Assessing Sensitivity Factors of Irrigation Delivery Structures

The flow behavior along an open-channel irrigation network can be assessed by determining the sensitivity of the irrigation structures. The importance of governing factors of the sensitivity and proportionality indicators is analyzed using a theoretical approach as well as practical results from historical data on a gated system in Sri Lanka and a gated and structured system in Pakistan. The influence of the discharge on the sensitivity indicator varies with the type of flow (overshot-undershot). For a common offtake (e.g., an orifice followed by a crest), sensitivity is at its peak at maximum discharge. The available head through the structure appears to be the most influential factor for sensitivity; the greater the head, the lower the sensitivity is. The submergence of the flow downstream of the structure is a reducing factor of the sensitivity that is important to consider for sensitive structures. Different methods for assessing the governing factors of sensitivity are discussed and illustrated using case studies. It is recommended that the sensitivity indicator be determined for the full supply depth in the parent canal and the maximum discharge through the offtake.     

Irrigation Offtake Sensitivity

This article is an attempt to develop an analytical framework to address sensitivity of irrigation offtakes. The perturbation of water depth and the deviation of the setting are considered for analysis. Sensitivity of delivery takes into account the impacts of the perturbations on the delivery (to the command area of the offtake). Sensitivity of conveyance assesses the effects on the conveyance discharge of the parent canal. Analytical formulations of six sensitivity indicators are provided. The concept of head loss equivalent is introduced to explicitly take into account the hydraulic behavior in the dependent canal downstream of the offtakes. Hydraulic perturbations are considered either as upstream deviations in the parent canal or downstream perturbations in the dependent canal.     

Statistical Sensitivity Analysis of Lattice Space Structures

This paper presents a statistical sensitivity analysis for shape distortions of space structures. The approach is based on a statistical shape‐distortion analysis on the structural errors and an adjoint method of sensitivity analysis. The statistical shape‐distortion analysis allows the stochastic errors to be represented by member‐length tolerances. The sensitivity analysis is performed to predict the effects of member‐length errors for lattice space antennas on the surface accuracy. The formulas presented in this paper give an effective approach to predict the effects of member‐length errors on the shape distortions, to obtain effective structural elements to correct the shape distortions, and to design tolerance errors of the structural elements. Numerical examples for statically determinate and indeterminate two‐dimensional truss beams have been demonstrated to identify the members contributing most to the errors. These results show that the errors of the longitudinal elements of the structure are important for designing accurate truss structures. Moreover, the validity and effectiveness of the present approach have been investigated.     

Operational Cost Benefits Study of Flexible On-Farm Irrigation Supply Systems

Efficient on-farm use of water and labor for all methods requires a water supply flexible in frequency, rate, and duration and under the control of the irrigator at the point of application. For surface irrigation, the use of large capacity systems for supply and distribution are essential and economical, especially when considering the reduced labor needs, increased irrigation efficiency, and reduced potential high water table problems resulting from having a large, flexible supply associated with a flexible arranged-demand schedule. Automation and stability of flow at the farm turnout, comparable to a domestic system with variable flow delivery conditions, are typically accomplished by use of large capacity semiclosed pipeline systems. A cost comparison of capital investment for various sized, flexible supply systems with resulting farm water and labor costs is presented which shows the great value from the upgraded management made possible.     

Sensitivity Statistics of 3D Structures under Parametric Uncertainty

Determination of sensitivity gradient is a major prerequisite for structural optimization, reliability assessment, and parameter identification. As the conventional deterministic sensitivity analysis cannot provide complete information, stochastic analysis is needed to tackle the uncertainties in structural parameters. This study focuses on the utility of the stochastic finite-element method for random response sensitivity analysis. The stochastic modeling of a random parameter is based on a commonly used 2D local averaging method generalized for a 3D case. The Choleski decomposition technique is then employed for digital simulation. The Neumann expansion based finite-element simulation method is extended for stochastic sensitivity analysis. This technique leads to a considerable saving of computational time. Example problems are used to compare the accuracy of this method to the direct Monte Carlo simulation and perturbation method in terms of varying stochasticity and efficiency in CPU time.     

Offtake Sensitivity, Operation Effectiveness, and Performance of Irrigation System

Analytical relationships between the control of canal water depth, the sensitivity of irrigation delivery structures, and the resulting internal performance are established at the system level. One system sensitivity indicator is derived for both adequacy and efficiency, and two for equity (coefficient of variation and Theil information index). The level of precision which reflects the effectiveness in controlling water depth is defined as a permissible variation of water depth at the cross-regulator (±ΔHR) about the target. The degree of influence exercised by the cross-regulator on offtakes is accounted for through an influence factor between zero and one. The behavior of three different irrigation systems in Sri Lanka and Pakistan is studied with both analytical system indicators and numerical hydraulic simulations. It shows good agreement for a range of precision between 0.02 and 0.2 m. These global system indicators can be used to define the precision level required to achieve a given performance, to estimate actual performance from recorded precision at regulators, and to diminish the system sensitivity, improving the performance for a given precision. Practical operating policies can be inferred from sensitivity information of irrigation systems without the necessity of a complex irrigation operation model.     

Justifying Materials Selection for Reinforced Concrete Structures. I: Sensitivity Analysis

A substantial amount of research has been performed on the use of high performance construction materials and their effects on the anticipated frequency of maintenance and on the time to repair or replacement. Practical implementation of this work has been limited due to the lack of useable methods and information on the life-cycle costs and benefits of alternative approaches in the preliminary design stages of projects, when decisions regarding materials selection are typically made. The lack of simple methods for making quick life-cycle economic comparisons typically results in the use of conventional materials because their impact on performance is well known, even though high-performance materials may actually be more cost effective. This paper identifies the most significant parameters for evaluating the time to corrosion of reinforced concrete structures.     

Sensitivity Analyses and Sensitivity Coefficients of Standardized Daily ASCE-Penman-Monteith Equation

The sensitivity of the standardized ASCE grass-reference Penman-Monteith evapotranspiration (ASCE-PM ETo) equation to climate variables in different regions has not yet been studied. Sensitivity analyses for the standardized daily form of the ASCE-PM equation were conducted on wind speed at 2?m height (U2), maximum and minimum air temperatures (Tmax and Tmin), vapor pressure deficit (VPD), and solar radiation (Rs) in the following regions of the United States: semiarid (Scottsbluff, Nebraska, and Bushland, Texas), a Mediterranean-type climate (Santa Barbara, California), coastal humid (Fort Pierce, Florida), inland humid and semihumid (Rockport, Missouri, and Clay Center, Nebraska), and an island (Twitchell Island, California). The sensitivity coefficients were derived for each variable on a daily basis. In general, ETo was most sensitive to VPD at all locations, while sensitivity of ETo to the same variable showed significant variation from one location to another and at the same location within the year. After VPD, ETo was most sensitive to U2 in semiarid regions (Scottsbluff, Clay Center, and Bushland) during the summer months. The Rs was the dominant driving force of ETo at humid locations (Fort Pierce and Rockport) during the summer months. At Santa Barbara, the sensitivity of ETo to U2 was minimal during the summer months. At Bushland, Scottsbluff, and Twitchell Island, ETo was more sensitive to Tmax than Rs in summer months, whereas it was equally sensitive to Tmax and Rs at Clay Center. The ETo was not sensitive to Tmin at any of the locations. The change in ETo was linearly related to change in climate variables (with r2 ≥ 0.96 in most cases), with the exception of Tmin, at all sites. Increase in ETo with respect to increase in climate variable changed considerably by month. On an annual average, a 1°C increase in Tmax resulted in 0.11, 0.06, 0.16, 0.07, 0.11, 0.08, and 0.10?mm increases in ETo at Scottsbluff, Santa Barbara, Bushland, Fort Pierce, Twitchell Island, Rockport, and Clay Center. A 1?m?s?1 increase in U2 resulted in 0.42, 0.18, 0.37, 0.28, 0.31, 0.20, and 0.26?mm increases in ETo at the same locations. A unit increase in Tmax resulted in the largest increase in ETo at Bushland, and a unit increase in Rs caused the largest increases in ETo at Fort Pierce. A 1?MJ?m?2?d?1 increase in Rs resulted in 0.05, 0.08, 0.06, 0.11, 0.05, 0.06, and 0.06?mm increases in ETo at the same locations. A 0.4?kPa increase in VPD resulted in 1.13, 0.54, 1.29, 0.57, 1.04, 1.10, and 1.22?mm increases in ETo at the same locations. The U2 had the most effect on ETo at Scottsbluff and Bushland, the two locations where dry and strong winds are common during the growing season. The sensitivity coefficient for Rs was higher during the summer months and lower during the winter months, and the opposite was observed for VPD (except for Twitchell Island). The decrease of the sensitivity coefficients for Rs corresponding to an increase in the sensitivity coefficient for VPD is due to a decrease in the energy term in favor of the increase in significance of the aerodynamic term of the standardized ASCE-PM equation in summer versus winter months. Because the ASCE-PM and the Food and Agriculture Organization paper number 56 Penman-Monteith (FAO56-PM) equations are identical when applied on a daily time step, the results of the sensitivity analyses and sensitivity coefficients of this study should be directly applicable to the FAO56-PM equation.     

Measuring On-Farm Irrigation Efficiency with Chloride Tracing under Deficit Irrigation

Water is a limited resource in agricultural production in arid climates. Under such conditions, high irrigation efficiency can be obtained either through implementation of efficient irrigation systems such as drip or sprinkler systems or through the age-old practice of deficit irrigation with gravity systems. The method used to increase irrigation efficiency is often dictated by economic and/or social factors. In either case, the effectiveness of water management at the farm level needs to be evaluated by measuring irrigation efficiency. The objective of this study was to evaluate the irrigation efficiencies for three crops in Southern New Mexico using the chloride technique. The chloride technique is a simple method in which the natural chloride in the irrigation water is used as a tracer to estimate the leaching fraction and the irrigation efficiency at the farm level. Soil samples were collected from various fields in 15 cm increments to a depth of 180 cm at the end of the irrigation season. The samples were analyzed for moisture and chloride content. In addition to the chloride technique, on-farm irrigation efficiencies were measured using applied water, yield, and water production functions. Water production functions and yields were used to estimate total evapotranspiration while flow measurements were used to calculate the amount of applied water. The results showed that high irrigation efficiency can be accomplished using deficit irrigation. Irrigation efficiency values ranged from 83 to 98%. Irrigation efficiencies using the chloride technique were compared with efficiencies estimated from direct flow measurements. The differences between the two methods ranged from 2 to 11.4%. The results showed that even though the chloride technique is subject to sampling errors and simplified theoretical assumptions, it can be used to estimate on-farm irrigation efficiency with considerable accuracy.     

Operational failure of large steel axles

Analysis of the failure of a shaft in the roof of the covered skating center at Krylatskoe (Moscow) indicates slow brittle failure by the hydrogen mechanism. Proposals are outlined for preventing defects that lead to brittle failure in such axles.     

烧结炉作业参数的探讨

针对河池冶金化工厂烧结炉自试产以来的生产情况,通过该厂技术人员在实践中不断地摸索和总结,把影响烧结块产量、质量的主要生产因素水分、炉料含硫量、返粉、混料时间、料层厚度,抽风负压、烧结时间等进行了分析和最佳组合,最终得出了一套适合脆硫铅锑精矿烧结的最佳工艺参数,使烧结块的产量、质量有很大的提高,烧结块平均结块率和平均利用率分别提高11.41%和14%,烧结块残硫降低了1.4%,保证了下一道工序的正常生产.为了巩固实践成果,我们把最佳工艺参数纳入以后的生产管理制度之中,并提出了巩固措施.     

Operational nucleation in martensitic transformations

Operational nucleation in martensitic transformations is accessible to measurement and governs the reaction kinetics. In essence, it involves the growth start-up of preexisting embryos, and is not concerned with the origin of such embryos. Another important feature is the fast chain-of-events triggered-off after the growth is initiated, leading to the sudden formation of observable martensitic plates. The model of operational nucleation and subsequent growth presented here provides a plausible explanation of the fine-scale phenomena, and permits calculation of the aspect ratio (or growth path) adopted by the advancing particle. E. C. Bain had a long-standing interest in the nature of martensitic nucleation. By strange coincidence, this was the subject of my last conversation with him.     

光伏灌溉系统的设计

介绍了光伏灌溉系统的相关配置方案、设计方法及主要设备参数的计算方式。光伏灌溉系统是解决缺水、缺电地区灌溉用水问题的新方法,对农业灌溉、荒漠治理有很好的利用价值。     

Measuring Irrigation Well Discharges

Irrigation wells frequently discharge directly into canals. Upstream elbows, the pump head, or other pipe fittings may produce a distorted flow profile that is detrimental to the proper installation and operation of commonly available pipe meters. Before attempts to condition the flow with longer discharge piping or straightening vanes, it is desirable to know how distorted the flow profile really is. If this information can be provided, the meter technician can determine whether a correction in the meter coefficient will suffice, or if flow conditioning equipment is needed, or whether flow conditioning equipment, if already installed, is working effectively. An economical method of field evaluating the result of an installed meter in this compromised situation is described. The method uses a conveniently fashioned pitot-tube system that can be clamped to the pump discharge pipe. It is used to quickly detect the velocity at several points across the pipe diameter. Distorted profiles can be detected and measured. Pitot-tube systems have long been used in pipe flows. Most require that special taps be drilled in the outflow pipe of the well. Some use special double-tube constructions that are difficult to build using simple machine-shop procedures. This pitot impact tube, with its static pressure companion tube, can be constructed using common shop techniques and standard small pipe fittings.     

Administering conscious sedation. Operational guidelines

The nurse must be aware of her or his role and responsibilities when implementing IVCS guidelines. Nurses performing IVCS must be knowledgeable of state and institutional guidelines for IVCS, medications included in IVCS, and the assessment, monitoring, and documentation required in caring for the patient receiving IVCS. The process of IVCS may seem tedious, but if an institution has clearly defined expectations, as provided in the IVCS guidelines, the process is much more understandable and can be readily instituted. The patient undergoing IVCS deserves the highest quality care possible with the fewest complications, a situation that can be achieved with proper preparation and implementation of an IVCS program.