MEMS based storage architecture for relational databases

Due to recent advances in semiconductor manufacturing, the gap between main memory and disks is constantly increasing. This leads to a significant performance bottleneck for Relational Database Management Systems. Recent advances in nanotechnology have led to the invention of MicroElectroMechanical Systems (MEMS) based storage technology to replace disks. In this paper, we exploit the physical characteristics of MEMS-based storage devices to develop a placement scheme for relational data that enables retrieval in both row-wise and column-wise manner. We develop algorithms for different relational operations based on this data layout. Our experimental results and analysis demonstrate that this data layout not only improves I/O utilization, but results in better cache performance for a variety of different relational operations. This research is supported by the NSF grants under IIS-0220152 CNF-0423336, and EIA 00-80134     

A Triple-Channel Encrypted Hybrid Fusion Technique to Improve Security of Medical Images

Assuring medical images protection and robustness is a compulsory necessity nowadays. In this paper, a novel technique is proposed that fuses the wavelet-induced multi-resolution decomposition of the Discrete Wavelet Transform (DWT) with the energy compaction of the Discrete Wavelet Transform (DCT). The multi-level Encryption-based Hybrid Fusion Technique (EbhFT) aims to achieve great advances in terms of imperceptibility and security of medical images. A DWT disintegrated sub-band of a cover image is reformed simultaneously using the DCT transform. Afterwards, a 64-bit hex key is employed to encrypt the host image as well as participate in the second key creation process to encode the watermark. Lastly, a PN-sequence key is formed along with a supplementary key in the third layer of the EbHFT. Thus, the watermarked image is generated by enclosing both keys into DWT and DCT coefficients. The fusions ability of the proposed EbHFT technique makes the best use of the distinct privileges of using both DWT and DCT methods. In order to validate the proposed technique, a standard dataset of medical images is used. Simulation results show higher performance of the visual quality (i.e., 57.65) for the watermarked forms of all types of medical images. In addition, EbHFT robustness outperforms an existing scheme tested for the same dataset in terms of Normalized Correlation (NC). Finally, extra protection for digital images from against illegal replicating and unapproved tampering using the proposed technique.     

Assessment of windfarm economics in relation to site wind resources applied to sites in Jordan

This paper describes an analytical method for estimation of the economical feasibility of a project for wind energy utilization in Jordan. The method is applied to a windfarm and is based on the wind speed distribution at the site considered and on the financial parameters for the complete plant and its running costs. For this method, equations were derived to calculate the cost of a kWh generated by wind turbines with different characteristics as a function of the capital investment per kW installed capacity. The method was applied to the sites at which Royal Scientific Society performs wind speed measurements, and the results indicate that some of these sites are well suited for cost efficient generation of electricity by wind energy. The results also show that a wind tribine which is designed to have a relatively low rated speed has a wider range of economical operation than a wind turbine with a higher rated speed for the sites investigated assuming that the maximum rated power for all for the wind turbines is held constant.     

Structural performance and economics of tall high strength RC buildings in seismic regions

For a multitude of economic and societal considerations, high rise structures are on the increase. This in turn promotes the use of high strength materials to reduce column size and construction times. Whereas design guidance and engineering understanding of high strength RC structures under static loading is well‐developed, little work has been undertaken on the economics of whole buildings and their performance under earthquake loading. In this paper, 10 buildings of 24 stories are designed and detailed according to modern seismic codes. The buildings are all nominally equivalent, using a stiffness equivalence criterion and its derivatives. The cost of construction is compared in terms of steel, concrete and formwork. The static inelastic response of the buildings is also assessed, followed by a full nonlinear dynamic analysis of all buildings using three earthquake records at the design acceleration and twice the design value. Comprehensive assessment of the static and dynamic results is undertaken. It is concluded that the cost increase is mainly due to the steel, whilst significant member reductions may be availed of by using high strength concrete. The behaviour of high strength concrete structures is not inferior to that of normal strength materials. Indeed, it is observed that lower levels of overstrength can be achieved in high strength materials than in their normal strength counterparts, mainly due to the over‐reinforcement of the latter to resist vertical forces. Recommendations on the use of equivalent cracked stiffness for period calculation in design, and also effective periods for use in displacement‐based design, are given. Copyright © 1999 John Wiley & Sons, Ltd.     

The design and seismic performance of low-rise long-span frames with semi-rigid connections

Moment-resisting steel frames are used frequently in low-rise and mid-rise buildings located in high seismic areas due to their high ductility and economic solutions. In these type of structures, strong-column weak-beam design requirements result in larger column sections and overdesign in low-rise long-span buildings. To mitigate this problem, moment-resisting steel frames with energy-dissipative semi-rigid/partial strength connections can be used as an alternative to perimeter frames. By using energy-dissipative semi-rigid connections, the strong-column weak-beam requirement is eliminated and more economical column sections are used. In this study, a three-span three-bay frame with 7 and 9 m span lengths is designed with semi-rigid connections having four different capacities in high seismic zones. Their seismic performance is evaluated analytically under three different earthquake levels by modeling connections with two different moment-hardening ratios and two different hysteretic behavior models. The design with reduced connection capacity resulted in an increase in the beam weights, a decrease in the column weights and an overall decrease in the structural weight. The seismic performances of 26 sample frames are evaluated with pushover and dynamic analyses under 25 real strong ground motion records. All of the sample frames satisfied the acceptance criteria and showed reliable performance under earthquake loading. The overdesign problem in low-rise long span-buildings is eliminated to some extent without using the perimeter frame approach. Furthermore, under some specific ground motion records, the top displacements in semi-rigid frames become lower than those of their rigid counterparts.     

Elastic lateral stability of I-shaped cellular steel beams

In this paper, the lateral stability of cellular steel beams is numerically investigated. The study is carried out using three-dimensional finite element modeling of simply supported I-shaped cellular steel beams with a broad spectrum of cross-sectional dimensions, span lengths and web perforation configurations. Stability analyses are carried out for beams subjected to equal end moments, mid-span concentrated loads and uniformly distributed loads. Finite element results reveal that, unlike the case of conventional beams with solid webs, the moment-gradient coefficient C_b is significantly influenced by the beam geometry and slenderness. In addition, the C_b coefficient of cellular beams depends on the web perforation configuration. Moment-gradient coefficient values that fluctuate closely to those values recommended by design codes are associated with pure elastic lateral torsional buckling (LTB) deformations. As the beam slenderness decreases, the web distortion increases, leading to the lateral distortional buckling (LDB) mode, which is associated with lower C_b values than code-recommended ones. Severe reduction in the C_b coefficient to values less than 1.1 is noticed for shorter-span beams where the response is dominated by non-lateral local buckling modes.A simplified approach is developed to enable accurate prediction of a moment modification factor κ_LB for cellular beams. The proposed κ_LB factor is provided by an empirical formula that is derived based on the best fit of the finite element results related to lateral buckling (LTB and LDB) modes only. The proposed approach allows for accurate and conservative evaluation of the critical moment associated with the lateral torsional/distortional buckling of cellular beams. Several numerical examples are worked out to illustrate the application of the proposed procedure.     

Soil-reinforcement interaction: Stress regime evolution in geosynthetic-reinforced soils

Understanding the stress regime that develops in the vicinity of reinforcements in reinforced soil masses may prove crucial to understanding, quantifying, and modeling the behavior of a reinforced soil structures. This paper presents analyses conducted to describe the evolution of stress and strain fields in a reinforced soil unit cell, which occur as shear stresses are induced at the soil-reinforcement interface. The analyses were carried out based on thorough measurements obtained when conducting soil-reinforcement interaction tests using a new large-scale device developed to specifically assess geosynthetic-reinforced soil behavior considering varying reinforcement vertical spacings. These experiments involved testing a geosynthetic-reinforced mass with three reinforcement layers: an actively tensioned layer and two passively tensioned neighboring layers. Shear stresses from the actively tensioned reinforcement were conveyed to the passively tensioned reinforcement layers through the intermediate soil medium. The experimental measurements considered in the analyses presented herein include tensile strains developed in the reinforcement layers and the displacement field of soil particles adjacent to the reinforcement layers. The analyses provided insights into the lateral confining effect of geosynthetic reinforcements on reinforced soils. It was concluded that the change in the lateral earth pressure increases with increasing reinforcement tensile strain and reinforcement vertical spacing, and it decreases with increasing vertical stress.     

Clay particles destabilize engineered nanoparticles in aqueous environments

Given the ubiquity of natural clay minerals, the most likely interaction of nanoparticles released into an aquatic environment will be with suspended clay minerals. Thus, the transport of engineered nanoparticles in the subsurface and the water column will most likely be altered by their interaction with these minerals. We studied the interactions of two of the most produced nanoparticles, Ag and TiO(2), and montmorillonite to determine how heteroaggregation can alter the stability of nanoparticle/clay mineral mixtures. Since at low pH montmorillonite has a negatively charged basal plane and positively charged edges, its interaction with these nanoparticles at different pH lead to unusual behaviors. There are six different interactions for each clay-nanoparticle pair. At pH values below the IEP of montmorillonite edge site, montmorillonite reduced the stability of both negatively charged Ag and positively charged TiO(2) nanoparticles. Surprisingly this enhanced coagulation only occurs within an intermediate ionic strength range. The spillover of the montmorillonite basal plane electric double layer to the montmorillonite edge may screen the electrostatic attraction between Ag and the montmorillonite edge at low ionic strength, whereas a repulsion between TiO(2) and montmorillonite face sites may restabilize the mixture.