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61.
严承华 《海军工程学院学报》2005,17(4):43-46
利用真正物理意义上的弹性模型来解决潜体运动图像变体匹配的问题,建立了海水介质中潜体运动图像的弹性模型,研究和实现了基于弹性网的潜体运动图像匹配算法.该算法较好地处理了某型潜体在不同时期同一区域尾迹图像之间的匹配问题,为研究潜体运动图像的形成和分析及探测运动潜体尾迹提供了决策手段和依据。 相似文献
62.
黄长征 《武汉理工大学学报(信息与管理工程版)》2003,25(4):79-81
对恒速成长公司股票的投资价值进行了弹性分析。结果表明,恒速成长公司投资价值的利率与业绩弹性既敏感地依赖于公司的成长速度和利率水平等内外部因素,也是刻画股票某种投机价值的恰当指标。 相似文献
63.
64.
刘兰 《武汉冶金管理干部学院学报》2004,14(4)
我国目前存在着非常严重的城镇失业问题 ,而且显示出明显的结构性矛盾。本文分析了导致失业的结构性质的原因 ,并提出了相应的治理对策 相似文献
65.
66.
Maximum stress intensity factors of a surface crack usually appear at the deepest point of the crack, or a certain point along
crack front near the free surface depending on the aspect ratio of the crack. However, generally it has been difficult to
obtain smooth distributions of stress intensity factors along the crack front accurately due to the effect of corner point
singularity. It is known that the stress singularity at a corner point where the front of 3 D cracks intersect free surface
is depend on Poisson's ratio and different from the one of ordinary crack. In this paper, a singular integral equation method
is applied to calculate the stress intensity factor along crack front of a 3-D semi-elliptical surface crack in a semi-infinite
body under mixed mode loading. The body force method is used to formulate the problem as a system of singular integral equations
with singularities of the form r
−3 using the stress field induced by a force doublet in a semi-infinite body as fundamental solution. In the numerical calculation,
unknown body force densities are approximated by using fundamental density functions and polynomials. The results show that
the present method yields smooth variations of mixed modes stress intensity factors along the crack front accurately. Distributions
of stress intensity factors are indicated in tables and figures with varying the elliptical shape and Poisson's ratio. 相似文献
67.
分析了双卧轴振动搅拌机的机构特点及其工作原理,建立了合理的振动搅拌叶片的数学模型;并通过对模型的分析和计算,得到了叶片固有频率、弹性常数和计算质量的计算公式,可以较准确地求出振动搅拌叶片的各参数. 相似文献
68.
Web-facing applications are expected to provide certain performance guarantees despite dynamic and continuous workload changes. As a result, application owners are using cloud computing as it offers the ability to dynamically provision computing resources (e.g., memory, CPU) in response to changes in workload demands to meet performance targets and eliminates upfront costs. Horizontal, vertical, and the combination of the two are the possible dimensions that cloud application can be scaled in terms of the allocated resources. In vertical elasticity as the focus of this work, the size of virtual machines (VMs) can be adjusted in terms of allocated computing resources according to the runtime workload. A commonly used vertical resource elasticity approach is realized by deciding based on resource utilization, named capacity-based. While a new trend is to use the application performance as a decision making criterion, and such an approach is named performance-based. This paper discusses these two approaches and proposes a novel hybrid elasticity approach that takes into account both the application performance and the resource utilization to leverage the benefits of both approaches. The proposed approach is used in realizing vertical elasticity of memory (named as vertical memory elasticity), where the allocated memory of the VM is auto-scaled at runtime. To this aim, we use control theory to synthesize a feedback controller that meets the application performance constraints by auto-scaling the allocated memory, i.e., applying vertical memory elasticity. Different from the existing vertical resource elasticity approaches, the novelty of our work lies in utilizing both the memory utilization and application response time as decision making criteria. To verify the resource efficiency and the ability of the controller in handling unexpected workloads, we have implemented the controller on top of the Xen hypervisor and performed a series of experiments using the RUBBoS interactive benchmark application, under synthetic and real workloads including Wikipedia and FIFA. The results reveal that the hybrid controller meets the application performance target with better performance stability (i.e., lower standard deviation of response time), while achieving a high memory utilization (close to 83%), and allocating less memory compared to all other baseline controllers. 相似文献
69.
Hamza Sahli Nabil Hameurlain Faiza Belala 《International Journal of Parallel, Emergent and Distributed Systems》2017,32(6):593-616
The few recent years have witnessed the appearance of a new kind of self-adaptive systems called cloud based-elastic systems. These systems are particularly appealing for their ability to maintain a decent quality of service and reduce a system’s operating cost at the same time. They achieve this by dynamically adjusting resources allocation in terms of elasticity. Meanwhile, complexity of structural and behavioural aspects related to cloud-based elastic systems increase the difficulty of designing and developing such systems. In this paper, we address this challenge by proposing a formal approach based on bigraphical reactive systems for modelling both structural and behavioural aspects of cloud-based elastic systems. In particular, we represent their behaviour in terms of client/application interactions and elasticity methods at different levels using bigraphical reaction rules. The feasibility of the proposed approach is illustrated through a motivating example running on the top of an Amazon Elastic Compute Cloud (EC2) infrastructure. 相似文献
70.
The physicochemical concept of turbulent drag reduction (the Toms effect) integrates physicochemical characteristics of polymer solutions with hydrodynamic and rheological flow parameters into a generalized equation, where the increment in volumetric flow rate QP is a function of the external shear stress τw, temperature, volume of macromolecular coils with immobilized solvent Vc and a function of their volume fraction Ψ = C · [η]/(1 + C · [η]). The QP depends on the coil intrinsic elasticity [G] = kT/Vc as well. This model allows one: (1) to describe the Toms effect in terms of useful elastic work spent by macromolecular coils with immobilized solvent to overcome the frictional forces (i.e. the forces of intermolecular interactions), (2) to forecast the initial conditions of the Toms effect (τ* ≈ (RT)/(M · [η])) and (3) to explain the unusual temperature dependence of the polymer solutions flow. 相似文献