Free‐surface effects on an oblique towing flat plate

Abstract

This paper applies a finite difference method in calculating the free surface profiles, the lateral hydrodynamic forces as well as the moments acting on a plate during the oblique towing of a flat plate on the free surface. The 3‐D fluid motion in the infinite region is approximated by the unsteady 2‐D flow in the finite region with an artificial open boundary on which a more relaxed Sommerfeld's radiation condition is imposed. The free surface profiles, nondimensional side forces and yawing moments are calculated by the present method and are compared satisfactorily with the experimental results [15], Chapman's results [4], and Yamasaki's computational results [16].     

How is a fully penetrated state formed in an anisotropic superconductor?

The fully penetrated state of anisotropic superconductors which are extended in thec-axis direction is analyzed using a model to describe the current distributions. Based on magnetooptical investigations on a rectangular single crystal and on a cubic melt-processed YBa₂Cu₃O_7– sample, the current distributions found in (a, b)-planes and (a, c)-planes with the external magnetic field perpendicular to the plane are discussed. The easy flux penetration along the CuO₂ layers is shown to have important consequences for the analysis of angledependent magnetization or torque measurements inc-axis direction extended samples.     

How close is close enough?

This is a non-trivial question when it comes to radiation dosimetry.The determination of absorbed dose or dose equivalent is oftenmore than an academic exercise or a research project. In themedical application of ionising radiation, the difference betweena dose delivered to a tumour being too low or too high can resultin either a recurrence or complications due to late effects.In this case, the dose has to be just right. And, the degreeof just-rightedness may require the combined standard uncertainty(with no coverage factor) to be just a few percent. If the radiationis being used to sterilise disposable medical products, a similarsituation can occur, although the required uncertainty may besomewhat larger. Too     

How big is the linear region of irreversible thermodynamics?

The driving forces of diffusion reach their largest values in thin films. Temperature and voltage gradients may be steep simply because the film is thin.The matter and energy fluxes of diffusion contain, in principle, a whole series of cross terms. Commonly, we take only first order terms and ignore those of second and higher order; we restrict ourselves to “small” temperature and voltage gradients, to “the linear region of irreversible thermodynamics”.But how big is “small”? The present paper proposes that the linear region of irreversible thermodynamics extends from complete equilibrium to limits in which the energy change in the carrier system (e.g. phonons or plasmons), over a distance of one mean free path along the energy gradient, is comparable with the total energy in the carrier system. If the energy is E and the mean free path is λ, the limit occurs when

$\text{λ▽E}\text{E→1}$

Within this limit, experiments in thermomigration and electromigration measure equilibrium properties. The “reduced heat of transport” of a crystal defect is rigorously identified as the thermal energy of the defect structure.     

The effect of mica surface “dehydroxylation” on particulate palladium vapor deposits

Electron energy loss spectroscopy (ELS) and palladium nucleation were used to study the influence of pre-and post-cleavage annealing on some surface properties of muscovite mica. Two ELS features at 28 eV and 16 eV indicate OH molecules on the mica surface and in the near-surface bulk respectively. On post-cleavage heating of the mica to temperatures above 400°C the two surface losses disappear, causing the simultaneous liberation of water, which is explained by a dehydration of the AlO(OH) layer of the mica lattice. The palladium nucleation and growth behavior is strongly influenced by the state of “dehydroxylation” of the mica surface. On “dehydroxylated” mica the particle number density of palladium is increased and the mean particle size decreased owing in principle to stronger interaction between the mica substrate and the palladium deposit.     

EC2000 and Measurement: How Much Precision is Enough?

As engineering faculty engage in the process of developing assessment plans to implement continuous quality improvement and satisfy the requirement of Engineering Criteria 2000 (EC2000), there is a concern about what measures are adequate to provide evidence that an engineering program is meeting its stated objectives. Some engineering programs are looking at using course grades as evidence that students are meeting the learning outcomes mandated by Criterion 3 of EC2000. After all, if there is a course in engineering design, why shouldn't grades be used to demonstrate that students are acquiring the skills necessary to meet the required outcome? The question remains as to whether or not course grades are adequate and/or efficient as a means to evaluate program effectiveness. This paper will define what is meant by educational inputs, processes, outputs, and outcomes in order to clarify the focus of the new “outcomes assessment” model of engineering education accreditation. A framework will be presented to clarify the meaning and scope of assessment activities needed to meet the information needs of academic programs and institutions. Models for course assessment and program assessment will be presented and the similarities and differences discussed.     

How to evaluate the degree of interdisciplinarity of an institution?

The Stirling index of the set of references of the corpus documents is widely used in the literature on interdisciplinary research and is defined as the integration score of the corpus under study. Such an indicator is relevant at the scale of a research institution, however, there is a gap between the integration scores of individual documents, and a global score computed on the whole set of references. The difference between the global index and the average of individual document indexes carries another relevant information about the corpus: it measures the diversity between the reference profiles of the corpus documents. It is, therefore, named between article index whereas the average of the individual article indexes is called within article index. The statistical properties of these two indexes as well as of the global index are derived from a general approximation method for distributions and lead to statistical tests which can be used to make meaningful comparisons between an institution indexes and benchmark values. The two dimensions of the global index provide a more acute information on the interdisciplinary practices of an institution researchers in a given research domain and is, therefore, likely to contribute to strategic and management issues.     

Tunable wettability on Pendelic marble: could an inorganic marble surface behave as a “self-cleaning” biological surface?

The sustainable protection of the Greek cultural heritage aims to strengthen Pendelic marble, to preserve its unique esthetic properties and its resistance to long weathering. Our main purpose was to design, apply, and study a system of controllable wettability appropriate to the hydrophilic nature of the surface of Pendelic marble. A very simple, cost effective, and easily reproducible method has been developed, to fabricate a composite protective hybrid nanostructured film via a bio-mimetic route. This is a modern technological method for self-cleaning surfaces mimicking nature’s phenomena and structures, such as the Lotus leaf hierarchical nano/microstructure. Our approach differs from the conventional conservation methods in that it is based on a top coating with nanostructured synthesis, consisting of a hydrophilic/hydrophobic silica mixture dispersed in organic solvents, applied by “alla prima” technique onto a fluorosilanic base matrix that has been coated onto Pendelic marble. The behavior of this new surface is critically examined in this document.     

How important is vehicle safety in the new vehicle purchase process?

Whilst there has been a significant increase in the amount of consumer interest in the safety performance of privately owned vehicles, the role that it plays in consumers’ purchase decisions is poorly understood. The aims of the current study were to determine: how important vehicle safety is in the new vehicle purchase process; what importance consumers place on safety options/features relative to other convenience and comfort features, and how consumers conceptualise vehicle safety. In addition, the study aimed to investigate the key parameters associated with ranking ‘vehicle safety’ as the most important consideration in the new vehicle purchase. Participants recruited in Sweden and Spain completed a questionnaire about their new vehicle purchase. The findings from the questionnaire indicated that participants ranked safety-related factors (e.g., EuroNCAP (or other) safety ratings) as more important in the new vehicle purchase process than other vehicle factors (e.g., price, reliability etc.). Similarly, participants ranked safety-related features (e.g., advanced braking systems, front passenger airbags etc.) as more important than non-safety-related features (e.g., route navigation systems, air-conditioning etc.). Consistent with previous research, most participants equated vehicle safety with the presence of specific vehicle safety features or technologies rather than vehicle crash safety/test results or crashworthiness. The key parameters associated with ranking ‘vehicle safety’ as the most important consideration in the new vehicle purchase were: use of EuroNCAP, gender and education level, age, drivers’ concern about crash involvement, first vehicle purchase, annual driving distance, person for whom the vehicle was purchased, and traffic infringement history. The findings from this study are important for policy makers, manufacturers and other stakeholders to assist in setting priorities with regard to the promotion and publicity of vehicle safety features for particular consumer groups (such as younger consumers) in order to increase their knowledge regarding vehicle safety and to encourage them to place highest priority on safety in the new vehicle purchase process.     

How necessary is a fast testkit for mitigation of pandemic flu?

It is widely feared that a novel, highly pathogenic, human transmissible influenza virus may evolve that could cause the next global pandemic. Mitigating the spread of such an influenza pandemic would require not only the timely administration of antiviral drugs to those infected, but also the implementation of suitable intervention policies for stunting the spread of the virus. Towards this end, mathematical modelling and simulation studies are crucial as they allow us to evaluate the predicted effectiveness of the various intervention policies before enforcing them. Diagnosis plays a vital role in the overall pandemic management framework by detecting and distinguishing the pathogenic strain from the less threatening seasonal strains and other influenza-like illnesses. This allows treatment and intervention to be deployed effectively, given limited antiviral supplies and other resources. However, the time required to design a fast and accurate testkit for novel strains may limit the role of diagnosis. Herein, we aim to investigate the cost and effectiveness of different diagnostic methods using a stochastic agent-based city-scale model, and then address the issue of whether conventional testing approaches, when used with appropriate intervention policies, can be as effective as fast testkits in containing a pandemic outbreak. We found that for mitigation purposes, fast and accurate testkits are not necessary as long as sufficient medication is given, and are generally recommended only when used with extensive contact tracing and prophylaxis. Additionally, in the event of insufficient medication and fast testkits, the use of slower, conventional testkits together with proper isolation policies while waiting for the diagnostic results can be an equally effective substitute.     

How much is a quantum controller controlled by the controlled system?

We consider unitary transformations on a bipartite system A × B. To what extent entails the ability to transmit information from A to B the ability to transfer information in the converse direction? We prove a dimension-dependent lower bound on the classical channel capacity C(A ← B) in terms of the capacity C(A → B) for the case that the bipartite unitary operation consists of controlled local unitaries on B conditioned on basis states on A. If the local operations are given by the regular representation of a finite group G we have C(A → B) = log |G| and C(A ← B) = log N where N is the sum over the degrees of all inequivalent representations. Hence the information deficit C(A → B) ? C(A ← B) between the forward and the backward capacity depends on the “non-abelianness” of the control group. For regular representations, the ratio between backward and forward capacities cannot be smaller than 1/2. The symmetric group S _n reaches this bound asymptotically. However, for the general case (without group structure) all bounds must depend on the dimensions since it is known that the ratio can tend to zero. Our results can be interpreted as statements on the strength of the inevitable backaction of a quantum system on its controller.     

How is it possible? Why didn't we do anything? A case history!

Two similar serious accidents occurred at a metal refining process installation within a 6-month time interval. The first one killed ten people, and the second accident one person. The accidents provide a typical case history of how a safety management system and a corresponding organisation could have prevented the occurrence of such an accident or, at least, have reduced its effects. The case is also interesting because it illustrates the physico-chemical complexities forming the root cause of the accidents.     

How is automated and self-driving vehicle technology presented in the news media?

The media continues to be a prominent and widely embraced channel for obtaining information on various topics, exerting considerable influence in shaping public opinions. This holds particularly true for the realm of automated vehicles (AVs), as the media consistently covers developments in this field, encompassing both positive aspects such as technological advancements, as well as negative occurrences like incidents involving self-driving cars colliding with pedestrians. The objective of this study was to utilize sentiment analysis techniques to evaluate the portrayal of AV technology in media news coverage. Data was retrieved from Sprinklr using keywords that are often associated with AVs. Over 1.7 million articles were collected on the keywords for relevant articles published between May 1, 2015 to May 24, 2021. Sentiment analysis was carried out on the cleaned data using three different models – VADER, TextBlob, and NRCLex. The sentiment analysis was separately conducted on the title and text of the articles. 2018 recorded the highest number of news articles on the AV technology. The number of negative sentiments in the title of articles published on the web in 2018 increased 12 times compared to the previous year. The negativity induced in 2018 in the news media did not continue in the next year, which explains that the technology experienced short term effects from the negative incidents associated with its early development. The news articles were also found to have subjectivity from the authors in the article text. The findings are expected to stimulate debates among industry players on how to bring the media along the journey of the development and eventual full deployment of AVs.     

How should the dynamics of an interacting degenerate Bose gas be described?

We show how a semiclassical representation of the atomic field may describe the interacting base gas at finite temperatures.     

How is wettability of titanium surfaces influenced by their preparation and storage conditions?

The effect of two different etching procedures with inorganic acids (HSE and CSE)—one using additionally strongly oxidising conditions due to the presence of CrO₃ (CSE)—and consecutive storage conditions (dry methanol and air) for previous corundum blasted titanium surfaces is compared with respect to their wettability behaviour and the potential of the etching processes for removing remaining blasting material. The etching procedures result in distinct different surface morphologies. Whereas the HSE surface shows sub-mm to sub-μm structures but neither porosity nor undercuts, the CSE surface is extremely rugged and porous with structures protruding the more homogeneously attacked areas by several micrometers. By EDX analysis both remaining blasting material and chromium and sulphur from the etching treatment has been detected on the CSE surfaces only. Both surfaces states show super-hydrophilic behaviour immediately after etching and storage up to 28 days in dry methanol. Whereas contact with air does not change super-hydrophilicity for the CSE samples, wettings angles of the HSE samples increase within minutes and reach about angles of about 60° and 90° after one and 2 days exposure to air, respectively. The increasing hydrophobicity is discussed with respect to the formation of a surface coverage from hydrocarbons originating from aromatic compounds present in traces in air.