The investigation on the aerodynamic characteristics of the high-attitude long-endurance (HALE) Diamond Joined-Wing configuration unmanned aerial vehicle ( UAV) was carried out by the theoretical analysis method and n...The investigation on the aerodynamic characteristics of the high-attitude long-endurance (HALE) Diamond Joined-Wing configuration unmanned aerial vehicle ( UAV) was carried out by the theoretical analysis method and numerical simulation. Research indicates that as the wing of the UAV is composed of the front wing and the after wing, the after wing has the ability to transmit the front wing's boundary layer to the after wing root which can inhibit the front wing's flow separation. Although the front wing was affected by the retardation of the after wing, the aerodynamic performance of the front wing was better than that of alone front wing in most cases. The after wing was also affected by the wake and downwash of the front wing, and its aerodynamic performance was greatly decreased. The characteristic curve of the pitching moment of the UAV had nonlinear characteristics. The flow field structure of the after wing changed by the front wing wake direct sweep and flow separation at the after wing root were the main reasons that non-linear ′rise′phenomenon occurred in two segments ( α = 0° and α = 8° ) of the characteristic curve of pitching moment. Moreover, coupling of the flow separation characteristic of the front wing and the after wing resulted in the pitching moment ′pitchup′ phenomenon. The lateral-directional static stability of the flat layout was weak. The HALE Diamond Joined-Wing configuration UAV ' s aerodynamic performance can be improved and the problems in engineering applications can be effectively alleviated by adjusting the overall layout parameters.展开更多
The joined-wing configuration reduces induced drag and structural weight by connecting the rear wing to the front wing.In addition,the rear wing can replace the role of the horizontal tail of a conventional aircraft,t...The joined-wing configuration reduces induced drag and structural weight by connecting the rear wing to the front wing.In addition,the rear wing can replace the role of the horizontal tail of a conventional aircraft,thus eliminating the aerodynamic drag and weight associated with the horizontal tail.This particular shape creates a highly coupled relationship between aerodynamics and structure,which must be fully considered during the overall design process to enhance aircraft performance.In this research,an aero-structural design model of the joined-wing aircraft is constructed based on high-fidelity computational fluid dynamics and structural finite element methods.The model is able to obtain accurate aerodynamic loads for the non-planar wing and to simulate the statically indeterminate structure of the closed wing configuration.The influence of the joined-wing shape parameters on the aerodynamic and structural disciplines,as well as the influence of geometric nonlinear characteristics,deformation constraints and buckling constraints on the structural weight are all taken into consideration.The model is applied to complete the aero-structural design optimization of a high-altitude long-endurance joined-wing aircraft,and wind tunnel tests are conducted.The test results verify the credibility of the design model proposed and the validity of the design environment.展开更多
D iamond高速并联抓取机械手已经在电池分拣领域取得了良好的应用效果。多机械手协同分选时,存在多种可能的布局,例如串联、并联、混联等。不同的布局对整个系统的可靠性、分拣效率、成本、可重构性都有显著的影响。本文对些问题进行了...D iamond高速并联抓取机械手已经在电池分拣领域取得了良好的应用效果。多机械手协同分选时,存在多种可能的布局,例如串联、并联、混联等。不同的布局对整个系统的可靠性、分拣效率、成本、可重构性都有显著的影响。本文对些问题进行了深入分析,并建立组合数学模型对不同布局的生产率进行量化,以指导设计者进行该型机械手的系统布局。展开更多
[目的]采用荟萃分析评价菱形与倒三角排列的空心钉内固定股骨颈骨折的临床疗效。[方法]计算机检索CNKI、维普、万方医学数据库、Sinomed、Pubmed、Embase、Web of Science、和The Cochrane Library等数据库,收集所有关于应用菱形和倒三...[目的]采用荟萃分析评价菱形与倒三角排列的空心钉内固定股骨颈骨折的临床疗效。[方法]计算机检索CNKI、维普、万方医学数据库、Sinomed、Pubmed、Embase、Web of Science、和The Cochrane Library等数据库,收集所有关于应用菱形和倒三角空心钉固定股骨颈骨折疗效对比的临床研究,检索时间均为建库至2022年3月。由2位研究者根据纳入与排除标准独立筛选文献、提取资料和评价纳入研究的方法学质量后,采用RevMan 5.4.软件进行荟萃分析。[结果]最终纳入5项研究,涉及387例患者,其中菱形组178例,倒三角组209例。荟萃结果显示:菱形组术中出血量显著多于倒三角组(P<0.05),末次随访Harris评分显著高于倒三角组(P<0.05),两组的手术时间、骨折不愈合率、股骨头缺血坏死率、退钉率和股骨颈短缩率的差异均无统计学意义(P>0.05)。[结论]菱形组在术后Harris评分优于倒三角组,倒三角组的出血量低于菱形组。两组在骨折不愈合率、股骨头缺血坏死率、退钉率、股骨颈短缩发生率等远期并发症方面无明显差异。展开更多
基金Sponsored by the Civil Aircraft Project(Grant No.MIE-2015-F-009)the Shaanxi Province Science and Technology Project(Grant No.2015KTCQ01-78)
文摘The investigation on the aerodynamic characteristics of the high-attitude long-endurance (HALE) Diamond Joined-Wing configuration unmanned aerial vehicle ( UAV) was carried out by the theoretical analysis method and numerical simulation. Research indicates that as the wing of the UAV is composed of the front wing and the after wing, the after wing has the ability to transmit the front wing's boundary layer to the after wing root which can inhibit the front wing's flow separation. Although the front wing was affected by the retardation of the after wing, the aerodynamic performance of the front wing was better than that of alone front wing in most cases. The after wing was also affected by the wake and downwash of the front wing, and its aerodynamic performance was greatly decreased. The characteristic curve of the pitching moment of the UAV had nonlinear characteristics. The flow field structure of the after wing changed by the front wing wake direct sweep and flow separation at the after wing root were the main reasons that non-linear ′rise′phenomenon occurred in two segments ( α = 0° and α = 8° ) of the characteristic curve of pitching moment. Moreover, coupling of the flow separation characteristic of the front wing and the after wing resulted in the pitching moment ′pitchup′ phenomenon. The lateral-directional static stability of the flat layout was weak. The HALE Diamond Joined-Wing configuration UAV ' s aerodynamic performance can be improved and the problems in engineering applications can be effectively alleviated by adjusting the overall layout parameters.
基金supported by the Fundamental Research FundsfortheCentralUniversities,China(No. 56XCA2205402)。
文摘The joined-wing configuration reduces induced drag and structural weight by connecting the rear wing to the front wing.In addition,the rear wing can replace the role of the horizontal tail of a conventional aircraft,thus eliminating the aerodynamic drag and weight associated with the horizontal tail.This particular shape creates a highly coupled relationship between aerodynamics and structure,which must be fully considered during the overall design process to enhance aircraft performance.In this research,an aero-structural design model of the joined-wing aircraft is constructed based on high-fidelity computational fluid dynamics and structural finite element methods.The model is able to obtain accurate aerodynamic loads for the non-planar wing and to simulate the statically indeterminate structure of the closed wing configuration.The influence of the joined-wing shape parameters on the aerodynamic and structural disciplines,as well as the influence of geometric nonlinear characteristics,deformation constraints and buckling constraints on the structural weight are all taken into consideration.The model is applied to complete the aero-structural design optimization of a high-altitude long-endurance joined-wing aircraft,and wind tunnel tests are conducted.The test results verify the credibility of the design model proposed and the validity of the design environment.
