Search results for "Abstract"

Nomograph for rapid technical and economic assessment of solar thermal systems for DHW production

2012

Abstract Different types of tools, software and empirical methods to size and assess the performance of solar thermal systems are available today. A quick and easy-to-use graphical tool is proposed here. It is based on a single diagram, called a nomograph, which embeds technical and economic information, allowing the optimisation of the size and performance of a solar thermal system starting from the main input parameters, such as the specific costs of the system and the auxiliary fuel. The optimal surfaces are calculated as a function of the fuel cost through several regressions made on data from the application of the F-Chart method for a set of system configurations. The authors have fou…

Solid-State Lighting: Simple, Fast, Bright, and Stable Light Sources (Adv. Mater. 7/2012)

2012

Sound and reusable components for abstract interpretation

2019

Abstract interpretation is a methodology for defining sound static analysis. Yet, building sound static analyses for modern programming languages is difficult, because these static analyses need to combine sophisticated abstractions for values, environments, stores, etc. However, static analyses often tightly couple these abstractions in the implementation, which not only complicates the implementation, but also makes it hard to decide which parts of the analyses can be proven sound independently from each other. Furthermore, this coupling makes it hard to combine soundness lemmas for parts of the analysis to a soundness proof of the complete analysis. To solve this problem, we propose to c…

An Exploratory Empirical Study of Internal Quality Attributes of Open Source Software Systems

2012

This exploratory empirical study has focused on open source software (OSS). Seven medium-sized OSS systems from the SourceForge repository were analysed. Over 100 internal quality attributes and programming practices were scrutinized by using two semi-automated source code analysis tools (FindBugs and SoftCalc). Many statistically significant relations were revealed by the conducted regression analyses. Seven so-called bad programming practices; as manifested by the measured source code inconsistencies were identified as having significant relations to internal software quality. Additionally we set and tested two hypotheses. That investigation provided mixed results partly supporting some o…

Space‐time dynamical models

2008

Purpose – The purpose is to present a new formal approach based on a partial integro‐differential equation, the space‐time state transition equation (STSTE), and on a set of general equations with which space‐time dynamical models of complex systems, such as social systems and ecosystems, can be built.Design/methodology/approach – The STSTE provides the partial derivative of the density of a state‐variable with regard to time as a sum of time rates and space‐time rates. Time rates describe the dynamics of the system for each space‐point irrespectively of the other points, whilst space‐time rates describe this evolution as a consequence of the relation of each space‐point with a given set of…

Topology of correlation-based minimal spanning trees in real and model markets

2003

We present here a topological characterization of the minimal spanning tree that can be obtained by considering the price return correlations of stocks traded in a financial market. We compare the minimal spanning tree obtained from a large group of stocks traded at the New York Stock Exchange during a 12-year trading period with the one obtained from surrogated data simulated by using simple market models. We find that the empirical tree has features of a complex network that cannot be reproduced, even as a first approximation, by a random market model and by the one-factor model.

Effects of distance and scale dependence in geographical models of cities and territories

2019

International audience; This third chapter questions the essential role of distance and scale dependence in models to analyzing the spatial configuration of human settlements and activities, as well as the processes that lead to their evolution, with reference to urban or regional study areas. The subject of study therefore concerns both the form of human settlements and the actions of people (individuals, groups) in their territory (or territories). A human settlement consists of the materialization in space-the physical inscription-of one or more human activities. It is characterized by a certain degree of sustainability. It can be a group of a few buildings or a larger group of thousands…

Description of x-ray beams using the fluorescence yields of a set of thick targets

1995

Quantitative methods in x-ray fluorescence analysis require a knowledge of the spectral distribution of the fluorescence-exciting beam. The use of XRF yield measurements of a set of thick pure element targets is proposed for the description of a fluorescence-exciting x-ray beam, without the need to obtain its spectral distribution. This new approach is derived theoretically and verified by comparing thin-target yields calculated from XRF yield measurements of thick pure element specimens with those obtained from a calculated spectral distribution. The difference between the two methods of obtaining the thin-target yields is within 9% relative error.

Order-disorder-and order-order-transitions in AB and ABC block copolymers: description by a simple model

1996

Based on the description of AB-block copolymers as micellar structures given by Semenov, the phase diagram of AB-diblock copolymers is calculated taking the homogeneously mixed system as a reference state. The predicted value (χN)c = 10.385 for a symmetric AB-diblock copolymer compares very well to the result of the original Random Phase Approximation theory (10.495). The simplicity of the model allows its extension to predict order-order transitions in ABC-triblock copolymers.

Joint Graph Learning and Signal Recovery via Kalman Filter for Multivariate Auto-Regressive Processes

2018

In this paper, an adaptive Kalman filter algorithm is proposed for simultaneous graph topology learning and graph signal recovery from noisy time series. Each time series corresponds to one node of the graph and underlying graph edges express the causality among nodes. We assume that graph signals are generated via a multivariate auto-regressive processes (MAR), generated by an innovation noise and graph weight matrices. Then we relate the state transition matrix of Kalman filter to the graph weight matrices since both of them can play the role of signal propagation and transition. Our proposed Kalman filter for MAR processes, called KF-MAR, runs three main steps; prediction, update, and le…