• Journal of Magnetics
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• v.16 no.4
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• pp.368-373
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• 2011

Particle size distributions in 10 nm magnetite ferrofluids are analyzed based on both dc and ac magnetic measurements. Modified log-normal distributions are used for fitting the experimental results, which allows for a proper account of the narrow distributions. The calculated average particle sizes are in good agreement with the TEM results. However the ac method gives a much narrower distribution width than that of the dc magnetization curve fit. The proposed measurements combined with the analysis methods are useful for the characterization of ferrofluids being considered for biomedical applications.

• Journal of Korean Institute of Industrial Engineers
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• v.16 no.1
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• pp.115-122
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• 1990

Kanban, a pull system for inventory control is in direct contrast to conventional push systems. In the pull system, the kind and quantity of items needed by the succeeding stage are withdrawn from the preceding stage, only at the rate and at the time they are consumed. In this paper, lot size models are formulated in two special cases of practical interests and simple solution procedures are adapted to minimize the total cost of the kanban system. An numerical example is solved to illustrate the method.

• Analytical Science and Technology
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• v.28 no.1
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• pp.33-39
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• 2015

CdS-QD particles are a nano-sized semiconducting crystal that emits light. Their optical properties show great potential in many areas of applications such as disease-diagnostic reagents, optical technologies, media industries and solar cells. The wavelength of emitting light depends on the particle size and thus the quality control of CdS-QD particle requires accurate determination of the size distribution. In this study, CdS-QD particles were synthesized by a simple ${\gamma}$-ray irradiation method. As a particle stabilizer polyvinyl pyrrolidone (PVP) were added. In order to determine the size and size distribution of the CdS-QD particles, sedimentation field-flow fractionation (SdFFF) was employed. Effects of carious parameters including the the flow rate, external field strength, and field programming conditions were investigated to optimize SdFFF for analysis of CdS-QD particles. The Transmission electron microscopy (TEM) analysis show the primary single particle size was ~4 nm, TEM images indicate that the primarty particles were aggregated to form secondary particles having the mean size of about 159 nm. As the concentration of the stabilizer increases, the particle size tends to decrease. Mean size determined by SdFFF, TEM, and dynamic light scattering (DLS) were 126, 159, and 152 nm, respectively. Results showed SdFFF may become a useful tool for determination of the size and its distribution of various types of inorganic particles.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12B
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• pp.2438-2446
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• 1999

Most of block based stereo pair compression schemes utilize the constant block size and searching area size for all the stereo pairs to find the best matching block. However, it is not efficient to use the same block size and size of searching area to all the stereo pairs, since each stereo pair has different disparity. In this Paper, we propose a method to calculate the total disparity of stereo pairs, and show how to determine the size of the block and searching area which are applied for the block based compression of the stereo pairs.

• Communications for Statistical Applications and Methods
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• v.16 no.4
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• pp.669-673
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• 2009

When a social scientist prepares to conduct a survey, he/she faces the problem of deciding an appropriate sample size. Sample size is closely connected with cost, time, and the precision of the sample estimate. It is thus important to choose a size appropriate for the survey, but this may be difficult for survey researchers not skilled in a sampling theory. In this study we propose a method to determine a sample size under certain assumptions when the quantity of interest is measured by a Likert scale.

• Structural Engineering and Mechanics
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• v.54 no.6
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• pp.1201-1216
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• 2015

This paper presents the details of size independent fracture energy and bi-linear tension softening relation for nano modified high strength concrete. Nano silica in powder form has been used as partial replacement of cement by 2 wt%. Two popular methods, namely, simplified boundary effect method of Karihaloo et al. (2003) and RILEM (1985) fracture energy with P-${\delta}$ tail correction have been employed for estimation of size independent fracture energy for nano modified high strength concrete (compressive strength ranges from 55 MPa to 72 MPa). It is found that both the methods gave nearly same values, which is an additional evidence that either of them can be employed for determination of size independent fracture energy. Bi-linear tension softening relation corresponding to their size independent fracture energy has been constructed in an inverse manner based on the concept of non-linear hinge from the load-crack mouth opening plots of notched three-point bend beams.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.549-552
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• 2007

Inventory management is an important factor for cost saving in a construction project. stock yard of general public residence site is secured. but site of the downtown area is not. inventory management of site was performed an intuition and an experience. According to inventory management of site is necessary systematic and efficient. This study examine general idea stock and inventory management. and suggests a EOQ determination method considering stock yard size. and particularity of site.

• Journal of Powder Materials
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• v.23 no.6
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• pp.409-413
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• 2016

Electrical wire explosion in liquid media is a promising method for producing metallic nanopowders. It is possible to obtain high-purity metallic nanoparticles and uniform-sized nanopowder with excellent dispersion stability using this electrical wire explosion method. In this study, Ni-Fe alloy nanopowders with core-shell structures are fabricated via the electrical explosion of Ni-Fe alloy wires 0.1 mm in diameter and 20 mm in length in de-ionized water. The size and shape of the powders are investigated by field-emission scanning electron microscopy, transmission electron microscopy, and laser particle size analysis. Phase analysis and grain size determination are conducted by X-ray diffraction. The result indicate that a core-shell structured Ni-Fe nanopowder is synthesized with an average particle size of approximately 28 nm, and nanosized Ni core particles are encapsulated by an Fe nanolayer.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.403-407
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• 2022

Grain size of material is important factor in evaluating mechanical properties. Methods for grain size determination are described in ASTM grain size standards. However, conventional method require pretreatment of the surface to clarify grain boundaries. In this study, the grain size from the surface image obtained from scanning electron microscope was measured using the watershed algorithm, which is a region-based method among image segmentation techniques. The shapes of the crystals are similar to each other, but the size and growth height are different. In addition, crystal grains are adjacent to each other, so it is very similar to the shape image of the topography. Therefore, grain boundaries can be efficiently detected using the Watershed algorithm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.1 s.173
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• pp.52-61
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• 2000

The role of quantitative nondestructive evaluation of defects is becoming more important to assure the reliability and the safety of structure, which can eventually be used for residual life evaluation of structure on the basis of fracture mechanics approach. Although ultrasonic technique is one of the most widely used techniques for application of practical field test among the various nondestructive evaluation technique, there are still some problems to be solved in effective extraction and classification of ultrasonic signal from their noisy ultrasonic waveforms. Therefore, crack size determination through a neural network based on the back-propagation algorithm using back-scattered ultrasonic signals is established in this study. For this purpose, aluminum plate containing vertical or inclined surface breaking crack with different crack length was used to receive the back-scattered ultrasonic signals by pulse echo method. Some features extracted from these signals and sizes of cracks were used to train neural network and the neural network's output of the crack size are compared with the true answer.