Academic literature on the topic 'Flexible Curves'

Este libro presenta una introducción al análisis de supervivencia avanzada y se recomienda como material de apoyo para los cursos de posgrado que se relacionen con estadística (como prerequisito se recomienda un curso de probabilidad y de procesos estocásticos, sin embargo, el texto incluye un repaso de algunos conceptos que se necesitan para el desarrollo de su contenido y que pretenden nivelar al lector a fin de que se familiarice con algunos conceptos necesarios para comprender el análisis de datos de supervivencia). Con este material se pretende discutir y exhibir la fusión entre el análisis clásico de supervivencia y los procesos estocásticos que representa un avance muy importante en el área y hacen más flexible el manejo de los estimadores de las funciones de supervivencia y de las funciones de riesgo o hazard acumulado, a la vez que permite estudiar sus propiedades de una manera intuitiva, exhaustiva y apropiada.

AbstractBased on the slenderness of wind power crane boom and the complexity of working environment, a mathematical model of rigid-flexible coupling dynamics including wind load and vibration characteristic analysis is carried out for the boom-hoisting system. The equivalent spring-damping system, spatial pendulum system and elastic double-force rod are used to simulate the elastic vibration of boom, the swing of lifting weight and the elastic vibration of wire rope, respectively. The kinematic characteristics of each component are described using a hybrid coordinate system. Simulation of wind loads through an instantaneous wind model consisting of the average and pulsating wind. Derivation of dynamic model for wind power crane under wind load based on the Lagrange equation. Taking a certain type of wind power crane as the research object, based on the derived mathematical model and ADAMS model, the response curves of boom and lifting weight are solved in MATLAB and ADAMS respectively for the rotary working condition, to verify the rationality and accuracy of the mathematical model and to obtain the influence of wind load on the swing angle of lifting weight. The analysis results provide a certain theoretical basis for crane structure design, control system design and wind turbine hoisting.

One of the key issues of thick layer manufacturing is matching the shape of the flexible cutting blade to the local surface curvature of the model to be created. In this paper we explore a method to find the best matching minimum strain energy (MSE) curve for a given B-spline curve. For this purpose we developed software to a) generate a dataset containing MSE curves for a range of settings of the cutting tool and b) find the best matching curve from this MSE dataset to the given target curve. Both the MSE and the target curves are represented as point sets, the target curves having a considerable higher point density than the curves in the MSE dataset. The best matching MSE curve is defined as the curve with the minimum directed Hausdorff distance to the target curve. It is found that despite the relative low density of the dataset, for several practical domains of target curve shape, a satisfying match can be found. Numerical results concerning the matching accuracy are presented.

Free Form Thick Layered Object Manufacturing (FF-TLOM) technology is based on foam cutting with a curved heated flexible cutting blade. Three single parameters shape the flexible blade. An infinite amount of blade shapes can be selected. However, many of these shapes are not suitable for cutting. Blade shapes with less than two inflexions can be applied successfully. When two inflexions are involved the blade; more than one different stable blade shape can be realized. For tool path creation and cutting procedures the blade shape must be known. A 2-D calculation algorithm based on (Kallay, 1987) is used. The calculation result is a minimum strain energy curve of a prescribed length, which is represented by a chain of segments. The shape is unfolded by rotating each segment under conditions of total energy decrease until no improvements are achieved. In this paper the process parameters are analyzed for sensitivity and influence on the accuracy and conditions of the blade shaping process. An overview of these parameters is given and the accuracy, computing time and trustworthiness of the implemented algorithm is checked. Typical FF-TLOM process characteristics are considered for its influence on the blade shape The elastic energy of curves is presented for a complete range of blade shapes. Regions of bi-stable blade shapes are perceived based on more than one blade inflexion. Finally a selection is presented for those minimum strain curves, which are applicable for the FF-TLOM technology.

Metallic strips flexible pipe (MSFP) is widely regarded as an alternative for submarine pipelines. This paper presents a methodology for calculating the fatigue life of MSFP. Firstly, given a specific working condition of MSFP, the dynamic responses of MSFP are calculated through OrcaFlex. The obtained results from the global analysis are then implemented into a finite element model in ABAQUS to determine the stress-history curves of each steel strips layer. The estimated fatigue life is calculated by rainflow counting algorithms, S-N curve and Miner’s rule which are coded in MATLAB. Additional study about average stress correction is carried out, which might be useful for its marine engineering applications.

In conventional MEMS parallel-plate capacitor designs, the moving electrode is commonly modeled as a rigid plate with flexible boundary conditions provided by a set of supporting beams. Such a capacitor generates limited tuning ratio up to 1.5 and its capacitance-voltage response is nonlinear. This paper presents novel designs where the moving electrodes are fixed-edge flexible plates. The plate displacement is selectively limited by a set of rigid steps, located between two electrodes, to generate a smooth and linear response and high tunability. Three different step heights are considered in the design and the linearity of the C-V curve is maximized by modifying the geometry of the plate, and changing the location and order of steps. Since the analytical solution for coupled electrostatic-structural physics in this case does not exist, ANSYS® FEM simulation is performed to obtain the C-V curves and optimize the design. Two designs with different electrode shapes, rectangular and circular, are developed. For rectangular-plate capacitors, tunabilities ranging from 120% to 140% and high linearity are achieved. Circular-plate designs, on the other hand, generate lower tunabilities and an extremely linear region in C-V curves. Design methodology introduced in this research is not limited to proposed geometries and can be extended to different topologies to obtain a combination of high tunability and linearity.

Abstract Theories of perfectly flexible elastic curves and surfaces are frequently used to describe diverse phenomena ranging from bioelasticity and fluid capillarity to rubber elasticity and the mechanics of structural networks. It is our aim here to present a treatment of the coupled response of such continua accounting for three-dimensional interactions in the presence of finite deformations and strains. A more expansive discussion of the subject of the present paper may be found in [1].

A full-scale airfield pavement test section was constructed and trafficked by the U.S. Army Engineer Research and Development Center (ERDC) to evaluate the performance of relatively thin airfield pavement structures. The test section consisted of 16 test items that included three asphalt pavement thicknesses and two different aggregate base courses. The test items were subjected to simulated aircraft traffic to evaluate their response and performance to realistic aircraft loads and to evaluate the effect of reductions in tire pressure on thin asphalt pavement. Rutting behavior, pavement cracking, instrumentation response, and falling weight deflectometer response were monitored at selected traffic intervals. The results of this study were used to extend existing Department of Defense pavement design and evaluation techniques to include the evaluation of airfield pavement sections that do not meet the current criteria for aggregate base quality and minimum asphalt concrete surface thickness. These performance data were used to develop new aggregate base failure design curves using existing stress-based design methodology.

This study uses simulations of state-dependent distributions of fiscal limits for 18 economies in Central America and the Caribbean to better understand governments¿ ability to service their debt, arising from endogenously determined dynamic Laffer curves. Using a small, open economy model to simulate macroeconomic fundamentals and fiscal policy interactions, the empirical findings produced results not previous available for these economies, showing varying and wider distributions of fiscal limits for the open economy model subject to terms-of-trade and flexible exchange rate shocks. This indicates that terms-of-trade and exchange rate volatility impacted the ability of national economies to service their debt. It is therefore prudent that policymakers and central bankers consider models that incorporate the use of trade and exchange rate volatility as a robust way of more accurately determining fiscal limits, which are a critical component in understanding governments' ability to service their debt.

Not in standard models. With conventional pricing frictions, imposing a flat Phillips curve also imposes a price level that is rigid with respect to supply shocks. In the New Keynesian model, price markup shocks need to be several orders of magnitude bigger than other shocks in order to fit the data, leading to unreasonable assessments of the magnitude of the increase in costs during inflationary episodes. To account for the facts, we propose a strategic microfoundation of shock-dependent price stickiness: prices are sticky with respect to demand shocks but flexible with respect to supply shocks. This friction is demand-intrinsic, in line with narrative accounts for the imperfect adjustment of prices. Firms can credibly justify a price increase due to a rise in costs, whereas it is harder to do so when demand increases. Inflation from supply shocks is efficient and does not justify a monetary policy response.

The objectives of this project were to develop nondestructive methods for detection of internal properties and firmness of fruits and vegetables. One method was based on a soft piezoelectric film transducer developed in the Technion, for analysis of fruit response to low-energy excitation. The second method was a dot-matrix piezoelectric transducer of North Carolina State University, developed for contact-pressure analysis of fruit during impact. Two research teams, one in Israel and the other in North Carolina, coordinated their research effort according to the specific objectives of the project, to develop and apply the two complementary methods for quality control of agricultural commodities. In Israel: An improved firmness testing system was developed and tested with tropical fruits. The new system included an instrumented fruit-bed of three flexible piezoelectric sensors and miniature electromagnetic hammers, which served as fruit support and low-energy excitation device, respectively. Resonant frequencies were detected for determination of firmness index. Two new acoustic parameters were developed for evaluation of fruit firmness and maturity: a dumping-ratio and a centeroid of the frequency response. Experiments were performed with avocado and mango fruits. The internal damping ratio, which may indicate fruit ripeness, increased monotonically with time, while resonant frequencies and firmness indices decreased with time. Fruit samples were tested daily by destructive penetration test. A fairy high correlation was found in tropical fruits between the penetration force and the new acoustic parameters; a lower correlation was found between this parameter and the conventional firmness index. Improved table-top firmness testing units, Firmalon, with data-logging system and on-line data analysis capacity have been built. The new device was used for the full-scale experiments in the next two years, ahead of the original program and BARD timetable. Close cooperation was initiated with local industry for development of both off-line and on-line sorting and quality control of more agricultural commodities. Firmalon units were produced and operated in major packaging houses in Israel, Belgium and Washington State, on mango and avocado, apples, pears, tomatoes, melons and some other fruits, to gain field experience with the new method. The accumulated experimental data from all these activities is still analyzed, to improve firmness sorting criteria and shelf-life predicting curves for the different fruits. The test program in commercial CA storage facilities in Washington State included seven apple varieties: Fuji, Braeburn, Gala, Granny Smith, Jonagold, Red Delicious, Golden Delicious, and D'Anjou pear variety. FI master-curves could be developed for the Braeburn, Gala, Granny Smith and Jonagold apples. These fruits showed a steady ripening process during the test period. Yet, more work should be conducted to reduce scattering of the data and to determine the confidence limits of the method. Nearly constant FI in Red Delicious and the fluctuations of FI in the Fuji apples should be re-examined. Three sets of experiment were performed with Flandria tomatoes. Despite the complex structure of the tomatoes, the acoustic method could be used for firmness evaluation and to follow the ripening evolution with time. Close agreement was achieved between the auction expert evaluation and that of the nondestructive acoustic test, where firmness index of 4.0 and more indicated grade-A tomatoes. More work is performed to refine the sorting algorithm and to develop a general ripening scale for automatic grading of tomatoes for the fresh fruit market. Galia melons were tested in Israel, in simulated export conditions. It was concluded that the Firmalon is capable of detecting the ripening of melons nondestructively, and sorted out the defective fruits from the export shipment. The cooperation with local industry resulted in development of automatic on-line prototype of the acoustic sensor, that may be incorporated with the export quality control system for melons. More interesting is the development of the remote firmness sensing method for sealed CA cool-rooms, where most of the full-year fruit yield in stored for off-season consumption. Hundreds of ripening monitor systems have been installed in major fruit storage facilities, and being evaluated now by the consumers. If successful, the new method may cause a major change in long-term fruit storage technology. More uses of the acoustic test method have been considered, for monitoring fruit maturity and harvest time, testing fruit samples or each individual fruit when entering the storage facilities, packaging house and auction, and in the supermarket. This approach may result in a full line of equipment for nondestructive quality control of fruits and vegetables, from the orchard or the greenhouse, through the entire sorting, grading and storage process, up to the consumer table. The developed technology offers a tool to determine the maturity of the fruits nondestructively by monitoring their acoustic response to mechanical impulse on the tree. A special device was built and preliminary tested in mango fruit. More development is needed to develop a portable, hand operated sensing method for this purpose. In North Carolina: Analysis method based on an Auto-Regressive (AR) model was developed for detecting the first resonance of fruit from their response to mechanical impulse. The algorithm included a routine that detects the first resonant frequency from as many sensors as possible. Experiments on Red Delicious apples were performed and their firmness was determined. The AR method allowed the detection of the first resonance. The method could be fast enough to be utilized in a real time sorting machine. Yet, further study is needed to look for improvement of the search algorithm of the methods. An impact contact-pressure measurement system and Neural Network (NN) identification method were developed to investigate the relationships between surface pressure distributions on selected fruits and their respective internal textural qualities. A piezoelectric dot-matrix pressure transducer was developed for the purpose of acquiring time-sampled pressure profiles during impact. The acquired data was transferred into a personal computer and accurate visualization of animated data were presented. Preliminary test with 10 apples has been performed. Measurement were made by the contact-pressure transducer in two different positions. Complementary measurements were made on the same apples by using the Firmalon and Magness Taylor (MT) testers. Three-layer neural network was designed. 2/3 of the contact-pressure data were used as training input data and corresponding MT data as training target data. The remaining data were used as NN checking data. Six samples randomly chosen from the ten measured samples and their corresponding Firmalon values were used as the NN training and target data, respectively. The remaining four samples' data were input to the NN. The NN results consistent with the Firmness Tester values. So, if more training data would be obtained, the output should be more accurate. In addition, the Firmness Tester values do not consistent with MT firmness tester values. The NN method developed in this study appears to be a useful tool to emulate the MT Firmness test results without destroying the apple samples. To get more accurate estimation of MT firmness a much larger training data set is required. When the larger sensitive area of the pressure sensor being developed in this project becomes available, the entire contact 'shape' will provide additional information and the neural network results would be more accurate. It has been shown that the impact information can be utilized in the determination of internal quality factors of fruit. Until now,

Con datos a agosto de 2022, todas las fuentes de información analizadas en este reporte, tanto las encuestas de hogares y como los registros de datos administrativos, muestran que el empleo mantiene crecimientos anuales importantes. La mayoría de indicadores del mercado laboral se encuentran en niveles similares o mejores a los presentados en el periodo prepandemia. Los segmentos que más aportaron al crecimiento en el empleo son el asalariado, el dominio de otras cabeceras y rural, y los segmentos poblacionales de mujeres, trabajadores sin educación superior y los no jefes de hogar. A pesar de las mejoras anuales destacables en los indicadores laborales, las series con ajuste estacional, que permiten la comparación mes tras mes de los indicadores, muestran que en los últimos meses el empleo, las vacantes y la participación laboral tienden a estabilizarse. Este comportamiento es más pronunciado en el mercado laboral urbano. Un indicador que muestra señales claras de estabilización es la tasa global de participación (TGP), que en el nivel nacional se ha mantenido alrededor del 63 % en el último semestre. La tasa de ocupación (TO) nacional también tiende a mantenerse estable desde julio, jalonada por el dominio urbano; mientras que en el dominio rural todavía se evidencian crecimientos mensuales de la ocupación. Este comportamiento explica la estabilización de la tasa de desempleo (TD) con ajuste estacional en el área urbana alrededor del 11,7 % y el mejor desempeño de la TD en el dominio rural y otras cabeceras, que en los últimos tres meses se redujo en casi 1 punto porcentual (pp). Por el lado de los salarios, se observan aumentos en los ingresos corrientes tanto en los segmentos asalariado como no asalariado. Sin embargo, la mayor inflación se traduce en que los salarios en el segmento asalariado hayan permanecido estables en términos reales. En el segmento no asalariado, caracterizado por su naturaleza más flexible, los ingresos laborales se han ajustado y se evidencian crecimientos reales anuales y trimestrales. Tanto los indicadores de holgura como los de cuellos de botella y las curvas de Beveridge muestran un mercado laboral estrecho. Dadas las previsiones en materia de crecimiento económico del equipo técnico del Banco de la República, consignadas en el Informe de Política Monetaria de octubre de 2022, los pronósticos indican que la TD urbana se mantendrá estable y terminaría 2022 alrededor del 11,2 % como escenario central. Para 2023 se prevé que dicho indicador, en promedio, se ubicaría entre el 9,9 % y 13,5 %, con un 11,7 % como valor más probable. Por el lado del dominio nacional, la tasa terminaría el año 2022 en el 10,6 %, y para 2023, en promedio, estaría entre el 9,2 % y 12,8 %, con un 11% como valor más probable. Estas predicciones implican ligeros incrementos en la TD durante 2023, los cuales serían consistentes con las menores previsiones de crecimiento económico para ese año. Por su parte, las estimaciones de la tasa de desempleo no inflacionaria (Nairu) sugieren una brecha de desempleo urbana negativa para finales de 2022. Estas estimaciones indicarían que la mayor estrechez del mercado laboral podría estar generando presiones inflacionarias; sin embargo, la brecha se vuelve no significativa en el año 2023. Este reporte se divide en dos secciones. La primera profundiza en los hechos coyunturales del mercado laboral descritos. La segunda estudia el tema de los indicadores de holgura del mercado laboral y la relación de estos con la inflación de salarios. Los indicadores de holgura son evaluados constantemente por los formuladores de política porque dan cuenta de la existencia de presiones inflacionarias desde el mercado laboral. La TD, que es el indicador de holgura laboral por excelencia, presenta algunas limitaciones que han sido suficientemente documentadas en la literatura especializada. Medidas análogas construidas a partir de información proveniente de las firmas, en ciertos contextos especiales, podrían tener mayor poder de predicción sobre la inflación de salarios. En este Reporte Especial se construye para Colombia la tasa de desempleo desde el punto de vista de la firma (TDF). La TDF es una modelación de la variación total de la TD que solo tiene en cuenta factores exclusivos de la demanda laboral de firmas, como son la tasa de vacantes (TV) y proxies de la tasa de renuncias. La TDF resultante supera a la TD en términos de predicción de inflación de salarios. Este nuevo indicador da luces sobre las señales mixtas que los indicadores de holgura mostraron al inicio de la pandemia, donde la TD presentó crecimientos exorbitantes, mucho mayores que las reducciones de la TV y, al mismo tiempo, los salarios nominales permanecieron constantes. Los resultados muestran que, en los primeros trimestres de la pandemia, la TD mostraba un mercado laboral bastante más holgado que la TDF. En la actualidad tanto la TD como la TDF están acopladas y muestran la misma señal en términos de la holgura del mercado laboral.