Laser cutting of 7050 Al alloy reinforced with Al2O3 and B4C composites

In the present study, laser cutting of 7050 aluminum alloy sheets reinforced with Al₂O₃ and B₄C particles are carried out. The cut geometry is examined using scanning electron microscope and the optical microscope. The lump parameter analysis technique is used to formulate and determine the kerf width size. The predictions for kerf width are compared with experimental data. The percentage kerf width size variation along the cut edges is determined and the influence of the laser power level and duty cycle of the laser pulses on the percentage kerf width size variation is examined. It is found that 7050 aluminum alloy reinforced with 20% Al₂O₃ composite results in relatively large kerf width size as compared to its counter parts that corresponding to 7050 aluminum alloy reinforced with 20% B₄C composite. The kerf width size predicted agreed with the experimental data for both composites.     

Cost effect of earthquake region and soil type for office buildings in Turkey

In this study, the change in the load-bearing system cost of a reinforced concrete office building has been investigated in relation to the earthquake regions and soil types. Three different office projects each with five stories were investigated. The structural design calculations have been made according to four different soil types and four different earthquake regions. According to each combination, concrete, steel and formwork adopted approximations were calculated to reach the rough cost of each office building. The changes in the cost of projects according to the soil type and earthquake region were examined with multiple regression analysis and analysis of variance. In general, the change in cost has been observed around 22% between first and fourth soil type and 14% between first and fourth earthquake region.     

Listening to Natural and Synthesized Speech while Driving: Effects on User Performance

The effects of message type (navigation, E-mail, news story), voice type (text-to-speech, natural human speech), and earcon cueing (present, absent) on message comprehension and driving performance were examined. Twenty-four licensed drivers (12 under 30, 12 over 65, both equally divided by gender) participated in the experiment. They drove the UMTRI driving simulator on a road consisting of straight sections and constant radius curves, thus yielding two levels of low driving-workload. In addition, as a control condition, data were collected while participants were parked. In all conditions, participants were presented with three types of messages. Each message was immediately followed by a series of questions to assess comprehension. Navigation messages were about 4 seconds long (about 9 words). E-mail messages were about 40 seconds long (about 100 words) and news messages were about 80 seconds long (about 225 words). For all message types, comprehension of text-to-speech messages, as determined by accuracy of response to questions, and by subjective ratings, was significantly worse than comprehension of natural speech (79 versus 83 percent correct answers; 7.7/10 versus 8.6/10 subjective rating). Driving workload did not affect comprehension. Interestingly, neither the speech used (synthesized or natural) nor the message type (navigation, E-mail, news) had a significant effect on basic driving performance measured by the standard deviations of lateral lane position and steering wheel angle.     

Experimental and Theoretical Electron Paramagnetic Resonance (EPR) Study on the Temperature-Dependent Structural Changes of Methylsulfanylmethane

Methylsulfonylmethane (or dimethyl sulfone), a naturally produced and vitally important organosulfur compound in living organisms, was irradiated with gamma rays, and the produced radicals were investigated using electron paramagnetic resonance spectroscopy at different temperatures. The structure and behavior of the radical changed when the temperatures varied. The hyperfine splitting of the CH(3) group was small, and the (33)S splitting was relatively high between 80 and -50 °C. When the temperature was between -50 and -160 °C, the (33)S splitting became small and the CH(3) splitting was higher. However, the group kept rotating; therefore, only the isotropic splitting values were measured, and the g-values were anisotropic. When the temperature decreased below -180 °C, the CH(3) group stopped rotating, and the hydrogen splitting values became nonequivalent due to an inhomogeneous electron distribution. The observed structures can be explained by referring to both the experimental and theoretically calculated values reported.     

瞬态压力突变下管道振动研究

提出非定常流动下管道径向振动控制方程,采用特征线法和有限差分法,并基于阀门快速关闭所引起瞬态压力突变的假设,求解瞬态压力突变下管道径向振动模型.通过数值计算与模型对比发现,该模型具有较好的稳定性.计算结果表明,管道径向振动对流动压力的影响不明显.     

Consistent dynamic model identification of the Stäubli RX-160 industrial robot using convex optimization method

Journal of Mechanical Science and Technology - Dynamic models of robot manipulators with standard dynamic parameters are required for simulations, model-based controller design and external force...     

Pollen morphological investigations of family Cactaceae and its taxonomic implication by light microscopy and scanning electron microscopy

The family Cactaceae is the diversified group of angiosperm plants whose pollen statistics has been used for taxonomic identification. In this article, we present the pollen morphology of eight species belong to seven taxonomically complex genera of Cactaceae including Astrophytum, Cylindropuntia, Echinocereus, Echinopsis, Mammillaria, Opuntia, and Thelocactus using light and scanning electron microscopy. The pollen grains were acetolyzed, measured, described, and electron photomicrographs were taken. Cactaceae can be characterized by presenting different palynomorphological features including pollen type, sculpturing, polar and equatorial diameter, aperture orientation, exine thickness, P/E ratio, and echini features. Four types of pollen shapes, that is, prolate spheroidal (three species), subprolate (two species), prolate (two species), and oblate spheroidal in Echinocereus reichenbachii were observed. The polar and equatorial diameter observed maximum in O. ficus indica 116.95 and 112.27 μm while minimum in M. compressa 38.42 and 21.05 μm. Pollen of two types, tricolpate in members of subfamily Cactioideae and pantoporate in the Opuntioideae were examined. The fertility percentage has been observed maximum in Opuntia macrocentra (83.84%) and minimum in Opuntia ficus‐indica (57.89%). Exine sculpturing showing great variations such as granulate, reticulate, granulate perforate and micro‐echinate foveolate ornamentation was examined only in Echinopsis eyriesii. A key to species, based on pollen micromorphological attributes, has been constructed for correct identification of complex cactus species.