An EOQ inventory model with time-varying demand and Weibull deterioration with shortages

An inventory model is considered in which inventory is depleted not only by demand, but also by deterioration. Hence, in this paper, we derive the EOQ model for inventory of items that deteriorate at a Weibull-distributed rate, assuming the demand rate with a continuous function of time. Moreover, the proposed model cannot be solved directly in a closed form, thus we used the computer software IMSL MATH/LIBRARY (1989) to find the optimal reorder time. Further, we also find that the optimal procedure is independent from the form of the demand rate. Finally, we also assume that the holding cost is a continuous, non-negative and non-decreasing function of time in order to generalize the EOQ model. Moreover, four numerical examples and sensitivity analyses are provided to assess the solution procedure.     

An EOQ model for deteriorating items with time-varying demand and shortages

The study explores the inventory replenishment policies for the cases with time-varying demand, linearly increasing deterioration rate, partial back-ordering, constant service level and equal replenishment intervals over a fixed planning horizon. Since it is difficult to solve the problem directly, we derive the upper bound of replenishment number for a specific planning horizon and find the solution of service level under a given number of replenishment. The optimal solutions of replenishment number and service level are then determined. Numerical examples and sensitivity analyses are also provided to illustrate the solution procedure.     

Inferences on the lifetime performance index for Weibull distribution based on censored observations using the max p-value method

In the service (or manufacturing) industries, process capability indices (PCIs) are utilised to assess whether product quality meets the required level. And the lifetime performance index (or larger-the-better PCI) C_L is frequently used as a means of measuring product performance, where L is the lower specification limit. Hence, this study first uses the max p-value method to select the optimum value of the shape parameter β of the Weibull distribution and β is given. Second, we also construct the maximum likelihood estimator (MLE) of C_L based on the type II right‐censored sample from the Weibull distribution. The MLE of C_L is then utilised to develop a novel hypothesis testing procedure provided that L is known. Finally, we give one practical example to illustrate the use of the testing procedure under given significance level α.     

Effect of pre-aging pH on the formation of yttrium aluminum garnet powder (YAG) via the solid state reaction method

Yttrium aluminum garnet (YAG) powder was successfully synthesized by a novel solid state reaction method. The starting materials including: yttrium oxide (Y₂O₃), boehmite (AlOOH) and cerium chloride (CeCl₃·7H₂O) are pre-aged at pH 1, 2 and 3, respectively, before calcining. According to the experimental results, the case of pre-aging at pH 1 is the best condition for the formation of YAG powder. The particle size of Y₂O₃ and AlOOH are reduced by the pre-aging at pH 1. It induces to shorten the diffusion distance of the solid state reaction. The pre-aging at pH 1 process leads the formation of YAG powder via solid state reaction more easily. The emission intensity of the product was increased by the decrease of the pre-aging pH, the increase of the calcination temperature and the increase of the heating time.     

Monthly Runoff Forecasting Using Variational Mode Decomposition Coupled with Gray Wolf Optimizer-Based Long Short-term Memory Neural Networks

Water Resources Management - Accurate and reliable monthly runoff forecasting plays an important role in making full use of water resources. In recent years, long short-term memory neural networks...     

Balanced detection spectral domain optical coherence tomography with a multiline single camera for signal-to-noise ratio enhancement

In this study, the use and advantages of balanced detection (BD) in spectral domain optical coherence tomography (SD-OCT) are demonstrated. A-scans are calculated as a combination of two phase-opposed interferometric spectra acquired simultaneously by using a multiline single camera spectrometer. Not only does this system suppress artifacts due to autocorrelation, but also the signal of interest is increased by a factor of 2 as experimentally verified. Our BD-based SD-OCT gives a signal-to-noise ratio improvement of 8-14?dB for the peak within 1?mm compared to standard SD-OCT using a single detection scheme. This method is validated by experimental measurement of a glass plate.     

基于公共光学基准的大尺寸空间角度测量关键技术

提出了基于公共光学基准的大尺寸空间的角度测量方法。通过在数米至十几米的大尺寸空间内建立公共光学基准,结合视觉测量和计算机图像处理技术,借助测量公共方向基准与各个几何元素之间的夹角,可简便地实现对大尺寸空间的异面几何元素之间夹角的测量。分析了建立公共光学基准的方法。按照所提出的测量方法,对相距7m的两条异面直线的空间夹角成功地进行了现场测量。     

Optimizing Hydropower Reservoir Operation Using Hybrid Genetic Algorithm and Chaos

Genetic algorithms (GA) have been widely applied to solve water resources system optimization. With the increase of the complexity and the larger problem scale of water resources system, GAs are most frequently faced with the problems of premature convergence, slow iterations to reach the global optimal solution and getting stuck at a local optimum. A novel chaos genetic algorithm (CGA) based on the chaos optimization algorithm (COA) and genetic algorithm (GA), which makes use of the ergodicity and internal randomness of chaos iterations, is presented to overcome premature local optimum and increase the convergence speed of genetic algorithm. CGA integrates powerful global searching capability of the GA with that of powerful local searching capability of the COA. Two measures are adopted in order to improve the performance of the GA. The first one is the adoption of chaos optimization of the initialization to improve species quality and to maintain the population diversity. The second is the utilization of annealing chaotic mutation operation to replace standard mutation operator in order to avoid the search being trapped in local optimum. The Rosenbrock function and Schaffer function, which are complex and global optimum functions and often used as benchmarks for contemporary optimization algorithms for GAs and Evolutionary computation, are first employed to examine the performance of the GA and CGA. The test results indicate that CGA can improve convergence speed and solution accuracy. Furthermore, the developed model is applied for the monthly operation of a hydropower reservoir with a series of monthly inflow of 38 years. The results show that the long term average annual energy based CGA is the best and its convergent speed not only is faster than dynamic programming largely, but also overpasses the standard GA. Thus, the proposed approach is feasible and effective in optimal operations of complex reservoir systems.     

基于差示扫描量热法的大豆原油掺伪 鉴别方法的建立

目的应用差示扫描量热仪(DSC)和油脂氧化稳定性测试仪(OSI)测试掺伪大豆原油的氧化稳定性(以诱导氧化时间表示),从而建立大豆原油掺伪的分析鉴别方法。方法设定OSI仪的氧化温度为110℃,氧气流量为20 L/h,DSC的氧化温度为110、120、130℃,氧气流量为50 m L/min,选择最佳氧化温度。记录各方法的诱导氧化时间。结果 DSC的诱导氧化时间随氧化温度提高不断缩短,确定130℃为DSC方法最佳氧化温度,不同比例掺伪大豆原油的OSI法的诱导氧化时间为320~495 min,DSC法诱导氧化时间为40~80 min。随着掺伪浓度增大,诱导氧化时间不断缩短。OSI法的掺伪检出限为掺伪浓度5%,DSC法的掺伪检出限为掺伪浓度10%。两种方法具有显著的正相关性:To(OSI110)=5.2480To(DSC130)+77.6799,r=0.9951。结论两种方法均可用于大豆原油掺伪鉴别,但DSC方法用量小,检测时间短,更适用快速鉴别。     

联用VIDAS法和API Listeria法对食品中李斯特氏菌检验及分类

联用ＶＩＤＡＳ法（酶联免疫自动分析法）和ＡＰＩ Ｌｉｓｔｅｒｉａ法;充分利用Ｖｉｄａｓ法的快速筛选性和ＡＰＥ Ｌｉｓｔ－ｅｒｉａ的最终确定性检验及分类食品中李斯特氏菌属。实验结果显示,它可以检验并判断李斯特氏菌属中所有的菌种;其鉴定周期可从原来的１０ｄ缩减到５ｄ,阴性结果的判断时间也从原来的７２ｈ,提前到现在的４８ｈ。该方法应用在１１５个实际样品中所得出的结果证明,联用方法较单一鉴定法快捷、有效。运用于食品中李斯特氏菌的检验和分类中,可以取得了令人满意的结果。