Characterization of Imperfections in a Martin-Puplett Interferometer Using Ray-Tracing

The effects of imperfections of quasioptical components due to misalignment and manufacturing accuracy on optical path lengths in a Martin-Puplett interferometer have been studied with ray-tracing simulations. Optical path lengths in a test interferometer have been measured and then reproduced as accurately as possible in a simulation by introducing several parameters describing the imperfections. The measurements of a polarizer frame, the profile of a roof mirror and the effect of mirror tilting provide support for the existence of the simulated imperfections. The method has been applied also to the diplexer of the heterodyne array receiver CHAMP⁺, operated by the Max Planck Institute for Radio Astronomy at the APEX telescope, to gain insights on how to improve the performance of the receiver.     

A theory of independent fuzzy probability for system reliability

Fuzzy fault trees provide a powerful and computationally efficient technique for developing fuzzy probabilities based on independent inputs. The probability of any event that can be described in terms of a sequence of independent unions, intersections, and complements may be calculated by a fuzzy fault tree. Unfortunately, fuzzy fault trees do not provide a complete theory: many events of substantial practical interest cannot be described only by independent operations. Thus, the standard fuzzy extension (based on fuzzy fault trees) is not complete since not all events are assigned a fuzzy probability. Other complete extensions have been proposed, but these extensions are not consistent with the calculations from fuzzy fault trees. We propose a new extension of crisp probability theory. Our model is based on n independent inputs, each with a fuzzy probability. The elements of our sample space describe exactly which of the n input events did and did not occur. Our extension is complete since a fuzzy probability is assigned to every subset of the sample space. Our extension is also consistent with all calculations that can be arranged as a fault tree. Our approach allows the reliability analyst to develop complete and consistent fuzzy reliability models from existing crisp reliability models. This allows a comprehensive analysis of the system. Computational algorithms are provided both to extend existing models and develop new models. The technique is demonstrated on a reliability model of a three-stage industrial process     

Electrical engineering for the liberal arts: radio and its history

A course for liberal arts students on the engineering and physics of radio is described. An historical presentation of the subject is given in the classroom. The course is suitable as part of the science requirement in university general education curricula and can serve as a model for how, using history, electrical engineering can be taught to students majoring in the liberal arts     

Modeling of interdiffusion in poly(vinyl acetate)–poly(methyl methacrylate)–toluene multicomponent systems

Work on interdiffusion has been mainly carried out in binary systems in the past, and this work has focused on polymer–solvent (S) systems and polymer blends. To understand and predict the interdiffusion of two solids in the presence of one S, we present a new mathematical model based on the Onsager approach. Within our model, interdiffusion kinetics are described with a modification of the reptation model for long polymer chains, and the chemical potential gradient is used as the driving force behind mass transfer. The chemical potential is calculated with a Flory–Huggins approach. The model was validated with 29 Raman spectroscopy experiments in poly(vinyl acetate)–poly(methyl methacrylate)–toluene systems at 20 °C. Monomer mobilities (L _i,0s) were determined for both polymers to show the independence of L _i,0 from the chain length. The L _i,0s were found to be strongly dependent on the S content. With the knowledge of phase equilibria and L _i,0s, interdiffusion in the ternary polymer–polymer–S system could be predicted by the introduced model. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47092.     

A Novel Approach to Catalysis for NO x Reduction in Diesel Exhaust Gas

With the introduction of stringent emission standards in the US in 2007 (Tier II Bin8, 5) an exhaust aftertreatment for NO _x reduction is required for compliance with the emission regulations. A new approach consists in the synergetic combination of existing technologies NSC (NO _x Storage Catalyst) and SCR (Selective Catalytic Reduction) with onboard generation of ammonia as the reducing agent for the SCR. It is shown in this work that the performance of the combined system exceeds those of each one considered separately, especially after ageing. The generation of ammonia is correlated to the ammonia selectivity during the regeneration of the NSC. The selectivity is primarily dependent on the temperature, A/F ratio (Air/Fuel) and the rich time. It is shown that the development of a suitable control strategy leads to a high level of NO _x reduction under transient conditions in an FTP driving cycle. Due to the complexity and high development costs of current exhaust aftertreatment systems, modelling and simulation were identified as an important aspect in the development process. A system simulation tool named ExACT (Exhaust Gas Aftertreatment Components Toolbox) developed at Daimler is presented. By using the simulation already at an early stage, specific development work can be carried out prior to the experimental work on an engine test bench.     

Loaded monopole antenna: Fourier series and admittance coefficientanalysis

A Fourier series method is presented for determining the self and mutual admittance between two generators driving a monopole antenna. It is shown that the admittances are useful in practical problems involving a monopole with a lumped load. They are applied to the loading of a base driven monopole to produce an outgoing travelling wave between generator and load     

A closed-form expression for the driving-point impedance of thesmall inverted L antenna

The conventional, small, monopole antenna is sometimes modified and bent into the shape of an inverted L. The inverted L antenna displays less capacitive reactance and higher radiation resistance than the monopole. Using a novel method, we derive a formula for the input impedance of the inverted L antenna. The technique involves extending the conventional Pocklington integral equation and the use of the antenna's effective length. The method can be adapted to other electrically small antennas     

Hamilton–Jacobi–Bellman Equations and Approximate Dynamic Programming on Time Scales

The time scales calculus is a key emerging area of mathematics due to its potential use in a wide variety of multidisciplinary applications. We extend this calculus to approximate dynamic programming (ADP). The core backward induction algorithm of dynamic programming is extended from its traditional discrete case to all isolated time scales. Hamilton–Jacobi–Bellman equations, the solution of which is the fundamental problem in the field of dynamic programming, are motivated and proven on time scales. By drawing together the calculus of time scales and the applied area of stochastic control via ADP, we have connected two major fields of research.