OVERVIEW OF THE BEST 2020 AXIAL-FLOW FAN DATA AND INCLUSION IN SIMILARITY CHARTS FOR THE SEARCH OF THE BEST DESIGN

The paper deals with the aerodynamic performance of ducted axial-flow fans available in the 2020 market and aims to create a general picture of the best designs and design trends, as a tool for fan designers. To this end, the paper first presents the general formulation of the similarity approach to the fan performance analysis, including the effects of rotational speed (which affects the validity of the Reynolds similarity) and turbomachine size (which can hinder the perfect geometrical similarity of some shape details). The second part reports a statistical survey of the axial-flow fan performance based on data from catalogues of major manufacturers, and compares the resulting Cordier-lines with optimum fan designs from empirical or CFD-based models available in the literature. In addition to the global performance at maximum aeraulic and total-to-static efficiencies, this survey uses the form of dimensionless Balje-Cordier charts to identify the trends and values of other design parameters, such as hub-to-tip ratio, blade count, and blade positioning angle. As a result, a summary of the aerodynamic performance of year 2020 best designs, the improvements achieved during the last forty years, and the present design trends in contra-rotating, vane-axial, and tube-axial fan types are made available to fan designers.

A Submodular Receding Horizon Control Strategy to Distributed Persistent Monitoring

This paper investigates the multi-agent persistent monitoring problem via a novel distributed submodular receding horizon control approach. In order to approximate global monitoring performance, with the definition of sub-modularity, the original persistent monitoring objective is divided into several local objectives in a receding horizon framework, and the optimal trajectories of each agent are obtained by taking into account the neighborhood information. Specifically, the optimization horizon of each local objective is derived from the local target states and the information received from their neighboring agents. Based on the sub-modularity of each local objective, the distributed greedy algorithm is proposed. As a result, each agent coordinates with neighboring agents asynchronously and optimizes its trajectory independently, which reduces the computational complexity while achieving the global performance as much as possible. The conditions are established to ensure the estimation error converges to a bounded global performance. Finally, simulation results show the effectiveness of the proposed method.

Driving liberal change? Global performance indices as a system of normative stratification in liberal international order

The existing literature on Global Performance Indices (GPIs) is mostly dominated by unit-level analyses focused on specifying the relevant properties of the GPIs and the motivations of state actors in being influenced by GPIs. This article advances a systemic approach, which conceives of GPIs as collectively constituting a system of normative stratification in International Relations (IR). By bringing together the literature on GPIs with the relevant IR literatures on international hierarchies and status-seeking, we identify the structural attributes of the GPI-based system of stratification, how these structural attributes shape the distribution of normative status positions among states, and how this distribution is likely to condition the pursuit of status by states. In particular, we argue that the disaggregated structure and relative ranking of states, respectively, generate status ambiguity and immobility, which both dissuade states from seeking higher moral status through improving their scores in the existing indices. We illustrate the patterns of status ambiguity and immobility present in the GPI-based system of stratification through an empirical analysis of the scores and rank positions of the United States, European Union (EU) members, and “rising powers” in five different indices in the past decade.

Framework on Performance Management in Automotive Industry: A Case Study

The purpose of this research is to identify the risks and deficiencies that affect the performance of companies that provide vehicle after-sales services. Thus, this paper highlights the results of a comparative study based on a questionnaire conducted at the level of six brands in the automotive industry. A model was developed to investigate the factors that affect the global performance of the after-sales sector and the authenticity of the information related to the issue studied. Moreover, based on the collected data, this study evaluates the strategies related to performance management used by the organizations studied. In the end, even if the results showed a score of 81% on the questionnaire, we found that companies that provide vehicle after-sales services have not implemented and do not maintain totally the strategies related to performance management. Consequently, the need for change can be emphasized. Based on the analyzed data in the second part of the paper, we identified deficiencies and risks in terms of the organization, operation and management of the service units. These results confirm that the vehicle repair service has a significant influence on employee and customer satisfaction, on the quality of the vehicles repaired and the repair completion time.

Numerical Investigation of Thermal-Flow Characteristics in Heat Exchanger with Various Tube Shapes

In this study, eight configurations of oval and flat tubes in annular finned-tube thermal devices are examined and compared with the conventional circular tube. The objective is to assess the effect of tube flatness and axis ratio of the oval tube on thermal-flow characteristics of a three-row staggered bank for Re (2600 ≤ Re ≤ 10,200). It has been observed that the thermal exchange rate and Colburn factor increase according to the axis ratio and the flatness, where O1 and F1 provide the highest values. O1 produces the lowest friction factor values of all the oval tubes at all Re, and F4 gives 13.2–18.5% less friction than the other tube forms. In terms of performance evaluation criterion, all of the tested tubes outperformed the conventional circular tube (O5), with O1 and F1 obtaining the highest values. The global performance criterion of O1 has been found to be 9.6–45.9% higher as compared to the other oval tube geometries at lower values of Re, and the global performance criterion increases with the increase in flatness. The F1 tube shape outperforms all the examined tube designs; thus, this tube geometry suggests that it be used in energy systems.

Kinematic Analysis of a Parallel Manipulator Driven by Perpendicular Linear Actuators

In this paper, a goniometer-type specimen stage with a linear actuation mechanism mounted on a rotation mechanism is introduced. The linear actuation mechanism was modeled as a spatial parallel manipulator consisting of a moving body, three linear actuators, and an anti-rotation mechanism. The three linear actuators were arranged perpendicular to each other. In the specimen stage, the linear actuators were in ball contact with the surface of a holder designed to hold a specimen. For the parallel manipulator, the ball contact was replaced with two prismatic joints and a spherical joint. The mobility of the manipulator without the anti-rotation mechanism was one degree of freedom greater than the number of actuators. Therefore, the redundant one degree-of-freedom motion was restrained using an anti-rotation mechanism with three rotation joints and two prismatic joints. The inverse and direct kinematics of the goniometer mechanism were derived and verified. In addition, the inverse Jacobian was derived, and local and global performance indices were analyzed by the terms of manipulability and isotropy. Finally, the goniometer-type specimen stage was designed by the global performance indices.

The impact of calibrating soil organic carbon model Yasso with multiple datasets

Soil Organic Carbon (SOC) models are important tools in determining global SOC distributions and how carbon stocks are affected by climate change. Their performances are, however, affected by data and methods used to calibrate them. Here we study how the Yasso SOC model performs if calibrated individually or with multiple datasets and how the chosen calibration method affected the parameter estimation. We found that when calibrated with multiple datasets, the model showed a better global performance compared to a single dataset calibration. Furthermore, our results show that more advanced calibration algorithms should be used for SOC models due to the multiple local maximas in the likelihood space.

An Investigation of Heat Transfer and Pressure Drop Enhancement of Various Perforated Circular Finned Tubes at Different Tube Tilt Angles

The thermal and flow performance of the circular annular finned tube heat exchanger with perforated fins were investigated numerically using ANSYS Fluent 2020 software, RNG k-e model with enhanced wall treatment, global performance criterion was introduced as evaluation factor of the heat exchanger performance, the parameters to be investigated were the number of holes, size of hole, tilt angle of the finned tube, fin height and spacing between fins. Agreement was found with literature that the tilt angle causes increase in heat transfer rate and increase in the pressure drop as well, but the change the global performance criterion as function to tilt angle depends on the fin heights, for higher fin heights the effective change of the pressure drop become greater than the increase in the heat transfer rate and the contrast occur in the cases of smaller fin heights, we have found that the perforation in tilted annular circular finned tubes causes an increase in the heat transfer rate and an enhancement in the total heat exchanger performance, increasing the number of holes will enhance the performance of the heat exchanger and the spacing increase reduces the heat exchanger performance.