Novel Stabilization Conditions for Uncertain Singular Systems with Time-Varying Delay

The problem of delay-dependent robust stabilization for continuously singular time-varying delay systems with norm-bounded uncertainties is investigated in this paper. First, based on some mathematical transform, the uncertain singular system is described in a form which involves the time-delay integral items. Then, in terms of the delay-range-dependent Lyapunov functional and the LMI technique, the improved delay-dependent LMIs-based conditions are established for the uncertain singular systems with time-varying delay to be regular, causal, and stable. Furthermore, by solving these LMIs, an explicit expression for the desired state feedback control law can be obtained; thus, the regularity, causality, and stability of the closed-loop system are guaranteed. In the end, numerical examples are given to illustrate the effectiveness of the proposed methods

Tuned mass damper parameters design for structural systems via linear matrix inequality and genetic algorithm

The tuned mass damper parameters designing for structural systems based on combining linear matrix inequality with genetic algorithm is of concern in this paper. Firstly, based on matrix transform, the novel model description with a singular style for structural systems is obtained, in which the possible coupling of those uncertainties is avoided. Secondly, an approach, which combines linear matrix inequality with genetic algorithm, is taken in this work to solving the optimization problems, and the optimized tuned mass damper parameters can be obtained by solving the optimization problems such that the tuned-mass-damper-controlled systems have a prescribed level of vibration attenuation performance. Furthermore, the obtained results are also extended to the uncertain cases. Finally, the effectiveness of the obtained theorems is demonstrated by numerical simulation results

The Impact of tariff increase on export and employment of Chinese firms

This paper examines the impact of the tariff increase implemented by the U.S. in 2018 on Chinese firms' export and subsequent employment adjustment. Under the influence of front run shipment and expected stock pile, the export volume increased by 10% after the tariff increase in 2018. While firm employment remains stable, the average working hour and wage increased. In 2019, with the impact of tariff increase gradually emerging, the export volume declined significantly. However, Chinese exporter did not cut jobs on a large scale. Instead, they reduced the per capita working hour and other employment costs, leading to a simultaneous decline in wage and non-cash benefits. The latter contributes to more than 42% of the decline. Our study indicates that the impact of tariff on employment is mainly reflected in the intensive rather than extensive margin

Vibration-Attenuation Controller Design for Uncertain Mechanical Systems with Input Time Delay

The problems of vibration-attenuation controller design for uncertain mechanical systems with time-varying input delay are of concern in this paper. Firstly, based on matrix transformation, the mechanical system is described as a state-space model. Then, in terms of introducing the linear varying parameters, the uncertain system model is established. Secondly, the LMI-based sufficient conditions for the system to be stabilizable are deduced by utilizing the LMI technique. By solving the obtained LMIs, the controllers are achieved for the closed-loop system to be stable with a prescribed level of disturbance attenuation. Finally, numerical examples are given to show the effectiveness of the proposed theorems

Fault Tolerant Vibration-Attenuation Controller Design for Uncertain Linear Structural Systems with Input Time-Delay and Saturation

The problem of fault tolerant vibration-attenuation controller design for uncertain linear structural systems with control input time-delay and saturation is investigated in this paper. The objective of designing controllers is to guarantee the asymptotic stability of closed-loop systems while attenuate disturbance from earthquake excitation. Firstly, based on matrix transformation, the structural system is described as state-space model, which contains actuator fault, input signal time-delay and saturation at the same time. Based on the obtained model, an LMIs-based condition for the system to be stabilizable is deduced. By solving these LMIs, the controller is established for the closed-loop system to be stable with a prescribed level of disturbance attenuation. The condition is also extended to the uncertain case. Finally, an example is included to demonstrate the effectiveness of the proposed theorems

Nitrogen Addition Effects on Wetland Soils Depend on Environmental Factors and Nitrogen Addition Methods: A Meta-Analysis

Identifying the effects of nitrogen (N) addition under key environmental factors and N addition methods can aid in understanding the paradigm of N addition in wetland ecosystems. In this study, we conducted a meta-analysis of 30 field studies of wetland ecosystems and selected 14 indicators. We found that the changes in soil TN and SOC contributed significantly to the changes in microbial community structure under N additions. The environmental factors and N addition methods altered the direction or size of N addition effects on wetland soil properties, microbial diversity and key C and N cycling genes. N-limited conditions and climate conditions determined the N addition effect direction on SOC, and saline-alkali conditions determined the N addition effect direction on microbial diversity and AOB abundance. Environmental heterogeneity and N addition methods determine the response of wetland soil to nitrogen application. Therefore, it is crucial to study the effects of environmental factors and N addition methods on the N deposition of wetland soils

Novel Stabilization Conditions for Uncertain Singular Systems with Time-Varying Delay

The problem of delay-dependent robust stabilization for continuously singular time-varying delay systems with norm-bounded uncertainties is investigated in this paper. First, based on some mathematical transform, the uncertain singular system is described in a form which involves the time-delay integral items. Then, in terms of the delay-range-dependent Lyapunov functional and the LMI technique, the improved delay-dependent LMIs-based conditions are established for the uncertain singular systems with time-varying delay to be regular, causal, and stable. Furthermore, by solving these LMIs, an explicit expression for the desired state feedback control law can be obtained; thus, the regularity, causality, and stability of the closed-loop system are guaranteed. In the end, numerical examples are given to illustrate the effectiveness of the proposed methods.Peer Reviewe

Nitrogen Addition Effects on Wetland Soils Depend on Environmental Factors and Nitrogen Addition Methods: A Meta-Analysis

Identifying the effects of nitrogen (N) addition under key environmental factors and N addition methods can aid in understanding the paradigm of N addition in wetland ecosystems. In this study, we conducted a meta-analysis of 30 field studies of wetland ecosystems and selected 14 indicators. We found that the changes in soil TN and SOC contributed significantly to the changes in microbial community structure under N additions. The environmental factors and N addition methods altered the direction or size of N addition effects on wetland soil properties, microbial diversity and key C and N cycling genes. N-limited conditions and climate conditions determined the N addition effect direction on SOC, and saline-alkali conditions determined the N addition effect direction on microbial diversity and AOB abundance. Environmental heterogeneity and N addition methods determine the response of wetland soil to nitrogen application. Therefore, it is crucial to study the effects of environmental factors and N addition methods on the N deposition of wetland soils

"I Bought This for Me to Look More Ordinary": a Study of Blind People Doing Online Shopping

Online shopping, by reducing the needs for traveling, has become an essential part of lives for people with visual impairments. However, in HCI, research on online shopping for them has only been limited to the analysis of accessibility and usability issues. To develop a broader and better understanding of how visually impaired people shop online and design accordingly, we conducted a qualitative study with twenty blind people. Our study highlighted that blind people's desire of being treated as ordinary had significantly shaped their online shopping practices: very attentive to the visual appearance of the goods even they themselves could not see and taking great pain to find and learn what commodities are visually appropriate for them. This paper reports how their trying to appear ordinary is manifested in online shopping and suggests design implications to support these practices