Flight experiment of thermal energy storage

Thermal energy storage (TES) enables a solar dynamic system to deliver constant electric power through periods of sun and shade. Brayton and Stirling power systems under current considerations for missions in the near future require working fluid temperatures in the 1100 to 1300+ K range. TES materials that meet these requirements fall into the fluoride family of salts. These salts store energy as a heat of fusion, thereby transferring heat to the fluid at constant temperature during shade. The principal feature of fluorides that must be taken into account is the change in volume that occurs with melting and freezing. Salts shrink as they solidify, a change reaching 30 percent for some salts. The location of voids that form as result of the shrinkage is critical when the solar dynamic system reemerges into the sun. Hot spots can develop in the TES container or the container can become distorted if the melting salt cannot expand elsewhere. Analysis of the transient, two-phase phenomenon is being incorporated into a three-dimensional computer code. The code is capable of analysis under microgravity as well as 1 g. The objective of the flight program is to verify the predictions of the code, particularly of the void location and its effect on containment temperature. The four experimental packages comprising the program will be the first tests of melting and freezing conducted under microgravity. Each test package will be installed in a Getaway Special container to be carried by the shuttle. The package will be self-contained and independent of shuttle operations other than the initial opening of the container lid and the final closing of the lid. Upon the return of the test package from flight, the TES container will be radiographed and finally partitioned to examine the exact location and shape of the void. Visual inspection of the void and the temperature data during flight will constitute the bases for code verification

Thermal Energy Storage Flight Experiment in Microgravity

The Thermal Energy Storage Flight Experiment was designed to characterize void shape and location in LiF-based phase change materials in different energy storage configurations representative of advanced solar dynamic systems. Experiment goals and payload design are described in outline and graphic form

Scaling analysis applied to the NORVEX code development and thermal energy flight experiment

A scaling analysis is used to study the dominant flow processes that occur in molten phase change material (PCM) under 1 g and microgravity conditions. Results of the scaling analysis are applied to the development of the NORVEX (NASA Oak Ridge Void Experiment) computer program and the preparation of the Thermal Energy Storage (TES) flight experiment. The NORVEX computer program which is being developed to predict melting and freezing with void formation in a 1 g or microgravity environment of the PCM is described. NORVEX predictions are compared with the scaling and similarity results. The approach to be used to validate NORVEX with TES flight data is also discussed. Similarity and scaling show that the inertial terms must be included as part of the momentum equation in either the 1 g or microgravity environment (a creeping flow assumption is invalid). A 10(exp -4) environment was found to be a suitable microgravity environment for the proposed PCM

Effect of Microgravity on Material Undergoing Melting and Freezing: the TES Experiment

This experiment is the first to melt and freeze a high temperature thermal energy storage (TES) material under an extended duration of microgravity. It is one of a series to validate an analytical computer program that predicts void behavior of substances undergoing phase change under microgravity. Two flight experiments were launched in STS-62. The first, TES-1, containing lithium fluoride in an annular volume, performed flawlessly in the 22 hours of its operation. Results are reported in this paper. A software failure in TES-2 caused its shutdown after 4 seconds. A computer program, TESSIM, for thermal energy storage simulation is being developed to analyze the phenomena occurring within the TES containment vessel. The first order effects, particularly the surface tension forces, have been incorporated into TESSIM. TESSIM validation is based on two types of results. First is the temperature history of various points of the containment structure, and second, upon return from flight, the distribution of the TES material within the containment vessel following the last freeze cycle. The temperature data over the four cycles showed a repetition of results over the third and fourth cycles. This result is a confirmation that any initial conditions prior to the first cycle had been damped out by the third cycle. The TESSIM simulation showed a close comparison with the flight data. The solidified TES material distribution within the containment vessel was obtained by a tomography imaging process. The frozen material was concentrated toward the colder end of the annular volume. The TESSIM prediction showed the same pattern. With the general agreement of TESSIM and the data, a computerized visual representation can be shown which accurately shows the movement and behavior of the void during the entire freezing and melting cycles

Offline Social Relationships and Online Cancer Communication: Effects of Social and Family Support on Online Social Network Building

This study investigates how social support and family relationship perceptions influence breast cancer patients’ online communication networks in a computer-mediated social support (CMSS) group. To examine social interactions in the CMSS group, we identified two types of online social networks: open and targeted communication networks. The open communication network reflects group communication behaviors (i.e., one-to-many or “broadcast” communication) in which the intended audience is not specified; in contrast, the targeted communication network reflects interpersonal discourses (i.e., one-to-one or directed communication) in which the audience for the message is specified. The communication networks were constructed by tracking CMSS group usage data of 237 breast cancer patients who participated in one of two National Cancer Institute-funded randomized clinical trials. Eligible subjects were within 2 months of a diagnosis of primary breast cancer or recurrence at the time of recruitment. Findings reveal that breast cancer patients who perceived less availability of offline social support had a larger social network size in the open communication network. In contrast, those who perceived less family cohesion had a larger targeted communication network in the CMSS group, meaning they were inclined to use the CMSS group for developing interpersonal relationships

Reproducible Increased Mg Incorporation and Large Hole Concentration in GaN Using Metal Modulated Epitaxy

The metal modulated epitaxy (MME) growth technique is reported as a reliable approach to obtain reproducible large hole concentrations in Mg-doped GaN grown by plasma-assisted molecular-beam epitaxy on c-plane sapphire substrates. An extremely Ga-rich flux was used, and modulated with the Mg source according to the MME growth technique. The shutter modulation approach of the MME technique allows optimal Mg surface coverage to build between MME cycles and Mg to incorporate at efficient levels in GaN films. The maximum sustained concentration of Mg obtained in GaN films using the MME technique was above 7 × 1020 cm-3, leading to a hole concentration as high as 4.5 × 1018 cm-3 at room temperature, with a mobility of 1.1 cm2 V-1 s-1 and a resistivity of 1.3 Ω cm. At 580 K, the corresponding values were 2.6 × 1019 cm-3, 1.2 cm2 V-1 s-1, and 0.21 Ω cm, respectively. Even under strong white light, the sample remained p-type with little change in the electrical parameters. © 2008 American Institute of Physics

Metal Modulation Epitaxy Growth for Extremely High Hole Concentrations Above 10(19) cm(-3) in GaN

The free hole carriers in GaN have been limited to concentrations in the low 1018 cm−3 range due to the deep activation energy, lower solubility, and compensation from defects, therefore, limiting doping efficiency to about 1%. Herein, we report an enhanced doping efficiency up to ~10% in GaN by a periodic doping, metal modulation epitaxy growth technique. The hole concentrations grown by periodically modulating Ga atoms and Mg dopants were over ~1.5 x 1019 cm−3. © 2008 American Institute of Physics

Expression and Reception: An Analytic Method for Assessing Message Production and Consumption in CMC

This article presents an innovative methodology to study computer-mediated communication (CMC), which allows analysis of the multi-layered effects of online expression and reception. The methodology is demonstrated by combining the following three data sets collected from a widely tested eHealth system, the Comprehensive Health Enhancement Support System (CHESS): (1) a flexible and precise computer-aided content analysis; (2) a record of individual message posting and reading; and (3) longitudinal survey data. Further, this article discusses how the resulting data can be applied to online social network analysis and demonstrates how to construct two distinct types of online social networks—open and targeted communication networks—for different types of content embedded in social networks

Predictors of the Change in the Expression of Emotional Support within an Online Breast Cancer Support Group: A Longitudinal Study

OBJECTIVES: To explore how the expression of emotional support in an online breast cancer support group changes over time, and what factors predict this pattern of change. METHODS: We conducted growth curve modeling with data collected from 192 participants in an online breast cancer support group within the Comprehensive Health Enhancement Support System (CHESS) during a 24-week intervention period. RESULTS: Individual expression of emotional support tends to increase over time for the first 12 weeks of the intervention, but then decrease slightly with time after that. In addition, we found that age, living situation, comfort level with computer and the Internet, coping strategies were important factors in predicting the changing pattern of expressing emotional support. CONCLUSIONS: Expressing emotional support changed in a quadratic trajectory, with a range of factors predicting the changing pattern of expression. PRACTICAL IMPLICATIONS: These results can provide important information for e-health researchers and physicians in determining the benefits individuals can gain from participation in should CMSS groups as the purpose of cancer treatment

Why blog? (then and now): Exploring the motivations for blogging by popular American political bloggers

Abstract Despite the impact that influential American political bloggers have had on public policies and the mainstream media agenda in recent years, very little research is currently available on the most widely read political bloggers. Through a survey of 66 top American political bloggers, the present study examines this elite group by analyzing their initial and current motivations for blogging as well as their online and offline behaviors. The findings demonstrate that nearly all motivations for blogging have increased over time, with the most substantial increases occurring in extrinsic motivations. The results also reveal a significant association between extrinsic motivations and blogger online and offline political participation. This study demonstrates that future research on political blogs needs to look beyond blog readers and blog content and investigate the influential political bloggers themselves. Keywords bloggers, extrinsic and intrinsic motivations, political blogs, political participation In the past several years, political bloggers have played a significant role in the development of the American mainstream news agenda and Washington politics. For example, By now, many of the country's most influential bloggers have been blogging about political topics and current events for years. Some of them have been concentrating on political issues from the very beginning, such as Markos Moulitsas, who made it clear on his first Daily Kos post, 'I am liberal. I make no apologies Yet despite the intriguing emergence of bloggers into legitimate political circles and their apparent influence on American media and public policies, very little research on the most widely read political bloggers is currently available. While there is a growing body of research focused on political blog content Political Blogs and Their Bloggers Although blogs have received a considerable amount of attention recently, there is no clear consensus among scholars, media professionals and blog users about the definition of the word 'blog' 3 found that when blog readers describe blogs, they emphasize the interactional attributes rather than any structural features. These authors argue that it is 'more useful and informative to consider blogs not in terms of academic definitions, but rather in the terms of those involved in the activity of blogging The presence and popularity of blogs, which have been around since the early days of the world wide web, grew exponentially after the 11 September 2001 terrorist attacks as writers sought new outlets to express their feelings about the uncertain times and readers searched for information unavailable in the mainstream media (Blood, 2002; Unlike traditional news, most political bloggers do not subscribe to journalistic norms of objectivity; rather, their writings tend to be grounded in strong ideological assumptions Political Blogger Motivations and Behaviors The content of a blog depends heavily on the intentions of its author or authors, with some blogs serving as news aggregators, some as more personal diaries and others as political soapboxes. As boyd (2006: 3) points out in arguing that blogs should be reconceptualized as a medium rather than a genre, blogging encapsulates a 'diverse set of practices that result in the production of diverse content'. Therefore, understanding why political bloggers choose to blog is useful for expanding our understanding of the content found on those blogs. Indeed, while laying out a framework for studying mainstream media effects, Scheufele (1999) argues for the importance of analyzing why journalists adopt certain frames rather than limiting our focus to frames themselves. Similarly, Carragee and Roefs Cognitive psychologists assert that an individual's behavior is influenced by both intrinsic and extrinsic motivations Several recent studies have begun to examine the question of why bloggers blog. While these studies focused on bloggers generally, it is important to distinguish between those who blog about personal, social and cultural topics and those who concentrate on political issues, as their motivations may differ. In his study of non-'A-list' political bloggers, Wallsten (2005) found these bloggers were primarily driven by two motivations: (1) a desire for self-expression on political issues (i.e. a form of political expression) and (2) a desire to influence the distribution of social goods and social values (i.e. a form of political participation). According to this categorization, political bloggers are driven by both intrinsic and extrinsic motivations, the former being intrinsic and the latter extrinsic as bloggers are rewarded by perceiving the influence of their content beyond themselves. Therefore, the present study provides an investigation into the motivations for political blogging, whether these motivations change over time and if these motivations impact blogger behavior. Following the work of H1: Extrinsic motivations for blogging will increase over the blogspan. RQ1: Will intrinsic motivations for blogging change over the blogspan? Extending the work of Sampling the Most Widely Read Political Blogs To determine the top blogs, indexing sites employ a number of different methods Measures In the survey, we developed 13 possible blogger motivations based on the previous research (Blood, 2002; Beyond questions concerning motivations, the survey also measured bloggers' online and offline political behavior. In terms of bloggers' offline political behavior, we adopted political participation items widely used in political communication research new media & society XX(X) paper petition, contributed money to a political campaign or cause, worked on a political campaign, contacted elected officials, wrote a letter to the editor of a newspaper or magazine, volunteered for a social group or cause and attended a protest or rally (M = 4.83, SD = 2.40, α = .86). Their response was recorded on an 11-point scale that ranged from 0 (not at all) to 10 (very frequently). Blogger online behaviors are broadly defined by two behavioral orientations of blogging: social interaction and information search In addition to these quantitative measures, bloggers were also asked the open-ended question, 'Why did you start a blog?' Responses to this question will appear later to provide further contextual information about this study's findings concerning motivations for blogging. Participants were also asked several other questions about party identification, media use and blog content that are beyond the scope of the current study. Results In response to our survey, participants rated the following three items highest for initial blogger motivations: 'to let off steam' (M = 7.00, SD = 2.93), 'to keep track of your thoughts' (M = 6.46, SD = 3.20) and 'to formulate new ideas' (M = 6.44, SD = 3.09). The three lowest initial motivators were 'to influence mainstream media' (M = 3.83, SD = 3.34), 'to help your political party or cause' (M = 4.58, SD = 3.69) and 'to serve as a political watchdog' (M = 4.79, SD = 3.40). As for current motivations for blogging, the three items that most strongly resonated with our respondents were 'to provide an alternative perspective to the mainstream media' (M = 7.87, SD = 2.43), 'to inform people about the most relevant information on topics of interest' (M = 7.61, SD = 2.31) and 'to influence public opinion' (M = 7.27, SD = 2.69). While none of these statements were considered among the top three initial motivations, the three weakest current motivators were very similar to the three lowest initial motivators: 'to influence mainstream media' (M = 5.25, SD = 3.06), 'to critique your political opponents' (M = 5.64, SD = 3.14) and 'to help your political party or cause' (M = 5.81, SD = 3.24). at SAGE Publications on March 20, 2015 nms.sagepub.com Downloaded from Ekdale et al. 9 To test the differences between initial and current levels of motivations for blogging among respondents, we conducted a paired-sample t-test. As shown in In terms of intrinsic motivations, thought process motivations also increased over the blogspan (initial: M = 6.49, SD = 2.69; current: M = 7.04, SD = 2.29; t = 2.02, d.f. = 62, p <.05), although the increase in 'to keep track of your thoughts' is not statistically significant (t = 0.96, d.f. = 60, p > .10). Finally, the catharsis motivation, 'to let off steam', was the only motivation to decrease from initial to current levels at the .1 significance level. The current mean score of 'to let of steam' was 6.57 (SD = 2.76), whereas the initial mean score was 7.00 (SD = 2.93) (t = −1.79, d.f. = 59, p < .1). To assess the relationship between motivations and behaviors, a hierarchical regression analysis was performed. The five demographic and partisanship variables were entered in a first block, followed by a second block consisting of the three types of blogger motivations: extrinsic, articulating ideas and catharsis. The equations of this model were run to make an initial assessment of which kinds of motivations have significant effects on bloggers' political behaviors. Discussion Based on the results of our survey, all motivations for blogging increased over the course of our participants' blogspans except for the motive 'to let off steam'. This finding demonstrates that for the top political bloggers included in our survey the activity of blogging reinforced their motivations for blogging. Overall, these bloggers were more motivated to blog now than when they first started blogging. In particular, the motivation 'to at SAGE Publications on March 20, 2015 nms.sagepub.com Downloaded from 10 new media & society XX (X) provide an alternative perspective to the mainstream media' exhibited the largest increase over time. This demonstrates that relative to when these bloggers first decided to provide their unique point-of-view online, they now saw an increased need to offer their perspective. They became more cognizant of the fact that, outside of traditional news media and day-to-day interactions, the blogosphere provided them with an outlet for disseminating information and expressing political opinions. Indeed, several of the responses to our open-ended motivation question indicate that many bloggers found blogging to be an effective outlet for providing alternative perspectives on political and social issues: I was skeptical of them at first -mostly saw them as vanity projects. Then I saw that they were capable of moving information around the traditional media bottlenecks and decided that it was something I could contribute to. (#33) First, I was frustrated out of my wits with the shallowness, and lack of context, background, and even facts, in political reporting. I started blogging so I could research and provide (for SOMEBODY) the information and context I wasn't seeing in establishment media. (#11