scholarly journals Passive hovering of a flexible -flyer in a vertically oscillating airflow

2019 ◽  
Vol 878 ◽  
pp. 113-146
Author(s):  
Xiang Zhang ◽  
Guowei He ◽  
Shizhao Wang ◽  
Xing Zhang
Keyword(s):  
Postural Stability ◽  
Driving Frequency ◽  
Spring Stiffness ◽  
Angular Oscillation ◽  
Symmetry Properties ◽  
Opposing Effects ◽  
Parameter Values ◽  
Insight Into ◽  
Study Offer ◽  
The Ideal

We numerically investigate the passive flight of a flexible $\unicode[STIX]{x039B}$-flyer in a vertically oscillating airflow with zero mean stream. The flexibility of the flyer is introduced by a torsion spring installed at the hinged joint. We study the effects of spring stiffness, density, resting angle and actuation efforts on the hovering performance. The results suggest that the occurrence of resonance in flexible flyers can result in significantly different performances in flexible and rigid flyers. It is found that flexibility can have two opposing effects, reducing or increasing the actuation efforts for hovering, depending on the range of driving frequency. This result is explained by the modulation of relative motion between the flyer and the imposed background flow due to the involvement of passive angular oscillation. The angular oscillation patterns, the wake symmetry properties and the postural stability behaviours under different driving conditions are also explored. Based on the findings of the present study, the ideal parameter values for stable hovering are suggested. The results of this study offer novel insight into the mechanism by which the flexibility of the flyer affects the passive hovering performance.

scholarly journals Reducing the metabolic energy of walking and running using an unpowered hip exoskeleton

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Tiancheng Zhou ◽  
Caihua Xiong ◽  
Juanjuan Zhang ◽  
Di Hu ◽  
Wenbin Chen ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Design Method ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Spring Stiffness ◽  
Spatiotemporal Parameters ◽  
The Common ◽  
Hip Flexion ◽  
Optimal Stiffness ◽  
Insight Into

Abstract Background Walking and running are the most common means of locomotion in human daily life. People have made advances in developing separate exoskeletons to reduce the metabolic rate of walking or running. However, the combined requirements of overcoming the fundamental biomechanical differences between the two gaits and minimizing the metabolic penalty of the exoskeleton mass make it challenging to develop an exoskeleton that can reduce the metabolic energy during both gaits. Here we show that the metabolic energy of both walking and running can be reduced by regulating the metabolic energy of hip flexion during the common energy consumption period of the two gaits using an unpowered hip exoskeleton. Methods We analyzed the metabolic rates, muscle activities and spatiotemporal parameters of 9 healthy subjects (mean ± s.t.d; 24.9 ± 3.7 years, 66.9 ± 8.7 kg, 1.76 ± 0.05 m) walking on a treadmill at a speed of 1.5 m s−1 and running at a speed of 2.5 m s−1 with different spring stiffnesses. After obtaining the optimal spring stiffness, we recruited the participants to walk and run with the assistance from a spring with optimal stiffness at different speeds to demonstrate the generality of the proposed approach. Results We found that the common optimal exoskeleton spring stiffness for walking and running was 83 Nm Rad−1, corresponding to 7.2% ± 1.2% (mean ± s.e.m, paired t-test p < 0.01) and 6.8% ± 1.0% (p < 0.01) metabolic reductions compared to walking and running without exoskeleton. The metabolic energy within the tested speed range can be reduced with the assistance except for low-speed walking (1.0 m s−1). Participants showed different changes in muscle activities with the assistance of the proposed exoskeleton. Conclusions This paper first demonstrates that the metabolic cost of walking and running can be reduced using an unpowered hip exoskeleton to regulate the metabolic energy of hip flexion. The design method based on analyzing the common energy consumption characteristics between gaits may inspire future exoskeletons that assist multiple gaits. The results of different changes in muscle activities provide new insight into human response to the same assistive principle for different gaits (walking and running).

Contrasting profiles of product returners and keepers

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Dong Hwan Lee
Keyword(s):  
New York ◽  
Household Income ◽  
Field Survey ◽  
Survey Study ◽  
Content Type ◽  
Demographic Profiles ◽  
Post Purchase ◽  
Practical Implications ◽  
Insight Into ◽  
Study Offer

Purpose This paper aims to investigate whether the consumers who return a product and those who end up keeping a product after experiencing post-purchase dissonance (PPD) possess distinct underlying characteristics. Design/methodology/approach Field survey study consisting of two separate surveys conducted with consumers of New York City and neighboring areas of New York and New Jersey. Findings Product returners and keepers exhibited disparate demographic profiles regarding gender and household income, along with ethnicity to some extent. The two groups also exhibited different predispositions with regard to confidence in the purchase decision and expectations about their purchase. Finally, returners and keepers were engaged in divergent thoughts, feelings and activities to cope with PPD. Practical implications The findings of this study offer marketing practitioners new knowledge and insight into understanding product returners and keepers and will assist them in developing strategies to reduce and manage increasing product returns by consumers more effectively. Originality/value This study is the first to present empirical evidence that product returners and keepers have distinct profiles of demographic characteristics and predispositions toward purchase. The study also has found divergent PPD coping strategies used by the two types of consumers, which exposes an obsolete understanding of PPD in the marketing literature.

scholarly journals New Insights on the Mechanism of Fatty Acids as Buccal Permeation Enhancers

Pharmaceutics ◽  
2018 ◽  
Vol 10 (4) ◽  
pp. 201 ◽  
Author(s):  
Cristina Padula ◽  
Silvia Pescina ◽  
Sara Nicoli ◽  
Patrizia Santi
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fluorescein Isothiocyanate ◽  
Penetration Enhancers ◽  
Systemic Delivery ◽  
Permeation Enhancers ◽  
Maximum Value ◽  
The Relationship ◽  
Insight Into ◽  
The Ideal

Buccal mucosa has recently received much attention as a potential route for systemic delivery of drugs, including biologics and vaccines. The aim of this work was to gain insight into the mechanism of fatty acids as buccal permeation enhancers, by studying the effect of a series of medium and long chain fatty acids on the permeation of a model high molecular weight and hydrophilic molecule, fluorescein isothiocyanate labelled dextran (FD-4, m.w. 4 kDa) across porcine esophageal epithelium. A parabolic relationship between fatty acid lipophilicity and enhancement was obtained, regardless of the presence and number of double bonds. The relationship, which resembles the well-known relationship between permeability and lipophilicity of transdermal delivery, presents a maximum value in correspondence of C10 (logP approx. 4). This is probably the ideal lipophilicity for the fatty acid to interact with the lipid domains of the mucosa. When the same analysis was performed on skin data, the same trend was observed, although the maximum value was reached for C12 (logP approx. 5), in agreement with the higher lipophilicity of the skin. The results obtained in the present work represent a significant advancement in the understanding of the mechanisms of action of fatty acids as buccal penetration enhancers.

scholarly journals Influence of additives on suspension structure

2021 ◽  
Vol 10 (1) ◽  
pp. 37-40
Author(s):  
Vesna Savić ◽  
Milica Martinović ◽  
Ivana Nešić ◽  
Jelena Živković ◽  
Ivana Gajić
Keyword(s):  
Zinc Oxide ◽  
The Other ◽  
Stability Tests ◽  
Polysorbate 20 ◽  
The Stability ◽  
Carbomer Gel ◽  
Suspension Structure ◽  
Insight Into ◽  
Study Offer ◽  
Measured Hardness

The aim of this study was to compare the stability and texture of three zinc oxide suspensions with different additives. Suspension 1 was made as official magistral formulation Suspensio album 7.5% from Formulae magistrales 2008. Suspension 2 was prepared when 1% carbomer gel was added to suspension 1 and suspension 3 was prepared when polysorbate 20 was added to suspension 2. After stability tests, texture analysis was performed on all suspensions. Following parameters were measured: hardness cycle 1, hardness cycle 2, cohesiveness, adhesiveness, resilience and springiness. The study showed that suspension 3 had the lowest value of hardness, and therefore the best spreadability. Also, suspension 3 was the least sticky of all three, since it was characterized with the lowest adhesiveness. Further, suspension 3 was the most cohesive and is predicted to withstand the stress during packing and use longer than others. On the other hand, the highest values of resilience and springiness were detected for suspension 1, while the lowest was related to suspension 2. Therefore, the best textural characteristics were assigned to suspension 3. This result is in accordance with the results of performed stability tests. The results of our study offer insight into potential improvements of the current magistral formulation Suspensio album 7.5%.

Impact of Age on Pay Satisfaction and Job Satisfaction Leading to Turnover Intention: A Study of Young Working Professionals in India

2011 ◽  
Vol 36 (4) ◽  
pp. 353-363 ◽  
Author(s):  
Rajashik Roy Choudhury ◽  
Varun Gupta
Keyword(s):  
Job Satisfaction ◽  
Turnover Intention ◽  
Turnover Intentions ◽  
Negative Relationship ◽  
Moderating Effect ◽  
Pay Satisfaction ◽  
The Relationship ◽  
Effect Of Age ◽  
Insight Into ◽  
Study Offer

In this study, the authors contribute insight into the relationship between pay satisfaction and turnover intention as well as between job satisfaction and turnover intention amongst young Indian professionals by segregating the respondents into two groups based on the median age. Data were collected from 230 working Indian executives, having median age of 25, from various industries such as Information Technology, Public Sector Units, Pharmacy, and Fast Moving Consumer Goods where they expressed their views on turnover intentions, job satisfaction & pay satisfaction in their respective organizations. The results revealed the negative relationship between turnover intention and job satisfaction and also between turnover intention and pay satisfaction. However, when age is introduced as a variable having a moderating effect on the above relationships, it was noticed that pay satisfaction is more significant than job satisfaction when it comes to intention to quit a job for employees who are relatively experienced having an age greater than the median age of 25; whereas, for employees less than the median age, turnover intention is driven more by job satisfaction than pay satisfaction. Findings from this study offer important implications for theory & research in turnover intention driven by factors like pay satisfaction and job satisfaction with the moderating effect of age of employees.

Collective (Mis)Representation of U.S. Immigration Laws

2021 ◽  
Vol 18 (5) ◽  
pp. 519-532
Author(s):  
Stephanie Pedron
Keyword(s):  
United States ◽  
The United States ◽  
Policy Outcomes ◽  
Immigration Policies ◽  
Collective Consciousness ◽  
Immigration Laws ◽  
Collective Representations ◽  
Insight Into ◽  
The U.S ◽  
The Ideal

This paper examines historic federal immigration policies that demonstrate how the United States has rendered entire groups of people living inside and outside of its territory as outsiders. Collective representations like the Statue of Liberty suggest that the U.S. is a nation that welcomes all immigrants, when in reality, the U.S. has historically functioned as a “gatekeeper” that excludes specific groups of people at different times. The concurrent existence of disparate beliefs within a society’s collective consciousness influences the public’s views toward citizenship and results in policy outcomes that contrast sharply from the ideal values that many collective representations signify. As restrictive immigration controls are refined, insight into how immigrant exclusion via federal policy has evolved is necessary to minimize future legislative consequences that have the potential to ostracize current and future Americans.

Discursive Inequity and the Internal Exclusion of Women Speakers

2019 ◽  
pp. 106591291987060 ◽  
Author(s):  
Edana Beauvais
Keyword(s):  
Historical Memory ◽  
Political Equality ◽  
Political Inequality ◽  
The Public ◽  
Political Exclusion ◽  
Group Members ◽  
The Public Sphere ◽  
Study Offer ◽  
Western Democracies ◽  
The Ideal

In today’s democracies, disempowered group members are no longer formally barred from the political arena. However, there is a concern that the historical memory of political inequality and exclusion remains as internalized cognitive dispositions, shaping behavior even after laws are changed. Focusing on the legacy of women’s political exclusion from the public sphere, I consider whether internal exclusions undermine women’s ability to influence political discourse even under conditions of formal political equality. All else being equal, do women and men in Western democracies have the same discursive influence? Are women particularly sensitive to men’s discursive authority? I help answer these questions using an experimental research design. The results of my study offer evidence that people are more willing to revise their opinions after hearing a man’s counterargument than after hearing a woman’s identical counterargument. This pattern appears to be driven by the way women respond to a man’s counterclaim. I discuss how gendered discursive inequities reinforce existing patriarchal structures, and the role that women inadvertently play in their own subjugation. I conclude by offering suggestions for better approximating the ideal of discursive gender equality.

Dynamic Topology Optimization of Compliant Mechanisms and Piezoceramic Actuators

2002 ◽  
Author(s):  
Hima Maddisetty ◽  
Mary Frecker
Keyword(s):  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Method ◽  
Mechanical Efficiency ◽  
Optimal Topology ◽  
Driving Frequency ◽  
Spring Stiffness ◽  
Piezoceramic Actuator ◽  
Near Resonance

A topology optimization method is developed to design a piezoelectric ceramic actuator together with a compliant mechanism coupling structure for dynamic applications. The objective is to maximize the mechanical efficiency with a constraint on the capacitance of the piezoceramic actuator. Examples are presented to demonstrate the effect of considering dynamic behavior compared to static behavior, and the effect of sizing the piezoceramic actuator on the optimal topology and the capacitance of the actuator element. Comparison studies are also presented to illustrate the effect of damping, external spring stiffness, and driving frequency. The optimal topology of the compliant mechanism is shown to be dependent on the driving frequency, the external spring stiffness, and if the piezoelectric actuator element is considered as design or non-design. At high driving frequencies, it was found that the dynamically optimized structure is very near resonance.

Restaurant tipping and customers’ susceptibility to emotional contagion

2016 ◽  
Vol 30 (7) ◽  
pp. 762-772 ◽  
Author(s):  
Paul Sergius Koku ◽  
Selen Savas
Keyword(s):  
Design Methodology ◽  
Emotional Contagion ◽  
Social Implications ◽  
Simultaneous Administration ◽  
Collectivist Culture ◽  
Content Type ◽  
Restaurant Managers ◽  
Practical Implications ◽  
Insight Into ◽  
Study Offer

Purpose This paper aims to examine the connection between restaurant tipping propensity and customers’ susceptibility to emotional contagion (EC) in an effort to shed more light on consumers’ inclination to pay more for a service than they are legally obligated to (that is to pay more than the price by tipping). Design/methodology/approach In this study, two different instruments (Tipping Motivations Scale and Emotional Contagion Scale) were simultaneously administered online to restaurant patrons. The simultaneous administration of the instruments allows the researchers to capture not only tipping propensity but also the linkage between tipping propensity and customers’ susceptibility to EC. Findings The results show that customers’ susceptibility to EC, social compliance and server actions has the most effect on intention to tip in restaurants in Turkey. These findings support the notion that universal human characteristics such as the tendency to reciprocate (Hatfield et al., 1993) influence consumers’ propensity to tip regardless of the culture. Research limitations/implications While the results of this study offer some insight into why restaurant patrons tip, the fact that the study was carried out only in Turkey which has a collectivist culture limits the generalizability of the results to other societies that may be individualistic in orientation. Practical implications The findings of this study can be used by restaurant managers in training their employees and improving their customer patronage, particularly patronage from repeat customers. Similarly, the results could be used by restaurant servers to improve their income. Social implications The results of the study have potential to enhance the mutually beneficial relationship that should exist between restaurants and restaurant patrons. Indirectly, the results of the study could improve collective societal good. Originality/value This study, to the best of the authors’ knowledge, is one of the first to use the Tipping Motivations Scale (Whaley et al., 2014) in a different culture (Eurasia) and explain consumers’ tipping propensity explicitly using the concept of EC.

A study on health care consumers’ diabetes term usage across identified categories

2014 ◽  
Vol 66 (4) ◽  
pp. 443-463 ◽  
Author(s):  
Jin Zhang ◽  
Yiming Zhao ◽  
Alexandra Dimitroff
Keyword(s):  
Health Care ◽  
Web Sites ◽  
Body Part ◽  
Consumer Health ◽  
Content Type ◽  
Usage Patterns ◽  
Use Behavior ◽  
Insight Into ◽  
Study Offer ◽  
Term Clustering

Purpose – The purpose of this paper is to investigate health care consumers’ diabetes term usage patterns based on Yahoo!Answers social question and answers (Q&A) forum, identified characteristics and relationships among terms within three pairs of related categories identified from the Q&A log, and revealed users’ diabetes term usage patterns. Design/methodology/approach – The Q&A analysis method allowed first-hand investigation of massive data from health care consumers. Visual term clustering analysis across categories was conducted using a multi-dimensional scaling (MDS) visualization method which provides an intuitive and interactive way to explore and discover term association patterns in a visual environment. Closely related categories were identified and corresponding visual term clustering analyses between categories (Sign & Symptom and Organ & Body Part; Diagnosis and Test; and Diagnosis and Medication) as well at the term level were analyzed. Findings – The findings show that there are close relationships between terms in two related categories. Related terms were grouped and patterns were revealed. All the stress values of the MDS analyses fall below 0.10 and RSQ for each of the combined categories is over 0.90 which indicate the investigated terms were well clustered in the visual analyses. Originality/value – The study provides a unique research methodology for similar consumer health research studies. The results of this study offer insight into consumer health term use behavior, and enrich existing thesauri and subject heading lists, enhance diabetes-related web sites or portals, and improve effectiveness of internal search engines.

Sign in / Sign up

Export Citation Format

Share Document