Accelerant‐promoted free radical polymerization of methacrylates by stabilized nitroxide unimolecular initiators: synthesis and characterization

BACKGROUND: This investigation evaluates the effectiveness of initiator adducts for living and controlled polymerization of methacrylates, crosslinking of dimethacrylates and thermal stabilities of the resulting polymers. Adducts of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy with benzoyl peroxide and with azobisisobutyronitrile were prepared and evaluated as stabilized unimolecular initiators for the free radical polymerization of methacrylate monomers using sulfuric acid as catalyst. The monomers used were methyl methacrylate, triethylene glycol dimethacrylate (TEGDMA) and ethoxylated bisphenol A dimethacrylate (EBPADMA). RESULTS: Successful polymerization was achieved at 70 and 130 °C with reaction times ranging from 45 min to 120 h. The dispersity (D) of poly(methyl methacrylate) (PMMA) was 1.09–1.28. The livingness and extent of control over polymerization were confirmed with plots of M_n evolution as a function of monomer conversion and of the first‐order kinetics. The glass transition temperature (T_g) for PMMA was 123–128 °C. The degradation temperature (T_d) for PMMA was 350–410 °C. T_d for poly(TEGMA) was 250–310 °C and for poly(EBPADMA) was 320–390 °C. CONCLUSION: The initiators are suitable for free radical living and controlled polymerization of methacrylates and dimethacrylates under mild thermal and acid‐catalyzed conditions, yielding medium to high molecular weight polymers with low dispersity, high crosslinking and good thermal stability. Copyright © 2008 Society of Chemical Industry     

Hydromagnetic squeeze film behavior in porous circular disks

An analysis is presented of the effect of a uniform transverse magnetic field on the squeeze film behavior when a circular disk with a porous facing approaches another disk with uniform velocity. Results for the pressure distribution, load-carrying capacity and film thickness are given as functions of time.     

Investigation into an artificial neural network based on-linecurrent controller for an HVDC transmission link

An artificial neural network (ANN) based current controller for a HVDC transmission link is described in this paper. Different ANN architectures and activation functions (AFs) are investigated for this ANN controller. Small (set current change) and large (DC-line fault) signal perturbations are applied to optimize the learning parameters for the controller. Performance evaluation of the ANN controller under noise conditions is studied. A comparison between a traditional PI and the proposed ANN controller is made for various system contingencies and it is shown that the latter has many attractive features     

Ultrasonic relaxation studies of the vitreous system Mo-P-O in the temperature range 4 to 300 K

A detailed study of ultrasonic relaxation in the entire vitreous range of the glass system MoO₃-P₂O₅ (0 to 83 mol% MoO₃) is presented. Pulse echo techniques were employed in the frequency range 15 to 135 MHz and temperature range 4 to 300 K. Ultrasonic absorption peaks were observed at various temperatures between 74 and 128 K depending upon glass composition and operating frequency. The composition dependence of the position and overall shape of the loss peaks was analysed in terms of an assumed loss of the standard linear solid type, with low dispersion, and a broad distribution of Arrhenius-type relaxation times with temperature-independent relaxation strengths (two-well formalism with a broad distribution of asymmetries). After a brief review of two-well formalism, a simple central force model of the microscopic origins of two-well systems is presented, to demonstrate that (in contrast to what has often been assumed previously) there is no need to postulate bond directionality effects to account for “acoustically active” two-well systems in glassy materials. Also given is a quantitative model of the deformation potential arising in phenomenological models of acoustic loss produced by two-well systems. The shape of the loss peaks (i.e. the shape of the relaxation spectra), and the mean activation energy determined from the frequency dependence of the loss-peak temperature (V _p), are both strongly composition-sensitive. Furthermore, they are found to correlate with the elastic properties of the glass system and the assumed bond force constants. The conclusion thus arrived at is that the acoustic loss is a property of the vitreous network as a whole rather than due to a second-order effect like the presence of dangling bonds or polar groups, or to network holes etc. Finally a microscopic phenomenological model is developed to account for the composition dependence of the observations. In particular, semi-theoretical formulae are used to expressV _p and the fractional number of two-well systems per oxygen atom,N, as a function of the bulk modulus and a mean cation-anion stretching force constant. Considerable success was thereby achieved in explaining the contrasting behaviour ofV _p andN.     

Workstation-based logic animation and microarchitecture emulationfor teaching introduction to computer engineering

The authors describe two software tools used for teaching logic design and analysis and basic computer organization in the introductory course on computer engineering at the authors' department. The first computer-aided instruction tool described is a schematic capture, simulation, and logic animation package targeted for teaching combinational and sequential logic concepts. The tool incorporates logic animation capability rather than waveform displays, which allows students to view and control logic values propagating throughout the entire network. The second tool teaches computer organization, including microprogramming concepts, by means of the graphical display of an instructional microprocessor architecture in which users are allowed to view and control internal registers, memory locations, and microcontrol store. Both of the computer-aided instructional tools run on UNIX workstations, with graphics displays, local hard-disk mass storage, and mouse input     

Building regulations are a barrier to affordable housing in Indian cities: the case of Ahmedabad

Cities in developing countries seldom consider the cost increases that regulations impose on development. To build legal housing, developers must meet a high minimum cost threshold established by mandatory standards. Many standards impose costs on building construction, make them less affordable to low-income households, deprive them access to legally built housing, and fuel the formation of slums. This study analyses the impact of relaxing a few mandatory building and site planning regulations on the cost of small two-room homes in Ahmedabad by developing two alternative layouts for the same site, one in accordance with prevalent regulations, and another after modifying a few regulations. It shows that rationalizing regulations can reduce housing cost by 34% and increase supply by as much as 75% without significantly lowering quality or compromising safety. It also shows that for a large portion of poor households, the costs imposed by mandatory standards are not trivial and have a high impact on the affordability of legally built housing. It recommends that if municipal authorities are interested in tackling the rapid growth of slums by expanding the supply of affordable housing, they should critically examine their building regulations and modify them to address the housing needs of their low-income residents.     

Analysis‐preserving video microscopy compression via correlation and mathematical morphology

The large amount video data produced by multi‐channel, high‐resolution microscopy system drives the need for a new high‐performance domain‐specific video compression technique. We describe a novel compression method for video microscopy data. The method is based on Pearson's correlation and mathematical morphology. The method makes use of the point‐spread function (PSF) in the microscopy video acquisition phase. We compare our method to other lossless compression methods and to lossy JPEG, JPEG2000, and H.264 compression for various kinds of video microscopy data including fluorescence video and brightfield video. We find that for certain data sets, the new method compresses much better than lossless compression with no impact on analysis results. It achieved a best compressed size of 0.77% of the original size, 25× smaller than the best lossless technique (which yields 20% for the same video). The compressed size scales with the video's scientific data content. Further testing showed that existing lossy algorithms greatly impacted data analysis at similar compression sizes. Microsc. Res. Tech. 78:1055–1061, 2015. © 2015 Wiley Periodicals, Inc.     

Coal washing scenario in India and future prospects

International Journal of Coal Science & Technology - Coal Washing Exploration in India dates back to 1900s; though, first coking coal washeries in India were installed after independence. At...