• Steel and Composite Structures
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• v.49 no.1
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• pp.81-89
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• 2023

A simplified calculation method of natural vibration characteristics of high-speed railway multi-span bridge-longitudinal ballastless track system is proposed. The rail, track slab, base slab, main beam, bearing, pier, cap and pile foundation are taken into account, and the multi-span longitudinal ballastless track-beam-bearing-pier-cap-pile foundation integrated model (MBTIM) is established. The energy equation of each component of the MBTIM based on Timoshenko beam theory is constructed. Using the improved Fourier series, and the Rayleigh-Ritz method and Hamilton principle are combined to obtain the extremum of the total energy function. The simplified calculation formula of the natural vibration frequency of the MBTIM under the influence of vertical and longitudinal vibration is derived and verified by numerical methods. The influence law of the natural vibration frequency of the MBTIM is analyzed considering and not considering the participation of each component of the MBTIM, the damage of the track interlayer component and the stiffness change of each layer component. The results show that the error between the calculation results of the formula and the numerical method in this paper is less than 3%, which verifies the correctness of the method in this paper. The high-order frequency of the MBTIM is significantly affected considering the track, bridge pier, pile soil and pile cap, while considering the influence of pile cap on the low-order and high-order frequency of the MBTIM is large. The influence of component damage such as void beneath slab, mortar debonding and fastener failure on each order frequency of the MBTIM is basically the same, and the influence of component damage less than 10m on the first fourteen order frequency of the MBTIM is small. The bending stiffness of track slab and rail has no obvious influence on the natural frequency of the MBTIM, and the bending stiffness of main beam has influence on the natural frequency of the MBTIM. The bending stiffness of pier and base slab only has obvious influence on the high-order frequency of the MBTIM. The natural vibration characteristics of the MBTIM play an important guiding role in the safety analysis of high-speed train running, the damage detection of track-bridge structure and the seismic design of railway bridge.

• Journal of Practical Engineering Education
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• v.15 no.1
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• pp.73-80
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• 2023

The advancement of online technology in the 21st century has increased online courses and web-based communication in higher education. This type of education is not limited by time or location and has made it possible to expand university campuses globally and broaden the reach of university education to the general public and students from other universities. Changes such as a decrease in the school-age population and a reorganization of the university structure have also created an opportunity to change the perception of online education. In this paper, we conducted surveys on K University students, high school seniors, and the general public to assess their satisfaction with online courses, identify areas that require massive online courses, and determine students' needs for the operation of massive online courses. The survey showed that K University students are generally satisfied with online courses. However, improvements are needed to ensure a smooth online course-taking environment, increase system uniformity, and enhance the overall online course environment. High school students have a strong preference for natural science and should be offered online courses in subjects such as mathematics and physics as prerequisites to prepare for their major classes. The general public prefers the humanities, which is evident in the purpose of the liberal arts lectures.

• Journal of the Korea Institute of Construction Safety
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• v.6 no.1
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• pp.12-18
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• 2024

High-rise, large-scale, and diversification of buildings are possible, and the reduction of concrete cross-sections reduces the weight of the structure, thereby increasing or decreasing the height of the floor, securing a large number of floors at the same height, securing a large effective space, and reducing the amount of materials, rebar, and concrete used for designating the foundation floor. In terms of site construction and quality, a low water binder ratio can reduce the occurrence of dry shrinkage and minimize bleeding on the concrete surface. It has the advantage of securing self-fulfilling properties by improving fluidity by using high-performance sensitizers, making it easier to construct the site, and shortening the mold removal period by expressing early strength of concrete. In particular, with the rapid development of concrete-related construction technology in recent years, the application of ultra-high-strength concrete with a design standard strength of 100 MPa or higher is expanding in high-rise buildings. However, although high-rise buildings with more than 120 stories have recently been ordered or scheduled in Korea, the research results of developing ultra-high-strength concrete with more than 130 MPa class considering field applicability and testing and evaluating the actual applicability in the field are insufficient. In this study, in order to confirm the applicability of ultra-high-strength concrete in the field, a preliminary experiment for the member of a reduced simulation was conducted to find the optimal mixing ratio studied through various indoor basic experiments. After that, 130 MPa-class ultra-high-strength concrete was produced in a ready-mixed concrete factory in a mock member similar to the life size, and the flow characteristics, strength characteristics, and hydration heat of concrete were experimentally studied through on-site pump pressing.

• Journal of the Korean Institute of Landscape Architecture
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• v.52 no.3
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• pp.33-45
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• 2024

The government is promoting the reorganization of the construction indusrty under the theme of reorganizing the production system. However, it has been pointed out that this is contrary to the increasingly specialized and technical skills of the landscaping field. Therefore, it is urgent to respond to the construction industry integration policy and improve an appropriate work system and the content of the landscape field. Therefore, this study investigated the intention of the industry to reorganize the production system and the production structure of the landscape field, so that it can be used as a reference for future changes. As a result of the survey, 1) the perception of the reorganization policy is a highly requesting step-by-step promotion that reflects the industry's will, 2) the system is divided into generalization and specialization and is highly opposed to integration, 3) appropriate design and construction costs are the most important directions for improving landscape construction projects, and 4) reestablishing the relationship with related civil engineering works is important for improving detailed construction types. Overall, it was pointed out that the current specialized landscape construction does not sufficiently reflect the changing landscape business and is only appropriate for subcontractors in other industries. Therefore, it is necessary to promote policies that reflect this. In the long run, it is urgent to establish the status of landscape construction as an independent object, and it is necessary to supplement the legal system and change the industry accordingly.

• Journal of the Economic Geographical Society of Korea
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• v.27 no.1
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• pp.38-52
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• 2024

Digital transformation industry contributes to the improvement of productivity in overall industrial production, the smart green industry for carbon neutrality and sustainable growth is growing as a future industry. The purpose of this paper is to explore the status and role of the industry in the future industry innovation ecosystem through the analysis of the growth drivers and location pattern changes of the smart green industry. The industry is on the rise in both metropolitan and non-metropolitan areas, and the growth of the industry can be seen in non-metropolitan and non-urban areas. In particular, due to the smart green industrial complex pilot project, the creation of Gwangju Jeonnam Innovation City, and the promotion of new and renewable energy policies, the emergence of core aggregation areas (HH type) in the coastal areas of Honam and Chungcheongnam-do, and the formation of isolated centers (HL type) in the Gyeongsang region, new and renewable energy production companies are being accumulated in non-metropolitan areas. Therefore, the smart green industry is expected to promote the formation of various specialized spokes in non-urban areas in the future industrial innovation ecosystem that forms a multipolar hub-spoke network structure, where policy factors are the triggers for growth.

• Journal of the Society of Disaster Information
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• v.20 no.1
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• pp.20-31
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• 2024

Purpose: Research and development of high-strength concrete enables high-rise buildings and reduces the self-weight of the structure by reducing the cross-section, thereby reducing the thickness of beams and slabs to build more floors. A large effective space can be secured and the amount of reinforcement and concrete used to designate the base surface can be reduced. Method: In terms of field construction and quality, the effect of reducing the occurrence of drying shrinkage can be confirmed by studying the combination of low water bonding ratio and minimizing bleeding on the concrete surface. Result: The ease of site construction was confirmed due to the high self-charging property due to the increased fluidity by using high-performance water reducing agents, and the advantage of shortening the time to remove the formwork by expressing the early strength of concrete was confirmed. These experimental results show that the field application of ultra-high-strength concrete with a design standard strength of 100 MPa or higher can be expanded in high-rise buildings. Through this study, we experimented and evaluated whether ultra-high-strength concrete with a strength of 130 MPa or higher, considering the applicability of high-rise buildings with more than 120 floors in Korea, could be applied in the field. Conclusion: This study found the optimal mixing ratio studied by various methods of indoor basic experiments to confirm the applicability of ultra-high strength, produced 130MPa ultra-high strength concrete at a ready-mixed concrete factory similar to the real size, and tested the applicability of concrete to the fluidity and strength expression and hydration heat.

• Magazine of the Korean Society of Agricultural Engineers
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• v.7 no.1
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• pp.861-876
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• 1965

During my stay in the Netherlands, I have studied the following, primarily in relation to the Mokpo Yong-san project which had been studied by the NEDECO for a feasibility report. 1. Unit hydrograph at Naju There are many ways to make unit hydrograph, but I want explain here to make unit hydrograph from the- actual run of curve at Naju. A discharge curve made from one rain storm depends on rainfall intensity per houre After finriing hydrograph every two hours, we will get two-hour unit hydrograph to devide each ordinate of the two-hour hydrograph by the rainfall intensity. I have used one storm from June 24 to June 26, 1963, recording a rainfall intensity of average 9. 4 mm per hour for 12 hours. If several rain gage stations had already been established in the catchment area. above Naju prior to this storm, I could have gathered accurate data on rainfall intensity throughout the catchment area. As it was, I used I the automatic rain gage record of the Mokpo I moteorological station to determine the rainfall lntensity. In order. to develop the unit ~Ydrograph at Naju, I subtracted the basic flow from the total runoff flow. I also tried to keed the difference between the calculated discharge amount and the measured discharge less than 1O~ The discharge period. of an unit graph depends on the length of the catchment area. 2. Determination of sluice dimension Acoording to principles of design presently used in our country, a one-day storm with a frequency of 20 years must be discharged in 8 hours. These design criteria are not adequate, and several dams have washed out in the past years. The design of the spillway and sluice dimensions must be based on the maximun peak discharge flowing into the reservoir to avoid crop and structure damages. The total flow into the reservoir is the summation of flow described by the Mokpo hydrograph, the basic flow from all the catchment areas and the rainfall on the reservoir area. To calculate the amount of water discharged through the sluiceCper half hour), the average head during that interval must be known. This can be calculated from the known water level outside the sluiceCdetermined by the tide) and from an estimated water level inside the reservoir at the end of each time interval. The total amount of water discharged through the sluice can be calculated from this average head, the time interval and the cross-sectional area of' the sluice. From the inflow into the .reservoir and the outflow through the sluice gates I calculated the change in the volume of water stored in the reservoir at half-hour intervals. From the stored volume of water and the known storage capacity of the reservoir, I was able to calculate the water level in the reservoir. The Calculated water level in the reservoir must be the same as the estimated water level. Mean stand tide will be adequate to use for determining the sluice dimension because spring tide is worse case and neap tide is best condition for the I result of the calculatio 3. Tidal computation for determination of the closure curve. During the construction of a dam, whether by building up of a succession of horizontael layers or by building in from both sides, the velocity of the water flowinii through the closing gapwill increase, because of the gradual decrease in the cross sectional area of the gap. 1 calculated the . velocities in the closing gap during flood and ebb for the first mentioned method of construction until the cross-sectional area has been reduced to about 25% of the original area, the change in tidal movement within the reservoir being negligible. Up to that point, the increase of the velocity is more or less hyperbolic. During the closing of the last 25 % of the gap, less water can flow out of the reservoir. This causes a rise of the mean water level of the reservoir. The difference in hydraulic head is then no longer negligible and must be taken into account. When, during the course of construction. the submerged weir become a free weir the critical flow occurs. The critical flow is that point, during either ebb or flood, at which the velocity reaches a maximum. When the dam is raised further. the velocity decreases because of the decrease\ulcorner in the height of the water above the weir. The calculation of the currents and velocities for a stage in the closure of the final gap is done in the following manner; Using an average tide with a neglible daily quantity, I estimated the water level on the pustream side of. the dam (inner water level). I determined the current through the gap for each hour by multiplying the storage area by the increment of the rise in water level. The velocity at a given moment can be determined from the calcalated current in m3/sec, and the cross-sectional area at that moment. At the same time from the difference between inner water level and tidal level (outer water level) the velocity can be calculated with the formula $h= \frac{V^2}{2g}$ and must be equal to the velocity detertnined from the current. If there is a difference in velocity, a new estimate of the inner water level must be made and entire procedure should be repeated. When the higher water level is equal to or more than 2/3 times the difference between the lower water level and the crest of the dam, we speak of a "free weir." The flow over the weir is then dependent upon the higher water level and not on the difference between high and low water levels. When the weir is "submerged", that is, the higher water level is less than 2/3 times the difference between the lower water and the crest of the dam, the difference between the high and low levels being decisive. The free weir normally occurs first during ebb, and is due to. the fact that mean level in the estuary is higher than the mean level of . the tide in building dams with barges the maximum velocity in the closing gap may not be more than 3m/sec. As the maximum velocities are higher than this limit we must use other construction methods in closing the gap. This can be done by dump-cars from each side or by using a cable way.e or by using a cable way.

• Korean Journal of Heritage: History & Science
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• v.55 no.3
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• pp.46-58
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• 2022

This study analyzed the documentation trend of garden components such as plants, infrastructure, unit facilities, and structures, based on 188 measurement drawings of 94 old houses in a report on the documentation of the national folklore cultural heritage. The findings are as follows. First, it was found that plants and structures continuously appeared as the subject of measurement drawings, while infrastructure was often omitted. It was confirmed that unit facilities, which are smaller than other components, were frequently excluded from the documentation subject as well due to frequent changes such as movement, loss, and expansion. Second, the level of expression in measurement drawings showed different aspects for each component. The unit facilities showed a large change over time with respect to the level of documentation, and the level of documentation was somewhat polarized, particularly toward the latter stage. This suggests that the level of documenting the drawings limited to specific facilities improved, but the overall level of drawings did not improve, such as a lack of diversification of expression techniques suitable for various unit facilities. On the other hand, it was confirmed that the level of documenting the drawings for plants, infrastructure and structures did not change to a significant degree, implying that no improvements were made to the expression of components. Third, as for the technique of detailed expression, in the case of plants, vegetation status was prepared without distinction of old or protected trees that have historical value. Above all, there was no record of the vegetation structure that could help grasp the vegetation landscape of the outer area. As for the infrastructure, there was no consistent expression technique to systematically convey topographic changes such as the height and slope of the land. In addition, since there was no subtype classification defined for unit facilities and structures, there was no subject or method of documentation. This study is meaningful in that it expanded the category of documentation, which has been concentrated on buildings in old houses, to gardens, and called attention to the need for documenting the gardens for the preservation and management of old houses as an integration of the building and outer area.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.252-260
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• 1996

In this article, we investigate into the structural changes of liposome to design its functional membranes by the synthesis of two types of liposomes, DPPC liposome and DTAB of hydrocarbon substance/DPPC liposome. The changes of membrane structures are evaluated by the CF fluorescent intensity measured above and below the phase transition temperature of the membrane, $t_c=41^{\circ}C$. CF fluorescent intensities are enhanced by the CF leakage from DPPC liposome at $45^{\circ}C$, while no changes are observed at $20^{\circ}C$. Under the same conditions, it is observed that the intensity enhanced by CF leakage from DPPC/DTAB liposome is larger than that of DPPC liposome alone, which suggests that DPPC/DTAB liposome has irregular arrangement. Under the presence of $Ca^{2+}$, Quin 2 fluorescent intensity in either DPPC liposome or DPPC/DTAB liposome is significantly increasing at $45^{\circ}C$, while almost none of the changes are observed at $20^{\circ}C$. The fluorescent intensity of DPPC liposome turns out to be larger than that of DPPC/DTAB liposome, which suggests that the DPPC/DTAB liposome is structurally more stable than the DPPC liposome. Additionally, when the analysis is done to observe changes in the shapes of membrane surfaces with ANS fluorescent, ANS fluorescent under DPPC or DPPC/DTAB liposome shows each of different appearances at $45^{\circ}C$ and $20^{\circ}C$ respectively. This result indicates that its respective membrane fluidity is changing above and below of the designated temperatures in phase transition. As to the magnitude of change of its membrane fluidity, DPPC liposome is much larger than DPPC/DTAB liposome. As far as the temperature in phase transition measured by DSC are concerned, it is $41^{\circ}C$ and $32^{\circ}C$ for DPPC and DPPC/DTAB liposome respectively, which suggests that DPPC/DTAB liposome has an irregular molecular arrangement in its structure. That is, it is summed up that DPPC/DTAB turns out to be structurally stable, even so, its structure is irregularly arranged.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.6
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• pp.327-340
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• 2017

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.