• Design & Manufacturing
• /
• 제17권3호
• /
• pp.48-54
• /
• 2023

In this study, an injection mold with ultra-small surface properties was manufactured using nanosecond laser processing. A superhydrophobic characteristic analysis was performed on the PET specimen manufactured through this. To this end, a hydrophobic pattern was defined using the Cassie-Baxter model. The defined features were selected with a spot diameter of 25um and pitch spacing of 30um and 35um. As a result of the basic experiment, it was confirmed that the fine pattern shape had an aspect ratio of 1:1 when the pitch interval was 35um and 20 iterations. Through the determined processing conditions, a hydrophobic pattern was implemented on the core surface of KP4. A specimen with a hydrophobic pattern was produced through injection molding. The height of the molded hydrophobic pattern is 20 ㎛ less than the depth of the core and the contact angle measurement results are 92.1°. This is a contact angle smaller than the superhydrophobic criterion. Molding analysis was performed to analyze the cause of this, and it was analyzed that the molding was not molded due to the lack of pressure in the injection machine.

• 한국강구조학회 논문집
• /
• 제26권3호
• /
• pp.155-167
• /
• 2014

강-콘크리트 합성보는 오랫동안 건물시공에 사용되어져 왔다. 합성보의 필수요소는 강재단면과 콘크리트 슬래브 사이의 전단접합이며, 주로 기계적 전단연결재가 사용되며 다양한 형상의 장치가 사용되어져 왔다. 본 연구는 앵글 전단연결재를 가진 push-out 실험체의 실험결과를 조사한 것이다. 앵글 전단연결재의 전단성능을 검토하기 위해서 모두 22개의 push-out 실험체를 설계하였으며, 앵글의 높이, 용접길이 및 앵글의 간격 등의 실험변수를 바탕으로 그 영향을 검토하였다. 실험결과를 바탕으로 앵글 전단연결재의 전단강도를 예측할 수 있는 설계식을 제안하였다.

• 대한족부족관절학회지
• /
• 제24권2호
• /
• pp.75-80
• /
• 2020

Purpose: The purpose of this study is to evaluate the results of Kidner procedure combined with medial displacement calcaneal osteotomy (MDCO) in patients with the symptomatic accessory navicular with hindfoot valgus. Materials and Methods: From January 2014 to January 2019, fifteen patients (15 cases) who had undergone a Kidner procedure combined with MDCO for symptomatic accessory navicular with hindfoot valgus were included. Their mean age was 36.3 years old (19~61 years old) and there were 6 males and 9 females. The clinical results were evaluated using visual analogue scale (VAS), American Orthopaedic Foot and Ankle Society (AOFAS) midfoot score, and postoperative subjective satisfaction. The radiographic results were evaluated using the talonavicular coverage angle and the anteroposterior talo-first metatarsal angle, the lateral talo-first metatarsal angle, the calcaneal pitch angle, and the hindfoot alignment angle. The postoperative complications were also evaluated. Results: The VAS and AOFAS midfoot scores continuously improved until 12 months after surgery. Subjective satisfaction after surgery was excellent in 10 cases and good in 5 cases. The hindfoot alignment angle significantly changed after surgery. Pain due to lateral impingement disappeared in five patients, and persisted in one patient. Five patients complained of irritation caused by their fixation devices, and all the symptoms improved after removal of the fixation devices. Conclusion: Kidner procedure combined with MDCO in patients with the symptomatic accessory navicular with hindfoot valgus showed good clinical results with satisfactory correction of hindfoot valgus. In particular, the clinical results showed continuous improvement until 12 months after surgery.

• 대한족부족관절학회지
• /
• 제17권2호
• /
• pp.143-149
• /
• 2013

Purpose: Open reduction and internal fixation of calcaneal fracture using plate has been used. While numerous plates have been manufactured, most of the conventional plates are designed for westerners, realistically the size is larger for Korean. The domestic products, on the other hand, often have the undesirable screw holes and path. Therefore, we measured the radiologic parameter of Korean calcaneus for providing the plate and screw hole placements. Materials and Methods: We measured the outer lines and angles with over the 20 years old 291 females and 322 males. A: Length of inferior plane of calcaneus, B: Length of anterior plane of calcaneus, C: Length from line A to sinus tarsi, D: Length from line A to posterior point of posterior facet, E: Length from line A to calcaneal tuberosity, F: Length of posterior facet, G: Length from anterior point of line A to C, H: Length from line C to line D, a: Angle between A and B, b: Gissane angle, c: Bohler angle, d: Calcaneal pitch angle using Marosis m-view$^{(R)}$. Results: Mean A, B, C, D, E, F, G, H were 63.6, 26.4, 23.2, 43.7, 40.5, 26.9, 12.8, 18.1 mm. Mean a, b, c, d angle were 105.8, 122.4, 32.4, $20.5^{\circ}$. Male's calcaneus is significantly bigger than female's (p<0.001). Conclusion: AP calcaneus length 63.6 mm, maximal height 43.7 mm is considered to be helpful in making the Korean calcaneal plate.

• 한국측량학회:학술대회논문집
• /
• 한국측량학회 2006년도 춘계학술발표회 논문집
• /
• pp.77-81
• /
• 2006

GPS cannot determine random errors such as multipath and signal cutoff caused by surrounding environment that determines the visibility of satellites and the speed of data creation and transmission is lower than the speed of vehicles, it is difficult to determine accurate dynamic positions. Thus this study purposed to implement a method of deciding the accurate dynamic position of vehicles by combining AHRS (Attitude Heading Reference System) IMU (Initial Measurement Unit) based on low-priced MEMS (Micro Electro Mechanical System) in order to provide the information of attitude, position and speed at a high transmission rate without external help. This study conducted an initialization test to decide dynamic position using AHRS IMU sensor, and derived attitude correction angles of vehicles against time through regression analysis. The roll angle was $y=(A{\times}10^{-6})x^2 -(B{\times}10^{-5})x+Cr{\times}10^{-2}$ and the pitch angle was $y=(A{\times}10^{-6})x^2-(B{\times}10^{-7})x+C{\times}10^{-2}$, each of which was derived from second-degree polynomial regression analysis. It was also found that the heading angle was stabilized with variation less than $1^{\circ}$ after 60 seconds.

• Wind and Structures
• /
• 제13권2호
• /
• pp.127-144
• /
• 2010

Pressure measurements on static and autorotating flat plates have been recently reported by Lin et al. (2006), Holmes, et al. (2006), and Richards, et al. (2008), amongst others. In general, the variation of the normal force with respect to the angle of attack appears to stall in the mid attack angle range with a large scale separation in the wake. To date however, no surface pressures have been measured on auto-rotating plates that are typical of a certain class of debris. This paper presents the results of an experiment to measure the aerodynamic forces on a flat plate held stationary at different angles to the flow and allowing the plate to auto-rotate. The forces were determined through the measurement of differential pressures on either side of the plate with internally mounted pressure transducers and data logging systems. Results are presented for surface pressure distributions and overall integrated forces and moments on the plates in coefficient form. Computed static force coefficients show the stall effect at the mid range angle of attack and some variation for different Reynolds numbers. Normal forces determined from autorotational experiments are higher than the static values at most pitch angles over a cycle. The resulting moment coefficient does not compare well with current analytical formulations which suggest the existence of a flow mechanism that cannot be completely described through static tests.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.1453-1460
• /
• 2003

The present study investigates the effects of rib arrangements and aspect ratios of a rectangular duct simulating the cooling passage of a gas turbine blade. Two different V-shaped rib configurations are tested with the aspect ratios (W/H) of 3 to 6.82. One is the continuous V-shaped rib configuration with $60^{\circ}$ attack angle, and the other is the discrete V-shaped rib configuration with $45^{\circ}$ attack angle. The square ribs with the pitch to height ratio of 10.0 are installed on the test section in a parallel arrangement for both rib configurations. Reynolds numbers based on the hydraulic diameter are changed from 10,000 to 30,000. A naphthalene sublimation method is used to measure local heat/mass transfer coefficients. For the continuous V-shaped rib configuration, two pairs of counter-rotating vortices are generated in a duct, and high transfer region is formed at the center of the ribbed walls of the duct. However, for the discrete V-shaped rib configuration with $45^{\circ}$ attack angle, complex secondary flow patterns are generated in the duct due to its geometric feature, and more uniform heat/mass transfer distributions are obtained for all tested cases

• 한국해양공학회지
• /
• 제32권3호
• /
• pp.208-212
• /
• 2018

In this paper, we focus on planing avoidance control for a supercavitating underwater vehicle based on the potential function method. The planing margin can be calculated using the relative position between the cavity center and vehicle center at the end of the vehicle. The planing margin was transformed into a limit variable such as the pitch angle and yaw angle limit. To prevent the vehicle attitude from exceeding the limit variable, a potential function based planing envelope protection method was proposed. The planing envelope protection system overrides commands from the tracking controller, and the vehicle attitude converges to a desired angle, in which the potential function is minimized. Numerical simulations were performed to analyze the physical feasibility and performance of the proposed method. The results showed that the proposed methods eliminated the planing, allowing the vehicle to follow tracking commands.

• 해양환경안전학회지
• /
• 제21권6호
• /
• pp.784-789
• /
• 2015

본 연구는 소형 고속정의 운항한계를 검토하기 위하여 수행되었다. 일반적으로 내항성능의 검토는 선형의 결정 단계 전에 이루어지지만 본 연구는 선박의 건조가 완료된 후에 이루어졌다. 검토 결과, 종동요, 수직 및 수평가속도, 슬래밍의 운동성능은 특정한 조우각을 제외하고는 만족하였으나 갑판침수의 경우에는 해석을 수행한 모든 조건에서 만족하지 않았다. 이것은 대상선박의 크기가 소형이기 때문에 선박의 속도나 파도와의 조우각보다는 해상상태가 설정한 내항성능 기준의 만족 여부에 더 큰 영향을 미쳤기 때문으로 보인다.

• 한국콘텐츠학회논문지
• /
• 제8권2호
• /
• pp.27-32
• /
• 2008

본 논문은 각변위 방식을 이용한 소화경로 모델링 및 경로에 대한 캡슐의 오리엔테이션 측정 방법을 제안하였다. 제안하는 방법은 캡슐 내시경의 자세를 3차원 방향벡터와 이의 회전성분으로 표현하였다. 소화경로에 대한 캡슐의 오리엔테이션 정보인 롤, 피치 그리고 요우 값은 각각 $1.6^{\circ}$ 이내의 오차를 보였다. 제안된 방법은 자기장을 이용한 오리엔테이션 측정에서 롤값 측정 문제를 해결하였다. 오일러 각을 이용한 기존의 오리엔테이션 측정 방식과 비교하여 알고리즘의 복잡도를 줄였다.