Conservation Agriculture and Climate Resilience

Climate change is predicted to increase the number and severity of extreme rainfall events, especially in Sub-Saharan Africa. In response, development agencies are encouraging the adoption of ‘climate-smart’ agricultural techniques, such as Conservation Agriculture (CA). However, little rigorous evidence exists to demonstrates the effect of CA on production or climate resilience, and what evidence there is, is hampered by selection bias. Using panel data from Zimbabwe, we test how CA performs during extreme rainfall events - both shortfalls and surpluses. We control for the endogenous adoption decision and find that while CA has little, or if anything, a nega-tive effect on yields during periods of average rainfall, it is effective in mitigating the negative impacts of rainfall shocks. Farmers who practice CA tend to receive higher yields compared to conventional farmers in years of both low and high rainfall. We conclude that the lower yields during normal rainfall seasons may be a proximate factor in low uptake of CA. Policy should focus promotion of CA on these climate resiliency benefits

Conservation agriculture and climate resilience

Agricultural productivity growth is vital for economic and food security outcomes which are threatened by climate change. In response, governments and development agencies are encouraging the adoption of ‘climate-smart’ agricultural technologies, such as conservation agriculture (CA). However, there is little rigorous evidence that demonstrates the effect of CA on production or climate resilience, and what evidence exists is hampered by selection bias. Using panel data from Zimbabwe, we test how CA performs during extreme rainfall events - both shortfalls and surpluses. We control for the endogenous adoption decision and find that use of CA in years of average rainfall results in no yield gains, and in some cases yield loses. However, CA is effective in mitigating the negative impacts of deviations in rainfall. We conclude that the lower yields during normal rainfall seasons may be a proximate factor in low uptake of CA. Policy should focus promotion of CA on these climate resilience benefits

TWO-WEEK LOAN COpy LBL-20235 PHASE AND AMPLITUDE CONTROL OF THE RADIO FREQUENCY WAVE IN THE TWO-BEAM ACCELERATOR*

ABSTRACT The sensitivity of the radio frequency (rf) wave generated by the free electron laser portion of a Two-Beam Accelerator (TBA) is analyzed, both analytically and numerically in a "resonant particle" approximation. It is shown that the phase of the rf wave is strongly dependent upon errors in the wiggler strength and wavelength and upon the electron beam characteristics of energy and current. The resulting phase error is shown to be unacceptable for a TBA, given reasonable errors in various components. A feedback system is proposed which will keep the rf wave phase within acceptable bounds. However, the feedback system is, at best, cumbersome and a simpler system would be desirable

A Study of Irregularities in File-Size Distributions

Understanding file sizes is critical to designing and evaluating filesystems. To uncover the effects of audio and video on the distributions found by previous studies, we gathered and analyzed data from a number of different systems at a small undergraduate institution, and attempted to fit curves to the observed size distributions. We found that audio files are already changing the size distributions found in previous years, and video files appear to be starting to do the same. We also found that popular distributions fit poorly in terms of statistical reliability, and that anomalous spikes in distributions are the norm. We discuss the reasons for the failure to achieve fits and implications for file system design and simulation

Conservation Agriculture and Climate Resilience

Climate change is predicted to increase the number and severity of extreme rainfall events, especially in Sub-Saharan Africa. In response, development agencies are encouraging the adoption of `climate-smart' agricultural techniques, such as conservation agriculture (CA). However, little rigorous evidence exists to demonstrates the effect of CA on production or climate resilience, and what evidence there is, is hampered by selection bias. Using panel data from Zimbabwe, we test how CA performs during extreme rainfall events - both shortfalls and surpluses. We control for the endogenous adoption decision and find that while CA has little, or if anything, a negative effect on yields during periods of average rainfall, it is effective in mitigating the negative impacts of rainfall shocks. Households that practice CA tend to receive higher yields compared to households using conventional methods in years of both low and high rainfall. We conclude that the lower yields during normal rainfall seasons may be a proximate factor in low uptake of CA. Policy should focus promotion of CA on these climate resiliency benefits. Acknowledgement

Phase and Amplitude Considerations for the Two-Beam Accelerator

Phase and amplitude considerations are made for a Two-Beam Accelerator and analytic formulas are obtained expressing the phase and amplitude errors in terms of magnetic wiggler errors, beam energy errors, beam current errors, and microwave field amplitude errors. The necessity of phase and amplitude control is shown and schemes are proposed which can accomplish this control

Extended tuning of distributed-feedback lasers in a bias-tee circuit via waveform optimization for MHz-rate absorption spectroscopy

International audienceVariations in injection-current waveform are examined using diplexed RF-modulation with continuouswave distributed-feedback (CW-DFB) lasers, with the aim to maximize the spectral tuning range and signal-tonoise ratio for MHz-rate laser absorption spectroscopy. Utilizing a bias-tee circuit, laser chirp rates are shown to increase by modulating the AC input voltage using square waves instead of sine waves and by scanning the laser below the lasing threshold during the modulation period. The effect of waveform duty cycle and leadingedge ramp rate are further examined. A spectral scan depth on the order of 1 cm −1 at a scan frequency of 1 MHz is achieved with a representative CW-DFB quantum cascade laser near 5 µm. Distortion of high-frequency optical signals due to detector bandwidth is also examined, and limitations are noted for applications with narrow spectral features and low-bandwidth detectors. Based on common detection system limitations, an optimization approach is established for a given detection bandwidth and target spectra. A representative optimization is presented for measurements of sub-atmospheric carbon monoxide spectra with a 200-MHz detection system. The methods are then demonstrated to resolve transient gas properties (pressure and temperature) via laser absorption spectroscopy at MHz rates in a detonation tube and shock tube facility. An appendix detailing a first-order model of high-speed distributed feedback laser tuning dynamics is also included to support the experimental observations of this work

Experience with an Automated Hoarding System

Hoarding is a technique in which a portable computer caches files before disconnecting from a network, so that the files will be available during the disconnection period. Predictive hoarding extends this approach to automatically predict the set of files that should be hoarded. We report the results of a study of the SEER predictive hoarding system, which examined both live and simulated usage. This is by far the most detailed study of hoarding that has been carried out to date. Our results show not only that predictive hoarding is feasible, but that SEER has excellent performance that significantly improves disk-space usage on mobile computers