781 research outputs found
Formation and Development of the Training System for Innovative Development of Regional Industry
The paper determines tendencies of modern economy development. The key role in the expanded reproduction of innovation processes in the regions in modern conditions belongs to the enhancement of human capital. Regions are actively increasing their efforts in creating innovative infrastructure, knowledge-intensive industries, while success of regional development is directly related to the effectiveness and cohesion of all innovation infrastructure elements. An indispensable condition for the successful development of innovative infrastructure and high-tech industries is the region economy saturation with highly qualified personnel, particularly mining, trained in view of the projected trends of innovative development
Dynamic Behavior in Piezoresponse Force Microscopy
Frequency dependent dynamic behavior in Piezoresponse Force Microscopy (PFM)
implemented on a beam-deflection atomic force microscope (AFM) is analyzed
using a combination of modeling and experimental measurements. The PFM signal
comprises contributions from local electrostatic forces acting on the tip,
distributed forces acting on the cantilever, and three components of the
electromechanical response vector. These interactions result in the bending and
torsion of the cantilever, detected as vertical and lateral PFM signals. The
relative magnitudes of these contributions depend on geometric parameters of
the system, the stiffness and frictional forces of tip-surface junction, and
operation frequencies. The dynamic signal formation mechanism in PFM is
analyzed and conditions for optimal PFM imaging are formulated. The
experimental approach for probing cantilever dynamics using frequency-bias
spectroscopy and deconvolution of electromechanical and electrostatic contrast
is implemented.Comment: 65 pages, 15 figures, high quality version available upon reques
Thermodynamic theory of epitaxial ferroelectric thin films with dense domain structures
A Landau-Ginsburg-Devonshire-type nonlinear phenomenological theory is
presented, which enables the thermodynamic description of dense laminar
polydomain states in epitaxial ferroelectric thin films. The theory explicitly
takes into account the mechanical substrate effect on the polarizations and
lattice strains in dissimilar elastic domains (twins). Numerical calculations
are performed for PbTiO3 and BaTiO3 films grown on (001)-oriented cubic
substrates. The "misfit strain-temperature" phase diagrams are developed for
these films, showing stability ranges of various possible polydomain and
single-domain states. Three types of polarization instabilities are revealed
for polydomain epitaxial ferroelectric films, which may lead to the formation
of new polydomain states forbidden in bulk crystals. The total dielectric and
piezoelectric small-signal responses of polydomain films are calculated,
resulting from both the volume and domain-wall contributions. For BaTiO3 films,
strong dielectric anomalies are predicted at room temperature near special
values of the misfit strain.Comment: 19 pages, 8 figure
Study of Theoretical and Observed Capacities of Bored Cast-Insitu Piles in Tuff, Braccia and Weathered Basalt
The termination depth of bored cast in situ piles poses serious problem to the field engineers particularly on weak weathered rock, stiff clays and dense sands. Some sort of decision making tool is available for driven piles in the form of driving formulae. The first part of paper deals with a simple method based on penetration resistance to the advancement of bore and its relation with end bearing and frictional resistance offered by formation. The second and third parts of paper deal with a newly conceived dynamic method for ascertaining the safe load on pile and its comparison with the safe load value derived from penetration resistance actually observed. The dynamic test proposed is simpler, quicker cost effective and shall be an excellent quality assurance tool for the bored cast-in-situ piles
Deterioration of Bored Cast in Situ Piles Due to Aggressive Water
Most of the data available from the cement industry and the literature exhibits performance of concrete cubes cured in normal water. Even the literature related to the durability of concrete deals mostly with concrete cured in normal water (closer to potable water in characteristics). However, the bored-cast-in-situ piles are cured in the ground water. The development of strength of concrete of bored cast-in-situ piles depends upon the quality of ground water. The effect of sulphates and chloride is well established and most of the codes stipulate permissible limits of pH, sulphates and chlorides contents in the ground water. In the last 20 years, authors have come across a number of situations where inspite of water being certified as satisfactory, from chlorides-sulphate point of view the pile shafts have shown deterioration beyond the conceivable limits. The authors have been working on the problem to establish the effect of quality of water with reference to Ryzner index and Marble test; a parameter that plays a significant role in deciding the quality of water and Marble test as proposed by DIN. The research work involves curing of cubes of same mix in a chemically analyzed ground water as well as normal water. The properties of the concrete like cube strength, elasticity, permeability and setting time are compared. Three types of cement in three grades of concrete are used. The cubes are tested for cube strength for 1, 7, 14, 28, 45 and 90. The findings of the research programme shall be presented into the pape
Direct Observations of Retention Failure in Ferroelectric Memories
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90388/1/1106_ftp.pd
Are we ready to replace physical mock exam with an online mock exam? a survey-based comparison
Background: Mock exams have become an integral part of urology training, presently conducted in a real classroom (physical mock exam- PME). We conducted a mock exam in a virtual classroom (online mock exam- OME) for 130 urology residents. A survey was conducted to compare OME and PME.
Methods: Questionnaire was developed, consisting of 16 questions, of which two question were matrix, others had options. For the matrix questions the candidates had to rate the components of the PME and OME on a scale of 1 to 5.
Results: Out of the 130, 103 (86.55%) were eligible for analysis. Regarding, ease of understanding the question and fulfilling the expectations both modalities were rated highly (95.15% versus 93.2%, p=0.552 and 89.32 versus 83.5%, p=0.221). OME fared better than PME, with regards to the questions addressing; ease of understanding the explanation (p=0.000), fluency of interaction (p=0.000), ability to concentrate (p=0.002), feeling of involvement (p=0.000), logistic convenience (p=0.001), ability to network and ability to balance commitments (p=0.000). PME was superior in interacting with peers (p=0.000), and peer motivation helping them concentrate better (p=0.001). Out of the 103 respondents 79 (66.39%) recommended an OME for future.
Conclusions: Online platform can be effectively used to conduct a mock exam. It is not only noninferior to PME but also has many advantages. This survey shows OME has a potential to replace PME
Evaluation of an anthropometric head surrogate exposed to chisel-nosed fragment simulating projectile impact
Fragment-induced penetrating injuries pose a significant threat in modern combat. Explosions from explosive devices generate metallic fragments that can lethally penetrate various body regions, with the head being particularly most vulnerable to fatality in terms of penetration. Hence, understanding the head’s response to fragment impact is crucial. To this end, this study investigated the ballistic response of an anatomically accurate anthropometric head surrogate to fragment impact. The head surrogate comprised simulants for the three major layers of the head (skin, skull, and brain). Using a pneumatic gas gun, we impacted chisel-nosed fragment simulating projectiles (FSPs) of 1.10-g and 2.79-g on the head surrogate. We analyzed the ballistic response of the head surrogate in terms of ballistic limit velocities (V50), energy densities (E50/A), and failure mechanisms in each layer. The results indicated sensitivity to the FSP size. The 1.10-g FSP had a ∼41% higher V50 and a ∼63% higher E50/A compared to the 2.79-g FSP. Additionally, each head surrogate layer exhibited distinct failure mechanisms. The skin simulant failed due to a combination of shearing and elastic hole enlargement, forming a cavity smaller than the size of the FSP. The skull simulant fractured, creating a cavity at the entry point matching the FSP size. The brain simulant failure involved shearing of the cavity and penetration of fractured skull fragments. We also observed no significant difference in response when introducing a flexible neck attachment on which the head surrogate was mounted. Furthermore, comparisons of an anthropometric (close-shape) head surrogate with a simplified open-shaped head surrogate revealed the minimal influence of the head curvature on the response due to the localized nature of fragment penetration. These findings provide a comprehensive understanding of the head surrogate’s mechanical response to fragment impact. The insights from this work hold significant value in the assessment of penetrating head injury, especially against small fragments. The results can be applied in modern warhead design and forensic investigations
Investigation of dynamic responses of skin simulant against fragment impact through experiments and concurrent computational modeling
Perforation of the skin by fragment impact is a key determinant of the severity of an injury and incapacitation during modern asymmetric warfare. Computational models validated against experimental data are thus desired for simulating the responses of a skin simulant against fragment impact. Toward this end, experiments and concurrent computational modeling were used to investigate the dynamic responses of the skin simulant against fragment impact. Fragment simulating projectiles (FSPs) of masses 1.10 g and 2.79 g were considered herein, and the responses of the skin simulant were investigated in terms of the threshold velocity, energy density, peak displacement, and failure mechanisms. The results illustrate numerous salient aspects. The skin simulant failure involved cavity shearing followed by elastic hole enlargement, and these results were sensitive to the strain rate. The best agreement between the simulated and experimental results was achieved when the input stress–strain curves to the simulation were based on the full spectrum of strain rates. When a single stress–strain curve corresponding to a specific strain rate was used as the input, the threshold velocity and peak displacement of the skin simulant were either underpredicted or overpredicted depending on the strain rate considered. The threshold velocity was also sensitive to the input failure strain; here, the best agreement was obtained when the failure strain was based on the theoretical limiting strain. When the FSP materials were changed to plastics, the threshold velocities increased by up to 33%; however, the energy densities and generated stresses exceeded the contusion and laceration thresholds of the skin
Nanostructuring Ferroelectrics via Focused Ion Beam Methodologies
As we reach the physical limit of Moore’s law and silicon based electronics, alternative schemes for memory and sensor devices are being proposed ona regular basis. The properties of ferroelectric materials on the nanoscale are key to developing device applications of this intriguing material class, and nanostructuring has been readily pursued in recent times. Focused ion beam (FIB) microscopy is one of the most signi cant techniques for achievingthis. When applied in tandem with the imaging and nanoscale manipulation afforded by proximal scanning force microscopy tools, FIB-driven nanoscale characterization has demonstrated the power and ability which simply may not be possible by other fabrication techniques in the search for innovative and novel ferroic phenomena. At the same time the process is not without pitfalls; it is time-consuming and success is not always guaranteed thus often being the bane in progress. This balanced review explores a brief history of the relationship between the FIB and ferroelectrics, the fascinating properties it has unveiled, the challenges associated with FIB that have led to alterna- tive nanostructuring techniques and nally new ideas that should be explored using this exciting technique
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