Pressure probe compensates for dimensional tolerance variations

Flexible, compressible spring-loaded pressure probe measures the static pressure between the rotor stages on an axial-flow fuel pump. This probe is used in installation where a drilled static pressure tap or a rigid impulse tube cannot be used. Its parameters must be specially determined for each installation

How to make agricultural extension demand-driven?: The case of India's agricultural extension policy

"Many countries have recognized the need to revive agricultural advisory or extension services (the terms are used interchangeably here) as a means of using agriculture as an engine of pro-poor growth; reaching marginalized, poor, and female farmers; and addressing new challenges, such as environmental degradation and climate change. In spite of ample experience with extension reform worldwide, identifying the reform options most likely to make extension more demand-driven remains a major challenge. The concept of demand-driven services implies making extension more responsive to the needs of all farmers, including women and those who are poor and marginalized. It also implies making extension more accountable to farmers and, as a consequence, more effective. This essay discusses various options for providing and financing agricultural advisory services, which involve the public and private sectors as well as a third sector comprising nongovernmental organizations and farmer-based organizations. We review the market and state failures, and the “community” failures (failures of non-governmental and farmer-based organizations) inherent in existing models of providing and financing agricultural extension services and then outline strategies to address those failures and make extension demand-driven. Then we examine India's Policy Framework for Agricultural Extension, which has demand-driven extension as one of its major objectives, and review available survey information on the state of extension in India. We conclude that although the framework proposes a wide range of strategies to make agricultural extension demand-driven, it is less specific in addressing the challenges inherent in those strategies. Moreover, it remains unclear whether the strategies proposed in the framework will be able to address one of the major problems identified by farm household surveys: access to agricultural extension." from Authors' AbstractDemand-driven agricultural advisory services, Extension reform, Agricultural extension work, Agricultural policy, Pro-poor growth, Farmers, Environmental degradation, Climate change, Public-private sector cooperation, Non-governmental organizations,

Development of a relatchable cover mechanism for a cryogenic IR-sensor

A cover mechanism for use on the Infrared Background Signature Survey (IBSS) cryostat was developed. The IBSS IR-instrument is scheduled for STS launch in early 1991 as a payload of the Shuttle Payload Satellite (SPS) 2. The cover is hinged, with a motorized rope drive. During ground processing, launch, entry, and landing, the cryostat, which houses the IR-instrument, is required to be a sealed vacuum tight container for cooling purposes and contamination prevention. When on orbit, the cover is opened to provide an unobstructed field of view for the IR-instrument. A positive seal is accomplished through the use of latch mechanism. The cover and the latch are driven by a common redundant actuator consisting of dc motors, spur gears, and a differential gear. Hall probe limit switches and position sensors (rotary variable transformer) are used to determine the position of the cover and the latch. The cover mechanism was successfully qualified for thermal vacuum (-25 to 35 C), acoustic noise, vibration (6 Gs sine, 9.7 G RMS) and life cycles. Constricting requirements, mechanical and electronic control design, specific design details, test results of functional performance, and environmental and life tests are described

Promises and realities of community-based agricultural extension

In view of the market failures and the state failures inherent in providing agricultural extension, community-based approaches, which involve farmers‘ groups, have gained increasing importance in recent years as a third way to provide this service. The paper discusses the conceptual underpinnings of community-based extension approaches, highlights theoretical and practical challenges inherent in their design, and assesses the evidence available so far on their performance. The paper reviews both quantitative and qualitative studies, focusing on three examples that contain important elements of community-based extension: the National Agricultural Advisory Services program of Uganda, the agricultural technology management agency model of India, and the farmer field school approach. The review finds that in the rather few cases where performance has been relatively carefully studied, elite capture was identified as a major constraint. Other challenges that empirical studies found include a limited availability of competent service providers, deep-seated cultural attitudes that prevent an effective empowerment of farmers, and difficulties in implementing farmers‘ control of service providers‘ contracts. The paper concludes that, just as for the state and the market, communities can also fail in extension delivery. Hence, the challenge for innovative approaches in agricultural extension is to identify systems that use the potential of the state, the market, and communities to create checks and balances to overcome the failures inherent in all of them.agricultural extension, Agricultural technology, community-based development, empowerment of farmers, innovative approaches, market failures, National Agricultural Advisory Services program,

Negative quantum capacitance in graphene nanoribbons with lateral gates

We present numerical simulations of the capacitive coupling between graphene nanoribbons of various widths and gate electrodes in different configurations. We compare the influence of lateral metallic or graphene side gate structures on the overall back gate capacitive coupling. Most interestingly, we find a complex interplay between quantum capacitance effects in the graphene nanoribbon and the lateral graphene side gates, giving rise to an unconventional negative quantum capacitance. The emerging non-linear capacitive couplings are investigated in detail. The experimentally relevant relative lever arm, the ratio between the coupling of the different gate structures, is discussed.Comment: 8 pages, 6 figure

Soliton Propagation in Chains with Simple Nonlocal Defects

We study the propagation of solitons on complex chains built by inserting finite graphs at two sites of an unbranched chain. We compare numerical findings with the results of an analytical linear approximation scheme describing the interaction of large-fast solitons with non-local topological defects on a chain. We show that the transmission properties of the solitons strongly depend on the structure of the inserted graph, giving a tool to control the soliton propagation through the choice of pertinent graphs to be attached to the chain.Comment: Published in the special issue of Physica D from a conference on 'Nonlinear Physics: Condensed Matter, Dynamical Systems and Biophysics' held in honour of Serge Aubr

Nonequilibrium wetting transitions with short range forces

We analyze within mean-field theory as well as numerically a KPZ equation that describes nonequilibrium wetting. Both complete and critical wettitng transitions were found and characterized in detail. For one-dimensional substrates the critical wetting temperature is depressed by fluctuations. In addition, we have investigated a region in the space of parameters (temperature and chemical potential) where the wet and nonwet phases coexist. Finite-size scaling analysis of the interfacial detaching times indicates that the finite coexistence region survives in the thermodynamic limit. Within this region we have observed (stable or very long-lived) structures related to spatio-temporal intermittency in other systems. In the interfacial representation these structures exhibit perfect triangular (pyramidal) patterns in one (two dimensions), that are characterized by their slope and size distribution.Comment: 11 pages, 5 figures. To appear in Physical Review

Critical Behaviour of Non-Equilibrium Phase Transitions to Magnetically Ordered States

We describe non-equilibrium phase transitions in arrays of dynamical systems with cubic nonlinearity driven by multiplicative Gaussian white noise. Depending on the sign of the spatial coupling we observe transitions to ferromagnetic or antiferromagnetic ordered states. We discuss the phase diagram, the order of the transitions, and the critical behaviour. For global coupling we show analytically that the critical exponent of the magnetization exhibits a transition from the value 1/2 to a non-universal behaviour depending on the ratio of noise strength to the magnitude of the spatial coupling.Comment: 4 pages, 5 figure

Response of stratospheric water vapor and ozone to the unusual timing of El Niño and the QBO disruption in 2015–2016

The stratospheric circulation determines the transport and lifetime of key trace gases in a changing climate, including water vapor and ozone, which radiatively impact surface climate. The unusually warm El Niño–Southern Oscillation (ENSO) event aligned with a disrupted Quasi-Biennial Oscillation (QBO) caused an unprecedented perturbation to this circulation in 2015–2016. Here, we quantify the impact of the alignment of these two phenomena in 2015–2016 on lower stratospheric water vapor and ozone from satellite observations. We show that the warm ENSO event substantially increased water vapor and decreased ozone in the tropical lower stratosphere. The QBO disruption significantly decreased global lower stratospheric water vapor and tropical ozone from early spring to late autumn. Thus, this QBO disruption reversed the lower stratosphere moistening triggered by the alignment of the warm ENSO event with westerly QBO in early boreal winter. Our results suggest that the interplay of ENSO events and QBO phases will be crucial for the distributions of radiatively active trace gases in a changing future climate, when increasing El Niño-like conditions and a decreasing lower stratospheric QBO amplitude are expected