Prospects of using different clad materials in a material test research reactor – Part 3 – The dynamic behavior

The effects of using different clad materials on the dynamics of a material test research reactor were studied. For this purpose, the aluminum clad of an MTR was replaced separately with stainless steel-316 and zircaloy-4. Simulations were carried out to determine the reactor performance under reactivity insertion and loss-of-flow transients. Nuclear reactor analysis code PARET was employed to carry out these calculations. It was observed that during the fast reactivity insertion transient, Al cladded fuel attained the maximum reactor power of 59.34 MW, while stainless steel-316 cladded attained 48.74 MW and zircaloy-4 cladded attained maximum power of 55.87 MW. During the slow reactivity insertion transient, Al cladded fuel attained the maximum reactor power of 12.38 MW, while stainless steel-316 cladded attained 12.23 MW and zircaloy-4 cladded attained maximum power of 12.34 MW. During the loss-of-flow transients, the reactor power of the stainless steel-316 cladded fuel remained slightly lower than the other two. The fuel temperature of stainless steel-316 and zircaloy-4 cladded fuels remained higher due to poor fuel–clad gap conductance.     

Evaluating Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data for alteration zone enhancement in a semi‐arid area,northern Shahr‐e‐Babak,SE Iran

The visible–near infrared (VNIR) and short wave infrared (SWIR) spectral bands of both the level 1B, radiance at sensor, and level 2, AST_07 surface reflectance data products of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument were evaluated and compared for mapping the alteration zones around porphyry copper deposits and occurrences at the northern Shahr‐e‐Babak, SE Iran. The level 1B data were converted to reflectance using internal average relative reflectance (IARR) method whereas the AST_07 dataset was processed as delivered. The porphyry copper mineralization occurs in Eocene, andesitic and basaltic rocks with zonal alteration patterns that are concentric and almost symmetrically arranged. The spectral signatures of alteration index minerals collected from field samples and the United States Geological Survey (USGS) spectral reference library, were considered in directed principal component analysis (DPCA) and spectral angle mapping (SAM) algorithms. Carrying out the DPCA method on three spectral bands enhanced the alteration haloes in the last principal component (PC) images. Generating RGB colour composite images using these PC images differentiated three alteration zones from the host rocks. The SAM results of the IARR calibrated dataset discriminated the propylitic, argillic and phyllic alteration zones. It is concluded that the higher spectral resolution of ASTER instrument is effective for mineral mapping. However, the method of conversion from radiance to reflectance is critical to the validity of the outputs and that the pseudo‐reflectance method using the IARR process may be more reliable than the standard reflectance product.     

MRT Letter: Optimal composite depth function for 3D shape recovery of microscopic objects

Generally, in shape from focus techniques, a single focus measure is used in estimating the three‐dimensional structure of microscopic objects. However, the performance of a single focus measure is limited to estimate accurately the depth map of diverse type of objects. To cope with this problem, we propose genetic programming based novel approach by developing an optimal composite depth (OCD) function for accurate depth estimation. This OCD function optimally combines the initial depth and focus information extracted from individual focus measures. An improved performance of this function is reported for synthetic and real world microscopic objects. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.     

Evolution of shell formation process in PP/PMMA/PS ternary blends: correlation between the melt rheology and phase morphology

Correlation between the melt rheology and phase morphology of PP/PMMA/PS ternary blends during the shell formation process were studied in detail. In this PP-matrix ternary system, theoretical predictions in agreement with the direct SEM observations demonstrated the core-shell morphology with PMMA and PS phases as core and shell phases, respectively. Morphological observations revealed that the complete shell formation takes place at about 12 and 9 wt% of PS minor phase in ternary blends composed of low and high viscosity PMMAs, respectively. In terms of rheological properties, this was corresponding to the maximum value on the storage modulus versus PS content (shell thickness) curves. Encapsulation of high viscosity PMMA core particles at lower PS contents was related to the bigger particles and low interfacial area in this system compared to the system with low viscosity PMMA core particles. At high PS contents, single and multi-core structures were observed for composite droplets of ternary blends containing low and high viscosity PMMAs, respectively. The single core morphology of low viscosity PMMA particles was related to the coalescence of core particles after the coalescence of the corresponding shells, while high viscosity PMMA cores are less likely to coalescence, leading to creation of multi-core morphology in latter system.     

Deploying swarm intelligence in medical imaging identifying metastasis,micro‐calcifications and brain image segmentation

This study proposes an umbrella deployment of swarm intelligence algorithm, such as stochastic diffusion search for medical imaging applications. After summarising the results of some previous works which shows how the algorithm assists in the identification of metastasis in bone scans and microcalcifications on mammographs, for the first time, the use of the algorithm in assessing the CT images of the aorta is demonstrated along with its performance in detecting the nasogastric tube in chest X‐ray. The swarm intelligence algorithm presented in this study is adapted to address these particular tasks and its functionality is investigated by running the swarms on sample CT images and X‐rays whose status have been determined by senior radiologists. In addition, a hybrid swarm intelligence‐learning vector quantisation (LVQ) approach is proposed in the context of magnetic resonance (MR) brain image segmentation. The particle swarm optimisation is used to train the LVQ which eliminates the iteration‐dependent nature of LVQ. The proposed methodology is used to detect the tumour regions in the abnormal MR brain images.Inspec keywords: swarm intelligence, image segmentation, brain, neurophysiology, medical image processing, biomedical MRI, computerised tomography, diagnostic radiography, bone, diseases, learning (artificial intelligence), particle swarm optimisation, iterative methods, tumours, medical disordersOther keywords: medical imaging identifying metastasis, microcalcifications, umbrella deployment, stochastic diffusion, metastasis identification, bone scans, mammographs, CT imaging, aorta, nasogastric tube, chest X‐ray, hybrid swarm intelligence‐learning vector quantisation approach, magnetic resonance brain image segmentation, particle swarm optimisation, iteration‐dependent nature, tumour regions, abnormal MR brain imaging     

Efficient Timing Budget Management for Accuracy Improvement in a Collaborative Object Tracking System

This paper presents the idea of managing the comprising computations of an application performed by an embedded networked system. An efficient algorithm for exploiting the timing slack of building blocks of the application is proposed. The slack of blocks can be utilized by replacing them with slower but cheaper, i.e. better, modules and by assigning the computations to the proper resources. Thus, our approach manages the comprising computations and system resources and can indirectly assist the realtime scheduling of computations on system resources. This is performed without compromising the timing constraints of the application and can lead to significant improvements in power dissipation, computation accuracy or other metrics of the application domain. Our algorithm is well-suited for arbitrary tree computations. Moreover, it delivers solutions that are desirably close to the optimal solution. Experimental results for a number of object tracking applications implemented in an networked system with embedded computation resources, exhibit a significant amount of slack utilization. Soheil Ghiasi received his B.S. from Sharif University of Technology, Tehran, Iran in 1998, and his M.S. and Ph.D. in Computer Science from the University of California, Los Angeles in 2002 and 2004, respectively. Currently, he is an assistant professor in the department of electrical and computer engineering at the University of California, Davis. His research interests include different aspects of Embedded and Reconfigurable system design. Elaheh Bozorgzadeh received the B.S. degree in Electrical Engineering from Sharif University of Technology, Iran in 1998, M.S. degree in Computer Engineering from Northwestern University in 2000, and Ph.D. degree in Computer Science from the University of California, Los Angeles, in 2003. She is currently as assistant professor in the Department of Computer Science at the University of California, Irvine. Her research interest includes VLSI CAD, design automation for embedded systems, and reconfigurable computing. She is a member of ACM and IEEE. Karlene Nguyen received her B.S. and M.S. from University of California, Los Angeles in 2001 and 2003, respectively. She has been working with Prof. Majid Sarrafzadeh for her M.S. degree. Her research interests include embedded hardware and software design. Majid Sarrafzadeh received his B.S., M.S. and Ph.D. in 1982, 1984, and 1987 respectively from the University of Illinois at Urbana-Champaign in Electrical and Computer Engineering. He joined Northwestern University as an Assistant Professor in 1987. In 2000, he joined the Computer Science Department at University of California at Los Angeles (UCLA). His recent research interests lie in the area of Embedded and Reconfigurable Computing, VLSI CAD, and design and analysis of algorithms. Dr. Sarrafzadeh is a Fellow of IEEE for his contribution to “Theory and Practice of VLSI Design.” He received an NSF Engineering Initiation award, two distinguished paper awards in ICCAD, and the best paper award in DAC. He has served on the technical program committee of numerous conferences in the area of VLSI Design and CAD, including ICCAD, DAC, EDAC, ISPD, FPGA, and DesignCon. He has served as committee chairs of a number of these conferences. He is on the executive committee/steering committee of several conferences such as ICCAD, ISPD, and ISQED. He is the program committee chair of ICCAD 2004. Professor Sarrafzadeh has published approximately 250 papers, is a co-editor of the book “Algorithmic Aspects of VLSI Layout” (1994 by World Scientific), and co-author of the book “An Introduction to VLSI Physical Design” (1996 by McGraw Hill). Dr. Sarrafzadeh is an Associate Editor of ACM Transaction on Design Automation (TODAES) and an Associate Editor of IEEE Transactions on Computer-Aided Design (TCAD) and ACM Transactions on design Automation (TODAES). Dr. Sarrafzadeh has collaborated with many industries in the past fifteen years including IBM, Motorola, and many CAD industries. He is the architect of the physical design subsystem of Monterey Design Systems main product. He is a co-founder of Hier Design, Inc.     

The Response of Framed Steel Structures to Fire

A combined computational fluid dynamics and structural stress investigation was conducted to study the response of steel structures to fire. The structure was a two-story building with six rooms. The fire was confined to one room on the first floor. The free convection of air and thermal radiation were both included in the analysis. The governing differential equations of flow and energy were solved by FLUENT. The air turbulence was modeled by the standard k-? model, and the radiation was simulated by the Discrete Transfer Radiation Model. The temperature of the beams and columns were subsequently used in the thermal stress analysis to obtain the deflection and total strain using ANSYS. The result of FLUENT analysis indicates that the air velocity was high in the middle of the room above the fire and adjacent to the ceiling. The temperatures of the beams and columns generally decreased away from the center, with a more rapid decrease toward the ends. It was also observed that radiation played an important role in fire modeling (i.e., 20–40% of the heat transfer took place by radiation). The ANSYS analysis indicated a maximum deflection of 28.66 mm at a beam-column joint in the room with fire at the first level of the structure. The corresponding steel column design load capacity is exhausted after 34 minutes of standard ISO 834 fire due to a combined temperature and gravity loads. The maximum strain was observed at the center of the longitudinal beam, and the minimum was on the steel members of the second floor.     

Laminar Fully Developed Flow in Periodically Converging–Diverging Microtubes

Laminar fully developed flow and pressure drop in linearly varying cross-sectional converging–diverging microtubes have been investigated in this work. These microtubes are formed from a series of converging–diverging modules. An analytical model is developed for frictional flow resistance assuming parabolic axial velocity profile in the diverging and converging sections. The flow resistance is found to be only a function of geometrical parameters. To validate the model, a numerical study is conducted for the Reynolds number ranging from 0.01 to 100, for various taper angles, from 2 to 15 degrees, and for maximum–minimum radius ratios ranging from 0.5 to 1. Comparisons between the model and the numerical results show that the proposed model predicts the axial velocity and the flow resistance accurately. As expected, the flow resistance is found to be effectively independent of the Reynolds number from the numerical results. Parametric study shows that the effect of radius ratio is more significant than the taper angle. It is also observed that for small taper angles, flow resistance can be determined accurately by applying the locally Poiseuille flow approximation.