• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.47-52
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• 2000

Recently, it is very necessary the development of the manufacturing techniques for high strength concrete(HSC) for the large-scale size and good quality of civil structure. But, the manufacture and quality control of HSC of which shrinkage, heat of hydration and workability at construction filed are considered, is very difficult due to its low water-cement ratio and high quantity of unit cement content. In the present study, we tried to know and assess the influences of chemical and physical properties of cement on the material properties of HSC. We analyzed basic properties of 4 kinds of cement whose chemical and physical properties are different each other through various tests such as chemical analysis and mortal test. Also, we performed the assessment of the material properties of HSC for each dement by the test for the conditions of same mix design and similar compressive strength. From the results in the study, the assessment of the important quality factors of cement influencing the properties of HSC may be utilized to quality control of applied cement to manufacture the HSC of high quality.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.132-137
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• 2001

Miniaturized specimen technology is useful to characterize the mechanical behavior using a minimum volume of material, because it is almost impossible to sample the conventional specimen for the fracture toughness test without damage to equipment. Test material was 1Cr-1Mo-0.25V steel which was widely used for turbine rotor material. Two kinds of miniaturized impact specimens were prepared, i.e., miniaturized specimen with side groove and without side groove. The correlation between ductile brittle transition temperature(DBTT) of full size impact specimen and that of miniaturized impact specimen was made. The characteristics of miniaturized impact specimens technique as well as fracture stress were discussed. Finally, we concluded that the characteristics of fracture stress change on aging time were similar to that of DBTT.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.186-191
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• 2001

A crack with electrically impermeable surfaces in an electrostrictive material subjected to uniform electric loading is analysed. The effect of electric yielding on stress intensity factor is investigated by using a small scale yielding model and a strip yield zone model. Complete forms of electric fields and elastic fields are derived by using complex function theory. The electrical yield zone shapes for two models are different each other. The two models, however, predict similar yield zone sizes under the small scale yielding conditions. It is found that the influence of electric yielding on the stress intensity factor is insensitive to the modeling of the electrical yield zone shape.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.121-125
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• 2003

Time-resolved photoluminescence from InGaN/GaN multi-quantum well structures was investigated for two different shapes of square- and trapezoidal wells grown by metal-organic chemical vapor deposition. To compare to the conventional square well structure with a radiative recombination lifetime of 0.170 nsec, the large value of lifetime of 0.540 nsec from trapezoidal well were found at room temperature. This value is similar to the value for GaN host material indicating no confinement effect of quantum well. Furthermore, the high resolution transmission electron microscopy image provides the In clustering effect in the trapezoidal well structure.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.30 no.2
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• pp.8-14
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• 2007

The powder blasting process has become an important machining technique for the cost effective fabrication of micro devices. This process is similar to sand blasting, and effectively removes hard and brittle materials. A large number of investigations on the abrasive jet machining with such output parameters as material removal rate, penetration and surface roughness have been carried out and reported by various authors. To achieve higher surface roughness, to increase material removal rate and to identify the influence of blasting parameters on the output parameters, we use the taguchi method which is one of the design methods of experiments. We can select process parameters to optimize the blasting process of glass. Experimental results indicate that the taguchi method is useful as a robust design methodology for the powder blasting process.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.8
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• pp.730-738
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• 2001

This work discusses the pressure droop, heat and mass transfer of the finned-tube heat exchangers having 7 mm tubes and offset strips in dehumidifying applications. It focuses on the fin material saving and the reduction of pressure drop. The experiment was conducted using three times scaled-up models to simulate the performance of the prototype. Eight kinds of fins having different strips and S shape edges were tested. the area density of the strip was a major factor and its shape and the location were secondary factors on the pressure drop, the heat and mass transfer. The reduced-area fin can almost equal the non-reduced fin in the aspect of heat and mass transfer. The strip fins proposed in the present work can considerably reduce both the pressure drop and the fin material for similar thermal load.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.1
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• pp.84-91
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• 2017

This paper is proposed to select the optimal finite element type in finite element analysis. Based on the NUREG reports, static analyses were performed using a commercial analysis program, $ABAQUS^{TM}$. In this study, we used a nonlinear kinematic hardening model proposed by Chaboche. The analysis result of solid elements by inputting the same material constants was different from the results of the NUREG report. This is resulted from the difference between shell element and solid element. Therefore, the material constants that have similar result to the experimental result were determined and compared according to element type. In case of using solid element for efficient finite element analysis, we confirmed that the use of C3D8I element type(incompatible mode 8-node linear brick element) leads the accurate result while reducing the analysis time.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.33-34
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• 2018

As a result of measuring the compressive strength and semi-adiabatic temperature rise of the mixed mortar, it was confirmed that the mortar mixed with the hydration heat reducing material is effective. On the other hand, the compressive strength showed similar strength to that of moderate heat Portland cement until the age 7 days, but after that, the tendency of the strength development to be delayed was confirmed.

• Geomechanics and Engineering
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• v.9 no.5
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• pp.631-644
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• 2015

This article considers the problems of cylindrical bending of functionally graded plates in which material properties vary through the thickness. The variation of the material properties follows two power-law distributions in terms of the volume fractions of constituents. In addition, this paper considers orthotropic materials rather than isotropic materials. The traction-free condition on the top surface is replaced with the condition of uniform load applied on the top surface. Numerical results are presented to show the effect of the material distribution on the deflections and stresses. Results show that, all other parameters remaining the same, the studied quantities (stress, deflection) of P-FGM and E-FGM plates are always proportional to those of homogeneous isotropic plates. Therefore, one can predict the behaviour of P-FGM and E-FGM plates knowing that of similar homogeneous plates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.418-421
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• 2001

The ceramic filters were developed using technology similar to that of quartz crystal and electro- mechanical filter. However, the key to this development involved the theoretical analysis of vibration modes and material improvements of piezoelectric ceramics. The primary application of ceramic filters has been for consumer-market use. Accordingly, a major emphasis has involved mass production technology, leading to low-priced devices. A typical ceramic filter includes monolithic resonators and capacitors packaged in unique configurations. Nakazawa developed a double-mode resonator as two acoustically coupled single resonators. And he developed 10.7MHz crystal filters using multi-energy trapping mode of thickness shear vibration. He succeeded in realizing a two-pole band pass filter response without external inductance by splitting a dot electrode to creak coupled symmetric and anti- symmetric vibration modes. Accordingly, the simulation for ceramic (inter were important. So that, this paper were investigated the pass frequency of filter on the electrode length and thickness of ceramic.