Active Control of Large Amplitude Nonlinear Free Vibrations and Nonlinear Supersonic Panel Flutter of Beams and Composite Plates Using Piezoelectric Self-Sensing Actuators

This thesis employs a coupled structural-electrical finite element modal formulation for the control of nonlinear free vibrations, and supersonic panel flutter of beams and composite plates with and without thermal environment. Multiple modes of the nonlinear free vibration and supersonic panel flutter are considered in the closed loop simulations. Two different controllers are designed and investigated. The first one is the output feedback controller comprised of a Linear Quadratic Regulator (LQR) and an Extended Kalman Filter (EKF). EKF considers the nonlinear state space matrix and has a gain sequence evaluated on-line. Thus the LQR/EKF nonlinear controller has more accurate state estimation over Linear Quadratic Gaussian (LQG) controller for the nonlinear dynamics. The second controller is the output feedback adaptive LQR/EKF controller. This adaptive controller includes a modal frequency identification and state estimation algorithm

An investigation on research and development cost reduction and channel strategies in competing supply chains

With the intensification of market competition, the competition form of firms is evolving from the competition among firms to the competition among supply chains. This paper considers a market with two competing supply chains consisting of one supplier and one manufacturer. The two supply chains compete on products’ quantities and research and development (R&D) level when the two manufacturers conduct technological innovation. This paper analyses the supply chain competition in three scenarios: two decentralized supply chains (DD), one decentralized supply chain and one centralized supply chain (DC) and two centralized supply chains (CC). The results indicate that the production quantity, the R&D level and the total profit of the integrated supply chain in DC scenario are the largest, CC scenario comes second, those of the DD scenario come third and those of the decentralized supply chain in DC scenario are the smallest. CC strategy is the supply chain system’s Nash equilibrium, which is good for the both supply chains, and there is no prisoner's dilemma

The Structure of Engineering Project Evaluation System: Model and Analysis

AbstractFrom the system theory perspective, the paper constructs a structure model of engineering project evaluation system that provides an analysis framework to project evaluation. The model analysis shows that engineering project evaluation system is a complex system. There are many feedback loops between the evaluation subject, the implement subject, evaluation criteria and evaluation results. The interaction between evaluation subject and project implement subject plays a decisive role in the function of project evaluation system. There will be a vicious feedback circle that affects project evaluation effect if project implement subject have effect on evaluation subject

Compressive Sensing Based on HQS for Image reconstruction

This work solves the image distortion problem caused by the noise generated during the sampling and reconstruction process, a compressive sensing algorithm based on half quadratic splitting (CS-HQS) is proposed to reconstruct images in this paper. For the part dominated by error terms, the regularization term is introduced and the second-order momentum adaptive gradient descent method is used to get the auxiliary variables. For the part dominated by the sparse prior of compressive sensing, the Bayesian maximum posterior inference is used to get the sparse coeffi cient. The combination of the two methods not only avoids the generation of random noise, but also enhances the stability of the model. The experimental results demonstrate that the strong robustness of the proposed algorithm

Dynamic Response of Pile-cap Structure Under Random Sea Wave Action

AbstractBased on Pierson-Moscowitz (P–M) sea wave spectrum and linear wave theory, this paper presents the techniques for simulating random wave action on slender piles of pile-cap structure in coastal engineering, and discusses the dynamic response of pile-cap structure under random wave action using Finite Element (FE) method. In this study, a full FE model of a realistic pile-cap structure of a sea platform is established. The dynamic time-history analysis of the structure under the random sea wave action is carried out in consideration of two different structural damping types. As contrast, the static and dynamic analyses of the structure under the characteristic wave are also conducted. By comparing the displacement and internal force induced in the structure based on the different approaches considered, it is found that the dynamic response under the random sea wave is largest, which could have serious implications for design of structures of this type

Intestinal Microecology in Pediatric Surgery-Related Gastrointestinal Diseases Current Insights and Future Perspectives

Intestinal microecology is established from birth and is constantly changing until homeostasis is reached. Intestinal microecology is involved in the immune inflammatory response of the intestine and regulates the intestinal barrier function. The imbalance of intestinal microecology is closely related to the occurrence and development of digestive system diseases. In some gastrointestinal diseases related to pediatric surgery, intestinal microecology and its metabolites undergo a series of changes, which can provide a certain basis for the diagnosis of diseases. The continuous development of microecological agents and fecal microbiota transplantation technology has provided a new means for its clinical treatment. We review the relationship between pathogenesis, diagnosis and treatment of pediatric surgery-related gastrointestinal diseases and intestinal microecology, in order to provide new ideas and methods for clinical diagnosis, treatment and research

Role of Elastic Phonon Couplings in Dictating the Thermal Transport across Atomically Sharp SiC/Si Interfaces

Wide-bandgap (WBG) semiconductors have promising applications in power electronics due to their high voltages, radio frequencies, and tolerant temperatures. Among all the WBG semiconductors, SiC has attracted attention because of its high mobility, high thermal stability, and high thermal conductivity. However, the interfaces between SiC and the corresponding substrate largely affect the performance of SiC-based electronics. It is therefore necessary to understand and design the interfacial thermal transport across the SiC/substrate interfaces, which is critical for the thermal management design of these SiC-based power electronics. This work systematically investigates heat transfer across the 3C-SiC/Si, 4H-SiC/Si, and 6H-SiC/Si interfaces using non-equilibrium molecular dynamics simulations and diffuse mismatch model. We find that the room temperature ITC for 3C-SiC/Si, 4H-SiC/Si, and 6H-SiC/Si interfaces is 932 MW/m2K, 759 MW/m2K, and 697 MW/m2K, respectively. We also show the contribution of the ITC resulting from elastic scatterings at room temperature is 80% for 3C-SiC/Si interfaces, 85% for 4H-SiC/Si interfaces, and 82% for 6H-SiC/Si interfaces, respectively. We further find the ITC contributed by the elastic scattering decreases with the temperature but remains at a high ratio of 67%~78% even at an ultrahigh temperature of 1000 K. The reason for such a high elastic ITC is the large overlap between the vibrational density of states of Si and SiC at low frequencies (< ~ 18 THz), which is also demonstrated by the diffuse mismatch mode. It is interesting to find that the inelastic ITC resulting from the phonons with frequencies higher than the cutoff frequency of Si (i.e., ~18 THz) can be negligible. That may be because of the wide frequency gap between Si and SiC, which makes the inelastic scattering among these phonons challenging to meet the energy and momentum conservation rules

Combination of Diabetes Risk Factors and Hepatic Steatosis in Chinese: The Cardiometabolic Risk in Chinese (CRC) Study

Aims Hepatic steatosis has been related to insulin resistance and increased diabetes risk. We assessed whether combination of diabetes risk factors, evaluated by the Finnish Diabetes Risk Score, was associated with risk of hepatic steatosis in an apparently healthy Chinese population. Research Design and Methods The study samples were from a community-based health examination survey in central China. In total 1,780 men and women (18–64 y) were included in the final analyses. Hepatic steatosis was diagnosed by ultrasonography. We created combination of diabetes risk factors score on basis of age, Body Mass Index, waist circumference, physical activity at least 4 h a week, daily consumption of fruits, berries or vegetables, history of antihypertensive drug treatment, history of high blood glucose. The total risk score is a simple sum of the individual weights, and values range from 0 to 20. Results: Hepatic steatosis was present 18% in the total population. In multivariate models, the odds ratios of hepatic steatosis were 1.20 (95%CI 1.15–1.25) in men and 1.25 (95%CI 1.14–1.37) in women by each unit increase in the combination of diabetes risk factors score, after adjustment for blood pressure, liver enzymes, plasma lipids, and fasting glucose. The area under the receiver operating characteristic curve for hepatic steatosis was 0.78 (95%CI 0.76–0.80), 0.76 in men (95%CI 0.74–0.78) and 0.83 (95%CI 0.79–0.87) in women. Conclusions: Our data suggest that combination of major diabetes risk factors was significantly related to risk of hepatic steatosis in Chinese adults

Neck circumference and early stage atherosclerosis: the cardiometabolic risk in Chinese (CRC) study

Background: Neck circumference (NC) has been previously related to cardiometabolic risk factors. In this study we examined the association between NC and early stage atherosclerosis in Chinese adults. Methods: The study samples were from a community-based health examination survey in central China. In total 2,318 men and women (18-64 y) were included in the final analyses. Carotid radial pulse wave velocity (crPWV), carotid femoral PWV (cfPWV), carotid artery dorsalis pedis PWV (cdPWV) and NC were measured. Results: After adjustment for age, sex, lipids, glucose, blood pressure, heart rate, body mass index (BMI), high NC was significantly associated with an increasing trend of cfPWV, cdPWV and crPWV (P = 0.001, 0.049, and 0.038; respectively). In addition, we found significant interaction between hypertension status and NC level in relation to cfPWV, adjusted for age, sex, BMI, fasting glucose, lipids and heart rate(P for interaction = 0.034). The associations between NC and cfPWV were significant (P = 0.02) among those with hypertension, but not significant among those without hypertension. Conclusions: Our data showed that high NC was associated with an increased risk of early stage atherosclerosis in Chinese adults, independent of other metabolic risk factors. Hypertension might modify the association between NC and cfPWV