The mechanical characteristics and acoustic behavior of rock masses are greatly influenced by stochastic joints.In this study,numerical models of rock masses incorporating intermittent joints with different numbers an...The mechanical characteristics and acoustic behavior of rock masses are greatly influenced by stochastic joints.In this study,numerical models of rock masses incorporating intermittent joints with different numbers and dip angles were produced using the finite element method(FEM)with the intrinsic cohesive zone model(ICZM).Then,the uniaxial compressive and wave propagation simulations were performed.The results indicate that the joint number and dip angle can affect the mechanical and acoustic properties of the models.The uniaxial compressive strength(UCS)and wave velocity of rock masses decrease monotonically as the joint number increases.However,the wave velocity grows monotonically as the joint dip angle increases.When the joint dip angle is 45°–60°,the UCS of the rock mass is lower than that of other dip angles.The wave velocity parallel to the joints is greater than that perpendicular to the joints.When the dip angle of joints remains unchanged,the UCS and wave velocity are positively related.When the joint dip angle increases,the variation amplitude of the UCS regarding the wave velocity increases.To reveal the effect of the joint distribution on the velocity,a theoretical model was also proposed.According to the theoretical wave velocity,the change in wave velocity of models with various joint numbers and dip angles was consistent with the simulation results.Furthermore,a theoretical indicator(i.e.fabric tensor)was adopted to analyze the variation of the wave velocity and UCS.展开更多
This paper explores the association between intestinal microecology and digestive health and disease recovery in children with pneumonia.Intestinal microecological imbalance is common in children with pneumonia,which ...This paper explores the association between intestinal microecology and digestive health and disease recovery in children with pneumonia.Intestinal microecological imbalance is common in children with pneumonia,which is closely associated with digestive health and disease recovery.Intestinal microecological imbalance may affect digestive enzyme activity,intestinal mucosal barrier function,and nutrient absorption,which in turn affects digestive health.In addition,intestinal microecological imbalances may be associated with immune regulation,inflammatory responses,and pathogen suppression,affecting disease recovery.Strategies to regulate intestinal microecology include probiotic supplementation,dietary modification,and pharmacological treatment.Currently,the study of intestinal microecology in children with pneumonia faces challenges,and there is a need for improved research methods,individualized treatment strategies,and the development of novel probiotics.In conclusion,the intestinal microecology of children with pneumonia is closely related to digestive health and disease recovery,and the regulation of intestinal microecology is of great significance to the treatment of children with pneumonia.Furthermore,future research should further explore the application of the microecology of the intestinal microecology in the treatment of children with pneumonia.展开更多
Wet dust removal systems used to control dust in the polishing or grinding process of Mg alloy products are frequently associated with potential hydrogen explosion caused by magnesium-water reaction.For purpose of avo...Wet dust removal systems used to control dust in the polishing or grinding process of Mg alloy products are frequently associated with potential hydrogen explosion caused by magnesium-water reaction.For purpose of avoiding hydrogen explosion risks,we try to use a combination of chitosan(CS)and sodium phosphate(SP)to inhibit the hydrogen evolution reaction between magnesium alloy waste dust and water.The hydrogen evolution curves and chemical kinetics modeling for ten different mixing ratios demonstrate that 0.4wt%CS+0.1wt%SP yields the best inhibition efficiency with hydrogen generation rate of almost zero.SEM and EDS analyses indicate that this composite inhibitor can create a uniform,smooth,tight protective film over the surface of the alloy dust particles.FTIR and XRD analysis of the chemical composition of the surface film show that this protective film contains CS and SP chemically adsorbed on the surface of ZK60 but no detectable Mg(OH)_(2),suggesting that magnesium-water reaction was totally blocked.Our new method offers a thorough solution to hydrogen explosion by inhibiting the hydrogen generation of magnesium alloy waste dust in a wet dust removal system.展开更多
AIM To prospectively evaluate the effect of local wound infiltration with ropivacaine on postoperative pain relief and stress response reduction after open hepatectomy.METHODS A total of 56 patients undergoing open he...AIM To prospectively evaluate the effect of local wound infiltration with ropivacaine on postoperative pain relief and stress response reduction after open hepatectomy.METHODS A total of 56 patients undergoing open hepatectomy were randomly divided into two groups:a ropivacaine group(wound infiltration with ropivacaine solution)and a control group(infiltration with isotonic saline solution).A visual analog scale(VAS)at rest and on movement was used to measure postoperative pain for the first 48 h after surgery.Mean arterial pressure(MAP),heart rate(HR),time to bowel recovery,length of hospitalization after surgery,cumulative sufentanil consumption,and incidence of nausea and vomiting were compared between the two groups.Surgical stress hormones(epinephrine,norepinephrine,and cortisol)were detected using enzyme-linked immunosorbent assay,and the results were compared. RESULTS VAS scores both at rest and on movement at 24 h and48 h were similar between the two groups.Significantly lower VAS scores were detected at 0,6,and 12 h in the ropivacaine group compared with the control group(P<0.05 for all).MAP was significantly lower at 6,12,and 24 h(P<0.05 for all);HR was significantly lower at 0,6,12,and 24 h(P<0.05 for all);time to bowel recovery and length of hospitalization after surgery(P<0.05 for both)were significantly shortened;and cumulative sufentanil consumption was significantly lower at 6,12,24,and 36 h(P<0.05 for all)in the ropivacaine group than in the control group,although the incidence of nausea and vomiting showed no significant difference between the two groups.The levels of epinephrine,norepinephrine,and cortisol were significantly lower in the ropivacaine group than in the control group at 24 and 48 h(P<0.01 for all). CONCLUSION Local wound infiltration with ropivacaine after open hepatectomy can improve postoperative pain relief,reduce surgical stress response,and accelerate postoperative recovery.展开更多
AIM:To access the efficacy of combination with amoxicillin and tetracycline for eradication of Helicobacter pylori(H.pylori),thus providing clinical practice guidelines.METHODS:Pub Med,EMBASE,Cochrane Central Register...AIM:To access the efficacy of combination with amoxicillin and tetracycline for eradication of Helicobacter pylori(H.pylori),thus providing clinical practice guidelines.METHODS:Pub Med,EMBASE,Cochrane Central Register of Controlled Trials,Science Citation Index,China National Knowledge Infrastructure,Wanfang,and Chinese Biomedical Literature databases and abstract books of major European,American,and Asian gastroenterological meetings were searched.All clinical trials that examined the efficacy of H.pylori eradication therapies and included both tetracycline and amoxicillin in one study arm were selected for this systematic review and meta-analysis.Statistical analysis was performed with Comprehensive Meta-Analysis Software(Version 2).Subgroup,meta-regression,and sensitivity analyses were also carried out.RESULTS:Thirty-three studies met the inclusion criteria.The pooled odds ratio(OR)was 0.90(95%CI:0.42-1.78)for quadruple therapy with amoxicillin and tetracycline vs other quadruple regimens,and total eradication rates were 78.1%by intention-to-treat(ITT)and 84.5%by per-protocol(PP)analyses in the experimental groups.The pooled eradication rates of 14-d quadruple regimens with a combination of amoxicillin and tetracycline were 82.3%by ITT and89.0%by PP,and those of 10-d regimens were 84.6%by ITT and 93.7%by PP.The OR by ITT were 1.21(95%CI:0.64-2.28)for triple regimens with amoxicillin and tetracycline vs other regimens and 1.81(95%CI:1.37-2.41)for sequential treatment with amoxicillin and tetracycline vs other regimens,respectively.CONCLUSION:The effectiveness of regimens employing amoxicillin and tetracycline for H.pylori eradication may be not inferior to other regimens,but further study should be necessary.展开更多
Medical models, or "phantoms," have been widely used for medical training and for doctor-patient interactions. They are increasingly used for surgical planning, medical computational models, algorithm verification a...Medical models, or "phantoms," have been widely used for medical training and for doctor-patient interactions. They are increasingly used for surgical planning, medical computational models, algorithm verification and validation, and medical devices development. Such new applications demand high-fidelity, patient-specific, tissue-mimicking medical phantoms that can not only closely emulate the geometric structures of human organs, but also possess the properties and functions of the organ structure. With the rapid advancement of three-dimensional (3D) printing and 3D bioprinting technologies, many researchers have explored the use of these additive manufacturing techniques to fabricate functional medical phantoms for various applications. This paper reviews the applications of these 3D printing and 3D bioprinting technologies for the fabrication of functional medical phantoms and bio-structures. This review specifically discusses the state of the art along with new developments and trends in 3D printed functional medical phantoms (i.e., tissue-mimicking medical phantoms, radiologically relevant medical phantoms, and physiological medical phantoms) and 3D bio-printed structures (i.e., hybrid scaffolding materials, convertible scaffolds, and integrated sensors) for regenerated tissues and organs.展开更多
The aim of this study was to determine the attenuation of gamma and X-rays with different energies caused by passage through different materials.To this end,different materials with a range of atomic numbers were chos...The aim of this study was to determine the attenuation of gamma and X-rays with different energies caused by passage through different materials.To this end,different materials with a range of atomic numbers were chosen to measure gamma and X-ray attenuation coefficients and to explore the mechanisms of interaction of gamma and X-rays with matter of various kinds.It is shown that the attenuation coefficients first decrease and then increase with increase in the radiation(photon)energy.The attenuation of gamma and X-rays passing through materials with high atomic number is greater than that in materials with low atomic number.The attenuation minimum is related to the atomic number of the irradiated materials.The larger the atomic number is,the lower the energy corresponding to attenuation minimum is.Photoelectric and Compton effects are the main processes when gamma rays pass through individual materials with high and low atomic numbers,respectively.Therefore,for radiotherapy and radiation protection,different methods should be considered and selected for the use of gamma and X-rays of different energies for use in different materials.展开更多
[ Objective ] This study aimed to provide basic data for studying the relationship between structure and property of cellulose microspheres by measuring molecular weight of cellulose and cellulose microspheres with vi...[ Objective ] This study aimed to provide basic data for studying the relationship between structure and property of cellulose microspheres by measuring molecular weight of cellulose and cellulose microspheres with viscosity method and gel permeation chromatography (GPC) method. [ Method] In viscosity method, cadmium ethylenediamine was used as the solvent, intrinsic viscosity η of the solution was determined at 25 ℃ by using a Ubbelohde viscometer, to calculate the molecular weight of cellulose; in GPC method, 8% LiC1 / N, N-dimethylacetamide (LiC1/DMAc) was used as the solvent and 0.5% LiC1/DMAc was used as the mobile phase to determine the relative molecular weight and distribution of cellulose and cellulose microspheres. In addition, the determination results were analyzed to compare these two methods. [ Result ] Viscosity-average molecular weight Mr/ of cellulose and cellulose microspheres determined with viscosity method were 224,532 and 16,686, respectively; weight-average molecular weight Mw of cellulose and cellulose microspheres determined with GPC method were 284,196 and 22,345, respectively. [ Conclusion] The determination results of (;PC method are relatively close to the actual value and could truly reflect the characteristics of molecular weialat distribution of eellulose and cellulose mierosr, heres.展开更多
Many articles have been published on intelligent manufacturing, most of which focus on hardware, soft-ware, additive manufacturing, robotics, the Internet of Things, and Industry 4.0. This paper provides a dif-ferent ...Many articles have been published on intelligent manufacturing, most of which focus on hardware, soft-ware, additive manufacturing, robotics, the Internet of Things, and Industry 4.0. This paper provides a dif-ferent perspective by examining relevant challenges and providing examples of some less-talked-about yet essential topics, such as hybrid systems, redefining advanced manufacturing, basic building blocks of new manufacturing, ecosystem readiness, and technology scalahility. The first major challenge is to (re-)define what the manufacturing of the future will he, if we wish to: ① raise public awareness of new manufacturing's economic and societal impacts, and ② garner the unequivocal support of policy- makers. The second major challenge is to recognize that manufacturing in the future will consist of sys-tems of hybrid systems of human and robotic operators; additive and suhtractive processes; metal and composite materials; and cyher and physical systems. Therefore, studying the interfaces between con- stituencies and standards becomes important and essential. The third challenge is to develop a common framework in which the technology, manufacturing business case, and ecosystem readiness can he eval- uated concurrently in order to shorten the time it takes for products to reach customers. Integral to this is having accepted measures of "scalahility" of non-information technologies. The last, hut not least, chal-lenge is to examine successful modalities of industry-academia-government collaborations through public-private partnerships. This article discusses these challenges in detail.展开更多
Based on aphid wax-honeydew marble and the hydrophobic wax structure of lotus and its derived applications with superareophilic and superhydrophobic properties,edible carnauba wax and beeswax particles were mixed and ...Based on aphid wax-honeydew marble and the hydrophobic wax structure of lotus and its derived applications with superareophilic and superhydrophobic properties,edible carnauba wax and beeswax particles were mixed and utilized to mimic lotus wax and wrap liquid,thus forming liquid marbles(LMs).Through the utilization of continuous production system(CPS),wax as an interfacial surfactant,water and solid,air-phase or mixed-phase marble content was produced.The edible liquid marble(ELM)could encapsulate water and food droplets.Edible solid marble(ESM)and edible solid hollow marbles(ESHMs)could be fabricated by applying pectin or syrup.Moreover,through the heating of wax powders with different melting temperatures,stable tablets and hollow capsules could be produced.The wax powder as interfacial surfactant could firmly bind with pectin through hydrogen bonds on ESM.The edible LMs can therefore be applied for residue reduction,corrosion reduction,biohazard prevention and cleaning in the food industry.The other phase LMs could act as novel tools in the pharmaceutical and food industries with the above-mentioned water transport,preservation,sustained releasing and selective releasing abilities.展开更多
A set of novel nonlinear variable structure excitation and steam-valving controllers are proposed in this paper. On the basis of the classical dynamic equations of a generator, excitation control and steam valving con...A set of novel nonlinear variable structure excitation and steam-valving controllers are proposed in this paper. On the basis of the classical dynamic equations of a generator, excitation control and steam valving control are simultaneously considered. Design of these controllers combines the differential geometry theory with the variable structure controlling theory. The mathematical model in the form of "an affine nonlinear system" is set up for the control design of a large-scale power plant. The dynamic performance of the nonlinear variable structure controllers proposed for a single machine connected to an infinite bus power system is simulated. Simulation results show that the nonlinear variable structure excitation and steam-valving controllers give satisfactory dynamic performance and good robustness.展开更多
A novel coordinated controller is proposed in the paper for SVC, excitation and steam valving for a single machine infinite system. Firstly, the nonlinear mathematic model of the system including the itation and steam...A novel coordinated controller is proposed in the paper for SVC, excitation and steam valving for a single machine infinite system. Firstly, the nonlinear mathematic model of the system including the itation and steam valving is exactly linearized via state feedback. Then, the quasi-linearized system after the exact lineariztion is controlled by the sliding model controller based on Lyapunov direct method. At last, the novel coordinated controller is compared with a traditional linear controller and a nonlinear optimal controller respectively by simulations. The simulation results show that the proposed controller gives better dynamic response and stronger robustness.展开更多
In this research, a modeling and experimental study was conducted to explore the effects of nanoparticle type (aluminum nanoparticles and carbon nanotubes), filler concentration and interactions between the nanopartic...In this research, a modeling and experimental study was conducted to explore the effects of nanoparticle type (aluminum nanoparticles and carbon nanotubes), filler concentration and interactions between the nanoparticle and reinforcing fibers on through-thickness conductivity of nanoparticle/epoxy nanocomposites and nanoparticle/fiber-reinforced multiscale composites. Multiple, notable micromechanical models were evaluated to predict through-thickness thermal conductivity of both composite systems, and then compared to the experimental results. The results showed that filler volume fraction ranges and thermal conductivity differences of the constituent materials for the thermal conductivity ratio (km/kf or kf/km) used in the models can affect the resulting predictions. Certain models were found to be suitable for varying conditions on the thermal conductivity ratio. Finite element models (FEM) were developed to reveal heat transport mechanisms of the resultant nanocomposites and multiscale composites. The nanocomposite design for finite element analysis (FEA) provided close predictions and performed better than the micromechanical models. On the multiscale composite system, predictions were concluded to be dependent upon the FEM design where the interactions between nanoparticles and fibers are critical to accurately determine the through-thickness thermal conductivity.展开更多
基金financial support from the National Key R&D Program of China(Grant No.2020YFA0711802).
文摘The mechanical characteristics and acoustic behavior of rock masses are greatly influenced by stochastic joints.In this study,numerical models of rock masses incorporating intermittent joints with different numbers and dip angles were produced using the finite element method(FEM)with the intrinsic cohesive zone model(ICZM).Then,the uniaxial compressive and wave propagation simulations were performed.The results indicate that the joint number and dip angle can affect the mechanical and acoustic properties of the models.The uniaxial compressive strength(UCS)and wave velocity of rock masses decrease monotonically as the joint number increases.However,the wave velocity grows monotonically as the joint dip angle increases.When the joint dip angle is 45°–60°,the UCS of the rock mass is lower than that of other dip angles.The wave velocity parallel to the joints is greater than that perpendicular to the joints.When the dip angle of joints remains unchanged,the UCS and wave velocity are positively related.When the joint dip angle increases,the variation amplitude of the UCS regarding the wave velocity increases.To reveal the effect of the joint distribution on the velocity,a theoretical model was also proposed.According to the theoretical wave velocity,the change in wave velocity of models with various joint numbers and dip angles was consistent with the simulation results.Furthermore,a theoretical indicator(i.e.fabric tensor)was adopted to analyze the variation of the wave velocity and UCS.
基金Shandong Province Traditional Chinese Medicine Science and Technology Project"Efficacy Evaluation of Acupoint Application Synergy Model Intervention in Bronchoscopic Treatment of Severe Mycoplasma Pneumonia in Children"(Project No.2020M177)。
文摘This paper explores the association between intestinal microecology and digestive health and disease recovery in children with pneumonia.Intestinal microecological imbalance is common in children with pneumonia,which is closely associated with digestive health and disease recovery.Intestinal microecological imbalance may affect digestive enzyme activity,intestinal mucosal barrier function,and nutrient absorption,which in turn affects digestive health.In addition,intestinal microecological imbalances may be associated with immune regulation,inflammatory responses,and pathogen suppression,affecting disease recovery.Strategies to regulate intestinal microecology include probiotic supplementation,dietary modification,and pharmacological treatment.Currently,the study of intestinal microecology in children with pneumonia faces challenges,and there is a need for improved research methods,individualized treatment strategies,and the development of novel probiotics.In conclusion,the intestinal microecology of children with pneumonia is closely related to digestive health and disease recovery,and the regulation of intestinal microecology is of great significance to the treatment of children with pneumonia.Furthermore,future research should further explore the application of the microecology of the intestinal microecology in the treatment of children with pneumonia.
基金This work was supported by the National Natural Science Foundation of China(52074066).
文摘Wet dust removal systems used to control dust in the polishing or grinding process of Mg alloy products are frequently associated with potential hydrogen explosion caused by magnesium-water reaction.For purpose of avoiding hydrogen explosion risks,we try to use a combination of chitosan(CS)and sodium phosphate(SP)to inhibit the hydrogen evolution reaction between magnesium alloy waste dust and water.The hydrogen evolution curves and chemical kinetics modeling for ten different mixing ratios demonstrate that 0.4wt%CS+0.1wt%SP yields the best inhibition efficiency with hydrogen generation rate of almost zero.SEM and EDS analyses indicate that this composite inhibitor can create a uniform,smooth,tight protective film over the surface of the alloy dust particles.FTIR and XRD analysis of the chemical composition of the surface film show that this protective film contains CS and SP chemically adsorbed on the surface of ZK60 but no detectable Mg(OH)_(2),suggesting that magnesium-water reaction was totally blocked.Our new method offers a thorough solution to hydrogen explosion by inhibiting the hydrogen generation of magnesium alloy waste dust in a wet dust removal system.
基金Supported by National Natural Science foundation of China,No.81571367 and No.81502050Scientific and Technological Project of Shandong Province,No.2016GSf201082
文摘AIM To prospectively evaluate the effect of local wound infiltration with ropivacaine on postoperative pain relief and stress response reduction after open hepatectomy.METHODS A total of 56 patients undergoing open hepatectomy were randomly divided into two groups:a ropivacaine group(wound infiltration with ropivacaine solution)and a control group(infiltration with isotonic saline solution).A visual analog scale(VAS)at rest and on movement was used to measure postoperative pain for the first 48 h after surgery.Mean arterial pressure(MAP),heart rate(HR),time to bowel recovery,length of hospitalization after surgery,cumulative sufentanil consumption,and incidence of nausea and vomiting were compared between the two groups.Surgical stress hormones(epinephrine,norepinephrine,and cortisol)were detected using enzyme-linked immunosorbent assay,and the results were compared. RESULTS VAS scores both at rest and on movement at 24 h and48 h were similar between the two groups.Significantly lower VAS scores were detected at 0,6,and 12 h in the ropivacaine group compared with the control group(P<0.05 for all).MAP was significantly lower at 6,12,and 24 h(P<0.05 for all);HR was significantly lower at 0,6,12,and 24 h(P<0.05 for all);time to bowel recovery and length of hospitalization after surgery(P<0.05 for both)were significantly shortened;and cumulative sufentanil consumption was significantly lower at 6,12,24,and 36 h(P<0.05 for all)in the ropivacaine group than in the control group,although the incidence of nausea and vomiting showed no significant difference between the two groups.The levels of epinephrine,norepinephrine,and cortisol were significantly lower in the ropivacaine group than in the control group at 24 and 48 h(P<0.01 for all). CONCLUSION Local wound infiltration with ropivacaine after open hepatectomy can improve postoperative pain relief,reduce surgical stress response,and accelerate postoperative recovery.
基金Supported by Grants from National Science and Technology Major Projects for"Major New Drugs Innovation and Development"of China,No.2011ZX09302-007-03
文摘AIM:To access the efficacy of combination with amoxicillin and tetracycline for eradication of Helicobacter pylori(H.pylori),thus providing clinical practice guidelines.METHODS:Pub Med,EMBASE,Cochrane Central Register of Controlled Trials,Science Citation Index,China National Knowledge Infrastructure,Wanfang,and Chinese Biomedical Literature databases and abstract books of major European,American,and Asian gastroenterological meetings were searched.All clinical trials that examined the efficacy of H.pylori eradication therapies and included both tetracycline and amoxicillin in one study arm were selected for this systematic review and meta-analysis.Statistical analysis was performed with Comprehensive Meta-Analysis Software(Version 2).Subgroup,meta-regression,and sensitivity analyses were also carried out.RESULTS:Thirty-three studies met the inclusion criteria.The pooled odds ratio(OR)was 0.90(95%CI:0.42-1.78)for quadruple therapy with amoxicillin and tetracycline vs other quadruple regimens,and total eradication rates were 78.1%by intention-to-treat(ITT)and 84.5%by per-protocol(PP)analyses in the experimental groups.The pooled eradication rates of 14-d quadruple regimens with a combination of amoxicillin and tetracycline were 82.3%by ITT and89.0%by PP,and those of 10-d regimens were 84.6%by ITT and 93.7%by PP.The OR by ITT were 1.21(95%CI:0.64-2.28)for triple regimens with amoxicillin and tetracycline vs other regimens and 1.81(95%CI:1.37-2.41)for sequential treatment with amoxicillin and tetracycline vs other regimens,respectively.CONCLUSION:The effectiveness of regimens employing amoxicillin and tetracycline for H.pylori eradication may be not inferior to other regimens,but further study should be necessary.
文摘Medical models, or "phantoms," have been widely used for medical training and for doctor-patient interactions. They are increasingly used for surgical planning, medical computational models, algorithm verification and validation, and medical devices development. Such new applications demand high-fidelity, patient-specific, tissue-mimicking medical phantoms that can not only closely emulate the geometric structures of human organs, but also possess the properties and functions of the organ structure. With the rapid advancement of three-dimensional (3D) printing and 3D bioprinting technologies, many researchers have explored the use of these additive manufacturing techniques to fabricate functional medical phantoms for various applications. This paper reviews the applications of these 3D printing and 3D bioprinting technologies for the fabrication of functional medical phantoms and bio-structures. This review specifically discusses the state of the art along with new developments and trends in 3D printed functional medical phantoms (i.e., tissue-mimicking medical phantoms, radiologically relevant medical phantoms, and physiological medical phantoms) and 3D bio-printed structures (i.e., hybrid scaffolding materials, convertible scaffolds, and integrated sensors) for regenerated tissues and organs.
基金supported by the National Natural Science Foundation of China(Nos.11475013,11975040 and U1832130)
文摘The aim of this study was to determine the attenuation of gamma and X-rays with different energies caused by passage through different materials.To this end,different materials with a range of atomic numbers were chosen to measure gamma and X-ray attenuation coefficients and to explore the mechanisms of interaction of gamma and X-rays with matter of various kinds.It is shown that the attenuation coefficients first decrease and then increase with increase in the radiation(photon)energy.The attenuation of gamma and X-rays passing through materials with high atomic number is greater than that in materials with low atomic number.The attenuation minimum is related to the atomic number of the irradiated materials.The larger the atomic number is,the lower the energy corresponding to attenuation minimum is.Photoelectric and Compton effects are the main processes when gamma rays pass through individual materials with high and low atomic numbers,respectively.Therefore,for radiotherapy and radiation protection,different methods should be considered and selected for the use of gamma and X-rays of different energies for use in different materials.
基金Supported by Natural Science Foundation of Guangxi(0991024Z)
文摘[ Objective ] This study aimed to provide basic data for studying the relationship between structure and property of cellulose microspheres by measuring molecular weight of cellulose and cellulose microspheres with viscosity method and gel permeation chromatography (GPC) method. [ Method] In viscosity method, cadmium ethylenediamine was used as the solvent, intrinsic viscosity η of the solution was determined at 25 ℃ by using a Ubbelohde viscometer, to calculate the molecular weight of cellulose; in GPC method, 8% LiC1 / N, N-dimethylacetamide (LiC1/DMAc) was used as the solvent and 0.5% LiC1/DMAc was used as the mobile phase to determine the relative molecular weight and distribution of cellulose and cellulose microspheres. In addition, the determination results were analyzed to compare these two methods. [ Result ] Viscosity-average molecular weight Mr/ of cellulose and cellulose microspheres determined with viscosity method were 224,532 and 16,686, respectively; weight-average molecular weight Mw of cellulose and cellulose microspheres determined with GPC method were 284,196 and 22,345, respectively. [ Conclusion] The determination results of (;PC method are relatively close to the actual value and could truly reflect the characteristics of molecular weialat distribution of eellulose and cellulose mierosr, heres.
文摘Many articles have been published on intelligent manufacturing, most of which focus on hardware, soft-ware, additive manufacturing, robotics, the Internet of Things, and Industry 4.0. This paper provides a dif-ferent perspective by examining relevant challenges and providing examples of some less-talked-about yet essential topics, such as hybrid systems, redefining advanced manufacturing, basic building blocks of new manufacturing, ecosystem readiness, and technology scalahility. The first major challenge is to (re-)define what the manufacturing of the future will he, if we wish to: ① raise public awareness of new manufacturing's economic and societal impacts, and ② garner the unequivocal support of policy- makers. The second major challenge is to recognize that manufacturing in the future will consist of sys-tems of hybrid systems of human and robotic operators; additive and suhtractive processes; metal and composite materials; and cyher and physical systems. Therefore, studying the interfaces between con- stituencies and standards becomes important and essential. The third challenge is to develop a common framework in which the technology, manufacturing business case, and ecosystem readiness can he eval- uated concurrently in order to shorten the time it takes for products to reach customers. Integral to this is having accepted measures of "scalahility" of non-information technologies. The last, hut not least, chal-lenge is to examine successful modalities of industry-academia-government collaborations through public-private partnerships. This article discusses these challenges in detail.
基金supported by the National Natural Science Foundation of China(No.51735013).
文摘Based on aphid wax-honeydew marble and the hydrophobic wax structure of lotus and its derived applications with superareophilic and superhydrophobic properties,edible carnauba wax and beeswax particles were mixed and utilized to mimic lotus wax and wrap liquid,thus forming liquid marbles(LMs).Through the utilization of continuous production system(CPS),wax as an interfacial surfactant,water and solid,air-phase or mixed-phase marble content was produced.The edible liquid marble(ELM)could encapsulate water and food droplets.Edible solid marble(ESM)and edible solid hollow marbles(ESHMs)could be fabricated by applying pectin or syrup.Moreover,through the heating of wax powders with different melting temperatures,stable tablets and hollow capsules could be produced.The wax powder as interfacial surfactant could firmly bind with pectin through hydrogen bonds on ESM.The edible LMs can therefore be applied for residue reduction,corrosion reduction,biohazard prevention and cleaning in the food industry.The other phase LMs could act as novel tools in the pharmaceutical and food industries with the above-mentioned water transport,preservation,sustained releasing and selective releasing abilities.
文摘A set of novel nonlinear variable structure excitation and steam-valving controllers are proposed in this paper. On the basis of the classical dynamic equations of a generator, excitation control and steam valving control are simultaneously considered. Design of these controllers combines the differential geometry theory with the variable structure controlling theory. The mathematical model in the form of "an affine nonlinear system" is set up for the control design of a large-scale power plant. The dynamic performance of the nonlinear variable structure controllers proposed for a single machine connected to an infinite bus power system is simulated. Simulation results show that the nonlinear variable structure excitation and steam-valving controllers give satisfactory dynamic performance and good robustness.
文摘A novel coordinated controller is proposed in the paper for SVC, excitation and steam valving for a single machine infinite system. Firstly, the nonlinear mathematic model of the system including the itation and steam valving is exactly linearized via state feedback. Then, the quasi-linearized system after the exact lineariztion is controlled by the sliding model controller based on Lyapunov direct method. At last, the novel coordinated controller is compared with a traditional linear controller and a nonlinear optimal controller respectively by simulations. The simulation results show that the proposed controller gives better dynamic response and stronger robustness.
文摘In this research, a modeling and experimental study was conducted to explore the effects of nanoparticle type (aluminum nanoparticles and carbon nanotubes), filler concentration and interactions between the nanoparticle and reinforcing fibers on through-thickness conductivity of nanoparticle/epoxy nanocomposites and nanoparticle/fiber-reinforced multiscale composites. Multiple, notable micromechanical models were evaluated to predict through-thickness thermal conductivity of both composite systems, and then compared to the experimental results. The results showed that filler volume fraction ranges and thermal conductivity differences of the constituent materials for the thermal conductivity ratio (km/kf or kf/km) used in the models can affect the resulting predictions. Certain models were found to be suitable for varying conditions on the thermal conductivity ratio. Finite element models (FEM) were developed to reveal heat transport mechanisms of the resultant nanocomposites and multiscale composites. The nanocomposite design for finite element analysis (FEA) provided close predictions and performed better than the micromechanical models. On the multiscale composite system, predictions were concluded to be dependent upon the FEM design where the interactions between nanoparticles and fibers are critical to accurately determine the through-thickness thermal conductivity.