• Proceedings of the KSME Conference
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• 2004.11a
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• pp.725-730
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• 2004

This paper has regarded mechanism design of cane-like passive type walking aid for the elderly using 3-RPS parallel manipulator. First, gait patterns of the elderly have been experimented. By means of motion capturing and image processing, we decided loaded forces and places of the cane when the elderly walked with a cane. Using these results we have developed a passive type walking aid. Second, the walking pattern has been simulated using dynamic analysis program, ADAMS and we find out the similarity between the real walking and the simulated walking. Finally after assuring the similarity, with adjusting the new mechanism design to the simulated walking we will decide whether the walking aid is safe and stable when the elderly walks with this cane-like walking aid. This paper will be basis for the development of the mechanism design applying 3-RPS parallel manipulator.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.12
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• pp.1281-1286
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• 2013

In this paper, a miniaturized stage with two prismatic-prismatic joints (2-PP) type parallel compliant mechanism driven by piezo actuators is proposed. This stage consists of two layers which are a motion guide layer and an actuation layer. The motion guide layer has 2-PP type parallel compliant mechanism to guide two translational motions, whereas the actuation layer has two leverage type amplification mechanisms and two piezo actuators to generate forces. Since the volume of the stage is too small to mount displacement sensors, the piezo actuators embedding strain gauge sensors are chosen. With the strain gauge-embedded piezo actuators, a semi-control is implemented, which results in hysteresis compensation of the stage. As the results, the operating range of $30{\mu}m$, the resolution of 20 nm, and the bandwidth of 400 Hz in each axis were obtained in the experiments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.424-430
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• 2013

This paper presents a new design works for the braking chopper system which is included in the propulsion system of KTX high speed train. Due to the current fed type synchronous motors used in the propulsion system, some different behaviors are shown comparing to the voltage type other chopper systems. Specially this chopper system acts either braking controlling or regenerative power controlling system with a parallel resistive load in the propulsion system. In this paper, an improved simple high power IGBT brake chopper system has proposed which is able to be replaced with an existing complicated GTO chopper system. The analytical approaches to the parallel load type current chopper system and the propper snubber circuits calculation were explained in this paper to control new chopper system. In addition, the thermal resistance of the cooling system for power dissipation of IGBT modules was calculated also. Finally several PC simulations have been done to clarify its availability.

• Journal of the Korean Mathematical Society
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• v.58 no.6
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• pp.1347-1365
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• 2021

For µ = (µ₁, …, µ_t) (µ_j > 0), ξ = (z₁, …, z_t, w) ∈ ℂ^n₁ × … × ℂ^n_t × ℂ^m, define $${\Omega}({\mu},t)=\{{\xi}{\in}\mathbb{B}_{n_1}{\times}{\cdots}{\times}\mathbb{B}_{n_t}{\times}\mathbb{C}^m:{\parallel}w{\parallel}^2 where $\mathbb{B}_{n_j}$ is the unit ball in ℂ^n_j (1 ≤ j ≤ t), C(χ, µ) is a constant only depending on χ = (n₁, …, n_t) and µ = (µ₁, …, µ_t), which is a special type of generalized Cartan-Hartogs domain. We will give some sufficient and necessary conditions for the boundedness of some type of operators on L^p(Ω(µ, t), ω) (the weighted L^p space of Ω(µ, t) with weight ω, 1 < p < ∞). This result generalizes the works from certain classes of generalized complex ellipsoids to the generalized Cartan-Hartogs domain Ω(µ, t).

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.655-658
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• 1999

In this paper, Parallel operation of two DC-DC converters which we have ever done before need two CTs to do load current sharing. However, we have proposed a new method called ZCT method that can share load current with only a CT as doing parallel operation two converters with same converter capacity. To confirm parallel performance by a proposed DC-DC converter parallel operation method, we have done computer simulation and experiment. It is certain that we have showed to achieve two converters current sharing performance efficiently through simulation and experiment at result.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.9
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• pp.863-869
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• 2005

We investigated quench characteristics of superconducting elements connected in series and parallel each other. The serial and parallel connections of superconducting elements causes a difficulty in simultaneous quench due to slight difference between their critical current densities. In other to induce simultaneous quench, we fabricated four type circuits; serially connected circuit before parallel connection, the circuit connected in parallel before serial connection, serially connected circuit before parallel connection with reactors, the circuit connected in Parallel before serial connection with reactors. We confirmed that the simultaneous quenches occurred in serial and parallel connections of superconducting elements using reactors. In addition, the power burden of superconducting elements was smaller than those of serial and parallel connections of superconducting elements without reactors.

• Honam Mathematical Journal
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• v.46 no.1
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• pp.114-119
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• 2024

In this article, we consider a connection of vectorial type in some sense which is not a metric connection. We will then discuss when this connection $\tilde{\nabla}^*$ has parallel torsion T, that is, $\tilde{\nabla}^*T=0$.

• Journal of the Korean Data and Information Science Society
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• v.14 no.4
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• pp.837-844
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• 2003

In this paper, we obtain the estimator of system reliability for the bivariate Pareto model with bivariate type 1 censored data. We obtain the estimators and approximated confidence intervals of the reliability for the parallel system based on likelihood function and the relative frequency, respectively. Also we present a numerical example by giving a data set which is generated by computer.

• The Journal of Korean Academy of Prosthodontics
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• v.22 no.1
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• pp.109-122
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• 1984

The purpose of this study was to analyze the magnitude and mode of the stress distribution induced in the supporting alveolar bone and periodontal ligament and, to determine the displacement of abutment teeth and telescope denture base by applying chewing force to the telescope denture quantitatively and qualitatively. Two finite element models of telescope denture that were restored the missing mandibular second molar with two abutment teeth which were constructed. In two different models, parallel and tapering type telescope crowns were constructed. These finite element models of two cases used for these experiment were a two-dimensional mesiodistal section of the mandibular second bicuspid and first molar. Chewing force of 25Kg that was devided in the ratio of 45/155 (29%) in bicuspid and 55/155 (35.5%) in molars was applied to telescope denture and abutment teeth respectively. The displacement of the telescope denture base and abutment teeth and the stress distribution in the periodontal ligament and alveolar bone were analized to investigate the influence of chewing force acting on the telescope denture and abutment teeth. The results were as follows: 1. Abutment teeth displaced mesially and the magnitude of displacement of abutment teeth in vertical direction were more than that of horizontal direction in two cases. The displacement of abutment teeth on the telescope denture treated with tapering type telescope crown were less than that of the parallel type crown. 2. The displacement of the telescope denture base that were treated with parallel type telescope crown were less than that of treated with tapering type telescope crown. 3. The stress induced in the alveolar bone and periodontal ligament on abutment teeth that treated with parallel type telescope crown were more than that of treated with tapering type telescope crown and more stress induced in the alveolar bone than in the periodontal ligament. 4. In the telescope denture, the magnitude of displacement of abutment teeth and stress induced in the periodontal ligament and alveolar bone were within physiologic limit.

• Journal of Radiation Protection and Research
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• v.41 no.2
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• pp.111-115
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• 2016

Background: The scattered photons cause reduction of the contrast of radiographic image and it results in the degradation of the quality of the image. In order to acquire better quality image, an anti-scattering x-ray gird should be equipped in radiography system. Materials and Methods: The X-ray anti-scattering grid of the inclined type based on the hybrid concept for that of parallel and focused type was tested by MCNP code. The MCNPX 2.7.0 was used for the simulation based test. The geometry for the test was based on the IEC 60627 which was an international standard for diagnostic X-ray imaging equipment-Characteristics of general purpose and mammographic anti-scatter grids. Results and Discussion: The performance of grids with four inclined shielding material types was compared with that of the parallel type. The grid with completely tapered type the best performance where there were little performance difference according to the degree of inclination. Conclusion: It was shown that the grid of inclined type had better performance than that of parallel one.