4,749 research outputs found
Evolution of the Pancaking Effect in a LCDM Cosmology
We explore the evolution of the large-scale anisotropy in the velocity field
caused by the gravitational pancaking effect assuming a LCDM universe. The
Millennium Run halo catalogs at four different redshifts, z=0, 0.5, 1 and z=2
are analyzed to find that the pancaking effect starts to intervene the
hierarchical structure formation at redshift z=2 when a characteristic pancake
scale is around 3 Mpc/h. It is also clearly shown how the degree and scale of
the pancaking effect changes with time. An analytic model based on the
Zel'dovich approximation is presented to explain quantitatively the evolution
of the velocity-pancake alignment. A cosmological implication of our finding
and a possibility of detecting a signal in real universe are discussed.Comment: accepted by ApJ, 21 pages, 6 figures, discussion and error analysis
improve
Predictability of reset switching voltages in unipolar resistance switching
In unipolar resistance switching of NiO capacitors, Joule heating in the
conducting channels should cause a strong nonlinearity in the low resistance
state current-voltage (I-V) curves. Due to the percolating nature of the
conducting channels, the reset current IR, can be scaled to the nonlinear
coefficient Bo of the I-V curves. This scaling relationship can be used to
predict reset voltages, independent of NiO capacitor size; it can also be
applied to TiO2 and FeOy capacitors. Using this relation, we developed an error
correction scheme to provide a clear window for separating reset and set
voltages in memory operations
Vertical Resolved Dust Mass Concentration and Backscatter Coefficient Retrieval of Asian Dust Plume Using Quartz Raman Channel in Lidar Measurements
In this work, we present a method for estimating vertical resolved mass concentration of dust immersed in Asian dust plume using Raman scattering of quartz (silicon dioxide, silica). During the Asian dust period of March 15, 16, and 21 in 2010, Raman lidar measurements detected the presence of quartz, and successfully showed the vertical profiles of the quartz backscatter coefficient. Since the Raman backscatter coefficient was connected with the Raman backscatter differential cross section and the number density of quartz molecules, the mass concentration of quartz in the atmosphere can be estimated from the quartz backscatter coefficient. The weight percentage from 40 to 70 % for quartz in the Asian dust was estimated from references. The vertical resolved mass concentration of dust was estimated by quartz mass concentration and weight percentage. We also present a retrieval method to obtain dust backscatter coefficient from the mixed Asian dust and pollutant layer. OPAC (Optical Properties of Aerosol and Clouds) simulations were conducted to calculate dust backscatter coefficient. The retrieved dust mass concentration was used as an input parameter for the OPAC calculations. These approaches in the study will be useful for characterizing the quartz dominated in the atmospheric aerosols and estimating vertical resolved mass concentration of dust. It will be especially applicable for optically distinguishing the dust and non-dust aerosols in studies on the mixing state of Asian dust plume. Additionally, the presented method combined with satellite observations is enable qualitative and quantitative monitoring for Asian dust
Finite-size scaling theory for explosive percolation transitions
The finite-size scaling (FSS) theory for continuous phase transitions has
been useful in determining the critical behavior from the size dependent
behaviors of thermodynamic quantities. When the phase transition is
discontinuous, however, FSS approach has not been well established yet. Here,
we develop a FSS theory for the explosive percolation transition arising in the
Erd\H{o}s and R\'enyi model under the Achlioptas process. A scaling function is
derived based on the observed fact that the derivative of the curve of the
order parameter at the critical point diverges with system size in a
power-law manner, which is different from the conventional one based on the
divergence of the correlation length at . We show that the susceptibility
is also described in the same scaling form. Numerical simulation data for
different system sizes are well collapsed on the respective scaling functions.Comment: 5 pages, 5 figure
In Situ deposition of YBCO high-T(sub c) superconducting thin films by MOCVD and PE-MOCVD
Metalorganic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T( sub c) greater than 90 K and Jc approx. 10 to the 4th power A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metalorganic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology
Future Community-Based Ecotourism (CBET) development
Ecotourism is an alternative form of tourism and is usually confused with natural and cultural tourism.CBET is fast becoming a popular biodiversity conservation tool that develops and benefits the local community. Based on the context of conservation theory and practice, Community-Based Ecotourism (CBET) is a form of community-based natural resource management. However, a sustainable CBET development through Community Capacity Building (CCB)programs is not something that it easily achievable. Local community’s capacity varies from one culture to another. It takes a high level of community participation, in order for it to come to a level where the community members themselves are motivated to participate and contribute to the development of the program. This fully qualitative research involved 15 respondents from the community of Kg. Selai, Bekok in Johor, Malaysia. The result show there are five factors that sustained the ecotourism development based for Orang Asli Community in Kg. Selai, namely, existing CBET development, past CBET development, local community participation in planning stage of tourism, local participation in implementation stage of tourism and participation in nature conservation
In-situ deposition of YBCO high-Tc superconducting thin films by MOCVD and PE-MOCVD
Metal-Organic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T(sub c) greater than 90 K and J(sub c) of approximately 10(exp 4) A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology
Analytic study of the three-urn model for separation of sand
We present an analytic study of the three-urn model for separation of sand.
We solve analytically the master equation and the first-passage problem. We
find that the stationary probability distribution obeys the detailed balance
and is governed by the {\it free energy}. We find that the characteristic
lifetime of a cluster diverges algebraically with exponent 1/3 at the limit of
stability.Comment: 5pages, 4 figures include
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