Burning velocities and kinetics of H2/NF3/N2, CH4/NF3/N2, and C3H8/NF3/N2 flames

The combustion characteristics and reaction mechanism of mixtures containing nitrogen trifluoride (NF₃) were investigated. Burning velocities for H₂/NF₃/N₂, CH₄/NF₃/N₂, and C₃H₈/NF₃/N₂ flames were determined for the first time at various equivalence ratios and N₂ mole fractions. The burning velocities of the latter two flames were similar and showed peaks at equivalence ratios of ∼1.0, while those of the H₂/NF₃/N₂ flames had the pronounced peak at low equivalence ratios where the formation of the wrinkled flames was observed. A detailed kinetic model was constructed to simulate the laminar burning velocities of H₂/NF₃/N₂ and CH₄/NF₃/N₂ flames. The model accurately reproduced the experimental results. Analyses of the reaction mechanism revealed the major reaction pathways that involve the decomposition of NF₃, the oxidation and chain-fluoridation of H₂ and CH₄, and the formation of N₂.     

Experimental study of several types of ground heat exchanger using a steel pile foundation

An experimental study of several types of ground heat exchangers (GHEs) installed in a steel pile foundation, including double-tube, U-tube, and multi-tube GHEs, was carried out at Saga University. Water flows through the heat exchangers and exchanges heat to or from the ground. The performance of GHEs was investigated under actual operation in the cooling mode with flow rates of 2, 4, and 8 l/min. Temperatures of the ground and GHE tube wall were measured to find the temperature distributions according to the depth of the ground and depth of the GHE tube wall. The temperatures of the inlet and outlet of circulated water were also measured to calculate the heat exchange rate. The double-tube had the highest heat exchange rate, followed by the multi-tube and U-tube GHEs. For example, the average heat exchange rate of GHEs over 24 h of continuous operation with a flow rate of 4 l/min was 49.6 W/m for the double-tube, 34.8 W/m for the multi-tube, and 30.4 W/m for the U-tube. An increasing flow rate increased the heat exchange rate of the GHEs. The heat exchange rates increased significantly for flow rate increases from 2 to 4 l/min, but only slightly changed from 4 to 8 l/min.     

Tribological Properties and Film Formation Behavior of Thermoreversible Gel Lubricants

The tribological properties of a new and unique thermoreversible gel lubricant (TR gel lube) were investigated. TR gel lube, which includes 10–40% of amide-type gelling agent in base fluid, is able to repeatedly alter or convert phase from gel state to liquid state at the melting point of the gelling agent. High-pressure rheological tests were performed in order to characterize the behavior of base oil and TR gel lube as a function of pressure and temperature. The effect of TR gel lube on ball bearing fatigue life was carried out by systematic tests using thrust ball bearings. The results of L ₁₀ life tests of TR gel lube showed a longer life than the conventional greases. This result was investigated from the oil film formation. It was found that the gelling agent played a key role in the lubricating properties. Some mechanisms such as adsorbed film formation and solid-like formation are proposed.     

Structure and formation of ant transportation networks

Many biological systems use extensive networks for the transport of resources and information. Ants are no exception. How do biological systems achieve efficient transportation networks in the absence of centralized control and without global knowledge of the environment? Here, we address this question by studying the formation and properties of inter-nest transportation networks in the Argentine ant (Linepithema humile). We find that the formation of inter-nest networks depends on the number of ants involved in the construction process. When the number of ants is sufficient and networks do form, they tend to have short total length but a low level of robustness. These networks are topologically similar to either minimum spanning trees or Steiner networks. The process of network formation involves an initial construction of multiple links followed by a pruning process that reduces the number of trails. Our study thus illuminates the conditions under and the process by which minimal biological transport networks can be constructed.     

Two-dimensional full-electromagnetic Vlasov code with conservative scheme and its application to magnetic reconnection

A detailed procedure of full-electromagnetic Vlasov simulation technique is presented. Our new unsplitting conservative scheme exactly satisfies the continuity equation for charge. The implicit Finite Difference Time Domain method is also adopted for computation of electromagnetic fields, which is not restricted by the CFL condition for light. The Geospace Environment Modeling magnetic reconnection challenge problem is adopted as a benchmark test. The characteristics of the present Vlasov code are studied by varying the resolution in configuration space.     

1.5-GHz high-T c superconducting microstrip bandpass filter of miniaturized configuration

A 1.5-GHz four-stage microstrip bandpass filter was designed with the miniaturized hairpin resonator structure to reduce the configuration in size. The filter was fabricated using high-T _c superconducting films on a 12 × 12 mm² LaAlO₃ substrate. The passband insertion loss of the filter was measured to be -0.4 dB at 77 K, while it was estimated by a planar electromagnetic simulator to around -19 dB when gold films are used instead of the superconducting films.     

Characterization of Cu Nanoparticles on TiO2 Photocatalysts Fabricated by Electroless Plating Method

Cu-modified TiO₂ photocatalysts (Cu/TiO₂) were fabricated by electroless plating and wet impregnation methods. Photocatalytic activity for H₂ production over Cu/TiO₂ by electroless plating method was higher than that over Cu/TiO₂ by impregnation method. Characterization of Cu nanoparticles by HRTEM, STEM-EDX, XRD and XAFS was studied. As compared to the wet impregnation method, the electroless plating method resulted in the formation of Cu nanoparticles with small size and uniform distribution on the TiO₂ surface, which caused the enhancement of H₂ production. XAFS measurement provided the evidences for the chemical state change of Cu species during the photocatalytic reaction. The process that Cu species varied from Cu²⁺ into Cu⁰ via Cu¹⁺ as the intermediate under photoirradiation is very important for the H₂ production, which indicates that the metallic Cu nanoparticles acted as the active sites and restrained the photogenerated charges recombination.     

Liquid lens using acoustic radiation force

A liquid lens is proposed that uses acoustic radiation force with no mechanical moving parts. It consists of a cylindrical acrylic cell filled with two immiscible liquids (degassed water and silicone oil) and a concave ultrasound transducer. The focal point of the transducer is located on the oil-water interface, which functions as a lens. The acoustic radiation force is generated when there is a difference in the acoustic energy densities of different media. An acoustic standing wave was generated in the axial direction of the lens and the variation of the shape of the oil-water interface was observed by optical coherence tomography (OCT). The lens profile can be rapidly changed by varying the acoustic radiation force from the transducer. The kinematic viscosity of silicone oil was optimized to minimize the response times of the lens. Response times of 40 and 80 ms when switching ultrasonic radiation on and off were obtained with a kinematic viscosity of 200 cSt. The path of a laser beam transmitted through the lens was calculated by ray-tracing simulations based on the experimental results obtained by OCT. The transmitted laser beam could be focused by applying an input voltage. The liquid lens could be operated as a variable-focus lens by varying the input voltage.     

Molecular structure of La3+-induced methanol dehydrogenase-like protein in Methylobacterium radiotolerans

La(3+) and not Ca(2+) increases methanol dehydrogenase (MDH) activity in Methylobacterium radiotolerans NBRC15690. La(3+)- and Ca(2+)-MDH-like proteins were found to be homodimeric (α(2)) and heterotetrameric (α(2)β(2)), respectively. N-terminal amino acid sequences of these proteins revealed that La(3+)- and Ca(2+)-MDH-like proteins were encoded by xoxF and mxaFI, respectively.