ABSTRACT
This article investigates the stability analysis problem for cyber-physical systems (CPSs) under denial-of-service (DoS) attacks. Based on the real-time data characterizing the suffered DoS attack, a necessary and sufficient condition for the closed-loop stability in the presence of DoS attacks is provided. Besides, by transforming stability analysis the system under DoS into stability analysis of an auxiliary system, novel sufficient conditions for the closed-loop stability, which can be verified more easily than the necessary and sufficient condition, are provided. Based on the proposed conditions, an online stability monitoring strategy, which triggers an alarm if the closed-loop stability is not guaranteed, is proposed. Finally, two examples are given to illustrate the effectiveness of the proposed strategy.
ABSTRACT
This paper investigates the resilient control problem for cyber-physical systems (CPSs) with multiple transmission channels under denial-of-service (DoS). First, a set of partial observers is designed to estimate partial states corresponding to different channels. Second, by combining the proposed partial observers, the finite-time observer technique and a switching scheme, a modified finite-time partial observer-based controller is proposed to stabilize the system in the presence of DoS. Compared with the existing results for the CPSs with multiple transmission channels, the computational burden of designing observer-based controller is reduced, and the resilience against DoS is improved by adopting the proposed finite-time partial observers. Especially, besides stability, the proposed resilient observer-based controller also provides better disturbance rejection performance.
ABSTRACT
This article concerns the problem of observer-based event-triggered control for cyber-physical systems (CPSs) under denial-of-service (DoS) attacks. In contrast to the existing studies where DoS attacks on different channels are the same, the considered attacks compromise each channel independently. Correspondingly, a decentralized event-triggered scheme is adopted based on the tradeoff between the transmission efficiency and tolerable attack intensity with guarantees on the closed-loop stability. Inspired by the Lyapunov theory for switched systems, the proposed stabilization criteria reveals a link between the tolerable attack intensity and the event-triggering parameters. An example is finally provided to illustrate the effectiveness of the proposed approaches.
ABSTRACT
Oxidative stress is involved in a variety of diseases. Prospective studies investigating the relationship between oxidative stress biomarkers and the status and development of colorectal cancer (CRC) are scarce; previous studies have failed to establish a relationship between the serum total oxidant/antioxidant status and CRC. Therefore, we compared the total serum oxidant/antioxidant levels of CRC patients and healthy subjects, and analyzed their clinical significance in the CRC. Fasting blood samples from 132 CRC patients and 64 healthy subjects were collected. Oxidative stress parameters, including total oxidant status (TOS) and total antioxidant status (TAS), were measured, and the oxidative stress index (OSI) was calculated. The TOS and OSI levels increased significantly (P<0.001) and the TAS level significantly decreased (P<0.001) in the CRC group compared to those in the healthy control group. Oxidative stress parameters differed significantly depending on the patient's smoking and drinking status (P<0.05). The preoperative and postoperative levels of TOS, TAS, and OSI did not differ significantly between primary sites (colon/rectum) and clinical stages (P>0.05).However, the levels of TOS, TAS, and OSI were significantly different between patients with no metastasis and those with metastases to two organs (P<0.05) Finally, the parameters are affected by smoking and drinking, and subsequent research should be conducted excluding the relevant influencing factors.
