MACRM: A Multi-agent Cluster Resource Management System

The falling cost of cluster computing has significantly increased its use in the last decade. As a result, the number of users, the size of clusters, and the diversity of jobs that are submitted to clusters have grown. These changes lead to a quest for redesigning of clusters' resource management systems. The growth in the number of users and increase in the size of clusters require a more scalable approach to resource management. Moreover, ever-increasing use of clusters for carrying out a diverse range of computations demands fault-tolerant and highly available cluster management systems. Last, but not the least, serving highly parallel and interactive jobs in a cluster with hundreds of nodes, requires high throughput scheduling with a very short service time. This research presents MACRM, a multi-agent cluster resource management system. MACRM is an adaptive distributed/centralized resource management system which addresses the requirements of scalability, fault-tolerance, high availability, and high throughput scheduling. It breaks up resource management responsibilities and delegates it to different agents to be scalable in various aspects. Also, modularity in MACRM's design increases fault-tolerance because components are replicable and recoverable. Furthermore, MACRM has a very short service time in different loads. It can maintain an average service time of less than 15ms by adaptively switching between centralized and distributed decision making based on a cluster's load. Comparing MACRM with representative centralized and distributed systems (YARN [67] and Sparrow [52]) shows several advantages. We show that MACRM scales better when the number of resources, users, or jobs increase in a cluster. As well, MACRM has faster and less expensive failure recovery mechanisms compared with the two other systems. And finally, our experiments show that MACRM's average service time beats the other systems, particularly in high loads

Microstructure-dependent dynamic behavior of torsional nano-varactor

Experiments depict that the physico-mechanical response of miniature devices is microstructure-dependent. However, the classic continuum theory cannot correctly predict the microstructure-dependency. In this paper, the strain gradient theory is employed to examine the dynamic behavior and instability characteristics of miniature varactor with trapezoidal geometry. The governing equation of the varactor is obtained incorporating the effects of Coulomb force, van der Waals (vdW) attraction, squeeze film damping and structural damping. The influences of microstructure on the dynamic instability of equilibrium points are studied by plotting the phase portrait and bifurcation diagrams. It is found that increase in the microstructure parameter enhances the torsional stability. In the presence of the applied voltage, the phase portrait shows the saddle-node bifurcation while for free-standing varactor a subcritical pitchfork bifurcation is observe

Numerical simulation of flow pattern at a divergent pier in a bend with different relative curvature radii using ansys fluent

In this work, the three-dimensional flow around piers in river meanders under rigid bed conditions was modeled. The software ANSYS FLUENT was used to perform the simulation. The study was carried out in a 180° curve accompanied by cylindrical piers with a diameter of 5 cm and a slope angle of 21° under rigid bed conditions. The results of the comparisons showed that this model can help simulate the flow pattern around inclined bridge piers in bended channels with acceptable accuracy. To analyze the flow pattern, the work was followed by studying the effect of the parameters that affect the physics of the problem: the relative radius of curvature of the curve, the location of the piers within the 180° curve, and the arrangement of the piers relative to the flow direction. The results showed that increasing the relative radius of curvature as well as the range of the bend reduced the tangential velocity values; the minimum tangential velocity value occurred at a relative radius of curvature of 5. With the pier group installed in the direction of flow, the maximum secondary flow power occurred at the 60° position at about 18.8%, while with the pier group installed across the flow, the maximum secondary flow power occurred at the 120° position at 14.2%. A comparison of the vorticity at the perpendicular and downstream positions showed that the vorticity values at the 60° and 120° positions were greater than the corresponding values at the 90° position in both cases

On a 3D material modelling of smart nanocomposite structures

Smart composites (SCs) are utilized in electro-mechanical systems such as actuators and energy harvesters. Typically, thin-walled components such as beams, plates, and shells are employed as structural elements to achieve the mechanical behavior desired in these composites. SCs exhibit various advanced properties, ranging from lower order phenomena like piezoelectricity and piezomagneticity, to higher order effects including flexoelectricity and flexomagneticity. The recently discovered flexomagneticity in smart composites has been investigated under limited conditions. A review of the existing literature indicates a lack of evaluation in three-dimensional (3D) elasticity analysis of SCs when the flexomagnetic effect (FM) exists. To address this issue, the governing equations will incorporate the term ∂/∂z, where z represents the thickness coordinate. The variational technique will guide us in further developing these governing equations. By using hypotheses and theories such as a 3D beam model, von Kármán's strain nonlinearity, Hamilton's principle, and well-established direct and converse FM models, we will derive the constitutive equations for a thick composite beam. Conducting a 3D analysis implies that the strain and strain gradient tensors must be expressed in 3D forms. The inclusion of the term ∂/∂z necessitates the construction of a different model. It should be noted that current commercial finite element codes are not equipped to accurately and adequately handle micro- and nano-sized solids, thus making it impractical to model a flexomagnetic composite structure using these programs. Therefore, we will transform the derived characteristic linear three-dimensional bending equations into a 3D semi-analytical Polynomial domain to obtain numerical results. This study demonstrates the importance of conducting 3D mechanical analyses to explore the coupling effects of multiple physical phenomena in smart structures

DESIGNING AN EFFICIENT OBSERVER FOR THE NON-LINEAR LIPSCHITZ SYSTEM TO TROUBLESHOOT AND DETECT SECONDARY FAULTS CONSIDERING LINEARIZING THE DYNAMIC ERROR

The presence of faults in a system leads to a lower value for efficiency, accuracy and speed, and, in some cases, even a complete breakdown. Thus, early fault detection is a major factor in efficiency and productivity of the procedure. In recent decades, many research studies have been conducted on troubleshooting and secondary fault detection. The current work presents an efficient and novel observer design capable of stabilizing the residue and dynamic error for the nonlinear Lipschitz systems with faults as well as a troubleshooting analysis and determining the formation of secondary faults in defective systems. The observer is designed based on linearizing dynamic error considering uncertainty, disturbance, and defects by employing non-linear gain factors instead of using state transformation. The dynamic error and residue stabilization of a non-linear faulty system have been discussed as well as the likelihood of secondary fault generation. The results indicate that the observer is able to determine fault-emergence, fault-disappearance and secondary fault formation well and quite fast

D. AFSHARI et al.: PREDICTION OF THE NUGGET SIZE IN RESISTANCE SPOT WELDING ... PREDICTION OF THE NUGGET SIZE IN RESISTANCE SPOT WELDING WITH A COMBINATION OF A FINITE-ELEMENT ANALYSIS AND AN ARTIFICIAL NEURAL NETWORK NAPOVEDOVANJE PODRO^JA PRETALITVE PRI

The goal of this investigation is to predict the nugget size for a resistance spot weld of thick aluminum 6061-T6 sheets 2 mm. The quality and strength of spot welds determine the integrity of the structure, which depends thoroughly on the nugget size. In this study, the finite-element method and artificial neural network were used to predict the nugget size. Different spot welding parameters such as the welding current and the welding time were selected to be used for a coupled, thermal-electrical-structural finite-element model. In order to validate the numerical results a series of experiments were carried out and the nugget sizes were measured. The results obtained with the finite-element analysis were used to build up a back-propagation, artificialneural-network model for the nugget-size prediction. The results revealed that a combination of these two developed models can accurately and rapidly predict the nugget size for a resistance spot weld. Keywords: resistance spot weld, nugget size, finite-element analysis, artificial neural network, aluminum alloys Cilj te preiskave je napovedati velikost podro~ja pretalitve pri uporovno zvarjeni aluminijasti plo~evini 6061-T6, debeli 2 mm. Kvaliteta in trdnost to~kastega zvara dolo~ata celovitost konstrukcije, kar je odvisno predvsem od velikosti podro~ja pretalitve. V tej {tudiji sta bili za napovedovanje velikosti podro~ja pretalitve uporabljeni metoda kon~nih elementov in umetna nevronska mre`a. Izbrani so bili razli~ni parametri varjenja, kot sta varilni tok in~as varjenja, za skupni termi~no-elektri~no-strukturni model kon~nih elementov. Za oceno numeri~nih rezultatov je bilo izvr{enih ve~preizkusov in izmerjena je bila velikost podro~ja pretalitve. Rezultati, dobljeni iz analize kon~nih elementov, so bili uporabljeni za gradnjo modela umetne nevronske mre`e za napovedovanje velikosti podro~ja pretalitve. Rezultati so odkrili, da kombinacija teh dveh razvitih modelov lahko zanesljivo in hitro napove velikost podro~ja pretalitve pri uporovnem to~kastem zvaru. Klju~ne besede: uporovni to~kasti zvar, velikost podro~ja pretalitve, analiza kon~nih elementov, umetna nevronska mre`a, zlitine aluminij

TEMPERATURE-DEPENDENT PHYSICAL CHARACTERISTICS OF THE ROTATING NONLOCAL NANOBEAMS SUBJECT TO A VARYING HEAT SOURCE AND A DYNAMIC LOAD

In this article, the influence of thermal conductivity on the dynamics of a rotating nanobeam is established in the context of nonlocal thermoelasticity theory. To this end, the governing equations are derived using generalized heat conduction including phase lags on the basis of the Euler–Bernoulli beam theory. The thermal conductivity of the proposed model linearly changes with temperature and the considered nanobeam is excited with a variable harmonic heat source and exposed to a time-dependent load with exponential decay. The analytic solutions for bending moment, deflection and temperature of rotating nonlocal nanobeams are achieved by means of the Laplace transform procedure. A qualitative study is conducted to justify the soundness of the present analysis while the impact of nonlocal parameter and varying heat source are discussed in detail. It also shows the way in which the variations of physical properties due to temperature changes affect the static and dynamic behavior of rotating nanobeams. It is found that the physical fields strongly depend on the nonlocal parameter, the change of the thermal conductivity, rotation speed and the mechanical loads and, therefore, it is not possible to neglect their effects on the manufacturing process of precise/intelligent machines and devices

Awareness of Academic Staff Physicians with Principles of Evidence-Based Medicine and its Application in Daily Practice

Introduction: The purpose of this study was to evaluate familiarity of academic staff physicians with EBM and its application in daily practice. Methods: This cross-sectional study was conducted in 2022 with the participation of academic staff physicians of Hamadan University of Medical Sciences in Iran. Data were collected using CEBM questionnaire and were analyzed with SPSS 20 software, using T-test and Spearman correlation statistical tests. Results: Out of 156 academic physicians, 97 (62.2%) completed the questionnaire, 62 (63.9%) were male, and 33 (34%) had participated in EBM workshops. Mean score of knowledge and attitude questions were 14.7± 3.9 and 3.8± 0.5 respectively. There was no significant difference between males and females in knowledge and attitudes (P >0.05). Physicians who participated in EBM workshops had higher scores in knowledge (P <0.05) but not in attitude (P= 0.06). Positive and significant correlation between age (r = 0.32, P = 0.001) and teaching experience (r = 0.28, P = 0.005) was observed with knowledge and attitude about EBM. 69.1% of participants used very little or not at all EBM in their daily practice. The most important obstacles were lack of time (49.5%) and specific information (22.7%). More than 65% of physicians tended to use EBM in their daily practice. Conclusion: The academic staff physicians of Hamadan, Iran had a positive attitude towards evidence-based medicine, but did not have enough information in this regard. Accordingly, its application in daily clinical work was relatively low. Holding EBM workshops is essential to increase awareness about EBM