We estimate the thermal properties of unsmooth Si nanowires,considering key factors such as size(diameter),surface texture(roughness)and quantum size effects(phonon states)at different temperatures.For nanowires with ...We estimate the thermal properties of unsmooth Si nanowires,considering key factors such as size(diameter),surface texture(roughness)and quantum size effects(phonon states)at different temperatures.For nanowires with a diameter of less than 20 nm,we highlight the importance of quantum size effects in heat capacity calculations,using dispersion relations derived from the modified frequency equation for the elasticity of a rod.The thermal conductivities of nanowires with diameters of 37,56,and 115nm are predicted using the Fuchs–Sondheimer model and Soffer’s specular parameter.Notably,the roughness parameters are chosen to reflect the technological characteristics of the real surfaces.Our findings reveal that surface texture plays a significant role in thermal conductivity,particularly in the realm of ballistic heat transfer within nanowires.This study provides practical recommendations for developing new thermal management materials.展开更多
Terahertz(THz)technology offers novel opportunities in biology and medicine,thanks to the unique features of THzwave interactions with tissues and cells.Among them,we particularly notice strong sensitivity of THz wave...Terahertz(THz)technology offers novel opportunities in biology and medicine,thanks to the unique features of THzwave interactions with tissues and cells.Among them,we particularly notice strong sensitivity of THz waves to the tissue water,as a medium for biochemical reactions and a main endogenous marker for THz spectroscopy and imaging.Tissues of the brain have an exceptionally high content of water.This factor,along with the features of the structural organization and biochemistry of neuronal and glial tissues,makes the brain an exciting subject to study in the THz range.In this paper,progress and prospects of THz technology in neurodiagnostics are overviewed,including diagnosis of neurodegenerative disease,myelin deficit,tumors of the central nervous system(with an emphasis on brain gliomas),and traumatic brain injuries.Fundamental and applied challenges in study of the THz-wave–brain tissue interactions and development of the THz biomedical tools and systems for neurodiagnostics are discussed.展开更多
The problem of in vrivo photoluminescence diagnostics of the tissues acessible by endoscopes is discussed.The spectral imaging module attachable to conventional rigid and flexible medical endoscopes is developed and d...The problem of in vrivo photoluminescence diagnostics of the tissues acessible by endoscopes is discussed.The spectral imaging module attachable to conventional rigid and flexible medical endoscopes is developed and described.It is based on a double acousto-optical tunable filter(AOTF)and a specialized optical coupling system.The module provides wide field of view(FOV),absence of image distortions,random spectral access,fast spectral image acquisition at any wavelength in the visible range and accurate measurement of reflectance spectrum in each pixel of the image.Images of typical biomedical samples are presented and discussed.Their spectra are compared to the reference data.展开更多
In the case of valuable cold-rolled Cu/Al clad plates,billet surface treatment before rolling is a significant process that can affect the bonding efficiency and quality.While the current studies primarily focus on th...In the case of valuable cold-rolled Cu/Al clad plates,billet surface treatment before rolling is a significant process that can affect the bonding efficiency and quality.While the current studies primarily focus on the influence of rolling parameters,insufficient attention has been paid to surface treatment.In this study,the effects of mechanical surface treatment on the bonding mechanism and bonding properties of cold-rolled Cu/Al clad plates were investigated.The results showed that different mechanical surface treatments have significant effects on the surface morphology,roughness,and residual stress.In addition,the effect of surface mechanical treatment on bonding quality was also observed to be critical.When the grinding direction was consistent with the rolling direction(RD),the bonding quality of the Cu/Al clad plates was significantly improved.After surface treatment along the RD for 20 s,the Cu/Al clad plates showed the highest shear strength(78 MPa),approximately four times as high as that of the unpolished samples.Simultaneously,the peel strength of this process was also significantly higher than that achieved via the other processes.Finally,on the basis of the surface morphology,roughness,and residual stress,the effect of surface treatment on the bonding mechanism and bonding properties of Cu/Al clad plates was analyzed.This study proposes a deeper understanding of the bonding behavior and bonding mechanism for cold rolled clad plates processed via mechanical surface treatment.展开更多
To increase accuracy of navigation parameters,a perspective measuring complex with intellectual components is developed.Conception of synthesis optimal structure of the measuring complex is realized basing on a select...To increase accuracy of navigation parameters,a perspective measuring complex with intellectual components is developed.Conception of synthesis optimal structure of the measuring complex is realized basing on a selective method using principles of the functional systems.Selection of measured information is finished by original numeric criterion of observation level of state vector components.Prediction is realized by algorithm of self-organization that makes synthesis of the optimal complication.Therefore mechanism of self-regulation is realized and accuracy of the selective navigation complex is increased.展开更多
After conducting a critical survey of the different categories of existing heat exchangers,the results of several experiments about the behaviour of a two-phase current in an open channel are reported.The results conf...After conducting a critical survey of the different categories of existing heat exchangers,the results of several experiments about the behaviour of a two-phase current in an open channel are reported.The results confirm the complexity of the problems induced in heat exchangers by flow maldistribution,especially when two-phase flows are considered in multi-channel systems.It is shown that severe misalignment of heat exchangers can lead to a loss of economic performance of more than 25%.Improper distribution of fluid flow causes longer fluid coils to form,and the liquid cochlea can eventually occupy a large space,thereby reducing heat transfer and disrupting the considered biphasic system.The use of a small diameter distribution pipe with properly spaced outlet holes seems to be a promising approach to fix many of these issues.It is found that the current distribution in the channels,in addition to the header pressure distribution,also depends on factors such as the geometry and the initial flow regime in the header.展开更多
In this study, recurrent networks to downscale meteorological fields of the ERA-40 re-analysis dataset with focus on the meso-scale water balance were investigated. Therefore two types of recurrent neural networks wer...In this study, recurrent networks to downscale meteorological fields of the ERA-40 re-analysis dataset with focus on the meso-scale water balance were investigated. Therefore two types of recurrent neural networks were used. The first approach is a coupling between a recurrent neural network and a distributed watershed model and the second a nonlinear autoregressive with exogenous inputs (NARX) network, which directly predicted the component of the water balance. The approaches were deployed for a meso-scale catchment area in the Free State of Saxony, Germany. The results show that the coupled approach did not perform as well as the NARX network. But the meteorological output of the coupled approach already reaches an adequate quality. However the coupled model generates as input for the watershed model insufficient daily precipitation sums and not enough wet days were predicted. Hence the long-term annual cycle of the water balance could not be preserved with acceptable quality in contrary to the NARX approach. The residual storage change term indicates physical restrictions of the plausibility of the neural networks, whereas the physically based correlations among?the components of the water balance were preserved more accurately by the coupled approach.展开更多
Experimental beneficiation processes of quartz concentrate in arc plasma torches of two different types and electric powers were studied. An emission scanning electron microscope and a universal laser analyzer were us...Experimental beneficiation processes of quartz concentrate in arc plasma torches of two different types and electric powers were studied. An emission scanning electron microscope and a universal laser analyzer were used to investigate the structures as well as the size distributions of grains and microparticles. Inductively coupled plasma–mass spectrometry was used to determine the chemical compositions of nonstructural solid-phase mineral impurities in quartz concentrate. Results related to the modified grains' structure and size distribution, the compositions of impurities, and the gas–liquid inclusions in the quartz concentrate were investigated. The total impurities concentrations in the processed grains were found to satisfy the IOTA-STD standard(industry standard for grading high quality fused quartz products). The optimal condition(i.e., the optimal specific plasma enthalpy) for the production of high-purity quartz in arc plasma torches was found to depend on the geological-genetic type and the structural and textural features(i.e., chemical composition and gas–liquid inclusions) of the quartz concentrate.展开更多
Artificial neural network(ANN) technology was applied to predict weld hot crack susceptibility of the T-type welded joints of aluminum alloys. A primary prediction model was established by training and testing models ...Artificial neural network(ANN) technology was applied to predict weld hot crack susceptibility of the T-type welded joints of aluminum alloys. A primary prediction model was established by training and testing models with different structures and committee models with different numbers of sub models. The models were improved by decreasing the input variables and data-covering space. Then welding hot crack prediction model committee for T-type joints of aluminum plates was developed. Its input parameters include base metal composition, filler metal composition and welding technique, the output parameter is the total length of the weld hot crack. The performance analysis shows that the predicted trend agrees well with the previous research work.展开更多
Studying the vibrational behavior of feed drive systems is important for enhancing the structural performance of computer numerical control(CNC)machines.The preload on the screw and nut position have a great influence...Studying the vibrational behavior of feed drive systems is important for enhancing the structural performance of computer numerical control(CNC)machines.The preload on the screw and nut position have a great influence on the vibration characteristics of the feed drive as two very important operational conditions.Rotational acceleration of the screw also affects the performance of the CNC feed drive when machining small parts.This paper investigates the influence of preload and nut position on the vibration characteristics of the feed drive system of a CNC metal cutting machine in order to be able to eliminate an observed resonance occurred at high rotational speeds of the screw,corresponding to high feed rates.Additionally,rational structural parameters of the feed drive system are selected in order to increase the rotational acceleration for improving the performance of the CNC machine.Experiments and analyses showed that by selecting specific parameters of feed drive system and simultaneously applying a certain value of preload,a 97%increase in rotational acceleration and 30%time reduction considering the vibration resistance at high rotational speeds can be achieved.展开更多
The issue of accelerated forestry plantation with high-quality wood using the best soils in terms of productivity,fertilizers,and intensive treatment has become quite relevant due to increased demand for forestry prod...The issue of accelerated forestry plantation with high-quality wood using the best soils in terms of productivity,fertilizers,and intensive treatment has become quite relevant due to increased demand for forestry products and higher requirements for environmentally friendly use of forest resources.This paper presents the results of a study on the impact of various techniques for treating coniferous plantations,including thinning,fertilization,and herbicide processing,on wood quality key indicators.The paper examined the wood density,correlation of early and late wood zones,and the cell wall thickness for 38-year-old pine trees grown on the sample plots of Siversky leskhoz(Leningrad region,Gatchinskiy district)at different treatment and density control techniques.It has been established that the highest basis density of wood corresponds to the samples grown at the density variant of 1 t/ha and double herbicides treatment,and the lowest basis density value was recorded at the option of 4 t/ha with combined treatment.It has been shown that the increase of width index for early wood is influenced by the lower density of 1 t/ha and one-time herbicide treatment,for late wood–by the lower density of 1 t/ha and repeated treatment with herbicides.The increase in average cell wall thickness for early and late wood is observed when the density increases up to 4 t/ha and double herbicides treatment.The results obtained provide a valuable scientific contribution to general forestry knowledge and have practical value in plantation forestry.展开更多
Improving the rail transport security requires development and implementation of neoteric monitoring and control facilities in conditions of increasing speed and intensity of the train movement and high level of terro...Improving the rail transport security requires development and implementation of neoteric monitoring and control facilities in conditions of increasing speed and intensity of the train movement and high level of terrorist threat. Use of Earth remote sensing (ERS), permitting to obtain information from large areas with a sufficiently high resolution, can provide significant assistance in solving the mentioned problems. This paper discusses the possibility of using various means of remote sensing such as satellites and unmanned aerial vehicles (UAV), also known as drones, for receiving information in different ranges of the electromagnetic spectrum. The paper states that joint using of both these means gives new possibilities in improving railroad security.展开更多
Aluminum matrix particulate reinforced composites are of significant interest to industry, but it’s difficult to provide stable properties for this group of material. The mechanical properties of metal matrix composi...Aluminum matrix particulate reinforced composites are of significant interest to industry, but it’s difficult to provide stable properties for this group of material. The mechanical properties of metal matrix composites are deeply influenced by the distribution of reinforcement particulates in the matrix. In this paper uniformity of SiC particles distribution in Al-based composites produced by stir casting and powder metallurgy technique is assessed. Analysis is carried out by means of classical and computer quantification metallographic image analysis methods. In addition, we suggest setting hardness distribution in cross section of samples as an indicator of reinforcement distribution uniformity in the matrix.展开更多
基金financial support from the China Scholarship Council.
文摘We estimate the thermal properties of unsmooth Si nanowires,considering key factors such as size(diameter),surface texture(roughness)and quantum size effects(phonon states)at different temperatures.For nanowires with a diameter of less than 20 nm,we highlight the importance of quantum size effects in heat capacity calculations,using dispersion relations derived from the modified frequency equation for the elasticity of a rod.The thermal conductivities of nanowires with diameters of 37,56,and 115nm are predicted using the Fuchs–Sondheimer model and Soffer’s specular parameter.Notably,the roughness parameters are chosen to reflect the technological characteristics of the real surfaces.Our findings reveal that surface texture plays a significant role in thermal conductivity,particularly in the realm of ballistic heat transfer within nanowires.This study provides practical recommendations for developing new thermal management materials.
基金The work was supported by the Russian Science Foundation,Project#22-22-00596.
文摘Terahertz(THz)technology offers novel opportunities in biology and medicine,thanks to the unique features of THzwave interactions with tissues and cells.Among them,we particularly notice strong sensitivity of THz waves to the tissue water,as a medium for biochemical reactions and a main endogenous marker for THz spectroscopy and imaging.Tissues of the brain have an exceptionally high content of water.This factor,along with the features of the structural organization and biochemistry of neuronal and glial tissues,makes the brain an exciting subject to study in the THz range.In this paper,progress and prospects of THz technology in neurodiagnostics are overviewed,including diagnosis of neurodegenerative disease,myelin deficit,tumors of the central nervous system(with an emphasis on brain gliomas),and traumatic brain injuries.Fundamental and applied challenges in study of the THz-wave–brain tissue interactions and development of the THz biomedical tools and systems for neurodiagnostics are discussed.
基金Project(2014CB046601)supported by the National Basic Research Program of ChinaProject(51675333)supported by the National Natural Science Foundation of China
基金financially supported by the National Key R&D Program of China (No.2018YFA0707300)the Natural Science Foundation of Shanxi Province,China (No.201801D221131)+2 种基金the National Natural Science Foundation of China (Nos.51905372,51904206,51805359,52075359)Shanxi Province Science and Technology Major Project,China (No.20181102011)China Postdoctoral Science Foundation (No.2020M670705)。
基金supported by Grant Nos.13-02-12210 and 14-00-10420 of Russian Foundation of Basic Research.
文摘The problem of in vrivo photoluminescence diagnostics of the tissues acessible by endoscopes is discussed.The spectral imaging module attachable to conventional rigid and flexible medical endoscopes is developed and described.It is based on a double acousto-optical tunable filter(AOTF)and a specialized optical coupling system.The module provides wide field of view(FOV),absence of image distortions,random spectral access,fast spectral image acquisition at any wavelength in the visible range and accurate measurement of reflectance spectrum in each pixel of the image.Images of typical biomedical samples are presented and discussed.Their spectra are compared to the reference data.
基金Supported by Major Program of National Natural Science Foundation of China(Grant No.U1710254)National Natural Science Foundation of China(Grant Nos.51904205,51804215)+3 种基金Shanxi Provincial Science and Technology Major Projects of China(Grant No.20181101008)Shanxi Provincial Natural Science Foundation of China(Grant No.201801D221221)China Postdoctoral Science Foundation(Grant No.2018M641681)Taiyuan Municipal Science and Technology Major Projects of China(Grant No.170203).
文摘In the case of valuable cold-rolled Cu/Al clad plates,billet surface treatment before rolling is a significant process that can affect the bonding efficiency and quality.While the current studies primarily focus on the influence of rolling parameters,insufficient attention has been paid to surface treatment.In this study,the effects of mechanical surface treatment on the bonding mechanism and bonding properties of cold-rolled Cu/Al clad plates were investigated.The results showed that different mechanical surface treatments have significant effects on the surface morphology,roughness,and residual stress.In addition,the effect of surface mechanical treatment on bonding quality was also observed to be critical.When the grinding direction was consistent with the rolling direction(RD),the bonding quality of the Cu/Al clad plates was significantly improved.After surface treatment along the RD for 20 s,the Cu/Al clad plates showed the highest shear strength(78 MPa),approximately four times as high as that of the unpolished samples.Simultaneously,the peel strength of this process was also significantly higher than that achieved via the other processes.Finally,on the basis of the surface morphology,roughness,and residual stress,the effect of surface treatment on the bonding mechanism and bonding properties of Cu/Al clad plates was analyzed.This study proposes a deeper understanding of the bonding behavior and bonding mechanism for cold rolled clad plates processed via mechanical surface treatment.
文摘To increase accuracy of navigation parameters,a perspective measuring complex with intellectual components is developed.Conception of synthesis optimal structure of the measuring complex is realized basing on a selective method using principles of the functional systems.Selection of measured information is finished by original numeric criterion of observation level of state vector components.Prediction is realized by algorithm of self-organization that makes synthesis of the optimal complication.Therefore mechanism of self-regulation is realized and accuracy of the selective navigation complex is increased.
文摘After conducting a critical survey of the different categories of existing heat exchangers,the results of several experiments about the behaviour of a two-phase current in an open channel are reported.The results confirm the complexity of the problems induced in heat exchangers by flow maldistribution,especially when two-phase flows are considered in multi-channel systems.It is shown that severe misalignment of heat exchangers can lead to a loss of economic performance of more than 25%.Improper distribution of fluid flow causes longer fluid coils to form,and the liquid cochlea can eventually occupy a large space,thereby reducing heat transfer and disrupting the considered biphasic system.The use of a small diameter distribution pipe with properly spaced outlet holes seems to be a promising approach to fix many of these issues.It is found that the current distribution in the channels,in addition to the header pressure distribution,also depends on factors such as the geometry and the initial flow regime in the header.
基金supported by the Erasmus Mundus Action 2 Programme of the European Union and the German Weather Service(DWD)and the Czech Hydrological-Meteorological Service(CHMI).
文摘In this study, recurrent networks to downscale meteorological fields of the ERA-40 re-analysis dataset with focus on the meso-scale water balance were investigated. Therefore two types of recurrent neural networks were used. The first approach is a coupling between a recurrent neural network and a distributed watershed model and the second a nonlinear autoregressive with exogenous inputs (NARX) network, which directly predicted the component of the water balance. The approaches were deployed for a meso-scale catchment area in the Free State of Saxony, Germany. The results show that the coupled approach did not perform as well as the NARX network. But the meteorological output of the coupled approach already reaches an adequate quality. However the coupled model generates as input for the watershed model insufficient daily precipitation sums and not enough wet days were predicted. Hence the long-term annual cycle of the water balance could not be preserved with acceptable quality in contrary to the NARX approach. The residual storage change term indicates physical restrictions of the plausibility of the neural networks, whereas the physically based correlations among?the components of the water balance were preserved more accurately by the coupled approach.
文摘Experimental beneficiation processes of quartz concentrate in arc plasma torches of two different types and electric powers were studied. An emission scanning electron microscope and a universal laser analyzer were used to investigate the structures as well as the size distributions of grains and microparticles. Inductively coupled plasma–mass spectrometry was used to determine the chemical compositions of nonstructural solid-phase mineral impurities in quartz concentrate. Results related to the modified grains' structure and size distribution, the compositions of impurities, and the gas–liquid inclusions in the quartz concentrate were investigated. The total impurities concentrations in the processed grains were found to satisfy the IOTA-STD standard(industry standard for grading high quality fused quartz products). The optimal condition(i.e., the optimal specific plasma enthalpy) for the production of high-purity quartz in arc plasma torches was found to depend on the geological-genetic type and the structural and textural features(i.e., chemical composition and gas–liquid inclusions) of the quartz concentrate.
文摘Artificial neural network(ANN) technology was applied to predict weld hot crack susceptibility of the T-type welded joints of aluminum alloys. A primary prediction model was established by training and testing models with different structures and committee models with different numbers of sub models. The models were improved by decreasing the input variables and data-covering space. Then welding hot crack prediction model committee for T-type joints of aluminum plates was developed. Its input parameters include base metal composition, filler metal composition and welding technique, the output parameter is the total length of the weld hot crack. The performance analysis shows that the predicted trend agrees well with the previous research work.
文摘Studying the vibrational behavior of feed drive systems is important for enhancing the structural performance of computer numerical control(CNC)machines.The preload on the screw and nut position have a great influence on the vibration characteristics of the feed drive as two very important operational conditions.Rotational acceleration of the screw also affects the performance of the CNC feed drive when machining small parts.This paper investigates the influence of preload and nut position on the vibration characteristics of the feed drive system of a CNC metal cutting machine in order to be able to eliminate an observed resonance occurred at high rotational speeds of the screw,corresponding to high feed rates.Additionally,rational structural parameters of the feed drive system are selected in order to increase the rotational acceleration for improving the performance of the CNC machine.Experiments and analyses showed that by selecting specific parameters of feed drive system and simultaneously applying a certain value of preload,a 97%increase in rotational acceleration and 30%time reduction considering the vibration resistance at high rotational speeds can be achieved.
文摘The issue of accelerated forestry plantation with high-quality wood using the best soils in terms of productivity,fertilizers,and intensive treatment has become quite relevant due to increased demand for forestry products and higher requirements for environmentally friendly use of forest resources.This paper presents the results of a study on the impact of various techniques for treating coniferous plantations,including thinning,fertilization,and herbicide processing,on wood quality key indicators.The paper examined the wood density,correlation of early and late wood zones,and the cell wall thickness for 38-year-old pine trees grown on the sample plots of Siversky leskhoz(Leningrad region,Gatchinskiy district)at different treatment and density control techniques.It has been established that the highest basis density of wood corresponds to the samples grown at the density variant of 1 t/ha and double herbicides treatment,and the lowest basis density value was recorded at the option of 4 t/ha with combined treatment.It has been shown that the increase of width index for early wood is influenced by the lower density of 1 t/ha and one-time herbicide treatment,for late wood–by the lower density of 1 t/ha and repeated treatment with herbicides.The increase in average cell wall thickness for early and late wood is observed when the density increases up to 4 t/ha and double herbicides treatment.The results obtained provide a valuable scientific contribution to general forestry knowledge and have practical value in plantation forestry.
文摘Improving the rail transport security requires development and implementation of neoteric monitoring and control facilities in conditions of increasing speed and intensity of the train movement and high level of terrorist threat. Use of Earth remote sensing (ERS), permitting to obtain information from large areas with a sufficiently high resolution, can provide significant assistance in solving the mentioned problems. This paper discusses the possibility of using various means of remote sensing such as satellites and unmanned aerial vehicles (UAV), also known as drones, for receiving information in different ranges of the electromagnetic spectrum. The paper states that joint using of both these means gives new possibilities in improving railroad security.
文摘Aluminum matrix particulate reinforced composites are of significant interest to industry, but it’s difficult to provide stable properties for this group of material. The mechanical properties of metal matrix composites are deeply influenced by the distribution of reinforcement particulates in the matrix. In this paper uniformity of SiC particles distribution in Al-based composites produced by stir casting and powder metallurgy technique is assessed. Analysis is carried out by means of classical and computer quantification metallographic image analysis methods. In addition, we suggest setting hardness distribution in cross section of samples as an indicator of reinforcement distribution uniformity in the matrix.