Thermal analysis of 9977 radioactive material package

The 9977 package is a certified type B transportation packaging that was designed to transport radioactive materials with a decay heat load of up to 19?W. The packaging was recently modified to accommodate increased content heat load (up to 38?W) by employing an aluminium heat dissipating sleeve outside the containment vessel (CV), as well as an aluminium spacer inside the CV holding two 3013 containers. This paper provides highlights of thermal analyses of the modified 9977 package that were performed to evaluate its compliance with the 10 CFR 71 regulatory safety requirements. Parametric studies were also performed to examine effects of (i) surface properties, e.g. light absorptivity and emissivity, of the packaging; (ii) total decay heat loads, ranging from 18 to 38?W; and (iii) distribution of decay heat load inside the CV on the temperature of the Viton O-ring seal. The results of thermal analyses show that for the normal condition of transport with insolation, increasing absorptivity and decreasing emissivity increase the temperature of the O-ring; decreasing heat load decreases the temperature of the O-ring, whereas changing heat load distribution has little effect on the temperature of the O-ring. Likewise, changing the thermal conductivity of the spacer inside the CVhas little effect on the temperature of the O-ring. Briefly discussed is the possible extension of the annual maintenance interval of the 9977 package, based on previous work and the data obtained in the long-term leak performance tests conducted by the Savannah River National Laboratory.     

Modeling heterogeneous bacterial populations exposed to antibiotics: The logistic‐dynamics case

In typical in vitro tests for clinical use or development of antibiotics, samples from a bacterial population are exposed to an antibiotic at various concentrations. The resulting data can then be used to build a mathematical model suitable for dosing regimen design or for further development. For bacterial populations that include resistant subpopulations—an issue that has reached alarming proportions—building such a model is challenging. In prior work, we developed a related modeling framework for such heterogeneous bacterial populations following linear dynamics when exposed to an antibiotic. We extend this framework to the case of logistic dynamics, common among strongly resistant bacterial strains. Explicit formulas are developed that can be easily used in parameter estimation and subsequent dosing regimen design under realistic pharmacokinetic conditions. A case study using experimental data from the effect of an antibiotic on a gram‐negative bacterial population exemplifies the usefulness of the proposed approach. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2385–2393, 2015     

Deformation and Fracture of β‐Silicon Nitride Micropillars

Room‐temperature deformation and fracture behaviors under microcompression of single crystal β‐silicon nitride (Si₃N₄) micropillars were investigated. Pillars were fabricated by focused ion beam (FIB) in large Si₃N₄ grains, located close to the basal and prismatic orientations, selected by electron backscatter diffraction (EBSD). The micromechanical test and the damage characterization were performed by nanoindentation and scanning electron microscopy (SEM), respectively. The elastic, plastic, and fracture properties, such as Young's modulus, yield stress, and rupture stress are considerably influenced by the pillar orientation. The activation of the type slip system was identified in case of basal oriented micropillars.     

Genetic algorithm optimization in building portfolio management

A significant proportion of building investment expenditure goes to replacement expenditure for organizations owning a large building stock or portfolio. Over the years, researchers have attempted to develop asset replacement models to aid decision-making in building portfolio management, based upon' a statistical or an heuristic approach. This study attempts to use genetic algorithms to develop models for forecasting long term asset replacement strategies, aiming at smoothing fluctuations of expenditure and resource requirements, and most importantly minimizing the total maintenance and replacement costs. Scenarios are presented to demonstrate how these can be achieved. Further refinement for practical application of the models is also presented.     

A web‐based performance assessment system for environmental protection: WePass

In response to the increasing public concern over the effects of construction waste on the environment, a performance assessment system has been designed to provide an instant, online assessment of how well a construction site performs environmentally, e.g. measuring the level of pollution generated from a construction site. Through the use of both Internet and database technologies, it is possible to collect and present data that are essential for environmental management online. To achieve this, a set of environmental performance parameters was derived through a postal questionnaire survey and interviews with experts in the field. A conceptual framework was developed, of which the key components were: template, knowledge base, output data and benchmark group. In combination, these factors provide a system that enables speedy assessment and effective management of environmental performance on construction sites, hence prompt decisions can be made and corrective actions can be taken before potential hazards turn into real disasters.     

Rational under‐pricing in bidding strategy: a real options model

Under‐pricing in construction tenders is a common phenomenon and is commonly explained by the need of cash flows and penetration strategy. However, these explanations involve profit cutting and therefore are not plausible in explaining a long‐term persistent phenomenon of under‐pricing. A real options model is proposed and using the binomial lattice method a real‐life construction project tender was analysed to examine how management flexibility and uncertainty provide real options value. When uncertainties of cost items in a tender exist and choices are available to defer and switch modes of construction, then a valuable option is available to the bidders. It amounts to about 4% of the lump sum tendered in our case. The under‐priced portion is the options value which the bidder is willing to pay for the flexibility and the uncertainty. These findings enable contractors to be more competitive and to estimate construction costs more accurately in devising their bid strategies.     

Cobalt molybdenum oxide catalysts for selective oxidation of cyclohexane

Oxidation of cyclohexane has been carried out using molecular oxygen over cobalt molybdenum oxide (CoMoO₄) catalysts in solvent free conditions. The catalysts were prepared using citrate method with three different molar ratios of Co:Mo, 1:1, 1:2, and 2:1 along with individual oxides for comparative studies. While all the catalysts showed significant activity and selectivity, CoMoO₄ with 1:1 ratio showed the best performance compared to the others with a conversion of 7.38%, with selectivity to cyclohexanol and cyclohexanone (KA oil) of 94.3%, in 1 h. The performance of the catalyst, has been studied as a function of oxygen pressure, reaction temperature, and catalyst loading. It was observed that the catalyst deactivates during the course of the reaction. The reasons for deactivation and methods for restoring the activity have been studied. A kinetic model is presented that captures the complex kinetics and matches well with the experimental data. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4384–4402, 2016     

Highly sensitive electrochemical sensor based on zirconium oxide-decorated gold nanoflakes nanocomposite 2,4-dichlorophenol detection

Journal of Applied Electrochemistry - In this study, a sensitive and selective electrochemical sensor based on a zirconia oxide-decorated gold nanoflake nanocomposite-modified glassy carbon...     

Product design: Formulation of a screen-printable sintering-type conductive paste

Due to the complexity of the screen-printing operation and the rheological behaviors of the screen-printable paste, such a paste is usually formulated by trial-and-error. In this report, a systematic procedure, based on heuristics and mechanistic models, for the design of a screen-printable paste is developed. The procedure is demonstrated by a case study of the formulation of a conductive paste of copper particles.     

Analysis of Modified Nucleotide Aptamer Library Generated by Thermophilic DNA Polymerases

One of the pivotal steps in aptamer selection is the amplification of target-specific oligonucleotides by thermophilic DNA polymerases; it can be a challenging task if nucleic acids possessing modified nucleotides are to be amplified. Hence, the identification of compatible DNA polymerase and modified nucleotide pairs is necessary for effective selection of aptamers with unnatural nucleotides. We present an in-depth study of using 5-indolyl-AA-dUTP (TAdUTP) to generate oligonucleotide libraries for aptamer selection. We found that, among the eight studied DNA polymerases, only Vent(exo-) and KOD XL are capable of adapting TAdUTP, and that replacing dTTP did not have a significant effect on the productivity of KOD XL. We demonstrated that water-in-oil emulsion PCR is suitable for the generation of aptamer libraries of modified nucleotides. Finally, high-throughput sequence analysis showed that neither the error rate nor the PCR bias was significantly affected by using TAdUTP. In summary, we propose that KOD XL and TAdUTP could be effectively used for aptamer selection without distorting the sequence space of random oligonucleotide libraries.