Kinetics of CO2 reforming of methane by catalytically activated metallic foam absorber for solar receiver-reactors

Ni–Cr–Al metallic foam absorber with high porosity was catalytically activated using a Ru/γ-Al₂O₃ catalyst, and was subsequently tested with respect to CO₂ reforming of methane in a small-scale volumetric receiver-reactor by using a sun-simulator. A chemical storage efficiency of 37% was obtained for a mean light flux of 325 kW m⁻². Furthermore, the activity and the stability of the metallic foam absorber were compared with those of a SiC foam absorber activated with the same Ru/γ-Al₂O₃ catalyst for 50 h of light irradiation, and it was found that the metallic foam absorber has superior catalytic stability in comparison to the SiC form absorber. In addition, unlike ceramic foams such as SiC, metallic foams feature superior plasticity, which prevents the emergence of cracks caused by mechanical or thermal shock.     

Thin-film transistors based on liquid-crystalline tetrafluorophenylter thiophene derivatives: thin-film structure and carrier transport

The authors fabricated thin films by solution processes using liquid-crystalline (LC) semiconductors, 5-alkyl-5’’-(4-hexyltetrafluorophenyl)-2,2’:5’,2’’-terthiophene (2–5). Films of 5-propyl-5’’-(4-hexyltetrafluorophenyl)-2,2’:5’,2’’-terthiophene (2) show similar molecular packing as their non-fluorinated counterparts. However, the degree of molecular packing ordering from X-ray diffraction measurement is higher, and the films exhibit a more crystal-like structure. Moreover, fluorination has a remarkable effect on their mesomorphic behaviors. Films of 2 consist of large size LC domains (in the range of 100 μm) at room temperature. Thin-film transistors (TFTs) of 2 show p-type operation with good hole mobility up to 0.027 cm²/Vs as well as improved operation stability under ambient conditions and high on/off ratio. Tetrafluorophenyl substitution leads to lowering of HOMO energy by 0.15 eV for 2 and 0.35 eV for 5, resulting in operation stability. Variable-temperature current-voltage measurements indicate intrinsic carrier transport in films of 2.     

ZnO nano-ridge structure and its application in inverted polymer solar cell

We report a unique nano-ridge structure of zinc oxide (ZnO) and its application in high performance inverted polymer solar cells. The ZnO nano-ridge structure was formed by a sol–gel process using a ramp annealing method. As the solvent slowly evaporated due to the low heating rate, there was sufficient time for the gel particles to structurally relax and pile up, resulting in a dense and undulated film. Nano-ridges with peak as high as 120 nm and valley to valley distance of about 500 nm were formed. This film provided an effective hole blocking layer and also an increased interfacial area for electron collection. An inverted bulk heterojunction polymer solar cell was fabricated using the ZnO nano-ridge film as the electron collecting layer. The device showed a high power conversion efficiency of 4.00%, an improvement of about 25% over similar solar cells made with a planar film of ZnO nanoparticles.     

Color and Vanadium Valency in V-Doped ZrO2

The distribution and chemical states of vanadium in V-doped ZrO₂ were studied to clarify the origin of the color of vanadium-zirconium yellow pigment in comparison with vanadium-tin yellow pigment. ESCA data and measurements of lattice constants of V-doped ZrO₂ revealed that vanadium was dissolved mainly as V⁴⁺ substituting for Zr in ZrO₂ lattice, and its solubility limit was 0.5 wt% as V₂O₅. It was found that the yellow color of vanadium-zirconium yellow was produced predominantly by the dissolved vanadium and that the contribution of vanadium oxide on ZrO₂ grains to the yellow color was about 1/30 of that of the dissolved vanadium when compared on the basis of equimolar quantity of vanadium. Most of the undissolved vanadium oxide was in an amorphous or a poorly crystallized state.     

Position command shaping for vibration suppression considering target position correction

This paper presents a command shaping technique based on a minimum jerk control approach that takes into consideration target position correction during motion, for the fast and precise positioning in vibratory mechatronic systems. The positioning controller is designed using a two‐degree‐of‐freedom control: a feedback compensator is synthesized by H_∞ control design to ensure the robust stability, while a feedforward compensator suppresses the vibration in response based on a coprime factorization expression of the plant mechanism. The command shaping, on the other hand, eliminates the corresponding vibration components of the primary and secondary models in the position command, where the continuity of jerk component in the command can be ensured against the target position correction. The effectiveness of the proposed shaping technique has been verified by experiments using a table drive system on a machine stand. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 38–47, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20838     

Antioxidative activities of bran extracts from twenty one pigmented rice cultivars

Ethanol–water (70:30, v/v) extracts from the bran of rice seeds from twenty one pigmented and one nonpigmented rice cultivars were evaluated for antioxidative activities using the following tests: inhibition of peroxidation of linoleic acid; inhibition of peroxidation of rabbit lipid erythrocyte membranes; reduction of potassium ferricyanide, and scavenging of superoxide anions and hydroxyl radicals. With some exceptions, extracts from the pigmented rice seeds had higher antioxidative activity than did the nonpigmented variety. The following pigmented cultivars had the highest antioxidative activities in all tests: Jumlalocal-1, Parnkhari 203, DZ78, LK1-3-6-12-1-1, and Elwee. A significant correlation was also noted between reducing power, inhibition of erythrocyte ghost membrane peroxidation, and superoxide anion and hydroxyl radical scavenging. The results suggest that: (a) ferricyanide reducing power might be a useful and simple index for large-scale evaluation of antioxidative potencies of natural products present in rice; (b) pigmented rice varieties with high antioxidative activities provide a source of antioxidants and a genetic resource to develop new health-promoting rice cultivars.     

On site experiments of the slanted soil treatment systems for domestic gray water.

In order to make a breakthrough for the acute problem of water shortage in the world, the key words "decentralization and re-use" are very important for new sustainable sanitation systems that will be developed. Therefore, we focused on a new treatments system called "a slanted soil treatment system" which combines a biotoilet system with a domestic grey water treatment system. Because this system is a low cost and compact system, the system can be easily introduced to homes in urban areas or in the suburbs of cities in many developing countries. In this study, we performed on site experiments carried out on Shikoku Island, Japan, for several years. We obtained the following results. The slanted soil treatment system could remove organic pollutants and total nitrogen and total phosphorus in grey water effectively. Furthermore, the system performance became high in the case of the high concentration of the influent water. The nitrification reaction and denitrification reaction were speculated to exist due to aerobic zones and anaerobic zones present in the slanted soil treatment system. The slanted soil treatment system could perform for approximately 3 years with zero maintenance. The plug flow model of 1st order reaction kinetics could describe the reaction in the slanted soil treatment system. However, it is necessary to improve the system to maintain the performance in all seasons.     

Emissions and environmental implications of mercury from artisanal gold mining in North Sulawesi,Indonesia

In artisanal gold mining practiced in North Sulawesi Island, Indonesia, gold is separated from ore by the use of mercury, which forms an amalgam with gold. All related processes are undertaken with a low level of technical knowledge and skills, no regulation, and with disregard for the safety of human and environment health. The situation is generating serious potential health and environmental risks in the area. As part of an ongoing monitoring program, total mercury concentrations were examined in water, bottom sediment and fish samples from three main rivers in Talawaan Watershed, which receives drainage from gold mining practices. Monitoring began in May-June 2000, almost 2 years after artisanal gold mining had begun. At that time, the mercury concentration in the sediment was generally low, except in places close to the gold processing plants. In the present study, a more systematic sampling and analysis was conducted in May-June 2001. Bottom surface sediments, water, and fish samples were collected at 12 sites along the three main rivers in the watershed. In addition, one site outside the watershed was sampled to serve as a control. Sample collections were conducted in three phases in duplicate, with two-week intervals between each phase. The mercury concentration observed in this study indicated that an increase took place along the three main rivers in the watershed. Solutions to this problem must be formulated as soon as possible in order to avoid a major health, economic, and ecological disaster arising from the continuing discharge of Hg. The present study proposes that mercury dispersion occur downstream of the mining.     

Functionalized Bilayer Membranes as Artificial Transaminase: Modification of the Active Site and Its Consequence in Catalytic Efficiency

The transamination reaction of l-phenylalanine with pyruvate as catalyzed by the artificial transaminase formed with synthetic bilayer aggregates was examined in aqueous media under mild kinetic conditions. Each catalyst system was constructed with a combination of a synthetic peptide lipid, a hydrophobic vitamin B₆ derivative, and metal ions. Modification of the active site in the present artificial transaminase was performed by changing a combination of molecular components constituting the catalytic system. While the catalytic activity was scarcely influenced by differences in aggregate structure, single- or multi-walled bilayer, and in copper-(II) concentration, molecular structures of the hydrophobic vitamin B₆ and an amino acid residue of the peptide lipid had significant effects on the reactivity.     

Precise disturbance modeling for improvement of positioning performance

This paper presents a modeling methodology for unknown disturbances in mechatronics systems, based on disturbance estimation using an iterative learning process. In disturbance modeling, nonlinear frictions are specially handled as disturbances in the mechanisms, which mainly degrade trajectory control performance. Friction can be mathematically modeled by using learned estimation data as a function of the displacement, velocity. acceleration, and jerk of the actuator. This model has the distinctive feature that friction compensation can be achieved with a generalization capability for different conditions. The proposed positioning control approach with disturbance modeling and compensation has been verified by experiments using a table drive system on a machine stand. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(2): 31–39, 2010; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/eej.20928