In many fields of high-tech industry the ultra-t hi n wall parts are employed. In this paper the experiments were carried out to dis cuss the surface microstructure of the camera’s guided drawtube by applying ult ras...In many fields of high-tech industry the ultra-t hi n wall parts are employed. In this paper the experiments were carried out to dis cuss the surface microstructure of the camera’s guided drawtube by applying ult rasonic vibration cutting device to the traditional lathe. The influence rule of the cutting condition on the surface roughness was put forward, which was drawn by comparing the ultrasonic cutting with the common cutting by use of the cemen ted carbide tool and the polycrystalline diamond (PCD) tool. The test results sh owed that the ultrasonic cutting performs better than the common cutting in the same condition. According to the test results analyzing, the surface characteriz ation is influenced clearly by the rigidity of the acoustic system and the machi ne tool, as well the setting height of the tool tip. Otherwise, the dense regula r low frequency vibration ripples will be scraped on the machined surface. When the tool tip is set higher than the rotating center of the work piece by three t imes of the amplitude of ultrasonic vibration, the vibration ripples behave alig ht; they turn light and shade alternatively when the tool tip is lower than the rotating center of the work piece by three times of the amplitude of ultrasonic vibration. According to the test result analyzing, the following conclusions are put forward: 1) The surface roughness in ultrasonic cutting is better than that in common cutting. Under a one third critical cutting velocity, the value of th e surface roughness in ultrasonic cutting rise slightly along with the cutting v elocity, while in common cutting it decreases contrast to the cutting velocity; the curves of the surface roughness in ultrasonic cutting and common cutting see m to be alike, both increase along with the feed rate and the cutting depth, but the value in ultrasonic cutting is smaller in the same condition.2) The influen ce of the coolant on the surface roughness cannot be ignored. The kerosene can b e employed to improve the surface roughness in ultrasonic machining.3) In ultras onic cutting process of aluminum alloy ultra-thin wall work piece, the PCD tool performs better than the cemented carbide tools.4) The vibration ripples result from the not enough rigidity of the acoustic system and the improper setting he ight of the tool tip. The departure of the tool tip from the rotating center of the work piece to some extent causes the vibration ripples on the machined surfa ce.展开更多
Based on the Boltzmann’s superposition principles of linear viscoelastic materials and the von K*-rm*-n’s hypotheses of thin plates with large deflections, a mathematical model for quasi-static problems of viscoelas...Based on the Boltzmann’s superposition principles of linear viscoelastic materials and the von K*-rm*-n’s hypotheses of thin plates with large deflections, a mathematical model for quasi-static problems of viscoelastic thin plates was given. By the Galerkin method in spatial domain, the original integro-partial-differential system could be transformed into an integral system. The latter further was reduced to a differential system by using the new method for temporal domain presented in this paper. Numerical results show that compared with the ordinary finite difference method, the new method in this paper is simpler to operate and has some advantages, such as, no storage and quicker computational speed etc.展开更多
High frequency shock load is often generated during pyrotechnic device working, which is detrimental to spacecraft structures and electric devices. Therefore, it is valuable to reduce the shock load in pyrotechnic dev...High frequency shock load is often generated during pyrotechnic device working, which is detrimental to spacecraft structures and electric devices. Therefore, it is valuable to reduce the shock load in pyrotechnic device design. Actually, there are several ways to decrease pyroshock loads, such as reduction of powder,installation of buffering structure, insulation of damageable devices, and so on. Considered assuring the function of pyrotechnic device and minimum of structure modification, shock absorbing structure is more propitious to be introduced in pyrotechnic device. In this paper, based on the method of thinwalled metal tube diameter-expanding, a thin-walled tube shock buffering structure was designed on a separate bolt. Built on the simplified structure of a separate bolt, the model of cone piston impacting thin-walled tube absorber was established, and the thin-walled tube shock absorbing characteristics and the relation between cone angles and absorber performance were analyzed. The results showed that the change of buffering force of thin-walled tube could be divided into four phases, and each phase was correspondent to the cone piston structure. In addition, as the cone angle increases, the max shock acceleration changes in the style of decrease-increase-decrease-increase, which is the result of coupled effects of cone piston max enter depth, buffering force and energy loss. In short, these results could establish the relationships between thin-walled tube absorbing performance and its structure, which is of significance to develop low-shock pyrotechnic device.展开更多
Ballistic experiments were conducted on thin steel plates that are normally impacted by hemisphericalnosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin st...Ballistic experiments were conducted on thin steel plates that are normally impacted by hemisphericalnosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin steel plates were analyzed. A new method was proposed according to the experimental results and the perforation phenomenon of the thin steel plates to determine the radius of the bulging region. In establishing this new method, a dynamic method combined with the plastic wave propagation concept based on the rigid plastic assumption was adopted. The whole perforation process was divided into four consecutive stages, namely, bulging deformation, dishing deformation, ductile hole enlargement, and projectile exit. On the basis of the energy conservation principle, a new model was developed to predict the residual velocities of hemispherical-nosed projectiles that perforate thin steel plates at low velocities.The results obtained from the theoretical calculations by the present model were compared with the experimental results. Theoretical predictions were in good agreement with the experimental results in terms of both the radius of the bulging region and the residual velocity of the projectile when the strain rate effects of the target material during each stage were considered.展开更多
In the paper, the experimental researches were carr ie d out to discuss the roundness forming rule and the influence of cutting paramet ers on roundness by ultrasonic vibration cutting of the camera’s guiding drawtu ...In the paper, the experimental researches were carr ie d out to discuss the roundness forming rule and the influence of cutting paramet ers on roundness by ultrasonic vibration cutting of the camera’s guiding drawtu be with 47.75 mm diameter and 0.6～1.5 mm wall thickness. The research results s h ow that the roundness error of ultra-thin wall parts in ultrasonic vibration cu tting is only one third of that in common cutting. The relations between the rou ndness error and the cutting parameters behave as: (1) The roundness error in co mmon cutting decreases gradually with the rise of cutting speed, while in ultras onic cutting, the roundness changes not obviously till the cutting speed is up t o a value, which is nearly equal to one third of the critical velocity. Then the roundness of workpiece will begin to increase slowly. (2) The roundness error i ncreases along with the feed rate both in common cutting and ultrasonic cutting. (3) Within the range of cutting depth in experiment, the influence of cutting d epth on the roundness error is more obvious in common cutting than that in ultra sonic vibration cutting. The conclusions are useful in machining such precise ul tra-thin wall parts. According to the tests, the following conclusions can be o btained: 1) Compared with common cutting, ultrasonic cutting can decrease effect ively roundness error of the workpiece. Under the same condition, the roundness error of the ultra-thin wall part in ultrasonic turning is about one third of t hat in common cutting. 2) In common cutting, cutting depth and feed rate have mu ch influence on the roundness and the influence of cutting velocity is little. W hile in ultrasonic cutting, the roundness was influenced heavily only when feed rate is more than 0.1 mm/r and cutting speed is more than 1/3 of the critical ro tation speed, cutting depth has little influence on the roundness in the experim ent. 3) Kerosene-oil is an optimum cutting fluid in machining ultra-thin wall workpiece. 4) To machine the ultra-thin wall precision part, ultrasonic cutting is the perfect method which can decrease the roundness error effectively an d ensure high quality of the surface.展开更多
Alloy thin film for advanced pressure sensors was manufactured by means of ion-beam sputtering SiO2 insulation film and NiCr thin film on the 17-4PH stainless steel elastic substrate. The thin film resistance was resp...Alloy thin film for advanced pressure sensors was manufactured by means of ion-beam sputtering SiO2 insulation film and NiCr thin film on the 17-4PH stainless steel elastic substrate. The thin film resistance was respectively heat-treated by four processes. The effects on stability of thin film alloy resistance were investigated, and paramaters of heat treatment that make thin film resistance stable were obtained. The experimental result indicates that the most stable thin film resistance can be obtained when it is heat-treated under protection of SiO2 and N2 at 673 K for 1 h, and then kept at 473 K for 24 h. Pressure sensor chips of high precision for harsh environments can be manufactured by this process.展开更多
As one of the most distinct tectonic blocks on the Earth’s surface, Tibetan Plateau draw great attention of the geoscientists from the world. Many authors have proposed various kinds of the mechanism to try to clarif...As one of the most distinct tectonic blocks on the Earth’s surface, Tibetan Plateau draw great attention of the geoscientists from the world. Many authors have proposed various kinds of the mechanism to try to clarify the evolution of the plateau. While many studies are often restricted to crustal units, the important role of the mantle part of the lithosphere (mantle lithosphere) during and after the collision process has not been appreciated widely. The purpose of the paper is to investigate the dynamic process of the thinning (delamination and convective removal) of the thickened lithosphere and its influence upon the uplift of the plateau.1\ Thickened lithosphere root\;Parsons and McKenzie (1978) proposed that the continental lithosphere could be thought of as consisting of two distinct parts: the mechanical and thermal boundary layers. The lower, and hotter, part is the thermal boundary layer. Its viscosity is sufficiently low that the force of gravity acting on density contrasts between the thermal boundary layer and the underlying mantle lead to the episodic sinking of the thermal boundary layer and its replacement by hot asthenosphere. When continental crust shortens and thickens, the mantle directly beneath it must also be displaced downward. In other words, mountain building process shortens horizontally and thickens vertically the mechanical boundary layer, and presumably the thermal boundary layer. And the process stretches the isotherms vertically, thus reducing the geothermal gradient. Houseman’s numerical experiments (1981) show that thickening of the thermal boundary layer enhances the density contrasts between it and the underlying asthenosphere, and so leads to its removal and replacement with hot asthenosphere. This phenomenon is called the instability of the thickened lithosphere.展开更多
The tree crown shape and the tree crown analytical characteristics of Larix ol-gensis in a plantation were studied.It was found that the photosynthetic capability of the tree crown declined gradually from the top part...The tree crown shape and the tree crown analytical characteristics of Larix ol-gensis in a plantation were studied.It was found that the photosynthetic capability of the tree crown declined gradually from the top parts of the crown to the lower parts. The crown could be obviously divided into two parts, the efficient crown and the inefficient crown. Tree growth was influenced by the structure of the efficient crown. The size and the leaf biomass of the efficient crown could be described by its radius. The height from ground to the bottom of the efficient crown of trees in the same stand was nearly the same. The crown of a tree with high potential volume growth efficiency was exposed. Based on the study of the crown structure, the conditions that should be satisfied for proper thinning of Larix olgensis plantation were suggested.展开更多
The Electroluminescence thin films of zinc sulfide do ped with erbium, fabricated by thermal evaporation with two boats, are analyzed by the technology of X-ray diffraction (XRD) and X-ray photoelectron spectrosc opy ...The Electroluminescence thin films of zinc sulfide do ped with erbium, fabricated by thermal evaporation with two boats, are analyzed by the technology of X-ray diffraction (XRD) and X-ray photoelectron spectrosc opy (XPS). The relationship between electroluminescence brightness and microst ructure of the thin films is obtained. The analysis results of XRD indicate th at the fabricated zinc sulfide thin films belong to the blende structure and hav e a trend of preferential orientation. The XPS measurements reveal the surface m icrostructure states formed mainly by oxygen absorption and carbon absorption th at effect on the EL excitation and relaxation luminescence process. The maximum photoelectron peak corresponding to the doped erbium is detected at a depth of 1 35nm to 350nm that formed the activation layer in the films. Analysis shows that the high brightness of the film devices is attributed to the crystalline planes of growth orientated in the (311), (400). In explanation of this phenomenon, th e status of the substitute energy for Er 3+ replacing Zn 2+ in the hos t lattice of zinc sulfide is discussed. All results of describing above are referable in researching of the electroluminescence excitation machnism of the t hin film devices and in favor of fabricating the thin film devices with high qua lity.展开更多
ABSTRACT A quantitative method for the assay of free cholesterol has been described in this paper. The experimental conditions for the determination of cholesterol in serum by Thin-layer chromatography were disscused....ABSTRACT A quantitative method for the assay of free cholesterol has been described in this paper. The experimental conditions for the determination of cholesterol in serum by Thin-layer chromatography were disscused. The solvent System was petroleum ether-ethyl acetate-glacial acetic acid (8o:20:1) and the spra-ying reagent was a solution of sulphuric acid and vanillin. Under the selected con-ditions, the peak area was linearly related to the cholesterol amount for the range between 80～700 ng per spot. The intraplate and interplate coefficients were 2.4% and 7.4% respectively. The recovery of cholesterol was 101.6%. The method presented was simple, rapid and accurate. The results of experi-mental investigation and clinical application were satisfactory.展开更多
In the structural design of the high pier,in order to analyze the strength and structure stability,the pier was often considered a thin-walled structure.Elastoplastic incremental theory was used to establish the model...In the structural design of the high pier,in order to analyze the strength and structure stability,the pier was often considered a thin-walled structure.Elastoplastic incremental theory was used to establish the model of elastoplastic stability of high pier.By considering the combined action of pile,soil and pier together,the destabilization bearing capacity was calculated by using 3-D finite element method(3-D FEM) for piers with different pile and section height.Meanwhile,the equivalent stress in different sections of pier was computed and the processor of destabilization was discussed.When the pier is lower,the bearing capacity under mutual effect of pile,soil and pier is less than the situation when mutual effect is not considered;when the pier is higher,their differences are not conspicuous.Along with the increase of the cross-sectional height,the direction of destabilization bearing capacity is varied and the ultimate capacity is buildup.The results of a stability analysis example are almost identical with the practice.展开更多
Being aimed at the inside wall wrinkling and sinking phenomenon of palladium-yttrium alloy thin wall spiral tube used for preparation of high purity hydrogen, extraction of hydrogen isotope, and purification and separ...Being aimed at the inside wall wrinkling and sinking phenomenon of palladium-yttrium alloy thin wall spiral tube used for preparation of high purity hydrogen, extraction of hydrogen isotope, and purification and separation of hydrogen in the winding process, this article analyzed the reasons for above phenomena, established a numerical simulation model of winding process of above tube, using elastic-plastic Finite Element method analyzed the max. tensile stress and max. compression stress and their locations, thereby provides a theory base for the control of working forming course of thin wall spiral tube.展开更多
With high rock slope in shiplock area, thin reinforced concrete lining walls are constructed for the shiplock system. The construction technology involves much complicated structures in formwork, frequent interference...With high rock slope in shiplock area, thin reinforced concrete lining walls are constructed for the shiplock system. The construction technology involves much complicated structures in formwork, frequent interference due to crossover working procedures, tight time schedule, high quality of reinforced concrete and showcase appearance requirements, hidden troubles affecting construction safety. With above-mentioned factors in consideration, a single-side-separated sliding formwork technology advanced from past sliding formwork experiences has been developed and applied successfully. This new technology is beneficial in quick and safe operation, capable to assure best quality and appearance of shiplock concrete works, and has filled up the gap in terms of construction sliding formwork in our country.展开更多
The effect of surface roughness of aluminum oxide (95%) substrate on the properties of Ni-Cr alloy thin film is studied.The thin films are prepared on the substrates with different roughness by using magnetron sputter...The effect of surface roughness of aluminum oxide (95%) substrate on the properties of Ni-Cr alloy thin film is studied.The thin films are prepared on the substrates with different roughness by using magnetron sputtering.The micro-structure,adhesive and electrical properties of the thin films were investigated by using scanning electron microscopy,scratch method and four-probe method.The burst voltage and current of the thin film transducers with different substrates were measured according to D-optimization method.The results show that the particle size,structural defect,resistivity and adhesion strength of the thin film increase with the increase of the substrate roughness.The difference among the burst time of the samples with difference substrate roughness gradually decreases with the increase of stimulation amount.The burst time is approximate to 20 μs in the charging voltage of 37 V.展开更多
文摘In many fields of high-tech industry the ultra-t hi n wall parts are employed. In this paper the experiments were carried out to dis cuss the surface microstructure of the camera’s guided drawtube by applying ult rasonic vibration cutting device to the traditional lathe. The influence rule of the cutting condition on the surface roughness was put forward, which was drawn by comparing the ultrasonic cutting with the common cutting by use of the cemen ted carbide tool and the polycrystalline diamond (PCD) tool. The test results sh owed that the ultrasonic cutting performs better than the common cutting in the same condition. According to the test results analyzing, the surface characteriz ation is influenced clearly by the rigidity of the acoustic system and the machi ne tool, as well the setting height of the tool tip. Otherwise, the dense regula r low frequency vibration ripples will be scraped on the machined surface. When the tool tip is set higher than the rotating center of the work piece by three t imes of the amplitude of ultrasonic vibration, the vibration ripples behave alig ht; they turn light and shade alternatively when the tool tip is lower than the rotating center of the work piece by three times of the amplitude of ultrasonic vibration. According to the test result analyzing, the following conclusions are put forward: 1) The surface roughness in ultrasonic cutting is better than that in common cutting. Under a one third critical cutting velocity, the value of th e surface roughness in ultrasonic cutting rise slightly along with the cutting v elocity, while in common cutting it decreases contrast to the cutting velocity; the curves of the surface roughness in ultrasonic cutting and common cutting see m to be alike, both increase along with the feed rate and the cutting depth, but the value in ultrasonic cutting is smaller in the same condition.2) The influen ce of the coolant on the surface roughness cannot be ignored. The kerosene can b e employed to improve the surface roughness in ultrasonic machining.3) In ultras onic cutting process of aluminum alloy ultra-thin wall work piece, the PCD tool performs better than the cemented carbide tools.4) The vibration ripples result from the not enough rigidity of the acoustic system and the improper setting he ight of the tool tip. The departure of the tool tip from the rotating center of the work piece to some extent causes the vibration ripples on the machined surfa ce.
文摘Based on the Boltzmann’s superposition principles of linear viscoelastic materials and the von K*-rm*-n’s hypotheses of thin plates with large deflections, a mathematical model for quasi-static problems of viscoelastic thin plates was given. By the Galerkin method in spatial domain, the original integro-partial-differential system could be transformed into an integral system. The latter further was reduced to a differential system by using the new method for temporal domain presented in this paper. Numerical results show that compared with the ordinary finite difference method, the new method in this paper is simpler to operate and has some advantages, such as, no storage and quicker computational speed etc.
文摘High frequency shock load is often generated during pyrotechnic device working, which is detrimental to spacecraft structures and electric devices. Therefore, it is valuable to reduce the shock load in pyrotechnic device design. Actually, there are several ways to decrease pyroshock loads, such as reduction of powder,installation of buffering structure, insulation of damageable devices, and so on. Considered assuring the function of pyrotechnic device and minimum of structure modification, shock absorbing structure is more propitious to be introduced in pyrotechnic device. In this paper, based on the method of thinwalled metal tube diameter-expanding, a thin-walled tube shock buffering structure was designed on a separate bolt. Built on the simplified structure of a separate bolt, the model of cone piston impacting thin-walled tube absorber was established, and the thin-walled tube shock absorbing characteristics and the relation between cone angles and absorber performance were analyzed. The results showed that the change of buffering force of thin-walled tube could be divided into four phases, and each phase was correspondent to the cone piston structure. In addition, as the cone angle increases, the max shock acceleration changes in the style of decrease-increase-decrease-increase, which is the result of coupled effects of cone piston max enter depth, buffering force and energy loss. In short, these results could establish the relationships between thin-walled tube absorbing performance and its structure, which is of significance to develop low-shock pyrotechnic device.
基金financially supported by the National Security Major Foundation Research Project(973)of China(6133050102)the National Natural Science Foundation of China(Grant No.51409253)
文摘Ballistic experiments were conducted on thin steel plates that are normally impacted by hemisphericalnosed projectiles at velocities higher than their ballistic limits. The deformation and failure modes of the thin steel plates were analyzed. A new method was proposed according to the experimental results and the perforation phenomenon of the thin steel plates to determine the radius of the bulging region. In establishing this new method, a dynamic method combined with the plastic wave propagation concept based on the rigid plastic assumption was adopted. The whole perforation process was divided into four consecutive stages, namely, bulging deformation, dishing deformation, ductile hole enlargement, and projectile exit. On the basis of the energy conservation principle, a new model was developed to predict the residual velocities of hemispherical-nosed projectiles that perforate thin steel plates at low velocities.The results obtained from the theoretical calculations by the present model were compared with the experimental results. Theoretical predictions were in good agreement with the experimental results in terms of both the radius of the bulging region and the residual velocity of the projectile when the strain rate effects of the target material during each stage were considered.
文摘In the paper, the experimental researches were carr ie d out to discuss the roundness forming rule and the influence of cutting paramet ers on roundness by ultrasonic vibration cutting of the camera’s guiding drawtu be with 47.75 mm diameter and 0.6～1.5 mm wall thickness. The research results s h ow that the roundness error of ultra-thin wall parts in ultrasonic vibration cu tting is only one third of that in common cutting. The relations between the rou ndness error and the cutting parameters behave as: (1) The roundness error in co mmon cutting decreases gradually with the rise of cutting speed, while in ultras onic cutting, the roundness changes not obviously till the cutting speed is up t o a value, which is nearly equal to one third of the critical velocity. Then the roundness of workpiece will begin to increase slowly. (2) The roundness error i ncreases along with the feed rate both in common cutting and ultrasonic cutting. (3) Within the range of cutting depth in experiment, the influence of cutting d epth on the roundness error is more obvious in common cutting than that in ultra sonic vibration cutting. The conclusions are useful in machining such precise ul tra-thin wall parts. According to the tests, the following conclusions can be o btained: 1) Compared with common cutting, ultrasonic cutting can decrease effect ively roundness error of the workpiece. Under the same condition, the roundness error of the ultra-thin wall part in ultrasonic turning is about one third of t hat in common cutting. 2) In common cutting, cutting depth and feed rate have mu ch influence on the roundness and the influence of cutting velocity is little. W hile in ultrasonic cutting, the roundness was influenced heavily only when feed rate is more than 0.1 mm/r and cutting speed is more than 1/3 of the critical ro tation speed, cutting depth has little influence on the roundness in the experim ent. 3) Kerosene-oil is an optimum cutting fluid in machining ultra-thin wall workpiece. 4) To machine the ultra-thin wall precision part, ultrasonic cutting is the perfect method which can decrease the roundness error effectively an d ensure high quality of the surface.
文摘Alloy thin film for advanced pressure sensors was manufactured by means of ion-beam sputtering SiO2 insulation film and NiCr thin film on the 17-4PH stainless steel elastic substrate. The thin film resistance was respectively heat-treated by four processes. The effects on stability of thin film alloy resistance were investigated, and paramaters of heat treatment that make thin film resistance stable were obtained. The experimental result indicates that the most stable thin film resistance can be obtained when it is heat-treated under protection of SiO2 and N2 at 673 K for 1 h, and then kept at 473 K for 24 h. Pressure sensor chips of high precision for harsh environments can be manufactured by this process.
文摘As one of the most distinct tectonic blocks on the Earth’s surface, Tibetan Plateau draw great attention of the geoscientists from the world. Many authors have proposed various kinds of the mechanism to try to clarify the evolution of the plateau. While many studies are often restricted to crustal units, the important role of the mantle part of the lithosphere (mantle lithosphere) during and after the collision process has not been appreciated widely. The purpose of the paper is to investigate the dynamic process of the thinning (delamination and convective removal) of the thickened lithosphere and its influence upon the uplift of the plateau.1\ Thickened lithosphere root\;Parsons and McKenzie (1978) proposed that the continental lithosphere could be thought of as consisting of two distinct parts: the mechanical and thermal boundary layers. The lower, and hotter, part is the thermal boundary layer. Its viscosity is sufficiently low that the force of gravity acting on density contrasts between the thermal boundary layer and the underlying mantle lead to the episodic sinking of the thermal boundary layer and its replacement by hot asthenosphere. When continental crust shortens and thickens, the mantle directly beneath it must also be displaced downward. In other words, mountain building process shortens horizontally and thickens vertically the mechanical boundary layer, and presumably the thermal boundary layer. And the process stretches the isotherms vertically, thus reducing the geothermal gradient. Houseman’s numerical experiments (1981) show that thickening of the thermal boundary layer enhances the density contrasts between it and the underlying asthenosphere, and so leads to its removal and replacement with hot asthenosphere. This phenomenon is called the instability of the thickened lithosphere.
文摘The tree crown shape and the tree crown analytical characteristics of Larix ol-gensis in a plantation were studied.It was found that the photosynthetic capability of the tree crown declined gradually from the top parts of the crown to the lower parts. The crown could be obviously divided into two parts, the efficient crown and the inefficient crown. Tree growth was influenced by the structure of the efficient crown. The size and the leaf biomass of the efficient crown could be described by its radius. The height from ground to the bottom of the efficient crown of trees in the same stand was nearly the same. The crown of a tree with high potential volume growth efficiency was exposed. Based on the study of the crown structure, the conditions that should be satisfied for proper thinning of Larix olgensis plantation were suggested.
文摘The Electroluminescence thin films of zinc sulfide do ped with erbium, fabricated by thermal evaporation with two boats, are analyzed by the technology of X-ray diffraction (XRD) and X-ray photoelectron spectrosc opy (XPS). The relationship between electroluminescence brightness and microst ructure of the thin films is obtained. The analysis results of XRD indicate th at the fabricated zinc sulfide thin films belong to the blende structure and hav e a trend of preferential orientation. The XPS measurements reveal the surface m icrostructure states formed mainly by oxygen absorption and carbon absorption th at effect on the EL excitation and relaxation luminescence process. The maximum photoelectron peak corresponding to the doped erbium is detected at a depth of 1 35nm to 350nm that formed the activation layer in the films. Analysis shows that the high brightness of the film devices is attributed to the crystalline planes of growth orientated in the (311), (400). In explanation of this phenomenon, th e status of the substitute energy for Er 3+ replacing Zn 2+ in the hos t lattice of zinc sulfide is discussed. All results of describing above are referable in researching of the electroluminescence excitation machnism of the t hin film devices and in favor of fabricating the thin film devices with high qua lity.
文摘ABSTRACT A quantitative method for the assay of free cholesterol has been described in this paper. The experimental conditions for the determination of cholesterol in serum by Thin-layer chromatography were disscused. The solvent System was petroleum ether-ethyl acetate-glacial acetic acid (8o:20:1) and the spra-ying reagent was a solution of sulphuric acid and vanillin. Under the selected con-ditions, the peak area was linearly related to the cholesterol amount for the range between 80～700 ng per spot. The intraplate and interplate coefficients were 2.4% and 7.4% respectively. The recovery of cholesterol was 101.6%. The method presented was simple, rapid and accurate. The results of experi-mental investigation and clinical application were satisfactory.
基金Project(06JJ5080) supported by the Hunan Natural Science Foundation of ChinaProject(05026B) supported by the Young Science Foundation of Central South University of Forestry and Technology
文摘In the structural design of the high pier,in order to analyze the strength and structure stability,the pier was often considered a thin-walled structure.Elastoplastic incremental theory was used to establish the model of elastoplastic stability of high pier.By considering the combined action of pile,soil and pier together,the destabilization bearing capacity was calculated by using 3-D finite element method(3-D FEM) for piers with different pile and section height.Meanwhile,the equivalent stress in different sections of pier was computed and the processor of destabilization was discussed.When the pier is lower,the bearing capacity under mutual effect of pile,soil and pier is less than the situation when mutual effect is not considered;when the pier is higher,their differences are not conspicuous.Along with the increase of the cross-sectional height,the direction of destabilization bearing capacity is varied and the ultimate capacity is buildup.The results of a stability analysis example are almost identical with the practice.
文摘Being aimed at the inside wall wrinkling and sinking phenomenon of palladium-yttrium alloy thin wall spiral tube used for preparation of high purity hydrogen, extraction of hydrogen isotope, and purification and separation of hydrogen in the winding process, this article analyzed the reasons for above phenomena, established a numerical simulation model of winding process of above tube, using elastic-plastic Finite Element method analyzed the max. tensile stress and max. compression stress and their locations, thereby provides a theory base for the control of working forming course of thin wall spiral tube.
文摘With high rock slope in shiplock area, thin reinforced concrete lining walls are constructed for the shiplock system. The construction technology involves much complicated structures in formwork, frequent interference due to crossover working procedures, tight time schedule, high quality of reinforced concrete and showcase appearance requirements, hidden troubles affecting construction safety. With above-mentioned factors in consideration, a single-side-separated sliding formwork technology advanced from past sliding formwork experiences has been developed and applied successfully. This new technology is beneficial in quick and safe operation, capable to assure best quality and appearance of shiplock concrete works, and has filled up the gap in terms of construction sliding formwork in our country.
文摘The effect of surface roughness of aluminum oxide (95%) substrate on the properties of Ni-Cr alloy thin film is studied.The thin films are prepared on the substrates with different roughness by using magnetron sputtering.The micro-structure,adhesive and electrical properties of the thin films were investigated by using scanning electron microscopy,scratch method and four-probe method.The burst voltage and current of the thin film transducers with different substrates were measured according to D-optimization method.The results show that the particle size,structural defect,resistivity and adhesion strength of the thin film increase with the increase of the substrate roughness.The difference among the burst time of the samples with difference substrate roughness gradually decreases with the increase of stimulation amount.The burst time is approximate to 20 μs in the charging voltage of 37 V.
