• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.123-126
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• 2005

This study provides a comprehensive experimental study on the dynamic characteristics of a flexible matrix composite(FMC) driveshaft. A primary objective is to verify the analytic results of the FMC drivetrain based on the equivalent complex modulus approach and the classical lamination theory. A testrig has been constructed, which consists of a FMC shaft, a foundation beam, bearings, external dampers and a driving motor. The frequency response functions and transient responses are obtained from the external excitation and the spinup testings. It turns out that the analytic results are in good agreement with the experimental ones.

• Archives of Plastic Surgery
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• 제49권1호
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• pp.25-28
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• 2022

The authors performed rigid reconstruction using the sandwich technique for full-thickness chest wall defects by using two layers of acellular dermal matrix and bone cement. We assessed six patients who underwent chest wall reconstruction. Reconstruction was performed by sandwiching bone cement between two layers of acellular dermal matrix. In all patients, there was no defect of the overlying soft tissue, and primary closure was performed for external wounds. The average follow-up period was 4 years (range, 2-8 years). No major complications were noted. The sandwich technique can serve as an efficient and safe option for chest wall reconstruction.

• 대한화장품학회지
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• 제23권3호
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• pp.24-38
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• 1997

Using the all-trans-retinol which is double-capsulated with matrix, we investigated its stability and the change of the epidermal thickness. The proprietary MDC comprise two steps of capsulation of retinol, i.e., primary microcapsulation with collagen and then secondary capsulation with gellan gum. We compared the activity of all-trans-retinol in various forms such as (1) simply in O/W, (2) in W/O emulsion, (3) in primary capsulted form in O/W emulsion, or (4) in MDC in O/W emulsion. After storage at 45$^{\circ}C$ for 4 weeks, retinol in MDC in O/W emulsion retained 92% of the activity compared to the standard material upon HPLC analysis, whereas the primary capsule gave 70%, the O/W emulsion form 47% and the W/O emulsion 78%. The retinol in MDC in O/W induced the siginificant increase in epidermal thickness compared to the vehicle.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.342-349
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• 2008

A selection method of primary degrees of freedom in dynamic condensation for nonproportional damping structures is proposed. Recently, many dynamic condensation schemes for complex eigenanalysis have been applied to reduce the number of degrees of freedom. Among them, iterative scheme is widely used because accurate eigenproperties can be obtained by updating the transformation matrix in every iteration. However, a number of iteration to enhance the accuracy of the eigensolutions may have a possibility to make the computation cost expensive. This burden can be alleviated by applying properly selected primary degrees of freedom. In this study, which method for selection of primary degrees of freedom is best fit for the iterative dynamic condensation scheme is presented through the results of a numerical experiment. The results of eigenanalysis of the proposed method is also compared to those of other selection schemes to discuss a computational effectiveness.

• 소음진동
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• 제9권1호
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• pp.97-102
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• 1999

Structure-borne noise is an important aspect to consider during the design and development of a vehicle. In this work. it was desired to identify the primary paths associated with structure-borne noise generated from the engine and front suspension. An experimental source-path-receiver model was used to characterize the system. A variety of primary sources such as engine. tires or exhaust system generate vibrations of the inner surfaces of the passenger compartment of a vehicle which subsequently radiate noise. The source was characterized by the force acting at the engine-to-body interface. and the path was characterized by pressure over force FRF's. The excitation forces were indirectly determined using dynamic stiffness of rubber mount or the system accelerance matrix. Through these analysis, path contribution diagram which is well expressed primary noise path is obtained.

• Journal of Welding and Joining
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• 제16권4호
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• pp.83-91
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• 1998

Cracking problems which high temperature plant components suffer during long-term service, occur very often at welded locations. The crack occurs due to accumulated creep damage near fusion line or at heat affected zone (HAZ). However, most of the studies on creep crack growth behavior have been performed with matrix metal not wit welded metal due to the difficulty of interpreting the test results. In this study, creep crack growth rates were measured with C(T) specimens whose cracks were formed along the fusion line or HAZ. The measured crack growth rates were characterized by {TEX}$C_{t}${/TEX}-parameter derived for elastic-primary-secondary creeping material. Since contribution of primary creep was significant for the tested 1Cr-0.5Mo steel, its effect was carefully studied. Effects of crack tip plasticity and material aging were also discussed.

• Animal cells and systems
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• 제15권1호
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• pp.19-27
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• 2011

Hepatocytes, the major epithelial cells of the liver, maintain their morphology in culture dishes coated with extracellular matrix (ECM) components such as collagen and fibronectin or biodegradable polymers (e.g. chitosan, gelatin). In these coated dishes, survival of cells and maintaining of liver-specific functions may increase. The aim of this study was to determine a suitable, cost-effective and simple system for hepatocyte isolation and culture which may be useful for various applications such as in vitro toxicology studies, hepatocyte transplantation and bioartificial liver (BAL) systems. In order to obtain primary cultures, hepatocytes were isolated from liver by an enzymatic method and cultured on plates coated with collagen, chitosan or gelatin. Collagen, gelatin-sandwich and gelatin-cell mixture methods were also evaluated. Morphology and attachment of the cells were observed by inverted microscope and scanning electron microscope (SEM). An MTT assay was used to determine cell viability and mitochondrial activity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권12호
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• pp.4600-4616
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• 2021

In cognitive radio networks where unlicensed secondary users opportunistically access to licensed spectrum unused by licensed primary users, spectrum sensing is one of the key issues in order to effectively use the frequency resource. For enhancing the sensing performance in energy detection-based spectrum sensing, spatial diversity based on multiple antennas is utilized. However, the sensing performance can be degraded when antennas are spatially correlated, resulting in inducing the harmful interference to primary users. To overcome this problem, in this paper, an advanced energy detector is proposed. In the proposed sensing method, a weight matrix based on the eigenvalues of the spatial channels without any prior information on the primary signals is defined and utilized. In numerical simulations, it is shown that the proposed detector outperforms the conventional detector with regard to false-alarm and detection probabilities when antenna are spatially correlated.

• 대한예방한의학회지
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• 제21권3호
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• pp.87-98
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• 2017

Objectives : The objective of present study is to evaluate anti-arthritic effects of dried pomegranate concentrate powders (PCP), Eucommiae Cortex aqueous (EC) and ethanolic (ECe) extracts, Achyranthis Radix aqueous (AR) and ethanolic (ARe) extracts on the primary cultured rat articular chondrocytes. Methods : MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium Bromide) assay was performed cytotoxic effect of test substances. In addition, anti-inflammatory effects were also observed on the lipopolysaccaride (LPS) treated chondrocytes through prostaglandin $E_2\;(PGE_2)$ production and 5-lipoxygenase (LPO) activities, and inhibitory effects on metalloproteinase (MMP)-2 and MMP-9 activities were observed on the recombinant human interleukin $(rhIL)-1{\alpha}$ treated chondrocytes with their extracellular matrix (ECM) related mRNA expressions - collagen type II, SOX9 and aggrecan. Results : As results, ECe and ARe showed obvious cytotoxicity against primary cultured rat articular chondrocytes at a dose level of 10 mg/ml, respectively. However, no obvious cytotoxic effects of PCP, EC and AR were demonstrated at a dose level of 10 mg/ml, on the primary cultured rat articular chondrocytes. In addition, treatment of LPS $50{\mu}g/ml$ induced significant increases of $PGE_2$ contents and 5-LPO activities indicating inflammatory responses of the primary cultured rat articular chondrocytes, and also decreases of cell viabilities, increases of MMP-2 and MMP-9 activities with decreases of extracellular matrix (ECM) related collagen type II, SOX9 and aggrecan mRNA expressions were observed by treatment of $rhIL-1{\alpha}$ 50 ng/ml, suggesting damages on the primary cultured rat articular chondrocytes and related ECM degradations. However, these inflammatory responses and related ECM degradations were inhibited by pretreatment of all test substances, in order of PCP > ECe > ARe > EC > AR, and $rhIL-1{\alpha}$ induced chondrocytes deaths are inhibited by treatment in order of PCP > EC > AR > ECe > ARe. Conclusions : Taken together, it is expected that mixed formulation of PCP as main components with appropriate proportion of EC and AR as additional components will be achieved a potent alternative medicinal food for osteoarthritis.

• 한국주조공학회지
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• 제14권6호
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• pp.530-540
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• 1994

Aluminium-silicon alloy(JIS AC8A) matrix composites reinforced with SiC particles were fabricated by spray-cast forming process, and the microstructure of powders and preforms produced were studied by using an optical and scanning electron microscopy. SiC particles were co-sprayed by mixed phase injection method during the spray casting process. Most of the composite powders formed by this mixed phase injection method exhibit morphology of particle-embedded type, and some exhibits the morphology of particle attached type due to additional attachment of the SiC particles on the surface of the powders in flight. The preforms deposited were resulted in dispersed type microstructure. The pre-solidified droplets and the deposited preform of SiC-reinforced aluminium alloy exhibit finer equiaxed grain size than that of unreinforced aluminium alloy. Eutectic silicons of granular type are crystallized at the corner of the aluminum grains in the preforms deposited, and some SiC particles seem to act as nucleation sites for primary/eutectic silicon during solidification. Such primary/eutectic silicons seem to retard grain growth during the continued spray casting process. It is envisaged from the microstructural observations for the deposited preform that the resultant distribution of SiC injected particles in the Al-Si microsturcture is affected by the amount of liquid phase in the top part of the preform and by the solidification rate of the preform deposited.