• Journal of Korean Neurosurgical Society
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• 제65권5호
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• pp.652-664
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• 2022

The Kernohan-Woltman notch phenomenon (KWNP) refers to an intracranial lesion causing massive side-to-side mass effect which leads to compression of the contralateral cerebral peduncle against the free edge of the cerebellar tentorium. Diagnosis is based on "paradoxical" motor deficit ipsilateral to the lesion associated with radiologic evidence of damage to the contralateral cerebral peduncle. To date, there is scarce evidence regarding KWNP associated neuroimaging patterns and motor function prognostic factors. A systematic review was conducted on Medline database from inception to July 2021 looking for English-language articles concerning KWNP, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The research yielded 45 articles for a total of 51 patients. The mean age was 40.7 years-old and the male/female sex ratio was 2/1. 63% of the patients (32/51) suffered from head trauma with a majority of acute subdural hematomas (57%, 29/51). 57% (29/51) of the patients were in the coma upon admission and 47% (24/51) presented pupil anomalies. KWNP presented the neuroimaging features of compression ischemic stroke located in the contralateral cerebral peduncle, with edema in the surrounding structures and sometimes compression stroke of the cerebral arteries passing nearby. 45% of the patients (23/51) presented a good motor functional outcome; nevertheless, no predisposing factor was identified. A Glasgow coma scale (GCS) of more than 3 showed a trend (p=0.1065) toward a better motor functional outcome. The KWNP is a regional compression syndrome oftentimes caused by sudden and massive uncal herniation and leading to contralateral cerebral peduncle ischemia. Even though patients suffering from KWNP usually present a good overall recovery, patients with a GCS of 3 may present a worse motor functional outcome. In order to better understand this syndrome, future studies will have to focus on more personalized criteria such as individual variation of tentorial notch width.

• Wind and Structures
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• 제37권3호
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• pp.211-227
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• 2023

To investigate the non-Gaussian feature of fluctuating wind pressures on rectangular high-rise buildings, wind tunnel tests were conducted on scale models with side ratios ranging from 1/9~9 in an open exposure for various wind directions. The high-order statistical moments, time histories, probability density distributions, and peak factors of pressure fluctuations are analyzed. The mixed normal-Weibull distribution, Gumbel-Weibull distribution, and lognormal-Weibull distribution are adopted to fit the probability density distribution of different non-Gaussian wind pressures. Zones of Gaussian and non-Gaussian are classified for rectangular buildings with various side ratios. The results indicate that on the side wall, the non-Gaussian wind pressures are related to the distance from the leading edge. Apart from the non-Gaussianity in the separated flow regions noted by some literature, wind pressures behind the area where reattachment happens present non-Gaussian nature as well. There is a new probability density distribution type of non-Gaussian wind pressure which has both long positive and negative tail found behind the reattachment regions. The correlation coefficient of wind pressures is proved to reflect the non-Gaussianity and a new method to estimate the mean reattachment length of rectangular high-rise building side wall is proposed by evaluating the correlation coefficient. For rectangular high-rise buildings, the mean reattachment length calculated by the correlation coefficient method along the height changes in a parabolic shape. Distributions of Gaussian and non-Gaussian wind pressures vary with side ratios. It is inappropriate to estimate the extreme loads of wind pressures using a fixed peak factor. The trend of the peak factor with side ratios on different walls is given.

• Composites Research
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• 제36권4호
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• pp.259-263
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• 2023

This study investigated the open hole tensile (OHT) properties of carbon fiber/epoxy composites and compared them to bolt joint tensile (BJT) properties. The net nominal modulus and strength (1376 MPa) were found to be higher than the gross nominal strength (1041 MPa), likely due to increasing hole size. The OHT and BJT specimens exhibited similar stiffness, as expected without bolt rotation causing secondary bending. OHT specimens experienced a sharp drop in stress indicating unstable crack propagation, delamination, and catastrophic failure. BJT specimens failed through shear out on the bolt side and bearing failure on the nut side, involving fiber kinking, matrix splitting, and delamination, resulting in lower strength compared to OHT specimens. The strength retention of carbon fiber/epoxy composites with open holes was 66%. Delamination initiation at the hole's edge caused a reduction in the stress concentration factor. Filling the hole with a bolt suppressed this relieving mechanism, leading to lower strength in BJT specimens compared to OHT specimens. Bolt joint efficiency was calculated as 15%. The reduction in strength in bolted joints was attributed to fiber-matrix splitting and delamination, aligning with Hart Smith's bolted joint efficiency diagram. These findings contribute to materials selection and structural reliability estimation for carbon fiber/epoxy composites. They highlight the behavior of open hole and bolt joint configurations under tensile loading, providing valuable insights for engineering applications.

• 천문학회보
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• 제46권1호
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• pp.43.1-43.1
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• 2021

In this study, we suggest a new method to estimate the mass of a halo coronal mass ejection (CME) using synthetic CMEs. For this, we generate synthetic CMEs based on two assumptions: (1) the CME structure is a full ice-cream cone, (2) the CME electron density follows a power-law distribution (ρ_cme=ρ₀r^-n). The power-law exponent n is obtained by minimizing the root mean square error between the electron number density distributions of an observed CME and the corresponding synthetic CME at a position angle of the CME leading edge. By applying this methodology to 57 halo CMEs, we estimate two kinds of synthetic CME mass. One is a synthetic CME mass which considers only the observed CME region (M_cme1), the other is a synthetic CME mass which includes both the observed CME region and the occulted area larger than 4 solar radii (M_cme2). From these two cases, we derive conversion factors which are the ratio of a synthetic CME mass to an observed CME mass. The conversion factor for M_cme1 ranges from 1.4 to 3.0 and its average is 2.0. For M_cme2, the factor ranges from 1.8 to 5.0 with the average of 3.0. These results imply that the observed halo CME mass can be underestimated by about 2 times when we consider the observed CME region, and about 3 times when we consider the region including the occulted area. Interestingly these conversion factors have a very strong negative correlation with angular widths of halo CMEs.We also compare the results with the CME mass estimated from STEREO observations.

• 대한토목학회논문집
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• 제26권4B호
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• pp.413-420
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• 2006

연안역에 설치되는 구조물로서 경관이나 해수 교환면에서 높은 기능을 가지고 있는 수중방파제의 건설이 증가하고 있다. 수중방파제의 경우, 천단이 정수면 아래에 위치하기 때문에 소형선박의 항해에 대한 표식으로서 일반적으로 부이가 많이 이용되고 있으나, 경관면 뿐만 아니라 쇄파파력에 의한 계류시스템의 파단과 같은 문제점이 지적되고 있다. 이로 인해, 최근에는 계류부이방식 대신에 자연에 가까운 경관을 창조할 수 있는 표식암을 이용하는 경우가 늘고 있으며, 이러한 표식암에 작용하는 파력의 정확한 예측은 설계 시 매우 중요하다. 본 연구에서는 불규칙 파동장을 대상으로 표식암에 작용하는 파력특성을 수리모형실험에 근거하여 검토하였다. 무차원 파력은 수중방파제상의 표식암 설치위치가 연안측으로 이동함에 따라 감소하는 경향을 보였다. 또한, Morison식을 이용하여 얻어진 항력계수와 관성력계수의 변동특성이 K.C.수의 변화와 연관되어 논의되었다.

• Geomechanics and Engineering
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• 제37권1호
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• pp.65-72
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• 2024

Water ingress poses a common and intricate geological hazard with profound implications for tunnel construction's speed and safety. The project's success hinges significantly on the precision of estimating water inflow during excavation, a critical factor in early-stage decision-making during conception and design. This article introduces an optimized model employing the gene expression programming (GEP) approach to forecast tunnel water inflow. The GEP model was refined by developing an equation that best aligns with predictive outcomes. The equation's outputs were compared with measured data and assessed against practical scenarios to validate its potential applicability in calculating tunnel water input. The optimized GEP model excelled in forecasting tunnel water inflow, outperforming alternative machine learning algorithms like SVR, GPR, DT, and KNN. This positions the GEP model as a leading choice for accurate and superior predictions. A state-of-the-art machine learning-based graphical user interface (GUI) was innovatively crafted for predicting and visualizing tunnel water inflow. This cutting-edge tool leverages ML algorithms, marking a substantial advancement in tunneling prediction technologies, providing accuracy and accessibility in water inflow projections.

• Wind and Structures
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• 제38권1호
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• pp.59-74
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• 2024

Large Eddy Simulation (LES) is used to explore the influence of vibration frequency and amplitude on the aerodynamic performance of a rectangular cylinder with an aspect ratio of B/D=5 (B: breadth; D: depth of cylinder) at a Reynolds number of 22,000 near resonance frequency. In smooth flow conditions, the research employs a sequence of three-dimensional simulations under forced vibration with diverse frequency ratios f_e / f_o = 0.8-1.2 (f_e : oscillation frequency; f_o : Strouhal frequency when the rectangular cylinder is stationary ) and oscillation amplitudes A_h/D = 0.05 - 0.3. The individual influences of f_e / f_o and A_h/D on the characteristics of integrated and distributed aerodynamic forces are the focal points of discussion. For the integrated aerodynamic force, particular emphasis is placed on the analysis of the dependence of velocity-proportional component C₁ and displacement-proportional component C₂ of unsteady aerodynamic force on amplitude and frequency ratio. Near the resonance frequency, the dependencies of C₁ and C₂ on amplitude are stronger than that of frequency ratio. For the distributed aerodynamic force, the increase in frequency and amplitude promotes the position of the main vortex core and reattachment to the leading edge in the streamwise direction. In the spanwise direction, vibration enhances the spanwise correlation of aerodynamic force to weaken the three-dimensional effect of the flow field, and a lower frequency ratio and larger amplitude amplify this effect.

• Journal of Animal Science and Technology
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• 제48권2호
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• pp.331-336
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• 2006

소의 개체 관리의 효율성을 높이기 위한 수단으로써 축사의 유도로에 시각제어를 처리하였을 때와 시각제어를 하지 않은 경우에 있어서 한우 집단의 이동시간을 비교하였다. 일반적인 파이프로 시설된 유도로에 비해 불투명한 청색 커튼을 처리 하였을 때 유도로를 통과하는 소의 이동시간이 짧아졌으며 짧은 유도로보다 긴 유도로에서 처리간 유의적인 차이가 나타났다. 아울러 본 실험을 통하여 유도로와 함께 유도로 입구 설계 역시 부드러운 곡선의 형태를 함으로써 소의 머뭇거림을 방지할 수 있음을 보여줬다.유도로가 긴 실험에서 crowd pen에서 선두 소가 유도로에 진입하기까지의 시간에서는 시각 제어 처리한 경우와 처리하지 않은 경우 간에 유의적인 차이가 없었다. 그러나 선두 소가 crowd pen 으로부터 우형기까지 진입하는 시간은 시각 제어 처리를 한 경우가 22.78±1.15초로 처리하지 않았을 때의 40.56±4.46초 보다 유의적으로 단축되었다. 또한 선두소가 유도로에 진입한 시간을 뺀 작업시간과 총 작업시간에 있어서도 시각제어 처리한 경우가 96.33±3.98, 104.56±3.89초로 시각제어를 하지 않은 경우의 121.89±5.54, 131.22±6.42초 보다 모두 유의적으로 단축되었다.유도로가 짧은 실험에서는 유도로가 긴 실험에 비하여 crowd pen의 모서리 모양이 직각으로 되어 시험축 집단의 유도로 진입이 부드럽지 않았다. holding pen에서 crowd pen으로 선두 소가 유도로를 진입한 시간에는 처리간 유의적인 차이가 없었다. 총시간에서 선두 소가 crowd pen을 진입한 시간을 뺀 작업시간에 있어서는 처리 간에 유의적인 차는 없었는데 이는 유도로로 연결된 crowd pen의 모서리 형태의 영향이 크게 작용한 것으로 추측된다. 총작업 시간은 시각제어처리가 209.89±6.06초로 처리하지 않았을 때의 243.56±10.53초 보다 유의적으로 단축됨을 보였다.

• 한국산학기술학회논문지
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• 제16권12호
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• pp.8314-8324
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• 2015

본 경쟁력 있는 국방력을 유지하기 위해서는 무기체계의 지속적인 양산도 중요하지만 유지보수 및 성능개량 또한 중요한 요소로 인식되게 되었다. 방위사업청의 주도로 국내 국방획득사업이 시스템공학을 기반으로 점차 과학화로 진전되면서, 무기체계획득에서 신연구개발사업 뿐만 아니라 성능개량사업에 대해서도 효율적 관리에 관심이 집중되게 되었다. 한편 국외상업구매는 국내 국방획득사업 형태의 하나로서, 지금까지 단순 구매사업으로 취급되어 왔는데, 특히 개조 개발이 필요한 경우 문제점이 많이 있음이 인지되었다. 본 연구에서는 무기체계 성능개량 사업 중 개조 개발이 수반되는 국외상업구매 사업에 대해서도 연구개발 수준의 프로세스를 적용해야 할 필요성을 제시하고, 관련 개선 프로세스를 연구하였다. 구체적으로 개조 개발단계 획득프로세스를 시스템공학 기반에 따라 정립하고, 요구문서 작성 프로세스와 템플릿을 도출하였다. 제안된 프로세스와 템플릿의 적용을 통해 국외상업구매를 통한 무기체계 성능개량 사업에서 개조 개발에 대한 정확한 요구분석과 효율적 사업수행 및 사업목표 달성에 대한 신뢰도 향상이 기대된다.

• 대한치과보철학회지
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• 제41권4호
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• pp.503-518
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• 2003

Statement of problem : There have been previous studies about considerable variations in machining accuracy and consistency in the implant-abutment-screw interfaces. Purpose : The purpose of this study was to evaluate the machining accuracy and consistency of implant/abutment/screw combinations on two randomly selected implants from each of four manufactures. Material and methods : In this study, screws were respectively used to secure a cemented abutment, to a hexlock implant fixture ; teflon coated titanium alloy screw(Torq-Tite) and titanium alloy screw in Steri--Oss system, gold-plated gold-palladium alloy screw(Gold-Tite) and titanium alloy screw in 3i system gild screw ana titanium screw in AVANA Dental Implant system, and titanium screws in Paragon System. The implants were perpendicularly mounted in polymethyl methacrylate autopolymerizing acrylic resin block(Orthodontic resin, Densply International Inc. USA) by use of dental surveyer. Each abutment screw was secured to the implant with recommended torque value using a digital torque controller. Each screw was again tightened after 10 minutes. All samples were cross sectioned with grinder-polisher unit(Omnilap 2000 SBT Inc) after embeded in liquid unsaturated polyester (Epovia, Cray Valley Inc) Results : There were the largest gaps in the neck areas of screws in hexagonal extension implants which were examined in this study. The leading edge of the abutment screw thread (superior surface) was in contact with the implant body thread, and the majority of the contacting surfaces were localized to the middle portion of the mating threads. Considerable variation in the contacting surfaces was noted in the samples evaluated. Amounts of contact in the abutment screw thread were larger for assemblies with Gold-Tite screw, gold alloy screw. Torq-Tite screw than those with titanium screws. The findings of intimate contact between the screw and screw seat were seen in all samples, regardless of manufacturers. However, microgap between the head and lateral neck surface of the screw and the abutment could be dectected in all samples. The findings of intimate contact between the platform of the implant and the bottom of the abutment were consistent in all samples, regardless of manufacturers. However, microgaps between the lateral surface of external hex of the fixture and the abutment could be dectected in all samples. Conclusion : Considerable variations in machining accuracy and consistency were noted in the samples and the implant-abutment-screw interfaces were incomplete. From the results of this study, further development of the system will be required, including improvements in pattern design.