5,482 research outputs found

    An experimental study of the dual-fuel performance of a small compression ignition diesel engine operating with three gaseous fuels

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    A dual-fuel engine is a compression ignition (CI) engine where the primary gaseous fuel source is premixed with air as it enters the combustion chamber. This homogenous mixture is ignited by a small quantity of diesel, the ‘pilot’, that is injected towards the end of the compression stroke. In the present study, a direct-injection CI engine, was fuelled with three different gaseous fuels: methane, propane, and butane. The engine performance at various gaseous concentrations was recorded at 1500 r/min and quarter, half, and three-quarters relative to full a load of 18.7 kW. In order to investigate the combustion performance, a novel three-zone heat release rate analysis was applied to the data. The resulting heat release rate data are used to aid understanding of the performance characteristics of the engine in dual-fuel mode. Data are presented for the heat release rates, effects of engine load and speed, brake specific energy consumption of the engine, and combustion phasing of the three different primary gaseous fuels. Methane permitted the maximum energy substitution, relative to diesel, and yielded the most significant reductions in CO2. However, propane also had significant reductions in CO2 but had an increased diffusional combustion stage which may lend itself to the modern high-speed direct-injection engine

    A Concise Introduction to Perturbation Theory in Cosmology

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    We give a concise, self-contained introduction to perturbation theory in cosmology at linear and second order, striking a balance between mathematical rigour and usability. In particular we discuss gauge issues and the active and passive approach to calculating gauge transformations. We also construct gauge-invariant variables, including the second order tensor perturbation on uniform curvature hypersurfaces.Comment: revtex4, 16 pages, 3 figures; v2: minor changes, typos corrected, reference added, version accepted by CQ

    Detached Eddy Simulation of Flap Side-Edge Flow

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    Detached Eddy Simulation (DES) of flap side-edge flow was performed with a wing and half-span flap configuration used in previous experimental and numerical studies. The focus of the study is the unsteady flow features responsible for the production of far-field noise. The simulation was performed at a Reynolds number (based on the main wing chord) of 3.7 million. Reynolds Averaged Navier-Stokes (RANS) simulations were performed as a precursor to the DES. The results of these precursor simulations match previous experimental and RANS results closely. Although the present DES simulations have not reached statistical stationary yet, some unsteady features of the developing flap side-edge flowfield are presented. In the final paper it is expected that statistically stationary results will be presented including comparisons of surface pressure spectra with experimental data

    An electron-deficient triosmium cluster containing the thianthrene ligand: Synthesis, structure and reactivity of [Os₃(CO)₉(μ3-η2-C₁₂H₇S₂)(μ-H)]

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    Reaction of [Os₃(CO)₁₀(CH₃CN)₂] with thianthrene at 80 °C leads to the nonacarbonyl dihydride compound [Os₃(CO)₉(μ-3,4-η²-C₁₂H₆S₂)(μ-H)₂] (1) and the 46-electron monohydride compound [Os₃(CO)₉(μ₃-η²-C₁₂H₇S₂)(μ-H)] (2). Compound 2 reacts reversibly with CO to give the CO adduct [Os₃(CO)₁₀(μ-η²-C₁₂H₇S₂)(μ-H)] (3) whereas with PPh₃ it gives the addition product [Os₃(CO)₉)(PPh₃)(μ-η²-C₁₂H₇S₂)(μ-H)] (4) as well as the substitution product 1,2-[Os₃(CO)₁₀ ((PPh₃)₂] (5) Compound 2 represents a unique example of an electron-deficient triosmium cluster in which the thianthrene ring is bound to cluster by coordination of the sulfur lone pair and a three-center-two-electron bond with the C(2) carbon which bridges the same edge of the triangle as the hydride. Electrochemical and DFT studies which elucidate the electronic properties of 2 are reported

    Peran Penyuluhan dalam Pemberdayaan Petani Kelapa Sawit Pola Swadaya di Kabupaten Kampar

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    The purposes of this research are : (1) To identify the role of extension on oil palm independent smallholder farmers; (2) To know empowerments level of the farmers (3) To analyse the relation between extension's role and empowerment of the farmers in Kampar District. This research was conducted at Sikijang Village at Tapung Hilir sub-district and Bukit Kemuning village at Tapung Hulu sub-district. Research's samples was determined by purposive sampling methods by consideration that the location has active extension activities and has farmers group. The sample number are 60 the farmers. Validity and reliability analysis has been done on the measuring instruments by conduction try out to 30 respondents. Data's analysis to acknowledge the first and second research purpose used Scale Likert's summated Rating (SLR), whereas multiple linear regression was used to acknowledge the third purpose of this research. The Result showed that: (1) Extension role has been instrumental in the farmers activities as seen from the education, dissemination, facilitation, consultation, supervision, monitoring and evaluation variables; (2) Extension activities has been going well in empowering human resources, productive economy, and the farmers institutional in Kampar Regency; and (3) Empowerment of the farmers affected significantly by the role of extension in education, facilitation and consultation, and monitoring and evaluation, while the role of extension does not significantly effecting on dissemination and supervision of the farmers empowerments

    Determination of the Elastic Constants of Composites Through the Inversion of Leaky Lamb Wave Data

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    Analysis and prediction of the response of composite laminates to external loads are essential for the design of composite structures. This in turn requires a precise knowledge of their mechanical properties including their constitutive behavior. It is reasonable to assume that, in the bulk, the overall behavior of unidirectional graphite/epoxy composites is the same as that of a homogeneous, transversely isotropic material with its symmetry axis along the fiber direction. Then the linear elastic response of the material can be described by means of five elastic constants. If the values of these constants can be determined, then the stress analysis of a laminate with a given number and stacking order of the laminae can, in principle, be carried out. However, the measurement of the elastic constants by conventional, destructive techniques is difficult and often, inaccurate. Thus, the availability of alternative, preferably nondestructive methods, for the determination of the elastic costants of the material would be extremely helpfu

    Uji Aktivitas Antioksidan Ekstrak Daun Patikan Kebo (Euphorbia Hirta L.)

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    Patikan kebo (euphorbia hirta L.) is a plant commonly found in the tropical regions. The objectiveof this research was to determine the antioxidant activity of Patikan kebo leaves extract and tocategorize the strength of the extract in blocking free radicals. This research was conducted by laboratoryexperiment using maceration extraction techniques. Antioxidant activity of the extract was tested using1,1-diphenyl-2-pikrilhidrazil (DPPH). Variation concentrations of the used of Patikan kebo leavesextract and vitamin c as a positive control used for analysis were of 20 ppm, 40 ppm, 60 ppm, and 80ppm. Analysis of the sample was conducted using spectronic UV-Vis. The result showed that Patikankebo leaves extract was a very strong antioxidant. It was proved by the number of IC50 less then 50. Thecalculation of IC50 of patikan kebo leaves extract was 11.50 mg/L

    Effect of Interaction between Bridge Piers on Local Scouring in Cohesive Soils

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    Local scour at the piers is one of the main reasons of bridge foundation undermining. Earlier research studies focused mainly on the scour at a single bridge pier; nevertheless, modern designs of the bridges comprise wide-span and thus group of piers rather than a single pier are usually used to support the superstructure. The flow and scour pattern around group of piers is different from the case of a single pier due to the interaction effect. Reviewing the literature of local scour around bridge piers group revealed that the local scour around bridge piers group founded in cohesive soil bed was not investigated, and most of the scour studies were related to scour in cohesionless soils. The objective of the present study is to investigate the effect of the interaction between two in-line (tandem) circular bridge piers of variable spacings founded in cohesive soil on the local scour. A set of laboratory flume experiments were conducted under the clear-water scour condition to investigate this effect. This study is the first that investigates experimentally the scour around group of bridge piers in cohesive bed. It was found that the maximum scour depth at the upstream pier of the two in-line piers occurred at a spacing of two times the diameter of the pier, scour at the downstream pier was reduced due to a sheltering effect, the interference effect will be reduced for pier spacings larger than three times of the pier diameter. A recent pier scour equation was used to estimate the scour depths at the two in-line piers in cohesive soil and compare the estimated value with the measured scour depths in the laboratory. The comparison indicated that the proposed scour equation overestimates the scour depths at both the upstream and the downstream pier

    Effect of Irrigation Levels on Yield Performance of Black Cumin

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    An experiment was conducted in the experimental field of Horticulture Department, Bangabandhu Sheikh MujiburRahman Agricultural University (BSMRAU), Salna, Gazipur during the period from 20 November, 2012 to 12 April, 2013 to determine the optimum level of irrigation for better yield and quality of black cumin. There were six different irrigation levels (I1 - no irrigation, I2 - three irrigation, I3 - four irrigation, I4 - six irrigation, I5 - eight irrigation and I6 - ten irrigation). Results revealed that the number of primary branches (6.33), secondary branches (11.84), tertiary branches (6.29), number of capsule per plant (18.64), capsule length (1.89 cm), diameter of capsule( 1.05 cm), number of seed per capsule (107.8), fresh seed yield per plant (3.84g), dry seed yield per plant (3.26g), 1000 seed weight (2.40g) and seed yield (1.77 t/ha) were observed maximum in I6(ten irrigation)
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