Definition Of Path Research Articles

A conceptual business model framework applied to air transport

The adoption of business models in different sectors has been disseminated exponentially as a result of organizational strategies, allowing the identification and definition of paths to be followed, and enhancing capture and value creation for consumers and the enterprise. In the case of the air transport sector, specifically the airlines, the proposition of new business models can contribute to creating competitive advantage. This study develops a conceptual business model framework applied to air transport, which prioritizes key components identified in the literature for designing business models for airlines. With the exploration of different aspects of business models and the identification of the main models used by airlines, the results demonstrate the need for the adoption of new models in this sector.

Improved source path localisation in ring applicators and the clinical impact for gynecological brachytherapy.

PurposeThe path of subsequent dwell positions of an afterloader source being moved through a ring applicator for cervix cancer brachytherapy deviates from an ideal circle and the position of marker wires. This can lead to deviations of several millimetres between real and assumed dwell positions for treatment planning with simplified source path models. The aim of this study was to test video- and autoradiography-based methods for source path determination, and to study the influence of dwell position accuracy on dose-volume histogram (DVH)-parameters.Material and methodsVideos of the exact motion of the source wire through three different (r = 26, 30, 34 mm) computed tomography/magnetic resonance (CT/MR) compatible plastic ring applicators were recorded. Observed dwell positions covering the whole length of each applicators channel were used to adjust the circular source path model. The agreement of the true source positions derived from video analysis with those of the corrected circular source path was verified using autoradiography. The impact of an accurate source path definition on dose planning was analysed by simulating clinically relevant uncertainties in 10 clinical treatment plans.ResultsDepending on the ring size, source path diameters had to be increased by 0.5-1.0 mm in order to achieve acceptable maximum differences between observed and corrected dwell positions (1.3-2.0 mm). Autoradiography analysis showed a positional accuracy within ± 3 mm (extended standard deviation k = 2). For shifts of ± 2.5 mm for even all dwell positions, the systematic and random variation of the D2cm3 for bladder, rectum, and sigmoid was within 3%, while the impact on DVH uncertainties was much smaller for clinical target volume (CTV)HR and gross tumour volume (GTV).ConclusionsIt is strongly advised to verify the real source path for ring applicators during acceptance testing in order to assure accurate source path definition and dose planning. Autoradiography can be used for source path verification with acceptable accuracy for treatment planning and dose reporting.

COOBBO: A Novel Opposition-Based Soft Computing Algorithm for TSP Problems

In this paper, we propose a novel definition of opposite path. Its core feature is that the sequence of candidate paths and the distances between adjacent nodes in the tour are considered simultaneously. In a sense, the candidate path and its corresponding opposite path have the same (or similar at least) distance to the optimal path in the current population. Based on an accepted framework for employing opposition-based learning, Oppositional Biogeography-Based Optimization using the Current Optimum, called COOBBO algorithm, is introduced to solve traveling salesman problems. We demonstrate its performance on eight benchmark problems and compare it with other optimization algorithms. Simulation results illustrate that the excellent performance of our proposed algorithm is attributed to the distinct definition of opposite path. In addition, its great strength lies in exploitation for enhancing the solution accuracy, not exploration for improving the population diversity. Finally, by comparing different version of COOBBO, another conclusion is that each successful opposition-based soft computing algorithm needs to adjust and remain a good balance between backward adjacent node and forward adjacent node.

Making CEGAR More Efficient in Software Model Checking

Counter-example guided abstraction refinement (CEGAR) is widely used in software model checking. With an abstract model, the state space is largely reduced, however, a counterexample found in such a model that does not satisfy the desired property may not exist in the concrete model. Therefore, how to check whether a reported counterexample is spurious is a key problem in the abstraction-refinement loop. Next, in the case that a spurious counterexample is found, the abstract model needs to be further refined where an NP-hard state separation problem is often involved. Thus, how to refine the abstract model efficiently has attracted a great attention in the past years. In this paper, by re-analyzing spurious counterexamples, a new formal definition of spurious paths is given. Based on it, efficient algorithms for detecting spurious counterexamples are presented. By the new algorithms, when dealing with infinite counterexamples, the finite prefix to be analyzed will be polynomially shorter than the one dealt with by the existing algorithms. Moreover, in practical terms, the new algorithms can naturally be parallelized that enables multi-core processors contributes more in spurious counterexample checking. In addition, a novel refining approach by adding extra Boolean variables to the abstract model is presented. With this approach, not only the NP-hard state separation problem can be avoided, but also a smaller refined abstract model can be obtained. Experimental results show that the new algorithms perform well in practice.

The Network Attack Model based on Hierarchical Expanded Stochastic Petri Net

In the paper, a global network attack model based on Hierarchical Expanded Stochastic Petri Net (HESPN) is presented. The model is suitable for the cooperative attack simulation and can describe both macroscopic network attack and microcosmic host attack synthetically. The dissertation represents model generation algorithm and digs for potential attack relationships among hosts according to the definition of rough path. Then utilize ant colony algorithm to find k-critical vulnerable paths after expanding sub Petri net. By analyzing rough paths and accurate paths synthetically, a network risk evaluation method is proposed.

AN APPLICATION OF SPACE SYNTAX TO CRITICAL WORKING SPACE ANALYSIS: THE CASE OF BUILDING CONSTRUCTION

The definition of critical space used in this paper is identical to the critical path definition employed in the critical path method (CPM). This definition implies that there is no extra floating space; thus, any conflict is expected to result in productivity loss. Space syntax is a theory developed to reveal the hidden interrelationships between spaces using architectural diagrams. Existing studies have indicated the potential for space syntax to identify critical spaces and to assist in reducing conflicts leading to productivity loss. However, there is not yet quantitative evidence demonstrating whether the quantitative parameters of relative convenience and relative control are suitable for analyses of dynamic construction spaces. This study is based on fuzzy theory and uses field observations, engineering personnel interviews, and questionnaires designed to utilize ＂fuzzy syntax＂. Moreover, this study further develops a method for critical space index analysis, which could be useful for the continued analysis of critical space.

Integrals Along Rough Paths via Fractional Calculus

Using fractional calculus, we introduce an integral along β-Holder rough paths for any β ∈ (0,1]. This is a natural generalization of the Riemann–Stieltjes integral along smooth curves. We prove that, under suitable conditions on the integrand, this integral is a continuous functional with respect to the Holder topology. As a result, this provides an alternative definition of the first level path of the rough integral along geometric Holder rough paths.

Influence of fiber paths on buckling load of tailored conical shells

The purpose of this paper is to propose a method for evaluation of varying stiffness coefficients of tailored conical shells (TCS). Furthermore, a comparison between buckling loads of these shells under axial load with the different fiber path is performed. A circular truncated conical shell subjected to axial compression is taken into account. Three different theoretical path containing geodesic path, constant curvature path and constant angle path has been considered to describe the angle variation along the cone length, along cone generator of a conical shell are offered. In the TCS with the arbitrary fiber path, the thickness and the ply orientation are assumed to be functions of the shell coordinates and influencing stiffness coefficients of the structure. The stiffness coefficients and the buckling loads of shells are calculated basing on classical shells theory (CST) and using finite-element analysis (FEA) software. The obtained results for TCS with arbitrary fiber path, thickness and ply orientation are derived as functions of shell longitudinal coordinate and influencing stiffness coefficients of structures. Furthermore, the buckling loads based on fiber path and ply orientation at the start of tailored fiber get to be different. The extent of difference for tailored fiber with start angle lower than 20 degrees is not significant. The results in this paper show that using tailored fiber placement could be applied for producing conical shells in order to have greater buckling strengths and lower weight. This work demonstrates the use of fiber path definitions for calculated stiffness coefficients and buckling loads of conical shells.

Extension of paths and cycles for hypergraphs

In [G.Y. Katona and H.A. Kierstead, Hamiltonian chains in hypergraphs, J. Graph Theory (1999) 30(3): 205–212] we defined the hamiltonian cycle in hypergraphs in a new way. The definition can be extended to paths and cycles as well. There are many results for hypergraphs that uses the traditional path and cycle definition of Berge, so almost all of them can be considered with the new definition. In this paper we will deal with such results.

Migration and Extension of Solar Active Longitudinal Zones

Solar active longitudes show a characteristic migration pattern in the Carrington coordinate system when they can be identified at all. By following this migration, the longitudinal activity distribution around the center of the band can be determined. The halfwidth of the distribution is found to be varying in Cycles 21 - 23, and in some time intervals it was as narrow as 20 - 30 degrees. It was more extended around maximum but it was also narrow when the activity jumped to the opposite longitude. Flux emergence exhibited a quasi-periodic variation within the active zone with a period of about 1.3 years. The path of the active longitude migration does not support the view that it might be associated with the 11-year solar cycle. These results were obtained for a limited time interval of a few solar cycles and, bearing in mind uncertainties of the migration path definition, are only indicative. For the major fraction of dataset no systematic active longitudes were found. Sporadic migration of active longitudes was identified only for Cycles 21 - 22 in the northern hemisphere and Cycle 23 in the southern hemisphere.

Lusk et al. Respond

We thank Schimek for his thoughtful letter. We agree that the American Association of State Highway and Transportation Officials (AASHTO) encourages bike paths; however, AASHTO’s definition of a bike path is a shared use path for pedestrians, skaters, wheelchair users, joggers, and other nonmotorized users. AASHTO discourages bicycle-only cycle tracks because, as noted by Schimek, AASHTO discourages bike lanes on the roadway separated from travel lanes by parked cars or raised barriers.1,2 Therefore, we agree with Schimek that the design of cycle tracks, such as those in Minneapolis, Minnesota, and New York City, are not included in AASHTO guidelines. As we discussed, our analysis suggested that these cycle tracks may have a higher crash rate than the other studied streets with cycle tracks because they are on busy urban arterials, which would include many intersections. At intersections, cyclist injuries increase with traffic volume, more specifically with the number of right and left turns by motor vehicles.3,4 In large cities, cyclists do need protection from motor vehicles, especially at intersections. Cycle tracks are associated with greater cycling and also, as concluded in a recent review of the literature, well-designed cycle tracks reduce cyclist injuries.5 We agree that three of the four comparison rates we cited are based on self-reports for specific populations. We had suggested that adequate comparisons for bicycle crash rates in US cities are lacking. Schimek generated a new bicycle injury rate for comparison, but it includes the overall estimated number of injured cyclists in the United States divided by the overall estimated length traveled by bicycle in the United States. We think that Schimek’s injury rate for the entire United States is not an appropriate comparison with the crash rate on studied cycle tracks, especially in urban New York City and Minneapolis. It is still noteworthy that Schimek’s injury rate estimate of 3.5 for all the states in the United States is higher than the overall crash rate of 2.3 that we found for the 19 cycle tracks across the United States. There is a need for more research on facility design, crashes, and bicycle activity in the United States. Our study does add to the best available evidence, which suggests that cycle tracks can reduce the risk of crashes while providing a more comfortable biking facility.6–8 We think it is time to change the AASHTO guidelines to improve roadways to take into account bicyclists needs, and to protect bicyclists from motor vehicles.

An XFEM-based methodology for fatigue delamination and permeability of composites

A methodology for the simulation of thermal fatigue delamination in composites and prediction of delaminated crack opening displacement (DCOD) and composite laminate permeability is presented. This is critical for the safe design of composite cryogenic fuel tanks. The methodology, which is based on an extended finite element method for simulation of crack growth, does not require a priori definition of initial crack (delamination) length or crack propagation path. In contrast, previous work required estimation of delamination length and corresponding number of thermal cycles based on experimental measurements. The methodology is validated against measurements from standardised static and fatigue delamination test methods. Prediction of delamination crack growth in a quasi-isotropic laminate under cryogenic fatigue loading is used to establish the effect of initial interlaminar defect length on subsequent crack growth, as well as the effect of delamination length on DCOD and permeability. A key additional benefit is that the proposed method can simulate both inter- and intralaminar crack growth in two- and three-dimensional geometries.

An investigation into the static response of fiber-reinforced open conical shell panels considering various types of orthotropy

In this study, bending of composite open conical shell panels subjected to various distributed mechanical loads with various types of orthotropy is investigated. The stiffness coefficients are assumed to be functions of the meridional and circumferential coordinates in panels, which are produced by various methods for the realistic applications. In the first case of orthotropic open conical shell panels, the orientation of fibers are assumed to be in the meridional and circumferential directions. The stiffness coefficients of this type of fiber-reinforced panel are usually assumed to be constant. It is shown that due to the geometry of the conical surface, thickness of laminate will be changed along the meridional direction. The effect of stiffness variation on the response of panel is considered for the first time. In the case of open conical shell panel, which is fabricated by molding the prepreg layers around a conical-shaped mandrel, angle between fibers and meridional lines and, consequently, stiffness coefficients are assumed to be functions of the circumferential coordinates. In the third type, open conical shell panel can be made by cutting from a filament wound circular conical shell. In this case, thickness and ply orientation are functions of the shell coordinates. In this article, different path definitions for variable stiffness filament wound shells are considered. The inclusion of this geometric complicating effect in static analysis will add considerably to the complication and cost of a solution scheme. This article presents some results to show when these assumptions have a significant effect on the end result. The governing equations are based on the first-order shear deformation theory. The governing equations are discretized at whole domain grid points, and the boundary conditions are implemented exactly at boundary grid points using the generalized differential quadrature method. Application of the generalized differential quadrature to the governing equations, solution domain and boundary conditions leads to a system of algebraic equations. Various combinations of clamped, simply supported and free boundary conditions are implemented. It is found that the present method can accurately analyze fiber-reinforced open conical shell panels with various types of orthotropy.

Mission Performance Simulation of Integrated Helicopter–Engine Systems Using an Aeroelastic Rotor Model

This paper presents an integrated approach, targeting the comprehensive assessment of combined helicopter engine designs within designated operations. The developed methodology comprises a series of individual modeling theories, each applicable to a different aspect of helicopter flight dynamics and performance. These relate to rotor blade modal analysis, three-dimensional flight path definition, flight dynamics trim solution, aeroelasticity, and engine performance. The individual mathematical models are elaborately integrated within a numerical procedure, solving for the total mission fuel consumption. The overall simulation framework is applied to the performance analysis of the Aérospatiale SA330 helicopter within two generic, twin-engine medium helicopter missions. An extensive comparison with flight test data on main rotor trim controls, power requirements, and unsteady blade structural loads is presented. It is shown that, for the typical range of operating conditions encountered by modern twin-engine medium civil helicopters, the effect of operational altitude on fuel consumption is predominantly influenced by the corresponding effects induced on the engine rather than on airframe rotor performance. The implications associated with the implicit coupling between aircraft and engine performance are discussed in the context of mission analysis. The potential to comprehensively evaluate integrated helicopter engine systems within complete three-dimensional operations using modeling fidelity designated for main rotor design applications is demonstrated. The proposed method essentially constitutes an enabler in terms of focusing the rotorcraft design process on designated operation types rather than on specific sets of flight conditions.

Complexity of a classical flow restoration problem

AbstractIn this article, we revisit a classical optimization problem occurring in designing survivable multicommodity flow networks. The problem, referred to as FR, assumes flow restoration that takes advantage of the so‐called stub release. As no compact linear programming (LP) formulation of FR is known and at the same time all known noncompact LP formulations of FR exhibit \documentclass{article}\usepackage{mathrsfs}\usepackage{amsmath}\pagestyle{empty}\begin{document}\begin{align*}\mathcal{NP}\end{align*} \end{document} ‐hard dual separation, the problem itself is believed to be \documentclass{article}\usepackage{mathrsfs}\usepackage{amsmath}\pagestyle{empty}\begin{document}\begin{align*}\mathcal{NP}\end{align*} \end{document} ‐hard, although without a proof. In this article, we study a restriction of FR (RFR) that assumes only elementary (cycle‐free) admissible paths—an important case virtually not considered in the literature. The two problems have the same noncompact LP formulations as they differ only in the definition of admissible paths: all paths (also those including cycles) are allowed in FR, while only elementary paths are allowed in RFR. Because of that, RFR is in general computationally more complex than FR. The purpose of this article, is three‐fold. First, the article reveals an interesting special case of RFR—the case with only one failing link—for which a natural noncompact LP formulation obtained by reducing the general RFR formulation still exhibits \documentclass{article}\usepackage{mathrsfs}\usepackage{amsmath}\pagestyle{empty}\begin{document}\begin{align*}\mathcal{NP}\end{align*} \end{document} ‐hard dual separation, but nevertheless this special case of RFR is polynomial. The constructed example of a polynomial multicommodity flow problem with difficult dual separation is of interest since, to our knowledge, no example of this kind has been known. In this article, we also examine a second special case of RFR, this time assuming two failing links instead of one, which turns out to be \documentclass{article}\usepackage{mathrsfs}\usepackage{amsmath}\pagestyle{empty}\begin{document}\begin{align*}\mathcal{NP}\end{align*} \end{document} ‐hard. This implies that problem RFR is \documentclass{article}\usepackage{mathrsfs}\usepackage{amsmath}\pagestyle{empty}\begin{document}\begin{align*}\mathcal{NP}\end{align*} \end{document} ‐hard in general (more precisely, for two or more failure states). This new result is the second contribution of the article. Finally, we discuss the complexity of FR in the light of our new findings, emphasizing the differences between RFR and FR. © 2013 Wiley Periodicals, Inc. NETWORKS, 2013

Measurement of Focal Plane for Microlens Array Using Metallographic Microscope

Twice-image method based on the Newton's formula, is used to measure the focal plane of the microlens array. The focal plane of the microlens array is measured by using the transmitted optical path, magnification, and high definition of the CCD camera of a metallographic microscope. Both the experimental setup and procedures are described in detail in the paper. Experimental results are also discussed thoroughly as well. It is a simple, convenient and economical method for checking the focal plane of a microlens array efficiently.

Non-linear analysis of fiber-reinforced open conical shell panels considering variation of thickness and fiber orientation under thermo-mechanical loadings

Non-linear bending analysis of moderately thick laminated conical panels under various thermo-mechanical loadings and boundary conditions is presented using the generalized differential quadrature (GDQ) method together with the Newton–Raphson iterative scheme. The stiffness coefficients are assumed to be functions of the meridional and circumferential coordinates in panels for the realistic applications. In the first case of orthotropic open conical shell panels, the orientation of fibers are assumed to be in the meridional and circumferential directions. The stiffness coefficients of this type of fiber-reinforced panel are usually assumed to be constant. It is shown that due to the geometry of the conical surface, thickness of laminate will be changed along the meridional direction. The effect of stiffness variation on the non-linear response of panel is considered for the first time. In the second type, open conical shell panel can be made by cutting from a filament wound circular conical shell. In this case, thickness and ply orientation are functions of the shell coordinates. In this paper, different path definitions for variable stiffness filament wound shells are considered. The inclusion of this geometric complicating effect in large deformation analysis will add considerably to the complication and cost of a solution scheme. Paper presents some results to show when these assumptions have a significant effect on the end result. Assuming the effects of shear deformation and initial curvature, based on the first-order shear deformation theory (FSDT) and von Kármán-type of geometric non-linearity, the governing system of equations is obtained. Comparisons of the predictions with those available in the literature and finite element analyses show very good agreement. More results for panels with particular boundary conditions and thermo-mechanical load are presented for future references. For the sake of brevity, numerical results which presented in this paper are limited to deflection responses only.

Sustainability ethics and metrics: Strategies for damage control and prevention

It is generally and increasingly believed that humanity’s survival depends on adoption of sustainable development practices, which are based on adequate satisfaction of quantitatively defined and interrelated economical, environmental and social criteria. One can then argue that sustainable development has a meta-ethical foundation, a definition of right and wrong paths stemming from what one might consider a Universal Truth that is humanity’s desire to survive. One finds that “sustainability” is very much in vogue as a positive attribute, and more and more extensively used erratically and often improperly and even fraudulently over the entire social spectrum. Since sustainability is of vital importance to our survival, using its terminology in vain diminishes its vitally important value by desensitizing society and sowing distrust. Importantly, unethical usage of sustainability concepts causes much harm to the development of credible sustainability science. This paper briefly defines sustainability and its quantitative metrics, presents examples of ongoing ethical and unethical use of the concept, and recommends a path towards damage control that includes the development of internationally acceptable standards for that vital concept. © 2013 L&H Scientific Publishing, LLC. All rights reserved.

Lagrangian Relaxation and Linear Intersection Based QoS Routing Algorithm

Abstract Due to the process of network convergence, the variety of types of traffic transmitted over a single medium increases steeply. This phenomenon can be handled by the existing networking structure although the protocols that are used and, especially, the underlying routing protocols need to be improved. The problem of finding the shortest path on the Internet can no longer be easily defined as there is an increasing number of different characteristics to describe a point-to-point link. The definition of the shortest path may differ for different traffic types. Therefore, in the mathematical models used to solve the modern routing problems multiple criteria must be taken into account. One of the interesting classes of the optimization problem is the problem of finding the solution that is minimized against one of the criteria under certain constraints with regard to the others. In this paper, two algorithms solving this kind of problems are presented and compared with a new solution proposed by the authors.

Truncation in “Quasi-Raster” Near-Field Acquisitions [Measurements Corner

This paper discusses how an innovative approach allows controlling the truncation error in near-field antenna characterization. In particular, the method - presented here for the case of aperture antennas and planar scanning - allows estimating the dimensions of the bounded portion of the scanning plane where the field data are collected, the number of field samples to be measured therein, and their locations. Furthermore, quasi-raster scanning is introduced. This allows a very convenient definition of the scanning path connecting the locations of the field-sampling points. The performance of the method is experimentally assessed.