14,165 research outputs found
Slug grazing effects on seedling and adult life stages of North American Prairie plants used in designed urban landscapes
Designed vegetation is a major contributor to ecosystem service provision incities, and as such the study of how herbivory and other ecological factors determine its
capacity to deliver such services, is long overdue. This study investigated the effect of slug grazing on the establishment and development of 26 species of North American prairie forbs and grasses used in sown or planted naturalistic communities in urban greenspace. The experiment was designed to provide slugs with the opportunity to choose between the plant species used, to mirror the situation that prevails in public greenspace. Slug density was manipulated through baiting with metaldehyde at different frequencies. Seedlings of prairie species were more palatable to slugs than adults.
Seedling establishment was significantly reduced in most species by slug grazing, with only seven species showing no significant increase in establishment in response to
baiting with metaldehyde. In many species successful establishment was based on moderate-high unpalatability and large or fast growing seedlings. Adult prairie plants
were typically more able to withstand slug damage, and once their shoots reached a certain size, grazing declined. This was not true of the most palatable species, which
even as adults were eventually eliminated by grazing in the absence of baiting. Phenology plays an important role in the survival of adults, with early emerging species
potentially subject to severe damage due to the limited availability of alternate food plants. As a group, prairie forbs are typically palatable to slugs, and unlikely to be
persistent in the most slug-rich urban situations
Treebank Embedding Vectors for Out-of-domain Dependency Parsing
A recent advance in monolingual dependency parsing is the idea of a treebank
embedding vector, which allows all treebanks for a particular language to be
used as training data while at the same time allowing the model to prefer
training data from one treebank over others and to select the preferred
treebank at test time. We build on this idea by 1) introducing a method to
predict a treebank vector for sentences that do not come from a treebank used
in training, and 2) exploring what happens when we move away from predefined
treebank embedding vectors during test time and instead devise tailored
interpolations. We show that 1) there are interpolated vectors that are
superior to the predefined ones, and 2) treebank vectors can be predicted with
sufficient accuracy, for nine out of ten test languages, to match the
performance of an oracle approach that knows the most suitable predefined
treebank embedding for the test set.Comment: Camera ready for ACL 202
Least Reliable Bits Coding (LRBC) for high data rate satellite communications
An analysis and discussion of a bandwidth efficient multi-level/multi-stage block coded modulation technique called Least Reliable Bits Coding (LRBC) is presented. LRBC uses simple multi-level component codes that provide increased error protection on increasingly unreliable modulated bits in order to maintain an overall high code rate that increases spectral efficiency. Further, soft-decision multi-stage decoding is used to make decisions on unprotected bits through corrections made on more protected bits. Using analytical expressions and tight performance bounds it is shown that LRBC can achieve increased spectral efficiency and maintain equivalent or better power efficiency compared to that of Binary Phase Shift Keying (BPSK). Bit error rates (BER) vs. channel bit energy with Additive White Gaussian Noise (AWGN) are given for a set of LRB Reed-Solomon (RS) encoded 8PSK modulation formats with an ensemble rate of 8/9. All formats exhibit a spectral efficiency of 2.67 = (log2(8))(8/9) information bps/Hz. Bit by bit coded and uncoded error probabilities with soft-decision information are determined. These are traded with with code rate to determine parameters that achieve good performance. The relative simplicity of Galois field algebra vs. the Viterbi algorithm and the availability of high speed commercial Very Large Scale Integration (VLSI) for block codes indicates that LRBC using block codes is a desirable method for high data rate implementations
Auditing database systems through forensic analysis
The majority of sensitive and personal data is stored in a number of different Database Management Systems (DBMS). For example, Oracle is frequently used to store corporate data, MySQL serves as the back-end storage for many webstores, and SQLite stores personal data such as SMS messages or browser bookmarks. Consequently, the pervasive use of DBMSes has led to an increase in the rate at which they are exploited in cybercrimes. After a cybercrime occurs, investigators need forensic tools and methods to recreate a timeline of events and determine the extent of the security breach. When a breach involves a compromised system, these tools must make few assumptions about the system (e.g., corrupt storage, poorly configured logging, data tampering). Since DBMSes manage storage independent of the operating system, they require their own set of forensic tools.
This dissertation presents 1) our database-agnostic forensic methods to examine DBMS contents from any evidence source (e.g., disk images or RAM snapshots) without using a live system and 2) applications of our forensic analysis methods to secure data. The foundation of this analysis is page carving, our novel database forensic method that we implemented as the tool DBCarver. We demonstrate that DBCarver is capable of reconstructing DBMS contents, including metadata and deleted data, from various types of digital evidence. Since DBMS storage is managed independently of the operating system, DBCarver can be used for new methods to securely delete data (i.e., data sanitization). In the event of suspected log tampering or direct modification to DBMS storage, DBCarver can be used to verify log integrity and discover storage inconsistencies
Source efficiency and sensor detectability factors in laser ultrasonics
Perhaps the greatest fundamental deterrent to the application of current laser ultrasonic technology has been the fact that the detection sensitivity or detectability of laser receiver systems, compared with their piezoelectric counterparts, is rather poor. That is to say that in general, and especially on a dollar-for-dollar basis, piezoelectric transducers are able to detect much smaller surface displacements than can easily be detected by laser methods. As will be discussed shortly, there are several strategies which may be used to overcome these detectability shortcomings. Indeed, several of these strategies have been investigated at the laboratory level and some implemented in full-scale systems which have been demonstrated to perform reliably and with good detectability even in an industrial or field inspection application [1]. In this latter case, however, the successful strategy pursued to improve laser ultrasonic detectability limits has not been inexpensive in terms of the cost of laser equipment necessary to reach satisfactory performance levels. Nevertheless, there are several inspection and process control applications where critical structural and materials property information can only be obtained by remote noncontact ultrasonic inspection, thus justifying the expense of such a sensor system
Physics of non-Gaussian fields and the cosmological genus statistic
We report a technique to calculate the impact of distinct physical processes
inducing non-Gaussianity on the cosmological density field. A natural
decomposition of the cosmic genus statistic into an orthogonal polynomial
sequence allows complete expression of the scale-dependent evolution of the
morphology of large-scale structure, in which effects including galaxy bias,
nonlinear gravitational evolution and primordial non-Gaussianity may be
delineated. The relationship of this decomposition to previous methods for
analysing the genus statistic is briefly considered and the following
applications are made: i) the expression of certain systematics affecting
topological measurements; ii) the quantification of broad deformations from
Gaussianity that appear in the genus statistic as measured in the Horizon Run
simulation; iii) the study of the evolution of the genus curve for simulations
with primordial non-Gaussianity. These advances improve the treatment of
flux-limited galaxy catalogues for use with this measurement and further the
use of the genus statistic as a tool for exploring non-Gaussianity.Comment: AASTeX preprint, 24 pages, 8 figures, includes several improvements
suggested by anonymous reviewe
Applied solar energy at the Shiraz Technical Institute
Factors affecting the application of solar energy and the preliminary design of a solar system to supplement the service hot water system at the Shiraz
Technical Institute are described. In addition to the solar energy demonstration, the educational benefits of selected solar projects and laboratory experiments are discussed. An effective, yet expandable, initial installation can be
made at reasonably low cost because advantage is taken of architectural features
of the buildings and the nature of the conventional service hot water heating
system. Opportunities for the future are also briefly considered
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