• Resources Recycling
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• v.20 no.1
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• pp.37-45
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• 2011

This study was conducted to recycle flotation tailings as non-sintered construction materials considering the economic and eco-friendly treatments. The particle size distribution( median $220\;{\mu}m$) of flotation tailings from Soon-shin mine was confirmed to be larger than that(median $140\;{\mu}m$) of tailings from Sam-kwang mine. Thus we investigated the properties of non-sintered eco-brick producted with the tailings from Sam-kwang mine and non-sintered water permeable block producted with the tailings from Soon-shin mine. Compressive strength of non-sintered water permeable block which was made with less than 25 wt% of tailings from Soon-shin mine was met with products class(over 14.70 MPa) of water permeable concrete(EL 245) from KEITL. Meanwhile, the coefficient of its permeability wasn't met with the products class( over $1.0{\times}10^{-2}\;cm/sec$). The properties of non-sintered eco-brick with less than 40 wt% of tailings from Sam-kwang mine were satisfied with third class in sintered clay brick products standard(KS L 4201). The non-sintered eco-brick as a result of leaching test on heavy metals by KSLT was verified to be environmentally stabile.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.103-116
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• 2008

In this study, in-situ testing method, Dynamic Cone Penetration Test(DCPT) was presented to establish a new compaction control criteria with using mechanical property like elastic modulus instead of unit weight for field compaction control. Soil chamber tests and in-situ tests were carried out to confirm DCPT tests can predict the designed elastic modulus after field compaction, and correlation analysis among the DCPT, CBR and resilient modulus of sub grade were performed. Also, DCPT test spacing criteria in the construction site was proposed from the literature review. In the result of laboratory tests, Livneh's equation was the best in correlation between PR of DCPT and CBR, George and Pradesh's equation was the best in the predicted resilient modulus. In the resilient modulus using FWD, Gudishala's equation estimates little larger than predicted resilient modulus and Chen's equation estimates little smaller. And KICT's equation estimates the modulus smaller than predicted resilient modulus. But using the results of laboratory resilient modulus tests considering the deviatoric and confining stress from the moving vehicle, the KICT's equation was the best. In the results of In-situ DCPT tests, the variation of PR can occur according to size distribution of penetrate points. So DCPT test spacing was proposed to reduce the difference of PR. Also it was shows that average PR was different according to subgrade materials although the subgrade was satisfied the degree of compaction. Especially large sized materials show smaller PR, and it is also found that field water contents have influence a lot of degree of compaction but a little on the average PR of the DCPT tests.

• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.5
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• pp.28-39
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• 2015

The purpose of this study is to analyze users' behavior and facility satisfaction and to suggest the practical solution plans for environmental improvement of trails in Suseong recreation park in Daegu. Therefore, satisfaction factor analysis on trails was carried out based on a field and questionnaire survey in Suseong recreation park. First, from users' behavior, 48% of users visited Suseong recreation park for walking. The greatest response to number of visits was once or twice a week, and average use time per visit was 80.4 minutes. In terms of trails, the greater responses to the number of visits were once(38.1%) or more than 5 times(23.8%), and average use time was 45.4 minutes. According to the results from the analysis of facility satisfaction, management condition, length, slope, and adjacent natural landscape of trails were evaluated at a satisfaction rate higher than 3.4 points. However, water pollution, and number of exits and parking lots were analyzed at a low rate of 2.75 and 2.78 points, respectively. In terms of analyzing determining factors of facility satisfaction for trails, use of facilities, walking convenience, surrounding landscapes, amenities, and noise had a significantly positive effect on satisfaction. In particular, walking convenience was the highest effect factor; its standardized coefficient was 0.533. The findings from this study can contribute to the improvement of the physical environment for trails of Suseong recreation park and provide basic data for plan and maintenance of similar waterside trails.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.767-774
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• 2006

This study has focused on the possibility for recycling of tailings from the sangdong tungsten mine as powder (TA) of self-compacting concrete (SCC). The experimental tests for entrapped water ratio were carried out in accordance with the specified method by Okamura. The rheological measurements of cement paste were conducted by using a commercially digital Brookfield viscometer (Model LVDV-II+) equipped with cylindrical spindles, also tests for slump-flow, time required to reach 500 mm of slump flow (sec), time required to flow through V-funnel (sec) and filling height of U-box test (mm) were carried out in accordance with the specified by the Japanese Society of Civil Engineering (JSCE). The results of this study, entrapped water ratio was decreased with increasing replacement of TA. Thickness of pseudo water film was increased, and mean plastic viscosity was decreased with increasing replacement of TA. And slump-flow of SCC was decreased with increasing replacement of TA. But time required to reach 500 mm of slump flow (sec), time required to flow through V-funnel (sec) and filling height of U-box test (mm) were satisfied a prescribed range. The mechanical properties including compressive strength, splitting tensile strength and elastic modulus were checked with the requirements specified by Korean Industrial Standard (KS). The compressive strength of SCC was decreased with increasing replacement of TA, splitting tensile strength and elastic modulus were similar to those of normal concrete.

• Journal of the Korean Institute of Landscape Architecture
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• v.39 no.6
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• pp.67-75
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• 2011

This study was carried out to investigate the changes in citizen satisfaction with parks and green spaces in Daegu. Three surveys were conducted using the same measurement tools in 1986, 2001, and 2010. Major results are as follows: 1. The overall satisfaction level with parks and green spaces increased remarkably over the last25years. Satisfaction levels with city spaces overall were higher than that of nearby surrounding areas. 2. Diversity of green spaces was the most distinguished indicator in increasing level of satisfaction while the management level of green space facilities showed the lowest improvement. 3. The factor analysis for individual variables for satisfaction resulted in two factors: functions and physical conditions were categorized as one factor, and indicators for the planning of green spaces were the other. Using a regression model, the major variables found for satisfaction were diversity, management level of woods, quantitative level, function of static recreation, and management level of facilities, respectively. 4. Regarding satisfaction level by the type of green spaces, green spaces by streets showed a remarkable increase while green spaces in industrial areas showed the lowest improvement. A factor analysis for each type of green space resulted in 3 factors: green spaces of urban parks, green spaces of urban recreational facilities, and green spaces of each district including residential areas and industrial areas.

• Nuclear Engineering and Technology
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• v.26 no.3
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• pp.345-354
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• 1994

Numerical Predictions including secondary flows have been Performed for fully developed turbulent single-phase rod bundle flows. The k-$\varepsilon$ turbulence model(two equation model) for the isotropic eddy viscosity, together with an algebraic stress model for generating secondary velocities, enabled the prediction of mean axial velocities, secondary velocities, and turbulent kinetic energy and turbulent stresses. Comparisons with experiment hate shown that the influence of secondary motion on mean flow and turbulence is dearly evident. The convective transport effects of secondary flow on the velocity field have been identified.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.775-786
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• 1992

Studies are made of the turbulent separation bubble in a two-dimensional semi-infinite blunt plate aligned to a uniform free stream when the oncoming free stream contains a pulsating component. The discrete-vortex method is applied to simulate this flow situations because this approach is effective to represent the unsteady motions of turbulent shear layer and the effect of viscosity near the solid surface. The two key external paramenters in the free stream, i.e., the amplitude of pulsation, A, and the frequency parameter St[=fH/ $U_{1}$], are dealt with in the present numerical computations, A particular frequency gives a minimum reattachment which is related to the drag reduction and the most effective frequency is dependent on the most amplified shedding frequency. The turbulent flow structure is scrutinized. A comparison between the unperturbed flow and the perturbed at the particular frequency of the minimum reattachment length of the separation bubble suggests that the large-scale structure is associated with the shedding frequency and the flow instabilities.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.441-448
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• 2012

This paper proposes a multiband Multi-Input Multi-output(MIMO) antenna for universal serial bus(USB) dongle application. The proposed MIMO antenna consists of a modified meander strip line and inverted L stub. The two radiating elements of the MIMO antenna are symmetrically placed with respect to the center of the ground plane. The fabricated antenna satisfied a VSWR below 3 and an efficiency over 35 % in the LTE band 13, 17(704 MHz-787 MHz), DCS/PCS/WCDMA band(1.71 GHz-2.17 GHz), and LTE band 7(2.5 GHz-2.7 GHz). The envelope correlation coefficient(ECC) has below 0.45 in the LTE band 13, 17 and 0.1 in the DCS/PCS/WCDMA band and LTE band 7, respectively.

• Journal of Radiation Protection and Research
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• v.23 no.2
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• pp.65-74
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• 1998

One of the important things in low level radioactivity measurement is determination of the optimized counting time. Counting strategy has to be established, in order to count the radioactivity of the sample by condition of optimized measurement. There were three kinds of counting strategies in this report ; about fixed time, about fixed count, to compared sample, background, and reference level. The best of them was satisfied rendition to give about condition of instrument and process, as an example, efficiency of detector, counter capacity, maximum and average background count rate of counter, reference level and limit of derision and detection, etc. Therefore, we can decide the optimized counting time in the screening and monitoring. And we can save the time for courting the sample of course the data of count will be counted by optimized accuracy finally, in rountine measurement of radioactivity these strategies will be used available.

• The Journal of the Convergence on Culture Technology
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• v.7 no.1
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• pp.194-201
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• 2021

The purpose of this study was to investigate the effect of perceived stress, self esteem, and major satisfaction on test anxiety in nursing students and to provide the basic data of to control test anxiety. Data were collected from 251 nursing students in B city and analyzed by t-test, ANOVA, Pearson correlation coefficient, and multiple regression using SPSS/WIN 22.0. The degree of test anxiety in nursing students was 2.97±.54. There were significant differences in test anxiety with respect to gender(F=-3.241, p=.001), college life satisfaction(F=5.682, p=.004). There was positive correlation between test anxiety and perceived stress(r=.361, p<.001), negative correlation were found between test anxiety and self esteem(r=-.186, p=.003). The factors affecting the test anxiety of the study subjects were perceived stress(β=.325, p<.001), gender(β=-.150, p=.013), with an explanatory power of 14%. Through this research can be used as basic data by identifying factors affecting test anxiety of nursing students.