• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1183-1189
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• 2002

In order to develope the porous alumina ceramics with high strength, the pore characteristics and compressive strength were investigated in terms of relation to the conditions of spark-plasma sintering and the contents of graphite as a pore precursor. Porous alumina bodies were successfully prepared by spark-plasma sintering and burning out graphite in air. High porous bodies were fabricated by sintering at 1000${\circ}C$ for 3 min under a pressure of 30 MPa, heating rate of 80${\circ}C$/min and on-off pulse type of 12:2. For example, alumina bodies prepared by the addition of 10∼30 vol% graphite showed high porosity of 50∼57%. Also, the open porosity increased with graphite content. The relationship between pore characteristics and graphite contents could be explained by percolation model depending on cluster number and size. Porous alumina bodies prepared by the addition of 10∼30 vol% graphite showed the high compressive strength of 55∼200 MPa. This great improvement in strength was considered to be mainly due to the spark-plasma discharges and the self-heating action between particles.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2E
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• pp.91-97
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• 1995

This paper describes the implementation of a multi-channel audio codec for HETV. This codec has the features of the 3/2-stereo plus low frequency enhancement, downward compatibility with the smaller number of channels, backward compatibility with the existing 2/0-stereo system(MPEG-1 audio), and multilingual capability. The encoder of this codec consists of 6-channel analog audio input part with the sampling rate of 48 kHz, 4-channel digital audio input part and three TMS320C40 /DSPs. The encoder implements multi-channel audio compression using a human perceptual psychoacoustic model, and has the bit rate reduction to 384 kbit/s without impairment of subjective quality. The decoder consists of 6-channel analog audio output part, 4-channel digital audio output part, and two TMS320C40 DSPs for a decoding procedure. The decoder analyzes the bit stream received with bit rate of 384 kbit/s from the encoder and reproduces the multi-channel audio signals for analog and digital outputs. The multi-processing of this audio codec using multiple DSPs is ensured by high speed transfer of date between DSPs through coordinating communication port activities with DMA coprocessors. Finally, some technical considerations are suggested to realize the problem of real-time operation, which are found out through the implementation of this codec using the MPEG-2 layer II sudio coding algorithm and the use of the hardware architecture with commercial multiple DSPs.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1115-1123
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• 2008

When constructing projects such as road embankments, bridge approaches, dikes or buildings on soft, compressible soils, significant settlements may occur due to the consolidation of these soils under the superimposed loads. The compressibility of the soil skeleton of a soft clay is influenced by such factors as structure and fabric, stress path, temperature and loading rate. Although it is possible to determine appropriate relations and the corresponding material parameters in the laboratory, it is well known that sample disturbance due to stress release, temperature change and moisture content change can have a profound effect on the compressibility of a clay. The early research of Tezaghi and Casagrande has had a lasting influence on our interpretation of consolidation data. The 24 hour, incremental load, oedometer test has become, more or less, the standard procedure for determining the one-dimensional, stress-strain behavior of clays. An important notion relates to the interpretation of the data is the ore-consolidation pressure ${\sigma}_p$, which is located approximately at the break in the slope on the curve. From a practical point of view, this pressure is usually viewed as corresponding to the maximum past effective stress supported by the soil. Researchers have shown, however, that the value of ${\sigma}_p$ depends on the test procedure. furthermore, owing to sampling disturbance, the results of the laboratory consolidation test must be corrected to better capture the in-situ compressibility characteristics. The corrections apply, strictly speaking, to soils where the relation between strain and effective stress is time independent. An important assumption in Terzaghi's one-dimensional theory of consolidation is that the soil skeleton behaves elastically. On the other hand, Buisman recognized that creep deformations in settlement analysis can be important. this has led to extensions to Terzaghi's theory by various investigators, including the applicant and coworkers. The main object of this study is to suggestion the modified compression index value to predict settlements by back calculating the $C_c$ from different numerical models, which are giving best prediction settlements for multi layers including very thick soft clay.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.13-22
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• 2010

Masonry infill walls are frequently used as interior partitions and exterior walls in low- or middle- rise RC buildings. In the design and assessment of buildings, the infill walls are usually treated as non-structural elements and they are ignored in analytical models because they are assumed to be beneficial to the structural responses. Therefore, their influences on the structural response are ignored. In the case of buildings constructed in the USA in highly seismic regions, infill walls have a lower strength and stiffness than the boundary frames or they are separated from the boundary frames. Thus, the previously mentioned assumptions may be reasonable. However, these systems are not usually employed in most other countries. Therefore, the differences in the seismic behaviors of RC buildings with/without masonry infill walls, which are ignored in structural design, need to be investigated. In this study, structural analyses were performed for a masonry infilled low-rise RC moment-resisting frame. The infill walls were modeled as equivalent diagonal struts. The seismic behaviors of the RC moment-resisting frame with/without masonry infill walls were evaluated. From the analytical results, masonry infill walls can increase the global strength and stiffness of a structure. Consequently, the interstory drift ratio will decrease but seismic forces applied to the structure will increase more than the design seismic load because the natural period of the structure decreases. Partial damage of the infill walls by the floor causes vertical irregularity of the strength and stiffness.

• Spatial Information Research
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• v.12 no.2
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• pp.165-179
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• 2004

With the spread of wireless internet, the interest in mobile applications and services is increasing. Korea Wireless Internet Standardization Forum has been establishing the standards for mobile platform and map service in the wireless internet environment. This study aims to present a paragon of mapping middleware that plays the role of broker for wireless internet map service: in particular, it focuses on the interoperability with generic map servers. In this study, we developed a method for applying current map servers to the wireless internet map service, and analyzed the request/response structure of the map servers which have different operation characteristics in order to allow our middleware to fully utilize the functionalities of the map servers. The middleware we developed is composed of .NET-based XML Web Services: it has a lightweight module for image map and a map representation module for choropleth map, symbol map, chart map, etc. This mapping middleware is a broker between mobile client and generic map server, and supports .NET clients and Java clients as well. Its component-based interoperability grants the extensibility for the wireless internet dedicated map servers of the future in addition to the current generic map servers.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.3
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• pp.49-55
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• 2017

In this study, gas turbine engine inlet duct was designed to satisfy uniform flow at aerodynamic interface plane (AIP). Haack-series was selected as nose cone profile and duct outer radius($r_o$) was designed to satisfy to match with area change rate between the nose cone and outer duct wall by the 1-D sizing. The design object of the inlet duct wall profile which has the gradual area change rate was uniform Mach number in the core flow region and minimum boundary later thickness at the both inner nose wall and outer duct wall. The flow characteristics inside the inlet duct was evaluated using CFD. The static pressure distribution at the AIP showed uniform pattern within 0.16%. Based on Mach number profile, the boundary layer thickness was 2% of channel height. Kiel temperature rake location was decided less than 100 mm in front of nose cone where the Mach number is less than 0.1 in order to maximize the temperature probe recovery rate.

• Nuclear Engineering and Technology
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• v.17 no.4
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• pp.290-301
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• 1985

600MW(e) CANDU Primary Heat Transport System (PHTS) is composed of the two “figure-of-eight” loops and is designed to operate with the 4% Reactor Outlet Header (ROH) quality at its rated power. This existence of the two compressible regions and the positive flow-qualitly-void feedbacks are the sources of the PHTS flow instability. To ensure the PHTS stability, ROH-ROH interconnect pipes are installed as passive systems. This paper describes the investigation of the PHTS flow instability at its design full power condition. Also studied are the interconnect effect and the inherent system damping effect on the system stability. The time domain stability analyses are accessed by using the ATHER/MOD-I code which is the improved version of the KAERI developed ATHER code. Under the most adverse system modelling, the “figure-of-eight” symmetric loop shows divergent flow oscillations. Under with the interconnect, the PHTS stability is remarkably enhanced so that the system becomes stable. However, even under the conservative pressurizer modelling, the PHTS shows the more convergent flow oscillations. With the interconnect and the pressurizer modelling, its stability is highly credited. Conclusively, the inherent system damping by pressurizer itself can credit the PHTS stability without the interconnect.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.601-611
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• 2016

The research, development and use of seismic isolation systems have been increasing with the gradual development of structure safety assurance methods for earthquakes. The High Damping Rubber Bearing (HDRB), one type of seismic isolation system, is a Laminated Rubber Bearing using special High Damping Rubber. However, as its damping function is slightly lower than that of the Lead Rubber Bearing, a similar seismic isolation system, its utilization has not been high. However, the HDRB has a superior damping force to the Natural Rubber Bearing, which has similar materials and shapes, and the existing Lead Rubber Bearing has a maleficence problem in that it contains lead. Thus, studies on HDRBs that do not use lead have increased. In this study, a test targeting the HDRB was done to examine its various dependence properties, such as its compressive stress, frequency and repeated loading. To evaluate the HDRB's seismic performance in response to several earthquake waves, the shaking table test was performed and the results analyzed. The test used the downscaled bridge model and the HDRB was divided into seismic and non-seismic isolation. Consequently, when the HDRB was applied, the damping effect was higher in the non-seismic case. However, its responses on weak foundations, such as in Mexico City, represented increased shapes. Thus, its seismic isolator.

• The KIPS Transactions:PartB
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• v.9B no.5
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• pp.663-672
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• 2002

In this paper, Using an automatic tracking system, behavior of an aquatic insect, Chironomus sp. (Chironomidae), was observed in semi-natural conditions in response to sub-lethal treament of a carbamate insecticide, carbofuran. The fourth instar larvae were placed in an observation cage $(6cm\times{7cm}\times{2.5cm)}$ at temperature of $18^\circ{C}$ and the light condition of 10 time (light) : 14 time (dark). The tracking system was devised to detect the instant, partial movement of the insect body. Individual movement was traced after the treatment of carbofuran (0.1ppm) for four days 2days : before treatment, 2 days : after treatment). Along with the other irregular behaviors, "ventilation activity", appearing as a shape of "compressed zig-zag", was more frequently observed after the treatment of the insecticide. The activity of the test individuals was also generally depressed after the chemical treatment. In order to detect behavioral changes of the treated specimens, wavelet analysis was implemented to characterize different movement patterns. The extracted parameters based on Discrete Wavelet Transforms (DWT) were subsequently provided to artificial neural networks to be trained to represent different patterns of the movement tracks before and after treatments of the insecticide. This combined model of wavelets and artificial neural networks was able to point out the occurrence of characteristic movement patterns, and could be an alternative tool for automatically detecting presences of toxic chemicals for water quality monitoring. quality monitoring.

• Polymer(Korea)
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• v.29 no.5
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• pp.468-474
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• 2005

PLGA and PCL copolymers initiated by carbitol as drug carriers were synthesized by ring-opening polymerization of L-lactide (LA), glycolide (GA), and $\varepsilon-caprolactone(\varepsilon-CL)$. Implantable wafers were simply fabricated by direct compression method after physical mixing of copolymers and bovine serum albumin-fluorescein isothiocyanate (BSA-FITC) as a model protein drug. The release amounts of BSA-FITC from wafers were determined by fluorescence intensity using the fluorescence spectrophotometer. Also, the release behavior of BSA-FITC on wafers was controlled by adding the additives such as collagen, small intestinal submucosa (SIS), poly(vinyl pyrrolidone) (PVP), and poly(thylene glycol) (PEG). The wafer prepared by PLGA and PCL exhibited slow release within $10\%$ for 30 days. But, those prepared by a variety of additives exhibited the controlled BSA release patterns with a dependence on the additive contents. furthermore, the wafers containing natural materials such as collagen and SIS showed more zero-order release profile than that with synthetic materials such as PVP and PEG. It was confirmed that the release of BSA from implantable wafers could be easily controlled by adding natural additives.