On scheduling a multiclass queue with abandonments under general delay costs

We consider a multiclass queueing system with abandonments and general delay costs. A system manager makes dynamic scheduling decisions to minimize long-run average delay and abandonment costs. We consider the three types of delay cost: (i) linear, (ii) convex, and (iii) convex–concave, where the last one corresponds to settings where customers may have a particular deadline in mind but once that deadline passes there is increasingly little difference in the added delay. The dynamic control problem for the queueing system is not tractable analytically. Therefore, we consider the system in the conventional heavy traffic regime and study the approximating Brownian control problem (BCP). We observe that the approximating BCP does not admit a pathwise solution due to abandonments. In particular, the celebrated cμ rule and its extension, the generalized cμ rule, which is asymptotically optimal under convex delay costs with no abandonments, are not optimal in this case. Consequently, we solve the associated Bellman equation, which yields a dynamic index policy (derived from the value function) as the optimal control for the approximating BCP. Interpreting that control in the context of the original queueing system, we propose practical policies for each of the three cases considered and demonstrate their effectiveness through a simulation study.     

Mechanism of nanocapsules of Matricaria recutita L. extract formation by the emulsion–diffusion process

Nanocapsules coated by medicinal plants have many applications in drug manufacturing. Medicinal plants can be loaded on nanocapsules with polyesteric triblock copolymer poly ethylene glycol–poly butylene adipate–poly ethylene glycol (PEG–PBA–PEG) as shell and olive oil can be introduced as a core of nanocapsules by a method known as polymer deposition solvent evaporation method. In this research, first, certain amount of polymer, Matricaria recutita extract and olive oil were mixed with acetone and then, water was added to the solution using magnetic stirrer. After which the acetone was removed by vacuuming and finally nanocapsules were found by freezing-drier. The study showed the size of nanocapsules depends on variety of factors such as the ratio of polymer to oil and concentration of polymers and plant extract. The nanocapsules were identified by scanning electron microscopy (SEM) and zeta potential sizer (ZPS), Fourier-transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR).     

Correction to: An improved quasi-zero stiffness vibration isolation system utilizing dry friction damping

Nonlinear Dynamics - Equation 7 should appear as follows     

IR signature estimation of an object or a target by taking into account atmospheric effects

In this study, a reference infrared (IR) image of an object or a target was analyzed, and the IR signature was calculated. Background and atmospheric effects were decomposed so that the calculation errors were minimized. Depending on the reference IR image, the IR signature at any distance and any angle was estimated while considering atmospheric effects. Calculated results were obtained from IR images taken from the same distance and angle, and were compared with the estimated results. The comparison of the measured and calculated signatures demonstrated the accuracy of the proposed method of estimation.     

An economic order quantity model with partial backordering and a special sale price

A constant unit purchase cost is one of the main assumptions in the classic economic order quantity model. In practice, suppliers sometimes offer special sale prices to stimulate sales or decrease inventories of certain items. In this paper we develop an EOQ model with a special sale price and partial backordering. We prove the convexity of the cost-reduction function if a special order is placed at the special sale price. A solution method is proposed and numerical examples are presented.     

Parylene to silicon nitride bonding for post-integration of high pressure microfluidics to CMOS devices

High pressure-rated channels allow microfluidic assays to be performed on a smaller footprint while keeping the throughput, thanks to the higher enabled flow rates, opening up perspectives for cost-effective integration of CMOS chips to microfluidic circuits. Accordingly, this study introduces an easy, low-cost and efficient method for realizing high pressure microfluidics-to-CMOS integration. First, we report a new low temperature (280 °C) Parylene-C wafer bonding technique, where O(2) plasma-treated Parylene-C bonds directly to Si(3)N(4) with an average bonding strength of 23 MPa. The technique works for silicon wafers with a nitride surface and uses a single layer of Parylene-C deposited only on one wafer, and allows microfluidic structures to be easily formed by directly bonding to the nitride passivation layer of the CMOS devices. Exploiting this technology, we demonstrated a microfluidic chip burst pressure as high as 16 MPa, while metal electrode structures on the silicon wafer remained functional after bonding.     

Dynamic power control in a fading downlink channel subject to an energy constraint

A central controller chooses a state-dependent transmission rate for each user in a fading, downlink channel by varying transmission power over time. For each user, the state of the channel evolves over time according to an exogenous continuous-time Markov chain (CTMC), which affects the quality of transmission. The traffic for each user, arriving at the central controller, is modeled as a finite-buffer Markovian queue with adjustable service rates. That is, for each user data packets arrive to the central controller according to a Poisson process and packet size is exponentially distributed; an arriving packet is dropped if the associated buffer is full, which results in degradation of quality of service. The controller forwards (downlink) the arriving packets to the corresponding user according to an optimally chosen transmission rate from a fixed set A _i of available values for each user i, depending on the backlog in the system and the channel state of all users. The objective is to maximize quality of service subject to an upper bound on the long-run average power consumption. We show that the optimal transmission rate for each user is solely a function of his own packet queue length and channel state; the dependence among users is captured through a penalty rate. Further, we explicitly characterize the optimal transmission rate for each user. This project is partially supported by Motorola grant # 0970-350-AF24. The authors thank Phil Fleming,Randy Berry and Achal Bassamboo for helpful comments.     

Inhibition of Survivin Restores the Sensitivity of Breast Cancer Cells to Docetaxel and Vinblastine

Combination therapy is considered a viable strategy to overcome the resistance to chemotherapeutics. Survivin as a member of the inhibitor of apoptosis protein (IAP) family, which is involved in resistance to various drugs. We investigated the role of combination therapy in downregulating survivin and increasing drug’s efficacy in MDA-MB-231 cells. MTT assay and DAPI staining were applied to study the anti-proliferative activity and apoptosis response of the agents. Real-time RT-PCR and Western blot analysis were applied to study survivin mRNA and protein. Our findings showed that combined treatment of cells with docetaxel and vinblastine reduces survivin expression and consequently decreases the IC₅₀ value of docetaxel from 70 to 5 nM (p?p?相似文献