• Title, Summary, Keyword: Dropper

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Elementary Students사, and Pre-service and In-service Elementary School Teachers사 Understanding on the Name and use. of Labware (초등학교 학생ㆍ예비 교사ㆍ현직 교사의 실험 기구 명칭과 용도에 대한 이해)

  • 여상인;이병문
    • Journal of Korean Elementary Science Education
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    • v.23 no.1
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    • pp.44-49
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    • 2004
  • This study was based upon the survey on the name of 13 basic experimental instruments used in elementary science class: Schale, evaporating dish, mortar & pestle, beaker, erlenmeyer flask, spuit(medicine dropper), graduated cylinder, balance, spatula, dropping bottle, gas collecting bottle, funnel, alcohol burner, and their uses. To implement this study, an open-ended, written questionnaire was administered to the subjects of in-service elementary school teachers, future elementary teachers who have attended at the Gyeongin national university of education, and elementary students in Korea. The findings of this study were as follows: The rates of in-service and pre-service elementary school teachers that knew correct name of experimental instruments were not high, the elementary school student's rates were especially very low. In this study, we found several reasons which they wrote inaccurately: the name to be represented at the textbook that they had studied, the confusion of the name about a fortis pronunciation, the recognition as the vocabulary like flask and cylinder to be meaningless, the habit to say in an everyday life, wrong expression in the internet and general book. All respondents had a wide range of perceptions of uses for the experimental instruments. Their understanding of uses for evaporating dish, erlenmeyer flask, balance, gas collecting bottle were very poor. And then most of them understood that graduated cylinder, beaker, and erlenmeyer flask were tools to measure the volume of solution or liquid, so they did not exactly distinguish the difference of their uses.

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A Fair Bandwidth Distribution Mechanism for the AF Service in a Diffserv Network (차등서비스 네트워크의 AF 서비스를 위한 공정한 대역분배 기법)

  • Mo, Sang-Dok;Chung, Kwang-Sue
    • Journal of KIISE:Information Networking
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    • v.32 no.6
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    • pp.732-744
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    • 2005
  • Previous works for the AE(Assured Forwarding) service in the Diffserv network have no sufficient consideration on the fairness of bandwidth share based on the target rate and the effect or RTT and UDP. Also Previous works act like Best-effort service in the UPN(under-Provisioned Network) condition. In this paper, in order to solve these problems, we propose the PFDSA(Proportionally Fair Differentiated Service Architecture) composed of tmTRA3CM(tcp-microflow based Target rate and an Aware Three color Marking), um3CM(udp-microflow based Three color Marker), TRBD(Target Rate Based Dropper), and target rate adjusting function. In the results of comparing the performance among existing mechanisms and the PFDSA, the PFDSA was able to mitigate the RTT and UDP effect better than the former. The PFDSA was shown to provide good performance for transmission rates proportional to various target rates in the UPN condition.

Analysis of the Major Design Parameters of a Pantograph-Railway Catenary System for Improving the Current Collection Quality (집전성능 향상을 위한 팬터그래프-전차선의 주요 설계 파라미터분석)

  • Cho, Yong Hyeon
    • Journal of the Korean Society for Railway
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    • v.17 no.1
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    • pp.7-13
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    • 2014
  • Stiffness variations and wave propagation/reflection in railway catenaries are the primary sources of contact loss between a pantograph and a railway contact wire. This paper analyzes which design parameter is more important for 200km/h conventional rail and 300km/h high-speed rail, in order to effectively reduce the contact loss. For the high-speed rail, the wave propagation and reflection in the overhead contact lines are more influential than the stiffness variation over a span. When the high-speed rail needs to speed-up, it is necessary to develop higher strength contact wires in order to increase the wave propagation speed. In addition, the dropper clamp mass should be reduced in order to alleviate the wave reflection. However, it is noted that the increase in the tension to a messenger wire could deteriorate the current collection quality, which contrasts with expectations. For the 200km/h conventional rail, the stiffness variation over a span is more influential than the wave propagation and reflection. Therefore, shortening span length, increasing the tension in the contact wire and optimizing the location of the droppers are recommended for a smoother stiffness variation over the span.

A Study on the Manual Skills of Experimental Apparatuses of Preservice Elementary School Teachers (초등 예비교사의 실험 기구 조작 능력에 대한 연구)

  • Lee, So-Ree;Choi, Hyun-Dong;Lim, Jae-Keun;Shin, Se-Young;Yang, Il-Ho
    • Journal of Science Education
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    • v.35 no.1
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    • pp.80-90
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    • 2011
  • The purpose of this study is to investigate manual skills of experimental apparatuses of pre-service elementary school teachers by examining and analyzing the process of experiments conducted by pre-teachers. For this study, 24 pre-service elementary school teachers were selected as the subjects and 4 experimental apparatuses were chosen through analyzing science textbooks from 3rd grade to 6th grade in elementary school. The selected experimental apparatuses were alcohol burner, dropper, microscope, instruments for making a prepared specimen. In addition, a task was carefully chosen to conduct an investigation in real settings and a series of evaluation standards was developed. While 3 subjects conducted experiments in separated and independent space at the same time, 3 collaborators observed the experiment process and recorded whether the subject met the evaluation standards or not, using O, X. The study suggests that pre-service elementary school teachers' manual skills of experimental apparatuses were under far below our projections. Particularly, in case of alcohol burner, the subjects showed lower ability to properly light the burners - which is to brush through the lampwick with fire - and to adjust the height of tripods according to the flame. Also, when it comes to dropper, they were not held the way they were supposed to be. In addition, when designing prepared specimen, the subjects used their hands instead of tweezers and often skipped the process of dripping water drop and wiping water with an oilpaper. Moreover, they did not know how to use a microscope properly so there were many times that they could not focus a microscope, failing to observe the objects. Educational implications are discussed.

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