The variational method is applied to calculate the dispersion characteristics of disc-loaded waveguide slow-wave structures. The parameters describing the waveguide discontinuities in disc-loaded waveguide are calcula...The variational method is applied to calculate the dispersion characteristics of disc-loaded waveguide slow-wave structures. The parameters describing the waveguide discontinuities in disc-loaded waveguide are calculated by the variational method. Then the dispersion characteristics of slow-wave structures are obtained using lossless microwave quadrupole theory. Good agreement was observed between results of the Variational method and those of field matching method and high frequency structure simulator. In the case of broad band, results of the variational method are better than those of field matching method.展开更多
The problem of diffraction of a plane acoustic wave by a finite soft (rigid) cone is investigated. This one is formulated as a mixed boundary value problem for the three-dimensional Helmholtz equation with Dirichlet (...The problem of diffraction of a plane acoustic wave by a finite soft (rigid) cone is investigated. This one is formulated as a mixed boundary value problem for the three-dimensional Helmholtz equation with Dirichlet (Neumann) boundary condition on the cone surface. The diffracted field is sought as expansion of unknown velocity potential in series of eigenfunctions for each region of the existence of sound pressure. The solution of the problem then is reduced to the infinite set of linear algebraic equations (ISLAE) of the first kind by means of mode matching technique and orthogonality properties of the Legendre functions. The main part of asymptotic of ISLAE matrix element determined for large indexes identifies the convolution type operator amenable to explicit inversion. This analytical treatment allows one to transform the initial diffraction problem into the ISLAE of the second kind that can be readily solved by the reduction method with desired accuracy depending on a number of truncation. All these determine the analytical regularization method for solution of wave diffraction problems for conical scatterers. The boundary transition to soft (rigid) disc is considered. The directivity factors, scattering cross sections, and far-field diffraction patterns are investigated in both soft and rigid cases whereas the main attention in the near-field is focused on the rigid case. The numerically obtained results are compared with those known for the disc.展开更多
目的:针对冲击波治疗腰椎间盘突出症(Lumbar Disc Herniation,LDH)的临床疗效进行系统评价。方法:检索国内外数据库资源中以冲击波疗法为主要干预措施治疗LDH的随机对照试验研究,针对符合纳入标准的研究进行质量评价,并采用Review Manag...目的:针对冲击波治疗腰椎间盘突出症(Lumbar Disc Herniation,LDH)的临床疗效进行系统评价。方法:检索国内外数据库资源中以冲击波疗法为主要干预措施治疗LDH的随机对照试验研究,针对符合纳入标准的研究进行质量评价,并采用Review Manager 5.3软件进行Meta分析。结果:纳入研究9项,涉及病例807例,Meta分析显示:①采用冲击波治疗组与推拿、功能锻炼对照组相比,临床有效率[相对危险度(RR)=1.25,95%置信区间(CI)(1.13,1.39),P<0.00001]的差异有统计学意义;②视觉模拟评分法(Visual Analogue Scale,VAS)评分亚组分析结果显示:冲击波与中频电疗、牵引、药物相比,均数差(MD)=–1.49,95%CI(-1.86,-1.12),P<0.00001)],差异有统计学意义。“冲击波+综合理疗(功能锻炼、理疗、推拿、针灸、牵引、超声波和药物)VS综合理疗(功能锻炼、理疗、推拿、针灸、牵引、超声波和药物)”结果显示(MD=–1.51,95%CI[–1.94,–1.07]),P<0.00001),差异有统计学意义。③日本骨科协会评估治疗分数(Japanese Orthopaedic Association,JOA)评分分析结果显示,冲击波组与对照组治疗后JOA评分(MD=3.83,95%CI[3.61,4.06],P<0.00001)的差异有统计学意义。④Oswestry功能障碍指数问卷表(Oswestry Disability Index,ODI)评分分析结果示,冲击波组与对照组ODI评分(MD=–2.81,95%CI[–6.64,1.02],P=0.15)的差异无统计学意义。⑤36项简明健康状况调查量表(The Mos 36-item Short From Health Survey,SF-36)评分结果显示,冲击波组与对照组SF-36评分(MD=11.46,95%CI[8.78,14.14],P<0.00001)的差异有统计学意义。结论:纳入研究分析结果提示,以冲击波疗法为主配合相应疗法对LDH的疗效可靠,可望通过后续更多大样本随机对照试验研究的实施加以佐证,为LDH临床治疗方法的选择提供新的参考依据。展开更多
为了降低制动器制动过程中产生的高频振动,通过对盘式制动器振动进行动力学建模,采用AFC(Active Force Control)控制理论与PID控制理论相结合,构造出有效的振动控制参数和AFC控制器。利用MATLAB/Simulink仿真平台,对AFC与PID联合控制下...为了降低制动器制动过程中产生的高频振动,通过对盘式制动器振动进行动力学建模,采用AFC(Active Force Control)控制理论与PID控制理论相结合,构造出有效的振动控制参数和AFC控制器。利用MATLAB/Simulink仿真平台,对AFC与PID联合控制下的制动器振动进行仿真,并与自由状态下的制动器振动进行对比分析。通过分析得到α≤0.022的情况下PID与AFC联合控制下制动盘在2 s左右振幅趋于稳定,制动盘振动幅值从1×10-3m降低到1×10-6m左右;而当α>0.022时AFC与PID联合控制会增大制动盘振动幅值。通过这种主动控制方法的研究为降低盘式制动器高频振动,进而降低高频振动引起的噪声,提高汽车NVH性能提供了依据。展开更多
文摘The variational method is applied to calculate the dispersion characteristics of disc-loaded waveguide slow-wave structures. The parameters describing the waveguide discontinuities in disc-loaded waveguide are calculated by the variational method. Then the dispersion characteristics of slow-wave structures are obtained using lossless microwave quadrupole theory. Good agreement was observed between results of the Variational method and those of field matching method and high frequency structure simulator. In the case of broad band, results of the variational method are better than those of field matching method.
文摘The problem of diffraction of a plane acoustic wave by a finite soft (rigid) cone is investigated. This one is formulated as a mixed boundary value problem for the three-dimensional Helmholtz equation with Dirichlet (Neumann) boundary condition on the cone surface. The diffracted field is sought as expansion of unknown velocity potential in series of eigenfunctions for each region of the existence of sound pressure. The solution of the problem then is reduced to the infinite set of linear algebraic equations (ISLAE) of the first kind by means of mode matching technique and orthogonality properties of the Legendre functions. The main part of asymptotic of ISLAE matrix element determined for large indexes identifies the convolution type operator amenable to explicit inversion. This analytical treatment allows one to transform the initial diffraction problem into the ISLAE of the second kind that can be readily solved by the reduction method with desired accuracy depending on a number of truncation. All these determine the analytical regularization method for solution of wave diffraction problems for conical scatterers. The boundary transition to soft (rigid) disc is considered. The directivity factors, scattering cross sections, and far-field diffraction patterns are investigated in both soft and rigid cases whereas the main attention in the near-field is focused on the rigid case. The numerically obtained results are compared with those known for the disc.
文摘目的:针对冲击波治疗腰椎间盘突出症(Lumbar Disc Herniation,LDH)的临床疗效进行系统评价。方法:检索国内外数据库资源中以冲击波疗法为主要干预措施治疗LDH的随机对照试验研究,针对符合纳入标准的研究进行质量评价,并采用Review Manager 5.3软件进行Meta分析。结果:纳入研究9项,涉及病例807例,Meta分析显示:①采用冲击波治疗组与推拿、功能锻炼对照组相比,临床有效率[相对危险度(RR)=1.25,95%置信区间(CI)(1.13,1.39),P<0.00001]的差异有统计学意义;②视觉模拟评分法(Visual Analogue Scale,VAS)评分亚组分析结果显示:冲击波与中频电疗、牵引、药物相比,均数差(MD)=–1.49,95%CI(-1.86,-1.12),P<0.00001)],差异有统计学意义。“冲击波+综合理疗(功能锻炼、理疗、推拿、针灸、牵引、超声波和药物)VS综合理疗(功能锻炼、理疗、推拿、针灸、牵引、超声波和药物)”结果显示(MD=–1.51,95%CI[–1.94,–1.07]),P<0.00001),差异有统计学意义。③日本骨科协会评估治疗分数(Japanese Orthopaedic Association,JOA)评分分析结果显示,冲击波组与对照组治疗后JOA评分(MD=3.83,95%CI[3.61,4.06],P<0.00001)的差异有统计学意义。④Oswestry功能障碍指数问卷表(Oswestry Disability Index,ODI)评分分析结果示,冲击波组与对照组ODI评分(MD=–2.81,95%CI[–6.64,1.02],P=0.15)的差异无统计学意义。⑤36项简明健康状况调查量表(The Mos 36-item Short From Health Survey,SF-36)评分结果显示,冲击波组与对照组SF-36评分(MD=11.46,95%CI[8.78,14.14],P<0.00001)的差异有统计学意义。结论:纳入研究分析结果提示,以冲击波疗法为主配合相应疗法对LDH的疗效可靠,可望通过后续更多大样本随机对照试验研究的实施加以佐证,为LDH临床治疗方法的选择提供新的参考依据。
文摘为了降低制动器制动过程中产生的高频振动,通过对盘式制动器振动进行动力学建模,采用AFC(Active Force Control)控制理论与PID控制理论相结合,构造出有效的振动控制参数和AFC控制器。利用MATLAB/Simulink仿真平台,对AFC与PID联合控制下的制动器振动进行仿真,并与自由状态下的制动器振动进行对比分析。通过分析得到α≤0.022的情况下PID与AFC联合控制下制动盘在2 s左右振幅趋于稳定,制动盘振动幅值从1×10-3m降低到1×10-6m左右;而当α>0.022时AFC与PID联合控制会增大制动盘振动幅值。通过这种主动控制方法的研究为降低盘式制动器高频振动,进而降低高频振动引起的噪声,提高汽车NVH性能提供了依据。
