• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.659-662
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• 2002

The present paper presents the experimental results for pressure drop in inclined tube bundles located in a rectangular duct. Measurements are made for pressure drop in triangular and rotated triangular tube arrays having P/d ratio of 1.6 and inclination angles of 30,45,60 and 90 degrees. The Reynolds number based on the free stream velocity and tube diameter ranges from $8{\times}10^2\;to\;6.3{\times}10^{4}$. The experimental results show that the magnitude of dimensionless pressure drop decreases significantly when the inclined angle is less than 45 degree. The measured data are compared with two existing correlations available in the literatures. The ESDU correlation agrees well with the present data far the triangular arrays. But some discrepancies are observed for the rotated triangular arrays when the inclined angles are 30 and 45 degrees. The Idel'chik correlation generally agrees well with the measured data for the rotated triangular arrays except for the inclined angle of 30 degree. The Idel'chik correlation needs modification for the triangular arrays. The modified Idel'chik correlation agrees well with the measured data within $10{\%}$. It is found that the present measured data can be applied to the evaluation and modification of previous correlations.

• Imaging Science in Dentistry
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• 제41권3호
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• pp.95-100
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• 2011

Purpose : The purpose of this study was to compare asymmetric mandibular prognathism individuals with symmetric mandibular prognathism individuals using a new alternate spherical coordinate system. Materials and Methods : This study consisted of 47 computed tomographic images of patients with mandibular prognathism. The patients were classified into symmetric and asymmetric groups. Mandibular and ramal lines were analyzed using an alternate spherical coordinate system. The length as well as midsagittal and coronal inclination angle of the lines was obtained. The bilateral differences of the spherical coordinates of the facial lines were statistically analyzed in the groups. Results : There were significant differences between the groups in bilateral difference of the length and midsagittal inclination angle of the lines (p<0.05). The bilateral difference of the length and midsagittal inclination angle of the lines has significant correlation with chin deviation (p<0.05). Conclusion : The new alternate spherical coordinate system was able to effectively evaluate facial lines. The bilateral difference of lengths and midsagittal inclination of the facial lines might contribute to the facial asymmetry in mandibular prognathism individuals.

• Nuclear Engineering and Technology
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• 제45권7호
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• pp.911-920
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• 2013

Experimental studies on both subcooled and saturated pool boiling of water were performed to obtain local heat transfer coefficients on a $3^{\circ}$ inclined tube of 50.8 mm diameter at atmospheric pressure. The local values were determined at every $45^{\circ}$ from the very bottom to the uppermost of the tube periphery. The maximum and minimum local coefficients were observed at the azimuthal angles of $0^{\circ}$ and $180^{\circ}$, respectively, in saturated water. The locations of the maxima and the minima were dependent on the inclination angle of the tube as well as the degree of subcooling. The major heat transfer mechanisms were considered to be liquid agitation generated by the sliding bubbles and the creation of big size bubbles through bubble coalescence. As a way of quantifying the heat transfer coefficients, an empirical correlation was suggested.

• 한국지반환경공학회 논문집
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• 제19권2호
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• pp.13-21
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• 2018

The magnitude and distribution of earth pressure on the excavation wall in jointed rock mass were examined by considering different wall permeability conditions as well as rock types and joint inclination angles. The study was numerically extended based on a physical model test (Son & Park, 2014), considering rock-structure interactions with the discrete element method, which can consider various characteristics of rock joints. This study focused on the effect of the permeability condition of excavation wall on the earth pressure in jointed rock masses under a groundwater condition, which is important but has not been studied previously. The study results showed that the earth pressure was highly influenced by wall permeability as well as rock type and joint condition. Earth pressure resulted from the study was also compared with Peck's earth pressure in soil ground, and the comparison clearly showed that the earth pressure in jointed rock mass can be greatly different from that in soil ground.

• 에너지공학
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• 제12권2호
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• pp.139-144
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• 2003

본 연구는 초음파 진동의 영향을 받는 풀비등 조건에서의 CHF 열전달 촉진현상을 이해하기 위해 수행되었다. 평판에 얇은 구리박판이 덮여 있는 시료와 증류수를 냉각제로 사용하여 초음파 유무, 경사각도의 변화 및 물의 과냉도 변화에 대하여 평판 가열면에서의 CHF를 측정하였다. 실험장치는 수조, 전원공급장치, 시험부, 초음파 발생장치, 데이터 획득장치 등으로 구성되었다. 실험조건은 3가지 과냉도에 대한 실험과 6가지 시편의 경사각도를 변화시켜 수행되었다. 측정값을 통해 초음파 진동이 CHF를 증진시키며, 그 영향은 경사각의 변화뿐만 아니라 과냉도에 따라서 크기가 달라지는 것을 알 수 있다. 초음파 진동에 의한 CHF증가율은 과냉도가 커질수록, 그리고 시편의 경사각도가 수직에서 수평하향 방향으로 기울어질수록 증가하였다. 가시화 실험을 통해 CHF 증가의 원인이 음장에서 기포 생성과 이탈의 동적거동과 밀접하게 관련되어 있음을 확인하였다.

• Knee surgery & related research
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• 제30권4호
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• pp.311-318
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• 2018

Purpose: The purpose of this study was to evaluate changes in the coronal alignment of the knee and ankle joints after open wedge high tibial osteotomy (OWHTO) to determine factors related to the recurrence (R) of the varus deformity by serial analysis. Materials and Methods: Sixty-four OWHTOs were enrolled in this study. The weight bearing line (WBL) ratio, joint line convergence angle (JLCA), knee joint inclination, mechanical axis-tibial plateau angle, talar inclination (TI), and distal tibia articular angle (DTAA) were serially assessed. Serial correlation analysis between all parameters was performed. Patients were divided into R group and no recurrence (NR) group according to the WBL ratio (55%) at postoperative one year. Results: The preoperative WBL ratio showed significantly negative correlation with serial changes of JLCA, TI, and DTAA (p<0.05). The JLCA, TI, and DTAA as well as WBL ratio showed a significantly larger degree of varus alignment in the R group than in NR group at postoperative 6 weeks and 1 year after OWHTO (p<0.05). Conclusions: Sufficient correction of the WBL and restoration of the JLCA during OWHTO are essential to prevention of the R of varus deformity after the surgery because they are the only modifiable factors during surgery. Level of Evidence: IV, Case series.

• Geomechanics and Engineering
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• 제20권5호
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• pp.461-474
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• 2020

Analysing the incompatible deformation and damage evolution around the tunnels in mixed strata is significant for evaluating the tunnel stability, as well as the interaction between the support system and the surrounding rock mass. To investigate this issue, confined compression tests were conducted on upper-soft and lower-hard strata specimens containing a circular hole using a rock testing system, the physical mechanical properties were then investigated. Then, the incompatible deformation and failure modes of the specimens were analysed based on the digital speckle correlation method (DSCM) and Acoustic Emission (AE) data. Finally, numerical simulations were conducted to explore the damage evolution of the mixed strata. The results indicate that at low inclination angles, the deformation and v-shaped notches inside the hole are controlled by the structure plane. Progressive spalling failure occurs at the sidewalls along the structure plane in soft rock. But the transmission of the loading force between the soft rock and hard rock are different in local. At high inclination angles, v-shaped notches are approximately perpendicular to the structure plane, and the soft and hard rock bear common loads. Incompatible deformation between the soft rock and hard rock controls the failure process. At inclination angles of 0°, 30° and 90°, incompatible deformations are closely related to rock damage. At 60°, incompatible deformations and rock damage are discordant due that the soft rock and hard rock alternately bears the major loads during the failure process. The failure trend and modes of the numerical results agree very well with those observed in the experimental results. As the inclination angles increase, the proportion of the shear or tensile damage exhibits a nonlinear increase or decrease, suggesting that the inclination angle of mixed strata may promote shear damage and restrain tensile damage.

• 한국지반환경공학회 논문집
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• 제16권2호
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• pp.33-43
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• 2015

This paper investigated the magnitude and distribution of earth pressure on the support system in jointed rock mass by considering different earth pressure coefficients, rock types and joint inclination angles. The study mainly focused on the effect of the earth pressure coefficients on the earth pressure. Based on a physical model test (Son & Park, 2014), extended studies were conducted considering rock-structure interactions based on the discrete element method, which can consider the joints characteristics of rock mass. The results showed that the earth pressure was highly influenced by the earth pressure coefficients as well as the rock type and joint inclination angles. The effects of the earth pressure coefficients increased when the rock suffered more weathering and has no joint slide. The test results were also compared with Peck's earth pressure for soil ground, and clearly showed that the earth pressure in jointed rock mass can be greatly different from that in soil ground. This study indicated the earth pressure coefficients considering the rock types and joint inclination angles are important parameters influencing the magnitude and distribution of earth pressure, which should be considered when designing the support systems in jointed rock mass.

• 한국생산제조학회지
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• 제23권6호
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• pp.539-546
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• 2014

This paper describes an ultra-precision electronic clinometer, which is based on the capacitive-based fluid type, for detection of small inclination angles. The main parts of the clinometer low-noise electronics are two capacitance measurement circuits for converting the capacitances of the capacitors of the clinometer into voltages, and a differential amplifier for obtaining the difference of the capacitances, which is proportional to the input inclination angle. A 16 bit analog to digital (AD) converter is also embedded into the same circuit board, whose output is sent to a PC via RS-232C, for achieving a small noise level down to tens of ${\mu}v$. A compensation method, which is referred to as the delay time method for shortening the stabilization time of the sensor was also discussed. Experimental results have shown the possibility of achieving a measurement resolution of $0.0001^{\circ}$ as well as the quick measurement with the delay time method.

• 대한족부족관절학회지
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• 제8권1호
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• pp.101-106
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• 2004

Purpose: To determine the efficacy of the SDBBA (Subtalar distraction bone block arthrodesis) procedure on patients with late complication of intra-articular calcaneal fractures including subtalar joint arthritis and anterior ankle impingement syndrome. Materials and Methods: Five cases in which the SDBBA procedure was implemented were followed for more than one year. All five patients were male with an average age of 56. Clinically, the American Orthopedic Foot and Ankle Society (AOFAS) ankle-hindfoot score and the pain score were assessed. Radiographically, the talocalcaneal height and the talar inclination angle were determined. Results: All five patients achieved subtalar joint fusion. The average pre-operative AOFAS score was 22.8 scores (range, 8-32 scores). At last follow-up, these scores improved to an average of 72.4 scores (range, 64-82 scores). The average pre-operative pain score was 8.2 scores (range, 7-10 scores). At last follow-up, these scores improved to an average of 13.2 (range, 12-15 scores). The average pre-operative talocalcaneal height was 72.8 mm (range, 70-77 mm), average post-operative talocalcaneal height improved to 79.8 mm (range, 78-84 mm). At final follow-up, these measurement was slightly decreased to average 78.6 mm (range, 74-83 mm). The average pre-operative talar inclination angle was 13.2 degrees (range, 12-15 degrees), average post-operative talar inclination angle improvedto 19.2 degrees (range, 15-24 degrees). At final follow-up, these measurement was slightly decreased to average 18.6 degrees (range, 12-24 degrees). Four patients achieved successful outcomes. One patient developed a wound infection with subsequent sural neuropathy as well as collapse of the bone graft. Conclusion: This study shows that the SDBBA procedure successfully restores the talocalcaneal height and tibio-talar relationship. This procedure is useful in surgically managed patients with talo-calcaneal height loss and anterior ankle impingement syndrome due to the late complications of calcaneal intra-articular fractures.