• Asian-Australasian Journal of Animal Sciences
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• v.15 no.8
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• pp.1121-1127
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• 2002

Sixteen crossbred (Bos indicus${\times}$Bos taurus) calves were randomly distributed in two groups (NP and LP) of eight calves each to study the effect of restricted (75%) protein supply on growth and immuno-biochemical response as an indicator of production and health of under-nourished animals during 3 to 9 months of age. The normal requirement of protein was provided to group NP and a less of 25% to group LP through calculated amount of concentrate and roughage in their daily ration. Assessment was made for weekly change in live weight, periodic alteration in blood metabolites and immunological status at six months of age in calves. An initial (during 3 to 6 months of age) depression (p<0.05) in growth was seen in low protein fed group (LP) compared to NP, which became non-significant in the later period of life (6 to 9 months of age). There was no significant effect on haemoglobin, total protein, albumin and globulin concentration except that of urea, which was decreased significantly (p<0.05) in animals fed on low protein diet ($19.83{\pm}1.25$ vs $25.93{\pm}1.29mg/dl$). The treatment effect that was seen in different periods of life was not uniform for other parameters except for urea, which showed a regular depression in LP compared to NP. The assessment of immunological status by indirect haemagglutination (IHA) test against Pasteurella multocida (P52 strain) was considerably (p<0.05) reduced in animals on LP ration compared to those on NP. It is thus argued that with poor nutrition (low protein) and state of compromised immunological response the production and health of the animals will be adversely affected.

• Korean Journal of Materials Research
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• v.8 no.11
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• pp.999-1004
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• 1998

$SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 축광성 형광체의 합성에 있어서 $B_2O_3$는 일반적으로 고상반응의 촉진을 위한 플럭스로서 첨가된다. 본 연구에서는 플럭스로 첨가되는 $B_2O_3$가 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 형광체의 결정구조 및 잔광 특성에 미치는 영향을 조사하였다. 합성된 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 형광체는 520nm에서 최대 피크를 갖는 폭넓은 발광 스펙트럼을 나타내었고, $B_2O_3$ 첨가량의 5wt%일 때 최대값을 나타내었다. $B_2O_3$의 첨가에 의해 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 결정 내부에는 균일 변형(uniform strain)이 발생하였고 이 결과로 결정격자의 a축과 c축의 길이 및 $\beta$각이 감소하여다. 그리고 $SrAl_2O_4$ 결정내부의 균일 변형은 $Eu^{2+}$이온의 여기과정에서 발생하는 정공(hole)의 포획 사이트인 음이온 결함(negative defect)을 다량 발생시키는 원인이 되고, 결과적으로 $SrAl_2O_4$:$Eu^{2+}, Dy^{3+}$ 결정의 잔광 특성을 향상시키는 것으로 생각되었다.

• Composites Research
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• v.30 no.6
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• pp.393-398
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• 2017

The shrinkage distribution of a dental composite (Clearfil AP-X, Kuraray, Japan) used for dental restoration was observed using a digital image correlation method. In order to analyze the shrinkage distribution formed during and after light irradiation, digital images were taken with different photographing conditions for each period. Optimal photographing conditions during LED irradiation were obtained through a preliminary experiment in which the exposure time was applied from 0.15 ms to 0.55 ms in 0.05 ms intervals. The DIC analysis results showed that the strain was non-uniform. For the initial 20 s of light irradiation the composite resin shrank to the level of 50~60% of the final curing shrinkage. Such large shrinkage amount of the composite resin lump affected the tensile stress concentration near the adhesive region between the composite resin and the substrate.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.247-250
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• 2005

The need for improved fuel efficiency, weight reduction has motivated the automotive industry to focus on aluminum alloys as a replacement for steel-based alloy. To cope with the needs for high structural rigidity with low weight, it is forecasted that substantial amount of cast components will be replaced by tubular parts which are mainly manufactured by the extruded aluminum tubes. The extrusion process is utilized to produce tubes and hollow sections. Because there is no weld seam, the circumferential mechanical properties may be uniform and advantageous for hydroforming. However the possibility of the occurrence of a surface defect is very high, especially due to the temperature increase from forming at high pressure when it comes out of the bearing and the roughness of the bearing, which cause the surface defects such as the dies line and pick-up. And when forming a extruded aluminum tube, the free surface of the tube becomes rough with increasing plastic strain. This is well known as orange peel phenomena and has a great effect not only on the surface quality of a product but also on the forming limit. In an attempt to increase the forming limit of the tubular specimen, in the present paper, surface asperities generated during the hydroforming process are polished to eliminate the weak positions of the tube which lead to a localized necking. It is shown that the forming limit of the tube can be considerably improved by simple method of polishing the surface roughness during hydroforming. And also the extent of the crack propagation caused by dies lines generated during the extrusion process is evaluated according to the deformed shape of the tube.

• Geomechanics and Engineering
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• v.10 no.3
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• pp.357-386
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• 2016

In this research work, an exact analytical solution for thermal stability of solar functionally graded rectangular plates subjected to uniform, linear and non-linear temperature rises across the thickness direction is developed. It is assumed that the plate rests on two-parameter elastic foundation and its material properties vary through the thickness of the plate as a power function. The neutral surface position for such plate is determined, and the efficient hyperbolic plate theory based on exact neutral surface position is employed to derive the governing stability equations. The displacement field is chosen based on assumptions that the in-plane and transverse displacements consist of bending and shear components, and the shear components of in-plane displacements give rise to the quadratic distribution of transverse shear stress through the thickness in such a way that shear stresses vanish on the plate surfaces. Therefore, there is no need to use shear correction factor. Just four unknown displacement functions are used in the present theory against five unknown displacement functions used in the corresponding ones. The non-linear strain-displacement relations are also taken into consideration. The influences of many plate parameters on buckling temperature difference will be investigated. Numerical results are presented for the present theory, demonstrating its importance and accuracy in comparison to other theories.

• Bulletin of the Society of Naval Architects of Korea
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• v.25 no.4
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• pp.58-68
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• 1988

This paper is concerned with mechanical properties of unidirectional laminate $[(0^{\circ})_{8T},\;(90^{\circ})_{8T}]$, composed of angle plies $[({\pm}15^{\circ})_{2S},\;({\pm}30^{\circ})_{2S},\;({\pm}45^{\circ})_{2S},\;({\pm}60^{\circ})_{2S},\;({\pm}75^{\circ})_{2S}$ and laminate $[(9^{\circ}/90^{\circ})_{2S},\;(90^{\circ}/{\pm}45^{\circ}/0^{\circ})_S,\;({\pm}45^{\circ}/0^{\circ}/{\pm}90^{\circ})_S,\;({\pm}45^{\circ}/90^{\circ}/0^{\circ})_S,\;(0^{\circ}/90^{\circ}/{\pm}45^{\circ})_S,\;(90^{\circ}/0^{\circ}/{\pm}45^{\circ})_S]$ under the condition of uniform strain tension. Also, experimental investigation was conducted $[10]_{8T}$, off-axis tensile test for intralaminar shear characterization. The experimental data on the failure criterion of tensor polynomial were compared with those from the classical laminate theory. Acoustic Emission experiments have been carried out to investigate the changes of the amplitude distributions of Acoustic Emission monitored during failure of tensile tests on Carbon/Epoxy composites.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.121-127
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• 2012

Cement has been traditionally used as a main binding material of high ductile fiber reinforced cementitious composites. The purpose of this paper is to investigate the feasibility of using alkali-activated slag and polyvinyl alcohol (PVA) fibers for manufacturing high ductile fiber reinforced cementless composites. Two mixture proportions with proper flowability and mortar viscosity for easy fiber mixing and uniform fiber dispersion were selected based on alkali activators. Then, the slump flow, compression, uniaxial tension and bending tests were performed on the mixes to evaluate the basic properties of the composites. The cementless composites showed an average slump flow of 465 mm and tensile strain capacity of approximately 2% of due to formation of multiple micro-cracks. Test results demonstrated a feasibility of manufacturing high ductile fiber reinforced composites without using cement.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.343-363
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• 2017

The objective of this work was finding out the most advisable testing conditions for an effective and robust characterization of the tensile strength (TS) of concrete disks. The independent variables were the loading geometry, the angle subtended by the contact area, disk diameter and thickness, maximum aggregate size, and the sample compression strength (CS). The effect of the independent variables was studied in a three groups of experiments using a factorial design with two levels and four factors. The likeliest location where failure beginning was calculated using the equations that account for the stress-strain field developed within the disk. The theoretical outcome shows that for failure beginning at the geometric center of the sample, it is necessary for the contact angle in the loading setup to be larger than or equal to a threshold value. Nevertheless, the measured indirect tensile strength must be adjusted to get a close estimate of the uniaxial TS of the material. The correction depends on the loading geometry, and we got their mathematical expression and cross-validated them with the reported in the literature. The experimental results show that a loading geometry with a curved contact area, uniform load distribution over the contact area, loads projected parallel to one another within the disk, and a contact angle bigger of $12^{\circ}$ is the most advisable and robust setup for implementation of BT on concrete disks. This work provides a description of the BT carries on concrete disks and put forward a characterization technique to study costly samples of cement based material that have been enabled to display new and improved properties with nanomaterials.

• Journal of Korean Association for Spatial Structures
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• v.4 no.4 s.14
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• pp.113-128
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• 2004

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of solid paraboloidal and complete (that is, without a top opening) paraboloidal shells of revolution with variable wall thickness. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. The ends of the shell may be free or may be subjected to any degree of constraint. Displacement components $u_r,\;u_{\theta},\;and\;u_z$ in the radial, circumferential, and axial directions, respectively, are taken to be sinusoidal in time, periodic in ${\theta}$, and algebraic polynomials in the r and z directions. Potential (strain) and kinetic energies of the paraboloidal shells of revolution are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four digit exactitude is demonstrated for the first five frequencies of the complete, shallow and deep paraboloidal shells of revolution with variable thickness. Numerical results are presented for a variety of paraboloidal shells having uniform or variable thickness, and being either shallow or deep. Frequencies for five solid paraboloids of different depth are also given. Comparisons are made between the frequencies from the present 3-D Ritz method and a 2-D thin shell theory.

• Computers and Concrete
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• v.15 no.4
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• pp.687-707
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• 2015

A finite element computer code for short-term analysis of steel-concrete composite structures is extended to study long-term effects under service loads, in the present work. Long-term effects are important in engineering design because they influence stress and strain distribution of the structural system and therefore contribute to the increment of deflections in these structures. For creep analysis, a rheological model based on a Kelvin chain, with elements placed in series, was employed. The parameters of the Kelvin chain were obtained using Dirichlet series. Creep and shrinkage models, proposed by the CEB FIP 90, were used. The shear-lag phenomenon that takes place at the concrete slab is usually neglected or not properly taken into account in the formulation of beam-column finite elements. Therefore, in this work, a three-dimensional numerical model based on the assemblage of shell finite elements for representing the steel beam and the concrete slab is used. Stud shear connectors are represented for special beam-column elements to simulate the partial interaction at the slab-beam interface. The two-dimensional representation of the concrete slab permits to capture the non-uniform shear stress distribution in the horizontal plane of the slab due to shear-lag phenomenon. The model is validated with experimental results of two full-scale continuous composite beams previously studied by other authors. Results are given in terms of displacements, bending moments and cracking patterns in order to shown the influence of long-term effects in the structural response and also the potentiality of the present numerical code.