• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.1
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• pp.67-77
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• 2008

Seismic isolation has been studied continuously as a solution of the seismic engineering to reduce the sectional forces and the damages of structures caused by earthquakes. To certify reliable design and installation of the seismic isolation systems, seismic isolation bearings should be fabricated under well planned quality control process, and proper evaluation tests for their seismic performance should be followed. In this study, shear property evaluation tests for the lead rubber bearings(LRB) and the rubber bearings(RB) were implemented and the temperature dependency tests were also implemented to evaluate the changes of shear properties according to the changes of temperature. After evaluation tests, the measured shear properties were compared to their design values and their deviation was analyzed comparing with the allowable error ranges specified in Highway Bridge Design Specifications. These results showed that a considerable number of isolation bearings have so large deviations from their design values that their error ranges were over or very close to the allowable ranges. And the test results for temperature dependency showed that the shear properties of isolation bearings would be changed in great degree by the change of temperature during their service period. If these two types of changes in their shear properties are superposed, it would possible that the changes of shear properties from their original design values are over than 50%.

• Tunnel and Underground Space
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• v.19 no.6
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• pp.473-478
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• 2009

The accuracy of point load apparatus is depend on point to point coaxial fitting. Also, the estimation of applied point load using the pressure gauge frequently lead to erroneous results. An improved point load apparatus has been developed in this study by mounting linear bearing on polished support rod, and eccentric error of point to point axis has been sustained less than 0.1 mm even under series of extreme work load conditions. Two digital displacement gauges are attached to measure the distance from point to point with sample specimen. A load cell mounted at the end of upper conical platen measure the applied net load on sample instead of preassure gauge. Total of 107 point load tests has been achieved to assure the quality and performance of developed apparatus. This exercise turned out to be successful.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.12
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• pp.1279-1284
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• 2012

Micro structures which are widely used at various fields are commonly fabricated by lithograph, etching and laser methods. Recently, with the emergence of micro tools and ultra-precision machine tools, fabrication of the micro structures obtained using end-milling are studied. However, there are some problems due to the diameter of the micro end-mill getting smaller below $100{\mu}m$. The micro run-out resulted from miniaturization of end-mills have influence seriously on accuracy of micro structures. The error of run-out with a tooling jig showed a decrease of about $9.3{\mu}m$. Furthermore, micro structures with width of $30{\mu}m$ could be applied through experiments of slot machining obtained using 30 and $50{\mu}m$ end-mill. Also, narrow angle structures with $30^{\circ}$ angle could be applied through analysis of machining acute angle structures. Based on basic experiments, micro fluidics channels and spiral patterns for air bearing were machined.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.174-180
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• 2015

In this paper, we propose the passive sonar signal processing technique for estimating target information using proximity sensor. This algorithm is performed by single sensor which is constituted underwater sensor network and has a hierarchical structure. The estimated parameter is the velocity, the depth, the distance and bearing at CPA situations and we can improve the accuracy of signal processing techniques through having a hierarchical structure. We verify the performance of the proposed method by computer simulation and then we check the result that 20% error can be occurred in maximum detectable range. We also confirm that proposed method has the reliability in the actual sea environment through the sea experiment.

• Journal of Korean Foot and Ankle Society
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• v.10 no.1
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• pp.56-59
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• 2006

Purpose: The purpose of this study is to find out the normal distal tibial articular surface angle in coronal plane in Koreans. This would be helpful as the basic data for ankle reconstruction after trauma or deformity correction. Materials and Methods: Weight bearing anteroposterior radiographs of 123 normal ankles were reviewed. A line parallel to the shaft of the tibia was made. Another line was drawn parallel to the articular surface of the distal tibia. The superolateral angle that subtended by these two lines was measured. Results: There were 72 males and 51 females. The mean age overall was 35.7 years old. The mean age for males was 31.9 ($28{\sim}36$) years old. The mean age for females was 41.1 ($37{\sim}45$) years old. The mean distal tibial articular surface angle was $90.8^{\circ}$. The mean distal tibial articular surface angle for males was $91.5^{\circ}$ and for females $89.9^{\circ}$. Conclusion: The mean distal tibial articular surface angle in coronal plane for Koreans is $90.8^{\circ}$. We can avoid the error of the varization at the ankle alignment when the correction was performed vertical or minimal valgus to tibia tuberosity axis in Korean people.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.2
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• pp.133-138
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• 2016

Force control and collision detection for a robot are usually conducted using a 6-axis force/torque sensor mounted at the end-effector. However, this scheme suffers from high-cost and the inability to detect collisions at the robot body. As an alternative, joint torque sensors embedded in each joint were used, which also suffered from various errors in torque measurement. To resolve this problem, a robot joint module with an improved joint torque sensor is proposed in this study. In the proposed torque sensor, a cross-roller bearing and disk-type coupling are added to prevent the moment load from adversely affecting the measurement of the joint torque under consideration. This joint design also aims to reduce the stress induced during the assembly process of the sensor. The performance of the proposed joint torque sensor was verified through various experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.6
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• pp.462-469
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• 2014

After drilling operations at the offshore plant, crude oil is producted under high pressure. After that time, oil recovery is reduced, because the pressure of the pipe inside is low during the secondary produce. At that time injection sea water at the pipe inside through water injection pump that the device increase to recovery. A variety of mathematical analysis during the detailed design analysis was not made through the dynamics characteristic at the domestic company. 2D model has reliability of analysis results for the uncomplicated model. Also element and the node the number of significantly less than in the 3D model. So, the temporal part is very effective. In addition, depending on the quality of mesh 3D is a real model and FEM model occurs error. So, user needs a lot of skill. In this paper, a 2D finite element analysis was performed through the dynamics analysis and the study model was validated.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.2
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• pp.168-175
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• 2009

This paper proposes an enhanced algorithm for sensorless control of 45,000rpm/22kw type Permanent Magnetic Synchronous Motor (PMSM) with air-foil bearing. The proposed algorithm is based on iterative adaptive flux observer for sensorless control of the motor in wide speed range by on-line estimating angle and velocity of rotor. Simulation error between actual and estimated angle of rotor is analyzed to enhance characteristics of frequency response of conventional adaptive flux observer, which results in stable response in wide range of speed. Using the iteration number for stable phase-delay characteristics, the observer enhances the dynamic characteristics of the observer within current control period. The experiment results show the reliable performance of the proposed algorithm through starting to high speed operating range.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.7
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• pp.671-676
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• 2016

This study is about design for the Rotational Instrument of the Industry factory which is used management safety and maintenance. We developed the multichannel vibration monitering system of the self-diagnosis for middle level CMS(Condition Monitoring System) market, and that system are new features to the expandability and flexibility. Normally one channel is used for treating one signal, but developed instrument can treat four channel with one signal processing card. One rack have redundant power supply and displace and it can check vibration measurement value in field without computer. Bearing fault detection is fundamental of vibration surveillance, but sometimes can not check with vibration velocity and acceleration. So it need the filtering and the amplitude modulation on the acceleration enveloping technology when irregular vibration is happened. We developed the vibration analysis instrument which is applied such technology. And the development prototype shows activated within the vibration error limit.

• Physical Therapy Korea
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• v.23 no.3
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• pp.40-47
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• 2016

Background: Assessments of Sit-to-Stand (STS) and gait functions are essential procedures in evaluating level of independence for the patients after stroke. In a previous study, we developed the software to analyze center of pressure (COP) in standing position on Wii Balance Board (WBB). Objects: This purpose of this study is to measure test-retest reliability of ground reaction forces, COP and time using WBB on STS and gait in healthy adults. Methods: Fifteen healthy participants performed three trials of STS and gait on WBB. The time (s), vertical peak (%) and COP path-length (cm) were measured on both tasks. Additionally, counter (%), different peak (%), symmetry ratio, COP x-range and COP y-range were analyzed on STS, 1st peak (%), 2nd peak (%) of weight were analyzed on gait. Intra-class correlation coefficient (ICC), standard error measurement (SEM) and smallest real difference (SRD) were analyzed for test-retest reliability. Results: ICC of all variables except COP path-length appeared to .676~.946 on STS, and to .723~.901 on gait. SEM and SRD of all variables excepting COP path-length appeared .227~8.886, .033~24.575 on STS. SEM and SRD excepting COP path-length appeared about .019~3.933, .054~11.879 on gait. Conclusion: WBB is not only cheaper than force plate, but also easier to use clinically. WBB is considered as an adequate equipment for measuring changes of weight bearing during balance, STS and gait test which are normally used for functional assessment in patients with neurological problems and elderly. The further study is needed concurrent validity on neurological patients, elderly patients using force plate and WBB.