Design of a polymer optical fiber luminescent solar concentrator

We present the design and optimization of a polymeric optical fiber luminescent solar concentrator (FLSC) and systematically investigate the impact of the geometrical and physical parameters of the fiber and active luminescent dopants on the FLSC performance. A multiplicity of individual FLSCs may be arranged on a surface to form a low‐weight and mechanically flexible solar concentrating fabric. In addition to these unique structural properties, we find that the overall optical‐to‐electrical conversion efficiency of the FLSC rivals that of reported flat slab LSCs while increasing the geometric gain, thereby potentially reducing the cost. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of sintering parameters (time and temperature) upon the fabrication process of organic binder-based metallic hollow sphere

Metallic hollow spheres (MHSs) are developed to be used in structural applications in syntactic and metal foams. These foams are lightweight and energy-absorbing structures which also can be used for acoustic insulation. In this study, the fabrication process of MHSs with optimum mechanical properties has been investigated. To achieve this goal, polystyrene spheres were coated with iron powder and an organic binder. During the multi-stage heat treatment, the green spheres were sintered into MHSs. Sintering was done at various temperatures (1125, 1150, 1175 and 1200°C) at different durations (3:30, 4:30 and 5:30?h). The influence of the different sintering durations and temperatures on mechanical features, microstructure and density was studied as well. The obtained results indicate that samples that were sintered at the temperature of 1175°C for 4:30?h resulted in superior mechanical and physical properties.     

Extending hoare logic to real-time

Classical Hoare triples are modified to specify and design distributed real-time systems. The assertion language is extended with primitives to express the timing of observable actions. Further the interpretation of triples is adapted such that both terminating and nonterminating computations can be specified. To verify that a concurrent program, with message passing along asynchronous channels, satisfies a real-time specification, we formulate a compositional proof system for our extended Hoare logic. The use of compositionality during top-down design is illustrated by a process control example of a chemical batch processing system.     

Extending hoare logic to real-time

Classical Hoare triples are modified to specify and design distributed real-time systems. The assertion language is extended with primitives to express the timing of observable actions. Further the interpretation of triples is adapted such that both terminating and nonterminating computations can be specified. To verify that a concurrent program, with message passing along asynchronous channels, satisfies a real-time specification, we formulate a compositional proof system for our extended Hoare logic. The use of compositionality during top-down design is illustrated by a process control example of a chemical batch processing system.     

Explicit solution to the large deformation of a cantilever beam under point load at the free tip using the variational iteration method-II

This study focuses on a new analytical method called the variational iteration method-II (VIM-II) for the differential equation of the large deformation of a cantilever beam under point load at the free tip. The rotation angles as well as the horizontal and vertical displacements of a cantilever beam with large deformation are calculated in an explicit analytical form. A comparison of the results with those of some numerical and analytical methods shows the simplicity and effectiveness of VIM-II. VIM-II is proven to be a powerful technique that can be used to obtain accurate solutions that cannot be provided otherwise by perturbation and other methods. The accuracy and convergence of the method are also investigated and compared with those of other methods. The results showed good agreement between VIM-II and other methods.     

A 4-stage 60-GHz low-noise amplifier in 65-nm CMOS with body biasing to control gain, linearity, and input matching

A 4-stage 60-GHz low-noise amplifier is designed and laid out in a 65?nm CMOS technology. Transmission lines are used to realize the power matching networks at the input, output, and between the stages. Based on foundry-provided models, extensive electromagnetic simulations with Momentum^? (a 2.5D simulator by Agilent) are performed on transmission lines, capacitors and I/O pads to model the behavior of the circuit at mm-wave frequencies. Furthermore, body biasing is used as a technique to control gain variability, linearity performance, and input matching of the designed LNA. Post-layout simulation results show that the LNA achieves a maximum gain of 21.3?dB at 60?GHz while consuming 20?mW from a 1.2?V supply. By changing the body bias voltage of the transistors in the two intermediate stages, the overall gain varies from 14 to 21.3?dB providing more than 7?dB of gain range. Adjusting the body biasing of the transistors in the last stage, results in a maximum IIP3 of more than 2?dBm for the overall amplifier. Also, the input return loss of the LNA is controlled by changing the bulk voltage of the input transistor in the first stage.     

An Efficient Measure for Quantification of Nonlinearity in Chemical Engineering Processes Based on I/O Steady-State Loci

Nonlinearity is virtually ubiquitous in chemical engineering plants, and assessing the degree of nonlinearity involved in a process is of special interest for process control purposes. In this paper, we introduce a simple nonlinearity measure to quantify the extent of nonlinearity in a dynamic system based on its normalized steady-state input/output loci. Our nonlinearity measure obviates the limitations of previous metrics in terms of computational effort and correct identification of highly nonlinear relationships. The measure is satisfactorily applicable to various I/O relationships—from truly linear to sinusoidal, for instance. In order to illustrate the efficiency of the proposed measure, four numerical examples concerning a double-effect evaporator, a jacketed continuously stirred tank reactor (CSTR) with an irreversible reaction, a CSTR involving van de Vusse reactions, and the Henson–Seborg–Pottmann CSTR are presented.     

An introduction to compositional methods for concurrency and their application to real-time

Formal methods to specify and verify concurrent programs with synchronous message passing are discussed. We stress the development towards compositional methods, i.e. methods in which the specification of a compound program can be inferred from specifications of its constituents without reference to the internal structure of those parts. Compositionality enables verification during the process of (top-down) design — the derivation of correct programs — instead of the more familiar a-posteriori verification based on already completed program codes. We sketch the transition from non-compositional towards compositional methods for concurrent programs, indicating the main principles behind compositionality. Having achieved a compositional framework based on classical Hoare triples, we discuss extensions to achieve a convenient formalism to specify and verify reactive systems that have an intensive interaction with their environment. Next this Hoare-style framework is adapted to specify and verify real-time properties, and a compositional proof method is formulated for real-time distributed computing. Compositional reasoning during top-down development of a real-time program is illustrated by an example concerning a watchdog timer. This work was partially supported by Esprit-bra project 3096: Formal Methods and Tools for the Development of Distributed and Real-Time Systems (spec).     

A new approach to accurate measurement of uniaxial joint angles based on a combination of accelerometers and gyroscopes

A new method of measuring joint angle using a combination of accelerometers and gyroscopes is presented. The method proposes a minimal sensor configuration with one sensor module mounted on each segment. The model is based on estimating the acceleration of the joint center of rotation by placing a pair of virtual sensors on the adjacent segments at the center of rotation. In the proposed technique, joint angles are found without the need for integration, so absolute angles can be obtained which are free from any source of drift. The model considers anatomical aspects and is personalized for each subject prior to each measurement. The method was validated by measuring knee flexion-extension angles of eight subjects, walking at three different speeds, and comparing the results with a reference motion measurement system. The results are very close to those of the reference system presenting very small errors (rms = 1.3, mean = 0.2, SD = 1.1 deg) and excellent correlation coefficients (0.997). The algorithm is able to provide joint angles in real-time, and ready for use in gait analysis. Technically, the system is portable, easily mountable, and can be used for long term monitoring without hindrance to natural activities.