• Current Optics and Photonics
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• v.3 no.6
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• pp.510-515
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• 2019

In this paper, we introduce a 1.3-㎛ 25-GHz waveguide-integrated vertical PIN type Ge-on-Si photodetector fabricated using a multi-project wafers service based on fringing field analysis in the depletion region. In general, 1.3-㎛ photodetectors fabricated using a commercial foundry service can achieve limited bandwidths because a significant amount of photo-generated carriers are located within a few microns from the input along the device length, and they are influenced by the fringing field, leading to a longer transit time. To estimate the response time, we calculate the fringing field in that region and the transit time using the drift velocity caused by the field. Finally, we compare the estimated value with the measured one. The photodetector fabricated has a bandwidth of 20.75 GHz at -1 V with an estimation error of <3 GHz and dark current and responsivity of 110 nA and 0.704 A/W, respectively.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.510-515
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• 2011

In this study, as a material used to replace silica fumes for high strength concrete, nano-silica compound with organic functional group for dispersion and with inorganic silica group that can cause a pozzolan reaction is synthesized, These nano silica compound is divided into IC, which is nano size $SiO_2$ with irregularly combined hydroxyl group and carboxyl group, and RC, which is nano size $SiO_2$ with regularly combined hydroxyl group and carboxyl group. The effects of these nano silica compound on the hydration of cement are reviewed. As a result, all of synthesized nano-silica compounds have excellent dispersion on the cement flow, we think that dispersion property is the effect of air entraining by synthesized nano-silica compounds. The result of the microstructure observation showed that the particle size of the synthesized nano-silica is smaller than silica fume and spread evenly among the cement particles. In initial The phenomenon of strength decreasing occurred due to delayed hydration reaction by the synthesized nano-silica with carboxyl(-COOH) and hydroxyl(-OH) functional group.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.7
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• pp.510-517
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• 2015

The free vibration and stability analysis of a spinning composite shaft modelled as a thin-walled closed beam is performed for several design parameters, such as ply angle, aspect ratio, and spin speed. The governing equations of spinning shafts based on the Timoshenko beam theory are derived via Hamilton's variational principle. Coriolis acceleration and anisotropy of constituent materials are incorporated in the derivation. The equations of motion are then transformed to the standard form of an eigenvalue problem for free vibration and stability analysis. Analytical results both for uniform circular cylindrical shaft and rectangular cross-section shaft are obtained by using extended Galerkin method, and the results are compared with those from FEM ANSYS analysis for a verification.

• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.510-516
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• 2007

After observing the alkali-silica reaction of the mortar that contains glass abrasive sludge, when evaluating it by a mineral or chemical point of view, it contained reactive silica $(59{\sim}67%)$ and $R_20$ elements $(4.3{\sim}9.8%)$. Also, when evaluated by the mortar bar method, an addition of 5 wt% of CRT glass abrasive sludge is judged harmless. However when adding more, there appear severe contractions, thus carefulness is needed while using. Less than 0.10% of expansion was measured when adding up to 30wt% of flat glass abrasive sludge. However, after 30 days of the measurement, more than 0.1% rate of expansion was measured when adding more than 5 wt%. Therefore, more detailed experiments are needed in case of more than 5 wt%.

• Journal of Preventive Medicine and Public Health
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• v.10 no.1
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• pp.3-15
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• 1977

In order to find out health problems among inhabitants in slum areas in Kwanak-Ku, Seoul, a series of health survey was conducted upon 510 households by interview from March to December, 1976. The results obtained were as follows: 1. Employments of householders were unstable; Out of 508 householders, 164(32.3%) were unemployed and 184 (36.2%) were daily or temporary employees. 2. Average number of households per house was 2.0 and average area of residential room per person was $4.0m^2$. 3. 476(93.3%) out of 510 households were supplied with tap water and rest of them made use of ground water as a source of drinking water. 4. Only 279(18.3%) out of 1527 live births were delivered at medical facilities, 496(32.7%) were at home attended by doctors or midwives and 358(25.1%) took prenatal care. The above findings were worse in urban slum area than in other urban area of relatively high economic level, but were better than in rural area of less medical facilities. 5. Initiation of treatment were delayed until their illnesses were advanced in most of the households, 472(92.5%) out 510. In the early stage of the illness, 131(25.6%) of the house-holds sought physicians in their clinics or general hospitals and 250 (40.9%) visited chemists, to toy drugs at first hand. Frequency of visits to physician increased to 52.8% as the disease aggravated in later stages. 6. Cost of medical expenditure per household amounted to 815 won, and was paid to, in the order of chemists, physicians, chinese herb stores, chinese herb doctors. 7. Concerning the health knowledge of the inhabitants, 273(53.9%) out of 506 respondents were aware of the infectivity of pulmonary tuberculosis, and 68(13.4%) of them checked regularly their chest findings by X-ray at least once every two years. 8. As for the family planning, although 448(87.3%) out of 510 respondents were in favor of it, 215 (41.8%) of them were actually practicing contraception. 9. About 40.6% (125 respondents) of them obtained information and knowledge concerning contraception through personal contact with family planning workers. 10. Nutritional status of housewives was generally poor: 49(38.3%) out of 128 housewives were found to be anemic and average serum protein level was $7.5{\pm}0.82g/dl$.

• Journal of the Korean Vacuum Society
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• v.6 no.2
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• pp.122-128
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• 1997

In this study, the PVDF organic thin films were fabricated by thermal evaporation deposition which is one of the dry-processing methods. The distance from heat source to substrate was 5 cm. The substrate temperature was maintained at $30 ^{\circ}C$ during deposition. The working pressure was about $2.0\times10^{-5}$Torr and the temperature of heat source was increased at the rate of 6 to $8^{\circ}C$/min. At $270^{\circ}C$, the shutter was opened and the deposition of PVDF has stared. As the electrical field intensity increased, $\alpha$ peaks such $530\textrm{cm}^{-1},795\textrm{cm}^{-1},1182\textrm{cm}^{-1}$ decreased, and $\beta$ peaks such as $510\textrm{cm}^{-1},1273\textrm{cm}^{-1}$ increased. The intensity of $530\textrm{cm}^{-1}$ peak was stronger than that of $510\textrm{cm}^{-1}$ peak velow the 71.4 kV/cm, intensity of electrical field. This result showed the characteristic of film mainly due to $\alpha$-mode. According to these results, the molecular structure of PVDF thin film is transformed from $\alpha$-mode with TGT or TG'T to $\beta$-mode with planar zigzag structure TT, as increasing of intensity of electrical field.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.6
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• pp.510-520
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• 2014

Unlike other mass production in small variety, shipbuilding process is a project-based method in single variety, which causes unpredictable volatility in the planning system. In shipyards, series of manufacturing processes from fabrication to erection is sequentially carried out. In order to predict unfavorable changes such as overload or low load of working volume, computerized simulation has been being gradually adopted. The data used in the simulation are processed from the database of the main scheduling and planning system. Thus the quality of those data is very crucial for the meaningful results. Unfortunately, research on the verification of data quality is very rare and hardly known to the authors. In this work, using the database of scheduling and product information system of a large domestic shipyard, the data required for the simulation are qualitatively analyzed and verified.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.6
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• pp.510-517
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• 2013

The ammonia-water based power generation cycle utilizing liquefied natural gas (LNG) as its heat sink has attracted much attention, since the ammonia-water cycle has many thermodynamic advantages in conversion of low-grade heat source in the form of sensible energy and LNG has a great cold energy. In this paper, we carry out thermodynamic performance analysis of a combined power generation cycle which is consisted of an ammonia-water regenerative Rankine cycle and LNG power generation cycle. LNG is able to condense the ammonia-water mixture at a very low condensing temperature in a heat exchanger, which leads to an increased power output. Based on the thermodynamic models, the effects of the key parameters such as source temperature, ammonia concentration and turbine inlet pressure on the characteristics of system are throughly investigated. The results show that the thermodynamic performance of the ammonia-water power generation cycle can be improved by the LNG cold energy and there exist an optimum ammonia concentration to reach the maximum system net work production.

• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.510-513
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• 2017

Patchouli oil extraction in general is still using conventional methods that require a long time of extraction. It is therefore necessary to develop extraction methods to obtain patchouli oil with optimum yield and quality. One of the new methods, which has been successfully developed, is microwave hydrodistillation (MHD). In addition to optimizing the extraction process of patchouli oil, this study also used microwave air-hydrodistillation (MAHD). Based on the research results, extraction using MAHD method can produce higher yield of patchouli oil when compared using MHD method. Also, based on the results of the analysis by GC-MS, extraction using MAHD method can produce quality of patchouli oil that is almost the same when compared using MHD method. This is supported by the results of the analysis by GC-MS, which showed that the content of patchouli alcohol is the main component of patchouli oil, and is almost the same for patchouli oil extracted using MHD method (26.32%) and MAHD method (25.23%).

• Journal of Environmental Health Sciences
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• v.35 no.6
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• pp.510-516
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• 2009

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) were measured in soil samples of Ansung in Kyonggi-province to investigate concentration distribution of PBDEs and PCBs. The 10 soil samples were collected using a stainless steel hand-held corer that was cleaned before and after each sample using hexane. Total concentration of PBDE and PCBs were 2,205.3 and 348.1 pg/g dry weight (DW) in soil sample, respectively. BDE-209 showed as the most abundant congener in soil samples which was related to imported amount and usage amount of deca-BDE technical mixture in Korea. Also, BDE-99, BDE-47, BDE-100 deposition in soil sample was higher than other congeners and was related to the imported and usage amount reported for penta-BDE technical mixture in Korea. Correlation coefficient between PBDE contribution and technical mixture formulation (Bromokal 70-5DE) were significant (r=0.91, p<0.01) which suggests the influence of sources in this technical mixtures.