• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.5
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• pp.57-63
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• 2010

Tolerance analysis is one of the most important processes to improve the image quality of products. High resolution camera module for mobile phones needs precision assembly technology since the module becomes smaller and thinner. This paper will focus on the unit tolerance and the assembly tolerance which can affect the performance of the module. Lens shading and relative illumination were used to evaluate the optical axis scatter for each component on camera and estimate the assembly yield rate based on the evaluation result. A program was developed to analyze the impact on optical axis by each module, then to optimize the dimensions and tolerance for reducing the scatter of optical axis assembly. Through the simulation, though a rate of relative illumination was declined in where optical axis is displaced $100{\mu}m$ from sensor center, MTF performance is not influenced by increasing in optical axis displacement. It was seen that assembly yield was improved in result of simulation after correcting optical axis tolerance.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.4
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• pp.99-105
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• 2014

The domestic airline industry undertakes the production of finished products by assembling existing self-described components via a design process which involves assembly and production steps, after which many of the finished products are exported. However, high reliability and stability must be guaranteed, because customers require high-precision components at the time of manufacturing. In the aircraft parts industry, the mass production of high-value-added parts is limited. Therefore, a small production scale depending on the part is used, as many types of conventional CNC lathe machines with X-axis and Z-axis as well as Z-axis and C-axis CNC milling are used. The parts also rely on high-pressure air to increase production. The most important factors are good stability during processing, as high-precision parts are required, as noted above. It was found that as the C-axis rotation speed increased, the diameter of the cutting tool decreased with a decrease in the surface roughness, while the workpiece rotation speed increased with an increase in the surface roughness.

• Korean Journal of Computational Design and Engineering
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• v.14 no.5
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• pp.291-296
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• 2009

This paper presents a post-processing algorithm for 5-axis machines with three rotary axes (3R-2L type). 5-axis machining needs the postprocessor for converting cutter location (CL) data to machine control (NC) data. The existing methods for post-processing use inverse kinematics equations from for-ward kinematics. However in case of 5-axis machines with three rotary axes, the inverse kinematics equations are not induced directly since the forward kinematics equations are non-linear. In order to get the joint values from the forward kinematics equations, previous algorithms use numerical method for the post-processing, which needs searching algorithms with computation time and may result in fail. This paper proposes a geometric method for the post-processing of 3 rotary type 5-axis machines. Our algorithm has three advantages: first, it does not need establishing forward kinematics equations. Second, it is reliable method that eliminates any numerical methods for the inverse kinematics, resulting in the exact solution. Finally, the proposed algorithm can also be applied to 2R-3L type of 5-axis machines.

• Journal of Sensor Science and Technology
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• v.24 no.2
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• pp.137-143
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• 2015

This paper describes the design of a two-axis force sensor with two step plate beams for measuring forces in an upper-limb rehabilitation robot. The two-axis force sensor is composed of a Fz force sensor and a Ty torque sensor. The Fz force sensor measures the force applied to a patient's arm pushed by a rehabilitation robot and the force of patient's arm. The Ty torque sensor measures the torque generated by a patient's arm motion in an emergency. The structure of sensor is composed of a force transmitting block, two step plate beams and two fixture blocks. The two-axis force sensor was designed using FEM (Finite Element Method), and manufactured using strain-gages. The characteristics test of the two-axis force sensor was carried out. as a test results, the interference error of the two-axis force sensor was less than 1.24%, the repeatability error of each sensor was less than 0.03%, and the non-linearity was less than 0.02%.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.45.2-45.2
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• 2019

The main-belt asteroid (5247) Krylov is known as a Non-Principal Axis (NPA) rotator. However, the shape model and spin state of this asteroid were not revealed. The physical model of an asteroid including spin state and shape is regarded to be important to understand its physical properties and dynamical evolution. Thus, in order to reconstruct the physical model of Kryolv, we applied the light curve inversion method using not only the optical light curves observed with ground-based telescopes in three apparitions during 2006, 2016, and 2017, but also the infrared light curves obtained with the Wide-field Infrared Survey Explorer (WISE) in 2010. We found that it is rotating in Short Axis Mode (SAM) with the rotation and precession periods of 368.71 hr and 67.277 hr, respectively. The orientation of the angular momentum vector is (298°, -58°) in the ecliptic coordinate system. The ratio of moments of inertia of the longest axis to the shortest axis is I_a/I_c = 0.36; the ratio of moments of inertia of the intermediate axis to the shortest axis is I_b/I_c = 0.96. Finally, the excitation level of this asteroid is found to be rather low with a ratio of the rotational kinetic energy to the basic spin state energy as E/E₀ ≃ 1.024. We will briefly discuss the possible evolutionary process of Krylov in this presentation.

• Journal of Sericultural and Entomological Science
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• v.16 no.2
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• pp.119-125
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• 1974

When the nomal silkworms reached active time of 3rd instar stage both non-moulting larva and normal silkworms from the same rearing tray were collected and fixed. The silkworms in 4th instar stage whose growth was as dwarfish as those in 1st and 2nd instar stages were also collected and fix with the normal silkworms. Non-moulting larva and normal silkworms were morphologically compared and the examined results from the tissue inspection are summarized as follows： 1. In spite of the fact that the normal silkworms reached the active eating time of 3rd instar stage non-moulting silkworms were dwarfish as if they had been reared for two days. Non-moulting silkworms which were observed at the time of 4th instar stage showed no much difference in their growth. 2. There was the tendency that the exuvial gland as was shown in Fig. 1 and 2 was flat cyslidium of ellipse and its size at thorax was small shile the gland at abdomen was big. 3. The exuvial gland at thorax has been reported to be bigger at thoracic base than at dorsal vessel but according to the present it was examined to be irregular. 4. The size of exuvial gland of silkworms in the active eating stage of 3rd instar was from 151.3${\mu}$ (major axis) to 94.5${\mu}$ (minor axis) at prothorax and from 568.6${\mu}$ (major axis) to 495.1${\mu}$ (minor axis) at 7th abdominal segment. The sire oe exuvial gland of non-moulting silkworm was 57.5${\mu}$ (major axis) to 51.3${\mu}$ (minor axis) at prothorax and from 91.5${\mu}$ (major axis) to 75.5${\mu}$ (minor axis) at 5th abdominal segment (see Fig. 1) 5. When the normal silkworms reached 4th instar active eating stage its exuvial gland was compared to that of dwarfish silkworm. The result was that the size of normal silkworm at prothorax was from 252.2${\mu}$ (major axis) to 131.6${\mu}$ (minor axis) and the size of exuvial gland at 7th abdominal segment was from 691.5${\mu}$ (major axis) to 493.4${\mu}$ (minor axis) while the sire of exuvial gland of non-moulting at prothorax was from 71.4${\mu}$ (major axis) to 61.5${\mu}$ (minor axis) and the size of the non-moulting silkworm's 8th abdominal segment was from 94.6${\mu}$ (major axis) to 71.5${\mu}$ (minor axis) (See Table 2) 6. There was a remarkable difference in the from of exuvial gland of non-moulting silkworm. The size of alveolar of the non-moulting silkworm was many times larger compared to that of normal silkworm 7. There was no great difference between secretory cells of normal and non-moulting silkworms but the granular type exuvial gland was small in sire compared to that of normal silkworm.

• Journal of Radiation Protection and Research
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• v.25 no.1
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• pp.31-36
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• 2000

In radiotherapy, it may happen to radiate surrounding normal tissue because of inconsistent field size by changing patient position during treatment. We are going to analyze errors reduced by using immobilization device with Electonic portal imaging device(EPID) in this study. We had treated the twenty-one patients in pelvic region with 10 MV X-ray from Aug. 1998 to Aug. 1999 at Chungnam National University Hospital. All patients were treated at supine position during treatment. They were separated to two groups, 11 patients without device and 10 patients with immobilization device. We used styrofoam for immobilization device and measured the errors of anterior direction for x, y axis and lateral direction for z, y axis from simulation film to EPID image using matching technique. For no immobilization device group, the mean deviation values of x axis and y axis are 0.19 mm. 0.48 mm, respectively and the standard deviations of systematic deviation are 2.38 mm, 2.19 mm, respectively and of random deviation for x axis and y axis are 1.92 mm. 1.29 mm, respectively. The mean deviation values of z axis and y axis are -3.61 mm. 2.07 mm, respectively and the standard deviations of systematic deviation are 3.20 mm, 2.29 mm, respectively and of random deviation for z axis and y axis are 2.73 mm. 1.62 mm, respectively. For immobilization device group, the mean deviation values of x axis and y axis are 0.71 mm. -1.07 mm, respectively and the standard deviations of systematic deviation are 1.80 mm, 2.26 mm, respectively and of random deviation for x axis and y axis are 1.56 mm. 1.27 mm, respectively. The mean deviation values of z axis and y axis are -1.76 mm. 1.08 mm, respectively and the standard deviations of systematic deviation are 1.87 mm, 2.83 mm, respectively and of random deviation for x axis and y axis are 1.68 mm, 1.65 mm, respectively. Because of reducing random and systematic error using immobilization device, we had obtained good reproducibility of patient setup during treatment so that we recommend the use of immobilization device in pelvic region of radiation treatment.

• The korean journal of orthodontics
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• v.26 no.6
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• pp.657-666
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• 1996

Orthopantomogram is commonly used to evaluate root parallelism. "Good parallelism" between roots is widely accepted as one of the guidelines of a successful orthodontic treatment. In case there was a large angle between crown axis and root axis, and if we valued only the position of crown in establishing occlusal relationship without considering of the situation of root, the problem of root arrangement between adjacent teeth would be occurred. The estimate of root parallelism in mesiodistal direction before and after orthodontic treatment must be emphasized. The intent of this study was to determine the clinical importance and correlation of the angle between crown axis and root axis. Orthopantomograms of 105 orthodontic patients being treated in Yonsei university were used in this study. Twenty-eight teeth in both maxilla and mandible were selected and analyzed quantitively to evaluate the angle between crown axis and root axis, and obtain the correlationship among the individual teeth. The results are as follows: 1. Among the teeth presenting normal distribution, the maxillary right canine showed the largest mean value( $5.73{\pm}4.42^{\circ}$), which was composed of the crown-root angles, and the mandibular left lateral incisor showed the smallest mean value( $0.60{\pm}3.76^{\circ}$). 2. The crown-root angles of the maxillary incisors and the first molars, and the mandibular central incisors and the first molars didn't show normal distribution and the ranges of these angles were dispersed. 3. Significant differences were present between the crown axis and the root axis except for lower first premolars. (p<0.05) 4. No significant difference was present for the crown-root angle between right and left side, (p<0.05) 5. No significant difference was present for the crown-root angle between male and female except for lower left first premolar. (p<0.05) 6. In the upper right quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, lateral incisor and canine. In the upper left quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor. In the lower right quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, first molar and second molar. In the lower left quadrant, significant correlations were present between crown-root angles of the central incisor and lateral incisor, lateral incisor and canine, first molar and second molar. (p<0.05)

• The Journal of Engineering Geology
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• v.27 no.1
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• pp.51-58
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• 2017

The purpose of this study was to quantitatively evaluate the state of rocks in load steps by using the low-frequency ultrasonic flaw detection method. The initial Vp-velocities measured with a CND tester were in the order of Z-axis < X-axis < Y-axis, with 1687.5 m/s along the X-axis, 1690.7 m/s along the Y-axis, 1548.3 m/s along the Z-axis, and an average of 1642.2 m/s. The overall average of the Q vlaues, measured with a Silver Schmidt hammer, was 62.6, which corresponds to a uniaxial compressive strength of ~105 MPa. The Vp-velocity, measured with a low-frequency ultrasonic flaw detector at load steps of 50%, 60%, 70%, and 80%, typically decreases in the order of X-axis < Y-axis < Z-axis with increasing load steps. This oder contrasts with that of the initial Vp-velocities. As the load step increases the factors that reduce the Vp-velocity in the X-axis direction are more influential than those in the Y-axis or Z-axis directions. This indicates that the initial state of rocks can vary and is dependent on the stress state.

• Journal of the Korean Society of Radiology
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• v.14 no.6
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• pp.811-817
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• 2020

This study aims to evaluate the Modulation Transfer Function (MTF) according to the change in the number of channels of the CT examination device by changing the posture of the patient to the X-axis and Y-axis in the wrist joint CT examination. Using a CT device and a wrist phantom, the test was performed by moving 0 (matched), 5, 10, and 15 cm in the X-axis around the isocenter, and the Z-axis was rotated by -20° and -40°. For the test, 16, -40 and 64 channels were used to check whether there was a difference for each number of channels. The examined images were compared by measuring the MTF values of the ulna and left and right sides of the radius. In the experiment where the isocenter was moved along the X-axis, the MTF value decreased with an increase in the moving distance, and the MTF value was found to be unaffected by the number of channels. In the experiment in which the wrist joint was rotated by -20° and -40° on the Z-axis, the degree of deviation and MTF were found to be irrelevant. It was not related to the number of channels either. In conclusion, the movement of the wrist along the X-axis should be restrained as much as possible for a wrist joint CT scan, whereas deviation around the Z-axis depending on the environment for the patient would not affect the MTF of the image.