• The korean journal of orthodontics
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• v.49 no.6
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• pp.393-403
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• 2019

Objective: Sliding mechanics using orthodontic miniscrews is widely used to stabilize the anchorage during extraction space closure. However, previous studies have reported that both posterior segment displacement and anterior segment displacement are possible, depending on the mechanical properties of the archwire. The present study aimed to investigate the effect of archwire stiffness and friction change on the displacement pattern of the maxillary posterior segment during anterior segment retraction with orthodontic miniscrews in sliding mechanics. Methods: A three-dimensional finite element model was constructed. The retraction point was set at the archwire level between the lateral incisor and canine, and the orthodontic miniscrew was located at a height of 8 mm from the archwire between the second premolar and first molar. Archwire stiffness was simulated with rectangular stainless steel wires and a rigid body was used as a control. Various friction levels were set for the surface contact model. Displacement patterns for the posterior and anterior segments were compared between the conditions. Results: Both the anterior and posterior segments exhibited backward rotation, regardless of archwire stiffness or friction. Among the conditions tested in this study, the least undesirable rotation was found with low archwire stiffness and low friction. Conclusions: Posterior segment displacement may be unavoidable but reducing the stiffness and friction of the main archwire may minimize unwanted rotations during extraction space closure.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.462-462
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• 2017

유량은 기후적 요인과 인간활동 요인에 의하여 변동된다. 특히 우리나라는 지난 30년 동안 전지구적인 기후변화와 특정지역에서의 인간활동의 변화가 급격하게 진행된 바 있으므로, 합리적인 수자원 계획을 수립하기 위해서는 두 가지 요소들로 인한 유량의 변동량을 정량적으로 분리하여 분석할 필요가 있다. 또한 우리나라와 같이 연강수량의 대부분이 특정 계절에 집중되는 국가나 유역에서는 월별, 계절별 및 년별로 구분된 수문분석을 시행하여야 보다 실질적인 수자원 관리계획을 수립할 수 있다. 그러나 유량의 변동량을 특정 원인별로 구분하여 분석하고자 하는 연구는 기존의 홍수나 가뭄 자체에 관한 연구에 비해 미미한 형편이며, 다양한 시간단위를 이용한 원인별 유량 변동량의 산정에 관한 연구는 더욱 찾아보기 힘들다. 따라서 본 연구에서는 기후변화로 및 인간활동으로 인한 유량 변동량을 정량적으로 분리하기 위하여 수문모형(hydrological model)을 이용한 방법과 수문학적 민감도 (hydrological sensitivity) 분석 방법을 소양강 상류유역 및 섬강 유역에 대해 적용하고 유량 변동량의 결과를 월별, 분기별 및 년별로 구분하여 제시하였다. 먼저 두 유역에 대한 기후변화 및 인간활동의 양상을 강수, 온도, 유량, 인구변화, 불투수층 변화의 추세를 통해 파악하였으며, 인간활동으로 인해 발생되는 급진적인 변동점을 탐색하기 위해 이중누가곡선, Pettitt 검정 및 베이지안 변동점 (Bayesian change point) 분석을 시행하였다. 탐색된 변동점을 활용하여 수문모형에 의한 유량 변동량을 정량화하기 위하여 변동점 이전 구간에 대해 보정 및 검증된 SWAT모형을 사용하였으며, 6가지의 Budyko 곡선 함수들로부터 각각 유량 변동량을 산정하여 수문모형에 의한 유량 변동량을 검증하였다. 최종적으로 수문모형을 이용한 방법을 통해 두 유역에 대한 기후변화 및 인간활동으로 인한 유량 변동량을 정량화하였다. 소양강 상류유역은 기후변화로 인한 유량 변동량이 인간활동으로 인한 유량변동량보다 상대적으로 크게 산정되었으며, 섬강 유역은 소양강 유역과 반대의 결과를 보이는 것으로 분석되었다. 특히 본 연구에서는 해당 분석결과를 월별 및 분기별로 구분하여 제시함으로써, 향후 특정 지역 및 시기에서의 합리적인 수자원 관리계획의 수립에 활용될 수 있는 기초적인 자료를 제공하였다.

• Nuclear Engineering and Technology
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• v.43 no.2
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• pp.133-140
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• 2011

In this paper, a deformation measurement technology for nuclear fuel rods is proposed. The deformation measurement system includes a high-definition CMOS image sensor, a lens, a semiconductor laser line beam marker, and optical and mechanical accessories. The basic idea of the proposed deformation measurement system is to illuminate the outer surface of a fuel rod with a collimated laser line beam at an angle of 45 degrees or higher. For this method, it is assumed that a nuclear fuel rod and the optical axis of the image sensor for observing the rod are vertically composed. The relative motion of the fuel rod in the horizontal direction causes the illuminated laser line beam to move vertically along the surface of the fuel rod. The resulting change of the laser line beam position on the surface of the fuel rod is imaged as a parabolic beam in the high-definition CMOS image sensor. An ellipse model is then extracted from the parabolic beam pattern. The center coordinates of the ellipse model are taken as the feature of the deformed fuel rod. The vertical offset of the feature point of the nuclear fuel rod is derived based on the displacement of the offset in the horizontal direction. Based on the experimental results for a nuclear fuel rod sample with a formation of surface crud, an inspection resolution of 50 ${\mu}m$ is achieved using the proposed method. In terms of the degree of precision, this inspection resolution is an improvement of more than 300% from a 150 ${\mu}m$ resolution, which is the conventional measurement criteria required for the deformation of neutron irradiated fuel rods.

• Asian Journal of Innovation and Policy
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• v.10 no.2
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• pp.195-211
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• 2021

This paper measures the economic impacts of the U.S. port investment strategies coping with the Panama Canal expansion. Using secondary import data, negative and positive estimates of the impacts were presented in this study. Reduced port activities into the West Coast Customs Districts negatively affect transportation and warehousing industries, among other effects. Still, they have simultaneous positive effects in other states from increased imports resulting from modal shifts and changes in the entry port located in the South and East coasts. This study applied the supply-driven National Interstate Economic Model that measures all interstate trade among the U.S. states to divert foreign imports from 15 Pacific Rim countries. For this purpose, the following assumption was adopted: larger ships using the canal will lead to a redirection of seaborne trade among U.S. (and other) ports and result in secondary effects, e.g., using different freight modes and regional growth spillovers. This study also accounted for the entry point change and significant port investments for foreign trade under alternative scenarios. The choice of ports for international trade depends on decisions about how to minimize multimodal delivery costs. The total direct reduction of transportation and warehousing activities associated with foreign imports in the West Coast ports was estimated at $3.3 billion, leading to total negative effects of $5.8 billion. Total positive impacts from the shift of transportation modes with the choice of an entry port and new warehousing activities for foreign imports in the selected 12 states varied. As expected, states that involved an entry port had the most prominent benefits, but Texas, New York, and New Jersey may be benefited through all the port enhancement projects in the U.S. Also, except for Transportation and Postal, and Warehousing industries, Construction is another dominant positive affected industry of the Canal expansion in the U.S.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.270-277
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• 2021

In the power ultrasound fields, the flange position for fixing the transducer is an important factor influencing on electro-mechanical efficiency of the transducer. We suggested a practical method that can determine the installation position of the flange for different resonance modes of the bolt-clamped type Langevin ultrasonic transducer. A semicircular wedge-shaped jig was manufactured and moved along the lateral surface of the transducer. The vibration characteristics were examined after a constant pressure was applied to the semicircular wedge-shaped jig. By observing the change of the input admittance of the transducer depending on the position of the pressure application, the optimum position for the flange installation could be determined. The resonant modes of the transducer were calculated by a Mason's equivalent circuit, and the particle velocity distribution for each resonance mode was calculated by a transmission line model. Since the optimum positions determined from an experimental result show a good correspondence with the node positions of the vibration modes calculated by the transmission line model, the validity of the suggested method was verified.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.305-311
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• 2019

In this study, present the most useful delay scan time by statistical analysis of SUVm data for 30 suspected pancreatic cancer patients. Two statistical analysis and a mathematical model was applied to the theoretical formula by glucose and insulin mechanics, and a mathematical model was created. Statistical analysis was performed via Metlab p/g. Optimal delay scan time was suggested by Metlab p/g for the change of SUV value over time.In this study, for diagnosis pancreatic cancer by dual time point PET/CT, propose optimal delay scan time 131.5 minuts. The proposed delay scan time showed statistical reliability applicable to the diagnosis of pancreatic cancer (p<0.05). Delayed scanning with the suggested delay scan time of 131.5 minutes is considered to be useful for the diagnosis of pancreatic cancer compared to general PET / CT scan.hen the delayed test is performed with the proposed delay scan time 131.5 minuts, Compared with general PET/CT scans.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.251-258
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• 2018

Recently, due to the increase in the traffic volume of vehicle, the collision of the vehicle collision has been increased so that the neck injuries of the passengers has been increased. In order to prevent this, vehicle collision analysis research using computer simulation has been actively carried out in consideration of the design point of car seat. In this study, I used the MADYMO program for analyzing the passenger behavior using a BioRID II dummy, and predicted the neck injuries of passengers according to the change of the backset at the rearward collision of the driving speed of 16km/h. As a result, it was found that the shorter the backset, the shorter the contact start time but the contact completion time was almost the same and the T1 acceleration showed that the acceleration increased with the backset. In addition, the tensile strength increases as the backset increases, and NIC (Neck Injury Criterion) increases as the head speed reaches the headrest.

• Journal of Korean Neurosurgical Society
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• v.62 no.2
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• pp.183-192
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• 2019

Objective : The objective of this study was to analyze patient-specific blood flow in ruptured aneurysms using obtained non-Newtonian viscosity and to observe associated hemodynamic features and morphological effects. Methods : Five patients with acute subarachnoid hemorrhage caused by ruptured posterior communicating artery aneurysms were included in the study. Patients' blood samples were measured immediately after enrollment. Computational fluid dynamics (CFD) was conducted to evaluate viscosity distributions and wall shear stress (WSS) distributions using a patient-specific geometric model and shear-thinning viscosity properties. Results : Substantial viscosity change was found at the dome of the aneurysms studied when applying non-Newtonian blood viscosity measured at peak-systole and end-diastole. The maximal WSS of the non-Newtonian model on an aneurysm at peak-systole was approximately 16% lower compared to Newtonian fluid, and most of the hemodynamic features of Newtonian flow at the aneurysms were higher, except for minimal WSS value. However, the differences between the Newtonian and non-Newtonian flow were not statistically significant. Rupture point of an aneurysm showed low WSS regardless of Newtonian or non-Newtonian CFD analyses. Conclusion : By using measured non-Newtonian viscosity and geometry on patient-specific CFD analysis, morphologic differences in hemodynamic features, such as changes in whole blood viscosity and WSS, were observed. Therefore, measured non-Newtonian viscosity might be possibly useful to obtain patient-specific hemodynamic and morphologic result.

• Journal of Korea Water Resources Association
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• v.52 no.1
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• pp.1-10
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• 2019

This study investigates the flow characteristics, such as velocity distributions, size and location of recirculation zone, longitudinal flow change rates, and bifurcation discharge ratio in the bifurcation channel by TELEMAC-2D, a 2D numerical model. The numerical model is validated by previous experimental results and the numerical results are in relatively good agreement with the experimental results, such as the water surface elevation and velocity distribution in the channels. As the inertial force and moment in the main channel decrease, the bifurcation discharge ratio increases, and the relative high velocity distribution becomes wider and the reverse velocity of the main stream decreases in the branch channel. As the bifurcation discharge ratio increases, the size of the recirculation zone in the branch channel decreases and it can be more clearly calculated by determining the point where the longitudinal froude number $Fr{\approx}0$ as well as drawing the distribution of the streamline distribution.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1395-1408
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• 2014

In this research, a River Recreation Index Model (RRIM) was developed to provide sufficient information on the water quality of rivers to the public in order to secure safety of publics. River Recreation Index (RRI) is an integrated water quality information for recreation activities in rivers and expressed as the point from 0 to 100. The proposed RRIM consisted of two sub models: Fecal Coliform Model (FCM) and Water Quality Index Model (WQIM). FCM predicted Fecal Coliform Grade (FCG) using a logistic regression and WQIM synthesized water quality parameters of, DO, pH, turbidity and chlorophyll a into Water Quality Index (WQI). FCG and WQI were integrated into RRI by the integrating algorithm. The proposed model was applied to upstream of Gangjeong Weir in Nakdong River, and compared with Real Time Water Quality Index (RTWQI) which is the existing water quality information system for recreation use. The results show that calculated RRI reflected change of integrated water quality parameters well. Especially chlorophyll a showed Pearson correlation coefficient -0.85 with RRI. Also, RRIM produced more conservative index than RTWQI because RRI was calculated considering uncertainty of water quality criteria. Further, RRI showed especially low values when fecal coliform was predicted as low grade.