galerkin(GTG) finite element methods. Effects of turbulence are taken into account with a two-equation $(k-\varepsilon)$ model with a compressibility correction. Injection pressures and slot widths are varied in the present study. Pressure, separation extents, and penetration heights are compared with experimental data. Favorable comparisons with experimental measurements are demonstrated.

• 대한기계학회논문집B
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• 제26권3호
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• pp.375-383
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• 2002

The flowfield of transverse jet in a supersonic air stream subjected to shock wave turbulent boundary layer interactions is simulated numerically by Generalized Taylor Galerkin(GTG) finite element methods. Effects of turbulence are taken into account with a two-equation (k-$\varepsilon$) model with a compressibility correction. Injection pressures and slot widths are varied in the present study. Pressure, separation extents, and penetration heights are compared with experimental data. Favorable comparisons with experimental measurements are demonstrated.

• 대한치과교정학회지
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• 제47권2호
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• pp.77-86
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• 2017

Objective: The aim of this study was to evaluate the skeletal and dentoalveolar changes after miniscrew-assisted rapid palatal expansion (MARPE) in young adults by cone-beam computed tomography (CBCT). Methods: This retrospective study included 14 patients (mean age, 20.1 years; range, 16-26 years) with maxillary transverse deficiency treated with MARPE. Skeletal and dentoalveolar changes were evaluated using CBCT images acquired before and after expansion. Statistical analyses were performed using paired t-test or Wilcoxon signed-rank test according to normality of the data. Results: The midpalatal suture was separated, and the maxilla exhibited statistically significant lateral movement (p < 0.05) after MARPE. Some of the landmarks had shifted forwards or upwards by a clinically irrelevant distance of less than 1 mm. The amount of expansion decreased in the superior direction, with values of 5.5, 3.2, 2.0, and 0.8 mm at the crown, cementoenamel junction, maxillary basal bone, and zygomatic arch levels, respectively (p < 0.05). The buccal bone thickness and height of the alveolar crest had decreased by 0.6-1.1 mm and 1.7-2.2 mm, respectively, with the premolars and molars exhibiting buccal tipping of $1.1^{\circ}-2.9^{\circ}$. Conclusions: Our results indicate that MARPE is an effective method for the correction of maxillary transverse deficiency without surgery in young adults.

• 대한치과교정학회지
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• 제47권2호
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• pp.100-107
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• 2017

Objective: To analyze the long-term changes in maxillary arch widths and buccal corridor ratios in orthodontic patients treated with and without premolar extractions. Methods: The study included 53 patients who were divided into the extraction (n = 28) and nonextraction (n = 25) groups. These patients had complete orthodontic records from the pretreatment (T1), posttreatment (T2), and postretention (T3) periods. Their mean retention and postretention times were 4 years 2 months and 17 years 8 months, respectively. Dental models and smiling photographs from all three periods were digitized to compare the changes in three dental arch width measurements and three buccal corridor ratios over time between the extraction and nonextraction groups. Data were analyzed using analysis of variance tests. Post-hoc multiple comparisons were made using Bonferroni correction. Results: Soft-tissue extension during smiling increased with age in both groups. The maximum dental width to smile width ratio (MDW/SW) also showed a favorable increase with treatment in both groups (p < 0.05), and remained virtually stable at T3 (p > 0.05). According to the MDW/SW ratio, the mean difference in the buccal corridor space of the two groups was $2.4{\pm}0.2%$ at T3. Additionally, no significant group ${\times}$ time interaction was found for any of the buccal corridor ratios studied. Conclusions: Premolar extractions did not negatively affect transverse maxillary arch widths and buccal corridor ratios. The long-term outcome of orthodontic treatment was comparable between the study groups.

• Journal of Korean Neurosurgical Society
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• 제66권1호
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• pp.44-52
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• 2023

Objective : This study aimed to investigate the efficacy of transverse process (TP) hook system at the upper instrumented vertebra (UIV) for preventing screw pullout in adult spinal deformity surgery using the pedicle Hounsfield unit (HU) stratification based on K-means clustering. Methods : We retrospectively reviewed 74 patients who underwent deformity correction surgery between 2011 and 2020 and were followed up for >12 months. Pre- and post-operative data were used to determine the incidence of screw pullout, UIV TP hook implementation, vertebral body HU, pedicle HU, and patient outcomes. Data was then statistically analyzed for assessment of efficacy and risk prediction using stratified HU at UIV level alongside the effect of the TP hook system. Results : The screw pullout rate was 36.4% (27/74). Perioperative radiographic parameters were not significantly different between the pullout and non-pullout groups. The vertebral body HU and pedicle HU were significantly lower in the pullout group. K-means clustering stratified the vertebral body HU ≥205.3, <137.2, and pedicle HU ≥243.43, <156.03. The pullout rate significantly decreases in patients receiving the hook system when the pedicle HU was from ≥156.03 to < 243.43 (p<0.05), but the difference was not statistically significant in the vertebra HU stratified groups and when pedicle HU was ≥243.43 or <156.03. The postoperative clinical outcomes improved significantly with the implementation of the hook system. Conclusion : The UIV hook provides better clinical outcomes and can be considered a preventative strategy for screw-pullout in the certain pedicle HU range.