Static stability of a three-dimensional space truss

In order to deploy large flexible space structures it is necessary to develop support systems that are strong and lightweight. The most recent example of this aerospace design need is vividly evident in the space station solar array assembly. In order to accommodate both weight limitations and strength performance criteria, ABLE Engineering has developed the Folding Articulating Square Truss (FASTMast) support structure. The FASTMast is a space truss/mechanism hybrid that can provide system support while adhering to stringent packaging demands. However, due to its slender nature and anticipated loading, stability characterization is a critical part of the design process. Furthermore, the dire consequences surely to result from a catastrophic instability quickly provide the motivation for careful examination of this problem. The fundamental components of the space station solar array system are the (1) solar array blanket system, (2) FASTMast support structure, and (3) mast canister assembly. The FASTMast once fully deployed from the canister will provide support to the solar array blankets. A unique feature of this structure is that the system responds linearly within a certain range of operating loads and nonlinearly when that range is exceeded. The source of nonlinear behavior in this case is due to a changing stiffness state resulting from an inability of diagonal members to resist applied loads. The principal objective of this study was to establish the failure modes involving instability of the FASTMast structure. Also of great interest during this effort was to establish a reliable analytical approach capable of effectively predicting critical values at which the mast becomes unstable. Due to the dual nature of structural response inherent to this problem, both linear and nonlinear analyses are required to characterize the mast in terms of stability. The approach employed herein is one that can be considered systematic in nature. The analysis begins with one and two-dimensional failure models of the system and its important components. From knowledge gained through preliminary analyses a foundation is developed for three-dimensional analyses of the FASTMast structure. The three-dimensional finite element (FE) analysis presented here involves a FASTMast system one-tenth the size of the actual flight unit. Although this study does not yield failure analysis results that apply directly to the flight article, it does establish a method by which the full-scale mast can be evaluated

Static stability of a three-dimensional space truss

Space station requirements for power have resulted in a need for photovoltaic solar arrays possessing large blanket surface area. However, due to the limited shuttle payload volume solar array designers have been driven to a deployable concept that by nature is extremely flexible. The principal support for this array system is the Folding Articulating Square Truss Mast (FASTMast). In order to accomodate service loads the FASTMast is expected to exhibit nonlinear behavior which could possibly result in structural instability. Presented herein are the results of the Lewis Research Center test and analysis efforts performed in an effort to characterize the FASTMast structural behavior in terms of stability. Results include those obtained from recent nonlinear testing and analysis involving a 1/10 segment of the FASTMast flight article. Implications of these results as they relate to expected behavior of the flight unit will also be discussed

Static stability of the Space Station solar array FASTMast structure

The combined loads test of the 3-Bay FASTMast marks the end of the Lewis Research Center (LeRC) effort to characterize the behavior of the principal Space Station solar array support structure. The primary objective of this test and analysis effort was to develop a method to predict structural stability failure modes under flight-like applied loads. Included at the beginning of this report is a brief historical perspective of the hardware design development and FASTMast structural stability problem evolution. Once an understanding of the solution process has been established, test and analysis details are presented and related to the postulated failure theories. The combined load test series subjected the structure to a combination of transverse, moment, and torsion loads similar to that expected in the service environment. Nonlinear finite element (FE) models were developed and large displacement analyses were performed to support the test effort and failure mode predictions. Details of the test configuration as well as test and analysis results are presented. The results were then critiqued to establish valid and successful support of the failure mode assessments. Finally, study conclusions are drawn and recommendations for safe operation of the FASTMast structure are presented for consideration

Absorbing customer knowledge: how customer involvement enables service design success

Customers are a knowledge resource outside of the firm that can be utilized for new service success by involving them in the design process. However, existing research on the impact of customer involvement (CI) is inconclusive. Knowledge about customers’ needs and on how best to serve these needs (articulated in the service concept) is best obtained from customers themselves. However, codesign runs the risk of losing control of the service concept. This research argues that of the processes of external knowledge, acquisition (via CI), customer knowledge assimilation, and concept transformation form a capability that enables the firm to exploit customer knowledge in the form of a successful new service. Data from a survey of 126 new service projects show that the impact of CI on new service success is fully mediated by customer knowledge assimilation (the deep understanding of customers’ latent needs) and concept transformation (the modification of the service concept due to customer insights). However, its impact is more nuanced. CI exhibits an “∩”-shaped relationship with transformation, indicating there is a limit to the beneficial effect of CI. Its relationship with assimilation is “U” shaped, suggesting a problem with cognitive inertia where initial learnings are ignored. Customer knowledge assimilation directly impacts success, while concept transformation only helps success in the presence of resource slack. An evolving new service design is only beneficial if the firm has the flexibility to adapt to change

Goserelin for Ovarian Protection During Breast-Cancer Adjuvant Chemotherapy

Premature ovarian failure is a devastating long-term toxic effect of chemotherapy for premenopausal women. The survival benefit of adjuvant chemotherapy in young women with operable hormone receptor–negative breast cancer is well known, but concern over becoming infertile may influence the choice of treatment for many women. A number of trials have investigated the combined use of a gonadotropin-releasing hormone (GnRH) agonist and adjuvant chemotherapy in an attempt to protect ovarian function in premenopausal women. Results of such studies were mixed, and there were few data on pregnancy outcomes. The aim of this randomized trial was to determine whether administration of the GnRH agonist goserelin with chemotherapy would reduce the rate of ovarian failure after adjuvant or neoadjuvant treatment of hormone-receptor–negative early-stage breast cancer. A total of 257 premenopausal women with operable hormone receptor–negative breast cancer were randomized to receive standard chemotherapy with goserelin (goserelin group) or standard chemotherapy without goserelin (chemotherapy-alone group). The rate of ovarian failure at 2 years was the primary study end point. Ovarian failure was defined as the absence of menses for the preceding 6 months and follicle-stimulating hormone levels in the postmenopausal range at 2 years. Conditional logistic regression was used to compare rates. Secondary end points evaluated included pregnancy outcomes and disease-free and overall survival. Of the 257 patients, 218 were eligible and could be evaluated: 113 in the chemotherapy-alone group and 105 in the goserelin group. Complete primary end-point data were available for 135 of the 218 patients who could be evaluated. Among these, the ovarian failure rate was 8% in the goserelin group and 22% in the chemotherapy-alone group; the odds ratio was 0.30, with a 95% confidence interval of 0.09 to 0.97; 2-sided P = 0.04. To determine the effect of the missing primary end-point data on the main study findings, sensitivity analyses were performed. The results of these analyses showed that the missing data had no significant effect on the association between treatment and stratification variables (age and planned chemotherapy regimen). Among the 218 patients who could be evaluated, more women became pregnant in the goserelin group than in the chemotherapy-alone group (21% vs 11%, P = 0.03). Kaplan-Meier curves showed that more women in the goserelin group had improved disease-free survival (P = 0.04) and overall survival (P = 0.05). Consistent with the findings of previous randomized trials, these data suggest that administration of a GnRH agonist with chemotherapy protects ovarian function, reducing the risk of early menopause and improving prospects for fertility. Although missing primary-end-point data weaken interpretation of the findings, there is no evidence that the missing data influenced the relative comparison between randomized groups

Customer Interaction and Innovation in Hybrid Offerings:Investigating Moderation and Mediation Effects for Goods and Services Innovation

Hybrid offerings are bundles of goods and services offerings provided by the same firm. Bundling value offerings affects how firms innovate, interact with customers, and customize their goods and services. However, it remains unclear how customer interaction might drive the innovation performance of various bundled components. Therefore, this study investigates the effects of customer interactions and service customization on both goods and services innovations in a hybrid offering context, using a unique data set of 146 information technology and manufacturing firms. Customer interaction appears beneficial to both goods and services innovation in a hybrid offerings context, but service customization has different direct effects on goods versus services innovation. As a potential mediator, customer knowledge mobilization resources exert different effects on the goods and services elements of hybrid offerings. Furthermore, for high-interaction customers, medium levels of technical modularity lead to most favorable innovation outcomes for services innovation. The results thus suggest that providers of hybrid offerings should foster customer interactions, to drive the innovation performance of the good and service components, while still making sure to implement service customization strategies. These findings have notable implications for service innovation research

An Assessment of the Exporting Literature: Using Theory and Data to Identify Future Research Directions

Exporting research is an established facet of the field of international marketing. That stated, the radical increase in recent export activity necessitates a sustained research effort devoted to the topic. In this article, the authors provide a qualitative review of the core theoretical exporting areas and evaluate the exporting domain quantitatively over six decades (1958–2016). For the quantitative analysis, they use multidimensional scaling and apply established bibliometric principles to offer an understanding of the field and to provide suggestions for future exporting research. For the evaluations, the authors used data from 830 articles with 52,191 citations from 35 journals. Using cocitation analysis as the basis to evaluate the data, they propose a series of intellectual structure implications on exporting that relate to internationalization process stages, dynamic capabilities, knowledge scarcity, social networks, export marketing strategy, absorptive capacity and learning, and nonlinear performance relationships involving marketing channel relationships

Cytotoxic and HIV-1 enzyme inhibitory activities of Red Sea marine organisms

BACKGROUND: Cancer and HIV/AIDS are two of the greatest public health and humanitarian challenges facing the world today. Infection with HIV not only weakens the immune system leading to AIDS and increasing the risk of opportunistic infections, but also increases the risk of several types of cancer. The enormous biodiversity of marine habitats is mirrored by the molecular diversity of secondary metabolites found in marine animals, plants and microbes which is why this work was designed to assess the anti-HIV and cytotoxic activities of some marine organisms of the Red Sea. METHODS: The lipophilic fractions of methanolic extracts of thirteen marine organisms collected from the Red Sea (Egypt) were screened for cytotoxicity against two human cancer cell lines; leukaemia (U937) and cervical cancer (HeLa) cells. African green monkey kidney cells (Vero) were used as normal non-malignant control cells. The extracts were also tested for their inhibitory activity against HIV-1 enzymes, reverse transcriptase (RT) and protease (PR). RESULTS: Cytotoxicity results showed strong activity of the Cnidarian Litophyton arboreum against U-937 (IC50; 6.5 μg/ml ±2.3) with a selectivity index (SI) of 6.45, while the Cnidarian Sarcophyton trochliophorum showed strong activity against HeLa cells (IC50; 5.2 μg/ml ±1.2) with an SI of 2.09. Other species showed moderate to weak cytotoxicity against both cell lines. Two extracts showed potent inhibitory activity against HIV-1 protease; these were the Cnidarian jelly fish Cassiopia andromeda (IC50; 0.84 μg/ml ±0.05) and the red algae Galaxura filamentosa (2.6 μg/ml ±1.29). It is interesting to note that the most active extracts against HIV-1 PR, C. andromeda and G. filamentosa showed no cytotoxicity in the three cell lines at the highest concentration tested (100 μg/ml). CONCLUSION: The strong cytotoxicity of the soft corals L. arboreum and S. trochliophorum as well as the anti-PR activity of the jelly fish C. andromeda and the red algae G. filamentosa suggests the medicinal potential of crude extracts of these marine organisms.The Medical Research Council, the Technology Innovation Agency and the University of Pretoria, South Africa.http://www.biomedcentral.com/bmccomplementalternmedam201