• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.236-245
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• 2021

It is very important for structure designer to understand the service life variation since a wide range of service life is evaluated with changing exposure conditions and design parameters. Recently, for zero-carbon, waste plastic has been used for fuel for clinker production and this yields increase in chloride content in cement. This study is for evaluation of changing service life in the concrete with increasing initial chloride content due to usage of plastic-SRF(Solid Refuse Fuel) considering various exposure conditions and design parameters. For this, 4 levels of initial chloride content were assumed, and the service life was assessed using LIFE 365 program considering various environmental conditions including 3 levels of surface chloride content. As for analysis parameters, critical/initial chloride content, blast furnace slag powder replacement ratio, W/B(Water to Binder) ratio, cover depth, and unit mass for binder are adopted. Service life decreases with increasing initial chloride content and a significant reduction of service life is not evaluated permitting up to 1,000ppm of initial chloride content. With increasing slag replacement ratio, a longer service life can be secured since blast furnace slag powder has the effect of reducing the diffusion of external chloride ions and fixing the free chloride. It is thought that increasing initial chloride content up to European standard is helpful for enhancing sustainability and reducing carbon emission. Though the reduction in service life due to an increase in the initial chloride content is not significant in slag-concrete with low surface chloride content, careful consideration for mixing design should be paid for the exposure environment with high surface chloride content.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.102-112
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• 2019

This paper studies impact fracture behavior under temperature variation and compressive flexural strength of cement composites using VAE(vinyl acetate ethylene) powder polymer and PVA(polyvinyl alcohol) fiber. Impact test were conducted in the temperature range selected for the $-35^{\circ}C$, $0^{\circ}C$ and $35^{\circ}C$. In this experimental study, impact test were carried out using a drop impact testing machine (Ceast 9350) to obtain such as displacement, time, and impact fracture energy of normal specimen and and cement composites specimen. As test results, the use of VAE powder polymer and PVA fiber were observed to enhance the flexural strength of mortar. The compressive strength of PVA fibers reinforced cement composites was slightly decreased at 28 days, but the flexural strength was observed to increase 24.4% of normal mortar strength. As a result of the drop impact tests, PVA fiber reinforced cement composites specimens showed microcracks due to energy dispersion and crack prevention with bridge effect of the fibers, and scabbing or perforation by impact was suppressed. On the other hand, the normal mortar and VAE powder polymer cement composites specimens were carried out to the perforation and macro crack. Most of normal mortar and the cement composites subjected to impact load on specimens shows mostly local brittle failure. The impact resistant performance of the specimen with PVA fiber was greatly improved due to the increase of flexure performance.

• Journal of Animal Science and Technology
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• v.44 no.4
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• pp.475-482
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• 2002

The experiment was conducted to evaluate a ventilation system, which was devised to encourage farmers to use the enclosed poultry housing system. The study was observed in the National Livestock Research Institute from May 9 to May 30 in 2002. The main results of the experiment are as follows: 1. Although the outside temperature of the enclosed poultry house was 9.6 ${\sim}$ 21.2$^{\circ}C$ with 11.6$^{\circ}C$ variation, the house with an excellent heat insulation was maintained at 32${\sim}$33$^{\circ}C$ in a variation of 2$^{\circ}C$ which is within the range of the optimal temperature for broiler, being aided with two small electric heaters. 2. The average of air flow rates of the upper, middle and low parts of the room in the broiler house were detected at 0.57, 0.22 and 0.04 m/sec, respectively. The air flow in the whole room was distibuted uniformly by a perforated duct. In conclusion, heat and humidity could be controlled without any problem in this enclosed housing system. Especially, air flow in all parts of the room was detected in uniform rates, resulting in the better ventilation performance with air inhalation through the duct and air exhaust through the side walls of the house.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.1 no.1
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• pp.1-8
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• 1981

Since the estuary is a very complex place in which the sea water and the fresh water meet, it is very difficult to make a general analytical description of salinity distribution in the estuary. As an attempt to investigate the characteristics of salinity variation in the estuary of the Geum River, the field observations were continuously carried out at three points near the Gunsan New Harbor at the time intervals 1 to 1.5 hours during one tidal cycle and the data were analysed. The following results were obtained; 1. It was reconfirmed that most of the ratios of the salinity to the conductivity were widely distributed between the range of 0.5 to 1.0. 2. The salinity showed the peak at the high water, and then it began to decrease gradually and had the lowest value 0 to 2 hours after the low water. 3. The density current was generally the intense mixing type and when the river discharge was very large it was of the moderate type. 4. The vertical salinity distribution was not significantly affected by the wave height. 5. The maximum vertical salinity differences were generally less than 10 g/l and the time of the occurrence of the minimum value was 0 to 3 hours after the low water when in the spring tide and in the neap tide it occurred 2 to 3 hours after the high water.

• Korean Journal of Medicinal Crop Science
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• v.13 no.4
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• pp.190-193
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• 2005

Hemp is cultivated to produce fiber and seeds for extracting vegetable oil. This study was carried out to obtain reliable data on fatty acid profile including ${\gamma}-linolenic$ acid (GLA) in seeds of hemp accessions with regard to suitability for both human nutrition and pharmaceutical purposes. The ratio of unsaturated fatty acid including ${\alpha}-linolenic$ acid were high but saturated fatty acid including palmitic acid were low in the seeds of hemp accessions, perilla and evening primrose. The ratio of GLA in fatty acid profile of evening primrose and hemp seeds were 12.5% and 2.1 %, respectively but not detected in perilla seeds. In the fatty acid profile of hemp seeds accessions, the range and coefficient of variation of GLA were $0.8%{\sim}3.8%$ and 42.9%, respectively which are highest among the fatty acid. Among the major characteristics and fatty acid ratios, flowering date and ${\alpha}-linolenic$ acid showed highly positive correlation but not showed any significant correlation between THC (Tetrahydrocannabinol) and any fatty acids. Among the fatty acid ratios, negative correlation were showed between palmitic acid and ${\gamma}-linolenic$ acid, and showed highly negative correlation between oleic acid and ${\alpha}-linolenic$ acid, linoleic acid and a-linolenic acid. The accessions of high GLA ratio were originated from Europe including Central Russia, and were short in flowering date and stem height.

• 한국해양학회지
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• v.5 no.1
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• pp.30-36
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• 1970

The water quality of the laver bed at Yongwon Ri, Changwon Gun was investigated during the spring and neap tide in March 1970. The effect of tide on the contents of various chemical constituents was irregular and the variation ranges of the contents were narrow. The pH value during flood and ebb tide was a constant of 8.2. The chlorosity range varied from 19.15 to 19.33g/l, the difference of 0.18g/l being comparatively small for coastal waters. The nutrient salts contents varied irregulary with the change in tide, but nitrite and soluble iron were not detected. In local distribution, chlorosity and silicate- silicon contents were found to be more at Sts. 1, 2 and 3 in the eastern area than at Sts. 4, 5 and 6 in the western area, wheras nitrate and ammonia contents were found to be more at Sts. 4, 5 and 6. The nitrate content was especially high, being twice as much as that at Sts. 1, 2 and 3 in the eastern area. In the spring tide, chlorosity was found, on the average, to be as much as 0.06g/l higher than in the neap tide, but the contents of nutrient salts were higher in the neap tide, especially the nitrate content was twice as much. When compared with other selected local laver beds, i.e., the tidal flats of the Nackdong and Somjin rivers, and of Wan Do Gun, the chlorosity level was highest but the nutrient salts contents level was, in general, slightly lower and the variation ranges narrow in the laver bed at Yongwon ri. The nitrate content, in particular was one tenth smaller than the others.

• The Korean Journal of Malacology
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• v.32 no.4
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• pp.269-277
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• 2016

We examined the seasonal variation of the proximate, amino acid, fatty acid composition and glycogen contents of triploid Pacific oyster cultured in western coastal waters of Korea in 2015. The specimens were collected in February, May, August and November from off-bottom farming site. The lipid content was the highest in winter season (February, $2.10{\pm}0.06%$), the protein content was the highest in autumn season (November, $9.09{\pm}0.04%$) while the moisture and ash content was the highest in summer season (August, $86.00{\pm}0.12%$ and $2.67{\pm}0.03%$, respectively). The total amino acid contents was the highest in winter season (1,011.5 mg / 100 g), decreased gradually and was the lowest in summer season (486.7 mg / 100 g). The total amino acid composition was dominated by taurine, aspartic acid, glutamic acid, glycine and alanine. In the fatty acid composition, the two fatty acids, eicosapentaenoic acid and docosahexaenoic acid, which comprised that as much as 50% of the total fatty acid contents, were dominated during all season. The glycogen content was the highest in summer season ($1.26{\pm}0.03g$ / 100 g) although it was stable during the other season with the range of $0.69{\pm}0.04-0.86{\pm}0.01g$ / 100 g. Taken together, these results suggest that triploid pacific oysters have high commercial value not only in winter season but in summer season because they do not spawn and have high contents of glycogen comparing with those of diploid oyster in this period.

• Journal of Korean Society of Forest Science
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• v.15 no.1
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• pp.43-48
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• 1972

The variation of numbers of resin canal in cotyledon at different growing stages are observed and results are summarized as follows: 1. Resin canals of cotyledon are not found in May, but in September the average number was 3.26. 2. Unlike in later-formed needles, cotyledon resin canals were external and the range of resin canal numbers are 1 to 5. 3. Correlation coefficients between growing stages and resin canal numbers are significant. And correlations between resin canal numbers and leaf thickness, or the number and cross-section area are also highly significant. 4. Low correlation between resin canal and cotyledon number is observed.

• The Journal of Engineering Geology
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• v.19 no.1
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• pp.63-70
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• 2009

The optical fiber cable acting as a sensor was embedded in the underground research tunnel and portal area in order to monitor their stability and the spatial temperature variation. This system includes two types of sensing function to monitor the distributed strain and temperature along the line, where sensor cable is installed, not a point sensing. According to the results of one year monitoring around the KURT, there is no significant displacement or movement at the tunnel wall and portal slope. However, it would be able to aware of some phenomena as an advance notice at the tunnel wall which indicates the fracturing in rockmass and shotcrete fragmentation before rock falls accidently as well as movement of earth slope. The measurement resolution for rock mass displacement is 1 mm per 1 m and it covers 30 km length with every 1m interval in minimum. In temperature, the cable measures the range of $-160{\sim}600^{\circ}C$ with $0.01^{\circ}C$ resolution according to the cable types. This means that it would be applicable to monitoring system for the safe operation of various kinds of facilities having static and/or dynamic characteristics, such as chemical plant, pipeline, rail, huge building, long and slim structures, bridge, subway and marine vessel. etc.

• Journal of Marine Life Science
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• v.5 no.1
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• pp.25-33
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• 2020

The Asan Bay, which has semi-diurnal tide with macro-tidal range, is affected by both freshwater discharge from the sluice gates in the sea dikes and tidal seawater inputs from the Yellow sea. Understanding water quality change in response to tides is important since tides can impact the short-term variations in physical and chemical water properties as well as the response of biological properties. The diel variations in water quality were seasonally investigated at 2 hour intervals from a fixed station in the Asan Bay. In the results, water temperature and salinity consistently fluctuated in phase or out of phase with tidal height. Especially salinity was positively correlated with tidal height. The concentrations of total suspended solids were higher in the bottom water than in the surface and fluctuated greatly over the tidal cycle recording higher values at low tide than at high tide. Nitrite+nitrate levels also fluctuated out of phase with tidal height and correlated negatively with tidal height. Other nutrients also showed a similar pattern. The pattern was distinct in July when freshwater was discharged before the field sampling. The concentrations of organic materials, total nitrogen and total phosphorus greatly fluctuated over the tidal cycle and were generally out of phase with tidal height. Most materials except particulate organic forms were correlated with salinity indicating that freshwater inputs were sources for the materials similarly to the dissolved inorganic nutrients. The results suggest that water quality (except dissolved oxygen and pH) and nutrients including organic materials was largely affected by tides in the Asan Bay.