3D printing technology can realize the rapid fabrication of complicated structures with short production chain,which just meet the requirements for space manufacturing in the future.This Special Issue features the cut...3D printing technology can realize the rapid fabrication of complicated structures with short production chain,which just meet the requirements for space manufacturing in the future.This Special Issue features the cutting-edge 3D printing technologies considering the space environment,focusing on the experimental validation and simulation on the 3D printing process and structural technologies,including whole process chain from raw materials,structural design,process,equipment,as well as functional verification.展开更多
A key component of future lunar missions is the concept of in-situ resource utilization(ISRU),which involves the use of local resources to support human missions and reduce dependence on Earth-based supplies.This pape...A key component of future lunar missions is the concept of in-situ resource utilization(ISRU),which involves the use of local resources to support human missions and reduce dependence on Earth-based supplies.This paper investigates the thermal processing capability of lunar regolith without the addition of binders,with a focus on large-scale applications for the construction of lunar habitats and infrastructure.The study used a simulant of lunar regolith found on the Schr?dinger Basin in the South Pole region.This regolith simulant consists of20 wt%basalt and 80 wt%anorthosite.Experiments were conducted using a high power CO_(2)laser to sinter and melt the regolith in a 80 mm diameter laser spot to evaluate the effectiveness of direct large area thermal processing.Results indicated that sintering begins at approximately 1180℃and reaches full melt at temperatures above 1360℃.Sintering experiments with this material revealed the formation of dense samples up to 11 mm thick,while melting experiments successfully produced larger samples by overlapping molten layers and additive manufacturing up to 50 mm thick.The energy efficiency of the sintering and melting processes was compared.The melting process was about 10 times more energy efficient than sintering in terms of material consolidation,demonstrating the promising potential of laser melting technologies of anorthosite-rich regolith for the production of structural elements.展开更多
Grain boundary(GB)segregation substantially influences the mechanical properties and performance of magnesium(Mg).Atomic-scale modeling,typically using ab-initio or semi-empirical approaches,has mainly focused on GB s...Grain boundary(GB)segregation substantially influences the mechanical properties and performance of magnesium(Mg).Atomic-scale modeling,typically using ab-initio or semi-empirical approaches,has mainly focused on GB segregation at highly symmetric GBs in Mg alloys,often failing to capture the diversity of local atomic environments and segregation energies,resulting in inaccurate structure-property predictions.This study employs atomistic simulations and machine learning models to systematically investigate the segregation behavior of common solute elements in polycrystalline Mg at both 0 K and finite temperatures.The machine learning models accurately predict segregation thermodynamics by incorporating energetic and structural descriptors.We found that segregation energy and vibrational free energy follow skew-normal distributions,with hydrostatic stress,an indicator of excess free volume,emerging as an important factor influencing segregation tendency.The local atomic environment's flexibility,quantified by flexibility volume,is also crucial in predicting GB segregation.Comparing the grain boundary solute concentrations calculated via the Langmuir-Mc Lean isotherm with experimental data,we identified a pronounced segregation tendency for Nd,highlighting its potential for GB engineering in Mg alloys.This work demonstrates the powerful synergy of atomistic simulations and machine learning,paving the way for designing advanced lightweight Mg alloys with tailored properties.展开更多
In order to increase the sustainability of future lunar missions,techniques for in-situ resource utilization(ISRU)must be developed.In this context,the local melting of lunar dust(regolith)by laser radiation for the p...In order to increase the sustainability of future lunar missions,techniques for in-situ resource utilization(ISRU)must be developed.In this context,the local melting of lunar dust(regolith)by laser radiation for the production of parts and larger structures was investigated in detail.With different experimental setups in normal and microgravity,laser spots with diameters from 5 mm to 100 mm were realized to melt the regolith simulant EAC-1A and an 80%/20%mixture of TUBS-T and TUBS-M,which are used as a substitute for the actual lunar soil.In the experiments performed,the critical parameters are the size of the laser spot,the velocity of the laser spot on the surface of the powder bed,the gravity and the wettability of the powder bed by the melt.The stability of the melt pool as a function of these parameters was investigated and it was found that the formation of a stable melt pool is determined by gravity for large melt pool sizes in the range of 50 mm and by surface tension for small melt pool sizes in the range of a few mm.展开更多
This research studies the effect of Mn-Co-La_(2)O_(3) coating synthesized by the electrodeposition method on the oxidation resistance and electrical conductivity of the Crofer 22 APU stainless steel interconnect plate...This research studies the effect of Mn-Co-La_(2)O_(3) coating synthesized by the electrodeposition method on the oxidation resistance and electrical conductivity of the Crofer 22 APU stainless steel interconnect plates in solid oxide fuel cells.The test samples were characterized by a field emission scanning electron microscope(FESEM)equipped with energy dispersive spectroscopy(EDS),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The oxidation kinetics of the coated and uncoated samples were studied by tracking their weight changes over time at 800°C,showing that the oxidation mechanism for all samples follows the parabolic law.Lower oxidation rate constant(k_(p))values of the coated sample compared with that of the uncoated one indicated a reduction in the oxidation rate of the steel substrate in the presence of the Mn-Co-La_(2)O_(3) coating.The examination of the cross-section of different samples after the isothermal oxidation for 500 h at 800°C exhibited that applying the composite coating leads to a decrease in the thickness of the chromia layer formed on the steel surface.Furthermore,under these conditions,the area-specific resistance(ASR)of the coated sample(13.11 mΩcm^(2))is significantly lower than that of the uncoated one(41.45 mΩcm^(2)).展开更多
Objective:Patient safety is a fundamental factor in improving the quality of care provided in hospitals.Therefore,it is considered a significant parameter by all healthcare organizations around the world.The present s...Objective:Patient safety is a fundamental factor in improving the quality of care provided in hospitals.Therefore,it is considered a significant parameter by all healthcare organizations around the world.The present study was conducted to investigate the attitude of nurses toward the patient safety climate during the Coronavirus Disease 2019(COVID-19)pandemic in the southeast of Iran.Methods:This is a cross-sectional descriptive study.Among all the nurses working in one of the hospitals in the southeast of Iran,171 nurses participated in the study through convenience sampling methods.The survey was conducted between June 1 and July 30,2020.A 2-part questionnaire including demographic information and an assessment of nurses'attitudes toward patients'safety climate was used for data collection in 2021.The content validity of the scale is(0.77)and reliability was re-calculated and confirmed by the present study with Cronbach's alpha(α=0.9).Data were analyzed by SPSS 20(IBM Corporation,Armonk,New York,United States)using descriptive and analytical statistical tests.Results:The mean score of safety climates was 3.2±5.20(out of 5 scores).The results showed that among all dimensions of the safety climate,only the education dimension was statistically significant between males and females(P<0.001).Also,there was a significant relationship between the overall average of the safety climate and its dimensions according to the people's position only in the dimension of supervisors'attitude(P<0.01)and burnout(P<0.01).Additionally,a significant correlation between the education level and the overall score of safety climate(P<0.01),as well as the supervisor's attitude dimension(P<0.01),was observed.Conclusions:The results showed that the safety climate was at a relatively favorable level.Considering the impact of nurses'attitudes on the safety climate of patients,its improvement seems necessary.It is recommended to design training courses and educate nurses in order to promote a patients safety climate in hospitals.展开更多
Hypertension is one of the most important risk factors for heart diseases today. The effect of hypertension in the elderly is higher than other age groups and it may lead to changes in their quality of life. By the in...Hypertension is one of the most important risk factors for heart diseases today. The effect of hypertension in the elderly is higher than other age groups and it may lead to changes in their quality of life. By the increase of age, the amount of self-care behaviors of patients with hypertension decreased. Therefore, control and self-care behaviors are so important. This study has been conducted to study self-regulation behaviors and Associated Factors in elderly patients with hypertension. This study was a cross sectional, descriptive analytic study, which was conducted using multistage sampling on the elderly 60 years and above with hypertension. The sample size was calculated 365 and the final sample size of 380 people was considered by possible losses. The instruments include of demographic and self-regulatory behaviors questionnaire. The results showed that self-regulation of behavior was 42.3% of the total score. In terms of quality, only 7.4% of the elderly had good behavior, 46.6% of poor performance, and the rest were mediocre performance. Age (p = 0.03), gender (p = 0.02), education (p = 0.001), income level (p = 0.03) and marital status (p = 0.001) significantly associated with behaviors of self-regulation. The results generally indicate unfavorable self-regulation of elderly patients with hypertension. Some variables such as gender, age, marital status, education and income levels were associated with these behaviors. So paying attention to the education of the elderly in care centers is essential.展开更多
A multi-physics numerical model was developed to investigate the influence of a steady magnetic field during partial penetration keyhole laser beam welding of an aluminum plate in fiat position.Three-dimensional heat ...A multi-physics numerical model was developed to investigate the influence of a steady magnetic field during partial penetration keyhole laser beam welding of an aluminum plate in fiat position.Three-dimensional heat transfer, fluid dynamics including phase transition and electromagnetic field partial differential equations were solved with the finite element differential equation solver COMSOL Multiphysics.The magnetic field was aligned perpendicularly to the welding direction.The main objective of these simulations was to estimate the critical value of the magnetic field needed to suppress convective flows in the weld pool during high-power(up to 20 kW)laser beam welding of aluminum alloys with up to 20 mm deep weld pool.It reveals that steady magnetic fields with corresponding Hartmann numbers Ha2-104 based on the half-width of the weld pool can effectively suppress convective flows in the weld pool.Moreover,the typically occurring wineglass-shape of the weld cross section caused by thermo-capillary flow is weakened.展开更多
The arc furnace technology is an ideally suited process for the treatment of hazardous and problematic waste. The operation conditions of the furnace can be adapted for optimal transformation of the waste material inp...The arc furnace technology is an ideally suited process for the treatment of hazardous and problematic waste. The operation conditions of the furnace can be adapted for optimal transformation of the waste material input into raw materials and usable products. The process can significantly reduce the impact of contaminated wastes and industrial residues, and enable material conversion and separation. Thus, the products of the process have various applications. The capability of the process is illustrated with three examples, the treatment of bottom ash and filter ash from waste incineration plants, of stainless steel slags and of chromium-containing residues from the refractory industry.展开更多
The main characteristic feature of deep penetration laser beam welding is a large temperature difference between the plasma cavity(keyhole)in the weld pool centre and the melting/solidification front.Large temperature...The main characteristic feature of deep penetration laser beam welding is a large temperature difference between the plasma cavity(keyhole)in the weld pool centre and the melting/solidification front.Large temperature gradients in the weld pool result in very intensive thermocapillary(Marangoni)convection.The weld pool surface width becomes very large and unstable.However,an externally applied oscillating magnetic field can stabilize the surface of the melt.In the present work this technology was used to stabilize the weld pool surface in partial penetration 4.4 kW Nd:YAG laser beam welding of AW-5754 aluminium alloy in PA position.An AC magnet was mounted on the laser welding head.The oscillating magnetic field was oriented perpendicular to the welding direction.It was found that the AC magnetic field can drastically reduce the surface roughness of welds.X-ray image analysis shows a drastic reduction of welds porosity.This effect can be explained as a result of electromagnetic rectification of the melt.展开更多
Objective: To investigate the frequency of integrase genes intI1, intI2 and intI3 of Escherichia coli strains, and their association with resistance to routinely used antibiotics. Methods: A total of 120 Escherichia c...Objective: To investigate the frequency of integrase genes intI1, intI2 and intI3 of Escherichia coli strains, and their association with resistance to routinely used antibiotics. Methods: A total of 120 Escherichia coli strains were collected from patients with urinary tract infection in Ahvaz, Southwest of Iran. Antibiotic susceptibility testing was performed. The presence of intI1, intI2, and intI3 genes was determined by polymerase chain reaction. Results: Antibiotic susceptibility testing disclosed the highest resistance rate to ampicillin (91.7%) followed by trimethoprim/sulfamethoxazole (65.8%), and ceftazidime (56.7%). The imipenem susceptibility rate was 91.7%. IntI1 and intI2 were identified in 74 (61.6%) and 8 (6.6%) of Escherichia coli strains, respectively, but intI3 was not found in any isolates. The presence of integrons was significantly associated with resistance to ampicillin, trimethoprim/sulfamethoxazole, ceftazidime, and ciprofloxacin antibiotics (P<0.05). Conclusions: The high resistant Escherichia coli isolates harboring class 1 integrons (intI1) were detected in patients with urinary tract infection in our region. Therefore, preventive strategies are necessary to restrict further dissemination of resistant strains.展开更多
文摘3D printing technology can realize the rapid fabrication of complicated structures with short production chain,which just meet the requirements for space manufacturing in the future.This Special Issue features the cutting-edge 3D printing technologies considering the space environment,focusing on the experimental validation and simulation on the 3D printing process and structural technologies,including whole process chain from raw materials,structural design,process,equipment,as well as functional verification.
文摘A key component of future lunar missions is the concept of in-situ resource utilization(ISRU),which involves the use of local resources to support human missions and reduce dependence on Earth-based supplies.This paper investigates the thermal processing capability of lunar regolith without the addition of binders,with a focus on large-scale applications for the construction of lunar habitats and infrastructure.The study used a simulant of lunar regolith found on the Schr?dinger Basin in the South Pole region.This regolith simulant consists of20 wt%basalt and 80 wt%anorthosite.Experiments were conducted using a high power CO_(2)laser to sinter and melt the regolith in a 80 mm diameter laser spot to evaluate the effectiveness of direct large area thermal processing.Results indicated that sintering begins at approximately 1180℃and reaches full melt at temperatures above 1360℃.Sintering experiments with this material revealed the formation of dense samples up to 11 mm thick,while melting experiments successfully produced larger samples by overlapping molten layers and additive manufacturing up to 50 mm thick.The energy efficiency of the sintering and melting processes was compared.The melting process was about 10 times more energy efficient than sintering in terms of material consolidation,demonstrating the promising potential of laser melting technologies of anorthosite-rich regolith for the production of structural elements.
基金Z.X.and T.A.S.acknowledge the financial support by the German Research Foundation(DFG)(Grant Nr.505716422)T.A.S.are grateful for the financial support from the DFG(Grant Nr.AL1343/7-1,AL1343/8-1 and Yi 103/3-1)+4 种基金Z.X.,S.K.K.and U.K.acknowledge financial support by the DFG through the projects A05,A07 and C02 of the SFB1394 StructuralChemical Atomic Complexity-From Defect Phase Diagrams to Material Properties,project ID 409476157Additionally,Z.X.and S.K.K.are grateful for funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(grant agreement No.852096 FunBlocks)J.G.acknowledges funding from the French National Research Agency(ANR),Grant ANR-21-CE08-0001(ATOUUM)and ANR-22-CE92-0058-01(SILA)The authors gratefully acknowledge the computing time provided to them at the NHR Center NHR4CES at RWTH Aachen University(project number p0020431 and p0020267)。
文摘Grain boundary(GB)segregation substantially influences the mechanical properties and performance of magnesium(Mg).Atomic-scale modeling,typically using ab-initio or semi-empirical approaches,has mainly focused on GB segregation at highly symmetric GBs in Mg alloys,often failing to capture the diversity of local atomic environments and segregation energies,resulting in inaccurate structure-property predictions.This study employs atomistic simulations and machine learning models to systematically investigate the segregation behavior of common solute elements in polycrystalline Mg at both 0 K and finite temperatures.The machine learning models accurately predict segregation thermodynamics by incorporating energetic and structural descriptors.We found that segregation energy and vibrational free energy follow skew-normal distributions,with hydrostatic stress,an indicator of excess free volume,emerging as an important factor influencing segregation tendency.The local atomic environment's flexibility,quantified by flexibility volume,is also crucial in predicting GB segregation.Comparing the grain boundary solute concentrations calculated via the Langmuir-Mc Lean isotherm with experimental data,we identified a pronounced segregation tendency for Nd,highlighting its potential for GB engineering in Mg alloys.This work demonstrates the powerful synergy of atomistic simulations and machine learning,paving the way for designing advanced lightweight Mg alloys with tailored properties.
基金supported by 40th DLR Parabolic Flight Campaign and within the project"Powder based Additive Manufacturing at reduced Gravitation"(Grant No.FKZ:50WM2068)European Space Agency,OSIP Off-Earth Manufacturing and Construction Campaign(Grant No.4000134280/21/NL/GLC/mk)。
文摘In order to increase the sustainability of future lunar missions,techniques for in-situ resource utilization(ISRU)must be developed.In this context,the local melting of lunar dust(regolith)by laser radiation for the production of parts and larger structures was investigated in detail.With different experimental setups in normal and microgravity,laser spots with diameters from 5 mm to 100 mm were realized to melt the regolith simulant EAC-1A and an 80%/20%mixture of TUBS-T and TUBS-M,which are used as a substitute for the actual lunar soil.In the experiments performed,the critical parameters are the size of the laser spot,the velocity of the laser spot on the surface of the powder bed,the gravity and the wettability of the powder bed by the melt.The stability of the melt pool as a function of these parameters was investigated and it was found that the formation of a stable melt pool is determined by gravity for large melt pool sizes in the range of 50 mm and by surface tension for small melt pool sizes in the range of a few mm.
文摘This research studies the effect of Mn-Co-La_(2)O_(3) coating synthesized by the electrodeposition method on the oxidation resistance and electrical conductivity of the Crofer 22 APU stainless steel interconnect plates in solid oxide fuel cells.The test samples were characterized by a field emission scanning electron microscope(FESEM)equipped with energy dispersive spectroscopy(EDS),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The oxidation kinetics of the coated and uncoated samples were studied by tracking their weight changes over time at 800°C,showing that the oxidation mechanism for all samples follows the parabolic law.Lower oxidation rate constant(k_(p))values of the coated sample compared with that of the uncoated one indicated a reduction in the oxidation rate of the steel substrate in the presence of the Mn-Co-La_(2)O_(3) coating.The examination of the cross-section of different samples after the isothermal oxidation for 500 h at 800°C exhibited that applying the composite coating leads to a decrease in the thickness of the chromia layer formed on the steel surface.Furthermore,under these conditions,the area-specific resistance(ASR)of the coated sample(13.11 mΩcm^(2))is significantly lower than that of the uncoated one(41.45 mΩcm^(2)).
基金supported by the Bam University of Medical Sciences,Bam,Iran。
文摘Objective:Patient safety is a fundamental factor in improving the quality of care provided in hospitals.Therefore,it is considered a significant parameter by all healthcare organizations around the world.The present study was conducted to investigate the attitude of nurses toward the patient safety climate during the Coronavirus Disease 2019(COVID-19)pandemic in the southeast of Iran.Methods:This is a cross-sectional descriptive study.Among all the nurses working in one of the hospitals in the southeast of Iran,171 nurses participated in the study through convenience sampling methods.The survey was conducted between June 1 and July 30,2020.A 2-part questionnaire including demographic information and an assessment of nurses'attitudes toward patients'safety climate was used for data collection in 2021.The content validity of the scale is(0.77)and reliability was re-calculated and confirmed by the present study with Cronbach's alpha(α=0.9).Data were analyzed by SPSS 20(IBM Corporation,Armonk,New York,United States)using descriptive and analytical statistical tests.Results:The mean score of safety climates was 3.2±5.20(out of 5 scores).The results showed that among all dimensions of the safety climate,only the education dimension was statistically significant between males and females(P<0.001).Also,there was a significant relationship between the overall average of the safety climate and its dimensions according to the people's position only in the dimension of supervisors'attitude(P<0.01)and burnout(P<0.01).Additionally,a significant correlation between the education level and the overall score of safety climate(P<0.01),as well as the supervisor's attitude dimension(P<0.01),was observed.Conclusions:The results showed that the safety climate was at a relatively favorable level.Considering the impact of nurses'attitudes on the safety climate of patients,its improvement seems necessary.It is recommended to design training courses and educate nurses in order to promote a patients safety climate in hospitals.
文摘Hypertension is one of the most important risk factors for heart diseases today. The effect of hypertension in the elderly is higher than other age groups and it may lead to changes in their quality of life. By the increase of age, the amount of self-care behaviors of patients with hypertension decreased. Therefore, control and self-care behaviors are so important. This study has been conducted to study self-regulation behaviors and Associated Factors in elderly patients with hypertension. This study was a cross sectional, descriptive analytic study, which was conducted using multistage sampling on the elderly 60 years and above with hypertension. The sample size was calculated 365 and the final sample size of 380 people was considered by possible losses. The instruments include of demographic and self-regulatory behaviors questionnaire. The results showed that self-regulation of behavior was 42.3% of the total score. In terms of quality, only 7.4% of the elderly had good behavior, 46.6% of poor performance, and the rest were mediocre performance. Age (p = 0.03), gender (p = 0.02), education (p = 0.001), income level (p = 0.03) and marital status (p = 0.001) significantly associated with behaviors of self-regulation. The results generally indicate unfavorable self-regulation of elderly patients with hypertension. Some variables such as gender, age, marital status, education and income levels were associated with these behaviors. So paying attention to the education of the elderly in care centers is essential.
基金Item Sponsored by the Deutsche Forschungsgemeinschaft (BonnGermany) Under Grant No.DFG GU 1211/2-1
文摘A multi-physics numerical model was developed to investigate the influence of a steady magnetic field during partial penetration keyhole laser beam welding of an aluminum plate in fiat position.Three-dimensional heat transfer, fluid dynamics including phase transition and electromagnetic field partial differential equations were solved with the finite element differential equation solver COMSOL Multiphysics.The magnetic field was aligned perpendicularly to the welding direction.The main objective of these simulations was to estimate the critical value of the magnetic field needed to suppress convective flows in the weld pool during high-power(up to 20 kW)laser beam welding of aluminum alloys with up to 20 mm deep weld pool.It reveals that steady magnetic fields with corresponding Hartmann numbers Ha2-104 based on the half-width of the weld pool can effectively suppress convective flows in the weld pool.Moreover,the typically occurring wineglass-shape of the weld cross section caused by thermo-capillary flow is weakened.
基金Part of the work was supported by the EU LIFE Program (LIFE03ENV/D/043-Recarc)
文摘The arc furnace technology is an ideally suited process for the treatment of hazardous and problematic waste. The operation conditions of the furnace can be adapted for optimal transformation of the waste material input into raw materials and usable products. The process can significantly reduce the impact of contaminated wastes and industrial residues, and enable material conversion and separation. Thus, the products of the process have various applications. The capability of the process is illustrated with three examples, the treatment of bottom ash and filter ash from waste incineration plants, of stainless steel slags and of chromium-containing residues from the refractory industry.
基金Item Sponsored by the German Collaborative Industrial Research Program (IGF) and the German Welding Society (DVS) Under Grant Nr.IGF-17.265 N/DVS-06.078
文摘The main characteristic feature of deep penetration laser beam welding is a large temperature difference between the plasma cavity(keyhole)in the weld pool centre and the melting/solidification front.Large temperature gradients in the weld pool result in very intensive thermocapillary(Marangoni)convection.The weld pool surface width becomes very large and unstable.However,an externally applied oscillating magnetic field can stabilize the surface of the melt.In the present work this technology was used to stabilize the weld pool surface in partial penetration 4.4 kW Nd:YAG laser beam welding of AW-5754 aluminium alloy in PA position.An AC magnet was mounted on the laser welding head.The oscillating magnetic field was oriented perpendicular to the welding direction.It was found that the AC magnetic field can drastically reduce the surface roughness of welds.X-ray image analysis shows a drastic reduction of welds porosity.This effect can be explained as a result of electromagnetic rectification of the melt.
文摘Objective: To investigate the frequency of integrase genes intI1, intI2 and intI3 of Escherichia coli strains, and their association with resistance to routinely used antibiotics. Methods: A total of 120 Escherichia coli strains were collected from patients with urinary tract infection in Ahvaz, Southwest of Iran. Antibiotic susceptibility testing was performed. The presence of intI1, intI2, and intI3 genes was determined by polymerase chain reaction. Results: Antibiotic susceptibility testing disclosed the highest resistance rate to ampicillin (91.7%) followed by trimethoprim/sulfamethoxazole (65.8%), and ceftazidime (56.7%). The imipenem susceptibility rate was 91.7%. IntI1 and intI2 were identified in 74 (61.6%) and 8 (6.6%) of Escherichia coli strains, respectively, but intI3 was not found in any isolates. The presence of integrons was significantly associated with resistance to ampicillin, trimethoprim/sulfamethoxazole, ceftazidime, and ciprofloxacin antibiotics (P<0.05). Conclusions: The high resistant Escherichia coli isolates harboring class 1 integrons (intI1) were detected in patients with urinary tract infection in our region. Therefore, preventive strategies are necessary to restrict further dissemination of resistant strains.
