• Journal of Korean Home Economics Education Association
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• v.6 no.2
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• pp.133-145
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• 1994

The purposes of this study are to investigate the relationship between the Piaget’s cognitive developmental theory and the practical course subject in elementary school which have the characteristics of skillful subject and living subject, and to discriminate the suitability of contents of the practical course subject for the childrens’level of cognitive development. This work could serve the theoretical background that the practical course subject presents practical experiences which lead the development of logicomathematical thinking abilities. The results of the content analysis shows that create activities develop the logicomathematical thinking abilities such as projective geometry, topology geometry, area conservation, length & distance conservation, and volume & mass conservation. And the most contents of the practical course subject are suitable for the childrens’level of cognitive development.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.421-426
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• 2005

Optimal design of serial connected PZT driven micro compressor was investigated. Modeling equations were derived using energy equation and mass conservation equation. The results show that mass flow rate was increased as number of connected micro compresses is increased. As pressure difference between suction port and discharge port in compressor group is increased, connected compressors have much more mass flow rate than single compressor. Mass flow rate is also increased as driving frequency is increased. And optimal design scale is suggested for highest efficiency or highest mass flow rate.

• Journal of applied mathematics & informatics
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• v.16 no.1_2
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• pp.53-68
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• 2004

Numerical solutions for the viscous Cahn-Hilliard equation are considered using the Crank-Nicolson type finite difference method which conserves the mass. The corresponding stability and error analysis of the scheme are shown. The decay speeds of the solution in $H^1-norm$ are shown. We also compare the evolution of the viscous Cahn-Hilliard equation with that of the Cahn-Hilliard equation numerically and computationally, which has been given as an open question in Novick-Cohen[13].

• Journal of Conservation Science
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• v.30 no.1
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• pp.33-38
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• 2014

The adhesive material was found for joining pottery fragments from Duurlig Nars, Mongolia estimated in AD 1C. In this study, analysis of natural substance for joining fragments of pottery was performed using gas chromatograph and mass spectrometer. As a result, it was identified triterpenoid substances, such as lupeol and betulin which were known to constituents of birch bark tar. It was suggested that Mongolian used adhesives made by birch bark tar for joining pottery fragments. Therefore if organic materials of ancient objects are systematically researched, it can provide significant evidence related to the way of life of ancient people.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.63-74
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• 2001

In this study, a cycle simulation program of a Unit-Injection(UI) system was developed to estimate the injection performance of newly designed injection system. A fundamental theory of the simulation program is based on the conservation law of mass. Loss of fuel mass in the system due to leakage, compressibility effect of the liquid fuel and friction loss in the control volume was considered in the algorithm f the program. For the evaluation of the simulation program developed, the experimental result which was offered by the Technical Research Center of Doowon Precision Industry Co. was incorporated. Two main parameters; the maximum pressure in the plunger chamber and total fuel mass(kg) injected into the engine cylinder per cycle, were measured and compared with the simulation results. It was found that the maximum error rate of the simulation result to the experimental output was less than 3% in the rated rotational speed (rpm) range of the plunger cam.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.271-278
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• 2020

The investigation into a full-scale 27 m high, by 6 m wide, thermosyphon loop. The simulation model is based on a one-dimensional axially-symmetrical control volume approach, where the loop is divided into a series of discreet control volumes. The three conservation equations, namely, mass, momentum and energy, were applied to these control volumes and solved with an explicit numerical method. The flow is assumed to be quasi-static, implying that the mass-flow rate changes over time. However, at any instant in time the mass-flow rate is constant around the loop. The boussinesq approximation was invoked, and a reasonable correlation between the experimental and theoretical results was obtained. Experimental results are presented and the flow regimes of the working fluid inside the loop identified. The results indicate that a series of such thermosyphon loops can be used as a cavity cooling system and that the one-dimensional theoretical model can predict the internal temperature and mass-flow rate of the thermosyphon loop.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.396-401
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• 2006

Dynamic behaviors of the impact damper are studied experimentally and numerically. In order to investigate wide range of excitation frequencies and amplitudes, a simple but high amplifying and bias-free experimental setup is designed. Experiments focused on the harsh operation condition demonstrate Accelerated mass loading which not only deteriorates the performance of the impact damper but also involves the structural resonance which should be avoided for the stability of the system. In the previous studies, instability or deterioration of the performance was reported for the off resonance frequency region. But this paper shows that the performance deterioration and structural resonances can be predicted. Using finite element modeling and analysis, accurate system parameters were derived and used for the numerical modeling employing the conservation of the momentum. Numerical study of the transient responses using 4th-order Runge-Kutta method demonstrates general performance of the system, and shows that accelerated mass loading phenomenon is deeply related with the vibration amplitudes and the mass of the auxiliary system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.2
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• pp.109-118
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• 2013

The absence of a simple and general analytical model has been a problem in the design and analysis of desiccant-assisted air-conditioning systems. In this study, such an analytical model has been developed based on the approximate integral solution of the coupled transient ordinary differential equations for the heat and mass transfer processes in a desiccant wheel. It turned out that the initial conditions should be determined by the solution of four linear algebraic equations including the heat and mass transfer equations for the air flow as well as the energy and mass conservation equations for the desiccant bed. It is also shown that time-averaged exit air temperature and humidity relations could be given in terms of the heat and mass transfer effectiveness.

• Journal of Microbiology and Biotechnology
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• v.18 no.5
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• pp.852-858
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• 2008

An extracellular protease (Mc1) was isolated from the nematode-trapping fungus Monacrosporium cystosporium by gel filtration, anion-exchange, and hydrophobic interaction chromatographies. This protease had a molecular mass of approximately 38 kDa and displayed an optimal activity at pH 7-9 and $56^{\circ}C$ (over 30 min). Its proteolytic activity was highly sensitive to the serine protease inhibitor PMSF (phenylmethylsulfonylfluoride, 0.1 mM), indicating that it belonged to the serine-type peptidase group. The Michaelis constant ($K_m$) and $V_max$ for substrate N-Suc-Ala-Ala-Pro-Phe-pNA were $1.67{\times}10^{-4}\;M$ and 0.6071 $OD_{410}$ per 30 s, respectively. This protease could degrade a broad range of substrates including casein, gelatin, BSA (bovine serum albumin), and nematode cuticle. Moreover, the enzyme could immobilize the free-living nematode Panagrellus redivivus and the pine wood nematode Bursaphelenchus xylophilus, suggesting that it might playa role in infection against nematodes. The encoding gene of Mc1 was composed of one intron and two exons, coding for a polypeptide of 405 amino acid residues. The deduced amino acid sequence of Mcl showed 61.4-91.9% identity to serine proteases from other nematode-trapping fungi. Our results identified that Mcl possessed biochemical properties including optimal reaction condition and substrate preference that are different from previously identified serine proteases.

• 한국약용작물학회:학술대회논문집
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• 2010.10a
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• pp.151-152
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• 2010