• Journal of The Korean Association For Science Education
• /
• v.42 no.6
• /
• pp.579-595
• /
• 2022

This study is a qualitative case study of secondary science teachers who are doing educational activities in YouTube. In particular, this study attempts to interpret this case based on Foucault's concept of 'Heterotopia', which means a space that allows for private freedom or deviance by reflecting various utopias without the norms and constraints from every day or real space. Five secondary science teachers who voluntarily opened a personal channel on the YouTube platform and actively uploaded their own videos related to science education participated in the study. In order to understand the experiences of five secondary science teachers, data were individually collected through semi-structured in-depth interviews, and the collected data were analyzed using qualitative case study method. For valid interpretation of the study, we also referred to the video contents, teacher training materials, and teaching and learning materials produced by the participants. As a result of the study, seven themes were revealed: 'Desire for one's own unique educational activities,' 'Youtube as an extended classroom space,' 'Expanded network of relationships beyond the classroom barrier,' 'Satisfaction of desire for recognition and experience of identity as a YouTuber,' 'Tension between the educational space and the YouTube,' 'Space to be reborn as a craftsman,' and 'Finding one's own direction as a Teacher-YouTuber.' Given those findings, we found that the identity and desire of secondary science teachers, which were limited in the existing secondary schools and classrooms, was expanded in a new space called YouTube. In addition, we suggested that YouTube could be a space where science teachers can realize their own ideals and feel the joy. And simple regulating teacher's behavior in Youtube space only based on norms and standards shared in traditional educational space would rather hinder their healthy construction of identity and growth.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.6 no.4
• /
• pp.331-340
• /
• 1982

Numerical analysis is made on the turbulent heat transfer with suspension of solid particles in circular tube with constant heat flux. The mean motion of suspending particles in mixture is treated as the secondary gas flow with virtual density and viscosity. Our modeling of turbulent transport phenomena of suspension flow is based on this assumption and conventional mixing length theory. This paper gives the evidence that the mixing length models can be extended to close the governing equations for two phase turbulent flow with solid boundary at a first order level. Results on Nusselt numbers obtained by analytical treatments are compared with available experimental data and discussed. They suggest that the most important parameters of two phase turbulent heat transfer phenomena are relative particle diameter to pipe diameter, gas-solid loading ratio, and specific heat of suspending material.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.6
• /
• pp.875-882
• /
• 2002

The modeling for turbulent flow through a porous media has not been confirmed because of a undetermined constant which appears in the governing equations. In present study, the turbulent porous modeling based on the local thermal equilibrium has been extended to the turbulent clear flow. A undetermined constant is also suggested by microscopic analysis. The microscopic analysis is performed in the flat tube with micro-channels, and it confirms that the undetermined constant is 0.99. It is shown that the results of the macroscopic analysis using confirmed constant agree well with those of the microscopic analysis with a maximum error of 3.5%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.902-907
• /
• 2002

An equivalent electroacoustic circuit approach of estimating the sound absorption coefficient for parallel perforated plate system is proposed. The proposed approach is validated by comparing the calculated absorption coefficients of a parallel single layer perforated plate system with the values measured by the two-microphone impedance tube method for various porosity and the number of perforated plate. The sound absorbing performances of parallel and series perforated plate systems are compared and discussed from a standpoint of frequency bandwidth with sound absorption. The proposed approach is further extended to the parallel double layer perforated plate system.

• Journal of Aerospace System Engineering
• /
• v.9 no.2
• /
• pp.13-18
• /
• 2015

Micro planar type liquid propellant thruster was fabricated by MEMS manufacturing process for micro/nano satellites applications. 90 wt.% hydrogen peroxide was used as propellant and for propellant decomposition, Pt/Al2O3 was used as catalyst. Micro thruster structure was made by 5 photosensitive glasses patterned with thruster component profiles. Objective thrust was 50 mN and required hydrogen peroxide mass flow was 2.1 ml/min, which was supplied by syringe pump and teflon tube in experimental test. Performance test said that average steady thrust was approximately 30 mN, around 60% of objective thrust, and transient time was about 5 sec. It is estimated that extended response time was due to high thermal energy loss of micro scale thruster and low enthalpy input by propellant mass flow.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.2
• /
• pp.133-140
• /
• 1984

A "two-fluid" equation model has been applied for predicting gas-solid suspension flows through a Venturi tube. In the "two-fluid"equation model, the bulk motion of the particles is considered as a continuum whose governing equation is obtained by averaging the conservation equations over a volume and expressing the equations in differential forms. Closure of the time-mean equations is achieved by modeling the turbulent correlations with an extended mixing-length theory. Proposed closure model is found to aptly simulate the dependency of the static pressure drop on the particle size, flow rate and the loading ratio.d the loading ratio.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.8 s.239
• /
• pp.921-926
• /
• 2005

In the idealized model problem of the interaction between a planar travelling shock and a symmetric vortex, the physics of shock distortion and quadrupole sound generation are well known to many researchers. However, the authors have distinguished the weak waves reflected and transmitted by the complicated photograph images obtained from a shock tube experiment. In this paper, we introduces a parametric study based on Navier-Stokes simulation and Rankin vortex model to see the difference of shock deformation shapes. Four combination of the strength of shock and vortex are respectively selected from a parameter plane of shock and vortex strength extended to the strong vortex region. The result shows clearly discernable wave morphology for the main parameters, which is not yet explicitly mentioned by other researchers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.6 no.3
• /
• pp.227-236
• /
• 1994

Steady flows of Newtonian and non-Newtonian fluids in the stenotic tubes with various stenotic shapes are numerically simulated. Validity of the modified power-law model as a constitutive equation for the purely viscous non-Newtonian fluid is discussed and the results of the power-law model are compared with those of the Carreau model, the Powell-Eyring model and experimental data for blood. Flow characteristics and reattachment lengths for non-Newtonian fluids in the stenotic tubes are presented extensively. Also, the analysis is extended to predict the influences of diameter ratio, stenosis spacing, number of stenosis and Reynolds number on the flow characteristics in the multiple stenotic tubes.

• Journal of Chest Surgery
• /
• v.28 no.10
• /
• pp.954-962
• /
• 1995

Extended lymph node dissection, which includes dissection of the cervical and superior mediastinal nodes[three-field dissection , has been performed to improve the long-term survival since 1982 in Japan. Recently, the 5-year survival rate after three-field dissection has been reported to be better than 40%. During the period, from April to June, 1995, 4 patients among 7 operable esophageal cancer patients underwent subtotal esophagectomy with systematic dissection of regional lymph nodes including superior mediastinal and cervical lymph nodes at St. Mary`s Hospital. The esophagogastric anastomoses were made in the neck and the ascending routes of gastric tube were posterior mediastinal route. The cancer stage of them were stage IIA & IIB and it was possible to operate on a curability II & III basis. The numbers of resected lymph nodes with the three field dissection were 40-55. Postoperative complications were transient recurrent laryngeal nerve paralysis and atelectasis in 2 patients respectively but there was no anastomotic leak nor stenosis.

• Journal of Chest Surgery
• /
• v.26 no.12
• /
• pp.969-971
• /
• 1993

The sternal turnover has a limited use in an asymmetrical funnel chest. However we tried `One-half sternal turnover` as a new operative approach for an asymmetrical funnel chest. Through the bilateral submammary skin incision, median sternotomy was made from xiphoid process to midsternum and extended horizontally. The segment of ribs were cut at the angle of depression. The en-bloc resected chest wall segment contained one-half sternum as well as a part of ribs and left half of rectus muscle. After turning over the en-bloc segment, reapproximation with wiring was done. Sternotomy wound was closed in layer after placing of substernal drainage tube. Postoperatively, the chest wall was stable and the recovery course was uneventful except left-sided minimal pneumothorax which was cured spontaneaously. The patient was discharged on postoperative 14th day.