ATRIUM SMOKE FILLING PROCESS BY COMPUTATIONAL FLUID DYNAMICS

Chow,W,K,Yin,R 한국화재소방학회 1997 한국화재소방학회 학술대회 논문집 Vol.1997 No.-

Atrium buildings are commonly found in Hong Kong since 1980. Those spaces are usually crowded with people and so fire protection systems have to be installed for providing a safe environment. Smoke control system was identified to be important but no clear design guidelines are available because the smoke filling process was not well-understood. In this paper., Computational Fluid Dynamics(CFD) or fire field model is applied to study the smoke filling pattern in atrium. Two common cases on smoke spreading out from a shop adjacent to the atrium; and with a fire located at the atrium floor itself were considered. Simulations with a modified form of the CFD package TEAM were performed. Application of the predicted results Is illustrated.

Bile acids inhibit duodenal secretin expression via orphan nuclear receptor small heterodimer partner (SHP).

Lam, Ian P Y,Lee, Leo T O,Choi, Hueng-Sik,Alpini, Gianfranco,Chow, Billy K C American Physiological Society 2009 American journal of physiology, Gastrointestinal a Vol.297 No.1

<P>Small heterodimer partner (SHP) is an orphan nuclear receptor in which gene expression can be upregulated by bile acids. It regulates its target genes by repressing the transcriptional activities of other nuclear receptors including NeuroD, which has been shown to regulate secretin gene expression. Here, we evaluated the regulation on duodenal secretin gene expression by SHP and selected bile acids, cholic acid (CA) and chenodeoxycholic acid (CDCA). In vitro treatment of CDCA or fexaramine elevated the SHP transcript level and occupancy on secretin promoter. The increase in the SHP level, induced by bile acid treatment or overexpression, reduced secretin gene expression, whereas this gene inhibitory effect was reversed by silencing of endogenous SHP. In in vivo studies, double-immunofluorescence staining demonstrated the coexpression of secretin and SHP in mouse duodenum. Feeding mice with 1% CA-enriched rodent chow resulted in upregulation of SHP and a concomitant decrease in secretin transcript and protein levels in duodenum compared with the control group fed with normal chow. A diet enriched with 5% cholestyramine led to a decrease in SHP level and a corresponding increase in secretin expression. Overall, this study showed that bile acids via SHP inhibit duodenal secretin gene expression. Because secretin is a key hormone that stimulates bile flow in cholangiocytes, this pathway thus provides a novel means to modulate secretin-stimulated choleresis in response to intraduodenal bile acids.</P>

Metal organic chemical vapor deposition of ZrO₂ thin films using the single precursor zirconium 3-methyl-3-pentoxide, Zr(mp)₄

Cho, W.,Jang, H. S.,An, K.-S.,Lee, Y. K.,Chung, T.-M.,Kim, C. G.,Kim, Y.,So, B.-S.,Hwang, J.-H.,Jung, D. SLACK INCORPORATED 2006 Journal of vacuum science & technology. an officia Vol.24 No.4

Big data pre-processing methods with vehicle driving data using MapReduce techniques

Cho, W.,Choi, E. Springer Science + Business Media 2017 The Journal of supercomputing Vol.73 No.7

<P>A huge amount of sensing data are generated by a large number of pervasive IoT devices. In order to find meaningful information from the big data, it is essential to perform pre-processing, in which many outlier data points need to be removed, because they deteriorate as time passes. Although pre-processing is essential in the big data field, there has been a significant lack of research works with case studies. In this paper, big data pre-processing methods are investigated and proposed. To evaluate the pre-processing methods for accurate analysis, we used a collection of digital tachograph (DTG) data. We obtained DTG sensing data of 6198 driving vehicles over a year. We studied five kinds of pre-processing methods: filtering ranges, excluding meaningless values, comparing filters from variables, applying statistical techniques, and finding driving patterns. In addition, we developed a MapReduce program using a Hadoop ecosystem and deployed big data to perform the pre-processing analysis. Through the pre-processing steps, we confirmed that the proportion of DTG sensing data points including any errors was up to 27.09%. Compared to the traditional brute-force way to detect, ours had 71.1% additional detection effect. In addition, we confirmed that outlier data points, which are difficult to detect through simple range error pre-processing, could be well detected.</P>

High-efficiency solid-state polymer electrolyte dye-sensitized solar cells with a bi-functional porous layer

Cho, W.,Kim, Y.,Song, D.,Choi, H.,Kang, Y. Royal Society of Chemistry 2014 Journal of Materials Chemistry A Vol.2 No.42

Power supply system for KSTAR neutral beam injector

Cho, W.,Bae, Y.S.,Han, W.S.,Jeong, J.H.,Kim, J.S.,Park, H.T.,Yang, H.L.,Oh, Y.K.,Kwak, J.G. Elsevier 2015 Fusion engineering and design Vol.96 No.-

<P><B>Abstract</B></P> <P>The power supply system in KSTAR neutral beam injector consists of low voltage and high current DC power supplies for plasma generator of ion source and high voltage and high current DC power supply for accelerator grid system. The arc discharge is initiated by an arc power supply supplying the arc voltage between the chamber wall and 12 filaments which are heated by individual filament power supply. The negative output of arc power supply is common to each positive output of 12 filament power supplies. To interrupt the arc discharging for the fault condition of the arc current unbalance, DCCT current monitor is placed at the positive output cable of the filament power supply. The plasma grid (G1) power supply has the maximum capability of 120kV/70A which consists of low voltage regulator with IGBT-switched chopper array system for the voltage control in unit of 600V and the high voltage rectified transformers to supply DC voltage of 20kV, 30kV, and 50kV. The output voltage of the G1 power supply is also connected to the input of the voltage divider system which supplies the gradient voltage to the gradient grid (G2) in the range of 80–90% of G1 voltage by changing tap of winding resistors in unit of 1%. The charged G1 voltage is turned on and off by the high voltage switch (HVS) system consisting of MOSFET fast semiconductor switches which can immediately be opened less than 1μs when the ion source grid breakdown occurs. The decelerating grid (G3) power supply is inverter system using capacitor-charge power supply to supply maximum −5kV/5A. The important component in power supply system is the surge absorber near the ion source to limit the arc energy deposited to accelerator grid. This paper presents configuration and features of power supply system, main controller, and interlock system of KSTAR NBI.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The power supply system in KSTAR NBI consists of DC power supplies for ion source. </LI> <LI> For operation NBI, DC High Voltage based on the low voltage transformer with chopper. </LI> <LI> The surge absorber near the ion source limit the energy deposited to accelerator grid. </LI> </UL> </P>

Tertiary amines: A new class of highly efficient organocatalysts for CO₂ fixations

Cho, W.,Shin, M.S.,Hwang, S.,Kim, H.,Kim, M.,Kim, J.G.,Kim, Y. Korean Society of Industrial and Engineering Chemi 2016 Journal of industrial and engineering chemistry Vol.44 No.-

<P>To realize a true green CO2 utilization process, the development of a catalytic system having no toxic components is essential. Herein, tertiary amines without any metal or halide additives are introduced as simple and green organocatalysts to activate CO2 and insert into epoxides, producing synthetically important cyclic carbonates. Among those amines, diamine such as N,N,N',N'-tetraethylethylenediamine exhibited a moderate to excellent efficiency. This new class of organocatalyst which does not have any toxic metals and halides is easy to handle and only requires as low as a 0.1 mol% loading. Additional favorable features include solvent free conditions and broad substrate scopes. (C) 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.</P>

A basis of spatial big data analysis with map-matching system

Springer Science + Business Media 2017 Cluster computing Vol.20 No.3

<P>The data collection of vehicle trajectories becomes the basis of big data analysis and prediction for a variety of purposes, such as vehicle navigation and movement analysis. A digital tachograph (DTG) is pre-installed on most commercial vehicles in South Korea and is highly valuable for analyzing eco-driving metrics such as safe driving and fuel consumption estimates. In order to properly analyze a large amount of GPS location information, it is necessary to find the exact match of the location data in space to the link in the digital road network data. We previously discovered the road information of the GPS coordinates using the commonly utilized map-matching technique. However, such a navigation map-matching technique requires a lot of supplementary corrections in order to rapidly and accurately navigate a large amount of data. In this study, we applied enhanced map-matching logics with Geohash as spatial index, long link vertex division, speed filtering, azimuth filtering, and map-matching weight logics. Also, we established and implemented a distributed analysis environment for the big data map-matching with HBase (a Hadoop-based NoSQL DB). This paper shows a spatial analysis system using the map-matching logics on the Hadoop MapReduce mechanism, which improved its performance.</P>

Efficient binary organic thiolate/disulfide redox mediators in dye-sensitized solar cells based on a carbon black counter electrode

Cho, W.,Song, D.,Lee, Y. G.,Chae, H.,Kim, Y.,Pyun, Y.,Nagarajan, S.,Sudhagar, P.,Kang, Y. Royal Society of Chemistry 2013 Journal of materials chemistry. A, Materials for e Vol.1 No.2

Tunable synthesis of hierarchical mesoporous silica via porogen-carrying organosilicates

Cho, W.,Lee, H.I.,Shim, B.S.,Cha, B.J.,Kim, J.M.,Char, K. Elsevier 2017 Microporous and mesoporous materials Vol.239 No.-

We describe the synthesis and characterization of hierarchically porous organic-inorganic hybrid silica with periodic 2-D hexagonal order and tunable location of secondary nanopores through co-condensation of tetraethylorthosilicate (TEOS) and a new type of amphiphilic organosilicate precursors. Our amphiphilic organosilicates offer unique tunability of secondary micropores by carefully controlled bond molecular structure and number of bonds between hydrophobic adamantylphenols pore-generating moieties and siloxane precursors. Small angle X-ray scattering (SAXS) and microscopy results show a good structural order of the organic-inorganic hybrid silica. In addition, <SUP>29</SUP>Si CP-MAS NMR spectra confirm the successful incorporation of organosilicate precursors into a silica framework. The primary cylindrical mesopores (~6.4 nm) were originated from the cooperative self-assembly of Pluronic P123 triblock copolymer templates while smaller meso-/micropores were derived from adamantylphenols groups. We have previously demonstrated that adam-graft SQ had an affinity for hydrophobic PO core blocks to be located close to PO segment, which resulted in small pores next to primary mesopores and the resultant increment of mesopore size as well as wrinkled silica walls. On the contrary, the secondary small pores were mainly generated within a silica network while the size of the primary mesopores unaffected with the addition of adam-bridge SQ due to its selective incorporation into a silica framework. Moreover, the organic-inorganic hybrid silica prepared with adam-bridge SQ showed higher thermal stability than that of adam-graft SQ and SBA-15 type mesoporous silica. It is attributed to more Si?O?Si bonds formed from the bridged structure as well as enhanced hydrogen-bonding interaction between adam-bridge SQ hybrid silica and P123 templates.