• Journal of the Korean Ceramic Society
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• v.26 no.3
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• pp.305-314
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• 1989

Effect of pH variation in starting solution for the making of hydroxyapatite powder was studied in relation to the sinterability of the powder and their mechanical properties of the sintered hydroxyapatite ceramics. The sinterability of hydroxyapatite powder prepared at different pH was found to be improved with increase in pH value of the starting solutions. Thus the powders prepared from the higher pH solutions including 10.5, 11.0 and 11.5 could be well densified almost upto theoretical density by firing for 1 hr at 1,00$0^{\circ}C$. But the powder based on pH 10 exhibited less sinterability even being fired at much higher temperature of 1,10$0^{\circ}C$, it gave only 90-95% of theoretical density. On the other hand the powder prepared on the lowest pH value 9.5 could not be well densified and it could obtain only 78% of theoretical density even by firing at 1,30$0^{\circ}C$ for 1hr. It was found that prismatic crystals of whitlockite were always included in the sintered bodies based on the lower pH values as a minority crystalline phase together with the major crystalline phase of hydroxyapatite and its inclusion might impair the sinterability of powder. However in the case of the higher pH, the powder contained only hydroxyapatite as a crystalline phase on sintering without any minorities. The sphere shape of crystals might help effectively the densification of the bodies. The best mechanical properties could be obtained from the body of pH 11 sintered at 1,10$0^{\circ}C$, which gave 99.5% of theoretical density, 662Kg/$\textrm{mm}^2$ of vickers hardness and 1,352Kg/$\textrm{cm}^2$ of diameteral compression strength.

• Journal of Pharmaceutical Investigation
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• v.38 no.2
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• pp.99-104
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• 2008

PLGA micro/nano particles encapsulating ranitidine as a hydrophilic model drug were prepared by the double-emulsion solvent evaporation method. Surface morphology investigation by scanning electron microscope (SEM) showed that the emulsification by sonication could produce nanoparticles, whereas microparticles were prepared using high speed homogenizer. Moreover, while nanohalf-shell structure instead of spherical nanoparticle could be produced by adding poloxamer into oil phase (MC) with PLGA 504H, the addition of poloxamer didn't change particle shape in case of PLGA 502H. On the other hand, microparticle with poloxamer had more surface pores than those without poloxamer. The size and polydispersity (PDI) of particles were determined by particle size analyzer. Effective diameters of particles were in the range of $400{\sim}800\;nm$ and $1200{\sim}3300\;nm$ in case of nanoparticles and microparticles, respectively. Encapsulation efficiencies were in the range of $1.2{\sim}2.9%$. The addition of poloxamer produced the particles with higher encapsulation efficiency. In vitro release study in phosphate buffer (pH 7.4) at $37^{\circ}C$ showed common large initial burst release. However, the relative slower release profile could be observed in case of microparticles. Poloxamer addition increased the release rate, which was thought to be related to the increased surface area of particles.

• Microbiology and Biotechnology Letters
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• v.42 no.2
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• pp.114-120
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• 2014

This study evaluated the effect of the zeta potential of silica-alumina on the behavior, in terms of purity, yield, fractional precipitation time, precipitate shape, size of fractional precipitation in the increased surface area, and the fractional precipitation process, for the purification of paclitaxel. As the zeta potential value of silica-alumina increased, the yield of paclitaxel concurrently increased while the precipitation time decreased. The use of alumina with the highest value of the zeta potential (+35.41 mV) as a surface area-increasing material dramatically reduced the precipitation time by 12 h compared with the results of the control. On the other hand, the purity of paclitaxel had almost no effect on changes in the zeta potential of silica-alumina. In addition, the precipitate size was inversely correlated with the absolute value of the zeta potential.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.387-392
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• 2020

This paper proposes a flow-rate control system for industrial valves. Industrial valves are used in piping systems to control the flow rate and pressure. In general, valves used in pipelines are classified into globe valves, butterfly valves, and ball valves according to the shape. Motor, hydraulic, and pneumatic systems are used for operating valves. The flow meter should measure the flow rate when configuring the flow-rate control system. On the other hand, because the flow rate of the valve can be expressed by flow coefficient, a control scheme is proposed using the pressure deviation, which measures at the front and rear of the valve. The transfer function for the valve, according to the control input, was estimated using the signal compression method. Based on the induced transfer function, the disturbance observer was designed to improve the command following the performance of the valve stem. The performance of the proposed control method is compared with the flow-rate control result using the flow meter used.

• Korean Institute of Interior Design Journal
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• v.19 no.1
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• pp.112-120
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• 2010

Generally, Interior design understood as shapes, lines, spaces, tones, quality, and principal. And people research these with a study of formative approach. The six elements of above categories are basis of expansion for the various designs. In this study, the represented design language is extracted by the basic 6 stages and re-divided into classes. This study presented by the Kobayashi-scale image of the current trends in the assignment to examine the cultural, functional, sensory vocabulary, three elements were classified by the assignment about 2008~2009 international fair by trend and design direction for the image. If we look into the categorized format of the design, it reflects mixed culture with emotional approach and shows direction of design constantly. Especially, compared to the year 2008, the design of year 2009 has tendency as an emotional translator regarding the verbal expression. In other words, it becomes more concrete to express the design of emotions for human beings. In addition, design shows detail of its flow with outcomes of past leading trend which was re-created shape. On the other hand, undeveloped cultures such as folk, historical, and unique cultures attract design leaders as it is. This research would make good relationship between designers and customers regarding the newly started international trend of design. Hereby I research with the method to reclassify the image of vocabulary from the image scale extract. It remains as a task to resolve ambiguous, complex and neutral expression for better understanding and definite analysis method to the public.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.5939-5944
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• 2014

The foam monitor is equipment for extinguishing fires, particularly for oil tankers or cargo areas of the carrying vessel. This equipment is installed on the cargo tank deck. Generally, the projection distance is important for designing an extinguishment. On the other hand, the form monitors in current industry have been designed by trial and error rather than by numerical analysis method. Therefore, the shape design of the new form of monitor is needed. In this study, numerical analysis was performed to determine the projection distance prediction, and experiment results were used to make a comparison with the analysis results. The proposed method was applied to the modified form of a newly designed monitor in a company.

• Archives of Plastic Surgery
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• v.34 no.1
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• pp.64-69
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• 2007

Purpose: The key of treatment in syndactyly is to separate the fused digits safely, and to create a normal web space with enough cutaneous coverage. Despite many techniques have described the correction of syndactyly, skin graft still remains the annoying one. We designed the pentagonal flap from hand dorsum to reconstruct the web space reliably and try to minimize the need for skin graft. Methods: Between July 2003 and August 2005, six cases of syndactyly were corrected at UCLA Medical Center and Hallym University Sacred Heart Hospital using dorsal pentagonal flap for web space reconstruction and straight incisions for the sides of digits to minimize the need for skin graft. The proximal edge of the pentagonal flap was designed in V shape to allow for easy closure of the donor site after advancement. The pentagonal flap was advanced volarly with the underlying dermofat tissues to form a digital web. In some cases, skin defects were unavoidable and covered with full thickness skin graft from the inguinal area. Results: Syndactyly were seen in 4 cases of Apert syndrome, 1 postburn scar webbing with PIP joint contracture and 1 recurrence after the incomplete reconstruction. In all Apert syndrome, straight line incision was used along the sides of the fingers and skin graft was needed. But, in 2 cases of incomplete type, we could save the need for skin graft only for the correction of syndactyly. We could get a good looking web space without any complications such as flap or graft loss. Conclusion: As a modification of Sherif's V-Y dorsal metacarpal flap, we believe pentagonal flap could be one of the easiest and safest way to reconstruct the web space of syndactyly in functional and cosmetic standpoint.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1073-1080
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• 2012

Incremental forming is a cold working process in which a small part of the material is being deformed and the area of local deformation is moving over the entire material. In this paper, we study description schemes to perform finite element analysis for the incremental forming. The selected description schemes to examine are the Lagrangian description and the arbitrary Lagrangian-Eulerian (ALE) description. The sliding boundary scheme coupled with ALE is also examined to overcome the distortion problems of elements on the contact surface. Results show that the ALE description with the sliding boundary scheme is most favorable in overcoming the distortion of elements. This description leads to make the simulation continued to the final stage of the incremental forming. On the other hand, the Lagrangian description as well as the original ALE description makes the elements much distorted and the analysis is stopped long before arriving at the final shape of deformation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.227-237
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• 2002

A numerical technique for simulating the aggregation of charged particles was presented with a Brownian dynamic simulation in the free molecular regime. The Langevin equation was used for tracking each particle making up an aggregate. A periodic boundary condition was used for calculation of the aggregation process in each cell with 500 primary particles of 16 nm in diameter. We considered the thermal force and the electrostatic force for the calculation of the particle motion. The electrostatic force on a particle in the simulation cell was considered as a sum of electrostatic forces from other particles in the original cell and its replicate cells. We assumed that the electric charges accumulated on an aggregate were located on its center of mass, and aggregates were only charged with pre-charged primary particles. The morphological shape of aggregates was described in terms of the fractal dimension. In the simulation, the fractal dimension for the uncharged aggregate was D$\_$f/ = 1.761. The fractal dimension changed slightly for the various amounts of bipolar charge. However, in case of unipolar charge, the fractal dimension decreased from 1.641 to 1.537 with the increase of the average number of charges on the particles from 0.2 to 0.3 in initial states. In the bipolar charge state, the average sizes of aggregates were larger than that of the uncharged state in the early and middle stages of aggregation process, but were almost the same as the case of the uncharged state in the final stage. On the other hand, in the unipolar charge state, the average size of aggregates and the dispersion of particle volume decreased with the increasing of the charge quantities.

• Journal of the Korean Society for Library and Information Science
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• v.49 no.4
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• pp.99-124
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• 2015

As the improvement of digital technologies increases the use of images from various fields, the domain of image retrieval has evolved and become a growing topic of research in the Library and Information Science field. The purpose of this study is to identify the knowledge structure of the image retrieval domain by using the author co-citation analysis and author bibliographic coupling as analytical tools in order to understand the domain's past and present. The data set for this study is 245 articles with 8,031 cited articles in the field of image retrieval from 1998 to 2013, from the Web of Science citation database. According to the results of author co-citation analysis for the past of the image retrieval domain, our findings demonstrate that the intellectual structure of image retrieval in the LIS field consists of predominantly user-oriented approaches, but also includes some areas influenced by the CBIR area. More specifically, the user-oriented approach contains six specific areas which include image needs, information seeking, image needs and search behavior, image indexing and access, indexing of image collection, and web image search. On the other hand, for CBIR approaches, it contains feature-based image indexing, shape-based indexing, and IR & CBIR. The recent trends of image retrieval based on the results from author bibliographic coupling analysis show that the domain is expanding to emerging areas of medical images, multimedia, ontology- and tag-based indexing which thus reflects a new paradigm of information environment.