39,995 research outputs found
EFFECTIVE SEDIMENT CONTROL IN A RESERVOIR
Sedimentation in a reservoir cannot be avoided. The average rate of sedimentation on the storage volume reduction of a reservoir in the world is about 1 % per year (Yoon,1992), meanwhile, the storage volume reduction in several reservoir in Indonesia reaches 1,64% to 2,83% per year (Atmojo,2012). These sediment’s accumulations in the reservoir will continually reduce the storage volume, thus the intended
functions of reservoirs for flood control (Atmojo, 2013), irrigation and water supply, electric generation, etc. will also reduced and not optimal.
Some of sediment control measures have been practiced in reducing sediment accumulation in reservoirs around the world. In principle, there are two approaches i.e., reduce the sediment input to a reservoir by land conservation, construction of check dam, sand pocket, diversion channel, etc. and reduce the sedimentation in the reservoir by sluicing, turbidity current, dredging, and flushing (Morris and Fan, 1998; Emamgholizadeh et al., 2006).
This paper presents the performance of sediment’s reduction from a reservoir by flushing, sluicing, and disturbing flushing based on some laboratories results (Atmojo,2012). It is expected that this paper can contribute to elicits some finding on the selection of which suitable method for sediment reduction from a reservoir
Advanced flight control system study
A fly by wire flight control system architecture designed for high reliability includes spare sensor and computer elements to permit safe dispatch with failed elements, thereby reducing unscheduled maintenance. A methodology capable of demonstrating that the architecture does achieve the predicted performance characteristics consists of a hierarchy of activities ranging from analytical calculations of system reliability and formal methods of software verification to iron bird testing followed by flight evaluation. Interfacing this architecture to the Lockheed S-3A aircraft for flight test is discussed. This testbed vehicle can be expanded to support flight experiments in advanced aerodynamics, electromechanical actuators, secondary power systems, flight management, new displays, and air traffic control concepts
NASA Tech Briefs Index, 1977, volume 2, numbers 1-4
Announcements of new technology derived from the research and development activities of NASA are presented. Abstracts, and indexes for subject, personal author, originating center, and Tech Brief number are presented for 1977
Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project: Current and advanced act control system definition study. Volume 2: Appendices
The current status of the Active Controls Technology (ACT) for the advanced subsonic transport project is investigated through analysis of the systems technical data. Control systems technologies under examination include computerized reliability analysis, pitch axis fly by wire actuator, flaperon actuation system design trade study, control law synthesis and analysis, flutter mode control and gust load alleviation analysis, and implementation of alternative ACT systems. Extensive analysis of the computer techniques involved in each system is included
Aeronautical Engineering: A special bibliography, supplement 60
This bibliography lists 284 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1975
Advanced flight control system study
The architecture, requirements, and system elements of an ultrareliable, advanced flight control system are described. The basic criteria are functional reliability of 10 to the minus 10 power/hour of flight and only 6 month scheduled maintenance. A distributed system architecture is described, including a multiplexed communication system, reliable bus controller, the use of skewed sensor arrays, and actuator interfaces. Test bed and flight evaluation program are proposed
Root Zone Sensors for Irrigation Management in Intensive Agriculture
Crop irrigation uses more than 70% of the world’s water, and thus, improving irrigation efficiency is decisive to sustain the food demand from a fast-growing world population. This objective may be accomplished by cultivating more water-efficient crop species and/or through the application of efficient irrigation systems, which includes the implementation of a suitable method for precise scheduling. At the farm level, irrigation is generally scheduled based on the grower’s experience or on the determination of soil water balance (weather-based method). An alternative approach entails the measurement of soil water status. Expensive and sophisticated root zone sensors (RZS), such as neutron probes, are available for the use of soil and plant scientists, while cheap and practical devices are needed for irrigation management in commercial crops. The paper illustrates the main features of RZS’ (for both soil moisture and salinity) marketed for the irrigation industry and discusses how such sensors may be integrated in a wireless network for computer-controlled irrigation and used for innovative irrigation strategies, such as deficit or dual-water irrigation. The paper also consider the main results of recent or current research works conducted by the authors in Tuscany (Italy) on the irrigation management of container-grown ornamental plants, which is an important agricultural sector in Italy
Morphology of rain water channelization in systematically varied model sandy soils
We visualize the formation of fingered flow in dry model sandy soils under
different raining conditions using a quasi-2d experimental set-up, and
systematically determine the impact of soil grain diameter and surface wetting
property on water channelization phenomenon. The model sandy soils we use are
random closely-packed glass beads with varied diameters and surface treatments.
For hydrophilic sandy soils, our experiments show that rain water infiltrates
into a shallow top layer of soil and creates a horizontal water wetting front
that grows downward homogeneously until instabilities occur to form fingered
flows. For hydrophobic sandy soils, in contrast, we observe that rain water
ponds on the top of soil surface until the hydraulic pressure is strong enough
to overcome the capillary repellency of soil and create narrow water channels
that penetrate the soil packing. Varying the raindrop impinging speed has
little influence on water channel formation. However, varying the rain rate
causes significant changes in water infiltration depth, water channel width,
and water channel separation. At a fixed raining condition, we combine the
effects of grain diameter and surface hydrophobicity into a single parameter
and determine its influence on water infiltration depth, water channel width,
and water channel separation. We also demonstrate the efficiency of several
soil water improvement methods that relate to rain water channelization
phenomenon, including pre-wetting sandy soils at different level before
rainfall, modifying soil surface flatness, and applying superabsorbent hydrogel
particles as soil modifiers
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