Exploring the fitness landscape and the run-time behaviour of an iterated local search algorithm for cost-based abduction

Cost-based abduction (CBA) is an important problem in reasoning under uncertainty, and can be considered a generalization of belief revision. CBA is known to be NP-hard and has been a subject of considerable research over the past decade. In this paper, we investigate the fitness landscape for CBA, by looking at fitness–distance correlation for local minima and at landscape ruggedness. Our results indicate that stochastic local search techniques would be promising on this problem. We go on to present an iterated local search algorithm based on hill-climbing, tabu search, and simulated annealing. We compare the performance of our algorithm to simulated annealing, and to Santos' integer linear programming method for CBA.     

Effects of time-inconsistent preferences on information technology infrastructure investments with growth options

Increasing information technology (IT) infrastructure spending and the capability of such projects to provide a platform for a firm to realize value from IT marks their importance. Effective management of IT infrastructure investments includes identification of embedded growth options in the infrastructure, and exercising them in a timely manner. Extant research has recognized that while managers could use real options thinking in IT investment management, managerial bias could affect the timing of option exercise and their realized value. We analyze the effect of time-inconsistent preferences of present-biased managers on the exercise time of real growth options and the realized value using a discrete time option valuation model. The results show that present-biased managers are more likely to exercise options early when the net payoffs are low, the option payoffs have high volatility, and the risk free discount rate is small. In addition, present biased managers are more likely to exercise a growth option early in its life when the project is performing well. We provide implications for practice and IT governance.     

The effect of design on the usability and real world effectiveness of medical devices: A case study with adolescent users

Adolescents are currently overlooked in many fields of healthcare research and as a result are often required to use medical devices that have been designed for use by either children or adults. This can lead to poor adherence and a reduction in health outcomes.     

Decentralised stabilisation for nonlinear time delay interconnected systems using static output feedback

In this paper, time delay interconnected systems are considered where the nominal isolated subsystems are fully nonlinear. The interconnections and the matched and mismatched disturbances are nonlinear and time-delayed. A decentralised static output feedback control strategy is proposed to stabilise the resulting interconnected system uniformly asymptotically. A novel approach is proposed to deal with the interconnections by introducing artificial interconnections, such that accessible information is fully exploited in the control design to reduce conservatism. Simulation results show the effectiveness of the proposed approach.     

Output feedback stabilization of SISO nonlinear systems via dynamic sliding modes

Previous work on asymptotic stabilization of SISO nonlinear systems using dynamic sliding mode control to produce dynamic state feedback has been developed further to produce dynamic output feedback. All the states in the feedback controller are replaced with estimated states which come from a semi-high gain observer. An upper bound of the semi-high gain parameter is explicitly given. It is proved that if the given differential I-O system is minimum phase and proper, local uniform asymptotic output feedback stabilization can be achieved. Pertinent examples are given to show how the method works for both differential inputoutput models and state space models.     

On discrete time output feedback min-max controllers

In this paper, a constructive design procedure is presented that solves the problem of realizing stabilizing discrete time min-max controllers via measured outputs for non-square systems with matched uncertainties. The conditions for the existence of such a controller will be given and a parameterization of the available design freedom will be proposed. An explicit procedure explains how a Lyapunov matrix, which satisfies both the discrete Riccati inequality and a structural constraint, is obtained. A numerical linear matrix inequality-based method, to optimally select the Lyapunov matrix, so that the computable upper bound on the allowable uncertainty is maximized, is suggested. The results of this paper will be illustrated by an aircraft example.     

Fragments from the forest: Aalto's requisitioning of forest place and matter

Alvar Aalto requisitioned aspects of Finnish vernacular culture in the process of generating his work. This was neither the cataloguing nor the transference of vernacular details, but the personal and creative response to the forest context and the vernacular crafting therein. The discussion of Aalto's personal strife will demonstrate the congruence between his own situation and that to which he is drawn for creative inspiration – i.e., between his personal 'gap' and the socio-cultural 'lack'. His example of softening or 'humanising' Modernism will be shown to be rooted in this congruence. The 'lack' indigenous buildings of Karelia were revisited in the wake of National Romanticism, and found to offer some thing of a natural order that seemed, perhaps incongruously to modern minds, to be compatible with contemporary human conditions.     

Evaluation of the influence of polyoxide‐based surfactants on the separation process of model emulsions of asphaltenes using the FTIR‐ATR technique

During extraction of crude oil, water is generally present in the oil. This water‐in‐oil (w/o) mixture undergoes turbulent flow that promotes sheer forces, resulting in the appearance of emulsions. These emulsions can be highly stable due to the presence of compounds with polar characteristics such as asphaltenes, which act as natural emulsifiers and form resistant films at the oil–water interface. Nonionic surfactants based on polyoxides are widely used to prevent the formation or to break down w/o emulsions. To shed more light on the destabilization mechanism of w/o emulsions promoted by these surfactants, in this study the techniques of tensiometry and Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR‐ATR) were applied to study the interface formed by poly(ethylene oxide)‐poly(propylene oxide) (PEO‐PPO) block copolymers and asphaltenic petroleum fractions. Initially, the critical micelle concentration of the copolymers in aqueous solution was determined. The results agreed with those found by tensiometry. The bottle test was used to evaluate the break‐down of the w/o emulsions in the presence of the PEO‐PPO block copolymers, and the results presented good agreement with those obtained by tensiometry and FTIR‐ATR. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization of a dimer preparation method for nanoscale organic aerosol

Nanoscale dimers have application in studies of aerosol physicochemical properties such as aerosol viscosity. These particle dimers can be synthesized using the dual tandem differential mobility analyzer (DTDMA) technique, wherein oppositely charged particle streams coagulate to form dimers that can be isolated using electrostatic filtration. Although some characterization of the technique has been published, a detailed thesis on the modes and theory of operation has remained outside the scope of prior work. Here, we present new experimental data characterizing the output DTDMA size distribution and the physical processes underlying its apparent modes. Key experimental limitations for both general applications and for viscosity measurements are identified and quantified in six distinct types of DTDMA experiments. The primary consideration is the production of an adequate number of dimers, which typically requires high mobility-selected number concentration in the range 25,000–100,000?cm^?3. The requisite concentration threshold depends upon the rate of spontaneous monomer decharging, which arises predominately from interactions of the aerosol with ionizing radiation within the coagulation chamber and is instrument location dependent. Lead shielding of the coagulation chamber reduced the first-order decharging constant from ～2.0?×?10^?5 s^?1 to ～0.8?×?10^?5 s^?1 in our laboratory. Dimer production at monomer diameters less than 40?nm is hindered by low bipolar charging efficiency. Results from the characterization experiments shed light on design considerations for general applications and for characterization of viscous aerosol phase transitions.

Copyright © 2019 American Association for Aerosol Research