Static Stability Research Articles

Study on friction characteristics between cotton stalk-residual film-external contact materials

Friction affects the crushing effect of materials. It is of great significance to explore the friction characteristics between cotton stalk-residual film-external contact materials for the analysis of the crushing mechanism of residual film. In view of this, the influence characteristics of inter residual films, residual films/external contact materials friction characteristics were explored. The inter-films static sliding friction coefficient fs and dynamic sliding friction coefficient fk are 0.425 and 0.372, the film/40Cr mean fs is 0.439. Meanwhile, the stalk/materials friction characteristics was analyzed. The response model of fs and static rolling stability Angle μe was constructed (Model coefficient p < 0.01, coefficient of determination R2 >0.93, calibration determination coefficient R2adj >0.86, coefficient of variation C.V >2.9%). The effects of different moisture content, sampling sites and external contact materials on the friction characteristics of inter-stalks and stalk/materials were explained.

An approach for formation design and flight performance prediction based on aerodynamic formation unit: Energy-saving considerations

The performance improvement of swarm drones through aerodynamic shape optimization may be challenging due to folded size constraints imposed by the specific launch approach. However, fixed-wing aircraft swarms can benefit from formation flight in terms of energy consumption. This study introduces the concept of the “aerodynamic formation unit”, which consists of two or three aircraft that form an inseparable unit of the formation. Considering the Unmanned Aerial Vehicle (UAV) distribution and wingtip vortex interference in the formation, two typical aerodynamic formation units are optimized by the variable-fidelity aerodynamic optimization method based on space mapping. The aerodynamic characteristics of the formation UAVs that affect flight performance, such as lift-to-drag ratio (L/D ratio) and static stability are analyzed by Computational Fluid Dynamics (CFD) simulations. The L/D ratio (cruising condition) of the following aircraft can be increased by 22.8% and 57.5% in the optimal units that involve two and three aircraft respectively. Moreover, this study conducts several CFD simulations for multi-aircraft formations formed by the units, which show that the average L/D ratio of the formation can be improved by more than 19%. These results verify the feasibility and effectiveness of the “aerodynamic formation unit” concept and the optimization framework for formation parameters.

The application of multi-criteria decision analysis in gaining a premier sort of stability in airplane safety

Improving the aeronautical safety has been of high importance for the experts. Different factors influence the static and dynamic stability of the plane. These factors play important roles in the plane safety. The static and dynamic safety include several factors. Taking all the technical criteria and elements into account, this article tries to find a suitable method for evaluating and eventually deciding on the best alternative. One of the methods of multi-criteria decision analysis is the concordance analysis (CA) which is an important way of evaluation in solving issues of different miscellaneous criteria that cannot be incorporated into one another. Also, Best-worst method (BWM), one of the most practical decision-making methods, is used in this article. Using the CA and BWMs and based on different criteria, this research prioritises the premier stability alternatives and uses them in the design and finally suggests a suitable alternative out of the influential linear and lateral ones. To do this, a combination of extant varieties including 15 criteria and three alternatives is used and the concordance and non-concordance collections and criteria are defined. The results showed that in addition to the fact that the use of both methods led to the same results; as a result, the linear, lateral and directional became the best options for aeroplane safety, respectively, for design purposes.

ОЦІНКА СТІЙКОСТІ ПРОТИ ПЕРЕКИДАННЯ БАГАТОВІСНИХ АВТОМОБІЛІВ ІЗ ДВОМА ДВОВІСНИМИ ПОВОРОТНИМИ ПЛАТФОРМАМИ

The emergence of four-axle cars with two rotating platforms revealed a problem related to the evaluation of the static stability of such cars against lateral overturning. The problem is caused by the fact that traction and braking forces have a point of application not in the point of contact of the wheels with the road on the axle. This means that in the process of turning the platform around its axis, the shoulder of the overturning (upsetting) moment will decrease for a car standing on a side slope. The article presents an improved method for evaluating the static lateral stability against overturning of four-axle cars with two rotating platforms in the transverse plane. The overturning (upsetting) and stabilizing moments are determined separately on the rotary platforms and on the car as a whole. The use of the stability coefficient as an indicator and criterion of static stability made it possible to obtain a mathematical apparatus for evaluating the stability of four-axle cars with two rotating two-axle platforms. The calculation and analysis of the results on the example of a four-axle car with two rotating two-axle platforms, which is on asphalt, a dirt road and off-road, made it possible to state that such a car has high static stability under the condition of overturning. The stability coefficient under the overturning condition is significantly higher than unity, which indicates a large margin of stabilizing moment. The coefficient of stability acquires the smallest value when the angles of rotation of the platforms are close to zero, while when the angles of rotation tend to 900, the value tends to infinity. When the rolling resistance coefficient increases, the value of the stability coefficient decreases for all values of the angles of rotation of the platforms and the side slope of the road. The direction of further research is the improvement of the designs of machines with rotary bridges and platforms and the study of their dynamic properties.

Noninstrumented Clinical Assessment of Static Postural Stability in Chronic Ankle Instability: A Systematic Review and Meta-Analysis.

Several clinical tests are available to assess static postural stability in individuals with chronic ankle instability (CAI); however, it is unclear which test should be used. To determine which noninstrumented clinical tests should be used to detect static postural stability deficits in individuals with CAI. We searched 4 databases from their inception to February 2023, and included studies comparing static postural stability in individuals with CAI and healthy controls using noninstrumented assessments. Two reviewers independently extracted study characteristics, participant information, static postural stability assessment methods, and results. We calculated the pooled standardized mean difference (SMD) and 95% confidence interval using a random effects meta-analysis and assessed the certainty of the evidence. Fourteen cross-sectional studies (293 participants with CAI and 284 healthy controls) were included. The meta-analysis showed no significant differences between the CAI and healthy groups in the double-leg stance condition of the Balance Error Scoring System (BESS) (SMD, -0.03; low-certainty evidence). Significant group differences were found in the BESS single-leg stance (SLS) on firm and foam surfaces (SLS firm: SMD, 0.47, very low-certainty evidence; SLS foam: SMD, 0.80, very low-certainty evidence), the tandem stance (TS) on firm and foam surfaces (TS firm: SMD, 0.39, low-certainty evidence; TS foam: SMD, 0.76, low-certainty evidence), and the total BESS in the foam conditions (SMD, 1.12, very low certainty evidence). Significant differences were also found between the CAI and healthy groups in the foot-lift (SMD, 1.24; very low certainty evidence) and time-in-balance tests (SMD, -0.94; very low certainty evidence). Due to the large magnitude of the differences, the SLS foam, TS foam, and the total BESS in the foam conditions, as well as the foot-lift test or time-in-balance test, may be the most appropriate to clinically identify static postural stability impairment in individuals with CAI.

Moving together-benefits of a 12-week online dance training intervention on static and dynamic postural stability and gait speed in older women: an exploratory pre-post study.

Physical inactivity negatively affects gait performance and postural stability in older adults resulting in a higher risk of fall accidents. Previous research has shown that in-person dance training improves various aspects of balance and lower-extremity function, however, little is known about the potential benefits of dance training delivered online on variables used for fall risk stratification in older adults. We aimed to explore the benefits of a 12-week online dance training intervention on static and dynamic postural stability and gait speed in older women. Forty-five older adults (44 women) were included in this exploratory pre-post study. The 12-week dance intervention consisted of two weekly 60-min classes in contemporary (improvisation) and salsa dance delivered online through Zoom video calls. Static and dynamic postural stability was assessed using the center of pressure (CoP) area and velocity (force platform), and the Mini Balance Evaluation Systems Test (Mini-BESTest), respectively. 10-m gait speed was measured using photo gates. Before and after comparisons were performed using paired sample t-tests. Thirty-two older women completed the study. There were no significant changes for static postural stability assessed by CoP area or velocity (P ≥ 0.218, Cohen d ≤ 0.234). The Mini-BESTest total score was significantly improved at post-intervention (23.88 ± 3.01) compared to baseline (22.56 ± 1.41, P = 0.007, d = 0.52). 10-m gait speed was significantly faster at post-intervention (1.68 ± 0.25 m/s) compared to baseline (1.57 ± 0.22 m/s, P < 0.001, d = 0.737). Although some caution is needed due to the uncontrolled study design, the results indicate that online dance training has a small effect on static postural stability but may be beneficial for gait speed and in particular dynamic postural control among older women. While the absolute increase in gait speed suggests limited clinical relevance, the change in Mini-BESTest score may reflect a clinically meaningful enhancement of dynamic postural control.

Elevated Mixed Layers during Great Lake Lake-Effect Events: An Investigation and Case Study from OWLeS

Abstract Data from rawinsondes launched during intensive observation periods (IOPs) of the Ontario Winter Lake-Effect Systems (OWLeS) field project reveal that elevated mixed layers (EMLs) in the lower troposphere were relatively common near Lake Ontario during OWLeS lake-effect events. Conservatively, EMLs exist in 193 of the 290 OWLeS IOP soundings. The distribution of EML base pressure derived from the OWLeS IOP soundings reveals two classes of EML, one that has a relatively low-elevation base (900–750 hPa) and one that has a relatively high-elevation base (750–500 hPa). It is hypothesized that the former class of EML, which is the focus of this research, is, at times, the result of mesoscale processes related to individual Great Lakes. WRF reanalysis fields from a case study during the OWLeS field project provide evidence of two means by which low-elevation base EMLs can originate from the lake-effect boundary layer convection and associated mesoscale circulations. First, such EMLs can form within the upper-level outflow branches of mesoscale solenoidal circulations. Evacuated Great Lakes–modified convective boundary layer air aloft then lies above ambient air of a greater static stability, forming EMLs. Second, such EMLs can form in the absence of a mesoscale solenoidal circulation when Great Lake–modified convective boundary layers overrun ambient air of a greater density. The reanalysis fields show that EMLs and layers of reduced static stability tied to Great Lakes–modified convective boundary layers can extend downwind for hundreds of kilometers from their areas of formation. Operational implications and avenues for future research are discussed.

Account of additional factors for damping torsional oscillations

Some parameters are influenced by the turbine unit's torsional oscillations. The fundamental comes from damping these oscillations, which are brought on by a departure in the turbine blades' speed from the device's prediction of the steam volume, and attenuation of fluctuations due to the distribution of energy in the turbine's productive components. The usual single-machine infinite bus system is used for the analysis. For various turbine-generator shafts and various generator operating situations, rotating mass mechanical system evaluations for small-signal stability and large disturbance are conducted. It is demonstrated that the shaft's “structural' damping (H) and “steam' damping (Kn) coefficients have a considerable impact on the damping of torsional modes. The goal of this work is to determine the effect of changing the damping factors in the mathematical model of the steam turbine shaft on the system's static stability, as well as the extent to which these variables' limits on damping rotational oscillations on the maximum torsional torques generated in the shaft masses. The mathematical model of the steam turbine shaft with a single machine and transmission line to an infinite bus system was simulated using Dymola software, and the static and dynamic effects of damping factors (H) and (Kn) on system stability were demonstrated. By evaluating the best case for parameters with the least influence on the system's stability, the results were obtained by changing the factors (Kn) from 0.005 to 0.5 and (H) from 0.005 to 0.2 and the extent of its effect on the maximum torque of the steam turbine masses and reducing it by 8.4 %, as well as by reducing the settling time of the system after disturbances occur and reaching to Steady state by about 90 %.

Identification of the Worst-Case Static Voltage Stability Margin Interval of AC/DC Power System Considering Uncertainty of Renewables

Identification of the Worst-Case Static Voltage Stability Margin Interval of AC/DC Power System Considering Uncertainty of Renewables

Novel Static Security and Stability Control of Power Systems Based on Artificial Emotional Lazy Q-Learning

Novel Static Security and Stability Control of Power Systems Based on Artificial Emotional Lazy Q-Learning

Extremely Randomized Trees Approach to Voltage Stability Assessment of Power Distribution System

In modern power grids, ensuring operational stability necessitates real-time assessment of static voltage stability. This paper presents an advanced ensemble machine learning approach to estimate voltage stability in power distribution systems using data from phasor measurement units (PMUs). The methodology integrates multiple machine learning techniques into a unified predictive model to minimize bias and variance. A critical feature of this approach is the inclusion of a feature pre-processing step to eliminate redundant and irrelevant features, enhancing computational efficiency through dimensionality reduction. Additionally, a minority oversampling method for regression is utilized to address data disparity, ensuring robust model performance. Various ensemble models were evaluated using mean square error metrics, with the Bagging model ExtraTrees outperforming other algorithms. The proposed method's efficacy is validated on a 30-bus IEEE system, highlighting its potential for real-time applications. This research offers a robust solution for maintaining grid reliability and preventing power outages by providing accurate, real-time voltage stability assessments.

Преодоление шагающим роботом препятствий, характерных для равнины

An upper estimate of the maximum width of the forbidden zone for foot fulcrums, which a walking robot can overcome in static stability mode, is presented. Using the examples of six-legged and four-legged robot, it is shown that the obtained estimate can't be improved. For this purpose, the sequences of the robot's foot placement have been formed, ensuring the achievement of the estimation meaning. The results of computer modeling and video materials illustrating the process of overcoming an obstacle by a six-legged robot are presented.

Enhancing the sustainability of energy networks through the utilization of smart consumers

Dynamic or static stability of electrical networks is maintained not only by the internal energy of the system but also by the utilization of a hot power reserve. In networks that incorporate renewable energy sources, this reserve should be commensurate with the power capacity of the renewable energy sources. However, this leads to an increase in economic costs. Additionally, the integration of renewable energy sources results in a decrease in the dynamic stability of the system due to the unregulated changes in the supplied energy. The objective of this research is to analyze the potential impact of renewable energy sources on network stability and explore possibilities for enhancing stability through adaptive operation of smart consumers. Renewable energy generation is characterized by temporal and concentration uncertainties, which can potentially disrupt the operation of the energy system. The primary approach employed in this study involves analyzing the potential influence of various operational modes of smart consumers, both during load commutation and energy source switching. The main outcome of this work is the development of a smart consumer algorithm. The devised operating principle mitigates the effects of unstable renewable energy operation or uncertain consumer behavior.

Series of exercise therapy in order to make the medial longitudinal arch in changing flat foot conditions, systematic literature review

Flat foot is a condition in which the foot has no or less arch in the arches longitudinal medial that cause the footprints become flatter than usual or seem to appears have no arch. Arches longitudinal medial is one of the pedis arches which plays an important role in the support and balance of the foot when walking. If this part becomes flat and being ignored, it will cause the limitation of walking activities, muscle imbalance, the changes of body alignment, and it can cause a risk of injury to someone as well. The aim of this paper is to identify whether the series of exercise therapy in order to make the Medial Longitudinal Arch in changing Flat Foot Conditions is an appropriate exercise method that can be carried out. This research is using the systematic literature review method with preferred reporting items for systematic reviews and meta-analytic. The data that is used in the article’s findings in Sinta accredited journals is Google Scholar &amp; Pubmed. The articles searched were based on the keywords, in which flat foot exercise therapy and changes in arches longitudinal medial, then being filtered based on the inclusion and exclusion criteria. It was 6 out of 20 articles were used as the main source in this study. The first finding of this research shows that a series of strengthening exercises such as tower curl exercise, heel raises exercise, short foot exercise, strengthening Ball Roll Exercise, calf stretch, and towel stretch can provide a curving effect or additional of the arches longitudinal medial on the flat foot. The second finding of this research is that providing training with the addition of kinesio tapping can improve postural control, increase proprioception, and increase static stability in the intrinsic muscles of the foot.

Characteristics of Fishing Vessels Owned by Fishermen from the Ujong Baroh Fish Landing Base (PPI) West Aceh Regency

Fishing vessel is one of an important thing among a fishing unit. All fishing activities are carried out on fishing vessel. In Indonesia, the shape and size of fishing vessels are vary, depending on the habits of the fishers and the area where the fishing vessels are built and operated. In West Aceh Regency, there are fishing vessels with various sizes. This study aims to identify the shape of fishing vessels measuring less than 10 gross tonnages (GT) at the Fish Landing Base (PPI) Ujong Baroh, West Aceh Regency. This identification is intended as a basis for reference in formulating fishing vessel design that follows the local wisdom of fishers in West Aceh Regency. This reference fishing vessel design can help the government and other parties provide aid fishing vessel for fishers in West Aceh Regency. The direct observation and measurement of fishing vessels were used in this research. Descriptive and numerical method used in analysis data. The number of sample was 27 fishing vessels consist of 10 sample with size of 1-5 GT and 17 with a size of 6-10 GT. The result show that fishing vessels in Aceh Barat District have a transom shape longitudinally and a round bottom or a round flat bottom shape transversely. All fishing vessels in West Aceh have a raked bow and a cruiser-shaped stern. The main dimensions ratio of group 6-10 GT is smaller than group 1-5 GT. The stability parameters of the two forms of fishing vessels follow the stability parameter values recommended by the International Maritime Organization (IMO). The static stability of fishing vessels with round flat bottom is better than round bottom.

Определение состояния аварийного корабля в процессе развития затопления отсеков

The article is focused on method of ship rolling processing during flooding of compartments. The main goal of such processing is in determination of the time moment, when the type of static stability diagram changes. The ship state corresponding to each of these types requires completely different methods of damage control, which is reflected in the knowledge base of the onboard intelligent system. In navigation conditions, and even more so in extreme situations, direct measurement of the stability characteristics of a marine object is impossible, so their indirect determination is required. The article presents the implementation of the procedural component of an on-board intelligent system based on an artificial neural network.

The Effects of Suspension Training on Dynamic, Static Balance, and Stability: An Interventional Study.

Background and Objectives: While suspension training devices are increasingly gaining popularity, there is limited evidence on their effects on balance, and no comprehensive assessment has been conducted. This study aimed to evaluate the effects of a 9-session suspension training program on dynamic and static balance, stability, and functional performance. Materials and Methods: A total of forty-eight healthy adults, aged between 18 and 30, participated in a 9-session suspension training program. The program included exercises targeting upper and lower body muscles as well as core muscles. Balance was comprehensively assessed using various dynamic balance tests, including the Y Balance Test (YBT) as the primary outcome, single-leg Emery test, and sideways jumping test. Static balance was evaluated through the monopedal and bipedal Romberg tests. Changes from baseline were analyzed using a one-way ANOVA test. Results: Thirty-nine participants (mean age: 21.8 years) completed the intervention. The intervention resulted in significant improvements in YBT, jumping sideways, Emery, and 30s-SST scores (p < 0.001). Platform measures indicated enhanced monopedal stability (p < 0.001) but did not show a significant effect on bipedal stability (p > 0.05). Conclusions: Suspension training is a safe and feasible method for improving dynamic balance and functional performance in healthy, untrained young adults. However, it does not appear to significantly impact the ability to maintain a static posture while standing.

Effect of quasi‐biennial oscillation on the intensity of the South China Sea summer monsoon

AbstractThe interannual relationship between the quasi‐biennial oscillation (QBO) and the South China Sea (SCS) summer monsoon intensity (SCSSMI) is investigated using the ERA5 data set in the period of 1953–2020. The QBO–SCSSMI connection is weak in El Niño‐Southern Oscillation (ENSO)‐related summer, but significant in neutral ENSO summer. In neutral ENSO summer, there is significant positive correlation between QBO and SCSSMI, that is, the SCSSMI is enhanced in the QBO westerly phase, while it is weakened in the QBO easterly phase with larger amplitude of the SCSSMI anomaly. QBO may modulate the SCSSMI in three possible ways. The QBO‐related temperature anomalies downward to the lower stratosphere directly affect the SCS monsoon convection by modulating the upper‐tropospheric stability and tropopause height over the SCS region. Moreover, the QBO‐related anomalous zonal wind downward to the lower stratosphere may regulate cross‐tropopause vertical wind shear and then modulate the convection development. Besides, the QBO‐related zonal wind and temperature signals propagating downward into the upper troposphere can affect the horizontal divergence by influencing the vertical vorticity and the geopotential via thermal forcing. Through those three processes, QBO directly affects the deep convection activities and then modulates the SCSSMI via internal dynamic adjustment. In the southern SCS, cross‐tropopause vertical wind shear makes a main contribution to deep convections, while upper‐tropospheric static stability makes a major contribution to deep convection in the northern SCS. The conclusions are also generally verified by the CMIP6 model simulation.

Multiple Grid-Connected Microgrids with Distributed Generators Energy Sources Voltage Control in Radial Distribution Network Using ANFIS to Enhance Energy Management

Voltage conditions and power quality for customers and utility equipment are significantly impacted by the addition of microgrid-generating sources within distribution networks. Designing the right control for distributed generators for the various generating units of a Microgrid is important in enabling the synchronization of renewable energy generation sources, energy storage unity, and integration of Microgrids into a radial distribution network. This research provides control mechanisms based on an adaptive technique employing ANFIS, to reduce fluctuation of voltage and current difficulties faced when multiple renewable energy sources and storage systems are incorporated into a distribution network. A step-by-step Voltage Source Converter (VSC) Controller was designed for controlling the DC voltage power sources used. The ANFIS training, test system modeling, and the distributed energy source were modeled in MATLAB/SIMULINK 2021a Software. Four microgrids were developed each consisting of a Photovoltaic plant, Wind Turbine, and Battery Storage System. Non-critical and critical loads were considered during the system testing. The simulated result reveals that the proposed control system works effectively in maintaining a constant system voltage of 340VAC which significantly mitigates system voltage and current fluctuation without using any static synchronous compensator (STATCOM) and power system stabilizers.

Study on the Properties Changes of Reversible Invert Emulsion during the Process from O/W to W/O with Alkali.

The reversible emulsion drilling fluid system combines the advantages of both oil-based and water-based drilling fluids, which can achieve ideal results in different stages of drilling and completion, and the system can be reused to effectively reduce costs. However, the research on reversible emulsions mainly focuses on the development of new reversible emulsifiers, while the specific phase transformation mechanism of reversible emulsion systems is still unclear. In this paper, a stable reversible emulsion was prepared using the reversible emulsifier DMOB as a raw material, and the reversible emulsion performance of the alkali response from the O/W emulsion phase to the W/O emulsion was studied. The microstructure of reversible emulsions was studied by a microscope, a cryogenic transmission electron microscopy, and a laser particle size analyzer. The changes in macroscopic properties of reversible emulsions in the process of alkali conversion were studied by pH, conductivity, demulsification voltage, static stability, viscosity, rheology, and other indicators, and the conversion mechanism of reversible emulsions from O/W emulsion ⟶ bicontinuous structure ⟶ O/W/O emulsion ⟶ W/O emulsion was clarified. The details are as follows: in the first stage, when the amount of NaOH ≤ 0.43 vol.%, the overall particle size of the emulsion decreases first and then increases with the increase in NaOH dosage. In the second stage, when the amount of NaOH was 0.45 vol.%, a double continuous structure was formed inside the emulsion. In the third stage, when the amount of NaOH is 0.48 vol.%, the O/W/O emulsion is formed, and with the increase in stirring time, the internal oil droplets gradually accumulate and are discharged from the water droplets, and finally, the W/O emulsion is formed. In the fourth stage, when the dosage of 0.50 vol.% ≤ NaOH ≤ 5.00 vol.%, the W/O emulsion was formed, and with the increase of NaOH dosage, the structure and compactness between water droplets increased first and then decreased. In the whole process, with the increase in the amount of NaOH solution, the total particle size of the emulsion first decreased and then increased.