• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.675-684
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• 2020

To prevent safety accidents caused by aging pipe infrastructure and to maintain water quality, construction projects for water and sewage pipes are actively conducted across Korea. This study analyzed the criteria situations, site survey details, and regulation revisions related to the calculation of construction cost standards for pipe laying and joining work. The analysis showed that the major causes for revision are the unclear construction scope, limitations in implementing some pipe materials due to installation facility types, workforce focused on ordinary labor, limitations of manual laying work, and the lack of tool hire cost and machine expense-calculation criteria. Field studies were conducted to categorize the pipes according to their features, in addition to identifying the use of lifting heavy equipment and light equipment. In addition, excavation and testing work conducted in connection to pipe laying, as well as the use of skilled labor, were investigated. The current study clarified the work scope through new common items, provides an organization based on the pipe material, adjusted the workforce ratio to focus more on skilled labor, and developed grounds for calculating machine expenses. These revisions were estimated to save approximately 1.28% of the construction costs in each project according to an analysis of the construction cost impact study. truction costs in each project, according to an analysis of construction cost impact study.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.4
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• pp.293-299
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• 1987

At various times and places all over the world men have become ill and some have died after eating shellfish that were intoxicated with paralytic shellfish poison(PSP) caused by Protogonyaulax spp. In late March, 1986, two persons were dead by ingesting wild sea mussels, Mytilur edulis, grown at bottom of an anchored waste ship to be dismantled at Gamchun Bay, Pusan, Korea. The samples were collected from the bottom of the ship during April $1\~April$ 8 of the year to find the cause of the food poisoning accident. The toxicity was estimated by bioassay with ICR male mouse, while the toxins were extracted and characterized. The toxins were extracted with acidified $80\%$ ethanol. The extract was defatted three times with dichloromethane, treated with activated charcoal, and then purified by chromatography on Bio-Gel P-2 and Bio-Rex 70. The toxic fractions obtained were analysed by cellulose acetate membrane electrophoresis, thin layer chromatography and high performance liquid chromatogaphy. The range and the average of PSP-toxicity of the samples were $132\~295\;MU/g$, 203 MU/g respectively. The amount of PSP was $26.4\~58.9{\mu}g/g$ of whole meat in range and $40.6{\mu}g/g$ in average. The toxicity of the digestive gland of the samples was 9 times higher than that of edible meat (except digestive gland) as $439\~979MU/g$, and it was about $70\%$ in total toxin. The compositional analytical results of the paralytic shellfish toxin, Gonyautoxin $1\~4$ were the major part of the PSP and Saxitoxin and neosaxitoxin were detected as the minor component. It was concluded that the food poisoning accident was caused not by Saxitoxins but by Gonyautoxins.

• Journal of the Korea Institute of Building Construction
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• v.11 no.4
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• pp.326-332
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• 2011

Carbon, Aramid, Boron and Glass fibers are used as fibrous materials to promote structural bearing strength. Of these fiber types, carbon fiber is the most commonly used material, and is characterized by having a one-way direction, which is strengthened by tensile strength due to the attached direction only, while other types of fibers are two-way. Therefore, when applied in the field, the attachment direction of fiber is a very important factor. However, when fiber direction is not mentioned in the design drawing, there sometimes is no improvement in structural strength, as the fiber is being installed by a site engineer or workers who lack structural knowledge. The purpose of this study was to propose an optimal direction of carbon fiber through a comparison & analysis of reinforcing efficiency with reinforced experimental columns that used carbon fibers in each of the inclined, horizontal and vertical directions. According to the results, horizontal direction in the reinforced column was improved by 153.43%, but vertical direction was 104.61% only, and it was understood this was due to increased tensile strength along the fiber direction. For this reason, it is necessary to include information regarding fiber direction in design and site management.

• Journal of the Korean Institute of Gas
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• v.21 no.3
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• pp.17-25
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• 2017

Recently, the need of alternate energy resources is increasing due to the global warming issue. The natural gas buried in the extremely cold regions of Alaska and Siberia is of much interest these days. However, the construction standards are needed to be used in extremely cold regions. Particularly, more research work need to be carried out on the trench stability so that the safety of the workers is ensured and the damage to the construction machinery can also be reduced resulting in smaller construction period. In this study, the process for lowering of the pipelines of 30 and 40 in. diameters in the ground conditions (silt and peat) of Yakutsk, Russia was analyzed. The slopes of the ground surface were considered as $0^{\circ}$, $10^{\circ}$, and $20^{\circ}$ to be excavated in summer and winter. The analysis results show that the weight of pipelayer affects the trench stability. Numerical analysis was performed by considering the types of pipelayers, distance between the trench and pipelayer, and the distance between the pipelayers placed longitudinally along the trench. The results show that as the distance between the pipelayer and the trench decreases, the factor of safety of the slope decreases with an increase in the slope of the ground surface. When the slope of the ground surface was $20^{\circ}$, the breakout surface was anticipated to continue from the pipelayer to the trench boundary. In winter season, stability problem of the trench was not observed when the slope of the ground surface was less than $20^{\circ}$.

• Journal of Sensor Science and Technology
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• v.33 no.1
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• pp.34-39
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• 2024

Energy harvesting technology that converts the wasted energy resources into electrical energy is emerging as a semipermanent power source for self-powered electronics and wireless low-power sensor systems. Among the various energy conversion techniques, flexible piezoelectric energy harvesters (f-PEHs), using materials with piezoelectric effects, have attracted significant interest because they can harvest a small mechanical energy into electrical signals without constraints of time and space in various environments. In this study, we used a flexible piezoelectric composite film fabricated by dispersing BaHf_xTi_(1-x)O₃ (x = 0, 0.01, 0.05, 0.1) piezoelectric powders inside a polymeric matrix to facilitate f-PEHs. The fabricated f-PEH with optimal Hf contents (x = 0.05) generated a maximum output voltage of 0.95 V and current signal of 130 nA with stable electrical/mechanical disabilities under periodically bending deformations. In addition, we demonstrated a cantilever-type f-PEH and investigated its potential as a sensor by characterizing the output performance under mechanical vibrations at various frequencies. This study provides the breakthrough for realizing self-powered energy harvesting and sensing systems by adopting the lead-free piezoelectric composites under vibrational environments.

• Korean Journal of Ecology and Environment
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• v.34 no.1 s.93
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• pp.30-44
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• 2001

In this study limnological characteristics of Lake Juam was surveyed from June 1993 to May 1994 in order to provides important information regarding water resources. Secchi disc transparency, epilimnetic chlorophyll a (chi-a), total nitrogen (TN), total phosphorus (TP) concentration and primary productivity were in the range of $2.0{\sim}4.5\;m$, $0.9{\sim}13.6\;mgChl/m^3$, 0.78$\{sim}$2.32 mgN/l, $11{\sim}56\;mgP/m^3$, $270{\sim}2.160\;mgCm^{-2}\;day^{-1}$, respectively. On the basis of TP, Chl-a and Secchi disc depth, the trophic state of Lake Juam can be classied as mesotrophic lake. The phosphorus inputs from non-point sources are concentrated in heavy rain episodes during the monsoon season. As a result, phosphorus concentration are higher in summer than in winter. TP loading from the watershed were estimated to be $0.9\;gPm^{-2}yr^{-1}$, which correspond to a boundary of the critical loading ($1.0\;gPm^{-2}yr^{-1}$) for eutrophication. From the results of the algal assay, both phosphous and nitrogen act as limiting nutrients in algal growth. The seasonal succession of phytoplankton community structure in Lake Juam was similar to that observed in other temperate lakes. Diatoms (Asterionella formosa and Aulacoseira granulate var. angustissima)fujacofeira BraHuJafa uar. aHgusHrsiaia) weredominant in spring and winter, cyanobacteria) were dominant in warm season. The organic carbon, nitrogen and phosphorus content of lake sediment were $9.5{\sim}14.0\;mgC/g$, $1.01{\sim}1.82\;mgN/g$ and $0.51{\sim}0.65\;mgP/g$, respectively. The allochthonous organic carbon loading from the watershed and autochthonous organic carbon loading by primary production of phytoplankton were determined to be 1,122 tC/yr and 6,718 tC/yr, respectively. To prevent eutrophication of Lake Juam, nutrient management of watershed should be focus on reduction of fertilizer application, proper treatment of manure, and conservation of topsoil as well as point source.

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.322-333
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• 2005

Total phosphorus (TP) and suspended solids (SS) were measured in the discharge waters from 5 drainage basins of Lake Yongdam, from April, 2002 till March, 2004. The responses of SS and TP to rainfall were analyzed and their loadings into Lake Yongdam were calculated. The inflowing rivers into Lake Yongdam were the Juja River, the Jeongja River, the Jinan River, the Geum River and the Guryang River. Among these rivers Jinan River showed the highest TP that fluctuated very much according to the flow rate. TP and the flow rates (Q) of each river showed positive correlations with empirical relationsip of $TP\;=\;6.32Q^{0.30}$ for the Juia River, $TP\;=\;8.58Q^{0.49}$ for the Jeongia River, $TP\;=\;307.92Q^{0.10}$, for the Jinan River, $TP\;=\;17.91Q^{0.47}$, for the Geum River, $TP\;=\;20.11Q^{0.53}$ for Guryang River. In April 2002 ${\sim}$ March 2003, phosphorus loadings from the Juja River, the Jeongja River, the Jinan River, the Geum River and the Guryang River were calculated to be 3,677, 11,430, 36,412, 89,651, and 42,226 kgP ${\cdot}$ $yr^{-1}$ respectively. And the specific loadings from the Juja River, the Jeongia River, the Jinan River, the Geum River and the Guryang River were calculated to be 0.3, 2.9, 13.6, 9.3, and 13.0 kgP ${\cdot}$ $km^{-2}$ ${\cdot}$ $yr^{-1}$ respectively. In April 2002 ${\sim}$ March 2004, the suspended particles loading from the Juja River, the Jeongia River, the Jinan River, the Geum River and the Guryang River were 673, 1,232, 4,232, 30,902, 80,202 ton ${\cdot}$ $yr^{-1}$ respectively. The Guryang River showed the largest contribution of SS loading.

• Journal of Korean Society of Forest Science
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• v.82 no.4
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• pp.311-318
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• 1993

This study was conducted to obtain necessary information to improve beekeeping farmhouses management and to establish related problem. Using data obtained from 50 beekeeping farmhouses in Korea, current status of management and optimum sales scale were analysed. The results of the study are summarized as follows ; 1. Managers of beekeeping farmhouses are relatively old(64% of them is over 50 years old) and highly educated and experienced(76% of them is in the business more than 10 years). 2. Only a portion of managers(38%) considers beekeeping as a major job, while the rest(62%) involves as a side job working with other agricultural business. 3. Major supply of labor force comes from family group. Total input of family labor is 6.4 months a year. Fourty-four percent of management units is migrating and 56% of them is settled in specific locations. 4. In 1991, the average number of conventional beehive casks per farmhouse is decreased by 2.94 casks but improved-type beehive casks is increased by 13.79 casks. Total number of beehive casks per farmhouse is increased by 12.66 casks during the year. 5. Major cost items of beekeeping farmhouses include bee colony aquisition cost, feeding cost, depreciation cost, wages in an order. The average yearly profit rate of farmhouses is about 29.4%. 6. The break-even point of honey sales is about 3 million won. The optimum sales scale was 52.2l, then average production cost was estimated 53,800Won.

• Korean Journal of Ecology and Environment
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• v.33 no.3 s.91
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• pp.222-229
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• 2000

Spatial and temporal variation of phosphorus in response to intensity of summer monsoon was evaluated in Taechung Reservoir during 1993${\sim}$1994. Total phosphorus (TP) averaged 31 ${\mu}$g/l during the study and varied from 6 to 197 ${\mu}$g/l. Concentrations of TP were highest in the headwaters during the monsoon of July${\sim}$August 1993, and these values were mainly made of particulate P and were closely associated (R$^{2}$=0.74, p<0.001) with high inorganic suspended solids (NVSS). In-lake TP in the headwaters was mainly influenced by the watershed runoff and declined toward the dam. Values of TP downlake was only one-fifth of the peak in the headwaters and had no correlation with NVSS. In 1994, inlake TP was markedly lower relative to 1993 and showed low spatial and temporal variation. Maximum TP during monsoon 1994 in the headwaters and mid-lake was 72% and 52% lower, respectively, than in those two zones in 1993 whereas TP downlake was similar between the two years. These results suggest that temporal variation downlake is much less influenced by seasonal inflow compared to the haedwaters. In 1993, mean TP before fall overturn, based on average value for all sites, was significantly (t=5.99, p<0.001) greater than the mean after fall overturn, whereas in 1994 mean TP after fall overturn (32 ${\mu}$g/l) was greater. This outcome indicates that in 1993 major P-input originated from the external source from the watershed during the intense monsoon, whereas in 1994 internal processes dominated during the weak monsoon. Overall data suggest that annual budget of inlake P is regulated by intensity of the summer monsoon, and phosphorus data measured at single site near the dam or headwater zone may not be represent seasonal trends of the system due to large spatial variation of Taechung Reservoir.

• Korean Journal of Agricultural Science
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• v.20 no.1
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• pp.25-33
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• 1993

This study was conducted to obtain necessary informations for improving of wildlife rearing management. The data was gathered by surveying with questionaire. One hundred and eighty farmers which was 60 of deer and pheasant, 30 of wild boar and fox rearing farmers respectively were investigated during the summer in 1992. The results of this study are as follows : 1. Most of managers considered their rearing as a side job but agriculture was appointed as a main job from most of them except wild boar managers. 2. The major cost items were breeding stock and feeding which occupied over than half. 3. The yearly profit was the highest in deer(25.5%) but the lowest in wild boar(10.3%). 4. The break-even point was the highest in wild boar(24 mil. won) but the lowest in pheasant(7.3 mil. won). 5. The optimum sales scale for a year was deer(11 heads), Pheasant(1,027 heads), Wild boar(69 heads) and Fox (102 heads).