• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1996.10a
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• pp.176-179
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• 1996

This paper describes the tip displacement of a flexible miniature arm controlled by the piezoelectric bimorph cells cemented on the surface of the arm. The arm is driven by the torques generated by the cells, and the endpoiht of the arm is controlled so that it moves in synchrony with the fluctuation of the target and maintains a constant distance to the surface of the traget. The voltage applied to the cells is controlled by a feedback signal composed of the tip displacement and the velocity. A theoretical solution is obtained by considering the cell-arm system as a stepped beam and applying time-discrete method to the governing equations of the system. The results are good agreement for a wide range of physical paramehers involved.

• Animal cells and systems
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• v.4 no.3
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• pp.201-214
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• 2000

Two quite different types of plant cells are analysed with regard to transduction of the gravity stimulus: (i) Unicellular rhizoids and protonemata of characean green algae; these are tube-like, tip-growing cells which respond to the direction of gravity. (ii) Columella cells located in the center of the root cap of higher plants; these cells (statocytes) perceive gravity. The two cell types contain heavy particles or organelles (sataoliths) which sediment in the field of gravity, thereby inducing the graviresponse. Both cell types were studied under microgravity conditions ($10^{-4}$/ g) in sounding rockets or spacelabs. From video microscopy of living Chara cells and different experiments with both cell types it was concluded that the position of statoliths depends on the balance of two forces, i.e. the gravitational force and the counteracting force mediated by actin microfilaments. The actomyosin system may be the missing link between the gravity-dependent movement of statoliths and the gravity receptor(s); it may also function as an amplifier.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.497-498
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• 2006

Powder Injection Molding (PIM) has recently been recognized as an advanced manufacturing technology for low-cost mass production of metal or ceramic parts of complicated geometry. With this regards, design technology of dental scaler tip PIM mold, which has complex shape, with the help of computer-aided analysis for powder injection molding process was developed. Compter aided analysis results, such as filling pattern, weldline formation, and air vent position prediction were investigated and eventually showed good agreements with experimental results.

• The Journal of Korean Society for Radiation Therapy
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• v.15 no.1
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• pp.29-33
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• 2003

I. Purpose Brachytherapy is the main component in treatment of patients with uterine cervical cancer. The reproducibility of applicator position in the same patient at repeated treatments was very important for accurate dose delivery. It was aimed to evaluate the change of applicator location between each high dose rate(HDR) brachytherapy insertion in the patients with uterine cervical cancer. II. Materials and Methods From January 1999 to October 2001, total 52 patients were treated with external beam radiotherapy and HDR brachytherapy (Microselectron, Nucletron). During six to seven times of brachytherapy, all patients had three treatment plans. From the orthogonal radiographs, we measured the following variables; height from upper border of pubic bone to os (HPO), distance from sacral promontory to tip of tandem (DST), distance from coccyx to os (DCO), distance from tip of right ovoid to os (DRO), distance from tip of left ovoid to os (DLO), and distance from center of the first tandem source to ovoid (DTO). To evaluate the reproducibility of applicator position, it was calculated the standard deviation of differences between three insertions for the 7 parameters in each patient. III. Results The ranges of standard deviations of interfractional differences for the variables were as follows. 1)HPO : $0{\sim}0.79cm$ 2)DST : $0{\sim}0.9cm$ 3)DCO : $0.06{\sim}0.76cm$ 4)DRO : $0{\sim}0.53cm$ 5)DLO : $0{\sim}0.45cm$ 6) DTO $0{\sim}0.36cm$ IV. Conclusions There was some change in applicator position on repeated implants in our study. But variation of the interfractional differences was minimal; in all parameters, there were less than 1 cm. We are continued to try for reducing the geometric variation between each procedure.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.1
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• pp.49-56
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• 2010

Objective: To evaluate nasal and upper lip changes after Le Fort I surgery by means of images taken with a three-dimensional computed tomography (3D-CT). Methods: Fifteen patients (9 female and 6 male, mean age 21.9 years) with preoperative and postoperative 3D-CT were studied. The patients underwent maxillary movement with impaction or elongation, and advancement or setback. With the 3D-CT which presents reconstructive soft tissue images, preoperative and postoperative measurement and analysis were performed for nasal tip projection angle, columellar angle, supratip break angle, nasolabial angle, interalar width, internostril width, columella length and nasal tip projection. Results: Postoperative interalar and internostril widening was significant for all categories of maxillary movement. However, there was little significant relation in all parameters between the amount and direction of maxillary movement. Interestingly, movement of the maxilla with upward did show a little decrease in the columellar angle, supra tip break angle and nasolabial angle. Also movement of the maxilla with forward did show a little advancement in the upper lip position. Conclusion: Changes to the nose clearly occur after orthognathic surgery. There was a significant increase in postoperative interalar width and internostril width with maxillary movement. However, no clear correlation could be determined between amount of change and maxillary movement. Interestingly, maxillary impaction did show a little decrease in the columellar angle, supra tip break angle and nasolabial angle. In addition, we used 3D-CT for more precise analysis as a useful tool.

• The Korean Journal of Pain
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• v.7 no.2
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• pp.211-216
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• 1994

Celiac plexus block is performed to relieve intractable upper abdominal cancer pain. Generally, celiac plexus blocks have been performed under control of X-ray fluoroscopy to determine the position of the needle tip and the spread of contrast media. During the period from March 1992 to February 1994, we have performed 21 cases of neurolytic celiac plexus block to alleviate pain of intra-abdominal malignancy. We retrospectively evaluated the location of the needle tip and the spread of contrast media. P-A views of simple abdomen demonstrated the locations of the needle tip: 66.7% of the left needle tips were in upper 3/1 of L1 (6 cases) and $T_{12}-L_1$ interspace (8 cases), 50% of the right needle tips were in upper 1/3 of $L_1$, (6 cases) and $T_{12}-L_1$ interspace (4 cases). Contrast media from the right needle spread upward to middle 1/3 of $T_{10}$ (5 cases) and middle 1/3 of $T_{11}$ (5 cases), downward to middle 1/3 of $L_1$ (6 cases) and lower 1/3 of $L_1$ (3 cases). Contrast media from the left needle were spread upward to middle 1/3 of $T_{10}$ (5 cases) and evenly to other spaces, downward to middle 1/3 of $L_1$, (4 cases) and $L_1-L_2$ interspace (6 cases). We analyze the spread of contrast media according to distance from needle tip by authors score system. Contrast media of right needle spread upward 6.1 and downward 3.4, that of left needle spread upward 6.5 and downward 3.7.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.790-798
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• 2008

Counter-rotating axial flow fan(CRF) consists of two counter-rotating rotors without stator blades. CRF shows the complex flow characteristics of the three-dimensional, viscous, and unsteady flow fields. For the understanding of the entire core flow in CRF, it is necessary to investigate the three-dimensional unsteady flow field between the rotors. This information is also essential to improve the aerodynamic characteristics and to reduce the aerodynamic noise level and vibration characteristics of the CRF. In this paper, experimental study on the three-dimensional unsteady flow of the CRF is performed at the design point(operating point). Flow fields in the CRF are measured at the cross-sectional planes of the upstream and downstream of each rotor using the $45^{\circ}$ inclined hot-wire. The phase-locked averaged hot-wire technique utilizes the inclined hot-wire, which rotates successively with 120 degree increments about its own axis. Three-dimensional unsteady flow characteristics such as tip vortex, secondary flow and tip leakage flow in the CRF are shown in the form of the axial, radial and tangential velocity vector plot and velocity contour. The phase-locked averaged velocity profiles of the CRF are analyzed by means of the stationary unsteady measurement technique. At the mean radius of the front rotor inlet and the outlet, the phase-locked averaged velocity profiles show more the periodical flow characteristics than those of the hub region. At the tip region of the CRF, the axial velocity is decreased due to the boundary layer effect of the fan casing and the tip vortex flow. The radial and the tangential velocity profiles show the most unstable and unsteady flow characteristics compared with other position of rotors. But, the phase-locked averaged velocity profiles of the downstream of the rear rotor show the aperiodic flow pattern due to the mixture of the front rotor wake period and the rear rotor rotational period.

• Restorative Dentistry and Endodontics
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• v.46 no.4
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• pp.51.1-51.13
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• 2021

Objectives: This study aimed to evaluate the effect of improper positioning single-peak and multi-peak lights on color change, microhardness of bottom and top, and surface topography of bulk fill and incremental composites after artificial aging for 1 year. Materials and Methods: Bulk fill and incremental composites were cured using multi-peak and single-peak light-emitting diode (LED) following 4 clinical conditions: (1) optimal condition (no angulation or tip displacement), (2) tip-displacement (2 mm), (3) slight tip angulation (α = 20°) and (4) moderate tip angulation (α = 35°). After 1-year of water aging, the specimens were analyzed for color changes (ΔE), Vickers hardness, surface topography (Ra, Rt, and Rv), and scanning electron microscopy. Results: For samples cured by single-peak LED, the improper positioning significantly increases the color change compared to the optimal position regardless of the type of composite (p < 0.001). For multi-peak LED, the type of resin composite and the curing condition displayed a significant effect on ΔE (p < 0.001). For both LEDs, the Vickers hardness and bottom/top ratio of Vickers hardness were affected by the type of composite and the curing condition (p < 0.01). Conclusions: The bulk fill composite presented greater resistance to wear, higher color stability, and better microhardness than the incremental composite when subjected to improper curing. The multi-peak LED improves curing under improper conditions compared to single-peak LED. Prevention of errors when curing composites requires the attention of all personnel involved in the patient's care once the clinical relevance of the appropriate polymerization reflects on reliable long-term outcomes.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.6-11
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• 1988

Alight-weight robot arm carrying a payload is modelled as a cantilever beam with a tip mass subjected to a high speed rotation. Equations of Motion, for modal control, are represented as discrete state variable form. Digital optimal control law with observer is developed to suppress the arm vibration and control the position of the joint angle. The effects of the number of controlled modes, weighting factors of the performance index, reference rotation time, and sampling time on the control performance are analyzed by computer simulation and experiments.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10a
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• pp.892-897
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• 1987

The ability of a robotic manipulator to recognize the shape of an object by feeling its band around the object is useful in many applications. Two-dimensional object contour tracking by force feedback is described. The system consists of IBM PC/AT, PUMA 560 manipulator, PUMA controller and a tip sensor. Position control is accomplished by using VAL command and the unmodified PUMA controller. A contour tracking algorithm is developed and tested on three different types of objects. The experimental results show that the objects' shapes can be successfully identified.