• 제목/요약/키워드: 모형실험

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Experimental Design of Column Flotation for Recovery of High Grade Molybdenite (고품위 몰리브덴 회수를 위한 컬럼부선 요인설계)

  • Hyun Soo Kim;Purev Oyunbileg;Chul-Hyun Park
    • Resources Recycling
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    • v.32 no.6
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    • pp.34-44
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    • 2023
  • In this work, column flotation using factorial design was performed for recovering high-grade molybdenite concentrate. First, the flotation concentrate from Samyang Mining Plant was regrinded to a mean size of 165, 116, 46.7, and 38.4 ㎛ for an increase of the liberation degree. Tests were carried out for various variables affecting column flotation, and then the concentrates with molybdenite grade and recovery of 98.3 % and 95.28 % were obtained, respectively. Also, regression was performed using the statistical analysis program (SPSS 25) with the factorial design and experimental data on particle size, flow wash-water velocity and depressant that affect high grade. From the results, a model equation was derived to predict the molybdenite grade (MG) and recovery (MR) with the relationship between column flotation variables. Factors such as depressant concentration + wash-water velocity and particle size + depressant concentration + wash-water velocity were smaller than the significance level (0.05) and had a significant effect on the dependent variable, grade, and in the recovery model, only particle size and wash-water velocity factors affected the dependent variable, recovery.

Effects of Health Care Nursing Policy Education on Nursing Students' Political Efficacy, Political Participation, and Political Interest (보건의료 간호정책 교육이 간호대학생의 정치효능감, 정치참여 및 정치 관심도에 미치는 효과)

  • MinJi Kim;Kyeng-Jin Kim
    • Journal of Industrial Convergence
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    • v.21 no.11
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    • pp.125-134
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    • 2023
  • This study attemped to examine the effects of health care nursing policy education on nursing students' political efficacy, political participation, and political interest. It attempted to guide the direction of policy education within nursing curriculum. The subjects consisted of 89 nursing students of G-university from March 8, 2023, to June 21, 2023, including 44 in the experimental group and 45 in the control group. The health care nursing policy class was developed using the ADDIE(Analysis, Design, Development, Implementation, Evaluation) model of instructional design. Data analysis used the SPSS 25.0 program through mean, standard deviation, and independent sample t-test. The experimental group that participated in this education showed statistically significant improvement in political efficacy(t=2.34, p<.05) and intrinsic political efficacy(t=2.75, p<.05), as well as passive political participation score(t=2.22, p<.05) compared to before the intervention. Based on the findings of this study, it is suggested that health care nursing policy education should be structured to enhance external political efficacy and promote active political participation in future nursing curriculum.

Correlation Between the Headphone's Acoustical Characteristics and Subjective Preferences (헤드폰의 음향적 특성과 주관적 선호도간의 상관 관계)

  • Lee, Ki-Seung;Lee, Seok-Pil
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.2
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    • pp.96-106
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    • 2009
  • In this paper, correlation between the headphone's acoustical characteristics and the subjective preferences is analyzed, and a possibility of predicting the subjective preferences using the acoustical characteristics is investigated, The headphone's acoustical characteristics include the total harmonic distortions, the variation of the frequency response which were measured by separate channel and the inter-aural correlation coefficients, Those characteristics were measured in a noise-free anechoic chamber, using a head and torso simulator, The subjective preferences were scored in terms of loudness, clearness, spaciousness, fullness and overall impression, In the subjective listening test, 12 subjects were participated who have plentiful listening experiences, The programs include 5 kinds of musics; korean popular song, pop song, light music, male-voice and classic, The 8 models of the headphones were employed, including 4 closed-type circumaural headphones, 2 open-type supraaural headphones and 2 intra-concha headphones, A significant test was carred on the results from the subjective test, using a two-way ANOVA test, The correlation coefficients between the acoustical parameters and the subjective preferences were computed, Experimental results showed that the variation of the magnitude of frequency response measured from a right channel revealed higher correlation with the subjective preferences. Whereas the inter-aural correlation coefficients have very low correlation coefficients.

Experimental study on structural integrity assessment of utility tunnels using coupled pulse-impact echo method (결합된 초음파-충격 반향 기법 기반의 일반 지하구 구조체의 건전도 평가에 관한 실험적 연구)

  • Jin Kim;Jeong-Uk Bang;Seungbo Shim;Gye-Chun Cho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.25 no.6
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    • pp.479-493
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    • 2023
  • The need for safety management has arisen due to the increasing number of years of operated underground structures, such as tunnels and utility tunnels, and accidents caused by those aging infrastructures. However, in the case of privately managed underground utility ducts, there is a lack of detailed guidelines for facility safety and maintenance, resulting in inadequate safety management. Furthermore, the absence of basic design information and the limited space for safety assessments make applying currently used non-destructive testing methods challenging. Therefore, this study suggests non-destructive inspection methods using ultrasonic and impact-echo techniques to assess the quality of underground structures. Thickness, presence of rebars, depth of rebars, and the presence and depth of internal defects are assessed to provide fundamental data for the safety assessment of box-type general underground structures. To validate the proposed methodology, different conditions of concrete specimens are designed and cured to simulate actual field conditions. Applying ultrasonic and impact signals and collecting data through multi-channel accelerometers determine the thickness of the simulated specimens, the depth of embedded rebar, and the extent of defects. The predicted results are well agreed upon compared with actual measurements. The proposed methodology is expected to contribute to developing safety diagnostic methods applicable to general underground structures in practical field conditions.

Development and Performance Evaluation of an Animal SPECT System Using Philips ARGUS Gamma Camera and Pinhole Collimator (Philips ARGUS 감마카메라와 바늘구멍조준기를 이용한 소동물 SPECT 시스템의 개발 및 성능 평가)

  • Kim, Joong-Hyun;Lee, Jae-Sung;Kim, Jin-Su;Lee, Byeong-Il;Kim, Soo-Mee;Choung, In-Soon;Kim, Yu-Kyeong;Lee, Won-Woo;Kim, Sang-Eun;Chung, June-Key;Lee, Myung-Chul;Lee, Dong-Soo
    • The Korean Journal of Nuclear Medicine
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    • v.39 no.6
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    • pp.445-455
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    • 2005
  • Purpose: We developed an animal SPECT system using clinical Philips ARGUS scintillation camera and pinhole collimator with specially manufactured small apertures. In this study, we evaluated the physical characteristics of this system and biological feasibility for animal experiments. Materials and Methods: Rotating station for small animals using a step motor and operating software were developed. Pinhole inserts with small apertures (diameter of 0.5, 1.0, and 2.0 mm) were manufactured and physical parameters including planar spatial resolution and sensitivity and reconstructed resolution were measured for some apertures. In order to measure the size of the usable field of view according to the distance from the focal point, manufactured multiple line sources separated with the same distance were scanned and numbers of lines within the field of view were counted. Using a Tc-99m line source with 0.5 mm diameter and 12 mm length placed in the exact center of field of view, planar spatial resolution according to the distance was measured. Calibration factor to obtain FWHM values in 'mm' unit was calculated from the planar image of two separated line sources. Te-99m point source with i mm diameter was used for the measurement of system sensitivity. In addition, SPECT data of micro phantom with cold and hot line inserts and rat brain after intravenous injection of [I-123]FP-CIT were acquired and reconstructed using filtered back protection reconstruction algorithm for pinhole collimator. Results: Size of usable field of view was proportional to the distance from the focal point and their relationship could be fitted into a linear equation (y=1.4x+0.5, x: distance). System sensitivity and planar spatial resolution at 3 cm measured using 1.0 mm aperture was 71 cps/MBq and 1.24 mm, respectively. In the SPECT image of rat brain with [I-123]FP-CIT acquired using 1.0 mm aperture, the distribution of dopamine transporter in the striatum was well identified in each hemisphere. Conclusion: We verified that this new animal SPECT system with the Phlilps ARGUS scanner and small apertures had sufficient performance for small animal imaging.

Characteristics of Wheat Flour Dough and Noodles with Amylopectin Content and Hydrocolloids (아밀로펙틴 함량 변화와 하이드로콜로이드 첨가에 의한 밀가루 반죽 및 국수의 특성)

  • Cho, Young-Hwa;Shim, Jae-Yong;Lee, Hyeon-Gyu
    • Korean Journal of Food Science and Technology
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    • v.39 no.2
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    • pp.138-145
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    • 2007
  • The effects of amylopectin and hydrocolloid (locust bean gum and guar gum) content on wheat flour dough and noodle properties were investigated. As the amount of amylopectin increased, the water absorption rate (farinograph), the tension (tension test), the gel stability (freeze-thawing treatment), and the springiness and the cohesiveness (TPA) increased, but the pasting temperature (RVA), the lightness and yellowness (color measurement), and the hardness (TPA) tended to decrease. In sensory evaluations, the scores for cohesiveness, springiness, and acceptability of cooked noodle increased as the proportion of amylopectin increased. The proper combination of amylose/amylopectin ratio and hydrocolloids improved the freeze-thaw stability and the sensory acceptability of wheat flour dough and noodle.

Prediction of Seabed Topography Change Due to Construction of Offshore Wind Power Structures in the West-Southern Sea of Korea (서남해에서 해상풍력구조물의 건설에 의한 해저지형의 변화예측)

  • Jeong, Seung Myung;Kwon, Kyung Hwan;Lee, Jong Sup;Park, Il Heum
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.31 no.6
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    • pp.423-433
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    • 2019
  • In order to predict the seabed topography change due to the construction of offshore wind power structures in the west-southern sea of Korea, field observations for tides, tidal currents, suspended sediment concentrations and seabed sediments were carried out at the same time. These data could be used for numerical simulation. In numerical experiments, the empirical constants for the suspended sediment flux were determined by the trial and error method. When a concentration distribution factor was 0.1 and a proportional constant was 0.05 in the suspended sediment equilibrium concentration formulae, the calculated suspended sediment concentrations were reasonably similar with the observed ones. Also, it was appropriate for the open boundary conditions of the suspended sediment when the south-east boundary corner was 11.0 times, the south-west was 0.5 times, the westnorth 1.0 times, the north-west was 1.0 times and the north-east was 1.0 times, respectively, using the time series of the observed suspended sediment concentrations. In this case, the depth change was smooth and not intermittent around the open boundaries. From these calibrations, the annual water depth change before and after construction of the offshore wind power structures was shown under 1 cm. The reason was that the used numerical model for the large scale grid could not reproduce a local scour phenomenon and they showed almost no significant velocity change over ± 2 cm/s because the jacket structures with small size diameter, about 1 m, were a water-permeable. Therefore, it was natural that there was a slight change on seabed topography in the study area.

A Review on Ultimate Lateral Capacity Prediction of Rigid Drilled Shafts Installed in Sand (사질토에 설치된 강성현장타설말뚝의 극한수평지지력 예측에 관한 재고)

  • Cho Nam Jun;Kulhawy F.H
    • Journal of the Korean Geotechnical Society
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    • v.21 no.2
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    • pp.113-120
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    • 2005
  • An understanding of soil-structure interaction is the key to rational and economical design for laterally loaded drilled shafts. It is very difficult to formulate the ultimate lateral capacity into a general equation because of the inherent soil nonlincarity, nonhomogeneity, and complexity enhanced by the three dimensional and asymmetric nature of the problem though extensive research works on the behavior of deep foundations subjected to lateral loads have been conducted for several decades. This study reviews the four most well known methods (i.e., Reese, Broms, Hansen, and Davidson) among many design methods according to the specific site conditions, the drilled shaft geometric characteristics (D/B ratios), and the loading conditions. And the hyperbolic lateral capacities (H$_h$) interpreted by the hyperbolic transformation of the load-displacement curves obtained from model tests carried out as a part of this research have been compared with the ultimate lateral capacities (Hu) predicted by the four methods. The H$_u$ / H$_h$ ratios from Reese's and Hansen's methods are 0.966 and 1.015, respectively, which shows both the two methods yield results very close to the test results. Whereas the H$_u$ predicted by Davidson's method is larger than H$_h$ by about $30\%$, the C.0.V. of the predicted lateral capacities by Davidson is the smallest among the four. Broms' method, the simplest among the few methods, gives H$_u$ / H$_h$ : 0.896, which estimates the ultimate lateral capacity smaller than the others because some other resisting sources against lateral loading are neglected in this method. But it results in one of the most reliable methods with the smallest S.D. in predicting the ultimate lateral capacity. Conclusively, none of the four can be superior to the others in a sense of the accuracy of predicting the ultimate lateral capacity. Also, regardless of how sophisticated or complicated the calculating procedures are, the reliability in the lateral capacity predictions seems to be a different issue.

Analysis of Atmosphere-Ocean Interactions over South China Sea and its Relationship with Northeast Asian Precipitation Variability during Summer (남중국해의 여름철 대기-해양 상호작용과 동아시아 강수량의 상관성 분석)

  • Jang, Hye-Yeong;Yeh, Sang-Wook
    • Atmosphere
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    • v.23 no.3
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    • pp.283-291
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    • 2013
  • This study investigates the changes in the atmosphere-ocean interactions over the South China Sea (SCS) by analyzing their variables in the period of 1979~2011 during the boreal summer (June-July-August). It is found that a simultaneous correlation coefficient between sea surface temperature (SST) and precipitation over SCS during summer is significantly changed before and after the late-1990s. That is, the variation of precipitation over SCS is negatively (positively) correlated with the SST variations before (after) the late-1990s. Our further correlation analysis indicates that the atmospheric forcing of the SST is dominant before the late-1990s accompanying with wind-evaporation feedback and cloud-radiation feedback. After the late-1990s, in contrast, the SST forcing of the atmosphere through the latent heat flux from the ocean to the atmosphere is dominant. It is found that the change in the relationship of atmosphere-ocean interactions over SCS are associated with the changes in the relationship with Northeast Asian summer precipitation. In particular, a simultaneous correlation coefficient between the precipitation over SCS and Northeast Asia becomes stronger during after the late-1990s than before the late-1990s. We argue that the increase of the SST forcing of the atmosphere over SCS may lead a direct relationship of precipitation variations between SCS and Northeast Asia after the late-1990s.

Three dimensional analysis of tooth movement using different sizes of NiTi wire on NiTi scissors-bite corrector (NiTi scissors-bite corrector의 와이어 굵기에 따른 3차원적 치아 이동 양상)

  • Jeon, Hyun-Ju;Park, Sun-Hyung;Jung, Sang-Hyuk;Chun, Youn-Sic
    • The korean journal of orthodontics
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    • v.39 no.1
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    • pp.43-53
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    • 2009
  • Objective: The purpose of this study was to compare the difference in three dimensional tooth movement using three different wire sizes($0.018{\times}0.025-in,\;0.016{\times}0.022-in$ 0.016-in) on a NiTi scissors-bite corrector. Methods: Computed tomography(CT) images of the experimental model before and after tooth movement were taken and reconstructed into three dimensional models for superimposition. The direction and the amount of tooth movement were measured and analyzed statistically. Results: The lingual and intrusive movements of the crown of the maxillary second molar were increased as the size of the NiTi wire increased. The roots of the maxillary second metals moved buccally except for the 0.016-in group. The intrusive movement of the roots of the maxillary second molars was increased as the size of the NiTi wire increased. Due to the use of orthodontic mini-implants, anchorage loss was under 0.2 mm on average. Conclusions: The $0.018{\times}0.025-in$ NiTi wire was most effective in lingual and intrusive movement of the maxillary second molar which was in scissors-bite position. Indirect skeletal anchorage with a single orthodontic mini-implant was rigid enough to prevent anchorage loss.