Suppression of Environmentally-Induced Vibrations in Tall Buildings by Hybrid Liquid Column Dampers

The conceptual development of hybrid liquid column dampers is presented. The system is based fundamentally on the concept of tuned liquid column dampers and modified to employ instantaneous optimal controls to affect the orifice and/or the liquid column pressure actively. Numerical modeling of the system and the development of the control algorithms are presented. The system's effectiveness in suppressing earthquake and wind induced motions in tall buildings is assessed and illustrated by numerical examples.     

The effect of gamma irradiation on the pressure dependence of the room temperature transition in PTFE

Some of the effect of gamma irradiation on the pneumatic pressure dependence of the well established room temperature transition (ca. 19 °C) in polytetra(fluoroethylene) are described. The experiments, conducted up to a maximum gamma dosage of 60 Mrad and a superimposed nitrogen pressure of 48.3 MPa indicate a significant reduction in the room temperature transition as well as its pressure dependence with the increasing of the gamma dosage. These data, combined with the observed and reported reduction in the free volume (actually net volume) are consistent with the proposition that irradiation process results in a reduction in the ‘effective internal pressure’ due to extensive bond scission. The latter process is manifested in an observed dramatic decrease in the molecular weight. Data on the compressibility and coefficient of thermal expansion, accompanied by thermodynamic arguments, indicate that the room temperature transition more closely resembles a second order transition as gamma dosage increases. This is consistent with a change in system behaviour progressing from a viscoelastic to that of a brittle glassy polymer as confirmed by monitoring the polymer creep behaviour following rapid pressurisation. Data for the ‘freshly’ irradiated specimens indicate highly transient post-irradiation induced changes in the polymer morphology.     

Synthesis and Characterization of Novel Thermoplastic Films for Removal of Heavy Metal Ions

The main objective of this study is to establish the applicability of novel thermoplastic films based on extracted gelatins from bovine (G_b) and bird (G_c) bones in addition to hide powder (HP), which blended with modified polyethylene (MPE) for the removal of heavy metal ions such as copper (II), chromium (VI), nickel (II) and zinc (II) from aqueous media. The chemical reaction between 2-oxoglutaric acid with furfural in presence of methyl amine, via Mannich reaction mechanism, resulted in chemical compound I. The chemical structure of product I was confirmed by different spectroscopic tools such as: nuclear magnetic resonance (¹³C- and ¹H-NMR) and Fourier transform infrared spectroscopy (FT-IR). The synthesized chemical product I was used as compatibilizing agent for blending G_b, G_c and Hp with MPE to obtain thermoplastic films using a polymer melting technique. The efficiency of the prepared films for absorption of different heavy metal ions from aqueous solution was investigated. The results indicated that the compatibilized films (MPE/I/HP) illustrated a maximum removal of zinc metal ions (～100%) under conditions of initial metal concentration about 240 mg/l. While, at initial metal concentration of about 150 mg/l, they exhibited excellent efficiency for removal of mixed metal ions of about 97–100% relative to the uncompatibilized ones (MPE/HP) 0%.     

Effect of natural polyphenols on physicochemical properties of crosslinked gelatin‐based polymeric biocomposite

This work was aimed to study the effect of natural polyphenols extract (Acacia nilotica bark) on physicochemical properties of crosslinked gelatin‐poly(acrylamide‐co‐acrylic acid), Gel‐poly(AAm‐co‐Ac), polymeric biocomposite film. Gelatin‐based composite films have extensive application as biocompatible biomaterial as drug carriers, cosmetics, and agricultural food packaging. The prepared composite films were characterized using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), in addition to the swelling and degradation behavior. UV‐Vis absorption spectra and scanning electron microscopy (SEM) were also applied to observe the interaction between Gel‐poly(AAm‐co‐Ac) and natural polyphenol (catechin). The study has demonstrated that the involvement of hydrogen bonding and hydrophobic interactions as the major forces involved in the stabilization of gelatin‐based polymeric biocomposite film by the plant polyphenols (catechin and gallic acid derivatives). Thermal stability studies of crosslinked gelatin‐based composite film revealed that A. nilotica bark extract stabilizes the gelatin molecules and leads to moderate increase of the denaturation temperatures relative to the uncrosslinked one. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The Stimulation of Sandstone Reservoirs Using DC Potential

Abstract

The authors describe the effect of direct current application in conjunction with waterflood on improving flow properties of Berea sandstone cores. Single- and two-phase flow experiments are conducted on a specially designed coreflood setup, under constant electrode potential. The results showed that core permeability may increase up to 223% when hydraulic gradient and electroosmotic flow are applied in the same direction. The effect is insignificant when they work in opposite direction. It is verified from experimental results that dislodgement of clay in colloidal form, resulting increase of effective pore throat diameter improved hydraulic permeability.     

Courant, Friedrichs and Lewy (CFL) impact on numerical convergence of highly transient flows

This paper addresses the critically important issue regarding the appropriate size of the discretisation elements whilst ensuring stability and reasonable computational work loads for the numerical simulation of highly transient flows. The simulation of outflow following the puncture of a hypothetical 100 m pipeline at 21.6 bara (2160 kPa) and 293.15 K is used as a case example. The pipeline is assumed to contain different classes of hydrocarbons including permanent gases and liquids, two-phase mixtures and flashing liquids. The simulated outflow data for varying discretisation time and distance elements, expressed in terms of a Courant, Friedrichs and Lewy (CFL) factor indicate that in the case of permanent fluids and two-phase mixtures, a hyperbolic increase in the computational run time with decreasing CFL factor is obtained. There is no CFL factor dependency with the simulated outflow data. However in the case of flashing liquids and their mixtures, although similar trends in the computation run times are observed, the prescribed CFL stability condition at CFL factors of less than 0.4 does not result in convergence.     

Development of a taste-masked oral suspension of clindamycin HCl using ion exchange resin Amberlite IRP 69 for use in pediatrics

Purpose: The purpose of this study is to develop an oral suspension of clindamycin resin complex for the potential use in pediatrics.

Methods: Several types of Ion exchange resins were screened for their binding efficiency with clindamycin. In order to develop a suspension formulation, several thickening agents, surfactants, sweeting, and flavoring agents were evaluated for their influence on the release of clindamycin from resinate. Rheological studies were also conducted to select the optimum amounts of the suspending agents. The release profiles of clindamycin in SGF and SIF were also evaluated from freshly prepared suspension and from suspension formulation after storage for 1 month at 25?°C and 40?°C. Clindamycin bitterness threshold was determined based on volunteers’ evaluation, and taste evaluation was conducted in 12 adult volunteers who evaluated the taste of the optimized suspension against clindamycin solution.

Results: Among all resins tested, Amberlite IRP 69 showed the highest binding efficiency to clindamycin. Several excipients were selected into the suspension formulation based on no or minimum influence on the release of clindamycin from the resinate complex. Moreover, xanthan gum was selected as the optimal suspending agent for the suspension. Clindamycin release profiles in SGF or SIF showed 90% release within 30?min from freshly prepared sample. Clindamycin exhibited good stability profiles at 25?°C and 40?°C over 1 month storage. The mean bitterness threshold of clindamycin was 12.5?μg/ml, and taste evaluation study in adults showed sustainable taste improvement for suspension over clindamycin solution.

Conclusion: Clindamycin/resin complexation has shown to be an efficient method to mask the taste of clindamycin and was developed into a suspension formulation that can be used in pediatrics.     

A fourth-order switched capacitor cascade structure for sigma-delta converters

This paper gives details of the design of a switched capacitor circuit for use in oversampling sigma-delta analogue-to-digital converters. the circuit is a fourth-order cascade of two second-order sections. Comparison with other multistage structures is also presented. It is shown that the proposed design has advantages over the possible alternative cascade of four first-order sections. It is also shown that it gives certain improvements in performance over the popular third-order cascade of a second-order and a first-order section, thus justifying the use of a higher order under the given technology and tolerance constraints.