This paper explores the potential of using the Sheet-based Gyroid TPMS structure as a potential heat sink design. The use of selective laser sintering as a fabrication method is investigated through assessing the accuracy of the printed samples to the designed samples. Scanning electron microscopy and micro-computed tomography are employed to visualize the external and internal microstructure of the printed samples. It is found that there is an inverse relation between the number of defects in a sample and its relative density.
Backward whirl vibration amplitude of rotary system is an important characteristic for early rotor failure detection which otherwise could lead to a serious environmental, health and safety implications. In order to minimize such consequences, an effort was pledged by many researches to study and simulate dynamic response of cracked rotor with breathing crack function for any such characteristics as Backward Whirl phenomena. Nevertheless, current studies presented in the literature have not addressed the transition from forward to backward whirl orbits at the critical backward whirl rotational speeds as a potential indicator for crack presence that can be used for early damage detection. Past numerical and theoretical studies/evaluation showed that the propagation of the fatigue/open crack in rotor systems could excite backward whirl orbits during passages through critical backward whirl rotational speeds. These backward whirl orbits cannot be theoretically excited in crack-free rotors, which make them a unique signature for crack detection in rotors. In the present work, it was proven that backward whirl can be captured using simple 2-DOF Jeffcott Rotor simulation with breathing crack at various crack depth and unbalance orientation angles with respect to transverse crack direction.
Nonlinear Energy Sinks (NESs) are local attachments used to rapidly and passively dissipate energy from a primary structure in a phenomenon known as Targeted Energy Transfer (TET). Single-Sided Vibro-Impact (SSVI) NESs are one type where impacts, usually between the top floor of the primary system and the NES, are utilized to further dissipate energy. In literature, researchers have mostly considered steel-to-steel impacts which mean a coefficient of restitution of approximately 0.7. In this work, the effect of changing this coefficient of restitution will be analyzed and investigated in a 2 Degree-Of-Freedom (DOF) physical primary structure which leads to significant enhancement in energy transfer and dissipation.
Dry reforming of methane (DRM) offers a greener source of energy. However, the Ni based catalysts used in this endothermic process suffer from coking and sintering. This paper explores nano-catalysts that can be used in this reaction obtained by a top-down and bottomup techniques. CoPt bimetallic nanocolloidal particles were synthesized via polyol method, while zeolite Y (CBV720) ball-milled. Electron microscopy and XRD were utilized to characterize the samples obtained. Results showed that monodispersed metal nanoparticles were obtained. Conversely, ball milling did not achieve nanosized particles.
Recently, a significant number of applications are directing their interest into origami patterns which have been widely used in creating novel deployed structures and devices. In aerospace applications, for instant; there is a crucial need for improving the packaging efficiency and this can be obtained through having a low packaging volume to the deployed size ratio. Other than occupying less space, these structures are light weight, flexible, affordable, and have a stiffness higher than the construction material stiffness. Therefore, it is desirable to find a novel fabrication method to form an origami-based structure from lightweight composite materials which can be easily manufactured and cost-effective. In this paper, different out of autoclave methods were experimented to reach a novel approach that is both simple and affordable. This technique was then implemented to manufacture a cylindrical self-deployable boom using fiber-reinforced composite. The proposed model undergone mechanical characterization of the folds that showed a nonlinear moment vs. curvature relationship and suggested the applicable parameters to be further tested. Micro-CT and SEM testing was conducted to show the microanalysis of the model under load. Overall, the fabrication method was proven to be successful and the structure showed a high energy recovery in the folds.
The study aims to evaluate the risk of Station Blackout (SBO) in a single unit from probabilistic risk assessment (PRA) perspective and to re-evaluate the extended station blackout in multi-unit nuclear power plants that shared their dedicated emergency deiseal generator. The initiated event of SBO for the NPP unit is a combination of a Loss of Offsite Power (LOOP) and loss of its Emergency Diesel Generators (EDGs) and if the shared Alternative Alternate Current Diesel Generator (AAC) is lost, the SBO event is extended. The electrical cross-tie is a sharing (donation) of a unit?s dedicated (EDG) from non-impacted unit to the unit under extended SBO of multi-unit NPP in one site. The results of Core Damage Frequencies (CDFs) have been presented for a single unit with two EDGs, with additional third EDG (without crosstie) and with crosstie EDG from another unit. To ensure that, the SBO risk is not underestimated, the benefit and risk of crosstie between units have to be quantified with specific considerations.
In this study, a comparison is conducted between some of the most common techniques used in the nanofluid literature for calculation of the van der Waals (vdW) and electrical doublelayer (EDL) interaction potentials between nanoparticles suspended in a water base fluid. Input parameters and operation conditions that represent practical nanofluid systems used in solar and thermal applications have been used. Limitations and ranges of validity for the different vdW and EDL results have been highlighted. All interaction potentials have been evaluated within the context of DLVO theory, which is the cornerstone for studying the kinetic stability and agglomeration of colloidal particles. Thus, recommendations have been provided with regards to the most appropriate vdW and EDL expressions to be used in the DLVO analysis of solar and thermal nanofluid systems.
Xenon oscillation is a serious issue in nuclear power plants that affects the efficiency of such power plants. Xenon oscillations result from the imbalance between three key parameters, flux distribution in the core, Xenon distribution, and lastly iodine distribution. An improved procedure to simulate and dampen Xenon oscillations by determining only two parameters namely, ?a? and the proportional constant for Xenon concentration difference on axial offset , is previously proposed by the authors (Shimazu, 2009; Al Nuaimi et al., 2019). These two parameters can be calculated from actual nuclear reactor data obtained from nuclear power plants during their operation. In this paper, the approach described earlier (Al Nuaimi et al., 2019) will be validated by solving for the two reactor parameters, ?a? and , through determination of the stability index, ? and angular velocity, ?. This can be done by using fitting algorithm on PWRs? real data in order to characterize the expected Xenon oscillations behavior.
