With increasing density and heterogeneity in unlicensed wireless networks,traditional MAC protocols,such as Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA)in Wi-Fi networks,are experiencing performance...With increasing density and heterogeneity in unlicensed wireless networks,traditional MAC protocols,such as Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA)in Wi-Fi networks,are experiencing performance degradation.This is manifested in increased collisions and extended backoff times,leading to diminished spectrum efficiency and protocol coordination.Addressing these issues,this paper proposes a deep-learning-based MAC paradigm,dubbed DL-MAC,which leverages spectrum data readily available from energy detection modules in wireless devices to achieve the MAC functionalities of channel access,rate adaptation,and channel switch.First,we utilize DL-MAC to realize a joint design of channel access and rate adaptation.Subsequently,we integrate the capability of channel switching into DL-MAC,enhancing its functionality from single-channel to multi-channel operations.Specifically,the DL-MAC protocol incorporates a Deep Neural Network(DNN)for channel selection and a Recurrent Neural Network(RNN)for the joint design of channel access and rate adaptation.We conducted real-world data collection within the 2.4 GHz frequency band to validate the effectiveness of DL-MAC.Experimental results demonstrate that DL-MAC exhibits significantly superior performance compared to traditional algorithms in both single and multi-channel environments,and also outperforms single-function designs.Additionally,the performance of DL-MAC remains robust,unaffected by channel switch overheads within the evaluation range.展开更多
The fatigue crack growth rate of a novel Ti-6Al-4V-1Mo titanium alloy,which is developed for laser directed energy deposition technique,was investigated before and after cyclic heat treatment(CHT).Changes in microstru...The fatigue crack growth rate of a novel Ti-6Al-4V-1Mo titanium alloy,which is developed for laser directed energy deposition technique,was investigated before and after cyclic heat treatment(CHT).Changes in microstructure,fracture surfaces,and crack growth paths were analyzed before and after CHT.Results indicate that in the stable crack growth region,the growth rates for the as-deposited and cyclic heat-treated specimens follow the relationships da/dN=1.8651×10^(−8)(ΔK)^(3.2271)and da/dN=1.4112×10^(−8)(ΔK)^(3.1125),respectively.Compared with that at the as-deposited state,the microstructure after CHT is transformed from a uniform basket-weave microstructure to a dual-phase microstructure consisting of near-sphericalαandβ-transformed matrix phases.The cyclic process also disrupts the continuity of the grain boundaryα(αGB)at the primaryβ-phase grain boundary.The coarsening of primaryαand the disruption ofαGB continuity are the primary factors to release stress concentration and promote crack deflection,thereby decreasing the fatigue crack growth rate.Additionally,the increased occurrence of crack branching,secondary cracking,and crack bridging in cyclic heat-treated specimens further reduces the crack driving force and slows the fatigue crack growth rate.展开更多
Early-stage gastric cancer;Extent of lymph node dissection;D1 dissection;D2 dissection;Recurrence rate;Survival rateObjective:To investigate the impact of different lymph node dissection scopes on postoperative recurr...Early-stage gastric cancer;Extent of lymph node dissection;D1 dissection;D2 dissection;Recurrence rate;Survival rateObjective:To investigate the impact of different lymph node dissection scopes on postoperative recurrence and survival rates in patients with early gastric cancer,providing evidence-based support for optimizing clinical surgical plans.Methods:A retrospective analysis was conducted on the clinical data of 100 patients with early gastric cancer who underwent surgical treatment at our hospital from October 2021 to October 2023.Patients were divided into Group D1(n=50)and Group D2(n=50)based on the extent of lymph node dissection.Group D1 underwent limited lymph node dissection(dissection of the first station of lymph nodes around the stomach),while Group D2 underwent standard lymph node dissection(dissection of the first and second stations of lymph nodes around the stomach).Surgical-related indicators,the incidence of postoperative complications,the 2-year recurrence rate,and the 2-year survival rate were compared between the two groups of patients.Results:The operative time,intraoperative blood loss,postoperative hospital stay,and the number of lymph nodes dissected were significantly higher in the D2 group than in the D1 group(all P<0.001).The overall incidence of postoperative complications was higher in the D1 group than in the D2 group,but the difference was not statistically significant(χ^(2)=0.884,P=0.766).After a 2-year follow-up,the recurrence rate was significantly higher in the D1 group than in the D2 group(χ^(2)=4.000,P=0.046).The 2-year survival rate was significantly lower in the D1 group than in the D2 group(χ^(2)=5.005,P=0.025).A total of 100 patients with early-stage gastric cancer were grouped according to the depth of invasion,degree of differentiation,and lymph node metastasis status,and the recurrence rates of different subgroups were compared.The results showed that the recurrence rate was higher in patients with T1b stage than in those with T1a stage(χ^(2)=5.005,P=0.025),higher in poorly differentiated patients than in moderately and well-differentiated patients(χ^(2)=4.155,P=0.042),and higher in patients with lymph node metastasis than in those without lymph node metastasis(χ^(2)=4.512,P=0.034).Conclusion:Compared with D1 limited lymph node dissection,D2 standard lymph node dissection can significantly reduce the postoperative recurrence rate and improve the 2-year survival rate in patients with early-stage gastric cancer without significantly increasing the risk of postoperative complications.Although the surgical trauma is slightly greater,the overall prognosis is better,making it a preferred surgical treatment option for patients with early-stage gastric cancer.展开更多
[Objectives]To investigate the effects of different planting densities and nitrogen application rates on the yield and quality of the tobacco cultivar Chuxue 80.[Methods]A field experiment was conducted in Hubei Provi...[Objectives]To investigate the effects of different planting densities and nitrogen application rates on the yield and quality of the tobacco cultivar Chuxue 80.[Methods]A field experiment was conducted in Hubei Province,evaluating various combinations of planting density and nitrogen rate for Chuxue 80.[Results]At the maturity stage,the TN1 treatment(5 kg N per 667 m^(2) with a density of 1900 plants per 667 m^(2))demonstrated the most favorable agronomic performance.The TN9 treatment(11 kg N per 667 m^(2) with a density of 1110 plants per 667 m^(2))achieved the highest wrapper tobacco yield and output value.Meanwhile,the TN5 treatment(8 kg N per 667 m^(2) with a density of 1515 plants per 667 m^(2))resulted in the best smoking quality.[Conclusions]The TN9 treatment,with a planting density of 1110 plants per 667 m^(2) and a nitrogen application rate of 11 kg per 667 m^(2),is recommended as the optimal cultivation practice for Chuxue 80 in Hubei Province.展开更多
Apparel exports China:The decline in exports widened from January to September(-2.4%,compared to-0.2%in January-June).Exports to the EU increased(+5.9%),though the growth rate moderated.Exports to the US saw a larger ...Apparel exports China:The decline in exports widened from January to September(-2.4%,compared to-0.2%in January-June).Exports to the EU increased(+5.9%),though the growth rate moderated.Exports to the US saw a larger contraction(January-June:-1.6%,January-September:-8.2%).While exports to ASEAN countries still fell by over 10%(-17.7%),shipments to the Philippines(+6.9%),Indonesia(+19.0%),and Cambodia(+64.9%)demonstrated stronger growth performance within the year.Regarding tariffs,on October 30,China and the US agreed to lower the rates on goods subject to additional duties(effectively reducing the average tariff rate on Chinese imports to the US from about 57%to approximately 47%,though this remains significantly higher than the 19.5%overall average rate applied to other countries).展开更多
The high-alloyed wrought superalloy GH4975 tends to form coarse MC carbides and eutectic(γ+γ′)phases,which adversely affect the cogging and homogenization process.To provide theoretical guidance for control of MC c...The high-alloyed wrought superalloy GH4975 tends to form coarse MC carbides and eutectic(γ+γ′)phases,which adversely affect the cogging and homogenization process.To provide theoretical guidance for control of MC carbides and eutectic(γ+γ′)formation,differential thermal analysis(DTA)was utilized to investigate the effect of cooing rate(10-90℃·min^(-1))on solidification behavior and micro-segregation of GH4975 alloy.According to the thermodynamic calculation and distribution characteristics of precipitates,the MC carbides can act as nucleation sites forγdendrites,but the nucleation ofγdendrites becomes less dependent on the MC carbide primers at higher cooling rates.As theγdendrites grow,the elements including Ti and Nb gradually accumulate in the residual liquid and leads to the formation of more MC carbides near the interdendritic region.Finally,the solidification is terminated with the formation of eutectic(γ+γ′).With an increase in cooling rate,the liquidus temperature rises,but the solidus temperature decreases,and thus the solidification range is obviously enlarged.The dendritic structure is significantly refined by the increase of cooling rate.The secondary dendrite arm spacing,λ_(2),as a function of cooling rate,T,can be expressed asλ_(2)=216.78T^(-0.42).Moreover,the increasing cooling rate weakens the back diffusion of Al,Ti,and Nb,increases the undercooling,and limits the growth of precipitates.Consequently,the sizes of MC carbides,eutectic(γ+γ′),and primaryγ′significantly decrease,but the area fraction of eutectic(γ+γ′)linerly increases as the cooling rate rises.Thus moderate cooling rate(such as 30℃·min^(-1))should be selected during the solidification process of GH4975 alloy.展开更多
Conglomerate rock's complex and heterogeneous microstructure significantly affects its mechanical properties,especially under dynamic loading.However,research on their dynamic behavior and fracture mechanisms is l...Conglomerate rock's complex and heterogeneous microstructure significantly affects its mechanical properties,especially under dynamic loading.However,research on their dynamic behavior and fracture mechanisms is limited.Through uniaxial compression tests and split Hopkinson pressure bar(SHPB)impact tests,the dynamic compressive mechanical properties and fracture mechanisms of conglomerate rock were studied.Nanoindentation and high-resolution X-ray computed tomography were employed to analyze the micro-mechanical behavior and internal structure of the conglomerate rock.Results indicate significant differences in mechanical properties between different gravel particles and cementing materials,with initial fractures primarily distributed at the gravel-cement interfaces.The dynamic mechanical properties of conglomerate rocks exhibit a clear strain rate dependency.Based on the stress−strain curves and failure characteristics,the dynamic compressive mechanical behavior can be categorized into two types using a critical strain rate.The dynamic compressive strength,peak strain,and toughness of conglomerate rock increased with the strain rate,with the strength at 54 s−1 being 2.6 times that at 6 s−1.The dynamic compressive fracture mechanism of conglomerate rock is related to the strain rate and microstructure;at low strain rates,gravel distribution is the key factor,whereas at high strain rates,gravel content becomes critical.展开更多
High-performance fiber fabrics and composites experienced transverse compression deformation at ultrahigh strain rates near the impact point when subjected to high-velocity impacts,which significantly affected their b...High-performance fiber fabrics and composites experienced transverse compression deformation at ultrahigh strain rates near the impact point when subjected to high-velocity impacts,which significantly affected their ballistic limits.In this paper,a fiber-scale experimental method for characterizing ultrahigh strain-rate transverse compression behavior was proposed.To begin with,in order to measure the extremely low stress and strain in small specimens,the conventional Hopkinson bar was reduced to the hundred-micron scale,thereby achieving wave impedance matching with single fibers.In addition,tangential and normal laser Doppler velocimetry(LDV)methods were employed to realize non-contact,high-precision,and high-speed axial velocity measurements of micron-scale incident and transmission bars,respectively.Meanwhile,a microscopic observation system was used to facilitate the installation of miniature fiber samples.The experimental setup and procedures were introduced,and the system accuracy was verified through sample-free loading tests based on one-dimensional stress wave propagation theory.Dynamic compression experiments on Graphene-UHMWPE fibers were carried out,followed by post-compression microstructural characterization via scanning electron microscopy(SEM).Results demonstrated that successful mechanical characterization was achieved at strain rates exceeding 105,an order of magnitude higher than the previously reported maximum rates.Furthermore,during the loading process,the fibers underwent uniform compression deformation while exhibiting pronounced strain-rate effects.This method offers a novel approach for dynamic mechanical characterization of microscale single fibers,enabling the development of comprehensive strain-ratedependent material models to guide the design of advanced composites and high-performance fibers.展开更多
When a porous rock is subjected to overall compressive loading,either increasing pore pressure or decreasing confining pressure could result in rock failure.The stress path and the applied pressure change rate may aff...When a porous rock is subjected to overall compressive loading,either increasing pore pressure or decreasing confining pressure could result in rock failure.The stress path and the applied pressure change rate may affect the initiation and propagation of fractures within brittle materials.Understanding the physical mechanisms leading to failure is crucial for underground engineering applications and geo-energy exploration and storage.We conducted triaxial compression experiments on porous Bentheim sandstone samples at different stress paths and pressure change rates.First,at a constant confining pressure of 35 MPa and pore pressure of 5 MPa,intact cylindrical samples were axially loaded up to about 85%of the peak strength.Subsequently,the axial piston position was fixed,and then either the pore pressure was increased or the confining pressure was decreased at two different rates(0.5 MPa/min or 2 MPa/min),leading to final catastrophic failure.The mechanical results revealed that samples subjected to higher rates of decreasing effective confining pressure exhibited larger stress drop rates,higher slip rates,higher total breakdown work,higher rates of acoustic emissions(AEs)before failure,and higher post-failure AE decay rates.In contrast,the applied stress path did not significantly affect rock failure characteristics.Comparison of located AE events with post-mortem microstructures of deformed samples shows a good agreement.The AE source type determined from the P-wave first-motion polarity shows that shear failure dominated the fracture process when approaching failure.Gutenberg-Richter b-values revealed a significant decrease before failure in all tests.Our results indicate that,in contrast to the stress path,the rate of effective stress change strongly affects fracturing behavior and AE rate changes.展开更多
The development of metallic mineral resources generates a significant amount of solid waste,such as tailings and waste rock.Cemented tailings and waste-rock backfill(CTWB)is an effective method for managing and dispos...The development of metallic mineral resources generates a significant amount of solid waste,such as tailings and waste rock.Cemented tailings and waste-rock backfill(CTWB)is an effective method for managing and disposing of this mining waste.This study employs a macro-meso-micro testing method to investigate the effects of the waste rock grading index(WGI)and loading rate(LR)on the uniaxial compressive strength(UCS),pore structure,and micromorphology of CTWB materials.Pore structures were analyzed using scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP).The particles(pores)and cracks analysis system(PCAS)software was used to quantitatively characterize the multi-scale micropores in the SEM images.The key findings indicate that the macroscopic results(UCS)of CTWB materials correspond to the microscopic results(pore structure and micromorphology).Changes in porosity largely depend on the conditions of waste rock grading index and loading rate.The inclusion of waste rock initially increases and then decreases the UCS,while porosity first decreases and then increases,with a critical waste rock grading index of 0.6.As the loading rate increases,UCS initially rises and then falls,while porosity gradually increases.Based on MIP and SEM results,at waste rock grading index 0.6,the most probable pore diameters,total pore area(TPA),pore number(PN),maximum pore area(MPA),and area probability distribution index(APDI)are minimized,while average pore form factor(APF)and fractal dimension of pore porosity distribution(FDPD)are maximized,indicating the most compact pore structure.At a loading rate of 12.0 mm/min,the most probable pore diameters,TPA,PN,MPA,APF,and APDI reach their maximum values,while FDPD reaches its minimum value.Finally,the mechanism of CTWB materials during compression is analyzed,based on the quantitative results of UCS and porosity.The research findings play a crucial role in ensuring the successful application of CTWB materials in deep metal mines.展开更多
One of the key challenges for underground rock reservoirs is ensuring prevention of the unwanted fluid leakage through rock fracture networks during their service life.Microbial-induced calcium carbonate precipitation...One of the key challenges for underground rock reservoirs is ensuring prevention of the unwanted fluid leakage through rock fracture networks during their service life.Microbial-induced calcium carbonate precipitation(MICP)technology has emerged as a promising bio-healing method for rock fractures with small apertures.In this study,a new“three-stage”injection strategy-based MICP(TS-MICP)bio-healing method was proposed,aiming to achieve a“three-high”performance that includes high bridging rate,high mechanical strength,and high homogeneity.A series of meter-scale rock fracture models were prepared to conduct TS-MICP grouting tests.Compared with the traditional injection strategy-based biohealing methods,the TS-MICP method significantly improved the bridging rate(32.1%e89.5%),mechanical properties(0.138e1.023 MPa),and homogeneity of CaCO_(3)precipitation(334.4%).Additionally,it achieved a higher material utilization rate(1.72 times higher),reducing the consumption of cementation solution(CS)by 258.8%,thereby demonstrating greater potential for field applications.The underlying mechanism for achieving high bridging rate and high homogeneity in CaCO_(3)precipitation can be attributed to the synergistic effects of the coupling injection strategy,which optimizes the advantages at each stage.In stage I,under the influence of gravity,the rapid flocculation and hydrogen bonding interactions of organic matter lead to formation of the dense and high-strength CaCO_(3)precipitation at the bottom using a low-concentration bacterial suspension(BS).This process establishes bridging steps along the wall sides for subsequent uniform CaCO_(3)precipitation.In stage II,concentrated BS is utilized to produce looser CaCO_(3)flocculation,which precipitates uniformly on the pre-existing bridging steps.In stage III,a two-step injection strategy was employed to reinforce the loose CaCO_(3)crystals formed in stages I and II,and finally forms a strong bridging effect with“three-high”performance.展开更多
Within the domain of Intelligent Group Systems(IGSs),this paper develops a resourceaware multitarget Constant False Alarm Rate(CFAR)detection framework for multisite MIMO radar systems.It underscores the necessity of ...Within the domain of Intelligent Group Systems(IGSs),this paper develops a resourceaware multitarget Constant False Alarm Rate(CFAR)detection framework for multisite MIMO radar systems.It underscores the necessity of managing finite transmit and receive antennas and transmit power systematically to enhance detection performance.To tackle the multidimensional resource optimization challenge,we introduce a Cooperative Transmit-Receive Antenna Selection and Power Allocation(CTRSPA)strategy.It employs a perception-action cycle that incorporates uncertain external support information to optimize worst-case detection performance with multiple targets.First,we derive a closed-form expression that incorporates uncertainty for the noncoherent integration squared-law detection probability using the Neyman-Pearson criterion.Subsequently,a joint optimization model for antenna selection and power allocation in CFAR detection is formulated,incorporating practical radar resource constraints.Mathematically,this represents an NPhard problem involving coupled continuous and Boolean variables.We propose a three-stage method—Reformulation,Node Picker,and Convex Power Allocation—that capitalizes on the independent convexity of the optimization model for each variable,ensuring a near-optimal result.Simulations confirm the approach's effectiveness,efficiency,and timeliness,particularly for large-scale radar networks,and reveal the impact of threat levels,system layout,and detection parameters on resource allocation.展开更多
Vehicular communication systems rely on secure vehicle-to-vehicle(V2V)communications for safety-critical information exchange.However,the presence of eavesdropping vehicles poses a significant challenge.This paper inv...Vehicular communication systems rely on secure vehicle-to-vehicle(V2V)communications for safety-critical information exchange.However,the presence of eavesdropping vehicles poses a significant challenge.This paper investigates the security of V2V communications in reconfigurable intelligent surface(RIS)-assisted vehicular communication systems with spectrum sharing.It proposes a three-stage alternating optimization(TSAO)algorithm to address the complex problem of multiple eavesdropped V2V links that reuse the spectrum already occupied by vehicle-toinfrastructure(V2I)links.To solve the mixed-integer and non-convex optimization problem due to coupled variables and complex constraints,the algorithm decomposes the original problem into three easily solvable sub-problems:RIS reflection coefficient optimization,vehicle transmission power optimization,and spectrum sharing optimization.First,the RIS reflection coefficients are optimized by using the penalty convex-concave procedure(CCP)method.Second,the optimal power points are determined in the power optimization sub-problem.Finally,the spectrum sharing optimization sub-problem is constructed as a weighted bipartite graph matching problem and solved by using the optimal matching algorithm.The TSAO algorithm not only maximizes the sum V2V secrecy rate but also ensures the quality-of-service(QoS)requirements of the V2I links.Simulation results validate the superiority of the proposed algorithm and highlight the improvement in the sum V2V secrecy rate achieved by utilizing RIS technology in vehicular communication systems with spectrum sharing.展开更多
As a critical department ensuring the sterility of hospital instruments,the Sterile Supply Center(SSC)directly impacts the sterility status of clinical instruments through its sterilization qualification rate.Geriatri...As a critical department ensuring the sterility of hospital instruments,the Sterile Supply Center(SSC)directly impacts the sterility status of clinical instruments through its sterilization qualification rate.Geriatric patients,due to physiological decline and compromised immune function,constitute a high-risk group for hospital-acquired infections,with more stringent requirements for instrument sterility.This paper analyzes the current status and influencing factors of sterilization qualification rates in SSCs,explores the mechanistic association between sterilization qualification rates and infections in geriatric departments,and proposes targeted strategies to improve sterilization qualification rates.It highlights the pivotal role of SSC instrument sterilization in infection prevention and control for geriatric patients,providing theoretical basis and practical guidance for optimizing SSC management,reducing infection rates in geriatric departments,and ensuring the safety of elderly patients’medical care.These findings aim to enhance overall infection management standards in hospitals.展开更多
On January 19,2026,China's first structural interest rate cut of the year took effect.The People's Bank of China announced a 0.25 percentage point reduction in relending and rediscount rates,targeting key sect...On January 19,2026,China's first structural interest rate cut of the year took effect.The People's Bank of China announced a 0.25 percentage point reduction in relending and rediscount rates,targeting key sectors like small and micro enterprises(SMEs),technological innovation,and green transition.For the textile industry,where small and medium-sized enterprises account for over 90%of traditional manufacturing,the policy benefits will inject strong momentum into the high-quality development from multiple dimensions,including reduced financing costs,support for transformation funds,and expansion of foreign trade markets.展开更多
OBJECTIVE: To evaluate the effects of Guasha therapy on the rating of perceived exertion(RPE) scale score, and heart rate variability(HRV).METHODS: A randomized controlled trial of Guasha(skin scraping) was compared w...OBJECTIVE: To evaluate the effects of Guasha therapy on the rating of perceived exertion(RPE) scale score, and heart rate variability(HRV).METHODS: A randomized controlled trial of Guasha(skin scraping) was compared with a sham scraping group and control group. Sixteen sessions within an 8-week period were completed. Sixty-five male weightlifters who had undergone normal weightlifting training for a mean of 5 years before study commencement were recruited. The RPEscale score of "snatch", "clean and jerk" maneuvers(85% of one-repetition maximum), and HRV were measured before and after the intervention.RESULTS: The RPE scale score for snatch, clean and jerk were reduced significantly after intervention in the Guasha group and sham group. However, there was a significant difference in the low frequency(LF) domain and LF/high frequency(HF) ratio(P <0.05): the LF domain decreased, and the LF/HF ratio decreased.CONCLUSION: Guasha could be used to reduce the RPE scale score, and increase the response to HRV.Guasha could be considered as an alternative to some types of recovery from sports training.展开更多
Simulation law and physical simulation were used to study the kinematic behavior of inclusions in electromagnetic separation. It was found that velocity of spherical non metallic particles shares different functions i...Simulation law and physical simulation were used to study the kinematic behavior of inclusions in electromagnetic separation. It was found that velocity of spherical non metallic particles shares different functions in different Reynolds number range. The function of spherical particle’s velocity has been got by confirming the relationship between Reynolds number and resistance coefficient when Reynolds number is 0.2 ～10. For non spherical particles, the moving behavior is influenced by shape and orientation while spherical coefficient has nothing to do with the velocity of irregular particles. The influence of orientation of cuboid particle on the electromagnetic expulsive force has been indicated by numerical computation. [展开更多
In order to design the relief system size of di-tert-butyl peroxide(DTBP) storage tanks,the runaway re-action of DTBP was simulated by accelerating rate calorimeter(ARC).The results indicated that under adiabatic cond...In order to design the relief system size of di-tert-butyl peroxide(DTBP) storage tanks,the runaway re-action of DTBP was simulated by accelerating rate calorimeter(ARC).The results indicated that under adiabatic conditions the initial exothermic temperature was 102.6 ℃,the maximum self-heating rate was 3.095×107 ℃·min-1,the maximum self-heating temperature was 375.9 ℃,and the pressure produced by unit mass was 4.512 MPa·g-1.Judged by ARC test,the emergency relief system for DTBP was a hybrid system.Based on Design Institute for Emergency Relief System(DIERS) method,the releasing mass flow rate W was determined by Leung methods,and the mass velocity G was calculated by two modified Omega methods.The two relief sizes calculated by monograph Omega method and arithmetic Omega method are close,with only 0.63% relative error.The monograph Omega method is more convenient to apply.展开更多
The determination of the local cooling rate has a great significance in optimizing the parameters of electroslag remelting(ESR)and improving the quality of the ingots.An innovative method was proposed for calibrating ...The determination of the local cooling rate has a great significance in optimizing the parameters of electroslag remelting(ESR)and improving the quality of the ingots.An innovative method was proposed for calibrating the local cooling rate of M42 high-speed steel(HSS)in the ESR process.After resolidification at different cooling rates under high-temperature laser confocal microscopy,the carbide network spacing of the specimen was observed using a scanning electron microscope.A functional relationship between the cooling rate and average carbide network spacing was established.The average local cooling rate of the solidification process of the M42 HSS ingot was calibrated.The results show that the higher the cool-ing rate,the smaller the network spacing of the carbides.For the steel ingot with a diameter of 360 mm,the average local cooling rate was 0.562℃/s at the surface,0.057℃/s at the position of 0.25D(where D is the diameter of the ingot),and 0.046℃/s at the center of the ingot.展开更多
Accurate and reliable river flow information is critical to planning and management for sustainable water resources utilization. Most of engineering activities related to hydrologic designs, flood, drought, reservoirs...Accurate and reliable river flow information is critical to planning and management for sustainable water resources utilization. Most of engineering activities related to hydrologic designs, flood, drought, reservoirs and their operations are heavily dependent on the river flow information derived from river rating curve. The rating curve for a given river section is normally developed from a set of direct stage-discharge measurements for different periods. This involves considerable labour, risk and resources, and presupposes a complex and extensive measuring survey. Extrapolating the rating curve beyond the measured range, as common in many cases, is fraught with errors and uncertainties, due to the complex hydraulic behaviour of the surface water profile in transition from section, channel, downstream and flood plain controls which are often poorly understood with direct measurements. Hydraulic modeling has recently emerged as one of the more promising methods to efficiently develop accurate rating curves for a river section with simple or complex hydraulic structures and conditions. This paper explores the use of a Hydraulic Engineering Center-River Analysis System (HEC-RAS) model to review and develop river rating curves for three hydrometric stations on two rivers in Kwale, coastal Kenya. The HEC-RAS models were set up based on topographical (cross section and longitudinal) survey data for the reaches and engineering drawings for the hydraulic structures commonly used as section controls for flow measurement. The model was calibrated under unsteady state conditions against measured stage-discharge data which were captured using a Velocity Current Meter (Valeport) and an Acoustic Doppler Current Profiler (ADCP) for both low and high flow. The rating curves were extracted from model results and the uncertainty associated with each rating curve analyzed. The results obtained by the HEC-RAS model were satisfactory and deemed acceptable for predicting discharge across the stage range at each river section.展开更多
基金supported in part by the National Key R&D Program of China under Grant 2021YFB1714100in part by the Shenzhen Science and Technology Program,China,under Grant JCYJ20220531101015033.
文摘With increasing density and heterogeneity in unlicensed wireless networks,traditional MAC protocols,such as Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA)in Wi-Fi networks,are experiencing performance degradation.This is manifested in increased collisions and extended backoff times,leading to diminished spectrum efficiency and protocol coordination.Addressing these issues,this paper proposes a deep-learning-based MAC paradigm,dubbed DL-MAC,which leverages spectrum data readily available from energy detection modules in wireless devices to achieve the MAC functionalities of channel access,rate adaptation,and channel switch.First,we utilize DL-MAC to realize a joint design of channel access and rate adaptation.Subsequently,we integrate the capability of channel switching into DL-MAC,enhancing its functionality from single-channel to multi-channel operations.Specifically,the DL-MAC protocol incorporates a Deep Neural Network(DNN)for channel selection and a Recurrent Neural Network(RNN)for the joint design of channel access and rate adaptation.We conducted real-world data collection within the 2.4 GHz frequency band to validate the effectiveness of DL-MAC.Experimental results demonstrate that DL-MAC exhibits significantly superior performance compared to traditional algorithms in both single and multi-channel environments,and also outperforms single-function designs.Additionally,the performance of DL-MAC remains robust,unaffected by channel switch overheads within the evaluation range.
基金National Key Research and Development Program of China(2024YFB4610803)。
文摘The fatigue crack growth rate of a novel Ti-6Al-4V-1Mo titanium alloy,which is developed for laser directed energy deposition technique,was investigated before and after cyclic heat treatment(CHT).Changes in microstructure,fracture surfaces,and crack growth paths were analyzed before and after CHT.Results indicate that in the stable crack growth region,the growth rates for the as-deposited and cyclic heat-treated specimens follow the relationships da/dN=1.8651×10^(−8)(ΔK)^(3.2271)and da/dN=1.4112×10^(−8)(ΔK)^(3.1125),respectively.Compared with that at the as-deposited state,the microstructure after CHT is transformed from a uniform basket-weave microstructure to a dual-phase microstructure consisting of near-sphericalαandβ-transformed matrix phases.The cyclic process also disrupts the continuity of the grain boundaryα(αGB)at the primaryβ-phase grain boundary.The coarsening of primaryαand the disruption ofαGB continuity are the primary factors to release stress concentration and promote crack deflection,thereby decreasing the fatigue crack growth rate.Additionally,the increased occurrence of crack branching,secondary cracking,and crack bridging in cyclic heat-treated specimens further reduces the crack driving force and slows the fatigue crack growth rate.
基金Shaanxi Provincial People’s Hospital Science and Technology Development Incubation Fund,“Research on the Role and Mechanism of PIGU in Regulating MUC-1 in Gastric Cancer Immune Escape”(Project No.:2023YJY-29)Shaanxi Provincial Natural Science Basic Research Program,“Research on the Mechanism and Clinical Significance of miR-140-5p Related to Gastric Cancer Recurrence and Metastasis”(Project No.:2023-JC-YB-639)。
文摘Early-stage gastric cancer;Extent of lymph node dissection;D1 dissection;D2 dissection;Recurrence rate;Survival rateObjective:To investigate the impact of different lymph node dissection scopes on postoperative recurrence and survival rates in patients with early gastric cancer,providing evidence-based support for optimizing clinical surgical plans.Methods:A retrospective analysis was conducted on the clinical data of 100 patients with early gastric cancer who underwent surgical treatment at our hospital from October 2021 to October 2023.Patients were divided into Group D1(n=50)and Group D2(n=50)based on the extent of lymph node dissection.Group D1 underwent limited lymph node dissection(dissection of the first station of lymph nodes around the stomach),while Group D2 underwent standard lymph node dissection(dissection of the first and second stations of lymph nodes around the stomach).Surgical-related indicators,the incidence of postoperative complications,the 2-year recurrence rate,and the 2-year survival rate were compared between the two groups of patients.Results:The operative time,intraoperative blood loss,postoperative hospital stay,and the number of lymph nodes dissected were significantly higher in the D2 group than in the D1 group(all P<0.001).The overall incidence of postoperative complications was higher in the D1 group than in the D2 group,but the difference was not statistically significant(χ^(2)=0.884,P=0.766).After a 2-year follow-up,the recurrence rate was significantly higher in the D1 group than in the D2 group(χ^(2)=4.000,P=0.046).The 2-year survival rate was significantly lower in the D1 group than in the D2 group(χ^(2)=5.005,P=0.025).A total of 100 patients with early-stage gastric cancer were grouped according to the depth of invasion,degree of differentiation,and lymph node metastasis status,and the recurrence rates of different subgroups were compared.The results showed that the recurrence rate was higher in patients with T1b stage than in those with T1a stage(χ^(2)=5.005,P=0.025),higher in poorly differentiated patients than in moderately and well-differentiated patients(χ^(2)=4.155,P=0.042),and higher in patients with lymph node metastasis than in those without lymph node metastasis(χ^(2)=4.512,P=0.034).Conclusion:Compared with D1 limited lymph node dissection,D2 standard lymph node dissection can significantly reduce the postoperative recurrence rate and improve the 2-year survival rate in patients with early-stage gastric cancer without significantly increasing the risk of postoperative complications.Although the surgical trauma is slightly greater,the overall prognosis is better,making it a preferred surgical treatment option for patients with early-stage gastric cancer.
基金Supported by Science and Technology Project of China Tobacco Zhejiang Industrial Co.,Ltd.(2023330000340093).
文摘[Objectives]To investigate the effects of different planting densities and nitrogen application rates on the yield and quality of the tobacco cultivar Chuxue 80.[Methods]A field experiment was conducted in Hubei Province,evaluating various combinations of planting density and nitrogen rate for Chuxue 80.[Results]At the maturity stage,the TN1 treatment(5 kg N per 667 m^(2) with a density of 1900 plants per 667 m^(2))demonstrated the most favorable agronomic performance.The TN9 treatment(11 kg N per 667 m^(2) with a density of 1110 plants per 667 m^(2))achieved the highest wrapper tobacco yield and output value.Meanwhile,the TN5 treatment(8 kg N per 667 m^(2) with a density of 1515 plants per 667 m^(2))resulted in the best smoking quality.[Conclusions]The TN9 treatment,with a planting density of 1110 plants per 667 m^(2) and a nitrogen application rate of 11 kg per 667 m^(2),is recommended as the optimal cultivation practice for Chuxue 80 in Hubei Province.
文摘Apparel exports China:The decline in exports widened from January to September(-2.4%,compared to-0.2%in January-June).Exports to the EU increased(+5.9%),though the growth rate moderated.Exports to the US saw a larger contraction(January-June:-1.6%,January-September:-8.2%).While exports to ASEAN countries still fell by over 10%(-17.7%),shipments to the Philippines(+6.9%),Indonesia(+19.0%),and Cambodia(+64.9%)demonstrated stronger growth performance within the year.Regarding tariffs,on October 30,China and the US agreed to lower the rates on goods subject to additional duties(effectively reducing the average tariff rate on Chinese imports to the US from about 57%to approximately 47%,though this remains significantly higher than the 19.5%overall average rate applied to other countries).
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52474362,52174317 and 51904146)the General Project Funded by Liaoning Province Education Department(Grant No.JYTMS20230943)。
文摘The high-alloyed wrought superalloy GH4975 tends to form coarse MC carbides and eutectic(γ+γ′)phases,which adversely affect the cogging and homogenization process.To provide theoretical guidance for control of MC carbides and eutectic(γ+γ′)formation,differential thermal analysis(DTA)was utilized to investigate the effect of cooing rate(10-90℃·min^(-1))on solidification behavior and micro-segregation of GH4975 alloy.According to the thermodynamic calculation and distribution characteristics of precipitates,the MC carbides can act as nucleation sites forγdendrites,but the nucleation ofγdendrites becomes less dependent on the MC carbide primers at higher cooling rates.As theγdendrites grow,the elements including Ti and Nb gradually accumulate in the residual liquid and leads to the formation of more MC carbides near the interdendritic region.Finally,the solidification is terminated with the formation of eutectic(γ+γ′).With an increase in cooling rate,the liquidus temperature rises,but the solidus temperature decreases,and thus the solidification range is obviously enlarged.The dendritic structure is significantly refined by the increase of cooling rate.The secondary dendrite arm spacing,λ_(2),as a function of cooling rate,T,can be expressed asλ_(2)=216.78T^(-0.42).Moreover,the increasing cooling rate weakens the back diffusion of Al,Ti,and Nb,increases the undercooling,and limits the growth of precipitates.Consequently,the sizes of MC carbides,eutectic(γ+γ′),and primaryγ′significantly decrease,but the area fraction of eutectic(γ+γ′)linerly increases as the cooling rate rises.Thus moderate cooling rate(such as 30℃·min^(-1))should be selected during the solidification process of GH4975 alloy.
基金Project(51978674)supported by the National Natural Science Foundation of China。
文摘Conglomerate rock's complex and heterogeneous microstructure significantly affects its mechanical properties,especially under dynamic loading.However,research on their dynamic behavior and fracture mechanisms is limited.Through uniaxial compression tests and split Hopkinson pressure bar(SHPB)impact tests,the dynamic compressive mechanical properties and fracture mechanisms of conglomerate rock were studied.Nanoindentation and high-resolution X-ray computed tomography were employed to analyze the micro-mechanical behavior and internal structure of the conglomerate rock.Results indicate significant differences in mechanical properties between different gravel particles and cementing materials,with initial fractures primarily distributed at the gravel-cement interfaces.The dynamic mechanical properties of conglomerate rocks exhibit a clear strain rate dependency.Based on the stress−strain curves and failure characteristics,the dynamic compressive mechanical behavior can be categorized into two types using a critical strain rate.The dynamic compressive strength,peak strain,and toughness of conglomerate rock increased with the strain rate,with the strength at 54 s−1 being 2.6 times that at 6 s−1.The dynamic compressive fracture mechanism of conglomerate rock is related to the strain rate and microstructure;at low strain rates,gravel distribution is the key factor,whereas at high strain rates,gravel content becomes critical.
基金financial support provided by the National Natural Science Foundation of China(Grant No.12302472)the Science and Technology Support Program of Jiangsu Province(Grant No.BK20230874)+2 种基金the Aeronautical Science Fund(ASF)(Grant No.2023Z057052005)the Research Fund of State Key Laboratory of Mechanics and Control for Aerospace Structures(Nanjing University of Aeronautics and Astronautics)(Grant No.MCAS-I-0124G02)the funding received from Jiangsu Hanvo Safety Product Co.,Ltd。
文摘High-performance fiber fabrics and composites experienced transverse compression deformation at ultrahigh strain rates near the impact point when subjected to high-velocity impacts,which significantly affected their ballistic limits.In this paper,a fiber-scale experimental method for characterizing ultrahigh strain-rate transverse compression behavior was proposed.To begin with,in order to measure the extremely low stress and strain in small specimens,the conventional Hopkinson bar was reduced to the hundred-micron scale,thereby achieving wave impedance matching with single fibers.In addition,tangential and normal laser Doppler velocimetry(LDV)methods were employed to realize non-contact,high-precision,and high-speed axial velocity measurements of micron-scale incident and transmission bars,respectively.Meanwhile,a microscopic observation system was used to facilitate the installation of miniature fiber samples.The experimental setup and procedures were introduced,and the system accuracy was verified through sample-free loading tests based on one-dimensional stress wave propagation theory.Dynamic compression experiments on Graphene-UHMWPE fibers were carried out,followed by post-compression microstructural characterization via scanning electron microscopy(SEM).Results demonstrated that successful mechanical characterization was achieved at strain rates exceeding 105,an order of magnitude higher than the previously reported maximum rates.Furthermore,during the loading process,the fibers underwent uniform compression deformation while exhibiting pronounced strain-rate effects.This method offers a novel approach for dynamic mechanical characterization of microscale single fibers,enabling the development of comprehensive strain-ratedependent material models to guide the design of advanced composites and high-performance fibers.
文摘When a porous rock is subjected to overall compressive loading,either increasing pore pressure or decreasing confining pressure could result in rock failure.The stress path and the applied pressure change rate may affect the initiation and propagation of fractures within brittle materials.Understanding the physical mechanisms leading to failure is crucial for underground engineering applications and geo-energy exploration and storage.We conducted triaxial compression experiments on porous Bentheim sandstone samples at different stress paths and pressure change rates.First,at a constant confining pressure of 35 MPa and pore pressure of 5 MPa,intact cylindrical samples were axially loaded up to about 85%of the peak strength.Subsequently,the axial piston position was fixed,and then either the pore pressure was increased or the confining pressure was decreased at two different rates(0.5 MPa/min or 2 MPa/min),leading to final catastrophic failure.The mechanical results revealed that samples subjected to higher rates of decreasing effective confining pressure exhibited larger stress drop rates,higher slip rates,higher total breakdown work,higher rates of acoustic emissions(AEs)before failure,and higher post-failure AE decay rates.In contrast,the applied stress path did not significantly affect rock failure characteristics.Comparison of located AE events with post-mortem microstructures of deformed samples shows a good agreement.The AE source type determined from the P-wave first-motion polarity shows that shear failure dominated the fracture process when approaching failure.Gutenberg-Richter b-values revealed a significant decrease before failure in all tests.Our results indicate that,in contrast to the stress path,the rate of effective stress change strongly affects fracturing behavior and AE rate changes.
基金Project(2022YFC2904103)supported by the National Key Research and Development Program of ChinaProjects(52374112,52274108)supported by the National Natural Science Foundation of China+1 种基金Projects(BX20220036,BX20230041)supported by the Postdoctoral Innovation Talents Support Program,ChinaProject(2232080)supported by the Beijing Natural Science Foundation,China。
文摘The development of metallic mineral resources generates a significant amount of solid waste,such as tailings and waste rock.Cemented tailings and waste-rock backfill(CTWB)is an effective method for managing and disposing of this mining waste.This study employs a macro-meso-micro testing method to investigate the effects of the waste rock grading index(WGI)and loading rate(LR)on the uniaxial compressive strength(UCS),pore structure,and micromorphology of CTWB materials.Pore structures were analyzed using scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP).The particles(pores)and cracks analysis system(PCAS)software was used to quantitatively characterize the multi-scale micropores in the SEM images.The key findings indicate that the macroscopic results(UCS)of CTWB materials correspond to the microscopic results(pore structure and micromorphology).Changes in porosity largely depend on the conditions of waste rock grading index and loading rate.The inclusion of waste rock initially increases and then decreases the UCS,while porosity first decreases and then increases,with a critical waste rock grading index of 0.6.As the loading rate increases,UCS initially rises and then falls,while porosity gradually increases.Based on MIP and SEM results,at waste rock grading index 0.6,the most probable pore diameters,total pore area(TPA),pore number(PN),maximum pore area(MPA),and area probability distribution index(APDI)are minimized,while average pore form factor(APF)and fractal dimension of pore porosity distribution(FDPD)are maximized,indicating the most compact pore structure.At a loading rate of 12.0 mm/min,the most probable pore diameters,TPA,PN,MPA,APF,and APDI reach their maximum values,while FDPD reaches its minimum value.Finally,the mechanism of CTWB materials during compression is analyzed,based on the quantitative results of UCS and porosity.The research findings play a crucial role in ensuring the successful application of CTWB materials in deep metal mines.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC3007102)the National Natural Science Foundation of China(Grant Nos.42477188 and 41925012).
文摘One of the key challenges for underground rock reservoirs is ensuring prevention of the unwanted fluid leakage through rock fracture networks during their service life.Microbial-induced calcium carbonate precipitation(MICP)technology has emerged as a promising bio-healing method for rock fractures with small apertures.In this study,a new“three-stage”injection strategy-based MICP(TS-MICP)bio-healing method was proposed,aiming to achieve a“three-high”performance that includes high bridging rate,high mechanical strength,and high homogeneity.A series of meter-scale rock fracture models were prepared to conduct TS-MICP grouting tests.Compared with the traditional injection strategy-based biohealing methods,the TS-MICP method significantly improved the bridging rate(32.1%e89.5%),mechanical properties(0.138e1.023 MPa),and homogeneity of CaCO_(3)precipitation(334.4%).Additionally,it achieved a higher material utilization rate(1.72 times higher),reducing the consumption of cementation solution(CS)by 258.8%,thereby demonstrating greater potential for field applications.The underlying mechanism for achieving high bridging rate and high homogeneity in CaCO_(3)precipitation can be attributed to the synergistic effects of the coupling injection strategy,which optimizes the advantages at each stage.In stage I,under the influence of gravity,the rapid flocculation and hydrogen bonding interactions of organic matter lead to formation of the dense and high-strength CaCO_(3)precipitation at the bottom using a low-concentration bacterial suspension(BS).This process establishes bridging steps along the wall sides for subsequent uniform CaCO_(3)precipitation.In stage II,concentrated BS is utilized to produce looser CaCO_(3)flocculation,which precipitates uniformly on the pre-existing bridging steps.In stage III,a two-step injection strategy was employed to reinforce the loose CaCO_(3)crystals formed in stages I and II,and finally forms a strong bridging effect with“three-high”performance.
基金supported by the National Natural Science Foundation of China(Nos.62071482 and 62471348)the Shaanxi Association of Science and Technology Youth Talent Support Program Project,China(No.20230137)+1 种基金the Innovative Talents Cultivate Program for Technology Innovation Team of Shaanxi Province,China(No.2024RS-CXTD-08)the Youth Innovation Team of Shaanxi Universities,China。
文摘Within the domain of Intelligent Group Systems(IGSs),this paper develops a resourceaware multitarget Constant False Alarm Rate(CFAR)detection framework for multisite MIMO radar systems.It underscores the necessity of managing finite transmit and receive antennas and transmit power systematically to enhance detection performance.To tackle the multidimensional resource optimization challenge,we introduce a Cooperative Transmit-Receive Antenna Selection and Power Allocation(CTRSPA)strategy.It employs a perception-action cycle that incorporates uncertain external support information to optimize worst-case detection performance with multiple targets.First,we derive a closed-form expression that incorporates uncertainty for the noncoherent integration squared-law detection probability using the Neyman-Pearson criterion.Subsequently,a joint optimization model for antenna selection and power allocation in CFAR detection is formulated,incorporating practical radar resource constraints.Mathematically,this represents an NPhard problem involving coupled continuous and Boolean variables.We propose a three-stage method—Reformulation,Node Picker,and Convex Power Allocation—that capitalizes on the independent convexity of the optimization model for each variable,ensuring a near-optimal result.Simulations confirm the approach's effectiveness,efficiency,and timeliness,particularly for large-scale radar networks,and reveal the impact of threat levels,system layout,and detection parameters on resource allocation.
基金National Natural Science Foundation of China(Nos.61772130,71171045 and 61901104)Innovation Program of Shanghai Municipal Education Commission,China(No.14YZ130)。
文摘Vehicular communication systems rely on secure vehicle-to-vehicle(V2V)communications for safety-critical information exchange.However,the presence of eavesdropping vehicles poses a significant challenge.This paper investigates the security of V2V communications in reconfigurable intelligent surface(RIS)-assisted vehicular communication systems with spectrum sharing.It proposes a three-stage alternating optimization(TSAO)algorithm to address the complex problem of multiple eavesdropped V2V links that reuse the spectrum already occupied by vehicle-toinfrastructure(V2I)links.To solve the mixed-integer and non-convex optimization problem due to coupled variables and complex constraints,the algorithm decomposes the original problem into three easily solvable sub-problems:RIS reflection coefficient optimization,vehicle transmission power optimization,and spectrum sharing optimization.First,the RIS reflection coefficients are optimized by using the penalty convex-concave procedure(CCP)method.Second,the optimal power points are determined in the power optimization sub-problem.Finally,the spectrum sharing optimization sub-problem is constructed as a weighted bipartite graph matching problem and solved by using the optimal matching algorithm.The TSAO algorithm not only maximizes the sum V2V secrecy rate but also ensures the quality-of-service(QoS)requirements of the V2I links.Simulation results validate the superiority of the proposed algorithm and highlight the improvement in the sum V2V secrecy rate achieved by utilizing RIS technology in vehicular communication systems with spectrum sharing.
文摘As a critical department ensuring the sterility of hospital instruments,the Sterile Supply Center(SSC)directly impacts the sterility status of clinical instruments through its sterilization qualification rate.Geriatric patients,due to physiological decline and compromised immune function,constitute a high-risk group for hospital-acquired infections,with more stringent requirements for instrument sterility.This paper analyzes the current status and influencing factors of sterilization qualification rates in SSCs,explores the mechanistic association between sterilization qualification rates and infections in geriatric departments,and proposes targeted strategies to improve sterilization qualification rates.It highlights the pivotal role of SSC instrument sterilization in infection prevention and control for geriatric patients,providing theoretical basis and practical guidance for optimizing SSC management,reducing infection rates in geriatric departments,and ensuring the safety of elderly patients’medical care.These findings aim to enhance overall infection management standards in hospitals.
文摘On January 19,2026,China's first structural interest rate cut of the year took effect.The People's Bank of China announced a 0.25 percentage point reduction in relending and rediscount rates,targeting key sectors like small and micro enterprises(SMEs),technological innovation,and green transition.For the textile industry,where small and medium-sized enterprises account for over 90%of traditional manufacturing,the policy benefits will inject strong momentum into the high-quality development from multiple dimensions,including reduced financing costs,support for transformation funds,and expansion of foreign trade markets.
基金the National Natural Science Foundation of China(Research of the Biological Effects and Mechanism of Different Guasha Therapies,No.30672720)the National Natural Science Foundation of China(Comparative Research of Different Acupuncture Stimulation Methods on The Expression of Effects in Acupoint Areas,No.81674079)
文摘OBJECTIVE: To evaluate the effects of Guasha therapy on the rating of perceived exertion(RPE) scale score, and heart rate variability(HRV).METHODS: A randomized controlled trial of Guasha(skin scraping) was compared with a sham scraping group and control group. Sixteen sessions within an 8-week period were completed. Sixty-five male weightlifters who had undergone normal weightlifting training for a mean of 5 years before study commencement were recruited. The RPEscale score of "snatch", "clean and jerk" maneuvers(85% of one-repetition maximum), and HRV were measured before and after the intervention.RESULTS: The RPE scale score for snatch, clean and jerk were reduced significantly after intervention in the Guasha group and sham group. However, there was a significant difference in the low frequency(LF) domain and LF/high frequency(HF) ratio(P <0.05): the LF domain decreased, and the LF/HF ratio decreased.CONCLUSION: Guasha could be used to reduce the RPE scale score, and increase the response to HRV.Guasha could be considered as an alternative to some types of recovery from sports training.
文摘Simulation law and physical simulation were used to study the kinematic behavior of inclusions in electromagnetic separation. It was found that velocity of spherical non metallic particles shares different functions in different Reynolds number range. The function of spherical particle’s velocity has been got by confirming the relationship between Reynolds number and resistance coefficient when Reynolds number is 0.2 ～10. For non spherical particles, the moving behavior is influenced by shape and orientation while spherical coefficient has nothing to do with the velocity of irregular particles. The influence of orientation of cuboid particle on the electromagnetic expulsive force has been indicated by numerical computation. [
文摘In order to design the relief system size of di-tert-butyl peroxide(DTBP) storage tanks,the runaway re-action of DTBP was simulated by accelerating rate calorimeter(ARC).The results indicated that under adiabatic conditions the initial exothermic temperature was 102.6 ℃,the maximum self-heating rate was 3.095×107 ℃·min-1,the maximum self-heating temperature was 375.9 ℃,and the pressure produced by unit mass was 4.512 MPa·g-1.Judged by ARC test,the emergency relief system for DTBP was a hybrid system.Based on Design Institute for Emergency Relief System(DIERS) method,the releasing mass flow rate W was determined by Leung methods,and the mass velocity G was calculated by two modified Omega methods.The two relief sizes calculated by monograph Omega method and arithmetic Omega method are close,with only 0.63% relative error.The monograph Omega method is more convenient to apply.
基金the National Natural Science Foundation of China(Nos.51974153,U1960203,and 51974156)the Joint Fund of State Key Laboratory of Marine Engineering and University of Science and Technology Liaoning(SKLMEA-USTL-201901,SKLMEA-USTL-201707)China Scholarship Council(201908210457).
文摘The determination of the local cooling rate has a great significance in optimizing the parameters of electroslag remelting(ESR)and improving the quality of the ingots.An innovative method was proposed for calibrating the local cooling rate of M42 high-speed steel(HSS)in the ESR process.After resolidification at different cooling rates under high-temperature laser confocal microscopy,the carbide network spacing of the specimen was observed using a scanning electron microscope.A functional relationship between the cooling rate and average carbide network spacing was established.The average local cooling rate of the solidification process of the M42 HSS ingot was calibrated.The results show that the higher the cool-ing rate,the smaller the network spacing of the carbides.For the steel ingot with a diameter of 360 mm,the average local cooling rate was 0.562℃/s at the surface,0.057℃/s at the position of 0.25D(where D is the diameter of the ingot),and 0.046℃/s at the center of the ingot.
文摘Accurate and reliable river flow information is critical to planning and management for sustainable water resources utilization. Most of engineering activities related to hydrologic designs, flood, drought, reservoirs and their operations are heavily dependent on the river flow information derived from river rating curve. The rating curve for a given river section is normally developed from a set of direct stage-discharge measurements for different periods. This involves considerable labour, risk and resources, and presupposes a complex and extensive measuring survey. Extrapolating the rating curve beyond the measured range, as common in many cases, is fraught with errors and uncertainties, due to the complex hydraulic behaviour of the surface water profile in transition from section, channel, downstream and flood plain controls which are often poorly understood with direct measurements. Hydraulic modeling has recently emerged as one of the more promising methods to efficiently develop accurate rating curves for a river section with simple or complex hydraulic structures and conditions. This paper explores the use of a Hydraulic Engineering Center-River Analysis System (HEC-RAS) model to review and develop river rating curves for three hydrometric stations on two rivers in Kwale, coastal Kenya. The HEC-RAS models were set up based on topographical (cross section and longitudinal) survey data for the reaches and engineering drawings for the hydraulic structures commonly used as section controls for flow measurement. The model was calibrated under unsteady state conditions against measured stage-discharge data which were captured using a Velocity Current Meter (Valeport) and an Acoustic Doppler Current Profiler (ADCP) for both low and high flow. The rating curves were extracted from model results and the uncertainty associated with each rating curve analyzed. The results obtained by the HEC-RAS model were satisfactory and deemed acceptable for predicting discharge across the stage range at each river section.
