Performance analysis of RF MEMS capacitive switch with non uniform meandering technique

This Paper reports on investigation of High C_on C_off ratio Capacitive Shunt RF MEMS Switch and detailed comparison between uniform three meander beam with non-uniform single meander beam RF MEMS switch. RF MEMS Switches are designed for operation in the range 5–40 GHz. Pull in analysis is performed with gold as a beam material. Simulation reveals that use of high K dielectric material can drastically improve the capacitance ratio of switch. For the same geometry, pull in voltage is 2.45 V for HfO₂, 2.7 V for Si₃N₄ and Capacitive Ratio of the switch with Si₃N₄ is 83.75 and Capacitive Ratio with HfO₂ is 223 at 2g₀ (air gap) and 0.8 μm thickness of beam. The Radio Frequency performance of RF MEMS switch is obtained by scattering parameters (insertion loss, Return loss and isolation) which are mainly dominated by down to up capacitance ratio and MEMS bridge geometries. RF analysis shows that insertion loss as low as ?0.4 dB at 20 GHz and isolation as high as 80 dB at 20 GHz can be achieved. Investigation of three uniform meander Design and non-uniform single meander design reveals that use of non-uniform design reduces the design complexity and saves substrate area still maintaining almost same device performance. S-parameter analysis is carried out to compare device performance for both structures. DC analysis of the proposed switch is carried out using Coventorware and RF analysis is performed in MATLAB.     

Resacetophenoneoxime-formaldehyde resins,IV. Chelation ion-exchange properties

Resacetophenoneoxime-formaldehyde resins showed to be selective chelating ion exchange resins for certain metal ions. A batch equilibrium method was used in the study of the selectivity of metal ion uptake. The method involved the measurement of distribution of a given metal ion between an aqueous solution and the resin. The study was carried out over a wide pH range and in media of various ionic strengths.     

Crack initiation and propagation paths for brittle failures in aligned and misaligned pipe butt fusion joints

Medium density polyethylene pipes of 63, 90, and 125mm outside diameter, together with 63mm high density polyethylene pipes, were butt fusion joined to give aligned and controlled misaligned joints. These fabricated systems were tested at elevated temperatures under constant and fluctuating internal pressure loading. For brittle failures at the butt fusion joint, a thorough examination has been made of the points of crack initiation and the crack propagation path in relation to weld microstructure, It has been observed that the butt fusion process induces the presence of a long sharp notch formed when the internal weld bead rolls towards the pipe. This notch initiates circumferential joint failures, particularly in misaligned butt joints. Points of disturbance on the inner weld bead appear capable of inducing axial cracks at the butt fusion joint but only for aligned joints. The microstructure at the butt fusion joint was seen to have little influence on the crack propagation path.     

High‐performance waterborne coatings based on epoxy‐acrylic‐graft‐copolymer‐modified polyurethane dispersions

Polyurethane dispersions (PUDs) have been an active area of research since the early 1940s because of legislative restrictions on the use of organic solvents in conventional solvent‐based products and also because PUDs exhibit almost the same high performance levels as solvent‐borne polyurethanes. In the present study, properties of conventional waterborne PUDs are modified with epoxy‐acrylic graft copolymer blocks. The epoxy‐acrylic graft copolymers were first modified with ethylene diamine to give amine‐terminated blocks which in turn reacted with isocyanate‐terminated prepolymer (prepolymer mixing process) to give modified PUDs. Several experimental sets were prepared with varying compositions. The experimental sets were also prepared using conventional poly(ethylene glycol) blocks and ethylene diamine chain‐extenders. The physico‐chemical properties and film characteristics of the experimental sets show the dramatic improvement in important mechanical properties of PUDs due to grafting with epoxy‐acrylic copolymer blocks. Copyright © 2004 Society of Chemical Industry     

Surface Tension Profiles under Various Microwave Radiation Modes

Surface tension of fluids is crucial for multiphase systems and is often controlled during industrial processes by introducing surfactants. In this study, effect of various microwave radiation modes on surface tension of water was investigated as an alternative physical method to manipulate the surface tension without using chemicals. It is found that surface tension decreased quickly while temperature increased during microwave. Once the radiation was turned off, the temperature returned rapidly as expected. However, surface tension did not recover so much. The minimum surface tension after microwave radiation depended on the power. Moreover, a second radiation can have additional reduction on surface tension.     

Structure‐Based Design of Novel Human Toll‐like Receptor 8 Agonists

Toll‐like receptor (TLR)‐8 agonists activate adaptive immune responses by inducing robust production of T helper 1‐polarizing cytokines, suggesting that TLR8‐active compounds might be promising candidate vaccine adjuvants. Recently, a C2‐butyl furo[2,3‐c]quinoline was reported with purely TLR8 agonistic activity. This compound was successfully co‐crystallized with the human TLR8 ectodomain, and the co‐crystal structure revealed ligand‐induced reorganization of the binding pocket of TLR8. The loss of a key hydrogen bond between the oxygen atom of the furanyl ring of the agonist and Thr 574 in TLR8 suggested that the furan ring is dispensable. Employing a disconnection strategy, 3‐ and 4‐substituted aminoquinolines were investigated. Focused structure‐based ligand design studies led to the identification of 3‐pentyl‐quinoline‐2‐amine as a novel, structurally simple, and highly potent human TLR8‐specific agonist (EC₅₀=0.2 μM ). Preliminary evaluation of this compound in ex vivo human blood assay systems revealed that it retains prominent cytokine‐inducing activity. Together, these results indicate the suitability of this compound as a novel vaccine adjuvant, warranting further investigation.     

Poly(triallyl phosphate) and its copolymers with allyl diglycol carbonate as solid state nuclear track detectors.

This paper describes the design and development of new polymers for solid state nuclear track detection. A monomer triallyl phosphate (TAP) has been synthesized and cast homo/ copolymerized with allyl diglycol carbonate (ADC) to get transparent thin films of poly(triallyl phosphate) (PTAP) and poly(TAP-co-ADC) polymers respectively, which were successfully explored for the first time for detection of alpha particles and fission fragments. The polymerization kinetics studies were carried out to generate constant rate polymerization profile for TAP and TAP: ADC monomer mixture. Poly(TAP-co-ADC) copolymer in 3:7 wt./wt. ratio showed better radiation sensitivity as compared to indigenously prepared PADC and commercially available CR-39 detectors.     

Co-processing of cefuroxime axetil by spray drying technique for improving compressibility and flow property

The aim of the present investigation was to improve the compressibility and flow property of cefuroxime axetil by co-processing it with mannitol and chitosan chlorhydrate using spray drying method. 3² full factorial design, having inlet air temperature and mannitol: chitosan chlorhydrate ratio as independent variables was used for the optimization. Statistical analysis of obtained results revealed that both independent variables had significant effect on response variables (p value?<?.05). Evaluation of dependent variables suggested, excellent to good flow properties (angle of repose, Carr's index, and Hausner's ratio) for all prepared batches. Desirability function was used for the selection of the optimized batch which was evaluated for Kawakita’s equation, Heckel’s plot to assess compression behavior of co-processed product under applied pressure. Result of this analysis revealed that the optimized batch product had better compressibility than physical mixture. The tablets prepared by directly compressing spray-dried product, exhibited excellent tensile strength acceptable friability (<1%) and similar release profile when compared with marketed formulation (Similarity factor 89.24 and dissimilarity factor 1.79). So the results of the present investigation concluded that cefuroxime axetil was successfully co-processed with above mentioned excipients by using spray drying method to make it directly compressible.     

Electrocoagulative treatment of mercury containing aqueous solutions

In recent years, electrocoagulation has been successfully used for wastewater treatment and is efficient in heavy metal ions removal. In the present work, electrocoagulation has been used for the removal of Hg(II) from synthetic wastewaters containing up to 20 mg/L of mercury. The electrode materials used are stainless steel (SS) and aluminum (Al). The effects of operating parameters, viz., current density, time of electrocoagulation, distance between electrodes, initial pH of the solution, presence of electrolyte in the solution and temperature have been studied. It was observed that more than 99% Hg(II) removal can be achieved by keeping the distance between SS and Al electrodes from 2 to 6 cm and initial pH range from 3 to 7. The results show that the pseudo second-order kinetics fits the data well. Also, preliminary cost estimation was reported.