• Steel and Composite Structures
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• v.38 no.1
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• pp.33-45
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• 2021

The Runge-Kutta method of 6th-order has been employed in this paper to analyze the flow of Casson nanofluid along permeable exponentially stretching cylinder. The modeled PDEs are changed into nonlinear ODEs through appropriate nonlinear transformations. The aim of the paper is to investigate the effects of different parameters such as Casson fluid parameter, slip parameter, suction parameter, Prandtl number, Lewis number, Brownian motion parameter, and thermophoresis parameter, with the variation of mass concentration profile. Numerical results are attained using a renowned numerical scheme shooting technique and for the authenticity of present methodlogy, the results are verified with earlier open text.

• Journal of Sensor Science and Technology
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• v.28 no.2
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• pp.106-112
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• 2019

Flexible impact force sensors composed of piezoelectric PZT/PDMS composite sandwiched between Al/PET films were fabricated and their voltage signal characteristics were evaluated under varying impact forces for electronic mitt applications. The piezoelectric impact force sensor on an ethylene-vinyl acetate (EVA) substrate exhibited an output voltage difference of no greater than 40 mV a periodical impact test in with the impact load was increased by as much as 240 N by a restoration time of 5 s in a five-time experiment, implying good sensing ability. Moreover, the impact force sensor embedded four electronic mitts showed a reliable sensitivity of less than 1 mV/N and good repeatability under 100 N-impact force during a cycle test executed 10,000 times. This indicated that the fabricated flexible piezoelectric impact sensor could be used in electronic mitt applications. However, the relatively low elastic limit of substrate material such as EVA or poly-urethane slightly deteriorated the sensitivity of the impact sensor embedded electronic mitt at over 200 N-impact forces.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.957-962
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• 2009

Sialon was produced by hot-pressing the mixtures of $Si_3N_4$, AlN and $Y_2O_3$ powders. All fracture tests were performed on a three-point loading system with a 30 mm bending span. Fracture toughness and Vickers hardness of smooth specimen were average 7.05 $MPa{\cdot}m^{0.5}$ and Hv = 1580, respectively. Density of three kinds of specimens, smooth specimen, smooth and healed specimen, smooth with $SiO_2$ colloidal coating and healed specimen, had beyond 99 % of theoretical density. Bending strength of smooth healed specimens had high strength more than 1 GPa. Crack healed specimens recovered as strength as smooth specimen. That is, cracked specimen with $SiO_2$ colloidal coating on cracked part recovered strength by heat treatment, completely. Crack healing of $Si_3N_4$ composite ceramics had contributed glassy $SiO_2$ to strength recovery. Limiting high temperature for bending strength of heat treated smooth specimen for bending strength was about 1273 K.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.37-38
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• 2007

This paper reports the characteristics of piezoelectric microspeakers that are audible in open air with high quality piezoelectric AlN thin film according to the materials properties. When we use a tensile-stressed silicon nitride diaphragm as a supporting layer, the Sound Pressure Level (SPL) is relatively small. However, the SPL of the fabricated microspeakers that have compressive-stressed composite diaphragm show higher output pressure than those of tensile-stressed diaphragm. It produces more than 60dB from 100Hz to 15kHz and the highest SPL is about 100dB at 9.3kHz with 20 Vpeak-to-peak sinusoidal input biases and at 10 mm distances from the fabricated microspeakers to the reference microphone.

• Steel and Composite Structures
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• v.20 no.3
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• pp.651-669
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• 2016

The behavior of shear connectors plays a significant role in maintaining the required strength of a composite beam in normal and hazardous conditions. Various types of shear connectors are available and being utilized in the construction industry according to their use. Channel connectors are a suitable replacement for conventional shear connectors. These connectors have been tested under different types of loading at ambient temperature; however, the behavior of these connectors at elevated temperatures has not been studied. This investigation proposes a numerical analysis approach to estimate the behavior of channel connectors under fire and compare it with the numerical analysis performed in headed stud and Perfobond shear connectors subjected to fire. This paper first reviews the mechanism of various types of shear connectors and then proposes a non-linear thermo-mechanical finite element (FE) model of channel shear connectors embedded in high-strength concrete (HSC) subjected to fire. Initially, an accurate nonlinear FE model of the specimens tested at ambient temperature was developed to investigate the strength of the channel-type connectors embedded in an HSC slab. The outcomes were verified with the experimental study performed on the testing of channel connectors at ambient temperature by Shariati et al. (2012). The FE model at ambient temperature was extended to identify the behavior of channel connectors subjected to fire. A comparative study is performed to evaluate the performance of channel connectors against headed stud and Perfobond shear connectors. The channel connectors were found to be a more economical and easy-to-apply alternative to conventional shear connectors.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.687-693
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• 2004

Composite membranes with a titania layer were prepared by soaking-rolling method with the titania sol of nanoparticles formed in the sol-gel process and investigated regarding the vapor permeation of various organic mixtures. The support modification was conducted by pressing $SiO_2$ xerogel of 500 nm in particle size under 10 MPa on the surface of a porous stainless steel (SUS) substrate and designed the multi-layered structure by coating the intermediate layer of ${\gamma}-Al_2O_3$. Microstructure of titania membrane was affected by heat-treatment and synthesis conditions of precursor sol, and titania formed at calcination temperature of 300$^{\circ}C$ with sol of [$H^+$]/[TIP]=0.3 possessed surface area of 210 $m^2$/g, average pore size of 1.25 nm. The titania composite membrane showed high $H_2/N_2$ selectivity and water/ethanol selectivity as 25-30 and 50-100, respectively. As a result of vapor permeation for water-alcohol and alcohol-alcohol mixture, titania composite membrane showed water-permselective and molecular-sieve permeation behavior. However, water/methanol selectivity of the membrane was very low because of chemical affinity of permeants for the membrane by similar physicochemical properties of water and methanol.

• Steel and Composite Structures
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• v.20 no.1
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• pp.167-184
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• 2016

This paper presents the details of Finite Element (FE) analysis carried out to determine the limiting deformation capacity and failure mode of Laced Steel-Concrete Composite (LSCC) beam, which was proposed and experimentally studied by the authors earlier (Anandavalli et al. 2012). The present study attains significance due to the fact that LSCC beam is found to possess very high deformation capacity at which range, the conventional laboratory experiments are not capable to perform. FE model combining solid, shell and link elements is adopted for modeling the beam geometry and compatible nonlinear material models are employed in the analysis. Besides these, an interface model is also included to appropriately account for the interaction between concrete and steel elements. As the study aims to quantify the limiting deformation capacity and failure mode of the beam, a suitable damage model is made use of in the analysis. The FE model and results of nonlinear static analysis are validated by comparing with the load-deformation response available from experiment. After validation, the analysis is continued to establish the limiting deformation capacity of the beam, which is assumed to synchronise with tensile strain in bottom cover plate reaching the corresponding ultimate value. The results so found indicate about $20^{\circ}$ support rotation for LSCC beam with $45^{\circ}$ lacing. Results of parametric study indicate that the limiting capacity of the LSCC beam is more influenced by the lacing angle and thickness of the cover plate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.170-170
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• 2009

aerosol deposition method(ADM)은 에어로졸화 된 고상의 원료분말을 노즐을 통해 분사시켜 소결과정을 거치지 않고도 상온에서 고밀도 후막을 제조할 수 있으며, 세라믹, 고분자, 금속 등의 다양한 코팅이 가능하다. 본 연구에서는 ADM들 이용하여 세라믹 후막 및 세라믹-폴리머 복합체 후막을 제조하였고 60 mm 노즐을 이용하여 대면적 세라믹 후막 성장도 시도되었다. 세라믹 후막의 원료로는 낮은 유전율과 우수한 품질계수를 갖는 $Al_2O_3$ 분말과 AlN의 분말이 사용되었으며, 세라믹에 비하여 높은 탄성과 1,500~2,000의 품질계수를 갖는 테프론(teflon) 분말이 세라믹과의 복합체 후막성장에 사용되었다. 세라믹-폴리머 복합체의 경우, 폴리머의 함유량에 따라 후막 내부의 결정립 크기가 20 때의 평균 결정립을 갚는 세라믹 후막에 비해 최대 10배 정도까지 증가하는 것을 확인할 수 있었으며, 이에 따라 후막에서의 유전특성 및 전기적인 특성, 열전도도, 투과율이 크게 변화하는 것을 확인할 수 있었다. 본 연구에서는 이러한 물성 변화에 대한 원인 고찰을 위하여 후막의 미세구조 및 화학조성 등에 다양한 분석이 이루어졌으며, 상온에서 성막되는 후막의 고분자 기판으로의 응용을 위한 최적의 공정조건을 제시하고자 한다.

• Archives of Pharmacal Research
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• v.29 no.7
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• pp.598-604
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• 2006

In many conventional drug delivery systems in vogue, failure to deliver efficient drug delivery at the target site/organs; is evident as a result, less efficacious pharmacological response is elicited. Microspheres can be derived a remedial measure which can improve site-specific drug delivery to a considerable extent. As an application, Lung-targeting Ofloxacin-loaded gelatin microspheres (GLOME) were prepared by water in oil emulsion method. The Central Composite Design (CCD) was used to optimize the process of preparation, the appearance and size distribution were examined by scanning electron microscopy, the aspects such as in vitro release characteristics, stability, drug loading, loading efficiency, pharmacokinetics and tissue distribution in albino mice were studied. The experimental results showed that the microspheres in the range of $0.32-22\;{\mu}m$. The drug loading and loading efficiency were 61.05 and 91.55% respectively. The in vitro release profile of the microspheres matched the korsmeyer’s peppas release pattern, and release at 1h was 42%, while for the original drug, ofloxacin under the same conditions 90.02% released in the first half an hour. After i.v. administration (15 min), the drug concentration of microspheres group in lung in albino mice was $1048\;{\mu}g/g$, while that of controlled group was $6.77\;{\mu}g/g$. GLOME found to release the drug to a maximum extent in the target tissue, lungs.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.4
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• pp.85-93
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• 2021

PURPOSE: This study aimed to examine the evaluation of muscle activity, muscle fatigue and balance in male high school Taekwondo athlete with a deformity of the medial longitudinal arch. METHODS: The 20 male high school Taekwondo athletes participated in the study they have been measured radiographic a medial longitudinal arch and divided into a medial longitudinal arch group (higher than 18.8°; MLA group, n = 12) and control group (lower than 18.8°; CON group, n = 8). All subjects were measured muscle activity (TA, PT, PL and PB), muscle fatigue (TA, PT, PL and PB) and balance (A-, AL-, L-, PL-, P-, PM-, M-, AM-direction and composite score; CS). RESULTS: The muscle activity of TP was significantly higher in MLA group compared to CON group (p = 031) and the muscle fatigue of TA was significantly lower in MLA group compared to CON group (p = .043). However, balance did not show significant differences between the groups. CONCLUSION: These results confirmed that male high school Taekwondo athlete with a deformity of medial longitudinal arch increase TP and decrease TA, but there was no difference on balance.