Design and simulation of pyroelectric detectors with nanometer size spider-web for low thermal conductance

We report the design and simulation of uncooled pyroelectric detectors which utilizes a nanometer sized mesh or truss to support the suspended detector. Pyroelectric detector is a class of thermal detector in which the change in temperature causes the change in the spontaneous polarization in the sensing material. Ca modified lead titanate (PCT) was selected as the thermometer in the detector because of its high pyroelectric figure of merit. The design and simulation of pyroelectric detectors have been conducted by simulating the structure with Intellisuite™. Finite element method (FEM) was used to simulate the structural and thermal properties of the device. The simulated detectors had a spider web-like structure with each of the strut (ring) of spider web had a width of 100 nm. In the design, the pyroelectric detectors utilized Ni_0.8Cr_0.2 absorber, PCT sensing layer, Ti electrodes, Al₂O₃ structural layer to obtain low thermal conductance between the detector and Si substrate. Three different types of pyroelectric detectors were designed and analyzed. The first design had linear electrode and simple spider web support. The value of the thermal conductance of this detector was found to be 3.98 × 10⁻⁸ W/K. The second design had a longer thermal path than the first one and the thermal conductivity of this device was found to be 2.41 × 10⁻⁸ W/K. High detectivity was obtained by reducing the thermal conductance between the sensing layer and the substrate or the heat sink in the third design. The design was optimized for the best result by modifying the shape, dimension and thickness of various layers namely absorber, electrodes, sensing layer, and struts. The thermal conductance between the sensor and the substrate using the third design was found to be as low as 4.57 × 10⁻⁹ W/K which is significantly lower than previously reported values. The thicknesses of the web structure, web support, electrodes, sensing layer, and absorber of the final structure were 2, 1, 0.5, 2, and 0.2 µm respectively for this value of thermal conductance. The absorber diameter was 50 µm and the diameter of the spider web was 200 µm. A total of 80 struts with 100 nm width were used in the design.

     

CRAN,H‐CRAN,and F‐RAN for 5G systems: Key capabilities and recent advances

The world of telecommunication is witnessing a swift metamorphosis towards fifth generation cellular networks. Particularly, the rapid shift from a user centric to a device centric communication has created a tremendous impact on service complexity and network requirements. The future networks present requisite needs in ubiquitous throughput, low latency, and high reliability. They are also envisioned to provide energy efficiency, spectrum reuse, network scalability, and robustness as well as improved quality of user experience, which proves to be of ultimate importance. Accordingly, government, academic, and industrial institutions are working together to fulfill these challenging goals. Their research efforts have been extensively reported in various topics and directions, such as heterogeneous small cell networks, millimeter wave communication, massive multiple input multiple output, network function virtualization, software‐defined network, and device‐to‐device communication. More interestingly, a revolutionary network architecture based on cloud computing and centralized processing is adopted as one of the best candidates for fifth generation. It is denoted Cloud Radio Access Network (CRAN) and (H‐CRAN) in heterogeneous networks. An upgraded version, namely, Fog RAN (F‐RAN), with caching and fog computing capabilities is also presented. Environmental friendly, it ensures flexibility and scalability with reduced expenditures. This paper presents the aforementioned key technological functionalities and surveys the benefits and challenges of CRAN, H‐CRAN, and F‐RAN.     

Experimental and numerical evaluation of the impact of folds on the pressure rating of CIPP liners

A cast-iron water main rehabilitated with a thermoplastic structural liner can be viewed as a hybrid pipe. Depending on the degree of corrosion of the host pipe, stress levels carried by the liner may vary significantly. Several limit states can be developed for a liner-pipe structural system. One such state is related to the presence of a longitudinal fold in a cured-in-place-pipe (CIPP) liner that coincides with gaps in the host pipe’s wall. This paper reports the results of an experimental testing and numerical modeling study undertaken to evaluate the impact of a longitudinal fold on the ability of a CIPP liner to resist internal pressures when there are significant gaps present in the host pipe’s wall. Two 3-D numerical models were constructed and validated using physical testing and the analytical solutions provided in ASTM F 2207-02. The results of a parametric study performed to estimate the stress concentration in the fold as a function of the fold’s geometry and level of applied internal pressure are also reported. An empirical approach is proposed as a basis for a guideline regarding the maximum allowable oversizing of CIPP liners in pressure pipes.     

Utilization of Trenchless Construction Methods by Canadian Municipalities

Trenchless technology is an emerging area of construction involving innovative methods, materials, and equipment used for the installation of new and the rehabilitation or replacement of existing underground infrastructure with minimal or no need for open cut excavation. This technology provides an alternative to traditional methods of open trenching construction, which is often associated with major disruptions to surface activities. The results of a survey of trenchless construction methods in Canada are presented in this paper. The survey, which was sent to 87 municipalities across Canada, provides an indication of current and future trends in the application of trenchless construction technologies in the municipal arena including type and frequency of technologies employed, percentage of projects that employed trenchless technologies, and contractor selection methods. The survey results indicate that trenchless technology is gaining increasing popularity among municipal engineers across Canada. The percentage of all municipal projects utilizing trenchless construction methods has grown over the past 5 years by 180% (new construction) and 270% (rehabilitation). The survey also revealed that the typical Canadian municipality spends $29.68∕capita on new construction of municipal service lines and $18.21∕capita on rehabilitation of existing lines.     

Tensile Properties and Fusion Zone Hardening for GMAW and MIEA Welds of a 7075-T651 Aluminum Alloy

Tensile and hardness values for 7075-T651 aluminum alloy in the as welded and post weld heat treated conditions（solubilization and artificial aging-T6）,obtained using GMAW and modified indirect electric arc（MIEA）welding processes are presented.Results showed that the base material along rolling direction exhibited a tensile strength of around 600 MPa and elongation of 11%.For the as welded condition,tensile strength was 260 MPa and elongation percent of 3%.This behavior was attributed to brittleness induced by the microstructural characteristics of the welded alloys,as well as high porosity.Hardness profiles along the welds were obtained and different welded zones were identified.A soft zone（＊100 HV0.1） in the heat affected zone for GMAW and MIEA was observed,the minimum hardness corresponding to weld metal（＊85 and ＊96 HV0.1for GMAW and MIEA,respectively）.The high dilution between filler and base metal during welding in MIEA allows to the Zn and Cu to flow from the base metal into the weld metal,inducing hardening by solution and subsequent artificial aging.In this regard,the hardness of the weld metal for MIEA increases by 56%,while the tensile strength reaches a value close to 400 MPa.For GMAW,non-favorable hardening effect was observed for the weld metal after solution and artificial aging.     

Erythrocyte Toxicities of Imidazolidinyl Urea and Diazolidinyl Urea

The addition of antimicrobial preservatives to pharmaceutical and cosmetic products is necessary to prevent microbial growth. However, the use of preservatives can also produce other undesirable effects. For several years, researchers have been investigating the use of alternative methods in safety assessment of cosmetic ingredients and formulations by means of variety methods. The aim of this study was to evaluate the erythrocyte toxicities of two commercial preservatives： imidazolidinyl urea and diazolidinyl urea. Relatively few studies about the cytotoxicity of these preservative are available. The determination of their cytotoxicity is an essential step to warrant their safe use. Erythrocyte toxicities were evaluated by assessment of the amount of hemoglobin released by red blood cells after their lysis. In this study, both imidazolidinyl urea and diazolidinyl urea showed cytotoxic activity against red blood cells. The imidazolidinyl urea induce a small release of hemoglobin after 120 min of incubation. But, the diazolidinyl urea induce a massive release of hemoglobin from the imidazolidinyl urea （a rate of 83% at concentrations of 6.25 mg/mL and 12.5 mg/mL）.     

Sorption properties of the iminodiacetate ion exchange resin,amberlite IRC‐718, toward divalent metal ions

The sorption properties of the commercially available cationic exchange resin, Amberlite IRC‐718, that has the iminodiacetic acid functionality, toward the divalent metal‐ions, Fe²⁺, Cu²⁺, Zn²⁺, and Ni²⁺ were investigated by a batch equilibration technique at 25°C as a function of contact time, metal ion concentration, mass of resin used, and pH. Results of the study revealed that the resin exhibited higher capacities and a more pronounced adsorption toward Fe²⁺ and that the metal‐ion uptake follows the order: Fe²⁺ > Cu²⁺> Zn²⁺ >Ni²⁺. The adsorption and binding capacity of the resin toward the various metal ions investigated are discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Unbiased high-throughput screening of reactive metabolites on the linear ion trap mass spectrometer using polarity switch and mass tag triggered data-dependent acquisition

Constant neutral loss (CNL) and precursor ion (PI) scan have been widely used for the in vitro screening of glutathione conjugates derived from reactive metabolites, but these two methods are only applicable to triple quadrupole or hybrid triple quadrupole mass spectrometers. Additionally, the success of CNL and PI scanning largely depends on structure and CID fragmentation pathways of GSH conjugates. In the present study, a highly efficient methodology has been developed as an alternative approach for high-throughput screening and structural characterization of reactive metabolites using the linear ion trap mass spectrometer. In microsomal incubations, a mixture of glutathione [GSH, gamma-glutamyl-cystein-glycin] and the stable-isotope labeled compound [GSX, gamma-glutamyl-cystein-glycin-(13)C2-(15)N] was used to trap reactive metabolites, resulting in formation of both labeled and unlabeled conjugates at a given isotopic ratio. A mass difference of 3.0 Da between the natural and labeled GSH conjugate (mass tag) at a fixed isotopic ratio constitutes a unique mass pattern that can selectively trigger the data-dependent MS(2) scan of both isotopic partner ions, respectively. In order to eliminate the response bias of GSH adducts in the positive and negative mode, a polarity switch is executed between the mass tag-triggered data dependent MS(2) scan, and thus ESI- and ESI+ MS(2) spectra of both labeled and nonlabeled GSH conjugates are obtained in a single LC-MS run. Unambiguous identification of glutathione adducts was readily achieved with great confidence by MS(2) spectra of both labeled and unlabeled conjugates. Reliability of this method was vigorously validated using several model compounds that are known to form reactive metabolites. This approach is not based on the appearance of a particular product ion such as MH(+) - 129 and anion at m/z 272, whose formation can be structure-dependent and sensitive to the collision energy level; therefore, the present method can be suitable for unbiased screening of any reactive metabolites, regardless of their CID fragmentation pathways. Additionally, this methodology can potentially be applied to triple quadrupole or hybrid triple quadrupole mass spectrometers.     

Carbon dioxide absorption by monoethanolamine in hollow fiber membrane contactors: A parametric investigation

A mathematical and numerical investigations on the gas–liquid absorption of carbon dioxide in monoethanolamine solutions in a hollow fiber membrane contactor device is described. The reactive absorption mechanism was built based on momentum and mass transport conservation laws in all three compartments involved in the process, i.e., the gas phase, the membrane barrier, and the liquid phase. The liquid absorbing solution flows in the fiber bore in which the velocity is assumed to obey a fully developed laminar flow, and the gas mixture circulates counter‐currently to the liquid flow in the shell side where the velocity is characterized by the Navier‐Stokes momentum balance equations. The average outlet gas and liquid concentrations, the reactive absorption flux, and the gas removal efficiencies are parametrically simulated with operational parameters such as gas flow rate, fresh inlet amine concentrations, and fiber geometrical characteristics. The shell velocity was described by other flow hydrodynamics models besides Navier‐Stokes and their simulated results were favorably compared to experimental data. © 2011 American Institute of Chemical Engineers AIChE J, 2012