C9-aldehyde hydrogenation over nickel/kieselguhr catalysts in trickle bed reactor

The objective of the present study was to select the optimal catalyst and operating conditions for the manufacture of C₉-alcohol, using C₉-aldehyde and hydrogen, in a trickle bed reactor. When CaO, Ce₂O₃ or MgO was added as a promoter to the Ni/kieselguhr catalyst, the BET and Ni surface areas were increased. In the reaction for the manufacture of C₉-alcohol, using C₉-aldehyde and hydrogen in a batch reactor, a Ni–MgO/kieselguhr catalyst showed the highest activity. In addition, the catalyst using Na₂CO₃ as a precipitant showed the highest activity. According to the result of an experiment to find the optimal reaction conditions for C₉-alcohol synthesis, using C₉-aldehyde and hydrogen in a trickle bed reactor loaded with Ni–MgO/kieselguhr catalyst, the highest yield of C₉-alcohol was 91.5 wt% at 130 °C, 400 psi and WHSV = 3. The C₉-aldehyde hydrogenation performance of the Ni–MgO/kieselguhr catalyst was similar to that of a Cu/ZnO/Al₂O₃ catalyst, but superior to that of Cu–Ni–Cr–Na/Al₂O₃ and Ni–Mo/Al₂O₃ catalysts. In a long-term catalysis test, the Ni–MgO/kieselguhr catalyst showed higher stability than the Cu/ZnO/Al₂O₃ catalyst.     

Positional isomerization of butene-2 over nanoporous MCM-48 catalysts

Positional isomerization of butene-2 to butene-1 was investigated over nanoporous MCM-48 catalysts. The effects of the method and the amount of aluminum incorporation into MCM-48 on the catalyst characteristics were studied, with respect to the butene-2 isomerization reaction. Incorporation of aluminum into MCM-48 using a post-synthetic grafting method (P) or direct sol-gel method (D) increases the total acid amount due to the increase in the Lewis acidity level. From the results of butene-2 isomerization, the yield of butene-1 was increased although the selectivity of butene-1 was decreased due to an increase of byproducts such as i-butene, cracked fraction, and C5+ hydrocarbons. This trend is nearly identical over both catalyst preparation methods; the effect of Al incorporation method on the butene-1 yield and the selectivity appeared negligible. The maximum yield of butene-1 was 27.1 wt% by feeding pure butene-2 in the reaction condition as follows: a temperature of 450 degrees C, atmospheric pressure, and with the WHSV at 70 h(-1).     

Robust control using recursive design method for flexible joint robot manipulators

A flexible joint robot manipulator can be regarded as a cascade of two subsystems: link dynamics and the motor dynamics. Using this structural characteristic, we propose a robust nonlinear recursive control method for flexible manipulators. The recursive design is done in two steps. First, a fictitious robust control for the link dynamics is designed as if it has a direct control input. As the fictitious control, a nonlinear H _∞-control using energy dissipation is designed in the sense of L ₂-gain attenuation from the disturbance caused by uncertainties to performance. In the process, Hamilton-Jacobi (HJ) inequality is solved by a more tractable nonlinear matrix inequality (NLMI) method. In the second step, the other fictitious and the actual robust control are designed recursively by using the Lyapunov’s second method. The proposed robust control is applied to a two-link robot manipulator with flexible joints in computer simulations. The simulation results show that the proposed robust control has robustness to the model uncertainty caused by changes in the link inertia and the joint stiffness.     

Oil spill environmental forensics: the Hebei Spirit oil spill case

After the Hebei Spirit oil spill (HSOS) in December 2007, mixtures of three types of Middle East crude oil (total 12,547 kL) were stranded along 375 km of coastline in Western Korea. Emergency responses together with 1.3 million volunteers' activity rapidly removed ca. 20% of spilled oil but the lingering oils have been found along the heavily impacted shorelines for more than 4 years. The HSOS was the worst oil spill case in Republic of Korea, and there were many issues and lessons to be shared. In this study, we summarized some of the oil spill environmental forensic issues that were raised after the HSOS. Rapid screening using on-site measurement, long-term monitoring of multimedia, fingerprinting challenges and evaluation of the extent of the submerged oil were introduced, which supported decision making process of oil spill cleanup, mitigation of debates among stakeholders and provided scientific backgrounds for reasonable compensation.     

Thermoelectric Properties of Indium-Selenium Nanocomposites Prepared by Mechanical Alloying and Spark Plasma Sintering

Indium-selenium-based compounds have received much attention as thermoelectric materials since a high thermoelectric figure of merit of 1.48 at 705?K was observed in In₄Se_2.35. In this study, four different compositions of indium-selenium compounds, In₂Se₃, InSe, In₄Se₃, and In₄Se_2.35, were prepared by mechanical alloying followed by spark plasma sintering. Their thermoelectric properties such as electrical resistivity, Seebeck coefficient, and thermal conductivity were measured in the temperature range of 300?K to 673?K. All the In-Se compounds comprised nanoscaled structures and exhibited n-type conductivity with Seebeck coefficients ranging from ?159???V?K^?1 to ?568???V?K^?1 at room temperature.     

The effects of functionalized graphene nanosheets on the thermal and mechanical properties of epoxy composites for anisotropic conductive adhesives (ACAs)

Functionalized graphene/epoxy composites were prepared using the epoxy resin diglycidyl ether of bisphenol A. Graphene oxide (GO) and Al(OH)₃-coated graphene (Al-GO) fillers were fabricated using the Hummers method and a simple sol–gel method, with aluminum isopropoxide as the aluminum precursor. X-ray photoelectron spectroscopy verified the successful formation of functional groups onto the GO and Al-GO. The dispersion of functionalized graphene fillers showed an even distribution within the epoxy resins. A dynamic mechanical analysis was used to investigate the changes in the mechanical properties of the epoxy composites, which included neat epoxy and epoxy with various concentrations of graphene-based fillers. The storage modulus and tan δ graphs illustrate the enhancement achieved by increasing the amount of filler. The composite with 3 wt.% GO had the highest storage modulus and glass transition temperature. The thermal conductivities of the composites with graphene-based fillers were enhanced compared to those without fillers. The 3 wt.% GO/epoxy composite had the highest thermal conductivity, which was nearly twice that of the neat epoxy resin.     

Investigation of freeze/thaw durability in polymer electrolyte fuel cells

This study aims to investigate the effect of different gas diffusion layers (GDLs) on freeze/thaw condition durability in polymer electrolyte fuel cells (PEFCs). Three kinds of GDLs–cloth, felt and paper type—with similar basic properties except thickness and bending stiffness were used. The changes in the properties and cell performance were investigated from the −30 to 70 °C range of freeze/thaw cycles. The I–V performance degradation was observed to be negligible for the felt GDL whereas the cloth and paper GDLs showed a marked I–V performance loss. No distinctive correlation between the changes in electrochemical properties, such as active metal surface area, hydrogen crossover rates and decreased I–V performance, was observed except an increase in ohmic resistance revealed by ac-impedance spectroscopy. The physical destruction of electrodes was also shown by scanning electron microscope (SEM) analysis.     

Effects of processing variables on melt cleanliness of AZ31B magnesium alloy investigated by quantitative evaluation of Fe and non-metallic inclusions

Impurities such as Fe, Ni and Cu and non-metallic inclusions such as oxides, nitrides, carbides, sulfides and fluorides are harmful to the quality and various properties of magnesium alloy sheets produced by twin-roll casting. In this study, the changes of the content of Fe and non-metallic inclusions in AZ31B magnesium alloys with melt temperature and isothermal holding time were quantitatively evaluated using EPMA and the metallographic method. The Fe content did not increase above the Fe content in the raw material, which implies that the dissolution of Fe from a steel crucible was suppressed effectively. The content of non-metallic inclusions, mainly consisting of oxide, fluoride and Fe-rich intermetallic compounds, did not change remarkably with the melt temperature but it increased with the isothermal holding time due to the continuous oxidation of the magnesium alloy melt on the melt surface.     

Multi-layer alignment control of a large area nano-imprinting stage

An XYθ stage for large area UV Nano-Imprinting Lithography (UV-NIL), which consists of linear actuators, translational/revolute joints, etc., has been modeled as flexible bodies. Multi-layer alignment control for the translation and angle offset cancellation has been performed in a virtual simulation environment using both ADAMS/Control and Matlab/SIMULINK. Furthermore, the vertical motions of three and four axis stages during the control action have been analyzed and compared to each other. The performed analysis can provide useful information for a high precision NIL stage development in the future. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Hong Jae Yim received B.S. and M.S degrees in mechanical engineering from Seoul National University, Korea, in 1979, 1983. He received Ph.D degree from Univ. of Iowa, USA. He is currently a professor in School of Mechanical & Automotive Engineering, Kookmin University. His research interests are in the area of computer aided kinematics and dynamics of mechanical systems.