Thermo-physical properties of silica gel for adsorption desalination cycle

Thermo-physical properties, surface characteristics and water vapor uptake capacity are key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle. In the AD cycles, silica gel is used as adsorbent due to their high water vapor uptake capacity, reliability, repeatability and inexpensiveness as compared to other adsorbents. Three types of commercially available silica gels (Type-RD 2560,Type-A5BW and Type-A⁺⁺) are investigated using a surface characteristic analyzer and their thermo-physical properties are evaluated using several analysis methods. The instrument used in this investigation employs the static volumetric method with liquid Nitrogen at 77 K as the filing fluid. The surface area of each adsorbent is studied using Brunauer–Emmett–Teller (BET) method whilst the pore size distribution (PSD) analysis is conducted with the Non-Local Density Functional Theory (NLDFT). It is observed that the Type-A⁺⁺ silica gel (granular type) possesses the highest surface area of 863.6 m²/g amongst the three parent silica gels studied. It has a two-maxima or bimodal distribution pattern where the pore diameters are distributed mostly between 10 Å and 30 Å. Water vapor uptake capacity of silica gels are studied with water vapor dosage apparatus and the results show that the Type-A⁺⁺ silica gel exhibits a highest equilibrium uptake at 537 cm³/g. These thermo-physical properties are essential for the design and the numerical simulation of AD cycles.     

Stackable ROADMs for minimizing lightpath interference during upgrade of in-service WDM networks

Bidirectional stackable ROADMs (BS-ROADMs) with 3-port optical add/drop multiplexers (OADMs) have been presented for minimizing the lightpath interference during reconfiguration of the ROADMs. The BS-ROADM is constructed by connecting some modules with different wavelengths, and it is reconfigured by adding new modules required in it. The reconfigurations of the BS-ROADMs are done for upgrading the in-service networks to support newly appeared traffic demand. The experimental results presented in this paper clarify that the BS-ROADM can multiplex and demultiplex the wavelengths successfully without limiting the pass-through wavelengths, providing the wavelength transparent networks. The reconfiguration of an in-service BS-ROADM can be made without influencing any lightpath in the network, and this type of BS-ROADMs is used for premium users. However, while adding a new module in comparatively low-cost BS-ROADMs in-service, the transmission break of some lightpaths might be taken place. The investigated transmission break time was limited within recovery time specified in the service level agreement for best-effort transmission, which has strong cost-effectiveness rather than high QoS. This upgradability of the BS-ROADMs adds more flexibility in coarse wavelength division multiplexing networks in terms of scalability and reconfigurability.     

Circuits simulation of switch devices furnished with gain cell combined to FeRAM

Abstract

This paper has described a new concept on programmable switch device furnished with gain cell combined to FeRAM. Compared with memories but ferroelectric memories under many aspects, they have even been favorably labeled the ideal memory because of their non-volatility, ease of programming and operation by low voltage. As the programming switch, which is very attractive for logic application, SRAM, anti-fuse, flash type devices are well known. They have been required that satisfy non-volatility and low-voltage programming simultaneously. Some structures with ferroelectric material have been proposed and studied as solution of these problems. However, it seemed hard that these type devices are realized now from a viewpoint of fabrication process and low voltage operation. Therefore, we propose a new switch device furnished with gain cell combined to FeRAM. We have studied and simulated this switch device by SPICE. This basic circuit is composed of two blocks. One is switching block that includes gain cell, and the other is memory block that is FeRAM. Circuits, which we designed, amplify bit line's voltage up to Vdd or ground at sense amplification according to FeRAM data. The bit line voltage determines the logic state for gate electrode of switch transistor. The way to read is destructive read out. However, we can transfer information of bit line voltage during plate line is low-level voltage. The way to write FeRAM is similar to conventional way. It is revealed that the basic circuit with FeRAM connected gain cell could work correctly in simulation. In addition, this kind of device is hopeful of many logic applications.     

Preparation and morphology of transparent poly(methyl methacrylate)–poly(dimethylsiloxane) hybrid materials using multifunctional silicone macromonomer

In this study, transparent poly(methylmethacrylate) (PMMA)‐silicone hybrid materials, P(MMA‐co‐SigUMAx), were prepared with methylmethacrylate (MMA) and multifunctional silicone macromonomer introduced methacryl groups. The transmittance of hybrid materials improved with increase of methacryl groups of silicone macromonomer and reached around 90% T. Atomic force microscopic analysis, scanning electron microscope examinations, and copolymerization kinetics estimation by proton nuclear magnetic resonance revealed that the silicone macromonomer randomly incorporated in the copolymer with MMA by the increase of methacryl groups and suppresses the aggregation of the silicone segment. The hybrid materials introduced over 10 wt % of silicone component had water‐shedding surface and the water contact angle was elevated from 65 to 95°. Though the mechanical properties of hybrid materials were lowered by introduction of flexible silicone component, thermal property such as 5 wt % weight loss temperature were improved. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Elongational viscosity for miscible and immiscible polymer blends. I. PMMA and AS with similar elongational viscosity

The effects of miscibility and blend ratio on uniaxial elongational viscosity of polymer blends were studied by preparing miscible and immiscible samples at the same composition by using poly(methyl methacrylate) (PMMA) and poly(acrylonitrile-co-styrene) (AS). Miscible polymer blend samples for the elongational viscosity measurement were prepared by using three steps: solvent blends, cast film, and hot press. A phase diagram of blend samples was made by visual observation of cloudiness. Immiscible blend samples were prepared by maintaining the prepared miscible samples at 200°C, which is higher than cloud points using a LCST (lower critical solution temperature) phase diagram. The phase structure of immiscible blends was observed by an optical microscope. The elongational viscosity of all samples was measured at 145°C, which is lower than the cloud-point temperature at all blend ratios. The elongational viscosity of PMMA and AS was similar to each other. The strain-hardening property of miscible blends in the elongational viscosity was only slightly influenced by the blend ratio, and this was also the case with immiscible blends. The strain-hardening property was only slightly influenced, whether it was miscible or immiscible at each blend ratio. Polydispersity in molecular weight for blend samples was not changed by GPC (gel permeation chromatography) analysis. Almost no change in the polydispersity of the molecular weight for blends and the similarity of elongational viscosity between PMMA and AS resulted in little influence of the blend ratio and miscibility on the strain-hardening property. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 757–766, 1999     

Effect of chain structure on the melt rheology of modified polypropylene

The effect of molecular structure of polypropylene (PP) on the melt rheological properties were investigated for electron irradiated polymer and di-2-ethylhexyl peroxy dicarbonate (EHPC)-treated polymer. The modifications were examined in terms of the rheological behaviors, molecular weight distribution, and the degree of branching. The high melt strength PP was obtained by irradiating with 50 and 80 kGy and adding EHPC. The modified PPs showed the strain hardening in the uniaxial elongational viscosity, though the linear elongational viscosity was lower than that of the unmodified PP. Low angle laser light-scattering measurements of the modified PPs showed the interesting results; high irradiation doses such as 50 and 80 kGy caused higher molecular weight chains branching. Nevertheless, the long branching chains were not detected for the EHPC modified PP, which also showed the strain hardening in uniaxial elongational flow. In this article, the relation between chain structure and rheological properties is discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1493–1500, 1999     

A 250-MHz single-chip multiprocessor for audio and video signalprocessing

A 250-MHz single-chip multiprocessor, which can implement multichannel decoding, encoding, and transcoding of various audio and video standards, was fabricated using 0.25-μm CMOS technology and consumes 2.38 W at 2.5 V. The multiprocessor integrates four processors and 64-kB shared level-2 cache and exploits coarse-grained parallelism inherent in audio and video signal processing with multithreaded programming. Three coprocessors and scratch-pad memory have been added to each processing element and perform subword parallel processing, background data transfer, and bitstream processing for audio and video signal processing. Useful-skew and clock gating have been utilized to achieve high-speed operation and low power consumption. Consequently, the multiprocessor achieves MPEG2 (MP@HL) video decoding at 20 frames/s     

Recent progress in CdZnTe crystals

CdZnTe crystals were grown by vertical gradient freezing (VGF) method with a Cd reservoir for controlling the Cd pressure under conditions such that the crystals are in equilibrium with a Cd vapor corresponding to the minimum deviation from stoichiometry. The precipitate size became smaller by a post growth annealing method in the VGF furnace after the crystal growth without using wafer annealing. The size became less than 2 μm. Precipitate-free crystals were also grown by controlling the cooling method. In addition, the carrier concentration of p-type CdZnTe crystals was reduced using polycrystals grown in pBN boats. We have found that the carrier concentration of p-type ingots is dependent on Na and Li impurity concentrations.     

Overall numerical simulation of extrusion blow molding process

This paper focuses on the overall numerical simulation of the parison formation and inflation process of extrusion blow molding. The competing effects due to swell and drawdown in the parison formation process were analyzed by a Lagrangian Eulerian (LE) finite element method (FEM) using an automatic remeshing technique. The parison extruded through an annular die was modeled as an axisymmetric unsteady nonisothermal flow with free surfaces and its viscoelastic properties were described by a K‐BKZ integral constitutive equation. An unsteady die‐swell simulation was performed to predict the time course of the extrudate parison shape under the influence of gravity and the parison controller. In addition, an unsteady large deformation analysis of the parison inflation process was also carried out using a three‐dimensional membrane FEM for viscoelastic material. The inflation sequence for the parison molded into a complex‐shaped mold cavity was analyzed. The numerical results were verified using experimental data from each of the sub‐processes. The greatest advantage of the overall simulation is that the variation in the parison dimension caused by the swell and drawdown effect can be incorporated into the inflation analysis, and consequently, the accuracy of the numerical prediction can be enhanced. The overall simulation technique provides a rational means to assist the mold design and the determination of the optimal process conditions.