• International Journal of Naval Architecture and Ocean Engineering
• /
• 제10권6호
• /
• pp.730-740
• /
• 2018

Hydrofoil is the direct component to generate thrust for underwater glider. It is significant to improve propulsion efficiency of hydrofoil. This study optimizes the shape of a hydrofoil using Free-Form Deformation (FFD) parametric approach and Surrogate-based Optimization (SBO) algorithm. FFD approach performs a volume outside the hydrofoil and the position changes of control points in the volume parameterize hydrofoil's geometric shape. SBO with adaptive parallel sampling method is regarded as a promising approach for CFD-based optimization. Combination of existing sampling methods is being widely used recently. This paper chooses several well-known methods for combination. Investigations are implemented to figure out how many and which methods should be included and the best combination strategy is provided. As the hydrofoil can be stretched from airfoil, the optimizations are carried out on a 2D airfoil and a 3D hydrofoil, respectively. The lift-drag ratios are compared among optimized and original hydrofoils. Results show that both lift-drag-ratios of optimized hydrofoils improve more than 90%. Besides, this paper preliminarily explores the optimization of hydrofoil with root-tip-ratio. Results show that optimizing 3D hydrofoil directly achieves slightly better results than 2D airfoil.

• Tribology and Lubricants
• /
• 제39권2호
• /
• pp.61-71
• /
• 2023

This study proposes a procedure for designing a labyrinth seal that meets both leakage flow rate and rotordynamic performance criteria (effective damping, amplification factor, separation margin, logarithmic decrement, and vibration amplitude). The seal is modeled using a one control volume (1CV) bulk flow approach to predict the leakage flow rate and rotordynamic coefficients. The rotating shaft is modeled with the finite element (FE) method and is assumed to be supported by two linearized bearings. Geometry, material and operating conditions of the rotating shaft, and the supporting characteristics of the bearings were fixed. A single labyrinth seal is placed at the center of the rotor, and the linearized dynamic coefficients predicted by the seal numerical model are inserted as linear springs and dampers at the seal position. Seal designs that satisfy both leakage and rotordynamic performance are searched by modifying five seal design parameters using the multi-grid method. The five design parameters include pre-swirl ratio, number of teeth, tooth pitch, tooth height and tooth tip width. In total, 12500 seal models are examined and the optimal seal design is selected. Finally, normalization was performed to select the optimal labyrinth seal designs that satisfy the system performance requirements.

• Restorative Dentistry and Endodontics
• /
• 제28권4호
• /
• pp.334-340
• /
• 2003

This study was performed to evaluate the actual temperature rise on the surface of Buchanan plugger using thermocouple. The heat carrier system 'System B Heatsource'(Model 1005, Analytic Technologies, Redmond, WA, USA) and the Buchanan pluggers of F, FM, M and ML sizes are used for this study. The temperature was set to 200^{\circ}C on digital display and the power level on it was set to 10. Five thermocouples were placed in direct contact with the surface of each size of Buchanan's pluggers at 1 mm increments from the tip to the 4 mm length of shank. The heat control spring was touched for 5 seconds. and the temperature rise on the surface of the pluggers were measured at 1 sec intervals for more than 5 seconds with an accuracy of 0.01 using Data Logger. The data were statistically analyzed by one-way ANOVA. The results were as follows. 1. The position at which the temperature peaked was approximately at 1~2 mm far from the tip of Buchanan plugger (p<0.01). 2. The peak temperature was $215.25{\pm}2.28^{\circ}C$ in F plugger. $185.94{\pm}2.19^{\circ}C$ in FM plugger, $169.51{\pm}9.12^{\circ}C$ in M plugger, and 160.79{\pm}1.27^{\circ}C in ML plugger and the peak temperature was highest in F plugger and followed by. in descending order. FM plugger. M plugger. ML plugger showed the lowest peak temperature (p<0.01). 3. The temperature on the plugger was decreased with the increase of touching time. This results suggest that the actual temperature on the surface of the pluggers does not correlate well with the temperature set on digital display. Heat concentrates around the tip. The larger plugger reveals lower temperature rise relatively.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.599-603
• /
• 2003

This paper present an error compensation system and On-Machine Measurement(OMM) system for improving the machining accuracy of ultra-precision lathe. The Fast-Tool-Servo(FTS) driven by a piezoelectric actuator is applied for error compensation system. The controller is implemented on the 32bit DSP for feedback control of piezoelectric actuator. The control system is designed to compensates three kinds of machining errors such as the straightness error of X-axis slide, the thermal growth error of the spindle. and the squareness between spindle and X-axis slide. OMM is preposed to measure the finished profile of workpiece on the machine-tool using capacitive sensor with highly accurate ruby tip probe guided by air bearing. The data acquisition system is linked to the CNC controller to get the position of each axis in real-time. Through the experiments, it is founded that the thermal growth of spindle and tile squareness error between spindle and X-axis slide influenced to machining error more than straightness error of X-axis slide in small travel length. These errors were simulated as a sinusoidal signal which has very low frequency and the FTS could compensate the signal less than 30 m. The implemented OMM system has been tested by measuring flat surface of 50 mm diameter and shows measurement error less than 400 mm

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
• /
• pp.382-387
• /
• 1992

In order to obtain desired arc welding performance, we already developed an arc welding robot system that enabled coordinated motions of dual arm robots. In this system one robot arm holds a welding target as a positioning device, and the other robot moves the welding torch. Concerning to such a dual arm robot system, the positioning accuracy of robots is one important problem, since nowadays conventional industrial robots unfortunately don't have enough absolute accuracy in position. In order to cope with this problem, our robot system employed teaching playback method, where absolute error are compensated by the operator's visual feedback. Due to this system, an ideal arc welding considering the posture of the welding target and the directions of the gravity has become possible. Another problem still remains, while we developed an original teaching method of the dual arm robots with coordinated motions. The problem is that manual teaching tasks are still tedious since they need fine movements with intensive attentions. Therefore, we developed a 3-dimensional vision guided robot control method for our welding robot system with coordinated motions. In this paper we show our 3-dimensional vision sensor to guide our arc welding robot system with coordinated motions. A sensing device is compactly designed and is mounted on the tip of the arc welding robot. The sensor detects the 3-dimensional shape of groove on the target work which needs to be weld. And the welding robot is controlled to trace the grooves with accuracy. The principle of the 3-dimensional measurement is depend on the slit-ray projection method. In order to realize a slit-ray projection method, two laser slit-ray projectors and one CCD TV camera are compactly mounted. Tactful image processing enabled 3-dimensional data processing without suffering from disturbance lights. The 3-dimensional information of the target groove is combined with the rough teaching data they are given by the operator in advance. Therefore, the teaching tasks are simplified

• Journal of Biosystems Engineering
• /
• 제10권1호
• /
• pp.13-23
• /
• 1985

Spraying method from the paddy-field levee is known to give insufficient penetration of the spray droplets to the rice stem of the densely grown plants, which is generally encountered at the last stage of rice growth. This study was intended to investigate the spraying system to solve this existing problem. As an approach, it was attempted to develop the boom-with-nozzle, between-the-row application system. Several types of nozzles and their different arrangements in the boom were tested in the field to measure the penetration-reaching distance and the uniformity of spray droplet distribution. The results of the study are summarized as follows: 1. Field experiments by the spraying method from the paddy-field levee showed to have practically no penetration of the spray droplets to the portion of the plant stem with the normal flow volume generally applied and thus need for improving present spraying method. 2. It was found that, considering both the uniformity of the spray droplet distribution and performance rate, the most efficient type of nozzle in the between-the-row boom-type spraying system was one that has core-insert hollow-cone with some clearance between the cone and tip. 3. When tested by applying the spraying method of between-the-row, the nozzle pressure did not affect the uniformity of spray droplet distribution. However, the nozzle pressure had a positive effect on the penetrating-reaching distance of the facing side of the rice stem and did not affect much on that of the opposite face of the stem. It was also found that the maximum pressure to affect the penetration-reaching distance was about $10kg/cm^2$. 4. The uniformity of the spray droplet distribution in the between-the-row system was greatly affected by the height and orientation of the nozzles in the boom. Based on experimental work for the different type of the boom-with-nozzle arrangements, it is recommended that the position of nozzle is set at about 0.45 m above the ground and two nozzles in the boom are oriented to be faced with each other with some angle such that the droplet stream from the nozzle would not directly face with each other.

• The Korean Journal of Pain
• /
• 제9권2호
• /
• pp.407-411
• /
• 1996

Stereotactic radiofrequency dorsal root ganglionotomy can be very useful procedures for the treatment of pain emanating from the lumbar segmental nerves. This procedure is reserved for patients who have failed conservative interventional treatments and in whom open surgical intervention is not an option. The advantages of the radiofrequency lesion method are presented, excellent control of the lesion process using temperature monitoring to quantify the lesion size, prevent boiling, and to produce differential destruction of neural tissue. The afferent fibers in the ventral root which are spared by dorsal rhizotomy but nerve fibers with their cells in the ganglion from either dorsal or ventral root can be destructed with stereotactic radiofrequency ganglionotomy. This technique is performed using a 100 mm cannula with a 5 mm active tip. Repeated lateral fluoroscopic view should be taken to make sure that cannlua still resides within the superior, dorsal quadrant or the foramen. With the cannula in this position, electrostimulation is performed and good paresthesia on the leg should be noted with 0.3 and 0.5 volt at 50 Hz stimulation. At 2Hz stimulation distinct dissociation between motor and sensory should be shown. Percutaneous lumbar ganglionotomy have carried out under local anesthesia on inpatient basis in 6 patients. A series of 5 patients with metastatic cancer pain and a patient with compression fracture have been relieved of pain without serious complications.

• 정보처리학회논문지B
• /
• 제16B권5호
• /
• pp.347-358
• /
• 2009

손동작을 인식하는 연구가 오랫동안 이뤄져 왔지만 대개의 시스템들이 값비싼 깊이 카메라를 사용하거나 여러 개의 카메라를 사용해 분석하는 등 그 비용이 크며 작동이 가능한 작업 공간이 지극히 제한적이었다. 본 논문에서는 가전제품을 원격 제어하기 위한 목적으로 두 개의 회전 모터를 사용해 작업 공간을 확대하고 저렴한 일반 카메라를 사용해서 효율적으로 손동작을 인식하기 위한 시스템을 제안한다. 이 시스템은 입력된 카메라의 자세 정보와 이미지상의 2차원적 손가락 위치 정보를 이용하여 3차원 궤적을 추정하고 이를 동작 평면으로 투영시켜 의미 있는 선형 동작 패턴으로 복원한다. 또한 본 논문에서는 개발된 시스템을 테스트하여 주어진 목적에 맞는 정확도를 가지는 작업 영역을 정의한다.

• 대한인간공학회:학술대회논문집
• /
• 대한인간공학회 1997년도 춘계학술대회논문집
• /
• pp.17-25
• /
• 1997

The evoked potentials for concentrations of solutions of the four qualities of tastes(i.e., sweet, salty, sour, and bitter tastes) were measured. The solution was applied to the chorda tympani nerve located on the left side of the tongue at 20mm from the tip and 15mm left from the center line. The evoked potentials were detected from Cz referred to A1(left lobe) with the ground at the Fpz position. The Maximum potential level and its latency were evaluated. The individual threshold level of concentration of the solutions of four tastes were measured. Artificial saliva was used as a control solution. The evoked positive potentials for four qualities of tastes (i.e., gustatory evokde potentials) were found to be around 150ms by averaging eight responses. The arbitrary concentration of the solutions were presented by the relative concentration, which was the ratio of the arbitrary concentration to the individual threshold level. The characteristic relations between the latency and the relative concentration ;and those between the potential level and the relative concentration were evaluated. These evalutions showed that (1) the latencies for salty and bitter tastes denoted the minimum values due to for the change of relative concentration, and that (2) the latency for sour taste decreased as the relative concentrations increased, while the latency for sweet taste denoted the inverse tendency, Sinificant differences between any two maximum potential levels were not recognized. A response latencies to sucrose were abolished after treatment of tongue by a sweet-suppressing agent.

• 대한치과교정학회지
• /
• 제50권4호
• /
• pp.238-248
• /
• 2020

Objective: To investigate the effects of the long-term use of a maxillary protraction facemask with miniplate (FM-MP) on pharyngeal airway dimensions in growing patients with cleft lip and palate (CLP). Methods: The study included 24 boys with CLP (mean age, 12.2 years; mean duration of FM-MP therapy, 4.9 years), divided into two groups according to the amount of A point advancement to the vertical reference plane (VRP): Group 1, > 4 mm; Group 2, < 2 mm; n = 12/group. After evaluating the skeletodental and airway variables using lateral cephalograms acquired before and after FM-MP therapy, statistical analyses were performed. Results: Group 1 showed greater forward and downward displacements of the posterior maxilla (posterior nasal spine [PNS]-horizontal reference plane [HRP]; PNS-VRP), greater increase in ANB, more forward tongue position (tongue tip-Pt vertical line to Frankfort horizontal plane), and greater increase in the oropharynx (superior posterior airway space [SPAS]; middle airway space [MAS]) and upper nasopharynx (PNS-adenoid2) than did Group 2. While maxillary advancement (A-VRP and PNS-VRP) correlated with increases in SPAS, MAS, and PNS-adenoid2, downward displacement of the PNS (PNS-HRP) correlated with increases in SPAS, MAS, PNS-adenoid1, and PNS-adenoid2, and with a decrease in vertical airway length (VAL). Mandibular forward displacement and decrease in mandibular plane correlated with increases in MAS. Conclusions: FM-MP therapy had positive effects on the oropharyngeal and nasopharyngeal airway spaces without increases in VAL in Group 1 rather than in Group 2. However, further validation using an untreated control group is necessary.