12,752 research outputs found
Scaling behavior of a one-dimensional correlated disordered electronic System
A one-dimensional diagonal tight binding electronic system with correlated
disorder is investigated. The correlation of the random potential is
exponentially decaying with distance and its correlation length diverges as the
concentration of "wrong sign" approaches to 1 or 0. The correlated random
number sequence can be generated easily with a binary sequence similar to that
of a one-dimensional spin glass system. The localization length (LL) and the
integrated density of states (IDOS) for long chains are computed. A comparison
with numerical results is made with the recently developed scaling technique
results. The Coherent Potential Approximation (CPA) is also adopted to obtain
scaling functions for both the LL and the IDOS. We confirmed that the scaling
functions show a crossover near the band edge and establish their relation to
the concentration. For concentrations near to 0 or 1 (longer correlation length
case), the scaling behavior is followed only for a very limited range of the
potential strengths.Comment: will appear in PR
Use of an approximate similarity principle for the thermal scaling of a full-scale thrust augmenting ejector
Full temperature ejector model simulations are expensive, and difficult to implement experimentally. If an approximate similarity principle could be established, properly chosen performance parameters should be similar for both hot and cold flow tests if the initial Mach number and total pressures of the flow field are held constant. Existing ejector data is used to explore the utility of one particular similarity principle; the Munk and Prim similarity principle for isentropic flows. Static performance test data for a full-scale thrust augmenting ejector are analyzed for primary flow temperatures up to 1560 R. At different primary temperatures, exit pressure contours are compared for similarity. A nondimensional flow parameter is then used to eliminate primary nozzle temperature dependence and verify similarity between the hot and cold flow experiments
Is Sustainable Development of Deserts Feasible?
Hot deserts that presently cover about one-fifth of the land area of our planet are rapidly devouring more and more arable lands mostly due to anthropogenic causes. We propose an interdisciplinary approach to revitalizing and commercializing hot deserts, which is based on systems thinking and Russian and NASA space technology experience in designing life-support systems for long-duration flights. We formulate ten principles for the design of sustainable life support systems in deserts, which can make the development of the deserts feasible. It is discussed how the principles can be employed to design and operate desert’s eco-industrial parks with greenhouses in which the transpired and evaporated moisture is collected and condensed. The potential benefits of setting up the eco-industrial parks in deserts include the slowdown and eventual reversal of the desertification trend, the migration of many industrial production facilities from mild-climate regions to deserts, the increased availability of potable water and food in deserts, the development of poor African countries, and the emergence of new investment markets
Effects of petroleum ether, ethanol and aqueous extracts of indigofera capitata on oedema induced activity of naja nigricollis venom in envenomed rats
The growing demand for herbal products has led to high increase of plant material traded across the world. Indigofera species provide some of these plants’ materials. Indigofera capitata is a plant of the family Fabaceae. The acute toxicity and effects pet.ether, ethanol and aqueous extracts of the plant were carried out in albino rats. The results of acute toxicity studied revealed that pet.ether, ethanol and aqueous extracts had LD50 values of 774.6, 1131.4 and 3807.8mg/kg respectively. These helped to determine the safeness and dosage used for in vivo activity of each extract. The results of the effects of the extracts indicated all the plant extracts had significant (p<0.05) and dose-dependent Oedema forming activity against LD99 Naja nigricollis envenomed rats. Highest reduction in edema forming activity of the extract are shown at dose of 300mg/kg(ethanol) and 1000mg/kg (aqueous) with lowest edema forming activity of 108.00±1.90 and 102.00±1.90 (% mm) respectively compared with the positive control group. The finding revealed that the plant can be used for treatment of snake bite more especially Naja nigricollis bite
Peranan Kota Bogor, Depok, Tangerang, Bekasi, dan Cianjur (Bodetabekjur) dalam Menyokong Pembangunan Kota Jakarta
Kawasan Jakarta, Bogor, Depok, Tangerang, Bekasi, Puncak, Cianjur, yang selanjutnya disebut sebagai Kawasan Jabodetabekpunjur, adalah kawasan strategis nasional yang meliputi seluruh wilayah Provinsi Daerah Khusus Ibukota Jakarta, sebagian wilayah Provinsi Jawa Barat, dan sebagian wilayah Provinsi Banten (Perpres. No. 54 tahun 2008). Tujuan penelitian ini adalah (1) mengidentifikasi sektor unggulan perekonomian wilayah kabupaten/kota di Kawasan Jabodetabekjur serta; (2) mengidentifikasi peranan kabupaten/kota sekitar (Bogor, Depok, Tangerang, Bekasi, Puncak, Cianjur) terhadap pembangunan fisik infrastuktur Kota Jakarta. Penelitian ini menggunakan metode wawancara terhadap 3 responden yang merupakan penentu kebijakan pembangunan di Kota Jakarta. Teknik analisis yang digunakan adalah deskriptif kuantitatif dan kualitatif. Hasil penelitian menunjukkan bahwa setiap kota di Jabodetabekjur dan Kabupaten Cianjur memiliki sektor basis yang didominasi oleh sektor tersier. Kabupaten sisanya memiliki sektor unggulan pada sektor primer dan sektor sekunder. Peranan utama dari kabupaten/kota pada Bodetabekjur adalah pembangunan transportasi massal, peningkatan kapasitas jalan
Bott--Kitaev periodic table and index theory
We consider topological insulators and superconductors with discrete
symmetries and clarify the relevant index theory behind the periodic table
proposed by Kitaev.
An effective Hamiltonian determines the analytical index, which can be
computed by a topological index. We focus on the spatial dimensions one, two
and three, and only consider the bulk theory.
In two dimensions, the -valued invariants are given by the first
Chern number. Meanwhile, -valued invariants can be computed by
the odd topological index and its variations.
The Bott-Kitaev periodic table is well-known in the physics literature, we
organize the topological invariants in the framework of KR-theory.Comment: 37 page
Studies on Control of Hazardous Noise from Portable 650 VA Power Generator
Experimental studies on the assessment and control of near-field noise levels due to the operation of a portable 650 VA power generator were undertaken at a residential building in Ara village, Moro local government, area of Kwara State. Smart sensor sound level meter AR824 (30-130 dB), meter rule and stop watch were used to measure the noise level produced at every two minutes risen time intervals for seven hundred and twenty minutes at ten different locations of one meter intervals. The background noise level of the environment was first taken and reported to be 47.60. The data obtained were analysed with Matlab R2010a. The results revealed that the 650 VA generating plant is safe for use when it is positioned at least 3 meters away to the building, offices, shops and so on
- …