• Journal of Welding and Joining
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• v.24 no.2
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• pp.71-78
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• 2006

It has been reported that good quality weld beads are not easily obtained during the $CO_2$ CW laser welding of primer coated plate. However, by introducing a small gap clearance in the lap position, the zinc vapor can escape through it and sound weld beads can be acquired. Therefore, this study examines for keyhole behavior by observing the laser-induced plasma and investigates the relation between keyhole behavior and formation of weld defect. Laser-induced plasma has accompanied with the vaporizing pressure of zinc ejecting from keyhole to surface of primer coated plate. This dynamic behavior of plasma was very unstable and this instability was closely related to the unstable motion of keyhole during laser welding. As a result of observing the composition of porosity, much of Zn element was found from inner surface of porosity. But Zn was not found from the dimple structure fractured at the weld metal. By analyzing of vaporizing element in laser welding, a component ratio of Zn was decreased by introducing a small gap clearance. Therefore we can prove that the major cause of porosity is the vaporization of primer in lap position. Mechanism of porosity-formation is that the primer vaporized from the lap position accelerates dynamic behavior of the key hole and the bubble separated from the key hole is trapped in the solidification boundary and romaines as porosity.

• Journal of Power Electronics
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• v.18 no.3
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• pp.714-722
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• 2018

This paper presents a wide-range speed control scheme of brushless DC (BLDC) motors based on a hall sensor with separated low- and normal-speed controllers. However, the use of the hall sensor signal is insufficient to detect motor speed in the low-speed region because of low sensor resolution and time delay. In the proposed method, a micro-stepping current control method according to the torque angle variation is presented. In this mode, the motor current frequency and rotating angle are determined by the reference speed without the actual speed fed by the hall sensor. The detected torque angle is used to adjust the current value in a limited band to control the current value in accordance with the load. The torque angle is detected exactly at the changing point of the hall sensor signal. The rotor can follow the rotating flux with the variable torque angle. In a normal speed range, the conventional vector control scheme is used to control the motor current with a PI speed controller using the hall sensor. The torque characteristics are analyzed on the basis of the back EMF and current shape. To adopt the vector control scheme, the continuous rotor position is estimated by the measured speed and hall sensor position. At the mode changing point between low and normal speed range, the proper initial current command and reference rotor position are calculated. The calculated current command can reduce the torque ripple during transient mode. The proposed method is simple but effective in extending the speed control range of a conventional BLDC motor with hall sensor without the need for a high-resolution encoder. The effectiveness of the proposed method is verified by various experiments on a practical BLDC motor.

• Journal of Veterinary Clinics
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• v.29 no.1
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• pp.112-117
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• 2012

This report evaluated the convenience and accessibility of a penile translocation surgery in the lateral recumbency of a calf using a tilt-up mobile compared with that of dorsal recumbency on the ground of a barn. One nine-month-old F-1 (Korean native sire x Holstein dam) calf was sedated with xylazine (0.03 mg/kg, IV) and restrained in the right lateral recumbency position on a tilt-up restraint mobile (90 cm high), whereas the other nine-month-old Korean native calf was administered xylazine (0.3 mg/kg, IV) and restrained in dorsal recumbency position on the ground of a barn, with assistance by one person. For the two calves, lidocaine was administered subcutaneously from the preputial orifice to the S-shaped penis. The preputial orifice was incised, and the preputial sheath and penis were separated bluntly, then laterally translocated to the site toward the left flank at a $40^{\circ}$ angle. Anti-inflammatory drug (ketoprofen) and antibiotics (penicillin) were administered following the surgery. The duration of surgery was 30 min shorter in the calf that received the surgery in lateral recumbency using the tilt-up mobile with operator's standing posture (60 min) than the one that underwent surgery in dorsal recumbency on the ground with operator's bending posture (90 min). One week after the surgery, the operation area, including the translocated preputial orifice, was healed without complications in both cases. The results detailed in this report demonstrate that penile translocation surgery in the lateral recumbency position using a tilt-up mobile might be used conveniently in calves due to the convenience of restraint, reduced surgery time, and reduced physical inconvenience for the surgeon.

• Korean Journal of Plant Taxonomy
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• v.41 no.2
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• pp.130-137
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• 2011

Pedicularis growing at Mt. Halla of Jeju Island is known as an endemic species of P. hallaisanensis Hurusawa. On the other hand, the plant is morphologically similar to P. amoena, P. spicata, and P. verticillata in gross morphology, so the taxonomic treatment of the taxon remains controversial. To clarify the taxonomic position of the plants, we examined external morphological characters and nuclear ribosomal DNA ITS sequences for P. hallaisanensis and its related species. The plants of Mt. Halla are clearly different from P. amoena and P. verticillata in the morphology of calyx lobes, the length of galea and lower lip, density of glandular hairs on plants, presences of the radical leaves after anthesis and molecular data. However, P. hallaisanensis is not clearly separated from P. spicata distributed in N. E. Asia on external morphological characters and DNA sequences of internal transcribed spacers. In this study, the morphological and molecular data suggested that P. hallaisanensis should be merged into the former species.

• Korean Journal of Applied Biomechanics
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• v.15 no.4
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• pp.153-168
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• 2005

The purposes of this study were to determine the influence of midsole hardness and sole thickness of sports shoes on ball flex angle and position with increment of running velocity. The subjects employed for this study were 10 college students who did not have lower extremity injuries for the last one year and whose running pattern was rearfoot striker of normal foot. The shoes used in this study had 3 different midsole hardness of shore A 40, shore A 50, shore A 60 and 3 different sole thickness of 17cm, 19cm, 21cm. The subjects were asked to run at 3 different speed of 2.0m/sec, 3.5m/sec, 5.0m/sec and their motions were videotaped with 4 S-VHS video cameras and 2 high speed video cameras and simultaneously measured with a force platform. The following results were obtained after analysing and comparing the variables. Minimum angle of each ball flex position were increased with the increment of running velocity and shoe sole thickness(P<0.05), but mid-sole hardness did not affect minimum ball flex angle. The position which minimum angle was shown as smallest was 'D'. Midsole hardness and sole thickness did not affect time to each ball flex minimum angle, total angular displacement of ball flex angle, and total angular displacement of torsion angle(P<0.05). The position which minimum angle was appeared to be earliest was similar at walking velocity, and E and F of midfoot region at running velocity. Total angular displacement of ball flex position tended to increase as shifted to heel. It was found that running velocity had effects on ball flex angle variables, but shoe sole thickness partially affected. It would be considered that running velocity made differences between analysis variables at walking and running when designing shoes. Also, it was regarded that shoes would be developed at separated region, because ball flex angle and position was shown to be different at toe and heel region. It is necessary that midsole hardness and thickness required to functional shoes be analyzed in the further study.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.4
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• pp.278-285
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• 1991

The authors propose to use the slot system in order to improve of the efficiency for the cambered otter boards. The experiment is divided into 2 parts, one is the efficiency model test, and the other is the visualization model test. The hydrodynamic characteristics of the model otter boards were tested by efficiency model test to measure the shearing, drag force of the models and visualization test using hydrogen bubble method to observe the streak-line and time-line of flow around the models, and milk spout method to observe the separation zone in the wake behind the models. This study tested for 5 models such ad without slot, slot position 0.2C, 0.4C, 0.6C and 0.8C. The results obtained are as follows: \circled1 The maximum C sub(L) of model otter board with slot position 0.6C in attack angle 27$^{\circ}$ was the highest of all models, it's value was 1.59. \circled2 In general, the L/D ratio of the one slot otter boards were 16~28% higher than otter board without slot. \circled3 The slot position 0.6C was better than any other slot position, and it's conformed by visiualization. \circled4 As to the model otter board with slot position 0.6C, flow speed of the back side was faster 1.3 to 1.7 times than in the front side. \circled5 The size of the separated zone in case of the model otter board with 0.6C was smaller than that of any other models.

• Journal of the Korean Chemical Society
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• v.37 no.9
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• pp.793-799
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• 1993

Ion-pair model was predominated over ion-interaction model in the retention mechanism of analytes when tetramethylammonium bromide (TMAB) was used as a counter-ion in the investigation of aromatic sulfonic acids on the reversed-phase liquid chromatography by $C_{18}$ column as a stationary phase. The capacity factors of analytes were influenced by the type and concentration of counter-ions, concentrations of methanol and co-anion, types and position of functional group, and the pH mobile phase. Components of analyte mixture could be separated under the optimum conditions by this method.

• Structural Engineering and Mechanics
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• v.20 no.2
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• pp.143-160
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• 2005

Modal analysis of cracked cantilever composite beams, made of graphite-fibre reinforced polyamide, is studied. By using the finite element and component mode synthesis methods, a numeric model applicable to investigate the vibration of cracked composite beams is developed. In this new approach, from the crack section, the composite beam separated into two parts coupled by a flexibility matrix taking into account the interaction forces. These forces are derived from the fracture mechanics theory as the inverse of the compliance matrix calculated with the proper stress intensity factors and strain energy release rate expressions. Numerical results are obtained for modal analysis of composite beams with a transverse non-propagating open crack, addressing the effects of the location and depth of the crack, and the volume fraction and orientation of the fibre on the natural frequencies and mode shapes. By means of modal data, the position and dimension of the defect can be found. The results of the study confirmed that presented method is suitable for the vibration analysis of cracked cantilever composite beams. Present technique can be easily extended to composite plates and shells.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.487-490
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• 2003

In this research, we will devise an obstacle avoidance algorithm for a previously unmanned vehicle. Whole systems consist mainly of the vehicle system and the control system. The two systems are separated; this system can communicate with the vehicle system and the control system through wireless RF (Radio Frequency) modules. These modules use wireless communication. And the vehicle system is operated on PIC Micro Controller. Obstacle avoidance method for unmanned vehicle is based on the Virtual Force Field (VFF) method. An obstacle exerts repulsive forces and the lane center point applies an attractive force to the unmanned vehicle. A resultant force vector, comprising of the sum of a target directed attractive force and repulsive forces from an obstacle, is calculated for a given unmanned vehicle position. With resultant force acting on the unmanned vehicle, the vehicle's new driving direction is calculated, the vehicle makes steering adjustments, and this algorithm is repeated.

• Journal of IKEEE
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• v.13 no.2
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• pp.220-223
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• 2009

A simple measurement system is built to estimate the dual-antenna diversity gain at 2.4GHz easily in open lab environment. To obtain multipath fading propagation channel, the system consists of two transmission horn that placed on opposite direction and a rotating stage mechanically changing the position of test dual-antenna with time over distance greater than one wavelength. Estimated diversity is nearly same as theoretical value such that measured diversity gain of 30mm separated is about 6dB similar to theoretical value of 5.7dB and increases monotonically with the increasing separation distance as predicted by the theory. Proposed measurement system that is simple enough to fit in a small space can evaluate the performance of various dual-antennas with a reasonable accuracy with lower 5% difference between the ten sets of measured waveform distribution and theoretical Rayleigh cumulative distribution.