桥梁交通振动辐射的低频噪声声场分布研究

交通荷载引起的桥梁振动辐射低频噪声为环境噪声污染的重要来源,分析该低频噪声声场分布特性对评价环境噪声污染程度提供重要依据。结合车桥耦合振动理论和声传播理论,建立了车桥耦合振动辐射低频噪声问题的边界元法求解体系,结合一座钢桥面板连续梁桥,对交通荷载作用下桥梁振动产生的低频噪声声场进行了实验分析和数值模拟,并考察了地面的声反射作用对桥梁附近声场分布和声压水平的影响。分析结果表明,边界元方法用于评价车桥振动辐射低频噪声问题具有较好的适用性和较高的精度,并且能够很好地反映声场在空间的分布规律。算例中的钢桥面板梁桥在车辆荷载作用下由振动引起的低频噪声声压水平与测点距离桥面的距离相关,桥面下方和上方的声压分布规律及水平相似。地面声反射对桥面附近声场的影响显著,考虑地面声反射时,地面与桥面间的距离是影响声压水平的重要因素。     

Boiling and drying accident of high-level liquid waste in a reprocessing plant: Examination of the NO2 and NO generation using the simulated waste

ABSTRACT

NO₂ and NO generated during a boiling and drying accident, which affects the release of volatilized radioactive Ru into the atmosphere, were examined using various samples including simulated high-level liquid waste and a thermogravimetric analyzer. NO₂ and NO in the gas flowing out of the analyzer were measured separately using a NOx analyzer equipped with NO₂ and NO sensors. The samples were heated to 600°C at constant heating rates of mainly 0.2 and 1°C min^?1 that was adopted taking into account the decay heat of high-level liquid waste. It was found that under 180°C some nitrates in the liquid waste mainly separated their nitrate groups as HNO₃ without generating NOx (a mixture of NO and NO₂) and above 300°C the residual HNO₃ in the waste participated in thermal decomposition generating NOx. The generation rates of NO₂ and NO were obtained as a function of time using Arrhenius type equations, and the O₂ rate was derived from these equations using the stoichiometry of the reactions that generate NO₂, NO, and O₂.     

Nitric oxide reduction by char and carbon monoxide: Fundamental kinetics of nitric oxide reduction in fluidizedbed combustion of coal

The reduction of nitric oxide during combustion of coal char in a fluidized-bed combustor was examined with respect to two reactions : a char-catalysed reaction; and a char-consuming reaction, which control nitric oxide emissions. The relative importance of the two reactions was investigated by measuring detailed material balances for the reactions. The product distribution was explained in terms of three fundamental parallel reaction paths. Reaction rates were investigated with a fixed-bed flow reactor over the temperature range 883–1194 K, the same as the fluidized bed combustor.     

Synthesis and properties of multiblock copolymers based on polydimethylsiloxane and piperazine-aromatic polyamides

Polydimethylsiloxane (PDMS)–polyamide multiblock copolymers were synthesized by three different methods, i.e., two-step low-temperature solution polycondensation, one-step solution polycondensation, and interfacial polycondensation. In the two-step method, α,ω-diacid chlorideterminated polyamide oligomers were prepared from trans-2,5-dimethylpiperazine (DMP) and terepthaloyl chloride (TPC) or isophthaloyl chloride (IPC) in chloroform in the presence of triethylamine, which in turn were subjected to reaction with α,ω-bis (3-aminopropyl) polydimethylsiloxane (PDMS–diamine) in the same solvent to from multiblock copolymers. In the one-step method, the reaction components, DMP, TPC (or IPC), and PDMS–diamine, were reacted altogether in chloroform in the presence of triethylamine. In the interfacial method, the reaction components were also reacted altogether in an aqueous sodium hydroxide–chloroform two-phase system. These polycondensations afforded the multiblock copolymers having inherent viscosities of 0.1–1.3 dL g^?1 in m-cresol. The PDMS–polyamide multiblock copolymers dissolved in formic acid and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), and transparent, ductile, and elastomeric films were obtained by casting from the HFIP solutions. The films of the multiblock copolymers prepared by three different methods exhibited similar properties by means of thermal analysis and tensile measurements. In the multiblock copolymers, the tensile strength and modulus of the films decreased with increasing the PDMS content, whereas the elongation at break increased.     

Spherical silicon solar cell with reflector cup fabricated by decompression dropping method

A spherical Si solar cell with a reflector cup was successfully fabricated by a dropping method at decompression state. In the dropping method, melted Si droplets were instilled at decompression state (0.5× 105Pa) to reduce crystal growth rate, dominating crystal quality such as dislocation density in crystal grains. Spherical Si solar cells were fabricated using the spherical Si crystals with a diameter of 1 mm and then mounted on a reflector cup. The current-voltage measurement of the solar cell shows an energy conversion efficiency of 11.1% (short-circuit current density ( Jsc ):24.7 mA·cm-2,open-circuit voltage: 601 mV, fill factor:74.6%). Minority carrier diffusion length determined by surface photovoltage method was 98 μm. This value can be enhanced by the improvement of crystal quality of spherical Si crystals. These results demonstrate that spherical Si crystals fabricated by the dropping method has a great potential for substrate material of high-efficiency and low-cost solar cells.     

Preparation and mechanical properties of chemically cross-linked hydroxypropyl cellulose solid films retaining cholesteric liquid crystalline order

Hydroxypropyl cellulose films were cast from liquid crystalline solutions with a crosslinking agent. The solubility test and the optical measurements of the resultant films were performed. The tensile, dynamic mechanical, and creep properties of the films were determined. The data of solubility in water determined that the cast films are cross-linked, and the data of circular dichroism spectra, that the cast films retain the cholesteric liquid crystalline order (right-handed sense). Both findings clarified that the cast films retain the cholesteric order fixed by cross-linking. The cross-linking depended on the pairs of the solvent–cross-linking agent. The mechanical properties also depended on the pairs: the tensile strength and moduli did not always increase with cross-linking. The creep resistance improved with cross-linking. The thermally activated Eyring process could be applied and the activated volumes were evaluated for water- and methanol-cast films. There were not clear phenomenological correlations between the mechanical properties of our films.     

Multiple Scattering Approximation in Heterogeneous Media by Narrow Beam Distributions

Fast realistic rendering of objects in scattering media is still a challenging topic in computer graphics. In presence of participating media, a light beam is repeatedly scattered by media particles, changing direction and getting spread out. Explicitly evaluating this beam distribution would enable efficient simulation of multiple scattering events without involving costly stochastic methods. Narrow beam theory provides explicit equations that approximate light propagation in a narrow incident beam. Based on this theory, we propose a closed‐form distribution function for scattered beams. We successfully apply it to the image synthesis of scenes in which scattering occurs, and show that our proposed estimation method is more accurate than those based on the Wentzel‐Kramers‐Brillouin (WKB) theory.     

Rapid estimation of peroxide content of soybean oil by measuring thermoluminescence

Thermoluminescence measurements can serve as a simple and rapid procedure for the estimation of peroxide content of soybean oil. The thermoluminescence intensity, measured at 100°C, increases in proportion (r=0.978) to the peroxide value (from 0.5 to 18.0 meq/kg) of soybean oil, without any interference by the tocopherol contents. The emission spectrum had a maximum wavelength at around 440–480 nm, suggesting that excited triplet carbonyls formed during thermal decomposition of hydroperoxides are involved. The thermoluminescence measurement is readily available for the simple and rapid estimation of the peroxide content of soybean oil, with no need for chemical reagents and delicate skills.     

Conjugate heat transfer between internal forced and external natural convections with wall conduction

A new method which combines analytical and numerical solutions is presented for analyzing coupled transport phenomena between multiple regions. The method was applied to simulate heat transfer from hot laminar forced downward convection in a parallel plate duct to external natural convection through a finite section of one wall. Obtained numerical results showed that the longitudinal wall conduction markedly relaxed the thermal interaction between the two convection systems. Experiments were also performed, using conducting walls made of aluminum, stainless steel and granite. Predicted temperature profiles agreed well with the experimental data.     

Scarab beetleAnomala albopilosa albopilosa utilizes a more complex sex pheromone system than a similar speciesA. cuprea

Four compounds have been identified as sex pheromone constituents of the scarab beetleAnomala albopilosa albopilosa, namely (R, Z)-5-(–)-(oct-1-enyl)oxacyclopentan-2-one (buibuilactone), 2-(E)-nonenol, 2-(E)-nonenal, and methyl benzoate (in the ratio 10:3:3:1). The diel rhythm of pheromone release inA. a. albopilosa showed a peak at the beginning of the scotophase, which is also a peak of mating activity. On the other hand, the similar speciesA. cuprea utilizes a two-constituent sex pheromone, having a common major component, but the pheromone is released both during scoto-and photophase. Temporal difference in mating activity and pheromone release along with chemical diversity seem to form the basis for maintaining species specificity in pheromonal communication betweenA. a. albopilosa andA. cuprea.