A comparative study of modeling and solution approaches for the coordinated lot-size problem with dynamic demand

In the coordinated lot-size problem, a major setup cost is incurred when at least one member of a product family is produced and a minor setup cost for each different item produced. This research consolidates the various modeling and algorithmic approaches reported in the literature for the coordinated replenishment problem with deterministic dynamic demand. For the two most effective approaches, we conducted extensive computational experiments investigating the quality of the lower bound associated with the model’s linear programming relaxation and the computational efficiency of the algorithmic approaches when used to find heuristic and optimal solutions. Our findings indicate the superiority of the plant location type problem formulation over the traditional approach that views the problem as multiple single-item Wagner and Whitin problems that are coupled by major setup costs. Broader implications of the research suggest that other classes of deterministic dynamic demand lot-size problems may also be more effectively modeled and solved by adapting plant location type models and algorithms.     

A comparison of plasma and electron beam-sterilization of PU catheters

Polyurethane (PU) catheters made of Pellethane 2363-80AE^® were treated in two different ways: a new treatment with low temperature plasma that could be used to decontaminate reusable polymer devices in hospitals, and an e-beam (EB) irradiation. Polymer structure and bulk properties were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR) and size exclusion chromatography (SEC). Although PU was strongly modified by the e-beam irradiation leading to branching of polymer chains, it had no or little impact on the thermo-mechanical properties of the catheters and on the hard/soft segment organization of PU. For plasma-treated samples, no modification in the polymer bulk was observed, confirming that plasma treatment might be considered as an alternative to e-beam irradiation. The analysis of surface modifications showed an evolution of superficial topology and chemical composition (grafting of oxygen and nitrogen species) of the catheters after treatment, with a more polar and hydrophilic surface.     

A branch-and-price algorithm for the two-stage guillotine cutting stock problem

We investigate the two-stage guillotine two-dimensional cutting stock problem. This problem commonly arises in the industry when small rectangular items need to be cut out of large stock sheets. We propose an integer programming formulation that extends the well-known Gilmore and Gomory model by explicitly considering solutions that are obtained by both slitting some stock sheets down their widths and others down their heights. To solve this model, we propose an exact branch-and-price algorithm. To the best of our knowledge, this is the first contribution with regard to obtaining integer optimal solutions to Gilmore and Gomory model. Extensive results, on a set of real-world problems, indicate that the proposed algorithm delivers optimal solutions for instances with up to 809 items and that the hybrid cutting strategy often yields improved solutions. Furthermore, our computational study reveals that the proposed modelling and algorithmic strategy outperforms a recently proposed arc-flow model-based solution strategy.     

The thermodynamics of aqueous borate solutions. II. Mixtures of boric acid with calcium or magnesium borate and chloride

Potentials for the cell without liquid juction

Tunable THz wave absorption by graphene-assisted plasmonic metasurfaces based on metallic split ring resonators

Journal of Nanoparticle Research - La(Ni0.75W0.25)O3 perovskite oxide was prepared via the sol–gel Pechini route. The pure crystalline phase was verified via X-ray diffraction measurements...     

Aging of a medical device surface following cold plasma treatment: Influence of low molecular weight compounds on surface recovery

The surface of medical devices is of great importance for biocompatibility. Surface properties can evolve with a material treatment, time, and storage conditions. In this work, poly(urethane) catheters sterilised by cold nitrogen plasma treatment, were subjected to air and temperature aging in order to evaluate the influence of humidity and temperature on surface recovery. The surface of catheters was analysed by contact angle measurements and XPS. Faster surface changes upon aging were observed at high temperature (45 °C) and relative humidity (90%). For the commercial poly(urethane) catheters analysed in this work, the importance of the nature and polymorphism of additives added to the polymer (lubricant, antioxidant) in the recovery process was demonstrated. Indeed, DSC and TSC showed that additive transitions (relaxation, melting…) could govern the aging process.     

Interrogation of a long-period grating using a mechanically scannable arrayed waveguide grating and a sampled chirped fiber Bragg grating

A novel technique to interrogate a long-period grating (LPG) using a mechanically scannable arrayed waveguide grating (AWG) is proposed. This technique is implemented based on space-to-wavelength mapping by mechanically scanning the input light beam along the input coupler facet of an AWG. By employing a sampled chirped fiber Bragg grating with multiple peaks as a reference, the central wavelength of the LPG is measured. An interrogation system with a resolution of 10 pm at a speed of 10 Hz is demonstrated. Furthermore, the technique proposed can potentially offer subpicometer resolution at a speed of 500 Hz.     

Wearable Capacitive Pressure Sensor for Contact and Non-Contact Sensing and Pulse Waveform Monitoring

Sensitive and flexible pressure sensors have invoked considerable interest for a broad range of applications in tactile sensing, physiological sensing, and flexible electronics. The barrier between high sensitivity and low fabrication cost needs to be addressed to commercialize such flexible pressure sensors. A low-cost sacrificial template-assisted method for the capacitive sensor has been reported herein, utilizing a porous Polydimethylsiloxane (PDMS) polymer and a multiwalled carbon nanotube (MWCNT) composite-based dielectric layer. The sensor shows high sensitivity of 2.42 kPa⁻¹ along with a low limit of detection of 1.46 Pa. The high sensitivity originates from adding MWCNT to PDMS, increasing the composite polymer’s dielectric constant. Besides this, the pressure sensor shows excellent stability at a cyclic loading of 9000 cycles, proving its reliability for long-lasting application in tactile and physiological sensing. The high sensitivity of the sensor is suitable for the detection of small deformations such as pulse waveforms as well as tactile pressure sensing. In addition, the paper demonstrates a simultaneous contact and non-contact sensing capability suitable for dual sensing (pressure and proximity) with a single data readout system. The dual-mode sensing capability may open opportunities for realizing compact systems in robotics, gesture control, contactless applications, and many more. The practicality of the sensor was shown in applications such as tactile sensing, Morse code generator, proximity sensing, and pulse wave sensing.