Topology Optimization Method Research on Hollow Wide-chord Fan Blade of a High-bypass Turbofan Engine

AbstractIn order to realize lightweight design of a high-bypass turbofan engine, topology optimization of vacuum structure on a wide-chord fan blade was carried out regarding mixed loading conditions as static strength, vibration and bird-strike. Without changing the leaf shape, relationship of performance indices on vacuum structure was analyzed with simplified mechanical model of loading conditions. Topology optimization designs were carried out according to the highly sensitive conditions. Vacuum structure layout of fan blade was constructed integrating the major load transfer paths in each design proposal. Performance indices of different fan blade structures were compared. Result shown that optimized fan blade can realize lightweight as well as meeting the strength design requirement

Transport spectroscopy in a time-modulated open quantum dot

We have investigated the time-modulated coherent quantum transport phenomena in a ballistic open quantum dot. The conductance $G$ and the electron dwell time in the dots are calculated by a time-dependent mode-matching method. Under high-frequency modulation, the traversing electrons are found to exhibit three types of resonant scatterings. They are intersideband scatterings: into quasibound states in the dots, into true bound states in the dots, and into quasibound states just beneath the subband threshold in the leads. Dip structures or fano structures in $G$ are their signatures. Our results show structures due to 2$\hbar\omega$ intersideband processes. At the above scattering resonances, we have estimated, according to our dwell time calculation, the number of round-trip scatterings that the traversing electrons undertake between the two dot openings.Comment: 8 pages, 5 figure

Study on High-Strength Ring Chain Dynamic Characteristics under Different Launch Parameters

The aim of this study is to investigate the mechanical characteristics of the high-strength ring chain under various launch parameters and the energy consumption caused by this. Particularly, the contact dynamics simulation was implemented in ABAQUS to study the launch characteristics impacted by different chain speeds different transportation loads, and the results were proved by experiments. The results show that stable stresses under different launch speeds are diverse, and the launch speed which makes the performance best is 5.6 m/min; stable stresses under different loads are diverse, and in the overload-launch process, the normal force of the chain increases multi-fold so that the chain will be great damaged; The energy consumption caused by the friction among high-strength ring chains under no-load operation occupies 23.8% of the resistance consumption. With the rise in loads, the total resistance consumption grow linearly. As a consequence, the research has great significance for the research of ring chain launch characteristics, the forecast of the chain's operating life and the efficiency improvement of electromotors.Исследованы механические характеристики высокопрочной кольцевой цепи транспортного оборудования при различных рабочих параметрах и связанное с этим энергопотребление. Динамическая контактная задача моделируется с помощью конечноэлементного пакета ABAQUS для различных транспортных нагрузок и скоростей движения цепи с последующей экспериментальной верификацией полученных результатов. Установлено, что оптимальное функционирование цепи соответствует скорости движения 5,65 м/мин, при которой деформация и напряжение являются стабильными. В режиме перегрузки нормальное напряжение возрастает многократно, что приводит к существенному повреждению цепи. Показано, что при холостом режиме работы цепи 23,8% потребляемой энергии расходуется на преодоление сил трения. При увеличении рабочей нагрузки наблюдается линейный рост потребляемой энергии. Полученные динамические механические характеристики цепи позволяют уточнить прогноз ее долговечности в условиях эксплуатации и усовершенствовать схему энергопитания электромоторов.Досліджено механічні характеристики високоміцного кільцевого ланцюга транспортного обладнання за різних робочих параметрів та зв язане з цим енергоспоживання. Динамічна контактна задача моделюється за допомогою скінченноелементного пакета ABAQUS для різних транспортних навантажень і швидкостей руху ланцюга з подальшою експериментальною верифікацією отриманих результатів. Установлено, що оптимальне функціонування ланцюга відповідає швидкості руху 5,65 м/хв., за якої деформація і напруга є стабільними. У режимі перевантаження нормальна напруга збільшується багаторазово, що призводить до суттєвого пошкодження ланцюга. Показано, що при холостому режимі роботи ланцюга 23,8% споживаної енергії витрачається на подолання сил тертя. Із підвищенням робочого навантаження відмічається лінійне зростання споживаної енергії. Отримані динамічні механічні характеристики ланцюга дозволяють уточнити прогноз його довговічності в умовах експлуатації та удосконалити схему енергоспоживання електромоторів

Shot noise in resonant tunneling through a zero-dimensional state with a complex energy spectrum

We investigate the noise properties of a GaAs/AlGaAs resonant tunneling structure at bias voltages where the current characteristic is determined by single electron tunneling. We discuss the suppression of the shot noise in the framework of a coupled two-state system. For large bias voltages we observed super-Poissonian shot noise up to values of the Fano factor $\alpha \approx 10$.Comment: 4 pages, 4 figures, accepted for Phys. Rev.

ac Josephson effect in the resonant tunneling through mesoscopic superconducting junctions

We investigate ac Josephson effect in the resonant tunneling through mesoscopic superconducting junctions. In the presence of microwave irradiation, we show that the trajectory of multiple Andreev reflections can be closed by emitting or absorbing photons. Consequently, photon-assisted Andreev states are formed and play the role of carrying supercurrent. On the Shapiro steps, dc component appears when the resonant level is near a series of positions with spacing of half of the microwave frequency. Analytical result is derived in the limit of infinite superconducting gap, based on which new features of ac Josephson effect are revealed.Comment: 11 pages, 3 figure

Resonant photon creation in a three dimensional oscillating cavity

We analyze the problem of photon creation inside a perfectly conducting, rectangular, three dimensional cavity with one oscillating wall. For some particular values of the frequency of the oscillations the system is resonant. We solve the field equation using multiple scale analysis and show that the total number of photons inside the cavity grows exponentially in time. This is also the case for slightly off-resonance situations. Although the spectrum of a cavity is in general non equidistant, we show that the modes of the electromagnetic field can be coupled, and that the rate of photon creation strongly depends on this coupling. We also analyze the thermal enhancement of the photon creation.Comment: 13 pages. New section on off-resonance motion is included. To appear in Physical Review