Lifetime Of Several Years Research Articles

Projected global sulfur deposition with climate intervention

Even with immediate implementation of global policies to mitigate carbon dioxide emissions, the impacts of climate change will continue to worsen over the next decades. One potential response is stratospheric aerosol injection (SAI), where sulfur dioxide is released into the stratosphere to block incoming solar radiation. SAI does not reduce the level of carbon dioxide in the atmosphere, but it can slow warming and act as a stopgap measure to give the world more time to pursue effective carbon reduction strategies. While SAI is controversial, it remains a technically feasible proposition. It ought to be thoroughly modeled both to characterize global risks better and to further the scientific community’s understanding of stratospheric aerosol dynamics. SAI relies on sulfate aerosols which have a lifetime of several years in the stratosphere but will eventually be deposited back onto Earth’s surface. While sulfate is an important nutrient for many ecosystems, high concentrations can cause acidification, eutrophication, and biodiversity loss. We use model outputs from the Geoengineering Model Intercomparison Project (GeoMIP) to track the impacts of sulfur deposition from SAI to various ecoregions through comparison with historical climate and future Shared Socioeconomic Pathway (SSP) scenarios. Our results demonstrate that dry sulfur deposition will continue to decline worldwide, regardless of scenario, from a high of 41 Tg S/yr in 1981 to under 20 Tg S/yr by 2100. Wet sulfur deposition, however, is much more uncertain and further work needs to be done in this area to harmonize model estimates. Under SAI, many ecoregions will experience notably different sulfur deposition regimes by the end of the century compared to historical trends. In some places, this will not be substantially different than the impacts of climate change under SSP2–4.5 or SSP5–8.5. However, in some ecoregions the model projections disagree dramatically on the magnitude of future trends in both emissions and deposition, with, for example, UKESM1–0-LL projecting that SO42- deposition in deciduous needleleaf forests under G6 Sulfur will reach 394 % of SSP2–4.5 deposition by the 2080 s while CESM2-WACCM projects that SO42- deposition will remain at 170 % of SSP2–4.5 deposition during that same time period. Our work emphasizes the lack of agreement between models and the importance of improving our understanding of SAI impacts for future climate decision-making.

Durability of intumescent coatings and recommendations for test concepts for a working life of more than 10 years

It is an essential requirement for all building products to ensure durability of their fire safety. Throughout the working life of products, intumescent coatings are aged by certain climatic factors. To predict a lifetime of several years, generally the behaviour of the intumescent coating is extrapolated based on accelerated artificial ageing. The established German and European procedures to assess the durability assume a working life of at least 10 years. For a longer period, additional evidence is required; yet the procedure and the specifications to justify this are not described. In addition to addressing this formal lack, from a scientific point of view it is necessary to investigate the degradation of intumescent coatings in detail and to propose a reliable test concept to assess durability for more than 10 years. This paper summarises the existing knowledge about the ageing of intumescent coatings. The results of various demanding weathering approaches are presented for two intumescent coatings tested in a joint research project. Moreover, formulations with a reduced amount of functionally relevant components were analysed to gain insight into the associated effects. Derived from these research results and knowledge, recommendations are proposed to assess the durability of intumescent coatings for more than 10 years based on a combination of verifications.

System design study of a VLEO satellite platform using the IRS RF helicon-based plasma thruster

To achieve a feasible lifetime of several years, most satellites are deployed in orbits higher than 400 km. Drag of residual atmosphere causes a slow orbit decay, resulting in the deorbit of the spacecraft. However, e.g. optical instruments or communication devices would significantly benefit from lower altitudes in the range of 150–250 km. A solution to achieve this could be the application of atmosphere-breathing electric propulsion (ABEP), where the residual atmosphere is used to generate continuous thrust that compensates the drag.Within the EU-funded DISCOVERER project, the Institute of Space Systems (IRS) developed an electrode-less RF Helicon-based Plasma Thruster (IPT) suitable for such applications. Ignition and preliminary discharge characterizations of the IPT have been carried out at IRS facilities, using argon, nitrogen and oxygen. To further characterize the plasma plume, a torsional pendulum has been designed to determine the (local) momentum flux in the plasma jet, as well as a three-axis magnetic B-dot probe to carry out time-varying magnetic field measurements. Various intake designs were investigated, opening the possibility to conduct studies on potential satellite platforms within the frame of the ESA-funded project RAM-CLEP.A design study for an Earth Observation and Telecommunication satellite operating at 150–250 km with an extended mission lifetime is currently being carried out. The first system assessment focused on the comparison of different spacecraft configurations (“slender body” and “flat body”) and intake designs (specular or diffuse) with regard to overall drag and ABEP performance requirements.In this contribution, the design approaches for the current thruster and the diagnostic methods are depicted. Moreover, the current status of the system assessment is presented. Upcoming experimental studies of the ABEP system e.g. within the ESA-project RAM-CLEP and additional activities planned on system assessment are outlined.

Cost and Performance Targets for Fully Electrochemical Ammonia Production under Flexible Operation

Methods to produce ammonia from air, water, and renewable electricity are necessary to transition ammonia production away from the CO2-emitting Haber–Bosch process. In this vein, a fully electric process in which water-splitting-derived hydrogen and air-separation-derived nitrogen are reacted in an electrochemical process to produce ammonia is attractive. Herein, we evaluated the cost-effectiveness of large-scale fully electric ammonia production relying on renewable electricity sources in conjunction with different types of storage and flexible operation using a mixed-integer linear programming framework. We found that ammonia can be produced in an economically competitive manner, i.e., at costs < 1 $/kg, at large scales if the electrochemical reactor can produce ammonia at partial currents exceeding 400 mA cm–2, energy efficiencies exceeding 30%, and process lifetimes of several years. In light of this, alternative chemistries that can reduce nitrogen at high rates and moderate (<2.5 V) overpotentials are necessary for economical, fully electrochemical ammonia production.

Impact of product gas impurities from dehydrogenation of perhydro-dibenzyltoluene on the performance of a 10 μm PdAg-membrane

The purification of the product gas from dehydrogenation of liquid organic hydrogen carriers (LOHC) by using PdAg-membranes is highly promising, since the low level of impurities in the released hydrogen stream allows low pressure operation and favours the coupling with the dehydrogenation step. Motivated by our recent short-term investigations indicating an influence of these impurities on the membrane performance the behaviour of the membrane by exposure to product gas was investigated in detail over a long period. In total, the membrane was operated for more than 200 days, including approx. 21 days under product gas from the LOHC-dehydrogenation. In the time period the performance has decreased by 88% and could be restored slowly but completely by using pure hydrogen. The degradation is caused by the coverage of active adsorption sites for the dissociation of hydrogen by hydrocarbons other than methane. The activation energy of permeation has almost tripled from 13 kJ mol−1 to 38 kJ mol−1 while desorption of impurities from the surface affect the process and its temperature dependence. SEM-analysis of the still 100%-selective membrane after more than 200 days of operation shows no significant changes in membrane morphology. Under the mild operating conditions, a lifetime of several years seems possible.

Solid Oxide Electrolyser Cell Testing up to the Above 30,000 h Time Range

Steam (and co-) electrolysis demonstration projects with solid oxide cells (SOC) have reached a power range of several hundred kW (e.g., /1/). This generates an urgent demand for verification of the durability of the cells as core electrolyser elements. Cell lifetimes of several years are required, which largely exceeds the commonly reported testing periods. Apart from economic considerations, cell (or short stack) testing allows a more precise control of the cell temperature together with less temperature variation across the surface. This, in turn, facilitates quantification of degradation, in particular for the practically required low degradation rates of <10 mV/kh. Appropriate durability was confirmed with a 23 kh steam electrolysis test with an electrolyte supported cell with a Ni/GDC hydrogen electrode (20 kh at -0.9 Acm-2 with 7.3 mV/kh voltage degradation /2/). This result represents an example for SOFC/SOEC reversibility holding even for a current density magnitude exceeding the commonly applied values under SOFC operation (higher current densities are feasible in the electrolysis mode owing to the more favourable thermal conditions, but they will, in general, imply the development of appropriate cells). Comparably low degradation was confirmed in a one year long test coupling steady-state and ON/OFF switching operation (80,000 cycles) for a cell with a thin 3YSZ electrode instead of the 6Sc1CeSZ in the 23 kh test /3/. ON/OFF stack switching is part of an operation strategy for matching a fluctuating load (such as coupling with renewable energy sources or grid stabilisation).In this contribution, emphasis will be put on a cell test of even longer duration (>30 kh so far) with an electrolyte supported cell, maintaining the current density above the typical SOFC values (initial part of the test in ref. /4/). The operation conditions are chosen for a cell voltage close to the thermal neutral voltage (Uth ~1.3 V), in accord with the requirements for stack operation. The use of an electrolyte of high ionic conductivity, 10Sc1CeSZ, allows a moderate initial temperature below 800°C at the not degraded cell. Temperature is later increased for compensation of degradation. For an appropriate setting of the initial testing parameters together with a low cell degradation and a sufficiently wide temperature window, one should then obtain an operation close to the theoretical efficiency limit with zero voltage degradation during the entire envisaged lifetime. As in our previous work, the long-term cell behaviour is traced with in-situ impedance spectroscopy without interrupting the DC current flow. The main focus of the degradation analysis refers to the ohmic degradation, which typically dominates in the cells of concern /2-4/.

Long-life type — The dominant fraction of EPFRs in combustion sources and ambient fine particles in Xi'an

Environmentally persistent free radicals (EPFRs) are new environmental health risk substances that have received much attention in recent years. The characterization of EPFRs is essential for understanding their sources and formation mechanisms in atmospheric particulate matter (PM), yet their physicochemical characteristics have not yet been fully and extensively studied. To clarify the nature of “persistent” free radicals in atmospheric PM, we systematically evaluated the decay characteristics of EPFRs in both combustion sources and ambient PM2.5 based on the planned measurement of EPFRs in a large number of samples (more than 130). The content of EPFRs changed over time for up to 2 years. This study quantifies EPFRs with different lifetimes in different sources of PM2.5. The results indicate that the EPFRs were dominated by the long-life type (>70%), with a 1/e lifetime of several years, in both combustion sources and ambient PM2.5. The decay characteristics of the EPFRs, including the temporal variations in the concentrations and g-factors of EPFRs in ambient PM2.5, were similar to those of combustion source samples but different from those of EPFRs produced by the interaction of metal oxides and aromatics. The interaction of metal oxides and aromatics may produce short-life EPFRs, and the formation mechanism of long-life EPFRs may be more complicated. This study provides important basic knowledge for understanding the sources and formation mechanisms of EPFRs in atmospheric PM.

Study of Operating Parameters for Accelerated Anode Degradation in SOFCs

AbstractSolid oxide fuel cell (SOFC) applications require lifetimes of several years on the system level. A big challenge is to demonstrate such exceptionally long lifetimes in ongoing R&amp;D projects. Accelerated or compressed testing are alternative methods to obtain this. Activities in this area have been carried out without arriving at a generally accepted methodology. This is mainly due to the complexity of degradation mechanisms on the single SOFC components as function of operating parameters. In this study, we present a detailed analysis of approx. 180 durability tests regarding degradation of single SOFC components as function of operating conditions. Electrochemical impedance data were collected on the fresh and long‐term tested SOFCs and used to de‐convolute the individual losses of single SOFC cell components – electrolyte, cathode and anode. The main findings include a time‐dependent effect on degradation rates and the domination of anode degradation for the evaluated cell types and operating conditions. Specifically, the steam content as determined by fuel inlet composition, current density and fuel utilization was identified as major parameter, more important than for example operating temperature. The obtained knowledge is adopted to identify optimal operation profiles in order to acquire accelerated testing for lifetime investigation of SOFCs.

Developing Evaluation Module for Battery Lifetime

Lithium-ion batteries (LiBs) have seen increasing use in automobiles and buildings over the past decade. Usable lifetimes of several years are sufficient for LiBs used in electronic devices, but infrastructure applications require lifetimes measured in decades. Users of LiBs are faced with uncertainty about LiB lifetimes, which hinders the spread of LiBs. Predicting LiB performance degradation and evaluating useful lifetimes by examining present performance is therefore important for planning. Our research group has developed an evaluation model for LiBs that comprises an empirically obtained degradation speed database and a method for recognizing LiB usage patterns.

A Lifetime Forecast Scheme for a Distributed Low Duty Cycle Multi-Hop Routing in Wireless Sensor Networks

Wireless sensor nodes become more and more attractive for a broad variety of application scenarios. Wireless Sensor Networks (WSNs) can be easily deployed and they require by design low maintenance effort. But running installations are still rare, because real world requirements and environmental conditions are even today a big challenge. Especially in multi-hop networks a minimum lifetime of several years cannot be achieved globally. In this paper, the authors present a Distributed Low Duty Cycle (DLDC) based Multi-Hop Routing (MHR) protocol for Wireless Sensor Networks guaranteeing a minimum network lifetime. The authors introduce a forecast scheme to calculate the expected life of a node with a minimal effort. The authors are convinced that by using a forecast scheme the network topology and the used protocols can be easily optimized before deploying the network. The authors evaluated their forecast scheme by measuring real sensor node parameters and simulating an example network in the Castalia simulation framework. The authors demonstrated that by using the proposed scheme an energy consumption forecast with a deviation of less than three per cent can be achieved.

Two-time scale fatigue modelling: application to damage

A temporal multiscale modelling applied to fatigue damage evolution in cortical bone is presented. Microdamage accumulation in cortical bone, ensued from daily activities, leads to impaired mechanical properties, in particular by reducing the bone stiffness and inducing fatigue. However, bone damage is also known as a stimulus to bone remodelling, whose aim is to repair and generate new bone, adapted to its environment. This biological process by removing fatigue damage seems essential to the skeleton lifetime. As daily activities induce high frequency cycles (about 10,000 cycles a day), identifying two-time scale is very fruitful: a fast one connected with the high frequency cyclic loading and a slow one related to a quasi-static loading. A scaling parameter is defined between the intrinsic time (bone lifetime of several years) and the high frequency loading (few seconds). An asymptotic approach allows to decouple the two scales and to take into account history effects (Guennouni and Aubry in CR Acad Sci Paris Ser II 20:1765–1767, 1986). The method is here applied to a simple case of fatigue damage and a real cortical bone microstructure. A significant reduction in the amount of computation time in addition to a small computational error between time homogenized and non homogenized models are obtained. This method seems thus to give new perspectives to assess fatigue damage and, with regard to bone, to give a better understanding of bone remodelling.

PEDAMACS: power efficient and delay aware medium access protocol for sensor networks

PEDAMACS is a Time Division Multiple Access (TDMA) scheme that extends the common single hop TDMA to a multihop sensor network, using a high-powered access point to synchronize the nodes and to schedule their transmissions and receptions. The protocol first enables the access point to gather topology (connectivity) information. A scheduling algorithm then determines when each node should transmit and receive data, and the access point announces the transmission schedule to the other nodes. The performance of PEDAMACS is compared to existing protocols based on simulations in TOSSIM, a simulation environment for TinyOS, the operating system for the Berkeley sensor nodes. For the traffic application we consider, the PEDAMACS network provides a lifetime of several years compared to several months and days based on random access schemes with and without sleep cycles, respectively, making sensor network technology economically viable.

Prolonging the lifetime of wireless sensor networks by cross-layer interaction

This article presents a cross-layered approach for networking in wireless sensor networks. WSNs differ greatly from traditional ad hoc wireless networks and therefore require the use of new types of network protocols that are energy-efficient to ensure a node lifetime of several years on a single battery and can operate without assistance of central managers in a dynamic network topology. We show that a tightly integrated set of networking protocols is a good solution to reach the target of highly energy-efficient WSNs. Our approach combines medium access organization with routing.

An Arctic Ocean cold core eddy

Detailed physical and chemical observations were obtained during September 1997 of a cold core eddy situated in the southern central Canada Basin of the Arctic Ocean. The eddy was about 20 km in diameter, had maximum current speeds exceeding 20 cm s−1, and extended from the base of the upper mixed layer, near 40 m, down to ∼400 m. Excess salt in the eddy core was consistent with addition of brine from ∼1 m of ice formation. Core tracer distributions indicated a lifetime exceeding 1 year and were consistent with an origin as near‐surface Pacific water with some admixed terrestrial runoff. The eddy was probably formed in association with a polynya along the Alaskan Chukchi Sea coast through local water densification from surface ice formation followed by development of frontal instabilities. Formation and subsequent migration of such eddies, which may have lifetimes of several years, provide a mechanism for transporting water from the Beaufort and Chukchi Sea coastal and shelf regions into the interior Canada Basin and for contributing to maintenance of the permanent halocline. Present light ice conditions throughout the Arctic Ocean favor the formation of such eddies and may contribute to enhanced ventilation of the halocline waters.

Dynamic shielding during ion bombardment of Ba dispenser cathodes

Ion bombardment (IB) resistivity is a key parameter for cathodes to be operated in TV tubes and CMT's over lifetimes of several years. Thus, accelerated stress tests with much higher ion dose rates than those present in real tube environment are normally used. Here, IB resistivity of Os/Ru-I and top layer Scandate cathodes was investigated. It was observed by variation of the dose rates, that Ba resupply modified the survived ion dose and led to a dynamic shielding of the rest of the surface complex/dipole below Ba. Enhanced IB resistivity w.r.t. total ion dose was observed for reduced ion dose rates. Based on a model of shielding an extrapolation from stress tests to real tube conditions has been established, where the correction factor is in the range of 1–8, depending on the test conditions.

Reproduction of the Florida Lancelet (Branchiostoma floridae): Spawning Patterns and Fluctuations in Gonad Indexes and Nutritional Reserves

The reproductive biology of the Florida lancelet (Branchiostoma floridae) is described from over 21,000 animals collected from early summer 1991 through late summer 1995. Collections were made daily during summer and less frequently during other seasons. Minimal length at sexual maturity was about 23 mm for both sexes. The ratio of males to females was 1:1 throughout the year, and no hermaphrodites were found. During the breeding season (late spring through late summer), the population spawned just after sunset at intervals of 1-15 days, with an average interval of roughly a week. The proportion of lancelets spawning on a given date ranged from a small fraction to about 90% of the adult population. Spawning dates were not significantly correlated with lunar phase or fluctuations in salinity or water temperature. Lancelets could be induced to spawn by electric shock in the laboratory, but only on dates when they spawned in the field. A daily determination of gonad indexes suggested that individual males and females could spawn and then ripen and spawn again in the same breeding season, possibly in as little as 1-2 weeks. Fin-ray indexes (assumed to be proportional to somatic nutritional reserves) were highest in winter, when the lancelets were apparently well nourished but not breeding, and consistently low during the summer breeding season, when the animals were repeatedly spawning and presumably draining their nutritional reserves. Additional key words: amphioxus, cephalochordate The subphylum Cephalochordata of phylum Chordata comprises about 25 species of lancelets (=amphioxus) living in shallow marine or estuarine habitats. Because of their phylogenetic ties to vertebrate chordates, lancelets have been extensively studied anatomically and embryologically for over a century. In contrast, much less is known of their ecology in general and reproductive biology in particular, partly due to the relative inaccessibility of large populations of lancelets. Although most lancelet species have a wide geographic distribution, they are typically rare through much of their range and occur at high densities in only a few scattered localities (e.g., Lagos Lagoon, Nigeria; Xiamen and Qingdao, China; Kingston Harbour, Jamaica; and Tampa Bay, Florida). Much of the work on lancelet reproduction (reviewed in Wickstead 1975) concerns temperate populations of Branchiostoma lanceolatum in Europe and B. belcheri in China. The reproduction of one tropical lancelet, B. nigeriense, has also been studied extenaCurrent address: Hopkins Marine Station, Stanford University, Pacific Grove CA 93950, USA. sively, although for an estuarine population exterminated once a year by fresh water runoff and replenished after each rainy season by animals from the open sea. These studies may give a distorted picture of reproduction in cephalochordates as a whole, because most lancelets have sub-tropical and tropical distributions and maximal lifetimes of several years. The purpose of the present study is to describe the reproductive biology of Branchiostoma floridae HUBBS 1922. In contrast to lancelets previously studied in detail, B. floridae is sub-tropical and has a maximal lifetime of several years (Stokes 1996); therefore, the reproductive biology of this species may more fairly represent that of cephalochordates generally. The population studied lives in Tampa Bay, Florida, and, from a previous description of larval settlement patterns (Stokes 1996), its breeding season is known to last from late spring through late summer. Our results also help clarify the role of lancelet finrays, which lack any homology with vertebrate finrays (Azariah 1965) and comprise retroperitoneal accumulations of glycoprotein and lipid (Holland & Holland 1991 a). Here we assume that fin-ray volumes This content downloaded from 157.55.39.223 on Wed, 24 Aug 2016 05:51:42 UTC All use subject to http://about.jstor.org/terms

Future possibilities for lunar occultation studies of faint X-ray sources

Lunar occultation can be considered of interest for future missions dedicated to X-ray astronomy only if instruments with a large enough collecting area are used. In this case, observations of the numerous, faint X-ray sources occulted by the moon during a typical satellite lifetime of several years, can, in principle, add good source positioning as a free bonus to a high-throughput, medium-imaging mission. In the practical case of the EPIC instrument aboard the XMM ESA satellite, a simple calculation shows the potential usefulness of this technique.

Neutron Diffraction - A Probe for Grain Size and Preferred Orientation in Zircaloy-Clad Uranium

AbstractA recent goal of the ANL Intense Pulsed Neutron Source (IPNS) has been the fabrication of a new enriched uranium target with increased neutron flux (by a factor of 3) which is dimensionally stable under irradiation. Neutron diffraction, using several instruments both at IPNS and MURR, has been used as a probe to characterize the target material vith respect to grain size and preferred orientation. The samples studied were portions of the uranium discs (4" diameter X 1/2" thick) which, when stacked, form the target assembly at IPNS. The old target discs were fabricated as slices from a fast cooled casting (arc-melted, water cooled in a cylindrical mold) and possess small grain size and negligible orientation. The new enriched target discs, on the other hand, are being fabricated from a slow cooled material (graphite book-mold, natural cooling) and, prior to additional treatment, have a large grain size and a high degree of preferred orientation which could produce dimensional changes during fission as the target is used. Our conclusion from this investigation is that a β-phase heat treatment (quench from 730°C) is necessary to produce a finer grain and more nearly random texture in thg new enriched material. Based on our detailed texture measurements the anticipated target lifetime of several years appears feasible.

The Suppression of Destructive Sparks in Parallel Plate Proportional Counters

We find that high energy background events produce localised sparks in parallel plate counters when operated in the proportional mode. These sparks increase dead-time and lead to degradation ranging from electrode damage to spurious pulsing and continuous breakdown. The problem is particularly serious in low energy photon detectors for X-ray astronomy which are required to have lifetimes of several years in the high radiation environment of space. For the parallel plate imaging detector developed for the European X-ray Observatory Satellite (EXOSAT) we investigate quantitatively the spark thresholds, spark rates and degradation processes. We discuss the spark mechanism, pointing out differences from the situation in spark chambers and counters. We show that the time profile of the sparks allows us to devise a spark suppression system which reduces the degradation rate by a factor of ~200.

An experimental investigation of the development of Porocephalus crotali (Pentastomida : Porocephalida) in the western diamondback rattlesnake ( Crotalus atrox)

The development of Porocephalus crotali in the rattlesnake definitive host ( Crotalus atrox) is described. Infective nymphs excyst, penetrate the body cavity by boring through the stomach mucosa, and, in as little as 12 days, enter the lung where they grow to maturity. Copulation, which was observed at 75 and 86 days post-infection, is followed by prolonged sperm storage in spermathecae. This heralds a long prepatent period. Egg production, commencing 230–250 days after infection, is massive and continuous over a lifetime of several years. Hook data indicates that at least three moults separate the infective nymph and the adult female making a minimum of nine for the complete development from the primary larva. There was little evidence of pathological symptoms.