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891.
Natural weathering has been applied to investigate the properties of recycled newspaper (RNP)-filled polypropylene (PP)/natural rubber (NR) composites. Three sizes of RNP (11 mm, 23 mm, and 53 mm) were used in this study. These composites were subjected to natural weathering conditions; i.e, tropical climate in Penang, Malaysia, for 3 and 6 months. Different techniques including mechanical tests, Fourier transform infrared spectrometry (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were used in order to obtain a comprehensive view of degradation occurring during the natural weathering of the composites. Results of mechanical tests show that an increasing content of RNP in composites decreased the tensile strength and elongation at break (EB), while increasing the Young's modulus after exposure of 3 and 6 months. Scanning electron microscopy on surfaces after weathering shows that the filler was poorly wetted by the matrix. This explains the reduction in tensile strength and elongation at break after weathering. The Fourier transform infrared spectrometry results on the composites after exposure to natural weathering indicate the presence of carbonyl, vinyl, and hydroxyl groups, which formed from various chemical reactions taking place during weathering. 相似文献
892.
Electrokinetic and rheological properties of Na-bentonite suspensions were investigated in the presence of various electrolyte solutions including LiCl, NaCl, KCl, NH4Cl, NaClO4, CH3COONa, NaNO3, Na2SO4, Na3PO4, CuCl2, MnCl2, CaCl2, BaCl2, NiCl2 and AlCl3. It was found that divalent cations (Cu2+, Mn2+, Ca2+, Ba2+ and Ni2+) and trivalent cation (Al3+) were potential determining cations for the Na-bentonite suspensions. Trivalent cation, Al3+, changed the surface charge of Na-bentonite from negative to positive. The zeta potential measurements showed that monovalent counter-cations and mono-, di- and tri-valent anions were indifferent ions for the Na-bentonite suspensions. The plastic viscosity and the Bingham yield stress values of the Na-bentonite suspensions were also determined in the presence of electrolyte solutions. 相似文献
893.
Static Performance of Finite Hydrodynamic Journal Bearings Lubricated by Magnetic Fluids with Couple Stresses 总被引:1,自引:0,他引:1
Based upon the Stokes micro-continuum theory, the problem of lubrication of finite hydrodynamic journal bearing lubricated
by magnetic fluids with couple stresses is investigated. By taking into account the couple stresses due to the microstructure
additives and the magnetic effects due to the magnetization of the magnetic fluid, modified Reynolds equation is obtained.
The effects of couple stresses are studied by defining the couple stress parameter L that can be considered as a measure of the chain length of the additive molecule. The magnetic effects of the magnetic fluid
are investigated by the magnetic coefficient γ. Using the finite-difference technique and for different values of couple stress
parameter and magnetic coefficient, the Reynolds equation is solved, and pressure distributions are obtained. The bearing
static characteristics namely load carrying capacity, attitude angle, friction coefficient, and side leakage flow are determined.
The results indicate that the influence of couple stresses and magnetic effects on the bearing characteristics are significantly
apparent. It is concluded that fluids with couple stresses are better than Newtonian fluids. The improvement of the bearing
characteristics is enhanced if the magnetic effects are present. 相似文献
894.
The results of a series of fatigue tests, on slender plate girders subjected to repeated shear loading, are summarised and used to establish a lower bound fatigue strength curve for the welded web boundary, based on geometric or principal surface stress ranges. The propagation of a semi-elliptical surface crack, through the thickness of a plate, is studied using fracture mechanics concepts. An extensive parametric study indicates that the initial crack size and aspect ratio, the geometric stress concentration at the weld toe, and the plate thickness, all have a significant influence on fatigue strength. It is concluded that the fracture mechanics approach requires specification of a number of parameters which are difficult to determine in practice. However, having specified a realistic crack size and aspect ratio and an approximate stress concentration at the weld toe, the solution can be calibrated against available experimental fatigue strength curves. 相似文献
895.
The adsorption of series of commercial nonionic ethoxylated fatty acid surfactants Co(EO)n (where n = 20, 40, and 80) onto low carbon mild steel is investigated at 25°C in 0.25 M H2SO4. The adsorption isotherms of both Co(EO)20 and Co(EO)80 are L‐shaped representing the formation of a monolayer while Co(EO)40 was beginning by an L‐shaped followed by the formation of a multilayer. The level of the plateau shown by these samples decreases in the order Co(EO)80 > Co(EO)20 > Co(EO)40. The effect of this adsorption on the protection of steel against corrosion in sulfuric acid has been studied. Potentiodynamic polarization studies clearly reveal the fact that these surfactants act as mixed‐type inhibitors. The inhibition efficiency increases with increasing the concentration as well as the hydrophilic chain length of these compounds. 相似文献
896.
Loop parallelization is an important issue in the acceleration of the execution of scientific programs. To exploit parallelism
in loops a system of equations representing the dependencies between the loop iterations and a system of non-equations indicating
the loop boundary conditions has to be solved. This is a NP-Complete problem. Our major contribution in this paper has been
to apply genetic algorithm to solve system of equation and non-equation resulted from loop dependency analysis techniques
to find two dependent loop iterations. We use distance vector to find the rest of dependencies. 相似文献
897.
A. Enis Çetin Kosmas Dimitropoulos Benedict Gouverneur Nikos Grammalidis Osman Günay Y. Hakan Habiboǧlu B. Uǧur Töreyin Steven Verstockt 《Digital Signal Processing》2013,23(6):1827-1843
This is a review article describing the recent developments in Video based Fire Detection (VFD). Video surveillance cameras and computer vision methods are widely used in many security applications. It is also possible to use security cameras and special purpose infrared surveillance cameras for fire detection. This requires intelligent video processing techniques for detection and analysis of uncontrolled fire behavior. VFD may help reduce the detection time compared to the currently available sensors in both indoors and outdoors because cameras can monitor “volumes” and do not have transport delay that the traditional “point” sensors suffer from. It is possible to cover an area of 100 km2 using a single pan-tilt-zoom camera placed on a hilltop for wildfire detection. Another benefit of the VFD systems is that they can provide crucial information about the size and growth of the fire, direction of smoke propagation. 相似文献
898.
在分析一般语音语料库建设方法的基础上,结合实际语料库需求和地域语言特点,提出了适用于电话信道维吾尔语口语语料库建设的设计规范及语音采集、标注方法,建立了时长300小时的电话信道维吾尔语口语语料库,并就电话信道对线性预测倒谱系数(LPCC)、梅尔倒谱系数(MFCC)、自适应成分加权特征(ACW)倒谱等语音特征参数的影响进行分析研究。 相似文献
899.
ShuWei Liu ChenHui Zhang Eryilmaz Osman XinChun Chen TianBao Ma YanZhong Hu JianBin Luo Erdemir Ali 《中国科学:技术科学(英文版)》2016,59(12):1795-1803
In this study, we mainly focus on the structural morphology and inter-atomic bonding state of tribofilms resulting from a highly-hydrogenated amorphous carbon (a-C:H) film in order to ascertain the underlying mechanisms for its superlubric behavior (i.e., less than 0.01 friction coefficient). Specifically, we achieved superlubricity (i.e., friction coefficients of down to 0.003) with this film in dry nitrogen and argon atmospheres especially when the tribo-pair is made of an a-C:H coated Si disk sliding against an a-C:H coated steel ball, while the a-C:H coated disk against uncoated ball does not provide superlubricity. We also found that the state of superlubricity is more stable in argon than in nitrogen and the formation of a smooth and uniformly-thick carbonaceous tribofilm appears to be one of the key factors for the realization of such superlubricity. Besides, the interfacial morphology of sliding test pairs and the atomic-scale bond structure of the carbon-based tribofilms also play an important role in the observed superlubric behavior of a-C:H films. Using Raman spectroscopy and high resolution transmission electron microscopy, we have compared the structural differences of the tribofilms produced on bare and a-C:H coated steel balls. For the a-C:H coated ball as mating material which provided superlow friction in argon, structural morphology of the tribofilm was similar or comparable to that of the original a-C:H coating; while for the bare steel ball, the sp2-bonded C fraction in the tribofilm increased and a fingerprint-like nanocrystalline structure was detected by high resolution transmission electron microscopy (HRTEM). We also calculated the shear stresses for different tribofilms, and established a relationship between the magnitude of the shear stresses and the extent of sp3-sp2 phase transformation. 相似文献
900.
Ertaç Hürdoğan Coskun Ozalp Osman Kara Mustafa Ozcanli 《International Journal of Hydrogen Energy》2017,42(36):23373-23378
Disposal of waste tires is one of the most important problems that should be solved. This problem can be solved by considering waste tires for production of hydrogen or fuel for diesel engines. This paper presents the studies on the performance and emission characteristics of a four stroke, four cylinders, naturally aspirated, direct-injected diesel engine running with various blends of waste tire pyrolysis oil (WTPO) with diesel fuel. Fuel properties, engine performance, and exhaust emissions of WTPO and its blends were analyzed and compared with those of petroleum diesel fuel. The experimental results showed that WTPO–diesel blends indicated similar performance with diesel fuel in terms of torque and power output of the test engine. It was found that the blends of pyrolysis oil of waste tire WTPO10 can efficiently be used in diesel engines without any engine modifications. 相似文献