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The purpose of this paper is to present an alternative algorithm for computing the stationary queue-length and system-length distributions of a single working vacation queue with renewal input batch arrival and exponential holding times. Here we assume that a group of customers arrives into the system, and they are served in batches not exceeding a specific number b. Because of batch arrival, the transition probability matrix of the corresponding embedded Markov chain for the working vacation queue has no skip-free-to-the-right property. Without considering whether the transition probability matrix has a special block structure, through the calculation of roots of the associated characteristic equation of the generating function of queue-length distribution immediately before batch arrival, we suggest a procedure to obtain the steady-state distributions of the number of customers in the queue at different epochs. Furthermore, we present the analytic results for the sojourn time of an arbitrary customer in a batch by utilizing the queue-length distribution at the pre-arrival epoch. Finally, various examples are provided to show the applicability of the numerical algorithm.

In this paper we consider a discrete-time Geo/G/1 queue with delayed Min(N, D)-policy. Using renewal process theory, total probability decomposition technique and z-transform, we study the transient and equilibrium properties of the queue length from an arbitrary initial state, and obtain both the recursive expressions of the transient state queue length distribution and the steady state queue length distribution at arbitrary time epoch n+. Furthermore, we derive the important relations between equilibrium queue length distributions at different time epochs n–, n and n+. Finally, we give some numerical examples about capacity decision in queueing systems to demonstrate the application of the analytical results reported in this paper.

Multilayer InSe is a promising material for high-performance optoelectronic applications because of its small direct band gap and good light absorption. However, as a photoconductive photodetector,...

Multilayer indium selenide (InSe) is a good candidate for high performance electronic and optoelectronic devices. The electrical performance of InSe is effectively regulated by dielectric layers, contact electrodes and surface doping. However, as a powerful tool to tune properties of materials, alloy engineering is absent for multilayer InSe. In this letter, for the first time, we investigate the electrical property of InSe1-xTex alloys and optoelectronic property of InSe-InSe0.82Te0.18p-n heterojunction. The electrical transport properties of InSe1-xTex alloys strongly depend on the content of Te composition. With the ratio of Te/Se increasing, the n-type electron transport behavior of InSe gradually transfers to the p-type hole transport behavior of InSe0.82Te0.18. The p-n InSe-InSe0.82Te0.18 heterojunction shows a rectification effect and a self-powered photodetection. The self-powered photodetector (SPPD) has a broad photodetection range from visible light (400 nm) to near-infrared (NIR) light (1000 nm). The responsivity (R) of SPPD is 14.1 mA/W under illuminated by NIR light (900 nm) at zero bias, which is comparable to some of the 2D heterojunctions NIR photodetectors measured with an external bias. The SPPD also shows a stable and fast response to NIR light (900 nm). This work demonstrates that the electrical transport properties of InSe1-xTex alloys significantly rely on the ratio of Te/Se and suggests that InSe-InSe1-xTex p-n heterojunction has a excellent potential for application in the self-powered optoelectronic device.

With the shortage of nonrenewable energy, renewable energy resources play an important role in practice. One of the most promising renewable energy is viewed as solar energy resources due to its cleanliness and the inexhaustibility. However, the quantitative assessment method on the reliability of a complicated solar energy generating system has been a considerable challenge. In this paper, we propose a Markov model to imitate a solar energy generating system with inverters in series, unreliable by-pass change-over switches, and common cause failure. Employing the renewal point technique and the Semi-Markov process theory, we build the quantitative reliability models of the system. Further, we develop a new algorithm to obtain the explicit form solution of reliability indices. An example illustrates that the proposed models and the algorithm are efficient and concise.

A core-shell surface-imprinted polymer was successfully synthesized on the surface of silica spheres by precipitation polymerization. The polymers were used to selectively identify dichlorophen in complex environmental system. The physical-chemical properties of the silica sphere molecularly imprinted polymers were analyzed by scanning electron microscopy and transmission electron microscopy scans characterization. The adsorption properties of core-shell polymers were examined by adsorption isotherms, kinetics and selectivity experiments. The Langmuir adsorption isotherm well fitted the adsorption experimental data, and an increase of temperature enhanced the adsorption capacity. The maximum binding capacity of imprinted polymers reached 72.46 mg g-1 at 318 K. Meanwhile, the adsorption data of binding experiments were well-fitting by the pseudo-second-order equation. Compared with nonimprinted polymer, the imprinted polymer not only has specific selectivity towards dichlorophen but also has higher adsorption performance. Moreover, via the regeneration experiments, it has been demonstrated that the MIPs have certain stability to the adsorption for the target, which provides a good reference for the adsorption of dichlorophen by the imprinted polymer in water.

The electronic and optoelectronic properties of 2D alloy Ga0.84In0.16Se were investigated for the first time. 2D Ga0.84In0.16Se FETs show p-type conduction behaviors. 2D Ga0.84In0.16Se photodetectors show high photoresponse in the visible light range of 500 to 700 nm. The responsivity value is 258 A/W for alloy photodetector (500 nm illumination), and it is 92 times and 20 times higher than those of 2D GaSe and InSe photodetectors, respectively. Moreover, the alloy photodetector exhibits good photoresponse stability and rapid photoresponse time. Our results demonstrate that 2D alloy Ga0.84In0.16Se has great potential for application in photodetection and sensor devices.

The Poisson cumulative sum (CUSUM) control chart is a method to monitor count data, which are commonly modeled by a Poisson distribution. However, the assumption of a Poisson distribution may not be valid in practice and the robustness of the Poisson CUSUM chart is shown to be poor when the volatility is greater than expected, a phenomenon known as overdispersion. Motivated by this, we propose an improved weighted Poisson CUSUM control chart based on the weighted log-likelihood ratio. For the purpose of discounting the unexplained volatility, smaller weights are assigned to the larger shifts. The continuity, monotonicity and convergence of the cumulative statistic proved in this paper make the design more practical. Compared with the conventional Poisson CUSUM and the Winsorized Poisson CUSUM control charts, the new weighted Poisson CUSUM scheme performs most robustly under overdispersion. In addition, the fast initial response (FIR) feature makes the chart more sensitive to start-up cases. A real-data example of monitoring daily orders on a start-up E-commerce company illustrates the superiorities of the proposed scheme.

The college impact model provides a valuable framework for explaining various college student learning outcomes. However, few quantitative studies have examined the effectiveness of college impact model in explaining engineering undergraduates&rsquo, sustainability consciousness, a critical learning outcome in engineering education. This study proposes a modified college impact model to test the structural links among curriculum experiences, sustainable agency beliefs, and engineering undergraduates&rsquo, sustainability consciousness, and to explore the moderating effect of gender on the structural model. Data are collected from 1804 senior engineering students enrolled in five traditional engineering disciplines at 14 first-class engineering universities in China. Structural equation modeling was used for testing the research model. The results demonstrate that (1) curricular emphasis has a significant direct impact on all three dimensions of students&rsquo, sustainability consciousness, while instructional practice has a significant direct influence on the sustainability knowingness dimension, (2) both curricular emphasis and instructional practice have a significant indirect influence on sustainability consciousness through the full or partial mediation of sustainable agency beliefs, and (3) gender moderates several paths in the structural model. Theoretical and practical implications are provided, and suggestions for future research are offered.

A new fabric defect detection algorithm is presented in this paper. Instead of a Gabor filter bank, an optimal Elliptical Gabor filter (EGF) is used in the proposed algorithm. For a given non-defec...

CuInSe2 has attracted great attention because of its superior optical properties, such as high optical absorption coefficient and direct-band-gap structure (1.1 eV). In this letter, for the first time, high-photoresponse-performance two-dimensional (2D) nonlayered CuInSe2 nanosheets were demonstrated. 2D CuInSe2 nanosheets showed typical p-type semiconducting transport behavior with a high-field-effect mobility of 180 cm2 V–1 s–1. Photodetectors based on 2D CuInSe2 were fabricated and showed a high response to the UV–visible spectral range (254–700 nm). The photoresponsivity and detectivity of 2D CuInSe2 photodetectors were calculated as 1900 A W–1 and 7 × 1011 Jones under 700 nm light illumination, respectively. Our results open a pathway for 2D nonlayered CuInSe2 nanosheet applications in future photodetection and photovoltaic devices.

In this work, the magnetic Fe3O4 imprinted polymers were prepared with the precipitation polymerization method. The polymers were used to selectively identify dichlorophen in complex environmental system. The scanning electron microscopy and transmission electron microscopy scans of magnetic Fe3O4 molecularly imprinted polymers (MMIPs) were carried out. The adsorption properties of MMIPs were examined by adsorption isotherms, kinetics, and selectivity experiments. The Langmuir adsorption isotherm well fitted the adsorption experimental data, and an increase of temperature enhanced the adsorption capacity. The equilibrium adsorption capacity of MMIPs at 318 K was 50.45 mg g–1. The data of kinetics experiments were well fitted by pseudo-second-order equation. Compared to nonimprinted polymer, the MMIPs had more specific selectivity and higher adsorption performance for chlorophene with similar structure. In addition, the regeneration experiments demonstrated that MMIPs have stable adsorption capacity for ta...

This paper presents a simple algorithm for computing the cumulative distribution function of the sojourn time of a random customer in an M/GL/1 queue with bulk-service of exactly size L. Both theoretical and numerical aspects related to this problem were not discussed by Chaudhry and Templeton in their monograph (1983). Our analysis is based on the roots of the so-called characteristic equation of the Laplace-Stieltjes transform (LST) of the sojourn time distribution. Using the method of partial fractions and residue theorem, we obtain a closed-form expression of sojourn time distribution, from which we can calculate the value of the distribution function for any given time t ∈ [0, + ∞). Finally, to ensure the reliability of the analytical procedure, employing the work done by Gross and Harris (1985), an effective way to validate the correctness of our results along with some numerical examples are also provided.

The properties of RLCUSUM control schemes used to monitor contaminated normally distributed processes are evaluated.An optimal design procedure for RLCUSUM control schemes is given. And several enhancements to RLCUSUM are considered.Compare robust likelihood CUSUM control charts with conventional CUSUM and GCUSUM, and conclude their pros and cons.Fast initial response feature is included, that makes the RLCUSUM control schemes more sensitive to start-up cases.An application is used to illustrate the implementation of RLCUSUM control schemes. In practice, the robust-likelihood cumulative sum (RLCUSUM) control charts, using truncation of the log-likelihood underpinnings of the CUSUM to ensure robust performance, which perform well to detect small shifts in the mean of heavy-tailed processes and have the ability to discount outliers. In this article, we evaluate the properties of RLCUSUM control schemes used to monitor the mean of contaminated normally distributed processes. An optimal design procedure for RLCUSUM control schemes is given, in addition, several enhancements to RLCUSUM are considered. These include a fast initial response feature that makes the RLCUSUM control schemes more sensitive to start-up cases, three types of truncation of RLCUSUM, which are cut off by horizontal ray, horizontal segment and oblique line respectively against both large and small shifts in a non-normality process. An extensive comparison with the conventional CUSUM and generalized likelihood ratio CUSUM (GCUSUM) in terms of average run length (ARL), shows that the RLCUSUM is more robust than the conventional CUSUM and GCUSUM control charts for its ARLs are monotonous against the process mean. Especially, the oblique line truncated RLCUSUM control chart has the best overall performance in the various cases of shifts. A final application based on monitoring packing 250g containers is used to illustrate the implementation of RLCUSUM control schemes.

Two different kinds of carbon-based amorphous molybdenum sulfide composite catalysts (activated carbon supported amorphous molybdenum sulfide and acetylene black supported amorphous molybdenum sulfide) had been prepared in a facile and scalable one-step liquid phase chemical method. The morphological and structural information of catalysts was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and it’s electro-catalytic HER activity were evaluated by linear sweep voltammetry(LSV), amperometric i-t technology and AC impedance technology. The as-prepared carbon-based amorphous molybdenum sulfides showed greatly enhanced electro-catalytic activity for HER compared with pure amorphous molybdenum sulfides. Especially, the nano-sized acetylene black supported molybdenum sulfide exhibited excellent electro-catalytic HER performances with a low onset potential of −116 mV versus reverse hydrogen electrode (RHE) and a small Tafel slope of 51 mV per decade.

Multilayer InSe has emerged as a promising candidate for applications in novel electronic and optoelectronic devices due to its direct bandgap, high electron mobility, and excellent photoresponse with a broad response range. Here, we report synthesis of superlattice InSe nanosheets by simple thermal annealing for the first time. The mobility is increased to 299.1 cm

Laser induced forward transfer technology has been reported to print various patterns of 2D and 3D structures in microfabrication for its fascinating characteristics such as non-contact and simple fabrication process. However, the efficiency and throughput are the drawback especially for manufacture of periodical polymer micro-stripes. Here, we proposed a laser interference induced forward transfer (LIIFT) technique, which could produce periodical polymer micro-stripes with high efficiency. The experiment results showed that the good micro-stripe of the polyimide (PI) had been transferred from the PI film, in which the thickness of the PI film, the laser fluence and the pulse number were ~1.2 µm, 39 mJ·cm−2 and 50, respectively. In addition, the relationship of the micro-stripes was systematically analyzed with the laser fluence, the pulse number and the thickness of donor film, respectively. Furthermore, the Fourier transform infrared(FT-IR)spectra showed that these characteristic valleys of the micro-stripe were coincident with those of the PI film, indicating that the micro-stripes transferred were not changed for their composition during the laser processing. Finally, the transferring process was discussed to analyze the formation of the transferred micro-stripes.

In this paper, we consider a discrete time working vacation queue with a utility function for the reward of receiving the service and the cost of waiting in the system. A more flexible switching mechanism between low and regular service states is introduced to enhance the practical value of the working vacation queue. Under different precision levels of the system information, namely observable, almost unobservable and fully unobservable cases, the utility function is studied from both the individual customer's and the system administrator's points of view. By analyzing the steady-state behavior of the system, the associated optimal joining decisions under different information scenarios are obtained. We find that for the fully observable queue, the joining threshold for individual optimization may be less than the one for social optimization in working vacation period. A similar situation also appears in almost unobservable case. Such phenomenon is not possible for the classic first come first served queue due to the fact that there is no vacation time and thus will not cause large fluctuations in customers' conditional waiting time. Additionally, we also conduct some numerical comparisons to demonstrate the effect of the information levels as well as system parameters on customer joining behavior. HighlightsBernoulli interruption of the vacation captures correlations between service and vacation times.Explicit expressions to allow computations of the equilibrium and optimal policies are derived.In some cases, socially optimal strategy accepts more customers than those who join individually.

We study a $$\delta $$ shock and wear model in which the system can fail due to the frequency of the shocks caused by external conditions, or aging and accumulated wear caused by intrinsic factors. The external shocks occur according to a Bernoulli process, i.e., the inter-arrival times between two consecutive shocks follow a geometric distribution. Once the system fails, it can be repaired immediately. If the system is not repairable in a pre-specific time D, it can be replaced by a new one to avoid the unnecessary expanses on repair. On the other hand, the system can also be replaced whenever its number of repairs exceeds N. Given that infinite operating and repair times are not commonly encountered in practical situations, both of these two random variables are supposed to obey general discrete distribution with finite support. Replacing the finite support renewal distributions with appropriate phase-type (PH) distributions and using the closure property associated with PH distribution, we formulate the maximum repair time replacement policy and obtain analytically the long-run average cost rate. Meanwhile, the optimal replacement policy is also numerically determined by implementing a two-dimensional-search process.

This paper considers a discrete-time Geo/G/1 queue under the Min(N,D)-policy in which the idle server resumes its service if either N customers accumulate in the system or the total backlog of the service times of the waiting customers exceeds D, whichever occurs first (Min(N,D)-policy). By using renewal process theory and total probability decomposition technique, the authors study the transient and equilibrium properties of the queue length from the beginning of the arbitrary initial state, and obtain both the recursive expression of the z-transformation of the transient queue length distribution and the recursive formula for calculating the steady state queue length at arbitrary time epoch n +. Meanwhile, the authors obtain the explicit expressions of the additional queue length distribution. Furthermore, the important relations between the steady state queue length distributions at different time epochs n -, n and n + are also reported. Finally, the authors give numerical examples to illustrate the effect of system parameters on the steady state queue length distribution, and also show from numerical results that the expressions of the steady state queue length distribution is important in the system capacity design.

In this paper, we deal with a discrete-time $Geo/G/1$ queueing system under the control of Min($N, V$)-policy in which the server takes single vacation whenever the system becomes empty. The Min($N, V$)-policy means that the server commences its service once the number of waiting customers reaches threshold $N$ or when its vacation time ends with at least one but less than $N$ customers waiting for processing, whichever occurs first. Otherwise, if no customer is presenting at the end of the server vacation, the server remains idle until the first arrival occurs. Under these assumptions, the $z$-transform expressions for the transient queue size distribution at time epoch $n^+$ are obtained by employing the renewal process theory and the total probability decomposition technique. Based on the transient analysis, the explicit recursive formulas of the steady-state queue length distribution at time epochs $n^+$, $n$, $n^-$ and outside observer's time epoch are derived, respectively. Additionally, the stochastic decomposition structure is presented and some other performance measures are also discussed. Furthermore, some computational experiments are implemented to demonstrate the significant application value of the recursive formulas for the steady-state queue size in designing system capacity. Finally, the optimal threshold of $N$ for economizing the system cost is numerically determined.

Different regions in China have different energy consumption characteristics and changing trends. This paper focuses on analyzing trends in energy consumption changes along the timeline for 30 regions in China. Using the Hybrid Input-Output Model, this paper decomposes energy consumption in 30 regions in 2007, 2012 and 2016 into energy embedded of final consumption expenditure, gross capital formation, inflow and outflow. We use these four dimensions as coordinates to draw a regional radar map. According to the changing characteristics of the radar map, 30 regions are divided into three groups. By analyzing the reasons for the changes in three regions, we draw the following conclusions. For regions where energy consumption is mainly inflow, the economically developed regions have to form a low energy consumption environment while achieving economic growth. The economically underdeveloped regions need to carry out energy conservation and emission reduction as well as ensuring the level of economic development. For some outflow regions with moderately economic development, it is necessary to balance the economic development and energy consumption control according to regional characteristics. For resource-rich regions which are in the process of transformation from agriculture to industrialization, they have to maintain the rapid development speed and strengthen their infrastructure with less energy consumption of buildings.

Multilayer InSe has attracted increasing attention due to its excellent electrical and optical properties, making it great potential application in high performance electronic and optoelectronic devices. Alloy engineering is a powerful method to tune electrical and optical properties of semiconductors. However, the alloy engineering has never been applied to multilayer InSe. In this work, for the first time, multilayer InSe0.82Te0.18 alloy photodetector was fabricated and the photodetection performance of multilayer InSe0.82Te0.18 alloy was investigated. Compared to multilayer InSe, the multilayer InSe0.82Te0.18 alloy shows a broader photoresponse region of 400–1100 nm, which is due to its smaller direct bandgap of 1.13 eV. The InSe0.82Te0.18 alloy photodetector exhibits higher photodetection performance than InSe device and the responsivity (R) values are significantly enhanced by 50–300 times, especially in near-infrared (NIR) light region. The R value is 7.1 A/W for 1100 nm light, which surpasses most of multilayer layered semiconductors based NIR photodetector. Moreover, the InSe0.82Te0.18 alloy photodetector owns a good photoresponse stability and relatively fast response time. This work demonstrates that InSe0.82Te0.18 alloy has a great potential application in NIR photodetector.

The authors describe a multifunctional magnetic molecularly imprinted phosphorescent nanoparticle probe for the selective determination of 2,4,6-trichlorophenol (2,4,6-TCP). The probe consists of a magnetite (Fe3O4) core that is coated with a molecularly imprinted polymer doped with Mn-doped ZnS quantum dots (QDs). The MIP was obtained by copolymerization of acrylamide, ethylene glycol dimethacrylate, and 2,4,6-TCP. The resulting nanoprobe shows strong phosphorescence (with excitation/emission peaks at 320/594 nm) due to the presence of the QDs, good magnetism, and high selectivity for 2,4,6-TCP. Under optimal detection condition, response is linear in the 0.1–30 μmol L−1 2,4,6-TCP concentration range. The imprinting factor is 8.84, and the detection limit is 35 nmol L−1. The method was successfully applied to the determination of 2,4,6-TCP in spiked river water and waste water.

The study presents a new approach for rapid and ultrasensitive detection of maltol using a glassy carbon electrode (GCE) modified with graphene oxide-wrapped tin oxide@carbon nanospheres (SnO2@C@GO). The morphological and components properties of SnO2@C@GO nanocomposites were investigated by means of X-ray diffraction spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, and electrochemical impedance spectroscopy. SnO2@C@GO nanocomposite on a GCE had a synergetic effect on the electrochemical oxidation of maltol by means of square wave voltammetry. Under the optimum conditions, anodic peak current response of maltol was linear with its concentration in the range of 80nM-10μM, and a detection limit of 12nM was achieved for maltol. The experiment results presented that the method showed good selectivity, sensitivity, reproducibility, and long-term stability, as well as excellent potential for use as an ideal inexpensive voltammetric method applicable for complex food matrices.