A new safety assessment method for parallel routes is presented. From the aspects of safety guard system of air traffic control(ATC) and considering the flight conflict as causing event of air collision accidents, t...A new safety assessment method for parallel routes is presented. From the aspects of safety guard system of air traffic control(ATC) and considering the flight conflict as causing event of air collision accidents, this paper fosters a four-layer safety guard of controller command, short-term conflict alerts (STCAs), pilot visual avoidance, and traffic alert collision avoidance system(TCAS). Then, the problem of parallel routes collision risk is divided into two parts:the calculation of potential flight conflict and the analysis of failure probability of the four-layer safety guard. A calculation model for controller interference times is induced. By using cognitive reliability and error analysis method(CREAM),the calculation problem to failure probability of controller sequencing flight conflicts is solved and a fault tree model of guard failure of STCA and TCAS is established. Finally, the Beijing-Shanghai parallel routes are taken as an example to be calculated and the collision risk of the parallel routes is obtained under the condition of radar control. Results show that the parallel routes can satisfy the safety demands.展开更多
Advanced microfluidic technology was used to examine the microscopic viscous and inertial effects evolution of water flow in rock joints. The influence of void space on fluid flow behaviour in rock joints under differ...Advanced microfluidic technology was used to examine the microscopic viscous and inertial effects evolution of water flow in rock joints. The influence of void space on fluid flow behaviour in rock joints under different flow velocities was experimentally investigated at the micro scale. Using advanced fabrication technology of microfluidic device, micro flow channels of semicircular, triangular, rectangular and pentagonal cavities were fabricated to simulate different void space of rock joints, respectively. Using the fluorescence labelling approach, the trajectory of water flow was captured by the microscope digital camera when it passed over the cavity under different flow velocities. The flow tests show that the flow trajectory deviated towards the inside of the cavity at low flow velocities. With the increase in flow velocity, this degree of flow trajectory deviation decreased until there was no trajectory deviation for flow in the straight parallel channel. The flow trajectory deviation initially reduced from the void corner near the entrance. At the same time, a small eddy appeared near the void corner of the entrance. The size and intensity of the eddy increased with the flow velocity until it occupied the whole cavity domain. The gradual reduction of flow trajectory near the straight parallel channel and the growth of eddy inside the cavity reflect the evolution of microscopic viscous and inertial forces under different flow velocities.The eddy formed inside the cavity does not contribute to the total flow flux, but the running of the eddy consumes flow energy. This amount of pressure loss due to voids could contribute to the nonlinear deviation of fracture fluid flow from Darcy's law. This study contributes to the fundamental understanding of non-Darcy's flow occurrence in rock joints at the micro scale.展开更多
Knowledge of the culture difference in inter-cultural communicative is of primary importance. It is so in Sino-American communication, especially in speech, one of the two means of communication through language, with...Knowledge of the culture difference in inter-cultural communicative is of primary importance. It is so in Sino-American communication, especially in speech, one of the two means of communication through language, with the other being writing. American and Chinese, brought up in different cultures, have different speech styles. Diversity in speech styles not only involves communication through verbal speech, but also through such non-verbal acts as kinesics, proxemics, and paralinguistic elements. Here the speech styles in the two cultures, American and Chinese, are contrasted with examples from a cultural perspective.展开更多
The biomedical co-continuous(β-TCP+MgO)/Zn-Mg composite was fabricated by infiltrating Zn-Mg alloy into porousβ-TCP+MgO using suction exsorption technique.The microstructure,mechanical properties and corrosion behav...The biomedical co-continuous(β-TCP+MgO)/Zn-Mg composite was fabricated by infiltrating Zn-Mg alloy into porousβ-TCP+MgO using suction exsorption technique.The microstructure,mechanical properties and corrosion behaviors of the composite were evaluated by means of scanning electron microscopy(SEM),X-ray diffraction(XRD),mechanical testing,electrochemical and immersion test.It was found that the molten Zn-Mg alloy had infiltrated not only into the pores but also into the struts of the porousβ-TCP+MgO scaffold to form a compact composite.The Zn-Mg alloy contacted to theβ-TCP+MgO scaffold closely,and no reaction layer can be found between the alloy and the scaffold.The compressive strength of the composite was as high as244MPa,which was about1000times higher than that of the original porousβ-TCP+MgO scaffold and2/3of the strength of the Zn-Mg bulk alloy.The electrochemical and immersion tests in simulated body fluid(SBF)solution indicated that the corrosion resistance of the composite was better than that of the Zn-Mg bulk alloy.The corrosion products on the composite surface were mainly Zn(OH)2.Appropriate mechanical and corrosion properties indicated that the(β-TCP+MgO)/Zn?Mg composite fabricated by suction exsorption would be a very promising candidate for bone substitute.展开更多
Based on our previously pulse-coupled integrate-and-fire neuron model in small world networks, we investigate the effects of different connectivity topologies on complex behavior of electroencephalographic-like signal...Based on our previously pulse-coupled integrate-and-fire neuron model in small world networks, we investigate the effects of different connectivity topologies on complex behavior of electroencephalographic-like signals produced by this model. We show that several times series analysis methods that are often used for analyzing complex behavior of electroencephalographic-like signals, such as reconstruction of the phase space, correlation dimension, fractal dimension, and the Hurst exponent within the rescaled range analysis (R/S). We lind that the different connectivity topologies lead to different dynamical behaviors in models of integrate-and-fire neurons.展开更多
Numerical computation models of air cooling heat transfer and flow behaviors in triangular wavy fin channels(TWFC) were established with structural parameters of fins considered.The air side properties of heat transfe...Numerical computation models of air cooling heat transfer and flow behaviors in triangular wavy fin channels(TWFC) were established with structural parameters of fins considered.The air side properties of heat transfer coefficient and pressure drop are displayed with variable structural parameters of fins and inlet velocities of cooling air.Within the range of simulation,TWFC has the best comprehensive performance when inlet velocity vin=4-10 m/s.Compared with those of straight fins,the simulation results reveal that the triangular wavy fin channels are of higher heat transfer performances especially with the fin structural parameters of fin-height Fh=9.0 mm,fin-pitch Fp=2.5-3.0 mm,fin-wavelength λ=14.0-17.5 mm and fin-wave-amplitude A=1.0-1.2 mm.The correlations of both heat transfer factor and friction factor are presented,and the deviations from the experimental measurements are within 20%.展开更多
An experiment was conducted at the Department of Horticulture, College of Agriculture and Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi (KNUST) Ghana from September, 2009 to April, 20...An experiment was conducted at the Department of Horticulture, College of Agriculture and Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi (KNUST) Ghana from September, 2009 to April, 2010, to determine the most appropriate drying method, as a post harvest practice, that would ensure high percentage germination ofAnnona squamosa seeds and its subsequent effect on seedling growth. The seeds were sun-dried, air-dried under shade or kept in the fresh state. Five treatments were used, namely, Freshly Sown seeds (Treatment 1, control), Seeds Air-Dried under Shade for one day (Treatment 2); Seeds Sun-Dried for one day (Treatment 3); Seeds Air-Dried under Shade for three consecutive days (Treatment 4); Seeds Sun-Dried for three consecutive days (Treatment 5). The experiment was arranged in a Completely Randomized Design (CRD) and replicated three times. Drying of Annona squamosa seeds had significant effect on earliness and number of seeds germinated. Air drying under shade and sun-drying for three consecutive days improved earliness to germination (26 days after sowing) and percent total germination but air-drying under shade had better effect on total seed germination, achieving 90% germination in 42 days after sowing. Furthermore, the prevailing ambient temperature of 30 ℃-32 ℃ enhanced germination of Annona squamosa seeds. The study concluded that for optimum germination, seeds of Annona squamosa should be either air-dried or sun-dried for three consecutive days and be incubated in an ambient temperature range of 30 ℃-32 ℃. In terms of growth, seedling growth in leaf production was better from seeds sun-dried for three consecutive days.展开更多
The traction behavior of space lubricating oil No. 4116 was measured and analyzed at various oil inlet temperatures below 0 ℃ and various rolling speeds under normal loads by a test rig simulating the operating condi...The traction behavior of space lubricating oil No. 4116 was measured and analyzed at various oil inlet temperatures below 0 ℃ and various rolling speeds under normal loads by a test rig simulating the operating conditions of space bearings. A traction coefficient calculation model was presented. The rheological property and rheological parameters of the lubricant at a low oil inlet temperature were analyzed based on the Tevaarwerk-Johnson model. The results showed that the lubricating oil No. 4116 was sensitive to the rolling speed and had lower sensitivity to the normal load. This lubricating oil is more suitable for applications under high speed when it is used below 0 ℃. It behaves as an elastic-plastic fluid operating below 0 ℃. Both the average limiting shear stress and the average elastic shear modulus have a negative correlation with the rolling speed and oil inlet temperature and have a positive correlation with the normal load.展开更多
The aim of this paper is to collect information about dairy cow's behaviour connected to different environmental conditions. During summer 2009 and winter 2010 experimental trials were arranged to verify the behaviou...The aim of this paper is to collect information about dairy cow's behaviour connected to different environmental conditions. During summer 2009 and winter 2010 experimental trials were arranged to verify the behaviour of dairy cows in a farm located in Po Plain (Italy). The barn was provided with an air-water cooling system, based on the use of fans and sprinklers placed only in the feeding alley. Two different trials were carried out. The first experiment was targeted on verifying the use of the cubicles by the cows in relation to the availability of the cooling system only in feeding area. The second trial aimed at testing the effectiveness of zone cooling systems placed in the front of cubicles. For this purpose three cubicles in the barn were provided with cooling systems, based on the input of high velocity conditioned air streams. The results clearly remark that the behaviour of the animals is greatly influenced by the environmental conditions. With high temperatures the use of the cubicles is deeply reduced and the animals prefer to stay in feeding area, thus benefiting from the cooling effect of water sprinkled by the showers and of the air streams created by the fans. With air temperatures increasing from 21℃ to 33 ℃ the cows reduce the staying in the cubicles, which gets down from 540 to 32% (r2 = 0.2608). As regards the efficacy of zone cooling system in the cubicles, the results are not particularly encouraging. The cows continue to use the cubicles without changing the behaviour in relation to the presence of conditioned air flow.展开更多
For simulating the real deactivation of hollow titanium silicalite(HTS) zeolite in commercial ammoximation process, HTS was treated by 10% NH_3·H_2O solution at 120 ℃ in stirred autoclave. It is found that a par...For simulating the real deactivation of hollow titanium silicalite(HTS) zeolite in commercial ammoximation process, HTS was treated by 10% NH_3·H_2O solution at 120 ℃ in stirred autoclave. It is found that a part of HTS zeolite crystals dissolved in the hot NH_3·H_2O solution, and the specific surface area and pore volume continuously decreased with the increase in NH_3 hydrothermal treatment time. Meanwhile, the transformation of framework Ti species into extraframework Ti species was detected by the spectroscopic methods. However, the extraframework Ti species were still in a highly dispersed state after the hydrothermal and thermal treatments as shown by TEM images, while the formation of new acid sites was not detected. Upon combining the results of characterization with catalytic performance of HTS, the main deactivation reason for this material had been determined, which might be attributed to the reduction of specific surface area and active centers after basic treatment and calcination of HTS samples. And then the possible mechanism of simulated deactivation of HTS zeolite was proposed, which could describe the elemental reaction steps much more visually and directly.展开更多
The dynamic mechanical properties of rock specimens after thermal treatment in the air-filled environment(AE:i.e.,at the free surface)have been extensively investigated,yet they are rarely estimated in the quasi-vacuu...The dynamic mechanical properties of rock specimens after thermal treatment in the air-filled environment(AE:i.e.,at the free surface)have been extensively investigated,yet they are rarely estimated in the quasi-vacuum environment(VE:i.e.,far from free surface),which is of special importance in engineering practice.Several precise laboratory tests(i.e.,split Hopkinson pressure bar test)on marble samples in both AE and VE were performed to investigate physical and dynamic mechanical behaviors of marble after heat treatment(25℃ to 900℃)in AE and VE.The tests results demonstrate that related properties of marble could be divided into three different stages by corresponding critical temperatures of 300℃ and 600℃,at which heat damage factors are 0.29(0.30)and 0.88(0.92)in VE(AE),respectively.The thermal damage developes more fully in AE than in VE.The thermal environment plays an important role,especially in Stage 3.Specifically,a conspicuous difference(greater than 20%)between AE and VE occurs in corresponding dynamic strength and the anti-deformation capacities of tested marble specimen.The influence of heat damage of rock is very important and valuable in engineering practice,particularly when the temperature is very high(greater than 600℃).展开更多
SiC_(p)/AZ91 composites were prepared by vacuum pressure infiltration.The microstructure,mechanical properties and wear resistance of composite were studied.Results indicated that SiC particles were uniformly distribu...SiC_(p)/AZ91 composites were prepared by vacuum pressure infiltration.The microstructure,mechanical properties and wear resistance of composite were studied.Results indicated that SiC particles were uniformly distributed in the metal matrix and had a good interface bonding with the metal matrix.Mg_(17)Al_(12) preferably precipitated near the SiC particles,and high-density dislocations were induced by the mismatch of the coefficient of thermal expansion(CTE)between the SiC particle and the AZ91 matrix,thereby accelerating the aging precipitation of the matrix.Compared with AZ91 alloy,the addition of SiC particles improves the hardness and compressive strength of the composite,which is mainly due to the load transfer strengthening and grain refinement strengthening mechanisms.Furthermore,a stable support surface-protecting matrix formed during the wear process because of the excellent wear resistance of SiC.展开更多
Sustainable building design in dry tropical areas recommends reducing exposure of buildings to solar radiation and/or designing efficient enclosures with satisfactory thermal inertia.We propose in this paper a study o...Sustainable building design in dry tropical areas recommends reducing exposure of buildings to solar radiation and/or designing efficient enclosures with satisfactory thermal inertia.We propose in this paper a study of the influence of the infiltration rate in the building and the coefficient of thermal transfer by convection of the walls, on the thermal comfort using TRNSYS software. All the models carried out were validated by recognized scientific criteria, namely correlation (R) and determination (R2) coefficients on the one hand and NBME and CVRMSE coefficients defined by ASHARE, 2002 on the other hand. The results obtained indicate that the modulation of the air infiltration rate allows the simulations on TRNSYS to be compared to in-situ measurements, with an annual average relative difference of 2.86% on the temperature difference. Furthermore, depending on the parameterization of the heat transfer coefficients by convection of the internal and external walls of walls used in the STD, the average annual difference can be reduced by 1% to 4% between the predictions and the measurements.展开更多
Vacuum die casting can reduce the'air entrapment'phenomenon during casting process.Based on the temperature measurements at metal-die interface with different processing parameters,such as slow shot speed(VL),...Vacuum die casting can reduce the'air entrapment'phenomenon during casting process.Based on the temperature measurements at metal-die interface with different processing parameters,such as slow shot speed(VL),high shot speed(VH),pouring temperature(Tp)and initial die temperature(Tm),inverse method was developed to determine the interfacial heat transfer coefficient(IHTC).The results indicate that a closer contact between the casting and die could be achieved when the vacuum system is used.It is found that the vacuum could strongly increase the values of IHTC and decrease the grain size in castings.The IHTC could have a higher peak value with increasing the Tp from680to720℃or the VL from0.1to0.4m/s.In addition,the influence of the VH and Tm on IHTC could be negligible.展开更多
The paper takes the relation between soundscapes and power struggles as its problem area and focuses on the role of music that is performed in public protests. It argues that music and street performances are conceive...The paper takes the relation between soundscapes and power struggles as its problem area and focuses on the role of music that is performed in public protests. It argues that music and street performances are conceived and therefore utilised as sonic acts of political struggle in urban realm. Starting with a general understanding of hearing mechanisms, the study elucidates the relationships among territoriality of soundscape, identity construction, social segregation and polarisation, and finally, power struggle. Within the framework of the intersection area of these concepts, the paper discusses the processes of politisation of soundscape through music as a form of protest event that is performed in public realm. Throughout the paper, it is focused on the significant cases of public protests as well as political events that occured in public space. The main emphasis is on the use of sound technologies to impose power on masses of people. The paper tackles the question of how the salient characteristics of soundscape are sonically adopted as means for counter-political acts in public realm.展开更多
Traditionally, microclimate, behavior and space design are characterized by a separation among climatologists, behavior researchers and designers. It is also unrealizable to apply the research results to the space des...Traditionally, microclimate, behavior and space design are characterized by a separation among climatologists, behavior researchers and designers. It is also unrealizable to apply the research results to the space design because of the gap created by the interdisciplinarity. In addition, although the relationships among space form, urban microclimate and people are intuitively understood, there are still not reasonable predictions on how a space affects the microclimate, and how the microclimate and space will affect people's sensation and behavior. By recording the microclimate and people's responses, this paper discusses the relationship between people's sensation and microclimate as well as people's behavior and open space in a busy downtown pedestrian street during hot summer. The research finds that shade plays a crucial role in outdoor comfort. All of the other objectively comfortable and acceptable microclimates differ significantly different shade situation. Simultaneously, space contradiction can be considered an essential factor for spatial utilization. This paper also provides proposal on canyon open space design based on this case study.展开更多
The buckling behavior of single layer space structure is very sensitive. The joint rigidity, moreover, is one of the main factors of stability which may determine the entire failure behavior. Thus, the reasonable stif...The buckling behavior of single layer space structure is very sensitive. The joint rigidity, moreover, is one of the main factors of stability which may determine the entire failure behavior. Thus, the reasonable stiffness of joint system, which is neither total pin assumption nor perfect fix condition, is very important to apply to the real single layer space one. Therefore, the purpose of this work was to investigate the buckling behavior of single layer space structure, using the development of the upgraded stiffness matrix for the joint rigidity. To derive tangential stiffness matrix, a displacement function was assumed using translational and rotational displacement at the node. The geometrical nonlinear analysis was simulated not only with perfect model but also with imperfect one. As a result, the one and two free nodal numerical models were investigated using derived stiffness matrix. It was figured out that the buckling load increases in proportion to joint rigidity with rise-span ratio. The stability of numerical model is very sensitive with the initial imperfection, responding of bifurcation in the structure.展开更多
Local hydrodynamics of a gas–liquid–solid system,such as bubble circulation regime,gas holdup,liquid velocity and axial profile of solid concentration,are studied in a two-stage internal loop airlift reactor.Empiric...Local hydrodynamics of a gas–liquid–solid system,such as bubble circulation regime,gas holdup,liquid velocity and axial profile of solid concentration,are studied in a two-stage internal loop airlift reactor.Empirical correlations for gas holdup and liquid velocity are proposed to ease the reactor design and scale-up.Different bubble circulation regimes were displayed in the first(lower) and second(upper) stages.Increasing superficial gas velocity and solid loading can promote regime transition of the second stage,and the gas holdup of the second stage is higher than that of the lower stage.In addition,the effects of solid loading on bubble behaviour are experimentally investigated for each stage.It is found that bubble size in the downcomer decreases with the presence of solid particles,and bubble size distribution widens under higher superficial gas velocity and lower solid loading.展开更多
基金Supported by the National High Technology Research and Development Program of China("863"Program)(2006AA12A105)~~
文摘A new safety assessment method for parallel routes is presented. From the aspects of safety guard system of air traffic control(ATC) and considering the flight conflict as causing event of air collision accidents, this paper fosters a four-layer safety guard of controller command, short-term conflict alerts (STCAs), pilot visual avoidance, and traffic alert collision avoidance system(TCAS). Then, the problem of parallel routes collision risk is divided into two parts:the calculation of potential flight conflict and the analysis of failure probability of the four-layer safety guard. A calculation model for controller interference times is induced. By using cognitive reliability and error analysis method(CREAM),the calculation problem to failure probability of controller sequencing flight conflicts is solved and a fault tree model of guard failure of STCA and TCAS is established. Finally, the Beijing-Shanghai parallel routes are taken as an example to be calculated and the collision risk of the parallel routes is obtained under the condition of radar control. Results show that the parallel routes can satisfy the safety demands.
基金support from the Australian Research Council-linkage Project
文摘Advanced microfluidic technology was used to examine the microscopic viscous and inertial effects evolution of water flow in rock joints. The influence of void space on fluid flow behaviour in rock joints under different flow velocities was experimentally investigated at the micro scale. Using advanced fabrication technology of microfluidic device, micro flow channels of semicircular, triangular, rectangular and pentagonal cavities were fabricated to simulate different void space of rock joints, respectively. Using the fluorescence labelling approach, the trajectory of water flow was captured by the microscope digital camera when it passed over the cavity under different flow velocities. The flow tests show that the flow trajectory deviated towards the inside of the cavity at low flow velocities. With the increase in flow velocity, this degree of flow trajectory deviation decreased until there was no trajectory deviation for flow in the straight parallel channel. The flow trajectory deviation initially reduced from the void corner near the entrance. At the same time, a small eddy appeared near the void corner of the entrance. The size and intensity of the eddy increased with the flow velocity until it occupied the whole cavity domain. The gradual reduction of flow trajectory near the straight parallel channel and the growth of eddy inside the cavity reflect the evolution of microscopic viscous and inertial forces under different flow velocities.The eddy formed inside the cavity does not contribute to the total flow flux, but the running of the eddy consumes flow energy. This amount of pressure loss due to voids could contribute to the nonlinear deviation of fracture fluid flow from Darcy's law. This study contributes to the fundamental understanding of non-Darcy's flow occurrence in rock joints at the micro scale.
文摘Knowledge of the culture difference in inter-cultural communicative is of primary importance. It is so in Sino-American communication, especially in speech, one of the two means of communication through language, with the other being writing. American and Chinese, brought up in different cultures, have different speech styles. Diversity in speech styles not only involves communication through verbal speech, but also through such non-verbal acts as kinesics, proxemics, and paralinguistic elements. Here the speech styles in the two cultures, American and Chinese, are contrasted with examples from a cultural perspective.
基金Project (51101039) supported by the National Natural Science Foundation of ChinaProject (E201005) supported by the Natural Science Foundation of Heilongjiang Province,China
文摘The biomedical co-continuous(β-TCP+MgO)/Zn-Mg composite was fabricated by infiltrating Zn-Mg alloy into porousβ-TCP+MgO using suction exsorption technique.The microstructure,mechanical properties and corrosion behaviors of the composite were evaluated by means of scanning electron microscopy(SEM),X-ray diffraction(XRD),mechanical testing,electrochemical and immersion test.It was found that the molten Zn-Mg alloy had infiltrated not only into the pores but also into the struts of the porousβ-TCP+MgO scaffold to form a compact composite.The Zn-Mg alloy contacted to theβ-TCP+MgO scaffold closely,and no reaction layer can be found between the alloy and the scaffold.The compressive strength of the composite was as high as244MPa,which was about1000times higher than that of the original porousβ-TCP+MgO scaffold and2/3of the strength of the Zn-Mg bulk alloy.The electrochemical and immersion tests in simulated body fluid(SBF)solution indicated that the corrosion resistance of the composite was better than that of the Zn-Mg bulk alloy.The corrosion products on the composite surface were mainly Zn(OH)2.Appropriate mechanical and corrosion properties indicated that the(β-TCP+MgO)/Zn?Mg composite fabricated by suction exsorption would be a very promising candidate for bone substitute.
基金*The project supported by National Natural Science Foundation of China under Grant No. 90203008 and the Doctoral Foundation of the Ministry of Education of China
文摘Based on our previously pulse-coupled integrate-and-fire neuron model in small world networks, we investigate the effects of different connectivity topologies on complex behavior of electroencephalographic-like signals produced by this model. We show that several times series analysis methods that are often used for analyzing complex behavior of electroencephalographic-like signals, such as reconstruction of the phase space, correlation dimension, fractal dimension, and the Hurst exponent within the rescaled range analysis (R/S). We lind that the different connectivity topologies lead to different dynamical behaviors in models of integrate-and-fire neurons.
基金Project(50976022) supported by the National Natural Science Foundation of ChinaProject(BY2011155) supported by the Provincial Science and Technology Innovation and Transformation of Achievements of Special Fund Project of Jiangsu Province,China
文摘Numerical computation models of air cooling heat transfer and flow behaviors in triangular wavy fin channels(TWFC) were established with structural parameters of fins considered.The air side properties of heat transfer coefficient and pressure drop are displayed with variable structural parameters of fins and inlet velocities of cooling air.Within the range of simulation,TWFC has the best comprehensive performance when inlet velocity vin=4-10 m/s.Compared with those of straight fins,the simulation results reveal that the triangular wavy fin channels are of higher heat transfer performances especially with the fin structural parameters of fin-height Fh=9.0 mm,fin-pitch Fp=2.5-3.0 mm,fin-wavelength λ=14.0-17.5 mm and fin-wave-amplitude A=1.0-1.2 mm.The correlations of both heat transfer factor and friction factor are presented,and the deviations from the experimental measurements are within 20%.
文摘An experiment was conducted at the Department of Horticulture, College of Agriculture and Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi (KNUST) Ghana from September, 2009 to April, 2010, to determine the most appropriate drying method, as a post harvest practice, that would ensure high percentage germination ofAnnona squamosa seeds and its subsequent effect on seedling growth. The seeds were sun-dried, air-dried under shade or kept in the fresh state. Five treatments were used, namely, Freshly Sown seeds (Treatment 1, control), Seeds Air-Dried under Shade for one day (Treatment 2); Seeds Sun-Dried for one day (Treatment 3); Seeds Air-Dried under Shade for three consecutive days (Treatment 4); Seeds Sun-Dried for three consecutive days (Treatment 5). The experiment was arranged in a Completely Randomized Design (CRD) and replicated three times. Drying of Annona squamosa seeds had significant effect on earliness and number of seeds germinated. Air drying under shade and sun-drying for three consecutive days improved earliness to germination (26 days after sowing) and percent total germination but air-drying under shade had better effect on total seed germination, achieving 90% germination in 42 days after sowing. Furthermore, the prevailing ambient temperature of 30 ℃-32 ℃ enhanced germination of Annona squamosa seeds. The study concluded that for optimum germination, seeds of Annona squamosa should be either air-dried or sun-dried for three consecutive days and be incubated in an ambient temperature range of 30 ℃-32 ℃. In terms of growth, seedling growth in leaf production was better from seeds sun-dried for three consecutive days.
基金supported by the National Science Foundation of China (Nos. 51105131 and 51475143)the Henan Provincial Key Scientific and Technological Project (No. 142102210110)the Tianjin Science and Technology Support Program
文摘The traction behavior of space lubricating oil No. 4116 was measured and analyzed at various oil inlet temperatures below 0 ℃ and various rolling speeds under normal loads by a test rig simulating the operating conditions of space bearings. A traction coefficient calculation model was presented. The rheological property and rheological parameters of the lubricant at a low oil inlet temperature were analyzed based on the Tevaarwerk-Johnson model. The results showed that the lubricating oil No. 4116 was sensitive to the rolling speed and had lower sensitivity to the normal load. This lubricating oil is more suitable for applications under high speed when it is used below 0 ℃. It behaves as an elastic-plastic fluid operating below 0 ℃. Both the average limiting shear stress and the average elastic shear modulus have a negative correlation with the rolling speed and oil inlet temperature and have a positive correlation with the normal load.
文摘The aim of this paper is to collect information about dairy cow's behaviour connected to different environmental conditions. During summer 2009 and winter 2010 experimental trials were arranged to verify the behaviour of dairy cows in a farm located in Po Plain (Italy). The barn was provided with an air-water cooling system, based on the use of fans and sprinklers placed only in the feeding alley. Two different trials were carried out. The first experiment was targeted on verifying the use of the cubicles by the cows in relation to the availability of the cooling system only in feeding area. The second trial aimed at testing the effectiveness of zone cooling systems placed in the front of cubicles. For this purpose three cubicles in the barn were provided with cooling systems, based on the input of high velocity conditioned air streams. The results clearly remark that the behaviour of the animals is greatly influenced by the environmental conditions. With high temperatures the use of the cubicles is deeply reduced and the animals prefer to stay in feeding area, thus benefiting from the cooling effect of water sprinkled by the showers and of the air streams created by the fans. With air temperatures increasing from 21℃ to 33 ℃ the cows reduce the staying in the cubicles, which gets down from 540 to 32% (r2 = 0.2608). As regards the efficacy of zone cooling system in the cubicles, the results are not particularly encouraging. The cows continue to use the cubicles without changing the behaviour in relation to the presence of conditioned air flow.
基金financially supported by the National Basic Research Program of China(973 Program,2006CB202508)the China Petrochemical Corporation(SINOPEC Group 20673054)
文摘For simulating the real deactivation of hollow titanium silicalite(HTS) zeolite in commercial ammoximation process, HTS was treated by 10% NH_3·H_2O solution at 120 ℃ in stirred autoclave. It is found that a part of HTS zeolite crystals dissolved in the hot NH_3·H_2O solution, and the specific surface area and pore volume continuously decreased with the increase in NH_3 hydrothermal treatment time. Meanwhile, the transformation of framework Ti species into extraframework Ti species was detected by the spectroscopic methods. However, the extraframework Ti species were still in a highly dispersed state after the hydrothermal and thermal treatments as shown by TEM images, while the formation of new acid sites was not detected. Upon combining the results of characterization with catalytic performance of HTS, the main deactivation reason for this material had been determined, which might be attributed to the reduction of specific surface area and active centers after basic treatment and calcination of HTS samples. And then the possible mechanism of simulated deactivation of HTS zeolite was proposed, which could describe the elemental reaction steps much more visually and directly.
基金Projects(51579239,42077240,51979280)supported by the National Natural Science Foundation of China。
文摘The dynamic mechanical properties of rock specimens after thermal treatment in the air-filled environment(AE:i.e.,at the free surface)have been extensively investigated,yet they are rarely estimated in the quasi-vacuum environment(VE:i.e.,far from free surface),which is of special importance in engineering practice.Several precise laboratory tests(i.e.,split Hopkinson pressure bar test)on marble samples in both AE and VE were performed to investigate physical and dynamic mechanical behaviors of marble after heat treatment(25℃ to 900℃)in AE and VE.The tests results demonstrate that related properties of marble could be divided into three different stages by corresponding critical temperatures of 300℃ and 600℃,at which heat damage factors are 0.29(0.30)and 0.88(0.92)in VE(AE),respectively.The thermal damage developes more fully in AE than in VE.The thermal environment plays an important role,especially in Stage 3.Specifically,a conspicuous difference(greater than 20%)between AE and VE occurs in corresponding dynamic strength and the anti-deformation capacities of tested marble specimen.The influence of heat damage of rock is very important and valuable in engineering practice,particularly when the temperature is very high(greater than 600℃).
基金financial supports from the National Natural Science Foundation of China(Nos.U1810208,51575230)the Science and Technology Development Program of Jilin Province,China(No.20190302059GX)。
文摘SiC_(p)/AZ91 composites were prepared by vacuum pressure infiltration.The microstructure,mechanical properties and wear resistance of composite were studied.Results indicated that SiC particles were uniformly distributed in the metal matrix and had a good interface bonding with the metal matrix.Mg_(17)Al_(12) preferably precipitated near the SiC particles,and high-density dislocations were induced by the mismatch of the coefficient of thermal expansion(CTE)between the SiC particle and the AZ91 matrix,thereby accelerating the aging precipitation of the matrix.Compared with AZ91 alloy,the addition of SiC particles improves the hardness and compressive strength of the composite,which is mainly due to the load transfer strengthening and grain refinement strengthening mechanisms.Furthermore,a stable support surface-protecting matrix formed during the wear process because of the excellent wear resistance of SiC.
文摘Sustainable building design in dry tropical areas recommends reducing exposure of buildings to solar radiation and/or designing efficient enclosures with satisfactory thermal inertia.We propose in this paper a study of the influence of the infiltration rate in the building and the coefficient of thermal transfer by convection of the walls, on the thermal comfort using TRNSYS software. All the models carried out were validated by recognized scientific criteria, namely correlation (R) and determination (R2) coefficients on the one hand and NBME and CVRMSE coefficients defined by ASHARE, 2002 on the other hand. The results obtained indicate that the modulation of the air infiltration rate allows the simulations on TRNSYS to be compared to in-situ measurements, with an annual average relative difference of 2.86% on the temperature difference. Furthermore, depending on the parameterization of the heat transfer coefficients by convection of the internal and external walls of walls used in the STD, the average annual difference can be reduced by 1% to 4% between the predictions and the measurements.
基金Project (2016YFB0301001) supported by the National Key Research and Development Program of ChinaProject (2015M580093) supported by the General Financial Grant from the China Postdoctoral Science Foundation of China
文摘Vacuum die casting can reduce the'air entrapment'phenomenon during casting process.Based on the temperature measurements at metal-die interface with different processing parameters,such as slow shot speed(VL),high shot speed(VH),pouring temperature(Tp)and initial die temperature(Tm),inverse method was developed to determine the interfacial heat transfer coefficient(IHTC).The results indicate that a closer contact between the casting and die could be achieved when the vacuum system is used.It is found that the vacuum could strongly increase the values of IHTC and decrease the grain size in castings.The IHTC could have a higher peak value with increasing the Tp from680to720℃or the VL from0.1to0.4m/s.In addition,the influence of the VH and Tm on IHTC could be negligible.
文摘The paper takes the relation between soundscapes and power struggles as its problem area and focuses on the role of music that is performed in public protests. It argues that music and street performances are conceived and therefore utilised as sonic acts of political struggle in urban realm. Starting with a general understanding of hearing mechanisms, the study elucidates the relationships among territoriality of soundscape, identity construction, social segregation and polarisation, and finally, power struggle. Within the framework of the intersection area of these concepts, the paper discusses the processes of politisation of soundscape through music as a form of protest event that is performed in public realm. Throughout the paper, it is focused on the significant cases of public protests as well as political events that occured in public space. The main emphasis is on the use of sound technologies to impose power on masses of people. The paper tackles the question of how the salient characteristics of soundscape are sonically adopted as means for counter-political acts in public realm.
文摘Traditionally, microclimate, behavior and space design are characterized by a separation among climatologists, behavior researchers and designers. It is also unrealizable to apply the research results to the space design because of the gap created by the interdisciplinarity. In addition, although the relationships among space form, urban microclimate and people are intuitively understood, there are still not reasonable predictions on how a space affects the microclimate, and how the microclimate and space will affect people's sensation and behavior. By recording the microclimate and people's responses, this paper discusses the relationship between people's sensation and microclimate as well as people's behavior and open space in a busy downtown pedestrian street during hot summer. The research finds that shade plays a crucial role in outdoor comfort. All of the other objectively comfortable and acceptable microclimates differ significantly different shade situation. Simultaneously, space contradiction can be considered an essential factor for spatial utilization. This paper also provides proposal on canyon open space design based on this case study.
基金Project(12 High-tech Urban C11) supported by High-tech Urban Development Program of Ministry of Land,Transport and Maritime Affairs,Korea
文摘The buckling behavior of single layer space structure is very sensitive. The joint rigidity, moreover, is one of the main factors of stability which may determine the entire failure behavior. Thus, the reasonable stiffness of joint system, which is neither total pin assumption nor perfect fix condition, is very important to apply to the real single layer space one. Therefore, the purpose of this work was to investigate the buckling behavior of single layer space structure, using the development of the upgraded stiffness matrix for the joint rigidity. To derive tangential stiffness matrix, a displacement function was assumed using translational and rotational displacement at the node. The geometrical nonlinear analysis was simulated not only with perfect model but also with imperfect one. As a result, the one and two free nodal numerical models were investigated using derived stiffness matrix. It was figured out that the buckling load increases in proportion to joint rigidity with rise-span ratio. The stability of numerical model is very sensitive with the initial imperfection, responding of bifurcation in the structure.
基金Supported by the State Key Laboratory of Chemical Engineering(SKL-ChE-16B01)China Postdoctoral Science Foundation(2016M601263)
文摘Local hydrodynamics of a gas–liquid–solid system,such as bubble circulation regime,gas holdup,liquid velocity and axial profile of solid concentration,are studied in a two-stage internal loop airlift reactor.Empirical correlations for gas holdup and liquid velocity are proposed to ease the reactor design and scale-up.Different bubble circulation regimes were displayed in the first(lower) and second(upper) stages.Increasing superficial gas velocity and solid loading can promote regime transition of the second stage,and the gas holdup of the second stage is higher than that of the lower stage.In addition,the effects of solid loading on bubble behaviour are experimentally investigated for each stage.It is found that bubble size in the downcomer decreases with the presence of solid particles,and bubble size distribution widens under higher superficial gas velocity and lower solid loading.