Search results

The purpose of this paper is to present a multi‐objective and multi‐point optimization method to support the preliminary design of an unmixed turbofan mounted on a sample UAV/UCAV aircraft.

An in‐house multi‐objective evolutionary algorithm, a flight simulator and a validated engine simulator are implemented and joined together using object‐oriented programming.

Optimal values are found of the pressure ratio and corrected mass flow of both the engine fan and compressor as they operate in on/off design conditions (multipoint approach), as well as the engine by‐pass ratio, that contextually minimize time and engine fuel consumption required to cover a fixed trajectory (mission profile). Furthermore, the optimal distribution of the thermodynamic quantities along the trajectory is determined.

The research deals with a preliminary design of an engine, therefore no detailed engine geometry can be found.

The paper shows how a multiobjective and multipoint approach to the design of an engine can affect the choice of the engine architecture. In particular, major practical implications regard how the mission profile can affect the choice of the design point: in fact, there is no longer a definitive design point but the design of a UAV/UCAV should be addressed as a function of the mission profile.

The paper presents a multiobjective and multipoint approach to engine optimization as a function of the mission profile.

This bibliography contains references to papers, conference proceedings, theses and books dealing with finite strip, finite prism and finite layer analysis of structures, materially and/or geometrically linear or non‐linear.

This paper synthesizes existing experimental research in the area of investor perceptions and offers directions for future research. Investor-related experimental research has grown substantially, especially in the last decade, as it has made valuable contributions in establishing causal links, examining underlying process measures, and examining areas with little available data. Within this review, I examine 121 papers and identify three broad categories that affect investor perceptions: information format, investor features, and disclosure credibility. Information format describes how investors are influenced by information salience, information labeling, reporting and accounting complexity, financial statement recognition, explanatory disclosures, and proposed disclosure changes. Investor features describes investors’ use of heuristics, investor preferences, and the effect of investor experience. Disclosure credibility is influenced by external and internal assurance, management credibility, disclosure characteristics, and management incentives. Using this framework, I summarize the existing research and identify areas that would benefit from additional research.

A three-dimensional (3D) printing error simulation approach is proposed to analyze the influence of tilted vertical beams on the 3D printing accuracy. The purpose of this study is to analyze the influence of such errors on printing accuracy and printing quality for delta-robot 3D printer.

First, the kinematic model of a delta-robot 3D printer with an ideal geometric structure is proposed by using vector analysis. Then, the normal kinematic model of a nonideal delta-robot 3D robot with tilted vertical beams is derived based on the above ideal kinematic model. Finally, a 3D printing error simulation approach is proposed to analyze the influence of tilted vertical beams on the 3D printing accuracy.

The results show that tilted vertical beams can indeed cause 3D printing errors and further influence the 3D printing quality of the final products and that the 3D printing errors of tilted vertical beams are related to the rotation angles of the tilted vertical beams. The larger the rotation angles of the tilted vertical beams are, the greater the geometric deformations of the printed structures.

Three vertical beams and six horizontal beams constitute the supporting parts of the frame of a delta-robot 3D printer. In this paper, the orientations of tilted vertical beams are shown to have a significant influence on 3D printing accuracy. However, the effect of tilted vertical beams on 3D printing accuracy is difficult to capture by instruments. To reveal the 3D printing error mechanisms under the condition of tilted vertical beams, the error generation mechanism and the quantitative influence of tilted vertical beams on 3D printing accuracy are studied by simulating the parallel motion mechanism of a delta-robot 3D printer with tilted vertical beams.

Due to the connectivity of the multiple devices and the systems on the same network, rapid development has become possible in Internet of Things (IoTs) for the last decade. But, IoT is mostly affected with severe security challenges due to the potential vulnerabilities happened through the multiple connectivity of sensors, devices and system. In order to handle the security challenges, literature presents a handful of security protocols for IoT. The purpose of this paper is to present a threat profiling and elliptic curve cryptography (ECC)-based mutual and multi-level authentication for the security of IoTs. This work contains two security attributes like memory and machine-related attributes for maintaining the profile table. Also, the profile table stores the value after encrypting the value with ECC to avoid storage resilience using the proposed protocol. Furthermore, three entities like, IoT device, server and authorization centre (AC) performs the verification based on seven levels mutually to provide the resilience against most of the widely accepted attacks. Finally, DPWSim is utilized for simulation of IoT and verification of proposed protocol to show that the protocol is secure against passive and active attacks.

In this work, the authors have presented a threat profiling and ECC-based mutual and multi-level authentication for the security of IoTs. This work contains two security attributes like memory and machine-related attributes for maintaining the profile table. Also, the profile table stores the value after encrypting the value with ECC to avoid storage resilience using the proposed protocol. Furthermore, three entities like, IoT device, server and AC performs the verification based on seven levels mutually to provide the resilience against most of the widely accepted attacks.

DPWSim is utilized for simulation of IoT and verification of the proposed protocol to show that this protocol is secure against passive and active attacks. Also, attack analysis is carried out to prove the robustness of the proposed protocol against the password guessing attack, impersonation attack, server spoofing attack, stolen verifier attack and reply attack.

This paper presents a threat profiling and ECC-based mutual and multi-level authentication for the security of IoTs.

In typical model-based calibration, linearization errors are derived inevitably, and non-negligible negative impact will be induced on the identification results if the rotational kinematic errors are not small enough or the lengths of links are too long, which is common in the industrial cases. Thus, an accurate two-step kinematic calibration method minimizing the linearization errors is presented for a six-DoF serial robot to improve the calibration accuracy.

The negative impact of linearization on identification accuracy is minimized by removing the responsible linearized kinematic errors from the complete kinematic error model. Accordingly, the identification results of the dimension-reduced new model are accurate but not complete, so the complete kinematic error model, which achieves high identification accuracy of the rest of the error parameters, is combined with this new model to create a two-step calibration procedure capable of highly accurate identification of all the kinematic errors.

The proportions of linearization errors in measured pose errors are quantified and found to be non-negligible with the increase of rotational kinematic errors. Thus, negative impacts of linearization errors are analyzed quantitatively in different cases, providing the basis for allowed kinematic errors in the new model. Much more accurate results were obtained by using the new two-step calibration method, according to a comparison with the typical methods.

This new method achieves high accuracy with no compromise on completeness, is easy to operate and is consistent with the typical method because the second step with the new model is conveniently combined without changing the sensors or measurement instrument setup.

The purpose of this study is to develop a modified parameter identification method and a novel measurement method to calibrate a 3 degrees-of-freedom (3-DOF) parallel tool head. This parallel tool head is a parallel mechanism module in a five-axes hybrid machine tool. The proposed parameter identification method is named as the Modified Singular Value Decomposition (MSVD) method. It aims to overcome the difficulty of choosing the algorithm parameter in the regularization identification method. The novel measurement method is named as the vector projection (VP) method which is developed to expand the measurement range of self-made measurement implements.

Newton Iterative Algorithm based on Least Square Method is analyzed by using the Singular Value Decomposition method. Based on the analysis result, the MSVD method is proposed. The VP method transforms the angle measurement into the displacement measurement by taking full advantage of the ability that the 3-DOF parallel tool head can move in the X – Y plane.

The kinematic calibration approach is verified by calibration simulations, a Rotation Tool Center Point accuracy test and an experiment of machining an “S”-shaped test specimen.

The kinematic calibration approach with the MSVD method and VP method could be successfully applied to the 3-DOF parallel tool head and other 3-DOF parallel mechanisms.

Organizations remain a vital sociological topic, but organizational sociology, as a subfield, has evolved significantly since its inception. In this paper, I argue that organization sociology is becoming increasingly disconnected from organizational theory, as currently conceived. The focus of sociological research on organizations has become more empirically grounded in the study of social problems and how organizations contribute to them. Sociologists continue to see organizations as important actors in society that play a role in shaping social order and as contexts in which social processes play out. I propose two main sociological approaches for organizational research, which I describe as “organizations within society” and “society within organizations.” The first approach examines the role of organizations as building blocks of social structure and as social actors in their own right. The second approach treats organizations as platforms and locations of social interactions and the building of community. These approaches are somewhat disconnected from the sort of grand theorizing that characterizes much of organizational theory. I argue that the problem-oriented sociology of these two approaches offers a vital way for organizational scholars to expand and theoretically revitalize the field.

In recent years, the proliferation of social commerce (s-commerce) has attracted many researchers to investigate the drivers of individuals' intentions. However, the empirical results reported in these studies were fragmented and inconsistent. This has led various meta-analyses to synthesize these findings, but without including a large number of s-commerce studies. In addition, investigating meta-analytically the effects of moderators such as the six dimensions of Hofstede's national culture is still lacking.

Drawing on nine theories and models, this meta-analysis aims to summarize the findings reported in 109 s-commerce studies published between 2011 and 2021 and to examine the moderating role of national culture. The correlation coefficient (r) has been used as the main effect size for this study. Based on the random-effects method, the CMA V3 software has been employed to calculate the weighted mean effect sizes.

The meta-analysis results showed that all the 11 hypothesized direct relationships are positive and significant. The moderator results also revealed that five out of six cultural dimensions significantly moderate the examined associations.

This research serves to enrich the existing s-commerce literature by addressing contradictory and mixed results reported in the empirical studies. This study is one of the first of its kind to investigate the role of Hofstede's six cultural dimensions as moderators in the field of s-commerce using the meta-analytic techniques.

In recent years, China’s growing global economic influence has attracted more foreign workers, requiring leaders to have effective communication skills to manage diverse personnel to drive innovations. Although previous research studies revealed the effects of a leader’s motivating language (ML) on employee’s innovativeness, the mechanism and the boundary conditions for stimulating the relationship between ML and innovative work behavior (IWB) are scarce. Therefore, this study aims to examine employee’s creative self-efficacy (CSE) as a mechanism and coworker support (CS) as a boundary condition in the relationship between ML’s dimensions and IWB.

To test the moderated mediation model, this study collected the data from 283 workers and their respective supervisors at a Beijing-based multinational network company. The research applied a quantitative approach. SPSS and AMOS were used to analyze the data.

ML’s dimensions are positively linked to IWB. CSE was found as a mediator in these relationships. CS did not play its moderation roles on ML – CSE, ML – IWB direct or ML – IWB indirect (via CSE) links. ML’s direction-giving speech is found to be more effective in predicting CSE and IWB.

This is the first paper to examine the impacts of the three dimensions of ML on IWB.