• The Korean Journal of Pain
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• v.10 no.2
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• pp.231-234
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• 1997

Background: The aim of this study was to examine the precise spreading pattern of contrast media in small increments in rabbits. Following pentobarbital anesthesia, the epidural puncture was done surgically with a blunt hook. Methods: The tip of epidural catheter was located at the mid-portion of T7 and T12, in the T7 group (n=7) and T12 group (n=8), respectively. Injection of the contrast media was started at 0.1 mL/kg and increased by 0.1 mL/kg up to a maximum of 0.6, mL/kg, under fluoroscopy. Results: In both groups, the extent of spread increased continuously as a Starling resistor with increasing injected volume(T7 group: $y=4.0+41.8x-28.1x^2$, T12 group: $y=0.2+57.7x-43.5x^2$) the total spread of contrast media was similar. The contrast media spread equally, both rostral and caudal, from catheter tip in T7 group; media spread approximately twice as far rostral as compared to caudal in T12 group (P<0.05). Conclusions: In rabbits, the position of epidural catheter tip should be positioned 2~3 segments below the aimed segment in lower thoracic or lumbar region, whereas in mid-thoracic region it should be positioned close to the level of aimed segment. Rabbits have relatively small epidural space therefore, the volume of injectant should be carefully determined with the suggested equations of this study.

• Journal of ILASS-Korea
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• v.9 no.2
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• pp.24-33
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• 2004

The effect of the working fluid flow conditions and nozzle geometry on the spray performance of a twin-fluid nozzle used in Selective Catalytic Reduction is investigated experimentally. The liquid pressure is varied in the range of 0.3atm to 1.5atm and the air pressure is varied from the 0.5atm to 3.0atm. relative position between liquid nozzle(internal nozzle) and air nozzle(external nozzle) tip changes front 1mm inside the air nozzle to 1mm outside the air nozzle. The orifice diameter of the air nozzle is varied with 5mm. 6mm and 7mm. Spray visualization is realized with CCD-Camera. SMD(Sauter Mean Diameter) and mean particle velocities are measured by PDPA(Phase Doppler Particle Analyzer) under various experimental conditions. The measuring point is 300mm away from the nozzle tip in the downstream spray. The experimental results are that spray angle is depended air flow rate because nozzle diameter, air pressure and nozzle tip relative positions are related air flow rate. SMD is depended air flow rate and water flow rate. Also, SMD is increased when water flow rate is bigger. SMD is decreased when Air flow rate is bigger.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.31 no.4
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• pp.350-355
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• 2005

There are various surgical methods for reconstruction of the nasal defect. Among them, there is some difference in the choosing the proper reconstruction method according to defect size and position. When the defect involved the tip, the columella, and the alar, the local flaps may be preferred, because they can provide sufficient amount of tissue. However, the composite grafts from the ear have been effectively used in reconstructions of smaller sized defects of the columella and ala. We excised total external nose because of squamous cell carcinoma on the nasal tip, columella, and nasal septum. We reconstructed the nasal tip, both alae, and columella with forehead flap. After division of the regional flap, we found partial necrosis of the columella and narrowness of the nostril. So, we used chondrocutaneous auricular composite grafts for reconstruction of the columella and both nostrils. We used the file-folder designed auricular composite graft for reconstruction of columella and the wedge shaped ear helical composite grafts for widening of nostrils. 6 months later, there were no significant problems, except some mismatched dark color in the grafted alar tissues. Here, we report a successful reconstruction of large nasal defect using combined two different reconstructive methods.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.6
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• pp.569-577
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• 2009

As the scale factor of model propellers utilized in cavitation test is about 40, it is difficult to find out practical countermeasures against the small area erosions on the blade tip region throughout model erosion tests. In this study, a partial propeller blade model was used for the observation of cavitation pattern for the eroded propeller. A partial propeller blade model was manufactured from 0.7R to tip with expanded profile and with adjustable device of angle of attack. Reynold's number of a partial propeller blade model is 7 times larger than that of a model propeller. Also, anti-singing edge and application of countermeasures to partial propeller blade model which produced in large scale can be more practical than a model propeller. For the observation of cavitation at high Reynold's number, high speed cavitation tunnel was used. To find out the most severe erosive blade position during a revolution, cavitation observation tests were carried out at 5 blade angle positions.

• Steel and Composite Structures
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• v.47 no.2
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• pp.239-251
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• 2023

The stiffness evaluation of cracked base metal is of great guidance to fatigue crack reinforcement. By carrying out fatigue tests and numerical simulation of typical cracking details in steel box girder, the strain-degradation law of cracked base metal was analyzed and the relationship between base metal stress and its displacement (stiffness) was explored. The feasibility of evaluating the stress of cracked base metal based on the stress field at the crack tip was verified. The results demonstrate that the stiffness of cracked base metal shows the fast-to-slow degradation trend with fatigue cracking and the base metal at 50mm or more behind the crack tip basically lose its bearing capacity. Drilling will further accelerate stiffness degradation with the increase of hole diameters. The base metal stress has a negative linear relation with its displacement (stiffness), The stress of cracked base metal is also related to stress intensity factor and its relative position (distance, included angle) to the crack tip, through which the local stiffness can be effectively evaluated. Since the stiffness is not uniformly distributed along the cracked base metal, the reinforcement patch is suggested to be designed according to the stiffness to avoid excessive reinforcement for the areas incompletely unloaded.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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• pp.1283-1289
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• 2013

The purpose of this study is to find the new method for estiming the spatial variations in a light source with utilizing the optical fiber sensory system. With this aim, firstly the asymmetry in the beam profile of a light source is evaluated by using the tipped optical fiber with 0, 10, 20, 30, 40, 45-degree angle. Secondly the variation of position in a light source is estimated by adjusting the relative position between the light source unit (XYZ stage, LED, Optical fiber) and the receiver unit (Photodiode, XYZ stage). Our experimental results show that the spatial variation of a light source can be resolved in terms of the variations in beam profile with varying the tip angle of an optical fiber and adjusting the relative distance between the light source unit and the receiver.

• The korean journal of orthodontics
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• v.48 no.1
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• pp.30-38
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• 2018

Objective: The purpose of this study was to investigate factors influencing the success rate of orthodontic microimplants (OMIs) using panoramic radiographs (PRs). Methods: We examined 160 OMIs inserted bilaterally in the maxillary buccal alveolar bone between the second premolars and first molars of 80 patients (51 women, 29 men; mean age, $18.0{\pm}6.1years$) undergoing treatment for malocclusion. The angulation and position of OMIs, as well as other parameters, were measured on PRs. The correlation between each measurement and the OMI success rate was then evaluated. Results: The overall success rate was 85.0% (136/160). Age was found to be a significant predictor of implant success (p < 0.05), while sex, side of placement, extraction, and position of the OMI tip were not significant predictors (p > 0.05). The highest success rate was observed for OMIs with tips positioned on the interradicular midline (IRML; central position). Univariate analyses revealed that the OMI success rate significantly increased with an increase in the OMI length and placement height of OMI (p = 0.001). However, in simultaneous analyses, only length remained significant (p = 0.027). Root proximity, distance between the OMI tip and IRML, interradicular distance, alveolar crest width, distance between the OMI head and IRML, and placement angle were not factors for success. Correlations between the placement angle and all other measurements except root proximity were statistically significant (p < 0.05). Conclusions: Our findings suggest that OMIs positioned more apically with a lesser angulation, as observed on PRs, exhibit high success rates.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.154-160
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• 1996

The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. The limitation of this control scheme is that the feedback signal does not account for additional dynamics of the tool post and the material removal process. If the tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surfice. However, as the accuracy requirement gets tighter and desired surface cnotours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining process prohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normal to the face of the workpiece can be filtered through an appropriate admittance transfer function to result in the estimated dapth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in additn to position feedback control. In this work, the design methodology on the admittance model-based control with a conventional controller is presented. The recursive least-squares algorithm with forgetting factor is proposed to identify the parameters and update the cutting process in real time. The normal cutting forces are measured to identify the cutting dynamics in the real diamond turning process using the precision dynamoneter. Based on the parameter estimation of cutting dynamics and the admitance model-based nanodynamic control scheme, simulation results are shown.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.5
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• pp.453-459
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• 2010

In this paper, the purpose is to investigate the stability of cracked cantilever T-beams subjected to axial force. In addition, an analysis of the natural frequency of a cracked beams as crack position, crack depth and tip mass is investigated. Based on the Euler-Bernoulli beam theory, the equation of motion is derived by the energy expressions using extended Hamilton's Principle. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. The results of this study will contribute to the safety test and stability estimation of structures of a cracked T-beams subjected to axial force.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1700-1703
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• 1997

The flexibility of the manipulator inevitably inducess the vibration at the end effector. For the increase in speed and accuracy at the end tip, in this work, position and vibration control of a flexible manipuator with a separate voice coil type actrator for vibration suppression, is studied. The flexible manipulator with a tip mass is modeled an Euler-Bernoulli beam. An H.inf. controller is designed in order to make the controlled system robust against unmodeled higher-order mode vibration of the manipulator, output sensor noise, and etc. Simulations and experiments show that the modeling of the system is valid and that robust vibration control of the flexible manipulator is efficiently achieved.