期刊文献+
共找到95,060篇文章
< 1 2 250 >
每页显示 20 50 100
Large-scale particle trapping by acoustic vortices with a continuously variable topological charge
1
作者 庄昊霏 张清源 +2 位作者 胡格昊 王青东 杜立彬 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第7期398-406,共9页
Strengthened directivity with higher-order side lobes can be generated by the transducer with a larger radius at a higher frequency. The multi-annular pressure distributions are displayed in the cross-section of the a... Strengthened directivity with higher-order side lobes can be generated by the transducer with a larger radius at a higher frequency. The multi-annular pressure distributions are displayed in the cross-section of the acoustic vortices(AVs)which are formed by side lobes. In the near field, particles can be trapped in the valley region between the two annuli of the pressure peak, and cannot be moved to the vortex center. In this paper, a trapping method based on a sector transducer array is proposed, which is characterized by the continuously variable topological charge(CVTC). This acoustic field can not only enlarge the range of particle trapping but also improve the aggregation degree of the trapped particles. In the experiments, polyethylene particles with a diameter of 0.2 mm are trapped into the multi-annular valleys by the AV with a fixed topological charge. Nevertheless, by applying the CVTC, particles outside the radius of the AV can cross the pressure peak successfully and move to the vortex center. Theoretical studies are also verified by the experimental particles trapping using the AV with the continuous variation of three topological charges, and suggest the potential application of large-scale particle trapping in biomedical engineering. 展开更多
关键词 acoustic vortices sector transducer array trapping particle continuously variable topological charge
下载PDF
A low-frequency pure metal metamaterial absorber with continuously tunable stiffness
2
作者 Xingzhong WANG Shiteng RUI +2 位作者 Shaokun YANG Weiquan ZHANG Fuyin MA 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2024年第7期1209-1224,共16页
To address the incompatibility between high environmental adaptability and deep subwavelength characteristics in conventional local resonance metamaterials,and overcome the deficiencies in the stability of existing ac... To address the incompatibility between high environmental adaptability and deep subwavelength characteristics in conventional local resonance metamaterials,and overcome the deficiencies in the stability of existing active control techniques for band gaps,this paper proposes a design method of pure metal vibration damping metamaterial with continuously tunable stiffness for wideband elastic wave absorption.We design a dual-helix narrow-slit pure metal metamaterial unit,which possesses the triple advantage of high spatial compactness,low stiffness characteristics,and high structural stability,enabling the opening of elastic flexural band gaps in the low-frequency range.Similar to the principle of a sliding rheostat,the introduction of continuously sliding plug-ins into the helical slits enables the continuous variation of the stiffness of the metamaterial unit,achieving a continuously tunable band gap effect.This successfully extends the effective band gap by more than ten times.The experimental results indicate that this metamaterial unit can be used as an additional vibration absorber to absorb the low-frequency vibration energy effectively.Furthermore,it advances the metamaterial absorbers from a purely passive narrowband design to a wideband tunable one.The pure metal double-helix metamaterials retain the subwavelength properties of metamaterials and are suitable for deployment in harsh environments.Simultaneously,by adjusting its stiffness,it substantially broadens the effective band gap range,presenting promising potential applications in various mechanical equipment operating under adverse conditions. 展开更多
关键词 elastic metamaterial absorber continuously tunable stiffness low-frequency vibration damping variable stiffness design pure metal structure
下载PDF
Design of Linear Functional Noncircular Gear with High Contact Ratio Used in Continuously Variable Transmission
3
作者 Yanan Hu Chao Lin +2 位作者 Chunjiang He Yongquan Yu Zhiqin Cai 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2023年第3期205-218,共14页
Continuously variable transmission(CVT)of noncircular gear has the technical advantages of large bearing capacity and high transmission efficiency.The key technology of CVT with noncircular gear has been broken throug... Continuously variable transmission(CVT)of noncircular gear has the technical advantages of large bearing capacity and high transmission efficiency.The key technology of CVT with noncircular gear has been broken through some countries,and is in the stage of deep application research.Although the characteristics and design methods of noncircular gear pairs have been continuously studied in China,the noncircular gear CVT is still in the preliminary exploration and research stage.The linear functional noncircular gear pair,whose transmission ratio is a linear function in the working section,to realize continuously variable transmission was the research object in this paper.According to the required transmission ratio in the working section,the transmission ratio function in the non-working section was constructed by using a polynomial.And then the influence of pitch curve parameters in the working section on which in the non-working section was also analyzed to obtain the pitch curve suitable for transmission of this gear pair.In addition,for improving the stability and bearing capacity of gear transmission,the noncircular gear pair transmission with high contact ratio was designed.Furthermore,the accurate value of the contact tooth length was calculated based on the gear principle and the characteristics of the involute tooth profile,from this the contact tooth length error was calculated by comparing the accurate value with its actual value obtained by the rolling experiment.Finally,an indirect method to verify the contact ratio by detecting the contact length error of the tooth profile was proposed. 展开更多
关键词 continuously variable transmission Noncircular gear Pitch curve Contact ratio Contact tooth profile
下载PDF
Application and management of continuous glucose monitoring in diabetic kidney disease 被引量:1
4
作者 Xin-Miao Zhang Quan-Quan Shen 《World Journal of Diabetes》 SCIE 2024年第4期591-597,共7页
Diabetic kidney disease(DKD)is a common complication of diabetes mellitus that contributes to the risk of end-stage kidney disease(ESKD).Wide glycemic var-iations,such as hypoglycemia and hyperglycemia,are broadly fou... Diabetic kidney disease(DKD)is a common complication of diabetes mellitus that contributes to the risk of end-stage kidney disease(ESKD).Wide glycemic var-iations,such as hypoglycemia and hyperglycemia,are broadly found in diabetic patients with DKD and especially ESKD,as a result of impaired renal metabolism.It is essential to monitor glycemia for effective management of DKD.Hemoglobin A1c(HbA1c)has long been considered as the gold standard for monitoring glycemia for>3 months.However,assessment of HbA1c has some bias as it is susceptible to factors such as anemia and liver or kidney dysfunction.Continuous glucose monitoring(CGM)has provided new insights on glycemic assessment and management.CGM directly measures glucose level in interstitial fluid,reports real-time or retrospective glucose concentration,and provides multiple glycemic metrics.It avoids the pitfalls of HbA1c in some contexts,and may serve as a precise alternative to estimation of mean glucose and glycemic variability.Emerging studies have demonstrated the merits of CGM for precise monitoring,which allows fine-tuning of glycemic management in diabetic patients.Therefore,CGM technology has the potential for better glycemic monitoring in DKD patients.More research is needed to explore its application and management in different stages of DKD,including hemodialysis,peritoneal dialysis and kidney transplantation. 展开更多
关键词 Diabetic kidney disease continuous glucose monitoring Glycemic monitoring HEMODIALYSIS Peritoneal dialysis Kidney transplantation
下载PDF
Comparative Analysis of Continuous versus Intermittent Proton Pump Inhibitor Therapy in Patients with Upper Gastrointestinal Bleeding Due to Ulcers
5
作者 Abraamyan Feruza Misra P. Neeladri 《Open Journal of Gastroenterology》 CAS 2024年第3期99-107,共9页
Upper gastrointestinal bleeding (UGIB) presents as a prevalent clinical challenge, with annual incidence rates ranging from 80 to 150 cases per 100,000 individuals. Guidelines for managing patients with UGIB due to bl... Upper gastrointestinal bleeding (UGIB) presents as a prevalent clinical challenge, with annual incidence rates ranging from 80 to 150 cases per 100,000 individuals. Guidelines for managing patients with UGIB due to bleeding ulcers recommend a continuous infusion of proton pump inhibitors (PPI). However, studies comparing intermittent dosing of PPI therapy show that this regimen achieves similar clinical benefits. If the clinical efficacy remains equivalent, intermittent dosing will be more cost-effective for patients and the health care system. Our research study aims to analyze the comparative effectiveness of intermittent versus continuous PPI therapy after endoscopic treatment in patients with UGIB, focusing on such endpoints as rebleeding risk at 3-and 7-day mortality rates. Methods: Resources searched included MEDLINE, EMBASE, PUBMED, and the Cochrane Central Register of Controlled Trials databases from January 2010 through December 2023 with the inclusion of meta-analysis, systematic review, review, or ACG guideline recommendations. Results of the analysis show how recommendations regarding high vs. low PPI regimen changed over time: from no difference in regimen in 2010 to recommending continuous regimen in 2012 to declaring insufficient evidence between choosing one regimen over another in 2013 to determine that both regimens were comparable to each other in 2014-2018 and finally to recommending both regimens in 2021. To conclude, our review shows that in patients with bleeding ulcers and high-risk endoscopic findings, intermittent PPI therapy is non-inferior to continuous PPI infusion for three days, seven days bleeding risk or mortality rates;however, it remains challenging to determine the most optimal intermittent regimen due to heterogeneity of RCTs included in meta-analyses, and further trials will need to be performed. 展开更多
关键词 Upper Gastrointestinal Bleeding PPI continuOUS INTERMITTENT BOLUS REGIMENS Review
下载PDF
Continuity of Care in Primary Health Care Affecting Control of Diabetes
6
作者 Raneem Alshahrani Ibtihaj Alawadh +1 位作者 Abdulelah Al Namlah Alia Hussain Zawawi 《International Journal of Clinical Medicine》 CAS 2024年第10期457-464,共8页
Background: Continuity of care is a distinguishing feature of primary care. Better continuity of care program showed a significant effect in controlling diabetes and it is complications. This study explores the effect... Background: Continuity of care is a distinguishing feature of primary care. Better continuity of care program showed a significant effect in controlling diabetes and it is complications. This study explores the effect of continuity of care on control of diabetes mellites in primary health care centres. Objectives: 1) To assess the effect of Continuity of care on controlling haemoglobin (Hb A1C) and fasting blood Sugar (FBS);2) To compare the control of Diabetes by using (Hb A1C and FBS) indices on same patient before and after application of chronic illness clinic;3) To identify the relation between age and gender affecting continuity of care in diabetic patient. Methods: It is a Prospective cohort study design. Included both gender and diabetic patient age above 24 years old. The data extracted from health care specialty center (HCSC) clinics in National guard hospital at Riyadh, through HCSC data base on three phases: 1) Phase 1: the data extracted of diabetic patients from October to November 2022 including MRN, diabetic patient, age, Hb A1C, Fasting blood glucose. 2) Phase 2: the same MRN extracted from phase 1 was extracted again retrospectively for six months from April to September 2022, to compare the indices before implanting the chronic illness clinic including Hb A1C, Fasting blood glucose. 3) Phase 3: prospectively from December 2022 to September 2023. Results: Among diabetic patients aged 60 years old and above showed better control of HbA1C and FBS comparing to these patients below age of 60 years old, with significant improvement of HbA1C after implanting chronic illness clinic. Conclusion: The significant improvement in the control of diabetic patients followed in primary health care centers reinforce the evidence of the importance of continuity of care. 展开更多
关键词 continuity of Care Primary Health Care Diabetes Mellites
下载PDF
NCCMF:Non-Collaborative Continuous Monitoring Framework for Container-Based Cloud Runtime Status
7
作者 Tao Zheng Wenyi Tang +1 位作者 Xingshu Chen Changxiang Shen 《Computers, Materials & Continua》 SCIE EI 2024年第10期1687-1701,共15页
The security performance of cloud services is a key factor influencing users’selection of Cloud Service Providers(CSPs).Continuous monitoring of the security status of cloud services is critical.However,existing rese... The security performance of cloud services is a key factor influencing users’selection of Cloud Service Providers(CSPs).Continuous monitoring of the security status of cloud services is critical.However,existing research lacks a practical framework for such ongoing monitoring.To address this gap,this paper proposes the first NonCollaborative Container-Based Cloud Service Operation State Continuous Monitoring Framework(NCCMF),based on relevant standards.NCCMF operates without the CSP’s collaboration by:1)establishing a scalable supervisory index system through the identification of security responsibilities for each role,and 2)designing a Continuous Metrics Supervision Protocol(CMA)to automate the negotiation of supervisory metrics.The framework also outlines the supervision process for cloud services across different deployment models.Experimental results demonstrate that NCCMF effectively monitors the operational state of two real-world IoT(Internet of Things)cloud services,with an average supervision error of less than 15%. 展开更多
关键词 Container-based cloud non-collaborative continuous monitor runtime status
下载PDF
GLOBAL CONVERGENCE OF A CAUTIOUS PROJECTION BFGS ALGORITHM FOR NONCONVEX PROBLEMS WITHOUT GRADIENT LIPSCHITZ CONTINUITY
8
作者 Gonglin YUAN Xiong ZHAO Jiajia YU 《Acta Mathematica Scientia》 SCIE CSCD 2024年第5期1735-1746,共12页
A cautious projection BFGS method is proposed for solving nonconvex unconstrained optimization problems.The global convergence of this method as well as a stronger general convergence result can be proven without a gr... A cautious projection BFGS method is proposed for solving nonconvex unconstrained optimization problems.The global convergence of this method as well as a stronger general convergence result can be proven without a gradient Lipschitz continuity assumption,which is more in line with the actual problems than the existing modified BFGS methods and the traditional BFGS method.Under some additional conditions,the method presented has a superlinear convergence rate,which can be regarded as an extension and supplement of BFGS-type methods with the projection technique.Finally,the effectiveness and application prospects of the proposed method are verified by numerical experiments. 展开更多
关键词 cautious BFGS nonconvex problems Lipschitz continuity projection technique global convergence
下载PDF
Continual Reinforcement Learning for Intelligent Agricultural Management under Climate Changes
9
作者 Zhaoan Wang Kishlay Jha Shaoping Xiao 《Computers, Materials & Continua》 SCIE EI 2024年第10期1319-1336,共18页
Climate change poses significant challenges to agricultural management,particularly in adapting to extreme weather conditions that impact agricultural production.Existing works with traditional Reinforcement Learning(... Climate change poses significant challenges to agricultural management,particularly in adapting to extreme weather conditions that impact agricultural production.Existing works with traditional Reinforcement Learning(RL)methods often falter under such extreme conditions.To address this challenge,our study introduces a novel approach by integrating Continual Learning(CL)with RL to form Continual Reinforcement Learning(CRL),enhancing the adaptability of agricultural management strategies.Leveraging the Gym-DSSAT simulation environment,our research enables RL agents to learn optimal fertilization strategies based on variable weather conditions.By incorporating CL algorithms,such as Elastic Weight Consolidation(EWC),with established RL techniques like Deep Q-Networks(DQN),we developed a framework in which agents can learn and retain knowledge across diverse weather scenarios.The CRL approach was tested under climate variability to assess the robustness and adaptability of the induced policies,particularly under extreme weather events like severe droughts.Our results showed that continually learned policies exhibited superior adaptability and performance compared to optimal policies learned through the conventional RL methods,especially in challenging conditions of reduced rainfall and increased temperatures.This pioneering work,which combines CL with RL to generate adaptive policies for agricultural management,is expected to make significant advancements in precision agriculture in the era of climate change. 展开更多
关键词 continual learning reinforcement learning agricultural management climate variability
下载PDF
Strengthening effect of prefabrication(10-12)tensile twinning on AZ80+0.4%Ce magnesium alloy and inhibition mechanism of discontinuous precipitation
10
作者 Zhen Wang Xi Zhao +5 位作者 Zhimin Zhang Yaojin Wu Kai Chen Xianwei Ren Dengkui Wang Wei Wang 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2024年第5期1918-1930,共13页
This paper provided an effective method to further improve the mechanical properties of the AZ80+0.4%Ce magnesium alloy wheel spoke.The effect of high strength and ductility was obtained with a yield strength of 295.3... This paper provided an effective method to further improve the mechanical properties of the AZ80+0.4%Ce magnesium alloy wheel spoke.The effect of high strength and ductility was obtained with a yield strength of 295.36 MPa,an elongation of 10%,by the combination of pre-deformation(7%deformation)and two-stage aging treatment(120℃/9 h+175℃/24 h).The evolution of the microstructure and properties of the alloy was explored under the coupling conditions of different pre-deformation degrees and multi-stage aging.The results show that,pre-deformation introduced a large number of(1012)tensile twinning and dislocations,which greatly promoted the probability of continuous precipitates(CPs)appearing.On the contrary,the discontinuous precipitates(DPs)were limited by the vertical and horizontal twin structure.As a result,the pre-nucleation method of two-stage aging increased the proportion of CPs by 34%-38%.Owing to the DPs was effectively suppressed,the alloy's yield strength has been greatly improved.Besides,under multi-stage aging,the twin boundaries induce protruding nucleation to form static recrystallization by hindering the migration of dislocations,and the matrix swallows the twins,then the texture gradually tilts from the two poles to the basal plane.As an important supplement,the grain refinement and oblique texture promoted the improvement of the yield strength of the component. 展开更多
关键词 Magnesium alloy Pre-deformed Two-stage aging Tensile twinning continuous precipitates Texture
下载PDF
Enhanced measurement precision with continuous interrogation during dynamical decoupling
11
作者 张军 杜鹏 +3 位作者 敬雷 徐鹏 尤力 张文献 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第3期88-94,共7页
Dynamical decoupling(DD)is normally ineffective when applied to DC measurement.In its straightforward implementation,DD nulls out DC signal as well while suppressing noise.This work proposes a phase relay method that ... Dynamical decoupling(DD)is normally ineffective when applied to DC measurement.In its straightforward implementation,DD nulls out DC signal as well while suppressing noise.This work proposes a phase relay method that is capable of continuously interrogating the DC signal over many DD cycles.We illustrate its efficacy when applied to the measurement of a weak DC magnetic field with an atomic spinor Bose-Einstein condensate.Sensitivities approaching standard quantum limit or Heisenberg limit are potentially realizable for a coherent spin state or a squeezed spin state of 10000 atoms,respectively,while ambient laboratory level noise is suppressed by DD.Our work offers a practical approach to mitigate the limitations of DD to DC measurement and would find other applications for resorting coherence in quantum sensing and quantum information processing research. 展开更多
关键词 quantum sensing continuous interrogation quantum magnetometer dynamical decoupling Heisenberg limit
下载PDF
MULTIFRACTAL ANALYSIS OF CONVERGENCE EXPONENTS FOR PRODUCTS OF CONSECUTIVE PARTIAL QUOTIENTS IN CONTINUED FRACTIONS
12
作者 Lulu FANG Jihua MA +1 位作者 Kunkun SONG Xin YANG 《Acta Mathematica Scientia》 SCIE CSCD 2024年第4期1594-1608,共15页
For each real number x∈(0,1),let[a_(1)(x),a_(2)(x),…,a_n(x),…]denote its continued fraction expansion.We study the convergence exponent defined byτ(x)=inf{s≥0:∞∑n=1(a_(n)(x)a_(n+1)(x))^(-s)<∞},which reflect... For each real number x∈(0,1),let[a_(1)(x),a_(2)(x),…,a_n(x),…]denote its continued fraction expansion.We study the convergence exponent defined byτ(x)=inf{s≥0:∞∑n=1(a_(n)(x)a_(n+1)(x))^(-s)<∞},which reflects the growth rate of the product of two consecutive partial quotients.As a main result,the Hausdorff dimensions of the level sets ofτ(x)are determined. 展开更多
关键词 continued fractions product of partial quotients Hausdorff dimension
下载PDF
Improvement and security analysis of multi-ring discrete modulation continuous variable quantum secret sharing scheme
13
作者 姜欢窈 聂敏 +3 位作者 杨光 孙爱晶 张美玲 裴昌幸 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第7期189-197,共9页
In order to avoid the complexity of Gaussian modulation and the problem that the traditional point-to-point communication DM-CVQKD protocol cannot meet the demand for multi-user key sharing at the same time, we propos... In order to avoid the complexity of Gaussian modulation and the problem that the traditional point-to-point communication DM-CVQKD protocol cannot meet the demand for multi-user key sharing at the same time, we propose a multi-ring discrete modulation continuous variable quantum key sharing scheme(MR-DM-CVQSS). In this paper, we primarily compare single-ring and multi-ring M-symbol amplitude and phase-shift keying modulations. We analyze their asymptotic key rates against collective attacks and consider the security key rates under finite-size effects. Leveraging the characteristics of discrete modulation, we improve the quantum secret sharing scheme. Non-dealer participants only require simple phase shifters to complete quantum secret sharing. We also provide the general design of the MR-DM-CVQSS protocol.We conduct a comprehensive analysis of the improved protocol's performance, confirming that the enhancement through multi-ring M-PSK allows for longer-distance quantum key distribution. Additionally, it reduces the deployment complexity of the system, thereby increasing the practical value. 展开更多
关键词 discrete modulation continuous variable quantum secret sharing scheme
下载PDF
Irregular initial solidification by mold thermal monitoring in the continuous casting of steels:A review
14
作者 Qiuping Li Guanghua Wen +3 位作者 Fuhang Chen Ping Tang Zibing Hou Xinyun Mo 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2024年第5期1003-1015,共13页
Occasional irregular initial solidification phenomena,including stickers,deep oscillation marks,depressions,and surface cracks of strand shells in continuous casting molds,are important limitations for developing the ... Occasional irregular initial solidification phenomena,including stickers,deep oscillation marks,depressions,and surface cracks of strand shells in continuous casting molds,are important limitations for developing the high-efficiency continuous casting of steels.The application of mold thermal monitoring(MTM) systems,which use thermocouples to detect and respond to temperature variations in molds,has become an effective method to address irregular initial solidification phenomena.Such systems are widely applied in numerous steel companies for sticker breakout prediction.However,monitoring the surface defects of strands remains immature.Hence,indepth research is necessary to utilize the potential advantages and comprehensive monitoring of MTM systems.This paper summarizes what is included in the irregular initial solidification phenomena and systematically reviews the current state of research on these phenomena by the MTM systems.Furthermore,the influences of mold slag behavior on monitoring these phenomena are analyzed.Finally,the remaining problems of the formation mechanisms and investigations of irregular initial solidification phenomena are discussed,and future research directions are proposed. 展开更多
关键词 irregular initial solidification mold thermal monitoring continuous casting mold slag THERMOCOUPLE
下载PDF
Effect of continuous nursing on rehabilitation of older patients with joint replacement after discharge
15
作者 Xiao-Yan Qi Hong-Yan Zhou Yu-Hong Xing 《World Journal of Clinical Cases》 SCIE 2024年第21期4558-4565,共8页
BACKGROUND Joint replacement is a common treatment for older patients with high incidences of hip joint diseases.However,postoperative recovery is slow and complications are common,which reduces surgical effectiveness... BACKGROUND Joint replacement is a common treatment for older patients with high incidences of hip joint diseases.However,postoperative recovery is slow and complications are common,which reduces surgical effectiveness.Therefore,patients require long-term,high-quality,and effective nursing interventions to promote rehabilitation.Continuity of care has been used successfully in other diseases;however,little research has been conducted on older patients who have undergone hip replacement.AIM To explore the clinical effect of continuous nursing on rehabilitation after discharge of older individuals who have undergone joint replacement.METHODS A retrospective analysis was performed on the clinical data of 113 elderly patients.Patients receiving routine nursing were included in the convention group(n=60),and those receiving continuous nursing,according to various methods,were included in the continuation group(n=53).Harris score,short form 36(SF-36)score,complication rate,and readmission rate were compared between the convention and continuation groups.RESULTS After discharge,Harris and SF-36 scores of the continuation group were higher than those of the convention group.The Harris and SF-36 scores of the two groups showed an increasing trend with time,and there was an interaction effect between group and time(Harris score:F_(intergroup effect)=376.500,F_(time effect)=20.090,Finteraction effect=4.824;SF-36 score:F_(intergroup effect)=236.200,Ftime effect=16.710,Finteraction effect=5.584;all P<0.05).Furthermore,the total complication and readmission rates in the continuation group were lower(P<0.05).CONCLUSION Continuous nursing could significantly improve hip function and quality of life in older patients after joint replacement and reduce the incidence of complications and readmission rates. 展开更多
关键词 continuous nursing DISCHARGE Older adults Joint replacement REHABILITATION EFFECT
下载PDF
THE ABSENCE OF SINGULAR CONTINUOUS SPECTRUM FOR PERTURBED JACOBI OPERATORS
16
作者 傅钲淇 黎雄 《Acta Mathematica Scientia》 SCIE CSCD 2024年第2期515-531,共17页
This paper is mainly about the spectral properties of a class of Jacobi operators(H_(c,b)u)(n)=c_(n)u(n+1)+c_(n-1)u(n-1)+b_(n)u(n),.where∣c_(n)−1∣=O(n^(−α))and b_(n)=O(n^(−1)).We will show that,forα≥1,the singula... This paper is mainly about the spectral properties of a class of Jacobi operators(H_(c,b)u)(n)=c_(n)u(n+1)+c_(n-1)u(n-1)+b_(n)u(n),.where∣c_(n)−1∣=O(n^(−α))and b_(n)=O(n^(−1)).We will show that,forα≥1,the singular continuous spectrum of the operator is empty. 展开更多
关键词 Jacobi operator singular continuous spectrum Prüfer variables
下载PDF
Path-Dependent Progressive Failure Analysis for 3D-Printed Continuous Carbon Fibre Reinforced Composites
17
作者 Yuan Chen Lin Ye 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2024年第4期84-93,共10页
In order to predict the damage behaviours of 3D-printed continuous carbon fibre(CCF)reinforced composites,when additional short carbon fibre(SCF)composite components are employed for continuous printing or special fun... In order to predict the damage behaviours of 3D-printed continuous carbon fibre(CCF)reinforced composites,when additional short carbon fibre(SCF)composite components are employed for continuous printing or special functionality,a novel path-dependent progressive failure(PDPF)numerical approach is developed.First,a progressive failure model using Hashin failure criteria with continuum damage mechanics to account for the damage initiation and evaluation of 3D-printed CCF reinforced polyamide(PA)composites is developed,based on actual fibre placement trajectories with physical measurements of 3D-printed CCF/PA constituents.Meanwhile,an elastic-plastic model is employed to predict the plastic damage behaviours of SCF/PA parts.Then,the accuracy of the PDPF model was validated so as to study 3D-printed CCF/PA composites with either negative Poisson's ratio or high stiffness.The results demonstrate that the proposed PDPF model can achieve higher prediction accuracies in mechanical properties of these 3D-printed CCF/PA composites.Mechanism analyses show that the stress distribution is generally aggregated in the CCF areas along the fibre placement paths,and the shear damage and matrix tensile/compressive damage are the key damage modes.This study provides a new approach with valuable information for characterising complex 3D-printed continuous fibre-matrix composites with variable mechanical properties and multiple constituents. 展开更多
关键词 3D printing continuous carbon fibre MODELLING Energy absorption Negative Poisson's ratio
下载PDF
Microstructure and mechanical properties of continuous drive friction welded Ti_(2)AlNb alloy under different rotational rates
18
作者 Zhi-qiang BU Xiu-ping MA +3 位作者 Jia-yun WU Zhen LÜ Hu CHEN Jin-fu LI 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2024年第10期3221-3232,共12页
Ti_(2)AlNb-based alloy was joined in a continuous drive friction welding machine under different rotational rates(500,1000 and 1500 r/min).The microstructure and mechanical properties of the joints were investigated.I... Ti_(2)AlNb-based alloy was joined in a continuous drive friction welding machine under different rotational rates(500,1000 and 1500 r/min).The microstructure and mechanical properties of the joints were investigated.It is shown that the weld zone(WZ) is fully composed of recrystallized B2 phase,and the grain size decreases with increasing rotational rate.The thermo-mechanically affected zone(TMAZ) suffers severe deformation during welding,due to which most of original precipitation phase is dissolved and streamlines are present.In the heat affected zone(HAZ),only the fine O phase is dissolved.The as-welded joint produced using 1000 r/min has the best mechanical properties,whose strength and elongation are both close to those of the base metal,while the as-welded joint obtained using 500 r/min exhibits the worst mechanical properties.Post-weld annealing treatment annihilates the deformation microstructure and fine O phase precipitates in the joints,consequently improving the mechanical properties significantly.Decomposed α_(2) phase is a weakness for the mechanical performance of the joint since microcracks are apt to form in it in the tensile test. 展开更多
关键词 Ti2AlNb alloy continuous drive friction welding MICROSTRUCTURE mechanical properties
下载PDF
Existence of a Hölder Continuous Extension on Embedded Balls of the 3-Torus for the Periodic Navier Stokes Equations
19
作者 Terry E. Moschandreou 《Advances in Pure Mathematics》 2024年第2期118-138,共21页
This article gives a general model using specific periodic special functions, which is degenerate elliptic Weierstrass P functions whose presence in the governing equations through the forcing terms simplify the perio... This article gives a general model using specific periodic special functions, which is degenerate elliptic Weierstrass P functions whose presence in the governing equations through the forcing terms simplify the periodic Navier Stokes equations (PNS) at the centers of cells of the 3-Torus. Satisfying a divergence-free vector field and periodic boundary conditions respectively with a general spatio-temporal forcing term which is smooth and spatially periodic, the existence of solutions which have finite time singularities can occur starting with the first derivative and higher with respect to time. The existence of a subspace of the solution space where v<sub>3</sub> is continuous and {C, y<sub>1</sub>, y<sub>1</sub><sup>2</sup>}, is linearly independent in the additive argument of the solution in terms of the Lambert W function, (y<sub>1</sub><sup>2</sup>=y<sub>2</sub>, C∈R) together with the condition v<sub>2</sub>=-2y<sub>1</sub>v<sub>1</sub>. On this subspace, the Biot Savart Law holds exactly [see Section 2 (Equation (13))]. Also on this subspace, an expression X (part of PNS equations) vanishes which contains all the expressions in derivatives of v<sub>1</sub> and v<sub>2</sub> and the forcing terms in the plane which are related as with the cancellation of all such terms in governing PDE. The y<sub>3</sub> component forcing term is arbitrarily small in ε ball where Weierstrass P functions touch the center of the ball both for inviscid and viscous cases. As a result, a significant simplification occurs with a v<sub>3 </sub>only governing PDE resulting. With viscosity present as v changes from zero to the fully viscous case at v =1 the solution for v<sub>3</sub> reaches a peak in the third component y<sub>3</sub>. Consequently, there exists a dipole which is not centered at the center of the cell of the Lattice. Hence since the dipole by definition has an equal in magnitude positive and negative peak in y<sub>3</sub>, then the dipole Riemann cut-off surface is covered by a closed surface which is the sphere and where a given cell of dimensions [-1, 1]<sup>3</sup> is circumscribed on a sphere of radius 1. For such a closed surface containing a dipole it necessarily follows that the flux at the surface of the sphere of v<sub>3</sub> wrt to surface normal n is zero including at the points where the surface of sphere touches the cube walls. At the finite time singularity on the sphere a rotation boundary condition is deduced. It is shown that v<sub>3</sub> is spatially finite on the Riemann Sphere and the forcing is oscillatory in y<sub>3</sub> component if the velocity v3</sub> is. It is true that . A boundary condition on the sphere shows the rotation of a sphere of viscous fluid. Finally on the sphere a solution for v3</sub> is obtained which is proven to be Hölder continuous and it is shown that it is possible to extend Hölder continuity on the sphere uniquely to all of the interior of the ball. 展开更多
关键词 Navier-Stokes PNS 3-Torus PERIODIC Ball Sphere Hölder continuOUS Riemann-Surface Uniqueness
下载PDF
Analysis of the Nursing Effect of Continuity of Care on Elderly Patients with Coronary Heart Disease Unstable Angina and its Impact on Quality of Life 被引量:1
20
作者 Ling Yan 《Journal of Clinical and Nursing Research》 2024年第2期185-190,共6页
Objective:To analyze the effect of using continuity of care for elderly patients with coronary heart disease(CHD)with unstable angina pectoris(UAP)and its impact on their quality of life.Methods:100 cases of elderly p... Objective:To analyze the effect of using continuity of care for elderly patients with coronary heart disease(CHD)with unstable angina pectoris(UAP)and its impact on their quality of life.Methods:100 cases of elderly patients with CHD with UAP admitted to our hospital from March 2022 to March 2023 were selected and grouped into an observation group and a control group of 50 cases each according to the randomized number table method.The nursing effect and quality of life of the observation group(continuity nursing)and the control group(routine nursing)were compared.Results:The total effective rate of nursing care was 96.00%observation group and 80.00%for the control group,and the differences were significant(χ2=6.061,P<0.05).Patients in the observation group had fewer episodes(1.42±0.21)times/week and a shorter duration(5.46±0.39)min,which were better than the control group(t=3.465,2.973;P<0.05).The depression self-rating depression scale(SDS)score(42.16±6.64)and anxiety self-rating scale(SAS)score(32.26±7.35)in the observation group were lower and the quality of life was higher as compared to that of the control group(P<0.05).Conclusion:Continuous nursing care improved the nursing effect of elderly CHD with UAP patients,promoted the alleviation of UAP symptoms,improved patient mentality,and improved their quality of life.Hence,continuous nursing care possesses significant clinical application value. 展开更多
关键词 continuity of care ELDERLY Coronary heart disease Unstable angina Nursing outcomes Quality of life
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部