A simple optical method for measuring the vibration amplitude of a speaker

A simple optical method has been proposed for measuring the vibration amplitude of a speaker vibrating with a frequency of approximately 10 kHz. The method is based on a multiple reflection between a vibrating speaker plane and a mirror parallel to that speaker plane. The multiple reflection can magnify a dispersion of the laser beam caused by the vibration, and easily make a measurement of the amplitude. The measuring sensitivity ranges between sub-microns and 1 mm. A preliminary experiment verified the reliability of this method.     

Methane production in a 100-L upflow bioreactor by anaerobic digestion of farm waste

Manure waste from dairy farms has been used for methane production for decades, however, problems such as digester failure are routine. The problem has been investigated in small scale (1–2 L) digesters in the laboratory; however, very little scale-up to intermediate scales are available. We report production of methane in a 100-L digester and the results of an investigation into the effect of partial mixing induced by gas upflow/recirculation in the digester. The digester was operated for a period of about 70 d (with 16-d hydraulic retention time) with and without the mixing induced by gas recirculation through an internal draft tube. The results show a clear effect of mixing on digester operation. Without any mixing, the digester performance deteriorated within 30–50 d, whereas with mixing continuous production of methane was observed. This study demonstrates the importance of mixing and its critical role in design of large scale anaerobic digesters.     

New bounds for the total cross-section and the zero-free radius of the scattering amplitude

The upper bound on σ_T(s) is deduced which seems to be an improvement over the existing ones if one supplements it with the behaviour of the slope parameter data. Bound on the zero-free radius of the scattering amplitude is also obtained.     

3D frictional contact of anisotropic solids using BEM

A numerical method to study three-dimensional (3D) contact problems in solids with anisotropic elastic behavior is developed in this work. This formulation is based on the Boundary Element Method (BEM) for computing the elastic influence coefficients and on projection functions over the augmented Lagrangian for contact restrictions fulfillment. The constitutive equations of the potential contact zone are Signorini’s contact conditions and Coulomb’s law of friction. The formulation uses a recently introduced explicit approach for fundamental solutions evaluation, which are valid for general anisotropic behavior meanwhile mathematical degeneracies are allowed. The accuracy and robustness of the proposed method is illustrated by solving some examples previously presented in the literature. This approach is further applied to study the influence of solids anisotropy on the contact problem.     

Preparation of 3D micro/nanostructured CeO2: Influence of organic/inorganic acids

CeO₂ is an important porous material with a wide range of applications in the abatement of volatile organic compounds (VOCs). In this paper, we prepared a series of novel three-dimensional (3D) micro/nanostructured CeO₂ materials via a solvothermal method. Organic acid-assisted synthesis and inorganic acid post-treatment were used to adjust the CeO₂ microstructures. The size of the 3D micro/nanostructures could be controlled in the range from 180 nm to 1.5 μm and the surface morphology changed from rough to smooth with the use of different organic acids. The CeO₂ synthesized with acetic acid featured a hierarchical porosity and showed good performance for toluene catalytic combustion: a T₅₀ of 187 °C and a T₉₀ of 195 °C. Moreover, the crystallite size, textural properties, and surface chemical states could be tuned by inorganic acid modification. After treatment with HNO₃, the modified CeO₂ materials exhibited improved catalytic activity, with a T₅₀ of ∼175 °C and a T₉₀ of ∼187 °C. We concluded that the toluene combustion activity is related to the porosity and the amount of surface active oxygen of the CeO₂. Both these features can be tuned by the co-work of organic and inorganic acids.     

Field study of a soft X-ray aerosol neutralizer combined with electrostatic classifiers for nanoparticle size distribution measurements

Most conventional aerosol neutralizers are based on radioactive sources, which are controlled by strict regulations restricting their handling, transport, and storage. The TSI 3087 soft X-ray (SXR) neutralizer circumvents these legal restrictions. The aim of the present work is to compare the performance of a standalone SXR aerosol neutralizer with that of conventional radioactive aerosol neutralizers based on ⁸⁵Kr (TSI 3077) and ²⁴¹Am (Grimm 5522) by performing field tests in a real environmental scenario. The results obtained when the SXR neutralizer was connected to a mobility particle sizer spectrometer (MPS), different from the device suggested by the manufacturer, were comparable with those obtained with the use of radioactive aerosol neutralizers. In changing the neutralizer, the particle number concentrations, measured with the MPS connected to the SXR neutralizer, almost remained within the 10% uncertainty bounds for the particle size interval 10–300 nm, when diffusion losses inside the SXR tube were considered. Based on our comparisons, the SXR neutralizer can be regarded as a standalone instrument that could solve the problems associated with legal restrictions on radioactive neutralizers and fulfil the need for a portable instrument for different field test purposes.     

PROPER ORTHOGONAL DECOMPOSITION OF RANDOM WIND PRESSURE FIELD

This paper discusses the application of the Proper Orthogonal Decomposition (POD) technique to randomly fluctuating wind pressure fields acting on a building surface. POD is a method of detecting a new coordinate system which can most efficiently represent the original fluctuating phenomena. This method can identify the deterministic or systematic structure hidden in the random fluctuations and thus help us to understand the phenomena better. It also demonstrates that the coordinate system employed is the most efficient, and can greatly reduce the amount of data that needs to be stored to re-examine the phenomena. Precautions in its application to random fields with mean values and with a singular condition are also mentioned. Furthermore, this paper introduces an example of the method's application to the evaluation of properties and the prediction of responses to wind forces acting on high-rise buildings; the validity of the method is also verified.     

The electronic absorption spectrum and excited state dipole moment of 3-fluoropyridine

The electronic absorption spectrum of 3-fluoropyridine in the vapour state and in solutions in different solvents in the region 3000-1900 Å has been measured and analysed. Three systems of absorption bands; n→π* transition I, π→π* transition II and π→π* transition III are identified. The oscillator strength of the absorption band systems due to the π→π* transition II and π→π* transition III and the excited state dipole moments associated with these transitions have been determined by the solvent-shift method.