1,596 research outputs found
Changes in Climate and Potential Evapotranspiration Across a Large Irrigated Area in Idaho
Ground level climatic measurements
were taken along a 50
km transect going from dry sagebrush
land into the center of a large
irrigated area in southern Idaho.
Measurements in May, when the
desert area was dry, indicated
that climatic changes across the
transect were minimal. In August,
when the desert was obviously very
dry, air temperatures decreased,
vapor pressure increased, and
windspeed was reduced about
40 percent within the irrigated
area. The results demonstrate
that any weather service agency or
group must consider the distance
from dry surroundings when selecting
sites that are to be representative of
climatic conditions over irrigated
fields
Climate Modification of Dry Desert Air by a Large Irrigation Project
Climatic changes caused by the evapotranspiration
of large amounts of irrigation
water may be important in irrigation scheduling,
weather forecasting and the management of irrigated
farmland. Results from previous studies
are often in disagreement as to the magnitude of
climatic modification by irrigation. Some
studies show only minimal changes (Fritschen and
Nixon, 1967, Fowler and Helvey, 1974) and others
show sizeable modifications (Davenport and
Hudson, 1967). Beebe (1974) reports that severe
storms as indicated by tornado's are more prevalent
over irrigated land in Texas. A recent
statistical report (Schickendanz, 1976) shows
rainfall increases, temperature anomalities, and
hail increases, all caused by irrigation.
Schickendanz work covered a very large area in
the Great Plains of the United States. Previously
reported studies differ greatly in size of
area involved and objectives. The studies reported
here had the objective of showing the
possible climate modification caused by a large
irrigation project in Idaho surrounded by a nonirrigated
sagebrush grass desert
Convergence of chiral effective field theory
We formulate the expansion for the mass of the nucleon as a function of pion
mass within chiral perturbation theory using a number of different ultra-violet
regularisation schemes; including dimensional regularisation and various
finite-ranged regulators. Leading and next-to-leading order non-analytic
contributions are included through the standard one-loop Feynman graphs. In
addition to the physical nucleon mass, the expansion is constrained by recent,
extremely accurate, lattice QCD data obtained with two flavors of dynamical
quarks. The extent to which different regulators can describe the chiral
expansion is examined, while varying the range of quark mass over which the
expansions are matched. Renormalised chiral expansion parameters are recovered
from each regularisation prescription and compared. We find that the
finite-range regulators produce consistent, model-independent results over a
wide range of quark mass sufficient to solve the chiral extrapolation problem
in lattice QCD.Comment: 13 pages, 13 figures; To appear in Progress in Particle and Nuclear
Physics; presented at Erice School on Quarks in Hadrons and Nuclei, September
200
A Design Comparison of Atmospheric Flight Vehicles for the Exploration of Titan
Titan, the largest moon of Saturn, is one of the most scientifically interesting locations in the Solar System. With a very cold atmosphere that is five times as dense as Earth s, and one and a half times the surface pressure, it also provides one of the most aeronautically fascinating environments known to humankind. While this may seem the ideal place to attempt atmospheric flight, many challenges await any vehicle attempting to navigate through it. In addition to these physical challenges, any scientific exploration mission to Titan will most likely have several operational constraints. One difficult constraint is the desire for a global survey of the planet and thus, a long duration flight within the atmosphere. Since many of the scientific measurements that would be unique to a vehicle flying through the atmosphere (as opposed to an orbiting spacecraft) desire near-surface positioning of their associated instruments, the vehicle must also be able to fly within the first scale height of the atmosphere. Another difficult constraint is that interaction with the surface, whether by landing or dropped probe, is also highly desirable from a scientific perspective. Two common atmospheric flight platforms that might be used for this mission are the airplane and airship. Under the assumption of a mission architecture that would involve an orbiting relay spacecraft delivered via aerocapture and an atmospheric flight vehicle delivered via direct entry, designs were developed for both platforms that are unique to Titan. Consequently, after a viable design was achieved for each platform, their advantages and disadvantages were compared. This comparison included such factors as deployment risk, surface interaction capability, mass, and design heritage. When considering all factors, the preferred candidate platform for a global survey of Titan is an airship
Irrigation Management -- Water Requirements and Water Balance
This paper seeks to discuss irrigation water requirement estimates in the
light of current practice, important developments during the 1970's, significant
research and future research and applications of that research. Each of
these are elaborated in more detail in the text of this paper.
A major addition to the science and art of estimating irrigation water requirements
has been to replace the often ambiguous "potential evapotranspiration"
with "reference crop evapotranspiration". In the past decade a series of experiments
relating irrigation water applications to crop yield now permit a
much better economic analysis of the use of water for irrigation. The estimation
of monthly irrigation water requirements was facilitated, particularly
for varying climatic conditions with the United Nations publication "Crop
Water Requirements" by Doorenbos and Pruitt (1977).
Estimation of daily water requirements for purposes of irrigation scheduling
has been refined by the development of an albedo model and a wind function
for the Penman method, that is variable throughout the season, Wright (1981).
Several western states are experiencing lawsuits or other legal deliberations
involving seasonal irrigation water requirements because of conflicts between
groups of water users or water right transfers from agriculture to industry
or municipal use. Irrigation scheduling continues to be refined from the
standpoints of predicting ET, verifying yield conditions and other factors
like production and peak pumping power reduction. Future research probably
will include emphasis on breeding crops that require less water, refinements
on the relationships between yields and water consumption, refinements in
methods of estimating irrigation water requirements, and the development of
irrigation schemes that minimize water and energy requirements.
For other methods and more detail the reader is referred to sources such as
Doorenbos and Pruitt (1977), Jensen (1974), Barman. et al. (1981)
Water Requirements (Chapter 6)
The main objective of irrigation is to provide plants with sufficient water
to prevent stress that may cause reduced yield or poor quality of harvest
(Haise and Hagan, 1967; Taylor, 1965). The required timing and amount of
applied water is governed by the prevailing climatic conditions, crop and
stage of growth, soil moisture holding capacity, and the extent of root
development as determined by type of crop, stage of growth, and soil
Gold as an inflation hedge?
This paper attempts to reconcile an apparent contradiction between short-run and long-run movements in the price of gold. The theoretical model suggests a set of conditions under which the price of gold rises over time at the general rate of inflation and hence be an effective hedge against inflation. The model also demonstrates that short-run changes in the gold lease rate, the real interest rate, convenience yield, default risk, the covariance of gold returns with other assets and the dollar/world exchange rate can disturb this equilibrium relationship and generate short-run price volatility. Using monthly gold price data (1976-1999), and cointegration regression techniques, an empirical analysis confirms the central hypotheses of the theoretical model
An Assessment of the Current Data Affecting Tritium Retention and its Use to Project Towards T Retention in ITER
Accurate calculation of polarization-related quantities in semiconductors
We demonstrate that polarization-related quantities in semiconductors can be
predicted accurately from first-principles calculations using the appropriate
approach to the problem, the Berry-phase polarization theory. For III-V
nitrides, our test case, we find polarizations, polarization differences
between nitride pairs, and piezoelectric constants quite close to their
previously established values. Refined data are nevertheless provided for all
the relevant quantities.Comment: RevTeX 4 pages, no figure
Religion and religious education : comparing and contrasting pupilsâ and teachersâ views in an English school
This publication builds on and develops the English findings of the qualitative study of European teenagersâ perspectives on religion and religious education (Knauth et al. 2008), part of âReligion in Education: A contribution to dialogue or a factor of conflict in transforming societies of European countries?â (REDCo) project. It uses data gathered from 27 pupils, aged 15-16, from a school in a multicultural Northern town in England and compares those findings with data gathered from ten teachers in the humanities faculty of the same school, collected during research for the Warwick REDCo Community of Practice. Comparisons are drawn between the teachersâ and their pupilsâ attitudes and values using the same structure as the European study: personal views and experiences of religion, the social dimension of religion, and religious education in school. The discussion offers an analysis of the similarities and differences in worldviews and beliefs which emerged. These include religious commitment/observance differences between the mainly Muslim-heritage pupils and their mainly non-practising Christian-heritage teachers. The research should inform the ways in which the statutory duties to promote community cohesion and equalities can be implemented in schools. It should also facilitate intercultural and interreligious understanding between teachers and the pupils from different ethnic and religious backgrounds
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