• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.04a
• /
• pp.336-342
• /
• 1997

In this paper, in order to analyze dynamic characteristics of automobile steering system consisting of many components, natural frequencies and transfer functions of each component and total system are found on FFT by experiments. Then, the data are transmitted to commercial package program, CADA-PC. By analyzing the data, the mode shape of each natural frequency and damping values are obtained. Also, the function of rubber coupling in column and telescoping effects on system are considered. C.A.E commercial program are used to compare with the results of experiments. For finite element modeling, I-DEAS is used. Data processing and post processing are operated on NASTRAN and XL, respectively. The ball-bearing and the linkage of shaft with column are modeled by spring elements. Stiffness is modified from the results of experiments. The results of those show close agreement. In the mode shape of total system, wheel mode is dominant at lower frequency while the column mode is main mode at higher . The role of rubber coupling in vibration isolation is clear on mode shape. Telescoping function makes natural frequency of column changed.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2000.05a
• /
• pp.90-91
• /
• 2000

The physiological systems that control blood fluidity are both complex and elegant. Blood must remain fluid within the vasculature and yet clot quickly when exposed to nonendothelial surfaces at sites of vascular injury. There are two principle mechanisms to control a delicate balance in higher organisms (Davie & Ratnoff, 1964). Present evidence suggests that the intrinsic pathway play an important role in the growth and maintenance of fibrin formation in the coagulation cascade while a second overlapping mechanism, called the extrinsic pathway, is critical in the initiation of fibrin formation. Coagulation factors is in two mechanisms, and in order to clot blood, they are activated by a cooperation with $Ca^{2+}$, phospholipid and vitamin K etc. For example, the human placental anticoagulant protein (PAP of PAP- I), which is a $Ca^{2+}$ -dependent phospholipid binding protein (Funakoshi et al., 1987) inhibited the activity of factor Xa, so that it prolonged fibrin formation. We wondered whether any other protein was involved in regulation of the coagulant system as an anticoagulant protein from natural organisms. Natural agents would have not harmful side-effects in comparision with chemically synthesized materials such as warfarin, aspirin, phenindione, etc.. But anticoagulant agents from natural, especially marine organisms have hardly been researched except for polysaccharides from marine algae. (omitted)

• Applied Microscopy
• /
• v.44 no.1
• /
• pp.15-20
• /
• 2014

Cytokeratin 19 (CK19) expressed in epidermis of skin, bulge region of hair follicle, outermost layer of outer root sheath and proximal and distal to bulge. Vimentin is a fibrous protein that localized in cytoplasm of fibroblast and forms cytoskeleton to maintain shape of cell and nucleus. In this study, CK19 and vimentin in skin were confirmed with light, fluorescence and transmission electron microscope. As a result, CK19 was localized epidermis, hair follicles, outer root sheath and nucleus of Merkel's cell. However, vimentin was localized some epidermis, dermis, hypodermis and nucleus of Merkel's cell. The role of CK19 is self-renewal and homeostasis in skin. Also, hair follicle regeneration and hair growth is known to be related. It is supposed that required of structural proteins that make up cytoskeleton is increased. Thereby, expression of CK19 is increased. It is considered that vimentin localized in order to stabilize structure of cell and cytoskeleton of fibroblasts. Also, CK19 and vimentin present in nuclei of Merkel's cell, and to act as a fibrous protein that make up end of a nerve fiber present in Merkel's cell and paracrine function of Merkel's cell.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
• /
• 2008.10a
• /
• pp.90-93
• /
• 2008

In natural language, it is common that repetitive constituents in an expression are to be left out and it is necessary to figure out the constituents omitted at analyzing the meaning of the sentence. This paper is on recognition of boundaries of parallel noun phrases by figuring out constituents omitted. Recognition of parallel noun phrases can greatly reduce complexity at the phase of sentence parsing. Moreover, in natural language information retrieval, recognition of noun with modifiers can play an important role in making indexes. We propose an unsupervised probabilistic model that identifies parallel cores as well as boundaries of parallel noun phrases conjoined by a conjunctive particle. It is based on the idea of swapping constituents, utilizing symmetry (two or more identical constituents are repeated) and reversibility (the order of constituents is changeable) in parallel structure. Semantic features of the modifiers around parallel noun phrase, are also used the probabilistic swapping model. The model is language-independent and in this paper presented on parallel noun phrases in Korean language. Experiment shows that our probabilistic model outperforms symmetry-based model and supervised machine learning based approaches.

• Fibers and Polymers
• /
• v.7 no.3
• /
• pp.229-234
• /
• 2006

Poly(vinyl acetate) (PVAc)/poly(vinyl alcohol) (PVA)/montmorillonite (MMT) clay nanocomposite microspheres with a core/shell structure have been developed via a suspension polymerization approach. In order to prepare the PVAc/ MMT and PVAc/PVA/MMT nanocomposite microspheres, which are promising precursor of PVA/MMT nanocomposite microspheres, suspension polymerization of vinyl acetate with organophilic MMT and heterogeneous saponification were conducted. A quaternary ammonium salt, cetyltrimethylammonium bromide, was mixed with the MMT in the monomer phase prior to the suspension polymerization. The rate of conversion decreased with an increase in MMT concentration. The incorporation of MMT into the PVAc was verified by FT-IR spectroscopy. Organic vinyl acetate monomers were intercalated into the interlayer regions of organophilic clay hosts and followed by suspension polymerization. Partially saponified PVA/MMT nanocomposite microspheres with a core/shell structure were successfully prepared by heterogeneous saponification.

• Ceramist
• /
• v.22 no.1
• /
• pp.56-69
• /
• 2019

Recent advances in low-power sensors and transmitters are driving the search for standalone power sources that utilize unused ambient energy. These energy harvesters can alleviate the issues related to the installation and maintenance of sensors. Particularly piezoelectric energy harvesters, with the ability to convert ambient mechanical energy into useful electricity, have received significant attention due to their high energy density, low cost and operational stability over wide temperature and pressure conditions. In order to maximize the generated electrical power, the natural frequency of the piezoelectric energy harvester should be matched with the dominant frequency of ambient vibrations. However, piezoelectric energy harvesters typically exhibit a narrow bandwidth, thus, it becomes difficult to operate near resonance under broadband ambient vibration conditions. Therefore, the resonating of energy harvesters is critical to generate maximum output power under ambient vibration conditions. For this, energy harvesters should have broadband natural frequency or actively tunable natural frequency with ambient vibrations. Here, we review the most plausible broadband energy harvesting techniques of the multi-resonance, nonlinearity, and self-resonance tuning. The operation mechanisms and recent representative studies of each technique are introduced and the advantages and disadvantages of each method are discussed. In addition, we look into the future research direction for the broadband energy harvester.

• Steel and Composite Structures
• /
• v.19 no.5
• /
• pp.1279-1298
• /
• 2015

In this paper, free vibration characteristics of a rotating double tapered functionally graded beam is investigated. Material properties of the beam vary continuously through thickness direction according to the power-law distribution of the volume fraction of the constituents. The governing differential equations of motion are derived using the Hamilton's principle and solved utilizing an efficient and semi-analytical technique called the Differential Transform Method (DTM). Several important aspects such as taper ratios, rotational speed, hub radius, as well as the material volume fraction index which have impacts on natural frequencies of such beams are investigated and discussed in detail. Numerical results are tabulated in several tables and figures. In order to demonstrate the validity and accuracy of the current analysis, some of present results are compared with previous results in the literature and an excellent agreement is observed. It is showed that the natural frequencies of an FG rotating double tapered beam can be obtained with high accuracy by using DTM. It is also observed that nondimensional rotational speed, height taper ratio, power-law exponent significantly affect the natural frequencies of the FG double tapered beam while the effects of hub radius and breadth taper ratio are negligible.

• Steel and Composite Structures
• /
• v.19 no.3
• /
• pp.635-659
• /
• 2015

In this study, natural frequency analysis of a large deflected cantilever laminated composite beam fixed at both ends, which forms the case of a pre-stressed curved beam, is investigated. The laminated beam is considered to have symmetric and asymmetric lay-ups and the effective flexural modulus of the beam is used in the analysis. In order to obtain the pre-stressed composite curved beam case, an external vertical concentrated load is applied at the free end of a cantilever laminated composite beam and then the loading point of the deflected beam is fixed. The non-linear deflection curve of the flexible beam undergoing large deflection is obtained by the Reversion Method. The curved laminated composite beam is modeled by using the Finite Element Method with a straight-beam element approach. The effects of orientation angle and vertical load on the natural frequency parameter for the first four modes are examined and the results obtained are given in graphics. It has been found that the effect of the load parameter, which forms the curved laminated beam, on the natural frequency parameter, almost disappears after a certain value of the load parameter. This certain value differs for each laminated curved beam and each vibration mode.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.6 no.4
• /
• pp.904-921
• /
• 2014

The main objective of this paper is to propose a new Finite Element (FE) model updating technique for damped beam structures. The present method consists of a FE model updating, a Degree of Freedom (DOF) reduction method and a damping matrix identification method. In order to accomplish the goal of this study, first, a sensitivity-based FE model updating method using the natural frequencies and the zero frequencies is introduced. Second, an Iterated Improved Reduced System (IIRS) technique is employed to reduce the number of DOF of FE model. Third, a damping matrix is estimated using modal damping ratios identified by a curve-fitting method and modified matrices which are obtained through the model updating and the DOF reduction. The proposed FE model updating method is verified using a real cantilever beam attached damping material on one side. The updated result shows that the proposed method can lead to accurate model updating of damped structures.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.1155-1160
• /
• 2008

In the present study investigated the heat dissipation characteristics of the natural convection type radiator by using the latent heat from a solid-liquid PCM(Phase Change Material). Total radiator volume size is $423{\times}295{\times}83\;mm$ and PCM tank size is $398{\times}270{\times}26\;mm$. The objective was elapsed time lower than maximum operating temperature. Experimental condition, in order to study the effects of the phase-change phenomenon, carried out the various mass flow rate, input electric power, and heat of fusion temperature of two type PCMs. For the above experimental conditions, the cooling performance by using the latent heat showed that heat absorption rate performs for about 3 hours from using PCM $38^{\circ}C$. However, cooling performance by using PCM $50^{\circ}C$ showed higher than surface temperature of heater block because of heat of fusion.