Using AC field measurement data at an arbitrary liftoff distance to size long surface-breaking cracks in ferrous metals

We propose a model-based inversion method to size long surface-breaking cracks in ferrous metals using alternative current field measurement (ACFM) data at an arbitrary liftoff distance. This method employs conjugate gradients optimization to invert measured surface ACFM signal to crack depth. To alleviate the adverse effect of sensor liftoff uncertainty on crack sizing, we propose a blind de-convolution algorithm for reconstructing respective surface ACFM crack signal. In this algorithm, the partially known filter function associated with the sensor liftoff is estimated from which the surface crack signal can be restored. The validity of the proposed inversion method is demonstrated by comparing the actual and predicted depths of several simulated and machine-made long cracks in mild steel test blocks.     

A Review: Highlighting the Links between Epigenetics,COVID-19 Infection,and Vitamin D

The highly transmittable and infectious COVID-19 remains a major threat worldwide, with the elderly and comorbid individuals being the most vulnerable. While vaccines are currently available, therapeutic drugs will help ease the viral outbreak and prevent serious health outcomes. Epigenetic modifications regulate gene expression through changes in chromatin structure and have been linked to viral pathophysiology. Since epigenetic modifications contribute to the life cycle of the virus and host immune responses to infection, epigenetic drugs are promising treatment targets to ameliorate COVID-19. Deficiency of the multifunctional secosteroid hormone vitamin D is a global health threat. Vitamin D and its receptor function to regulate genes involved in immunity, apoptosis, proliferation, differentiation, and inflammation. Amassed evidence also indicates the biological relations of vitamin D with reduced disease risk, while its receptor can be modulated by epigenetic mechanisms. The immunomodulatory effects of vitamin D suggest a role for vitamin D as a COVID-19 therapeutic agent. Therefore, this review highlights the epigenetic effects on COVID-19 and vitamin D while also proposing a role for vitamin D in COVID-19 infections.     

A decision‐making approach for detecting the primary user emulation attack in cognitive radio networks

Cognitive radio network (CRN) is a promising technology, which enables secondary users to use the free spectrum channels without causing detrimental interference with the primary user (PU). Nevertheless, CRN is subject to numerous cyber attacks that have a negative impact on its performance. Among the CRN attacks, the primary user emulation (PUE) attack is known to be one of the malicious attacks threatening CRN security. Several attacks detection techniques, based on attacker localization, have been investigated in the literature. These techniques include the trilateration, received signal strength indication (RSSI), and network coding approach as well. However, most of these techniques do not consider the uncertainty related to CRN, which can be modeled by a cost function defined as a weighted sum of conditional probabilities. In this paper, a localization technique, relied on a trilateration computation and a Bayesian model, is proposed for PUE position detection purpose under uncertainty conditions assumption. Particularly, the estimation of PUE position is performed through trilateration method based on RSSI at the anchor nodes for the signal coming from either PU or PUE, whereas, the Bayesian decision model, based on a cost function, is involved to check the PU legitimacy. The simulation results show that the decision‐making approach "Security, productivity, Balancing" influences directly the zone of the PUE attack detection.     

A hexameric transmembrane pore revealed by two-dimensional crystallization of the large mechanosensitive ion channel (MscL) of Escherichia coli

We have established a reconstitution method of the detergent-solubilized recombinant large mechanosensitive ion channel of Escherichia coli (MscL) that yielded two-dimensional crystals. For that purpose, we have developed a new protocol using Triton X-100 to solubilize and purify the MscL protein. This protocol not only allowed an increase in the protein yield but also made it possible to obtain a homogeneous delipidated and reproducible preparation of the purified protein. When examined by the patch-clamp method MscL channels were found to be fully functional, exhibiting characteristic conductance and activation by pressure. For electron crystallography the homogeneous Triton X-100-purified recombinant MscL was further reconstituted at low lipid-to-protein ratios using Bio-Beads SM2 to remove the detergent. Two-dimensional crystals, exhibiting a p6 plane group symmetry, have been produced and examined by negative stain electron microscopy. Image processing of selected micrographs yielded a projection map at 15-A resolution that provided the first explicit structural information about the molecular boundary and homohexameric organization of the MscL channels in the membrane bilayer.     

A triangular conforming element for laminated shells

A 30 degree of freedom (DOF) conforming shell element is developed for laminated composite materials. This element is 10-noded and has a triangular shape. Sander's thin shell theory is used. The element is used to perform both static and dynamic analysis on a composite cylindrical shell. Results obtained by the present element are compared with those available in the literature (exact, experimental, and numerical) for simple support and cantilever boundary conditions. These comparisons show that one can get reasonably accurate results with the present element and good convergence characteristics.     

Intersubband optical absorption in (In,Ga)N/GaN double quantum wells considering applied electric field effects

Journal of Computational Electronics - In the present paper, we theoretically examine the total absorption coefficient related to inter-conduction subband 1S–2P transitions in symmetric...     

Image noise level estimation based on higher-order statistics

Multimedia Tools and Applications - Noise level estimation is a required step for many preprocessing algorithms in computer vision such as image denoising. In this paper, a model-based technique...     

Cements in the 21st century: Challenges,perspectives, and opportunities

Since its widespread use in concrete began over 100 years ago, the chemical composition and physical properties of portland cement have changed only incrementally in response to various and competing pressures of constructability and cost. Instead, the construction demands have been met largely through the development and introduction of chemical admixtures that are added to the binder during mixing. These same demands persist into the 21^st Century and are just as important now as before, yet newer driving forces are simultaneously pushing the industry both toward more automated construction and toward more sustainable concrete materials that generate lower CO₂ and have longer service life. These new cement binder formulations and new construction technologies are expected to go well outside the bounds of traditional portland cement compositions and batching and placing practices. This study examines the origins of these new market demands and the influence they are having on the construction industry. Seven scientific or technological pathways are identified that will be critical for enabling the kinds of transformational changes in cement and concrete construction that the industry needs: (i) additive manufacturing, (ii) designer admixtures, (iii) curated materials data repositories, (iv) computationally designed composites, (v) big data and smart materials, (vi) alternative binder compositions, and (vii) next‐generation instrumentation.     

Studying Mn- and Ni-doped ZnO Thin Films Synthesized by the Sol–Gel Method

In this work, Zn_0.97TM_0.03O (TM = Mn, Ni) thin films are deposited onto glass substrates by the sol–gel method, and the effects of transition metal (TM) substitution on the structural, optical, and magnetic properties of these films are investigated. X-ray diffraction patterns reveal that all the films have Wurtzite structure. Optical transmittance of the films is recorded in the wavelength range of 200–800 nm, and the band gap of the films is determined. Optical constants of the films are calculated using a pointwise unconstrained minimization algorithm. Absorption edge of the films show a small shift depending on the dopant elements. Magnetic analyzing indicates that both Ni-doped and undoped ZnO films are ferromagnetic at room temperature but for Mn-doped films, paramagnetic contribution is dominated.     

The instructional benefits of dynamic visualizations in the acquisition of basketball tactical actions

Recent studies exploring the effects of dynamic visualizations on learning compared with static visualizations have yielded mixed results. Procedural motor learning is one of the few fields in which dynamic representations have shown to be effective. Many of the studies have suggested that this advantage is mainly due to the activation of the “mirror‐neuron system.” This study explores this explanation in physical education domain and analysed the effects of instructional media (video vs. photographs), showing tactical actions in basketball, on learning outcomes (i.e., game understanding and game performance), cognitive load (i.e., mental effort invested and estimated difficulty), and attitudes (i.e., attention, enjoyment, engagement, and challenge) in secondary school students. For all of the indicators, the results show that learning from video was more effective than learning from photographs. These findings have implications for the effective design of instructional media and provide confirmation of the superiority of video for teaching tactical actions involving the entire body.