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This study aims to investigate the hydraulic behaviour of a pilot-scale, two-staged, vertical flow constructed wetland (VFCW) for septage treatment, in terms of factors such as hydraulic retention time and hydraulic loading rate and its influence on the treatment dynamics. Because of intermittent feeding mode of VFCW systems and variation in its loading, its hydraulic behaviour is highly variable and need to be understood to optimize its treatment performance.

Tracer test were carried out using bromide ion with varying hydraulic loading rates (HLR) of 6.82 cm/d, 9.09 cm/d and 11.40 cm/d (i.e. equivalent to 75 L/d, 100L/d and 125 L/d). Tracer data is then analysed using the Residence Time Distribution (RTD) method.

RTD analysis showed that the increase in HLR increases the average hydraulic retention time (HRT). Subsequently, the increase in HLR results in a lower recovery of effluent, resulting in poor productivity in treatment. The study also showed that the removal of nitrogen and organic matter improved with increasing HRT. However, observations show no correlation between HRT and total solids removal.

A performance evaluation method (by tracer) is proposed to understand the hydraulics of flow in constructed wetlands, which has not been widely studied. Additionally, the dynamics of treatment in VFCWs treating septage may also be revealed by the tracer method. The study can be applied to any constructed wetlands designed for treatment of wastewater, septage or sludge.

The treatment performance of two‐stage secondary treatment consisting of a trickling filter followed by activated sludge process for treatment of combined municipal and industrial wastewater is determined. The municipal wastewater treatment plant is located in Solon, Ohio, where the treatment units include grit tanks, primary clarifiers, trickling filters, aeration tanks, secondary clarifiers, tertiary filters and chlorine contact tanks. The treatment performance data for a 12‐month period in 1989 was evaluated. The average total plant flow was 2.82 MGD (millions gallons per day) which consisted of 2.19 MGD industrial wastewater and 0.63 MGD domestic wastewater. Raw wastewater was of a high strength mainly due to the contribution from industrial sources. After different degrees of treatment the values of total suspended solids (TSS) and biochemical oxygen demand (BOD) met US Environmental Protection Agency standards. This plant has good treatment performance with 99 per cent BOD and 98 per cent TSS removal efficiencies.

The purpose of this paper is to evaluate the green energy generation potential of the organic fraction of municipal solid waste (OFMSW) through anaerobic digestion (AD) route in India and its benefits.

In this study, performances of some AD plants presently operating successfully in India have been studied in the field (Section 3.1). Primary data collected from this study has been used to evaluate the biogas generation potential of OFMSW in Indian condition (Section 4). To ensure the validity, this gas generation potential has been compared with the gas yield data observed by the other researchers and with the gas yields of AD plants of some technology providers at some parts of the world (Section 4.1). From the future population projection (year 2030) and the future per capita waste generation rate obtained from the literature survey, estimation has been made for future quantity of municipal solid waste (MSW) (year 2030) (Section 2.3). Based on these data, the green energy generation potential from the bio-degradable portion of MSW through AD route, in India, has been evaluated (Section 4.2), and its economic and environmental benefits have been analyzed (Section 5) .

This secondary research work reveals that from the bio-degradable portion of MSW, India can generate about 583 MW of green energy daily and produce about 5.1 mil MT of bio fertilizer per annum presently, and these may go up to 2,273 MW and 19.5 mil MT, respectively, in the year 2030. Generation of green energy from OFMSW, in India, may save coal consumption of about 3.04 mil MT and reduce 35.42 mil MT of CO₂ emissions per annum presently. Moreover, utilization of the bio-degradable portion of the MSW stream may save about 550 acres (2.23 sq. km) of landfill area per year presently and in total may save about 8,182 hectare (82.5 sq. km) of landfill area during the period of 15 years time.

The population growth and future per capita waste generation rate are based on census report of Govt of India and survey report of World Bank, respectively. Separate collection of bio-degradable portion of MSW has not yet been developed properly in India.

This study reveals that in India, the high-moisture-content, low-calorific-value bio-degradable waste in India can be used for the generation of substantial amount of green energy in India, which in addition to financial gains would reduce the waste quantity at landfill site, conserve natural resources, save land, reduce green house gas emission, generate employment and help to protect environment. Considering these benefits and advantages, evaluated in this study, policy makers and city managers may review their approaches toward solid waste management system of their cities to meet the challenges of huge increase of MSW in the years to come in India. More research works may be initiated to improve the AD system of organic waste, and more capital may be employed in waste management business in India.

Numbers of research works have been carried out by other researchers for estimation of energy generation potential through AD of OFMSW for different countries; but no such work could be found to identify such potential and its benefits in India. This research work demonstrates how MSW can be used as a wealth for green energy production in India. The originality of this paper is the analysis of green energy generation potential from the low calorific value MSW in India.

The breakdown of laminar flow in the clearance space of a journal is considered, and the point of transition is considered in relation to experiments carried out with ‘bearings’ of large clearance. Experiments involving flow visualization with very large clearance ratios of 0.05 to 0.3 show that the laminar regime gives way to cellular or ring vertices at the critical Reynolds number predicted by G. I. Taylor for concentric cylinders even in the presence of an axial flow and at a rather higher Reynolds number in the case of eccentric cylinders. The effect of the transition on the axial flow between the cylinders is small. The critical speed for transition as deduced by Taylor, is little affected by moderate axial flows and is increased by eccentricity. The effect of critical condition on the axial‐flow characteristics of the bearing system appears to be negligible, again for moderate axial flows. Assuming that the results can be extrapolated to clearances applicable to bearing operation, the main conclusion of this paper is that the breakdown of laminar flow, which is a practical possibility in very high‐speed bearings, is delayed by eccentric operation.

The purpose of this paper is to develop a novel type of full‐size flight control iron bird based on a passive electronic hydraulic servo loading system.

On the basis of mathematical modeling of passive loading system math model, the detailed design process of the flight control iron bird is presented. Subsequently, the system digital simulation and physical verification are also given.

Experimental results show that the proposed approach can reduce the redundant forces and improve the system dynamic and force‐tracking accuracy.

This newly‐developed flight control iron bird system has been successfully applied in the flight control system design of some fighters.

The proposed approach for flight control iron bird is new and significant for the design of fighter flight control systems.

It is well known that the prefabricated vertical drain (PVD) installation process generates a significant soil disturbance around PVD. This disturbed zone significantly affects the rate of settlement and excess pore pressure dissipation. However, the characteristics of these zones were still uncertain and difficult to quantify; there remains large discrepancy among researchers. This study aims to develop a simple analytical solution for radial consolidation analysis of PVD-installed deposit considering mandrel-induced disturbance.

The proposed solution takes into account the nonlinear distributions of both horizontal hydraulic conductivity and compressibility toward the drain. The proposed solution was applied to analyze field behavior of test embankment in New South Wales, Australia.

Both effects significantly increased the time required to achieve a certain degree of consolidation. The effect of hydraulic conductivity on the consolidation rate was more significant than the effect of compressibility variation. And, the increased compressibility in the soil-disturbed zone due to mandrel installation significantly increased vertical strain of the PVD-improved soil deposit. The predicted results using the proposed analytical solution were in good agreement with the field measurements.

A geotechnical engineer could use the proposed analytical solution to predict consolidation behavior of drainage-installed ground.

Consolidation behavior of PVD-installed ground could be reasonably predicted by using the proposed solution with considering variations of both hydraulic conductivity and compressibility due to PVD installation.

The aim of this paper is to investigate hydraulic system performance using vegetable‐based palm oil as hydraulic fluid.

The hydraulic system performance test at different operating conditions, such as pressure, speed and oil ageing, was performed using a Yuken vane pump test rig. The endurance system performance test was also conducted for 200 and 400 h. The effect of speed on flow slip coefficient in discrete and continuous tests was studied. In discrete testing, pressure of 35 and 200 bar and speed of 750 and 1,439 rpm were used in determining flow slip coefficient. The instantaneous data were recorded in a computer using an analog‐to‐digital data acquisition system with respect to time and the parameters stored were reservoir temperature, return line temperature, suction and delivery pressures, instantaneous flow rate, total flow, total running time and torque. The obtained results were interpolated for future prediction of the system performance.

The experimental and interpolated results showed that slip coefficient decreases with increasing pump speed. The effect of aging condition on volumetric efficiency showed that the efficiency increases with aging period due to increase in oil viscosity.

This vegetable‐based palm oil could be a potentially useful substitute for mineral‐based energy transport media such as hydraulic fluid.

The investigation of hydraulic system performance using palm oil as hydraulic fluid is scarce in the literature. Therefore, the current study is quite new for the hydraulic system performance and it is hoped that it will provide a high value to researchers for further research before it can be used as hydraulic fluid.

A method for optimizing net positive suction head required of axial‐flow pumps has been proposed by the present author, which is based on the two‐dimensional potential flow model and without considering the tip gap effect. The objective of the paper is to confirm if the method is just and feasible for the case of viscous fluid flow in impellers with tip gap.

A series of steady, three‐dimensional, noncavitating and cavitating, turbulent, incompressible flows of water through two axial‐flow pump impellers were calculated by using CFD code Fluent. The two impellers included a reference one with constant circulation at outlet and an optimized one with variable circulation designed with the author's method and code. In computations, the throttling and unthrottling approaches were used, respectively. Comparison of hydraulic performance, averaged flow variables at the impeller inlet and exit, flow in the tip gap, flow variables on blade surfaces and suction performance between the optimized and reference impellers was made.

It was confirmed that the optimized impeller has better hydraulic and suction performances. The method for optimizing with variable flow circulation profile along blade span at the outlet to impeller is proper and practical. Additionally, an unstable regime in the head curves of two impellers is presented. In the regime, a stall occurs on the pressure side of the blade and a hysteresis exists, which causes a hysteresis‐loop.

The effect of suction entry on flow is represented approximately by using a free‐vortex and uniform axial velocity. The diffusing component behind the impellers is not taken into account. The unsteadiness of flow is not considered, which would have a connection with stall pattern in an axial‐flow impeller.

The hydraulic and suction performances and flow variables of two axial‐flow pump impellers with tip clearance are obtained successfully with CFD. Stall and hysteresis as well as hysteresis‐loop in head curve are observed by using throttling and unthrottling approaches.

FOR a number of years now it has been evident that a successor to the well‐tried Vickers Viscount and Convoir 240/340/440 series was required. However, the big problem was to design an aircraft such that its economics and passengerappealweresub‐stantially better than the machines it would ultimately replace. Other important factors which had to be con‐sidered were improved reliability, easier and cheaper maintenance, higher standards of safety and means of reducing ramp times. Furthermore, the difficult choice of passenger capacity and cruising speed had to be made. Probably the easiest decision was to employ the twin‐engine configuration with the power plants placed in the now familiar rear position, one on cither side of the fuselage.

IN a departure from usual practice this issue concentrates to a large extent upon a single subject — Mechanical Handling. It coincides with that industry's exhibition at Earls Court from the 9th to 19th of this month, to be opened by the Rt. Hon. Christopher Chataway, M.P., Minister for Industrial Development. In consequence it was necessary to defer some regular features for a time, for which we apologise.