bluuebunny/crossref_metadata_2025_split huggingface dataset:
A nonlinear stability analysis of elastic flight vehicle
Authors: Shamaghdari Saeed , Nikravesh S.K.Y. 
Published: March 2013

PurposeThe purpose of this paper is to present a nonlinear model along with stability analysis of a flexible supersonic flight vehicle system.Design/methodology/approachThe mathematical state space nonlinear model of the system is derived using Lagrangian approach such that the applied force, moment, and generalized force are all assumed to be nonlinear functions of the system states. The condition under which the system would be unstable is derived and when the system is stable, the region of attraction of the system equilibrium state is determined using the Lyapunov theory and sum of squares optimization method. The method is applied to a slender flexible body vehicle, which is referenced by the other researchers in the literature.FindingsIt is demonstrated that neglecting the nonlinearity in external force, moment and generalized force, as it was assumed by other researchers, can cause significant variations in stability conditions. Moreover, when the system is stable, it is shown analytically here that a reduction in dynamic pressure can make a larger region of attraction, and thus instability will occur in a larger angle of attack, greater angular velocity and elastic displacement.Practical implicationsIn order to carefully study the behavior of aeroelastic flight vehicle, a nonlinear model and analysis is definitely necessary. Moreover, for the design of the airframe and/or control purposes, it is essential to investigate region of attraction of equilibrium state of the stable flight vehicle.Originality/valueCurrent stability analysis methods for nonlinear elastic flight vehicles are unable to determine the state space region where the system is stable. Nonlinear modeling affects the determination of the stability region and instability condition. This paper presents a new approach to stability analysis of the nonlinear flexible flight vehicle. By determining the region of attraction when the system is stable, it is demonstrated analytically, in this research, that decreasing the dynamic pressure can produce larger region of attraction.
Robust flutter analysis and control of a wing
Authors: Fatehi Mahdi , Moghaddam Majid , Rahim Mohammad 
Published: March 2013

PurposeThe purpose of this paper is to present a novel approach in aeroservoelastic analysis and robust control of a wing section with two control surfaces in leading‐edge and trailing‐edge. The method demonstrates how the number of model uncertainties can affect the flutter margin.Design/methodology/approachThe proposed method effectively incorporates the structural model of a wing section with two degrees of freedom of pitch and plunge with two control surfaces on trailing and leading edges. A quasi‐steady aerodynamics assumption is made for the aerodynamic modeling. Basically, perturbations are considered for the dynamic pressure models and uncertainty parameters are associated with structural stiffness and structural damping and are accounted for in the model by a Linear Fractional Transformation (LFT) model. The control commands are applied to a first and second order electro‐mechanical actuator.FindingsDynamic performance of aeroelastic/aeroservoelastic system including time responses, system modal specifications, critical flutter speeds, and stability margins are extracted and compared with each other. Simulation results are validated through experiments and are compared to other existing methods available to the authors. Results of simulations with four structural uncertainties and first order controllers have a good agreement with experimental test results. Furthermore, it is shown that by using a high gain second order controller, the aeroservoelastic (ASE) system does not have any coupling nature in frequency response.Originality/valueIn this study, modeling, simulation, and robust control of a wing section have been investigated utilizing the μ‐Analysis method and the wing flutter phenomenon is predicted in the presence of multiple uncertainties. The proposed approach is an advanced method compared to conventional flutter analysis methods (such as V‐g or p‐k) for calculating stability margin of aeroelastic/aeroservoelastic systems.
Gravity gradient torque of spacecraft orbiting asteroids
Authors: Wang Yue , Xu Shijie 
Published: March 2013

PurposeThe purpose of this paper is to present a full fourth‐order model of the gravity gradient torque of spacecraft around asteroids by taking into consideration of the inertia integrals of the spacecraft up to the fourth order, which is an improvement of the previous fourth‐order model of the gravity gradient torque.Design/methodology/approachThe fourth‐order gravitational potential of the spacecraft is derived based on Taylor expansion. Then the expression of the gravity gradient torque in terms of gravitational potential derivatives is derived. By using the formulation of the gravitational potential, explicit formulations of the full fourth‐order gravity gradient torque are obtained. Then a numerical simulation is carried out to verify the model.FindingsIt is found that the model is more sound and precise than the previous fourth‐order model due to the consideration of higher‐order inertia integrals of the spacecraft. Numerical simulation results show that the motion of the previous fourth‐order model is quite different from the exact motion, while the full fourth‐order model fits the exact motion very well. The full fourth‐order model is precise enough for high‐precision attitude dynamics and control around asteroids.Practical implicationsThis high‐precision model is of importance for the future asteroids missions for scientific explorations and near‐Earth objects (NEOs) mitigation.Originality/valueIn comparison with previous models, a gravity gradient torque model around asteroids that is more sound and precise is established. This model is valuable for high‐precision attitude dynamics and control around asteroids.
A directional control system for UCAV automatic takeoff roll
Authors: Zhang Yunpeng , Duan Haibin 
Published: March 2013

PurposeThe purpose of this paper is to develop a directional and roll control system for unmanned combat air vehicle (UCAV) automatic takeoff roll, with the objective of keeping the UCAV along the runway centerline and keeping the wings level, especially when there is a crosswind.Design/methodology/approachThe nonlinear model of the UCAV during takeoff roll is established. The model is linearized about the lateral‐directional equilibrium point at different forward speeds. The approximate directional model and roll model are extracted using time‐scale decomposition technique. Then the directional control law and roll control law are developed using gain scheduling approach. Nose wheel steering, differential brake and rudder are used as the primary directional control device at low, medium and high speeds, respectively, according to both the qualitative and quantitative analysis of their control effectiveness at different speeds. A priority matrix is developed to determine the secondary control device which is used if the primary control device fails, thus the directional control system can have a certain degree of fault tolerance.FindingsThis work developed the directional control law and roll control law by using gain scheduling approach. Experimental results verified that the developed directional and roll control system has high robustness and satisfactory fault tolerance: it can guarantee a safe takeoff under a 50 ft/sec crosswind, even if one directional control device fails, which satisfies the relevant criteria in MIL‐HDBK‐1797.Practical implicationsThe directional and roll control system developed can be easily applied to practice and can steer the UCAV during takeoff roll safely, which will considerably increase the autonomy of the UCAV.Originality/valueThe paper shows how time‐scale decomposition technique is employed to extract the approximate directional model and roll model, which simplifies model analysis and control law design. A fault‐tolerant directional control system is designed to improve safety during takeoff.
Combined fatigue experiments on full scale turbine components
Authors: Hu Dianyin , Wang Rongqiao 
Published: March 2013

PurposeThe purpose of this paper is to perform experiments on a full scale turbine blade attached to a part of actual turbine disc at elevated temperature, which can accurately predict the life of a fir‐tree contact under high cycle fatigue (HCF)/low cycle fatigue (LCF) combined loading. Moreover, the effect of shot‐peening on the fatigue lives of the turbine attachments is investigated experimentally by comparing those of unpeened ones.Design/methodology/approachAn experimental system for a full scale turbine blade attached to a part of actual turbine disc at elevated temperature is established in this paper, with a new HCF/LCF combined loading scheme and a design of blade clamp. The new combined fatigue loading method achieves a noninterfering treatment of the high cycle and low cycle loading by placing low cycle loading exerting point to the back of the mortise. Then fatigue tests were performed on six used turbine components to investigate the effect of shot‐peening on fatigue life compared with the unpeened ones.FindingsThis test system ingeniously achieves HCF/LCF combined loading of the full scale turbine component, and a special design of the blade clamp successfully simulates the stress field of the turbine blade. Experimental life data show that the shot‐peening process greatly improves the used turbine fir‐tree attachment's life.Practical implicationsThe present study provides an experimental method to simulate HCF/LCF combined loading of a full scale fir‐tree turbine attachment at elevated temperature at laboratory.Originality/valueCompared with the unpeened turbine components, the fatigue lives of the shot‐peened ones are increased greatly. Mean life of the shot‐peened turbine attachment is 5.23 times longer than that of the unpeened.
Aircraft flutter prediction using experimental modal parameters
Authors: Pankaj Achuthan C. , Shanthini G. , Shivaprasad M.V. , Manjuprasad M. 
Published: March 2013

PurposeTraditional dynamic and flutter analysis demands a detailed finite element model of the aircraft in terms of its mass and stiffness distribution. However, in absence of these details, modal parameters obtained from experimental tests can be used to predict the flutter characteristics of an aircraft. The purpose of this paper is to develop an improved and reliable method to predict the flutter characteristics of an aircraft structure of unknown configuration under an anticipated aerodynamic loading using software such as MSC Nastran and experimental modal parameters (such as mode shapes, natural frequencies and damping) from ground vibration tests.Design/methodology/approachA finite element model with nodes representing the test points on the aircraft is created with appropriate boundary constraints. A direct matrix abstraction program has been written for NASTRAN software that carries out a normal modes analysis and replaces the mass normalized eigenvalues and vectors with the experimentally obtained modal parameters. The flutter analysis proceeds with the solution of the flutter equation in the flutter module of NASTRAN.FindingsThe method has been evaluated for a light composite aircraft and its results have been compared with flight flutter tests and the flutter speeds obtained from the finite element model with actual stiffness and mass distributions of the aircraft.Research limitations/implicationsThe methodology developed helps in the realistic prediction of flutter characteristics of a structure with known geometric configuration and does not need material properties, mass or stiffness distributions. However, experimental modal parameters of each configuration of the aircraft are required for flutter speed estimation.Practical implicationsThe proposed methodology requires experimental modal parameters of each configuration of the aircraft for flutter speed estimation.Originality/valueThe paper shows that an effective method to predict flutter characteristics using modal parameters from ground vibration tests has been developed.
Solution space research for interplanetary trajectory
Authors: Zhao Zunhui , Shang Haibin , Cui Pingyuan , Huang Xiangyu 
Published: March 2013

PurposeThe purpose of this paper is to present a solution space searching method to study the initial design of interplanetary low thrust gravity assist trajectory.Design/methodology/approachFor reducing the complexity and nonlinearity of the initial design problem, a sixth degree inverse polynomial shape based approach is brought. Then some improvements are provided for solving the parameters in the shape function and a quasi‐lambert solver is brought through the shape based method, the thrust profile can be generated under the given time of flight, boundary states including positions and velocities for low thrust phase. Combining gravity assist model, the problem is summarized and an improved pruning technique is used for searching the feasible solution space for low thrust gravity assist trajectory.FindingsUsing the solution space searching method, the feasible solution region would be generated under the given mission condition. The treatment about gravity assist demonstrates more accurate than previous method. Also another advantage is that the searching method can be used to design different types of mission trajectory, including flyby and rendezvous trajectories.Practical implicationsThe method can be used as an efficient approach to search the feasible region for the complex low thrust gravity assist trajectory, and it can provide appropriate initial guesses for the low thrust gravity assist trajectory in mission design phase.Originality/valueFeasible solution space would be obtained through the searching method. The quasi‐Lambert solver in the paper is found under the shape‐based method and relative improvement, and it shows its availability during the searching process. Through mission trajectory design, the effectiveness of the method is shown.
Auditors' moral philosophies and ethical beliefs
Authors: Kung Fan‐Hua , Li Huang Cheng 
Published: March 2013

PurposeThe purpose of this paper is to investigate the influence of moral philosophy on the ethical beliefs of auditors. The paper argues that an individual's moral philosophy is the key factor in how one views ethical issues and largely determines the ethical choices one makes. The paper also seeks to discover the influence of personal values on the reasoning processes associated with ethics and to explore whether the personal value preferences of auditors, as a manifestation of their moral philosophy, influence their ethical beliefs and (presumably) their subsequent actions.Design/methodology/approachThe authors designed a survey instrument to assess the value preferences, moral philosophies, and reactions of practicing auditors to judgment dilemmas. They then employed structural equation modeling to examine the sensitivity of auditors to the competence and integrity of clients with the aim of gaining insight into the ethical beliefs of auditors in general.FindingsThese results show that value preferences alone fail as predictors of ethical beliefs. Instead, personal values have an indirect influence on ethical beliefs via moral philosophy. Moreover, auditors strongly motivated by values based on self‐enhancement were negatively associated with idealism in ethics and positively associated with relativism. Therefore, it can be concluded that idealist auditors were more likely to condemn the actions of clients that violated moral norms, while relativist auditors were more permissive.Originality/valueThe results identify the role of moral philosophy as a mediator for the personal values and ethical beliefs of auditors, shedding light on how personal values can influence ethical sensitivity.
Design management capability and product innovation in SMEs
Authors: Fernández‐Mesa Anabel , Alegre‐Vidal Joaquín , Chiva‐Gómez Ricardo , Gutiérrez‐Gracia Antonio 
Published: March 2013

PurposeThe aim of this paper is to present design management as a dynamic capability and to analyze its mediating role between organizational learning capability and product innovation performance in small and medium enterprises (SMEs).Design/methodology/approachStructural equation modeling is used to test the research hypotheses based on data from the Italian and Spanish ceramic tile industries. The data are derived from the responses of 182 companies (50 percent of the target population) to a questionnaire addressed to Product Development Managers and Human Resource Managers.FindingsThe results suggest that organizational learning capability enhances product innovation through the mediation of design management capability. The authors find an interesting interplay between organizational learning, design management capability and product innovation that can be very useful to better understand how to improve innovation performance. This finding shows that design management, as a dynamic capability, emerges from learning and allows the firm to adapt to environmental changes.Originality/valueSeveral works have studied dynamic capabilities but without specifying the nature of these capabilities. More recent empirically‐based studies conceptualize and refer to specific dynamic capabilities. In this paper, the authors present design management as a dynamic capability. This study aims also to develop a better understanding of how organizational learning capability impacts on the product innovation performance of SMEs and how this relationship is mediated by design management capability.
Tracking politics with POWER
Authors: Moreira Silvio , Batista David S. , Carvalho Paula , Couto Francisco M. , Silva Mario J. 
Published: March 2013

PurposePOWER is an ontology of political processes and entities. It is designed for tracking politicians, political organizations and elections, both in mainstream and social media. The aim of this paper is to propose a data model to describe political agents and their relations over time.Design/methodology/approachThe authors propose a data model to describe political agents (politicans, political instutions and political associations) and their relations over time. The model is formalized as an ontology using the RDF format and the population is performed in two steps. First, a bootstrap process loads data collected from authoritative sources. Then, the ontology is enriched with alternative media names extracted from the web.FindingsThe ontology is published as a public resource following the guidelines of linked data and semantic web standards can be accessed via SPARQL endpoint.Originality/valueThe authors have developed an ontology for the political domain tailored to aid in the tasks of named entity recognition and resolution. It represents the complexity and dynamic nature of relations between political agents (politicians, political associations and political institutions) over time.
A model of student involvement in the quality assurance system at institutional level
Authors: Elassy Noha 
Published: March 2013

PurposeThis paper aims to create a theoretical model of student involvement in the institutional quality assurance process at their universities.Design/methodology/approachThe model suggested in this paper was created and developed from a critical examination of relevant literature on stakeholder involvement in decision making and quality assurance processes, regarding different disciplines.FindingsThis paper presents a theoretical model of student involvement in the institutional quality assurance with its diminutions, categories and 20 rungs of student activities. It suggests a definition of student involvement term, regarding participating in the quality assurance process at higher education institutions. The importance of involving students in quality assurance procedures has been discussed. The paper provides some international experiences about student involvement in institutional QAP depending on the categories of student involvement activities that were suggested in the theoretical model.Originality/valueThe paper reveals a comprehensive model of student involvement that allows a full understanding of the extent and nature of the activities which higher education students undertake when they involve themselves in the quality assurance process at their institution.
Managing a supply chain's web of risk
Authors: Chakravarty Vikram 
Published: March 2013

PurposeThis purpose of this article is to look at how companies focused on optimizing their supply chain through global sourcing and just‐in‐time (JIT) delivery systems to dramatically cut the cost of production, now must learn to reduce their exposure to a variety of complex risks.Design/methodology/approachThe article traces how in the aftermath of the March 2011 earthquake and tsunami in Japan, many manufacturers around the world suddenly discovered how exposed their operations were to unanticipated interruption in their supply chain.FindingsThe author suggests steps companies can take to analyze risk, to prevent supply chain disruption and to manage its consequences when it happens.Practical implicationsFor identifiable individual risks, a company can choose a variety of mitigation approaches: avoid; transfer; mitigate; minimize; respond; monitor; accept.Originality/valueThe paper presents at a five‐level approach where improved risk management can be tackled at five levels of increasing sophistication: level 1 – efficient firefighting; level 2 – insurance; level 3 – core risk management; level 4 – return‐risk optimization; and level 5 – distributed operations for uncertainty and complexity.
Embracing connectedness: insights from the IBM 2012 CEO study
Authors: Berman Saul , Korsten Peter 
Published: March 2013

PurposeThis article seeks to highlight some of the findings of the 2012 IBM CEO Study, Leading through Connection, based on interviews with CEOs and public sector leaders in every part of the world.Design/methodology/approachThe study was designed to determine how technology is fundamentally changing how stakeholders engage.FindingsA major finding was that CEOs are focusing on how recent advances in technology allow companies to re‐imagine connections among people – customers, employees, partners and investors.Research limitations/implicationsBetween September 2011 and January 2012, IBM met face to face with 1,709 CEOs and senior public sector leaders in 64 countries and 18 industries.Practical implicationsCEOs are reevaluating how they engage partners. Boundaries between organizations are becoming more porous. Interactions span more functions and are more continuous.Originality/valueThe study points to two conclusions. These are, first, empowering employees through values. For CEOs, organizational openness offers tremendous upside potential – empowered employees, free‐flowing ideas, more creativity and innovation, happier customers, better results. Teams will need processes and tools that inspire collaboration on a massive scale. Second, amplifying innovation with partnerships. Rising complexity and escalating competition have made partnering a core innovation strategy for many organizations.