• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.7
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• pp.515-522
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• 2018

An orthogonal frequency division multiplexing with coded direct index modulation(OFDM-CDIM) system that can achieve higher performance and spectral efficiency than previous OFDM systems is proposed. Previous OFDM with index modulation(IM) and OFDM-IM using dual modes systems allocate additional data to indices of respective subcarriers through combining operation with high complexity and then transmit them. However, the proposed system directly allocates the mode selection information to each subcarrier without performing additional operations. Then, the system selects and transmits one symbol in the selected mode. Furthermore, only the data allocated to the index of the subcarrier is encoded, and a good performance improvement effect is obtained with a high code rate. Simulation results show quantitatively that an OFDM-CDIM system using four modes improves bit error rate performance and transmission efficiency in additive white Gaussian noise and Rayleigh fading channel environments compared with a conventional OFDM system using 4-ary quadrature amplitude modulation.

• Asian Journal of Atmospheric Environment
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• v.4 no.3
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• pp.141-149
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• 2010

Aerosol size and number concentration were observed in the atmospheric boundary layer over Beijing (from near the ground to 1,200 m) on March 15 (a clear day) and 16 (a dusty day), 2005. The results were further compared with lidar measurements in order to understand the dependency of extinction on the particle size distribution and their vertical changes. The boundary layer atmosphere was composed of several sub-layers, and a dry air layer appeared between 400 and 1,000 m under the influence of dust event. In this dry air layer, the concentration of the fine-mode particles (diameter smaller than $1.0\;{\mu}m$) was slightly lower than the value on the clear day, while the concentration of coarse-mode particles (diameter larger than $1.0\;{\mu}m$) was remarkably higher than that on the clear day. This situation was attributed to the inflow of an air mass containing large amounts of Asian dust particles and a smaller amount of fine-mode particles. The results strongly suggest that the fine-mode particles affect light extinction even in the dusty atmosphere. However, quantitatively the relation between extinction and particle concentration is not satisfied under the dusty atmospheric conditions since laser beam attenuates in the atmosphere with high concentration of particles. Laser beam attenuation effect becomes larger in the relation between extinction and coarse particle content comparing the relation between extinction and fine particle content. To clarify this problem technically, future in situ measurements such as balloon-borne lidar are suggested. Here extinction was measured at 532 nm wavelength. Measurements of extinction at other wavelengths are desired in the future.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.5
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• pp.58-64
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• 2008

A 6Gbps 1:2 demultiplexer(DEMUX) IC using $0.18{\mu}m$ CMOS was designed and fabricated. For high speed performance current mode logic(CML) flipflop was used and inductive peaking technology was used so as to obtain higher speed than conventional Current mode logic flipflop. On-chip spiral inductor was designed to maximize the inductive peaking effect using stack structure. Total twelve inductors of $100{\mu}m^2$ area increase was used. The measurement was processed on wafer and 1:2 demultiplexer with and without micro stacked spiral inductors were compared. For 6Gbps data rate measurement, eye width was improved 7.27% and Jitter was improved 43% respectively. Power consumption was 76.8mW and eye height was 180mV at 6 Gbps

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.631-638
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• 2015

In this study, semiquantitative failure mode, effects, and criticality analysis (FMECA) for the reliability analysis of a solid rocket propulsion system is performed. The semiquantitative FMECA is composed of failure mode and effects analysis (FMEA) and criticality analysis (CA). To perform FMECA, the structure of the solid rocket propulsion system is divided into 43 parts down to the component level, and FMEA is conducted at the design stage considering 137 potential failure modes. CA is then conducted for each failure mode, during which the criticality number is estimated using the failure rate databases. The results demonstrate the relationship between potential failure modes, causes, and effects, and their risk priorities are evaluated qualitatively. Additionally, several failure modes with higher criticality and severity values are selected for high-priority improvement.

• Journal of Biosystems Engineering
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• v.12 no.4
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• pp.9-15
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• 1987

The vibrational characteristics of a radial-ply (155SR13 4PR) and a biased-ply tire (6.15-134PR) were investigated for examining the effects of tires with different structure on the ride characteristics of the vehicle. The natural frequencies at the tread band, mode shapes, and damping factors of two tires at the state of plane vibration were determined experimentally. The test work was performed at four levels of the inflation pressure, ranging from 171.7 kPa to 245.2 kPa, and three levels of the vertical load, deviating by 10% from the standard load designated by the Department of Transportation of the United States of America. The following results were drawn by the analysis of the test results: 1. The first-order natural frequencies of the radial-ply and the biased-ply tires at the tread band were 112 Hz and 159 Hz, respectively, at the state o f the free vibration when the inflation pressure of 196.2 kPa was applied. It was known that the biased-ply tire has higher resonant frequency than the radial-ply tire and the natural frequencies of the both tires move to the high frequency range as t he inflation pressure is increased. 2. The vibration modes of both tires were quite different. No big difference in mode shapes was examined as the inflation pressure was increased. But the natural frequencies of two tires were changed. For the radial-ply tire, no difference in mode shape was found whether the vertical load was applied or not. But a significant difference in mode shape was examined for the biased-ply tire. 3. Any difference was not found in damping factor as the different inflation pressures were applied. 4. When no vertical load was applied, damping factors of the radial-ply and biased-ply tire at the state of the natural vibration ranged from 2.6 to 5.9%, and from 4.1 to 7.8%, respectively. It was estimated that the radial-ply tire would have better cushioning than the biased-ply tire since the vertical spring rate of the radial-ply tire was much less than that of the biased-ply tire, even though the damping effect of the radial-ply tire was smaller than that of the biased-ply tire.

• Journal of Adhesion and Interface
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• v.6 no.4
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• pp.1-6
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• 2005

In this work, the effect of chemical treatments on surface properties of SiC was investigated in crack resistance properties of SiC/epoxy composites. The surface properties of SiC were determined by acid/base values and FT-IR measurements. Also the crack resistance properties of the composites were studied in critical strain energy release rate mode II ($G_{IIC}$) measurements. As a result, the acidically treated SiC had higher acid value than that of untreated SiC or basically treated SiC. The crack resistance properties of the composites had been improved in the specimens treated by acidic solution. These results were could be attributed to the acide-base intermolecular interaction between SiC and epoxy resin, resulting in increase of the degree of adhesion at interfaces.

• The KIPS Transactions:PartC
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• v.16C no.1
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• pp.57-64
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• 2009

In order to efficiently provide IP based Wireless Broadband services in Mobile WiMAX, schemes for more efficiently utilizing a limited bandwidth in radio links are needed. Robust Header Compression (ROHC), a standard header compression scheme proposed by IETF, Bi-directional Optimistic (O) mode provides higher compression efficiency and robustness compared with Payload Header Suppression (PHS) which is an optional header compression scheme for mobile WiMAX [1, 2]. However, if consecutive packet losses occur because of a Shadow Region of Mobile WiMAX or bit errors, header decompression failure rate of the ROHC O mode increases due to inconsistency of the compression information between the Compressor and the Decompressor. Therefore, a complementary mechanism is needed. In this paper, we propose an approach for the dynamic adjustment of an optimistic parameter, which has an effect on both the compression efficiency and the robustness, for improving the performance of ROHC O mode. We also analyze the performance of the proposed approach using an OPNET simulator.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.167-174
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• 2004

Statement of problem: Removable partial denture and complete denture often require denture base relines to improve the fit against the tissue-bearing mucosa because of gradual changes in edentulous ridge contours and resorption of underlying bone structure. Purpose: This study was performed to investigate the effect of surface design on bond strength of relining denture base resins to denture base acrylic resin. Materials and method: Heat curing resin(Lucitone 199, Dentsply U.S.A. and Vertex, Dentimex, Holland), self curing resin(Tokuso rebase, Tokuyama, Japan), and visible light curing resin(Triad, Dentsply, U.S.A.) were used in this study. The surface designs were classified as butt, bevel and rabbet joint and the bond strengths were measured by Universial Testing Machine (Zwick 2020, Zwick Co., Germany). Results and Conclusion: The obtained results from this study were as follows ; 1. The bond strength of Vertex resin was higher than those of Tokuso rebase and Triad. 2. The bond strength of rabbet and bevel joint was higher than that of butt joint. 3. The failure mode of Triad and Tokuso rebase was mainly adhesive, but cohesive failure was shown mainly in vertex.

• Journal of Plant Biology
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• v.9 no.1_2
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• pp.17-21
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• 1966

The mutual relationships of boron, Ca and sucrose were studied in relation to in vitro pollen growth and pollen bursting, by using conventient pollen from Crinum asiaticum for experiment. Crinum pollen are paticularly sensitive to Ca. Addition of very small amount of boron to cultural media was apparently synergistic to the action of sucrose and Ca in pollen germination and tube elongation. This action was extended to a higher level of boron concentraton. Combined application of boron, Ca and sucrose always gave the better results in pollen growth and protection against pollen bursting much more than when used singly. This indicated that there is a direct relationship between better growth of pollen and increased rigidity of pollen cell wall. A higher level of Ca concentration tended to increase bursting rate of pollen grains and decrease that of pollen tubes, while boron always depressed the rate of bursting. This was considered due to increased failure in pollen germination at high level of Ca that favors pollen tube elongation. The fact that Ca show an antagonistic effect on the suppressive action of high level of boron in pollen growth and shows different effect in response to pollen bursting from boron, suggested mode of Ca and boron action in the presence of sucrose is quiate different, although to increase in rigidity of pollen cell wall by them is in common nature. It was postulated therefore that Ca acts on pectins of pollen cell wall largely as "non-metabolic" and boron as "metabolic" promoter is pollen growth and protecting pollen bursting, since boron and Ca have common nature in strengthening the pollen cell wall but act differently.but act differently.

• Korean Journal of Breeding Science
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• v.40 no.3
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• pp.228-233
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• 2008

This study was carried out to get the genetic information on the germination rate and fat acidity after 12 weeks' storage at $35^{\circ}C$. Germination rate decreased with longer storage period, while fat acidity increased. Germination rate was higher in the order of Koshihikari, Hanmaeum and Unkwangbyeo after 12 weeks' storage at $35^{\circ}C$. Fat acidity of Koshihikari and Hanmaeum was gradually increased, but that of Unkwangbyeo was dramatically increased after 4 weeks' storage at $35^{\circ}C$. The genetic mode on germination rate and fat acidity using the joint scaling test was shown to be additive-dominance gene effects. Additive([d]) effect was higher than dominance effect([h]) in all crosses. The average degree of dominance, [h]/[d], was less than 1, indicating that germination rate and fat acidity was partially dominant. Germination rate and fat acidity based on frequency distribution of 2 crosses were quantitative characters expressed by polygenes.