International Conference on Irrigation Management Transfer, Wuhan, China, 20-24 September 1994. Vol. 1. Draft conference papers.

Irrigation managementDamsLocal managementPrivatizationWater users' associationsCase studiesTube wellsIrrigation designLarge scale systemsPerformanceCost recoveryUser chargesSustainability

International Conference on Irrigation Management Transfer, Wuhan, China, 20-24 September 1994. Vol.3. Draft conference papers.

Irrigation managementIrrigation systemsFarmer participationPrivatizationSocial aspectsFarmers' associationsWater users' associationsTrainingPolicyFarmer participationEconomic aspectsFarmer managed irrigation systemsIrrigation programsRehabilitationWater resource management

International Conference on Irrigation Management Transfer, Wuhan, China, 20-24 September 1994. Vol.2. Draft conference papers.

IndonesiaAustraliaIndiaSri LankaNigeriaVietnamBangladeshDominican RepublicTanzaniaNigerPhilippinesColombiaEgyptUzbekistanPeruNepalMexicoThailandIrrigation managementDamsLocal managementPrivatizationWater users' associationsWater distributionCanal irrigationTube well irrigationSocial aspectsFarmers' associationsLand reformSustainability

Space shuttle orbiter auxiliary power unit development challenges

When the flying spacecraft was approved for development, a power unit for the hydraulic system had to be developed. Unlike other systems on the orbiter, there was no precedent in earlier spacecraft for a hydraulic system nor for the power unit to drive the hydraulic pumps. The only prototypes available were airplane auxiliary power units (APU), which were not required to operate in the severe environments of a spacecraft nor to have the longevity of an orbiter hydraulic power unit. The challenge was to build a hydraulic power unit which could operate in 0g or 3g, in a vacuum or at sea level pressure, and at -65 F or 225 F, which would be capable of restarting while hot, and which would be capable of sustaining the hydraulic loads for the life of the orbiter. The basic approach to providing hydraulic power for the orbiter was to use a small, high speed, monopropellant fueled turbine power unit to drive a conventional aircraft type hydraulic pump. The stringent requirements imposed on the orbiter APU quickly made this machine different from existing aircraft APUs

Gas-to-hydraulic power converter

A gas piston driven hydraulic piston pump is described in which the gas cycle is of high efficiency by injecting the gas in slugs at the beginning of each power stroke. The hydraulic piston is disposed to operate inside the as piston, and the two pistons, both slidably but nonrotatably mounted, are coupled together with a rotating but non-sliding motion transfer ring extending into antifriction grooves in the sidewalls of the two pistons. To make the hydraulic piston move at a constant speed during constant hydraulic horsepower demand and thus exert a constant pressure on the hydraulic fluid, these grooves are machined with variable pitches and one is the opposite of the other, i.e., the gas piston groove increases in pitch during its power stroke while the hydraulic piston groove decreases. Any number of piston assembly sets may be used to obtain desired hydraulic horsepower

Hydraulic calipers

Hydraulic calipers determine area of annular openings in irregular or concealed passages. With modifications the device could be adapted to investigations of cross-sectional changes in heat flow passages, ducts, conduits, and heat exchanger elements

Scaling behaviour of pressure driven micro hydraulic systems

This paper presents a lumped network approach for the modelling and design of micro-hydraulic systems. A hydraulic oscillator has been built consisting of hydraulic resistors, capacitors and transistors (pressure controlled valves). The scaling of micro-hydraulic networks consisting of linear resistors, capacitors and inertances has been studied. An important result is that to make smaller networks faster, driving pressures should increase with reducing size

Hydraulic actuator motion limiter ensures operator safety

Device regulates action of hydraulic linkage to control column to minimize hazard to operator. Primary components of device are flow rate control valve, limiter accumulator, and shutoff valve. Limiter may be incorporated into other hydraulic systems to prevent undue wear on hydraulic actuators and associated components

Distribution of xylem hydraulic resistance in fruiting truss of tomato influenced by water stress

In this study xylem hydraulic resistances of peduncles (truss stalk), pedicels (fruit stalk) and the future abscission zone (AZ) halfway along the pedicel of tomato (Lycopersicon esculentum L.) plants were directly measured at different stages of fruit development, in plants grown under two levels of water availability in the root environment. The xylem hydraulic connection between shoot and fruits has previously been investigated, but contradictory conclusions were drawn about the presence of a flow resistance barrier in the pedicel. These conclusions were all based on indirect functional measurements and anatomical observations of water-conducting tissue in the pedicel. In the present study, by far the largest resistances were measured in the AZ where most individual vessels ended. Plants grown at low water availability in the root environment had xylem with higher hydraulic resistances in the peduncle and pedicel segments on both sides of the AZ, while the largest increase in hydraulic resistance was measured in the AZ. During fruit development hydraulic resistances in peduncle and pedicel segments decreased on both sides of the AZ, but tended to increase in the AZ. The overall xylem hydraulic resistance between the shoot and fruit tended to increase with fruit development because of the dominating role of the hydraulic resistance in the AZ. It is discussed whether the xylem hydraulic resistance in the AZ of tomato pedicels in response to water stress and during fruit development contributes to the hydraulic isolation of fruits from diurnal cycles of water stress in the shoot

The hydraulic bump: The surface signature of a plunging jet

When a falling jet of fluid strikes a horizontal fluid layer, a hydraulic jump arises downstream of the point of impact provided a critical flow rate is exceeded. We here examine a phenomenon that arises below this jump threshold, a circular deflection of relatively small amplitude on the free surface, that we call the hydraulic bump. The form of the circular bump can be simply understood in terms of the underlying vortex structure and its height simply deduced with Bernoulli arguments. As the incoming flux increases, a breaking of axial symmetry leads to polygonal hydraulic bumps. The relation between this polygonal instability and that arising in the hydraulic jump is discussed. The coexistence of hydraulic jumps and bumps can give rise to striking nested structures with polygonal jumps bound within polygonal bumps. The absence of a pronounced surface signature on the hydraulic bump indicates the dominant influence of the subsurface vorticity on its instability