• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.23-31
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• 1998

Kind 1 propeller shaft in ships is the shaft which is provided with effective measures against corrosion by sea water, or the shaft which is made of approved corrosion resistance materials. The propeller shaft other than specified above is Kind 2. Thus, this study is mainly concerned with the resistance to fatigue damage in sea water against stress concentrations due to the notches. The results obtained can be summarized as follows; (1) The stress increases with curing time, however, when the curing time reaches at 96 hours the stress becomes a constant value. The elongation decreases with curing time, however, when the curing time reaches at 48 hours the elongation becomes a constant value. Thus, in case of FRP coating on propeller shaft, it is necessary to cure for 48 hours at least. (2) The relation of $\sigma$$_n$-K$_t$ is to be classified into two parts, which is a part where fracture nominal stress, $\sigma$$_n$, decreases with increasing $K_t$, and a part where $\sigma$$_n$ is nearly constant independent of $K_t$. (3) According to a linear notch mechanics, the measure of severity controlling the fracture in notched FRP body is the notch root radius, $\rho$. The notched static strength of an arbitrary specimen will be estimated from $\sigma$$_{max}$ -1/$\rho$ curve. (4) Through the observation of cross section after fatigue test, the part of interface was kept good condition irrespective of loading conditions.

• Steel and Composite Structures
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• v.36 no.4
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• pp.481-492
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• 2020

To study the rail mapped deformation caused by the pier settlement of simply - supported bridges with China Railway Track System III (CRTS III) slab ballastless track (SBT) system under the mode of non-longitudinal connection ballastless track slab, this study derived an analytical solution to the mapped relationships between pier settlement and rail deformation based on the interlayer interaction mechanism of rail-pier and principle of stationary potential energy. The analytical calculation results were compared with the numerical results obtained by ANSYS finite element calculation, thus verifying the accuracy of analytical method. A parameter analysis was conducted on the key factors in rail mapped deformation such as pier settlement, fastener stiffness, and self-compacting concrete (SCC) stiffness of filling layer. The results indicate that rail deformation is approximately proportional to pier settlement. The smaller the fastener stiffness, the smoother the rail deformation curve and the longer the rail deformation area is. With the increase in the stiffness of SCC filling layer, the maximum positive deformation of rail gradually decreases, and the maximum negative deformation gradually increases. The deformation of rail caused by the pier settlement of common-span bridge structures will generate low-frequency excitation on high-speed trains.

• Journal of the Korean Society for Nondestructive Testing
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• v.13 no.2
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• pp.40-47
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• 1993

Composites composed of a precipitation harden 2124 alloy matrix reinforced by SiC whiskers, which are fabricated by powder metallugy, are suscepttible to fatigue damage due to the pile-up of moving dislocation and the microcrack initiation along SiC-Al interfaces, especially at the external surfaces of a body. The initial process, such as pile-up of dislocation or microcrack, that corresponds to the stage I during fatigue failure process are too small to be detected and characterized by conventional ultrasonic technique. This paper describes the applicability of an acoustic microscope with Line-Focus-Beam(LFB) lens of 225MHz to evaluate fatigue damage of SiC whiskers reinforced Al alloy. The specimens which were 6.6mm thick, 13mm wide, and 105mm long in the gage section were fatigued in tension-tension under load control. The velocity of leaky surface and leaky pseudosurface acoustic waves are obtained by FFT analysis technique from V(z) curve which is a record of output of piezoelectric transducer. These results are discussed with the change of number of fatigue cycles. The result obtained by acoustic microscope is compared with that by ultrasonic technique generated at 5MHz with conventional surface wave transducers.

• Journal of the Korean Ceramic Society
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• v.44 no.2 s.297
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• pp.110-115
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• 2007

The effects of $TiO_2$ in the glasses on the shrinkage and dielectric properties of BNT-glass composites have been investigated. Without $TiO_2$ addition, BNT-glass composite showed two humps in the shrinkage curve, which are related with crystallization of $BaTi(BO_3)_2\;and\;Bi_4Ti_3O_{12}$. However, the increase of $TiO_2$ addition resulted in the decrease of 2nd hump in the shrinkage. The increased dielectric constant with $TiO_2$ addition might be due to the reduced crystallization of $Bi_4Ti_3O_{12}$. A dielectric constant of 52, a quality factor of 5088 GHz, and a temperature coefficient of resonant frequency of $-0.16ppm/^{\circ}C$ were obtained for a specimen containing $TiO_2$-added glasses, without sacrificing the benefits of high ${\varepsilon}_r$ and low TCF of BNT ceramics.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.575-581
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• 2012

The electrochemical oxygen demand (ECOD) is an additional sum parameter, which has not yet found the attention it deserves. It is defined as the oxygen equivalent of the charge consumed during an electrochemical oxidation of the solution. Only one company has yet developed an instrument to determine the ECOD. This instrument uses $PbO_2$-electrodes for the oxidation and has been successfully implemented in an automatic on-line monitor. A general problem of the ECOD determination is the high overpotential of electrochemical oxidations of most organic compounds at conventional electrodes. Here we present a new approach for the ECOD determination, which is based on the use of a solid composite electrodes with highly efficient electro-catalysts for the oxidation of a broad spectrum of different organic compounds. Lead dioxide as an anode material has found commercial application in processes such as the manufacture of sodium per chlorate and chromium regeneration where adsorbed hydroxyl radicals from the electro-oxidation of water are believed to serve as the oxidizing agent. The ECOD sensors based on the Au/$PbO_2$ electrode were operated at an optimized applied potential, +1.6 V vs. Ag/AgCl/sat. KCl, in 0.01 M $Na_2SO_4$ solution, and reduced the effect of interference ($Cl^-$ and $Fe^{2-}$) and an expended lifetime (more than 6 months). The ECOD sensors were installed in on-line auto-analyzers, and used to analyze real samples.

• Journal of the Korean Wood Science and Technology
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• v.45 no.5
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• pp.572-579
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• 2017

Determination of the wood content in wood plastic composite (WPC) is crucial to form reliable WPC market. WPC with simple formulation consisting of only two components (wood flour and polypropylene) was examined using thermogravimetric analysis (TGA) and accelerator mass spectrometry (AMS) for determining wood content in the WPC. TGA method using derivative peak temperature (DTp) of polypropylene under low heating rate ($5^{\circ}C/min$) showed more reliable calibration curve and lower error factor compared to method of using the percentage of weight loss of wood flour. In addition, AMS using bio-based carbon content showed greater reliability for the determination of wood content in the WPC in comparison with the TGA method.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1369-1389
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• 2015

In order to investigate the behaviour of lying multi-stud connectors in cable-pylon anchorage zone, twenty-four push-out tests are carried out with different stud numbers and diameters. The effect of concrete block width and tensile force on shear strength is investigated using the developed and verified finite element model. The results show that the shear strength of the lying multi-stud connectors is reduced in comparison with the lying single-stud connector. The reduction increases with the increasing of the number of studs in the vertical direction. The influence of the stud number on the strength reduction of the lying multi-stud connectors is decreased under combined shear and tension loads compared with under pure shear. Yet, due to multi-stud effect, they still can't be ignored. The concrete block width has a non-negligible effect on the shear strength of the lying multi-stud connectors and therefore should be chosen properly when designing push-out specimens. No obvious difference is observed between the strength reductions of the studs with 22 mm and 25 mm diameters. The shear strengths obtained from the tests are compared with those predicted by AASHTO LRFD and Eurocode 4. Eurocode 4 generally gives conservative predictions of the shear strength, while AASHTO LRFD overestimates the shear strength. In addition, the lying multi-stud connectors with the diameters of 22 m and 25 mm both exhibit adequate ductility according to Eurocode 4. An expression of load-slip curve is proposed for the lying multi-stud connectors and shows good agreement with the test results.

• Korean Journal of Veterinary Research
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• v.42 no.4
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• pp.485-493
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• 2002

The purpose of this study was to develope a computer program to help with gross diagnosis of protein-energy balance and feeding management practice and with the prediction about the risk possibility of productive disease such as reproductive and metabolic disorders by evaluating fat, protein, and milk urea nitrogen (MUN) from individual cow milk in dairy herd Somatic cell counts also represent the condition of udder health. The principal flow charts of this program was to check on herd management, sampling the composite milk, analysis the milk composition, conversion of data from milking equipment to program, input and analysis of data in program, and report. This program is compatible with window 95/98 system. The major analytical elements of this program were presented as; the profile of herd lactation curve analysis of the test-day milk production level, the distribution of somatic cell count, the fat to protein ratio to evaluate body energy balance, and the interpretation of dietary protein-energy balance by milk protein and MUN contents for individual cows. This program using milk fat, protein, MUN, and somatic cell counts will serve as a monitoring tool for the protein-energy balance and the feeding management practice, and for distribution of mastitis in individual cows. It will also be used to manage the nutritional and reproductive disorders and mastitis at the farm level.

• Computers and Concrete
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• v.10 no.2
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• pp.135-147
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• 2012

At mesoscale, concrete is considered as a three-phase composite material consisting of the aggregate particles, the cement matrix and the interfacial transition zone (ITZ). The reconstruction of the internal structures for concrete composites requires the identification of the boundary of the aggregate particles and the cement matrix using digital imaging technology followed by post-processing through MATLAB. A parameter study covers the subsection transformation, median filter, and open and close operation of the digital image sample to obtain the optimal parameter for performing the image processing technology. The subsection transformation is performed using a grey histogram of the digital image samples with a threshold value of [120, 210] followed by median filtering with a $16{\times}16$ square module based on the dimensions of the aggregate particles and their internal impurity. We then select a "disk" tectonic structure with a specific radius, which performs open and close operations on the images. The edges of the aggregate particles (similar to the original digital images) are obtained using the canny edge detection method. The finite element model at mesoscale can be established using the proposed image processing technology. The location of the crack determined through the numerical method is identical to the experimental result, and the load-displacement curve determined through the numerical method is in close agreement with the experimental results. Comparisons of the numerical and experimental results show that the proposed image processing technology is highly effective in reconstructing the internal structures of concrete composites.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8C
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• pp.637-644
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• 2012

In this paper, a new compact power divider is suggested. Instead of the quarter wavelength transmission line(TX-line)s for the branches of the conventional Wilkinson's power divider design method, we use our composite right- and left-handed(CRLH) TX-line zeroth order resonator(ZOR) bandpass filters of one twelfth wavelength and reduce the physical length of the power divider. Besides, the filters in the branches can secure the passband for power-division. To validate the proposed power divider, we take an L-band for millitary satellaite transponder as the test case and the performances of the circuit and full-wave simulation results with the CRLH properties of the structure are shown with the dispersion curve and E-field at the ZOR. The measurement is compared with the simulation results. Also, the size reduction effect by the proposed scheme is addressed