870 research outputs found
Wang-Landau Algorithm: a Theoretical Analysis of the Saturation of the Error
In this work we present a theoretical analysis of the convergence of the
Wang-Landau algorithm [Phys. Rev. Lett. 86, 2050 (2001)] which was introduced
years ago to calculate the density of states in statistical models. We study
the dynamical behavior of the error in the calculation of the density of
states.We conclude that the source of the saturation of the error is due to the
decreasing variations of the refinement parameter. To overcome this limitation,
we present an analytical treatment in which the refinement parameter is scaled
down as a power law instead of exponentially. An extension of the analysis to
the N-fold way variation of the method is also discussed.Comment: 7 pages, 5 figure
Oil Transportation in Pipelines with the Existence of Ice
PresentationWhen the ambient temperature is below freezing point, ice may form in the oil transportation pipelines, which can cause flow assurance issues, such as restricting flow path or even plugging the pipeline. Ice plugging was reported to delay the restart of the Poplar pipeline system gathering crude oil from Montana and North Dakota. [1] Ice may also pose threats to the Trans-Alyeska Pipeline System (TAPS). The declining throughput makes the oil get colder much faster. If oil temperature falls below the freezing point, ice forms and leads to flow assurance issues, such as coating critical valves, accumulating in the pipeline, and restricting flow. [2] This paper investigates the fundamentals of ice formation in the pipeline and its effect on the transportation system. A 2-inch diameter carbon steel flow loop was instrumented to measure pressure, temperature, and differential pressure. The experimental results show that ice formation can restrict flow at the low sport in front of the flow meter, the inserted thermocouples, and the perforated plate. Annular ice deposition was found at the pipe wall. The morphology of the deposition is rime ice, indicating the deposition is due to small ice crystals sticking to the pipe surface. It was found that the formation of annular deposition requires a negative temperature gradient. The effect of water cuts and fluid properties on plugging tendency is discussed. The mechanisms for ice deposition along the pipe and plugging at the pipe components are proposed
“They’re in the Shadows”: School Counselors Share the Lived Experiences of Latino/a Undocumented Students
Latino/a undocumented students are among the population of students who are in danger of not graduating or pursuing college due to the unique set of challenges they face navigating education in the U.S. This study aims to understand undocumented students\u27 experiences and the factors that impede them from furthering their education. As professionals in education, school counselors can offer a unique perspective on the barriers that college-bound undocumented students face when pursuing higher education. Using a phenomenological approach, data was gathered from counselors (N=14) across 10 school districts. The findings revealed undocumented students are faced with a myriad of challenges, socio-emotionally, academically, and career-wise, as they prepare to transition from high school to college
Interactions between HLA-B and leukocyte immunoglobulin like receptors B2 (LILRB2) correlate with HIV-1 disease outcomes
Characterization of LR-115 Type 2 Detectors for Monitoring Indoor Radon 222: Determination of the Calibration Factor
The city of Lima, capital of Peru, has about 11 million inhabitants. Lima has no records about the indoor Radon 222 concentration levels in dwellings. Hereby, we are planning to register the indoor radon concentrations in Lima and in other cities of Peru in the next three years. First, we will determine the calibration factor for the detectors which will be used in our measurements. For this purpose, Solid State Nuclear Tracks Detectors of nitrocellulose nitrate (LR-115 type 2) were used.The calibration process using a Radium 226 source was described to obtain the calibration factor. Linear response in tracks number was found in relation with irradiation time and its stability after time at the calibration chamber
Finite-Size Scaling and Universality in the Spin 1 Quantum XY Chain
The spin-1 XY chain in a transverse field is studied using finite-size
scaling. The ground state phase diagram displays a paramagnetic, an ordered
ferromagnetic and an ordered oscillatory phase. The paramagnetic-ferromagnetic
transition line belongs to the universality class of the 2D Ising model. Along
this line, universality is confirmed for the finite-size scaling functions of
several correlation lengths and for the conformal operator content.Comment: Latex 8 pages, 2 uucompressed figure
Extended States in a One-dimensional Generalized Dimer Model
The transmission coefficient for a one dimensional system is given in terms
of Chebyshev polynomials using the tight-binding model. This result is applied
to a system composed of two impurities located between sites of a host
lattice. It is found that the system has extended states for several values of
the energy. Analytical expressions are given for the impurity site energy in
terms of the electron's energy. The number of resonant states grows like the
number of host sites between the impurities. This property makes the system
interesting since it is a simple task to design a configuration with resonant
energy very close to the Fermi level .Comment: 4 pages, 3 figure
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