SENSITIVITY ANALYSIS AND OPTIMIZATION OF ELASTIC-PLASTIC STRUCTURES

Elastic-plastic analysis problems formulated as quadratic programming problems involve energy functional and equilibrium and yield constraints that depend on the design, material and loading. In this paper we consider the problem of determining the variation of structural response with respect to variations of these parameters. A general result for discrete structures is presented and implications for optimal design are discussed.     

A note on the observed and predicted flow patterns around islands— Flat Holm,the Bristol Channel

Abstract

Multispectral scanner (MSS) data from the Natural Environment Research Councils (NERC) aircraft flown over the island of Flat Holm in the Bristol Channel, U.K. have been used in association with a System Probatoire d'Observation de la Terre, high-resolution visible scanner (SPOT HRV) image of the same area to identify the major surface water flow patterns around the island. Theoretical scaling parameters for shallow water flows are used to predict wake form and compared with the MSS and SPOT HRV images. Initial results indicate that the mathematical approach gives a useful approximation to the observed flow patterns though additional information on tidal currents throughout the tidal cycle and detailed bathymetry in the area are required to further the predictive model.     

Equivalence of quadratic performance criteria†

Two quadratic cost functionals are defined to be equivalent, if they generate the same optimal control law. Necessary and sufficient conditions are derived in terms of the system parameters and the quadratic weighting matrices for two cost functionals to be equivalent.     

A brief history of the octopus imaging facility to celebrate its 10th anniversary

Octopus (Optics Clustered to OutPut Unique Solutions) celebrated in June 2020 its 10th birthday. Based at Harwell, near Oxford, Octopus is an open access, peer reviewed, national imaging facility that offers successful U.K. applicants supported access to single molecule imaging, confocal microscopy, several flavours of superresolution imaging, light sheet microscopy, optical trapping and cryoscanning electron microscopy. Managed by a multidisciplinary team, Octopus has so far assisted >100 groups of U.K. and international researchers. Cross‐fertilisation across fields proved to be a strong propeller of success underpinned by combining access to top‐end instrumentation with a strong programme of imaging hardware and software developments. How Octopus was born, and highlights of the multidisciplinary output produced during its 10‐year journey are reviewed below, with the aim of celebrating a myriad of collaborations with the U.K. scientific community, and reflecting on their scientific and societal impact.     

Enabling the detection of UV signal in multimodal nonlinear microscopy with catalogue lens components

Using an optical system made from fused silica catalogue optical components, third‐order nonlinear microscopy has been enabled on conventional Ti:sapphire laser‐based multiphoton microscopy setups. The optical system is designed using two lens groups with straightforward adaptation to other microscope stands when one of the lens groups is exchanged. Within the theoretical design, the optical system collects and transmits light with wavelengths between the near ultraviolet and the near infrared from an object field of at least 1 mm in diameter within a resulting numerical aperture of up to 0.56. The numerical aperture can be controlled with a variable aperture stop between the two lens groups of the condenser. We demonstrate this new detection capability in third harmonic generation imaging experiments at the harmonic wavelength of ～300 nm and in multimodal nonlinear optical imaging experiments using third‐order sum frequency generation and coherent anti‐Stokes Raman scattering microscopy so that the wavelengths of the detected signals range from ～300 nm to ～660 nm.     

Effect of EHL Contact Conditions on the Behavior of Traction Fluids

New infinitely variable transmission (IVT) systems are under development for the automotive industry as a means to achieving significant fuel economy benefits. These systems rely on the lubricating fluid to transmit the drive train loads across the interface of the transmission components. This requires the development of new fluids that exhibit high traction properties under elastohydrodynamic lubrication (EHL) conditions. However, it has been reported recently that the traction performance of some fluids can reduce dramatically as temperature is reduced. This may place severe operational limits on IVT systems and suggests that the low-temperature traction properties of fluids for these systems should be studied in order to understand the mechanism for the observed reduction in traction.

The work reported here is an experimental study aimed at identifying whether low temperature traction reduction is related to a fundamental change in rheological behavior specific to the fluids tested or to more generic changes in the EHL contact conditions. A series of model experiments were performed using a mini traction machine (MTM) on three high-viscosity polybutene samples. The results have been mapped against previously reported non-dimensional parameters used to identify different EHL regimes. The results show that dramatic reductions in traction occur when the contact transitions from the rigid piezo-viscous (RP) toward the rigid iso-viscous (RI) region. Similar results were also found for two other high-viscosity fluids of different molecular structure and lower traction properties. The results support the hypothesis that the reduction in traction observed at low temperature is due to a change in EHL contact conditions rather than being solely due to a change in the rheological performance of the test fluids.     

Gate-keepers or judges: peer reviews in construction management

Peer review has a momentous influence upon the lives of those who seek to publish, upon the credibility of an academic discipline and upon the way it develops. It is used widely within the academic community on the assumption that it encourages high standards of scholarly writing by providing an informed, fair, reasonable and professional opinion about the merits of research work. This paper reports an experiment which tested the extent to which peer review in construction management serves this function. The results indicate that the outcome of the peer review process is not significantly different from random, and that there is little consistency in the reasons advanced for rejection or revision.     

Conditions for exponomial output control

A closed-form expression for the output of a multivariable linear system with an input that is the product of a polynomial vector and an exponential function is derived without reference to the theory of the Laplace transform. When the exponent of the exponential factor in the input coincides with one of the natural modes (eigenvalues) of the system, the Drazin inverse of a matrix is used to derive a closed-form expression for the output. Using this expression, necessary and sufficient conditions for an input to produce a predetermined output are derived. These conditions are expressed in terms of a block matrix known as the system matrix. These results include some results appearing in the literature dealing with the problem of characterizing those input functions that will yield zero output. A tracking result is included which shows that, for a stable system, asymptotic tracking of a predetermined reference signal is possible if, and only if, the signal can be tracked instantaneously.     

Estimation technique for non-stationary parameters with application to disposal of inventories subject to obsolescence

In this paper we develop a parameter estimation procedure for a stochastic process when that process is non-stationary. Although the estimation procedure itself is very general, we derive the model for the particular case of a Poisson process with parameter µ(t) subject to exponential decay. We then illustrate the application of this particular model to a fundamental problem in the management of inventories subject to obsolescence, i.e. how to identify excess inventories in sufficient time to ensure that stocks are cleared before the end of the season.     

DESIGNING A RESILIENT WATERSCAPE USING A LIVING LAB AND CATALYZING POLYCENTRIC GOVERNANCE

The both polycentric governance and Living Labs concepts are based on decentralized participatory planning, co-design, and decisionmaking. While the concept of Living Lab is still emerging, the Isar-Plan (2000 ~ 2011) pioneered the approach for selecting, co-designing, and implementing nature-based solutions along the Isar River in Munich, Germany. Despite multiple governing authorities involved in the decisionmaking process of the Isar-Plan, the polycentric governance that led to the success of the project has to date not been analyzed. This paper presents the results of an ex-post-analysis of the Isar-Plan restoration planning process based on stakeholder interviews and a literature review. The contribution describes the evolution of Isar-Plan governance arrangements and discusses the Living Lab approaches to cooperative governance. The analysis demonstrates how polycentricity facilitated trust, learning, and the co-design of a resilient waterscape. The paper concludes that Living Labs can be a way of applying polycentric governance when autonomous and multi-scale decision-makers are collaboratively involved in the design of policy solutions, and vice-versa.