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Graphitic carbon nitrides (g-C N ) are a class of 2D polymeric materials mainly composed of carbon and nitrogen atoms. g-C N are attracting dramatically increasing interest in the areas of sensing, imaging, and therapy, due to their unique optical and electronic properties. Here, the luminescent properties (mainly includes photoluminescence and electrochemiluminescence), and catalytic and photoelectronic properties related to sensing and therapy applications of g-C N materials are reviewed. Furthermore, the fabrication and advantages of sensing, imaging and therapy systems based on g-C N materials are summarized. Finally, the future perspectives for developing the sensing, imaging and therapy applications of the g-C N materials are discussed.

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This paper presents a control-theoretic approach to the performance management of Internet Web servers to meet service-level agreements. In particular, a CPU frequency management problem is studied to provide response time guarantees with minimal energy cost. It is argued that linear time-invariant modeling and control may not be sufficient for the system to adapt to dynamically varying load conditions. Instead, a Linear-parameter-varying (LPV) approach is presented in this paper, where workload arrival and service parameters are chosen as scheduling parameters to characterize time-varying operating conditions. Modeling the performance management of a Web server as an LPV system has been extensively discussed in this paper; we have derived firstprinciples models based on analyzing transient and steady-state queueing dynamics as well as empirical models using system identification algorithms. LPVcontrollers are then designed for the derived LPV system models. Using real Web server workloads, the performance of LPV control compares favorably to various linear control designs and a design based on the conventional queueing theory. The proposed LPV modeling and control framework can be generalized to incorporate more sophisticated workload models and more complicated server environments. In addition, due to the LPV nature of Web systems with respect to load conditions, the proposed approach can be applied to a variety of resource management problems and used for middleware designs.Index Terms-hosting center, linear-parameter-varying (LPV) modeling and control, performance management, quality of service (QoS), web server.

The effects of defect states on the fluorescence (FL) and electrochemiluminescence (ECL) properties of graphite phase carbon nitride (g-CN) are systematically investigated for the first time. The g-CN nanosheets (CNNSs) obtained at different condensation temperatures are used as the study models. It can be found that all the CNNSs have two kinds of defect states, one is originated from the edge of CNNSs (labeled as CN-defect) and the other is attributed to the partially carbonization regions (labeled as C-defect). Both two kinds of defect states substantially affect the luminescent properties of CNNSs. Both the FL and ECL signals of CNNSs contain a band gap emission and two defect emissions. For the FL of CNNSs, decreasing the density of defect states can increase efficiently the FL quantum yield, while increasing the density of defect states can make the FL spectra red shift. For the ECL of CNNSs, increasing the density of CN-defect states and decreasing the density of C-defect states are greatly important to improve the ECL activity. This work provides a deep insight into the FL and ECL mechanisms of g-CN, and is of significance in tuning the FL and ECL properties of g-CN. Also, it will greatly promote the applications of CNNSs based on the FL and ECL properties.