• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.3
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• pp.189-196
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• 2003

In this study, the vertical opening of the non-float midwater pair trawl net was maintained by controlling the length of upper warp. This was because the head rope was able to be kept linearly and the working depth was not nearly as changed with the variation of flow speed as former experiments in this series of studies have demonstrated. We confirmed that the opening efficiency of the non-float midwater pair trawl net was able to be developed according to the increase in front weight and wing-end weight. In this study, we described the opening efficiency of the non-float midwater pair trawl net according to the variation of front weight and wing-end weight obtained by model experiment in circulation water channel. We compared the opening efficiency of the proto type with that of the non-float type. The results obtained can be summarized as follows：1. The hydrodynamic resistance was almost increased linearly in proportion to the flow speed and was increased in accordance with the increase in front weight and wing-end weight. The increasing rate of hydrodynamic resistance was displayed as an increasing tendency in accordance with the increase in flow speed. 2. The net height of the non-float type was almost decreased linearly in accordance with the increase in flow speed. As the reduced rate of the net height of the non-float type was smaller than that of the net height of the proto type against increase of flow speed, the net height of the non-float type was bigger than that of the proto type over 4.0 knot. The net width of the non-float type was about 10 m bigger than that of the proto type and the change rate of net width varied by no more than 2 m according to the variation of the front weight and wing-end weight. 3. The mouth area of the non-float type was maximized at 1.75 ton of the front weight and 1.11 ton of the wing-end weight, and was smaller than that of the proto type at 2.0∼3.0 knot, but was bigger than that of the proto type at 4.0∼5.0 knot. 4. The filtering volume was maximized at 3.0 knot in the proto type and at 4.0 knot in the non-float type. The optimal front weight was 1.40 ton.

• Korean Journal of Soil Science and Fertilizer
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• v.21 no.4
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• pp.373-379
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• 1988

This experiment was carried out to investigate the effects of long-term applications of rice straw and compost on the physical and mechanical properties of paddy fields and the yearly variation of rice yield in Fluvio-Marine plain of Jeonbug series. Amounts of rice straw and compost applied in this experiment were 500kg/10a, 1,000kg/10a respectively, and the nitrogen levels were 0, 15 and 20kg/10a. This experiment were continued for 9 years from 1979 to 1987. The results are summarized as follows: 1. Clay and silt ratios were decreased but versa in sand ratio, by the long-term application of rice straw and compost. 2. Bulk density in the long-term application of organic matter was lower in surface soil of non-application than nitrogen application (15kg/10a) and in rice straw than compost. 3. Solid ratio went down, but liquid and gaseous ratio went up especially, by organic matter application liquid ratio were increased by compost and gaseous ratio were increased by in rice straw. 4. Aggregates of bigger than 2mm were increased by long-term application of organic matter, and the effects was better in rice straw than compost. Accumulative aggregate of 2mm was 66.5% in nitrogen of 15kg/ 10a with rice straw, which showed the increase of 9.1% in comparison with the non-application of nitrogen and organic matter. 5. Liquid limit, plastic limit and plastic index were high in order of rice straw, compost and control, and liquid index was lower in compost than in rice straw. 6. Cole value was higher in vertical than horizontal and highest in the application of rice straw with nitrogen of 15kg/10a. Cone and shearing resistance were lowest in the application of rice straw with nitrogen. In total vertical pressure friction was higher in the long-term application of organic matter than control. 7. The change of yield index was higher in the long-term application of compost than rice straw in non-nitrogen and it showed the yearly competitive variation between the long-term application of compost and rice straw in nitrogen of 10kg/10a. In nitrogen application of 20kg/10a, it was increased from 6th year by rice straw application.

• Journal of Popular Narrative
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• v.25 no.3
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• pp.67-99
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• 2019

This paper analyzed romance novels imported into Korea in the 1980s and examined the traits of Korean girls' culture at that time. To this end, This paper chose as subjects the series of 'high-teen romance' published by Samjungdang, 'princess bestseller' by Seoul Publishing and the 'silhouette romance' by Joongang Ilbo in the 1980s. Through the aspects of the paperback romances, the traits of the artist, the content of the work, and the response of the reader, this paper analyzed the position and affection of romance as a genre in Korean culture in the 1980s. In the 1980s, most of the paperback romances available in Korea were translations of the modern and progressive present lines of Harlequin Enterprise's category romance. There were also many writers who were mostly introduced with progressive characters like Charlotte Lamb. The Harlequin romance depicts a story of sensual love. These translated 1980s paperback romance novels allowed girls in Korea to freely imagine the problems of sex and love. In particular, it showed a new perspective on women's sexuality. In Korean love novels, the sexuality of women was treated as an object for the gaze of men. The novels of female writers as college student who criticized this dealt with women's sexuality, but focused on criticism and resistance to the ideology of chastity. The paperback romance made it possible for women to freely enjoy their sexuality by escaping the ethical standards of reality. In addition, the paperback romance was an escape from the frustration of love. Romantic love in Korean love novels did not lead to the unification of mind and body, and always ended in tragedy. On the contrary, the paperback romance started with the fear of the girl who felt love for the first time, showed the process of winning over anxiety, confirming love and reaching a happy marriage. Through this, girls understood general love that was not subordinated to the ideology of chastity, and accepted love positively. The process of establishing romance as a genre in Korean culture and the traits of its readers have not yet been sufficiently clarified yet. This paper compared the romance genre with the other love novels of the day, explaining the position and meaning of the romance genre in Korean culture in the 1980s. Through this, we were able to chart the historical development of the Korean romance genre.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.9 no.1
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• pp.1-18
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• 1973

For regulating the depth of midwater trawl nets towed at the optimum constant speed, the changes in the shape of warps caused by adding a weight on an arbitrary point of the warp of catenary shape is studied. The shape of a warp may be approximated by a catenary. The resultant inferences under this assumption were experimented. Accordingly feasibilities for the application of the result of this study to the midwater trawl nets were also discussed. A series of experiments for basic midwater trawl gear models in water tank and a couple of experiments of a commercial scale gears at sea which involve the properly designed depth control devices having a variable attitude horizontal wing were carried out. The results are summarized as follows: 1. According to the dimension analysis the depth y of a midwater trawl net is introduced by $$y=kLf(\frac{W_r}{R_r},\;\frac{W_o}{R_o},\;\frac{W_n}{R_n})$$) where k is a constant, L the warp length, f the function, and $W_r,\;W_o$ and $W_n$ the apparent weights of warp, otter board and the net, respectively, 2. When a boat is towing a body of apparent weight $W_n$ and its drag $D_n$ by means of a warp whose length L and apparent weight $W_r$ per unit length, the depth y of the body is given by the following equation, provided that the shape of a warp is a catenary and drag of the warp is neglected in comparison with the drag of the body: $$y=\frac{1}{W_r}\{\sqrt{{D_n^2}+{(W_n+W_rL)^2}}-\sqrt{{D_n^2+W_n}^2\}$$ 3. The changes ${\Delta}y$ of the depth of the midwater trawl net caused by changing the warp length or adding a weight ${\Delta}W_n$_n to the net, are given by the following equations: $${\Delta}y{\approx}\frac{W_n+W_{r}L}{\sqrt{D_n^2+(W_n+W_{r}L)^2}}{\Delta}L$$ $${\Delta}y{\approx}\frac{1}{W_r}\{\frac{W_n+W_rL}{\sqrt{D_n^2+(W_n+W_{r}L)^2}}-{\frac{W_n}{\sqrt{D_n^2+W_n^2}}\}{\Delta}W_n$$ 4. A change ${\Delta}y$ of the depth of the midwater trawl net by adding a weight $W_s$ to an arbitrary point of the warp takes an equation of the form $${\Delta}y=\frac{1}{W_r}\{(T_{ur}'-T_{ur})-T_u'-T_u)\}$$ Where $$T_{ur}^l=\sqrt{T_u^2+(W_s+W_{r}L)^2+2T_u(W_s+W_{r}L)sin{\theta}_u$$ $$T_{ur}=\sqrt{T_u^2+(W_{r}L)^2+2T_uW_{r}L\;sin{\theta}_u$$ $$T_{u}^l=\sqrt{T_u^2+W_s^2+2T_uW_{s}\;sin{\theta}_u$$ and $T_u$ represents the tension at the point on the warp, ${\theta}_u$ the angle between the direction of $T_u$ and horizontal axis, $T_u^2$ the tension at that point when a weights $W_s$ adds to the point where $T_u$ is acted on. 5. If otter boards were constructed lighter and adequate weights were added at their bottom to stabilize them, even they were the same shapes as those of bottom trawls, they were definitely applicable to the midwater trawl gears as the result of the experiments. 6. As the results of water tank tests the relationship between net height of H cm velocity of v m/sec, and that between hydrodynamic resistance of R kg and the velocity of a model net as shown in figure 6 are respectively given by $$H=8+\frac{10}{0.4+v}$$ $$R=3+9v^2$$ 7. It was found that the cross-wing type depth control devices were more stable in operation than that of the H-wing type as the results of the experiments at sea. 8. The hydrodynamic resistance of the net gear in midwater trawling is so large, and regarded as nearly the drag, that sweeping depth of the gear was very stable in spite of types of the depth control devices. 9. An area of the horizontal wing of the H-wing type depth control device was $1.2{\times}2.4m^2$. A midwater trawl net of 2 ton hydrodynamic resistance was connected to the devices and towed with the velocity of 2.3 kts. Under these conditions the depth change of about 20m of the trawl net was obtained by controlling an angle or attack of $30^{\circ}$.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.4
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• pp.223-231
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• 2012

The purpose of this study is to investigate basically the mechanism of heat transfer by the resolution of complex fluid flow inside a sophisticated designed screw dryer for the treatment of sewage sludge by using numerical analysis and experimental study. By doing this, the result was quite helpful to obtain the design criteria for enhancing drying efficiency, thereby achieving the optimal design of a multiple screw type dryer for treating inorganic and organic sludge wastes. One notable design feature of the dryer was to bypass a certain of fraction of the hot combustion gases into the bottom of the screw cylinder, by the fluid flow induction, across the delicately designed holes on the screw surface to agitate internally the sticky sludges. This offers many benefits not only in the enhancement of thermal efficiency even for the high viscosity material but also greater flexibility in the application of system design and operation. However, one careful precaution was made in operation in that when distributing the hot flue gas over the lump of sludge for internal agitation not to make any pore blocking and to avoid too much pressure drop caused by inertial resistance across the lump of sludge. The optimal retention time for rotating the screw at 1 rpm in order to treat 200 kg/hr of sewage sludge was determined empirically about 100 minutes. The corresponding optimal heat source was found to be 150,000 kcal/hr. A series of numerical calculation is performed to resolve flow characteristics in order to assist in the system design as function of important system and operational variables. The numerical calculation is successfully evaluated against experimental temperature profile and flow field characteristics. In general, the calculation results are physically reasonable and consistent in parametric study. In further studies, more quantitative data analyses such as pressure drop across the type and loading of drying sludge will be made for the system evaluation in experiment and calculation.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.2
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• pp.213-230
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• 2008

The aim of this study was to analyze the initial movement and the stress distribution of each tooth and periodontal ligament during the lingual lever-arm retraction of 6 maxillary incisors using FEA. Two kinds of finite element models were produced: 2-properties model (simple model) and 24-properties model (multi model) according to the material property assignment. The subject was an adult male of 23 years old. The DICOM images through the CT of the patient were converted into the 3D image model of a skull using the Mimics (version 10.11, Materialise's interactive Medical Image Control System, Materialise, Belgium). After series of calculating, remeshing, exporting, importing process and volume mesh process was performed, FEA models were produced. FEA models are consisted of maxilla, maxillary central incisor, lateral incisor, canine, periodontal ligaments and lingual traction arm. The boundary conditions fixed the movements of posterior, sagittal and upper part of the model to the directions of X, Y, Z axis respectively. The model was set to be symmetrical to X axis. Through the center of resistance of maxilla complex, a retraction force of 200g was applied horizontally to the occlusal plane. Under this conditions, the initial movements and stress distributions were evaluated by 3D FEA. In the result, the amount of posterior movement was larger in the multi model than in the simple model as well as the amount of vertically rotation. The pattern of the posterior movement in the central incisors and lateral incisors was controlled tipping movement, and the amount was larger than in the canine. But the amount of root movement of the canine was larger than others. The incisor rotated downwardly and the canines upwardly around contact points of lateral incisor and canine in the both models. The values of stress are similar in the both simple and multi model.

• Journal of Korea Soil Environment Society
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• v.4 no.1
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• pp.109-118
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• 1999

Recently, transport parameters of conservative solutes such as KCl in a porous medium have been successfully determined using time domain reflectometry (TDR) . This study was initiated to Investigate the applicability of TDR technique to monitoring the fate of a heavy metal ion in a sandy soil and the distribution of its concentration along travel distance with time. A column test was conducted in a laboratory that consists of monitoring both resident and flux concentrations of $ZnCl_2$in a sandy soil under a breakthrough condition. A tracer of $ZnCl_2$(10 g/L) was injected onto the top surface of the sample as pulse type as soon as a steady-state condition was achieved. Time-series measurements of resistance and electrical conductivity were performed at 10 cm and 20 cm of distances from the inlet boundary by horizontal-positioning of parallel TDR metallic rods and using an EC-meter for the effluent exiting the bottom boundary respectively. In addition. Zn ions of the effluent were analyzed by ICP-AES. Since the mode and position of concentration detected by TDR and effluent were different, comparison between ICP analysis and TDR-detected concentration was made by predicting flux concentration using CDE model accommodating a decay constant with the transport parameters obtained from the resident concentrations. The experimental results showed that the resident concentration resulted in earlier and higher peak than the flux concentration obtained by EC-meter, implying the homogeneity of the packed sandy soil. A close agreement was found between the predicted from the transport parameters obtained by TDR and the measured $ZnCl_2$concentration. This indicates that TDR technique can also be applied to monitoring heavy metal concentrations in the soil once that a decay constant is obtained for a given soil.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.3
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• pp.440-447
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• 2009

This study was performed to compare the wear resistance of sealant and flowable resins for analyzing the effect of flowable resin as a sealant in preventive resin restorations. Specimens were made and Vicker's hardness number and surface roughness were measured. SEM observations of the polished and abraded surfaces were established. Kruskal-Wallis rank test and Mann-Whitney U test at the significant level of ${\alpha}$=0.05 were used. The following results were obtained: 1. The microhardness was decreased among groups in following order: Z350 (3M ESPE, U.S.A), Estelite (Tokuyama Dental, Japan) and Ultraseal (Ultradent, U.S.A). There were significant differences in all groups (p<0.0001). 2. The surface roughness was decreased among groups in following order: Ultraseal XT plus, Palfique Estelite LV and Filtek Z350 flowable. However, there is no statistically significant differences in roughness among Estellite, Z350 and Ultraseal at the significance level of ${\alpha}$=0.05, with p=0.116 3. SEM observation of the unworn and worn surfaces revealed the qualitative differences in the wear appearance among groups. The results in this study indicate that flowable resin is better than sealant in aspect of physical properties.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.4
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• pp.241-248
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• 1993

An experiment was conducted in 1990~1991 to study the effects of various soil amelioration on the soil productivity and machine workability at tidal land paddy field of Kyewhado Substation, Homam Crop Experiment Station. The soil, Munpo Series(fine sandy loam, Typic Fluvaquents) was treated with gipsum, rice straw, rice straw compost and foreign soil(at 20cm depth) after deep ploughing. The results are surmerized as follows. 1. Sand and clay were slightly increased, while silt was slightly decreased in the rice straw and compost plots. The soil texture was changed from loam to sand loam by the addition of foreign soil 2. Soil bulk density and porosity was decreased in the rice straw, compost and foreign soil addition plots. 3. Cone penetration resistance was $12.5kg/cm^2$ at 10cm of soil depth before experiment and $12.5kg/cm^2$ at 20cm of soil depth after experiment except control, and the root zone was expended down to 20cm. 4. Soil salt content before experiment was 0.46 and 0.48% for surface soil(10cm) and subsoil(20cm), respectively ; The salt content of ameliorated plot was 0.26~0.32% and 0.16~0.31%, respectively, indicating good leaching of soil salt by the soil improvements. 5. The yields of rice in different treatments were in the order of the foreign soil addition > compost > gypsum > rice straw > control.

• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.651-662
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• 2022

The electrochemical impedance spectroscopy(EIS) method was used to evaluate the concrete deterioration process related to chloride-induced steel corrosion with various corrosion levels(initiation, rust propagation and acceleration periods). The impressed current technique, with four total current levels of 0C, 13C, 65C and 130C, was used to accelerate steel corrosion in concrete cylinder samples with w/c ratio of 0.4, 0.5, and 0.6, immersed in a 0.5M NaCl solution. A series of EIS measurements was performed to monitor concrete deterioration during the accelerated corrosion test in this study. Some critical parameters of the equivalent circuit were obtained through the EIS analysis. It was observed that the charge transfer resistance(R_c) dropped sharply as the impressed current increased from 0C to 13C, indicating a value of approximately 10kΩcm². However, the sensitivity of R_c significantly decreased when the impressed current was further increased from 13C to 130C after corrosion of steel had been initiated. Meanwhile, the double-layer capacitance value(C_dl) linearly increased from 50×10^-6μF/cm² to 250×10^-6μF/cm² as the impressed current in creased from 0C to 130C. The results in this study showed that monitoring C_dl is an effective measurement parameter for evaluating the progress of internal concrete damages(de-bonding between steel and concrete, micro-cracks, and surface-breaking cracks) induced by steel corrosion. The findings of this study provide a fundamental basis for developing an embedded sensor and signal interpretation method for monitoring concrete deterioration due to steel corrosion at various corrosion levels.