The effect of time and environment on the dimension precision and mass of LOM prototypes was experimentally investigated.It is to identify the stability of the dimension of LOM prototypes after forming.The results sho...The effect of time and environment on the dimension precision and mass of LOM prototypes was experimentally investigated.It is to identify the stability of the dimension of LOM prototypes after forming.The results show that the dimension and the mass tendency to grow,which is mainly caused by elastic recovery and moisture absorption and is characterized principally by the growth of Z dimension.Self restraint can be a significant factor to influence Z growth of LOM prototypes.展开更多
Metastable liquid phase separation and rapid solidification in a metastable miscibility gap were investigated on the Cu60Co30Cr10 alloy by using the electromagnetic levitation and splat-quenching.It is found that the ...Metastable liquid phase separation and rapid solidification in a metastable miscibility gap were investigated on the Cu60Co30Cr10 alloy by using the electromagnetic levitation and splat-quenching.It is found that the alloy generally has a microstructure consisting of a（Co,Cr）-rich phase embedded in a Cu-rich matrix,and the morphology and size of the（Co,Cr）-rich phase vary drastically with cooling rate.During the electromagnetic levitation solidification processing the cooling rate is lower,resulting in an obvious coalescence tendency of the（Co,Cr）-rich spheroids.The（Co,Cr）-rich phase shows dendrites and coarse spheroids at lower cooling rates.In the splat quenched samples the（Co,Cr）-rich phase spheres were refined significantly and no dendrites were observed.This is probably due to the higher cooling rate,undercooling and interface tension.展开更多
Ultrasonic arc spray atomization (UASA) method was used to prepare high-melting-point, immiscible AgNi15 (mass fraction, %) composite particles. Sieving was used to determine the size distribution of the AgNi15 partic...Ultrasonic arc spray atomization (UASA) method was used to prepare high-melting-point, immiscible AgNi15 (mass fraction, %) composite particles. Sieving was used to determine the size distribution of the AgNi15 particles. The morphology, rapidly solidified structure and metastable solution expansion of the AgNi15 particles were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), respectively. The results show that the AgNi15 composite particles are spherical and well-dispersed, and the mass fractions of the particles with diameters <74μm and <55 μm are 99.5% and 98%, respectively. The rapidly solidified structure of the AgNi15 particles consists of spherical nickel-richβ(Ni)-phase particles dispersed throughout a silver-richα(Ag)-phase matrix andα(Ag)-phase nanoparticles dispersed throughout largerβ(Ni)-phase particles. The silver and nickel in the AgNi15 particles form a reciprocally extended metastable solution, and the solid solubility of nickel in the silver matrix at room temperature is in the range of 0.16%?0.36% (mole fraction).展开更多
The metastable liquid phase separation and rapid solidification behaviours of Co61.8Cu38.2 alloy were investigated by using differential thermal analysis （DTA） in combination with glass fluxing, electromagnetic levi...The metastable liquid phase separation and rapid solidification behaviours of Co61.8Cu38.2 alloy were investigated by using differential thermal analysis （DTA） in combination with glass fluxing, electromagnetic levitation （EML） and drop tube techniques. It is found that the liquid phase separation process and the solidification microstructures intensively depend on the experimental processing parameters, such as undercooling level, cooling rate, gravity level, liquid surface tension and the wetting state of crucible. Large undercooling and surface tension difference of the two liquids tend to facilitate further separation and cause severe macrosegregation. On the other hand, rapid cooling and low gravity effectively suppress the coalescence of the minority phase, Severe maerosegregation patterns are formed in the bulk samples processed by both DTA and EML. In contrast, disperse structures with fine spherical Cu-rich spheres homogeneously distributed in the matrix of Co-rich phase have been obtained in drop tube.展开更多
Purpose： The emergency physicians face significant clinical uncertainty when multiple trauma patients arrive in the emergency department （ED）. The priorities for assessment and treatment of polytrauma patients are ...Purpose： The emergency physicians face significant clinical uncertainty when multiple trauma patients arrive in the emergency department （ED）. The priorities for assessment and treatment of polytrauma patients are established in the primary survey. Focused assessment with sonography for trauma （FAST） is very essential clinical skill during trauma resuscitation. Use of point of care ultrasound among the trauma team working in the primary survey in emergency care settings is lacking in Suez Canal University Hospitals even ultrasound machine not available in ED. This study aims to evaluate the accuracy of FAST in hemodynam- ically unstable polytraumatized patients and to determine its role as an indication of laparotomy. Methods： This study is a cross-sectional study included 150 polytrauma patients with a blunt mechanism admitted in Suez Canal University Hospital. Firstly primary survey by airway check, cervical spine securing with neck collar, maintenance of breathing/circulation and management of life threading conditions if present were conducted accordingly to ATLS （advanced trauma life support） guidelines. The patients were assessed in the primary survey using the FAST as a tool to determine the presence of intra- abdominal collection. Results： A total of 150 patients, and FAST scans were performed in all cases. The sensitivity and specificity were 92.6% and 100%, respectively. The negative predictive value was 92%, while the positive predictive value of FAST was 100%. The accuracy of FAST was 96%. Conclusion： FAST is an important method to detect intra-abdominal fluid in the initial assessment in hemodynamically unstable polytrauma patients with high accuracy.展开更多
Mathematical models are disappointing due to uneven distribution of the air gap magnetic field and significant un- modeled dynamics in magnetic bearing systems. The effectiveness of control deteriorates based on an in...Mathematical models are disappointing due to uneven distribution of the air gap magnetic field and significant un- modeled dynamics in magnetic bearing systems. The effectiveness of control deteriorates based on an inaccurate mathematical model, creating slow response speed and high jitter. To solve these problems, a model-free adaptive control （MFAC） scheme is proposed for a three-degree-of-freedom hybrid magnetic bearing （3-DoF HMB） control system. The scheme for 3-DoF HMB depends only on the control current and the objective balanced position, and it does not involve any model information. The design process of a parameter estimation algorithm is model-free, based directly on pseudo-partial-derivative （PPD） derived online from the input and output data information. The rotor start-of-suspension position of the HMB is regulated by auxiliary bearings with different inner diameters, and two kinds of operation situations （linear and nonlinear areas） are present to analyze the validity of MFAC in detail. Both simulations and experiments demonstrate that the proposed MFAC scheme handles the 3-DoF HMB control system with start-of-suspension response speed, smaller steady state error, and higher stability.展开更多
A combustion set-up of an innovative nonslagging cyclone combustor called 'Spouting-Cyclone Combustor (SCC)' ) with two-stage combustion, organized in orthogonal vortex flows, was established and the experime...A combustion set-up of an innovative nonslagging cyclone combustor called 'Spouting-Cyclone Combustor (SCC)' ) with two-stage combustion, organized in orthogonal vortex flows, was established and the experimental studies on the fast ignition and stable combustion of coarse coal particles in this combustor were carried out. The flame temperature versus ignition time and the practical faSt ignition procedure were obtained; The stable coal combustion can be achieved after a short period ignition, and the temperature fields in SCC were obtained. These results show that it is possible to obtain highly efficient and clean combustion of unground coal particles by using this technology.展开更多
Lean premixed combustion,which allows for reducing the production of thermal NOx,is prone to combustion instabilities.There is an extensive research to develop a reduced physical model,which allows-without time-consum...Lean premixed combustion,which allows for reducing the production of thermal NOx,is prone to combustion instabilities.There is an extensive research to develop a reduced physical model,which allows-without time-consuming measurements-to calculate the resonance characteristics of a combustion system consisting of Helmholtz resonator type components (burner plenum,combustion chamber).For the formulation of this model numerical investigations by means of compressible Large Eddy Simulation (LES) were carried out.In these investigations the flow in the combustion chamber is isotherm,non-reacting and excited with a sinusoidal mass flow rate.Firstly a combustion chamber as a single resonator subsequently a coupled system of a burner plenum and a combustion chamber were investigated.In this paper the results of additional investigations of the single resonator are presented.The flow in the combustion chamber was investigated without excitation at the inlet.It was detected,that the mass flow rate at the outlet cross section is pulsating once the flow in the chamber is turbulent.The fast Fourier transform of the signal showed that the dominant mode is at the resonance frequency of the combustion chamber.This result sheds light on a very important source of self-excited combustion instabilities.Furthermore the LES can provide not only the damping ratio for the analytical model but the eigenfrequency of the resonator also.展开更多
文摘The effect of time and environment on the dimension precision and mass of LOM prototypes was experimentally investigated.It is to identify the stability of the dimension of LOM prototypes after forming.The results show that the dimension and the mass tendency to grow,which is mainly caused by elastic recovery and moisture absorption and is characterized principally by the growth of Z dimension.Self restraint can be a significant factor to influence Z growth of LOM prototypes.
基金Projects(51171152,50871088) supported by the National Natural Science Foundation of ChinaProject(20126102110048) supported by Doctoral Fund of Ministry of Education of China+2 种基金Project(SKLSP201202) supported by Foundation of State Key Laboratory of Solidification,ChinaProject(2012JC2-02) supported by Natural Science Basic Research Plan in Shaanxi Province,ChinaProject (JC201268) supported by the NPU Foundation for Fundamental Research,China
文摘Metastable liquid phase separation and rapid solidification in a metastable miscibility gap were investigated on the Cu60Co30Cr10 alloy by using the electromagnetic levitation and splat-quenching.It is found that the alloy generally has a microstructure consisting of a（Co,Cr）-rich phase embedded in a Cu-rich matrix,and the morphology and size of the（Co,Cr）-rich phase vary drastically with cooling rate.During the electromagnetic levitation solidification processing the cooling rate is lower,resulting in an obvious coalescence tendency of the（Co,Cr）-rich spheroids.The（Co,Cr）-rich phase shows dendrites and coarse spheroids at lower cooling rates.In the splat quenched samples the（Co,Cr）-rich phase spheres were refined significantly and no dendrites were observed.This is probably due to the higher cooling rate,undercooling and interface tension.
基金Project(2009CC010)supported by the Application Basic Research Foundation of Yunnan Province,ChinaProject(51264037)supported by the National Natural Science Foundation of China
文摘Ultrasonic arc spray atomization (UASA) method was used to prepare high-melting-point, immiscible AgNi15 (mass fraction, %) composite particles. Sieving was used to determine the size distribution of the AgNi15 particles. The morphology, rapidly solidified structure and metastable solution expansion of the AgNi15 particles were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), respectively. The results show that the AgNi15 composite particles are spherical and well-dispersed, and the mass fractions of the particles with diameters <74μm and <55 μm are 99.5% and 98%, respectively. The rapidly solidified structure of the AgNi15 particles consists of spherical nickel-richβ(Ni)-phase particles dispersed throughout a silver-richα(Ag)-phase matrix andα(Ag)-phase nanoparticles dispersed throughout largerβ(Ni)-phase particles. The silver and nickel in the AgNi15 particles form a reciprocally extended metastable solution, and the solid solubility of nickel in the silver matrix at room temperature is in the range of 0.16%?0.36% (mole fraction).
文摘The metastable liquid phase separation and rapid solidification behaviours of Co61.8Cu38.2 alloy were investigated by using differential thermal analysis （DTA） in combination with glass fluxing, electromagnetic levitation （EML） and drop tube techniques. It is found that the liquid phase separation process and the solidification microstructures intensively depend on the experimental processing parameters, such as undercooling level, cooling rate, gravity level, liquid surface tension and the wetting state of crucible. Large undercooling and surface tension difference of the two liquids tend to facilitate further separation and cause severe macrosegregation. On the other hand, rapid cooling and low gravity effectively suppress the coalescence of the minority phase, Severe maerosegregation patterns are formed in the bulk samples processed by both DTA and EML. In contrast, disperse structures with fine spherical Cu-rich spheres homogeneously distributed in the matrix of Co-rich phase have been obtained in drop tube.
文摘Purpose： The emergency physicians face significant clinical uncertainty when multiple trauma patients arrive in the emergency department （ED）. The priorities for assessment and treatment of polytrauma patients are established in the primary survey. Focused assessment with sonography for trauma （FAST） is very essential clinical skill during trauma resuscitation. Use of point of care ultrasound among the trauma team working in the primary survey in emergency care settings is lacking in Suez Canal University Hospitals even ultrasound machine not available in ED. This study aims to evaluate the accuracy of FAST in hemodynam- ically unstable polytraumatized patients and to determine its role as an indication of laparotomy. Methods： This study is a cross-sectional study included 150 polytrauma patients with a blunt mechanism admitted in Suez Canal University Hospital. Firstly primary survey by airway check, cervical spine securing with neck collar, maintenance of breathing/circulation and management of life threading conditions if present were conducted accordingly to ATLS （advanced trauma life support） guidelines. The patients were assessed in the primary survey using the FAST as a tool to determine the presence of intra- abdominal collection. Results： A total of 150 patients, and FAST scans were performed in all cases. The sensitivity and specificity were 92.6% and 100%, respectively. The negative predictive value was 92%, while the positive predictive value of FAST was 100%. The accuracy of FAST was 96%. Conclusion： FAST is an important method to detect intra-abdominal fluid in the initial assessment in hemodynamically unstable polytrauma patients with high accuracy.
基金Project supported by the National Natural Science Foundation of China （Nos. 51707082 and 51607080）, the Natural Science Foundation of Jiangsu Province, China （Nos. BK20170546 and BK20150510）, the China Postdoctoral Science Foundation （No. 2017M620192）, and the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Mathematical models are disappointing due to uneven distribution of the air gap magnetic field and significant un- modeled dynamics in magnetic bearing systems. The effectiveness of control deteriorates based on an inaccurate mathematical model, creating slow response speed and high jitter. To solve these problems, a model-free adaptive control （MFAC） scheme is proposed for a three-degree-of-freedom hybrid magnetic bearing （3-DoF HMB） control system. The scheme for 3-DoF HMB depends only on the control current and the objective balanced position, and it does not involve any model information. The design process of a parameter estimation algorithm is model-free, based directly on pseudo-partial-derivative （PPD） derived online from the input and output data information. The rotor start-of-suspension position of the HMB is regulated by auxiliary bearings with different inner diameters, and two kinds of operation situations （linear and nonlinear areas） are present to analyze the validity of MFAC in detail. Both simulations and experiments demonstrate that the proposed MFAC scheme handles the 3-DoF HMB control system with start-of-suspension response speed, smaller steady state error, and higher stability.
文摘A combustion set-up of an innovative nonslagging cyclone combustor called 'Spouting-Cyclone Combustor (SCC)' ) with two-stage combustion, organized in orthogonal vortex flows, was established and the experimental studies on the fast ignition and stable combustion of coarse coal particles in this combustor were carried out. The flame temperature versus ignition time and the practical faSt ignition procedure were obtained; The stable coal combustion can be achieved after a short period ignition, and the temperature fields in SCC were obtained. These results show that it is possible to obtain highly efficient and clean combustion of unground coal particles by using this technology.
文摘Lean premixed combustion,which allows for reducing the production of thermal NOx,is prone to combustion instabilities.There is an extensive research to develop a reduced physical model,which allows-without time-consuming measurements-to calculate the resonance characteristics of a combustion system consisting of Helmholtz resonator type components (burner plenum,combustion chamber).For the formulation of this model numerical investigations by means of compressible Large Eddy Simulation (LES) were carried out.In these investigations the flow in the combustion chamber is isotherm,non-reacting and excited with a sinusoidal mass flow rate.Firstly a combustion chamber as a single resonator subsequently a coupled system of a burner plenum and a combustion chamber were investigated.In this paper the results of additional investigations of the single resonator are presented.The flow in the combustion chamber was investigated without excitation at the inlet.It was detected,that the mass flow rate at the outlet cross section is pulsating once the flow in the chamber is turbulent.The fast Fourier transform of the signal showed that the dominant mode is at the resonance frequency of the combustion chamber.This result sheds light on a very important source of self-excited combustion instabilities.Furthermore the LES can provide not only the damping ratio for the analytical model but the eigenfrequency of the resonator also.
