Subsystem Structure Research Articles

Retrofit Fault-Tolerant Flight Control Design Under Control Effector Damage

In this paper a theoretical framework for retrofit reconfigurable flight control is developed and applied to a large class of nonlinear models of aircraft dynamics. The proposed approach solves a difficult problem of retrofit control design that retains a baseline controller and, at the same time, accommodates severe structural damage so that the overall system is stable and the control objective is met This is accomplished using minimum prior information regarding the baseline controller. It is shown that the retrofit control design strongly depends on the properties of the nominal closed-loop system, which consists of the unperturbed system dynamics and the dynamics of the nominal controller. Using those properties in a judicious manner, it is shown that a retrofit control signal that compensates control effector damage and resulting state-dependent disturbances can be designed using the failure detection and identification subsystem and variable structure adaptation of suitably chosen signals within the proposed retrofit control architecture. In this paper, the focus is on the compensation of the control effector damage and resulting disturbances. It is shown that the proposed retrofit control design results in asymptotic convergence of the tracking error to zero. Its properties are illustrated through simulations of a high-performance aircraft dynamics. The end result of the paper is a retrofit reconfigurable control design framework that is well suited for a large class of problems encountered in reconfigurable flight control.

Thermal fatigue analysis of small-satellite structure

The small-satellite thermal subsystem main function is to control temperature ranges on equipments, and payload for the orbit specified. Structure subsystem has to ensure the satellite structure integrity. Structure integrity should meet two constraints; first constraint is accepted fatigue damage due to cyclic temperature, and second one is tolerable mounting accuracy at payload and Attitude Determination and Control Subsystem (ADCS) equipments’ seats. First, thermal analysis is executed by applying finite-difference method (IDEAS) and temperature profile for satellite components case is evaluated. Then, thermal fatigue analysis is performed applying finite-element analysis (ANSYS) to calculate the resultant damage due to on-orbit cyclic stresses, and structure deformations at the payload and ADCS equipments seats.

C*-algebras associated with presentations of subshifts ii. ideal structure and lambda-graph subsystems

AbstractA λ-graph system is a labeled Bratteli diagram with shift transformation. It is a generalization of finite labeled graphs and presents a subshift. InDoc. Math.7 (2002) 1–30, the author constructed aC*-algebraO£associated with a λ-graph system £ from a graph theoretic view-point. If a λ-graph system comes from a finite labeled graph, the algebra becomes a Cuntz-Krieger algebra. In this paper, we prove that there is a bijective correspondence between the lattice of all saturated hereditary subsets of £ and the lattice of all ideals of the algebraO£, under a certain condition on £ called (II). As a result, the class of theC*-algebras associated with λ-graph systems under condition (II) is closed under quotients by its ideals.

Why Policy Issue Networks Matter: The Advanced Technology Program and the Manufacturing Extension Partnership

Why Policy Issue Networks Matter: The Advanced Technology Program and the Manufacturing Extension Partnership, Paul M. Hallacher, Lanham, Maryland: Rowman & Littlefield Publishers, 2005, pp. ix, 181.The argument that the rigid institutional arrangements of the past, namely subgovernments, have given way to decentralized, more open and informal policy issue networks is increasingly supported by a burgeoning body of case study literature. Paul Hallacher's book is an example of one such study that attempts to go beyond this observation and hypothesize the causal connections between policy subsystem structure and policy outcomes in the area of American cooperative technology policy. The United States provides a suitable environment for examining the hypothetical link between policy subsystem and outcome in this policy area because of the differences in political culture at the federal and state levels with regards to government in assisting industry. These differences have manifested themselves as open conflict between Democrats and Republicans over interventionist policy.

Operator quantum error-correcting subsystems for self-correcting quantum memories

The most general method for encoding quantum information is not to encode the information into a subspace of a Hilbert space, but to encode information into a subsystem of a Hilbert space. Recently this notion has led to a more general notion of quantum error correction known as operator quantum error correction. In standard quantum error-correcting codes, one requires the ability to apply a procedure which exactly reverses on the error-correcting subspace any correctable error. In contrast, for operator error-correcting subsystems, the correction procedure need not undo the error which has occurred, but instead one must perform corrections only modulo the subsystem structure. This does not lead to codes which differ from subspace codes, but does lead to recovery routines which explicitly make use of the subsystem structure. Here we present two examples of such operator error-correcting subsystems. These examples are motivated by simple spatially local Hamiltonians on square and cubic lattices. In three dimensions we provide evidence, in the form a simple mean field theory, that our Hamiltonian gives rise to a system which is self-correcting. Such a system will be a natural high-temperature quantum memory, robust to noise without external intervening quantum error-correction procedures.

Computer supported mathematics with Ω mega

Classical automated theorem proving of today is based on ingenious search techniques to find a proof for a given theorem in very large search spaces—often in the range of several billion clauses. But in spite of many successful attempts to prove even open mathematical problems automatically, their use in everyday mathematical practice is still limited. The shift from search based methods to more abstract planning techniques however opened up a paradigm for mathematical reasoning on a computer and several systems of that kind now employ a mix of interactive, search based as well as proof planning techniques. The Ω mega system is at the core of several related and well-integrated research projects of the Ω mega research group, whose aim is to develop system support for a working mathematician as well as a software engineer when employing formal methods for quality assurance. In particular, Ω mega supports proof development at a human-oriented abstract level of proof granularity. It is a modular system with a central proof data structure and several supplementary subsystems including automated deduction and computer algebra systems. Ω mega has many characteristics in common with systems like NuPrL, CoQ, Hol, Pvs, and Isabelle. However, it differs from these systems with respect to its focus on proof planning and in that respect it is more similar to the proof planning systems Clam and λ Clam at Edinburgh.

Three-dimensional nonlinear analysis for seismic soil–pile-structure interaction

A three-dimensional method of analysis is presented for the seismic response of structures constructed on pile foundations. An analysis is formulated in the time domain and the effects of material nonlinearity of soil on the seismic response are investigated. A subsystem model consisting of a structure subsystem and a pile-foundation subsystem is used. Seismic response of the system is found using a successive-coupling incremental solution scheme. Both subsystems are assumed to be coupled at each time step. Material nonlinearity is accounted for by incorporating an advanced plasticity-based soil model, HiSS, in the finite element formulation. Both single piles and pile groups are considered and the effects of kinematic and inertial interaction on seismic response are investigated while considering harmonic and transient excitations. It is seen that nonlinearity significantly affects seismic response of pile foundations as well as that of structures. Effects of nonlinearity on response are dependent on the frequency of excitation with nonlinearity causing an increase in response at low frequencies of excitation.

Design of amall deployable satellite

One of the scientific satellite programmes of Rome University “La Sapienza”, called DeSat, is here reported, with major emphasis on the mechanical and structure subsystems. The principal payload of the entire system is represented by a titanium recirculating ball screw boom whose mass reaches one third of the total mass budget. The goal of the mission is to space qualify a new micro-satellite multipurpose platform, called LEO-MicroBAR, and to qualify the titanium linear actuator. Both the two systems have been developed by the Aerospace and Astronautics Engineering Department (AAED). The boom will be used to investigate the validity of its design for space applications, like precise off platform positioning of devices and instruments, GPS interferometry, sensor measurements and robotics. It will be shielded against space interactions by a titanium bellow system whose main functions will be impact protection, antirotation, boom passive thermal control. The satellite geometry, when the boom is in deployed configuration, is highly stretched and the name “deployable satellite” was natural. The large deployment mechanism, compared to the small bus, has influenced the design of every satellite subsystem leading to innovative solutions in terms of design, materials, equipment and instruments.

연성하중해석을 이용한 위성체 구조부재의 최적화

인공위성에서 위성 구조체의 임무는 위성체의 모든 부품을 제반 환경조건 하에서 안전하게 지지하는 것이다. 위성 구조체의 안전성은 위성체 및 발사체 모델의 결합 및 하중함수로 표현되는 발사하중을 부가한 연성하중해석을 통해 최종적으로 검증된다. 본 연구에서는 구조체 무게의 감소를 위해, 발사하중상태 하에의 위성구조에 대해 직접 최적화알고리듬을 적용하였다. 위성 구조부재의 손상여부의 판단을 위한 가속도 반응은 연성하중해석의 결과를 바탕으로 얻었다. 최적화 결과, 구조부재 중량은 약 12%의 감소를 보였으며, 하니콤 심재의 두께가 성능에 크게 기여함을 알 수 있었다. In spacecraft system, structure subsystem has the mission of supporting all the components safely under various space environmental conditions. The safety of spacecraft structure is finally verified from the coupled load analysis, which is a branch of load analysis which combines the launch vehicle and satellite. This study introduces the optimization algorithm to reduce the weight of spacecraft structure under launch environmental conditions directly. The acceleration responses are obtained by the introduction of coupled load analysis, which lead to check the failure of spacecraft structural members. The results show a 12% saving of structural weight and this saving is mainly driven by the thickness of honeycomb core, which strongly affects the natural frequencies of platforms and panels.

Investigation of fluorinated C60 by means of optical spectroscopy

The photoluminescence and absorption properties of C 60 fluorides have been examined. We have found that the obtained optical spectra are shifted gradually to the higher energy side due to the partial elimination of the π-electron subsystem from the molecule. We derived the relationship between the icosahedral C 60 skeleton structure and π-electron subsystem under the influence of F attachment and treated it on the basis of absorption spectra . The excitation with the highest efficiency of luminescent relaxation is probably due to CF bonds.

Iron and copper K-edge XAS study of serotransferrin and ovotransferrin.

The active metal site structure of transferrin with iron and copper atoms is investigated using metal K-XANES. Theoretical analysis of experimental data has been performed on the basis of full multiple-scattering theory. This approach made it possible to study the origin of XANES fine details and to investigate the local structure around active metal sites. A deep insight into the local structure and electronic subsystem of Fe, Cu transferrins is obtained. For example, in the case of Cu substitution of Fe in the active centre, the best fit of theoretical spectra to experiment has been obtained for distances 3% smaller between the Cu atom and the nearest neighbours.

Partitioned procedures for the transient solution of coupled aeroelastic problems – Part II: energy transfer analysis and three-dimensional applications

We consider the problem of solving large-scale nonlinear dynamic aeroelasticity problems in the time-domain using a fluid/structure partitioned procedure. We present a mathematical framework for assessing some important numerical properties of the chosen partitioned procedure, and predicting its performance for realistic applications. Our analysis framework is based on the estimation of the energy that is artificially introduced at the fluid/structure interface by the staggering process that is inherent to most partitioned solution methods. This framework also suggests alternative approaches for time-discretizing the transfer of aerodynamic data from the fluid subsystem to the structure subsystem that improves the accuracy and the stability properties of the underlying partitioned method. We apply this framework to the analysis of several partitioned procedures that have been previously proposed for the solution of nonlinear transient aeroelastic problems. Using two- and three-dimensional, transonic and supersonic, wing and panel aeroelastic applications, we validate this framework and highlight its impact on the design and selection of a staggering algorithm for the solution of coupled fluid/structure equations.

Blind adaptive filtering of speech from noise of unknown spectrum using a virtual feedback configuration

The paper describes a single-receiver blind adaptive filter (BAF) of speech from noise where neither speech nor noise are accessible, nor are their parameters known. The only prior knowledge employed by the BAF is that human speech is nonstationary whereas the noise is assumed to be quasistationary, i.e., stationary over a longer interval than that of any speech phoneme. The RAF has a four subsystem structure. The system consists of an identifying subsystem that is followed by a speech/noise parameter-separator. The noise is identified based on the stationary features of speech and noise. A feedforward subsystem sets optimization neighborhood to the virtual feedback subsystem where a cost-functional is minimized to jointly minimize the stationary part of the output while maximizing its nonstationary part. The system has been tested for performance for different signal to noise ratios (SNR) and for different types of noise parameters. Improvements for various noises range from 14-36 dB for -20 dB SNR inputs.

Decentralized Control of Nonlinear Large-Scale Systems Using Dynamic Output Feedback

In this paper, a class of nonlinear large-scale systems with similar subsystems is studied. Both matched and unmatched uncertainties are considered by utilizing their bounding functions, and the interconnections take a more general form than considered previously. Based on a constrained Lyapunov equation, a nonlinear dynamic output feedback decentralized controller is presented. Unlike existing results, matched uncertainties are considered in the control design; by using a decomposition of the interconnections, the known and uncertain interconnections are treated separately; thus, the robustness is improved and conservativeness is reduced significantly. The computation effort for solving the Lyapunov equation is greatly reduced by taking into account the similar subsystem structure. Finally, simulation is used to illustrate the effectiveness of our results.

Nonlinear analysis of 3D seismic interaction of soil–pile–structure systems and application

To investigate more precisely the seismic response of interactive soil–pile–structure systems, a three-dimensional finite element subsystem methodology with an advanced plasticity-based constitutive model for soils has been developed. The structure subsystem is represented by space frame elements while the pile–soil subsystem is idealized as an assemblage of solid elements. By means of the δ*-version of the hierarchical single surface (HiSS) modelling approach for cyclic behavior of soft clays, tangent matrices of the soil properties are formulated with distinct constitutive laws for individual stress–strain regimes such as virgin loading, unloading, and reloading. A successive-coupling, incremental solution scheme in the time domain is created to take account of both inertial and kinematic soil–pile–structure interactions simultaneously. The seismic inputs can be any combination of three-dimensional motions. The proposed methodology may be used to analyse the seismic responses of structures for different support excitations such as rigid ground motion, interactive pile-foundation motion, and, for long span structures, non-uniform free-field motion.

All-Optical Packet Routing - Architecture and Implementation

We report in this paper the architectural design and implementation of all-optical packet networks. Using photonic switches to route information, an all-optical network has the advantages of bit rate, wavelength, and signal format transparencies. Within the transparency distance, the network is capable of handling a widely heterogeneous mix of traffic. We will describe our research on the implementation of all-optical backbone switches. The switch components including frame synchronizers, frame delineation units, frame header over-writing units, wavelength converters, frame concentrators, and WDM buffers were constructed at 2.5 Gb/s. Their subsystem and device structure as well as preliminary performance are reported.

Structural transition to electrolyte-water solvent and changes in the molecular dynamics of water and properties of solutions

A model of concentration transition “ions and complexes in a water structure → ionic and ionicaqueous clusters → polymer structures of salt and crystal hydrate melts” is suggested. The appearance of cluster nanostructures outside the first zone of a waterlike structure is regarded as a general characteristic of solutions. The characteristics of solutions, phase equilibria, and salts of complex composition are interpreted based on this model. Investigation of the complex dielectric constant of electrolytic solutions in the SHF and EHF bands (7–119 GHz) at high concentrations showed that there are two dispersion regions in which the relaxation times differ by a factor of 5–10. Relaxation processes are separated, the numbers of molecules in hydration shells are calculated, and relaxation times are determined for bulky tetrahedral water with hydration shells of ions, for clusters, and for ionicaqueous polymer chains. It is shown that the two structure subsystems of water molecules in concentrated solutions may be described using the limited rotator/generalized diffusion molecular model.

Superspace group descriptions of the symmetries of incommensurate urea inclusion compounds

Urea inclusion compounds are a class of incommensurate composite crystals. The urea molecules form a three-dimensionally connected network, with approximate space group symmetry P6$_{1}$22. This network contains tunnels (channels), which accommodate guest molecules. The periodicities of the urea subsystem and the guest subsystem along the tunnel axis are mutually incommensurate. Depending on temperature, the guest subsystem exists with various degrees of disorder. This paper reports the application of the superspace formalism to describe the symmetries of incommensurate urea inclusion compounds. A list of superspace groups is given, compatible with the urea subsystem structure, and describing the possible guest subsystem structures. Particular attention is given to the relation between superspace symmetry, the various types of (dis)order in the guest subsystem, and the point-symmetry of the guest molecules. Incommensurate urea inclusion compounds containing n-alkane, diacyl peroxide and $\alpha $, $\omega $-dibromoalkane guest molecules are analysed in detail.

Abstract mathematical model of general management information systems

In order to suit general MIS[1] to the change of the management state, this paper presents an abstract model which is relatively independent of the management state. The basic idea is to determine a new classifying standard, which is not influenced by the current management state but rather make a classification according to the object which is related with the information. Thus, we get the abstract model SS, which contains organization structure subsystem SS, analysis structure subsystem SS 2and relation structure subsystem SS 3.

Earthquake Response of Structure-Elevator System

This paper studies the seismic response of structure-elevator systems. Dynamic models are developed to represent the structure and elevator counterweight subsystems, with nonlinear contact elements between the counterweight and the guide rails. The computational output is given in terms of maximum rail stresses, relative elastic deflections, and interaction forces between counterweight and guide rails. Numerical methods are developed and analysis is performed to study the seismic response of the combined system. The structure subsystem is represented by six flexural modes (i.e., three for each of two horizontal axes), while the counterweight subsystem is modeled with four degrees of freedom. A nonlinear contact element with air gaps, viscous damper, Coulomb friction, and variable stiffness of guide rail is developed to model the dynamic interaction between structure and counterweight subsystems. Nonlinear time-history dynamic analysis was carried out using step-by-step integration of the 20 first-order di...