• Journal of Ocean Engineering and Technology
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• v.25 no.2
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• pp.85-91
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• 2011

Many protection methods such as surface coating, electric protection, or other methods have been applied to the numerous steel structures widely used in continental and marine areas to control their corrosion, which is done from an economic point of view. Most of these steel structures are primarily protected by coating methods. However, some steel piles under seawater are protected by the electric protection method, that is, either using an impressed current or a sacrificial anode method. Furthermore, environmental contamination may cause a severely corrosive environment, which, in turn, causes the accelerated corrosion of steel structures. Subsequently, coated steel structures could deteriorate more rapidly than the designed lifetime because of the acid rain caused by air pollution, etc. Therefore, a coating of marine paint exposed to seawater, that is, underwater hardening painting, is increasingly required to be fast drying as well as highly corrosion resistant. In this study, five types of underwater hardening paints were prepared with different resin series and additives. Their corrosion and water resistances were investigated using electrochemical methods such as corrosion potential, polarization curves, impedance and cyclic voltammogram measurements, etc. Even though it is generally accepted that the corrosion resistance of bare steel tends to increase with a shift of the corrosion potential in the noble direction, the corrosion resistance of a sample with a coating exhibited a relatively better tendency when it had a lower corrosion potential in this study. The corrosion current density was also decreased with a decrease in the diffusion limiting current density, which may mean that there is some relationship between corrosion and water resistance. The S sample of the ceramic resin series showed the relatively best corrosion and water resistance among those of samples, while the worst corrosion and water resistance were observed for the R sample of the epoxy resin series. The corrosion and water resistance of those samples tended to deteriorate with an increase in the immersion days, and their corrosion and water resistances were considered to be apparently improved by the types of resin and additives.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1998.04b
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• pp.6-6
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• 1998

In 1957, the first magnetic disk drive compatible with a movable head was introduced as an external file memory device for computer system. Since then, magnetic disks have been improved by increasing the recording density, which has brought about the development of a high performance thin film magnetic head. The thin film magnetic head has a magnetic circuit on a ceramic substrate using IC technology. The physical property of the substrate material is very important because it influences the tribology of head/disk interface and also manufacturing process of the head. $Al_{2}O_{3}$-TiC ceramics, so called ALTIC, is known to be one of the best substrate materials which satisfies this property requirement. Even though the head is not in direct contact with the disk, frequent instantaneous contacts are unavoidable due to its high rotating speed and the close gap between them. This may cause damage in the magnetic recording media and, thus, it is very important that the magnetic head has a good wear resistance. $Al_{2}O_{3}$-TiC ceramics has an excellent tribological property in head/disk interface. Manufacturing process of thin film head is similar to that of IC, which requires extremely smooth and flat surface of the substrate. The substrate must be readily sliced into the heads without chipping. $Al_{2}O_{3}$-TiC ceramics has excellent machineability and mechanical properties. $Al_{2}O_{3}$-TiC ceramics was first developed at Nippon Tungsten Co. as cutting tool materials in 1968, which was further developed to be used as the substrate materials for thin film head in collaboration with Sumitomo Special Metals Co., Ltd. in 1981. Today, we supply more than 60% of the substrates for thin film head market in the world. In this paper, we would like to present the sintering process of $Al_{2}O_{3}$-TiC ceramics and its property in detail.

• Korean journal of applied entomology
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• v.23 no.4 s.61
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• pp.215-220
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• 1984

Mulberry dwarf, paulownia witches' broom, jujube witches' broom, and sumach witches' broom are known to be associated with mycoplamalike organisms(MLO) in Korea. Simple microscopic detection of MLO infection in these plants was attempted. Periwinkle plant was also tested. Application of $0.2\%\;and\;0.4\%$ solution of Dienes' stain gave diagnoatic value for MLO-induced diseases of periwinkle and mulberry. Among the various plant parts examined, young herbaceous stem just below the apical part gave the best result. Density of staining reaction was proportional to disease severity. Longitudial sections were superior to transverse sections in confirming MLO infection by staining. Light source without blue filter was useful for increasing the color contrast between sieve tube and xylem vessel and for eliminating misinterpretation. Paulownia, jujube, and sumach samples gave no clear difference in staining reaction between healthy and diseased sections even when various modifications of Dienes' staining procedure were tried.

• Journal of Powder Materials
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• v.22 no.4
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• pp.271-277
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• 2015

As wrought stainless steel, sintered stainless steel (STS) has excellent high-temperature anti-corrosion even at high temperature of $800^{\circ}C$ and exhibit corrosion resistance in air. The oxidation behavior and oxidation mechanism of the sintered 316L stainless was reported at the high temperature in our previous study. In this study, the effects of additives on high-temperature corrosion resistances were investigated above $800^{\circ}C$ at the various oxides ($SiO_2$, $Al_2O_3$, MgO and $Y_2O_3$) added STS respectively as an oxidation inhibitor. The morphology of the oxide layers were observed by SEM and the oxides phase and composition were confirmed by XRD and EDX. As a result, the weight of STS 316L sintered body increased sharply at $1000^{\circ}C$ and the relative density of specimen decreased as metallic oxide addition increased. Compared with STS 316L sintered parts, weight change ratio corresponding to different oxidation time at $900^{\circ}C$ and $1000^{\circ}C$, decreased gradually with the addition of metallic oxide. The best corrosion resistance properties of STS could be improved in case of using $Y_2O_3$. The oxidation rate was diminished dramatically by suppression the peeling on oxide layers at $Y_2O_3$ added sintered stainless steel.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.4
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• pp.61-69
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• 2002

This study was conducted to develop revegetation methods for the restoration of the steep slopes by seed attached ripping net revegetation methods. In general, steep slopes with decomposed granite soils and ripping rock are easy to erode by precipitation and impossible to revegetate only using hydroseeding with core net mulching because of poor soil fertility. The Seed Attached Ripping Net Revegetation Methods(SALNRM) will be the most popular and sustainable methods to restore decomposed granite soils and ripping rock exposed slopes. The main results are summarized as follows; 1. The net size with $1.5cm{\times}1.0cm$ density was more suitable for growing plants, and increasing the ratio of the slow release fertilizer was better to make early coverage and to grow germinated plants. 2. The fertilizer bag made by the ratio of Peatmose : Vermiculite : Perlite : Quick release fertilize r : Slow release fertilizer = 10 : 2 : 5 : 3 : 4 (v : v) was the best for plant's growth. 3. According to the seed mixture experiments, even though not using foreign grasses, the SALNRM using native plants can make diverse plant composition. 4. The SALNRM will make same early ground coverage by only using native plants like using foreign grasses. The SALNRM would become the popular revegetation methods to restore decomposed granite soils and ripping rock exposed slopes in Korea.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.661-666
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• 1998

Active reaction sites and electrochemical O2 reduction kinetics on La_{1-x}Sr_xMnO_{3+{\delta}} (x=0.1-0.4)/YSZ (yttria-stabilized zirconia) electrodes are investigated in the temperature range of 700-900 ℃ at $Po_2=10^{-3}$-0.21 atm. Results of the steady-state polarization measurements, which are formulated into the Butler-Volmer formalism to extract transfer coefficient values, lead us to conclude that the two-electron charge transfer step to atomically adsorbed oxygen is rate-limiting. The same conclusion is drawn from the $Po_2$-dependent ac impedance measurements, where the exponent m in the relationship of $I_o$ (exchange current density) ∝ $P_{o_{2}}^m$ is analyzed. Chemical analysis is performed on the quenched Mn perovskites to estimate their oxygen stoichiometry factors (δ) at the operating temperature (700-900 ℃). Here, the observed δ turns out to become smaller as both the Sr-doping contents (x) and the measured temperature increase. A comparison between the 8 values and cathodic activity of Mn perovskites reveals that the cathodic transfer coefficients $({\alpha}_c)$ for oxygen reduction reaction are inversely proportional to δ whereas the anodic ones $({\alpha}_a)$ show the opposite trend, reflecting that the surface oxygen vacancies on Mn perovskites actively participate in the $O_2$ reduction reaction. Among the samples of x= 0.1-0.4, the manganite with x=0.4 exhibits the smallest 8 value (even negative), and consistently this electrode shows the highest ${\alpha}_c$ and the best cathodic activity for the oxygen reduction reaction.

• Journal of Bio-Environment Control
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• v.19 no.4
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• pp.333-342
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• 2010

For the energy-saving production of fresh vegetables in poor environment such as the Antarctic, a container-type plant factory was designed and developed. To maximize space usage of the 20 feet container ($L5.9m{\times}W2.4m{\times}H2.4m$), a three-level hydroponic cultivation system was installed and the nutrient solution was supplied by bottom watering. Using this system, 3 lettuce cultivars were grown under different the light source (light intensity). After 2 weeks from the transplanting, fluorescent lamp ($145\;{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$) showed the best fresh weight of top part and leaf area. However, After 4 weeks, fluorescent lamp plus metal halide lamp ($150\;{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$) led to the optimum growth of the each lettuce cultivar. The cultivar, 'Cheongchima', showed the best fresh weight of top part and leaf area, followed by 'Jeokchukmyeon' and 'Lollo rosa'. The chlorophyll concentrations (SPAD) showed no significant difference among the sources of lights. However, 'Cheongchima' showed relatively high chlorophyll concentration. With the above results, we found that the growth of lettuce is depend on light intensity and even at same intensity, the growth is different among the cultivars. Therefore, the selection of optimum cultivar should be considered in the plant factory system that has only weak light density.

• KSBB Journal
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• v.8 no.5
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• pp.431-437
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• 1993

Active carbon which has the smallest bulk and wet density was found as the best support media among 4 different kinds of materials(celite, natural zeolite, Pusuk stone, active carbon) to make a proper fluidized-bed with small energy consumption. Its minimum and optimum fluidization velocity were found as 0.03cm/sec and 0.25cm/sec, respectively. As organic loading rate for methane fermentation was increased, CODcr removal efficiencies of all the media were decreased. But, CODcr, removal efficiencies of active carbon was maintained more than 90% in this experimental range of the organic loading rate. Larger amount of microorganism was adsorbed on the active carbon which has very high specific surface area. At the organic loading rate of 16g CODcr,/l day, its adsorbed cell mass was 157mg/g. Comparing natural zeolite with roast celite, adsorbed cell mass did not increase in proportion to specific surface area of the media. Even though roast celite has the same specific surface area as the Pusuk stone, its organic removal ability was superior to that of the Pusuk stone, which explains that the relatively great surface roughness and the positive surface charge are important for cell adsorption. It was concluded that the support media for anaerobic fluidized reactor should have small wet density and small fuidization velocity, if possible, in order to increase cell adsorption by reducing the fluid shear stress.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.3
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• pp.163-171
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• 2017

Effects of different packaging methods for maintaining the shelf life and postharvest quality of iceberg lettuce (Lactuca sativa L.) were studied after harvesting in summer season. Lettuce heads were packaged in plastic crate with or without different films such as (A) Individual lettuce head sealed packaging with linear low density polyethylene (LLDPE) film; (B) Packaging lettuce head in plastic crate and wrapped with LLDPE film; (C): Individual lettuce head sealed packaging with perforated high density polyethylene (HDPE) film; (D) Packaging lettuce head in plastic crate and wrapped with perforated HDPE; and (E) Packaging lettuce head in plastic crate without any film (control), and stored at $2^{\circ}C$ for 35 days. Several quality parameters such as fresh weight loss, SPAD (soil & plant analyzer development) meter value, respiration rate, moisture content and appearance of lettuce were investigated. The lettuce wrapped with individually-sealed LLDPE film showed the lowest weight loss and the highest SPAD value rendering the best appearance index among the treataments throughout the three-week storage period at $2^{\circ}C$. Extending the freshness of iceberg lettuce during low temperature storage will definitely increase the salability potential in the domestic market even during summer season.

• Korean Journal of Digital Imaging in Medicine
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• v.11 no.2
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• pp.115-119
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• 2009

I think this will be valuable reference for assuring consistency and homogeneity of clarity and managing dental radiation equipment by experimentation of dental radiation equipment permanent which based on KS C IEC 61223-3-4 standard and KS C IEC 61223-2-7. Put a dental radiation generator and experiment equipment as source and film(sensor) length within 30 em, place the step-wedge above the film(sensor). Tie up tube voltage 60 kVp, tube current 7 mA and then get an each image through CCD sensor and film by changing the exposure time as 0.12sec, 0.25sec, 0.4sec. Repeat the test 5times as a same method. Measure the concentration of each stage of film image, which gained by experiment, using photometer. And the image that gained by CCD sensor, analyze the pixel value's change by using image J, which is analyzing image program provided by NIH(National Institutes of Health). In case of film, while 0.12sec and 0.25sec show regular rising pattern of density gap as exposure time's increase, 0.4sec shows low rather than 0.12sec and 0.25sec. In case of CCD sensor density test, the result shows opposite pattern of film. This makes me think that pixels of CCD's sensor can have 0~255 value but it becomes saturation if the value is over 255. The way that getting clear reception during decreasing human's exposed radiation is one of maintaining an equipment as a best condition. So we should keeping a dental radiation equipment's condition steadily through cyclic permanent test after factor examination. Even digital equipment doesn't maintain a permanent, it can maintain a clarity by post processing of image so that hard to set it as standard of permanent test. Therefore it would be more increase the accuracy that compare a film as standard image. Thus I consider it will be an important measurement to care for dental radiation equipment and warrant homogeneity, consistency of dental image's clarity through comparing pattern which is the result from factor test against cyclic permanent test.