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61.
62.
Human walking influences indoor air quality mainly by resuspending dust particles settled on the floor. This study characterized walking‐induced particle resuspension as a function of flooring type, relative humidity (RH), surface dust loading, and particle size using a consistent resuspension mechanism. Five types of flooring, including hardwood, vinyl, high‐density cut pile carpet, low‐density cut pile carpet, and high‐density loop carpet, were tested with two levels of RH (40% and 70%) and surface dust loading (2 and 8 g/m2), respectively. Resuspension fraction ra (fraction of surface dust resuspended per step) for house dust was found to be varied from 10?7 to 10?4 (particle size: 0.4–10 µm). Results showed that for particles at 0.4–3.0 µm, the difference in resuspension fraction between carpets and hard floorings was not significant. For particles at 3.0–10.0 µm, carpets exhibited higher resuspension fractions compared with hard floorings. Increased RH level enhanced resuspension on high‐density cut pile carpet, whereas the opposite effect was observed on hard floorings. Higher surface dust loading was associated with lower resuspension fractions on carpets, while on hard floorings the effect of surface dust loading varied with different RH levels.  相似文献   
63.
A localized fire in a 3-D tunnel is analyzed by solving a combined-mode natural-convection and radiation problem. Nonlocal thermal equilibrium between air and smoke is considered. Separate energy equations are used for the two species. The density and temperature fields required for the solution of the energy equation are computed using the lattice Boltzmann method. The finite-volume method is used to compute radiative information. The energy equations are solved using the fully explicit upwind scheme. The Boussinesq approximation is used to account for the buoyancy effect. Effects of the scattering albedo, the convection-radiation parameter, and the wall emissivities on temperature profiles in the tunnel have been studied.  相似文献   
64.
This paper develops an integrated production-recycling system over a finite time horizon. Here, the dynamic demand is satisfied by production and recycling. The used units are bought back and then either recycled or disposed of which are not repairable. The used units are collected continuously from the customers. Recycling products can be used as new products which are sold again. The rate of production and disposal are assumed to be function of time. The setup cost is reduced over time due to “Learning curve” effect. The optimum results are presented both in tabular form and graphically.  相似文献   
65.
Nepal, one of the least developed countries, is characterized by low per capita energy consumption and hugely dominated by traditional energy sources. Despite having enormous potential of hydro-electricity, only 50% of the total population has access to grid electricity. Firewood is the primary energy source for domestic purposes in rural environments. Due to geographical remoteness, a scattered consumer, higher costs of supply and maintenance, low consumption and low level of households’ income linking the rural areas to national electricity grid is difficult and implausible. In order to solve the energy problem in rural areas, Nepal’s government has initiated the production and distribution of several renewable energy technologies. Among several renewable technologies, micro-hydropower has been one of the most promising and widely adopted decentralized technologies to distribute electricity in rural areas. This article begins with a general overview of energy situation in Nepal. Present status and perspective of micro-hydro plants have also been discussed. Similarly, the dynamics of the relationship between electricity and socio-economic development has been analyzed by means of a typical rural electrification project in Tangting, Nepal by assessing the impacts of electricity on health, education, environment, and income in the village. The community has greatly benefitted from the arrival of environment friendly and affordable electricity. It has been concluded that the task of providing electricity to more remote and isolated villages is still challenging in Nepal. More systematic and comprehensive study supported by research and development is required to extend micro-hydro based electricity in more remote and poor communities of Nepal.  相似文献   
66.
Anup Das  Sourabh Ghosh 《Polymer》2011,52(17):3800-3810
Stimulus responsive hydrogels are being considered as one of the most crucial biomaterials of current generation. A new technique has been established for developing hydrogels based on Acrylic acid (AAc) and N-[3-(Dimethylamino)propyl]-methacrylamide (DMAPMA), and relevant mechanism has been delineated. Aqueous redox copolymerization of different molar ratios of AAc and DMAPMA at 41 ± 1 °C, leading to the formation of interlocked nanogels of ∼300 nm diameter, which acted as the building blocks of a series of superabsorbent hydrogels having robust, honey-comb type three-dimensional architecture. Monomer composition, monomer feed ratio and water content in feed has been found to be important factors in the development of the stable poly(AAc-co-DMAPMA) hydrogel membranes (PADMAs) without any active crosslinking agent. At the cues of pH change from 7.0 to 3.5, pulsatile swelling-deswelling behavior varied, ranging from ∼5900% to ∼60% (mass) respectively, underlining smart hydrogel characteristics needed for specific biomedical applications. Elastic modulus of the gels, equilibrated at pH 7.0, is recorded to be >15 kPa under uniaxial compression. Underlying mechanism of the formation of such robust three-dimensional structures in poly(AAc-co-DMAPMA) hydrogel membranes, and the origin of hierarchical ‘nano-to-macro’ scale morphological features has been proposed.  相似文献   
67.
Submerged arc welding is well-known for its very high deposition rate and thus the capability to join very high thickness metal pieces in large structural applications. Fillet joints are mostly used in structural applications which can be extensively seen in shipbuilding, bridge construction, house buildings, automobile or any other large structures. Thermal stresses generates in a fusion welded joint due to high temperature gradient, which is the cause of the residual stresses upon cooling followed by the angular deformation and failure of the welded structure. As an effect of the thermal gradient, the induced longitudinal, transverse residual stress & angular distortion can vary in single sided and double sided submerged arc welded fillet joints, during designing & manufacturing welded structures which should be taken into account. The main objective of this paper is to quantify the amount of residual stresses and angular deformation in a fillet welding joint. An elasto-plastic thermomechanical model has been developed for predicting residual stresses. A comparison of the residual stress and angular deformation between single and double sided fillet weld joint has been made. The simulation results reveal that the amount of residual stress present in the single sided fillet weld is more and unbalanced in both side of the center of weld line compared to the double sided fillet weld and the predicted results have been matched with the experiments as well as published literatures.  相似文献   
68.
In this communication, the formation mechanism of the electroactive β phase, morphology and the dielectric activities of increasing doping concentration (0–1.2 M.W % of mullite) of Fe2+ ion-doped, mullite-impregnated polyvinylidene fluoride (PVDF) nanocomposite have been investigated. Differential thermal analysis (DTA) confirms the formation of an electroactive β phase, and Fourier transform infrared spectroscopy (FTIR) showed that the β phase increases simultaneously and attains the maximum increment of 2.6 times compared to pristine PVDF. X-ray diffraction (XRD) spectra also agreed well with the β-phase increment behaviour and also confirmed the presence of required mullite phases. Field emission scanning electron microscopy (FESEM) images indicate the strong interaction between the polymer matrix and different concentrations of Fe2+ ion-doped mullite particles, resulting in enhanced electroactive β phase formation and large dielectric constant of the nanocomposite films followed by significant low dielectric loss with high ac conductivity compared to pristine PVDF films at room temperature. This doped polymer composite can be used as a high dielectric separator and, using this separator, we have successfully fabricated a high-charge-storage device. This paper also demonstrates that the loading of conductive Fe2+ ions within the highly insulating mullite matrix has a critical concentration for the enhancement and nucleation of the electroactive β phase of the PVDF polymer. In this critical concentration, the highest formation of a β network and maximum numbers of homogeneously distributed iron-doped mullite (FeM) particles in PVDF matrix improves the effective interfacial polarization by Maxwell–Wagner–Sillar (MWS) polarization effect which is responsible for the enhancement of dielectric constant and ac conductivity followed by significant tangent loss. So, it can be concluded that the incorporation of Fe2+-doped mullite into PVDF matrix is an effective way to fabricate a high dielectric separator of high-charge-storage electronic devices.  相似文献   
69.
SnO2 nanowires and nanobelts have been grown by the thermal evaporation of Sn powders. The growth of nanowires and nanobelts has been investigated at different temperatures (750–1000°C). The field emission scanning electron microscopic and transmission electron microscopic studies revealed the growth of nanowires and nano-belts at different growth temperatures. The growth mechanisms of the formation of the nanostructures have also been discussed. X-ray diffraction patterns showed that the nanowires and nanobelts are highly crystalline with tetragonal rutile phase. UV-visible absorption spectrum showed the bulk bandgap value (∼ 3–6 eV) of SnO2. Photoluminescence spectra demonstrated a Stokes-shifted emission in the wavelength range 558–588 nm. The Raman and Fourier transform infrared spectra revealed the formation of stoichiometric SnO2 at different growth temperatures.  相似文献   
70.
Conventional stereo imaging uses area CCDs for which depth perception error has been analyzed in our past research (Comput. Vision Image understand. 63 (3) (1996) 447). In this work we analyze the depth perception error for a stereo system that uses two rotating linear CCD cameras to create cylindrical stereo images. Theoretical analysis shows certain advantages to cylindrical stereo imaging over conventional methods. Initial experimental results are presented to validate the theoretical results. Unlike normal area CCDs, cylindrical images captured by rotating linear CCD cameras can produce very high-resolution images thereby substantially reducing the error in 3D estimation.  相似文献   
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