• 한국항공우주학회지
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• 제46권3호
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• pp.257-268
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• 2018

본 논문은 한국형 전투기 개발 시 적의 위협에 대한 취약성 분석을 위해 요구되는 고속 관통자가 표적을 관통하는 기구에 대해 수치 해석적으로 연구한 결과이다. 표적은 1 mm~6.3 mm 두께를 갖는 준 무한평면의 알루미늄(Aluminum) 2024 재질을 고려하였다. 관통자는 반구형 노즈 형상을 갖는 강(steel) 재질로, 입사속도는 350~3353 m/s까지, 질량은 0.32~16 g까지 갖는 것으로 고려하였다. 수치해석을 위해 사용된 실 사격 데이터는 THOR 방정식으로부터 추정하여 유추하였다. 수치해석 결과 표적을 관통하는 과정에서 관통자의 탄도한계속도는 관통자의 질량에 대한 지수 함수적으로 감소하는 수식으로 형식화(closed form of formalization) 하였다. 관통 후 잔류속도 및 잔류질량은 표적의 두께와 관통자의 질량 및 입사속도에 의존된 지수 함수적으로 감소하는 수식으로 각각 형식화하였다.

• 대한조선학회논문집
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• 제35권2호
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• pp.104-113
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• 1998

선박 생산 현장에서는 선체의 곡가공을 위해 선상가열법이 널리 사용되고 있다. 최근 선박 생산성 향상을 위하여 선상가열법에 의한 강판 곡가공 자동화 시스템에 대한 연구가 활발히 진행되고 있으나, 그 연구들은 주로 각각의 가정된 역학 모델을 도입하여 가열에 의한 판의 변형 거동을 해석하는 데에 집중되고 있고, 실제 곡면 가공에 이용될만한 실용성있는 가열선 결정 방법을 제시하는 것은 드물다. 본 논문에서는 선상가열 공정을 시뮬레이션하기 위해 새로운 가열선 결정 알고리즘을 제안한다. 이 알고리즘의 특징은 가공곡면과 목적곡면의 차이를 나타내는 변위차이곡면의 곡률을 계산하는 것이다. 몇 가지의 전형적인 곡면 형상에 대해 점검한 결과, 실용성과 적용 가능성을 확인하였다.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1115-1122
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• 2002

The present experiment investigates the effects of pore density f of aluminum foam heat sinks, the jet-to-jet spacing X and the nozzle plate-to-target surface spacing H of 3$\times$3 square impinging arrays on the averaged Nusselt number. The performance of the aluminum foam heat sinks and the rectangular plate heat sink is evaluated in terms of the enhancement factor. /equation omitted/. The multiple impinging jet with X/d=4.0 displays higher Nusselt numbers than single impinging jet for 12.0$\leq$H/d$\leq$20.0. With the variation of the jet-to-jet spacing, the aluminum foam heat sink of 10 PPI show higher Nusselt numbers than the 20 and 40 PPI aluminum foam heat sinks. Further, the 10 PPI aluminum foam heat sink demonstrates 26% higher enhancement factor than the rectangular plate heat sink in the range of 7000$\leq$Re$\leq$11000.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1426-1437
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• 2002

Using the Lagrangian explicit time-integration finite element code NET3D which can treat three-dimensional high-velocity impact problems, oblique penetration processes of long rod projectile with yaw against thin plate are simulated. Through the comparison of simulation result with experimental result and other code's computational result, the adaptability and accuracy of NET3D is evaluated under the complex situation in which yaw angle and oblique angle exist simultaneously. Main research contents to be handled in this paper include the followings. First, the accuracy and efficiency estimation of NET3D code result obtained from the oblique penetration simulations of long rod projectile with yaw against thin plate. Second, the effect of increasing impact velocity. Third, the effect of initial yaw for the spaced-plate target. Residual velocities, residual lengths, angular velocities, and final deformed configurations obtained from the NET3D computations are compared with the experimental results and other code's computational results such as Eulerian code MESA and Lagrangian code EPIC. As a result of comparisons, it has been found that NET3D code is superior to EPIC code and MESA code in the prediction capability of residual velocity and residual length of penetrator. The key features obtained from the experiment can be successfully reproduced through NET3D simulations. Throughout the study, the applicability and accuracy of NET3D as a metallic armor system design tool is verified.

• 한국표면공학회지
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• 제41권2호
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• pp.76-82
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• 2008

We investigated sterilization characteristics of UV lights by counting the number of bacteria units with varying sterilization time and distance from the light source. We focused on an idea that UV light of 184.9 nm could generate ozone and developed a new sterilizer. The UV-ozone duplex system sterilized bacteria faster than UV-only sterilizers. To reduce shadowing effects by target objects, we used UV transparent quartz plate as a support and put a reflecting plate. Distribution of UV irradiation intensity and ozone supply were analyzed by a 3D model and measured by a semiconductor UV sensor. But even with an Al reflector, multi-layered pens could not be treated properly from UV irradiation only. Ozone generating lamp could treat more uniformly multi-layered pens with a stirring fan by supplying ozone to shadowed surfaces.

• 설비공학논문집
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• 제2권4호
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• pp.295-302
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• 1990

The purpose of this study is augmentation of heat transfer without additional power in two-dimensional impinging air jet. The technique of heat transfer augmentation used in this experiment is to place rod bundles in front of the flat heated surface. The effects of rod diameter, nozzle-to-target plate distance and the nozzle exit velocity on heat transfer have been investigated. The main conclusions obtained from this experiment are as follows. High heat transfer augmentation is achieved by means of flow acceleration and thinning of boundary layer by placing rod bundles in front of the flat plate. Average heat transfer coefficient becomes maximum in the case of H/B=10,D=4mm. For H/B=2,D=4mm, maximum heat transfer augmentation has been determined to be about 1.5 times larger than that of the flat plate. Heat transfer augmentation by placing the rod bundles at 12m/s is to be about 2 times more than increasing nozzle exit velocity from 12m/s to 18m/s.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제9권3호
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• pp.166-171
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• 2009

In recent years, video detection systems have been implemented in various infrastructures such as airport, public transportation, power generation system, water dam and so on. Recognizing moving objects in video sequence is an important problem in computer vision, with applications in several fields, such as video surveillance and target tracking. Segmentation and tracking of multiple vehicles in crowded situations is made difficult by inter-object occlusion. In the system described in this paper, the mean shift algorithm is firstly used to filter and segment a color vehicle image in order to get candidate regions. These candidate regions are then analyzed and classified in order to decide whether a candidate region contains a license plate or not. And then some characters in the license plate is recognized by using the fuzzy ARTMAP neural network, which is a relatively new architecture of the neural network family and has the capability to learn incrementally unlike the conventional BP network. We finally design a license plate recognition system using the mean shift algorithm and fuzzy ARTMAP neural network and show its performance via some computer simulations.

• Structural Engineering and Mechanics
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• 제20권4호
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• pp.451-463
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• 2005

Structural members commonly employed in marine and off-shore structures are usually fabricated from plates and shells. Collision of this class of structures is usually modeled as plate and shell structures subjected to dynamic impact loading. The understanding of the dynamic response and energy transmission of the structures subjected to low velocity impact is useful for the efficient design of this type of structures. The transmissions of transient energy flow and dynamic transient response of these structures under low velocity impact are presented in the paper. The structural intensity approach is adopted to study the elastic transient dynamic characteristics of the plate structures under low velocity impact. The nine-node degenerated shell elements are adopted to model both the target and impactor in the dynamic impact response analysis. The structural intensity streamline representation is introduced to interpret energy flow paths for transient dynamic response of the structures. Numerical results, including contact force and transient energy flow vectors as well as structural intensity stream lines, demonstrate the efficiency of the present approach and attenuating impact effects on this type of structures.

• Journal of Dental Anesthesia and Pain Medicine
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• 제18권5호
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• pp.295-300
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• 2018

Background: Removal of the plate following Le Fort I osteotomy and BSSO (bilateral sagittal split osteotomy) is a common procedure. However, patients who undergo plate removal experience intense pain and discomfort. This study investigated the half-maximal effective concentration ($Ce_{50}$) of remifentanil in the prevention of plate removal pain under sedation using dexmedetomidine. Methods: The study evaluated 18 patients, between 18 and 35 years of age, scheduled for elective surgery. Remifentanil infusion was initiated after sedation using dexmedetomidine, and started at a dose of 1.5 ng/mL on the first patient via target-controlled infusion (TCI). Patients received a loading dose of $1.0{\mu}g/kg$ dexmedetomidine over 10 min, followed by a maintenance dose of $0.7{\mu}g/kg/h$. When the surgeon removed the plate, the patient Modified Observer's Assessment of Alertness/Sedation (MOAA/S) score was observed. Results: The Ce of remifentanil ranged from 0.9 to 2.1 ng/mL for the patients evaluated. The estimated effect-site concentrations of remifentanil associated with a 50% and 95% probability of reaching MOAA/S score of 3 were 1.28 and 2.51 ng/mL, respectively. Conclusion: Plate removal of maxilla can be successfully performed without any pain or adverse effects by using the optimal remifentanil effect-site concentration ($Ce_{50}$, 1.28 ng/mL; $Ce_{95}$, 2.51 ng/mL) combined with sedation using dexmedetomidine.

• 대한조선학회논문집
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• 제56권4호
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• pp.308-315
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• 2019

In this study, numerical simulations of slamming impact pressure acting on the flat plate and wedge type models using the cartesian-grid system and Modified Marker-Density Method (MMD method) were performed and the results were examined. The flat plate and wedge type models were selected as target objects, the turbulence characteristics were considered by applying the Sub-Grid Scale (SGS) turbulence model. Through this study, how the pressure acting on the target objects according to the incident angle influences the slamming impact pressure was examined and the results were compared with the flow characteristics of other experimental results. Also, the degree of slamming impact pressure is evaluated with respect to the cartesian-grid system and MMD method, which is easy to use and has a high degree of calculation for free surface.