A MICROSTRUCTURAL MODEL OF THE THERMAL CONDUCTIVITY OF DISPERSION TYPE FUELS WITH A FUEL MATRIX INTERACTION LAYER

Williams, A.F.,Leitch, B.W.,Wang, N. Korean Nuclear Society 2013 Nuclear Engineering and Technology Vol.45 No.7

This paper describes a finite element model of the microstructure of dispersion type nuclear fuels, which can be used to determine the effective thermal conductivity of the fuels during irradiation. The model simulates a representative region of the fuel as a prism shaped unit cell made of brick elements. The elements within the unit cell are assigned material properties of either the fuel or the matrix depending on position, in such a way as to represent randomly distributed fuel particles with a size distribution similar to that of the as manufactured fuel. By applying an appropriate heat flux across the unit cell it is possible to determine the effective thermal conductivity of the unit cell as a function of the volume fraction of the fuel particles. The presence of a fuel/matrix interaction layer is simulated by the addition of a third set of material properties that are assigned to the finite elements that surround each fuel particle. In this way the effective thermal conductivity of the material may also be determined as a function of the volume fraction of the interaction layer. Work is on going to add fission gas bubbles in the fuel as a fourth phase to the model.

A Microstructural Model of the Thermal Conductivity of Dispersion Type Fuels with a Fuel Matrix Interaction Layer

A.F. Williams,B.W. Leitch,N. Wang 한국원자력학회 2013 Nuclear Engineering and Technology Vol.45 No.7

This paper describes a finite element model of the microstructure of dispersion type nuclear fuels, which can be used todetermine the effective thermal conductivity of the fuels during irradiation. The model simulates a representative region of thefuel as a prism shaped unit cell made of brick elements. The elements within the unit cell are assigned material properties ofeither the fuel or the matrix depending on position, in such a way as to represent randomly distributed fuel particles with a sizedistribution similar to that of the as manufactured fuel. By applying an appropriate heat flux across the unit cell it is possible todetermine the effective thermal conductivity of the unit cell as a function of the volume fraction of the fuel particles. Thepresence of a fuel/matrix interaction layer is simulated by the addition of a third set of material properties that are assigned tothe finite elements that surround each fuel particle. In this way the effective thermal conductivity of the material may also bedetermined as a function of the volume fraction of the interaction layer. Work is on going to add fission gas bubbles in the fuelas a fourth phase to the model.

Studies of various single phase natural circulation systems for small and medium sized reactor design

Wibisono, A.F.,Ahn, Y.,Williams, W.C.,Addad, Y.,Lee, J.I. North-Holland Pub. Co 2013 Nuclear engineering and design Vol.262 No.-

Passive safety is a primary motive behind the development of small and medium sized reactors of various coolants. After the Fukushima accident, there is an increased interest in a nuclear reactor's reliance on passive safety systems. Most of the existing passive systems, regardless of the reactor type, utilize buoyancy force to drive the cooling flow. Hence, it is essential to evaluate if the naturally developed cooling flow is sufficient to maintain the heated surface temperature of the fuel elements below the design limit. Evaluating passively driven flows can be quite a challenging task in both two phase natural circulation systems and also in single phase natural circulation systems. Previous research works have found that single phase heat transfer can be deteriorated and becomes uncertain when the driving force of a system is shifted from external force (forced convection) to self generated buoyancy force or a combination of both (natural or mixed convection). In this paper, single phase gas, water, and liquid metal reactors with passive systems are reviewed briefly. A simple theoretical analysis of each reactor type is performed to find the tendency of the shift in the operating heat transfer regime into the deteriorated region. The analysis results show that single phase water system can maintain operation within the forced convection regime but the operating regime gets closer to the deteriorating heat transfer regime as the system's physical size reduces from a large nuclear power plant to the small and medium reactor scale. The gas cooled system has a high tendency to operate in the deteriorated heat transfer regime when the driving force changes from forced to natural. Meanwhile the liquid metal system demonstrates more margins to operate outside from the deteriorated heat transfer region compared to the two other fluid systems. However further studies are needed to clearly identify the boundaries of the deteriorated heat transfer regime for each coolant since the deterioration greatly depends on the thermophysical properties variation of the coolant and the near-wall flow behavior of the coolant with respect to temperature change.

Dynamic characteristics and response analysis of accelerating underwater structures

Liu, Zhengxing,Williams, F.W.,Jemah, A.K. Techno-Press 1998 Structural Engineering and Mechanics, An Int'l Jou Vol.6 No.6

A coupling system for a structure accelerating through a fluid is considered which is composed of the structure and the fluid in a finite surrounding volume. Based on the variational principle, the finite element equations of hydrodynamic pressure and structural elastic vibration are deduced. A numerical method is given for the dynamic character and response of the structure which takes the coupled fluid into account. The effect of axial inertial forces on the dynamic character and response of rapidly accelerating structures is also considered.

On balance of uncertainty in shadowed sets

M. A. Ibrahim,T. O. William-West,A. F. D. Kana,D. Singh 원광대학교 기초자연과학연구소 2020 ANNALS OF FUZZY MATHEMATICS AND INFORMATICS Vol.19 No.3

A shadowed set, $S$, facilitates crisp decision-making with a fuzzy set $F$. It is constructed with the aid of different optimization-based principles. Among these principles, the requirement of uncertainty balance guarantees preservation of the uncertainty of $F$ in $S$. In order to gain further insight on uncertainty balance, some essential mathematical properties which characterize uncertainty-balance-based objective function, $J(\alpha)$, are studied. These properties provide theoretical explanation for interpreting and analyzing $J(\alpha)$ and its ensuing optimum partition threshold $\alpha$. Two senses of uncertainty balance are discussed in this paper. Their combined efficiency in enhancing clustering results is illustrated with the aid of synthetic data set used in shadowed $C$-means clustering. Finally a need for five-region shadowed sets, $S_5$, is pointed out. A closed-form formula for determining its optimum thresholds is proposed and exemplified on typical fuzzy set and synthetic dataset.

Graphene Veils and Sandwiches

Yuk, Jong Min,Kim, Kwanpyo,Alemá,n, Benjamí,n,Regan, William,Ryu, Ji Hoon,Park, Jungwon,Ercius, Peter,Lee, Hyuck Mo,Alivisatos, A. Paul,Crommie, Michael F.,Lee, Jeong Yong,Zettl, Alex American Chemical Society 2011 NANO LETTERS Vol.11 No.8

<P>We report a new and highly versatile approach to artificial layered materials synthesis which borrows concepts of molecular beam epitaxy, self-assembly, and graphite intercalation compounds. It readily yields stacks of graphene (or other two-dimensional sheets) separated by virtually any kind of “guest” species. The new material can be “sandwich like”, for which the guest species are relatively closely spaced and form a near-continuous inner layer of the sandwich, or “veil like”, where the guest species are widely separated, with each guest individually draped within a close-fitting, protective yet atomically thin graphene net or veil. The veils and sandwiches can be intermixed and used as a two-dimensional platform to control the movements and chemical interactions of guest species.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-8/nl201647p/production/images/medium/nl-2011-01647p_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl201647p'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl201647p'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl201647p'>ACS Electronic Supporting Info</A></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl201647p'>ACS Electronic Supporting Info</A></P>

KEPLER-1647B: THE LARGEST AND LONGEST-PERIOD<i>KEPLER</i>TRANSITING CIRCUMBINARY PLANET

Kostov, Veselin B.,Orosz, Jerome A.,Welsh, William F.,Doyle, Laurance R.,Fabrycky, Daniel C.,Haghighipour, Nader,Quarles, Billy,Short, Donald R.,Cochran, William D.,Endl, Michael,Ford, Eric B.,Gregori American Astronomical Society 2016 The Astrophysical journal Vol.827 No.1

<P>We report the discovery of a new Kepler transiting circumbinary planet (CBP). This latest addition to the stillsmall family of CBPs defies the current trend of known short-period planets orbiting near the stability limit of binary stars. Unlike the previous discoveries, the planet revolving around the eclipsing binary system Kepler-1647 has a very long orbital period (similar to 1100 days) and was at conjunction only twice during the Kepler mission lifetime. Due to the singular configuration of the system, Kepler-1647b is not only the longest-period transiting CBP at the time of writing, but also one of the longest-period transiting planets. With a radius of 1.06 +/- 0.01 RJup, it is also the largest CBP to date. The planet produced three transits in the light curve of Kepler-1647 (one of them during an eclipse, creating a syzygy) and measurably perturbed the times of the stellar eclipses, allowing us to measure its mass, 1.52 +/- 0.65M(Jup). The planet revolves around an 11-day period eclipsing binary consisting of two solar-mass stars on a slightly inclined, mildly eccentric (e(bin) = 0.16), spin-synchronized orbit. Despite having an orbital period three times longer than Earth's, Kepler-1647b is in the conservative habitable zone of the binary star throughout its orbit.</P>

Shadowed set approximation of fuzzy sets based on nearest quota of fuzziness

T. O. William-West,A. M. Ibrahim,A. F. D. Kana 원광대학교 기초자연과학연구소 2019 ANNALS OF FUZZY MATHEMATICS AND INFORMATICS Vol.17 No.2

Shadowed set approximation of fuzzy sets has been introduced and enhanced to exploit some optimization-based principles which define the quality of its approximation. It found its applications in granular computing, cluster computing and recommender systems. This paper introduces a new approach accompanied with an algorithm; based on a principle of uncertainty invariance, to simplify fuzzy sets by inducing its best approximation which possesses the nearest quota of fuzziness as encountered in the original fuzzy set. Some numerical examples are provided to demonstrate how to implement the proposed method. The new approach is useful in preserving the uncertainty and information inherently associated with a given fuzzy set. A comparative study is made with related methods. The results of some evaluation indices on the approximation effectiveness illustrate the essence of the proposed method.

Tissue inhibitor of metalloproteinases-2 binding to membrane-type 1 matrix metalloproteinase induces MAPK activation and cell growth by a non-proteolytic mechanism.

D'Alessio, Silvia,Ferrari, Giovanni,Cinnante, Karma,Scheerer, William,Galloway, Aubrey C,Roses, Daniel F,Rozanov, Dmitri V,Remacle, Albert G,Oh, Eok-Soo,Shiryaev, Sergey A,Strongin, Alex Y,Pintucci, G American Society for Biochemistry and Molecular Bi 2008 The Journal of biological chemistry Vol.283 No.1

<P>Membrane-type 1 matrix metalloproteinase (MT1-MMP), a transmembrane proteinase with a short cytoplasmic domain and an extracellular catalytic domain, controls a variety of physiological and pathological processes through the proteolytic degradation of extracellular or transmembrane proteins. MT1-MMP forms a complex on the cell membrane with its physiological protein inhibitor, tissue inhibitor of metalloproteinases-2 (TIMP-2). Here we show that, in addition to extracellular proteolysis, MT1-MMP and TIMP-2 control cell proliferation and migration through a non-proteolytic mechanism. TIMP-2 binding to MT1-MMP induces activation of ERK1/2 by a mechanism that does not require the proteolytic activity and is mediated by the cytoplasmic tail of MT1-MMP. MT1-MMP-mediated activation of ERK1/2 up-regulates cell migration and proliferation in vitro independently of extracellular matrix proteolysis. Proteolytically inactive MT1-MMP promotes tumor growth in vivo, whereas proteolytically active MT1-MMP devoid of cytoplasmic tail does not have this effect. These findings illustrate a novel role for MT1-MMP-TIMP-2 interaction, which controls cell functions by a mechanism independent of extracellular matrix degradation.</P>

Down Syndrome Developmental Brain Transcriptome Reveals Defective Oligodendrocyte Differentiation and Myelination

Olmos-Serrano, J.,Kang, H.,Tyler, William A.,Silbereis, John C.,Cheng, F.,Zhu, Y.,Pletikos, M.,Jankovic-Rapan, L.,Cramer, Nathan P.,Galdzicki, Z.,Goodliffe, J.,Peters, A.,Sethares, C.,Delalle, I.,Gold Cell Press 2016 Neuron Vol.89 No.6

Trisomy 21, or Down syndrome (DS), is the most common genetic cause of developmental delay and intellectual disability. To gain insight into the underlying molecular and cellular pathogenesis, we conducted a multi-region transcriptome analysis of DS and euploid control brains spanning from mid-fetal development to adulthood. We found genome-wide alterations in the expression of a large number of genes, many of which exhibited temporal and spatial specificity and were associated with distinct biological processes. In particular, we uncovered co-dysregulation of genes associated with oligodendrocyte differentiation and myelination that were validated via cross-species comparison to Ts65Dn trisomy mice. Furthermore, we show that hypomyelination present in Ts65Dn mice is in part due to cell-autonomous effects of trisomy on oligodendrocyte differentiation and results in slower neocortical action potential transmission. Together, these results identify defects in white matter development and function in DS, and they provide a transcriptional framework for further investigating DS neuropathogenesis.