Norm optimization techniques for improved structural reanalysis

An approximate structural reanalysis method that is based on a binomial series expansion and that employs operations of matrix scaling and norm minimization is presented in this paper. It is shown that the scaling operation significantly reduces several unfavourable effects of the magnitude and nature of design changes on the prediction quality of the model. Norm minimization provides a very effective and optimal scaling factor in a simplified manner. The most significant achievement of the work is the development of an effective and efficient reanalysis model that provides near-exact response quantities even when large and strongly dispersed changes are introduced in the design. The potential capacity of the proposed method of improvement is demonstrated using numerical examples. Graphical interpretation of the concept is also provided.     

Status and Potential of Spate Irrigation in Ethiopia

This article discusses spate irrigation in Ethiopia and aims to take stock of the current status of spate irrigation development. It summarizes experiences so far and formulates a number of recommendations on the development of this upcoming resource management system. It argues that raised weirs are useful mainly in areas where a large head for spate flow diversion is required, but that traditional earthen structures with conical stone/gabion reinforcements are cost-effective and technically adequate for floodwater distribution and management. It contends that the practical successes of sediment settling ponds (gravel traps) are at best mixed. Even where a small basin is justified, it can only ever trap a small proportion of the incoming sediment load. It is better to allow large floods with excessive sediment load (>100,000 ppm) to by-pass upstream intakes to be diverted lower down the system, and provide additional livelihood opportunities in downstream areas in the form of rangeland and agro-forestry development. This is particularly useful in the lowlands of Ethiopia with large pastoral community where spate irrigation is yet to make in-roads. The article further explains that water rights in spate are different from the sharing and allocation of perennial flows—they are dynamic and respond to a situation that differs from year to year as well as within a year and that a certain degree of inequity among users is inevitable. Keeping the command area compact can ensure two or more irrigation turns and this can highly increase productivity as crops are no longer in the ‘stress zone’. To transform spate irrigation in Ethiopia from subsistence to a business-oriented production system, the article proposes the promotion of cash crops including pulses and oil seeds as well as encouraging investors to go for bio-fuel development and agro-forestry in the lowland areas where huge potential exist. To avoid vehement conflicts that may arise among the settled agricultural and pastoral communities due to the implementation of the business-oriented production system, the traditional rights of the pastoral communities must be respected and their rangeland and water resources be safeguarded. For maximum yield, soil moisture conservation measures such as pre-irrigation land preparation, deep ploughing and mulching are essential as is the conjunctive use of spate flow and groundwater. Last, but most important, the article emphasizes that farmers need to be placed at the heart of any spate irrigation development programme as primary beneficiaries, managers and operators as well as part of the decision making institution.     

On optimal topology of grillage structures

Two problems of optimum topological design of grillages are discussed: (1) the Equilibrium Linear Programming (ELP), where the analysis model is based only on equilibrium conditions and (2) the Nonlinear Program (NLP), where the ELP formulation is extended to include compatibility conditions. The structural topology is optimized by allowing elimination of elements. Three different force method formulations are presented for each of the problems. It is shown that the optimal topology for the NLP problem might correspond to a singular point in the design space. The optimal topology for the ELP problem is obtained by solving a linear program (LP).

Conditions for selecting a geometry of Multiple Optimal Topologies (MOT) are derived. The objective function for the MOT geometry is shown to be independent of the redundant forces, and some of the optimal topologies are usually statically determinate structures. In such cases the lower bound on the optimal value obtained by the ELP solution is equal to the final global optimum. Examples are given to illustrate how the optimal topology and its corresponding load path change with the geometric parameters. Design procedures that combine automated optimization and CAD techniques are most suitable for solving the presented problems.

     

Decadal Analysis of River Flow Extremes Using Quantile-Based Approaches

Next to the traditional analysis of trends in time series of hydro-climatological variables, analysis of decadal oscillations in these variables is of particular importance for the risk assessment of hydro-climatological disasters and risk-based decision-making. Conventional parametric and nonparametric tests, however, need implementing a set of background assumptions related to serial structure and statistical distribution of data. They neither focus on the extreme events and their probability of occurrence. In order to get rid of these limitations, we suggest a modified version of the Sen Method (SM), combined with the Quantile Perturbation Method (QPM) for examining temporal variation of extreme hydrological events. The developed method is tested for decadal analysis of monthly and annual river flows at 10 hydrometric stations in the Qazvin plain in Iran. The results show oscillatory patterns in extreme river flow quantiles, with a positive anomaly during the 1990s and a negative one during the 2000s. It is also shown that the concurrent use of the two methods allows to set a complete picture on the temporal changes in high and low extremes in historical river flow observations in different seasons.     

Effect of ripening conditions on the physicochemical and antioxidant properties of tomato (Lycopersicon esculentum Mill.)

Food Science and Biotechnology - This study was conducted to assess the physicochemical changes and overall nutritional implications of greenhouse-grown “TY Megaton” and...     

Structural optimization in design planes

A new optimal design procedure based on successive optimization in design planes is presented. It is intended to improve the convergence properties of the solution process and to reduce the computational effort. Optimization is carried out at each iteration cycle in a two-dimensional design plane, formed by the current design and a selected direction vector in the design space. Applying the scaling operation, optimization in a design plane is reduced to a problem of a single independent variable. The computational effort is further reduced by introducing approximate behaviour models for the selected design planes.

The procedures of selecting a design plane and optimization in the plane are repeated until the final optimum is achieved. Since all intermediate designs are feasible, the solution process can always be terminated with an improved feasible design. Various methods can be employed to introduce design planes; some of them are investigated in this study.

Numerical experience with the proposed procedure shows that the final optimum can be achieved in a small number of iteration cycles. This feature is particularly important for problems where other algorithms fail to arrive at the optimum in a reasonable number of iterations.     

Synthesis,effectiveness, and working mechanism of humic acid‐{sodium 2‐acrylamido‐2‐methylpropane sulfonate‐co‐N,N‐dimethyl acrylamide‐co‐acrylic acid} graft copolymer as high‐temperature fluid loss additive in oil well cementing

Monomers of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS®), N,N–dimethyl acrylamide (NNDMA) and acrylic acid (AA) were grafted on humic acid as backbone by aqueous free radical copolymerization in such a manner that a graft copolymer possessing lateral terpolymer chains was obtained. Molar ratios between AMPS®, NNDMA, and AA were found to be 1 : 1.54 : 0.02 and the ratio between backbone and graft chain was 20 : 80 wt %. The synthesized fluid loss additive (FLA) was characterized by size exclusion chromatography (SEC), charge titration, and Brookfield viscometry. Thermogravimetric and SEC analysis revealed stretched backbone worm architecture for the polymer whereby humic acid constitutes the backbone decorated with lateral graft chains. Grafting was confirmed by SEC data (R_g) and by ineffectiveness of a blend of AMPS®‐NNDMA‐AA copolymer with humic acid. Their performance as high temperature FLA was studied at 150°C by measuring static filtration properties of oil well cement slurries containing 35% bwoc of silica fume and 1.2% bwoc AMPS®‐co‐itaconic acid retarder. At this temperature, 1.0% bwoc graft copolymer achieves API fluid loss value of 40 mL, thus confirming high effectiveness. The graft copolymer viscosifies cement slurries less than other common synthetic FLAs. The working mechanism of the graft copolymer was found to rely on adsorption onto surface of hydrating cement, as was evidenced by adsorption and zeta potential measurements. Adsorption is hardly affected by temperature and results in constriction of the filter cake pores. The study provides insight into performance of cement additives under the harsh conditions of high temperature and high pressure. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Working mechanism of poly(vinyl alcohol) cement fluid loss additive

The working mechanism of poly(vinyl alcohol) (PVA, M_w ～ 200,000 g mol^?1), a fluid loss control additive (FLA) applied in oil well cementing, was investigated. First, characteristic properties of PVA such as solubility and particle size in cold and hot water, minimum film forming temperature, adsorption on cement, viscosity of cement pore solution and static filtration properties of cement slurries treated with PVA were determined. It was found that the working mechanism of PVA relies on hydrated, but water‐insoluble PVA particles (d₅₀ ～ 2.4 μm). During cement slurry filtration, they coalesce into a polymer film. This film effectively plugs the pores of the cement filter cake. The sample studied here becomes water‐soluble at temperatures > 40°C (d₅₀ decreases to ～50 nm) and looses its effectiveness. Addition of highly anionic dispersants such as ß‐naphthalenesulfonate formaldehyde (BNS) or acetone formaldehyde sulfite (AFS) polycondensate extends the temperature range at which PVA works from 40°C to ～60°C. This effect is ascribed to lower solubility of PVA in the presence of these dispersants. The study reveals that decreased performance of PVA caused by higher temperatures is not the result of thermal degradation of the polymer, but is owed to its increasing water‐solubility. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of a dispersing fluid loss additive based on humic acid graft copolymer suitable for cementing high temperature (200°C) oil wells

A humic acid graft copolymer possessing both water‐retention and dispersing properties in cement slurry was synthesized by grafting lateral chains of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS®), N,N‐dimethylacrylamide (NNDMA), and acrylic acid (AA) onto a backbone of humic acid using aqueous free radical polymerization. The graft copolymer is composed of 20 wt % humic acid backbone and 80 wt % graft chain (molar ratio AMPS/NNDMA/AA = 1 : 0.31 : 0.03), it exhibits a M_w of 323 kDa and is highly anionic in cement pore solution. The influence of this specific molecular design on cement flow properties is unraveled. When tested at 200°C, the graft copolymer achieved very low cement fluid loss values (～50 mL) at low rheology. This behavior differentiates it from most common synthetic high temperature fluid loss additives which excessively viscosify cement slurries. The working mechanism of the graft copolymer was found to rely on adsorption onto the surface of hydrating cement. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Evaluation of modified adaptive k-means segmentation algorithm

Computational Visual Media - Segmentation is the act of partitioning an image into different regions by creating boundaries between regions. k-means image segmentation is the simplest prevalent...