Selective oxidation of alcohols using octahedral molecular sieves: influence of synthesis method and property–activity relations

Manganese oxides having a tunnel structure (OMS-2) have been utilized as selective catalysts for alcohol oxidation. In this study manganese oxide catalysts were synthesized in different media and modified by exchanging the tunnel cation by H⁺, using acid treatment or exchanging with NH₄⁺ followed by thermolysis. Various alcohol oxidations were performed using these catalysts to ascertain the influence of synthesis method on their activity. A correlation is made between lattice oxygen instability and activity of the catalysts, which indicates involvement of the lattice oxygen in the mechanism. The exchange of the tunnel cation with the smaller H⁺ ions leads to weakening of the Mn–O bond, as verified by temperature programmed desorption (TPD) results. Only the chemisorbed oxygen on the surface (O⁻) and the lattice oxygen in the layers close to the surface is involved in the oxygen transfer during the reaction.     

Thin-Wall Aluminum Die-Casting Technology for Development of Notebook Computer Housing

Silicon-based aluminum casting alloys are known to be one of the most widely used alloy systems mainly due to their superior casting characteristics and unique combination of mechanical and physical properties. However,manufacturing of thin-walled aluminum die-casting components,less than 1.0 mm in thickness,is generally known to be very difficult task to achieve aluminum casting alloys with high fluidity.Therefore,in this study,the optimal die-casting conditions for producing 297 mm×210 mm×0.7 mm thin-walled aluminum component was examined experimentally by using 2 different gating systems,tangential and split type,and vent design.Furthermore,computational solidification simulation was also conducted.The results showed that split type gating system was preferable gating design than tangential type gating system at the point of view of soundness of casting and distortion generated after solidification.It was also found that proper vent design was one of the most important factors for producing thin-wall casting components because it was important for the fulfillment of the thin-wall cavity and the minimization of the casting distortion.     

Diagnostic Value of Salivary miRNA in Head and Neck Squamous Cell Cancer: Systematic Review and Meta-Analysis

Several studies have highlighted the diagnostic potential of salivary microRNA (miRNA) in head and neck squamous cell cancer (HNSCC). The purpose of this meta-analysis was to summarize published studies and evaluate the diagnostic accuracy of salivary miRNA in HNSCC detection. In this meta-analysis, we systematically searched PubMed, EMBASE, and Cochrane Library databases for studies on miRNA and HNSCC diagnosis. Pooled sensitivity, specificity, and diagnostic odds ratio (DOR) with a summary receiver-operating characteristic curve were calculated using a bivariate random-effect meta-analysis model. Furthermore, subgroup analyses were conducted to explore the main sources of heterogeneity. Seventeen studies from ten articles, including 23 miRNA and a total of 759 subjects, were included in this meta-analysis. The pooled sensitivity and specificity of salivary miRNA in the diagnosis of HNSCC were 0.697 (95% CI: 0.644–0.744) and 0.868 (95% CI: 0.811–0.910), respectively. The overall area under the curve was 0.803 with a DOR of 12.915 (95% CI: 9.512–17.534). Salivary miRNAs are a promising non-invasive diagnostic biomarker with moderate accuracy for HNSCC. These results must be verified by large-scale prospective studies.     

Thermogravimetric study of coal and petroleum coke for co-gasification

As a preliminary study of gasification of coal and petroleum coke mixtures, thermogravimetric analyses were performed at various temperatures (1,100, 1,200, 1,300, and 1,400 °C) and the isothermal kinetics were analyzed and compared. The activation energies of coal, petroleum coke and coal/petroleum coke mixture were calculated by using both a shrinking core model and a modified volumetric model. The results showed that the activation energies for the anthracite and petroleum coke used in this study were 9.56 and 11.92 kcal/mol and reaction times were 15.8 and 27.0 min. In the case of mixed fuel, however, the activation energy (6.97 kcal/mol) and reaction time (17.0 min) were lower than the average value of the individual fuels, confirming that a synergistic effect was observed in the coprocessing of coal and petroleum coke. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

The valuation of RFID investment using fuzzy real option

Net present value (NPV) and return on investment (ROI) are commonly used to evaluate investment in new technologies. Sometimes, however, measuring the value of investment in new IT becomes very difficult due to its wide scope of application coupled with embedded options in its adoption. Therefore, comprehensive but easily understandable methodologies are needed to solve the complicated problems resulting from the complexity of new technologies. This paper employs a real option analysis to evaluate RFID adoption in the supply chain. Real options analysis should be a better way to evaluate a disruptive technology like RFID. However, the pure (probabilistic) real option rule characterizes the present value of expected cash flows and the expected costs by a single number, which is not realistic in many cases. To solve the problem, this paper considers the real option rule in a more realistic setting, namely, when the present values of expected cash flows and expected costs are estimated by trapezoidal fuzzy numbers. Specifically, it drew out their means and variance and presented a method of calculating fuzzy real options through numerical value examples of RFID investment assuming the current value of expected cash flow and investment costs using trapezoid fuzzy number fuzzy real options. Since advanced information technology such as RFID has very high risk and options such as change, extension, delay and withdrawal, etc., investment valuation using the real options technique should be done, and in the process, in a more realistic and practical approach, the fuzzy real options model presented in this study is judged to be useful.     

Experimental studies of 1 ton/day coal slurry feed type oxygen blown, entrained flow gasifier

Experimental Studies of a 1 Ton/Day coal slurry feed type oxygen blown, entrained flow gasifier have been performed with the slurry concentration and gasifier temperature at 65% and above 1,300 ‡C, respectively. The characteristics of ash fusion temperature with addition of CaO as a flux were investigated to maintain the proper slag tapping condition in the range of reaction temperature. As the flux addition increased, ash fusion temperature showed a eutectic effect with the eutectic at around 20–30% CaO. In order to analyze the gasification characteristics, the effects of O₂/coal feed ratio on the product gas composition, heating value, gasifier temperature and cold gas efficiency were evaluated. From the results, it was shown in the case of Kideco coal that the cold gas efficiency was 44–60% and the heating value was 1,700-2,200 kcal/Nm³, while Drayton coal showed a cold gas efficiency of 55–62% and a heating value of 1,800-2,200 kcal/Nm³. In the case of Datong coal, the cold gas efficiency was 38–65%, and the heating value was 2,000-2,300 kcal/Nm³. Also, the results showed that the optimal operating condition of O₂/coal ratio for the three different coals was 0.9. Presented at the Int’/Symp. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

Experimental and theoretical study on the characteristics of vacuum residue gasification in an entrained-flow gasifier

About 200,000 bpd (barrel/day) vacuum residue oil is produced from oil refineries in Korea. These are supplied to use asphalt, high sulfur fuel oil, and upgrading residue hydro-desulfurization units. High sulfur fuel oil can be prepared by blending oil residue with light distillate to bring fuel oil characteristics in the range of commercial specifications, which will become more stringently restrictive in the near future in Korea. Vacuum residue oil has high energy content; however, due to its high viscosity, high sulfur content and high concentration of heavy metals are representative of improper low grade fuel, which is considered difficult to gasify. At present, over 20 commercial scale IGCC (Integrated Gasification Combined Cycle) plants using feedstocks with vacuum residue oil for gasification are under construction or operating stage worldwide. Recently, KIER (Korea Institute of Energy Research) has been studying the vacuum residue gasification process using an oxygen-blown entrained-flow gasifier. The experiment runs were evaluated under a reaction temperature of 1,200-1,250 C, reaction pressure of 1.0 kg/cm², oxygen/V.R ratio of 0.8-1.2 and steam/V.R ratio of 0.4-0.7. Experimental results show a syngas composition (CO+H₂), 77-88%; heating value, 2,300-2,600 kcal/Nm³; carbon conversion, 95-99, and cold gas efficiency, 68-72%. Also, equilibrium modeling was used to predict the vacuum residue gasification process and the predicted values reasonably well agreed with experimental data.     

Optimal design of a squeeze film damper using an enhanced genetic algorithm

This paper represents that an enhanced genetic algorithm (EGA) is applied to optimal design of a squeeze film damper (SFD) to minimize the maximum transmitted load between the bearing and foundation in the operational speed range. A general genetic algorithm (GA) is well known as a useful global optimization technique for complex and nonlinear optimization problems. The EGA consists of the GA to optimize multi-modal functions and the simplex method to search intensively the candidate solutions by the GA for optimal solutions. The performance of the EGA with a benchmark function is compared to them by the IGA (Immune-Genetic Algorithm) and SQP (Sequential Quadratic Programming). The radius, length and radial clearance of the SFD are defined as the design parameters. The objective function is the minimization of a maximum transmitted load of a flexible rotor system with the nonlinear SFDs in the operating speed range. The effectiveness of the EGA for the optimal design of the SFD is discussed from a numerical example.     

Antioxidant Properties of Flavone C-Glycosides from Atractylodes japonica Leaves in Human Low-density Lipoprotein Oxidation

ABSTRACT: Three antioxidant flavone C -glucosides, isoorientin, vitexin, and isovitexin, were identified for the 1st time from Atractylodes japonica leaves by an activity-guided fractionation with various analytical techniques including column chromatography, high-performance liquid chromatography (HPLC), fast atom bombardment mass spectrometry (FAB-MS), and nuclear magnetic resonance (NMR). Hydroxyl and superoxide anion radicals scavenging activities of these compounds were examined using electron spin resonance (ESR). Inhibitory activities of these compounds on human low-density lipoprotein (LDL) oxidation were evaluated by malondialdehyde (MDA) and thiobarbituric acid-reactive substances (TBARS), both representing intermediates of lipid peroxidation. These flavone C -glucosides displayed about 50% of scavenging activity against hydroxyl radicals at the concentrations below 10 μ M . The superoxide dismutase (SOD)-equivalent activities of isoorientin, vitexin, and isovitexin at 1 m M were 31.37, 2.71, and 2.63 unit/mL, respectively. Isoorientin at 1 μ M exhibited over 60% inhibition of MDA formed during copper-mediated human LDL oxidation. Amounts of free MDA in LDL treated with isoorientin, vitexin, isovitexin, and control were 20.06, 40.73, 34.08, and 48.03 n M /mg protein, respectively. These compounds also prolonged the lag phase time of the conjugated diene formation. There was a positive correlation between the free radical scavenging activities and the inhibitory effects on the LDL oxidation of these compounds. These results suggest that the flavone C -glucosides isolated from the leaves of A japonica possess beneficial antioxidant properties against free radicals as well as LDL oxidation.     

Acidic Polysaccharide Extracts from Gastrodia Rhizomes Suppress the Atherosclerosis Risk Index through Inhibition of the Serum Cholesterol Composition in Sprague Dawley Rats Fed a High-Fat Diet

Obesity is associated with a broad spectrum of cardio-metabolic disturbances, including atherosclerosis and cardiovascular disease (CDV). A high-fat diet has been shown to cause an elevation of the plasma cholesterol levels in humans, and the control of serum cholesterol has been demonstrated to be important in the prevention of CVD and atherosclerosis. The aims of this study were to demonstrate that crude and acidic polysaccharide extracts from Gastrodia rhizomes suppress atherosclerosis through the regulation of serum lipids in Sprague Dawley (SD) rats fed a high-fat diet. We examined the concentrations of serum lipids, including total cholesterol, triglycerides, high-density lipoproteins (HDL) cholesterol, and low-density lipoproteins (LDL) cholesterol, in SD rats fed a high-fat diet and evaluated the atherogenic index. Here, we show that both crude and acidic polysaccharide extracts from Gastrodia rhizomes inhibited the total cholesterol and LDL levels. Moreover, there was a significantly suppressed atherosclerosis risk due to the acidic polysaccharide extract from Gastrodia rhizome. Taken together, our results suggested that acidic polysaccharide extracts from Gastrodia rhizomes might be beneficial for lowering the incidence of CVD and atherosclerosis by reducing the de novo synthesis of total cholesterol and the LDL levels.