Traditional Mechanical Model Research Articles

The Finite Element Model Study of the Pre-Twisted Euler Beam

Based on the traditional mechanical model of straight beam, the paper makes a systematic analysis and research on the pre-twisted Euler beam finite element numerical model. The paper uses two-node model of 12 degrees of freedom, axial displacement interpolation function using 2-node Lagrange interpolation function, beam transverse bending displacements (u and υ) still use the cubic displacement, bending with torsion angle displacement function using cubic polynomial displacement function. Firstly, based on the author previous literature on the flexure strain relationship, the paper deduces the element stiffness matrix of the pre-twisted beam. Finally, by calculating the pre-twisted rectangle section beam example, and contrasting three-dimensional solid finite element using ANSYS, the comparative analysis results show that pre-twisted Euler beam element stiffness matrix has good accuracy.

The Application of Finite Element Analysis Software MSC.Marc in Numerical Simulation of Fabric

The draping and buckling of woven fabric are simulated with the finite element method based on the micro-mechanical constitutive model and orthotropic constitutive model under gravity load. Compared with the traditional orthotropic mechanical model of the fabric, the micro-mechanical constitutive model characterizes the special properties of woven fabric due to its micro-weaving structures. The woven fabric sheet is discretized with 8-nodes shell elements which are designed for finite deformation and suffice to describe the large rotation of fabric sheet during draping, for the sake of simplicity, the nodes of the fabric sheet on the edges of the desk are assumed to be fixed. Compared with the experimental ones, the simulation results with the micro-mechanical constitutive model are in good agreement with the observations. The work paves the way for developing a virtual clothes trial system.

The Evolutionary Economic Geography of Regional Economic Development in Asia

The paper will review representations of regional development models in terms of their assumptions (peeled away like an onion) and in terms of their level of complexity, very much in the tradition of Peter Allen's classification system. Some applied models of regional economic development in Asia will be presented in more detail and compared to each other in terms of their ability to understand development and to gain knowledge about real world problem solutions. The paper shows with examples how complex systems of the kind using economic geography, can be used effectively in policy making in a very specific set of geographies. These new approaches capture economic restructuring across geographies in a way that they offer policy choice hitherto unseen and unrecognizable.Understanding reality and gaining knowledge about a problem require us to reduce the real complexity of any particular situation to a simpler, more understandable system by making specific simplifying assumptions. It is shown that there exist representations that, while being sufficiently simple to be understood, remain sufficiently representative of reality and yield significant power to make a big difference to regional economic development in Asia when compared to other, less useful representations. For instance, what is important to be explained in dynamic socio-economic systems is the structural change in terms of degree of heterogeneity of agent populations in space, the modularity and hierarchy of a system, and similar aspects of composite structural existence. Traditional mechanical models of regional economic development assume away structural change with the assumption of completeness of network connections among agents in the system, thereby imposing a simplifying homogeneity on economic agents that significantly reduces explanatory power.

Gradient of Soil Constitutive Model

For the soil is a very complex natural material, significant strain gradient effect exist in soil analysis. Based on the "gradient" phenomenon, we add the plastic strain gradient hardening item into the traditional Cambridge yield surface. By using the consistency conditions and associated flow rule, we get the explicit expression of plastic strain gradient stiffness matrix. And the finite element method of plastic strain gradient is also shown in this article. Plastic strain gradient is actually a phenomenological non-local model containing microstructure information of the material. It may overcome the difficulties in simulating the gradient phenomenon by traditional mechanical model.

Allometric Scaling Law Questions the Traditional Mechanical Model for Axillary Lymph Node Involvement in Breast Cancer

To find a quantitative relationship between tumor size and frequency of axillary lymph node involvement. The frequency of axillary node involvement versus primary tumor volume was analyzed in 10 selected series of patients incorporating a total of 57,244 women with resectable breast cancer. The average number of events per unit volume resulting in tumor spread to axillary lymph nodes before tumor surgical removal Theta(V)/V, was estimated under simple probabilistic assumptions. The allometric scaling law Theta(V)/V = 0.0586V(-0.7457) was estimated on the data, fitting the proportion of lymph node involvement on tumor volume V (in microliters). The estimate 0.7457 (95% CI, 0.7200 to 0.7713) suggests that the true scaling exponent, under the assumed model, may be the fractional value, which characterizes scaling relationships for a wide variety of biologic variables at both the whole organism level and organ level. Results suggest that the phenomenon should be related to some internal structural trait of the tumor. The vascular network seems to be the best candidate. This result does not support a mere mechanical model of lymphatic tumor spread. A more complex biology-based model of lymphohematogenous spread is suggested, in which the axillary nodes draining the lymph from the primary tumor may become activated by factors produced by both tumor cells and tumor stroma, thus favoring cell-selective homing of otherwise circulating tumor cells. The success of fractal features related to the internal architecture brings additional support to the consideration of primary breast cancer as an organ-like structure.

The connection between the dynamic intensity model and the vibronic intensity model for f–f transitions

In this paper we discuss intensity mechanisms of interest for rare-earth ions in optical materials. More specifically, we investigate the character of two models—first, a semi-classical dynamic intensity model, and second, a more traditional quantum mechanical vibronic intensity model. We focus on the case of f–f transitions and show that the predicted oscillator strengths then are the same under very reasonable approximations. We emphasize that this connection between the models cannot be made in the case of f–d transitions. The dynamic intensity model has an interesting classical interpretation. We show that it is very convenient to apply this approach together with classical dynamical techniques such as molecular dynamics simulation or the classical Monte Carlo method. The classical approach simplifies both the interpretation and calculation of vibronic oscillator strengths in complex systems. The concept of an effective temperature works as a bridge between the two models; so realistic predictions can be obtained even at low temperatures.

A Review of Surgical Simulation With Attention to Validation Methodology

The use of simulation technology for teaching and evaluating surgical skills has gained considerable attention in recent years. This is driven by interest in quality of care, concerns over increasing operative complexity, constraints on the use of animal models, limited available patient material, medicolegal pressures, and fiscal mandates for cost-effective performance. Traditional mechanical models are yielding to techniques dependent on electronic technology, including virtual reality. Data to support the validity of simulation techniques for surgical training, assessment, and certification represent only a fraction of the literature available on the subject. Literature searches were conducted in MEDLINE and ERIC, covering the period from 1966 to the present. The electronic and bioengineering literature was not surveyed due to the extensive literature on technology development, distinct from assessment of context specific validity. The search results and the bibliographies of key review articles were examined to identify articles that contained original data, measured performance between cohorts, defined performance measures, and described a standard against which performance was compared. Most of the literature pertaining to simulation techniques for surgical training has been published within the past 5 years and consist of review, opinion, and feasibility articles. There is an emerging body of evidence to establish the validity of simulation techniques for assessing surgical skills. Further refinement of simulation techniques, identification of specific performance measures, longitudinal evaluations, and comparison to practice outcomes are still needed to establish the validity and the value of surgical simulation for teaching and assessing surgical skills prior to considering implementation for certification purposes.

The future of simulators in GI endoscopy: An unlikely possibility or a virtual reality?

The future of simulators in GI endoscopy: An unlikely possibility or a virtual reality?

Mechanical environment associated with rotator cuff tears

A simplified 2-dimensional finite element model was used to investigate the stress environment in the supraspinatus tendon. The extrafibrillar matrix and collagen fiber were modeled with fiber-reinforced composite elements. The stress was evaluated at humeroscapular elevation angles of 0°, 30°, and 60°. Two acromion conditions were simulated. In the first set of conditions there was no subacromial impingement. In the second set there was subacromial impingement of the bursal side. Impingement was simulated by producing a 1-mm indentation on the bursal surface, an indentation similar to the type of impingement associated with deltoid contraction. The results demonstrated that subacromial impingement generates high stress concentrations in and around the critical zone. Such high stress could initiate a tear; tears that result from stress point to an extrinsic mechanism. However, we found that high stress and potential tears caused by impingement may occur on the bursal side, the articular side, or within the tendon. This result is unaccounted for by traditional mechanical models in which only bursal-sided partial tears are initiated by subacromial impingement.

Muscle dynamics: dependence of muscle length on changes in external load.

A phenomenological theory of muscle dynamics has been elaborated on the basis of data obtained in experiments on hind limb extensor muscles of narcotized cat. Functional dependence of muscle length on external load was explored in conditions of a constant frequency of the efferent stimulation. It was shown that the system under study could be presented for a rather wide class of input signals as a system with nonlinear statics and linear dynamics. The nonlinear statics was shown to be determined mainly by the hysteretical effects of muscle contraction, whereas dynamic element was described by the first order linear differential equation corresponding to the traditional three-component mechanical model of the muscle. A hypothesis was proposed to explain the hysteresis in active muscle on the basis of functioning of the troponin-tropomyosin regulatory complex. Elaborated mathematical model of muscle dynamics can be used to predict and evaluate changes in the muscle length evoked by arbitrary changes in the external load.

Interdiurnal variability of total solar and sky radiation on a horizontal surface at Athens, Greece : Karapiperis, P. P., University of Athens, COMPLES, Bulletin, 5, Nov. 1963, 4 pp.

Although the traditional phenomenological mechanical model of rock salt based on macro-mechanical experiments adequately describes its macroscopic mechanical behavior, the effect of the microstructure of this mineral on its macro-mechanical properties and intrinsic physical deformation and failure processes remains unclear. Therefore, in this study, scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) were used to investigate the grain boundaries and grain size distribution, and a nanoindentation technique was employed to analyze the elastic characteristics of the grains, to better understand the structural and mechanical characteristics of rock salt on a microscopic scale. Furthermore, a multiscale numerical model of polycrystalline rock salt based on the microstructure was established, using the specified particle size Voronoi polyhedron modeling method and the discrete element method. In addition, numerical models were constructed with different embedded grain size distribution characteristics, enabling the effects of the distribution parameters on the mechanical behavior to be clarified in detail. The results indicated that the macroscopic mechanical behavior of rock salt is simultaneously determined by the physical and mechanical properties of the grains and grain boundaries. In addition, the resulting simulation results based on the numerical models indicate that the strength and ductility of rock salt are affected by the average diameter, heterogeneity index and skewness coefficient.