Assessing the future of air freight

The role of air cargo in the current transportation system in the United States is explored. Methods for assessing the future role of this mode of transportation include the use of continuous-time recursive systems modeling for the simulation of different components of the air freight system, as well as for the development of alternative future scenarios which may result from different policy actions. A basic conceptual framework for conducting such a dynamic simulation is presented within the context of the air freight industry. Some research needs are identified and recommended for further research. The benefits, limitations, pitfalls, and problems usually associated with large scale systems models are examined

Infrastructure dynamics: A selected bibliography

The term infrastructure is used to denote the set of life support and public service systems which is necessary for the development of growth of human settlements. Included are some basic references in the field of dynamic simulation, as well as a number of relevant applications in the area of infrastructure planning. The intent is to enable the student or researcher to quickly identify such applications to the extent necessary for initiating further work in the field

Air freight demand models: An overview

A survey is presented of some of the approaches which have been considered in freight demand estimation. The few existing continuous time computer simulations of aviation systems are reviewed, with a view toward the assessment of this approach as a tool for structuring air freight studies and for relating the different components of the air freight system. The variety of available data types and sources, without which the calibration, validation and the testing of both modal split and simulation models would be impossible are also reviewed

Planning and evaluation parameters for offshore complexes

Issues are presented for consideration in the planning and design of offshore artificial complexes. The construction of such complexes, their social, economic, and ecological impacts, and the legal-political-institutional environments within which their development could occur, are discussed. Planning, design, and construction of near-shore complexes located off the Mid-Atlantic coast of the United States is emphasized

The role of the helicopter in transportation

A general overview is presented of the role that the helicopter plays in the current aviation scene with special emphasis on its use in the airport access function. Technological problems of present-day aircraft are discussed along with some plausible solutions. The economic and regulatory aspects of commercial helicopter operations are presented. Finally six commercial operations utilizing helicopters are reviewed and conditions that enhance the success of the helicopter in the airport access function are proposed

The environmental analysis of helicopter operations by Federal agencies: Current procedures and research needs

The technical, economic, and environmental problems restricting commercial helicopter passenger operations are reviewed. The key considerations for effective assessment procedures are outlined and a preliminary model for the environmental analysis of helicopters is developed. It is recommended that this model, or some similar approach, be used as a common base for the development of comprehensive environmental assessment methods for each of the federal agencies concerned with helicopters. A description of the critical environmental research issues applicable to helicopters is also presented

Combinatorics of linear iterated function systems with overlaps

Let $\bm p_0,...,\bm p_{m-1}$ be points in ${\mathbb R}^d$, and let $\{f_j\}_{j=0}^{m-1}$ be a one-parameter family of similitudes of ${\mathbb R}^d$: $$f_j(\bm x) = \lambda\bm x + (1-\lambda)\bm p_j, j=0,...,m-1,$$ where $\lambda\in(0,1)$ is our parameter. Then, as is well known, there exists a unique self-similar attractor $S_\lambda$ satisfying $S_\lambda=\bigcup_{j=0}^{m-1} f_j(S_\lambda)$. Each $\bm x\in S_\lambda$ has at least one address $(i_1,i_2,...)\in\prod_1^\infty\{0,1,...,m-1\}$, i.e., $\lim_n f_{i_1}f_{i_2}... f_{i_n}({\bf 0})=\bm x$. We show that for $\lambda$ sufficiently close to 1, each $\bm x\in S_\lambda\setminus\{\bm p_0,...,\bm p_{m-1}\}$ has $2^{\aleph_0}$ different addresses. If $\lambda$ is not too close to 1, then we can still have an overlap, but there exist $\bm x$'s which have a unique address. However, we prove that almost every $\bm x\in S_\lambda$ has $2^{\aleph_0}$ addresses, provided $S_\lambda$ contains no holes and at least one proper overlap. We apply these results to the case of expansions with deleted digits. Furthermore, we give sharp sufficient conditions for the Open Set Condition to fail and for the attractor to have no holes. These results are generalisations of the corresponding one-dimensional results, however most proofs are different.Comment: Accepted for publication in Nonlinearit

General aviation and community development

The summer program is summarized. The reports presented concern (1) general aviation components, (2) general aviation environment, (3) community perspective, and (4) transportation and general aviation in Virginia

Multifractal properties of tribonacci chains

We introduce two one-dimensional tight-binding models based on the tribonacci substitution—the hopping and on-site tribonacci chains—which generalize the Fibonacci chain. For both hopping and on-site models, a perturbative real-space renormalization procedure is developed. We show that the two models are equivalent at the fixed point of the renormalization-group flow, and that the renormalization procedure naturally gives the local resonator modes. Additionally, the Rauzy fractal, inherent to the tribonacci substitution, is shown to serve as the analog of conumbering for the tribonacci chain. The renormalization procedure is used to repeatedly subdivide the Rauzy fractal into copies of itself, which can be used to describe the eigenstates in terms of local resonator modes. Finally, the multifractal dimensions of the energy spectrum and eigenstates of the hopping tribonacci chain are computed, from which it can be concluded that the tribonacci chains are critical

Facial emotion recognition in refugee children with a history of war trauma.

Over 36 million children are currently displaced due to war, yet we know little about how these experiences of war and displacement affect their socioemotional development-notably how they perceive facial expressions. Across three different experiments, we investigated the effects of war trauma exposure on facial emotion recognition in Syrian refugee (n = 130, Mage = 9.3 years, 63 female) and Jordanian nonrefugee children (n = 148, Mage = 9.4 years, 66 female) living in Jordan (data collected 2019-2020). Children in the two groups differed in trauma exposure, but not on any of our measures of mental health. In Experiment 1, we measured children's biases to perceive an emotion using morphed facial expressions and found no evidence that biases differed between refugees and nonrefugees. In Experiment 2, we adapted a novel perceptual scaling task that bypasses semantic knowledge, and again found no differences between the two group's discrimination of facial expressions. Finally, in Experiment 3, we recorded children's eye movements as they identified Middle Eastern actors' facial expressions, and again found no differences between the groups in either their identification accuracies or scanning strategies. Taken together, our results suggest that exposure to war-related trauma and displacement during early development, when reported by the caregiver but not always recollected by the child, does not appear to alter emotion recognition of facial expressions. (PsycInfo Database Record (c) 2023 APA, all rights reserved)