The aim of this research is to determine the effect of bridging liquid surface tension and specific surface area on strength factor of coal agglomerates. The production of coal agglomerates of the range 15-27.51 mm wa...The aim of this research is to determine the effect of bridging liquid surface tension and specific surface area on strength factor of coal agglomerates. The production of coal agglomerates of the range 15-27.51 mm was achieved. The crushing strength of the agglomerates was determined for good handling of fine （coal-liquid mixture） to improve fugitive dust control, decrease in transportation losses, reduce risk of coal freezing, lower risk of spontaneous combustion, etc. in iron and steel industries, railway corporations and coal corporations. Kerosene （paraffin oil） was used as a binder and the agglomerated coal oil mixture was pelletized using balling technique （disc）. Mechanical and physical tests like compressive strength test, etc. were carried out. The relationship between the bridging liquid surface tension and specific surface area on strength factor of coal agglomerates showed that there is considerable variation in these parameters in the coal powder systems.展开更多
The effects of structural modeling （bar slip in lap splice）, ground motion selection process （epsilon effect） and size of a structure （number of bays and stories） on the fragility of reinforced concrete ordinary...The effects of structural modeling （bar slip in lap splice）, ground motion selection process （epsilon effect） and size of a structure （number of bays and stories） on the fragility of reinforced concrete ordinary moment resisting frames are investigated. An analytical model is developed to account for bar slip in lap splice, which exhibits good correlation with existing experimental data. Then, incremental dynamic analysis is used to derive the fragility curves for four model structures. The model structures simulate frames with a different number of bays and stories. Finally, the fragility curves are corrected for the epsilon effect. The results show that slip in the lap splice can significantly increase the failure probability, especially for the collapse prevention limit state. At the same time, it is found that spectral shape has a significant impact on the fragility curves. It is also found that accounting for or ignoring bar slip or epsilon effects increases the probability of failure for larger structures. This indicates an unconservative bias in the safety of larger structures.展开更多
The Northridge earthquake inflicted various levels of damage upon a large number of Caltrans' bridges not retrofitted by column jacketing.In this respect,this study represents results of fragility curve developmen...The Northridge earthquake inflicted various levels of damage upon a large number of Caltrans' bridges not retrofitted by column jacketing.In this respect,this study represents results of fragility curve development for two (2) sample bridges typical in southern California,strengthened for seismic retrofit by means of steel jacketing of bridge columns.Monte Carlo simulation is performed to study nonlinear dynamic responses of the bridges before and after column retrofit.Fragility curves in this study are represented by lognormal distribution functions with two parameters and developed as a function of PGA.The sixty (60) ground acceleration time histories for the Los Angeles area developed for the Federal Emergency Management Agency (FEMA) SAC (SEAOC-ATC CUREe) steel project are used for the dynamic analysis of the bridges. The improvement in the fragility with steel jacketing is quantified by comparing fragility curves of the bridge before and after column retrofit.In this first attempt to formulate the problem of fragility enhancement,the quantification is made by comparing the median values of the fragility curves before and after the retrofit.Under the hypothesis that this quantification also applies to empirical fragility curves developed on the basis of Northridge earthquake damage,the enhanced version of the empirical curves is developed for the ensuing analysis to determine the enhancement of transportation network performance due to the retrofit.展开更多
The hydrodynamic efficiency of the vertical porous structures is investigated under regular waves by use of physical models. The hydrodynamic efficiency of the breakwater is presented in terms of the wave transmission...The hydrodynamic efficiency of the vertical porous structures is investigated under regular waves by use of physical models. The hydrodynamic efficiency of the breakwater is presented in terms of the wave transmission （kt）, reflection （kr） and energy dissipation （ka） coefficients. Different wave and structural parameters affecting the breakwater efficiency are tested. It is found that, the transmission coefficient （kt） decreases with the increase of the relative water depth （h/L）, the wave steepness （Hi^L）, the relative breakwater widths （B/L, B/h）, the relative breakwater height （D/h）, and the breakwater porosity （n）. The reflection coefficient （kr） takes the opposite trend of kt when D/h=l.25 and it decreases with the increasing h/L, HJL and B/L when D/h〈1.0. The dissipation coefficient （kd） increases with the increasing h/L, HilL and B/L when D/h〈_l.O and it decreases when D/h=l.25. In which, it is possible to achieve values ofkt smaller than 0.3, k~ larger than 0.5, and kd larger than 0.6 when D/h=1.25, B/h=0.6, h/L〉0.22, B/L〉O. 13, and H/L 〉0.04. Empirical equations are developed for the estimation of the transmission and reflection coefficients. The results of these equations are compared with other experimental and theoretical results and a reasonable agreement is obtained.展开更多
This paper deals with the exact detection analysis of the Ordered-Statistic(OS) processor along with OS Greatest Of(OSGO) and OS Smallest Of(OSSO) modified versions, for M postdetection integrated pulses when the oper...This paper deals with the exact detection analysis of the Ordered-Statistic(OS) processor along with OS Greatest Of(OSGO) and OS Smallest Of(OSSO) modified versions, for M postdetection integrated pulses when the operating environment is nonhomogeneous. Analytical results are presented in multiple-target case as well as in regions of clutter power transitions. The primary and the secondary interfering targets are assumed to be fluctuating in accordance with the SWII target fluctuation model. As the number of noncoherently integrated pulses increases,lower threshold values and consequently better detection performances are obtained in both homogeneous and multiple target background models. However, the false alarm rate performance of OSSO-CFAR(Constant False Alarm Rate) scheme at clutter edges is worsen with increasing the postdetection integrated pulses. As predicted, the OSGO-CFAR detector accommodates the presence of spurious targets in the reference window, given that their number is within its allowable range in each local window, and controls the rate of false alarm when the contents of the reference cells have clutter boundaries.展开更多
Japan lacked resources is a large import country and also a large consuming country.So it is turned society structure system of consumption goods stocked in domestic,which leads to 450 millions ton waste material.Rece...Japan lacked resources is a large import country and also a large consuming country.So it is turned society structure system of consumption goods stocked in domestic,which leads to 450 millions ton waste material.Recently,because of continuing development of intermediate handling and recycled utilization technology,finally disposed waste materials approximately 30 millions ton.The quantity of concrete product is consumed 300 millions ton per year unprecedented,beau case of large scope,it is expected valid and large absorption industry of recycled material. The purpose of this paper is to do a report on applied present status and future assignment of recycled material and building structure in Japan.展开更多
Since the pesticides are considered as an essential component for crops production through controlling pests, they have shown a negative effect on crops and soil environment when used intensively. This experiment was ...Since the pesticides are considered as an essential component for crops production through controlling pests, they have shown a negative effect on crops and soil environment when used intensively. This experiment was conducted at Wadi Soba farm (Sharq Elneel) Khartoum, Sudan. It aimed to study the effect of Sevin residuals on carrot growth and Azotobacter spp. colonies growth. Carrot planted in late February 2013, Sevin pesticide (2.5 L/ha and 5 L/ha) was added to estimate plant height, dry weight, the number of plant leaves and the number of Azotobacter spp. colonies isolated from the carrot rhizosphere (0 - 15 cm). The obtained results showed that the Sevin recommended dose (2.5 L/ha) relatively had a positive effect on the plant height, dry weight, and the number of plant leaves. The average of plant height for recommended dose was 59.67 cm compared to control (53.67 cm) and high dose (27.33 cm). The average of plant dry weight obtained by the recommended dose was 503.33 g and for control was 476.67 g and for high dose was 166.7 g, it decreased 67% from control and recommended dose. The average of plant leaves number were 25.34, 13.66 and 21.33 for recommended dose, high dose and control respectively, the number of leaves increased about 16% by recommended dose and decreased 35% by high dose. The average of Azotobacter spp. colonies obtained by high dose of Sevin demonstrated a lower numbers which were 20 × 104, 5.67 × 106 and 0.33 × 108 compared with control (78.33 × 104, 44 × 106 and 15.33 × 108) and the recommended dose (64 × 104, 33 × 106 and 7 × 108). The high dose of Sevin had a negative effect on both carrot growth and Azotobacter spp. colonies growth.展开更多
In this research a new process for semi-solid casting of ductile iron based on the high nucleation rate combined with locally mechanical stirring is presented. In this process at first fully liquid ductile iron was po...In this research a new process for semi-solid casting of ductile iron based on the high nucleation rate combined with locally mechanical stirring is presented. In this process at first fully liquid ductile iron was poured on the peripheral surface of a wheel rotating against pouring direction. At this stage, the solid crystals nucleated at the chilling surface were pushed to the melt by a heat resistance steel cutter and finally the semi-solid slurry was generated. Reheating treatment was done on the samples to achieve more efficiency of semi-solid casting process. The effects of the travelling distance of solid particles during casting, the reheating time and temperature were examined. The results showed that the process effectively changes the dendrite structure to globular one.展开更多
The aim of this investigation was to improve power performance of Savonius hydraulic turbine utilizing small stream for electric generation.An attempt was made to increase the power coefficient of runner by the use of...The aim of this investigation was to improve power performance of Savonius hydraulic turbine utilizing small stream for electric generation.An attempt was made to increase the power coefficient of runner by the use of flat shield plate placed upstream of the runner.The difference of the power coefficient is discussed in relation to clearance between the runner and the bottom wall and the rotation direction of the runner.The flow field around the runner was also examined visually to clarify influences of setting conditions on the power performance.From this study it was found that the power coefficient is achieved for 0.47 by only using a flat shield plate,the increase is up to 80% over the runner without the plate.Moreover,it is the proper condition that clearance ratio is 0.73 in this study.展开更多
Miniaturized optical benches process free-space light propagating in-plane with respect to the substrate and have a large variety of applications,including the coupling of light through an optical fiber.High coupling ...Miniaturized optical benches process free-space light propagating in-plane with respect to the substrate and have a large variety of applications,including the coupling of light through an optical fiber.High coupling efficiency is usually obtained using assembled micro-optical parts,which considerably increase the system cost and integration effort.In this work,we report a high coupling efficiency,monolithically integrated silicon micromirror with controlled three-dimensional(3D)curvature that is capable of manipulating optical beams propagating in the plane of the silicon substrate.Based on our theoretical modeling,a spherical micromirror with a microscale radius of curvature as small as twice the Gaussian beam Rayleigh range provides a 100%coupling efficiency over a relatively long optical path range.Introducing dimensionless parameters facilitates the elucidation of the role of key design parameters,including the mirror’s radii of curvature,independent of the wavelength.A micromachining method is presented for fabricating the 3D micromirror using fluorinated gas plasmas.The measured coupling efficiency was greater than 50%over a 200-mm optical path,compared to less than 10%afforded by a conventional flat micromirror,which was in good agreement with the model.Using the 3D micromirror,an optical cavity was formed with a round-trip diffraction loss of less than 0.4%,resulting in one order of magnitude enhancement in the measured quality factor.A nearly 100%coupling was also estimated when matching the sagittal and tangential radii of curvature of the presented micromirror’s surface.The reported class of 3D micromirrors may be an advantageous replacement for the optical lenses usually assembled in silicon photonics and optical benches by transforming them into real 3D monolithic systems while achieving wideband high coupling efficiency over submillimeter distances.展开更多
In this paper, some preliminary calculations and the experiments were performed to figure out the flow field, in which some rods were normally inserted into the main flow surrounded by a porous cavity. As a result, it...In this paper, some preliminary calculations and the experiments were performed to figure out the flow field, in which some rods were normally inserted into the main flow surrounded by a porous cavity. As a result, it is found that the starting shock wave severely interacts with the rods, the bow shock wave, its reflections, and the porous wall, which are numerically well predicted at some conditions. Moreover, inserting the rods makes the pressure on the upper wall in the porous region increase when the main flow in the porous region is completely supersonic. The calculations also suggest that three rods cause the widest suction area.展开更多
This paper will present the characteristics of flow behavior and thermal field of both free and impingement jet issued from a circular orifice nozzle at Re=8900.The flow behavior of a single round jet and impingement ...This paper will present the characteristics of flow behavior and thermal field of both free and impingement jet issued from a circular orifice nozzle at Re=8900.The flow behavior of a single round jet and impingement jet was observed by smoke flow visualization recorded by a high speed camera using 5000 frame per second.Heat transfer coefficient on the impingement surface was measured by means of infrared camera (TVS-8500,Avio) with a two-dimensional array of Indeum-Antimony (In Sb) sensors varying in the separation distance between the nozzle and the target plate.The heat transfer coefficient changes in time and spatial.Therefore,the root mean square distribution of the heat transfer was obtained from the data.As a result,it was confirmed that the longitudinal vortex was observed outside of the ring vortex,and then the longitudinal vortex was penetrated in the jet flow.Moreover,the high value of root mean square of the heat transfer coefficient has spread radially in stripy manner,which is caused as the results of the longitudinal vortexes flowing in the radial direction on the impingement plate.展开更多
The unsteady behavior of flow driven by a jet suddenly injected into a cell is numerically studied by solving the axisymmelric two-dimensional compressible Navier-Stokes equations. The system of the calculation is a m...The unsteady behavior of flow driven by a jet suddenly injected into a cell is numerically studied by solving the axisymmelric two-dimensional compressible Navier-Stokes equations. The system of the calculation is a model of the laser ablation of a certain duration followed by a discharging process through the exit hole at the down- stream end of the cell. In the calculations, the contour of the cell is changed while other parameters such as the Mach number of the jet, its duration, and the diameter of the cell exit are fixed. Monitoring the velocity at the exit hole is used to investigate the influence of the shape on the interaction between the shock wave and the jet. As the result, it was found that the velocity peak value and its arrival time at the downstream end of the cell exit are determined by the diameter of the cell.展开更多
In this paper, dual underexpanded impinging jets are experimentally studied by measuring unsteady wall staticpressure and temperature fields using high response semiconductor pressure sensors and infrared imaging cam-...In this paper, dual underexpanded impinging jets are experimentally studied by measuring unsteady wall staticpressure and temperature fields using high response semiconductor pressure sensors and infrared imaging cam-era(100 captures per sec) with dual converging sonic nozzles. The flow field is also visualized by means of highspeed schlieren system( up to 70000 frame per second) to clarify the unsteady behavior of the jet structures suchas barrel shock wave, and Mach disk. Experiments were performed with a blow down tunnel changing the parameterssuch as the nozzle to plate distance, the distance between the two nozzles, and wind tunnel pressure ratio.The nozzle to plate distance L and the distance between the two nozzles H are non-dimensionalized by the nozzlediameter D covering H/D=1.5, 2.0, and 3, L/D= 2, 3,and 4, and po/pb=1.0 - 5.0, where po and pb are stagnationpressure and back pressure respectively. Although the response of the infrared camera is quite different fromthat of the high speed camera, the unsteady correlation between the pressure and temperature fields is confirmedunder some conditions. Also the high speed schlieren pictures and the wall static pressure fluctuations suggestthat the generation of the Mach disk promote the unsteady behavior of the jets. After the confirmation of the correlation,a simple way to find the severe fluctuating region can be provided according to the two dimensional unsteadytemperature images without a lot of unsteady pressure measurements.展开更多
A protective coating can aid in reducing mechanical harm to food during harvesting,handling,and trans-portation,resulting in fewer bruises,wounds,and other injuries,thereby improving the overall quality of the produce...A protective coating can aid in reducing mechanical harm to food during harvesting,handling,and trans-portation,resulting in fewer bruises,wounds,and other injuries,thereby improving the overall quality of the produce.In this study,coatings with 1%(w/v)chitosan(CS)and 0.6%(w/v)diepoxy-polyethylene glycol(PEG)were prepared by the co-blending method.According to the findings,increasing the PEG concentration enhanced the moisture content,water vapor permeability,and contact angle properties.In addition,when viewed by scanning electron microscopy(SEM),the morphology of the films containing more PEG appeared rougher and denser.In addition,at room temperature,the freshness of‘Nanguo’pears and the antifungal efficacy of the coating against Penicillium italicum(P.italicum)and Botrytis cinerea(B.cinerea)were evaluated.According to the findings,the weight loss or total soluble solids of pears coated with CS or PEG did not differ significantly during storage.The fruit respiration rate and ascorbic acid(AA)and malondialdehyde(MDA)contents were maintained after coating CS insertion with PEG.The CS-PEG composite coating successfully inhibits the growth of P.italicum and B.cinerea(P.italicum>B.cinerea),according to an in vitro antifungal activity assay that was improved by adding PEG.According to principal component analysis(PCA)results,the CS-PEG coating significantly impacts pear sensory evaluation and firmness.At room temperature,the shelf life of pears with a CS-PEG coat has been extended from 15 days to 25 days.展开更多
文摘The aim of this research is to determine the effect of bridging liquid surface tension and specific surface area on strength factor of coal agglomerates. The production of coal agglomerates of the range 15-27.51 mm was achieved. The crushing strength of the agglomerates was determined for good handling of fine （coal-liquid mixture） to improve fugitive dust control, decrease in transportation losses, reduce risk of coal freezing, lower risk of spontaneous combustion, etc. in iron and steel industries, railway corporations and coal corporations. Kerosene （paraffin oil） was used as a binder and the agglomerated coal oil mixture was pelletized using balling technique （disc）. Mechanical and physical tests like compressive strength test, etc. were carried out. The relationship between the bridging liquid surface tension and specific surface area on strength factor of coal agglomerates showed that there is considerable variation in these parameters in the coal powder systems.
文摘The effects of structural modeling （bar slip in lap splice）, ground motion selection process （epsilon effect） and size of a structure （number of bays and stories） on the fragility of reinforced concrete ordinary moment resisting frames are investigated. An analytical model is developed to account for bar slip in lap splice, which exhibits good correlation with existing experimental data. Then, incremental dynamic analysis is used to derive the fragility curves for four model structures. The model structures simulate frames with a different number of bays and stories. Finally, the fragility curves are corrected for the epsilon effect. The results show that slip in the lap splice can significantly increase the failure probability, especially for the collapse prevention limit state. At the same time, it is found that spectral shape has a significant impact on the fragility curves. It is also found that accounting for or ignoring bar slip or epsilon effects increases the probability of failure for larger structures. This indicates an unconservative bias in the safety of larger structures.
基金MCEER/FHWA under Contract No.DTFH 61-98-C-00094Caltrans under Contract No.59A0304
文摘The Northridge earthquake inflicted various levels of damage upon a large number of Caltrans' bridges not retrofitted by column jacketing.In this respect,this study represents results of fragility curve development for two (2) sample bridges typical in southern California,strengthened for seismic retrofit by means of steel jacketing of bridge columns.Monte Carlo simulation is performed to study nonlinear dynamic responses of the bridges before and after column retrofit.Fragility curves in this study are represented by lognormal distribution functions with two parameters and developed as a function of PGA.The sixty (60) ground acceleration time histories for the Los Angeles area developed for the Federal Emergency Management Agency (FEMA) SAC (SEAOC-ATC CUREe) steel project are used for the dynamic analysis of the bridges. The improvement in the fragility with steel jacketing is quantified by comparing fragility curves of the bridge before and after column retrofit.In this first attempt to formulate the problem of fragility enhancement,the quantification is made by comparing the median values of the fragility curves before and after the retrofit.Under the hypothesis that this quantification also applies to empirical fragility curves developed on the basis of Northridge earthquake damage,the enhanced version of the empirical curves is developed for the ensuing analysis to determine the enhancement of transportation network performance due to the retrofit.
文摘The hydrodynamic efficiency of the vertical porous structures is investigated under regular waves by use of physical models. The hydrodynamic efficiency of the breakwater is presented in terms of the wave transmission （kt）, reflection （kr） and energy dissipation （ka） coefficients. Different wave and structural parameters affecting the breakwater efficiency are tested. It is found that, the transmission coefficient （kt） decreases with the increase of the relative water depth （h/L）, the wave steepness （Hi^L）, the relative breakwater widths （B/L, B/h）, the relative breakwater height （D/h）, and the breakwater porosity （n）. The reflection coefficient （kr） takes the opposite trend of kt when D/h=l.25 and it decreases with the increasing h/L, HJL and B/L when D/h〈1.0. The dissipation coefficient （kd） increases with the increasing h/L, HilL and B/L when D/h〈_l.O and it decreases when D/h=l.25. In which, it is possible to achieve values ofkt smaller than 0.3, k~ larger than 0.5, and kd larger than 0.6 when D/h=1.25, B/h=0.6, h/L〉0.22, B/L〉O. 13, and H/L 〉0.04. Empirical equations are developed for the estimation of the transmission and reflection coefficients. The results of these equations are compared with other experimental and theoretical results and a reasonable agreement is obtained.
文摘This paper deals with the exact detection analysis of the Ordered-Statistic(OS) processor along with OS Greatest Of(OSGO) and OS Smallest Of(OSSO) modified versions, for M postdetection integrated pulses when the operating environment is nonhomogeneous. Analytical results are presented in multiple-target case as well as in regions of clutter power transitions. The primary and the secondary interfering targets are assumed to be fluctuating in accordance with the SWII target fluctuation model. As the number of noncoherently integrated pulses increases,lower threshold values and consequently better detection performances are obtained in both homogeneous and multiple target background models. However, the false alarm rate performance of OSSO-CFAR(Constant False Alarm Rate) scheme at clutter edges is worsen with increasing the postdetection integrated pulses. As predicted, the OSGO-CFAR detector accommodates the presence of spurious targets in the reference window, given that their number is within its allowable range in each local window, and controls the rate of false alarm when the contents of the reference cells have clutter boundaries.
文摘Japan lacked resources is a large import country and also a large consuming country.So it is turned society structure system of consumption goods stocked in domestic,which leads to 450 millions ton waste material.Recently,because of continuing development of intermediate handling and recycled utilization technology,finally disposed waste materials approximately 30 millions ton.The quantity of concrete product is consumed 300 millions ton per year unprecedented,beau case of large scope,it is expected valid and large absorption industry of recycled material. The purpose of this paper is to do a report on applied present status and future assignment of recycled material and building structure in Japan.
文摘Since the pesticides are considered as an essential component for crops production through controlling pests, they have shown a negative effect on crops and soil environment when used intensively. This experiment was conducted at Wadi Soba farm (Sharq Elneel) Khartoum, Sudan. It aimed to study the effect of Sevin residuals on carrot growth and Azotobacter spp. colonies growth. Carrot planted in late February 2013, Sevin pesticide (2.5 L/ha and 5 L/ha) was added to estimate plant height, dry weight, the number of plant leaves and the number of Azotobacter spp. colonies isolated from the carrot rhizosphere (0 - 15 cm). The obtained results showed that the Sevin recommended dose (2.5 L/ha) relatively had a positive effect on the plant height, dry weight, and the number of plant leaves. The average of plant height for recommended dose was 59.67 cm compared to control (53.67 cm) and high dose (27.33 cm). The average of plant dry weight obtained by the recommended dose was 503.33 g and for control was 476.67 g and for high dose was 166.7 g, it decreased 67% from control and recommended dose. The average of plant leaves number were 25.34, 13.66 and 21.33 for recommended dose, high dose and control respectively, the number of leaves increased about 16% by recommended dose and decreased 35% by high dose. The average of Azotobacter spp. colonies obtained by high dose of Sevin demonstrated a lower numbers which were 20 × 104, 5.67 × 106 and 0.33 × 108 compared with control (78.33 × 104, 44 × 106 and 15.33 × 108) and the recommended dose (64 × 104, 33 × 106 and 7 × 108). The high dose of Sevin had a negative effect on both carrot growth and Azotobacter spp. colonies growth.
文摘In this research a new process for semi-solid casting of ductile iron based on the high nucleation rate combined with locally mechanical stirring is presented. In this process at first fully liquid ductile iron was poured on the peripheral surface of a wheel rotating against pouring direction. At this stage, the solid crystals nucleated at the chilling surface were pushed to the melt by a heat resistance steel cutter and finally the semi-solid slurry was generated. Reheating treatment was done on the samples to achieve more efficiency of semi-solid casting process. The effects of the travelling distance of solid particles during casting, the reheating time and temperature were examined. The results showed that the process effectively changes the dendrite structure to globular one.
基金supported by KAKENHI No.2231004 and Ministry of Environment
文摘The aim of this investigation was to improve power performance of Savonius hydraulic turbine utilizing small stream for electric generation.An attempt was made to increase the power coefficient of runner by the use of flat shield plate placed upstream of the runner.The difference of the power coefficient is discussed in relation to clearance between the runner and the bottom wall and the rotation direction of the runner.The flow field around the runner was also examined visually to clarify influences of setting conditions on the power performance.From this study it was found that the power coefficient is achieved for 0.47 by only using a flat shield plate,the increase is up to 80% over the runner without the plate.Moreover,it is the proper condition that clearance ratio is 0.73 in this study.
基金This work was partially supported by the Information Technology Industry Development Agency(ITIDA)through the ITAC program.
文摘Miniaturized optical benches process free-space light propagating in-plane with respect to the substrate and have a large variety of applications,including the coupling of light through an optical fiber.High coupling efficiency is usually obtained using assembled micro-optical parts,which considerably increase the system cost and integration effort.In this work,we report a high coupling efficiency,monolithically integrated silicon micromirror with controlled three-dimensional(3D)curvature that is capable of manipulating optical beams propagating in the plane of the silicon substrate.Based on our theoretical modeling,a spherical micromirror with a microscale radius of curvature as small as twice the Gaussian beam Rayleigh range provides a 100%coupling efficiency over a relatively long optical path range.Introducing dimensionless parameters facilitates the elucidation of the role of key design parameters,including the mirror’s radii of curvature,independent of the wavelength.A micromachining method is presented for fabricating the 3D micromirror using fluorinated gas plasmas.The measured coupling efficiency was greater than 50%over a 200-mm optical path,compared to less than 10%afforded by a conventional flat micromirror,which was in good agreement with the model.Using the 3D micromirror,an optical cavity was formed with a round-trip diffraction loss of less than 0.4%,resulting in one order of magnitude enhancement in the measured quality factor.A nearly 100%coupling was also estimated when matching the sagittal and tangential radii of curvature of the presented micromirror’s surface.The reported class of 3D micromirrors may be an advantageous replacement for the optical lenses usually assembled in silicon photonics and optical benches by transforming them into real 3D monolithic systems while achieving wideband high coupling efficiency over submillimeter distances.
文摘In this paper, some preliminary calculations and the experiments were performed to figure out the flow field, in which some rods were normally inserted into the main flow surrounded by a porous cavity. As a result, it is found that the starting shock wave severely interacts with the rods, the bow shock wave, its reflections, and the porous wall, which are numerically well predicted at some conditions. Moreover, inserting the rods makes the pressure on the upper wall in the porous region increase when the main flow in the porous region is completely supersonic. The calculations also suggest that three rods cause the widest suction area.
文摘This paper will present the characteristics of flow behavior and thermal field of both free and impingement jet issued from a circular orifice nozzle at Re=8900.The flow behavior of a single round jet and impingement jet was observed by smoke flow visualization recorded by a high speed camera using 5000 frame per second.Heat transfer coefficient on the impingement surface was measured by means of infrared camera (TVS-8500,Avio) with a two-dimensional array of Indeum-Antimony (In Sb) sensors varying in the separation distance between the nozzle and the target plate.The heat transfer coefficient changes in time and spatial.Therefore,the root mean square distribution of the heat transfer was obtained from the data.As a result,it was confirmed that the longitudinal vortex was observed outside of the ring vortex,and then the longitudinal vortex was penetrated in the jet flow.Moreover,the high value of root mean square of the heat transfer coefficient has spread radially in stripy manner,which is caused as the results of the longitudinal vortexes flowing in the radial direction on the impingement plate.
基金the National Institute of Advanced Industrial Science and Technology(AIST)
文摘The unsteady behavior of flow driven by a jet suddenly injected into a cell is numerically studied by solving the axisymmelric two-dimensional compressible Navier-Stokes equations. The system of the calculation is a model of the laser ablation of a certain duration followed by a discharging process through the exit hole at the down- stream end of the cell. In the calculations, the contour of the cell is changed while other parameters such as the Mach number of the jet, its duration, and the diameter of the cell exit are fixed. Monitoring the velocity at the exit hole is used to investigate the influence of the shape on the interaction between the shock wave and the jet. As the result, it was found that the velocity peak value and its arrival time at the downstream end of the cell exit are determined by the diameter of the cell.
文摘In this paper, dual underexpanded impinging jets are experimentally studied by measuring unsteady wall staticpressure and temperature fields using high response semiconductor pressure sensors and infrared imaging cam-era(100 captures per sec) with dual converging sonic nozzles. The flow field is also visualized by means of highspeed schlieren system( up to 70000 frame per second) to clarify the unsteady behavior of the jet structures suchas barrel shock wave, and Mach disk. Experiments were performed with a blow down tunnel changing the parameterssuch as the nozzle to plate distance, the distance between the two nozzles, and wind tunnel pressure ratio.The nozzle to plate distance L and the distance between the two nozzles H are non-dimensionalized by the nozzlediameter D covering H/D=1.5, 2.0, and 3, L/D= 2, 3,and 4, and po/pb=1.0 - 5.0, where po and pb are stagnationpressure and back pressure respectively. Although the response of the infrared camera is quite different fromthat of the high speed camera, the unsteady correlation between the pressure and temperature fields is confirmedunder some conditions. Also the high speed schlieren pictures and the wall static pressure fluctuations suggestthat the generation of the Mach disk promote the unsteady behavior of the jets. After the confirmation of the correlation,a simple way to find the severe fluctuating region can be provided according to the two dimensional unsteadytemperature images without a lot of unsteady pressure measurements.
基金The outstanding youth science fund project of Inner Mongolia agri-cultural university(2017XQG-4)The Excellent Youth Training program of the College of Food Science and Engineering of Inner Mongolia Agricultural University(SPYQ202101)+2 种基金Young innovative talent of grassland talent project of Inner Mongolia(2020)Talent Develop-ment Fund of Inner Mongolia Autonomous Region(2021)China Scholarship Council launched a scholarship program(2019),China.
文摘A protective coating can aid in reducing mechanical harm to food during harvesting,handling,and trans-portation,resulting in fewer bruises,wounds,and other injuries,thereby improving the overall quality of the produce.In this study,coatings with 1%(w/v)chitosan(CS)and 0.6%(w/v)diepoxy-polyethylene glycol(PEG)were prepared by the co-blending method.According to the findings,increasing the PEG concentration enhanced the moisture content,water vapor permeability,and contact angle properties.In addition,when viewed by scanning electron microscopy(SEM),the morphology of the films containing more PEG appeared rougher and denser.In addition,at room temperature,the freshness of‘Nanguo’pears and the antifungal efficacy of the coating against Penicillium italicum(P.italicum)and Botrytis cinerea(B.cinerea)were evaluated.According to the findings,the weight loss or total soluble solids of pears coated with CS or PEG did not differ significantly during storage.The fruit respiration rate and ascorbic acid(AA)and malondialdehyde(MDA)contents were maintained after coating CS insertion with PEG.The CS-PEG composite coating successfully inhibits the growth of P.italicum and B.cinerea(P.italicum>B.cinerea),according to an in vitro antifungal activity assay that was improved by adding PEG.According to principal component analysis(PCA)results,the CS-PEG coating significantly impacts pear sensory evaluation and firmness.At room temperature,the shelf life of pears with a CS-PEG coat has been extended from 15 days to 25 days.
