Coastal ecosystem restoration is accelerating globally as a means of enhancing shoreline protection, carbon storage, water quality, fisheries, and biodiversity. Among the most substantial of these ...efforts have been those focused on re-establishing oyster reefs across the US Atlantic and Gulf coasts. Despite considerable investment, it is unclear how the scale of and approaches toward oyster restoration have evolved. A synthesis of 1768 projects undertaken since 1964 reveals that oyster substrate restoration efforts have primarily been concentrated in the Chesapeake Bay and the Gulf Coast, have been heavily reliant on oyster shell, and have re-established 4.5% of the reef area that has been lost across all regions. By comparing costs to ecosystem service benefits, we discovered that the return-on-investment of oyster restoration varies widely, but generally increases with project size. To facilitate the recovery of coastal ecosystems and their services, scientists and resource managers must adopt a new restoration paradigm prioritizing investment in sites that maximize economic and ecological benefits and minimize construction costs.
To reduce the computation burden and eliminate the weighting factor in conventional speed prediction control, a direct voltage-vector selection-based model-predictive direct-speed control (MP-DSC) ...method is proposed in this paper. An extended sliding-mode load-torque observer is designed to observe the motor speed and the load torque, which improves the robustness of the system and reduces the influence of measurement noise. Then, the reference voltage vector that includes the system speed and current information is predicted based on the deadbeat control principle. This reference voltage vector is used to construct a cost function, which only includes the error between the reference voltage vector and the candidate voltage vector. Thus, the weighting factor in conventional MP-DSC method is avoided in the proposed method. In addition, a voltage-vector selection method is developed to quickly determine candidate voltage vectors and to ensure the current does not exceed current limit. Finally, the proposed MP-DSC method is experimentally compared with a model-predictive torque and speed control.
Building information models (BIMs) are increasingly being applied throughout a building's lifecycle for various applications, such as progressive construction monitoring and defect detection, ...building renovation, energy simulation, and building system analysis in the Architectural, Engineering, Construction, and Facility Management (AEC/FM) domains. In conventional approaches, as-is BIM is primarily manually created from point clouds, which is labor-intensive, costly, and time consuming. This paper proposes a method for automatically extracting building geometries from unorganized point clouds. The collected raw data undergo data downsizing, boundary detection, and building component categorization, resulting in the building components being recognized as individual objects and their visualization as polygons. The results of tests conducted on three collected as-is building data to validate the technical feasibility and evaluate the performance of the proposed method indicate that it can simplify and accelerate the as-is building model from the point cloud creation process.
•A method of automatic building geometry extraction from point cloud is proposed.•Components of building envelope were recognized and modeled from point clouds.•The proposed method was validated by testing on three as-is building data.
N-jettiness subtractions for NNLO QCD calculations Gaunt, Jonathan R.; Stahlhofen, Maximilian; Tackmann, Frank J. ...
The journal of high energy physics,
09/2015, Volume:
2015, Issue:
9
Journal Article
Peer reviewed
Open access
A
bstract
We present a subtraction method utilizing the
N
-jettiness observable,
T
N
, to perform QCD calculations for arbitrary processes at next-to-next-to-leading order (NNLO). Our method employs ...soft-collinear effective theory (SCET) to determine the IR singular contributions of
N
-jet cross sections for
T
N
→ 0, and uses these to construct suitable
T
N
-subtractions. The construction is systematic and economic, due to being based on a physical observable. The resulting NNLO calculation is fully differential and in a form directly suitable for combining with resummation and parton showers. We explain in detail the application to processes with an arbitrary number of massless partons at lepton and hadron colliders together with the required external inputs in the form of QCD amplitudes and lower-order calculations. We provide explicit expressions for the
T
N
-subtractions at NLO and NNLO. The required ingredients are fully known at NLO, and at NNLO for processes with two external QCD partons. The remaining NNLO ingredient for three or more external partons can be obtained numerically with existing NNLO techniques. As an example, we employ our results to obtain the NNLO rapidity spectrum for Drell-Yan and gluon-fusion Higgs production. We discuss aspects of numerical accuracy and convergence and the practical implementation. We also discuss and comment on possible extensions, such as more-differential subtractions, necessary steps for going to N
3
LO, and the treatment of massive quarks.
In the United States like in many other countries throughout the globe, construction workers are more likely to be injured on the job than workers in any other industry. This poor safety performance ...is responsible for huge human and financial losses and has motivated extensive research. Unfortunately, safety improvement in construction has decelerated in the last decade and traditional safety programs have reached saturation. Yet major construction companies and federal agencies possess a wealth of empirical knowledge in the form of huge databases of digital construction injury reports. This knowledge could be used to better understand, predict, and prevent the occurrence of construction accidents. Unfortunately, due to the lack of a clear methodology and the high costs of manual large-scale content analysis, these valuable data have yet to be extracted and leveraged. Recently, researchers have proposed a framework allowing meaningful empirical data to be extracted from accident reports. However, the resource limitations inherent to manual content analysis still remain. The present study tested the proposition that manual content analysis of injury reports can be eliminated using natural language processing (NLP). This paper describes (1) the overall strategy and methodology used in developing the system, and specifically how key challenges with decoding unstructured reports were overcome; (2) how the system was built through an iterative process of coding and testing against manual content analysis results from a team of seven independent analysts; and (3) the implications and potential uses of the data extracted. The results indicate that the NLP system is capable of quickly and automatically scanning unstructured injury reports for 101 attributes and outcomes with over 95% accuracy. The main contribution of this research is to empower any organization to quickly obtain a large and highly reliable structured attribute and outcome data set from their databases of unstructured accident reports. Such structured data are a necessary prerequisite to the application of statistical modeling techniques, allowing the extraction of new safety knowledge and finally the amelioration of safety management.
•A natural language processing system is proposed.•The system is based on hand-coded rules and dictionaries of keywords.•Injury reports are scanned for 102 attributes and outcomes with over 95% accuracy.•Large databases of unstructured injury reports can now efficiently be leveraged.
The major obstacle to Martian colonization is the mission cost which requires significant reduction. From the structural engineering point of view, importing materials and structural elements from ...Earth or massive excavations on the surface of Mars require an enormous amount of energy; thus, inflatable and under-surface structures as the main options for Martian colonization seem unrealistically expensive. Construction of affordable buildings onsite using only in situ sources may represent an ideal solution for Martian colonization. On the other hand, solar energy, at the early stage of colonization, would be the only available, practical, and low-cost energy source on Mars. Though, for sustainable and broad colonization, the energy required for construction and the construction cost should be minimized. Here, we propose three types of simple (relatively optimized), perforated, and algorithmic shape-optimized Martian structures to minimize the material and energy required for construction as well as the construction cost using only in situ resources. These structural forms can be considered remarkable steps towards sustainable structural construction and colonization on Mars. Also, these innovative structures were designed to minimize the tensile stress (maximize the compressive stress) and enable the use of in situ concrete. Our data indicate that compared to our previous study, the material and energy required for construction as well as the construction cost can be reduced by more than 50%. Acceptance criteria and limitations appropriate to the Martian environment, and desirable structural and material behaviors were defined to evaluate whether or not the behavior of a structure under the applied loads and conditions will be acceptable. To detect potential issues for onsite construction and evaluate the geometry of the models, a 1:200 3D model of the best structural form was printed.
Buildability, i.e. the ability of a deposited material bulk to retain its dimensions under increasing load, is an inherent prerequisite for formwork-free digital concrete construction (DC). Since DC ...processes are relatively new, no standard methods of characterization are available yet. The paper presents direct printing test as a practice-oriented approach, in which buildability test parameters are determined by taking various process aspects and construction costs into consideration. In doing so, direct links between laboratory buildability tests and target applications are established. A systematic basis for calculating the time interval (TI) to be followed during laboratory testing is proposed for the full-width printing (FWP) and filament printing (FP) processes. The proposed approach is verified by applying it to a high-strength, printable, fine-grained concrete. Comparative analyses of FWP and FP revealed that to test the buildability of a material for FP processes, higher velocities of the printhead should be established for laboratory tests in comparison to those needed for FWP process, providing for equal construction rates.
•Practice-oriented approach for characterizing buildability is proposed.•The applicability of the model in quantifying the economic viability of 3D-printing is demonstrated.•Proposed buildability approach is verified by tests on a printable concrete.•Specimen height and time interval are specified as parameters for buildability tests on printable concretes.•Variations regarding buildability test specifications for full-width and filament printing techniques are described.
Feature selection aims to select a small subset of informative features that contain most of the information related to a given task. Existing feature selection methods often assume that all the ...features have the same cost. However, in many real world applications, different features may have different costs (e.g., different tests a patient might take in medical diagnosis). Ignoring the feature cost may produce good feature subsets in theory but they can not be used in practice. In this paper, we propose a random forest-based feature selection algorithm that incorporates the feature cost into the base decision tree construction process to produce low-cost feature subsets. In particular, when constructing a base tree, a feature is randomly selected with a probability inversely proportional to its associated cost. We evaluate the proposed method on a number of UCI datasets and apply it to a medical diagnosis problem where the real feature costs are estimated by experts. The experimental results demonstrate that our feature-cost-sensitive random forest (FCS-RF) is able to select a low-cost subset of informative features and achieves better performance than other state-of-art feature selection methods in real-world problems.
Building Information Modelling (BIM) serves as a useful tool in facilitating the on-site assembly services (OAS) of prefabricated construction for its benefits of powerful management of physical and ...functional digital presentations. However, the benefits of using BIM in the OAS of prefabricated construction cannot be cultivated with an incomplete, inaccurate, and untimely data exchange and lack of real-time visibility and traceability. To deal with these challenges, an Internet of Things (IoT)-enabled platform is designed by integrating IoT and BIM for prefabricated public housing projects in Hong Kong. The demands of the stakeholders were analysed; then smart construction objects (SCOs) and smart gateway are defined and designed to collect real-time data throughout the working processes of on-site assembly of prefabricated construction using the radio frequency identification (RFID) technology. The captured data is uploaded to cloud in real-time to process and analyse for decision support purposes for the involved site managers and workers. Visibility and traceability functions are developed with BIM and virtual reality (VR) technologies, through which managers can supervise the construction progress and approximate cost information in a real-time manner. The IoT-enabled platform can provide various decision support tools and services to different stakeholders, for improving the efficiency and effectiveness of daily operations, decision making, collaboration, and supervision throughout on-site assembly processes of prefabricated construction.
•Current BIM system has drawbacks.•A platform is developed by integrating internet of things and BIM technologies.•Intelligent decisions could be made to inform managers and workers.•Managers can supervise the construction progresses and cost information in real time manner.
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