Perfect simulation for interacting point processes, loss networks and Ising models

We present a perfect simulation algorithm for measures that are absolutely continuous with respect to some Poisson process and can be obtained as invariant measures of birth-and-death processes. Examples include area- and perimeter-interacting point processes (with stochastic grains), invariant measures of loss networks, and the Ising contour and random cluster models. The algorithm does not involve couplings of the process with different initial conditions and it is not tied up to monotonicity requirements. Furthermore, it directly provides perfect samples of finite windows of the infinite-volume measure, subjected to time and space ``user-impatience bias''. The algorithm is based on a two-step procedure: (i) a perfect-simulation scheme for a (finite and random) relevant portion of a (space-time) marked Poisson processes (free birth-and-death process, free loss networks), and (ii) a ``cleaning'' algorithm that trims out this process according to the interaction rules of the target process. The first step involves the perfect generation of ``ancestors'' of a given object, that is of predecessors that may have an influence on the birth-rate under the target process. The second step, and hence the whole procedure, is feasible if these ``ancestors'' form a finite set with probability one. We present a sufficiency criteria for this condition, based on the absence of infinite clusters for an associated (backwards) oriented percolation model.Comment: Revised version after referee of SPA: 39 page

Firm Strategy and Foreign Direct Investment: An Examination of the Economic Performance of U.S. Multinational Firms

International Relations/Trade, Production Economics,

Loss network representation of Peierls contours

We present a probabilistic approach for the study of systems with exclusions, in the regime traditionally studied via cluster-expansion methods. In this paper we focus on its application for the gases of Peierls contours found in the study of the Ising model at low temperatures, but most of the results are general. We realize the equilibrium measure as the invariant measure of a loss-network process whose existence is ensured by a subcriticality condition of a dominant branching process. In this regime, the approach yields, besides existence and uniqueness of the measure, properties such as exponential space convergence and mixing, and a central limit theorem. The loss network converges exponentially fast to the equilibrium measure, without metastable traps. This convergence is faster at low temperatures, where it leads to the proof of an asymptotic Poisson distribution of contours. Our results on the mixing properties of the measure are comparable to those obtained with ``duplicated-variables expansion'', used to treat systems with disorder and coupled map lattices. It works in a larger region of validity than usual cluster-expansion formalisms, and it is not tied to the analyticity of the pressure. In fact, it does not lead to any kind of expansion for the latter, and the properties of the equilibrium measure are obtained without resorting to combinatorial or complex analysis techniques.Comment: 42 pages. Revised version after the first referee repor

Economic Performance of U.S. Multinational Agribusinesses: Foreign Direct Investment and Firm Strategy

This paper empirically assesses the sequential relationships among firm strategic factors, FDI activity, and economic performance for a sample of U.S.-based Multinational agribusinesses. The most important findings of this research is a positive direct effect of FDI on performance, the complementary effect between FDI and firm strategic factors (positive and significant interaction terms) on performance, and the positive effect of FDI on performance given some thresholds of firm strategic factors. Specifically, it provides insights about the direct effect of FDI on performance, as well as about the joint effect of firm size and FDI, marketing intensity and FDI, and capital intensity and FDI on performance. These findings provide evidence that FDI activity is an important factor for U.S. agribusiness financial strength.Economic performance, Foreign direct investment, Firm strategic factors, Agribusiness, Agribusiness, International Relations/Trade, Marketing, F230, L250,

Experimental evaluation of Stress Intensity Factors from strain fields using Digital Image Correlation

P Lopez-Crespo, A. Garcia-Gonzalez, Experimental evaluation of Stress Intensity Factors from strain fields using Digital Image Correlation, Proceedings of Jornadas Idmati 2014, Barcelona, junio de 2014Optical techniques offer many benefits to experimentalist compared with gauge methods. Optical techniques such as holographic interferometry, electronic speckle pattern interferometry, photo- and thermoelasticity, and various grid methods are non-contact, full-field and can have high resolution. However, they are expensive or require special surface preparation or provide reliable measurements only in certain locations (fringes). Moreover, these techniques are hard to apply in field conditions. In contrast, the image correlation technique is cheap, easy, versatile and requires minimal surface preparation. It is ideally suited for field application. In this work a two-dimensional image correlation method was used to measure in-plane displacement fields near crack tip. Linear elasticity was assumed outside the crack tip plasticity zone. In the elastic region Muskhelishvili's complex functions approach was used to calculate the stress intensity factors from the measured displacements. functions were used to calculate the stress intensity factors from the measured displacements. Computationally the problem is that of solving an overdetermined system of non-linear equations. In this work genetic algorithm was used to find the solution. The method was applied to fatigue cracks in 2 and 3 mm thick Al 7010 alloy plates loaded under mixed mode (I+II). The stress intensity factors were calculated to within 10-20% of the nominal applied values. In addition the crack tip location was calculated. The sensitivity of the technique to the experimental noise and the issues of the location and the number of the experimental data points will be discussed. Finally the extention of the method to a real time monitoring will be analysed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Diisopropylamide and TMP turbo-grignard reagents : a structural rationale for their contrasting reactivities

A neutral dimeric molecule in crystal form, the diisopropylamido turbo-Grignard reagent "(iPr2N)MgCl⋅LiCl" (see structure; blue N, red O, green Mg, yellow Cl, black C) separates into several charged ate species in dynamic exchange with each other in THF solution as determined by a combination of EXSY and DOSY NMR studies

Consumer Confidence in the Food System, Media Coverage and Stock Prices of Food Companies: A Regression Analysis

A series of recent and serious food safety incidents have generated a national debate over the significant costs that they impose on various stakeholders - consumers, industry, or the government. This paper examines the impact of media coverage of food safety and defense issues on consumer confidence in food safety, and measures the response of stock prices of food companies to changes in consumer confidence. Results show that, increases in media coverage have a negative impact on consumer confidence, and that decreases in the levels of consumer confidence on food safety have a negative impact on stock prices of food companies, in particular for the larger firms. These findings confirm that the financial performance of food the industry is negatively affected by category-specific food safety events, and the effects of media coverage on consumer confidence in the safety of the food system.Agribusiness, Food Consumption/Nutrition/Food Safety,

HAAS AUTOMATION UMC750 5AXIS MILL ASSEMBLY PROCESS IMPROVEMENT

The improvement of the current assembly of the motor and casting components for the Haas UMC-750 5-Axis vertical CNC mill includes the evaluation, development and proposal of a new pair of material handling carts. To meet these deliverables, a student team began by assessing the assembly workstation, defining the problem to be solved, researching ergonomics in material handling equipment and drafting the final design of the improved cart models using SolidWorks. The final design considered the initial improvement request from the client, as well as better ergonomic features to enhance the safety of the operators. It was estimated that the new design can provide Haas Automation with savings in material cost and production of the cart. At the same time, by improving the design, the new carts reduce risk of employee injury by decreasing the use of an overhead crane for assembling the motor components. The SolidWorks models and engineering drawings will be presented to Haas Automation in the hope of a future implementation

On Chern-Simons Quivers and Toric Geometry

We discuss a class of 3-dimensional N=4 Chern-Simons (CS) quiver gauge models obtained from M-theory compactifications on singular complex 4-dimensional hyper-Kahler (HK) manifolds, which are realized explicitly as a cotangent bundle over two-Fano toric varieties V^2. The corresponding CS gauge models are encoded in quivers similar to toric diagrams of V^2. Using toric geometry, it is shown that the constraints on CS levels can be related to toric equations determining V^2.Comment: 14pg, 1 Figure, late