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Jang, Hongseok,Shuli, Xing,Lee, Malrey,So, Hyoungseok,So, Seungyoung American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.10
<P>This study was to investigate the effects of granulated blast furnace slag (GBFS) on the color expression of black colored mortar. For this purpose, color evaluation and was carried out on white Portland cement (WPC) mortar mixed with of carbon amino silica black (CASB) by changing the proportion of GBFS. Each mortar was measured at five locations on the surface and averaged. Color can be evaluated by measurements of tristimulus values L*, a* and b*, represented in the chromatic space CIELAB. Artificial Neural Networks (ANN) model is constructed, trained and tested using these data. The data used in the ANN model are arranged in a format of 3 input parameters that cover the WPC, GBFS, days and, an output parameter which is the color parameters of the black colored mortar. The results showed that ANN can be an alternative approach for the analyzing the color parameters using mortar ingredients as input parameters. And one-step secant back-propagation as the final training algorithm is the most suitable.</P>
Hongseok Jang,서세관,조대성 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.1
This study assessed the compressive and tensile strengths and modulus of elasticity of waste polyethylene terephthalate (PET) using the ASTM standard tests. In addition, short carbon and glass fibers were mixed with waste PET to examine the improvements in ductility and strength during compression. The bonding was examined via field-emission scanning electron microscopy. The strength degradation of the waste PET tested under UV was 40–50%. However, it had a compressive strength of 32.37 MPa (equivalent to that of concrete), tensile strength of 31.83 MPa (approximately ten times that of concrete), and a unit weight of 12–13 kN/m3 (approximately half that of concrete). A finite element analysis showed that, compared with concrete, a waste PET pile foundation can support approximately 1.3 times greater loads. Mixing reinforcing fibers with waste PET further mitigated this, thereby extending ductility. Waste PET holds excellent potential for use in foundation piles, especially while mitigating brittleness using short reinforcing fibers and avoiding UV degradation.
Emission characteristic of ammonia in cement mortars using different sand from area of production
Hongseok Jang,Hyoungseok So,Seungyoung So 대한환경공학회 2016 Environmental Engineering Research Vol.21 No.3
This paper discusses the influence of organic matter contained in aggregate on the emission characteristic of ammonia (NH₃) from cement mortar. NH₃ can be released to indoor-outdoor environment through diffusion in mortar (or concrete) and have resulted in the increasing air pollution, and especially well known as a harmful gas for the human body. The concentration of NH₃ released from cement concrete was then compared to the contents of organic matter contained in the aggregate. The result indicates that the contents of organic matter in the aggregate significantly differ with types of aggregate from different areas of production. The organic matter becomes organic nitrogen through the process of microbial breakdown for a certain period and pure ammonium ion (NH₄+) is produced from the organic nitrogen. The NH₄ + was reacted with alkaline elements in the cement and released as NH₃ from cement concrete through a volatile process. The released NH₃ was proportional to the contents of NH₄+ adsorbed in the aggregate from different areas of production and the concentrations of NH₃ emission from cement mortar according to the aggregate differ by more than 4 times.
Fire resistance and residual strength of reactive powder concrete Using metakaolin
Hongseok Jang,Jebang Yi,Seungyoung So 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.6
This study investigates the fire resistance characteristics of reactive powder concrete according to changes in the cement content per unit area, mixing ratio of metakaolin (MK), and content of polypropylene fiber. A fire test was conducted, and the resulting residual strength characteristics were investigated through flexural and compressive strength measurements, as well as condition rating classification based on visual evaluation. MK effectively reduced the initial high content of calcium hydroxide, thereby reducing the water vapor pressure generated during pyrolysis and slowing spalling. Furthermore, the pore structure and loose tissue were effective for relieving the water vapor pressure in the event of a fire.
장홍석(Hongseok Jang),정국상(Kugsang Jeong),최덕재(Deokjai Choi) 한국정보과학회 2005 한국정보과학회 학술발표논문집 Vol.32 No.1
유비쿼터스 컴퓨팅과 센서 네트워크의 발달로 인해 센서의 관리에 대한 필요성이 커지고 있다. 그러나 기존의 관리 기능이 없는 센서 정보 전달 방법은 의미 없는 불필요한 정보의 전달로 효율적인 센서 통신을 저해하고 수많은 이벤트 통보로 인한 이벤트 플러딩 문제를 일으킨다. 이러한 문제를 해결하기 위해서는 단순한 값의 전달뿐만 아니라 정보를 저장하고 관리할 수 있는 구조가 필요하다. 유비쿼터스 환경에 적합한 센서 관리 구조로서 정보의 저장과 관리에 유용한 SNMP 네트워크 관리 프로토콜을 제안한다. 센서측에 SNMP 에이전트를 직접 탑재함으로써 정보를 저장하고 효율적인 센서 관리가 가능하고 장비의 이상이 발생했을 때에도 적절한 지역적인 관리를 함으로써 효율적인 센서 관리가 가능하다.