Evaluation of on-board hydrogen storage methods for hypersonic vehicles

Hydrogen is the foremost candidate as a fuel for use in high speed transport. Since any aircraft moving at hypersonic speeds must have a very slender body, means of decreasing the storage volume requirements below that for liquid hydrogen are needed. The total performance of the hypersonic plane needs to be considered for the evaluation of candidate fuel and storage systems. To accomplish this, a simple model for the performance of a hypersonic plane is presented. To allow for the use of different engines and fuels during different phases of flight, the total trajectory is divided into three phases: subsonic-supersonic, hypersonic and rocket propulsion phase. The fuel fraction for the first phase is found be a simple energy balance using an average thrust to drag ratio for this phase. The hypersonic flight phase is investigated in more detail by taking small altitude increments. This approach allowed the use of flight profiles other than the constant dynamic pressure flight. The effect of fuel volume on drag, structural mass and tankage mass was introduced through simplified equations involving the characteristic dimension of the plane. The propellant requirement for the last phase is found by employing the basic rocket equations. The candidate fuel systems such as the cryogenic fuel combinations and solid and liquid endothermic hydrogen generators are first screened thermodynamically with respect to their energy densities and cooling capacities and then evaluated using the above model

Sustainable development of smallholder crop-livestock farming in developing countries

Meeting the growing demand for animal-sourced food, prompted by population growth and increases in average per-capita income in low-income countries, is a major challenge. Yet, it also presents significant potential for agricultural growth, economic development, and reduction of poverty in rural areas. The main constraints to livestock producers taking advantage of growing markets include; lack of forage and feed gaps, communal land tenure, limited access to land and water resources, weak institutions, poor infrastructure and environmental degradation. To improve rural livelihood and food security in smallholder crop-livestock farming systems, concurrent work is required to address issues regarding efficiency of production, risk within systems and development of whole value chain systems. This paper provides a review of several forage basedstudies in tropical and non-tropical dry areas of the developing countries. A central tenet of this paper is that forages have an essential role in agricultural productivity, environmental sustainability and livestock nutrition in smallholder mixed farming systems

Interoperability between Heterogeneous Federation Architectures: Illustration with SAML and WS-Federation

International audienceDigital identity management intra and inter information systems, and, service oriented architectures, are the roots of identity federation. This kind of security architectures aims at enabling information system interoperability. Existing architectures, however, do not consider interoperability of heterogeneous federation architectures, which rely on different federation protocols.In this paper, we try to initiate an in-depth reflection on this issue, through the comparison of two main federation architecture specifications: SAML and WS-Federation. We firstly propose an overall outline of identity federation. We furthermore address the issue of interoperability for federation architectures using a different federation protocol. Afterwards, we compare SAML and WS-Federation. Eventually, we define the ways of convergence, and therefore, of interoperability

New records of Decapod Crustaceans (Decapoda: Pontoniinae and Inachidae) associated with sea anemones in Turkish waters

Three anemone-associated decapod crustaceans, two shrimp species, Periclimenes amethysteus and P. aegylios (Caridea: Palaemonidae: Pontoniinae), and the crab Inachus phalangium (Brachyura: Inachidae), all collected from the Dardanelles, are reported for the first time from Turkish coasts. Another inachid crab, Macropodia czernjawskii is also reported for the first time to occur in association with the sea anemone, Anemonia viridis. Periclimenes scriptus was the fifth decapod species recorded associated with sea anemones within the present study, and while this species has already been reported from Turkish waters, this is the first time it is recorded from the Dardanelles (the Turkish Straits System)

Numerical study of two-body correlation in a 1D lattice with perfect blockade

We compute the dynamics of excitation and two-body correlation for two-level "pseudoatoms" in a 1D lattice. We adopt a simplified model where pair excitation within a finite range is perfectly blocked. Each superatom is initially in the ground state, and then subjected to an external driving laser with Rabi frequency satisfying a Poissonian distribution, mimicking the scenario as in Rydberg gases. We find that two-body quantum correlation drops very fast with the distance between pseudoatoms. However, the total correlation decays slowly even at large distance. Our results may be useful to the understanding of Rydberg gases in the strong blockade regime

Diet Composition of Six Anuran Species (Amphibia: Anura) in Terminalia Forest, Mindanao Island, Philippines

The diet of six anuran species (Kaloula conjuncta, Philautus acutirostris, Polypedates leucomystax, Occidozyga laevis, Fejervarya cancrivora and Rana granducola) was determined using the gut content analysis. Nineteen food items were identified with Hymenoptera: Formicidae as the most frequently occurring food item appearing in the guts of 5 out of 6 species.  Coleoptera, Diptera, and Orthoptera followed appearing in 4 out of 6 species. The constantly frequent occurring food item for each species was: Hymenoptera for K. conjuncta and P. leucomystax; Hemiptera for O. laevis; and Orthoptera for R. grandocula. Degree of food preference (DFP) differed for each food item. Preferential food items (2<DFP<3) were Hymenoptera for K. conjuncta and P. leucomystax and Orthoptera for R. granducola. Presence of accidental occurrence and occasionally preferred food items was prominent in P. acutirostris. The occurrence of tadpole in the gut of O. laevis suggesting batracophagy is reported here. The recovery of food items that serve as bioindicators for water quality suggest that the water quality in the area was good. Thus, this study strongly supports the protection of the area for conservation of both anurans and their prey

Using Recurrent Phenotypical Selection to Improve Drought Tolerance of Red Clover

Red clover is one of the most important forage legumes in the world. It is utilized extensively in European and North American farming systems. Approximately, 4 million hectares of red clover are grown globally each year for forage production, soil improvement, and as a pollen and nectar source for pollinators (Riday, 2010). In North America, red clover is widely used in temperate regions for pasture, hay, and silage in combination with grasses for soil improvement and as a pollen and nectar source for bumblebees (Bombus). In the northwest, it is also grown for seed production (Anderson et al., 2016) with Oregon farmers producing 89 % of the US total (USDA-NASS, 2019). Drought stress conditions negatively affect the productivity of red clover, therefore, developing red clover cultivars that are highly tolerant to drought is needed for changing climatic conditions. The main objective of this study was to select red clover germplasm with improved drought tolerance and to subsequently develop commercial cultivars with higher herbage accummulation and persistence when grown in low soil moisture conditions

Deposition and Characterization of CdS, CuS and ZnS Thin Films Deposited by SILAR Method

Cadmium sulfide, copper sulfide and zinc sulfide films were grown on Si(111) substrate by successive ionic layer adsorption and reaction method at room temperature. The crystalline structure and morphology of obtained films were characterized by X-ray diffraction, scanning electronic microscope and energy dispersive X-ray analysis methods. The films were polycrystalline and showed preferred orientation. The surface morphology of these films looked relatively smooth and homogeneous in the scanning electron microscope image. The energy dispersive X-ray analysis spectra showed that the expected elements exist in the thin films

Improving the performance of bright quantum dot single photon sources using amplitude modulation

Single epitaxially-grown semiconductor quantum dots have great potential as single photon sources for photonic quantum technologies, though in practice devices often exhibit non-ideal behavior. Here, we demonstrate that amplitude modulation can improve the performance of quantum-dot-based sources. Starting with a bright source consisting of a single quantum dot in a fiber-coupled microdisk cavity, we use synchronized amplitude modulation to temporally filter the emitted light. We observe that the single photon purity, temporal overlap between successive emission events, and indistinguishability can be greatly improved with this technique. As this method can be applied to any triggered single photon source, independent of geometry and after device fabrication, it is a flexible approach to improve the performance of solid-state systems, which often suffer from excess dephasing and multi-photon background emission