Compensation for Uneven Surfaces When Building Laser Deposited Structures

Direct Laser Deposition (DLD) is a blown-powder laser deposition process that can be used to quickly produce, modify or repair fully-dense metallic parts by a layered manufacturing method. However, uneven substrate surfaces often cause variation in the deposited layer which is magnified by succeeding layers. Research carried out at the University of Liverpool has resulted in a non-feedback layer height controlling process based on controlling the shape of the powder streams emitted from a four-port side feed nozzle. This method limits deposited layer height by causing a sharp reduction of catchment efficiency in the vertical plane at a fixed distance from the powder feed nozzle, and is therefore capable of depositing a consistent layer height in spite of power, powder flow or process velocity variation. This paper demonstrates how this method of layer height control can compensate for irregular substrate surfaces in the production of accurate DLD parts.Mechanical Engineerin

Extruding the vortex lattice: two reacting populations of dislocations

A controllable soft solid is realised in vortex matter in a type II superconductor. The two-dimensional unit cell area can be varied by a factor of $10^4$ in the solid phase, without a change of crystal symmetry offering easy exploration of extreme regimes compared to ordinary materials. The capacity to confine two-dimensional vortex matter to mesoscopic regions provides an arena for the largely unexplored metallurgy of plastic deformation at large density gradients. Our simulations reveal a novel plastic flow mechanism in this driven non-equilibrium system, utilising two distinct, but strongly interacting, populations of dislocations. One population facilitates the relaxation of density; a second aids the relaxation of shear stresses concentrated at the boundaries. The disparity of the bulk and shear moduli in vortex matter ensures the dislocation motion follows the overall continuum flow reflecting density variation

Pseudo-nonstationarity in the scaling exponents of finite-interval time series

The accurate estimation of scaling exponents is central in the observational study of scale-invariant phenomena. Natural systems unavoidably provide observations over restricted intervals; consequently, a stationary stochastic process (time series) can yield anomalous time variation in the scaling exponents, suggestive of nonstationarity. The variance in the estimates of scaling exponents computed from an interval of N observations is known for finite variance processes to vary as ~1/N as N for certain statistical estimators; however, the convergence to this behavior will depend on the details of the process, and may be slow. We study the variation in the scaling of second-order moments of the time-series increments with N for a variety of synthetic and “real world” time series, and we find that in particular for heavy tailed processes, for realizable N, one is far from this ~1/N limiting behavior. We propose a semiempirical estimate for the minimum N needed to make a meaningful estimate of the scaling exponents for model stochastic processes and compare these with some “real world” time series

Seishin Habitus: Spiritual Capital and Japanese Rowing

Sport occupies an important place in educational curriculum, such as club activities in Japanese schools and universities; is it also imbued with what Bourdieu suggests are guaranteed capital properties? That is, can physical education help to accrue capital and can such capital become cultural and economic capital? Further, is this capital similar to that resulting from academic education? Although Western culture recognizes Cartesian differentiation, mind and body are seen as one in the Japanese understanding of the individual, unified by the concept of spirit (this is different to the concept of soul). Recognizing this concept of the body is crucial in addressing the question of transferring educational (in this case physical) capital into forms of cultural capital. This paper investigates the responses of members of a Japanese University Rowing club when addressing questions dealing with various uses of the body in rowing and perceived opportunities for future employment

Heterozygous deletion of both sclerostin (Sost) and connexin43 (Gja1) genes in mice is not sufficient to impair cortical bone modeling

Connexin43 (Cx43) is the main gap junction protein expressed in bone forming cells, where it modulates peak bone mass acquisition and cortical modeling. Genetic ablation of the Cx43 gene (Gja1) results in cortical expansion with accentuated periosteal bone formation associated with decreased expression of the Wnt inhibitor sclerostin. To determine whether sclerostin (Sost) down-regulation might contribute to periosteal expansion in Gja1 deficient bones, we took a gene interaction approach and crossed mice harboring germline null alleles for Gja1 or Sost to generate single Gja1+/-and Sost+/-and double Gja1+/-;Sost+/-heterozygous mice. In vivo μCT analysis of cortical bone at age 1 and 3 months confirmed increased thickness in Sost-/-mice, but revealed no cortical abnormalities in single Gja1+/-or Sost+/-mice. Double heterozygous Gja1+/-Sost+/-also showed no differences in mineral density, cortical thickness, width or geometry relative to wild type control mice. Likewise, 3-point bending measurement of bone strength revealed no significant differences between double Gja1+/-;Sost+/-or single heterozygous and wild type mice. Although these data do not exclude a contribution of reduced sclerostin in the cortical expansion seen in Gja1 deficient bones, they are not consistent with a strong genetic interaction between Sost and Gja1 dictating cortical modeling

Water resources management in a homogenizing world: Averting the Growth and Underinvestment trajectory

Biotic homogenization, a de facto symptom of a global biodiversity crisis, underscores the urgency of reforming water resources management to focus on the health and viability of ecosystems. Global population and economic growth, coupled with inadequate investment in maintenance of ecological systems, threaten to degrade environmental integrity and ecosystem services that support the global socioeconomic system, indicative of a system governed by the Growth and Underinvestment (G&U) archetype. Water resources management is linked to biotic homogenization and degradation of system integrity through alteration of water systems, ecosystem dynamics, and composition of the biota. Consistent with the G&U archetype, water resources planning primarily treats ecological considerations as exogenous constraints rather than integral, dynamic, and responsive parts of the system. It is essential that the ecological considerations be made objectives of water resources development plans to facilitate the analysis of feedbacks and potential trade-offs between socioeconomic gains and ecological losses. We call for expediting a shift to ecosystem-based management of water resources, which requires a better understanding of the dynamics and links between water resources management actions, ecological side-effects, and associated long-term ramifications for sustainability. To address existing knowledge gaps, models that include dynamics and estimated thresholds for regime shifts or ecosystem degradation need to be developed. Policy levers for implementation of ecosystem-based water resources management include shifting away from growth-oriented supply management, better demand management, increased public awareness, and institutional reform that promotes adaptive and transdisciplinary management approaches

Measuring the Stochastic Monetary Benefits of Multiple Inlet Irrigation in Arkansas Rice Production

Irrigation fuel costs represent a significant portion of rice production expenses. Multiple inlet (MI) irrigation represents a water saving alternative to conventional flood irrigation. This study uses simulation to calculate the range of monetary benefits to MI in rice production. Water savings from MI relative to conventional flood irrigation along with rice yields, rice prices, and prices for key production inputs (diesel and fertilizer) are simulated, and stochastic rice net returns above variable and fixed expenses are calculated for different pump lifts with and without MI. Monetary benefits to MI are measured as the difference in net returns with and without MI. The results indicate MI monetary benefits depend greatly on pump lift and the presence or absence of a yield increase. Monetary benefits to MI increase as pump lifts become larger, and relatively small increases in yield resulting from MI irrigation can greatly enhance its payoff.cost, cumulative distribution functions, multiple inlet irrigation, net return, rice, stochastic, Farm Management,

An Economic Risk Analysis of No-till Management for the Rice-Soybean Rotation System used in Arkansas

Arkansas is the top domestic rice producer, representing nearly half of total U.S. rice production. Sediment is one of the major pollutants in rice producing areas of Arkansas. In order to mitigate this problem no-tillage management is often recommended. No-tillage is not well understood by farmers who believe that no-till is less profitable due to lower yields offsetting cost savings. This study evaluates the profitability and variability of no-till in the typical rice-soybean rotation used in Arkansas rice production. Crop yields, prices and prices for key production inputs (fuel and fertilizer) are simulated for the rotation, and net return distributions for rice, soybean and the two-year rotation are evaluated for no-till and conventional till using stochastic efficiency with respect to a function (SERF) analysis. The results indicate that both risk neutral and risk-averse rice producers would prefer no-till over conventional till management in the two year rice-soybean rotation, and that no-till soybeans contribute greatly to the overall profitability of the rotation.simulation, rice-soybean, no tillage-profitability, risk analysis, Environmental Economics and Policy, Farm Management, Resource /Energy Economics and Policy,

A stochastic theory for temporal fluctuations in self-organized critical systems

A stochastic theory for the toppling activity in sandpile models is developed, based on a simple mean-field assumption about the toppling process. The theory describes the process as an anti-persistent Gaussian walk, where the diffusion coefficient is proportional to the activity. It is formulated as a generalization of the It\^{o} stochastic differential equation with an anti-persistent fractional Gaussian noise source. An essential element of the theory is re-scaling to obtain a proper thermodynamic limit, and it captures all temporal features of the toppling process obtained by numerical simulation of the Bak-Tang-Wiesenfeld sandpile in this limit.Comment: 9 pages, 4 figure