• Resources Recycling
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• v.24 no.2
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• pp.3-12
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• 2015

We researched characteristics of heat recovery rate and fouling according to structures and materials in heat exchangers like water preheater and air preheater. Economizer and air preheater have used in thermal electric power plant. we made small incinerator and heat exchangers to carry out simulated experiment. We observed fouling formation and change of heat recovery rate, combusting powdered coal for 24 hr. In economizer, fin tube type had the largest amount of fouling formation, followed by tube line type > pipe type > auto washing type according to structures. As heat recovery rate, fin tube showed highest recovery rate, followed by auto washing type > pipe type > tube line type. In air preheater, fin tube type had the largest amount of fouling formation, followed by fin plate type > pipe type > pipe type coated by teflon > pipe type coated by ceramic according to structures. And then, heat recovery rate showed the same oder.

• Geophysics and Geophysical Exploration
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• v.5 no.2
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• pp.118-125
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• 2002

The hydrogeologic structure in the Chojung area was evaluated from a set of geological and geophysical investigations: detailed geological survey, vertical electric sounding (VES), borehole logging, and controlled-source magnetotelluric (CSMT) survey. Among these, CSMT soundings were taken for integrated interpretation to extend hydrogeologic structure with depth. The result of CSMT survey along with VES and borehole logging provides the vertical geologic boundary connected with hydrogeologic structure, and also indicates the depth of aquifer in granite basement. To interpret the geologic boundary and aquifer characteristics using CSMT data, we adopted the technique of 1-D inversion with smoothness-constrained method and 2-D continuous profiling with 1-D Bostick inversion and spatial filtering. The methodology tested and adopted in this study would be useful and required for providing a more information to the structure of fractured aquifer system.

• Journal of Environmental Health Sciences
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• v.3 no.1
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• pp.27-44
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• 1976

This study was carried out to evaluate the harmful factors in working environments and to investigate the labor productivity after improvement of environments, surveying 93 industrial establishments of 10 industries located in Youngdeungpo industrial area in Seoul. The results obtained were as follows: 1) The highest noise level of 125dB(A) was indicated at the rolling process of transport equipment manufacturing industry. 2) The best illumination level was shown in precise machinery industry and the worst was indicated in rubber products, metallic products and transport equipment manufacturing industries. 3) Thermal conditions were above threshold limit value (TLV) at more than two processes of all industries except printing industry. 4) The highest dust concentration was determined in textile and wearing manufacturing industry. 5) Organic solvents were detected at 52 processes in 93 industrial establishments and 33 processes of them showed higher than TLV. The results about harmful chemicals were as follows: a) sulfur dioxide ($SO_2$)was determined higher than TLV on welding process of metallic product manufacturing industry and heat treatment process of transport equipment manufacturing industry. b) Carbon monoxide (CO) concentration was 700ppm at heat treatment process of transport equipment manufacturing industry, indicating 14 times of TLV. c) vinylchloride concentration in the air of PVC raw material mixing process and PVC preparation process of chemical product manufacturing industry was determined higher than TLV. d) Hydrochloride (HCl) concentration in the air of wire expanding process of transport equipment manufacturing industry was determined higher than TLV. 7) Higher values of lead concentration than TLV were determined at lead welding metallic product manufacturing industry and type planting process of process of printing industry, $1.8mg/m^3$ and $0.3mg/m^3$ respectively. 9) 22, 968 of 52, 855 workers (i.e. 43.5%) in 93 industries were exposed to various harmful agents. 10) It was found that the improvement of illumination in electric apparatus manufacturing industry (from 20~40 lux to 420 lux) resulted in an increase in productivity of 6.5% per capita and a decrease in faulty products of 19%. 11) Improvement of environments using local exhaust ventilation system resulted in a decrease of harmful substances lower than TLV and an increase in productivity of 11.4%. 12) Improvement of shovelling tools based on ergonomics resulted in a reduction in energy expenditure of 25.3% and an increase in productivity of 32.2% per capita.

• Journal of Sensor Science and Technology
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• v.24 no.6
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• pp.404-411
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• 2015

A stoichiometric mixture of evaporating materials for $BaAl_2Se_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $BaAl_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were $610^{\circ}C$ and $410^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $BaAl_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $8.29{\times}10^{-16}cm^{-3}$ and $278cm^2/vs$ at 293 K, respectively. The temperature dependence of the energy band gap of the $BaAl_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=3.4205eV-(4.3112{\times}10^{-4}eV/K)T^2/(T+232 K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $BaAl_2Se_4$ have been estimated to be 249.4 meV and 263.4 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $BaAl_2Se_4/GaAs$ epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $A_1$-, $B_1$-exciton for n =1 and $C_{31}$-exciton peaks for n=31.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.942-945
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• 2010

The development of decentralized power has appeared as part of an effort to decrease the energy loss and the cost for electric power facilities through installing small renewable energy generation systems including solar and wind power generation. Recently a new era for decentralized power environment in building is coming in order to handle the climatic and environmental change occurred all over the world. Especially solar and wind power generation systems can be easily set up and are also economically feasible, and thus many industrial companies enter into this business. This paper suggests the overall architecture for the decentralized renewable power system and the prediction method of power on climatic change. The ultimate goal is to help manage the overall power efficiently and thus provide the technological basis for achieving zero-energy house.

• Korean Journal of Materials Research
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• v.3 no.3
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• pp.261-271
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• 1993

Functionally Gradient Materials(FGM) of 4.5Pb($Ni_{1/3}Nb_{2/3})O_3$-55PZT and PLZT(lO/70 /30, 11/60/40) were prepared. Its dielectric and piezoelectric strain properties were investigated. The FGM were pressed into A/B/ A configuration using two kinds of films, one layer(A) was eliminated from FGM by polishing after sintering at $l250^{\circ}C$, 2 hrs. The acrylic binder system was successfully applied for crack free film through doctor blade method. The thickness of gradent layer in FGM was about 30${\mu}$m. Dielectric properties of FGM show the average value of each side layer. The strain-electric field characteristics of FGM were significantly improved comparison with the other single compositions. The prepared FGM piezoelectric actuator shows about 3${\mu}$m/IOOV displacement.

• Korean Journal of Materials Research
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• v.7 no.3
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• pp.175-179
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• 1997

bliniaturization oi microwave circuit components is an important issue with the development in the mobile communication. Capacitors, inductors anti hybrid devices of these are building blocks of electric circuits, and the fabrication of these devices using thin film technology will influence on the miniaturization of electronic devices In this paper, we report the successful fabrication of the inductors, capacitors and LC hybrid devices using a ferroelectric and a ferromagnetic oxide thin iilm. Au, stable at high temperatures in oxidizing ambient, is patterned by lift-off process, and oxide thin films are deposited by ion beam sputtering and chemical vapor deposition. These devices are characterized by a network analyzer in 0.5-15GtIz range We got the inductance of 5nH, capacitance oi 10, 000 pF and resonant frequencies of $10^{6}-10^{9}Hz$.

• Food Science of Animal Resources
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• v.32 no.4
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• pp.467-475
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• 2012

This study was carried out to investigate the effect of the addition level (0 ppm, 400 ppm, 800 ppm, and 1,200 ppm) of green tea extract on the lactic acid bacteria, oxidative stability, and aroma in kimchi-fermented sausage. The sample sausages were fermented at $24^{\circ}C/RH$ 89% until attained to a pH value of 4.9 (for 17 h), and then dried at $10^{\circ}C/RH$ 75-80% for 6 d. The lactic acid bacteria count and pH value were 7.5-7.7 Log CFU/g sausage and 4.30-4.33, respectively, at 6 d of ripening. The results of those did not show significant differences among all treatments. The formation of TBARS (2-thiobarbituric acid reactive substances) was significantly lowered by increasing the addition level of green tea extract. During ripening periods, the CIE $L^*$ and $a^*$ values decreased; however, the $b^*$ value increased due to the addition of green tea extract. Utilizing an electric nose, the aroma pattern was clearly discriminated between green tea extract treatments and the control. Therefore, in kimchi-fermented sausages, the high addition level of green tea extract improved the lipid oxidation stability. In addition, regardless of the addition level, green tea extract changed the aroma while reducing the color stability. Moreover, it did not have any effect on the growth of lactic acid bacteria.

• Resources Recycling
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• v.6 no.3
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• pp.15-21
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• 1997

Flyash from a coal-hed power plan1 is produced approximtcly 3 million tons m 1996 and causes the serious environmentalpmblem due to the disposal in the ash pond. Flyash is an accepted additive in concrete where it adds strength, sulfate ateresistanceand reduced cost, provided acccptablc levcls of unbunrned carbon are mmtmed This papzr describes to investigate thc technicalfeasibility of a dry triboelcctrostatlcp roccss to scparate unburned carbon h m f lyash into economically valuable produck Puliclesof unburned carbon and flyash can be impded positivc and negative surface charzes. rcapeclively. with a copper tniochargcr dueto dirferences in the work function values of thc particles and the tnbacharger. and cm he separated by passing thcm throuph anexternal electic field. A laboratory s d e separation system consists of r sacw feeder for ash supply, a tniocharger, verticalcollecling copper plates, power supplies, a flow meter, and a fan. Separation tests taking into account separahian efficiency and ashrecovery showed that flyash recovery was sh-nngly dependent an thc tnbocharger geomzhy, elect"c ficld strength. flyssh s ~ c a,n dash feeding late. Optimal separation conditions were flyash size less than 125 Fm and electric field shcngrh of 200 kV1m. Ovcr 80%of the flyash with 7% lass on ignition was recovered at wrbon contznts less than 3%bon contznts less than 3%

• Korean Journal of Construction Engineering and Management
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• v.21 no.5
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• pp.64-73
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• 2020

The government announced a plan for fund support to the enterprises with high possibility of recovery and early restructuring for the enterprises with low recovery by objectifying credit assessment system. Such announcement of government could be extended to restructuring risk of middle standing enterprises with low financial soundness by establishing the basis to prepare prompt restructuring by reinforcing the basis for restructuring through capital market. This research analyzed financial soundness based on the financial evaluation of bank by selecting 10 middle standing construction companies which focused on housing business in 2019, based on such analysis result, it was confirmed that there was a high possibility of restructuring risk. This research determined that there would be a decrease in growth rate of construction industry on the whole in 2020 due to fall of economic growth rate and reinforced real estate regulation, accordingly, there's a big possibility for middle standing construction companies with paid-in capital ratio due to its low possibility of maintenance of stable credit rating. This research established KCSI assessment model by utilizing the material of a reliable research institute in order for middle standing construction companies to evade restructuring risk, and indicated risk ratio differentiated per each item through a working-level expert survey. Such research result could suggest credit risk reduction method to middle standing construction company management staffs, and prepare a basis to evade restructuring risk.