Flow and acoustic characteristics of subsonic and supersonic jets from convergent nozzle

Acoustic and flow characteristics of subsonic and supersonic jets from convergent nozzle

Children's play space and safety management: rethinking the role of play equipment standards

The provision of stimulating and engaging play space for children and young people is increasingly recognized as an important societal goal, not the least because it provides the young with opportunities to develop and gain experience in experimenting with risk. Research in several disciplines now suggests that achievement of this goal has however been impeded in recent decades, and reasons commonly cited have included fear of injury and avoidance of litigation. International standards on play equipment have also been promulgated and justified in terms of securing young people’s “safety,” most usually narrowly defined as injury reduction. There appears to be a widespread presumption that measures aimed at injury prevention are necessarily beneficial overall for young people’s welfare. In this article, we subject European standards for play equipment and surfacing to scrutiny. In particular, we examine underlying motives, consistency of purpose, use of evidence, philosophical leanings, scope, practicalities of application, systems of management, and legal ramifications. From this, we identify a number of fundamental issues that suggest that as a consequence of compartmentalized thinking and misunderstandings, these standards have invaded areas of decision making beyond their legitimate territory. The consequence of this is that play provision is skewed away from what are properly play provision objectives. In such circumstances, local decision makers are often disempowered, and their ability to provide optimal play spaces thereby circumscribed

Automated operation of a home made torque magnetometer using LabVIEW

In order to simplify and optimize the operation of our home made torque magnetometer we created a new software system. The architecture is based on parallel, independently running instrument handlers communicating with a main control program. All programs are designed as command driven state machines which greatly simplifies their maintenance and expansion. Moreover, as the main program may receive commands not only from the user interface, but also from other parallel running programs, an easy way of automation is achieved. A program working through a text file containing a sequence of commands and sending them to the main program suffices to automatically have the system conduct a complex set of measurements. In this paper we describe the system's architecture and its implementation in LabVIEW.Comment: 6 pages, 7 figures, submitted to Rev. Sci. Inst

In Search of the Right Trousers Pattern - Comparison of Four Different Pattern Making Methods in Affordance with Different Body Shapes

Clothing comfort is one of the major concerns in the clothing industry. Various pattern making methods have been introduced to the industry with consideration to clothing comfort. This study evaluates four pattern making methods known as the ESMOD, Bunka, Aldrich, and Armstrong methods. The work focuses on trouser patterns and uses two subjects who have similar height, weight and BMI but have different body shapes and body sizes. The body measurement data of the two subjects were collected using a three-dimensional body scanner and patterns of the four different methods were developed accordingly. The fit of experimental garments were examined by two subjects and experts using questionnaires and were analysed

Damping of bulk excitations over an elongated BEC - the role of radial modes

We report the measurement of Beliaev damping of bulk excitations in cigar shaped Bose Einstein condensates of atomic vapor. By using post selection, excitation line shapes of the total population are compared with those of the undamped excitations. We find that the damping depends on the initial excitation energy of the decaying quasi particle, as well as on the excitation momentum. We model the condensate as an infinite cylinder and calculate the damping rates of the different radial modes. The derived damping rates are in good agreement with the experimentally measured ones. The damping rates strongly depend on the destructive interference between pathways for damping, due to the quantum many-body nature of both excitation and damping products.Comment: 5 pages, 4 figure

Analytic Representation of The Dirac Equation

In this paper we construct an analytical separation (diagonalization) of the full (minimal coupling) Dirac equation into particle and antiparticle components. The diagonalization is analytic in that it is achieved without transforming the wave functions, as is done by the Foldy-Wouthuysen method, and reveals the nonlocal time behavior of the particle-antiparticle relationship. We interpret the zitterbewegung and the result that a velocity measurement (of a Dirac particle) at any instant in time is, as reflections of the fact that the Dirac equation makes a spatially extended particle appear as a point in the present by forcing it to oscillate between the past and future at speed c. From this we infer that, although the form of the Dirac equation serves to make space and time appear on an equal footing mathematically, it is clear that they are still not on an equal footing from a physical point of view. On the other hand, the Foldy-Wouthuysen transformation, which connects the Dirac and square root operator, is unitary. Reflection on these results suggests that a more refined notion (than that of unitary equivalence) may be required for physical systems

Unique Mass Texture for Quarks and Leptons

Texture specific quark mass matrices which are hermitian and hierarchical are examined in detail . In the case of texture 6 zeros matrices, out of sixteen possibilities examined by us, none is able to fit the low energy data (LED), for example, $V_{us} = 0.2196 \pm 0.0023$, $V_{cb} = 0.0395 \pm 0.0017$, $\frac{V_{ub}}{V_{cb}} = 0.08 \pm 0.02$, $V_{td}$ lies in the range $0.004 - 0.013$ (PDG). Similarly none of the 32 texture 5 zeros mass matrices considered is able to reproduce LED. In particular, the latest data from LEP regarding $|V_{ub}|/|V_{cb}|(=0.093\pm0.016)$ rules out all of them. In the texture 4 zeros case, we find that there is a unique texture structure for $U$ and $D$ mass matrices which is able to fit the data.Comment: 12 pages, LaTeX,some changes in the references,minor changes in the text,to appear in Phys Rev D(Rapid communications

Avoiding a dystopian future for children's play

Describes the conflict between children's freedom to play and the quest for safety and makes recommendations for the future