516 research outputs found

    Effects of Rotation, Site, and Clone on the Chemical Composition of Populus Hybrids

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    Chemical content values were determined for three Populus clones grown on two dissimilar sites by component (wood, bark, and wood/bark specimens), tissue age (1-, 2- and 4-years-old), and rotation. The chemical content values obtained included extractives, holocellulose, alpha-cellulose, and lignin. In general, analysis of the data for the wood, bark, and wood/bark specimens indicated that: 1) wood was high in holocellulose and alpha-cellulose content compared to bark, 2) bark was high in lignin and extractive content values compared to wood, and 3) wood/bark chemical content values were between the values for the wood and bark specimens.The chemical content data were analyzed to identify: 1) significant differences between rotations by component (wood, bark, and wood/bark) for a given age, clone, and site, and 2) significant differences between sites for four-year-old wood, bark and wood/bark specimens of a given rotation, and clone. Statistical analyses indicated that significant differences existed among clones, sites, ages, and rotations. Within the wood, bark and wood/bark specimens, tissue age, rotation, and site influenced the chemical content values more than the parentage. Potential chemical yields derived from the three Populus hybrid clones investigated will depend on component, age, rotation, and site with limited parentage effects

    Pulp and Papermaking Properties of A Hybrid Poplar Clone Grown Under Four Management Strategies and Two Soil Sites

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    A study was undertaken to evaluate the pulp and papermaking properties of short rotation intensive culture (SRIC), three-year-old, Populus hybrid grown under four management strategies (control, irrigation, fertilization, and fertilization/irrigation) on two sites with either favorable or unfavorable inherent conditions for high biomass yields. No large differences in total pulp yields were observed with management strategy, although the fertilization/irrigation growth strategy produced debarked chips that gave slightly higher total pulp yields with lower permanganate numbers than did debarked chips obtained from the other three growth strategies. In addition, no significant differences (P ≤ 0.05) in total kraft pulp yields were observed between sites. As expected, the wood/bark chip mixture for each management strategy and site produced significantly lower pulp yields with higher permanganate numbers compared to the debarked chips.Handsheet strength evaluation studies were conducted using these pulps, and no statistical differences in handsheet breaking length, tear, burst, and M.I.T. fold were measured among management strategies or sites. However, longer fibers were measured from wood obtained from trees grown on the Basher (favorable) site. No statistical differences in handsheet properties were measured between debarked and total tree pulps. Results of this study indicated that neither the growth management strategy nor the soil site influenced handsheet strength properties for three-year-old Populus hybrid. These observations imply that the silviculturalist should grow SRIC Populus trees that produce the highest biomass yield at lowest possible cost

    Chemical Composition of Second Rotation Populus Hybrid NE-388

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    The influence of management strategy and rotation on specific gravity and chemical content (extractive, holocellulose, alpha-cellulose, and Klason lignin) values for second rotation 4-year-old Populus Hybrid NE-388 wood and bark specimens were investigated. Specific gravity values for wood were lowest for fertilization and fertilization/irrigation strategies and for bark were highest for fertilization and fertilization/irrigation strategies compared to control and irrigation strategies. Management strategies had little effect on the holocellulose and alpha-cellulose values for the second rotation. Management strategy and rotation had significant effects on extractive and Klason lignin contents for bark and the extractive content for wood. Second rotation average specific gravity values for wood were similar to or higher than first rotation values and average Klason lignin content values for bark were higher than first rotation values

    Comparison of Selected Fuel and Chemical Content Values for Seven Populus Hybrid Clones

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    Fuel and chemical content values were determined for seven Populus clones by component (wood, bark, and wood/bark specimens) and tissue age (1 to 8 years old). The fuel and chemical content values obtained included: gross heat of combustion, extractives, holocellulose, alpha-cellulose, lignin, and ash. In general, analysis of the data for the wood, bark, and wood/bark specimens indicated that: 1) wood was higher in holocellulose and alpha-cellulose content than bark; 2) bark was higher in gross heat of combustion, lignin, extractive, and ash content values than wood; and 3) combined wood/bark fuel and chemical content values were usually between the individual values for the wood and bark.Statistical analyses indicated that significant differences existed within and among clones. Within the wood, bark, and wood/bark specimens, tissue age influenced the chemical content values more than the parentage. Potential chemical yields derived from the seven Populus hybrid clones investigated will depend on component and age with limited parentage effects

    Experimental Investigation of Roughness Effects on Transition on Blunt Spherical Capsule Shapes

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    The present contribution reviews recent experimental results of roughness effects on boundary layer transition on capsule geometries with spherical windward geometries. Experiments in three wind tunnel facilities are considered. The ACE Tunnel of Texas AM University, USA, provided Mach 6 experiments with distributed roughness at relatively low Reynolds numbers, 2.5 10(exp 5) < Re(sub d) < 5 10(exp 5), with d denoting the capsule diameter. The observed boundary layer transition compared well with correlations based on transient growth theory, even though the roughness heights were in the order of boundary layer thickness. Larger Reynolds numbers, 1 10(exp 6) < Re(sub d) < 310(exp 6), could be assessed in the hypersonic Ludwieg tube, HLB, of TU Braunschweig, Germany. Transition is observed at rather low, subcritical roughness values in the order of 20 m for a roughness patch placed about the geometric center of the capsule model. These experiments varied fluctuation levels of the freestream. The authors assume that the observed transitions that occur downstream of the subcritical roughness patch are due to freestream disturbances in the tunnel, which interact with small roughness heights. Additional experiments in the HLB facility with patches of larger roughness height support the relevance of transient growth theory for low-to-medium roughness heights, relative to boundary layer thickness. The effects of Reynolds numbers and total flow enthalpy on transition with isolated roughness were investigated in the HIEST facility of JAXA, Japan. Here, a model insert with roughness elements of varying height for tripping transition to turbulence was employed. The results are compared to known trip effectiveness correlations for isolated roughness. Overall, the transient growth correlation seems to represent roughness-induced transition behavior on the ACE and HLB entry capsule shapes with roughness over the entire capsule surface. These experiment are however for perfect gases. Comparable experiments on roughness induced transition in a high-enthalpy facility are still needed to confirm the validity of transient-growth correlation for vehicle design

    Analyzing a fleet solution using scenarios

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    Transportation is one of the most important logistics activities, accounting for a significant part of the logistics costs and with high level of impact in terms of the service level provided to the customer. To counteract the upward trend in costs, it is fundamental to identify a transport strategy that can reduce costs and, at the same time, does not adversely affect the service levels agreed with customers. The main objective of this research is to propose a methodology for companies to identify, from a set of scenarios proposed and through a comparative analysis of scenarios, a new fleet solution, allowing the Company under study to reduce its transport costs without harming the current service level agreements with its customers. This research is grounded on a case study methodology. The case study used is of a small Portuguese company that produces, imports and distributes a wide range of products. The distribution is conducted based on both its own fleet and subcontracted transportation. The comparative analysis of scenarios allowed identifying the current transportation solution as the most advantageous one for the company. A roadmap to address fleet solution is provided.info:eu-repo/semantics/acceptedVersio

    Development of a mechanism to facilitate the safety stock planning configuration in ERP

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    Safety stock planning in ERP in general is dependent upon the planner having the experience to simulate planning scenarios. This paper focuses on the development of a mechanism to calculate adequate safety stocks in accordance with required service levels while enabling efficient configuration of the ERP safety stock parameters. The proposed mechanism could be of great benefit to industrial firms as it offers the ability to classify demand patterns, proposes replenishment strategies that are consistent with the demand profile, calculates key parameters and identifies the changes required to the ERP master data. The associated real world application is able to identify potential to save approximately £1.2 M in stock reductions and, more importantly, allows targeted actions to be implemented at material level. These results demonstrated that the proposed mechanism can be considered as a valuable new development for manufacturing industry to gain the competitive advantage

    A mathematical model for the onset of avascular tumor growth in response to the loss of p53 function

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    We present a mathematical model for the formation of an avascular tumor based on the loss by gene mutation of the tumor suppressor function of p53. The wild type p53 protein regulates apoptosis, cell expression of growth factor and matrix metalloproteinase, which are regulatory functions that many mutant p53 proteins do not possess. The focus is on a description of cell movement as the transport of cell population density rather than as the movement of individual cells. In contrast to earlier works on solid tumor growth, a model is proposed for the initiation of tumor growth. The central idea, taken from the mathematical theory of dynamical systems, is to view the loss of p53 function in a few cells as a small instability in a rest state for an appropriate system of differential equations describing cell movement. This instability is shown (numerically) to lead to a second, spatially inhomogeneous, solution that can be thought of as a solid tumor whose growth is nutrient diffusion limited. In this formulation, one is led to a system of nine partial differential equations. We show computationally that there can be tumor states that coexist with benign states and that are highly unstable in the sense that a slight increase in tumor size results in the tumor occupying the sample region while a slight decrease in tumor size results in its ultimate disappearance
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