CATALYTIC PRODUCTION OF GRAPHITIC NANORODS VIA THE GAS PHASE DECOMPOSITION OF ETHYLENE OVER SUPPORTED NICKEL

The catalytic growth of high aspect ratio carbon nanorods by ethylene decomposition over nickel/silica is presented as a viable low-cost selective route to a high-value product. This study focuses on the role of catalyst preparation in determining carbon yield and structural characteristics and considers the application of a 10% w/w Ni loading prepared by impregnation and precipitation/deposition. The latter is characterized by a narrower dispersion of smaller Ni particles (average diameter?=?2.4?nm) but lower carbon yields. Doping this catalyst with KBr resulted in a 40-fold increase in carbon production with >95% having rod diameters <10?nm; doping the impregnated catalyst had little effect on catalyst performance. High-resolution transmission electron microscopy and temperature programmed oxidation were employed to characterize the catalysts and the carbon product; the effect of temperature (673–873?K) on carbon yield is also reported.     

EVALUATION OF PERFORMANCE OF THE 1 MW CERAMIC TUBE RECEIVER AT THE WEIZMANN INSTITUTE OF SCIENCE

Simulations were performed to evaluate the performance of a subsystem of the Thermochemical Pipeline Project (WITP) of the Weizmann Institute of Science. This subsystem includes a compressor, a 41 m long pipe, a cavity-type central receiver, and a mass-flow control element. The results show that the solar energy available for absorption into the tubes amounts to 1884 MWh/year, under the assumption that the working fluid (air) enters the cavity at 300 K and leaves at 1200 K. For bright days conditions, the average efficiency of the system increases from 56% (at 7 A.M. ) to 69% (at midday), with a yearly average efficiency of 63%. The mass flow is represented by the correlation:

where F_M is the total mass flow rate of the working fluid (kg/s(, and E_in is the total solar energy entering into the cavity (MW).

It is suggested to increase the performance of the receiver by: 1) exploiting a part of the solar power flux existing as spillage, and 2) capturing the energy of the hot air otherwise dissipated by convection.

It is suggested to increase the performance of the receiver by: 1) exploiting a part of the solar power flux existing as spillage, and 2) capturing the energy of the hot air otherwise dissipated by convection.     

PUTTING ARTISTS ON THE MAP: THE GEOGRAPHY OF ARTISTS IN CUYAHOGA COUNTY,OHIO

ABSTRACT: Across the country, urban leaders are developing arts‐focused urban policy, but much remains unknown about artists’ geography—particularly in contracting, rustbelt cities. Using Cuyahoga County, Ohio, this article describes the geography of artists and explores methodologies for predicting artist‐concentrated neighborhoods. The research questions if, and how, scholars can predict artist neighborhoods and design policies to support and nurture these locations. It maps and analyzes existing patterns using survey, property, and Census data, and predicts artist‐friendly neighborhoods via a regression model. The analysis reveals neighborhoods’ residual capacity for artists and directs initial policy recommendations for an artist‐focused vacant land reutilization initiative. For scholars, the findings contribute to a rapidly growing body of literature about the relationship between artists, neighborhood revitalization, and urban policy. For practitioners, the research investigates one strategy for shaping land policy in the post‐2008 housing market.     

Aspects of the Tribology of the Plastic Bonded Explosive (PBX) 9404*

The coefficient of friction, μ, of PBX 9404 was measured on stainless steel, aluminum, polytetrafluoroethylene (PTFE), and the explosive itself between ambient and 135°C at a rotational speed of 0.0025 rad/s. The mean surface roughness, R _a , of the various materials was analyzed by an optical profilometer. For PBX 9404 on stainless steel, μ increased from 0.22 at 25?°C to 0.34 at 95?°C, then decreased to about 0.23 at 125?°C. With aluminum μ increased from about 0.08 at 25?°C to 0.48 at 115?°C, then decreased slightly. Against PTFE μ was sigmoidal, increasing from about 0.3 at 25?°C to about at 0.49 above 115?°C. Against PBX 9404 itself, μ averaged 0.54 independent of temperature, but tended to increase during the measurement, probably because of adhesion of nitrocellulose to itself.     

Enhanced modal control of flexible structures via innovations feedthrough

Active control of large flexible structures in space requires the control of a very large dimensional system with one of substantially lower dimension. Modern modal control (MMC) has been developed previously to deal with this active structure problem ; however, control and observation spillover (as well as modelling error) can seriously degrade the controller performance by causing pole-shifts from the desired closed-loop locations. In this paper, the original MMC is enhanced by the addition of an innovations feedthrough term to the control law and a residual mode aggregation term to the state estimator. Under conditions presented the enhanced MMC can eliminate the observation spillover from critical residual modes ; hence, the spillover-induced pole shifting in these modes can be mitigated without changing the design of the original MMC. As shown, the trade-off is that the number of residual modes that can bo so enhanced is directly related to the number of available sensors     

Development of a knowledge-based decision support system for diagnosing malfunctions of advanced production equipment

This paper presents a case study documenting the development of an expert system for diagnosing the malfunctions of a machine used by the NEC Corporation to mount chips on integrated circuit boards. Development of the expert system was justified by the inability of operators to efficiently diagnose many malfunctions of the chip-mounting machine, the associated cost of production delays, and the disruption incurred when experts were forced to leave unrelated tasks to help operators troubleshoot malfunctions. The first step in development of the expert system was to elicit and organize the machine designer's knowledge. This process resulted in a hierarchical classification of malfunction symptoms and causes, a set of 15 flow diagrams documenting the designer's troubleshooting procedures for particular malfunction symptoms, and a matrix documenting design information. The flow diagrams were translated into a large logic network diagram, which was directly translated into a set of 94 rules. An additional set of 270 rules were derived from the design matrix. The resulting 364 rules were then implemented in an expert system using the KES shell. On-site validation revealed that 92% of the chip-mounting machine's malfunctions occurring in 1988-1989 were successfully diagnosed by the expert system. Future directions of this research will be oriented toward the development of a general purpose expert system capable of diagnosing the malfunctions of other similar production equipment.     

EFFECT OF SUCROSE ON THE MECHANICAL AND ACOUSTIC PROPERTIES OF FREEZE‐DRIED AGAR,K‐CARRAGEENAN AND GELLAN GELS1

Agar, K‐carrageenan and gellan gels (2%) with and without infused sucrose (5, 10 and 12.5%) were freeze dried and the mechanical and acoustic signatures of the resulting solid sponges recorded. For comparison, agar gels with 5 and 10% starch were also prepared and likewise tested. The presence of the sugar, or starch, in the dried gels increased their density in a manner that could not be predicted from the corresponding stoichiometric relations between the gum and additive indicating that the sugar, or starch, were not inert fillers. In general, the presence of the sucrose in the dried gel solid matrix increased the brittleness of the sponges. The effect could be quantified in terms of the increase in the mechanical signature's apparent fractal dimension (Richardson's and Kolmogorov's). The more brittle dried gels also had a “richer” acoustic signature whose apparent fractal dimension was determined with the “blanket” algorithm. Despite the irregular and jagged appearance of all the dry gels stress‐strain relationships, they could be described by the same kind of a three parameter empirical model originally derived for soft baked products and polymeric foams. Although the added sugar, or starch, stiffened the dehydrated gels the effect could not be quantified unambiguously because of the differences in the density and in the overall shape of the stress‐strain curve.     

Fractionation of Lactoperoxidase and Lactoferrin from Bovine Whey Using a Cation Exchange Membrane

A microporous membrane containing immobilized sulfonic acid moieties was used for the rapid fractionation of the cations lactoperoxidase (LP) and lactoferrin (LF) from whey. The breakthrough curves of LP and LF, the LP activity and LF concentration in the elution peaks for different whey loading volumes, and the stability of membrane performance over repeated cycles of loading and elution were measured. Recovery was unaffected by an 8-fold scale-up exercise and repeated cycling, and was 73–6% for LP and 50–5% for LF. The membrane system was more rapid, smaller in size, and used a higher flow rate than traditional bead-based systems.