Assessment Of System Stability Research Articles

Enhancing stability and tribological applications using hybrid nanocellulose-copper (II) oxide (CNC-CuO) nanolubricant: An approach towards environmental sustainability

The primary aim of the present study is to assess the stability and efficacy of hybrid nanocellulose (CNC) and copper (II) oxide (CuO) nanoparticles when integrated into engine oil as a lubricant for piston ring-cylinder liner applications. The assessment of system stability was conducted by employing zeta potential measurements. Furthermore, the coefficient of friction and specific wear rate were determined by using hydrodynamic lubrication in circumstances characterised by high speed and low load, as well as boundary lubrication in situations characterised by low speed and high load. The trials used a specially constructed friction and wear testing device miming the contact geometry between piston rings and cylinder liners in an internal combustion engine. Alongside SAE 40 oil, several nanoparticle concentrations (0.1%, 0.3%, 0.5%, 0.7%, and 0.9% added to SAE 40) were examined. The stability of the nanolubricant increased from 0.1% to 0.5% concentration and then declined at 0.9% concentration, according to the zeta potential data. The graph showed that the 0.5% concentration of the nanolubricant had the highest mean zeta potential, indicating exceptional stability. The CNC-CuO nanolubricants showed notable reductions in the friction coefficient regarding tribological performance. The friction coefficient reduced between 33% and 44% in mixed lubrication and 48% and 50% in boundary lubrication. There was a 9–13% decrease in the friction coefficient when hydrodynamic lubrication was used. The CNC-CuO nanolubricant only showed light scuffing, while the SAE 40 sample showed severe exfoliation and scuffing. Wear rates had been enhanced by 33.5%. Overall, the 0.5% concentration of CNC-CuO nanoparticles improved the engine oil's thermophysical properties and performance.

Assessment of the Response Time to Information Messages in the Conditions of a Farms Based on the Methodology of Real-Time Systems

As you know, modern farms equipp many technological devices, the operation of which directly affects the volume of agricultural products, the period of readiness, their quality, shelf life, etc., in this regard, the issues of assessing the response time and reaction to information flows are relevant. The article presents the results of constructing a model based on real-time systems for assessing system stability and the response time of a subject (farmer) to information messages from IoT devices to the subject’s smartphone, depending on the time of performing current, priority and critical technological operations, their relevance, as well as on the level of information noise and the availability of resources. The analysis of the model revealed that an increase in the number of control objects and information messages increases the system response delay time from 0 to 36.5 hours which will especially depends on the receipt of priority and critical messages. The article offers solutions to reduce the response time, in particular by dividing the message flow into production and personal, resource optimization, using digital technologies (IoT), databases and improving the information skills of farmers.

Tangling and instability effect analysis of initial in-plane/out-of-plane angles on electrodynamic tether deployment under gravity gradient

The space debris occupies the orbit resources greatly, which seriously threats the safety of spacecraft for its high risks of collisions. Many theories about space debris removal have been put forward in recent years. The Electro Dynamic Tether (EDT), which can be deployed under gravity gradient, is considered to be an effective method to remove debris in low orbit for its low power consumption. However, in order to generate sufficient Lorentz force, the EDT needs to be deployed to several kilometers, which increases the risks of tangling and the instability of the EDT system. In the deployment process, different initial in-plane/out-of-plane angles, caused by direction error at initial release or the initial selection of ejection, affect the motion of EDT system seriously. In order to solve these problems, firstly, this paper establishes the dynamic model of the EDT system. Then, based on the model, safety metrics of avoiding tangling and assessing system stability during EDT deployment stage are designed toquantitatively evaluate the EDT system security. Finally, several numerical simulations are established to determine the safety ranges of the initial in-plane/out-of-plane angles on the EDT deployment.

Stability Analysis and Design of Composite Structures

AbstractThe direct analysis method is the primary means of assessing system stability within a standard specification. This method, and in particular its use of reduced stiffness, has been thoroughly validated for use in frames consisting of structural steel members. However, appropriate stiffness reductions have not yet been established nor has the method as a whole been validated for frames with steel-concrete composite columns. Through comparisons between second-order inelastic analysis results and results from the design methodology on a parametric suite of small frames, the current design provisions are evaluated in this paper. The results indicate that while the current design provisions are safe and accurate for the majority of common cases, there exist cases in which the current provisions result in high levels of unconservative error. Modifications to the current design provisions are proposed to address these issues.

BOCS Based Power System Stability Margin Estimation

This paper focuses on the estimation of the stability index of a power system after a severe disturbance. The description of the stability margin has always been a challenging issue but by introducing a ball-on-concave-surface system, the assessment of the power system stability is equivalent to the analysis to the motion state of the ball on concave. According to the continuous measurement of PMU, the parameter of the concave can be determined which is useful to judge the stability margin of the power system. Tests have been conducted on the systems with two generators and results show it can be accurate and reliable.

Dynamic processes in regulation and some implications for biofeedback and biobehavioral interventions.

Systems theory has long been used in psychology, biology, and sociology. This paper applies newer methods of control systems modeling for assessing system stability in health and disease. Control systems can be characterized as open or closed systems with feedback loops. Feedback produces oscillatory activity, and the complexity of naturally occurring oscillatory patterns reflects the multiplicity of feedback mechanisms, such that many mechanisms operate simultaneously to control the system. Unstable systems, often associated with poor health, are characterized by absence of oscillation, random noise, or a very simple pattern of oscillation. This modeling approach can be applied to a diverse range of phenomena, including cardiovascular and brain activity, mood and thermal regulation, and social system stability. External system stressors such as disease, psychological stress, injury, or interpersonal conflict may perturb a system, yet simultaneously stimulate oscillatory processes and exercise control mechanisms. Resonance can occur in systems with negative feedback loops, causing high-amplitude oscillations at a single frequency. Resonance effects can be used to strengthen modulatory oscillations, but may obscure other information and control mechanisms, and weaken system stability. Positive as well as negative feedback loops are important for system function and stability. Examples are presented of oscillatory processes in heart rate variability, and regulation of autonomic, thermal, pancreatic and central nervous system processes, as well as in social/organizational systems such as marriages and business organizations. Resonance in negative feedback loops can help stimulate oscillations and exercise control reflexes, but also can deprive the system of important information. Empirical hypotheses derived from this approach are presented, including that moderate stress may enhance health and functioning.

Energy-efficiency enhancement and displacement-offset elimination for hybrid vibration control

New insights into our previously proposed hybrid-type method for vibration control are highlighted in terms of energy analysis, such as the assessment of energy efficiency and system stability. The hybrid method improves the bang-bang active method by combining it with an energy-recycling approach. Its simple configuration and low energy-consumption property are quite suitable especially for isolated structures whose energy sources are strictly limited. The harmful influence of the external voltage is assessed, as well as its beneficial performance. We show a new chattering prevention approach that both harvests electrical energy from piezoelectric actuators and eliminates the displacement-offset of the equilibrium point of structures. The amount of energy consumption of the hybrid system is assessed qualitatively and is compared with other control systems. Experiments and numerical simulations conducted on a 10-bay truss can provide a thorough energy-efficiency evaluation of the hybrid suppression system having our energy-harvesting system.

An optimization problem in the electricity market

New types of optimization problems are faced by the generating companies that operate on deregulated electricity markets. The characteristics of these problems depend on the various market structures. In the framework of the recently settled Italian electricity market, one of these new problems is the transition from hourly energy programs, defined by the market, to more detailed power generation dispatches, defined for intervals of 15 min. Such a more detailed plan is needed on the one hand by the national system operator (Terna, Rete Elettrica Nazionale) for the assessment of power system stability and security, and on the other hand by the power plant operators for its implementation. The transition procedure should respect the hourly energy constraints and take the main operating constraints of the generating units into account. The paper presents possible solutions of the problem through linear optimization models and reports computational results on real-world instances.

손실감소를 통한 고속철도부하를 포함한 154[㎸]벼 배전계통의 시스템 안정도 평가

손실감소를 통한 고속철도부하를 포함한 154[㎸]벼 배전계통의 시스템 안정도 평가

Deposit Insurance and Market Assessment of Banking System Stability: Evidence from Denmark

Deposit Insurance and Market Assessment of Banking System Stability: Evidence from Denmark

Dynamic performance, interaction, and the characteristic locus method: a quantitative approach

The characteristic locus method, in addition to its role in the assessment of system stability, is also an effective approach for evaluating tracking accuracy, interaction and dynamic/static loop performance. However, with regard to the evaluation of the latter three, there exists a degree of ambiguity and personal judgement, in addition to a requirement for a priori assumptions about proper problem conditioning. This paper stipulates quantitative bounds/measures of accuracy, interaction and loop assessment that identify the pertinent open-loop system factors affecting the particular performance aspect, and thus provide unambiguous measures to aid system design. Additionally, eigenvector scaling is introduced in order to tighten the bounds.

Stability assessment of machine systems described by receptance

The usual approach [1] of finding the stability regions' boundaries is insufficient when the system dynamics is considered in other than the speed or the frequency domain, as it gives no indication on which side, if any, of a boundary stability prevails. This paper presents a method of assessing system stability on the basis of its numerical receptance matrix, obtained from computation or experiment. An approximation approach [2] is adopted to obtain the characteristic equation and its roots that determine the system stability. The numerical procedures presented permit not only assessment of the system stability but also yield an analytical form for the experimentally measured receptances. This processing is usually necessary as a smoothing procedure to eliminate spurious effects, e.g., instabilities related to the measurement errors, when experimental data are used in computational processes. Actual application cases are also presented.