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In a boundary layer ingestion (BLI) propulsion system, the fan operates continuously under distorted inflow conditions, leading to an increment of aerodynamic loss and in turn impacting the potential fuel burn reduction of the aircraft. Usually, in the preliminary design stage of a BLI propulsion system, it is essential to assess the impact of fuselage boundary layer fluids on fan aerodynamic performances under various flight conditions. However, the hub region flow loss is one of the major loss sources in a fan and would greatly influence the fan performances. Moreover, the inflow distortion also results in a complex and highly nonlinear mapping relation between loss and local physical parameters. It will diminish the prediction accuracy of the commonly used low-fidelity computational approaches which often incorporate traditional physics-based loss models, reducing the reliability of these approaches in evaluating fan performances. Meanwhile, the high-fidelity full-annulus unsteady Reynolds-averaged Navier–Stokes (URANS) approach, even though it can give rather accurate loss predictions, is extremely time-consuming. This study aims to develop a fast and accurate hub loss prediction method for a BLI fan under distorted inflow conditions.

This paper develops a data-driven hub loss prediction method for a BLI fan under distorted inflows. To improve the prediction accuracy and applicability, physical understandings of hub flow features are integrated into the modeling process. Then, the key physical parameters related to flow loss are screened by conducting a sensitivity analysis of influencing parameters. Next, a quasi-steady assumption of flow is made to generate a training sample database, reducing the computational time by acquiring one single sample from the highly time-consuming full-annulus URANS approach to a cost-efficient single-blade-passage approach. Finally, a radial basis function neural network is used to establish a surrogate model that correlates the input parameters and the output loss.

The data-driven hub loss model shows higher prediction accuracy than the traditional physics-based loss models. It can accurately capture the circumferentially and radially nonuniform variation trends of the losses and the associated absolute magnitudes in a BLI fan under different blade load, inlet distortion intensity and rotating speed conditions. Compared with the high-fidelity full-annulus URANS results, the averaged relative prediction errors of the data-driven hub loss model are kept less than 10%.

The originality of this paper lies in developing a new method for predicting flow loss in a BLI fan rotor blade hub region. This method offers higher prediction accuracy than the traditional loss models and lower computational time cost than the full-annulus URANS approach, which could realize fast evaluations of fan aerodynamic performances and provide technical support for designing high-performance BLI fans.

The purpose of this study is to identify the motivating factors that influence repeat participation among university student volunteers at a world-renowned food festival. The direct and indirection relationship (through attitude toward volunteering) was tested. Additionally, the moderating role of class standing between student volunteers' motivations, attitudes and repeat volunteer intention was assessed.

Researchers applied a quantitative methodology to data collected after the festival volunteering experience. The research team collected 205 useable surveys from university student volunteers at the Food Network and Cooking Channel South Beach Wine and Food Festival (SOBEWFF®). Structural equation modeling was used to test the relationships among volunteer motivations, attitude toward volunteering and intention to continue volunteering. Lastly, a multiple-group analysis was applied to test the moderating role of class standing.

The results showed the motivating factors purposive, personal enrichment and family traditions were significant in predicting attitude toward volunteering. These motivations did not significantly affect intention to continue volunteering; thus researchers found only an indirect relationship (through attitude toward volunteering) between volunteering motivations and intention to continue volunteering. Additionally, a positive attitude toward volunteering resulted in an intention to continue volunteering. Lastly, testing the moderating role of class standing revealed significant results on three pathways, indicating that students are motivated to volunteer differently based upon class standing (freshman through junior vs. senior, graduate).

The data were collected prior to COVID-19, and the ways in which COVID-19 has impacted the events industry and the scape of future events are yet to be determined.

Festival organizers and managers should appeal to different motivations of potential student volunteers depending on their class standing. For example, results of the moderator “class standing” indicated that the relationship between personal enrichment motivation and attitude toward volunteering was strongest and significant among freshmen, sophomores and juniors, but insignificant among seniors and graduate students. Thus, freshmen through juniors are more highly motivated to obtain practical experiences, and this motivation results in a positive attitude toward volunteering.

This study tests the moderating role of class standing to help predict intention to continue volunteering at a special event. The research is further unique by extending an understanding of the validity and reliability of the special events volunteer motivations scale.

For an axial-flow compressor rotor, the upstream inflow conditions will vary as the aircraft faces harsh flight conditions (such as taking off, landing or maneuvering) or the whole compressor operates at off-design conditions. With the increase of upstream boundary layer thickness, the rotor blade tip will be loaded and the increased blade load will deteriorate the shock/boundary layer interaction and tip leakage flows, resulting in high aerodynamic losses in the tip region. The purpose of this paper is to achieve a better flow control for tip secondary flows and provide a probable design strategy for high-load compressors to tolerate complex upstream inflow conditions.

This paper presents an analysis and application of shroud wall optimization to a typical transonic axial-flow compressor rotor by considering the inlet boundary layer (IBL). The design variables are selected to shape the shroud wall profile at the tip region with the purpose of controlling the tip leakage loss and the shock/boundary layer interaction loss. The objectives are to improve the compressor efficiency at the inlet-boundary-layer condition while keeping its aerodynamic performance at the uniform condition.

After the optimization of shroud wall contour, aerodynamic benefits are achieved mainly on two aspects. On the one hand, the shroud wall optimization has reduced the intensity of the tip leakage flow and the interaction between the leakage and main flows, thereby decreasing the leakage loss. On the other hand, the optimized shroud design changes the shock structure and redistributes the shock intensity in the spanwise direction, especially weakening the shock near the tip. In this situation, the shock/boundary layer interaction and the associated flow separations and wakes are also eliminated. On the whole, at the inlet-boundary-layer condition, the compressor with optimized shroud design has achieved a 0.8 per cent improvement of peak efficiency over that with baseline shroud design without sacrificing the total pressure ratio. Moreover, the re-designed compressor also maintains the aerodynamic performance at the uniform condition. The results indicate that the shroud wall profile has significant influences on the rotor tip losses and could be properly designed to enhance the compressor aerodynamic performance against the negative impacts of the IBL.

The originality of this paper lies in developing a shroud wall contour optimization design strategy to control the tip leakage loss and the shock/boundary layer interaction loss in a transonic compressor rotor. The obtained results could be beneficial for transonic compressors to tolerate the complex upstream inflow conditions.

The purpose of this research paper is to examine whether enduring involvement theory plays a role in predicting craft beer and food festival visitors' experience of the festivalscape. Though craft beer and brewing is a growing area of research, there has been limited studies and theory application in this area. Around the world, craft breweries are increasing in number and producing more unique styles of beer as the demand for craft beer increases. Craft beer consumers visit many of these breweries and are attracted to craft beer festivals in which they can sample multiple local, regional, national and international craft beers.

A quantitative methodology was used based on data collected at the site of the festival. Researchers collected 204 useable surveys from visitors attending the North Miami Brewfest in North Miami, Florida, USA. Structural equation modeling was employed to examine the relationships among enduring involvement, festivalscape, satisfaction, revisit intention and word-of-mouth.

The results revealed that enduring involvement is significant in predicting all four factors of festivalscape (food/beverage quality, convenience, facility and festival staff). The festivalscape factors facility, food quality and festival staff predicted festival attendee satisfaction which in turn predicted both revisit intention and word-of-mouth. However, the festivalscape factor convenience did not influence satisfaction.

The authors surveyed only one festival in one region in South Florida. Further studies can survey multiple festivals in multiple regions to increase the generalizability of the research model. Enduring involvement theory could be applied to other niche areas in hospitality and tourism in the future (in addition to craft beer tourism).

Craft beer festival organizers should appeal to craft beer clubs, breweries and publications to attract those with a commitment to the craft beer industry to their event. People with an enduring, lasting commitment to craft beer are more likely to have a positive experience of the festivalscape at the event. Lastly, festival organizers should focus on the festivalscape factors facility, festival staff and food and beverage quality to influence satisfaction at the event.

This project applies enduring involvement theory in a festival setting. The research is further unique by adding enduring involvement as a predictor of festivalscape experience.

With the increasing heat dissipation of electronic devices, the cooling demand of electronic products is increasing gradually. A water-cooled microchannel heat exchanger is an effective cooling technology for electronic equipment. The structure of a microchannel has great impact on the heat transfer performance of a microchannel heat exchanger. The purpose of this paper is to analyze and compare the fluid flow and heat transfer characteristic of a microchannel heat exchanger with different reentrant cavities.

The three-dimensional steady, laminar developing flow and conjugate heat transfer governing equations of a plate microchannel heat exchanger are solved using the finite volume method.

At the flow rate range studied in this paper, the microchannel heat exchangers with reentrant cavities present better heat transfer performance and smaller pressure drop. A microchannel heat exchanger with trapezoidal-shaped cavities has best heat transfer performance, and a microchannel heat exchanger with fan-shaped cavities has the smallest pressure drop.

The fluid is incompressible and the inlet temperature is constant.

It is an effective way to enhance heat transfer and reduce pressure drop by adding cavities in microchannels and the data will be helpful as guidelines in the selection of reentrant cavities.

This paper provides the pressure drop and heat transfer performance analysis of microchannel heat exchangers with various reentrant cavities, which can provide reference for heat transfer augmentation of an existing microchannel heat exchanger in a thermal design.

Collaborative robots (cobots) are widely used in various manipulation tasks within complex industrial environments. However, the manipulation capabilities of cobot manipulation planning are reduced by task, environment and joint physical constraints, especially in terms of force performance. Existing motion planning methods need to be more effective in addressing these issues. To overcome these challenges, the authors propose a novel method named force manipulability-oriented manipulation planning (FMMP) for cobots.

This method integrates force manipulability into a bidirectional sampling algorithm, thus planning a series of paths with high force manipulability while satisfying constraints. In this paper, the authors use the geometric properties of the force manipulability ellipsoid (FME) to determine appropriate manipulation configurations. First, the authors match the principal axes of FME with the task constraints at the robot’s end effector to determine manipulation poses, ensuring enhanced force generation in the desired direction. Next, the authors use the volume of FME as the cost function for the sampling algorithm, increasing force manipulability and avoiding kinematic singularities.

Through experimental comparisons with existing algorithms, the authors validate the effectiveness and superiority of the proposed method. The results demonstrate that the FMMP significantly improves the force performance of cobots under task, environmental and joint physical constraints.

To improve the force performance of manipulation planning, the FMMP introduces the FME into sampling-based path planning and comprehensively considers task, environment and joint physical constraints. The proposed method performs satisfactorily in experiments, including assembly and in situ measurement.

An accurate and fast dynamic analysis innovative approach for vehicle parts is provided for engineering practice.

This paper presents an innovative dynamic analysis approach for vehicle parts based on parallel optimization algorithm with CUDA.

This project is supported by the National Science Foundation of China (No. 51805076, No. U1708255 and No. 51775093), the Fundamental Research Funds for the Central Universities (No. N170503011) and the Natural Science Foundation of Liaoning Province, China (No. 20180551058).

This paper presents an innovative approach for vehicle parts using parallel optimization algorithm based on CUDA, which can improve the computing accuracy and speed effectively.

The relationship between sex and tourism remains ambiguous in the tourism literature. Few studies have examined the underlying motivations behind sex-driven travel, and little is known about factors inhibiting tourists' procurement of commercial sex when traveling. Therefore, this study explored male Chinese tourists' perceived constraints during decision-making and developed a comprehensive scale to assess constraints to commercial sex consumption overseas.

Data were obtained from male Chinese tourists purchasing commercial sex while traveling overseas. This study involved a four-stage process as recommended by Churchill (1979) for scale development research. In Stage 1, preliminary items were generated through a comprehensive review of the constraints literature and in-depth interviews with 16 sex tourists, which generated an initial 26 items. During the second stage to purify the measurement items, six items were eliminated, resulting in 20 items. Stage 3 involved exploratory factor analysis (N = 275) to extract the scale's underlying factor structure. Results revealed a five-factor structure with sufficient evidence of internal reliability given Cronbach's alpha coefficients between 0.722 and 0.843. The final stage included confirmatory factor analysis (N = 259) to verify the scale's reliability and validity.

Ultimately, 20 items were developed to measure sex tourists' perceived constraints toward engaging in commercial sex services overseas based on five factors: structural constraints, intrapersonal constraints, interpersonal constraints, value conflicts and service supply–related constraints.

This study advances the scope of sex tourism research by verifying how these five constraints are independent, generalized and can influence the procurement of sexual services overseas. This study is the first in sex tourism research to explore the difficulties facing sex tourists. Results offer marketers important insight on how to better address these constraints while providing a safe and legal sex tourism experience.

Knowledge search is considered a broad concept and semi-intentional behavior. The path and boundary conditions through which search strategies affect intra-organizational knowledge creation remain elusive. Drawing on recombinant search theory and knowledge-based view, the authors seek to identify knowledge complexity as an important intermediate variable between knowledge search and innovation performance, such as research and development (R&D) output and R&D output quality. A second goal of this study is to examine the moderating roles of government support and technological turbulence.

The authors employed a longitudinal panel of 609 global pharmaceutical firms and obtained the firms' patent records from 1980 to 2015 for the analysis. The authors used generalized estimating equations (GEE) to evaluate the models and tested the consistency via panel fixed-effects estimations.

The authors' findings show that organizational routine-guided search has a negative effect on knowledge complexity, while routine-changing search exerts a positive impact on knowledge complexity. Governmental support and technological turbulence moderate these relationships. Notably, knowledge complexity has an inverted U-shaped relationship with innovation performance.

The authors' research context, the pharmaceutical industry, may constrain the generalizability of our findings. In addition, potential types of routine-guided and routine-changing search behaviors were not considered.

Despite these limitations, this study offers important implications. First, knowledge complexity transmits the effects of knowledge search on innovation performance. Practitioners should balance routine-guided and routine-changing search processes to build and manage complex knowledge. Second, a moderate level of knowledge complexity is the key to good R&D output and R&D output quality.

The study identifies knowledge complexity as one important intermediate variable between knowledge search behaviors and intra-organizational knowledge creation.

The purpose of this paper is to present a simple yet effective force control scheme for collaborative robots by addressing the problem of disturbance rejection in joint torque: inherent actuator flexibility and nonlinear friction.

In this paper, a joint torque controller with an extended state observer is used to decouple the joint actuators from the multi-rigid-body system of a constrained robot and compensate the motor friction. Moreover, to realize robot force control, the authors embed this controller into the impedance control framework.

Results have been given in simulations and experiments in which the proposed joint torque controller with an extended state observer can effectively estimate and compensate the total disturbance. The overall control framework is analytically proved to be stable, and further it is validated in experiments with a robot testbed.

With the proposed robot force controller, the robot is able to change its stiffness in real time and therefore take variable tasks without any accessories, such as the RCC or 6-DOF F/T sensor. In addition, programing by demonstration can be realized easily within the proposed framework, which makes the robot accessible to unprofessional users.

The main contribution of the presented work is the design of a model-free robot force controller with the ability to reject torque disturbances from robot-actuator coupling effect and motor friction, applicable for both constrained and unconstrained environments. Simulation and experiment results from a 7-DOF robot are given to show the effectiveness and robustness of the proposed controller.