• Journal of the Korean Wood Science and Technology
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• v.21 no.4
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• pp.64-72
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• 1993

Mechanical properties of 15 mm thick, three-layer particleboard were studied by varying resin content, specific gravity, mat moisture content, pressing time and pressing temperature. Based on the results of the study, Multiple regression models were developed to estimate the mechanical properties of three-layer particleboard. The results of this study showed the mechanical properties of particleboard were highly related with resin content. specific gravity and mat moisture content in decending order. The mechanical properties were able to estimated as the linear function of resin content and specific gravity. However, the effects of change in mat moisture content on the mechanical properties showed a non-linear pattern. The mechanical properties curves over mat moisture content reached peaks at 15 %, and then decreased at 18 % and 21 % of mat moisture contents. On the other hand, the effects of pressing time and pressing temperature on the mechanical properties of particleboard were not significant.

• Corrosion Science and Technology
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• v.11 no.1
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• pp.29-36
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• 2012

The resistance spot welding of high strength steel degrades the weldability because of its high strength with rich chemical composition and coating layer to protect from corrosion. During the each resistance welding process the electrodes tip reacts with coating layer, then subsequently deteriorates and shorten electrode life. In this study, the Al-coated HPF (Hot Press Forming) steels and Zn-coated TRIP steels were used to investigate the electrode life for resistance spot welding. Experimental results show that the reactivity of Al-coating on HPF steels to electrode tip surface behaviors different from the conventional Zn-coated high strength steels. The electrode tip diameter and nugget size in electrode life test of Al-coated HPF steels are observed to be constant with respect to weld numbers. For Al-coated HPF steels, the hard aluminum oxide layer being formed during high temperature heat treatment process reduces reactivity with copper electrode during the resistance welding process. Eventually, the electrode life in resistance spot welding of Al-coated HPF steels has the advantage over the galvanized steel sheets.

• Design & Manufacturing
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• v.11 no.3
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• pp.25-28
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• 2017

The production of carbon fiber reinforced thermoplastics(CFRTP) parts using an injection/compression molding process that differs from the conventionally used fabrication methods was investigated Before the application of composite molding in the injection/compression molding process, a simple compression molding experiment was performed using a hydraulic press machine to determine the characteristics of resin impregnation and to obtain a basic physical property data for the CFRTP. Based on these results, injection/compression molded specimens were manufactured and an additional insert/over molding process was applied to improve the impregnation rate of the molded specimens. The results demonstrated that the tensile strength of the molded parts using the faster injection/compression process was similar to that of a hydraulic press molded product.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.921-929
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• 2010

Group communication that involves the setup of a list of users has been a topic of interest in mobile industry. Push to Talk over Cellular (PoC), a group communication service for cellular phone network, is a type of half duplex communications that allows a single person to reach an active talk group without making several calls, but a single button press. Based on this service, we build a new protocol called Push to Talk over Mobile Wimax that uses group communication service in 802.16e network. Also, weper formed simulation to verify and evaluate performance of the designed service in Mobile Wimax network. From the results of performance evaluation, network administrators can evaluate the stability of network and make a better of network's shortcoming and have decision to build the robust network.

• Advances in aircraft and spacecraft science
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• v.10 no.4
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• pp.303-315
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• 2023

The primary goal of this research is to investigate flow separation phenomena using various turbulence models. Also investigated are the effects of free-stream turbulence intensity on the flow over a NACA 0018 airfoil. The flow field around a NACA 0018 airfoil has been numerically simulated using RANS at Reynolds numbers ranging from 100,000 to 200,000 and angles of attack (AoA) ranging from 0° to 18° with various inflow conditions. A parametric study is conducted over a range of chord Reynolds numbers for free-stream turbulence intensities from 0.1 % to 0.5 % to understand the effects of each parameter on the suction side laminar separation bubble. The results showed that increasing the free-stream turbulence intensity reduces the length of the separation bubble formed over the suction side of the airfoil, as well as the flow prediction accuracy of each model. These models were used to compare the modeling accuracy and processing time improvements. The K- SST performs well in this simulation for estimating lift coefficients, with only small deviations at larger angles of attack. However, a stall was not predicted by the transition k-kl-omega. When predicting the location of flow reattachment over the airfoil, the transition k-kl-omega model also made some over-predictions. The Cp plots showed that the model generated results more in line with the experimental findings.

• Korean journal of communication and information
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• v.28
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• pp.111-140
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• 2005

Most of studies on the press during the period of Japanese occupation in Korea have focused on the activities of newspapers in 1920s. These past studies didn't examine the whole process of change of the press under the Japanese occupation in Korea. Thus, this study tried to investigate the change of the tenor of Korean newspaper editorials on the ruling policies during the end of the colonial period in Korea as a part of attempts exceeding the limit of past studies. After the outbreak of the war between China and Japan in 1937, the Korean newspapers were full of stereotyped editorials resembling in a way official gazette. Dong-A Ilbo and Cho-Sun Ilbo represented the purpose of the war was to emancipate Asian countries from Western imperialist countries and to establish the peace of the Asia. Simultaneously, two newspapers played an important role in assimilating the Korean people into the Japanese and mobilizing them to the war, The tenor of these editorials was affected by intensified control over the press and the change of the consciousness of journalists. In conclusion, these newspapers had a harmful influence on the Korean people as a weapon to the movement to organize and mobilize them. Therefore the interest for researching on the pro-Japanese press should be taken in view of 'resistance' and 'collaboration.'

• Korean journal of communication and information
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• v.76
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• pp.151-182
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• 2016

The right to be forgotten (RTBF) has been a population notion to address privacy issues associated with the digitalization of information and the dissemination of such information over the global digital network. In May 2014, the European Court of Justice (ECJ) laid down a landmark RTBF decision to grant individuals the right to be de-listed from search results. ECJ's RTBF decision sparked an increased interest in RTBF in South Korea. Academic and non-academic commentators have provided a mistaken or outstretched interpretation of RTBF in claiming that removal of news articles should be read into RTBF in Korean law. Moreover, the Press Arbitration Commission of Korea (PAC) has proposed revising the Press Arbitration Act (PAA) to allow the alleged victims of news reporting to request the deletion of news stories. This article examines the notion of RTBF from its origin to the latest development abroad and also critically explores Korean laws regulation freedom of expression to evaluate if Korea needs the proposed PAA revision.

• Korean journal of communication and information
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• v.29
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• pp.233-269
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• 2005

The purpose of the study is to explore the characteristics of lawsuits against investigative reporting programs of the broadcast media. This study proposed three research questions: (1) what were the characteristics of court derisions on the investigative reporting programs? (2) what were the reasonings on which judges rely in the lawsuits for a right of reply? (3) what were the critical issues and how the libel laws were applied in balancing between the freedom of the press and the protection of individual rights. To answer these questions, the study employed quantitative and qualitative methods analysing 35 related cases. This study revealed that investigative reporting programs must deal with the Issues of 'public figures' and 'matters of public concern' to be protected under the freedom of the press. The study also found that the broadcast media must prove legitimate public interests and the truth of the facts to prevail in a case. In 1999, the Constitutional Court of Korea held that pubic figures in libel cases must be regarded differently from private figures. In accordance with the decision, the Supreme Court has applied differing criteria for public figures in libel cases. However, courts have not set a clear definition of the public figure yet. To advocate the freedom of the press, as the results of this study indicate, TV producers and journalists should behave lawfully in the course of newsgathering and provide the opportunities of reply for their news sources.

• Journal of Technologic Dentistry
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• v.31 no.2
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• pp.45-52
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• 2009

Esthetic restorations have been widely used in dental practice, although many studies have focused on the development and improvement of all ceramic restorations. The success of esthetic restorations depends primarily on an optimal bond strength between various veneered ceramics and core materials for esthetic restorations. The purpose of this study was to compare the shear bond strength between various veneered ceramics and core materials for esthetic restorations. 30 metal cores and 20 zirconia cores were fabricated and divided into five groups according to veneered ceramic materials such as Creation porcelain powder, Cercon Ceram Kiss, and IPS e.max ZirPress. Thirty spacimens were prepared using Creation porcelain powder, veneered 3mm height and 3mm in diameter, over the metal cores (n=10). Twenty specimens were prepared using Cercon Ceram Kiss and Zirpress, veneered 3mm height and 3mm in diameter, over the zirconia cores (n=10). The shear bond strength test was performed in a universal testing machine with a crosshead speed of 1mm/min. Ultimate shear bond strength data were analyzed with One-way ANOVA and the Scheffe's test (p=.05). Within the limits of this study, the following conclusions were drawn: The mean shear bond strengths (MPa) were: 18.44 for Uni metal VH/Creation (NCUC); 18.72 for Heraenium/Creation (NCHC); 16.23 for Wirobond C/Creation (NCWC); 13.88 for Zirconia core/$110{\mu}m$ $Al_2O_3$ sandblasting/Cercon Ceram Kiss (ZS110P); 14.61 for Zirconia core/No surface treatment/IPS e.max ZirPress (ZNTH). The mean shear bond strength for NCUC (Uni metal VH/Creation), NCHC (Heraenium/Creation) and NCWC (Wirobond C/Creation) were significantly superior to ZS110P (Zirconia core/$110{\mu}m$ $Al_2O_3$ sandblasting/Cercon Ceram Kiss) and ZNTH(Zirconia core/No surface treatment/IPS e.max ZirPress) (p<0.05).

• Earthquakes and Structures
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• v.12 no.6
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• pp.713-723
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• 2017

Steel plate shear walls (SPSWs) are effective lateral systems which have high initial stiffness, appropriate ductility and energy dissipation capability. Recently, steel plate shear walls with low yield point strength (LYP), were introduced and they attracted the attention of designers. Structures with this new system, besides using less steel, are more stable. In the present study, the effects of plates with low yield strength on the seismic design parameters of steel frames with steel plate shear walls are investigated. For this purpose, a variety of this kind of structures with different heights including the 2, 5, 10, 14 and 18-story buildings are designed based on the AISC seismic provisions. The structures are modeled using ANSYS finite element software and subjected to monotonic lateral loading. Parameters such as ductility (${\mu}$), ductility reduction ($R_{\mu}$), over-strength (${\Omega}_0$), displacement amplification ($C_d$) and behavior factor (R) of these structures are evaluated by carrying out the pushover analysis. Analysis results indicate that the ductility, over-strength and behavior factors decrease by increasing the number of stories. Also, the displacement amplification factor decreases by increasing the number of stories. Finally, the results were compared with the suggestions provided in the AISC code for steel plate shear walls. The results indicate that the values for over-strength, behavior and displacement amplification factors of LYP steel plate shear wall systems, are larger than those proposed by the AISC code for typical steel plate shear wall systems.