Reversal Point Research Articles

Time-domain numerical continuation of periodic orbits for harmonically forced hysteretic nonlinear systems with Iwan joints

Coulomb sliders are used widely in order to model frictional interfaces. In many applications, the nonlinear Frequency Response Functions (FRFs) of these systems is desired, but it is extremely computationally expensive to use time-domain integration methods to compute the steady-state response. The nonlinear force and stiffness of these devices depends on the position of sliders, and the implicit nature of the slider positions makes these systems hysteretic and therefore non-trivial to address using conventional continuation methods. This paper proposes a novel numerical method, dubbed ”Hysteresis Identification via Reversal Points or (HIRP)” that can compute the steady-state harmonically forced response of frictional nonlinear systems. For this purpose, a quasi-static algorithm is introduced which can evaluate the state of sliders at any time based on the reversal points over a period. This reduces the number of state variables needed in the continuation routine by at least an order of magnitude. The method has been tested by computing the harmonic response of a hysteretic system with multiple Coulomb sliders. The method is evaluated on multi-degree of freedom systems with Iwan joints, demonstrating that the method can be a valuable tool for predicting the nonlinear, steady-state response of hysteretic systems.

Capital Management Strategy in Down Trending Market for Profit Maximization

The majority of short-term investors and long-term investors go for following the trend based on fundamental analysis more than technical analysis. In India, many retail investors lose a huge amount of money due to insufficient strategy and lack of knowledge about investments. While buying a stock, the investor has decided the final selling price and duration of investment and the investor simply trades on the daily candle or closing price of the market. This paper provided an efficient strategy for managing the adversities of the market, that is, following the downtrend though the investor is overall bullish for a stock, exiting the trade at breakeven point or when the end of downtrend is confirmed before or after the breakeven point. At this point of market reversal, which is now lower than the previous buying price, entering the market with the remaining capital after profit and loss and with same or little higher return goal, the expected returns on investments can be redeemed at a faster rate. The price at which investment goals can be achieved is given by the healing index.

Hydraulic hysteresis of natural pyroclastic soils in partially saturated conditions: experimental investigation and modelling

In many geotechnical applications, especially in the study of weather-induced landslides, a reliable soil hydraulic characterization in unsaturated conditions is required. Currently, the experimental techniques that neglect the hydraulic hysteresis represent the greatest limitation to landslide forecasting. In this paper, a procedure to obtain an unsaturated soil hydraulic characterization on natural pyroclastic samples is proposed and verified. The approach enables the evaluation of the soil hydraulic properties along the main drying path and wetting/drying cycles to fully quantify the effects of the hydraulic hysteresis. Pyroclastic soil samples collected at a test site at Mount Faito in the Campania region (southern Italy) were tested. The experimental investigation consisted of a sequence of testing phases: a constant-head hydraulic conductivity test, a forced evaporation test followed by several wetting–drying cycles, and a drying test in a pressure plate apparatus. The hysteretic model proposed by Parker and Lenhard (1987) was adopted to fit the data, while inverse modelling of the forced evaporation tests allowed to derive the model parameters. Therefore, the main drying and wetting branches and the soil response to drying and wetting cycles from any reversal point were reproduced with the model, which suitably described the hysteretic behaviour of the pyroclastic soil under all conditions and along all paths.

Combined measurement and simulation of piston ring cylinder liner contacts with a reciprocating long-stroke tribometer

One approach to decrease emissions and improve the efficiency of combustion engines is reducing friction losses, especially in the interface between piston ring and cylinder liner. Usual model-like tribometer tests cover piston ring cylinder liner operating conditions at reversal points. This study introduces an innovative method using a new reciprocating long-stroke tribometer at component level as well as a new elastohydrodynamic simulation model enabling a greater range of operating conditions through higher velocities. The process of friction data evaluation is clarified studying crank angle resolved friction data and the effect of viscous properties is tested. The simulation allows investigating the local nominal gap height and the division of the pressure in its hydrodynamic and asperity contact contributions in detail. The results show that this combined tribological testing method obtains a quantifiable distinction between the investigated tribological systems. Additionally, a high correlation between measured friction results and simulation is achieved in general, which prospectively allows further investigations and parameter studies of reciprocating contacts.

Kea (Nestor notabilis) show flexibility and individuality in within-session reversal learning tasks

The midsession reversal paradigm confronts an animal with a two-choice discrimination task where the reward contingencies are reversed at the midpoint of the session. Species react to the reversal with either win-stay/lose-shift, using local information of reinforcement, or reversal estimation, using global information, e.g. time, to estimate the point of reversal. Besides pigeons, only mammalian species were tested in this paradigm so far and analyses were conducted on pooled data, not considering possible individually different responses. We tested twelve kea parrots with a 40-trial midsession reversal test and additional shifted reversal tests with a variable point of reversal. Birds were tested in two groups on a touchscreen, with the discrimination task having either only visual or additional spatial information. We used Generalized Linear Mixed Models to control for individual differences when analysing the data. Our results demonstrate that kea can use win-stay/lose-shift independently of local information. The predictors group, session, and trial number as well as their interactions had a significant influence on the response. Furthermore, we discovered notable individual differences not only between birds but also between sessions of individual birds, including the ability to quite accurately estimate the reversal position in alternation to win-stay/lose-shift. Our findings of the kea’s quick and flexible responses contribute to the knowledge of diversity in avian cognitive abilities and emphasize the need to consider individuality as well as the limitation of pooling the data when analysing midsession reversal data.

(Invited) Leveraging Reversible Chemistry for Materials Sustainability in Energy Storage

The development of next-generation energy storage devices and systems for electric vehicles (EVs) relies on materials with significantly improved performance and lower cost. The increasing amount of lithium-ion battery (LIBs) consumption will result in the resource shortage and price increase of lithium and precious transition metals (Co, Ni etc.); the wastes generated from disposal of used batteries can cause severe environment pollution. In this context, design of energy-efficient recycling and regeneration process for spent batteries is attracting growing interest. From a reversible chemistry point of view, this talk will introduce a potential strategy to directly recycle and regenerate spent LIBs using a “non-destructive” approach, which will lead to new electrode materials that can show the same level of performance as the native materials. Such a strategy combines fundamental understanding and process optimization for remanufacturing of energy materials. Therefore, it can potentially offer a sustainable solution for future energy storage.

Emergy evaluation of the integrated gasification combined cycle power generation systems with a carbon capture system

An Integrated Gasification Combined Cycle (IGCC) power generation system has a significant effect on improving resource utilization efficiency. Carbon capture and storage (CCS) has been widely adopted to control greenhouse gas emissions. The integration of the two systems can further reduce CO2 emissions but cause elevated investment costs. As an effective tool to evaluate resource utilization efficiency and environmental impact, emergy analysis on coal and biomass based IGCC power generation systems with/without CCS is conducted in this paper. The coal based IGCC systems are simulated in Aspen plus to obtain the electricity generated under different CCS scales. For other systems, the data for emergy evaluation are from references. The sustainabilities under different CO2 tax values are compared. The factors impacting the sustainabilities are discussed. The results show that when CCS is not considered, all IGCC systems are superior to coal and biomass direct-fired systems in terms of sustainability. After CCS is integrated, the sustainability of biomass based IGCC system is still higher than that of biomass direct-fired systems, while coal based IGCC systems are less sustainable than coal direct-fired systems under low CO2 tax. The sustainabilities of Texaco-IGCC systems increase with CCS scales when CO2 tax is higher than 0.0220 $/kg, emphasizing CCS at a larger scale. For the Shell-IGCC systems, a higher CO2 tax (0.3880 $/kg) is preferred for the promotion of large scale CCS. In the scenario that the cost emergy transformity improves, the CO2 tax value at the point of sustainabilities reversal will decrease.

Research on Critical Liquid-Carrying Model in Wellbore and Laboratory Experimental Verification

Liquid loading in gas wells may slash production rates, shorten production life, or even stop production. In order to reveal the mechanism of liquid loading in gas wells and predict its critical flowrates, theoretical research and laboratory experiments were conducted in this work. A new model of liquid-film reversal was established based on Newton’s law of internal friction and gas–liquid two-phase force balance, with the critical reverse point obtained using the minimum gas–liquid interface shear force method. In this model, the influences of the pipe angle on the liquid film thickness were considered, and the friction coefficient of the gas–liquid interface was refined based on the experimental data. The results showed that the interfacial shear force increases by increasing the liquid superficial velocity, which leads first to an increase of the critical liquid-carrying gas velocity and then to a decrease, and the critical production also decreases. With 0° as the vertical position of the pipeline and an increase of the inclination angle, the critical liquid-carrying velocity first increases and then decreases, and the maximum liquid-carrying velocity appears in the range of 30–40°. In addition, the critical liquid-carrying gas velocity is positively correlated with the pipe diameter. Compared with the previous model, the model in this work performed better considering its prediction discrepancy with experiment data was less than 10%, which shows that the model can be used to calculate the critical liquid-carrying flow rate of gas wells. The outcome of this work provides better understanding of the liquid-loading mechanism. Furthermore, the prediction model proposed can provide guidance in field design to prevent liquid loading.

Review of and a new approach to elastic modulus evaluation for fatigue design of metallic components

The elastic modulus is a key parameter for the description of material properties when evaluating metallic components under service loads. In particular, when evaluating strain-controlled tests for the application of the strain-life approach, there are numerous different possibilities in standards for determining this material parameter. These can lead to different results and confront the user with a certain challenge in selecting the most suitable method. In this publication, an overview of different evaluation methods is given and a new evaluation method is presented, in which the elastic modulus is determined using the reversal points of a strain-controlled cyclic test under macroscopic linear-elastic deformation. This allows a simple and clear, widely user-independent determination of the elastic modulus. In addition, the differences between the new and the commonly used evaluation methods are shown, using the example of the aluminum alloy EN AW-7075, and their influence on the strain-life curve, the PSWT and PJ damage parameter curves, and the cyclic stress-strain curve by Ramberg-Osgood are investigated.

Physical model test study on the working performance of integrated foundation pit supporting structure

The integration of underground single structure and retaining structure is a new type of foundation pit support, and its working performance needs to be further studied. The physical model test was carried out on the diaphragm wall structure of “two walls in one” in this paper. The soil settlement and the earth pressure of the outside of the foundation pit and the stress of the integrated supporting structure were analyzed when the excavation depth is different. The analysis showed that the settlement of soil behind the wall gradually increased with the increase of excavation depth of the foundation pit. when it was 1H e away from the diaphragm wall, the maximum of soil settlement occurred, which was 0.08%H e (H e is the maximum excavation depth). With the increase of excavation depth, the state changed from static to active. Under the same condition, the bending moment of the wall increased first and then decreased with the depth. The reverse bending point is near 1.23H e .

Drained Triaxial Compressive Shear Response of Cemented Paste Backfill (CPB)

Cemented paste backfill (CPB) has been widely used as local and regional underground support to reduce host rock wall closure in mined-out areas and also to reduce rockfall and rockburst incidents. However, analyzing the rock mass—CPB interactions in the first month after backfill placement must account for the CPB’s time-dependent strength, stiffness, and volume change characteristics during binder hydration. This article presents the first such comprehensive study made for CPB from the Williams mine in Ontario, Canada. Monotonic isotopically consolidated drained compressive triaxial tests were conducted on cured CPB specimens using the lubricated-ends test technique. The specimens had 3.0–7.5% Cement Content (CC); Curing Times (CTs) were from 3 to 28 days; and the confining stress ranged from 25 to 350 kPa. During shearing, all tests exhibited an initial contractive phase leading to a Characteristic State (CHS or point of volumetric strain reversal) followed by dilation with a maximum dilation rate corresponding to peak stress at the Failure State (FS). Both CHS and FS are adequately described by the Mohr–Coulomb criterion and a framework formulation was proposed to predict the evolution of CHS and FS based on CC and CT. Furthermore, the volumetric strains at CHS and FS can be defined as linear functions of the respective axial strains at the CHS and FS. Quantification of the observed behaviors through these functional relationships can help develop future constitutive models that better represent CPB’s transient response to triaxial stress loading while curing, which is essential to understanding as-placed backfill properties and its interaction with surrounding rock mass.

An analytical Generalized Reciprocal Method (GRM) for near-surface seismic refraction investigations

Seismic refraction is one of the active seismic methods that work based on seismic waves that are refracted following the layers of the earth beneath the surface. Seismic refraction surveying is an important tool for determining the geometries and elastic wave propagation velocities of near-surface layer for oil bearing structures. Based on the data acquisition sketch obtained, the acquisition is carried out using the In-Line technique. There are two sources of vibration chosen, namely at the forward and reverse points, the distance between the 5-meter geophone and the distance between the source of the vibration and the geophone of 5 meters. The seismic data processing technique used in this study is the Generalized Reciprocal Method (GRM). This method determines the value of analysis, XY Optimum distance, time-depth analysis value, and depth. In interpreting seismic data, the calculation results that have been made are validated for accuracy using Software. From the research that has been done, it can be known as modeling subsurface structure. There are three layers, the first layer is 6 m-10m deep, while the second layer is 18m-22m deep. In the range of about 0m-20m, the first layer has a velocity of 507.74 m/s, the second layer has a velocity of 1420.43 m/s and the third layer has a velocity of 2522.30 m/s. In the range of about 20m-80m the first layer has a velocity of 550.12 m/s, the second layer has a velocity of 1575.11 m/s and the third layer has a velocity of 2607.45 m/s. In the range of about 80m-100m, the first layer has a velocity of 482.34 m/s, the second layer has a velocity of 1301.09 m/s and the third layer has a velocity of 2400.86 m/s.

Allometric scaling relationships of Larix potaninii subsp. chinensis traits across topographical gradients

The variation of phenotypic traits with environmental gradient can reveal the plant adapting strategies and predict reactions to future climate changes. However, it remains elusive, especially for alpine timberline tree species. To quantify the variation and explore the patterns of twig, leaf, stoma traits, and determine the scaling relationships along the topographic gradients, 576 current-year branches of Larix potaninii ssp. chinensis were collected and scaling relationships were analyzed. The results showed that the twig, leaf and stoma traits varied nonlinearly along altitudinal gradients (2900–3500 m) in both sunny and shady slopes, with a reversal point at about 3250 m, at which the optimum growth of twig length (78.53 mm), twig cross-sectional area (3.35 mm2), internode length (13.14 mm), leaf length (19.30 mm), specific leaf area (0.01 mm2mg−1), stomatal length (47.05 µm) and density (160.20 mm−2). In addition, the values of leafing intensity, leaf number and stomatal density on sunny slope, 1.52 mm−3, 88.79 and 160.20 mm−2 respectively, were higher than that on shady slope. Moreover, the relationships between leaf-twig traits were significantly correlative, and the leaf area-twig cross-sectional area and leaf intensity-leaf area scaling relationships were allometric (slope ≠ 1 or slope ≠ −1) and showed common slope with different y-intercept across altitudes and slope aspects (P < 0.01). Overall, the scaling relationships of different traits across topographical gradients were governed by functional coordination. The twig-size-leaf-size always maintains the balance between geometric dimension and mass in a certain growth rate. The inverse proportion in leaf size and number revealed its maximizing limited resource use efficiency.

Glucose-responsive hydrogel-based microneedles containing phenylborate ester bonds and N-isopropylacrylamide moieties and their transdermal drug delivery properties

Microneedles with self-regulated drug releasing behaviors are desirable and promising to improve the treatment quality of diabetics. Here, we fabricate a phenylboronic acid-based hydrogel microneedle patch (MNP) with glucose responsiveness and excellent biocompatibility for drug delivery at 37 °C. In this hydrogel-based MNP, the glucose-responsive properties are realized by introducing reversible phenylborate ester crosslinking points based on phenylboronic acid units and diol-containing units. The reversible crosslinking points also improve the mechanical strength for skin insertion. This novel phenylboronic acid-based hydrogel MNP lays the foundation for fabrication of a sensitive, safe and stable transdermal drug delivery system.

Physicochemical properties of modified epoxy used for reinforcing concrete by carbon fiber reinforced polymer

This work is an experimental investigation about the properties of sand-powder adhesive subjected to high temperature. Thus, three main mixtures were tested. These mixes contain three different sand to adhesive ratios; 0:1, 1:1 and 1.5:1. The Simultaneous of Thermal Analyzers (STA); represent real-time measurement, change of sample weight analysis and heat flow were investigated. The results indicated that the physicochemical properties (residual mechanical properties, residual weight, weight losing rate, glass transition temperature (Tg), Carbonate point or extrapolated onset temperature (To), and heat flow) have been remarkably enhanced by the addition of sand-powder. The addition of sand resulted in increased epoxy resistance to high heat. When the sand-powder exposed to 550 ° C, the weight loss of the epoxy was 52%, 30% and 25% for sand to adhesive ratios equal to 0, 1, and 1.5 % respectively. In other words, the epoxy containing a high proportion of sand retained 25% of its weight under the influence of a high temperature degree. Adding sand increases the temperature and time necessary to reach the first and second carbonation point. Adding sand to adhesive increase the temperature needed to reach the glazing point Tg and the point of reversal in the curve derived from loss of weight.

Reverse –Transcription Spin chain reaction of RNA molecule into DNA molecule

Here we have study the conceptual properties of DNA molecules that can be mapped in the Heisenberg spin system, and the reduction in the formation of the effect of temperature through the quantum phase transition (QPT) when the refining time occurs. Delayed free rotation of molecules, reverse replication is a complement that uses RNA molecules to produce single-stranded DNA molecules and aids in the diffusion of DNA molecules. This explains the large ternary stress observed near the reverse copy point. We have projected the curve extent which is created to be in good agreement.

Thyroid eye disease: Redefining its management-A review.

Thyroid eye disease (TED) is a debilitating, vision threatening disease that dramatically alters patients' quality of life. Until recently, the management of TED is a long arduous course with supportive therapy, followed by an extensive surgical treatment plan to reverse the disease endpoints. Teprotumumab offers an early, safe therapeutic intervention to help reverse disease end points such as diplopia and proptosis and improve quality of life.

Groundwater quality trend and trend reversal assessment in the European Water Framework Directive context: an example with nitrates in Italy

Groundwater resources are of utmost importance in sustaining water related ecosystems, including humans. The long-lasting impacts from anthropogenic activities require early actions, owing to the natural time lag in groundwater formation and renewal. The European Union (EU) policy, within the implementation of the Water Framework Directive (WFD), requires Member States to identify and reverse any significant and sustained upward trend in the concentration of pollutants, defining specific protection measures to be included in the River Basin Management Plans (RBMP). In Italy, official guidelines for trend and trend reversal assessment have been published recently. Statistical methods, such as the Mann-Kendall test for trend analysis and the Sen’s method for estimating concentration scenarios, should be applied at the fixed terms stated by the WFD implementation cycles to identify upward trends, while the Pettitt test is proposed for the identification of trend reversal. In this paper, we present an application of a slightly modified version of the Italian Guidelines to a groundwater body in Northern Italy featuring nitrate pollution and discuss its advantages and limitations. In addition to Pettitt test, for the trend reversal analysis, we apply the Mann-Kendall test in two sections and compare the results. We conclude that this method seems more reliable than Pettitt test to identify a reversal point in quality time series. The overall procedure can be easily applied to any groundwater body defined at risk across Europe, for the assessment of the upward trends of pollutants and their reversal, even with little chemical monitoring data. Although focused on the EU legislative framework, this procedure may be relevant for a wider context, allowing to individuate upward trend as early warning for contamination processes in an integrated water resources management context.

Methods for the development of stochastic competence in mathematics lessons at school

Stochastic Oscillator is the full name of one of the most popular technical indicators, which is included in 80% of all existing trading strategies, if not more. It is a favorite tool for identifying trend reversal points for both beginners and seasoned pros. And all thanks to its simplicity and high efficiency. The following article investigates the ways to promote stochastic competence in a school setting.

Extension of the local strain approach to transient material behavior and residual stresses

AbstractIn engineering practice generally empirical durability concepts, such as the Local Strain Approach (LSA) [1], are used for the fatigue life estimation of components. The LSA calculation is based on a given series of reversal points of the elastic stress history, e.g. computed in terms of a finite element model of the component. The fatigue life of components is subject to various factors. During the forming processes of steel‐alloy components, residual stresses are induced into components. In addition, steel‐alloys exhibit a cyclic transient material behavior, for example cyclic strain hardening with different characteristics under tensile and compressive loadings. While the state‐of‐the‐art LSA assumes stabilized cyclic material behaviour throughout the entire fatigue life of the component, this assumption is not adequate for residual stress‐afflicted components.