Influence of friction forces on the motion of VTOL aircraft during landing operations on ships at sea

Equations describing the friction forces generated during landing operations on ships at sea were formulated. These forces depend on the platform reaction and the coefficient of friction. The platform reaction depends on the relative sink rate and the shock absorbing capability of the landing gear. The friction coefficient varies with the surface condition of the landing platform and the angle of yaw of the aircraft relative to the landing platform. Landings by VTOL aircraft, equipped with conventional oleopneumatic landing gears are discussed. Simplifications are introduced to reduce the complexity of the mathematical description of the tire and shock strut characteristics. Approximating the actual complicated force deflection characteristic of the tire by linear relationship is adequate. The internal friction forces in the shock strut are included in the landing gear model. A set of relatively simple equations was obtained by including only those tire and shock strut characteristics that contribute significantly to the generation of landing gear forces

Wind Tunnel Test of Low Boom Equivalent Body at Mach 4

A body of revolution, representing the equivalent area distribution of a low boom aircraft design cruising at 24,384 meters at a Mach number of 4, was tested to determine whether its theoretical sonic boom characteristics could be experimentally verified. Results indicate that the essential features of the ground signature are well predicted

Why High and Low Performers Leave and What They Find Elsewhere: Job Performance Effects on Employment Transitions

Little is known about how high and low performers differ in terms of why they leave their jobs, and no work examines whether pre-quit job performance matters for post-quit new-job outcomes. Working with a sample of approximately 2,500 former employees of an organization in the leisure and hospitality industry, we find that the reported importance of a variety of quit reasons differs both across and within performance levels. Additionally, we use an ease-of-movement perspective to predict how pre-quit performance relates to post-quit employment, new-job pay, and new-job advancement opportunity. Job type, tenure, and race interacted with performance in predicting new-job outcomes, suggesting explanations grounded in motivation, signaling, and discrimination in the external job market

Unit-Level Voluntary Turnover Rates and Customer Service Quality: Implications of Group Cohesiveness, Newcomer Concentration, and Size

Despite substantial growth in the service industry and emerging work on turnover consequences, little research examines how unit-level turnover rates affect essential customer-related outcomes. The authors propose an operational disruption framework to explain why voluntary turnover impairs customers’ service quality perceptions. Based on a sample of 75 work units and data from 5,631 employee surveys, 59,602 customer surveys, and organizational records, results indicate that unit-level voluntary turnover rates are negatively related to service quality perceptions. The authors also examine potential boundary conditions related to the disruption framework. Of three moderators studied (group cohesiveness, group size, and newcomer concentration), results show that turnover’s negative effects on service quality are more pronounced in larger units and in those with a greater concentration of newcomers

Climate Change, Insurability of Large-scale Disasters and the Emerging Liability Challenge

This paper focuses on the interaction between uncertainty and insurability in the context of some of the risks associated with climate change. It discusses the evolution of insured losses due to weather-related disasters over the past decade, and the key drivers of the sharp increases in both economic and insured catastrophe losses over the past 20 years. In particular we examine the impact of development in hazard-prone areas and of global warming on the potential for catastrophic losses in the future. In this context we discuss the implications for insurance risk capital and the capacity of the insurance industry to handle large-scale events. A key question that needs to be addressed is the factors that determine the insurability of a risk and the extent of coverage offered by the private sector to provide protection against extreme events where there is significant uncertainty surrounding the probability and consequences of a catastrophic loss. We discuss the concepts of insurability by focusing on coverage for natural hazards, such as earthquakes, hurricanes and floods. The paper also focuses on the liability issues associated with global climate change, and possible implications for insurers (including D&O), given the difficulty in identifying potential defendants, tracing harm to their actions and apportioning damages among them. The paper concludes by suggesting ways that insurers can help mitigate future damages from global climate change by providing premium reductions and rate credits to companies investing in risk-reducing measures.

Evaluating The Effectiveness of Terrorism Risk Financing Solutions

The 9/11 attacks in the United States, as well as other attacks in different parts of the world, raise important questions related to the economic impact of terrorism. What are the most effective ways for a country to recover from these economic losses? Who should pay for the costs of future large-scale attacks? To address these two questions, we propose five principles to evaluate alternative programs. We first discuss how a federal insurance program with mandatory coverage and a laissez faire free-market approach for providing private insurance will fare relative to these principles. We conclude that neither solution is likely to be feasible here in the United States given the millions of firms at risk and the current structure of insurance regulation. We then evaluate how well the U.S. Terrorism Risk Insurance Act (TRIA), a public-private program to cover commercial enterprises against foreign terrorism on U.S. soil, meets the five principles. In particular, we show that TRIA has had a positive effect on availability of terrorism coverage and also has significantly contributed to reducing insurance premiums. TRIA is scheduled to terminate at the end of the year, but pending legislation would extend the program for fifteen years after December 31 (HR. 2761). In this paper, we show that such a long-term extension might have important impacts on the market. This could increase the take-up rate, as prices might be even lower than they are today. We show also, however, that if TRIA were extended for a long period of time in its current form, some insurers could "game" the program by collecting ex ante a large amount of premiums for terrorism insurance, while being financially responsible for only a small portion of the claims ex post. The general taxpayer and the general commercial policyholder (whether or not covered against terrorism) would absorb the residual insured losses. This raises major equity issues inherent in the design of the program.

Implications of symmetries in the scalar sector

Symmetries play a very important r\^ole in Particle Physics. In extended scalar sectors, the existence of symmetries may permit the models to comply with the experimental constraints in a natural way, and at the same time reduce the number of free parameters. There is a strong interplay among internal symmetries of the scalar potential, its CP properties and mass degeneracies of the physical scalars. Some of these aspects were discussed in this talk.Comment: 8 pages, to be published in the Proceedings of DISCRETE2018: 6th Symposium on Prospects in the Physics of Discrete Symmetries, 26-30 Nov 2018. Vienna, Austri

Symmetries and Mass Degeneracies in the Scalar Sector

We explore some aspects of models with two and three SU(2) scalar doublets that lead to mass degeneracies among some of the physical scalars. In Higgs sectors with two scalar doublets, the exact degeneracy of scalar masses, without an artificial fine-tuning of the scalar potential parameters, is possible only in the case of the inert doublet model (IDM), where the scalar potential respects a global U(1) symmetry that is not broken by the vacuum. In the case of three doublets, we introduce and analyze the replicated inert doublet model, which possesses two inert doublets of scalars. We then generalize this model to obtain a scalar potential, first proposed by Ivanov and Silva, with a CP4 symmetry that guarantees the existence of pairwise degenerate scalar states among two pairs of neutral scalars and two pairs of charged scalars. Here, CP4 is a generalized CP symmetry with the property that $({\rm CP}4)^n$ is the identity operator only for integer $n$ values that are multiples of 4. The form of the CP4-symmetric scalar potential is simplest when expressed in the Higgs basis, where the neutral scalar field vacuum expectation value resides entirely in one of the scalar doublet fields. The symmetries of the model permit a term in the scalar potential with a complex coefficient that cannot be removed by any redefinition of the scalar fields within the class of Higgs bases (in which case, we say that no real Higgs basis exists). A striking feature of the CP4-symmetric model is that it preserves CP even in the absence of a real Higgs basis, as illustrated by the cancellation of the contributions to the CP violating form factors of the effective ZZZ and ZWW vertices.Comment: 52 pages, 2 figures, second revised version with new material, as published by JHE