Ingot metallurgy (IM) aluminum has long been the subject and attracted the attention of many metallurgists and textural researchers of materials. Due to the introduction of large amounts of ex situ interfaces, however...Ingot metallurgy (IM) aluminum has long been the subject and attracted the attention of many metallurgists and textural researchers of materials. Due to the introduction of large amounts of ex situ interfaces, however, the textures in powder metallurgy (PM) processed aluminum has been rarely reported. In this article, a pure aluminum plate was prepared via PM route. The starting billet was first produced with uni-axially cold compaction and flat hot-extrusion and then followed by cold rolling processes. The hot-extruded and cold rolling deformation textures of the pure PM aluminum at 50%, 80% and 90% cold rolling reductions were studied by orientation distribution functions (ODFs) analysis. The finite element polycrystal model (FEPM) was finally utilized to simulate the cold rolling textural evolution at various stages of cold rolling. In FEPM simulation, the initial hot-extruded textures were taken into account as inputs. The results showed that typical β-fiber texture formed in pure PM aluminum with the cold rolling reduction increased till 80%, and there was not much change after excessive cold rolling deformation. Homogeneous slip is not the only deformation mode in PM processed pure aluminum plate at over 80% cold rolling reduction. The experimental results were qualitatively in good agreement with the simulated ones.展开更多
The kinematic design of a reconfigurable miniature parallel kinematic machineis dealt with. It shows that the reconfigurability may be realized by packaging a tripod-basedparallel mechanism with fixed length struts in...The kinematic design of a reconfigurable miniature parallel kinematic machineis dealt with. It shows that the reconfigurability may be realized by packaging a tripod-basedparallel mechanism with fixed length struts into a compact and rigid frame with which the differentconfigurations can be formed. Utilizing a dual parameter model, the influences of the geometricalparameters on the dexterous performance and the workspace/machine volume ratio are investigated. Anovel global performance index for the dimensional synthesis is proposed and optimized, resulting ina set of dimensionless geometrical parameters.展开更多
By a novel technique-cathodic micro-arc electro-deposition (CMED), ZrO_2coatings were deposited on an FeCrAl alloy. Experimental results show that the necessary conditionsfor obtaining ZrO_2 coatings are to apply a pu...By a novel technique-cathodic micro-arc electro-deposition (CMED), ZrO_2coatings were deposited on an FeCrAl alloy. Experimental results show that the necessary conditionsfor obtaining ZrO_2 coatings are to apply a pulse peak voltage over a critical value and addmoderate amounts of ZrO_2 colloidal particles and Zr(NO_3)_4 in the aqueous solution. Theas-deposited coatings are porous because hydrogen, water, and other vapors are generated andreleased from the coatings to the solution during the spark reaction. The coatings containmonoclinic and tetragonal crystalline ZrO_2 with certain degree of amorphous structure. Theprocessing parameters and mechanism of CMED were discussed.展开更多
Using state assignment to minimize power dissipation and area for finite state ma-chines is computationally hard. Most of published results show that the reduction of switchingactivity often trades with area penalty. ...Using state assignment to minimize power dissipation and area for finite state ma-chines is computationally hard. Most of published results show that the reduction of switchingactivity often trades with area penalty. In this paper, a new approach is proposed. Experimentalresults show a significant reduction of switching activity without area penalty compared withprevious publications.展开更多
Review of X-ray dark-field imaging under development is presented. Its goal is its application to clinical diagnosis of organs that have been invisible by the ordinary techniques. In order to clinically visualize tiss...Review of X-ray dark-field imaging under development is presented. Its goal is its application to clinical diagnosis of organs that have been invisible by the ordinary techniques. In order to clinically visualize tissues in detail one needs high contrast and high spatial resolution say ～50 μm. This X-ray optics comprises a Bragg asymmetric monochro-collimator and a Bragg case or a Laue case filter with capability of analyzing angle in a parallel position. Their diffraction index is 4,4,0 and the X-ray energy 35 keV (λ= 0.0354 nm). The filter has 0.6 mm thickness in the Bragg case or 1.075 mm or 2.15 mm thickness in the Laue case. Under this condition only the refracted X-rays from object can transmit through the filter while the beam that may receive absorption and/or phase change will not. Soft tissues at human joints thus taken show high contrast images so that the DFI is promising for clinical diagnosis. Preliminary X-ray absorption images of another clinical candidates of ear bones are also shown.展开更多
In this short review,we highlight instances where interstitials have been shown to substantially increase the yield strength and work-hardening rate(WHR)of f.c.c.alloys,particularly high entropy alloys,medium entropy ...In this short review,we highlight instances where interstitials have been shown to substantially increase the yield strength and work-hardening rate(WHR)of f.c.c.alloys,particularly high entropy alloys,medium entropy alloys,TWIP steels and stainless steels.However,the common practice of describing interstitial strengthening in f.c.c.alloys using models that are used to explain substitutional strengthening appears to be neither appropriate nor accurate.Here we suggest,based on the literature,that the yield strength increase due to interstitials in f.c.c.alloys is more appropriately described by a linear dependence on the concentration:due to a paucity of experimental studies,the dependence of the yield strength and WHR on misfit parameters is currently unclear.Thus,the source of the strengthening remains unclear.A feature that has been observed in several f.c.c.alloys is that interstitial additions lead to a change from wavy to planar slip although the origin of this change,which may be related to changes in stacking fault energy as well as other factors,remains unclear.The paper concludes by outlining areas of future research,including the need to develop a new model for interstitial strengthening in f.c.c.alloys.展开更多
Fe-3Cr-0.5Mo-0.3C and Fe-3Cr-l.4Mn-0.5Mo-0.367C sintered alloys were plasma nitrided at different temperatures. Characterization was performed by microhardness measurement, optical microscopy, SEM and XRD. Both materi...Fe-3Cr-0.5Mo-0.3C and Fe-3Cr-l.4Mn-0.5Mo-0.367C sintered alloys were plasma nitrided at different temperatures. Characterization was performed by microhardness measurement, optical microscopy, SEM and XRD. Both materials had similar nitriding case properties. 1.4% manganese did not change the as-sintered microstructure considerably. It was observed that monophase compound layer, formed with increasing temperature. Compound layer thickness increased with increasing temperature while nitriding depth increased up to a level and then decreased. Core softening was more pronounced at higher temperature owing to cementite coarsening.展开更多
Opto-thermal transient emission radiometry(OTTER) is a infrared remote sensing technique, which has been successfully used in in vivoskin moisture content and skin moisture depth profiling measurements. In present pap...Opto-thermal transient emission radiometry(OTTER) is a infrared remote sensing technique, which has been successfully used in in vivoskin moisture content and skin moisture depth profiling measurements. In present paper, we extend this moisture content measurement capability to analyze the moisture content of fruit(tomato, grape, etc.) skins, and to study the relationship between fruits ripening process and their surface moisture and moisture depth profiles.展开更多
A Particle Image Velocimetry (PIV) method based on the image separation andreconstruction with the median filter and triangular Bezier patch was proposed to measure multiplevelocity fields from single-camera images in...A Particle Image Velocimetry (PIV) method based on the image separation andreconstruction with the median filter and triangular Bezier patch was proposed to measure multiplevelocity fields from single-camera images in the present study. The method was examined on syntheticPIV images with the Green-Taylor two-phase vortex flows and the test results showed high accuracyand highly correct tracking percent compared with the exact solution. An experiment of the bubblyjet flow was also conducted as a practical demonstration of the present method. As a result, it isconfirmed from the simulation image examination and the experimental measurement that the proposedmethod shows a good performance in the measurement of bubble and particle phases.展开更多
The formation of ceramic coatings on metal substrate by cathodic electrolytic deposition (CELD) has received more attention in recent years. But only thin filmscan be prepared via CELD. Yttrium stabilized zirconia (YS...The formation of ceramic coatings on metal substrate by cathodic electrolytic deposition (CELD) has received more attention in recent years. But only thin filmscan be prepared via CELD. Yttrium stabilized zirconia (YSZ) ceramic coatings were deposited on FeCrAI alloy by a novel technique--cathodic micro-arc electrodeposition (CMED).The result shows that, when a high pulse electric field is applied to the cathode which was pre-deposited with a thin YSZ film, dielectric breakdown occurs and micro-arc discharges appear. Coatings with reasonably thickness of-300μm and crystalline structure can be deposited on the cathode by utilizing the energy of the micro-arc. The thickness of the as-deposited coating is dominated by the voltage and the frequency. Y2O3 is co-deposited with ZrO2 when Y(NO3)3 was added to the electrolyte, which stabilize t-phase, t′-phase and c-phase of ZrO2 at room temperature. The amount of the m-ZrO2 in the coating is diminished by increasing the concentration of Y(NO3)3 in the electrolyte.This report describes the processing of CMED and studies the microstructure of the deposited YSZ coatings.展开更多
A new CMOS quaternary D flip-flop is implemented employing a multiple-valuedclock. PSpice simulation shows that the proposed flip-flop has correct operation. Compared withtraditional multiple-valued flip-flops, the pr...A new CMOS quaternary D flip-flop is implemented employing a multiple-valuedclock. PSpice simulation shows that the proposed flip-flop has correct operation. Compared withtraditional multiple-valued flip-flops, the proposed multiple-valued CMOS flip-flop is characterizedby improved storage capacity, flexible logic structure and reduced power dissipation.展开更多
Bubble-bubble interaction in free rising bubbly flows is experimentally investigated in the present study. The velocity vectors of the bubbles are measured by a stereoscopic bubble-tracking technique and then the rela...Bubble-bubble interaction in free rising bubbly flows is experimentally investigated in the present study. The velocity vectors of the bubbles are measured by a stereoscopic bubble-tracking technique and then the relative velocity vectors of two nearest-neighbor bubbles are calculated with high statistical reliability. With the measurement data at Reynolds number ranging from 5 to 75, the vertical attraction and the horizontal repulsion are confirmed for Re<10 as known by the past study based on Navier-Stokes simulation. The new finding of the present measurement is that the bubbles of Re>30 have repulsive velocity bothin the horizontal and the vertical directions as those rise closely. Moreover, the three-dimensional structure of the bubble-bubble interaction is discussed with the data analysis of the interaction vector fields.展开更多
文摘Ingot metallurgy (IM) aluminum has long been the subject and attracted the attention of many metallurgists and textural researchers of materials. Due to the introduction of large amounts of ex situ interfaces, however, the textures in powder metallurgy (PM) processed aluminum has been rarely reported. In this article, a pure aluminum plate was prepared via PM route. The starting billet was first produced with uni-axially cold compaction and flat hot-extrusion and then followed by cold rolling processes. The hot-extruded and cold rolling deformation textures of the pure PM aluminum at 50%, 80% and 90% cold rolling reductions were studied by orientation distribution functions (ODFs) analysis. The finite element polycrystal model (FEPM) was finally utilized to simulate the cold rolling textural evolution at various stages of cold rolling. In FEPM simulation, the initial hot-extruded textures were taken into account as inputs. The results showed that typical β-fiber texture formed in pure PM aluminum with the cold rolling reduction increased till 80%, and there was not much change after excessive cold rolling deformation. Homogeneous slip is not the only deformation mode in PM processed pure aluminum plate at over 80% cold rolling reduction. The experimental results were qualitatively in good agreement with the simulated ones.
基金This project is supported by National Natural Science Foundation of China (No.50075059) Tianjin Science and Technology Commission (No. 99370111 andNo.003802111).
文摘The kinematic design of a reconfigurable miniature parallel kinematic machineis dealt with. It shows that the reconfigurability may be realized by packaging a tripod-basedparallel mechanism with fixed length struts into a compact and rigid frame with which the differentconfigurations can be formed. Utilizing a dual parameter model, the influences of the geometricalparameters on the dexterous performance and the workspace/machine volume ratio are investigated. Anovel global performance index for the dimensional synthesis is proposed and optimized, resulting ina set of dimensionless geometrical parameters.
基金This work was financially supported by the National Natural Science Foundation of China (No.59971009) Beijing Key Laboratory for Corrosion, Erosion and Surface Technology.
文摘By a novel technique-cathodic micro-arc electro-deposition (CMED), ZrO_2coatings were deposited on an FeCrAl alloy. Experimental results show that the necessary conditionsfor obtaining ZrO_2 coatings are to apply a pulse peak voltage over a critical value and addmoderate amounts of ZrO_2 colloidal particles and Zr(NO_3)_4 in the aqueous solution. Theas-deposited coatings are porous because hydrogen, water, and other vapors are generated andreleased from the coatings to the solution during the spark reaction. The coatings containmonoclinic and tetragonal crystalline ZrO_2 with certain degree of amorphous structure. Theprocessing parameters and mechanism of CMED were discussed.
基金Supported by NNSF of China(Key International Cooperative Project No.60010121219)
文摘Using state assignment to minimize power dissipation and area for finite state ma-chines is computationally hard. Most of published results show that the reduction of switchingactivity often trades with area penalty. In this paper, a new approach is proposed. Experimentalresults show a significant reduction of switching activity without area penalty compared withprevious publications.
文摘Review of X-ray dark-field imaging under development is presented. Its goal is its application to clinical diagnosis of organs that have been invisible by the ordinary techniques. In order to clinically visualize tissues in detail one needs high contrast and high spatial resolution say ～50 μm. This X-ray optics comprises a Bragg asymmetric monochro-collimator and a Bragg case or a Laue case filter with capability of analyzing angle in a parallel position. Their diffraction index is 4,4,0 and the X-ray energy 35 keV (λ= 0.0354 nm). The filter has 0.6 mm thickness in the Bragg case or 1.075 mm or 2.15 mm thickness in the Laue case. Under this condition only the refracted X-rays from object can transmit through the filter while the beam that may receive absorption and/or phase change will not. Soft tissues at human joints thus taken show high contrast images so that the DFI is promising for clinical diagnosis. Preliminary X-ray absorption images of another clinical candidates of ear bones are also shown.
基金supported by the U.S.Department of Energy,Office of Science,Basic Energy Sciences,under Award#DE-SC0018962.
文摘In this short review,we highlight instances where interstitials have been shown to substantially increase the yield strength and work-hardening rate(WHR)of f.c.c.alloys,particularly high entropy alloys,medium entropy alloys,TWIP steels and stainless steels.However,the common practice of describing interstitial strengthening in f.c.c.alloys using models that are used to explain substitutional strengthening appears to be neither appropriate nor accurate.Here we suggest,based on the literature,that the yield strength increase due to interstitials in f.c.c.alloys is more appropriately described by a linear dependence on the concentration:due to a paucity of experimental studies,the dependence of the yield strength and WHR on misfit parameters is currently unclear.Thus,the source of the strengthening remains unclear.A feature that has been observed in several f.c.c.alloys is that interstitial additions lead to a change from wavy to planar slip although the origin of this change,which may be related to changes in stacking fault energy as well as other factors,remains unclear.The paper concludes by outlining areas of future research,including the need to develop a new model for interstitial strengthening in f.c.c.alloys.
文摘Fe-3Cr-0.5Mo-0.3C and Fe-3Cr-l.4Mn-0.5Mo-0.367C sintered alloys were plasma nitrided at different temperatures. Characterization was performed by microhardness measurement, optical microscopy, SEM and XRD. Both materials had similar nitriding case properties. 1.4% manganese did not change the as-sintered microstructure considerably. It was observed that monophase compound layer, formed with increasing temperature. Compound layer thickness increased with increasing temperature while nitriding depth increased up to a level and then decreased. Core softening was more pronounced at higher temperature owing to cementite coarsening.
文摘Opto-thermal transient emission radiometry(OTTER) is a infrared remote sensing technique, which has been successfully used in in vivoskin moisture content and skin moisture depth profiling measurements. In present paper, we extend this moisture content measurement capability to analyze the moisture content of fruit(tomato, grape, etc.) skins, and to study the relationship between fruits ripening process and their surface moisture and moisture depth profiles.
文摘A Particle Image Velocimetry (PIV) method based on the image separation andreconstruction with the median filter and triangular Bezier patch was proposed to measure multiplevelocity fields from single-camera images in the present study. The method was examined on syntheticPIV images with the Green-Taylor two-phase vortex flows and the test results showed high accuracyand highly correct tracking percent compared with the exact solution. An experiment of the bubblyjet flow was also conducted as a practical demonstration of the present method. As a result, it isconfirmed from the simulation image examination and the experimental measurement that the proposedmethod shows a good performance in the measurement of bubble and particle phases.
文摘The formation of ceramic coatings on metal substrate by cathodic electrolytic deposition (CELD) has received more attention in recent years. But only thin filmscan be prepared via CELD. Yttrium stabilized zirconia (YSZ) ceramic coatings were deposited on FeCrAI alloy by a novel technique--cathodic micro-arc electrodeposition (CMED).The result shows that, when a high pulse electric field is applied to the cathode which was pre-deposited with a thin YSZ film, dielectric breakdown occurs and micro-arc discharges appear. Coatings with reasonably thickness of-300μm and crystalline structure can be deposited on the cathode by utilizing the energy of the micro-arc. The thickness of the as-deposited coating is dominated by the voltage and the frequency. Y2O3 is co-deposited with ZrO2 when Y(NO3)3 was added to the electrolyte, which stabilize t-phase, t′-phase and c-phase of ZrO2 at room temperature. The amount of the m-ZrO2 in the coating is diminished by increasing the concentration of Y(NO3)3 in the electrolyte.This report describes the processing of CMED and studies the microstructure of the deposited YSZ coatings.
文摘A new CMOS quaternary D flip-flop is implemented employing a multiple-valuedclock. PSpice simulation shows that the proposed flip-flop has correct operation. Compared withtraditional multiple-valued flip-flops, the proposed multiple-valued CMOS flip-flop is characterizedby improved storage capacity, flexible logic structure and reduced power dissipation.
基金This work was supported as Grant In Aid Research by the Japanese Ministry ofEducation Science and Culture (GrantNos: CN15560135 and CN15760104)
文摘Bubble-bubble interaction in free rising bubbly flows is experimentally investigated in the present study. The velocity vectors of the bubbles are measured by a stereoscopic bubble-tracking technique and then the relative velocity vectors of two nearest-neighbor bubbles are calculated with high statistical reliability. With the measurement data at Reynolds number ranging from 5 to 75, the vertical attraction and the horizontal repulsion are confirmed for Re<10 as known by the past study based on Navier-Stokes simulation. The new finding of the present measurement is that the bubbles of Re>30 have repulsive velocity bothin the horizontal and the vertical directions as those rise closely. Moreover, the three-dimensional structure of the bubble-bubble interaction is discussed with the data analysis of the interaction vector fields.
