Electrical Conductivity Based Flow Regime Recognition of Two-phase Flows in Horizontal pipeline

An experimental method of resolving flow regimes by utilizing the conductivity data measured by Electrical Resistance Tomography (ERT) is presented. The method applies Boolean logic and frequency analysis of the ERT signal in order to identify five typical flow regimes in horizontal pipe namely: bubble, plug, slug, stratified and annular. The relative conductivity signal obtained from the tomograms is converted to binary form in order to perform Boolean logical operation with the binary templates of typical flow patterns. The overall conductivity of the tomogram is used to extract frequency information of the flow. Flow pattern is identified by the statistical analysis of the combination of this information. The recognition method was evaluated using experimental data from horizontal pipeline for different flow conditions. The identification of the flow regimes from the method was verified using the conductivity images from ERT

Structural and Physical Properties of CaFe4As3 Single Crystals

We report the synthesis, and structural and physical properties of CaFe4As3 single crystals. Needle-like single crystals of CaFe4As3 were grown out of Sn flux and the compound adopts an orthorhombic structure as determined by X-ray diffraction measurements. Electrical, magnetic, and thermal properties indicate that the system undergoes two successive phase transitions occurring at TN1 ~ 90 K and TN2 ~ 26 K. At TN1, electrical resistivities (\rho(b) and \rho(ac)) are enhanced while magnetic susceptibilities (\chi(b) and \chi(ac)) are reduced in both directions parallel and perpendicular to the b-axis, consistent with the scenario of antiferromagnetic spin-density-wave formation. At TN2, specific heat reveals a slope change, and \chi(ac) decreases sharply but \chi(b) has a clear jump before it decreases again with decreasing temperature. Remarkably, both \rho(b) and \rho(ac) decrease sharply with thermal hysteresis, indicating the first-order nature of the phase transition at TN2. At low temperatures, \rho(b) and \rho(ac) can be described by {\rho} = {\rho}0 + AT^\alpha ({\rho}0, A, and {\alpha} are constants). Interestingly, these constants vary with applied magnetic field. The ground state of CaFe4As3 is discussed.Comment: 15 pages, 8 figures, Submitted to Physical Review

Coffee Production in Kavre and Lalitpur Districts, Nepal

Coffee (Coffea spp) is an important and emerging cash crop having potential to provide farmers employment and income generation opportunities. This crop is well adapted to the climatic conditions of mid-hills of Nepal. Thus, majority of the farmers are attracted towards cultivation of coffee because of demands in national and International market. Coffee is now becoming integral part of farming system in rural areas. However, information on performance of coffee and farmers response has not been well documented. Therefore, we undertook the present work to analyze demography, ethnicity, household occupation, literacy status, average land holding, coffee cultivation area, livelihood and sources of income of coffee growers, production and productivity, pricing, cropping pattern of the coffee and problesm faced by them in mid hill district of Kavrepalanchowk (hereafter ‘Kavre') and Lalitpur Districts. All the samples were taken randomly and selected from coffee producing cooperative of Kavre and Lalitpur. Our analysis showed that the male farmer dominant over female on adopting coffee cultivation in both districts with higher value in Kavre. Brahmin and Chetri ethnic communities were in majority over others in adopting the coffee cultivation. Literate farmers were more dominant over illiterates on adopting the coffee cultivation, The mean land holding was less, ranging from 0.15 to 2.30 ha for coffee cultivation, the history of coffee cultivation in Kavre showed that highest number of farmers were engaged in coffee farming from last 16 years. The mean yield of fresh cherry was 1027.20 kg/ha in Kavre, while it was 1849.36 kg/ha in Lalitpur. The study revealed that majority of the coffee plantations were between 6-10 years old. The major problems facing by coffee farmers were diseases spread, lack of irrigation facility and drying of plants. Despite of that the coffee farming was one of the rapidly emerging occupations among the farmers in both district of Nepal

Spin-Orbit Scattering and Quantum Metallicity in Ultra-Thin Be Films

We compare and contrast the low temperature magnetotransport properties of ultra-thin, insulating, Be films with and without spin-orbit scattering (SOS). Beryllium films have very little intrinsic SOS, but by "dusting" them with sub-monolayer coverages of Au, one can introduce a well controlled SOS rate. Pure Be films with sheet resistance R >R_Q exhibit a low-temperature negative magnetoresistance (MR) that saturates to the quantum resistance R_Q = h/e^2. This high-field quantum metal phase is believed to represent a new ground state of the system. In contrast, the corresponding negative MR in Be/Au films is greatly diminished, suggesting that, in the presence of strong SOS, the quantum metal phase can only be reached at field scales well beyond those typically available in a low temperature laboratory.Comment: 12 pages, 4 figures, to appear in PR

Competing magnetic states, disorder, and the magnetic character of Fe3Ga4

The physical properties of metamagnetic Fe$_3$Ga$_4$ single crystals are investigated to explore the sensitivity of the magnetic states to temperature, magnetic field, and sample history. The data reveal a moderate anisotropy in the magnetization and the metamagnetic critical field along with features in the specific heat at the magnetic transitions $T_1=68$ K and $T_2=360$ K. Both $T_1$ and $T_2$ are found to be sensitive to the annealing conditions of the crystals suggesting that disorder affects the competition between the ferromagnetic (FM) and antiferromagnetic (AFM) states. Resistivity measurements reveal metallic transport with a sharp anomaly associated with the transition at $T_2$. The Hall effect is dominated by the anomalous contribution which rivals that of magnetic semiconductors in magnitude ($-5 \mu \Omega$ cm at 2 T and 350 K) and undergoes a change of sign upon cooling into the low temperature FM state. The temperature and field dependence of the Hall effect indicate that the magnetism is likely to be highly itinerant in character and that a significant change in the electronic structure accompanies the magnetic transitions. We observe a contribution from the topological Hall effect in the AFM phase suggesting a non-coplanar contribution to the magnetism. Electronic structure calculations predict an AFM ground state with a wavevector parallel to the crystallographic $c$-axis preferred over the experimentally measured FM state by $\approx$ 50 meV per unit cell. However, supercell calculations with a small density of Fe-antisite defects introduced tend to stabilize the FM over the AFM state indicating that antisite defects may be the cause of the sensitivity to sample synthesis conditions.Comment: 13 pages, 14 figures, and 4 supplementary table

Effect of Chemical Doping on the Thermoelectric Properties of FeGa3

Thermoelectric properties of the chemically-doped intermetallic narrow-band semiconductor FeGa3 are reported. The parent compound shows semiconductor-like behavior with a small band gap (Eg = 0.2 eV), a carrier density of ~ 10(18) cm-3 and, a large n-type Seebeck coefficient (S ~ -400 \mu V/K) at room temperature. Hall effect measurements indicate that chemical doping significantly increases the carrier density, resulting in a metallic state, while the Seebeck coefficient still remains fairly large (~ -150 \mu V/K). The largest power factor (S2/{\rho} = 62 \mu W/m K2) and corresponding figure of merit (ZT = 0.013) at 390 K were observed for Fe0.99Co0.01(Ga0.997Ge0.003)3.Comment: 5 pages, 4 figures, To be appear in Journal of Applied Physic

Structure and physical properties of the noncentrosymmetric superconductor Mo3 Al2 C

We have synthesized polycrystalline samples of the noncentrosymmetric superconductor Mo3 Al2 C by arc and RF melting, measured its transport, magnetic and thermodynamic properties, and computed its band structure. Experimental results indicate a bulk superconducting transition at Tc ∼9.2 K while the density of states at the Fermi surface is found to be dominated by Mod orbitals. Using the measured values for the lower critical field Hc1, upper critical field Hc2, and the specific heat C, we estimated the thermodynamic critical field Hc(0), coherence length ξ (0), penetration depth λ (0), and the Ginzburg-Landau parameter κ (0). The specific-heat jump at Tc, ΔC/γ Tc =2.14, suggests that Mo3 Al 2 C is moderately to strongly coupled, consistent with the fast opening of the gap, as evidenced by the rapid release of entropy below Tc from our electronic specific-heat measurements. Above 2 K the electronic specific heat exhibits the power-law behavior, suggesting that synthesis of single crystals and measurements at lower temperature are needed to establish whether the gap is anisotropic. The estimated value of the upper critical field H c2 (0) is close to the calculated Pauli limit, therefore further studies are needed to determine whether the absence of an inversion center results in a significant admixture of the triplet component of the order parameter. © 2010 The American Physical Society