• The Journal of the Korea Contents Association
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• v.11 no.9
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• pp.453-458
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• 2011

This study aimed to figure out the change of exposure dose to the radiologist according to the C-arm angle change. For the exam it was fixed with 101 kvp and 4.9mA for the exposure time with 3 seconds and 5 seconds respectively. C-arm Tube was located both under and over, then the average was taken after performing for 5 times with the change of angle from -30 degree to 0, 30, 60 and 90 degree. The detector measured in 160cm high from the position of the radiologist who operates the C-arm. The measurement was shown its highest result at -30 degree followed by 0, 30, 60, 90 from the highest order. Over tube method is higher than under tube method. Therefore, to reduce the exposure dose of the radiologist, it is required for using under tube method instead of over tube method. When the angle change is made, it is recommended to use the angle that tube is growing further apart from the radiologist. And it is also necessary to shorten exposed time as much as possible to create the same quality image and also to reduce the exposure dose.

• The Journal of Korean Physical Therapy
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• v.26 no.2
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• pp.56-61
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• 2014

Purpose: The aim of this study was to investigate relationship between the angle of the first metatarsophalangeal joint (1st MPJ) and the dimensions of the abductor hallucis; dorso-plantar (DP) thickness, medio-lateral (ML) width, and cross-sectional area (CSA), in subjects with and without hallux valgus. Methods: Sixty feet, mean (SD) age of 22.5 (2.1) years old, were included in this study (hallux valgus = 30; control = 30). An X-ray device was used for measurement of the angle of the 1st MPJ, and an ultrasound system was used for determination of mean (SD) DP thickness, ML width, and CSA of the abductor hallucis muscle in each foot from three trials. Results: The results showed the DP thickness, ML width, and CSA of the abductor hallucis did not differ significantly between subjects with and without hallux valgus. In addition, the correlations between the angle of the 1st MPJ and DP thickness, ML width, and CSA of the abductor hallucis showed poor correlation (Pearson r=-0.09, -0.20, and -0.18, respectively). Conclusion: Based on these findings, we speculate that morphological changes to the abductor hallucis muscle cannot be representative of the angle of the 1st MPJ, and also cannot be used in differentiation between subjects with and without hallux valgus.

• Journal of the Korean Society of Safety
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• v.24 no.2
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• pp.83-88
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• 2009

The objective of this paper was to evaluate the effectiveness of horizontal, vertical, asymmetric and coupling multipliers for manual material handling. Lifting tasks with 5 different horizontal distances ($30{\sim}70cm$) for 6 vertical distances(ankle, knee, waist, elbow, shoulder and head height) were experimented. The muscle activity and muscle exertion level during asymmetric load handling(without trunk flexion) was experimented. Lifting tasks with and without handle tote box for three postures(straight, bending, right angle posture) were experimented. The degrading tendency did not appeared almost in $60{\sim}70cm$ interval's horizontal distance. As a result of ANOVA, MVC paid attention to horizontal and vertical distance but cross effect was insignificant(p<0.01). The change of the MVC according to the horizontal, vertical distance appeared similar from of RWL. The results of normalized MVC measurement were decreased about 16%, 24%, 34% respectively as the asymmetry angle was $30^{\circ}$, $60^{\circ}$, $90^{\circ}$. RMS EMG values of right erector spinae muscles were decreased as the work posture went to $90^{\circ}$ and those of left erector spinae muscles were increased until the asymmetry angle was $40^{\circ}$ but decreased continually over $40^{\circ}$. 7 subjects, activities of left and right latissimus dorsi muscles were maintained constantly, while for remainer, those were irregular. MVC reduced maximum 23% by type of handle. MVC was highest in straight posture, but was lowest in right angle posture. As a result of ANOVA, MVC paid attention to posture, coupling(p<0.01). To all handle types, biceps brachii activity was increased in right angle posture, but reduced in straight posture. Based on the results of this study, it is suggested that the NIOSH guideline should not be directly applied to Korean without reasonable reexamination. In addition, we need to afterward study through an age classification.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1078-1084
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• 2010

The tracking performance of a big parabola tracking antenna system for tracking and receiving of the signal from the vehicle is impacted by many factors of the internal and the external of the system. In this paper, we analyze the tracking error due to the radio refraction in the application of the tracking and positioning of the vehicle by using radio frequency. The real measurement data are used for the analysis which had been acquired by using GPS and the tracking systems of C- and S-band frequencies in NARO Space centre. To verify the correlation between the tracking errors measured and the radio refraction, we review the error factors and the accuracies of the tracking systems, and the characteristics of the refractivity. The analysis shows that there are angular errors which are due to the radio refraction and not to be neglected, compared to the accuracies of the tracking systems, in case of low elevation angle less than 10 degrees. Also, the tracking errors depend on the target altitude as well as the elevation angle for the case of the target in the troposphere. It is recommended to correct the tracking angle considering the target altitude and elevation angle for the precise target positioning.

• Journal of the Korean institute of surface engineering
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• v.53 no.3
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• pp.116-123
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• 2020

Ion beam irradiation induces self-organization of nanostructure on the surface of polymer film. We show that the incident angle of Ar ions on polyethylene naphthalate(PEN) film changes self-organized nanostructure. PEN film was irradiated by argon ion beams with the ion incident angle of 0°, 30°, 45°, 60°, and 80°. Nanostructure was altered from dimple to ripple structure as the angle increases. The ripple structure changed to pillar structure after 60°due to that the shallow incident angle increased the ion energy transfer per depth up to 50 eV/Å, which value could induce excessive surface heating and oligomer formation reacting as a physical mask for anisotropic etching. And quantitative analysis of the nanostructures was adapted by using ABC model and fractal dimension theory.

• The korean journal of orthodontics
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• v.18 no.1 s.25
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• pp.7-24
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• 1988

The stable occlusion in function is thought as important as the esthetics in form, in order to preserve the healthy oral condition. The stable occlusion requires the harmony between the condylar guidance factors and the anterior guidance factors. The aim of this study was to evaluate the quantitative relationship between the condylar guidance factors and the anterior guidance factors, estimating statistically the measurement of the condylar paths by Pantronic and those of the anterior guidance factors, craniofacial morphology by roentgenocephalometry in 46 relatively good functional occlusion. The results of this study were as follows. 1. The measurements of the protrusive condylar path inclinations were $36.41^{\circ}$ in the right, $35.63^{\circ}$ in the left, $36.28^{\circ}$ in the mean. The measurements of Fisher's angles were $8.17^{\circ}$ in the right, $6.43^{\circ}$ in the left, $6.87^{\circ}$ in the mean. 2. The anterior facial height and the lower anterior facial height made a negative correlation with the protrusive condylar path inclination. 3. The articular eminence angle relative to the artificial articulator plane showed a positive correlation with the maximum protrusive condylar path. 4. SNA and SNB made a negative correlation with the articular eminence angle, and AAP-GoMe, AAP-DcGn, the facial height ratio had a positive correlation with the articular eminence angle. 5. The angulation of maxillary incisor lingual slope, overbite and the ratio of overbite to overiet showed a positive correlation with the articular eminence angle. 6. The angulation of maxillary incisor lingual slope , overbite, and the ratio of overbite to overjet made a positive correlation with the inclination of occlusal plane, functional occlusal plane. 7. Overbite and the ratio of overbite to overjet had a positive correlation with the angulation of maxillary incisor lingual slope. 8. The anterior guidance factors were more influenced by the mean protrusive condylar path inclination and the maximum Fisher's angle, and the regression equations of those were made.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.846-854
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• 1999

Measurements of the local heat transfer coefficients were made on a hemispherically convex surface with a round oblique impinging jet. The liquid crystal transient method was used for these measurements. This method, which is a variation on the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystal for the surface temperature measurements. The Reynolds number used was 23000 and the nozzle-to-surface distance was L/d=2, 4, 6, 8, and 10 and the jet angle was $\alpha$=$0^{\circ}\; 15^{\circ}\;30^{\circ}C\; and \;40^{\circ}C$. In the experiment, the Nusselt number at the stagnation point decreases as the jet angle increases and has the maximum value for L/d=6. The X-axis Nusselt number distributions exhibit Secondary maxima at $0^{\circ}C\re $\alpha$\re 15^{\circ}C, L/d\le6$ for X/d＜0(upstream) and at $0^{\circ}C\re $\alpha$40^{\circ}C,\;L/d\le4\;and\; at\; 30^{\circ}C\re $\alpha$$\leq$40^{\circ}C,\;L/d\le 6 $for X/d＞0(downstream). The secondary maxima occurs at long distance from the stagnation point as the jet angle increases or the nozzle-to-surface distance decreases. The Y-axis Nusselt number distributions exhibit secondary maxima at Y/d=$\pm$2 for $0^{\circ}C\le a\le30^{\circ}C\; and\; L/d\le4, and \;for\;$\alpha$=40^{\circ}C$and L/d=2. The displacement of the maximum Nusselt number from the stagnation point increases as the jet angle increases or the nozzle-to-surface distance decreases and the maximum distance is about 0.67 times of the nozzle diameter. The ratio of the maximum Nusselt number to the stagnation Nusselt number increases as the jet angle increases.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.100-100
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• 2016

전자파표면유속계는 대표적인 비접촉식 계측기기로 최근 유량조사를 위해 활발하게 활용되고 있다. 국내에서 사용되고 있는 전자파표면유속계는 평수기 저유속에서도 측정이 가능하고 편각 측정이 가능하도록 개발되어 한 측정 지점에서 다 지점의 유속이 측정이 가능해 평수기 홍수기에 비교적 적은 인원으로 빠른 시간에 유량측정이 가능하다. 하지만 국내의 경우 전자파표면유속계가 과연 얼마만큼의 정확한 유속을 측정하는지에 대한 분석이 다소 부족한 실정으로 특히, 실제 하천에서 정확한 분석은 수행되지 않은 상태에서 유량 측정에 사용되고 있다. 전자파표면유속계를 실제 하천에서 사용할 경우 발생 할 수 있는 오차의 요인으로는 교량과 같이 높은 지점에서 측정을 수행할 경우 측정영역(Footprint or Illuminated area)에 따른 오차가 발생할 수 있는 가능성이 있고, 동일 측정 지점에 대해 수직각과 편각에 변화에 따른 유속 측정 오차가 발생할 수 있다. 이에 본 연구에서는 국내에서 개발된 Mutronics사의 전자파표면유속계(MWSCM; Microwave Water Surface Current Meter)에 레이저포인터를 부착하여 표면유속 약 0.5m/s ~ 1m/s의 자연 하천과 매우 유사한 실제 소하천 규모의 한국건설기술연구원 안동실험센터 직선하천에서 수직각(Tilt angle) 및 편각(Yaw angle)을 변화시켜가며 유속를 측정하였다. 그리고 측정된 결과를 활용하여 수직각과 편각의 변화에 따른 전자파표면유속계의 측정영역을 검토하였고, 동일한 측정 지점에 micro-ADV를 이용해 측정된 연직유속분포를 외삽하여 산정된 표면유속과 비교하여 전자파표면유속계의 측정 정확도를 분석하였다. 분석결과, 수직각(Tilt angle) 15도 이하에서는 유속 측정의 정확도가 떨어지는 것으로 나타났고, 편각(Yaw angle)이 커질수록 측정영역이 커지게 되어 변동 계수가 증가하는 것으로 나타났다. 그리고 전자파표면유속계의 측정 오차는 측정영역에 민감하게 반응하는 것으로 나타나 실제 전자파표면유속계를 이용한 유량측정 시 측정영역을 고려한 측정이 수행되어야 할 것으로 판단된다.

• Asian Spine Journal
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• v.12 no.6
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• pp.1053-1059
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• 2018

Study Design: Retrospective review. Purpose: To detect the effect of cannulated (poly-axial head) and solid (mono-axial head) screws on the local kyphotic angle, vertebral body height, and superior and inferior angles between the screw and the rod in the surgical management of thoracolumbar fractures. Overview of Literature: Biomechanics studies showed that the ultimate load, yield strength, and cycles to failure were significantly lower with cannulated (poly-axial head) pedicle comparing to solid core (mono-axial head). Methods: The medical charts of patients with thoracolumbar fractures who underwent pedicle screw fixation with cannulated or solid pedicle screws were retrospectively reviewed; the subjects were followed up from January 2011 to December 2015. Results: Total 178 patients (average age, $36.1{\pm}12.4years$; men, 142 [84.3%]; women, 28 [15.7%]) with thoracolumbar fractures who underwent surgery and were followed up at Hamad Medical Corporation were classified, based on the screw type as those with cannulated screws and those with solid screws. The most commonly affected level was L1, followed by L2 and D12. Surgical correction of the local kyphotic angle was significantly different in the groups; however, there was no significant difference in the loss of correction of the local kyphotic angle of the groups. Surgical correction of the reduction in the vertebral body height showed statistical significance, while the average loss of correction in the reduction of the vertebral body height was not significantly different. The measurement of the angles made by the screws on the rods was not significantly different between the cannulated (poly-axial head) and solid (mono-axial head) screw groups. Conclusions: Solid screws were superior in terms of providing increased correction of the kyphotic angle and height of the fractured vertebra than the cannulated screws; however, no difference was noted between the screws in the maintenance of the superior and inferior angles of the screw with the rod.

• Investigative Magnetic Resonance Imaging
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• v.22 no.4
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• pp.218-228
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• 2018

Purpose: The objective of this study is to determine the effect of physical changes on MR temperature imaging at 7.0T and to examine proton-resonance-frequency related changes of MR phase images and T1 related changes of MR magnitude images, which are obtained for MR thermometry at various magnetic field strengths. Materials and Methods: An MR-compatible capacitive-coupled radio-frequency hyperthermia system was implemented for heating a phantom and swine muscle tissue, which can be used for both 7.0T and 3.0T MRI. To determine the effect of flip angle correction on T1-based MR thermometry, proton resonance frequency, apparent T1, actual flip angle, and T1 images were obtained. For this purpose, three types of imaging sequences are used, namely, T1-weighted fast field echo with variable flip angle method, dual repetition time method, and variable flip angle method with radio-frequency field nonuniformity correction. Results: Signal-to-noise ratio of the proton resonance frequency shift-based temperature images obtained at 7.0T was five-fold higher than that at 3.0T. The T1 value increases with increasing temperature at both 3.0T and 7.0T. However, temperature measurement using apparent T1-based MR thermometry results in bias and error because B1 varies with temperature. After correcting for the effect of B1 changes, our experimental results confirmed that the calculated T1 increases with increasing temperature both at 3.0T and 7.0T. Conclusion: This study suggests that the temperature-induced flip angle variations need to be considered for accurate temperature measurements in T1-based MR thermometry.