• Title/Summary/Keyword: impact tests

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The Impact of Argument-Based Inquiry Approach on Elementary School Students' Critical Thinking in Elementary School Science Class (초등학교 과학수업에서 논의기반 탐구수업이 초등학생의 비판적 사고에 미치는 영향)

  • Jiaeng Park;Jeonghee Nam
    • Journal of the Korean Chemical Society
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    • v.68 no.4
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    • pp.221-234
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    • 2024
  • The purpose of this study was to examine the impact of Argument-based Inquiry approach on elementary school students' critical thinking in elementary school science class. For this purpose, 23 students from two 5th grade elementary school classes in a metropolitan city were selected. One class (11 students) was assigned as the experimental group which Argument-based inquiry approach on 10 topics were applied. To determine the impact of Argument-based Inquiry approach on critical thinking, we analyzed the results of critical thinking tests before and after class and recordings of the discussion process of students in the experimental group. As a result of the critical thinking analysis, the average score of the experimental group in the deduction section was statistically and significantly higher than that of the comparative group. And as a result of analysis of recordings of the discussion process, students used deductive reasoning more often than inductive reasoning, and their use of this reasoning increased significantly at the claim·evidence stage.

Improvements in the Environmental Impact Assessment on Seawater and Sediment Qualities for Coastal Dredging Projects (연안준설 사업에 따른 해양 수질 및 퇴적물 영향평가 개선 방안)

  • Kim, Yeong-Tae;Kim, Gui-Young;Jeon, Kyeong-Am;Lee, Dae-In;Yu, Jun;Kim, Hee-Jung;Kim, In-Chul;Eom, Ki-Hyuk
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.19 no.2
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    • pp.119-128
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    • 2013
  • Since the early 2000s, demand for coastal dredging projects have been significantly increased, and the dredged sediments have showed the continuing marked increases through the multiple projects with other coastal development and constructions. As significant or potential degradation of marine environment has been mounting, we checked the current situation of marine environmental impact assessment through marine water and sediment qualities in relation with dredging projects of the sea area utilization consultation statements submitted in 2011. While analysis percentages of the general items were usually higher, harmful components such as metals revealed wide variation of analysis percentages. In the event of analysis of metals, the pre-treatment process (full digestion) and analysis method were not properly implemented in accordance with the guidelines for preparation of consultation statements. Although not specified in the guidelines, verification procedures (tests of recovery efficiency and detection limit) to secure the reliability were almost ignored. As a result, most of developers did conduct poor marine environmental impact assessment on coastal dredging and related projects. We suggested that the responsible government authority should establish new detailed guidelines on the sea area utilization consultation for more strict evaluation and diagnosis of marine environment and distinctly request the developer to obey the guidelines by complementing the system of the sea area utilization consultation.

A Study on the Applicability of Acrylic Water Leak Repair Materials used to Repair Cracks in Conduits and Underground Structures (관거 및 지하구조물 균열 보수에 사용되는 아크릴 누수 보수재의 적용성에 대한 연구)

  • Eunmi Lee;Kyungik Gil
    • Journal of Wetlands Research
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    • v.26 no.2
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    • pp.139-146
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    • 2024
  • Various injection materials, such as asphalt-based injection materials, urethane-based injection materials, cement- based injection materials, and acrylic-based injection materials, are used for the repair of aged conduits and underground structures with cracks. In this study, research was conducted on an environmentally friendly acrylic- based leak repair material that exhibits good curing properties even in humid conditions and stability in temperature fluctuations. To compare the performance of the improved acrylic leak repair material with the existing acrylate injection material, experiments were conducted using KS standard methods, including underwater length change rate tests, underwater leakage resistance tests, and chemical performance tests. The comparative experiments revealed that the improved acrylic leak repair material showed no changes in shrinkage due to humidity, temperature variations, or chemical reactions compared to the existing acrylate injection material. In the underwater resistance test, the improved acrylic leak repair material did not show any leakage. Additionally, to assess the environmental impact of the improved acrylic leak repair material, acute fish toxicity tests and acute oral toxicity tests were conducted, and the results showed no mortality and no specific concerns with the test specimens. The experimental results led to the conclusion that the improved acrylic leak repair material is considered to be superior in performance, environmentally safe, and harmless to the human body. Based on various experimental results, it is inferred that the improved acrylic leak repair material is suitable for use as a repair material for cracks in manholes and underground structures compared to the existing acrylate repair material. This study aims to propose valuable data for future technological development by evaluating the applicability of acrylic leak repair materials.

Impact Properties and Fractography of Structural Materials for LNG Tank at Cryogenic Temperatures (LNG 저장탱크용 재료의 극저온 충격특성과 파면해석)

  • Shin Hyung-Seop;Lee Hae-Moo;Shin Ju-Yeong;Park Jong-Seo
    • Journal of the Korean Institute of Gas
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    • v.2 no.1
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    • pp.99-106
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    • 1998
  • In order to investigate the impact properties of structural materials for LNG tank, instrumented Charpy impact tests were carried out at cryogenic temperatures. $9\%$ Ni steel showed a superior fracture resistance because of less degradation in toughness until 77 K. From the load-deflection curve obtained by an instrumented methods it was found that with the decrease of temperature from 173 K to 77 K, the peak load in the curve increased, but the total absorbed energy decreased. In addition, the energy absorbed during the crack growth was larger than one absorbed in the process of crack initiation. In SUS304L material, the energy absorbed in the process of the crack initiation was relatively large, but the energy absorbed in the process of crack growth was small, the behavior of absorbed energy was well agreed with the observations of the fracture surface which showed a relatively smooth fracture surface. The absorbed Charpy impact energy in the case of A5083 alloy was lower as compared with other steels, and some cracks were observed along the crack propagation direction at the fracture surface of 77 K.

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An Empirical Study of the Causal Relationship between Job Performance, Job Stress, and Turnover Intention of Salesperson (영업사원의 직무성과, 직무스트레스와 이직의도 간의 인과관계에 대한 실증적 연구 - 직무교육과 전환손실의 조절역할을 중심으로 -)

  • Ahn, Kwang Ho;Moon, Chung Tae
    • Asia Marketing Journal
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    • v.11 no.3
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    • pp.125-149
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    • 2009
  • Many studies have been conducted to find the causal factors that influence salesforce performance and turnover behavior. This study focuses on the turnover intention of salesperson. Specifically this study argues that the causal relationship among job performance, job stress and turnover intention will be mediated by job conflict of salesperson. We develop the hypotheses from the conceptual framework and empirically test them for the salespersons of lifetime insurance companies. Based on the previous studies and conceptual framework developed in this study, we derive 8 hypotheses. <Figure 1> shows the conceptual framework from which hypotheses are derived. Hypotheses for the empirical test are as follows: H1: Job performance will have negative impact on the turnover intention. H2: Job performance will have negative impact on the job conflict. H3: Job stress will have the positive relationship with the turnover intention. H4: Job stress will have the positive relationship with the job conflict. H5: Job conflict will have the positive relationship with the turnover intention. H6: The negative impact of job performance on the job conflict will be moderated by job education/training. H7: The positive impact of job stress on the job conflict will be moderated by job training. H8: The positive impact of job conflict on the turnover intention will be moderated by the switching costs. To test the 8 hypotheses, we estimate the level of fitness and parameters of structure equation model by using AMOS 5.0. <Table 1> shows the results of empirical tests for hypotheses. <Table 2> shows the moderating effect of job training. <Table 3> shows the moderating effect of switching costs. This empirical study finds interesting results. The job training has the moderating effect on the causal relationship between job performance and job conflict. But it is found that the job training has not the moderating effect on the causal relationship between job performance and job conflict. These results may be due to the fact that Korean insurance company mainly focuses on training of the job skill and knowledge, not motivational elation of salesforce.

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Development of a hip model for impact testing of bedsore prevention cushions (욕창예방 방석의 충격시험용 둔부 모형 개발)

  • JUNG, SUNGBAE;YUK, SUNWOO;Ki-Won Choi;Sangsoo Park
    • The Journal of the Convergence on Culture Technology
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    • v.10 no.3
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    • pp.7-11
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    • 2024
  • The bedsore prevention cushion serves to prevent the skin on the buttocks of a wheelchair user from being damaged through friction with the wheelchair seat. This is because it absorbs some of the weight applied to the wheelchair seat and allows the weight to be applied evenly to the entire contact surface. For the impact test, which is part of the performance testing of bedsore prevention cushions, a hip model that represents the sitting posture of a wheelchair user is required. In this study, a hip model was manufactured for impact testing of bedsore prevention cushions for wheelchairs. Performance tests for pressure bedsore prevention cushions for wheelchairs include KSP 0236, a Korean standard, and KS P ISO 16840-2, an ISO international standard. The hip model proposed in KS P ISO 16840-2 was more suitable for impact testing of bedsore prevention cushions for wheelchairs. However, the guidelines for making hip models proposed by international standards need to be modified to reflect the advancement of model making technology and use easier methods. We propose a new hip model production method that produces a hip model out of plastic all at once and additionally attaches SS-41 steel plates processed into the shape of the hip to make the mass of the model similar to the human body.

Experimental Study on Combined Failure Damage of Bi-directional Prestressed Concrete Panel under Impact-Fire Loading (충돌 후 화재에 대한 이방향 프리스트레스트 콘크리트 패널부재의 복합 파괴손상에 관한 실험적 연구)

  • Yi, Na-Hyun;Lee, Sang-Won;Choi, Seung-Jai;Kim, Jang-Ho Jay
    • Journal of the Korea Concrete Institute
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    • v.26 no.4
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    • pp.429-440
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    • 2014
  • Since the World Trade Center and Pentagon attacks in 2001, terror, military attack, or man-made disaster caused impact, explosion, and fire accident have frequently occured on civil infrastructures. However, structural behavior researches on major Prestressed Concrete (PSC) infrastructures such as bridges, tunnels, Prestressed Concrete Containment Vessel (PCCVs), and LNG tanks under extreme loading are significantly lacking. Especially, researches on possible secondary fire scenarios after terror, bombing, collision of vehicles and vessels on concrete structures have not been performed domestically where most of the past researches related to extreme loadings on structures focused on an independent isolated extreme loading scenario. Due to the outcry of public concerns and anxiety of potential terrorist attacks on major infrastructures and structures, a study is urgently needed at this time. Therefore, in this study, the bi-directional prestressed concrete $1400{\times}1000{\times}300mm$ panels applied with 430 kN prestressing force using unbonded prestressing thread bars were experimentally evaluated under impact, fire, and impact-fire combined loadings. Due to test site restrictions, impact tests were performed with 14 kN impactor with drop heights of 10m and 3.5 m to evaluate impact resistance capacity. Also, fire and impact-fire combined loading were tested using RABT fire loading curve. The measured residual strength capacities of PSC and RC specimens applied with impact, fire, impact-fire combined loadings were compared with the residual strength capacity of undamaged PSC and RC specimens for evaluation. The study results can be used as basic research data for related research areas such as protective design and numerical simulation under extreme loading scenarios.

Analysis of Flaking Strength by Rolling Friction of ADI (구상흑연주철의 구름마찰에 대한 강도해석)

  • Lee, Han-Young
    • Journal of Korea Foundry Society
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    • v.14 no.3
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    • pp.267-273
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    • 1994
  • The structure of austempered ductile cast iron, called ADI, consists of graphite, retained austenite, and bainite. The bainite component of them is considered a useful structure for exriting materials for roll of rolling mill. Therefore, the ADI can be considered applicable to material for rolling contact element. The diverse tests, such as rolling contact friction test, impact test, and X-ray reflection test, were carried out to investigate the possibility of it`s application. The result of this study showed that the expected fact was confirmed. The specimen showed that the best performance had the structure of the low bainite containing the stable retained austenite of about 20%.

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Study on the Origins of Surface Cracks at Room Temperature in Fe-Cr-Al Alloy Billets (Fe-Cr-Al계 합금 빌렛의 상온 표면균열 원인에 관한 연구)

  • Kim S. W;Park J. H;Kim I. B.
    • Korean Journal of Materials Research
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    • v.14 no.1
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    • pp.19-27
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    • 2004
  • Metallurgical and mechanical experiments were performed to explain unexpected surface cracks encountered in fabricating ground rolled-billet of Fe-Cr-Al alloys at room temperature. The toughness of these alloys containing between 220 and 236 ppm (C+N) has been assessed using notched-bar impact tests. According to our results, with a larger grain size, a higher interstitial content of (C+N) or a smaller size of precipitates, ductile to brittle temperature(DBTT) increased and absorbed energy decreased at room temperature. These results suggest that the surface cracks at room temperature stem from a poor resistance to brittle fracture, due to dislocation movement by the finely dispersed carbides within grains under the condition of higher (C+N) content.

Health Monitoring Method for Bridges Using Ambient Vibration Data due to Traffic Loads (교통하중에 의한 상시미진동을 이용한 교량의 건전도 감시기법)

  • 이종원
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2000.04a
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    • pp.218-225
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    • 2000
  • This paper presents intermediate results of an on-going research for identification of the modal and the stiffness parameters of a bridge based on the ambient vibration data caused by the traffic loadings. The main algorithms consist of the random decrement method incorporating band-pass filters for estimation of the free vibration signals the cross spectral density method for identification of the modal parameters and the neural networks technique for estimation of the element-level stiffness changes. An experimental study is carried out on a scaled bridge model with a composite section subjected to various moving vehicle loadings. Vertical accelerations are measured at several locations on the girder. The estimated frequencies and mode shapes are found to be well-compared with those obtained from the impact tests. The estimated stiffness changes using the neural networks are found to be very good for the case with the simulated data. However the accuracy is found to be not quite satisfactory for the case with the experimental data particularly for the small value of the stiffness changes.

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