Deployable Tensegrity Reflectors for Small Satellites

Future small satellite missions require low-cost, precision reflector structures with large aperture that can be packaged in a small envelope. Existing furlable reflectors form a compact package which, although narrow, is too tall for many applications.An alternative approach is proposed, consisting of a deployable “tensegrity” prism forming a ring structure that deploys two identical cable nets (front and rear nets) interconnected by tension ties; the reflecting mesh is attached to the front net. The geometric configuration of the structure has been optimized to reduce the compression in the struts of the tensegrity prism. A small-scale physical model has been constructed to demonstrate the proposed concept. A preliminary design of a 3-m-diam, 10-GHz reflector with a focal-length-to-diameter ratio of 0.4 that can be packaged within an envelope of 0.1 x 0.2 x 0.8 m^3 is presented

Perceived Risk and Trust Associated with Purchasing at Electronic Marketplaces

Understanding consumer behavior is of vital importance to consumer oriented e-business models today. In this paper we report on a study into the relationships between consumer perceptions of risk and trust and the intention to purchase at a C2C electronic marketplace. Distinguishing for electronic marketplace settings is that consumer behavior is subject to perceptions of both selling party and the institutional structures of the intermediary operating the system. Building upon the well-established literature of trust we consider the concepts of institutional trust and party trust. We extend this categorization by introducing the concepts of institutional risk and party risk. Next, we adopt the process of measurement instrument development as put forward by Churchill (1979). We develop measurement instruments for institutional trust (4 items), institutional risk (5 items) and party risk (4 items). All measurement scales contain acceptable alpha’s and are unidimensional. An empirical study is applied to explore the relationships between the risk and trust types and consumer purchase intention. The results reveal significant, direct effects of party trust and party risk. Second order effects of institutional trust and institutional risk are investigated and reported. The paper concludes with general observations and recommendations for further research

Results of REXUS12's Suaineadh Experiment : Deployment of a spinning space web in micro gravity conditions

On the 19th of March 2012, the Suaineadh experiment was launched onboard the sounding rocket REXUS12 (Rocket Experiments for University Students) from the Swedish launch base ESRANGE in Kiruna. The Suaineadh experiment served as a technology demonstrator for a space web deployed by a spinning assembly. The deployment of this web is a stepping stone for the development of ever larger structures in space. Such a structure could serve as a substructure for solar arrays, transmitters and/or antennas. The team was comprised of students from the University of Strathclyde (Glasgow, UK), the University of Glasgow (Glasgow, UK) and the Royal Institute of Technology (Stockholm, Sweden), designing, manufacturing and testing the experiment over the past 24 months. Following launch, the experiment was ejected from the ejection barrel located within the nosecone of the rocket. Centrifugal forces acting upon the space webs spinning assembly were used to stabilise the experiment’s platform. A specifically designed spinning reaction wheel, with an active control method, was used. Once the experiment’s motion was controlled, a 2 m by 2 m space web is released. Four daughter sections situated in the corners of the square web served as masses to stabilise the web due to the centrifugal forces acting on them. The four daughter sections contained inertial measurement units (IMUs). Each IMU provided acceleration and velocity measurements in all three directions. Through this, the positions of the four corners could be found through integration with respect to known time of the accelerations and rotations. Furthermore, four cameras mounted on the central hub section captured high resolution imagery of the deployment process. After the launch of REXUS12, the recovery helicopter was unable to locate the ejected experiment, but 22 pictures were received over the wireless connection between the experiment and the rocket. The last received picture was taken at the commencement of web deployment. Inspection of these pictures allowed the assumption that the experiment was fully functional after ejection, but perhaps through tumbling of either the experiment or the rocket, the wireless connection was interrupted. A recovery mission in the middle of August was only able to find the REXUS12 motor and the payload impact location

Non-pharmacological Management of Osteoporotic Vertebral Fractures: A Qualitative Analysis of Patient and Health-Care Professional Perspectives and Experiences

Introduction: Osteoporosis is a chronic disease that is characterized by a femoral neck or lumbar spine bone mineral density (BMD) less than 2.5 standard deviations below the mean of young adult females and encompasses changes to bone structure and bone quality, resulting in reduced strength and increased risk of fracture. Vertebral fractures are the most prevalent fracture in women with osteoporosis, affecting at least 20% of the older population. Vertebral fracture incidence and prevalence increase steadily with age and may appear without any symptoms. Once someone becomes symptomatic, they can experience a plethora of changes to their physical, social, and psychological functioning. Currently, information on non-pharmacological strategies to address consequences of vertebral fracture exist; however, lack of awareness of guidelines and inconsistences among the literature on the effect of non-pharmacological strategies may reduce their use and effectiveness. Objective: We have discovered that a gap in research exists in treatment/management of vertebral fractures, especially the use of non-pharmacological interventions. Considering that recommendations available are targeted towards individuals living with osteoporosis with or without vertebral fractures, our objective was to understand health care professionals' (HCPs) and individuals living with vertebral fractures’ experiences and perceptions of post-vertebral fracture rehabilitation, use of non-pharmacological strategies, and virtual rehabilitation. Methods: We performed a qualitative analysis using semi-structured interviews. Semi-structured interviews were conducted over web conference or telephone with both individuals living with vertebral fractures and HCPs within Canada. We used criterion sampling to recruit physicians (mainly geriatricians, family physicians and physiatrists) and allied health professionals (physiotherapists and nurses who work in geriatrics). We also used purposeful sampling to recruit individuals who are BoneFitTM trained, are specialists in osteoporosis care, are clinician researchers with experience with this population, or clinicians who self-declare an interest and see patients with osteoporosis. Individuals living with vertebral fractures were recruited from the Canadian Osteoporosis Patient Network (COPN), social media, and our Bone health and Exercise Science Lab email distribution list. Individuals living with vertebral fractures were included if they had been diagnosed with a vertebral fracture in the past, regardless of location of fracture. Questions for the interview guide were centred on non-pharmacological treatments such as exercise, spine sparing and movement modification, pain management, and nutrition. Considering that our intention is to inform the development of an online exercise/education intervention to provide information on exercises, nutrition, pain management and safe movement, we also asked about the attributes that both individuals living with vertebral fractures and HCPs would find important in the development of an online tool. To inform the semi-structured interview guide, we used the Diffusion of Innovations Theory, and the APEASE criteria. Interviews were audio recorded and transcribed verbatim. Once the interviews were completed and transcribed, two researchers conducted an inductive thematic and content analysis. Results: 13 HCPs (7F, 6M, aged 46 ± 12 years) were interviewed. Two major themes emerged from our interviews: acuity of fracture matters when selecting rehabilitation strategies; and roadblocks to rehabilitation. Early rehabilitation interventions included pain and osteoporosis medicine, education on harmful and high-risk movements, and non-pharmacological strategies to help reduce patient pain and increase early mobilization. Rehabilitation in the chronic stage of vertebral fractures incorporated more exercise-based strategies to help increase strength, mobility and functionality and was informed by a comprehensive assessment. Regardless of the stage of recovery, barriers such as delayed identification of fracture, delayed or no referral to physiotherapy, and lack of knowledge of osteoporosis or vertebral fracture among HCPs may reduce the access to or effectiveness of non-pharmacological interventions. HCPs believed that virtual rehabilitation that includes an online educational component, an online assessment, and online exercise classes in groups tailored to individuals could be a feasible alternative; however, concerns related to the online assessment such as the inability to perform manual strength testing, and patient confidence in using technology were voiced. 10 individuals living with vertebral fractures (9F, 1M, aged 71 ± 7.9 years) were interviewed. Five major themes emerged from our interviews: chronic pain from spine fractures contributes to activity limitations and other consequences; fracture identification may be delayed, influencing care trajectory; living with fear; being dissatisfied with fracture management; and non-pharmacological strategies can help patients “get back into the game of life”. We have identified that the experience of vertebral fracture recovery among patients involves a substantial amount of back pain, mobility related issues, and psychological and social impairments. Rehabilitation provided to patients was dependent on the identification of fracture and was delayed, either from patient reluctance to see a HCP initially, or due to issues related to radiological diagnosis and access to an X-ray. Pain medication was perceived as helpful in reducing pain but non-pharmacological alternatives to reduce pain and improve mobility was emphasized as important, and patients believed that they should be advised. Rehabilitation in the chronic stages of vertebral fracture recovery involved more non-pharmacological interventions, such as weight-bearing exercise and education on safe movement and activity modifications and was facilitated by physiotherapy. To improve access to non-pharmacological options, education and exercise delivered online via virtual rehabilitation was perceived positively and could be an acceptable and feasible strategy; however, participants were concerned about access to technology and the individualization of programs in a group setting. Conclusion: We have identified that rehabilitation provided by HCPs was dependent on the acuity or stability of fracture, and that non-pharmacological strategies were facilitated by physiotherapy. To select and individualize physical therapy interventions, physiotherapists emphasized using assessments to determine patient goals, physical functioning, and identify co-morbidities. To improve access and address barriers, virtual rehabilitation could be a feasible and effective alternative for patients but may require further evaluation. We have identified that individuals who suffer a vertebral fracture report chronic back pain that influences their ability to perform activities of daily living, impacting psychological and social well-being. To address consequences of vertebral fractures pain medication was used and considered helpful, but that non-pharmacological strategies, facilitated by physiotherapy, was considered important and should be advised; however, barriers to fracture identification and access and referral to physiotherapy may limit the use of these options. To improve access to non-pharmacological strategies, patients believe that virtual rehabilitation could be a feasible and effective alternative but may require further evaluation

Post-launch analysis of the deployment dynamics of a space web sounding rocket experiment

Lightweight deployable space webs have been proposed as platforms or frames for a construction of structures in space where centrifugal forces enable deployment and stabilization. The Suaineadh project was aimed to deploy a 2×2m2 space web by centrifugal forces in milli-gravity conditions and act as a test bed for the space web technology. Data from former sounding rocket experiments, ground tests and simulations were used to design the structure, the folding pattern and control parameters. A developed control law and a reaction wheel were used to control the deployment. After ejection from the rocket, the web was deployed but entanglements occurred since the web did not start to deploy at the specified angular velocity. The deployment dynamics was reconstructed from the information recorded in inertial measurement units and cameras. The nonlinear torque of the motor used to drive the reaction wheel was calculated from the results. Simulations show that if the Suaineadh started to deploy at the specified angular velocity, the web would most likely have been deployed and stabilized in space by the motor, reaction wheel and controller used in the experiment

Strategic orientations and digital marketing tactics in cross-border e-commerce: Comparing developed and emerging markets

In this article, the impact of strategic orientations on the use of digital marketing tactics and, subsequently, on the international business performance of small electronic retailers (e-retailers) in cross-border electronic commerce (e-commerce) is analysed. Furthermore, these relationships are compared between e-retailers originating in both developed and emerging e-commerce markets. Using a sample of 446 small business-to-consumer e-retailers from 20 European countries, we find that the deployment of digital marketing tactics has a positive effect on international business performance. Of the strategic orientations examined, foreign market orientation is most associated with the use of digital marketing tactics. Remarkably, growth orientation only has a positive effect on e-retailers from developed e-commerce markets, while customer orientation negatively affects e-retailers from emerging e-commerce markets. The differences between e-retailers from developed and emerging e-commerce markets are prominent and show that markets should not be considered as either uniform or generalisable

User-generated content (UGC) in tourism: Benefits and concerns of online consumers

This study reports an attempt to enhance our understanding of the reasons behind virtual world usage. By providing a mixture of utilitarian and hedonic value, virtual worlds represent an emerging class of multipurpose information systems (MPIS). Previous research seems to fall short in explaining MPIS adoption, especially since key extrinsic and intrinsic motivators are not considered. Drawing upon IT adoption research, motivation theory and the consumer behavior literature, this research extends available works and provides insight into the influence and roles of extrinsic and intrinsic motivation. Hypotheses are postulated and tested using a sample of 1627 users of the virtual world Second Life. The results confirm the majority of the hypotheses and support the comprehensive model. The findings indicate instantaneous effects of extrinsic and intrinsic motivation, and highlight reinforcing effects of intrinsic motivation. Implications for research and practice are discussed