Effect of particle size on the microstructure and properties of kinetic sprayed nickel coatings

This study aims to examine the effect of particle size on the microstructure and corresponding properties in kinetic sprayed coatings of commercially pure nickel (CP-Ni) in conjunction with finite element modeling (FEM). Prior to the experiments, the adhesion factors (interface temperature, contact time and contact area), rebound factor (relative recovery energy) and the resultant critical velocities of CP-Ni for different particle sizes and temperatures were estimated by FEM. Based on the simulations, three different sized CP-Ni powders were successfully deposited onto mild steel substrates using a powder preheating system. Here we suggest optimized windows of operation for particle sizes of CP-Ni based on the microstructure and properties of the coatings (i.e. deposition efficiency, bond strength and micro-hardness) which are in good correspondence with the simulation results.     

Assessment of the crack growth characteristics at the low corrosion fatigue limit of an A106 Gr b steel pipe weld

In the area of heavy construction, welding processes are vital in the production and maintenance of pipelines and power plants. The fusion welding process generates formidable welding residual stresses and metallurgical change, which increase the crack driving force and reduce the resistance of brittle fracture as well as environmental fracture. This is a serious problem with many alloys as well as A106 Gr B steel pipe. This pipe, used in petrochemical and heavy chemical plants, either degrades due to corrosive environments, e.g., chlorides and sulfides, and/or becomes damaged during service due to the various corrosion damage mechanisms. Thus, in this study, the sulfide corrosion fatigue strength of multi-pass welded A106 Gr B steel pipe was evaluated in a 5.0 wt.% NaCl solution that was saturated with H2S gas at room temperature on the basis of NACE TM 0177-90. The crack growth characteristics of the welded pipe were then assessed at the low limit of sulfide corrosion fatigue strength, which was previously obtained from the sulfide corrosion fatigue (SCF) tests. From the results, in terms of the SCF, all the specimens failed at the heat-affected zone, where a high welding residual stress distributes. It was found that the fatigue crack grew at the low corrosion fatigue limit (σ _{SCFun-notched}), which was 32 % (160MPa) of the ultimate tensile strength (502MPa) of the welded specimens.     

Studies on process parameters for chlorine dioxide production using IrO2 anode in an un-divided electrochemical cell

Chlorine dioxide is potentially a powerful oxidant with environmentally compatible application in several strategic areas relating to pollution control typically for water disinfection, and its sustained production is a key factor for its successful application. Although increased attention has been paid for on-line chlorine dioxide generation by several chemical and electrochemical methods, the details are mostly confined as patents. We studied in this work the electrochemical generation of chlorine dioxide from an un-buffered solution of sodium chlorite and sodium chloride mixture in an un-divided electrochemical cell under constant current mode, with a view to optimize various process parameters, which have a direct bearing on the chlorine dioxide formation efficiency under laboratory conditions. The effect of feed flow rate (10-150 ml min(-1)), feed solution pH (2.3-5.0), concentration of sodium chloride (0-169.4mM), concentration of sodium chlorite (0-7.7 mM), and the applied current (100-1200 mA) on the formation of dissolved ClO(2) gas in solution and the pH of the product-containing solution was investigated by performing single pass experiments, with no circulation, in a cell set-up with Ti/IrO(2) anode and Ti/Pt cathode. The current efficiency and the power consumption were calculated for the optimized conditions.     

Application of immobilized nanotubular TiO(2) electrode for photocatalytic hydrogen evolution: reduction of hexavalent chromium (Cr(VI)) in water

In this study, immobilized TiO(2) electrode is applied to reduce toxic Cr(VI) to non-toxic Cr(III) in aqueous solution under UV irradiation. To overcome the limitation of powder TiO(2), a novel technique of immobilization based on anodization was applied and investigated under various experimental conditions. The anodization was performed at 20V-5 degrees C for 45min with 0.5% hydrofluoric acid, and then the anodized samples were annealed under oxygen stream in the range 450-850 degrees C. Based on the results of the experiments, the photocatalytic Cr(VI) reduction was favorable in acidic conditions, with approximately 98% of the Cr(VI) being reduced within 2h at pH 3. Among the samples tested under same anodizing condition, the nanotubular TiO(2) annealed at 450 and 550 degrees C showed highest reduction efficiencies of Cr(VI). In addition, the surface characterizations (zeta potential, XRD, and SEM) of these samples proved that the Cr(VI) reduction efficiency was higher under acidic conditions and at a lower annealing temperature. From this research, it was concluded that the anodized TiO(2) has the potential to be a useful technology for environmental remediation as well as photocatalytic hydrogen production from water.     

A study of solid particle flow characterization in solar particle receiver

The solid particle receiver (SPR) is a direct absorption receiver in which solar energy heats a curtain of falling ceramic particle to a temperature in excess of 1000 °C. A small scale test platform was built to investigate particle flow properties. The curtain was comprised of approximately 697 μm ceramic particles that were dropped within the receiver cavity of the test platform. Tests were conducted to experimentally determine the distribution of particles velocity, curtain thickness, and curtain opacity along a drop length of approximately 3 m. Velocity data were measured using a high speed digital camera to obtain images of the particle flow at 1000 frames per second with an exposure time of 100 μs. Five mass flow rates ranging from 1 kg/s-m to 22 kg/s-m were examined, and it was found that all flows approached a terminal velocity of about 6-7 m/s in a vertical drop distance of 3 m. The experimental results were validated with computational results and were found in excellent agreement with the simulation results. In addition, a similar study was performed with various sizes of the particles to better understand how the particle flow characteristics were affected by the size of the particles.     

Output power characteristic of WEC for a buoy

Floating devices, such as a cavity resonance device, take advantage of both the water motion and the wave induced motions of the floating body itself. In the design of a wave energy converter (WEC), the most significant factor is that an optimum length of the internal water column should exists, that is, a length in which maximum power is converted near the heaving resonance. A theoretical analysis of this power generated by a pneumatic-type WEC is performed, and the results obtained from the analysis are used for a real WEC for a buoy. The length of the internal water column corresponds to that of the water mass in the water column. If designed properly, a WEC can take advantage not only of the cavity resonance but also of the heaving motion of the buoy. This paper presents the test results of the generation characteristic of a WEC and the harmful effect of fouling in the internal water column. The results are then applied to the design of a WEC for a buoy. This paper was recommended for publication in revised form by Associate Editor Jae Young Lee Jin-Seok Oh was born in Kyung-Nam, Korea. He received the B. E. degree in Marine Engineering from Korea Maritime University in 1983. Since 1983, he has been with the Zodiac (England Company) including early 4 years of System Engineer. He received the M.E. and Ph. D. degrees from Korea Maritime University, Busan, Korea in 1989 and 1996, respectively. He had been with the Agency for Defense Development (ADD) as a researcher from 1989 to 1992. In 1996, he joined the Division of Mechatronics Engineering at Korea Maritime University. His research interests include electrical drive systems, robot control and PC-based Control applications.     

Multi-agent based traffic simulation and integrated control of freeway corridors: Part 2 integrated control optimization

This research aims to optimize the traffic signal cycle and the green light time per traffic signal cycle at ramps and intersections in arterials to maximize the passing traffic volume and minimize the delaying traffic volume in freeway corridors. For this purpose, we developed the MATDYMO (multi-agent for traffic simulation with vehicle dynamics model) and validated it with comparison to commercial software, TRANSYT-7F, for an interrupted flow model and to URFSIM (urban freeway traffic simulation model) for an uninterrupted flow model. These comparisons showed that MATDYMO is able to estimate the traffic situation with only incoming traffic volume. Using MATDYMO, ramp metering and traffic signal control can be optimized simultaneously. We extracted 80 sampling points from the DOE (Design of Experiment) and derived each response from MATDYMO. Then, a neural network was adopted to approximate the objective function, and simulated annealing was used as an optimization method. There are three cases of the objective function: maximization of the freeway traffic volume, minimization of the delay of ramps and arterials, and the satisfaction of both cases. The optimization results showed that traffic flow in freeway corridors can be maintained to a steady stream by ramp metering and signal control. This paper was recommended for publication in revised form by Associate Editor Kyongsu Yi Myung-Won Suh is a professor of Mechanical Engineering. During 1986–1988, he worked in Ford motor company as researcher. During 1989–1995, he worked in technical center of KIA motors. He took a BS Degree in Mechanical Engineering from Seoul National University and an MS Degree in Mechanical Engineering from KAIST, South Korea. He obtained his Doctorate at University of Michigan, USA, in 1989. His research areas include the structure and system optimization, advanced safety vehicle and reliability analysis & optimization. Chul-Ho Bae is a PhD candidate at Sungkyunkwan University in Suwon, South Korea. He accomplished fellowship work as researcher at Mississippi State University, USA, in 2003 and 2005. He worked in Institute of Advanced Machinery and Technology (IMAT) as a Research Assistant in 2004. He was a part time Lecturer in computer aided Mechanical Engineering of Ansan College of Technology, Suwon Science College, and Osan College during 2004–2005. He took a BS Degree in Mechanical Design and an MS Degree in Mechanical Engineering from the Sungkyunkwan University. His research interests include computer aided engineering, reliability engineering, and optimization.     

Effect of partially hydrolyzed oat β-glucan on the weight gain and lipid profile of mice

Oat β-glucan hydrolysates with different molecular weights were prepared and their physicochemical, hypocholesterolemic, and weight-reducing characteristics were evaluated. The enzymatic hydrolysis by cellulase caused a decrease in the molecular weight of oat β-glucan (1450–370 × 10³ g/mol), which also affected swelling power and bile acid/fat binding capacities. In addition, mice were fed high-fat diet supplemented with β-glucans with three different molecular weights (1450, 730, 370 × 10³ g/mol). The diets treated with β-glucans significantly reduced the body weight of the mice. However, the molecular weight of β-glucans did not appear to significantly affect the serum lipid profile.     

Global Lysine Acetylome Analysis of LPS-Stimulated HepG2 Cells Identified Hyperacetylation of PKM2 as a Metabolic Regulator in Sepsis

Sepsis-induced liver dysfunction (SILD) is a common event and is strongly associated with mortality. Establishing a causative link between protein post-translational modification and diseases is challenging. We studied the relationship among lysine acetylation (Kac), sirtuin (SIRTs), and the factors involved in SILD, which was induced in LPS-stimulated HepG2 cells. Protein hyperacetylation was observed according to SIRTs reduction after LPS treatment for 24 h. We identified 1449 Kac sites based on comparative acetylome analysis and quantified 1086 Kac sites on 410 proteins for acetylation. Interestingly, the upregulated Kac proteins are enriched in glycolysis/gluconeogenesis pathways in the Kyoto Encyclopedia of Genes and Genomes (KEGG) category. Among the proteins in the glycolysis pathway, hyperacetylation, a key regulator of lactate level in sepsis, was observed at three pyruvate kinase M2 (PKM2) sites. Hyperacetylation of PKM2 induced an increase in its activity, consequently increasing the lactate concentration. In conclusion, this study is the first to conduct global profiling of Kac, suggesting that the Kac mechanism of PKM2 in glycolysis is associated with sepsis. Moreover, it helps to further understand the systematic information regarding hyperacetylation during the sepsis process.     

Evaluation of the microbial contamination of fresh produces and their cultivation environments from farms in Korea

Food Science and Biotechnology - In this study, a total of 195 samples including fresh produce and farming environments was used to perform the microbial risk assessment. Levels of total aerobic...