• 한국공작기계학회논문집
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• 제11권2호
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• pp.17-23
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• 2002

A cylindrical capacitance-type spindle displacement sensor was developed and its effectiveness as a system to monitor cutting forces during hard turning was tested in this research. The sensor was installed between the face of spindle cover and the chucking element and measured pure radial motion of the spindle under the condition with presence of roundness error at measured surface. To prove the effectiveness of the developed system hard aiming tests using ceramic inserts and tool steel as workpiece were conducted. The workpiece was hardened up to 65 Rc. The variations of pure radial motion of the spindle ware measured during the cutting tests. The signals from the sensor showed the same pattern of cutting force variations from the tool dynamometer due to the progress of tool wear. As the flank wear of the ceramic tool increased both static component of cutting forces and the amount of center shift of spindle orbit increased, Results from the research showed that the developed sensor could be utilized as an effective and cheap on-line sensing device to monitor cutting conditions and tool performance in the un-manned machining center.

• 한국안전학회지
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• 제19권4호
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• pp.123-128
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• 2004

This study investigated effect of arm posture, repetition of wrist motion and external load on perceived discomfort. The arm postures were controlled by shoulder flexion, elbow flexion, and ist motions such as flexion, extension, radial deviation and ulnar deviation. An experiment was conducted to measure discomfort scores for experimental treatments using the magnitude estimation, in which the L16 orthogonal array was adopted for reducing the size of experiment. The results showed that while the effect of the shoulder flexion, repetition of wrist motion and external load was statistically significant at $\alpha=0.05$or 0.10, that of the elbow and wrist motions was not. Discomfor ratings increased linearly as levels of wrist repetition and external load increased. This implies that the existing posture classification schemes such as OWAS, RULA, which do not properly consider effect of motion repetition and external load, may underestimate postural load. Based on the regression equation for wrist repetition and external load, isocomfort region indicating the region within which discomfort scores were expected to be the same was proposed. It is recommended that when assessing risk of postures or developing new posture classification schemes, motion repetition and external load as well as posture itself be fully taken into consideration for precisely evaluating postural stress.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권2호
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• pp.147-154
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• 2016

Purpose: To evaluate statistical differences among three measurements of range of motion (ROM) with Rapael Smart Glove (RSG) group 1, 2 and manual goniometer group. To investigate reference value of the kinematic analysis for range of motion (ROM) of distal upper extremity with Rapael Smart Glove (RSG). Methods: Sixteen normal persons without limitation of motion (LOM) enrolled in the study. The study was performed at two separate times and by two investigators on 16 normal adults. We compared ROM with RSG for measuring joint angles. We compared degrees of forearm supination/pronation, wrist flexion/extension and radial deviation/ulnar deviation during ROM of 16 participants using RSG. After one week, degrees of each motion were measured in the same way by other investigator to evaluate the reliability. Results: Statistical differences among three groups were showed. Most results of paired t-test between two RSG groups were over 0.05 and exceptions are supination, extension, and finger %. Conclusion: Our findings demonstrate that ROM of normal persons obtained by kinematic analysis with RSG are not valid as normal reference value for distal upper extremity motion. But, the reliability of between two RSG groups was showed with paired t-test and Pearson's correlation except supination, extension and finger %.

• 대한의용생체공학회:의공학회지
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• 제24권6호
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• pp.543-548
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• 2003

Injuries of wrist in upper extremity is common onset in industrialized world. The development of joint arthroplasty and mechanical joint is area of research for biomechanical engineer and surgeon for a decade. Therefore. the knowledge of characteristic of joint motion is essential to develop the artificial wrist joint. In this study. the joint motions of wrist required for activities of daily living (ADLs). including personal hygiene and care. and general home activity were measured using flexible electrogoniometer. Total of 25 different daily activities were separated into four groups and tested on 15 subjects who did not show any abnormality of their joint functions. The maximum functional range of motion required for ADLs were obtained and standardized for analysis and comparison. Also. a least functional range of motion for ADLs were investigated. Results revealed that any significant differences were not found in least functional range of motion between left and right wrist to perform ADLs. However. a significant difference was found in different ADLs. Therefore. least range of motion obtained in this study can be used as basic data to design artificial joint and set a goal for surgeon to achieve appropriate treatment from patients.

• Bulletin of the Korean Chemical Society
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• 제19권4호
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• pp.422-428
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• 1998

In the present paper, we report a molecular dynamics (MD) simulation of non-rigid zeolite-A framework only as the base case for a consistent study of the role of intraframework interaction on several zeolite-A systems using the same technique in our previous studies of rigid zeolite-A frameworks. Usual bond stretching, bond angle bending, torsional rotational, and non-bonded Lennard-Jones and electrostatic interactions are considered as intraframework interaction potentials. The comparison of experimental and calculated structural parameters confirms the validity of our MD simulation for zeolite-A framework. The radial distribution functions of non-rigid zeolite-A framework atoms characterize the vibrational motion of the framework atoms. Mean square displacements are all periodic with a short period of 0.08 ps and a slow change in the amplitude of the vibration with a long period of 0.53 ps. The displacement auto-correlation (DAC) and neighbor-correlation (DNC) functions describe the up-and-down motion of the framework atoms from the center of α-cage and the back-and-forth motion on each ring window from the center of each window. The DAC and DNC functions of the framework atoms from the center of α-cage at the 8-ring windows have the same period of the up-and-down motion, but those functions from the center of 8-ring window at the 8-ring windows are of different periods of the back-and-forth motion.

• Investigative Magnetic Resonance Imaging
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• 제23권4호
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• pp.328-340
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• 2019

Purpose: To generate phase images with free of motion-induced artifact and susceptibility-induced distortion using 3D radial ultrashort TE (UTE) MRI. Materials and Methods: The field map was theoretically derived by solving Laplace's equation with appropriate boundary conditions, and used to simulate the image distortion in conventional spin-warp MRI. Manufacturer's 3D radial imaging sequence was modified to acquire maximum number of radial spokes in a given time, by removing the spoiler gradient and sampling during both rampup and rampdown gradient. Spoke direction randomly jumps so that a readout gradient acts as a spoiling gradient for the previous spoke. The custom raw data was reconstructed using a homemade image reconstruction software, which is programmed using Python language. The method was applied to a phantom and in-vivo human brain and abdomen. The performance of UTE was compared with 3D GRE for phase mapping. Local phase mapping was compared with T₂* mapping using UTE. Results: The phase map using UTE mimics true field-map, which was theoretically calculated, while that using 3D GRE revealed both motion-induced artifact and geometric distortion. Motion-free imaging is particularly crucial for application of phase mapping for abdomen MRI, which typically requires multiple breathold acquisitions. The air pockets, which are caught within the digestive pathway, induce spatially varying and large background field. T₂* map, that was calculated using UTE data, suffers from non-uniform T₂* value due to this background field, while does not appear in the local phase map of UTE data. Conclusion: Phase map generated using UTE mimicked the true field map even when non-zero susceptibility objects were present. Phase map generated by 3D GRE did not accurately mimic the true field map when non-zero susceptibility objects were present due to the significant field distortion as theoretically calculated. Nonetheless, UTE allows for phase maps to be free of susceptibility-induced distortion without the use of any post-processing protocols.

• Clinics in Shoulder and Elbow
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• 제9권1호
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• pp.50-59
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• 2006

Purpose: The nonoperative outcome of elbow dislocations with associated radial head and coronoid fractures are often unsatisfactory because of chronic instability and stiffness from proloned immobilization, Therefore we managed these injuries with well programed surgical appproaches. Method: Ten patients with this injury were evaluated retrospectively from May 1998 to June 2004 after a minimum of 12 months. These injuries include elbow dislocation and associated fractures of both the radial head and the coronoid process. All ten patients were treated by one clinic operatively with similar scheduled surgical methods which started on the lateral side and terminated on the medial side of the elbow. Radial head and neck fractures were classified Mason types, as two and three types respectively with six and four cases and six cases were fixated. Coronoid process were fixated with screws anteroposterior directly or anchor suture in all cases, each type was classified one, two and three. where were three type one, four type two, and three type three were according to Regan and Morrey classification. Results: The outcome was three resulting in excellent, four good, two normaland and the remaining case was one poor according to the Mayo Elbow Performance score. At a terminal follow up, the range of motion of the elbow averaged flection contracture, $6^{\circ}(0{\sim}20^{\circ})$ and further flection, $129^{\circ}(115{\sim}140^{\circ})$. Two patients had complications requiring additional care. One, displaced coronoid process which was repaired with capsule and the other patient experienced, palsy of ulnar nerve and contracted elbow joint. Conclusions: Usage of early operation as the minimum injury of medial ligaments complex and the rigid fixation of fractures to prompt motion with our scheduled management for elbow dislocations with associated radial head and coracoid fractures provided excellent results.

• 한국안전학회지
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• 제20권2호
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• pp.11-17
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• 2005

Rotational motion in the atmosphere around a fire may have a profound influence on the fire plume. This process underlies the occurrence of fire whirls. Fire whirls are rare but highly destructive phenomenon which were observed in a large forest, urban and building fires. The present study aims to investigate of the effect of rotation Strength on the fire whirl characteristics expeimentally. Experiments are performed for various sizes of fire source with different rotation strength. From the experimental observations, it is noted that the mean centerline temperature is gradually increased and mean radial temperature is decreased as increases rotation strength. The characteristic mean flame height of fire based on the visible observation is increased as increases of dimensionless swirl parameter, $\Omega/\alpha$, represented by swirl induced motion to buoyancy driven motion.

• 한국공작기계학회논문집
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• 제17권1호
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• pp.132-136
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• 2008

Axis of rotation error on rotary system are significant; such as the spindle radial error motion of a aligner, wire bonder and inspector machine which results in the poor state of manufactured goods. In this paper, the simple stage which consists of one PZT actuator and rotary encoder, is analyzed and measured by high resolution capacitance type displacement sensor. As the result of experiment, the paper discusses several issues that must be considered when designing rotary stage driven by PZT.

• 한국소음진동공학회논문집
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• 제15권10호
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• pp.1186-1194
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• 2005

In this paper, we have systematically formulated the equations concerned to the in-plane and out-of-plane motions and deformations of a thick circular beam by using the kinetic and strain energies in order to analyse natural frequencies of a thick ring. The effects of variation of radius of curvature across the cross-section and also the effects of bending shear, extension and twist are considered. The equations of motion for natural vibration analysis of a ring are obtained utilizing the cyclic symmetry of vibration modes of the ring. The frequencies calculated using thick ring model and thin ring model are compared and discussed with the ones obtained from finite element analysis using the method of cyclic symmetry with 20-node hexahedral solid elements for rings with the different ratio of radial thickness to mean radius.