• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.477-477
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• 2008

For more than three decades, the gate dielectrics in CMOS devices are $SiO_2$ because of its blocking properties of current in insulated gate FET channels. As the dimensions of feature size have been scaled down (width and the thickness is reduced down to 50 urn and 2 urn or less), gate leakage current is increased and reliability of $SiO_2$ is reduced. Many metal oxides such as $TiO_2$, $Ta_2O_4$, $SrTiO_3$, $Al_2O_3$, $HfO_2$ and $ZrO_2$ have been challenged for memory devices. These materials posses relatively high dielectric constant, but $HfO_2$ and $Al_2O_3$ did not provide sufficient advantages over $SiO_2$ or $Si_3N_4$ because of reaction with Si substrate. Recently, $HfO_2$ have been attracted attention because Hf forms the most stable oxide with the highest heat of formation. In addition, Hf can reduce the native oxide layer by creating $HfO_2$. However, new gate oxide candidates must satisfy a standard CMOS process. In order to fabricate high density memories with small feature size, the plasma etch process should be developed by well understanding and optimizing plasma behaviors. Therefore, it is necessary that the etch behavior of $HfO_2$ and plasma parameters are systematically investigated as functions of process parameters including gas mixing ratio, rf power, pressure and temperature to determine the mechanism of plasma induced damage. However, there is few studies on the the etch mechanism and the surface reactions in $BCl_3$ based plasma to etch $HfO_2$ thin films. In this work, the samples of $HfO_2$ were prepared on Si wafer with using atomic layer deposition. In our previous work, the maximum etch rate of $BCl_3$/Ar were obtained 20% $BCl_3$/ 80% Ar. Over 20% $BCl_3$ addition, the etch rate of $HfO_2$ decreased. The etching rate of $HfO_2$ and selectivity of $HfO_2$ to Si were investigated with using in inductively coupled plasma etching system (ICP) and $BCl_3/Cl_2$/Ar plasma. The change of volume densities of radical and atoms were monitored with using optical emission spectroscopy analysis (OES). The variations of components of etched surfaces for $HfO_2$ was investigated with using x-ray photo electron spectroscopy (XPS). In order to investigate the accumulation of etch by products during etch process, the exposed surface of $HfO_2$ in $BCl_3/Cl_2$/Ar plasma was compared with surface of as-doped $HfO_2$ and all the surfaces of samples were examined with field emission scanning electron microscopy and atomic force microscope (AFM).

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.707-713
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• 2008

Characteristics of minimum fluidization velocity and pressure fluctuations were investigated in an annular fluidized bed whose diameter was 0.102 m and 2.0 m in height. Effects of gas velocity, particle size and bed temperature on the minimum fluidization velocity and pressure fluctuations were examined. The values of minimum fluidization velocity obtained by means of three different methods were very similar each other. The correlation dimension could be a quantitative parameter for expression the resultant complex behavior of gas and solid mixture in the annular fluidized bed. The value of correlation dimension increased with increasing gas velocity, fluidized particle size and temperature in the bed. The minimum fluidization velocity could be determined by means of correlation dimension of pressure fluctuations as well as pressure drop in the bed and standard deviation of pressure fluctuations. The minimum fluidization velocity increased with increasing particle size but decreased with increasing bed temperature in annular fluidized beds. The minimum fluidization velocity was well correlated in therms of correlation dimension as well as operating variables within experimented conditions of this study.

• Management & Information Systems Review
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• v.36 no.3
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• pp.71-87
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• 2017

This study was conducted to examine differences in the relationship between experiential variables and outcome variables of experiential variables. In this regard, this research tries to construct the items based on past researches and to suggest the problems of the items of past researches. The analysis of various aspects of experiential variables and the validation tests of some models are presented to suggest what the optimal model is and the following suggestions can be made. First, respondents may not feel that the three dimensions of sensation, emotion, and cognition are significantly different. Depending on the respondents, there is a possibility that they may not be able to perceive much of the linguistic difference. The results of this study are summarized as follows. From this point of view, this study suggest that it would be suitable to proceed with the thesis with the experience of simplifying the combination of the five experiences in some combination. Second, there is a correlation between experiential variables, and the effect on outcome variables may vary from one variable to another. And, when there are two outcome variables, assuming a model that affects only the first outcome variable among the experience variables, it is the most suitable model in relation to the performance variable of experience.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.595-608
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• 2013

This paper is proposed the computation method of moored ship motion considering harbor resonance, and estimated that the harbor resonance have an effect on moored ship motion. The computation of harbor resonance was used CGWAVE model and the computation of moored sip motion was used the Green function method expressed by three dimensions. This method was verified with the field observation data of moored ship motion, and the application of actual harbor was investigated with wave field data and down time record data in Pohang New Harbor. The resonance periods in Pohang New Harbor that obtained from wave field data were 80, 33, 23, 8 minute, which are the long waves, and 42, 54, 60 second, which are the infra-gravity waves inside harbor slip. The simulated results of harbor resonance were corresponded with the wave field data. This study was investigated on 5,000 ton, 10,000 ton and 30,000 ton ship sized in Pier 8 of Pohang New Harbor that the harbor resonance has effect on moored ship motion from simulated results of ship motion in case of included resonance and excluded resonance. In case of included resonance, the ship motion have increased by 12~400 percent when compared with results of excluded resonance. We could find that the harbor resonance have still more an effect on the surge and heave motions of a large size ship and the roll and yaw motions of a small size ship.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.307-313
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• 2010

In this study, alternative designs for the bends used in district heating pipes are investigated. The district heating pipes, which are subjected to temperatures of 10 to $120^{\circ}C$ and a water pressure of $16\;kgf/cm^2$, have to withstand thermomechanical cyclic loads when in use. These pipes comprise three concentric tubes: a steel pipe (internal), polyurethane (PUR) insulator (middle), and a high-density polyethylene (HDPE) case (external). In addition, the bends in the district heating pipe system are covered with foam pads that cause aging. In this study, an alternative bend design that does not involve the use of a foam pad is proposed to overcome the aging problem in the bends. In the proposed design, "shear rings" are added to the surface of a bend, and its dimensions are determined by a combination of the statistical (Taguchi) method and FEM. The geometrical parameters such as thickness, height, and number of the rings significantly affect the design optimization, and hence, they affect the results of the FEM.

• Bulletin of the Society of Naval Architects of Korea
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• v.8 no.1
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• pp.67-94
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• 1971

Korean fisheries industry holds 57,255 boats amounting to 269,079 tons in gross as of the end of 1967. The boats of the size under 30G.T., about sixty-two per cent of the total in tonnage, are utilized in coastal and their contribution to the total production of Korean fisheries industry is estimated at over seventy-five percent. Hull forms and construction method of them are partly in transition stage to the western tradition from the oriental tradition, which employs the chine-type straight-framed section, and tick and wide wooden planking fastened on naturally bent timber frames. And only about a half of them are mechanized. About fifty-seven per cent, 7,525 boats amounting to 91,751 gross tons, of the coastal and inshore fishing boats are those of the size ranging 5G.T. to 30G.T., which are engaged mostly in draft-and gill-netting, angling, longlining, anchovy seining, squid fishing and set-netting. The important fishing boats forming main structure of the inshore fishing fleets can be classified as 5G.T.-class multi-purpose boats, 10G.T.-class angling/longlining boats and 20G.T.-class drift-/gill-netters mostly utilized in the east-sea, 15G.T.-class anchovy seiner in the south-sea-sea, 20G.T.- and 28G.T.-class stow-netters in the west sea. Each of the three sea regions, east, south, and west, of Korean water has distinctly different characters from one another in topography, geology and sea aspects, and consequently in marine resources, fishing grounds and fishing tactics desired. Hence, the finishing boats in each sea region have also their own characters in hull form, structural features, deck design and equipments. In this report, analyzing the characteristics of the existing inshore fishing boats ranging 5G.T. to 30G.T. in size from view points of naval architecture and engineering, the author made an integrated investigation of their characteristics, covering size and principal dimensions, hull form, deck design, structural features and mechanization, in close connection with the natural circumstances of Korean water and local techno-socio-economic problems, and, finally, made some suggestions for the rational improvement or modernization of the inshore fishing boats. Further details of the characteristics of Korean inshore finishing boats are referred to the drawings of them compiled by the author and given in the reference[23] listed at the end of this report.

• Imaging Science in Dentistry
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• v.47 no.3
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• pp.165-174
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• 2017

Purpose: This study was performed to investigate the influence of object shape and distance from the center of the image on the volumetric accuracy of cone-beam computed tomography (CBCT) scans, according to different parameters of tube voltage and current. Materials and Methods: Four geometric objects(cylinder, cube, pyramid, and hexagon) with predefined dimensions were fabricated. The objects consisted of Teflon-perfluoroalkoxy embedded in a hydrocolloid matrix (Dupli-Coe-Loid TM; GC America Inc., Alsip, IL, USA), encased in an acrylic resin cylinder assembly. An Alphard Vega Dental CT system (Asahi Roentgen Ind. Co., Ltd, Kyoto, Japan) was used to acquire CBCT images. OnDemand 3D (CyberMed Inc., Seoul, Korea) software was used for object segmentation and image analysis. The accuracy was expressed by the volume error (VE). The VE was calculated under 3 different exposure settings. The measured volumes of the objects were compared to the true volumes for statistical analysis. Results: The mean VE ranged from -4.47% to 2.35%. There was no significant relationship between an object's shape and the VE. A significant correlation was found between the distance of the object to the center of the image and the VE. Tube voltage affected the volume measurements and the VE, but tube current did not. Conclusion: The evaluated CBCT device provided satisfactory volume measurements. To assess volume measurements, it might be sufficient to use serial scans with a high resolution, but a low dose. This information may provide useful guidance for assessing volume measurements.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.3
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• pp.288-299
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• 2003

Statement of problem: Many kinds of post and core systems are in the market, but there are no clear selection criteria for them. Purpose: The purpose of this study was to compare the flexural strength and modulus of elasticity of core materials, and measure the bending strength of post systems made of a variety of materials. Material and Methods: The flexural strength and elastic modulus of thirteen kinds core buildup materials were measured on beams of specimens of $2.0{\times}2.0{\times}24{\pm}0.1mm$. Ten specimens per group were fabricated and loaded on an lnstron testing machine at a crosshead speed of 0.25mm/min. A test span of 20 mm was used. The failure loads were recorded and flexural strength calculated with the measured dimensions. The elastic modulus was calculated from the slopes of the linear portions of the stress-stram graphs. Also nine kinds commercially available prefabricated posts made of various materials with similar nominal diameters, approximately 1.25mm, were loaded in a three-point bend test until plastic deformation or failure occurred. Ten posts per group were tested and the obtained data were anaylzed with analysis of variance and compared with the Tukey multiple comparison tests. Results: Clearfil Photo Core and Luxacore had flexural strengths approaching amalgam, but its modulus of elasticity was only about 15% of that of amalgam. The strengths of the glass ionomer and resin modified glass ionomer were very low. The heat pressed glass ceramic core had a high elastic modulus but a relatively low flexural strength approximating that of the lower strength composite resin core materials. The stainless steel, zirconia and carbon fiber post exhibited high bending strengths. The glass fiber posts displayed strengths that were approximately half of the higher strength posts. Conclusion: When moderate amounts of coronal tooth structure are to be replaced by a post and core on an anterior tooth, a prefabricated post and high strength, high elastic modulus core may be suitable. CLINICAL IMPLICATIONS In this study several newly introduced post and core systems demonstrated satisfactory physical properties. However when the higher stress situation exists with only a minimal ferrule extension remaining a cast post and core or zirconia post and pressed core are desirable.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.1
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• pp.125-133
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• 2010

Researches and studies which have been conducted so far on external confinement of long span concrete columns have mainly concentrated on concentric loading. But, long span bridge concrete columns over the sea are mainly subjected to concentrated axial load, and at the same time lange amount of moment by eccentric load. This paper experimentally investigates the performance of externally confined high-strength concrete columns subjected to loading mechanism and evaluates the effectiveness of two confinement materials carbon fibre and high performance glass fibre. Twelve short columns with the same dimensions were cast and tested Six columns were reinforced with hoop bars, the remaining six columns were reinforced with spiral bars and wrapped with three layers of carbon failure and high performance glass FRP sheets. Test variables considered were the shape of internal reinforcement and strengthening materials according to loading location. The experimental results showed that eccentric load could obviously lower down the maximum failure load of FRP-confined concrete columns, compared with the columns under concentric load. And compared with the carbon FRP-confined reinforced concrete columns, high performance glass FRP-confined columns displayed a higher load capacity and ductility, when tested both concentrically and eccentrically.

• Journal of the Korean Society for information Management
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• v.15 no.2
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• pp.163-191
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• 1998

The im of the present study is to introduce and develop the concept and theory of conspectus for the first time in Korea, and to propose a new evaluation model for book collection by actually applying the developed methodology to the collection of a special library dedicated to Biblical Studies. Conspectus is a standardized and objective evaluation method that classifies the main collection according to the division, category, subject, and then gives each collection ots appropriate collection level code by analyzing the classified collection in terms of three different dimensions, which are Current Collection Level(CL), Acquisition Commitment Level(AC), and Collection Goal Level(GL). To evaluate the collection of the sample library, shelflist analysis, list checking, acquisition data in ordering process by their main subject, and survey of its users have been carried out, and all of their results ahve been indicated in terms of eleven collection level codes developed by WLN Conspectus. T e collection of sample library was evaluated as '3cW' for CL, '4W' for AC, and '4W' for GL when the Conspectus methodology was applied for evaluation. This study could be utilized as an collection evaluation model for theological libraries, and become a basis to bring about more active cooperative collection development among related libraries.