An arithmetic-geometric mean inequality approach for determining the optimal production lot size with backlogging and imperfect rework process

Some classical studies on economic production quantity (EPQ) models with imperfect production processes have focused on determining the optimal production lot size. However, these models neglect the fact that the total production-inventory costs can be reduced by reworking imperfect items for a relatively small repair and holding cost. To account for the above phenomenon, we take the out of stock and rework into account and establish an EPQ model with imperfect production processes, failure in repair and complete backlogging. Furthermore, we assume that the holding cost of imperfect items is distinguished from that of perfect ones, as well as, the costs of repair, disposal, and shortage are all included in the proposed model. In addition, without taking complex differential calculus to determine the optimal production lot size and backorder level, we employ an arithmetic-geometric mean inequality method to determine the optimal solutions. Finally, numerical examples and sensitivity analysis are analyzed to illustrate the validity of the proposed model. Some managerial insights are obtained from the numerical examples.     

A new method for microcapsule characterization: use of fluorogenic genipin to characterize polymeric microcapsule membranes

Numerous microcapsule systems have been developed for a wide range of applications, including the sustained release of drugs, cell transplantation for therapy, cell immobilization, and other biotechnological applications. Despite the fact that microcapsule membrane is a dominant factor governing overall microcapsule performance, its characterization is challenging. We report a new method for characterizing microcapsule membranes, using the most common alginate-poly-L-lysine-alginate (APA) microcapsule as an example. Our data demonstrate that genipin, a naturally derived reagent extracted from gardenia fruits, interacts with poly-L-lysine (PLL) and generates fluorescence. This fluorescence allows clear visualization and easy analysis of the PLL membrane in the APA microcapsules using confocal laser scanning microscopy. The results also show that PLL binding correlates to the reaction variables during PLL coating such as PLL concentration and coating time. In addition, five other different microcapsule formulations consisting of PLL and/or chitosan membranes were examined, and the results imply that this method can be extended to characterize a variety of microcapsule membranes. These findings suggest that genipin can serve as a fluorogenic marker for rapid characterization of microcapsule membranes, a superior method that would have important implications for microcapsule research and potential in many other applications.     

The Synthesis of Chitosan Decorated Reduced Graphene Oxide‐Ferrocene Nanocomposite and its Application in Electrochemical Detection Rhodamine B

Chitosan (CS) decorated reduced graphene oxide‐Ferrocene nanocomposite (RGO?Fc?CS) was synthesized by a one‐pot reaction. In the synthesis process of RGO?Fc?CS, GO?Fc was successfully self‐assembled via the π–π interaction, which had the features of large surface area and the high load. Then GO‐Fc and CS linked via one‐pot under alkaline conditions. The FT?IR, TGA, SEM were employed to characterize the successful synthesis of RGO?Fc?CS composites. A miniature electrochemical system was fabricated by RGO?Fc?CS modified glassy carbon electrode (expressed as RGO?Fc?CS/GCE) for the sensitive detection of RhB enantiomers via DPV. Electrochemical results revealed that the RGO?Fc?CS/GCE exhibited high molecular recognition toward RhB. Due to the synergy between the RGO?Fc and CS, the RGO?Fc?CS/GCE showed a linear range of 0.001–70 μM with a LOD of 0.5 nM, indicating that RGO?Fc?CS/GCE has broad application prospects to simplify monitor RhB real‐time.     

Emerging Two-Dimensional Nanomaterials for Cancer Therapy

Two-dimensional (2D) nanomaterials have drawn tremendous attention due to their unique physicochemical properties and promising applications in the fields of electronics, energy storage, and catalysis. Recently, the biomedicine community has gradually started to recognize the great potential of these nanostructured materials for biomedical applications – in particular those related to cancer therapy. In this review, we provide a brief overview of a few representative 2D nanomaterials, discuss their preparation strategies and physicochemical properties, and highlight their applications in cancer nanomedicine. We expect that this review will shed some light on the new opportunities associated with 2D nanomaterials for biomedical research.     

Auto‐Tandem Cooperative Catalysis Using Phosphine/Palladium: Reaction of Morita–Baylis–Hillman Carbonates and Allylic Alcohols

Auto‐tandem catalysis (ATC), in which a single catalyst promotes two or more mechanistically different reactions in a cascade pattern, provides a powerful strategy to prepare complex products from simple starting materials. Reported here is an unprecedented auto‐tandem cooperative catalysis (ATCC) for Morita–Baylis–Hillman carbonates from isatins and allylic carbonates using a simple Pd(PPh₃)₄ precursor. Dissociated phosphine generates phosphorus ylides and the Pd leads to π‐allylpalladium complexes, and they undergo a γ‐regioselective allylic–allylic alkylation reaction. Importantly, a cascade intramolecular Heck‐type coupling proceeds to finally furnish spirooxindoles incorporating a 4‐methylene‐2‐cyclopentene motif. Experimental results indicate that both Pd and phosphine play crucial roles in the catalytic Heck reaction. In addition, the asymmetric versions with either a chiral phosphine or chiral auxiliary are explored, and moderate results are obtained.     

2D Monoelemental Germanene Quantum Dots: Synthesis as Robust Photothermal Agents for Photonic Cancer Nanomedicine

As a new family member of the emerging two‐dimensional (2D) monoelemental materials (Xenes), germanene has shown promising advantages over the prototypical 2D Xenes, such as black phosphorus (BP) and graphene. However, efficient manufacture of novel germanene nanostructures is still a challenge. Herein, a simple top‐down approach for the liquid‐exfoliation of ultra‐small germanene quantum dots (GeQDs) is presented. The prepared GeQDs possess an average lateral size of about 4.5 nm and thickness of about 2.2 nm. The functionalized GeQDs were demonstrated to be robust photothermal agents (PTAs) with outstanding photothermal conversion efficacy (higher than those of graphene and BPQDs), superior stability, and excellent biocompatibility. As a proof‐of‐principle, 2D GeQDs‐based PTAs were used in fluorescence/photoacoustic/photothermal‐imaging‐guided hyperpyrexia ablation of tumors. This work could expand the application of 2D germanene to the field of photonic cancer nanomedicine.     

Effect of microarc oxidation coating on fatigue performance of Ti-Al-Zr alloy

Ceramic coatings of different thickness were fabricated on Ti6Al2Zr1Mo1V alloy by microarc oxidation (MAO), and the effect of the coating on fatigue life was evaluated by 810 Material Test System. The microstructure, phase and chemical composition of the coatings were determined by SEM, XRD and EDS techniques. The coating mainly consists of rutile and a small amount of anatase TiO₂. With oxidation time ranging from 10 to 30 min, the coating thickness increases from 13 to 25 μm, while the interface between coating and substrate becomes more zigzag, characterized by increasing overgrowth regions of coating into substrate. Under the same cyclic stress of 750 MPa, the fatigue life decreases from 2.08 × 10⁶ cycles for uncoated specimen to about 3 × 10⁴ cycles for microarc oxidized specimen. Under the cyclic stress, the thicker the coating, the more cracks initiate in the overgrowth regions of coating into substrate near the interface, which are considered as the notch sites of stress concentration to induce the crack initiation, also is the key factor to cause the facture.     

MIMO量子信道的空间自由度研究

量子通信是一个量子密钥分发过程,目前采用的通信技术严重制约了量子密钥分发的比特率.将多输入多输出（MIMO）技术应用于量子通信系统,提高量子密钥分发的比特率,促进量子通信向高速大容量发展.然而,量子场本身不可避免地存在量子噪声约束容量的增长,限制了可利用空间资源,即空间自由度.文中采用光子场的量子化和满足Schrdinger方程条件的电磁场波动方程推导出MIMO量子信道的空间自由度上限,为开发稳健的MIMO量子通信空时处理算法和优化设计高性能MIMO量子通信系统提供理论基础和技术支持. 关键词： 多输入多输出 量子密钥分发 Schrdinger方程 光子场的量子化     

H2O在SrTiO3-(001)TiO2表面上吸附和解离的密度泛函理论研究

利用密度泛函理论研究了0.25单层(ML),0.5ML,0.75ML和1ML吸附率下H2O在SrTiO3-(001)TiO2表面上的吸附行为.比较了不同吸附率下分子吸附和解离吸附的稳定性,利用微动弹性带(nudged elastic band)方法计算了H2O的解离势垒.结果表明:在低吸附率(0.25ML和0.5ML)时,H2O表现为解离吸附;在0.75ML吸附率下,分子吸附和解离吸附同时存在;而在全吸附(吸附率为1ML)时,分子吸附更稳定.基于对H2O分子与表面之间以及H2O分子之间的电荷转移和相互作用的分析,讨论了吸附率对H2O吸附和解离的影响.