11,394 research outputs found
Nonperturbative contributions to a resummed leptonic angular distribution in inclusive neutral vector boson production
We present an analysis of nonperturbative contributions to the transverse
momentum distribution of bosons produced at hadron colliders. The
new data on the angular distribution of Drell-Yan pairs measured
at the Tevatron is shown to be in excellent agreement with a perturbative QCD
prediction based on the Collins-Soper-Sterman (CSS) resummation formalism at
NNLL accuracy. Using these data, we determine the nonperturbative component of
the CSS resummed cross section and estimate its dependence on arbitrary
resummation scales and other factors. With the scale dependence included at the
NNLL level, a significant nonperturbative component is needed to describe the
angular data.Comment: 36 pages, 10 figures, regular article. Revised version accepted for a
publication in Phys.Rev.
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Cyclin B1/CDK1-regulated mitochondrial bioenergetics in cell cycle progression and tumor resistance.
A mammalian cell houses two genomes located separately in the nucleus and mitochondria. During evolution, communications and adaptations between these two genomes occur extensively to achieve and sustain homeostasis for cellular functions and regeneration. Mitochondria provide the major cellular energy and contribute to gene regulation in the nucleus, whereas more than 98% of mitochondrial proteins are encoded by the nuclear genome. Such two-way signaling traffic presents an orchestrated dynamic between energy metabolism and consumption in cells. Recent reports have elucidated the way how mitochondrial bioenergetics synchronizes with the energy consumption for cell cycle progression mediated by cyclin B1/CDK1 as the communicator. This review is to recapitulate cyclin B1/CDK1 mediated mitochondrial activities in cell cycle progression and stress response as well as its potential link to reprogram energy metabolism in tumor adaptive resistance. Cyclin B1/CDK1-mediated mitochondrial bioenergetics is applied as an example to show how mitochondria could timely sense the cellular fuel demand and then coordinate ATP output. Such nucleus-mitochondria oscillation may play key roles in the flexible bioenergetics required for tumor cell survival and compromising the efficacy of anti-cancer therapy. Further deciphering the cyclin B1/CDK1-controlled mitochondrial metabolism may invent effect targets to treat resistant cancers
Modelling and simulation of solar thermal power generation network
In the smart grid context, the article combines SEGS-VI solar thermal power station parameters to establish a solar thermal power generation system model. The thesis is based on the First and Second laws of thermodynamics. It uses the white box model analysis method of the energy system to calculate the solar thermal power generation system-concentrating and collecting subsystem, heat exchange subsystem, and power subsystem to obtain the subsystems dissipation of each process. Finally, the article uses the white box model analysis of the total energy system to treat the subsystems as white boxes, and connects them to form a white box network, makes a reasonable evaluation of the energy consumption status of the total energy system, and finds the weak links in the energy use process of the system. Provide a basis for system energy saving
Control and Stability of Residential Microgrid with Grid-Forming Prosumers
The rise of the prosumers (producers-consumers), residential customers equipped with behind-the-meter distributed energy resources (DER), such as battery storage and rooftop solar PV, offers an opportunity to use prosumer-owned DER innovatively. The thesis rests on the premise that prosumers equipped with grid-forming inverters can not only provide inertia to improve the frequency performance of the bulk grid but also support islanded operation of residential microgrids (low-voltage distribution feeder operated in an islanded mode), which can improve distribution gridsā resilience and reliability without purposely designing low-voltage (LV) distribution feeders as microgrids.
Today, grid-following control is predominantly used to control prosumer DER, by which the
prosumers behave as controlled current sources. These grid-following prosumers deliver active and
reactive power by staying synchronized with the existing grid. However, they cannot operate if
disconnected from the main grid due to the lack of voltage reference. This gives rise to the increasing
interest in the use of grid-forming power converters, by which the prosumers behave as voltage sources. Grid-forming converters regulate their output voltage according to the reference of their own and exhibit load sharing with other prosumers even in islanded operation. Making use of grid-forming
prosumers opens up opportunities to improve distribution gridsā resilience and enhance the genuine
inertia of highly renewable-penetrated power systems.
Firstly, electricity networks in many regional communities are prone to frequent power outages. Instead of purposely designing the community as a microgrid with dedicated grid-forming equipment, the LV feeder can be turned into a residential microgrid with multiple paralleled grid-forming prosumers. In this case, the LV feeder can operate in both grid-connected and islanded modes. Secondly, gridforming prosumers in the residential microgrid behave as voltage sources that respond naturally to the varying loads in the system. This is much like synchronous machines extracting kinetic energy from rotating masses. āGenuineā system inertia is thus enhanced, which is fundamentally different from the āemulatedā inertia by fast frequency response (FFR) from grid-following converters.
Against this backdrop, this thesis mainly focuses on two aspects. The first is the small-signal stability
of such residential microgrids. In particular, the impact of the increasing number of grid-forming
prosumers is studied based on the linearised model. The impact of the various dynamic response of
primary sources is also investigated. The second is the control of the grid-forming prosumers aiming to provide sufficient inertia for the system. The control is focused on both the inverters and the DC-stage converters. Specifically, the thesis proposes an advanced controller for the DC-stage converters based on active disturbance rejection control (ADRC), which observes and rejects the ātotal disturbanceā of the system, thereby enhancing the inertial response provided by prosumer DER. In addition, to make better use of the energy from prosumer-owned DER, an adaptive droop controller based on a piecewise power function is proposed, which ensures that residential ESS provide little power in the steady state while supplying sufficient power to cater for the demand variation during the transient state. Proposed strategies are verified by time-domain simulations
Propagation of angular momentum in charged pion decay and related processes
There are confusions about angular momentum propagation in scattering or
decay processes involving the transition between particle systems that appear
to transform differently under Lorentz transformations. This paper provides an
analysis of the transformation properties of the states and interactions for a
few typical processes within the standard model of particle physics, and
performs explicit calculations showing how angular momentum transfers in these
processes. We shall show that angular momentum conservation is completely
consistent with the calculation in quantum field theory
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