• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.2 s.25
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• pp.1-6
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• 2007

When the water content within concrete swells, diverse problems occur such as drop in durability. Due to this reason, a change is being managed in the unit water contents by using electric capacity measurements, high frequency heating methods, and unit-volume mass measurements, which are methods of measuring the unit water contents. Particularly, Japan is prescribing the guideline of management on a change in unit water content unit quantity $({\pm}10,\;15,\;20kg//m^3,\;etc.)$. However, the guideline of Japan dose not consider a fall in durability, and is decided on the value of pass-fail criteria by random fabrication errors and measurement errors. Consequently, this study was aimed to investigate the influence of a change In water content within concrete due to an addend caused by management error and to an artificial addend, upon drop in durability.

• Journal of the Korean Graphic Arts Communication Society
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• v.14 no.1
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• pp.115-131
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• 1996

The PVT(pressure-volume-temperature) relation of main-chain dimer liquid crystals having structures such as $\alpha$,$\omega$-bis[(4,4`-cyanobiphenyl) oxy] alkane(CBA-n with=9, 10) were studied. these dimer liquid crystals are known to form an enantiotropic nematic mesophase. In this work, we have determined the volume change as a function of temperature and pressure by using a GNOMIX PVT apparatus. In the V-Tcurves obtaind from isobaris mearements on various pressures, volume changes were observed at the nematic-isotropiz and nematic-crystal phase transitions. The volume changes at the transition exhibit slight odd-even effect with respect to the number of methylene unit n. The values of the (S)v obtained at the NI transition for CBA-9 and -10 were 6.9 and 12.6J/mol k. The valuesof (S)v for the CN transition were estimated on the basis of DSC(differential scanning calorimetry) data: 58.8(CBA-9) and 65.3J/mol k (CBA-10). For both transition, it was found that the correction about the volume change is significant, ranging from 40% to 60% of the total transition entropy observed under constant pressure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.9
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• pp.872-880
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• 2004

The fault detection and diagnosis technology may be applied in order to decrease the energy consumption and the maintenance cost of the air-conditioning system. In this study, an air handling unit fault test apparatus was built and fault diagnosis algorithms were applied to diagnose various faults of an air handling unit. Test results showed the good diagnosis for applied faults. Therefore, these algorithms may be effectively used to develope the real time fault detection and diagnosis system for the air handling unit.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.745-748
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• 2008

On investigation about quick measurement technology of unit water at range of W/B=35% in high strength, the average error of the Di-electric constant moisture tester A has measured more than $23.0kg/m^3$ unit water content of design and the average error of the method of unit volume weigh was less than $-9.6kg/m^3$. The average error with mixing factor has influenced with a kind of sand, but had not influenced with unit water content of design. Therefore, it will be for introduce business decide require more than a study about cement, sand, superplasticizer, etc.

• Industrial Engineering and Management Systems
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• v.11 no.1
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• pp.11-17
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• 2012

Along with the recent trend toward increasing variety and shorter life of products in the market, evaluation of risk for economic investment alternatives is of practical importance in manufacturing companies. This paper assumes that each alternative is composed of demand volume and unit sales price as income factors, and unit variable cost and fixed cost as expense factors. The paper assumes that these four factors move worse from the originally expected values, toward the direction of decreasing profit. Values of these four factors are also assumed to fluctuate from year to year over the entire multi-period. By applying the analysis of the breakeven points to each of the four factors, safer area against these changes is represented on the two dimensional domain called normalized total-cost unit-cost domain. A practical numerical example is analyzed to verify the validity of the proposed method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.132-133
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• 2015

In this research by examining the influence that low quality aggregate has on the strength of concrete through testing, the lowering of strength according to use of low quality coarse aggregate was reviewed. The results showed that when using low quality coarse aggregate, due to the quality of aggregate a high volume of units was required, and this caused the compression strength to be lowered. In conclusion it was confirmed that if the low quality aggregate was used as is without mix correction this would lead to faulty construction and if the aggregate was corrected to about 60 kg/m3 mix correction, this would lead to an economically infeasible concrete mix.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.57-60
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• 2002

The stiffness model has been proposed to predict elastic constants of twisted yarn composites. The model is based upon the unit cell structure, the coordinate transformation, and the volume averaging of compliance constants for constituent materials. For the correlation of analytic results with experiments, composite samples of various yarn twist angle were tested. The samples were fabricated by the RTM process using glass yarns and epoxy resin. The correlations of elastic constants showed relatively good agreements. The model provides the predictions of the three-dimensional engineering constants, which are valuable input data for the analytic characterization of textile composites made of twisted yarn.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.81-84
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• 2002

An approach for predicting the effective thermal conductivities of fiber-reinforce composite has been developed based on a thermal-electrical analogy. The unit cell of the composite laminate is divided into regular volume elements and the material properties have been given to each element. By constructing the series-parallel thermal resistance network, the thermal conductivities of composite both in-plane and out-of-plane direction have been predicted. Graphite/Epoxy composite is used for a balanced plain-weave composite laminate. By comparing the predicted results and the previous works, good agreement has been found.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.150-156
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• 2016

This paper compares the performances of permanent-magnet synchronous (PMS) and permanent-magnet vernier (PMV) machines for low-speed and high-torque applications. For comparison with the PMS machines, we consider two types of the PMV machine. The first one has surface-mounted permanent magnets (PMs) on the rotor and the other has PMs inserted on both sides of the stator and rotor. The PMS and PMV machines are designed to meet the condition of equal output power per unit volume. We analyze the magnetic fields of the machines using a two-dimensional finite element analysis (FEA). We then compare their performances in terms of the generated torque characteristics, power factor, loss, and efficiency.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1757-1764
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• 1997

The geometric and elastic models based on the unit cell have been proposed to predict the geometric characteristics and the engineering constants of plain and satin woven composites. In the geometric model, length and inclined angle of the yarn crimp and the fiber volume fraction of woven composites have been predicted. In the elastic model, the coordinate transformation has been utilized to transform the elastic constants of the yarn crimp to those of woven composites, and the effective elastic constants have been determined from the volume averaging of the constituent materials. Good correlations between the model predictions and the experimental results of carbon/epoxy and glass/epoxy woven composites have been observed. Based on the model, the effect of various geometric parameters and materials on the three-dimensional elastic properties of woven composites can be identified.