• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.529-534
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• 2014

Pyrotechnic devices are widely used for space appendages. However, a cube satellite requirements do not permit the use of explosive pyrotechnic device. A nichrome burn wire release has typically been used for holding and release of deployable appendages of the cube satellite due to its simplicity and low cost. However, relatively low mechanical constraint force and system complexity for application of multi-deployable systems are disadvantages of the conventional mechanism. To overcome these drawbacks, we developed a hinge driving segmented nut type holding and release mechanism based on the nichrome burn wire release. The functional performance of the mechanism has been verified through release function test, static load test and shock level measurement test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.3
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• pp.274-280
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• 2016

Hinge driving type holding and release mechanism based on the burn wire release for application of cubesat is main payload of STEP Cube Lab. (Cube Laboratory for Space Technology Experimental Project) to be launched at 2015. It has high constraint force, low shock level as well as surmounting drawbacks of conventional nichrome burn wire release method that has relatively low constraint force and system complexity for application of multi-deployable systems. In this paper, we have proposed a flight model of holding and release mechanism for the verification of the constraint force and deployment status signal acquisition. To validate the effectiveness of the flight model, launch and on-orbit environment verification test have been performed.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.123-128
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• 2022

This paper proposes a non-explosive separation device for the deployable SAR antenna. This device utilises a Ni-Cr wire to restrain the antenna's belt mechanism, and joule-heating is used to minimise the impact of deployment. After the Ni-Cr wire has been cut, the device is deployed through the preload of the belt mechanism. Considering the design load(99g) and preload conditions, FEM analysis for AL7050 and Ti was performed. This analysis revealed that the amount of deformation for AL7050 was 0.256 mm with a margin of +0.09. In addition, by performing orbital thermal analysis, the temperature distribution for AL7050 in the worst cold case is confirmed as -50 to +2℃ and -10 to +90℃ in the worst hot case. This analysis confirmed that the separation device would remain stable even in the worst environment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1827-1836
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• 1997

In this paper, the clamping type forging of helical gears has been investigated. Clamping type forging is an operation in which the product is constrained to extrude sideways through an orifice in the container wall. Punch is cylindrical shaped. The punch compresses a cylindrical bilet placed in a die insetr. As a consequence the material flows in a direction perpendicular to that of punch movement. The forging has been analysed by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, an involute curve has been introduce to re4present tooth profile of the gear. Numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth, helix angle, friction factor and initial height of billet on the forging of helical gears. Some firgiing experiments were catrried out with aluminium alloy to show the validity of the analysis. Good agreement was found between the predicted values of the forging load and obtained from the experimental results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.2
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• pp.185-191
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• 2008

Optimal damping layout of the constrained viscoelastic damping layer on beam is identified with temperatures by using a gradient-based numerical search algorithm. An optimal design problem is defined in order to determine the constrained damping layer configuration. A finite element formulation is introduced to model the constrained layer damping beam. The four-parameter fractional derivative model and the Arrhenius shift factor are used to describe dynamic characteristics of viscoelastic material with respect to frequency and temperature. Frequency-dependent complex-valued eigenvalue problems are solved by using a simple re-substitution algorithm in order to obtain the loss factor of each mode and responses of the structure. The results of the numerical example show that the proposed method can reduce frequency responses of beam at peaks only by reconfiguring the layout of constrained damping layer within a limited weight constraint.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.29-34
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• 2007

The fault current limiting characteristics of a flux-lock type superconducting fault current limiter(SFCL) according to fault angles were investigated. From the electrical equivalent circuit with the magnetization branch, the inner magnetic flux of this SFCL due to fault angles was induced and its effect on the limited fault current was analyzed. From the fault current limiting experiments, the exciting current, which described the saturation of the iron core, was calculated and its dependence on the fault angle was analyzed. Before the fault happened, the exciting current did not happen, that it kept zero value. However, after the fault happened, the exciting current flowed and, the exciting current in case of the additive polarity winding showed higher value than for the case of the subtractive polarity winding. The analysis results were compared with the experimental ones, and experimental results agreed with the analysis ones.

• Clinics in Shoulder and Elbow
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• v.16 no.2
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• pp.170-177
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• 2013

Total elbow arthroplasty is still in its infancy compared with other arthroplasties, such as knee or hip arthroplasties. Implant design has been evolving with clinical experiences; however, there are only limited data on the long-term clinical outcome of elbow arthroplasty in the literature. The design of total elbow prostheses can be divided into three categories: linked (constrained or semi-constrained), unlinked (unconstrained), and convertible types. The choice between an unlinked (unconstrained) implant and a linked (semi-constrained) implant depends on joint stability and adequacy of the bone stock. Linked elbow arthroplasty has provided high patient satisfaction, and pain relief thanks to proper patient selection, advancement of implant design, improvement in cement techniques, meticulous surgical technique, and appropriate postoperative rehabilitation. Concerns remain about the use of this implant in young or high-demand patients. This article focuses on the linked (semi-constrained) prostheses, which provides an overview of the current state of linked total elbow arthroplasty.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.510-511
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• 2006

하나의 철심을 매개로 각 상의 1, 2차 권선이 동일한 권선비로 결선된 삼상 일체화된 자속구속형 초전도 사고전류제한기의 동작특성을 모델링하였다. 삼상 일체화된 자속구속형 사고전류제한기는 평상시에 각 상의 두 코일에서 유기되는 자속이 서로 상쇄되어 철심내부의 자속은 발생하지 않게 되지만 임의의 한 상에서 단락사고가 발생할 경우 삼상이 분리된 사고전류제한기와 달리 사고상 뿐 아니라 건전상에 연결된 초전도소자도 ��치가 발생하는 특징이 있다. 등가회로를 이용한 모델링을 통해 삼상이 분리된 경우와 삼상이 일체화된 경우의 동작특성을 비교 분석하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.4
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• pp.70-74
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• 1998

Robust control for DC motor is needed according to the highest precision of industrial automation. However, when a motor control system with PID contoller has an effect of load disturbance, it is very difficult to guarantee the robustness of control system. In this paper, PID-supervision hybrid control methods for motor control system (without the supervisory controller) is stable in the sense that the error is inside the constraint set, the supervisory control is idle. If the error hits the boundary of the constraint, the supervisory controller beings operation to force the error back to the constraint set. We prove that the PID-supervision hybrid control system is globally stable in the sense that the error is guaranteed to be within the tolerance limits specified by the system designer.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.121-130
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• 2007

To investigate the enhancement in strength and deformation capacities of concrete confined by FRP composites, tests under axial loads were carried out on three groups of thirty six short columns in circular section with diverse GFRP confining reinforcement. The major test variables considered include fiber content or orientation, wrap or tube type by varying the end loading condition, and continuous or discontinuous confinement depending on the presence of vortical spices between its two halves. The circumferential FRP strains at failure for different types of confinements were also investigated with emphasis. Various analytical models capable of predicting the ultimate strength and strain of the confined concrete were examined by comparing to observed results. Tests results showed that FRP wraps or tubes provide the substantial increase in strength and deformation, while partial wraps comprising the vertical discontinuities fail in an explosive manner with less increase in strength, particularly in deformation. A bilinear stress-strain response was observed throughout all tests with some variations of strain hardening. The failure hoop strains measured on the FRP surface were less than those obtained from the tensile coupons in all tests with a high degree of variation. In overall, existing predictive equations overestimated ultimate strengths and strains observed in present tests, with a much larger scatter related to the latter. For more accuracy, two simple design- oriented equations correlated with present tests are proposed. The strength equation was derived using the Mohr-Coulomb failure criterion, whereas the strain equation was based on entirely fitting of test data including the unconfined concrete strength as one of governing factors.