• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.603-608
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• 2014

Underwater acoustic materials are installed in order to reduce reflection, transmission and radiation of an underwater structure. The acoustic performance of the materials should be evaluated in accurately-controlled environment in terms of temperature and static pressure. In this paper, three pulse tubes, which is equipped with temperature and pressure controllers, are designed and developed to evaluate echo reduction and transmission loss for evaluating the performance below 10 kHz and 30kHz, respectively. The new procedures of the evaluation are suggested to improve the accuracy and the validation for the developed pulse tubes is carried out by comparing theoretical values to experimental ones.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 봄 학술발표회 논문집
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• pp.187-194
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• 1999

Laminated rubber bearings are widely used as a key component in seismic isolation of structural systems subjected to earthquake loadings. The combination of rubber layers and reinforcing steel shims makes the bearings conditionally unstable similar to buckling of ordinary columns. The shear flexibility of these short columns can lead to relatively low buckling Toads which may be further reduced when high shear strains are simultaneously imposed As an analytical approach, the area reduction formula has been proposed to account for the reduction in buckling load due to shear, but the degree of conservatism is unknown. In order to complement analytical approaches, a non-linear finite element analysis can be used. In this paper, a numerical study which aims at determining the effect of high shear strain on the critical load of elastomeric bearings is presented. From the load-displacement curve at each specified shear displacement, the buckling load can be obtained using the Southwell procedures. The results obtained are then compared against the theoretical predictions in order to examine the validity and the conservatism of the theoretical formulas.

• 대한전자공학회논문지
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• 제25권1호
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• pp.108-114
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• 1988

We have developed a program that minimizes the chip area with effective code assignment of microinstructions when the control part of VLSI system is implemented in the PLA. While conventional algorithms are composed of one pass, the algorithm proposed in this paper is composed of two passes and it consists of three principal procedures: a procedure for the determination of the code assignment order, a procedure for the code assignment and a procedure for the reduction of the code length. especially, we have proposed a new method of folding back for the reduction of the code length. We have obtained the result of 4 bit code length and 9 product terms when 11 micro-instructions and 6 microoperations were given as a inputs. Therefore, we have certified that it could be used efficiently for the control part of the processors.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.1168-1173
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• 2001

Compressors are the main source of noise of refrigerators and air-conditioning unit. Recent studies on the sound propagation of rotary compressors showed that the accumulator is a significant source of noise generation. This paper describes a design change of a rotary compressor for noise reduction using topology optimization. Topology optimization has been developed and used to find the most effective structural configuration in the early stage of design procedures. FE model of the rotary compressor composed of all the components is built for the topology optimization. Topology optimization results show that the empirical design for the present structure fail to constrain some resonance modes and a new component is required.

• 소음진동
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• 제6권4호
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• pp.521-528
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• 1996

Recently, higher speed optical disk drives including computer CD-ROM drives tend to be increasingly demanded to read or write the enormous volume of digital data. To this end, both structure and controller designs of the optical pick-ups should be improved concurrently. In this paper, the pick-up during auto-focusing motion is mathematically modelled retaining all its peculiar features. The model turns out a linear time invariant system suitable for a control design namedH${\infty}$ which ensures robust stability in the presence of system uncertainties. Numerical simulations are performed to demonstrate the robustness with appropriate performance specifications being satisfied. In addition, as the implementation issue of it, procedures of temporal discretization as well as model reduction of the controller are also addressed.

• Communications for Statistical Applications and Methods
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• 제22권2호
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• pp.173-180
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• 2015

We propose a selection procedure of principal components in principal component regression. Our method selects principal components using variable selection procedures instead of a small subset of major principal components in principal component regression. Our procedure consists of two steps to improve estimation and prediction. First, we reduce the number of principal components using the conventional principal component regression to yield the set of candidate principal components and then select principal components among the candidate set using sparse regression techniques. The performance of our proposals is demonstrated numerically and compared with the typical dimension reduction approaches (including principal component regression and partial least square regression) using synthetic and real datasets.

• 한국유체기계학회 논문집
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• 제7권1호
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• pp.45-50
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• 2004

Two phenomena often encountered in liquid flow, which were completely absent in gas or vapor flow, were cavitation and flashing. These phenomena were of significant interest in any comprehensive discussion of control valves or contracted devices since their occurrence would affect the device sizing procedures, might introduce noise and vibration, and also may limit the life expectancy of device components and the immediate downstream piping. Thus, this study aimed to find the reduction method of occurred cavitation in system by the computer simulation. A derivative six model with different dimensions of cavity were adopted. From the results, it was found that the length of the cavity was mote important factor to reduce the pressure drop over the control valves or contracted devices than the depth of the cavity. And the pressures along the centerline of the contracted devices were dropped two times in the case of haying the large length (Lc=1.5D) of cavity.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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• pp.214-224
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• 1999

The design response spectrum has been widely used in seismic design to estimate force and deformation demands of structures imposed by Earthquake Ground Motion (EQGM). Inelastic Design Response Spectra (IDRS) to specify design yielding strength in seismic codes are obtained by reducing the ordinates of Linear Elastic Design Response Spectrum (LEDRS) by strength reduction factor (R). Since a building is designed using reduced design spectrum (IDRS) rather than LEDRS in current seismic design procedures it allows structures behave inelastically during design level EQGM. Inelastic Response Spectra (IRS) depend not only on the characteristics of the expected ground motion at a given site, but also on the dynamic properties and nonlinear characteristics of a structure. However, it has not been explicitly investigated the effect of different hysteretic models on IRS. In this study, the effect of hysteretic models on IRS is investigated.

• The Korean Journal of Pain
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• 제24권4호
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• pp.231-234
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• 2011

Kummell's disease is a spinal disorder characterized by delayed post-traumatic collapse of a vertebral body with avascular necrosis. Although definitive treatment for Kummell's disease has not been established, it has been reported that percutaneous vertebroplasty or kyphoplasty has shown good results. However, these procedures are not recommended for severely collapsed vertebral bodies because of the risk of cement leakage or technical difficulties. Authors report a rare case of spontaneous reduction in vertebral height by the insertion of a working cannula into the vertebral body in Kummell's disease.

• 대한소아치과학회지
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• 제25권3호
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• pp.613-618
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• 1998

A dentigerous cyst is an epithelium-lined sac that surrounds the crown of an impacted, embedded, or unerupted tooth. Many surgical procedures have been described for the elimination of dentigerous cyst, but they can be devided into two basic group: enucleation and marsupialization. Marsupialization is a conservative technique which allows the reduction or elimination of a cystic lesion by making it an accessory compartment to the oral cavity and it is the best way to conserve a tooth affected by dentigerous cyst and to permit its eruption, especially in young patient. After using marsupialization to treat dentigerous cyst associated with the crown of unerupted premolar in young patient, the results were as follows: 1. Reduction of bony expansion and rapid bone regeneration without infection and recurrence were observed. 2. Normally spontaneous eruption of involved teeth were permitted, as well as loss of affected tooth was avoided. 3. Follow-up examinations revealed no complication and recurrence.