Modeling of mechanical resonators used for nanocrystalline materials characterization and disease diagnosis of HIVs

The modeling and performance of mechanical resonators used for mass detection of bio-cells, nanocrystalline materials characterization, and disease diagnosis of human immune-viruses (HIVs) are investigated. To simulate the real behavior of these mechanical resonators, a novel distributed-parameter model based on Euler–Bernoulli beam theory is developed. This model is equipped with a micromechanical model and an atomic lattice model to capture the inhomogeneity nature of the material microstructure. Compared with lumped-parameter model predictions, the results show that this developed model best fits with the real behavior of the mechanical resonators when detecting the mass of vaccinia virus. In terms of material characterization, the developed model gives very good estimations for the densities and Young’s moduli of the grain boundary of both the nanocrystalline silicon and nanocrystalline diamond. For disease diagnosis, it is shown that the number of human immune-deficiency virus particles in a liquid sample can be easily detected when using the proposed model. The results also show that the developed model is beneficial and can be used to design mechanical resonators made of nanocrystalline materials with the ability to control the resonators’ sizes and the material structure.     

Effects of processing conditions on microstructure and mechanical properties of equal-channel-angular-pressed titanium

This review presents an investigation on effects of the processing conditions on the microstructural evolution and mechanical properties of commercial pure titanium processed by Equal Channel Angular Pressing (ECAP). An overview of ECAP processing is presented. A discussion on the microstructure evolution of ECAPed titanium emphasising effects of the ECAP-route type, processing temperature, number of ECAP passes, and mechanical/thermal treatments is presented. Moreover, the variations of the mechanical properties (yield strength, tensile strength, and ductility) of titanium as functions of the grain size are reported for the different conditions of ECAP processing. In addition, the best estimates of the Hall–Petch parameters for titanium processed by ECAP, ECAP followed by mechanical and/or thermal annealing are reported.     

Bayesian belief-based model for reliability improvement of the digital reactor protection system

Nuclear Science and Techniques - This paper introduces some latest developments regarding the X-ray imaging methodology and applications of the X-ray imaging and biomedical application beamline...     

Propagation of ultrasonic waves through demineralized cancellous bone

Ultrasonic velocity is determined in a number of bovine cancellous (spongy) bone samples by using a double-probe-through-transmission ultrasonic pulse technique. The ultrasonic velocity, total mineral content, bone density, and solid volume fraction of the specimen were determined. The relation between fast velocity and each of the other parameters was examined to explore the best correlation using linear, logarithmic, power, and exponential relationships. There is a strong positive relationship between ultrasonic velocity and each of the other parameters. The exponential model fits the data better than the linear model, logarithmic model, and power model. Biot's theory also is used to predict the velocity of ultrasound in the demineralized bone. It is shown that the transmission of ultrasonic pulses in the cancellous bone samples can be adequately described using Biot's theory. The different parameters occurring in the Biot theory have been measured independently, and the calculation has been compared with measured velocity of water-saturated bone samples. The correlation coefficients for regression analysis between the experimental velocities and those predicted by Biot's theory are greater than 0.86.     

Repair of Cracked Steel Girders Connected to Concrete Slabs Using Carbon-Fiber-Reinforced Polymer Sheets

This paper presents the results of an experimental study on the repair of artificially damaged steel–concrete composite beams repaired using adhesively bonded carbon-fiber-reinforced polymer (CFRP) sheets. Eleven, 2 m long, beams composed of W150×22 steel sections with 465×75?mm concrete slabs were tested in four-point bending. Severe damage was first introduced in ten beams by saw cutting the tension flange completely at mid span, to simulate a fatigue crack or a localized severe corrosion. Standard modulus (SM) and high modulus (HM) CFRP sheets were then used to repair nine damaged beams. The length and number of CFRP layers applied to the cracked flange on the underside, or on both sides, were varied. Results showed that the damage had reduced flexural strength and stiffness by 60 and 54%, respectively. Nevertheless, CFRP-repaired beams achieved various levels of recovery, and in some cases, exceeded the original capacities. The strength of beams repaired with sheets, ranging in length from 8 to 97% of the span, varied from 46–116% of the original undamaged strength, whereas the stiffness range was 86–126% of original stiffness. SM-CFRP failed by debonding whereas HM-CFRP was ruptured. Bonding the sheets to both sides of the flange was not very advantageous over bonding to the underside only.     

Mode localization phenomenon of functionally graded nanobeams due to surface integrity

International Journal of Mechanics and Materials in Design - This is the first study on the mode localization and surface stress-based deflection phenomena of functionally graded (FG) nanobeams due...     

Study of selected trace elements in cancerous and non-cancerous human breast tissues from Sudanese subjects using instrumental neutron activation analysis

This study was performed to investigate the influence of cancer on selected trace elements among Sudanese patients with confirmed breast cancer. Instrumental neutron activation analysis was used to estimate contents of Se, Zn, Fe, Cr, Rb, Cs, Co and Sc in 40 subjects. Wilcoxon signed ranks test was used to examine if there was any difference in the concentrations of elements from normal and malignant tissues. It was found that Se, Zn and Cr elements from the malignant tissues are significantly elevated (P < 0.05) compared to the normal tissue. The results obtained have shown consistency with results obtained by some previous studies.     

Application independent interactive environment for power systemseducation

The authors present an interactive software package for the simulation of power system stability studies. The package is intended as a supplementary tool for the teaching of power system stability courses at the graduate level. The development of the package was done exclusively for IBM-PC and compatible computers. The hardware mainly requires VGA display and 640 kbyte of memory. Professional libraries used for the development of the package include Meta Windows, graphics Menu, and Object Professional. The authors describe the methods used for the integration of various analysis programs and the organization of the data and information pertinent to a system study     

Buckling characteristics of nanocrystalline nano-beams

The buckling and the postbuckling characteristics of nanocrystalline nano-beams with/without surface stress residuals are investigated. A hybrid model is proposed where a non-classical beam model is incorporated with a size-dependent micromechanical model. The micromechanical model has the merit of accounting for the beam material structure effects, i.e. the grain size and the grain boundary effects. To account for the beam size effects, the couple stress theory is implemented where some measures are added to capture the grain rigid rotation effects. The proposed hybrid model is harnessed to derive the governing equations of a nano-beam subjected to an axial compressive load accounting for the mid-plane stretching according to von-Karman kinematics and the surface stress residuals. Analytical solutions for the prebuckling and postbuckling configurations and natural frequencies as functions of the applied compressive axial load are derived. The effects of the beam material structure and the beam size on the beam’s prebuckling characteristics and the postbuckling configurations and natural frequencies are studied. The obtained results reveal that both the size and the material structure of nanobeams have great impacts on their buckling characteristics.     

Modeling of postulated accident release of MoO3 powder from ETRR-2 Stack

The postulated accident modeled in this study simulates the release of ⁹⁹MoO₃ powder, activated by neutrons, to the environment through the ventilation system of the universal cell of ETRR-2 (Egyptian second nuclear research reactor). The simulation was carried out in both the normal and abnormal situation cases. The ⁹⁸MoO₃ powder was contained in an ampoule of quartz surrounded with a tight Aluminum can. The can is purposed to be irradiated in the ETRR-2 irradiation grid with a neutron flux of 1.4 × 1014 n/cm² s to produce ⁹⁹MoO₃. The Aluminum can was delivered after irradiation to the universal cell to remove the quartz ampoule to the outside the Aluminum can. During the process of removing the quartz ampoule from the Aluminum can, the ampoule may be broken due to a human error and the ⁹⁹MoO₃ powder released in the universal cell that is connected to the hot cell ventilation system. The postulated radiation doses to the public at various downwind distances were calculated using the health physics computer code HotSpot 2.06 developed at the Lawrence Livermore National Laboratory, USA. This study is a complementary study for ⁹⁹MoO₃ production safety document. The results indicated that the persons who are within downwind distances for all metrological conditions (A–F classes) would receive a committed effective dose (CED) less than the permissible dose for both the normal and abnormal cases.