• 한국분무공학회지
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• 제18권1호
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• pp.35-43
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• 2013

The empirical correlations for the prediction of breakup length of liquid jet in uniform cross flow are reviewed and classified in this study. The breakup length of liquid jets in cross flow was normally discussed in terms of the distances from the nozzle exit to the column breakup location in the x and y directions, called as column fracture distance and column fracture height, respectively. The empirical correlations for the prediction of column fracture distance can be classified as constant form, momentum flux ratio form, Weber number form and other parameter form, respectively. In addition, the empirical correlations for the prediction of column fracture height can be grouped as momentum flux ratio form, Weber number form and other parameter form, respectively. It can be summarized that the breakup length of liquid jet in a cross flow is a basically function of the liquid to air momentum flux ratio. However, Weber number, liquid-to-air viscosity ratio and density ratio, Reynolds number or Ohnesorge number were incorporated in the empirical correlations depending on the investigators. It is clear that there exist the remarkable discrepancies of predicted values by the existing correlations even though many correlations have the same functional form. The possible reasons for discrepancies can be summarized as the different experimental conditions including jet operating condition and nozzle geometry, measurement and image processing techniques introduced in the experiment, difficulties in defining the breakup location etc. The evaluation of the existing empirical correlations for the prediction of breakup length of liquid jet in a uniform cross flow is required.

• Steel and Composite Structures
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• 제47권1호
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• pp.19-36
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• 2023

An experimental study of eleven PVC-FRP Confined Concrete (PFCC) column-Reinforced Concrete (RC) beam joints reinforced with Core Steel Tube (CST) under axial compression is carried out. All specimens are designed in accordance with the principle of "weak column and strong joint". The influences of FRP strips spacing, length and steel ratio of CST, height and stirrup ratio of joint on mechanical behavior are investigated. As the design anticipated, all specimens are destroyed by column failure. The failure mode of PFCC column-RC beam joint reinforced with CST is the yielding of longitudinal steel bars, CST and stirrups of column as well as the fracture of FRP strips and PVC tube. The ultimate bearing capacity decreases as FRP strips spacing or joint height increases. The effects of other three studied parameters on ultimate bearing capacity are not obvious. The strain development rules of longitudinal steel bars, PVC tube, FRP strips, column stirrups and CST are revealed. The effects of various studied parameters on stiffness are also examined. Additionally, an influence coefficient of joint height is introduced based on the regression analysis of test data, a theoretical formula for predicting bearing capacity is proposed and it agrees well with test data.

• Journal of Korean Neurosurgical Society
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• 제64권6호
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• pp.944-949
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• 2021

Objective : The stability is an important factor to decide the treatment plan in thoracolumbar burst fracture patients. Patients with an unstable burst fracture generally need operative management. Decrease in vertebral body height, local kyphosis, involvement of posterior column, and/or canal compromise are considered important factors to determine the treatment plan. On the other hand, in thoracolumbar injury classification system (TLICS), surgery is recommended in patients with TLICS of more than 5 points. The purpose of this study was to apply the TLICS score in patients with thoracolumbar burst fractures and to distinguish the differences of treatment plan on burst fracture. Methods : All patients, diagnosed as a thoracolumbar burst fracture between January 2006 and February 2019 were included in this study. Unstable thoracolumbar burst fracture was defined as burst fracture with neurologic deficit, three-column injury, kyphosis over 30 degrees, decrease of anterior body height over 40 percent and canal comprise more than 50%. TLICS score was measured with morphology, neurological involvement and posterior ligamentous complex integrity. The existence of instability was compared with TLICS score. Results : Total 233 patients (131 men, 102 women) were included in this study. In Denis classification, 51 patients (21.9%) diagnosed as stable burst fracture while 182 patients (78.1%) had unstable burst fracture. According to TLICS, 72 patients (30.9%) scored less than 4, while 161 patients (69.1%) scored 4 or more. All the patients with stable burst fracture scored 2 in TLICS. Twenty-one patients (9.0) scored 2 in TLICS but diagnosed as unstable burst fracture. Thirteen patients had over 40% of vertebra body compression, four patients had more than 50% of canal compromise, three patients had both body compression over 40% and kyphosis over 30 degrees, one patients had both body compression and canal compromise. Fifteen patients presented kyphosis over 30 degrees, and three (20%) of them scored 2 in TLICS. Seventy-three patients presented vertebral body compression over 40% and 17 (23.3%) of them scored 2 in TLICS. Fifty-three patients presented spinal canal compromise more than 50%, and five (9.4%) of them scored 2 in TLICS. Conclusion : Although the instability of thoracolumbar burst fracture was regarded as a critical factor for operability, therapeutic strategies by TLICS do not exactly match with the concept of instability. According to the concept of TLICS, it should be reconsidered whether the unstable burst fracture truly unstable to do operation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.203-206
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• 2005

Reinforced concrete(RC) column-bent piers represent one of the popular piers used in highway bridges of Korea. Seismic performance of RC column-bent piers under bi-directional seismic loadings was experimentally investigated. Six column bent piers were constructed with two circular supporting columns which were made in 400 mm diameter and 2,000 mm height. Test parameters are different transverse reinforcement ratio and loading pattern. Three specimens were loaded with bi-directional lateral forces which were main cyclic loads in the longitudinal direction and sub-cyclic loads in the transverse direction. Other three specimens were loaded in the opposite way. Test results indicated that lateral strength and ductility of the latter specimens were bigger than those of the former specimens. Plastic hinge was formed with the spall of cover concrete and the fracture of the longitudinal reinforcing steels in the bottom part of two supporting columns for the former three specimens. Similar behavior was observed in the top and bottom parts of two supporting columns for the latter three specimens.

• Journal of Acupuncture Research
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• 제26권4호
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• pp.1-9
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• 2009

목적 : 한양방 협진을 통한 보존적 입원 치료를 받은 급성 흉요추 압박골절 환자군에서의 압박골절 compression ratio의 급성기 내의 변화를 기록 분석하여 차후 환자군의 예후를 예측하고자 하였다. 방법 : 한양방 협진병원 척추센터에 입원하여 보존치료를 시행한 발병 2주 내의 압박골절 환자 중 2회 이상의 시점에서 압박골절 부위의 측면 X-ray 영상이 있는 환자 16명의 기록을 수집하였다. X-ray상 급성 압박골절이 발생한 추체(n=19)의 anterior wall과 posterior wall의 높이를 입원 1주차, 입원 2주차, 입원 3주차와 최종 영상 확보 시점의 X-ray에서 측정해 wedge fracture에 해당하는 anterior column fracture가 있는 추체(n=14)에 한해 anterior height/posterior height의 공식을 통해 compression ratio를 산출하였다. 2차적 지표로 입원 1주차에서 입원 3주차까지 환자의 VAS(visual analog scale) 통증 척도 점수를 분석하였다. 그 외 연령, 성별, 입원 기간, 총 치료기간, 당뇨, 골다공증, 골밀도, 압박골절 기왕력, 압박골절의 형태의 빈도와 비율을 분석하였다. 결과 : 1. 전방 골주 단독 골절에서의 compression ratio는 입원 1주차에서 3주차, 그리고 최종 영상 확보시점까지 각각 20.92${\pm}$10.42, 25.22${\pm}$10.90, 25.57${\pm}$11.04, 25.07${\pm}$11.94로 기록되었다. 시점간에는 통계적으로 유의한 compression ratio의 차이가 나타나지 않았다. 2. 통증 VAS 점수 평균은 입원 1주차부터 3주차까지 각각 7.44${\pm}$2.07, 4.67${\pm}$1.63, 3.00${\pm}$1.80으로 기록되었다. 시점간 모두 통계적으로 유의한 감소가 있었다(1주차-2주차 p=.003, 1주차-3주차 p<.000 2주차-3주차 p=0.021). 결론 : 본 연구의 협진 입원치료 압박골절의 compression ratio는 입원 1주차 시점에서 최종 follow-up 시점까지 유의한 차이를 보일 만큼의 추가적인 추체 높이 감소를 보이지 않아 향후 좋은 예후를 예상할 수 있다. 통증 VAS 점수는 모든 주별 시점간에서 유의하게 감소되었다.

• Journal of Korean Neurosurgical Society
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• 제55권3호
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• pp.142-147
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• 2014

Objective : A thoracolumbar burst fracture is usually unstable and can cause neurological deficits and angular deformity. Patients with unstable thoracolumbar burst fracture usually need surgery for decompression of the spinal canal, correction of the angular deformity, and stabilization of the spinal column. We compared two struts, titanium mesh cages (TMCs) and expandable cages. Methods : 33 patients, who underwent anterior thoracolumbar reconstruction using either TMCs (n=16) or expandable cages (n=17) between June 2000 and September 2011 were included in this study. Clinical outcome was measured by visual analogue scale (VAS), American Spinal Injury Association (ASIA) scale and Low Back Outcome Score (LBOS) for functional neurological evaluation. The Cobb angle, body height of the fractured vertebra, the operation time and amount of intra-operative bleeding were measured in both groups. Results : In the expandable cage group, operation time and amount of intraoperative blood loss were lower than that in the TMC group. The mean VAS scores and LBOS in both groups were improved, but no significant difference. Cobb angle was corrected higher than that in expandable cage group from postoperative to the last follow-up. The change in Cobb angles between preoperative, postoperative, and the last follow-up did not show any significant difference. There was no difference in the subsidence of anterior body height between both groups. Conclusion : There was no significant difference in the change in Cobb angles with an inter-group comparison, the expandable cage group showed better results in loss of kyphosis correction, operation time, and amount of intraoperative blood loss.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2005년도 학술발표회 논문집
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• pp.284-291
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• 2005

A RC column-bent pier represents one of the most popular piers used in highway bridges. Seismic performance of reinforced concrete (RC) column-bent piers under bidirectional seismic loadings was experimentally investigated. Six column bent-piers were constructed with two circular supporting columns which were made in 400mm diameter and 2,000mm height. Test parameters are different transverse reinforcement and loading pattern. These piers were tested under lateral load reversals with the axial load of $0.1f_{ck}A_g$. Three specimens were subjected to bidirectional lateral load cycles which consisted of two main longitudinal loads and two sub transverse loads in one load cycle. Other three specimens were loaded in the opposite way. Test results indicated that lateral strength and ductility of the latter three specimens were generally bigger than those of the former three specimens. Plastic hinges were formed with the spall of cover concrete and the fracture of the longitudinal reinforcing steels in the bottom plastic hinge of two supporting columns for the former three specimens. Similar behavior was observed in the top and bottom parts of two supporting columns for the latter three specimens.

• Steel and Composite Structures
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• 제35권1호
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• pp.13-27
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• 2020

To investigate the stress-strain relation of PVC-FRP Confined Concrete (PFCC) column with RC ring beam joint subjected to eccentric compression, the experiment of 13 joint specimens, which were designed with principle of "strong joint and weak column", were presented. Several variable parameters, such as reinforcement ratio, width and height of ring beam, FRP strips spacing and eccentricity, were considered. The specimens were eventually damaged by the crushing of concrete, the fracture of PVC tube and several FRP strips. With the FRP strips spacing or eccentricity increased, the ultimate carrying capacity of specimens declined. The strain of FRP strips and axial strain of PVC tube decreased as FRP strips spacing decreased. The decrease of eccentricity would slow down the development of strain of FRP strips and axial strain of PVC tube. The slope of stress-strain curve of PFCC column decreased as FRP strips spacing or eccentricity increased. The ultimate strain of PFCC column reduced as FRP strips spacing increased, while the effect of eccentricity on the ultimate strain of PFCC was not distinct. Considering the influence of eccentricity on the stress-strain relation, a modified stress-strain model for conveniently predicting the weak PFCC column and strong RC ring beam joint under eccentric compression was proposed and it was in good agreement with the experimental data.

• 한국강구조학회 논문집
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• 제29권2호
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• pp.169-180
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• 2017

본 연구에서는 국내 소규모 철골조 건축물에서 실제 시공된 보-기둥 약축 접합부에 대한 현황조사를 바탕으로 시공성을 향상시킨 약축접합부 상세를 제안하였으며, 제안된 약축접합부에 대한 반복가력 실험을 통해 접합부 내진성능을 평가하였다. 실험변수는 보-기둥 접합부에 사용된 볼트의 개수이다. 실험결과, 본 연구에서 제안하고 있는 보-기둥 약축 접합부의 거동은 수평 스티프너에 연결되는 고력볼트의 개수의 의해 결정되는 것으로 나타났다. 접합부에 4개 이상의 볼트접합이 사용될 경우 현행 기준에서 요구하는 부분 강접합 요구조건을 만족시키는 것으로 나타났다. 모든 실험체는 플랜지 연결플레이트의 연단쪽 보 플랜지 볼트 구멍 주위에서 국부적인 지압파괴와 파단 등이 발생하였다. 하지만, 웨브 높이와 플랜지 폭이 작은 기둥을 사용할 경우, 접합부에 사용되는 고력볼트의 개수가 제한적으로 사용되어야 할 것으로 판단되므로 향후 이 부분에 대한 추가적인 연구가 필요하다.

• Clinics in Shoulder and Elbow
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• 제22권1호
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• pp.29-36
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• 2019

Background: The execution of fibular allograft augmentation in unstable proximal humerus fractures (PHFs) was technically demanding. In this study, the authors evaluated the clinical and radiographic outcomes after tricortical iliac allograft (TIA) augmentation in PHFs. Methods: We retrospectively assessed 38 PHF patients treated with locking-plate fixation and TIA augmentation. Insertion of a TIA was indicated when an unstable PHF showed a large cavitary defect and poor medial column support after open reduction, regardless of the presence of medial cortical comminution in preoperative images. Radiographic imaging parameters (humeral head height, HHH; humeral neck-shaft angle, HNSA; head mediolateral offset, HMLO; and status of the union), Constant score, and range of motion were evaluated. Patients were grouped according to whether the medial column support after open reduction was poor or not (groups A and B, respectively); clinical outcomes were compared for all parameters. Results: All fractures healed radiologically (average duration to complete union, 5.8 months). At final evaluation, the average Constant score was 73 points and the mean active forward flexion was $148^{\circ}$. Based on the Paavolainen assessment method, 33 patients had good results and 5 patients showed fair results. The mean loss of reduction was 1.32 mm in HHH and 5.02% in HMLO. None of the parameters evaluated showed a statistically significant difference between the two groups (poor and not poor medial column support). Conclusions: In unstable PHFs, TIA augmentation can provide good clinical and radiological results when there are poor medial column support and a large cavitary defect after open reduction.