Output Feedback NCS of DoS Attacks Triggered by Double-Ended Events

In recent years, the research of the network control system under the event triggering mechanism subjected to network attacks has attracted foreign and domestic scholars’ wide attention. Among all kinds of network attacks, denial-of-service (DoS) attack is considered the most likely to impact the performance of NCS significantly. The existing results on event triggering do not assess the occurrence of DoS attacks and controller changes, which will reduce the control performance of the addressed system. Aiming at the network control system attacked by DoS, this paper combines double-ended elastic event trigger control, DoS attack, and quantitative feedback control to study the stability of NCS with quantitative feedback of DoS attack triggered by a double-ended elastic event. Simulation examples show that this method can meet the requirements of control performance and counteract the known periodic DoS attacks, which save limited resources and improve the system’s antijamming ability.

Automating event location monitoring for induced seismicity

Permanent reservoir monitoring is important for cases of induced seismicity in which there may be a risk to people or to the environment. In such cases, accurately locating microearthquakes and assessing their hazard level can help keep production at safe levels. The process can benefit greatly from the use of automation. With the shift toward full-waveform microearthquake location algorithms and workflows, greater accuracy and information can be retrieved compared to that offered by traditional traveltime estimation techniques, but the complexity of these workflows and run-time costs can be higher. Results are presented from an automatic elastic event location and moment tensor inversion workflow that has been highly parallelized on clustered computer hardware. Run times that previously took up to several days to complete using a manually intensive execution of the workflow now can be achieved in approximately 1 hour. Some 180 events recorded at the Groningen gas field and ranging in magnitude from 0.1 to 3.4 MW (ML) have been located and analyzed with the automatic workflow. The results indicate equivalent location accuracy when compared to the manually intensive workflow execution. However, larger errors are noted in the depth positions of some events and in the range and nature of the focal mechanism, as derived from moment tensor inversion. High grading of the manual and automatic results has been performed and used to study the geomechanical behavior of the microearthquakes in the Groningen region, which exhibit mainly dip-slip, double-couple motion, in areas of previous production activity.

Elastic recovery and reloading of hardness impressions with a conical indenter

ABSTRACTThe present work is concerned with the analysis of elastic unloading data in conventional methods of analysis of nanoindentation test data. Experimental and finite element results are used to show that the reloading of a residual impression with and without the presence of residual stress is an elastic event, and further shows that the estimation of modulus and hardness computed using established techniques is in error due to the assumption the sides of the residual impression are straight. This work calls into question the validity of commonly used methods of test and analysis of instrumented indentation test data that use the elastic unloading data as the basis for the calculation of modulus and hardness of the specimen material.

On Lensless Imaging of Organics with Neutrons, X-Rays, Helium Atoms and Low Energy Electrons: Damage and Iterative Phase Retrieval

Recent experiments with X-rays and high energy electrons have shown that image recovery from diffracted intensities is possible for non-periodic objects using iterative algorithms. Application of these methods to biological molecules raises the crucial problem of radiation damage, which may be quantified by Q = ΔE σi/σe, the amount of energy deposited by inelastic events per elastic event. Neutrons, helium atoms and low energy electrons below most ionization thresholds produce the smallest values of Q (see for TMV imaged at 60 eV). For neutrons (λ = 10-2Å, and deuterated, 15N-abelled molecules) Q is ∼3000 times smaller (∼50 times for λ = 1.8Å) than for electrons (80- 500keV) and about 4x 106 times smaller than for soft X-rays (1.5Å). Since σe for neutrons is about 105 times smaller than for electrons (and about 10 times smaller than for soft X-rays), a 105 times higher neutron dose is required to obtain the same S/N in a phase contrast image compared with electrons, if other noise sources are absent.

Inelastic Scattering and Beam Damage of Biological Molecules

There are two kinds of interactions which an incident electron can experience in traversing a thin specimen. It can be elastically scattered from the atomic nuclei without losing energy. Or it can be inelastically scattered from the atomic electrons and impart energy to the specimen. Elastic interactions are useful for high resolution imaging and produce negligible damage. Inelastic interactions, however, can result in molecular or chemical damage. This is important in biological electron microscopy, since experiments have shown that for 30 KeV electrons in carbon one gets 1.6 inelastic events for every elastic event. Moreover, this ratio increases slightly with voltage.The energy loss spectrum of electrons which have traversed thin specimens is directly related to the probability of exciting a particular electronic level.

TARGET TRANSPARENCY AND HIGH-ENERGY COLLISION MECHANISM

Two mechanisms of high-energy inelastic collisions are given, each of which causes an increase in the target radius and its transparency. Thus, the mechanism of shrinkage in the diffraction peak of the elastic event or, in other words, the reason why the target radius can become infinity in the high-energy limit is clarified.