• Magazine of the Korea Concrete Institute
• /
• v.3 no.3
• /
• pp.129-139
• /
• 1991

The mechanical hehavior of relIlforced concrete beams with steel fibers is investigated 111 the present study. An expenmental program was set up and several series of rem forced concrete beams have been tested, including two senes of singly-reinforced concrete beams and one senes of doubly-reinforced concrete beams. It was found from th, :se measurements that the crack widths lIlcrease almost llIlearly With the lIlcrease of steel stress and that the crack Widths at the same loadlJ1g stages are greatly reduced as the contents of steel fibers increase. The present study also IJ1chcates that the ductiiIty and the ultJmate resistance are remarkably enhanced due to the addition of steel fibers. A theoretical mex1e1 for the flexural analysis of fiber-reinforced concrete beam which takes into account the effects of fibers JS also proposed.

• Preventive Nutrition and Food Science
• /
• v.4 no.4
• /
• pp.231-235
• /
• 1999

Three black rices(Suwon 415, Iksan 427 and Sanghaehyanghyeolla) harvested in Korea were examined in their pasting characteristics, and minor nutrients(vitamins and minerals) in comparison to those of a brown rice (Dongjinbyo), whereas Iksan 427 and Sanghaehyanghyeolla were waxy rices(0.4 and 0.6%, respectively). Iksan 427 and Sanghaehyanghyeolla showed similar viscosity pattern with significantly low pasting temperatures and viscosity. Brown rice showed higher pasting viscosity and pasting temperature than black rices, and its viscosity pattern was similar to Suwon 415. Brown rice and Suwon 415 displayed higher hardness but lower adhesiveness of their gels. Black rices contained more non-carbohydrate components and dietary fiber than brown rice. From the amino acid analysis, black rices contained more acid amino acids (aspartic and glutamic acids) than brown rice. Among the black rices, Suwon 415 had the highest content of total essential amino acids(4.3%). Black rices also contained higher amounts of vitamin B complexes (thiamin, riboflavin and niacin) and minerals(K, Mg and Ca) than brown rice. Sanghaehyanghyeolla showed an exceptionally high amount of Ca (12mg%).

• Fibers and Polymers
• /
• v.5 no.4
• /
• pp.289-296
• /
• 2004

The kinetic parameters, including the activation energy E, the reaction order n, and the pre-exponential factor Z, of the degradation of the copolymers based on the poly(L-lactide) (PLLA) or poly(p-dioxanone-co-L-lactide) (PDO/PLLA) and diol-terminated poly(ethylene glycol) (PEG) segments have been evaluated by the single heating methods of Friedman and Freeman-Carroll. The experimental results showed that copolymers exhibited two degradation steps under nitrogen that can be ascribed to PLLA or PDO/PLLA and PEG segments, respectively. However, copolymers exhibited almost single degradation step in air. Although the values of initial decomposition temperature were scattered, copolymers showed the lower maximum weight loss rate and degradation-activation energy in air than in nitrogen whereas the higher value of temperature at the maximum rate of weight loss was observed in air.

• Carbon letters
• /
• v.18
• /
• pp.30-36
• /
• 2016

Well-dispersed Ag₃VO₄ nanoparticles @polyacrylonitrile (PAN) nanofibers were synthesized by an easily controlled, template-free method as a photo-catalyst for the degradation of methylene blue. Their structural, optical, and photocatalytic properties have been studied by X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy equipped with rapid energy dispersive analysis of X-ray, photoluminescence, and ultraviolet-visible spectroscopy. The characterization procedures revealed that the obtained material is PAN nanofibers decorated by Ag₃VO₄ nanoparticles. Photocatalytic degradation of methylene blue investigated in an aqueous solution under irradiation showed 99% degradation of the dye within 75 min. Finally, the antibacterial performance of Ag₃VO₄ nanoparticles @PAN composite nanofibers was experimentally verified by the destruction of Escherichia coli. These results suggest that the developed inexpensive and functional nanomaterials can serve as a non-precious catalyst for environmental applications.

• Journal of the Korean Ceramic Society
• /
• v.44 no.5 s.300
• /
• pp.144-147
• /
• 2007

Calcium metaphosphate (CMP) nanofibers with a diameter of ${\sim}600nm$ were prepared using electrospun CMP/polyvinylpyrrolidone (PVP) fibers through a process of drying for 5 h in air followed by annealing for 1 h at $650^{\circ}C$ in a vacuum. The viscosity of the CMP/PVP precursor containing 0.15 g/ml of PVP was 76 cP. Thermal analysis results revealed that the fibers were crystallized at $569^{\circ}C$. The crystal phase of the as-annealed fiber was determined to be ${\delta}-CMP\;({\delta}-Ca(PO_3)_2)$. However, the morphology of the fibers changed from smooth and uniform (as-spun fibers) to linked-particle characteristics with a tubular form most likely due to the decomposition of the inner PVP matrix. It is expected that this large amount of available surface area has the potential to provide unusually high bioactivity and fast responses in clinical hard tissue applications.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.831-836
• /
• 2000

During machining, since more than 50% compliance of the cutting point in machine tool structures comes from headstocks, with the remainder coming from beds, slides and structural joints, the structural analysis of the headstock is very important to improve the static and dynamic performances. Especially, in case of machining hard and brittle materials such as glasses and ceramics with the grinding machine, the reinforced headstock with the high damping material is demanded. Since the fiber reinforced composite materials have excellent properties for structures, owing to its high specific modulus, high damping and low thermal expansion, it is expected that the dynamic and thermal characteristics of the headstock will be improved if they are employed as the materials fur headstock. In this paper, the design and the manufacturing methods as well as the static and dynamic characteristics of a steel-composite hybrid headstock were investigated analytically and experimentally to improve the performance of the grinding machine system.

• Steel and Composite Structures
• /
• v.22 no.6
• /
• pp.1281-1299
• /
• 2016

This paper deals with the analysis of vibration of antisymmetric angle-ply plates using spline method for higher order shear theory. Free vibration of laminated plates is addressed to show the capability of the present method in the vicinity of higher order shear deformation theory and simply supported edges of plates. The coupled differential equations are obtained in terms displacement and rotational functions. These displacement and rotational functions are approximated using cubic and quantic spline. A generalized eigenvalue problem is obtained and solved numerically for an eigenfrequency parameter and an associated eigenvector of spline coefficients. The antisymmetric angle-ply fiber orientation are taken as design variables. Numerical results enable us to examine the frequencies for various geometric and material parameters and accuracy and effectiveness of the proposed method is also verified by comparative study.

• Proceedings of the KAIS Fall Conference
• /
• 2000.10a
• /
• pp.55-60
• /
• 2000

The adsorption isotherms can be assigned to typical Type I for Ag and Cu-treated ACFs and Type I and Type II for Ni-treated ACFs. From the DSC analysis, A $g_{0.9}$-ACF occurs only exothermic curve at the temperature of $203^{\circ}C$, and relatively stable composition curves were formed. But C $u_{0.3}$-ACF and C $u_{0.4}$-ACF occur endothermic curves at the temperature of 57.26, 107.02 and $215.87^{\circ}C$. N $i_{1.0}$-ACF occurs large endothermic curves at 59.26, 98.40 and $208.89^{\circ}C$ and N $i_{0.8}$-ACF are shown endothermic curves at 59.26 and $157.77^{\circ}C$. From the biological results, the percentages of the antibacterial effects were 96.5-100 for Ag-ACFs, 92.3-99.8 for Cu-ACFs and 95.5-100 for Ni-ACFs, respectivelylyvelylyly

• The Journal of Korea Robotics Society
• /
• v.12 no.1
• /
• pp.26-32
• /
• 2017

Previous shape sensors including bend sensors and optic fiber based sensors are widely used in various applications including goniometer and surgical robots. But theses sensors have large nonlinearity, limited in the range of sensing curvature, and sometimes are expensive. This study suggests a new concept of bend sensor using cable-conduit which consists of the outer sheath and the inner wire. The outer sheath is made of helical coil whose length of the central line changes as the sheath bends. This length change of the central line can be measured with the length change of the inner cable. The modeling and the experimental results show that the output signal of the proposed sensor is linearly related with the bend angle of the sheath with root mean square error of 5.3% of $450^{\circ}$ sensing range. Also the polynomial calibration of the sensor can decrease the root mean square error to 2.1% of the full sensing range.

• Journal of Sensor Science and Technology
• /
• v.6 no.5
• /
• pp.362-368
• /
• 1997

The remote real-time uranium concentration analysis using nitrogen laser, optode, photomultiplier and optical fiber is studied. The optode for the remote collection of uranium fluorescence is designed. The fluorescence intensity at time zero is calculated in order to exclude the quenching effect and the temperature fluctuation and used for more precise estimation. The fluorescence change is very sensitive to the uranium concentration change. The method shows the detection limit of 0.06ppm and the linearity between 0.1ppm and 2ppm of the aqueous uranium concentration.