• Macromolecular Research
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• 제15권1호
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• pp.44-50
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• 2007

This study investigated the effect of ultrasound irradiation on the blend of poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). The blends of PLA/PBAT(50/50) (PBAT50) were prepared in a melt mixer with an ultrasonic device attached. Thermal, rheological, and mechanical properties, morphology, and biodegradability of the sonicated blends were analysed. The viscosity of the sonicated blends was increased by the ultrasound irradiation owing to the strong interaction. The morphology of the sonicated blends was significantly dependent on the duration o the ultrasound irradiation. For PBAT50, the phase size reduction was maximized when the blends were ultrasonically irradiated for 30 sec. At longer duration of ultrasound irradiation, the PBAT phase underwent flocculation. Measurement of the tensile properties showed an increased breakage tensile stress and an enhanced Young's modulus when the blends were properly irradiated. This improvement was ascribed to better adhesion between the PLA matrix and the PBAT domain and to better dispersion of the PBAT phase. However, the tensile properties were maximized after excessive energy irradiation, which was ascribed to an emulsifying effect leading to coalescence of the PBAT phase. Impact strength was increased to reach a peak with the ultrasound irradiation, and was higher than the untreated sample for all sonicated samples due to the difference of failure mechanism between the tensile test and the impact test.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.186-194
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• 2004

Experiments were conducted to determine the structural static and dynamic characteristics of air foil bearings. The housing of the bearing on the journal was driven by an impact hammer which was used to simulate dynamic forces acting on the bump loll with various leading condition. Two different bump foils (Cu-coated bump and viscoelastic bump) were tested and the static and dynamic coefficients of two bump foils compared, based on the experimental measurements for a wide range of operating conditions. The static and dynamic characteristics of air foil bearings were extracted 0rpm the frequency response function by least square method and IV(Instrumental Variable) method. The experiment was tested at 0rpm and $10,000\~16,000rpm$, and loaded on $50\~150N$. From the test results, the possibility of the application of high load and high speed condition is suggested.

• Structural Engineering and Mechanics
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• 제68권4호
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• pp.399-408
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• 2018

Cable supported structures have been widely used in civil engineering. Cable tension estimation has great importance in cable supported structures' analysis, ranging from design to construction and from inspection to maintenance. Even though the Bernoulli-Euler beam element is commonly used in the traditional finite element method for calculation of frequency and cable tension estimation, many elements must be meshed to achieve accurate results, leading to expensive computation. To improve the accuracy and efficiency, a dynamic finite element method for estimation of cable tension is proposed. In this method, following the dynamic stiffness matrix method, frequency-dependent shape functions are adopted to derive the stiffness and mass matrices of an exact beam element that can be used for natural frequency calculation and cable tension estimation. An iterative algorithm is used for the exact beam element to determine both the exact natural frequencies and the cable tension. Illustrative examples show that, compared with the cable tension estimation method using the conventional beam element, the proposed method has a distinct advantage regarding the accuracy and the computational time.

• International Journal of Reliability and Applications
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• 제15권2호
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• pp.85-98
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• 2014

Accelerated life testing (ALT) is a well famous technique in life testing and reliability studies, this is particularly used to induce so high stress leading to failure of the highly reliable units quickly under stipulated duration of time. The step-stress ALT is one of the systematic experimental strategy of ALT applied to fail the units in steps. In this article we focus on two important issues (i) necessity of life tests at higher steps with relevant causes (ii) to develop a new optimum test plan for 3-step SSALT under the modified cumulative exposure model proposed by Khamis and Higgins (1998). It is assumed that the lifetime of test units follows Rayleigh distribution and its scale parameter at constant stress level is assumed to be a log-linear function of the stress. The maximum likelihood estimates of the parameters involved in the step-stress ALT model are obtained. A simulation study is performed for numerical investigation of the proposed new optimum plan 3-step, step-stress ALT. The necessity of the life test units at 3-step step-stress is also numerically examined in comparison to simple step-stress setup.

• Asian Pacific Journal of Cancer Prevention
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• 제16권6호
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• pp.2187-2191
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• 2015

Background: Protrusive structures formed by migrating and invading cells are termed lamellipodia, filopodia, invadopodia and podosomes. Lamellipodia and filopodia appear on the leading edges of migrating cells and function to command the direction of the migrating cells. Invadopodia and podosomes are special F-actin-rich matrix-degrading structures that arise on the ventral surface of the cell membrane. Invadopodia are found in a variety of carcinomatous cells including squamous cell carcinoma of head and neck region whereas podosomes are found in normal highly motile cells of mesenchymal and myelomonocytic lineage. Invadopodia-associated protein markers consisted of 129 proteins belonging to different functional classes including WASP, NWASP, cortactin, Src kinase, Arp 2/3 complex, MT1-MMP and F-actin. To date, our current understanding on the role(s) of these regulators of actin dynamics in tumors of the orofacial region indicates that upregulation of these proteins promotes invasion and metastasis in oral squamous cell carcinoma, is associated with poor/worst prognostic outcome in laryngeal cancers, contributes to the persistent growth and metastasis characteristics of salivary gland adenoid cystic carcinoma, is a significant predictor of increased cancer risk in oral mucosal premalignant lesions and enhances local invasiveness in jawbone ameloblastomas.

• Macromolecular Research
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• 제15권4호
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• pp.343-347
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• 2007

Novel composite membranes, which delivered high separation performance for propylene/propane mixtures, were developed by coating inert poly(ethylene-co-propylene) rubber (EPR) onto a porous polyester substrate, followed by the physical distribution of $AgBF_4$. Scanning electron microscopy-wavelength dispersive spectrometer (SEM-WDS) revealed that silver salts were uniformly distributed in the EPR layer. The physical dispersion of the silver salts in the inert polymer matrix, without specific interaction, was characterized by FT-IR and FT-Raman spectroscopy. The high separation performance was presumed to stem from the in-situ dissolution of crystalline silver ionic aggregates into free silver ions, which acted as an active propylene carrier within a propylene environment, leading to facilitated propylene transport through the membranes. The membranes were functional at all silver loading levels, exhibiting an unusually low threshold carrier concentration (less than 0.06 of silver weight fraction). The separation properties of these membranes, i.e. the mixed gas selectivity of propylene/propane ${\sim}55$ and mixed gas permeance ${\sim}7$ GPU, were stable for several days.

• International Journal of Internet, Broadcasting and Communication
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• 제7권2호
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• pp.142-148
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• 2015

The main purpose of this squib is to provide a new principled account for variation of canonical sentence structure in Korean and Japanese based on the linguistic data commonly observed in some dialects of Korean and Japanese. Unlike the English case in which Comp(lementizer) such as 'that' in an embedded clause freely drops as far as the ECP (Lasnik & Saito 1992) is obeyed, some dialects of both Korean and Japanese show interesting linguistic data very different from those of English, thereby leading us to reasonably doubt the traditionally-accepted paradigm of the canonical sentence structure of CP for all languages. In this squib I propose, based on Korean & Japanese dialects and by developing the Minimal Structure Principle (MSP) ($Bo{\check{s}}kovi{\acute{c}}$ 1997, p. 25), that the cannonical structure of a sentence is not fixed, from the beginning at all, to be one single maximal category, CP. Instead, it should be decided to be either CP or IP, based on the feature of [${\pm}$markedness] and MSP, and the marked (or non-cannonical) embedded sentence needs to satisfy ECP for adjacency (or feature-licensing by the matrix verb in the MP terminology).

• Journal of Information Technology Applications and Management
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• 제11권1호
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• pp.137-159
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• 2004

In the past days, most of studies about website and Online behavior have been mainly focused on the adoption of website and internet shopping or internet shopping mall. But the model of website revisit behavior has not been made and the leading theory of website usage behavior has not been existed. Lately, many researches on commercial website revisiting behavior are emphasizing the role of intention, attitude, satisfaction in online visiting behavior such as Jarvenpaa et al. [1997, 1999, 2000], Wang et al. [2001], Moon & Kim [2001], Heijden[2003], Sultan et al. [2002], Yoon [2000], Shankar et al. [2002a, 2002b], Mcknight et al. [2002], Chen & Dhillon [2003] and so on. The purpose of this paper is two-folds. The one is to find the affecting factors on the website users' revisit behavior in commercial website and the other is to search more influencing ones on the determinant factors, to analyze research model using in LISREL. The EFA and reliability test was executed by for finding the validity and reliability, covariance matrix analysis was executed for the purpose of testing the 13 hypotheses. The major finding of this paper would be summarized as followed : (1) The roles of satisfaction and attitude to the revisit behavior are very important and both variables have determining effects in commercial website revisit behavior. (2) The determining factors in positively affecting website users' satisfaction are attitude, perceived usefulness, design. (3) The determining factors in positively affecting website users' attitude are perceived usefulness, design, perceived ease of use, and negatively affecting factor was perceived risk in website.

• 한국지능시스템학회논문지
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• 제15권2호
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• pp.185-190
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• 2005

본 논문은 파리미터의 불확실성을 포함하는 Takagi-Sugeno(T-S) 퍼지 시스템을 위한 체계적인 출력 추종 제어기 설계기법을 제안한다. 불확실 T-S 퍼지 시스템은 효과적인 설계를 위하여 퍼지 입력 공간의 발화도의 우세성에 따르는 몇 개의 불확실 선형 시스템으로 표현된다. 출력 추종 제어 오차는 일반화된 리아푸노프 함수에 의하여 해석된다. 이에 따라 출력 추종 제어기 설계 문제는 몇 개의 불확실 선형 시스템의 안정화 문제로 변환된다. 강인 추종 제어기 설계 조건은 선형행렬 부등식의 형태로 유도된다. 마지막으로 파라미터 불확실성을 포함하는 혼돈 로렌Cm 카오스 시스템의 출력 추종 문제를 고려하여 본 논문에서 제안한 기법의 효용성을 입증한다.

• Journal of Electrochemical Science and Technology
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• 제7권2호
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• pp.97-114
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• 2016

Lithium batteries based on elemental sulfur as the cathode-active material capture great attraction due to the high theoretical capacity, easy availability, low cost and non-toxicity of sulfur. Although lithium/sulfur (Li/S) primary cells were known much earlier, the interest in developing Li/S secondary batteries that can deliver high energy and high power was actively pursued since early 1990’s. A lot of technical challenges including the low conductivity of sulfur, dissolution of sulfur-reduction products in the electrolyte leading to their migration away from the cathode, and deposition of solid reaction products on cathode matrix had to be tackled to realize a high and stable performance from rechargeable Li/S cells. This article presents briefly an overview of the studies pertaining to the different aspects of Li/S batteries including those that deal with the sulfur electrode, electrolytes, lithium anode and configuration of the batteries.