Highway and runway traction studies - The problem, history, objectives, and NASA program

Review of highway and runway traction studie

Relativistic Quasilinear Diffusion in Axisymmetric Magnetic Geometry for Arbitrary-Frequency Electromagnetic Fluctuations

A relativistic bounce-averaged quasilinear diffusion equation is derived to describe stochastic particle transport associated with arbitrary-frequency electromagnetic fluctuations in a nonuniform magnetized plasma. Expressions for the elements of a relativistic quasilinear diffusion tensor are calculated explicitly for magnetically-trapped particle distributions in axisymmetric magnetic geometry in terms of gyro-drift-bounce wave-particle resonances. The resonances can destroy any one of the three invariants of the unperturbed guiding-center Hamiltonian dynamics.Comment: 22 pages, Latex, to appear in Physics of Plasma

Some effects of adverse weather conditions on performance of airplane antiskid braking systems

The performance of current antiskid braking systems operating under adverse weather conditions was analyzed in an effort to both identify the causes of locked-wheel skids which sometimes occur when the runway is slippery and to find possible solutions to this operational problem. This analysis was made possible by the quantitative test data provided by recently completed landing research programs using fully instrumented flight test airplanes and was further supported by tests performed at the Langley aircraft landing loads and traction facility. The antiskid system logic for brake control and for both touchdown and locked-wheel protection is described and its response behavior in adverse weather is discussed in detail with the aid of available data. The analysis indicates that the operational performance of the antiskid logic circuits is highly dependent upon wheel spin-up acceleration and can be adversely affected by certain pilot braking inputs when accelerations are low. Normal antiskid performance is assured if the tire-to-runway traction is sufficient to provide high wheel spin-up accelerations or if the system is provided a continuous, accurate ground speed reference. The design of antiskid systems is complicated by the necessity for tradeoffs between tire braking and cornering capabilities, both of which are necessary to provide safe operations in the presence of cross winds, particularly under slippery runway conditions

Effects of an abasic site on triple helix formation characterized by affinity cleaving

The stability of triple helical complexes of pyrimidine oligodeoxyribonucleotides containing one abasic 1,2- dideoxy-D-ribose (ø) residue was examined by affinity cleaving. Within a pyrimidine third strand, the triplets ø·AT, ø·GC, ø·TA and ø·CG are significantly less stable than the triplets, T- AT, C + GC and GTA. The decrease in binding produced by an abasic residue is similar to that observed with imperfectly matched natural base triplets, with ø · AT and ø · GC being less stable than ø · TA and ø · CG triplets for the sequences studied

Demonstration of the Complementarity of One- and Two-Photon Interference

The visibilities of second-order (single-photon) and fourth-order (two-photon) interference have been observed in a Young's double-slit experiment using light generated by spontaneous parametric down-conversion and a photon-counting intensified CCD camera. Coherence and entanglement underlie one-and two-photon interference, respectively. As the effective source size is increased, coherence is diminished while entanglement is enhanced, so that the visibility of single-photon interference decreases while that of two-photon interference increases. This is the first experimental demonstration of the complementarity between single- and two-photon interference (coherence and entanglement) in the spatial domain.Comment: 21 pages, 7 figure

Estimating Be Star Disk Radii using H-alpha Emission Equivalent Widths

We present numerical models of the circumstellar disks of Be stars, and we describe the resulting synthetic H-alpha emission lines and maps of the wavelength-integrated emission flux projected onto the sky. We demonstrate that there are monotonic relationships between the emission line equivalent width and the ratio of the angular half-width at half maximum of the projected disk major axis to the radius of the star. These relationships depend mainly upon the temperatures of the disk and star, the inclination of the disk normal to the line of sight, and the adopted outer boundary for the disk radius. We show that the predicted H-alpha disk radii are consistent with those observed directly through long baseline interferometry of nearby Be stars (especially once allowance is made for disk truncation in binaries and for dilution of the observed H-alpha equivalent width by continuum disk flux in the V-band).Comment: 12 pages, 2 figures, ApJL in pres

A Theory on Information Security

This paper proposes a theory on information security. We argue that information security is imperfectly understood and aim to bring about an altered understanding of why efforts are made to engage in information security. The goal of information security is widely recognised as the confidentiality, integrity and availability of information however we argue that the goal is actually to simply create resources. This paper responds to calls for more theory in information systems, places the discussion in philosophical context and compares various definitions. It then identifies the key concepts of information security, describes the relationships between these concepts, as well as scope and causal explanations. The paper provides the theoretical base for understanding why information is protected, in addition to theoretical and practical implications and suggestions for future research

Towards Governance of Information Security Incident Response

Organizations are increasingly digitizing their business models to complement or even replace physical contact with customers and suppliers. With this shift online comes an increase in information security attacks, which are occurring more frequently due to the increased attack surface, vulnerabilities in security controls, and a target-rich environment. Organizations prevent attacks however some attacks are still successful and result in security incidents that degrade operations. When an organization is successfully breached, the organization must respond to the incident as quickly as possible to ensure continued operations and business resilience. However, guidance is lacking for governance of the response function. In a thematic review, we find good governance plays a key role in smooth and efficient incident response and this paper extends knowledge about governance of information security incident response by identifying key governance concepts that improve incident response efforts within organizations

Information Security Strategy in Organisations: Review, Discussion and Future Research Directions

Dependence on information, including for some of the world’s largest organisations such as governments and multi-national corporations, has grown rapidly in recent years. However, reports of information security breaches and their associated consequences continue to indicate that attacks are still escalating on organisations when conducting these information-based activities. Clearly, more research is needed to better understand how organisations should formulate strategy to secure their information. Through a thematic review of academic security literature, we (1) analyse the antecedent conditions that motivate the potential adoption of a comprehensive information security strategy, (2) the current perspectives of strategy and (3) the yields and benefits that could be enjoyed post-adoption. Our contributions include a definition of information security strategy. We argue for a paradigm shift to extend from internally-focussed protection of organisation-wide information towards a strategic view that considers the inter-organisational level. Our findings are then used to suggest future research directions

Emission Line Flickering from the Secondary Star in Cataclysmic Variables? A study of V3885 Sagitarii

Spectrophotometric observations of H-alpha and He I 6678 emission lines of the nova-like Cataclysmic Variable V3885 Sgr are presented and analyzed. The binary orbital period was determined as P = 0.20716071(22) days. Doppler Tomography was performed with both H-alpha and He I lines. Disc radial emissivity profiles were also computed. The tomography mapping of flickering sources was performed using the H-alpha line, from which we concluded that the flickering is not uniformly distributed on the disc. The observed tomogram of the flickering was compared with simulations, suggesting that the most intense flickering source in the H-alpha is not located in the accretion disc. It is proposed that the main line flickering source may be associated with the illuminated secondary star.Comment: 19 pages, 10 figures, 1 table. Accepted to be published on AJ. to donwload high resolution figures: http://www.astro.iag.usp.br/~fabiola/V3885_hires.pd