827 research outputs found
Identification of Structural Parameters Based on HHT and NExT
Signal processing approaches are widely used in the field of earthquake engineering, especially in the identification of structural modal parameters. Hilbert-Huang Transformation (HHT) is one new signal processing approach, which can be used to identify the modal frequency, damping ratio, mode shape, even the interlayer stiffness of the shear-type structure, incorporating with Natural Excitation Technique (NExT) method to take information from the response records of the structure. The stiffness of the structure is of great importance to judge the loss of its bearing capacity after earthquake. However, all of modal parameters are required to calculate the stiffness of the structure by use of HHT and NExT, which means that the response records shall contain all of modal information. However, it has been found that the responses of the structure recorded only contain the former order modal information; even it is excited by earthquake. Therefore, it is necessary to found a formula (formulas) to calculate the stiffness only using limited modal parameters. In this paper, the calculation formulas of the interlayer stiffness of shear-type structure are derived by using of the flexibility method, which indicate that all of interlayer stiffnesses could be worked out as long as any one set of modal parameters is obtained. After that, Taking Sheraton-Universal Hotel subjected to North Bridge earthquake in 1994 as an example, HHT and NExT are used to identify its modal parameters, the derived formulas are used to calculate the interlayer stiffnesses, and their applicability and accuracy are verified
Empirical and human response studies of personalized ventilation combined with underfloor air distribution system
Ph.DNUS-DTU JOINT PH.D
Discrimination of approved drugs from experimental drugs by learning methods
<p>Abstract</p> <p>Background</p> <p>To assess whether a compound is druglike or not as early as possible is always critical in drug discovery process. There have been many efforts made to create sets of 'rules' or 'filters' which, it is hoped, will help chemists to identify 'drug-like' molecules from 'non-drug' molecules. However, among the chemical space of the druglike molecules, the minority will be approved drugs. Classifying approved drugs from experimental drugs may be more helpful to obtain future approved drugs. Therefore, discrimination of approved drugs from experimental ones has been done in this paper by analyzing the compounds in terms of existing drugs features and machine learning methods.</p> <p>Results</p> <p>Four methodologies were compared by their performance to classify approved drugs from experimental ones. The best results were obtained by SVM, in which the accuracy is 0.7911, the sensitivity is 0.5929, and the specificity is 0.8743. Based on the results, consensus model was developed to effectively discriminate drugs, which further pushed the correct classification rate up to 0.8517, sensitivity up to 0.7242, specificity up to 0.9352. The applications on the Traditional Chinese Medicine Ingredients Database (TCM-ID) tested the methods. Therefore this model has been proven to be a potent tool for identifying drug molecules.</p> <p>Conclusion</p> <p>The studies would have potential applications in the research of combinatorial library design and virtual high throughput screening for drug discovery.</p
Robust Power Allocation for UAV-aided ISAC Systems with Uncertain Location Sensing Errors
Unmanned aerial vehicle (UAV) holds immense potential in integrated sensing
and communication (ISAC) systems for the Internet of Things (IoT). In this
paper, we propose a UAV-aided ISAC framework and investigate three robust power
allocation schemes. First, we derive an explicit expression of the Cram\'er-Rao
bound (CRB) based on time-of-arrival (ToA) estimation, which serves as the
performance metric for location sensing. Then, we analyze the impact of the
location sensing error (LSE) on communications, revealing the inherent coupling
relationship between communication and sensing. Moreover, we formulate three
robust communication and sensing power allocation problems by respectively
characterizing the LSE as an ellipsoidal distributed model, a Gaussian
distributed model, and an arbitrary distributed model. Notably, the
optimization problems seek to minimize the CRB, subject to data rate and total
power constraints. However, these problems are non-convex and intractable. To
address the challenges related to the three aforementioned LSE models, we
respectively propose to use the -Procedure and alternating
optimization (-AO) method, Bernstein-type inequality and successive
convex approximation (BI-SCA) method, and conditional value-at-risk (CVaR) and
AO (CVaR-AO) method to solve these problems. Finally, simulation results
demonstrate the robustness of our proposed UAV-aided ISAC system against the
LSE by comparing with the non-robust design, and evaluate the trade-off between
communication and sensing in the ISAC system
- …