The scissor lift contains multiple stages of cross bars which can convert a linear displacement between any two points on the series of cross bars into a vertical displacement multiplied by a mechanical advantage factor. This factor depends on the position of the points chosen to connect an actuator and the number of cross bar stages. The amount of force required from the actuator is also amplified, and can result in very large forces required to begin lifting even a moderate amount of weight if the actuator is not in an optimal position.
Actuator force is not constant, since the load factor decreases as a function of lift height. Types of lifts can be classified as follows:- Classification based on the type of energy used a Hydraulic lifts www. A very brief analysis of each component follows thus: I.
Scissors arms II. Hydraulic cylinder III. Top plat form IV. Base plat form V. Wheels Scissors Arms: this component is subjected to buckling load and bending load tending to break or cause bending of the components. Hence based on strength, stiffness, plasticity an hardness. A recommended material is stainless steel. Hydraulic Cylinder: this component is considered as a strut with both ends pinned. It is subjected to direct compressive force which imposes a bending stress which may cause buckling of the component.
It is also subjected to internal compressive pressure which generates circumferential and longitudinal stresses all around the wall thickness.
Hence necessary material property must include strength, ductility, toughness and hardness. The recommended material is mild steel. Top Platform: this component is subjected to the weight of the workman and his equipment, hence strength is required, the frame of the plat form is mild steel and the base is wood.
Base Platform: this component is subjected to the weight of the top plat form and the scissors arms. It is also responsible for the stability of the whole assembly, therefore strength.
Hardness and stiffness are needed mechanical properties. Mild steel is used. Considerations made during the design and fabrication of a single acting cylinder is as follows: a. Functionality of the design b. Manufacturability c. The journal aims to provide an international platform for the dissemination of research and engineering applications related to water and hydraulic problems in the Asia-Pacific region. The journal provides a wide distribution at affordable subscription rate, as well as a rapid reviewing and publication time.
The journal particularly encourages papers from young researchers. Papers that require extensive language editing, qualify for editorial assistance with American Journal Experts, a Language Editing Company that Elsevier recommends. The journal welcomes papers in all topics of hydraulics, in particular articles on sustaina. The Journal plays a specific role in promoting a cross-sectorial approach encompassing all aspects of river and floodplain management, with a truly global perspective, and available to subscribers at a reasonable price.
The Journal is a response by the scientific and professional community to the World Water Vision and calls by the World Water Council and Global Water Partnership for an integrated approach to water resources management.
Papers will be accepted in all areas of. The Journal of Ecohydraulics TJoE embodies the varied research undertaken in ecohydraulics covering water resources and aquatic life, ecology, biology, hydraulics, engineering, geoscience, environmental science, climate change and other related fields, with an emphasis on the integration of these disciplines.
The Journal is of interest to academics involved in fundamental or applied sciences, as well as practitioners and policy makers working at the applied environmental management end of the spectrum, including those who seek innovative solutions to environmental assessment, impacts of and mitigation for existing or new projects. A range of approaches are invited — from physical and numer. This peer-reviewed Journal launched in publishes papers and practical case studies on all aspects of hydro-environment engineering and research.
Practically-oriented papers and case studies are particularly welcome. Papers cover fluid systems in the hydrosphere, such as rivers, lakes, coastal waters and groundwater within an engineering context, and including hydraulic machinery, hydraulic structures, water supply, treatment and drainage systems. In Iverson Analysis, used of the average values of the time-dependent in the One-dimensional unsteady state. Rennie and Bunt investigated Operation of the hydraulic ram pump.
They studied various impulse valves and drive pipe diameters experimentally Young Harralson and Cozens Provided a rationale base for design goals of the ram pump and experiments planned and confirmation previous experiments with using the numerical method of characteristics. Schiller and Kahangire , with using numerical methods showed the exact theories to predict the performance of ram pumps are complex.
They assumed four phases in cycle of ram pump and Regardless of the effect of pressure waves during acceleration due to the complexity. In their model, increase speed or decrease spead during acceleration and duration of the impulse valve closure are linearly. Output model are quantity delivered, pump efficiency and cycle time. They concluded that a general empirical formula is difficult to compare different designs.
Results from this theory are compared with measurements of plexiglass model of a hydraulic ram. Verspuy and Tijsseling , described the operation of ram pump with a simple mathematical model. In their model fluid-structure interaction mechanisms are not included for the sake of simplicity.
These equations containing empirical factors dependent upon ram size, delivery head, material and wall thickness of the drive pipe and the configuration of the impulse valve. Young , presented a simplified analysis for ram pump action and offered four equations for design ram pumps. Najm et al. Maratos Investigated the relationship between quantity delivered and drive pipe diameter and checked the change of velosity in cycle time on the velosity-time diagram.
Suarda and Wirawan examined effect of air chamber on the ram pump performance. They showed that efficiency of the ram pumps without air chamber was obout 1 per cent and efficiency of the ram pump with air chamber was about 20 per cent.
O'Brien and Gosline carried out experiments on a 26 mm ram pump of the Gould type. In the O'Brien and Gosline experiments, the length of drive pipe was The static head to close impulse valve was 0. Lansford and Dugan performed three series of tests on each of two Rife ram pumps of diameters 51 mm and mm with different valve loads and strokes.
For 51 mm of ram pump, drive pipe length was The valve loading was not reported, thus it was not possible to determine values of static head to close impulse valve. Krol performed experiments on the 51mm ram pump. Valve strokes ranged from 1. The drive pipe length and the supply head were In the first, proposed an equation for predicting the efficiency of the ram pump using nonlinear regression. Then the results of the proposed equation are evaluated and compared with the Krol experiments data.
As well, with development of the hydro-informatics the Artificial Neural Network model has been used. The results of these models are statically compared according to the root mean square error RMSE , mean percentage error MPE , standard error of the estimate SEE , modeling efficiency EF , correlation coefficient R 2 and The gradient of regression line between results and observations, m, is calculated for evaluating the performance of the equation in a way that the intercept of the equation is zero.
It is worth noting that when the m value is close to one, the predicted results are close to the observations. The ranges of experimental data included in the present study are summarized in table 1. Unlike traditional linear regression, which is restricted to estimating linear models, nonlinear regression can estimate models with arbitrary relationship between independent and dependent variables.
In this study the statistical analysis was performed using nonlinear regression on the efficiency results using a statistical package for social sciences SPSS. In the present study, independent and dependent variables are h hm and qh Qc H respectively. The below equation is yielded from nonlinear regression to determine efficiency of the ram pump. ANN is one of the most common network models and generally presented a system of interconnected neurons which can compute values from inputs.
A neuron consists of multiple inputs and a single output. There is an input layer that acts as a distribution structure for the data being presented to the networks. This layer is not used for any type of processing. After this layer, one or more processing layers follow called the hidden layers.
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