Theories and quantification of thymic selection

The peripheral T cell repertoire is sculpted from prototypic T cells in the thymus bearing randomly generated T cell receptors (TCR) and by a series of developmental and selection steps that remove cells that are unresponsive or overly reactive to self-peptide–MHC complexes. The challenge of understanding how the kinetics of T cell development and the statistics of the selection processes combine to provide a diverse but self-tolerant T cell repertoire has invited quantitative modeling approaches, which are reviewed here

Improvements of Zeyded method for calculating flutter of flat panels

Method for calculating flutter boundaries and estimating stresses in infinite spanwise array of panels is presented. Numerical analyses are included for pinned edge panels, isotropic panel material, zero viscous damping, and no elastic foundation. Design flutter boundaries are presented for aluminum panels on Saturn spacecraft trajectory

Career Development: An Integrated Analysis

Career theories are developed to help us make sense of the complexity of career choice and development. The intricacy of the subject matter is such that career theories most often focus on one or two aspects of the phenomenon. As such the challenges of integrating the theories with each other, and integrating them within career practice, are not insignificant. In this chapter, I offer an overview of the theoretical landscape which illustrates how the theories align with each other to build up a comprehensive picture of career choice and development. The chapter will introduce a wide range of theoretical frameworks, spanning seven decades and numerous academic disciplines, and will discuss the most well-known theorists alongside less familiar names. The chapter will be structured around four concepts: identity, environment, career learning, and psychological career resources, and suggestions are offered for the incorporation of theories in career practice

Viscous theory of surface noise interaction phenomena

A viscous linear surface noise interaction problem is formulated that includes noise production by an oscillating surface, turbulent or vortical interaction with a surface, and scattering of sound by a surface. The importance of viscosity in establishing uniqueness of solution and partitioning of energy into acoustic and vortical modes is discussed. The results of inviscid two dimensional airfoil theory are used to examine the interactive noise problem in the limit of high reduced frequency and small Helmholtz number. It is shown that in the case of vortex interaction with a surface, the noise produced with the full Kutta condition is 3 dB less than the no Kutta condition result. The results of a study of an airfoil oscillating in a medium at rest are discussed. It is concluded that viscosity can be a controlling factor in analyses and experiments of surface noise interaction phenomena and that the effect of edge bluntness as well as viscosity must be included in the problem formulation to correctly calculate the interactive noise

The determinants of successful partnering: a transaction cost perspective

Support is emerging for the assertion that partnering can have a significant beneficial influence on project relationships and project outcomes. However, not all of the evidence bears this out: there are some examples of less-than-successful experiments with partnering approaches. Questions quite naturally arise as to whether any particular elements or aspects of partnering have differed in some of the documented examples, thus giving rise to their relative success or failure. In order to answer such questions there is a need for a theoretical framework against which to analyse the relative performance of partnering projects. In this paper, the authors propose an approach based upon aspects of Transaction Cost Economics (TCE) theory. It is argued that two main factors, contractual incompletedness and opportunism, are fundamental in determining whether project relationships are adversarial or not. The validity of the approach is examined by applying it retrospectively to a strategic partnering agreement involving more than 80 individual building projects. This agreement had been the subject of a four-year study and had been found to produce benefits in a number of areas, not least in the avoidance of conflict and disputes. After analysis, evidence for the reduction of contractual incompletedness was mixed, however the opportunistic inclinations of the participants (specifically, the contractors) were effectively attenuated by a clearly observable combination of factors, which included preselection criteria, and the use of appropriate management and commercial frameworks in which to operate. The case study suggests a prima facie validity to the analytical approach that was adopted, which merits further testing: the next stages being to develop and refine the framework, and to carry out comparative multi-case research on a number of different partnering projects

A mission synthesis algorithm for editing variable amplitude fatigue signals

This paper presents a wavelet-based fatigue data editing algorithm, known as Wavelet Bump Extraction (WBE), to summarise long record of fatigue loadings. The key point of this algorithm is to produce a shorter time history (mission signal) that retains the majority of the original fatigue damage whilst preserving cycle sequence information. In WBE, features or bumps are identified in characteristic frequency bands using the Daubechies’ wavelet transform. Comparison of the fatigue life between the original and mission signals was performed to validate the algorithm. The fatigue life was predicted using a variable amplitude fatigue damage model and the results showed a good correlation between the damage caused by the original and mission signals. Finally, the findings suggest that WBE is a suitable approach for producing a shortened mission signal for accelerated fatigue testing

A mission synthesis algorithm for fatigue damage analysis

This paper presents a signal processing based algorithm, the Mildly Nonstationary Mission Synthesis (MNMS), which produces a short mission signal from long records of experimental data. The algorithm uses the Discrete Fourier Transform, Orthogonal Wavelet Transform and bump reinsertion procedures. In order to observe the algorithm effectiveness a fatigue damage case study was performed for a vehicle lower suspension arm using signals containing tensile and compressive preloading. The mission synthesis results were compared to the original road data in terms of both the global signal statistics and the fatigue damage variation as a function of compression ratio. Three bump reinsertion methods were used and evaluated. The methods differed in the manner in which bumps (shock events) from different wavelet groups (frequency bands) were synchronised during the reinsertion process. One method, based on time synchronised section reinsertion, produced the best results in terms of mission signal kurtosis, crest factor, root-mean-square level and power spectral density. For improved algorithm performance, bump selection was identified as the main control parameter requiring optimisation

Arithmetic properties of eigenvalues of generalized Harper operators on graphs

Let \Qbar denote the field of complex algebraic numbers. A discrete group $G$ is said to have the $\sigma$-multiplier algebraic eigenvalue property, if for every matrix $A$ with entries in the twisted group ring over the complex algebraic numbers M_d(\Qbar(G,\sigma)), regarded as an operator on $l^2(G)^d$, the eigenvalues of $A$ are algebraic numbers, where $\sigma$ is an algebraic multiplier. Such operators include the Harper operator and the discrete magnetic Laplacian that occur in solid state physics. We prove that any finitely generated amenable, free or surface group has this property for any algebraic multiplier $\sigma$. In the special case when $\sigma$ is rational ($\sigma^n$=1 for some positive integer $n$) this property holds for a larger class of groups, containing free groups and amenable groups, and closed under taking directed unions and extensions with amenable quotients. Included in the paper are proofs of other spectral properties of such operators.Comment: 28 pages, latex2e, paper revise

Sound insulation design of modular construction housing

This paper provides an insight into the acoustic issues of modular housing using the Verbus System of construction. The paper briefly summarises the history of the development of Verbus modular housing and the acoustic design considerations of the process. Results are presented from two sound insulation tests conducted during the course of the project. The results are discussed in terms of compliance with Approved Document E1 and increased performance standards such as EcoHomes2