The rapid prediction of aerodynamic performance is critical in the conceptual and preliminary design of hypersonic vehicles. This study focused on axisymmetric body configurations commonly used in such vehicles and pr...The rapid prediction of aerodynamic performance is critical in the conceptual and preliminary design of hypersonic vehicles. This study focused on axisymmetric body configurations commonly used in such vehicles and proposed a multi-fidelity neural network (MFNN) framework to fuse aerodynamic data of varying quality. A data-driven prediction model was constructed using a pointwise modeling method based on generating lines to input geometric features into the network. The MFNN framework combined low-fidelity and high-fidelity networks, trained on aerodynamic performance data from engineering rapid computation methods and CFD, respectively, using spherically blunted cones as examples. The results showed that the MFNN effectively integrated multi-fidelity data, achieving prediction accuracy close to CFD results in most regions, with errors under 5% in key stagnation areas. The model demonstrated strong generalization capabilities for varying cone dimensions and flight conditions. Furthermore, it significantly reduced dependence on high-fidelity data, enabling efficient aerodynamic performance predictions with limited datasets. This study provides a novel methodology for rapid aerodynamic performance prediction, offering both accuracy and efficiency, and contributes to the design of hypersonic vehicles.展开更多
In hypersonic boundary layers,the optimal disturbance is notably caused by normalmode instabilities,such as Mack second mode.However,recent experimental and numerical efforts have demonstrated the dominance of nonmoda...In hypersonic boundary layers,the optimal disturbance is notably caused by normalmode instabilities,such as Mack second mode.However,recent experimental and numerical efforts have demonstrated the dominance of nonmodal growth in hypersonic flows with the presence of moderate nose bluntness.In this study,resolvent analysis and parabolized stability equation analysis are performed to investigate the instabilities over a blunt-tip wedge.Main parameters include Mach number 5.9,unit Reynolds number 91.5×10~6/m,half wedge angle 5°,and nose radii ranging from 2.54 mm to 15.24 mm.Two novel growth patterns of travelling waves are identified to compete,whose nature is the intersection of the energy gain of optimal and sub-optimal disturbances.Pattern A with large spanwise wavelengths has the signature of slow energy amplification over a long distance which concentrates in the entropy layer.By contrast,pattern B with relatively small spanwise wavelengths presents rapid transient growth inside the boundary layer.A systematic study is performed on the growth/attenuation mechanism of disturbance patterns and the effects of wall temperature and nose radius.Wall cooling is found to be an alternative control strategy aimed at nonmodal instabilities.The receptivity to slow acoustic waves is considered when the effect of bluntness is studied.An estimated amplitude response favorably reproduces the reversal-like phenomenon.The lift-up/Orr mechanism analysis provides an explanation of energy growth for nonmodal responses.展开更多
The primary Mach Reflection(MR)and pressure/heating loads on V-shaped Blunt Leading Edges(VBLEs)with variable elliptic cross-sections and conic crotches are theoretically investigated in this study.The simplified cont...The primary Mach Reflection(MR)and pressure/heating loads on V-shaped Blunt Leading Edges(VBLEs)with variable elliptic cross-sections and conic crotches are theoretically investigated in this study.The simplified continuity method is used to forecast the shock configurations.The theoretical predictions and the numerical simulations for the Mach stem and the triple point as well as the curved shock accord well.Based on the theoretical model,an analysis of the impact of the axial ratio a/b of the cross-sectional shape and the eccentricity e of the crotch sweep path on shock structures is carried out.The shock configurations obtained from the theoretical model enable the derivation of the transition boundaries between the primary MR and the same family Regular Reflection(sRR).It is found that the increase of a/b and e can both facilitate the primary MR to sRR transition.The resulting transition and the corresponding generation of the wall pressure and heat flux are then investigated.The results indicate that higher values of the ratio a/b can significantly reduce the wall pressure and heating loads by inducing the primary MR to sRR transition.Conversely,the increase in the eccentricity e results in increased loads,despite causing the same transition.展开更多
There exists a severe strength-crack tolerance trade-off in dilute magnesium(Mg)alloys.Herein,a heterogeneous Mg-0.6Al-0.6Mn-0.5Zn-0.2Ce-0.2Nd(A200-10)alloy with a high density of dislocations was obtained through low...There exists a severe strength-crack tolerance trade-off in dilute magnesium(Mg)alloys.Herein,a heterogeneous Mg-0.6Al-0.6Mn-0.5Zn-0.2Ce-0.2Nd(A200-10)alloy with a high density of dislocations was obtained through low-temperature extrusion and short-term annealing.The microstructure consists of recrystallized(RXed)and unrecrystallized(unRXed)regions,with a precisely controlled volume fraction ratio of 3:1.The heterogeneous A200-10 alloy exhibits a high tensile yield strength(TYS)of~306 MPa and a superior tensile elongation(TEL)of~18.4%.Based on quasi-in-situ electron backscattered diffraction(EBSD)and scanning electron microscope(SEM)-digital image correlation(DIC)analysis,we find that plastic deformation occurs preferentially in the RXed regions,mediated by the mobiledislocations.As strain increases,strain gradient gradually accumulates at the interface between RXed and un RXed regions,generating hetero-deformation induced(HDI)strengthening and hardening.Besides,there is significant intergranular slip transfer in RXed regions,which can coordinate partial strain incompatibility.Furthermore,heterogeneous interfaces play a crucial role in enhancing crack tolerance.The heterogeneous interface functions as a bridging ligament to withstand stresses,and activates non-basal slips in the un RXed grains near the crack tip.Such activation of extra dislocations not only alleviates stress concentration but also dissipates the energy essential for microcrack propagation,thus effectively blunting the crack tip.Accordingly,the heterogeneous A200-10 alloy obtains an excellent strength and elongation combination.This work is anticipated to provide a valuable avenue for the development of Mg alloys with outstanding performance by regulating the appropriate heterostructure.展开更多
BACKGROUND Motorcycle accidents often result in abdominal trauma in patients seeking emergency care.Injuries to the hollow viscera,including the duodenum,jejunum,urinary bladder,and colorectum,are relatively common.In...BACKGROUND Motorcycle accidents often result in abdominal trauma in patients seeking emergency care.Injuries to the hollow viscera,including the duodenum,jejunum,urinary bladder,and colorectum,are relatively common.In contrast,owing to the protective function of the anterior rib cage,gastric rupture is exceptionally rare,with an incidence of<1.7%.Gastric rupture typically occurs in the anterior wall and rarely presents as multiple ruptures.This report describes an unusual case of multiple gastric ruptures resulting from blunt trauma.CASE SUMMARY A 21-year-old man,who was involved in a motorcycle collision at 70 km/hour after consuming a large meal,presented with hypotension.Physical examination revealed abdominal tenderness.Laboratory test results indicated elevated amylase,lipase,and liver enzyme levels.Computed tomography showed pneumoperitoneum,hemoperitoneum,and gastric wall discontinuation,suggesting gastric perforation alongside pancreatic,splenic,and hepatic injuries.Angiographic embolization was performed because of active contrast leakage in the left gastric and right gastroepiploic arteries.Emergency laparotomy revealed substantial blood loss,hematoma,and gastric contents scattered throughout the abdominal cavity.Two 10 cm gastric perforations in the anterior and posterior walls were identified,as well as severe liver damage,splenic injury,and pancreatic contusion.Surgical interventions included primary closure of the gastric wall,splenectomy,and partial hepatectomy.After temporary abdominal closure,the patient underwent a second surgery without further bleeding.The gastric repair site was resected and reinforced for optimal tissue healing.CONCLUSION Gastric rupture following blunt trauma is fatal.However,patients without severe complications can recover through surgical interventions and postoperative care.展开更多
Vortex-induced vibration of hydrofoils is concerned with structural safety and noise level in hydraulic machinery and marine engineering.The research on vibration characteristics under different operating conditions i...Vortex-induced vibration of hydrofoils is concerned with structural safety and noise level in hydraulic machinery and marine engineering.The research on vibration characteristics under different operating conditions is significant.In this study,numerical simulations are conducted to investigate the vortex-induced vibration responses of an elastically suspended hydrofoil with blunt trailing edge in pitch direction.The work studies the effects of four parameters,namely the structural natural frequency,mass ratio,initial attack angle,and Reynolds number on vibration characteristics,with special emphasis on frequency lock-in.Results indicate that as the structural natural frequency changes,the vibration amplitude may increase substantially within a certain frequency range,in which the vortex shedding frequency locks into the structural natural frequency,and frequency lock-in occurs.In addition,with increasing the mass ratio,the frequency range of lock-in becomes narrower,and both the upper and lower thresholds decrease.As the initial attack angle increases from 0◦to 6◦,the lock-in range gets reduced.Over the three Reynolds numbers(6×10^(5),9×10^(5),and 12×10^(5)),the lock-in range remains virtually unchanged.Moreover,for a certain structural natural frequency,modifying the mass ratio,initial attack angle,and Reynolds number could effectively suppress the vibration amplitude.展开更多
The optical rays that form the image of an object and propagate a supersonic flow over a vehicle are refracted by the density variations.A numerical analysis of the aero-optical characteristics of supersonic flow over...The optical rays that form the image of an object and propagate a supersonic flow over a vehicle are refracted by the density variations.A numerical analysis of the aero-optical characteristics of supersonic flow over blunt wedge with a cavity window is carried out.A hybrid method of Reynold averaged Navier-Stokes and direct simulation Monte Carlo(RANS/DSMC) is employed to simulate the flowfield.Refraction factor is introduced to evaluate the flowfield's aero-optical characteristic.The results show that mean flow's aero-optical effects are mainly caused by the shock wave,the expansion wave and the turbulent boundary layer.Fluctuation flow's aero-optical effects are mainly caused by the turbulent boundary layer and the shock wave induced by the cavity window.The aero-optical effects at the leading side of window are caused by the mean density variations,while the effects at the trailing side are caused by the density fluctuations.Different draft angles of the cavity window are investigated.The airborne optical devices of supersonic vehicle should be mounted in the middle of the cavity window with a large draft angle.展开更多
Since acupuncture came to western countries,research has been done to try and prove whether or not it is effective.Current Acupuncture research is most often based on the sham needle which was first designed by K Stre...Since acupuncture came to western countries,research has been done to try and prove whether or not it is effective.Current Acupuncture research is most often based on the sham needle which was first designed by K Streitberger and J Kleinhenz in 1998.The sham acupuncture needles are developed for the control group and do not penetrate the skin.Sham acupuncture has been used in randomized controlled trial（RCT） for diseases which normally benefit from acupuncture treatment.The sham needle is not the best placebo needle though.Because of the use of sham acupuncture,the result of those research shows acupuncture having no effect or it shows there is no significant difference between real acupuncture（verum） and sham acupuncture（placebo）.However,a detailed introduction of the Nine Classical Needles（ancient） and the Nine Modern Needles（SHI＇s nine needles） shows that the use of sham acupuncture in RCT research is flawed by design.This then casts doubt on the findings and conclusions reached by using sham acupuncture in RCT acupuncture research.展开更多
A self-developed double-nozzle gas atomization technique was used to produce AlSi10Mg powder.Effects of delivery tube diameter,gas pressure,and melt superheat on powder characteristics were investigated.The concepts o...A self-developed double-nozzle gas atomization technique was used to produce AlSi10Mg powder.Effects of delivery tube diameter,gas pressure,and melt superheat on powder characteristics were investigated.The concepts of bluntness and outgrowth were introduced to analyze powder sphericity and satellite index quantitatively.The results showed that the median diameters of all atomized powders ranged from 25 to 33μm.The highest yield rate(72.13%)of fine powder(<50μm)was obtained at a superheat of 350 K.The powder size decreased with increasing melt superheat but increased with increasing delivery tube diameter.Powders with bluntness values between 96%and 98%accounted for over 60%.The outgrowth values demonstrated that 70%-85%of all powders did not contain satellite particles,with few powders adhered two or three particles.Not only Al and Si phases were present but also a metastable Al9Si phase was detected.展开更多
BACKGROUND:Point-of-care ultrasound(POCUS)has become increasingly integrated into the practice of emergency medicine.A common application is the extended focused assessment with sonography in trauma(eFAST)exam.The Ame...BACKGROUND:Point-of-care ultrasound(POCUS)has become increasingly integrated into the practice of emergency medicine.A common application is the extended focused assessment with sonography in trauma(eFAST)exam.The American College of Emergency Physicians has guidelines regarding the scope of ultrasound in the emergency department and the appropriate documentation.The objective of this study was to conduct a review of performed,documented and billed eFAST ultrasounds on trauma activation patients.METHODS:This was a retrospective review of all trauma activation patients during a 10-month period at an academic level-one trauma center.A list comparing all trauma activations was crossreferenced with a list of all billed eFAST scans.Medical records were reviewed to determine whether an eFAST was indicated,performed,and appropriately documented.RESULTS:We found that 1,507 of 1,597 trauma patients had indications for eFAST,but 396(27%)of these patients did not have a billed eFAST.Of these 396 patients,87(22%)had documentation in the provider note that an eFAST was performed but there was no separate procedure note.The remaining 309(78%)did not have any documentation of the eFAST in the patient’s chart although an eFAST was recorded and reviewed during ultrasound quality assurance.CONCLUSION:A significant proportion of trauma patients had eFAST exams performed but were not documented or billed.Lack of documentation was multifactorial.Emergency ultrasound programs require appropriate reimbursement to support training,credentialing,equipment,quality assurance,and device maintenance.Our study demonstrates a significant absence of adequate documentation leading to potential revenue loss for an emergency ultrasound program.展开更多
This study successfully deals with the inhomogeneous dimension problem of load separation assumption, which is the theoretical basis of the normalization method. According to the dimensionless load separation principl...This study successfully deals with the inhomogeneous dimension problem of load separation assumption, which is the theoretical basis of the normalization method. According to the dimensionless load separation principle, the normalization method has been improved by intro- ducing a forcible blunting correction. With the improved normalization method, the J-resistance curves of five different metallic materials of CT and SEB specimens are estimated. The forcible blunting correction of initial crack size plays an important role in the J-resistance curve estima- tion, which is closely related to the strain hardening level of material. The higher level of strain hardening leads to a greater difference in JQ determined by different slopes of the blunting line. If the blunting line coefficient recommended by ASTM E1820-11 is used in the improved nor- realization method, it will lead to greater fracture resistance than that processed by the blunting line coefficient recommended by ISO 12135-2002. Therefore, the influence of the blunting line on the determination of JQ must be taken into full account in the fracture toughness assessment of metallic materials.展开更多
AIM: To retrospectively evaluate the preoperative diagnostic approaches and management of colonic injuries following blunt abdominal trauma. METHODS: A total of 82 patients with colonic injuries caused by blunt trauma...AIM: To retrospectively evaluate the preoperative diagnostic approaches and management of colonic injuries following blunt abdominal trauma. METHODS: A total of 82 patients with colonic injuries caused by blunt trauma between January 1992 and December 2005 were enrolled. Data were collected on clinical presentation, investigations, diagnostic methods, associated injuries, and operative management. Colonic injury-related mortality and abdominal complications were analyzed. RESULTS: Colonic injuries were caused mainly by motor vehicle accidents. Of the 82 patients, 58 (70.3%) had other associated injuries. Laparotomy was performed within 6 h after injury in 69 cases (84.1%), laparoscopy in 3 because of haemodynamic instability. The most commonly injured site was located in the transverse colon. The mean colon injury scale score was 2.8. The degree of faecal contamination was classified as mild in 18 (22.0%), moderate in 42 (51.2%), severe in 14 (17.1%), and unknown in 8 (9.8%) cases. Sixty-seven patients (81.7%) were treated with primary repair or resection and anastomosis. Faecal stream diversion was performed in 15 cases (18.3%). The overall mortality rate was 6.1%. The incidence of colonic injury- related abdominal complications was 20.7%. The only independent predictor of complications was the degree of peritoneal faecal contamination (P = 0.02). CONCLUSION: Colonic injuries following blunt trauma are especially important because of the severity and complexity of associated injuries. A thorough physical examination and a combination of tests can be used to evaluate the indications for laparotomy. One stage management at the time of initial exploration is mostoften used for colonic injuries.展开更多
The hypersonic boundary-layer receptivity to slow acoustic waves is investigated for the Mach 6 flow over a 5-degree half-angle blunt cone with the nose radius of 5.08 mm. The plane acoustic wave interacts with the bo...The hypersonic boundary-layer receptivity to slow acoustic waves is investigated for the Mach 6 flow over a 5-degree half-angle blunt cone with the nose radius of 5.08 mm. The plane acoustic wave interacts with the bow shock, and generates all types of disturbances behind the shock, which may take various routes to generate the boundarylayer unstable mode. In this paper, two routes of receptivity are investigated in detail.One is through the disturbance in the entropy layer. The other is through the slow acoustic wave transmitted downstream the bow shock, which can excite the boundary-layer mode due to the synchronization mechanism. The results show that, for a low frequency slow acoustic wave, the latter route plays a leading role. The entropy-layer instability wave is able to excite the first mode near the neutral point, but its receptivity efficiency is much lower.展开更多
Blunt diaphragmatic lesions (BDL) are uncommon in trauma patients, but they should be promptly recognized as a delayed diagnosis increases morbidity and mortality. It is well known that BDL are often overlooked at ini...Blunt diaphragmatic lesions (BDL) are uncommon in trauma patients, but they should be promptly recognized as a delayed diagnosis increases morbidity and mortality. It is well known that BDL are often overlooked at initial imaging, mainly because of distracting injuries to other organs. Sonography may directly depict BDL only in a minor number of cases. Chest X-ray has low sensitivity in detecting BDL and lesions can be reliably suspected only in case of intra-thoracic herniation of abdominal viscera. Thanks to its wide availability, time-effectiveness and spatial resolution, multi-detector computed tomography (CT) is the imaging modality of choice for diagnosing BDL; several direct and indirect CT signs are associated with BDL. Given its high tissue contrast resolution, magnetic resonance imaging can accurately depict BDL, but its use in an emergency setting is limited because of longer acquisition times and need for patient’s collaboration.展开更多
Indirect traumatic optic neuropathy(ITON) refers to optic nerve injury resulting from impact remote to the optic nerve. The mechanism of injury is not understood, and there are no confirmed protocols for prevention, m...Indirect traumatic optic neuropathy(ITON) refers to optic nerve injury resulting from impact remote to the optic nerve. The mechanism of injury is not understood, and there are no confirmed protocols for prevention, mitigation or treatment. Most data concerning this condition comes from case series of civilian patients suffering blunt injury, such as from sports- or motor vehicle-related concussion, rather than military-related ballistic or blast damage. Research in this field will likely require the development of robust databases to identify patients with ITON and follow related outcomes, in addition to both in-vivo animal and virtual human models to study the mechanisms of damage and potential therapies.展开更多
Hydraulic fracture is important in unconventional oil and gas exploration.During the propagation of the hydraulic fracture,the crack tip is blunted due to the development of the process zone in the near-tip area.In th...Hydraulic fracture is important in unconventional oil and gas exploration.During the propagation of the hydraulic fracture,the crack tip is blunted due to the development of the process zone in the near-tip area.In this study,the blunting of the hydraulic fracture in polymethyl methacrylate specimens due to multi-timescale stress concentration is investigated.The ratio of the initiation toughness to the arrest toughness of the blunted hydraulic fracture is measured using both the dynamic and the static methods.Results show that a hydraulic fracture can be blunted with the time span of stress concentration from 1 ms to 600 s.It is also shown that the blunting of hydraulic fracture is a highly localized process.The morphology of the blunted crack depends on the stress distribution in the vicinity of the crack tip.展开更多
Pressure wave plays an important role in the occurrence of behind armor blunt trauma(BABT),and ballistic gelatin is widely used as a surrogate of biological tissue in the research of BABT.Comparison of pressure wave i...Pressure wave plays an important role in the occurrence of behind armor blunt trauma(BABT),and ballistic gelatin is widely used as a surrogate of biological tissue in the research of BABT.Comparison of pressure wave in the gelatin behind armor for different rifle bullets is lacking.The aim of this study was to observe dynamic changes in pressure wave induced by ballistic blunt impact on the armored gelatin block and to compare the effects of bullet type on the parameters of the transient pressure wave.The gelatin blocks protected with National Institute of Justice(NIJ) class III bulletproof armor were shot by three types of rifle bullet with the same level of impact energy.The transient pressure signals at five locations were recorded with pressure sensors and three parameters(maximum pressure,maximum pressure impulse,and the duration of the first positive phase) were determined and discussed.The results indicated that the waveform and the twin peak of transient pressure wave were not related to the bullet type.However,the values of pressure wave's parameters were significantly affected by bullet type.Additionally,the attenuation of pressure amplitude followed the similar law for the three ammunitions.These findings may be helpful to get some insight in the BABT and improve the structure design of bullet.展开更多
Based on load separation theory, the load separation parameter Spb method is an effective approach for estimating the J-resistance curve from records of load versus displacement directly, using one sharp cracked speci...Based on load separation theory, the load separation parameter Spb method is an effective approach for estimating the J-resistance curve from records of load versus displacement directly, using one sharp cracked specimen and an additional reference blunt cracked specimen. However, the effect of the reference blunt cracked specimen on J-resistance determination was not explicitly considered in past work. In this paper, a modified load separation parameter Spb method was developed to eliminate this effect, and then a unique estimation of instantaneous crack length for one sharp cracked specimen could be obtained. Furthermore, a forced blunting calibration method was also adopted to determine the instantaneous crack length in the load inseparable region, referring to a normalization method. Experiments on steam turbine rotator steel Cr2Ni2MoV were carried out to estimate J-resistance curves using an unloading compliance method. By removing unload and reload data from load-displacement records, the J-resistance curve for the same sharp cracked specimen was estimated using the modified separation parameter Spb method. The results indicate that the modified Spb method completely eliminates the effect of the reference blunt cracked specimen on the instantaneous crack length determination of the sharp cracked specimen. However, different J-resistance curves in a small range of crack extension are present when different blunting coefficients are used in the blunting line equation. The J-resistance curve obtained from the modified Spb method agrees well with that obtained from the compliance method.展开更多
In the real flow for high altitude,the initiation mechanism of the oblique detonation involves the coupling of complex wave structures and combustion waves,which may result in the phenomenon of extinction.The approach...In the real flow for high altitude,the initiation mechanism of the oblique detonation involves the coupling of complex wave structures and combustion waves,which may result in the phenomenon of extinction.The approach of stable initiation is one of the key factors that restricting the oblique detonation engine from theory to practice.The wave structure,initiation characteristics and characteristic parameters of the flow field are analyzed,the two-dimensional Euler equation considering the detailed chemical reactions of multi-component are solved.First,the approaches of blunt bump and transverse jet are combined used to shorten the detonation distance of the oblique detonation.Results show that these methods can promote the accelerated initiation of the oblique detonation effectively,and the detonation distance can be shortened more than 90%.There are two wave structures induced by the blunt bump:weak coupled and strong coupled,adding the transverse jet promotes the transition between these two wave structures.Then,the shape of the bump and the characteristic parameters of the transverse jet are optimized.The streamline-shape bump can eliminate the recirculation zone formed after the circle bump and the ellipse bump.The transverse jet will produce an oblique detonation wave at the front of the jet position,which changes the wave structure and initiation mode of the oblique detonation wave.It is expected to reveal the accelerated initiation mechanism of oblique detonation under the induction zone disturbance and complex flow environment,deepen the understanding of the detonation law of oblique detonation wave under real flow conditions,and provide a scientific basic for the development of the combustor of the oblique detonation engine.展开更多
To investigate the effect of different disturbances in the upstream, we present numerical simulation of transition for a hypersonic boundary layer on a 5-degree half-angle blunt cone in a freestream with Mach number 6...To investigate the effect of different disturbances in the upstream, we present numerical simulation of transition for a hypersonic boundary layer on a 5-degree half-angle blunt cone in a freestream with Mach number 6 at 1-degree angle of attack. Evolution of small disturbances is simulated to compare with the linear stability theory （LST）, indicating that LST can provide a good prediction on the growth rate of the disturbance. The effect of different disturbances on transition is investigated. Transition onset distributions along the azimuthal direction are obtained with two groups of disturbances of different frequencies. It shows that transition onset is relevant to frequencies and amplitudes of the disturbances at the inlet, and is decided by the amplitudes of most unstable waves at the inlet. According to the characteristics of environmental disturbances in most wind tunnels, we explain why transition occurs leeside-forward and windside-aft over a circular cone at an angle of attack. Moreover, the indentation phenomenon in the transition curve on the leeward is also revealed.展开更多
文摘The rapid prediction of aerodynamic performance is critical in the conceptual and preliminary design of hypersonic vehicles. This study focused on axisymmetric body configurations commonly used in such vehicles and proposed a multi-fidelity neural network (MFNN) framework to fuse aerodynamic data of varying quality. A data-driven prediction model was constructed using a pointwise modeling method based on generating lines to input geometric features into the network. The MFNN framework combined low-fidelity and high-fidelity networks, trained on aerodynamic performance data from engineering rapid computation methods and CFD, respectively, using spherically blunted cones as examples. The results showed that the MFNN effectively integrated multi-fidelity data, achieving prediction accuracy close to CFD results in most regions, with errors under 5% in key stagnation areas. The model demonstrated strong generalization capabilities for varying cone dimensions and flight conditions. Furthermore, it significantly reduced dependence on high-fidelity data, enabling efficient aerodynamic performance predictions with limited datasets. This study provides a novel methodology for rapid aerodynamic performance prediction, offering both accuracy and efficiency, and contributes to the design of hypersonic vehicles.
基金supported by the Hong Kong Research Grants Council(Nos.15216621,15204322,25203721)the National Natural Science Foundation of China(No.12102377)。
文摘In hypersonic boundary layers,the optimal disturbance is notably caused by normalmode instabilities,such as Mack second mode.However,recent experimental and numerical efforts have demonstrated the dominance of nonmodal growth in hypersonic flows with the presence of moderate nose bluntness.In this study,resolvent analysis and parabolized stability equation analysis are performed to investigate the instabilities over a blunt-tip wedge.Main parameters include Mach number 5.9,unit Reynolds number 91.5×10~6/m,half wedge angle 5°,and nose radii ranging from 2.54 mm to 15.24 mm.Two novel growth patterns of travelling waves are identified to compete,whose nature is the intersection of the energy gain of optimal and sub-optimal disturbances.Pattern A with large spanwise wavelengths has the signature of slow energy amplification over a long distance which concentrates in the entropy layer.By contrast,pattern B with relatively small spanwise wavelengths presents rapid transient growth inside the boundary layer.A systematic study is performed on the growth/attenuation mechanism of disturbance patterns and the effects of wall temperature and nose radius.Wall cooling is found to be an alternative control strategy aimed at nonmodal instabilities.The receptivity to slow acoustic waves is considered when the effect of bluntness is studied.An estimated amplitude response favorably reproduces the reversal-like phenomenon.The lift-up/Orr mechanism analysis provides an explanation of energy growth for nonmodal responses.
基金support of the National Natural Science Foundation of China(Nos.U20A2069,12302389,12372295)the Natural Science Foundation of Fujian Province,China(No.2023J01046)。
文摘The primary Mach Reflection(MR)and pressure/heating loads on V-shaped Blunt Leading Edges(VBLEs)with variable elliptic cross-sections and conic crotches are theoretically investigated in this study.The simplified continuity method is used to forecast the shock configurations.The theoretical predictions and the numerical simulations for the Mach stem and the triple point as well as the curved shock accord well.Based on the theoretical model,an analysis of the impact of the axial ratio a/b of the cross-sectional shape and the eccentricity e of the crotch sweep path on shock structures is carried out.The shock configurations obtained from the theoretical model enable the derivation of the transition boundaries between the primary MR and the same family Regular Reflection(sRR).It is found that the increase of a/b and e can both facilitate the primary MR to sRR transition.The resulting transition and the corresponding generation of the wall pressure and heat flux are then investigated.The results indicate that higher values of the ratio a/b can significantly reduce the wall pressure and heating loads by inducing the primary MR to sRR transition.Conversely,the increase in the eccentricity e results in increased loads,despite causing the same transition.
基金Financial support from The National Natural Science Foundation of China(Nos.52222409,U24A20104,and52401049)The National Key Research and Development Program(No.2024YFB3408900)Partial financial support comes from the Fundamental Research Funds for the Central Universities,JLU。
文摘There exists a severe strength-crack tolerance trade-off in dilute magnesium(Mg)alloys.Herein,a heterogeneous Mg-0.6Al-0.6Mn-0.5Zn-0.2Ce-0.2Nd(A200-10)alloy with a high density of dislocations was obtained through low-temperature extrusion and short-term annealing.The microstructure consists of recrystallized(RXed)and unrecrystallized(unRXed)regions,with a precisely controlled volume fraction ratio of 3:1.The heterogeneous A200-10 alloy exhibits a high tensile yield strength(TYS)of~306 MPa and a superior tensile elongation(TEL)of~18.4%.Based on quasi-in-situ electron backscattered diffraction(EBSD)and scanning electron microscope(SEM)-digital image correlation(DIC)analysis,we find that plastic deformation occurs preferentially in the RXed regions,mediated by the mobiledislocations.As strain increases,strain gradient gradually accumulates at the interface between RXed and un RXed regions,generating hetero-deformation induced(HDI)strengthening and hardening.Besides,there is significant intergranular slip transfer in RXed regions,which can coordinate partial strain incompatibility.Furthermore,heterogeneous interfaces play a crucial role in enhancing crack tolerance.The heterogeneous interface functions as a bridging ligament to withstand stresses,and activates non-basal slips in the un RXed grains near the crack tip.Such activation of extra dislocations not only alleviates stress concentration but also dissipates the energy essential for microcrack propagation,thus effectively blunting the crack tip.Accordingly,the heterogeneous A200-10 alloy obtains an excellent strength and elongation combination.This work is anticipated to provide a valuable avenue for the development of Mg alloys with outstanding performance by regulating the appropriate heterostructure.
文摘BACKGROUND Motorcycle accidents often result in abdominal trauma in patients seeking emergency care.Injuries to the hollow viscera,including the duodenum,jejunum,urinary bladder,and colorectum,are relatively common.In contrast,owing to the protective function of the anterior rib cage,gastric rupture is exceptionally rare,with an incidence of<1.7%.Gastric rupture typically occurs in the anterior wall and rarely presents as multiple ruptures.This report describes an unusual case of multiple gastric ruptures resulting from blunt trauma.CASE SUMMARY A 21-year-old man,who was involved in a motorcycle collision at 70 km/hour after consuming a large meal,presented with hypotension.Physical examination revealed abdominal tenderness.Laboratory test results indicated elevated amylase,lipase,and liver enzyme levels.Computed tomography showed pneumoperitoneum,hemoperitoneum,and gastric wall discontinuation,suggesting gastric perforation alongside pancreatic,splenic,and hepatic injuries.Angiographic embolization was performed because of active contrast leakage in the left gastric and right gastroepiploic arteries.Emergency laparotomy revealed substantial blood loss,hematoma,and gastric contents scattered throughout the abdominal cavity.Two 10 cm gastric perforations in the anterior and posterior walls were identified,as well as severe liver damage,splenic injury,and pancreatic contusion.Surgical interventions included primary closure of the gastric wall,splenectomy,and partial hepatectomy.After temporary abdominal closure,the patient underwent a second surgery without further bleeding.The gastric repair site was resected and reinforced for optimal tissue healing.CONCLUSION Gastric rupture following blunt trauma is fatal.However,patients without severe complications can recover through surgical interventions and postoperative care.
基金the National Natural Science Foundation of China(Nos.52171316 and 51479116)。
文摘Vortex-induced vibration of hydrofoils is concerned with structural safety and noise level in hydraulic machinery and marine engineering.The research on vibration characteristics under different operating conditions is significant.In this study,numerical simulations are conducted to investigate the vortex-induced vibration responses of an elastically suspended hydrofoil with blunt trailing edge in pitch direction.The work studies the effects of four parameters,namely the structural natural frequency,mass ratio,initial attack angle,and Reynolds number on vibration characteristics,with special emphasis on frequency lock-in.Results indicate that as the structural natural frequency changes,the vibration amplitude may increase substantially within a certain frequency range,in which the vortex shedding frequency locks into the structural natural frequency,and frequency lock-in occurs.In addition,with increasing the mass ratio,the frequency range of lock-in becomes narrower,and both the upper and lower thresholds decrease.As the initial attack angle increases from 0◦to 6◦,the lock-in range gets reduced.Over the three Reynolds numbers(6×10^(5),9×10^(5),and 12×10^(5)),the lock-in range remains virtually unchanged.Moreover,for a certain structural natural frequency,modifying the mass ratio,initial attack angle,and Reynolds number could effectively suppress the vibration amplitude.
文摘The optical rays that form the image of an object and propagate a supersonic flow over a vehicle are refracted by the density variations.A numerical analysis of the aero-optical characteristics of supersonic flow over blunt wedge with a cavity window is carried out.A hybrid method of Reynold averaged Navier-Stokes and direct simulation Monte Carlo(RANS/DSMC) is employed to simulate the flowfield.Refraction factor is introduced to evaluate the flowfield's aero-optical characteristic.The results show that mean flow's aero-optical effects are mainly caused by the shock wave,the expansion wave and the turbulent boundary layer.Fluctuation flow's aero-optical effects are mainly caused by the turbulent boundary layer and the shock wave induced by the cavity window.The aero-optical effects at the leading side of window are caused by the mean density variations,while the effects at the trailing side are caused by the density fluctuations.Different draft angles of the cavity window are investigated.The airborne optical devices of supersonic vehicle should be mounted in the middle of the cavity window with a large draft angle.
文摘Since acupuncture came to western countries,research has been done to try and prove whether or not it is effective.Current Acupuncture research is most often based on the sham needle which was first designed by K Streitberger and J Kleinhenz in 1998.The sham acupuncture needles are developed for the control group and do not penetrate the skin.Sham acupuncture has been used in randomized controlled trial（RCT） for diseases which normally benefit from acupuncture treatment.The sham needle is not the best placebo needle though.Because of the use of sham acupuncture,the result of those research shows acupuncture having no effect or it shows there is no significant difference between real acupuncture（verum） and sham acupuncture（placebo）.However,a detailed introduction of the Nine Classical Needles（ancient） and the Nine Modern Needles（SHI＇s nine needles） shows that the use of sham acupuncture in RCT research is flawed by design.This then casts doubt on the findings and conclusions reached by using sham acupuncture in RCT acupuncture research.
基金Project(51627805) supported by the National Natural Science Foundation of ChinaProject(2015A030312003) supported by the Natural Science Foundation of Guangdong Province,China+1 种基金Projects(2014B010129003,2015B020238008,2016B090931006,2017B090901025) supported by the Science and Technology Research Department of Guangdong Province,ChinaProject(201604016049) supported by the Science and Technology Bureau of Guangzhou City,China
文摘A self-developed double-nozzle gas atomization technique was used to produce AlSi10Mg powder.Effects of delivery tube diameter,gas pressure,and melt superheat on powder characteristics were investigated.The concepts of bluntness and outgrowth were introduced to analyze powder sphericity and satellite index quantitatively.The results showed that the median diameters of all atomized powders ranged from 25 to 33μm.The highest yield rate(72.13%)of fine powder(<50μm)was obtained at a superheat of 350 K.The powder size decreased with increasing melt superheat but increased with increasing delivery tube diameter.Powders with bluntness values between 96%and 98%accounted for over 60%.The outgrowth values demonstrated that 70%-85%of all powders did not contain satellite particles,with few powders adhered two or three particles.Not only Al and Si phases were present but also a metastable Al9Si phase was detected.
文摘BACKGROUND:Point-of-care ultrasound(POCUS)has become increasingly integrated into the practice of emergency medicine.A common application is the extended focused assessment with sonography in trauma(eFAST)exam.The American College of Emergency Physicians has guidelines regarding the scope of ultrasound in the emergency department and the appropriate documentation.The objective of this study was to conduct a review of performed,documented and billed eFAST ultrasounds on trauma activation patients.METHODS:This was a retrospective review of all trauma activation patients during a 10-month period at an academic level-one trauma center.A list comparing all trauma activations was crossreferenced with a list of all billed eFAST scans.Medical records were reviewed to determine whether an eFAST was indicated,performed,and appropriately documented.RESULTS:We found that 1,507 of 1,597 trauma patients had indications for eFAST,but 396(27%)of these patients did not have a billed eFAST.Of these 396 patients,87(22%)had documentation in the provider note that an eFAST was performed but there was no separate procedure note.The remaining 309(78%)did not have any documentation of the eFAST in the patient’s chart although an eFAST was recorded and reviewed during ultrasound quality assurance.CONCLUSION:A significant proportion of trauma patients had eFAST exams performed but were not documented or billed.Lack of documentation was multifactorial.Emergency ultrasound programs require appropriate reimbursement to support training,credentialing,equipment,quality assurance,and device maintenance.Our study demonstrates a significant absence of adequate documentation leading to potential revenue loss for an emergency ultrasound program.
基金supported by the National Natural Science Foundation of China(Nos.11472228 and 11202174)the Sichuan Provincial Youth Science and Technology Innovation Team(No.2013TD0004)
文摘This study successfully deals with the inhomogeneous dimension problem of load separation assumption, which is the theoretical basis of the normalization method. According to the dimensionless load separation principle, the normalization method has been improved by intro- ducing a forcible blunting correction. With the improved normalization method, the J-resistance curves of five different metallic materials of CT and SEB specimens are estimated. The forcible blunting correction of initial crack size plays an important role in the J-resistance curve estima- tion, which is closely related to the strain hardening level of material. The higher level of strain hardening leads to a greater difference in JQ determined by different slopes of the blunting line. If the blunting line coefficient recommended by ASTM E1820-11 is used in the improved nor- realization method, it will lead to greater fracture resistance than that processed by the blunting line coefficient recommended by ISO 12135-2002. Therefore, the influence of the blunting line on the determination of JQ must be taken into full account in the fracture toughness assessment of metallic materials.
文摘AIM: To retrospectively evaluate the preoperative diagnostic approaches and management of colonic injuries following blunt abdominal trauma. METHODS: A total of 82 patients with colonic injuries caused by blunt trauma between January 1992 and December 2005 were enrolled. Data were collected on clinical presentation, investigations, diagnostic methods, associated injuries, and operative management. Colonic injury-related mortality and abdominal complications were analyzed. RESULTS: Colonic injuries were caused mainly by motor vehicle accidents. Of the 82 patients, 58 (70.3%) had other associated injuries. Laparotomy was performed within 6 h after injury in 69 cases (84.1%), laparoscopy in 3 because of haemodynamic instability. The most commonly injured site was located in the transverse colon. The mean colon injury scale score was 2.8. The degree of faecal contamination was classified as mild in 18 (22.0%), moderate in 42 (51.2%), severe in 14 (17.1%), and unknown in 8 (9.8%) cases. Sixty-seven patients (81.7%) were treated with primary repair or resection and anastomosis. Faecal stream diversion was performed in 15 cases (18.3%). The overall mortality rate was 6.1%. The incidence of colonic injury- related abdominal complications was 20.7%. The only independent predictor of complications was the degree of peritoneal faecal contamination (P = 0.02). CONCLUSION: Colonic injuries following blunt trauma are especially important because of the severity and complexity of associated injuries. A thorough physical examination and a combination of tests can be used to evaluate the indications for laparotomy. One stage management at the time of initial exploration is mostoften used for colonic injuries.
基金Project supported by the National Natural Science Foundation of China(Nos.11472188 and11332007)the National Key Research and Development Program of China(No.2016YFA0401200)
文摘The hypersonic boundary-layer receptivity to slow acoustic waves is investigated for the Mach 6 flow over a 5-degree half-angle blunt cone with the nose radius of 5.08 mm. The plane acoustic wave interacts with the bow shock, and generates all types of disturbances behind the shock, which may take various routes to generate the boundarylayer unstable mode. In this paper, two routes of receptivity are investigated in detail.One is through the disturbance in the entropy layer. The other is through the slow acoustic wave transmitted downstream the bow shock, which can excite the boundary-layer mode due to the synchronization mechanism. The results show that, for a low frequency slow acoustic wave, the latter route plays a leading role. The entropy-layer instability wave is able to excite the first mode near the neutral point, but its receptivity efficiency is much lower.
文摘Blunt diaphragmatic lesions (BDL) are uncommon in trauma patients, but they should be promptly recognized as a delayed diagnosis increases morbidity and mortality. It is well known that BDL are often overlooked at initial imaging, mainly because of distracting injuries to other organs. Sonography may directly depict BDL only in a minor number of cases. Chest X-ray has low sensitivity in detecting BDL and lesions can be reliably suspected only in case of intra-thoracic herniation of abdominal viscera. Thanks to its wide availability, time-effectiveness and spatial resolution, multi-detector computed tomography (CT) is the imaging modality of choice for diagnosing BDL; several direct and indirect CT signs are associated with BDL. Given its high tissue contrast resolution, magnetic resonance imaging can accurately depict BDL, but its use in an emergency setting is limited because of longer acquisition times and need for patient’s collaboration.
文摘Indirect traumatic optic neuropathy(ITON) refers to optic nerve injury resulting from impact remote to the optic nerve. The mechanism of injury is not understood, and there are no confirmed protocols for prevention, mitigation or treatment. Most data concerning this condition comes from case series of civilian patients suffering blunt injury, such as from sports- or motor vehicle-related concussion, rather than military-related ballistic or blast damage. Research in this field will likely require the development of robust databases to identify patients with ITON and follow related outcomes, in addition to both in-vivo animal and virtual human models to study the mechanisms of damage and potential therapies.
基金the support from the China National Science and Technology Major Project"Changning-Weiyuan shale gas development demonstration project"(2016ZX05062)the support from the China National Petroleum Corporation:"Research on Influencing Factors of Gas Hydrate Sand Production and Experimental Design"(No.CPETQ201921)。
文摘Hydraulic fracture is important in unconventional oil and gas exploration.During the propagation of the hydraulic fracture,the crack tip is blunted due to the development of the process zone in the near-tip area.In this study,the blunting of the hydraulic fracture in polymethyl methacrylate specimens due to multi-timescale stress concentration is investigated.The ratio of the initiation toughness to the arrest toughness of the blunted hydraulic fracture is measured using both the dynamic and the static methods.Results show that a hydraulic fracture can be blunted with the time span of stress concentration from 1 ms to 600 s.It is also shown that the blunting of hydraulic fracture is a highly localized process.The morphology of the blunted crack depends on the stress distribution in the vicinity of the crack tip.
基金supported by the National Basic Scientific Research Project(Grant NO.JCKYS2019209C001)National Key Research and Development Program of China(Grant NO.2017YFC0822301&Grant NO.2018YFC0807206)National Natural Science Foundation of China(Grant NO.11772303)。
文摘Pressure wave plays an important role in the occurrence of behind armor blunt trauma(BABT),and ballistic gelatin is widely used as a surrogate of biological tissue in the research of BABT.Comparison of pressure wave in the gelatin behind armor for different rifle bullets is lacking.The aim of this study was to observe dynamic changes in pressure wave induced by ballistic blunt impact on the armored gelatin block and to compare the effects of bullet type on the parameters of the transient pressure wave.The gelatin blocks protected with National Institute of Justice(NIJ) class III bulletproof armor were shot by three types of rifle bullet with the same level of impact energy.The transient pressure signals at five locations were recorded with pressure sensors and three parameters(maximum pressure,maximum pressure impulse,and the duration of the first positive phase) were determined and discussed.The results indicated that the waveform and the twin peak of transient pressure wave were not related to the bullet type.However,the values of pressure wave's parameters were significantly affected by bullet type.Additionally,the attenuation of pressure amplitude followed the similar law for the three ammunitions.These findings may be helpful to get some insight in the BABT and improve the structure design of bullet.
基金Project (No 11072205) supported by the National Natural Science Foundation of China
文摘Based on load separation theory, the load separation parameter Spb method is an effective approach for estimating the J-resistance curve from records of load versus displacement directly, using one sharp cracked specimen and an additional reference blunt cracked specimen. However, the effect of the reference blunt cracked specimen on J-resistance determination was not explicitly considered in past work. In this paper, a modified load separation parameter Spb method was developed to eliminate this effect, and then a unique estimation of instantaneous crack length for one sharp cracked specimen could be obtained. Furthermore, a forced blunting calibration method was also adopted to determine the instantaneous crack length in the load inseparable region, referring to a normalization method. Experiments on steam turbine rotator steel Cr2Ni2MoV were carried out to estimate J-resistance curves using an unloading compliance method. By removing unload and reload data from load-displacement records, the J-resistance curve for the same sharp cracked specimen was estimated using the modified separation parameter Spb method. The results indicate that the modified Spb method completely eliminates the effect of the reference blunt cracked specimen on the instantaneous crack length determination of the sharp cracked specimen. However, different J-resistance curves in a small range of crack extension are present when different blunting coefficients are used in the blunting line equation. The J-resistance curve obtained from the modified Spb method agrees well with that obtained from the compliance method.
基金supported by the National Natural Science Foundation of China(No.12202365)the Guangdong Basic and Applied Basic Research Foundation,China(Nos.2022A1515011565,2023A1515010031)+2 种基金the Natural Science Foundation of Chongqing,China(No.2022NSCQMSX5709)the Foundation of State Key Laboratory of High Temperature Gas Dynamics,China(No.2021KF10)the China Postdoctoral Science Foundation(Nos.2021M692633,2022T150534).
文摘In the real flow for high altitude,the initiation mechanism of the oblique detonation involves the coupling of complex wave structures and combustion waves,which may result in the phenomenon of extinction.The approach of stable initiation is one of the key factors that restricting the oblique detonation engine from theory to practice.The wave structure,initiation characteristics and characteristic parameters of the flow field are analyzed,the two-dimensional Euler equation considering the detailed chemical reactions of multi-component are solved.First,the approaches of blunt bump and transverse jet are combined used to shorten the detonation distance of the oblique detonation.Results show that these methods can promote the accelerated initiation of the oblique detonation effectively,and the detonation distance can be shortened more than 90%.There are two wave structures induced by the blunt bump:weak coupled and strong coupled,adding the transverse jet promotes the transition between these two wave structures.Then,the shape of the bump and the characteristic parameters of the transverse jet are optimized.The streamline-shape bump can eliminate the recirculation zone formed after the circle bump and the ellipse bump.The transverse jet will produce an oblique detonation wave at the front of the jet position,which changes the wave structure and initiation mode of the oblique detonation wave.It is expected to reveal the accelerated initiation mechanism of oblique detonation under the induction zone disturbance and complex flow environment,deepen the understanding of the detonation law of oblique detonation wave under real flow conditions,and provide a scientific basic for the development of the combustor of the oblique detonation engine.
基金Project supported by the National Natural Science Foundation of China (Nos. 90716007 and 10632050)the National Natural Science Foundation of China for Distinguished Young Scholars (No. 10802058)the Specialized Research Fund for the Doctoral Program of Higher Education (No. 200800561087)
文摘To investigate the effect of different disturbances in the upstream, we present numerical simulation of transition for a hypersonic boundary layer on a 5-degree half-angle blunt cone in a freestream with Mach number 6 at 1-degree angle of attack. Evolution of small disturbances is simulated to compare with the linear stability theory （LST）, indicating that LST can provide a good prediction on the growth rate of the disturbance. The effect of different disturbances on transition is investigated. Transition onset distributions along the azimuthal direction are obtained with two groups of disturbances of different frequencies. It shows that transition onset is relevant to frequencies and amplitudes of the disturbances at the inlet, and is decided by the amplitudes of most unstable waves at the inlet. According to the characteristics of environmental disturbances in most wind tunnels, we explain why transition occurs leeside-forward and windside-aft over a circular cone at an angle of attack. Moreover, the indentation phenomenon in the transition curve on the leeward is also revealed.
