159 research outputs found
Модернизация теплообменных аппаратов различной производительности на основе численного моделирования
Выпускная квалификационная работа 104 с., 49 рис., 10 табл., 20 источников, 3 прил.
Ключевые слова: математическое моделирование, теплообменник, топливный газ, интенсификаторы теплообмена, принудительная конвекция, турбулентность, расчетная сетка, присоединительный вихрь, тепловой поток, геометрическая модель.
Объектом исследования является теплообменный аппарат, применяемый для нагрева топливного газа перед подачей его на горелочные устройства.
Цель работы - исследование интенсифицированного теплообмена при турбулентном течении теплоносителя в прямых круглых трубах с итенсификаторами теплообмена и анализ эффективности различных турбулизаторов.Final qualifying work 104 p., 49 fig., 10 tab., 20 sources, 3 application.
Keywords: mathematical modeling, heat exchanger, fuel gas, to vary the heat transfer, forced convection, turbulence, computational grid, connecting a whirlwind, heat flow, the geometric model.
The object of research is the heat exchanger that is used to heat the fuel gas before it is fed to the burners.
Objective - research intensified heat exchange in turbulent flow of coolant in straight circular pipes with itensifikatorami heat exchange and analysis of the effectiveness of different turbulence.
The study was carried out mathematical modeling of the object of study with the use of ANSYS package applications, analysis of the results and evaluation of the effectiveness of different types of turbulence
Experimental observation of an enhanced anisotropic magnetoresistance in non-local configuration
We compare non-local magnetoresistance measurements in multi-terminal Ni
nanostructures with corresponding local experiments. In both configurations,
the measured voltages show the characteristic features of anisotropic
magnetoresistance (AMR). However, the magnitude of the non-local AMR signal is
up to one order of magnitude larger than its local counterpart. Moreover, the
non-local AMR increases with increasing degree of non-locality, i.e., with the
separation between the region of the main current flow and the voltage
measurement region. All experimental observations can be consistently modeled
in terms of current spreading in a non-isotropic conductor. Our results show
that current spreading can significantly enhance the magnetoresistance signal
in non-local experiments
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The Beagle 2 microscope
The Beagle 2 microscope provides optical images of the Martian surface at a resolution 5x higher than any other experiment currently planned. By using a novel illumination system it images in three colors and can also detect fluorescent materials
Magnetization reversal of an individual exchange biased permalloy nanotube
We investigate the magnetization reversal mechanism in an individual
permalloy (Py) nanotube (NT) using a hybrid magnetometer consisting of a
nanometer-scale SQUID (nanoSQUID) and a cantilever torque sensor. The Py NT is
affixed to the tip of a Si cantilever and positioned in order to optimally
couple its stray flux into a Nb nanoSQUID. We are thus able to measure both the
NT's volume magnetization by dynamic cantilever magnetometry and its stray flux
using the nanoSQUID. We observe a training effect and temperature dependence in
the magnetic hysteresis, suggesting an exchange bias. We find a low blocking
temperature K, indicating the presence of a thin
antiferromagnetic native oxide, as confirmed by X-ray absorption spectroscopy
on similar samples. Furthermore, we measure changes in the shape of the
magnetic hysteresis as a function of temperature and increased training. These
observations show that the presence of a thin exchange-coupled native oxide
modifies the magnetization reversal process at low temperatures. Complementary
information obtained via cantilever and nanoSQUID magnetometry allows us to
conclude that, in the absence of exchange coupling, this reversal process is
nucleated at the NT's ends and propagates along its length as predicted by
theory.Comment: 8 pages, 4 figure
Observation of insulator-metal transition in EuNiO under high pressure
The charge transfer antiferromagnetic (T =220 K) insulator EuNiO
undergoes, at ambient pressure, a temperature-induced metal insulator MI
transition at T=463 K. We have investigated the effect of pressure (up
to p~20 GPa) on the electronic, magnetic and structural properties of
EuNiO using electrical resistance measurements, {151}^Eu nuclear
resonance scattering of synchrotron radiation and x-ray diffraction,
respectively. With increasing pressure we find at p =5.8 GPa a transition
from the insulating state to a metallic state, while the orthorhombic structure
remains unchanged up to 20 GPa. The results are explained in terms of a gradual
increase of the electronic bandwidth with increasing pressure, which results in
a closing of the charge transfer gap. It is further shown that the
pressure-induced metallic state exhibits magnetic order with a lowervalue of
T (T ~120 K at 9.4 GPa) which disappears between 9.4 and 14.4 GPa.Comment: 10 pages, 3 figure
Mems based bridge monitoring supported by image-assisted total station
In this study, the feasibility of Micro-Electro-Mechanical System (MEMS) accelerometers and an image-assisted total station (IATS) for short-and long-term deformation monitoring of bridge structures is investigated. The MEMS sensors of type BNO055 from Bosch as part of a geo-sensor network are mounted at different positions of the bridge structure. In order to degrade the impact of systematic errors on the acceleration measurements, the deterministic calibration parameters are determined for fixed positions using a KUKA youBot in a climate chamber over certain temperature ranges. The measured acceleration data, with a sampling frequency of 100 Hz, yields accurate estimates of the modal parameters over short time intervals but suffer from accuracy degradation for absolute position estimates with time. To overcome this problem, video frames of a passive target, attached in the vicinity of one of the MEMS sensors, are captured from an embedded on-axis telescope camera of the IATS of type Leica Nova MS50 MultiStation with a practical sampling frequency of 10 Hz. To identify the modal parameters such as eigenfrequencies and modal damping for both acceleration and displacement time series, a damped harmonic oscillation model is employed together with an autoregressive (AR) model of coloured measurement noise. The AR model is solved by means of a generalized expectation maximization (GEM) algorithm. Subsequently, the estimated model parameters from the IATS are used for coordinate updates of the MEMS sensor within a Kalman filter approach. The experiment was performed for a synthetic bridge and the analysis shows an accuracy level of sub-millimetre for amplitudes and much better than 0.1 Hz for the frequencies. © 2019 M. Omidalizarandi et al
Nuclear Resonance Vibrational Spectroscopy of Iron Sulfur Proteins
Nuclear inelastic scattering in conjunction with density functional theory
(DFT) calculations has been applied for the identification of vibrational modes
of the high-spin ferric and the high-spin ferrous iron-sulfur center of a
rubredoxin-type protein from the thermophylic bacterium Pyrococcus abysii
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