Ultrasonic metal sheet thickness measurement without prior wave speed calibration

Conventional ultrasonic mensuration of sample thickness from one side only requires the bulk wave reverberation time and a calibration speed. This speed changes with temperature, stress, and microstructure, limiting thickness measurement accuracy. Often, only one side of a sample is accessible, making in situ calibration impossible. Non-contact ultrasound can generate multiple shear horizontal guided wave modes on one side of a metal plate. Measuring propagation times of each mode at different transducer separations, allows sheet thickness to be calculated to better than 1% accuracy for sheets of at least 1.5 mm thickness, without any calibration

Can Frustration Preserve a Quasi-Two-Dimensional Spin Fluid?

Using spin-wave theory, we show that geometric frustration fails to preserve a two-dimensional spin fluid. Even though frustration can remove the interlayer coupling in the ground-state of a classical anti-ferromagnet, spin layers innevitably develop a quantum-mechanical coupling via the mechanism of ``order from disorder''. We show how the order from disorder coupling mechanism can be viewed as a result of magnon pair tunneling, a process closely analogous to pair tunneling in the Josephson effect. In the spin system, the Josephson coupling manifests itself as a a biquadratic spin coupling between layers, and for quantum spins, these coupling terms are as large as the inplane coupling. An alternative mechanism for decoupling spin layers occurs in classical XY models in which decoupled "sliding phases" of spin fluid can form in certain finely tuned conditions. Unfortunately, these finely tuned situations appear equally susceptible to the strong-coupling effects of quantum tunneling, forcing us to conclude that in general, geometric frustration cannot preserve a two-dimensional spin fluid.Comment: 12 pages, 3 figure

Emergent Critical Phase and Ricci Flow in a 2D Frustrated Heisenberg Model

We introduce a two-dimensional frustrated Heisenberg antiferromagnet on interpenetrating honeycomb and triangular lattices. Classically the two sublattices decouple, and "order from disorder" drives them into a coplanar state. Applying Friedan's geometric approach to nonlinear sigma models, we show that the scaling of the spin-stiffnesses corresponds to the Ricci flow of a 4D metric tensor. At low temperatures, the relative phase between the spins on the two sublattices is described by a six-state clock model with an emergent critical phase.Comment: 4+ pages, 2 figure

Are food exposures obtained through commercial market panels representative of the general population? Implications for outbreak investigations

Current methods of control recruitment for case-control studies can be slow (a particular issue for outbreak investigations), resource-intensive and subject to a range of biases. Commercial market panels are a potential source of rapidly recruited controls. Our study evaluated food exposure data from these panel controls, compared with an established reference dataset. Market panel data were collected from two companies using retrospective internet-based surveys; these were compared with reference data from the National Diet and Nutrition Survey (NDNS). We used logistic regression to calculate adjusted odds ratios to compare exposure to each of the 71 food items between the market panel and NDNS participants. We compared 2103 panel controls with 2696 reference participants. Adjusted for socio-demographic factors, exposure to 90% of foods was statistically different between both panels and the reference data. However, these differences were likely to be of limited practical importance for 89% of Panel A foods and 79% of Panel B foods. Market panel food exposures were comparable with reference data for common food exposures but more likely to be different for uncommon exposures. This approach should be considered for outbreak investigation, in conjunction with other considerations such as population at risk, timeliness of response and study resources

Reading maps in the dark. Route planning for development geography in a post-ist world

The symposium on "Land Management and Sustainable Development in Rural and Urban Environments of the Third World" at the 1996 International Geographical Congress in The Hague focused on geographical research in land society relationships. The range of papers provided a variety of case studies of local land management in terms of livelihood strategies and the wider politico-socio-economic and ecological context in which they operate. They also highlighted the contradictions and tensions between different systems of knowledge about the environment, and the ways in which one may be privileged over others. These are implicit in most of the papers - in some, modernising knowledge is promoted for the solution of the problems of a modernising economy (for example, managing urban pollution in Malaysia), while in others institutional, political and technical knowledge is undergoing profound change, whereby the local continues to resist, adapt to, or be replaced by the forces of globalisation . Most papers in this collection make implicit distinctions between the familiar, and some would say, stereo-typical characterisations of different knowledges (scientific, western and modern on the one hand and indigenous and traditional on the other), although it is a much debated point whether it is useful to make a distinction between them at all (Agrawal 1996)

Analisis Pembangunan Desa melalui Pemberdayaan Masyarakat (Studi di Desa Dauh Peken Kec. Tabanan, Kab. Tabanan)

Rural development in Dauh Peken Village is now continuously be improved in terms of both economic and social. It currently requires the participation of the whole society and the government to get involved to realize the development of the village. Through a community empowerment program in economics and the environment, the Village Government Dauh Peken seeks to create village development desired by the community in accordance with the potential contained in the village. The problems of the background for this study is the lack of funds, which not is available yet from facilities and supporting infrastructure activities, lack of training, there has been no serious attention from the government, as well as poverty. This research was conducted by descriptive qualitative data collection techniques such as in-depth interviews. This study analyzes how rural development through community empowerment with the concept of community empowerment is composed of economic indicators, commodity choice and type of business, human resource management and career development, the development of a network of partnerships, logistics and financial management and the development of facilities and infrastructure. Environmental indicators, physical environment and social environment. Results from this study showed that rural development through community empowerment is still not effective due to the economic empowerment of facilities and infrastructures supporting activities are not yet available and the lack of serious attention from the government regarding the distribution work product results. Based on five (5) economic indicators were used, the only indicator of the commodity choice and type of business showed good results whereas other indicators such as human resources management and career development, the development of a network of partnerships, logistics and financial management and the development of facilities and infrastructure is still less than the maximum. In the field of environmental empowerment by 2 (two) indicators used, the physical environment has shown good results, but the social environment is still less than the maximum