• Applied Microscopy
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• v.25 no.3
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• pp.99-107
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• 1995

The morphological changes of primary solid particles as a function of process time on hypereutectic Al-15.5wt%Si alloy during semi-solid state processing with a shear rate of $200s^{-1}$ are studied. In this alloy, it was observed that primary Si crystals are fragmented at the early stage of stirring and morphologies of primary Si crystals change from faceted to spherical during isothermal shearing for 60 minutes. To understand the role of Al dissolved in the primary Si crystal by shear stress at high temperature, lattice parameters of the primary Si crystals are determined as a variation of high order Laue zone(HOLZ) line positions measured from convergent beam electron diffraction(CBED) pattern. The lattice parameter of the primary Si crystal in the rheocast Al-15.5wt%Si alloy shows tensile strain of about 5 times greater than that of the gravity casting. Increase of the lattice parameter by rheocasting is due to the increased amount of Al dissolved in the primary Si crystal accelerated by shear stress at high temperature. The amounts of solute Al in the primary Si crystal are measured quantitatively by EPMA method to confirm the CBED analysis.

• Polymer(Korea)
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• v.38 no.6
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• pp.735-743
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• 2014

The rheological measurement of polypropylene (PP) has been performed using a rheometer, an intrinsic viscometer, and an MI machine to predict the molecular weight and the molecular weight distribution. Also, GPC has been used for the determination of the molecular structure. The distribution broadness parameter using modified Carreau model has been used to make the correlation between the rheological parameter and the molecular structure instead of the rheological PI (polydispersity index) which is determined from the cross of modulus from the dynamic oscillatory measurement. Even though the rheological PI is useful to determine the molecular weight distribution of the PP using controlled rheology, which has narrow and uniform molecular weight distribution, but not suitable to determine the molecular weight distribution of the PP made from direct polymerization which has broad and various molecular weight distribution. However the distribution broadness parameter which determined from the index of the shear thinning of the PP melt well predicts the molecular weight distribution of PP.

• Proceedings of the Acoustical Society of Korea Conference
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• 1997.06a
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• pp.68-74
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• 1997

Ship radiated noise is an infortant parameter which dtermines Anti Submarine Warfare(ASW) countermeansure or passive Sonar detection and classification performance. Its measurement should be performed under controlled ocean acoustic environment. In data reduction of the measured data from hydrophone array, theeffect fo ambient noise, surface reflection and bottom reflection etc. should be compensated to obtain the source level of the ship radiated noise. This study describes the measurement hydrophone array design criteria based on the analysis of transimission anomaly due to the surface reflection.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.496-500
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• 1996

An air flow measurement device is proposed. The thermal characteristic of a semiconductor element is adopted as a cooling parameter of thermal convection rate. The difference between forced convection and natural convection of two Zener diodes results enough difference in temperature. Experiment at various air flow conditions shows the measuring capability of the air flow in a duct. This measuring device has some merits, such as a reliability n hard field condition, simple circuit for signal processing, small volume of the element, less air flow resistance, independance of various ai temperature. The experimental result shows that it is an exact and usefull air flow measurement device.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.645-646
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• 2006

The oscillation amplitude of a probe tip is an important parameter to determine the resolution of atomic force microscopy (AFM) techniques. In this work, we introduce a new method for the measurement of the oscillation amplitude of a quartz tuning fork tip sub-nanometer resolution.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1984.10a
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• pp.22-24
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• 1984

The mode spot size is a fundamental parameter of a single mode optical fibre which determines especially the spilces and the microbending loss. The spot-size measurement is recognised to be a useful mean to define the cut-off wavelength of single-mode fibres, ESI parameters and to predict the modal dispersion. To determine the ESI parameters, this paper is based on the use of a Ronchi ruling.

• Proceedings of the ESK Conference
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• 1996.04a
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• pp.264-269
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• 1996

Facial expression is innate communication skill of human. Human can recognize theri psychological state by facial parameters which contain surface movement, color, humidity and etc. This study is to quantify or qualify human emotion by measurement of facial electromyography (EMG) and facial movement. The measurement is taken at the facial area of frontalis and zygomaticus The results is indicative to discriminate the positive and negative respond of emotion and to extract the parameter sensitive to positive and negative facial-expression. The facial movement according to EMG shows the possibility of non-invasive technique of human emotion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.9
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• pp.1480-1490
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• 1997

A method by which the system parameter matrices can be estimated from measured time data of excitation force and acceleration has been studied. The acceleration data are integrated numerically to obtain the velocities and displacements, and the systm parameters are estimated from these data by solving equations of motion. The characteristics of the method have been investigated through its application to simulated data of 1 DOF and 2 DOF systems and experimental data measured from a simple structure. It was found that the method is very sensitive to measurement noise and the accuracy of the estimated parameters can be improved by averaging the repeatedly measured data and removing the noise. One of the main advantages of the parameter estimation method is that no a priori information about the system under test is required. The method can be easily extended to non-linear parameter estimation.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1086-1093
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• 2011

To fabricate the aluminum alloys with good drawability, the textures evolution of the AA5182 sheets due to the change of lid parameter after rolling and subsequent annealing was studied. The measurement of the deformation textures was carried out for the sheets with high reduction ratio and the change of the recrystallization texture was investigated after heat-treatments of the rolled sheets in various I/d parameters. Rolling without lubrication and subsequent annealing led to the formation of favorable rot-$C_{ND}$ {001}<110> and ${\gamma}$-fiber ND//<111> textures in AA5182 sheets. From the results, the ${\gamma}$-fiber ND//<111> component well evolved during rolling at high lid parameter of 6.77. The initial shear deformation texture, especially, ${\gamma}$-fiber ND//<111> was not rotated during heat treatment in holding time of 180~7,200 seconds on AA5182 with I/d parameter of 6.77. Therefore, the AA5182 sheets were fabricated by controlling I/d parameter having well evolved ${\gamma}$-fiber ND//<111> which was advantageous in good drawability of the sheets.

• Journal of Environmental Science International
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• v.4 no.5
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• pp.427-435
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• 1995

In order to discuss the differences among the SMP(Surface Moisture Availability Parameter), by previous researchers on the basis of their own theoretical and empirical background, we assessed the SMP according to the soil types and volumetric soil water contents. The results are as follows. There are differences among all the five SMAPs. There's a tendency that the larger grain size, the higher value of parameters. And they divided into two groups for their value: one group has parameters with exponential function and the other with cosine and linear function. The maximum difference between the two groups appears when the volumetric soil water contents are 0.07m3m-3 for sand, 0.l1m3m-3 for loam, 0.12 for clay, and 0.13m3m-3 for silt loam. So, these differences must be considered when we estimate the surface evaporation rate. From field data, the paddy field soil around Junam reservoir is classified as a silt has high wetness, 0.56. So, the parameter obtained from the field measurement is much higher than that of Clapp and Hornberger(1978)'s Table. This study treated the SMP for a certain point of time in winter season. But if we measured the soil water contents continuously, we could obtain better time-dependent parameter. Key words : SMAP(Surface Moisture Availability Parameter), Paddy field, Volumetric soil water content, Evaporation, Capillary potential.