Water-propellant resistojets for man-tended platforms

The selection of a propulsion system for a man-tended platform has been influenced by the planned use of resistojets for drag make-up on the manned space station. For that application a resistojet has been designed that is capable of operation with a wide variety of propellants, including water. The reasons for the selection of water as the propellant and the performance of water as a propellant are discussed. The man-tended platform and its mission requirements are described

Introducing smart grids : practical experience of a DSO

One of the main issues for Distribution System Operators is the introduction of so-called smart grids. Enexis B.V., one of the major Distribution System Operators in The Netherlands started two years ago with the preparation of a large-scale roll-out of distribution automation, which can be considered as a part, or form of a smart grid. In the preparation and the pilot phase of the project it became clear however that a lot of practical issues had to be solved before smart grids can be rolled out. This contribution describes the experiences of Enexis and compares theory and practice of the introduction of smart grids

Maximum PV-penetration in low-voltage cable networks

As a consequence of the increasing amount of PV-systems connected to the LV-network the question arises whether these networks are able to cope with large amounts of PV. In this paper it is investigated whether problems have to be expected in typical LV networks in the Netherlands. It is shown that exceeding of the regulatory voltage levels is the first limiting factor for integration of PV, followed by overloading of components. In most parts of the network no problems will arise as a consequence of PV, as it is not possible to place enough PV panels to cause problems. Areas with increased risk can be identified on forehand

Performance and endurance tests of a multipropellant resistojet for space station auxiliary propulsion

This paper presents the results of an effort to demonstrate the technology readiness of a long-life multipropellant resistojet for space station auxiliary propulsion. Experiments were performed to evaluate the compatibility of grain-stabilized platinum tubes at temperatures up to 1400 deg C in environments of CO2, CH4, NH3, H2O, and H2. All samples tested showed extrapolated lifetimes in excess of 10,000 hr based on 10 percent mass loss as end-of-life. However, samples tested in an ammonia atmosphere at 1400 deg C showed severe pitting, which raised concerns about the compatibility of grain-stabilized platinum with ammonia-containing atmospheres. Additional tests showed that reducing the metal temperature to about 900 deg C (+ or - 100 deg C) significantly reduced this adverse effect

NEW NETWORK DESIGN STANDARDS FOR THE GRID CONNECTION OF LARGE CONCENTRATIONS OF DISTRIBUTED GENERATION

ABSTRACT Connecting large concentrations of Distributed Generation to the distribution networks usually requires high investments in network extension. This contribution describes how Enexis used its Risk Based Asset Management approach to develop new network design standards for the grid connection of large concentrations of DG in a cost-effective way

Practice-Oriented Optimization of Distribution Network Planning Using Metaheuristic Algorithms

Distribution network operators require more advanced planning tools to deal with the challenges of future network planning. An appropriate planning and optimization tool can identify which option for network extension should be selected from available alternatives. However, many optimization approaches described in the literature are quite theoretical and do not yield results that are practically relevant and feasible. In this paper, a distribution network planning approach is proposed which meets requirements originating from network planning practice to guarantee realistic outcomes. This approach uses a state-of-the-art evolutionary algorithm: Gene-pool Optimal Mixing Evolutionary Algorithm. The performance of this algorithm, as well as the proposed model, is demonstrated using a real-world case study

Inverse association between atopy and melanoma: A case-control study

Heightened cutaneous immune surveillance in atopic patients may inhibit development of melanoma. The aim of this study was to analyse the association between atopy and melanoma (development and outcome). A total of 188 cases of melanoma and 596 healthy controls were interviewed by telephone with a standardized questionnaire on atopic, demographic and melanoma characteristics. Cases were matched with controls on important confounders (age, sex, sunburn sensitivity, hair colour, number of moles, sunburn as juvenile, ever sunbed use, familial melanoma). Melanoma outcome data (disease relapse and death) within cases were retrieved. Analysis showed a general inverse association between atopy and melanoma development, but this was statistically significant only for a history of personal atopy (odds ratio 0.53, 95% confidence interval: 0.30-0.96, p-value = 0.04). Among melanoma patients, atopy did not affect survival or progression. In conclusion, this study suggests an inverse association between a history of atopy and melanoma development, but not with disease progression

It is not always chlorhexidine: Identification of benzoxonium chloride and lauramine oxide as culprit allergens in a popular antiseptic in Switzerland.

A popular antiseptic spray in Switzerland (Merfen spray), containing chlorhexidine digluconate, benzoxonium chloride and lauramine oxide, is frequently used to treat skin wounds. However, it is also increasingly reported as a major cause of adverse skin reactions, including allergic contact dermatitis (ACD). To investigate the contact allergens responsible for ACD from this antiseptic. Patch tests were performed on seven patients with a clinical history compatible with contact dermatitis from this antiseptic mixture. All patients presented with acute eczematous reactions following contact with either Merfen spray alone, or with multiple products including this spray. Patients showed positive reactions to this product in both patch tests and repeated open application tests (ROATs). Four patients showed dose-dependent reactions to both benzoxonium chloride and lauramine oxide. One patient showed a dose-dependent reaction to the former and a non-dose-dependent reaction to the latter. Finally, two subjects showed responses only to lauramine oxide. One patient reacted to chlorhexidine digluconate 0.5% aq. in addition to both other allergens. Two commercially unavailable allergens, that is, benzoxonium chloride and/or lauramine oxide were identified as major causes of ACD from Merfen antiseptic spray, whereas chlorhexidine digluconate was a contributing culprit in only one patient

Aerospace Fuels From Nonpetroleum Raw Materials

Recycling human metabolic and plastic wastes minimizes cost and increases efficiency by reducing the need to transport consumables and return trash, respectively, from orbit to support a space station crew. If the much larger costs of transporting consumables to the Moon and beyond are taken into account, developing waste recycling technologies becomes imperative and possibly mission enabling. Reduction of terrestrial waste streams while producing energy and/or valuable raw materials is an opportunity being realized by a new generation of visionary entrepreneurs; several relevant technologies are briefly compared, contrasted and assessed for space applications. A two-step approach to nonpetroleum raw materials utilization is presented; the first step involves production of supply or producer gas. This is akin to synthesis gas containing carbon oxides, hydrogen, and simple hydrocarbons. The second step involves production of fuel via the Sabatier process, a methanation reaction, or another gas-to-liquid technology, typically Fischer-Tropsch processing. Optimization to enhance the fraction of product stream relevant to transportation fuels via catalytic (process) development at NASA Glenn Research Center is described. Energy utilization is a concern for production of fuels whether for operation on the lunar or Martian surface, or beyond. The term green relates to not only mitigating excess carbon release but also to the efficiency of energy usage. For space, energy usage can be an essential concern. Another issue of great concern is minimizing impurities in the product stream(s), especially those that are potential health risks and/or could degrade operations through catalyst poisoning or equipment damage; technologies being developed to remove heteroatom impurities are discussed. Alternative technologies to utilize waste fluids, such as a propulsion option called the resistojet, are discussed. The resistojet is an electric propulsion technology with a powered thruster to vaporize and heat a propellant to high temperature, hot gases are subsequently passed through a converging-diverging nozzle expanding gases to supersonic velocities. A resistojet can accommodate many different fluids, including various reaction chamber (by-)products

Emotional reasoning and anxiety sensitivity: associations with social anxiety disorder in childhood

Background Two specific cognitive constructs that have been implicated in the development and maintenance of anxiety symptoms are anxiety sensitivity and emotional reasoning, both of which relate to the experience and meaning of physical symptoms of arousal or anxiety. The interpretation of physical symptoms has been particularly implicated in theories of social anxiety disorder, where internal physical symptoms are hypothesized to influence the individual's appraisals of the self as a social object. Method The current study compared 75 children on measures of anxiety sensitivity and emotional reasoning: 25 with social anxiety disorder, 25 with other anxiety disorders, and 25 nonanxious children (aged 7–12 years). Results Children with social anxiety disorder reported higher levels of anxiety sensitivity and were more likely than both other groups to view ambiguous situations as anxiety provoking, whether physical information was present or not. There were no group differences in the extent to which physical information altered children's interpretation of hypothetical scenarios. Limitations This study is the first to investigate emotional reasoning in clinically anxious children and therefore replication is needed. In addition, those in both anxious groups commonly had comorbid conditions and, consequently, specific conclusions about social anxiety disorder need to be treated with caution. Conclusion The findings highlight cognitive characteristics that may be particularly pertinent in the context of social anxiety disorder in childhood and which may be potential targets for treatment. Furthermore, the findings suggest that strategies to modify these particular cognitive constructs may not be necessary in treatments of some other childhood anxiety disorders