The application of coordinate transformation matrix into the multi-degree of freedom vibration control

This paper describes the application of the coordinate transformation matrices into the multi-degree of freedom vibration control. An example with an aluminum beam supported by dual actuators is used to derive how to create both the input transformation matrix and the output transformation matrix. In order to achieve the synchronous movement of the dual actuators, the direct actuator control test and 2DOF control test have been performed. By comparing with the results of the direct actuator control test without using the transformation matrix, the 2DOF control test proves that the transformation matrix is a powerful tool for a significant improvement in test control accuracy

Study on multi-axis sine vibration test control techniques

This paper describes several key aspects about multi-axis sine vibration test control techniques including the identification of the system frequency response function, synchronization of the input and output signals, the generation of the sinewave, the control algorithm, etc. A multi-axis sine vibration controller is developed based on these key techniques and the major framework of the controller is introduced. Finally, a dual axial experiment is carried out by the controller. The test results show the feasibility of the control algorithm and the good control strategy of the multi-axis sine vibration controller in which the key techniques are realized

The application of improved signal summing method into the spacecraft force limited vibration test

This paper provides an improved signal summing method for the spacecraft force limited vibration test system with eight force transducers. The key point for this method is to change the combination way of the signals coming out of the eight force transducers while the formulas inside the signal conditioning amplifier have been used skillfully. This method had been successfully adopted in the spacecraft force limited vibration test and the accuracy requirements of key force and moment signals have been met. And this method has been proved to be a very powerful tool for providing the critical force and moment data used to determine the force limited profile during the spacecraft dynamic test

Establishment of a gnotobiotic pig model of Clostridioides difficile infection and disease

Clostridioides difficile (C. difficile) is a gram-positive, spore-forming, anaerobic bacterium known to be the most common cause of hospital-acquired and antibiotic-associated diarrhea. C. difficile infection rates are on the rise worldwide and treatment options are limited, indicating a clear need for novel therapeutics. Gnotobiotic piglets are an excellent model to reproduce the acute pseudomembranous colitis (PMC) caused by C. difficile due to their physiological similarities to humans and high susceptibility to infection. Here, we established a gnotobiotic pig model of C. difficile infection and disease using a hypervirulent strain. C. difficile-infected pigs displayed classic signs of C. difficile infection, including severe diarrhea and weight loss. Inoculated pigs had severe gross and microscopic intestinal lesions. C. difficile infection caused an increase in pro-inflammatory cytokines in samples of serum, large intestinal contents, and pleural effusion. C. difficile spores and toxins were detected in the feces of inoculated animals as tested by anaerobic culture and cytotoxicity assays. Successful establishment of this model is key for future work as therapeutics can be evaluated in an environment that accurately mimics what happens in humans. The model is especially suitable for evaluating potential prophylactics and therapeutics, including vaccines and passive immune strategies.Instituto de VirologíaFil: Nyblade, Charlotte. Virginia Polytechnic Institute and State University. Virginia-Maryland College of Veterinary Medicine. Department of Biomedical Sciences and Pathobiology; Estados UnidosFil: Parreño, Gladys Viviana. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología e Innovaciones Tecnológicas; ArgentinaFil: Parreño, Gladys Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Parreño, Gladys Viviana. Virginia Polytechnic Institute and State University. Virginia-Maryland College of Veterinary Medicine. Department of Biomedical Sciences and Pathobiology; Estados UnidosFil: Zhou, Peng. Virginia Polytechnic Institute and State University. Virginia-Maryland College of Veterinary Medicine. Department of Biomedical Sciences and Pathobiology; Estados UnidosFil: Hensley, Casey. Virginia Polytechnic Institute and State University. Virginia-Maryland College of Veterinary Medicine. Department of Biomedical Sciences and Pathobiology; Estados UnidosFil: Oakes, Vanessa. Virginia Polytechnic Institute and State University. Virginia-Maryland College of Veterinary Medicine. Department of Biomedical Sciences and Pathobiology; Estados UnidosFil: Mahsoub, Hassan M. Virginia Polytechnic Institute and State University. Virginia-Maryland College of Veterinary Medicine. Department of Biomedical Sciences and Pathobiology; Estados UnidosFil: Mahsoub, Hassan M. Virginia Polytechnic Institute and State University. Center for Emerging, Zoonotic, and Arthropod‑Borne Pathogens; Estados UnidosFil: Kiley, Kelsey. Virginia Polytechnic Institute and State University. Virginia-Maryland College of Veterinary Medicine. Department of Biomedical Sciences and Pathobiology; Estados UnidosFil: Frazier, Maggie. Virginia Polytechnic Institute and State University. Virginia-Maryland College of Veterinary Medicine. Department of Biomedical Sciences and Pathobiology; Estados UnidosFil: Frazier, Annie. Virginia Polytechnic Institute and State University. Virginia-Maryland College of Veterinary Medicine. Department of Biomedical Sciences and Pathobiology; Estados UnidosFil: Zhang, Yongrong. University of Maryland at Baltimore. Department of Microbial Pathogenesis; Estados UnidosFil: Feng, Hanping. University of Maryland at Baltimore. Department of Microbial Pathogenesis; Estados UnidosFil: Yuan, Lijuan. Virginia Polytechnic Institute and State University. Virginia-Maryland College of Veterinary Medicine. Department of Biomedical Sciences and Pathobiology; Estados UnidosFil: Yuan, Lijuan. Virginia Polytechnic Institute and State University. Center for Emerging, Zoonotic, and Arthropod‑Borne Pathogens; Estados Unido

Dynamic monitoring and static analysis: New approaches for intrusion detection

In this dissertation, we describe how we develop novel approaches for host-based anomaly detection. We investigate new ways to improve detection capability without sacrificing false positive performance and efficiency, and present new methods using both dynamic monitoring and static analysis techniques. Most former work used fixed-length subsequences within the system call traces. We propose a novel variable-length pattern extraction algorithm, called LookN, based on loss-less compression techniques. This algorithm is applied on system call traces for anomaly detection purposes. It is computationally simple and efficient. The call stack of program execution can be a very good information source for intrusion detection. There was no prior work on dynamically extracting information from call stack and effectively using it to detect exploits. We propose another new method that we call Vt-Path to do anomaly detection using call stack information. The basic idea is to extract return addresses from the call stack, and generate abstract execution path between two program execution points. Experiments show that our method can detect some attacks that cannot be detected by other approaches, while its convergence and false positive performance is comparable to or better than the other approaches. Models constructed using static analysis have the highly desirable feature that they do not produce false alarms; however, they may still miss attacks. Prior work has shown a trade-off between efficiency and precision. In particular, the more accurate models based upon pushdown automata (PDA) are very inefficient to operate due to non-determinism in stack activity. We present techniques for determinizing PDA models. We provide a formal analysis framework of PDA models and introduce the concepts of determinism and stack-determinism. We then present the VPStatic model, which achieves determinism by extracting information about stack activity of the program. Our results shows that reasonable efficiency needs not be sacrificed for model precision, and deterministic PDA are more efficient to operate than stack-deterministic PDA. In summary, we study different ways to improve intrusion detection system performance. We explore different information sources, different model generating approaches, and different ways of using the information. Several new approaches are proposed

The Enterotoxicity of Clostridium difficile Toxins

toxin