Simple Degenerate Formulation for Large Displacement Analysis of Beams

A finite-element formulation for the large displacement analysis of beams is proposed. It is based on the degeneration approach: The governing equations for a general solid are directly discretized. The assumptions of the Timoshenko beam theory are implemented in the discretization process by devising beam elements and utilizing the penalty method. The formulation for 2D beam analysis is first presented and the 3D formulation follows. Characteristically, the proposed beam elements possess relative nodes and rotations are excluded from nodal variables. The beam formulations thus developed are quite simple and straightforward. It is noteworthy that unlike conventional formulations, the present formulation for 3D beam analysis is just a simple extension of the 2D case, which can be attributed mainly to the avoidance of rotations in nodal variables. In numerical examples, the approximate penalty number is investigated first by analyzing a cantilever beam, and it turns out to be 103 times Young's modulus. With this value, example problems are solved and excellent agreement with the existing solutions is observed, confirming the validity of the present formulation.     

Production Scheduling for Precast Plants using a Flow Shop Sequencing Model

There are two alternatives for production organization in precast factories—namely, the comprehensive method and the specialized method. Production scheduling under the specialized alternative has been found to be a difficult optimization problem if heterogeneous elements are involved. A flow shop sequencing model that incorporates actual constraints encountered in practice is proposed for this difficult case of precast production scheduling. The model is solved using a genetic algorithm (GA). The traditional minimize makespan and the more practical minimize tardiness penalty objective functions are optimized separately, as well as simultaneously using a normalized weighted GA. Comparisons between the GA and classical heuristic rules show that the GA can obtain good schedules for the model, giving a family of solutions that are at least as good as those produced by the use of heuristic rules.     

Velocity Pulse Model for Turbulent Diffusion from Flowing Water into a Sediment Bed

The “velocity pulse model” simulates the transfer of turbulence from flowing water into a sediment bed, and its effect on the diffusional mass transfer of a solute (e.g., oxygen, sulfate, or nitrate) in the sediment bed. In the “pulse model,” turbulence above the sediment surface is described by sinusoidal variations of vertical velocity in time. It is shown that vertical velocity components dampen quickly inside the sediment when the frequency of velocity fluctuations is high and viscous dissipation is strong. Viscous dissipation (ν) inside the sediment is related to the apparent viscosity depending on the structure of the sediment pore space, i.e., the porosity and grain diameter, as well as inertial effects when the flow is turbulent. A value ν/ν0 between 1 and 20 (ν0 is kinematic viscosity of water) has been considered. Turbulence penetration into the sediment is parametrized by the Reynolds number Re = UL/ν and the relative penetration velocity W/U, where U=amplitude of the velocity pulse; and W=penetration velocity; L = WT=wave length of the velocity pulse; and T is its period. Amplitudes of vertical velocity components inside the sediment and their autocorrelation functions are computed, and the results are used to estimate eddy viscosity inside the sediment pore system as a function of depth. Diffusivity in the sediment pore system is inferred by using turbulent or molecular Schmidt numbers. Turbulence penetration from flowing water can enhance the vertical diffusion coefficient in a sediment bed by an order of magnitude or more. Penetration depth of turbulence is higher for low frequency velocity pulses. Vertical diffusivity inside the pore system is shown to decrease more or less exponentially with depth below the sediment/water interface. Vertical diffusivities in a sediment bed estimated by the “velocity pulse model” can be used in pore water quality models to describe vertical transport from or into flowing surface water. The analysis has been conducted for a conservative material, but source and sink terms can be added to the vertical transport equation.     

A continuous penalty function method for inverse treatment planning

Conventional inverse treatment planning attempts to calculate dose distributions that may not be feasible given the specified dose levels to various anatomical structures. A technique for inverse treatment planning has been developed that uses only target dose levels which are easily selectable to be feasible. A nonlinear constrained minimization problem is formulated to reflect the goal of sparing critical organs as much as possible while delivering a certain target dose within specified uniformity. The objective function is the squared dose delivered to critical organs. The constraints require the delivery of certain target dose within specified uniformity and non-negative pencil beam weights. A continuous penalty function method is introduced as a method for solving the large-scale constrained minimization problem. The performance of the continuous penalty function method is optimized by numerical investigation of few numerical integration schemes and a pair of weighting functions which influence the utility of the method. Clinical examples are presented that illustrate several features of the technique. The properties of the continuous penalty function method suggest that it may be a viable alternative to conventional inverse treatment planning.     

Intracellular fluorescent probe concentrations by confocal microscopy

A general method is described that takes advantage of the optical sectioning properties of a confocal microscope to enable measurement of both absolute and relative concentrations of fluorescent molecules inside cells. For compartments within cells that are substantially larger than the point spread function, the fluorescence intensity is simply proportional to the concentration of the fluorophore. For small compartments, the fluorescence intensity is diluted by contributions from regions outside the compartment. Corrections for this dilution can be estimated via calibrations that are based on the intensity distribution found in a computationally synthesized model for a cell or organelle that has been blurred by convolution with the microscope point spread function. The method is illustrated with four test cases: estimation of intracellular concentration of a fluorescent calcium indicator; estimation of the relative distribution between the neurite and soma of a neuronal cell of the InsP3 receptor on the endoplasmic reticulum; estimation of the distribution of the bradykinin receptor along the surface of a neuronal cell; and relative distribution of a potentiometric dye between the mitochondria and cytosol as a means of assaying mitochondrial membrane potential.     

钢铁生产过程富余煤气动态优化分配模型

基于混合整数线性规划,以操作成本最小为目标函数建立了富余煤气优化分配模型.与前人的优化模型相比,本文模型选取了较短的时间步长,并考虑了锅炉权重因子及煤气柜权重因子对优化结果的影响.根据国内某钢铁企业生产数据进行计算,发现优化结果对煤气柜权重因子和锅炉权重因子敏感,因此合理确定煤气柜权重因子和锅炉权重因子十分重要.优化模拟计算与现场经验调度的结果相比,降低了煤气柜储气量波动,提高了锅炉45.9%的发电量,煤气系统运行稳定性增强.      

一种块体–颗粒–杆件的耦合方法及其在隧道支护模拟中的应用

为了模拟隧道开挖过程中边帮的失稳垮塌过程以及锚杆对隧道的支护过程,提出了一种基于罚弹簧的块体–颗粒–杆件的耦合方法.该耦合方法基于连续–非连续的数值模拟方法(CDEM),采用离散颗粒簇表征隧道周边松动圈以内的破碎岩体,采用块体单元表征松动圈以外的完整岩体,采用杆件单元描述锚杆及锚索等杆系类支护结构,采用插值耦合的方式实现杆件单元与离散颗粒及块体单元间力与位移的传递,从而实现高应力环境下隧道开挖失稳过程的模拟及支护效果的评价.颗粒与块体之间采用1根法向线性弹簧及2根切向线性弹簧进行耦合,法向弹簧引入拉伸断裂本构,切向弹簧引入Mohr–Coulomb脆性断裂本构.杆件与颗粒及杆件与块体之间的耦合模式基本一致,包含1根沿着杆件轴向的罚弹簧S_gn及1根垂直于杆件轴向的罚弹簧S_gs,S_gn主要用于描述杆件与围岩之间的拉拔效应及推压效应,S_gs则主要用于描述杆件与围岩之间的侧向挤压效应.圆形盾构隧道弹性场分析、预应力锚杆加固矩形巷道模拟、全长连接锚杆对岩块的锚固作用分析、以及碎裂岩体中的隧道开挖支护效果分析等案...     

Evaluation of segmentation algorithms for generation of patient models in radiofrequency hyperthermia

Time-efficient and easy-to-use segmentation algorithms (contour generation) are a precondition for various applications in radiation oncology, especially for planning purposes in hyperthermia. We have developed the three following algorithms for contour generation and implemented them in an editor of the HyperPlan hyperthermia planning system. Firstly, a manual contour input with numerous correction and editing options. Secondly, a volume growing algorithm with adjustable threshold range and minimal region size. Thirdly, a watershed transformation in two and three dimensions. In addition, the region input function of the Helax commercial radiation therapy planning system was available for comparison. All four approaches were applied under routine conditions to two-dimensional computed tomographic slices of the superior thoracic aperture, mid-chest, upper abdomen, mid-abdomen, pelvis and thigh; they were also applied to a 3D CT sequence of 72 slices using the three-dimensional extension of the algorithms. Time to generate the contours and their quality with respect to a reference model were determined. Manual input for a complete patient model required approximately 5 to 6 h for 72 CT slices (4.5 min/slice). If slight irregularities at object boundaries are accepted, this time can be reduced to 3.5 min/slice using the volume growing algorithm. However, generating a tetrahedron mesh from such a contour sequence for hyperthermia planning (the basis for finite-element algorithms) requires a significant amount of postediting. With the watershed algorithm extended to three dimensions, processing time can be further reduced to 3 min/slice while achieving satisfactory contour quality. Therefore, this method is currently regarded as offering some potential for efficient automated model generation in hyperthermia. In summary, the 3D volume growing algorithm and watershed transformation are both suitable for segmentation of even low-contrast objects. However, they are not always superior to user-friendly manual programs for contour generation. When the volume growing algorithm is used, the contours have to be postprocessed with suitable filters. The watershed transformation has a large potential if appropriately developed to 3D sequences and 3D interaction features. After all, the practicality and feasibility of every segmentation method critically depend on various details of the user software as pointed out in this article.     

Induction of a subgroup of acute phase protein genes in mouse liver by hyperthermia

We have demonstrated that two members of the acute phase reactant family of positively regulated genes, alpha 1-acid glycoprotein (AGP-1 and AGP-2) and C-reactive protein (CRP) are induced by hyperthermia, while two others, the serum amyloid A (SAA) and alpha 1-antitrypsin (AT) genes, are not. Albumin (ALB), a negative acute phase reactant gene, is also induced by hyperthermia. The AGP-1, AGP-2, and CRP genes require glucocorticoids, but not IL-6, IL-1 beta or TNF alpha in response to hyperthermia. As with LPS, the C/EBP beta mRNA levels increased, while the C/EBP alpha mRNA levels decreased in response to LPS. In contrast to the LPS response, C/EBP delta was unchanged. Protein pool levels and DNA-binding activities of the 35 and 20 kDa C/EBP beta isoforms increase, whereas protein pool levels of the 42 kDa C/EBP alpha decrease and the 30kDa remained high. These studies suggest that the synthesis of specific C/EBP alpha and C/EBP beta isoforms is induced by hyperthermia, and that the regulation of the AGP-1 and AGP-2 genes during heat stress may involve one of these isoforms. The difference between the responses to hyperthermia and LPS is that the former, may not involve the participation of cytokines. Furthermore, since cis-acting heat shock elements (HSE) are located in the promoter regions of the ALB, CRP, and C/EBP beta genes, these regulatory sequences may be involved in the in vivo activation of these genes by hyperthermia.     

钢铁企业产品价格精准管控模型的研究

在钢铁企业进入微利时代的形势下,按照充分利用市场机制,平衡产需,实现销售收入最大化的方法,建立了价格优化决策的模型,利用罚函数的方法对非线性规划模型进行求解,得出最优价格,形成了价格精准管理的系统构架。     

Handling of Constraints in Finite-Element Response Sensitivity Analysis

In this paper, the direct differentiation method (DDM) for finite-element (FE) response sensitivity analysis is extended to linear and nonlinear FE models with multi-point constraints (MPCs). The analytical developments are provided for three different constraint handling methods, namely: (1) the transformation equation method; (2) the Lagrange multiplier method; and (3) the penalty function method. Two nonlinear benchmark applications are presented: (1) a two-dimensional soil-foundation-structure interaction system and (2) a three-dimensional, one-bay by one-bay, three-story reinforced concrete building with floor slabs modeled as rigid diaphragms, both subjected to seismic excitation. Time histories of response parameters and their sensitivities to material constitutive parameters are computed and discussed, with emphasis on the relative importance of these parameters in affecting the structural response. The DDM-based response sensitivity results are compared with corresponding forward finite difference analysis results, thus validating the formulation presented and its computer implementation. The developments presented in this paper close an important gap between FE response-only analysis and FE response sensitivity analysis through the DDM, extending the latter to applications requiring response sensitivities of FE models with MPCs. These applications include structural optimization, structural reliability analysis, and finite-element model updating.     

MCG simulations with a realistic heart-torso model

Magnetocardiograms (MCG's) simulated with a high-resolution heart-torso model of an adult subject were compared with measured MCG's acquired from the same individual. An exact match of the measured and simulated MCG's was not found due to the uncertainties in tissue conductivities and cardiac source positions. However, general features of the measured MCG's were reasonably represented by the simulated data for most, but not all of the channels. This suggests that the model accounts for the most important mechanisms underlying the genesis of MCG's and may be useful for cardiac magnetic field modeling under normal and diseased states. MCG's were simulated with a realistic finite-element heart-torso model constructed from segmented magnetic resonance images with 19 different tissue types identified. A finite-element model was developed from the segmented images. The model consists of 2.51 million brick-shaped elements and 2.58 million nodes, and has a voxel resolution of 1.56 x 1.56 x 3 mm. Current distributions inside the torso and the magnetic fields and MCG's at the gradiometer coil locations were computed. MCG's were measured with a Philips twin Dewar first-order gradiometer SQUID-system consisting of 31 channels in one tank and 19 channels in the other.     

基于变邻域搜索的热轧圆钢批量调度多目标优化方法

针对热轧圆钢的批量调度问题,考虑实际生产中工艺规程和交货期对轧制单元连续加工的影响,建立了以最小化设备调整时间、拖期生产惩罚和钢种跳跃惩罚为优化目标的数学模型,并设计了一种嵌入EDD规则的变邻域搜索算法.算法首先结合模型的约束特征,采用约束满足技术生成初始解;根据实际生产需求,将最小化设备调整时间作为主要目标,设计变邻域搜索算法实现目标优化,其中,运用混合算子构造邻域结构和局部搜索,并引入模拟退火接受准则来控制迭代过程中产生的新解;同时,为了最小化拖期惩罚和钢种跳跃惩罚,在求解过程中嵌入了EDD规则以及钢种排序规则.实验结果表明,模型和算法是可行且有效的.      

Pre-clinical evaluation of a microwave planar array applicator for superficial hyperthermia

Multi-element hyperthermia applicators have an advantage over single-aperture devices in that the power deposition pattern across the applicator surface may be adjusted to improve the resultant temperature distribution. This capability can be used to compensate for irregular tumour geometry as well as heterogeneity of thermal and power absorption parameters within the tissue. This paper evaluates the first commercially available microwave system of this type designed for superficial hyperthermia. The applicator (16-element planar array, 915 MHz, 15.2 x 15.2 cm footprint) was evaluated by the following: (1) measuring absolute SAR distributions in muscle-equivalent liquid phantom with an intervening 1 cm thick layer of fat phantom by scanning a calibrated E-field sensor, and (2) power output measurements using calorimetric methods. The SAR distributions measured for each individual aperture exhibited significant irregularities and differing power deposition patterns. A priori knowledge of these different power deposition characteristics was used to provide appropriate illumination schemes which could be used as initial starting points for producing clinically useful power deposition patterns. Measurements of these composite patterns demonstrate the adjustable nature and flexibility of the heating capabilities of this applicator, which includes 50% iso-SAR coverage that can be extended to the applicator perimeter. This clearly illustrates the clinical utility and potential advantages of this system over single-aperture devices for superficial hyperthermia.     

Genetically induced temporal changes in RNA synthesis and transport in local hyperthermia of the liver

The time character of RNA synthesis and transport in liver cells of linear and hybrid rats after local liver hyperthermia has been investigated. In response to the action of local liver hyperthermia the rhythmic changes of RNA synthesis and transport velocity are observed. Its time character is different in various genetic lines. The new functional relations between elements of the genetic information realization system are established against the background of the investigated influence. Their character is determined by the peculiarities of organism genotype.     

Displacement Accuracy of Discontinuous Deformation Analysis Method Applied to Sliding Block

Discontinuous deformation analysis (DDA) is a discrete element method that was developed for computing large deformation in fractured rock masses. In this paper, we present an alternative derivation of the basic theory of DDA for planar (two-dimensional) problems, and we address the accuracy of the DDA method for sliding blocks using sensitivity analyses. Results of analyses with different parameters show that the residual and relative errors in the displacement of a frictional sliding block are controlled by the perturbation in the initial time steps of the simulation. In addition, we expose a systematic error induced by the DDA penalty formulation. Overall, the initial perturbation of the solution decreases with decreasing friction angle and increasing contact penalty and, counterintuitively, decreases with increasing time step size. All analyses show that the long runout behavior of the system trends toward the analytic solution, independent of the initial perturbation. The resulting precision of the long runout simulation is more than sufficient for all problems of engineering interest.     

Simulation of electromagnetically induced hyperthermia: a finite element gridding method

A finite element gridding method for simulating electromagnetically (EM) induced hyperthermia is presented. The method uses patient CT data as its primary input, with critical structures manually outlined (on a graphics workstation) for explicit demarcation. The paper outlines the various stages involved in mesh creation, including procedures for conforming the finite element representation of critical structures to their smooth boundaries, modelling of heating equipment, and modelling of the outer boundaries. The procedure for generating the finite element model is illustrated for an example treatment. Additionally, the results of computing the SAR in six patients are compared to measured values. The comparison reveals agreement between the model prediction and actual treatment within the limits of measurement error.     

A flexible algorithm for construction of 3-D vessel networks for use in thermal modeling

A new algorithm for the construction of artificial blood vessel networks is presented. The algorithm produces three-dimensional (3-D) geometrical representations of both arterial and venous networks. The key ingredient of the algorithm is a 3-D potential function defined in the tissue volume. This potential function controls the paths by which points are connected to existing vessels, thereby producing new vessel segments. The potential function has no physiological interpretation, but, by adjustment of parameters governing the potential, it is possible to produce networks that have physiologically meaningful geometrical properties. If desired, the veins can be generated counter current to the arteries. Furthermore, the potential function allows fashioning of the networks to the presence of bone or air cavities. The resulting networks can be used for thermal simulations of hyperthermia treatment.     

Changes in muscle blood flow distribution during hyperthermia

Blood flow is a critical parameter for obtaining satisfactory temperature distributions during clinical hyperthermia. This study examines the changes in blood flow distribution in normal porcine skeletal muscle before, during and after a period of regional microwave hyperthermia. The baseline blood flow distribution during general anaesthesia and after the insertion of the thermal probes was established independently in order to isolate the changes due to hyperthermia. General anaesthesia alone and thermocouple insertion during anesthesia had no significant effect on the muscle blood flow distribution. Regional microwave heating generated a non-uniform blood flow distribution which was a function of the tissue temperature distribution. Blood flow was greater in those tissues samples in which higher temperatures were recorded and less in those sampled further from the applicators peak SAR (Specific Absorption Rate). The increase in blood flow appears to be primarily a local phenomenon. Although muscle blood flow may be considered to be uniform prior to heating, this does not hold during hyperthermia treatment. Therefore, the non-uniform nature of the blood distribution during heating should be incorporated into any practical bioheat transfer model.     

HSP 70 synthesis in clinical hyperthermia patients: preliminary results of a new technique

PURPOSE: Although thermotolerance may be an important variable in clinical hyperthermia, few means have been described to measure its effect or duration in the clinical setting. This study was undertaken to determine if heat shock protein 70 could be used as an assay to predict the presence of retained thermotolerance in human tumors. METHODS AND MATERIALS: Tissue samples were obtained from patients undergoing hyperthermia and assayed for heat shock protein 70 synthesis. Eight patients having advanced, persistent, or recurrent malignant tumors had open-ended thermometry catheters placed into the lesion being heated. Through these catheters, tissue samples were obtained using a fine needle aspiration technique. Attempts were made to obtain samples before and after the first three heat treatments. Some samples were labeled immediately with radioactive methionine (35S) at 37 degrees C for 4-8 hr, others were given a test heat dose in vitro and then labeled. Protein synthesis profiles were analyzed by gel electrophoresis and autoradiography. RESULTS: Preliminary results show that it is possible to obtain tissue from hyperthermia patients in a safe and practical manner, that the rate of heat shock protein 70 synthesis can be measured in a variety of tumors, and that the persistence of thermotolerance in the clinical setting can be shown by the inability to reinduce heat shock protein 70 synthesis. CONCLUSION: The measurement of heat shock protein 70 using the described technique may provide an assay for retained thermotolerance in clinical hyperthermia. Technical difficulties which need to be addressed include obtaining sufficient tissue in all patients, confirming the presence of tumor in the obtained tissue, and obtaining tissue at more frequent intervals to best determine the kinetics of thermotolerance.