Changes In Dynamic Properties Research Articles

Role of organic cation orientation in formamidine based perovskite materials

The rotation of organic cations is considered to be an important reason for the dynamic changes in stability and photoelectric properties of organic perovskites. However, the specific effect of organic cations rotation on formamidine based perovskite is still unknown. In our work, first-principles calculations based on density functional theory are used to examine the effect of the rotation of formamidine cations in FAPbI3 and FA0.875Cs0.125PbI3. We have comprehensively calculated the structure, electronic and optical properties of them. We found a coupling effect between formamidine cations rotation and cesium atom. This coupling effect changes the inclination angle of octahedron to regulate electron distribution, band gaps, and optical absorption. Hence, changing the cation orientation and substitution atom is a feasible way to dynamically adjust the energy band, dielectric constant and absorption edge of perovskite. Preparing perovskite with tunable properties is just around the corner through this way.

Reaction induced interfacial instability of miscible fluids in a channel

When a less viscous miscible fluid displaces a more-viscous one under a pressure-driven channel flow, unstable Kelvin–Helmholtz (K–H)-type billows are formed at the miscible interface. In this paper, we investigate whether such instability can be induced by a simple ($\textbf {A}+ \textbf {B} \rightarrow \textbf {C}$)-type chemical reaction. Here a miscible solution of one reactant $\textbf {A}$ is displacing another isoviscous reactant $\textbf {B}$ and producing a more-viscous product $\textbf {C}$ at the reactive front. It is found that because of a local increase in viscosity gradient due to the formation of more-viscous product $\textbf {C}$, K–H-type billows are formed at the $\textbf {A}$–$\textbf {C}$ interface. The changes in dynamical properties of such billows are examined by varying the governing parameters such as the mobility ratio $R_{c}$, Damköhler number $Da$, Péclet number $Pe$ and Reynolds number $Re$. Interestingly, we have found that even at high reaction rates (sufficiently large $Da$) for $R_{c}=1$, the interface remains stable and for larger values of $R_{c} (=3, 5)$ the K–H billows are observed. It is also noticed that a laminar horseshoe-type vortex develops near the wall at the channel inlet where the less-viscous reactant pushes the more-viscous product. We have computed numerically the onset time ($t_{on}$) of instability to understand the early-stage developments of the K–H billows. For different values of $Da$, we have shown the unstable and stable time zones in the ($t_{on}$–$R_{c}$) space. The bipartite ($t_{on}$–$R_{c}$) space also depicts the critical ($Da$-, $Pe$- and $Re$-dependent) $R_{c}$ value for which instability can be triggered in a finite desirable time. The delay in the onset of instability is observed with increasing $Pe$. Further it is shown that $t_{on}$ can be linearly scaled with $Pe$ to have a modified onset time ($t^{*}_{on}$), which establishes a proportionate dynamics with respect to $Pe$ in the early stages of the instability. Moreover, a reverse dependency of onset on lower $R_{c}$ values for higher Reynolds numbers is observed.

Study On The Vibration Amplitudes Of Reinforced Concrete Bridge Piers Using ABAQUS Software

The Dynamic characteristics such as damping ratio and natural frequency are an important indicator for predicting the dynamic behavior of bridges, but it is customary during the design that the designer assess the dynamic properties of the dynamic analysis because it is very difficult to determine the damping of the origin before construction and damping is taken as a predetermined constant value independent of the response amplitude and frequency of the structure. In the dynamic analysis of constructions design some experimental research has been concerned with the determination of dynamic structural properties and their relationship with the response amplitude experimentally, but the changes in dynamic properties with vibration amplitude has never been taken During dynamic analysis, further analytical treatments and computer modeling were required to study different cases based on the experimental results available by simulating them with a computer model. Dynamic characteristics are very essential to accurately determine the dynamic response, and it is necessary to study the effect of changes of the actual dynamic characteristics of bridges, which were determined by measuring their vibration in the results of dynamic analysis and comparing them with results that do not take into account the changes of dynamic properties and with laboratory results in order to assess the role of. Dynamic analysis inputs in simulating vibrations by monitoring their responses. As a result, it was found that the dynamic properties are independent of the shape of the external exactions. Also, it was concluded that relationships express the change of dynamic properties in terms of vibration amplitudes. And Similar reliance of the dynamic characteristics to the vibration amplitude is confirmed for the pier model, where the increase of the amplitude of the acceleration is accompanied by a decrease in the natural frequency, and an increase in the damping ratio is obvious. Before choosing design values when considering the dynamic characteristics of a structure, we need to give unique concentration to the predictable vibration amplitudes. Dynamic characteristics changes during dynamic analysis should be considered to produce analytical results that simulate experimental results and are closer to reality.

Interactions and Dynamics in Aqueous Solutions of pH-Responsive Polymers: A Combined Fluorescence and Dielectric Relaxation Study.

Interaction and dynamics of aqueous solutions of pH-responsive smart polymers are investigated via steady-state, time-resolved fluorescence emission spectroscopy with the help of external local reporter coumarin 153 (C153), while MHz to GHz dielectric relaxation spectroscopic (DRS) measurement reports the intrinsic medium relaxation features. A series of pH-responsive random copolymers (DPL-DP60) comprising of a pH-responsive moiety 2-((leucinyl)oxy)ethyl methacrylate (l-Leu-HEMA) and hydrophobic methyl methacrylate (MMA) are synthesized and characterized. A balance between the pH-responsive (l-Leu-HEMA) and the hydrophobic (MMA) content dictates the phase transition pH, which is found to be ∼5-7 for these aqueous copolymer solutions (1 mg/mL). Dynamic light scattering measurements in aqueous solutions of these polymers reflect a small particle size (∼2-8 nm) at solution pH below their individual phase transition pH, while a large particle size (∼140-340 nm) forms beyond their phase transition pH. No signature of a phase transition pH-driven abrupt change in static and dynamic properties of aqueous polymer solutions has been registered from pH-dependent dielectric relaxation as well as solute (C153)-centric fluorescence measurements. A significant impact of varying the l-Leu-HEMA/MMA segment ratio on steady-state fluorescence emission and rotational anisotropy decay of the fluorophore solute (C153) has been observed. MHz to GHz DRS in aqueous solutions of these pH-responsive polymers reflects bulk water-like dielectric features.

Kinematic-Model-Free Redundancy Resolution Using Multi-Point Tracking and Control for Robot Manipulation

Robots have been predominantly controlled using conventional control methods that require prior knowledge of the robots’ kinematic and dynamic models. These controllers can be challenging to tune and cannot directly adapt to changes in kinematic structure or dynamic properties. On the other hand, model-learning controllers can overcome such challenges. Our recently proposed model-learning orientation controller has shown promising ability to simultaneously control a three-degrees-of-freedom robot manipulator’s end-effector pose. However, this controller does not perform optimally with robots of higher degrees-of-freedom nor does it resolve redundancies. The research presented in this paper extends the state-of-the-art kinematic-model-free controller to perform pose control of hyper-redundant robot manipulators and resolve redundancies by tracking and controlling multiple points along the robot’s serial chain. The results show that with more control points, the controller is able to reach desired poses in fewer steps, yielding an improvement of up to 66%, and capable of achieving complex configurations. The algorithm was validated by running the simulation 100 times, and it was found that, in 82% of the times, the robot successfully reached the desired target pose within 150 steps.

Mode Shape-Based Damage Detection Method (MSDI): Experimental Validation

The main principle of vibration-based damage detection in structures is to interpret the changes in dynamic properties of the structure as indicators of damage. In this study, the mode shape damage index (MSDI) method was used to identify discrete damages in plate-like structures. This damage index is based on the difference between modified modal displacements in the undamaged and damaged state of the structure. In order to assess the advantages and limitations of the proposed algorithm, we performed experimental modal analysis on a reinforced concrete (RC) plate under 10 different damage cases. The MSDI values were calculated through considering single and/or multiple damage locations, different levels of damage, and boundary conditions. The experimental results confirmed that the MSDI method can be used to detect the existence of damage, identify single and/or multiple damage locations, and estimate damage severity in the case of single discrete damage.

Effects of reamberin infusion on dynamic changes in oxidative stress and blood rheological properties in patients with acute myocardial infarction and type 2 diabetes mellitus after percutaneous transluminal angioplasty

Effects of reamberin infusion on dynamic changes in oxidative stress and blood rheological properties in patients with acute myocardial infarction and type 2 diabetes mellitus after percutaneous transluminal angioplasty

Properties of silica-filled rubber compounds vs. epoxidized oil content and degree of epoxidation

Epoxidized vegetable oils are well-known as biobased, sustainable additives for polymers. However, relatively little work has been done to explore their effects on silica-filled rubber composites in depth. In order to address this knowledge gap, high purity epoxidized soybean (Glycine max (L.) Merr.) oils with varying levels of epoxidation were synthesized and compounded with a model silica-filled styrene-butadiene rubber formulation. The green properties, process characteristics, and cured properties (quasi-static and dynamic mechanical characteristics) of the resultant compounds were then assessed. A ∼7 % decrease in mixing energy was observed with the inclusion of ∼0.8 vol% of 100 % epoxidized soybean oil. Changes in cure kinetics and dynamic mechanical properties were observed as a function of epoxy group concentration. The changes in dynamic mechanical properties are explained in terms of changes in silica dispersion state as a consequence of epoxidized soybean oil addition.

How multisite phosphorylation impacts the conformations of intrinsically disordered proteins.

Phosphorylation of intrinsically disordered proteins (IDPs) can produce changes in structural and dynamical properties and thereby mediate critical biological functions. How phosphorylation effects intrinsically disordered proteins has been studied for an increasing number of IDPs, but a systematic understanding is still lacking. Here, we compare the collapse propensity of four disordered proteins, Ash1, the C-terminal domain of RNA polymerase (CTD2'), the cytosolic domain of E-Cadherin, and a fragment of the p130Cas, in unphosphorylated and phosphorylated forms using extensive all-atom molecular dynamics (MD) simulations. We find all proteins to show V-shape changes in their collapse propensity upon multi-site phosphorylation according to their initial net charge: phosphorylation expands neutral or overall negatively charged IDPs and shrinks positively charged IDPs. However, force fields including those tailored towards and commonly used for IDPs overestimate these changes. We find quantitative agreement of MD results with SAXS and NMR data for Ash1 and CTD2' only when attenuating protein electrostatic interactions by using a higher salt concentration (e.g. 350 mM), highlighting the overstabilization of salt bridges in current force fields. We show that phosphorylation of IDPs also has a strong impact on the solvation of the protein, a factor that in addition to the actual collapse or expansion of the IDP should be considered when analyzing SAXS data. Compared to the overall mild change in global IDP dimension, the exposure of active sites can change significantly upon phosphorylation, underlining the large susceptibility of IDP ensembles to regulation through post-translational modifications.

Exploiting Temporal Dynamics in Product Reviews for Dynamic Sentiment Prediction at the Aspect Level

Online reviews and ratings play an important role in shaping the purchase decisions of customers in e-commerce. Many researches have been done to make proper recommendations for users, by exploiting reviews, ratings, user profiles, or behaviors. However, the dynamic evolution of user preferences and item properties haven’t been fully exploited. Moreover, it lacks fine-grained studies at the aspect level. To address the above issues, we define two concepts of user maturity and item popularity, to better explore the dynamic changes for users and items. We strive to exploit fine-grained information at the aspect level and the evolution of users and items, for dynamic sentiment prediction. First, we analyze three real datasets from both the overall level and the aspect level, to discover the dynamic changes (i.e., gradual changes and sudden changes) in user aspect preferences and item aspect properties. Next, we propose a novel model of Aspect-based Sentiment Dynamic Prediction (ASDP), to dynamically capture and exploit the change patterns with uniform time intervals. We further propose the improved model ASDP+ with a bin segmentation algorithm to set the time intervals non-uniformly based on the sudden changes. Experimental results on three real-world datasets show that our work leads to significant improvements.

Rigidity percolation uncovers a structural basis for embryonic tissue phase transitions

SummaryEmbryo morphogenesis is impacted by dynamic changes in tissue material properties, which have been proposed to occur via processes akin to phase transitions (PTs). Here, we show that rigidity percolation provides a simple and robust theoretical framework to predict material/structural PTs of embryonic tissues from local cell connectivity. By using percolation theory, combined with directly monitoring dynamic changes in tissue rheology and cell contact mechanics, we demonstrate that the zebrafish blastoderm undergoes a genuine rigidity PT, brought about by a small reduction in adhesion-dependent cell connectivity below a critical value. We quantitatively predict and experimentally verify hallmarks of PTs, including power-law exponents and associated discontinuities of macroscopic observables. Finally, we show that this uniform PT depends on blastoderm cells undergoing meta-synchronous divisions causing random and, consequently, uniform changes in cell connectivity. Collectively, our theoretical and experimental findings reveal the structural basis of material PTs in an organismal context.

Designing efficient soil resistivity measurement technique for agricultural wireless sensor network

SummaryThis paper presents the study and method for measuring the electrical properties of the agricultural soil using a wireless sensor network to counter the dynamic changes in electrical properties of soils under variable rainfall and flood conditions. Soil moisture and nutrients can be correlated with the resistance of soil, which is the essential electrical property of the soil. Resistivity can help us to classify different agricultural soil types and can be used for real‐time monitoring of crop fields. The diverse resistivity soil patterns may help to classify the physical, chemical and biological properties of soil. In our research work, we have taken soil from different districts of Madhya Pradesh state and classified it based on resistivity. We have also designed a low‐cost resistivity sensor module with a mathematical justification of the results. The new sensor module has been tested on different soil samples of Madhya Pradesh, and wireless sensor network (WSN) has been proposed to collect and process the data for application in the agriculture fields. The paper also describes the challenges and the various methodologies for the measurement of soil resistivity and moisture using the Internet of Things (IoT) architecture.

Fermion-induced dynamical critical point

Dynamical phase transition (DPT) characterizes the abrupt change of dynamical properties in nonequilibrium quantum many-body systems. It has been demonstrated that extra quantum fluctuating modes besides the conventional order parameter field can drastically change the properties of equilibrium phase transitions. However, the counterpart phenomena in DPTs have rarely been explored. Here, we study the DPT in the Dirac system after a sudden quench, and find that the fermion fluctuations can round a putative first-order DPT into a dynamical critical point, which is referred to as a fermion-induced dynamical critical point (FIDCP). It is also a nonthermal critical point, in which the universal short-time scaling behavior emerges despite the system goes through a first-order transition after thermalization. In the novel scenario of FIDCP, the quantum Yukawa coupling $g_q$ is indispensable for inducing the FIDCP albeit irrelevant in the infrared scale. We call these variables {\it indispensable irrelevant scaling variables}. Moreover, a dynamical tricritical point which separates the first-order DPT and the FIDCP is discovered by tuning this indispensable irrelevant scaling variable. We further mention possible experimental realizations.

Reinforcement effect of polypropylene fiber on dynamic properties of cemented tailings backfill under SHPB impact loading

Dynamic loads such as blasting may lead to diverse levels of failure in cemented tailings backfill (CTB) under diverse strain rates and frequency spectral amplitudes. Hence, changes in dynamic properties of filling due to these loads should be studied as a function of strain rates for CTB mixtures. In this study, the dynamic characteristics of CTB samples containing polypropylene fiber contents were examined with the use of split Hopkinson pressure bar (SHPB) system and high speed photography technology. The experimental results illustrate that the backfill has a damping influence on the elastic wave. The original waveform noise of CTB with fiber is higher than the one without fiber, and the average strain rate changes the reflected waveform. The effect is greater than the impact velocity. Secondly, the dynamic strength of CTB with fiber is higher than the static strength, which obeys a great effect of the strain rate. Meanwhile, the backfill (with fiber) stress-strain characteristics show a ‘double peak’ phenomenon, and the difference between the first and the second peak stresses decreases with increasing fiber content. The failure mode analysis demonstrated that the fiber reinforcement stopped the development of big cracks during the tensile fiber pull-out failure regime. Lastly, the findings of the present study can offer an important reference to the overall design of backfilling regarding the understanding of the good dynamic characteristics and the reduction of operational costs.

Resonant acoustic rheometry for non-contact characterization of viscoelastic biomaterials

Resonant Acoustic Rheometry (RAR) is a new, non-contact technique to characterize the mechanical properties of soft and viscoelastic biomaterials, such as hydrogels, that are used to mimic the extracellular matrix in tissue engineering. RAR uses a focused ultrasound pulse to generate a microscale perturbation at the sample surface and tracks the ensuing surface wave using pulse-echo ultrasound. The frequency spectrum of the resonant surface waves is analyzed to extract viscoelastic material properties. In this study, RAR was used to characterize fibrin, gelatin, and agarose hydrogels. Single time point measurements of gelled samples with static mechanical properties showed that RAR provided consistent quantitative data and measured intrinsic material characteristics independent of ultrasound parameters. RAR was also used to longitudinally track dynamic changes in viscoelastic properties over the course of fibrin gelation, revealing distinct phase and material property transitions. Application of RAR was verified using finite element modeling and the results were validated against rotational shear rheometry. Importantly, RAR circumvents some limitations of conventional rheology methods and can be performed in a high-throughput manner using conventional labware. Overall, these studies demonstrate that RAR can be a valuable tool to noninvasively quantify the viscoelastic mechanical properties of soft hydrogel biomaterials.

Survivability of Lactobacillus acidophilus and quality attributes of puffed pounded-unripe rice supplemented with probiotics using a fluidized-bed coating method

Value-added breakfast cereals are receiving increased interest due to changes in lifestyles and modern trends of health awareness among consumers. Among various cereal grains, puffed pounded-unripe rice (PPUR) was chosen because of its excellent health beneficial properties. Feasibility of supplementing the probiotic bacteria Lactobacillus acidophilus (LA5) into PPUR was investigated using a fluidized-bed coating method. Suitable fermentation conditions were tested based on a pH criterion of 4.5. Three types of cell host solutions as sucrose, skim milk and maltodextrin were examined as suitable carriers, and optimal coating condition was determined. Product qualities were evaluated for stability. Results showed that milk fermented for 24 hrs gave the highest viable cell count of approximately 109 to 1010 CFU/mL when optimally mixed with distilled water at milk: water ratio of 45:105. Skim milk was determined as the most suitable host giving the highest retention of LA5 cell count. Coating condition at a feed rate of 10 mL/min, coating time of 5 mins and constant temperature at 50°C gave the highest survival rates of LA5. Moisture contents and water activity (aw) values of all coated products ranged from 3.38-3.72% wb and 0.201-0.232, respectively. Regarding textural properties, coated PPUR showed increased hardness and crispiness compared with uncoated samples, while the variation of coating conditions had no significant effects. Dynamic changes in viable LA5 cell count, textural properties, aw, peroxide value and thiobarbituric acid values fitted well with various kinetic orders. Findings indicated the feasibility of adding probiotics to dry products associated with suitable coating solution and offered guidance for product development and process design.

Residual Mode Vector‐Based Structural Damage Identification with First‐Order Modal Information

Damage identification based on the change of dynamic properties is an issue worthy of attention in structure safety assessment, nevertheless, only a small number of discontinuous members in existing structure are damaged under service condition, and the most remaining members are in good condition. According to this feather, we developed an effective damage location and situation assessment algorithm based on residual mode vector with the first mode information of targeted structure, which utilized the quantitative relationship between first natural modes of global structure with the change of the element stiffness. Firstly, the element damage location is determined with exploitation of the sparseness of element stiffness matrices based on the discontinuity of damaged members. Then, according to the distribution characteristics of the corresponding residual mode vector, the nodal equilibrium equation about the damage parameter is established based on the residual mode vector, and the damage coefficients of structural elements are evaluated with the proposed equations. Two numerical examples are given to verify the proposed algorithm. The results showed that the proposed damage identification method is consistent with the preset damage. It can even accurately identify large‐degree damages. The proposed algorithm only required the first‐order modal information of the target structures and held few requirements of analysis resource; hence when compared with existing methods, it has obvious advantages for structural damage identification.

Changes of dynamic properties of mobile scenes at various steps of their manufacturing

Mobile stage construction is a huge challenge for designers due to a very wide range of variable factors influencing it, such as wind or temperature, the value of which in this case depends on the geographical location. An inherent element of the impact of these factors are the accompanying different, both constant and variable loads. Detailed identification of these loads is as important as the analysis of the dynamic properties of the structure. The more so as the analyzed structure appears in two configurations, first as a semitrailer, and then as a stage.

Response surface-based model updating to detect damage on reduced-scale masonry arch bridge

Response surface (RS) methods, a combination of mathematical and statistical techniques, have been widely used in design optimization, response prediction, and model validation in structural engineering systems. However, its usage in structural damage identification, especially for historic structures has not been quite common. For this purpose, this study attempts to investigate damage detection in a masonry arch bridge. Within the scope of this, a reduced-scale model of a one span historical masonry arch bridge was built in a laboratory environment. To determine the modal parameters of the reduced-scaled bridge model, operational modal analysis (OMA) was performed under ambient vibrations. Signals originated by sensitive accelerometers were collected to quantify the vibratory response of the reduced-scaled model bridge. The experimental natural frequencies, mode shapes, and damping ratios resulting from these measurements were figured out by using the Enhanced Frequency Domain Decomposition (EFDD) technique. The three-dimensional model of the reduced-scale bridge was created in the ANSYS finite element (FE) software program to expose the analytical dynamic characteristics of the bridge model. The results obtained in the experimental application were compared with those of the finite-element analysis of the bridge model. The calibration of the numeric model was utilized depending on the experimental modal analysis results of the reduced-scale bridge by using the RS method. Design of experiments was constructed by using central composite design, and the RS models were generated by performing the genetic aggregation approach. The optimum results between the experimental and numerical analyses were found by using the RS optimization. Then, regional damages created on the scaled model and the changes of dynamic properties of the damaged case were evaluated. The damage location was approximately identified by using the RS method in the calibrated finite-element model. The results demonstrated that the RS-based FE updating approach is an effective way for damage detection and localization in masonry type structures.

Shifts in the structure and function of wheat root-associated bacterial communities in response to long-term nitrogen addition in an agricultural ecosystem

Nitrogen (N) input in terrestrial ecosystems is increasing due to its deposition from anthropogenic activities, especially in agriculture, which can have pronounced effects on belowground microbial communities. However, our understanding of the long-term effects of N addition on microbial communities in the plant-soil system is still limited. Here, we used an Ion S5™ XL sequencing platform to explore the structural and functional characteristics of root-associated bacterial communities in winter wheat (Triticum aestivium) under long-term N addition. The N fertilization experiment involved five treatments (0, 90, 180, 270, and 360 kg N ha−1) in a farmland ecosystem over 14 years. Bacterial communities shifted significantly with increasing N level in three soil-root compartments (bulk soil, rhizosphere, and root interior) of wheat plants at two growth stages (jointing and filling). These shifts were associated with dynamic changes in soil properties, mainly pH, nitrate-N, and ammonium-N levels. There was a community shift between slow-growing oligotrophs and fast-grow copiotrophs with increasing N addition, indicating distinct survival strategies of bacteria across soil-root compartments and wheat growth stages. Potential biomarkers, including nitrifying, denitrifying, and N-fixing genera were identified to predict very high N concentration in each soil-root compartment. Significant variation was detected in the relative abundance of predicted functional genes related to N metabolism (denitrification, nitrification, and N fixation) across the three compartments, two growth stages, and five N levels. These results indicate that bacterial communities respond differentially to long-term high N input in the soil-root compartments of wheat plants during different growth stages.