Coherent Dynamics of Charge Carriers in {\gamma}-InSe Revealed by Ultrafast Spectroscopy

For highly efficient ultrathin solar cells, layered indium selenide (InSe), a van der Waals solid, has shown a great promise. In this paper, we study the coherent dynamics of charge carriers generation in {\gamma}-InSe single crystals. We employ ultrafast transient absorption spectroscopy to examine the dynamics of hot electrons after resonant photoexcitation. To study the effect of excess kinetic energy of electrons after creating A exciton (VB1 to CB transition), we excite the sample with broadband pulses centered at 600, 650, 700 and 750 nm, respectively. We analyze the relaxation and recombination dynamics in {\gamma}-InSe by global fitting approach. Five decay associated spectra with their associated lifetimes are obtained, which have been assigned to intraband vibrational relaxation and interband recombination processes. We extract characteristic carrier thermalization times from 1 to 10 ps. To examine the coherent vibrations accompanying intraband relaxation dynamics, we analyze the kinetics by fitting to exponential functions and the obtained residuals are further processed for vibrational analysis. A few key phonon coherences are resolved and ab-initio quantum calculations reveal the nature of the associated phonons. The wavelet analysis is employed to study the time evolution of the observed coherences, which show that the low-frequency coherences last for more than 5 ps. Associated calculations reveal that the contribution of the intralayer phonon modes is the key determining factor for the scattering between free electrons and lattice. Our results provide fundamental insights into the photophysics in InSe and help to unravel their potential for high-performance optoelectronic devices

Investigation on Laser-induced Breakdown Spectroscopy of Potassium Chloride Solution

peer reviewedThe experimental setup for laser—induced breakdown spectroscopy test was designed with pulsed Nd：YAG laser，spectrograph and ICCD and so on．Furthermore the potassium chloride solution spectra signals were detected by this setup．The spectra lines of the trace elements such as natrium (20mg／1)，magnesium(1 mg／1)，calcium(3 mg／1)are recorded．Experiment results show that delay time is one of the important parameters when qualitative analysis．It is easy for LIBS technology to detect multi—elements simultaneity if delay time is appropriate，and qualitative analysis has demonstrated that the feasibility of detecting trace poisonous metals in waste water using LIBS

Formosania immaculata, a new species of hillstream loach (Teleostei, Cypriniformes, Gastromyzontidae) from the Ou-Jiang River, Southeast China

Formosania immaculata, a new species, is described from the Ou-Jiang basin in Zhejiang Province, Southeast China. It is distinguished from other species of the genus by having a combination of the following characteristics: body without obvious mottling; snout length longer than postorbital length; abdominal scaleless area extending to middle of pectoral-fin base; shorter rostral barbels, the outermost pair length 112.9%–140.0% of eye diameter; and shorter lower lip papillae, length 19.9%–24.4% of eye diameter. Its validity is also affirmed by its distinct Cytb gene sequence divergence from all congeners and its monophyly recovered in a Cytb gene-based phylogenetic analysis

Laboratory and Field Performance Evaluation of High-Workability Ultra-Thin Asphalt Overlays

The defects of poor workability and inadequate pavement performance of the ultra-thin asphalt overlay limited its application in the preventive maintenance of pavements. In this study, a high-workability ultra-thin (HWU) asphalt overlay scheme was proposed. A high-strength-modified asphalt binder and an optimized HWU-10 gradation were used to prepare the HWU asphalt mixture and explore its laboratory performance. Furthermore, the HWU asphalt mixture was used for the test road paving. Based on the field performance test results before and after the test road for one year of traffic operation, the application performance of the HWU asphalt mixture and styrene-butadiene-styrene (SBS)-modified asphalt mixture was compared and analyzed. The results showed that the HWU asphalt mixture possessed satisfactory laboratory pavement performance, and its high-temperature stability and moisture damage resistance were better than those of the SBS-modified asphalt mixture. The asphalt mixture prepared using HWU-10 gradation was easily compacted and showed good workability. After one year of operation, all field performance of the ultra-thin overlay paved with HWU asphalt mixture met the specification requirements, but its flatness and skid resistance decreased. It is worth mentioning that the HWU asphalt mixture was significantly better than the SBS-modified asphalt mixture in terms of performance degradation resistance and rutting resistance. The studies to enhance the road intersection pavement performance and ensure the homogeneous dispersion of polyester fibers in the asphalt mixture will be considered in the future

GCWOAS2: Multiobjective Task Scheduling Strategy Based on Gaussian Cloud-Whale Optimization in Cloud Computing

An important challenge facing cloud computing is how to correctly and effectively handle and serve millions of users’ requests. Efficient task scheduling in cloud computing can intuitively affect the resource configuration and operating cost of the entire system. However, task and resource scheduling in a cloud computing environment is an NP-hard problem. In this paper, we propose a three-layer scheduling model based on whale-Gaussian cloud. In the second layer of the model, a whale optimization strategy based on the Gaussian cloud model (GCWOAS2) is used for multiobjective task scheduling in a cloud computing which is to minimize the completion time of the task via effectively utilizing the virtual machine resources and to keep the load balancing of each virtual machine, reducing the operating cost of the system. In the GCWOAS2 strategy, an opposition-based learning mechanism is first used to initialize the scheduling strategy to generate the optimal scheduling scheme. Then, an adaptive mobility factor is proposed to dynamically expand the search range. The whale optimization algorithm based on the Gaussian cloud model is proposed to enhance the randomness of search. Finally, a multiobjective task scheduling algorithm based on Gaussian whale-cloud optimization (GCWOA) is presented, so that the entire scheduling strategy can not only expand the search range but also jump out of the local maximum and obtain the global optimal scheduling strategy. Experimental results show that compared with other existing metaheuristic algorithms, our strategy can not only shorten the task completion time but also balance the load of virtual machine resources, and at the same time, it also has a better performance in resource utilization

Gas-Path Health Estimation for an Aircraft Engine Based on a Sliding Mode Observer

Aircraft engine gas-path health monitoring (GPHM) plays a critical role in engine health management (EHM). Among model-based approaches, the Kalman filter (KF) has been widely employed in GPHM. The main shortcoming of KF-based scheme lies in the lack of robustness against uncertainties. To enhance robustness, this paper describes a new GPHM architecture using a sliding mode observer (SMO). The convergence of the error system in uncertainty-existing circumstances is demonstrated, and the proposed method is developed to estimate components’ performance degradations regardless of modeling uncertainties. Simulations using a nonlinear model of a turbofan engine are presented, in which health monitoring problems are handled by the KF and the SMO, respectively. Results indicate the proposed approach possesses better diagnostic performance compared to the KF-based scheme, and the SMO shows its strong robustness and great potential to be applied to GPHM