Optimization of complex cutting tools using a multi-dexel based material removal simulation

Multi-dexel based material removal simulations provide a fast and flexible way to compute process forces and tool deflections for milling and turning operations. This allows an advanced process planning including detection of collisions for complex toolpaths. However, using dexel simulations for designing cutting tools has rarely been investigated. Especially the position of individual cutting edges is not considered, because current approaches only subtract the sweep volume of the tool envelop instead of the rake face. This paper presents a new method to design cutting tools using material removal simulations and a detailed tool geometry representation. The discretization of the tool allows an efficient calculation of the engagement conditions of individual cutting edges. The method is used to optimize novel porcupine milling cutters with round indexeble inserts, which produces a geometry analogous to serrated end mills. Based on the calculated forces, the positions of individual indexable inserts are adjusted to minimize the maximum radial force. An optimum has been found that reduces radial force by 12% compared to conventional porcupine milling cutters with squared inserts. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of The 17th CIRP Conference on Modelling of Machining Operation

Wave Energy In The United Kingdom: A Review Of The Programme June 1975 - March 1982

The paper sets out the need for an inexhaustible supply of energy and describes the management system established to examine wave energy as one of the contenders for that role. It then describes the work which has been done in the UK, setting out the various costing figures obtained and the decision making processes which controlled the funding. It concludes that the work is very close to reaching a valuable result and should not be stopped until a prototype has been built

Compositional and kinetic controls on liquid immiscibility in ferrobasalt-rhyolite volcanic and plutonic series

peer reviewedWe present major element compositions of basalts and their differentiation products for some major tholeiitic series. The dry, low-pressure liquid lines of descent are shown to approach or intersect the experimentally-defined compositional space of silicate liquid immiscibility. Ferrobasalt-rhyolite unmixing along tholeiitic trends in both volcanic and plutonic environments is supported by worldwide occurrence of immiscible globules in the mesostasis of erupted basalts, unmixed melt inclusions in cumulus phases of major layered intrusions such as Skaergaard and Sept Iles, and oxide-rich ferrogabbros closely associated with plagiogranites in the lower oceanic crust. Liquid immiscibility is promoted by low-pressure, anhydrous fractional crystallization that drives the low Al2O3, high FeO liquids into the two-liquid field. Kinetic controls can be important in the development of two-liquid separation. The undercooling that occurs at the slow cooling rates of plutonic environments promotes early development of liquid immiscibility at higher temperature. In contrast rapid cooling in erupted lavas leads to large undercoolings and liquid immiscibility develops at significantly lower temperatures. Unmixing leads to the development of a compositional gap characterized by the absence of intermediate compositions, a feature of many tholeiitic provinces. The compositions of experimental unmixed silica-rich melts coincide with those of natural rhyolites and plagiogranites with high FeOtot and low Al2O3, suggesting the potential role of large-scale separation of immiscible Si-rich liquid in the petrogenesis of late-stage residual melts. No trace of the paired ferrobasaltic melt is found in volcanic environments because of its uneruptable characteristics. Instead, Fe-Ti±P-rich gabbros are the cumulate products of immiscible Fe-rich melts in plutonic settings. The immiscibility process may be difficult to identify because both melts crystallize the same phases with the same compositions. The two liquids might form incompletely segregated emulsions so that both liquids continue to exchange as they crystallize and remain in equilibrium. Even if segregated, both melts evolve on the binodal surface and exsolve continuously with decreasing temperature. The two liquids do not differentiate independently and keep crystallizing the same phases with differentiation. Further evolution by fractional crystallization potentially drives the bulk liquid out of the two-liquid field so that very late-stage liquids could evolve into the single melt phase stability field. © 2013 Elsevier Ltd

Automated free text marking with Paperless School

The Paperless School automarking system utilises a number of novel approaches to address the challenge of providing both summative and formative assessments with little or no human intervention. The Paperless School system is designed primarily for day-to-day, low stakes testing of essay and short-text student inputs. It intentionally sacrifices some degree of accuracy to achieve ease of set up, but nevertheless provides an accurate view of the abilities of each student by averaging marks over a number of essays. The system is designed to function as a back-end service to an Learning Management System (LMS), thus facilitating the marking of large numbers of texts. This should enable considerable teacher resources to be freed up for other teaching tasks. In this paper we will discuss some of the issues involved in bringing computational linguistics to bear in the educational context. We will cover • how Blooms Taxonomy (the pedagogical model underlying most formal grading schemes) can be represented in software. • an overview of the steps required to derive a grade that will sufficiently closely predict the grade a human marker would give. • extending the system to include formative assessment, via intelligent comment banks

Advanced process design for re-contouring using a time-domain dynamic material removal simulation

The repair of components often requires the removal of excess weld material. This removal is considered as re-contouring. Re-contouring processes have to be designed individually for each case of damage to fulfil the high quality requirements. Therefore, a prognosis of the machined surface topography is crucial. The material removal simulation introduced in this paper allows the prediction of process stability and surface topography for 5-axis ball end milling including dynamic effects. Different process strategies for re-contouring of Ti-6Al-4V welds are examined. It is shown, that selecting suitable process parameters can lead to high surface quality while maintaining productivity. © 2019 The Author(s)

Superconductor-Nanowire Devices from Tunneling to the Multichannel Regime: Zero-Bias Oscillations and Magnetoconductance Crossover

We present transport measurements in superconductor-nanowire devices with a gated constriction forming a quantum point contact. Zero-bias features in tunneling spectroscopy appear at finite magnetic fields, and oscillate in amplitude and split away from zero bias as a function of magnetic field and gate voltage. A crossover in magnetoconductance is observed: Magnetic fields above ~ 0.5 T enhance conductance in the low-conductance (tunneling) regime but suppress conductance in the high-conductance (multichannel) regime. We consider these results in the context of Majorana zero modes as well as alternatives, including Kondo effect and analogs of 0.7 structure in a disordered nanowire.Comment: Supplemental Material here: https://dl.dropbox.com/u/1742676/Churchill_Supplemental.pd

Thermal structure and exhumation history of the Lesser Himalaya in central Nepal

The Lesser Himalaya (LH) consists of metasedimentary rocks that have been scrapped off from the underthrusting Indian crust and accreted to the mountain range over the last ~20 Myr. It now forms a significant fraction of the Himalayan collisional orogen. We document the kinematics and thermal metamorphism associated with the deformation and exhumation of the LH, combining thermometric and thermochronological methods with structural geology. Peak metamorphic temperatures estimated from Raman spectroscopy of carbonaceous material decrease gradually from 520°–550°C below the Main Central Thrust zone down to less than 330°C. These temperatures describe structurally a 20°–50°C/km inverted apparent gradient. The Ar muscovite ages from LH samples and from the overlying crystalline thrust sheets all indicate the same regular trend; i.e., an increase from about 3–4 Ma near the front of the high range to about 20 Ma near the leading edge of the thrust sheets, about 80 km to the south. This suggests that the LH has been exhumed jointly with the overlying nappes as a result of overthrusting by about 5 mm/yr. For a convergence rate of about 20 mm/yr, this implies underthrusting of the Indian basement below the Himalaya by about 15 mm/yr. The structure, metamorphic grade and exhumation history of the LH supports the view that, since the mid-Miocene, the Himalayan orogen has essentially grown by underplating, rather than by frontal accretion. This process has resulted from duplexing at a depth close to the brittle-ductile transition zone, by southward migration of a midcrustal ramp along the Main Himalayan Thrust fault, and is estimated to have resulted in a net flux of up to 150 m^2/yr of LH rocks into the Himalayan orogenic wedge. The steep inverse thermal gradient across the LH is interpreted to have resulted from a combination of underplating and post metamorphic shearing of the underplated units

Potential Agronomic Benefits of Wood Ash Application on Reclaimed Surface Mined Lands

Wood ash is a by-product generated by paper companies, lumber manufacturing plants and utilities that bum wood products, bark and papermill sludge as a means of disposal and/or energy production. Large quantities of wood ash are generated by these industries since wood generally contains 6 to 10% ash. Most of these ashes are landfilled or discarded in lagoons. However, the increasing expense of landfill disposal has led to increased interest in the land application of industry generated wood ash

Dynamic modelling of lettuce transpiration for water status monitoring

Real-time information on the plant water status is an important prerequisite for the precision irrigation management of crops. The plant transpiration has been shown to provide a good indication of its water status. In this paper, a novel plant water status monitoring framework based on the transpiration dynamics of greenhouse grown lettuce plants is presented. Experimental results indicated that lettuce plants experiencing adequate water supply transpired at a higher rate compared to plants experiencing a shortage in water supply. A data-driven model for predicting the transpiration dynamics of the plants was developed using a system identification approach. Results indicated that a second order discrete-time transfer function model with incoming radiation, vapour pressure deficit, and leaf area index as inputs sufficiently explained the dynamics with an average coefficient of determination of . The parameters of the model were updated online and then applied in predicting the transpiration dynamics of the plants in real-time. The model predicted dynamics closely matched the measured values when the plants were in a predefined water status state. The reverse was the case when there was a significant change in the water status state. The information contained in the model residuals (measured transpiration – model predicted transpiration) was then exploited as a means of inferring the plant water status. This framework provides a simple and intuitive means of monitoring the plant water status in real-time while achieving a sensitivity similar to that of stomatal conductance measurements. It can be applied in regulating the water deficit of greenhouse grown crops, with specific advantages over other available techniques

Fertilizer, Tillage, and Dairy Manure Contributions to Nitrate and Herbicide Leaching

Few studies have examined the water quality impact of manure use in no-tillage systems. A lysimeter study in continuous corn (Zea mays L.) was performed on Maury silt loam (fine, mixed, semiactive, mesic Typic Paleudalf) to evaluate the effect(s) of tillage (no-till [NT] and chisel-disk [CD]), nitrogen fertilizer rate (0 and 168 kg N ha−1), and dairy manure application timing (none, spring, fall, or fall plus spring) on NO3–N, atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), and alachlor [2-chloro-2′-6′-diethyl-N-(methoxymethyl)acetanilide] concentrations in leachate collected at a 90-cm depth. Herbicides were highest immediately after application, declining to less than 4 μg L−1 in about two months. Manure and manure timing by tillage interactions had little effect on leachate herbicides; rather, the data suggest that macropores rapidly transmitted atrazine and alachlor through the soil. Tillage usually did not significantly affect leachate NO3–N, but no-tillage tended to cause higher NO3–N. Manuring caused higher NO3–N concentrations; spring manuring had more impact than fall, but fall manure contained about 78% of the N found in spring manure. Nitrate under spring “only fertilizer” treatment exceeded 10 mg L−138% of the time, compared with 15% for spring only manure treatment. After three years, manured soil leachate NO3–N exceeded that for soil receiving only N fertilizer. Soil profile (90 cm) NO3–N after corn harvest exceeding 22 kg N ha−1 was associated with winter leachate NO3–N greater than 10 mg N L−1 Manure can be used effectively in conservation tillage systems on this and similar soils. Accounting for all N inputs, including previous manure applications, will be important