• Title/Summary/Keyword: Scaled distance

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Nonlinearity effect on the dynamic behavior of the clayey basin edge

  • Hadi Khanbabazadeh
    • Geomechanics and Engineering
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    • v.36 no.4
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    • pp.367-380
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    • 2024
  • Investigations has shown that the correct estimation of the effective amplification period is as important as the amplification value itself. It gets more important in 2D basins. This study presents a quantitative coefficient for consideration of the nonlinearity effect in terms of amplification value and the shift in its period which is missing or ineffectively considered in the previous studies. To attain this goal, by the application of a time domain fully nonlinear method, the deviation of the more common equivalent linear results from the basin nonlinear behavior under strong ground motions is investigated quantitatively. Also, despite the increase in the damping ratio, the possibility of the increase in the amplification due to the increase in motion strength is shown. To make the results useful in engineering practice, by introducing nonlinearity ratio, the effect of the nonlinearity is quantitatively estimated for two soft and stiff clayey basins with three different depths under a set of motions scaled to two target spectrum. Results show that at the 100 m depth soft clayey basin, while the nonlinearity ratio shows a 35% deviation at the basin edge part under DD1 motion level, its effect moves to the central part with 20% effect under DD3 motion level. By the increase in depth to 150 m, the results show a decrease in the overall effect of the nonlinear behavior for both clay types. At this depth, the nonlinearity ratio gives a 30% and 17% difference on a limited distance from outcrop at the soft clayey basin under DD1 and DD3 motion levels, respectively. At the 30 m depth basins, the nonlinearity ratio shows up to 25% difference for different cases. The presented ratio would be introduced as nonlinearity coefficients for consideration of the nonlinearity effects in the codes. The presented quantitative margins will help the designer to have a better understanding of the amplification period change because of nonlinearity over 2D basin surface.

Effects of a new stirrup hook on the behavior of reinforced concrete beams

  • Zehra Sule Garip;Furkan Erdema
    • Structural Engineering and Mechanics
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    • v.91 no.3
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    • pp.263-277
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    • 2024
  • The primary aim of this study is to introduce an innovative configuration for stirrup hooks in reinforced concrete beams and analyze the impact of factors such as stirrup spacing, placement, and hook lengths on the structural performance of reinforced concrete beam elements. A total of 18 specimens were produced and subjected to reversed cyclic loading, with two specimens serving as reference specimens and the remaining 16 specimens utilizing a specifically developed stirrup hook configuration. The experiment used reinforced concrete beams scaled down to half their original size. These beams were built with a shear span-to-depth ratio of 3 (a/d=3). The experimental samples were divided into two distinct groups. The first group comprises nine test specimens that consider the contribution of concrete to shear strength, while the second group consists of nine test specimens that do not consider this contribution. The preparation of reference beam specimens for both groups involved the utilization of standard hooks. The stirrup hooks in the test specimens are configured with a 90-degree angle positioned at the midpoint of the bottom section of the beam. The criteria considered in this study included the distance between hooks, hook angle, stirrup spacing, hook orientation, and hook length. In the experimental group examining the contribution of concrete on shear strength, it was noted that the stirrup hooks of both the R1 reference specimen and specific test specimens displayed indications of opening. However, when the contribution of concrete on shear strength was not considered, it was observed that none of the stirrup hooks proposed in the R0 reference specimen and test specimens showed any indications of opening. Neglecting the contribution of concrete in the assessment of shear strength yielded more favorable outcomes regarding structural robustness. The study found that the strength values obtained using the suggested alternative stirrup hook were similar to those of the reference specimens. Furthermore, all the test specimens successfully achieved the desired strengths.

A survey on the EMF Levels of Study and Electric Appliances in Korea (국내 전철 및 가전제품을 대상으로 한 전자장 수준 실태조사)

  • Jang, Seong Ki;Cho, Yong Sung;Lee, Seok Jo;Yoo, Seong Wha;Jung, Kyung Mi;Lim, Jun Ho
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.15 no.1
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    • pp.71-81
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    • 2005
  • The purposes of this study was to collect, analyze, and describe the MF exposure levels from subways in Korea and to measure and evaluate the MF levels generated from electric appliances used at general homes. The target subway lines were Seoul Metropolitan Line 1 to Line 8, Bundang Line, Incheon Line, Daegu Line, Gwangju Line, and Busan Line 1 and Line 2. We measured at each station in those subway lines and, all the train types (pantograph-equipped, motor-equipped, and common), and platform types(facing and isolating) were investigated by the distance(80, 200, 400 cm) from the train on 19 targeted subway lines using 3 magnetic field measuring devices (EMDEXII, Enertech Co.) during the survey from January till October, 2004. On the other hand, the levels of the 60Hz magnetic fields generated from 14 items of home electric appliances such as electric blankets, hair dryers, electric razors, etc. were measured at 10 general homes using 5 EMDEXII meters with a sampling interval of 1.5 second by the distance(surface, 30, 50, 100, 300cm ) from the target electric appliances. The survey results in the whole subway lines examined in this study were as follows; Seoul Metropolitan Line 4 using AC(alternating current) power source showed the highest mean value of $2.85{\mu}T$, followed by Seoul Metropolitan Line 1 running between Seoul and Incheon using AC($2.78{\mu}T$), Seoul Metropolitan Line 1 between Seoul and Uijongbu using AC($2.73{\mu}T$), Bundang Line using AC($1.79{\mu}T$), Seoul Metropolitan Line 1 connected from Yongsan using AC($1.67{\mu}T$), Seoul Metropolitan Line 1 between Seoul and Suwon using AC($0.79{\mu}T$), and so on. In general, the intensity of the magnetic field in the subway systems in Korea was significantly higher when using AC($2.14{\pm}0.91{\mu}T$) than when using DC($0.29{\pm}0.44{\mu}T$) power source. Among the home electric appliances examined, microwave ovens showed the highest mean value of $7.69{\mu}T$, followed by hair dryers($6.47{\mu}T$), vacuum cleaners($5.27{\mu}T$), televisions ($2.26{\mu}T$), electric blankets($1.38{\mu}T$), personal computers ($0.81{\mu}T$), and so on. Two items of electric appliances showed the excess value of $0.2{\mu}T$ at the distance of 30cm in the MF exposure level; electric razors $1.58{\pm}2.13{\mu}T$ and vacuum cleaners $0.48{\pm}0.44{\mu}T$. As a whole, this study showed a tendency that the shift of the MF levels according to the increase of distance from the electric appliances was lower than those of the results surveyed in UK and USA. As a result, this study is expected to suggest meaningful data for the future study in exposure assessment of magnetic fields and for the establishment of guidelines for subways and electric appliances in Korea. More detailed and large scaled exposure assessment studies should be performed continuously to get the various and useful information on health risk assessment of MFs in Korea.

Evaluation of Air Ion According to the Distance in Large Flat Park - Focused on Olympic Park in Songpa-gu, Seoul - (대규모 평지형 공원 내 거리별 공기이온 평가 - 서울시 송파구 올림픽공원을 사례로 -)

  • Kim, Jeong Ho;Lee, Sang Hoon;Lee, Myung-Hun;Yoon, Yong Han
    • Korean Journal of Environment and Ecology
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    • v.34 no.5
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    • pp.491-499
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    • 2020
  • Increasing impervious surfaces can cause various physical and mental illnesses as well as further problems like deterioration of the thermal environment and disconnection of the water circulation system in the downtown area. This study is intended to suggest baseline data for the future creation or remodelation of large-scaled urban parks in consideration of human health on the aspect of climate by analyzing air ions condition and correlation analysis between air ions and meteorological elements depending on distances from the center in the urban park. The study site was divided into four types by distances from the center of Olympic Park in Songpa-gu, Seoul, then classified as A and B. After selecting 80 points to record, land coverage and vegetation status were investigated, and then meteorological elements and air ions were measured. First, the green space rate by section is A section Center (90%)> Inner (70%)> Outer-inner (10%) = Outer (10%), B section Center (100%)> Inner (60%)> Outer- In order of inner (30%)> Outer (0%). Second, for weather factors, the temperature was analyzed by Outer (24.18℃) > Outer-inner (22.90℃) > Inner (22.43℃) > Center (21.719℃). For relative humidity, center (46.49%) > Inner (43.36%) > Outer-inner (42.41%) > Outer (38.53%) was analyzed. Third, In the case of cations in the air ions, Outer(435.71ea/㎤) > Outer-inner(415.16ea/㎤) > Inner (389.46ea/㎤) > Center (352.64ea/㎤). In the case of negative ions, Center (569.72ea/㎤) > Inner (499.83ea/㎤) > Outer-inner(410.58ea/㎤) > Outer (292.02ea/㎤). It was analyzed to increase toward Center, and analyzed to decrease with increasing distance from road. For the Air ion index, it was analyzed as Center (1.67) > Inner (1.31) > Outer-inner (1.08) > Outer (0.71). Negative irons was analyzed to increase when its measuring points close to the center and decrease with shortening distance to the road. Fourth, as a result of correlation analysis, positive(+) correlation is negative ions and ion index. These were measured to increase as the recording points closing to the center of the park from the road. The negative(-) correlation is temperature, solar radiation, and positive ions. These increased as getting closer to the road.

Development of Commercial-scaled Pervaporation Hollow Fiber Membrane System for High Pressure and High Temperature Applications (고온 고압용 상업적 규모의 중공사 투과증발 막시스템 개발)

  • Yeom, Choong Kyun;Kang, Kyeong Log;Kim, Joo Yeol;Ahn, Hyo Sung;Kwon, Konho
    • Membrane Journal
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    • v.23 no.4
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    • pp.257-266
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    • 2013
  • The main purpose of this study is to develop a commercial scale of pervaporative process equipped with hollow fiber membrane modules, being able to effectually purify organic solvent at high temperature well over its boiling point under high vapor pressure. Three constituent technologies have been developed; 1) to fabricate braid-reinforced hollow fiber membrane stable in high pressure and high temperature application, 2) to design and fabricate a commercial scale of hollow fiber membrane module, and 3) to design and fabricate a pilot scale of pervaporation equipment system. The developed hollow fiber membrane possesses a membrane performance superior to the membrane of Sulzer (Germany) which is the most-well known for pervaporation process, and the membrane module equips hollow fiber membranes of $4.6m^2$ and the pervaporation system can treat organic liquid at 200 L/h, which is based on the dehydration of 95 wt% isopropyl alcohol (IPA). Since the membrane module is designed to flow in and pass through the inside of individual hollow fiber membrane, not to involve both the formation of feed's dead volume observed in flat-sheet membrane module and the channeling of feed occurring inside hollow fiber bundle which lower membrane performance seriously, it showed excellent separation efficiency. In particular, the module is inexpensive and has less heat loss into its surrounding, in compared with flat-sheet membrane module. In addition, permeant can be removed effectively from the outer surface of hollow fiber membrane because the applied vacuum is conveyed uniformly through space between fibers into respective fiber, even into one in the middle of the hollow fiber bundle in which the space between fibers is uniform in distance. Since the hollow fiber membrane pervaporation system is the first one ever developed in the world, our own unique proprietary technology can be secured, preoccupying technical superiority in export competitive challenges.

Robust Designs of the Second Order Response Surface Model in a Mixture (2차 혼합물 반응표면 모형에서의 강건한 실험 설계)

  • Lim, Yong-Bin
    • The Korean Journal of Applied Statistics
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    • v.20 no.2
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    • pp.267-280
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    • 2007
  • Various single-valued design optimality criteria such as D-, G-, and V-optimality are used often in constructing optimal experimental designs for mixture experiments in a constrained region R where lower and upper bound constraints are imposed on the ingredients proportions. Even though they are optimal in the strict sense of particular optimality criterion used, it is known that their performance is unsatisfactory with respect to the prediction capability over a constrained region. (Vining et at., 1993; Khuri et at., 1999) We assume the quadratic polynomial model as the mixture response surface model and are interested in finding efficient designs in the constrained design space for a mixture. In this paper, we make an expanded list of candidate design points by adding interior points to the extreme vertices, edge midpoints, constrained face centroids and the overall centroid. Then, we want to propose a robust design with respect to D-optimality, G-optimality, V-optimality and distance-based U-optimality. Comparing scaled prediction variance quantile plots (SPVQP) of robust designs with that of recommended designs in Khuri et al. (1999) and Vining et al. (1993) in the well-known examples of a four-component fertilizer experiment as well as McLean and Anderson's Railroad Flare Experiment, robust designs turned out to be superior to those recommended designs.

A Link-Based Label Correcting Multi-Objective Shortest Paths Algorithm in Multi-Modal Transit Networks (복합대중교통망의 링크표지갱신 다목적 경로탐색)

  • Lee, Mee-Young;Kim, Hyung-Chul;Park, Dong-Joo;Shin, Seong-Il
    • Journal of Korean Society of Transportation
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    • v.26 no.1
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    • pp.127-135
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    • 2008
  • Generally, optimum shortest path algorithms adopt single attribute objective among several attributes such as travel time, travel cost, travel fare and travel distance. On the other hand, multi-objective shortest path algorithms find the shortest paths in consideration with multi-objectives. Up to recently, the most of all researches about multi-objective shortest paths are proceeded only in single transportation mode networks. Although, there are some papers about multi-objective shortest paths with multi-modal transportation networks, they did not consider transfer problems in the optimal solution level. In particular, dynamic programming method was not dealt in multi-objective shortest path problems in multi-modal transportation networks. In this study, we propose a multi-objective shortest path algorithm including dynamic programming in order to find optimal solution in multi-modal transportation networks. That algorithm is based on two-objective node-based label correcting algorithm proposed by Skriver and Andersen in 2000 and transfer can be reflected without network expansion in this paper. In addition, we use non-dominated paths and tree sets as labels in order to improve effectiveness of searching non-dominated paths. We also classifies path finding attributes into transfer and link travel attribute in limited transit networks. Lastly, the calculation process of proposed algorithm is checked by computer programming in a small-scaled multi-modal transportation network.

High-Altitude Environment Simulation of Space Launch Vehicle in a Ground-Test Facility (지상시험장비를 통한 우주발사체 고공환경모사 기법 연구)

  • Lee, Sungmin;Oh, Bum-Seok;Kim, YoungJun;Park, Gisu
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.45 no.11
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    • pp.914-921
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    • 2017
  • The experimental research on a high-altitude environment simulation of space launch vehicle is important for securing independent technologies with launching space vehicles and completing missions. This study selected an altitude of 65 km for the experiment environment where it exceeded Mach number of 6 after the launch of Korean Space Launch Vehicle(KSLV-II). Shock tunnel was used to replicate the flight condition. After flow establishment, in order to confirm aerodynamic characteristics and normal and oblique shockwaves, the flow verification was carried out by measuring stagnation pressure and heat flux of a forebody model, and shockwave stand-off distance of a hemispherical model. In addition, a shock-free technique to recover free-stream condition has been developed and verified. From the results of the three verification tests, it was confirmed that the flow was replicated with the error of about ${\pm}3%$. The error between the slope angle of inclined shockwave of the scaled down transition section model using the shock-free shape and the slope angle of the horizontal plate model, and between the theoretical and the experimental value of the static pressure of the model were confirmed to be 2% and 1%, respectively. As a result, the efficiency of the shockwave cancellation technique has been verified.

Experimental Study of the Effect of Vibration on the Geomunoreum Lava Tube System in Jeju (제주 거문오름 용암동굴계의 진동영향에 관한 실험적 연구)

  • Song, Jae-Yong;Lee, Geun-Chun;Ahn, Ung-San;Lim, Hyun-Muk;Seo, Yong-Seok
    • The Journal of Engineering Geology
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    • v.30 no.3
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    • pp.327-345
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    • 2020
  • The effects of ground vibration on lava tubes during construction were studied to aid design of management and preservation measures for lava tubes. Ground conditions were assessed by RMR (Rock mass rating) and Q-system classifications for the Geomunoreum lava tubes, and vibration velocity was measured during in situ blasting tests in the Manjanggul and Yongcheondonggul lava tubes. Results indicate that the higher the rock quality, the greater the effect of vibration, although there is no clear linear relationship due to ground heterogeneity. A relationship derived between vibration velocity (PPV) and intensity (dB(V)) on the basis of blasting tests indicates that a vibration level of < 0.285 cm/sec meets the regulatory limit of 0.371 cm/sec and 65 dB(V) during daytime, and 0.285 cm/sec and 60 dB(V) during night. For blasting vibrations, square- and cube-root scaled distances are linearly correlated, with R2 ≥ 0.76. On the basis of this correlation, explosive-charge weights meeting the 0.2 cm/sec vibration criterion for cultural heritage were estimated to be 2.88 kg at 50 m distance, and 11.52 kg at 100 m.

Parents' concern for child oral health (부모의 자녀에 대한 구강건강 관심도 조사)

  • Kim, Kyung-Seon;Kim, Sun-Ju;Kim, Chang-Hee
    • Journal of Korean society of Dental Hygiene
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    • v.7 no.4
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    • pp.405-418
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    • 2007
  • The purpose of this study was to examine the interest level of mothers in oral health. The subjects in this study were 184 mothers whose children attended daycare centers in the city of K. A survey was conducted from March 15 through April 30, 2007, and SPSS WIN 11.5 program was employed to analyze their answer sheets. The findings of the study were as follows: 1. A group of mothers whose children brushed their teeth three times a day on the average made up 55.7 percent of those who were at the age of 35 and under. Among the mothers having three or more children, those mothers accounted for 59.1 percent. The daily mean toothbrushing frequency of children was higher among the better-educated mothers. 2. Concerning dietary and oral guidance, the mothers whose academic background was better curbed their children's excessive sugar intake more often, and the gap between them and the others was statistically significant(pE.05). As to the importance of oral health by the number of child and academic credential, those who had two children(36.0%) taught them the importance of oral health frequently(pE.01), and the better-educated mothers taught about it often(pE.05). The gap between the groups and the others was significant. 3. As for experience of visiting dental institutions, the working mothers visited dental institutions more often than the stay-at-home mothers, and the gap between them was statistically significant(pE.05). Regarding purpose of the visit, the largest group aimed to get treatment(64.6%), followed by having a dental checkup(14.6%) and receiving preventive treatment(13.5%). As to any inconveniences in using dental institutions, those who were working and who were in the upper income bracket found it more inconvenient to do that because of a long distance or time constraints. The gap between them and the others was significant. 4. In regard to concern for dental care, the mothers who were better educated(pE.001) and whose family income was 3 million won or more had their teeth scaled more often, and the gap between them and the others was statistically significant(pE.01). The rate of the regular visitors of dental institutions stood at 32.7 percent of the junior-college graduates, 31.0 percent of the mothers receiving college or higher education and 10.1 percent of the high-school graduates(pE.01). And those who earned larger income paid a visit to dental institutions more often and on a regular basis. The gap between them and the others was statistically significant(pE.05).

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