Dependence of loading time on control parameters in a standard vapour-oaded magneto-optical trap

Loading time is one of the most important dynamic characteristics of a magneto-optical trap. In this paper, we primarily report on a detailed experimental study of the effects of some magneto-optical trap control parameters on loading time, including the background vacuum pressure, the magnetic field gradient, and the intensities of trapping and repumping lasers. We compare the results with previous theoretical and experimental results, and give qualitative analysis. These experimental investigations offer some useful guidelines to coatrol the loading time of magneto-optical traps. The controllable loading time achieved is helpful to enhance the signal-to-noise ratio of photoassociation spectroscopy, which is remarkably improved from 7 to 28.6.

Effects of intermittent loading time and stress ratio on dwell fatigue behavior of titanium alloy Ti-6Al-4V ELI used in deep-sea submersibles

Different components of deep-sea submersibles,such as the pressure hull,are usually subjected to intermittent loading,dwell loading,and unloading during service.Therefore,for the design and reliability assessment of structural parts under dwell fatigue loading,understanding the effects of intermittent loading time on dwell fatigue behavior of the alloys is essential.In this study,the effects of the intermittent loading time and stress ratio on dwell fatigue behavior of the titanium alloy Ti-6 Al-4 V ELI were investigated.Results suggest that the dwell fatigue failure modes of Ti-6 Al-4 V ELI can be classified into three types,i.e.,fatigue failure mode,ductile failure mode,and mixed failure mode.The intermittent loading time does not affect the dwell fatigue behavior,whereas the stress ratio significantly affects the dwell fatigue life and dwell fatigue mechanism.The dwell fatigue life increases with an increase in the stress ratio for the same maximum stress,and specimens with a negative stress ratio tend to undergo ductile failure.The mechanism of dwell fatigue of titanium alloys is attribute to an increase in the plastic strain caused by the part of the dwell loading,thereby resulting in an increase in the actual stress of the specimens during the subsequent loading cycles and aiding the growth of the formed crack or damage,along with the local plastic strain or damage induced by the part of the fatigue load promoting the cumulative plastic strain during the dwell fatigue process.The interaction between dwell loading and fatigue loading accelerates specimen failure,in contrast to the case for individual creep or fatigue loading alone.The dwell fatigue life and cumulative maximum strain during the first loading cycle could be correlated by a linear relationship on the log–log scale.This relationship can be used to evaluate the dwell fatigue life of Ti alloys with the maximum stress dwell.

Experimental study on remodeling strength of granular materials under different loads and lengths of time

Remodeled clay and sand rock specimens were prepared by designing lateral confinement and water drainage experiments based on the stress exerted on granular materials in a waste dump.An in situ test was conducted in an internal waste dump;the physical and mechanical parameters of the remodeled rock mass dumped at different time and depths were measured.Based on statistics,regression analysis was performed with regard to the shearing stress parameters acquired from the two tests.Other factors,such as remodeling pressure(burial depth),remodeling time(amount of time since waste was dumped),and the corresponding functional relationship,were determined.Analysis indicates that the cohesion of the remodeled clay and its remodeling pressure are correlated by a quadratic function but are not correlated with remodeling time length.In situ experimental results indicate that the shear strength of reshaped granular materials in the internal dump is positively correlated with burial depth but poorly correlated with time length.Cohesion Cand burial depth H follow a quadratic function,specifically for a short time since waste has been dumped.As revealed by both in situ and laboratory experiments,the remodeling strength of granular materials varies in a certain pattern.The consistency of such materials verifies the reliability of the remodeling experimental program.

Analysis of seasonal position variation for selected GNSS sites in Poland using loading modelling and GRACE data

In this study we compared weekly GNSS position time series with modelled values of crustal deformations on the basis of Gravity Recovery and Climate Experiment （GRACE） data. The Global Navigation Satellite Systems （GNSS） time series were taken from homogeneously reprocessed global network solutions within the International GNSS Service （IGS） Reprucessing 1 project and from regional solutions performed by Warsaw University of Technology （WUT） European Permanent Network （EPN） Local Analysis Center （LAC） within the EPN reprocessing project. Eight GNSS sites from the territory of Poland with observation timespans between 2.5 and 13 years were selected for this study. The Total Water Equivalent （TWE） estimation from GRACE data was used to compute deformations using the Green＇s function formalism. High frequency components were removed from GRACE data to avoid aliasing problems. Since GRACE observes mainly the mass transport in continental storage of water, we also compared GRACE deformations and the GNSS position time series, with the deformations computed on the basis of a hydrosphere model. We used the output of Water GAP Hydrology Model （WGHM） to compute deformations in the same manner as for the GRACE data. The WGHM gave slightly larger amplitudes than GNSS and GRACE. The atmospheric non-tidal loading effect was removed from GNSS position time series before comparing them with modelled deformations. The results confirmed that the major part of observed seasonal variations for GNSS vertical components can be attributed to the hy- drosphere loading. The results for these components agree very well both in the amplitude and phase. The decrease in standard deviation of the residual GNSS position time series for vertical components corrected for the hydrosphere loading reached maximally 36% and occurred for all but one stations for both global and regional solutions. For horizontal components the amplitudes are about three times smaller than for vertical components therefore the comparison is much more complicated and the conclusions are ambiguous.

Factors impacting nanoindentation testing results of the cuticle of dung beetle Copris ochus Motschulsky

The cuticle of dung beetle is a layered composite material in micro- or nano-scale. Dung beetle can fly, walk and dig. It can shovel and compact dung of mammals into balls. It use foreleg to walk, midleg and hindleg to hold and impel dung ball. Its two foreleges as digging legs are developed. The factors impacting the nanoindentation testing results of the femur cuticle of forelegs of dung beetle Copris ochus Motschulsky were examined. The nanomechanical test instrument used for the tests was Hysitron nanomechanical system. The results shown that the holding time and loading time are important factors im- pacting the accuracy of such indentation properties as reduced modulus (Er) and the harness ( H ) of the femur cuticle of the forelegs of dung beetle Copris ochus Motschulsky in nanoscale. There exists a threshold holding time of 20 s for the reduced modulus of the femur cuticle. The tests of nanoindentation creep property and the regression analysis of relationship between the depth increment at the maximum load and the time further confirmed the correction of the above threshold holding time. There exist visco-elastic-plastic behaviour and creep phenomenon in the femur cuticle during indenting. Its creep property during the holding procedure at maximum load can be regressed by a general logarithmic equation. The equation fitted by the testing data is ? h = 54.83452 ln(0.00723t +1.00486), where, ? h is the depth increment at the maximum load and t is the time.

Modification of Wirsching’s Model for Fatigue Reliability Analysis

First, Wirsching's model, which is widely employed in fatigue reliability anlysis of marine and offshore structures, is analysed systematically. It is found that the very important random variable A in Wirsching's model can not be directly determined from fatigue experiment because of the irreversibility of fatigue test, and in fact, what Wirsching studied from testing results is not A but a of the statistical Miner's rule. Second, by use of the statistical Miner's rule, a modified Wirsching's model is proposed. Thirdly and more importantly, based on the two-dimensional probabilistic Miner's rule, a new model is established for fatigue reliability analysis of structural components subjected to specified cyclic loading of variable amplitude or stochastic time history. In the end, an example is presented, from which it will be seen that this new model is very convenient to use and feasible to engineering practice.

Elastodynamic analysis at an interface of viscous fluid/thermoelastic micropolar honeycomb medium due to inclined load

In this paper, the effect of angle inclination at the interface of a viscous fluid and thermoelastic micropolar honeycomb solid due to inclined load is investigated. The inclined load is assumed to be a linear combination of normal load and tangential load. Laplace transform with respect to time variable and Fourier transform with respect to space variable are applied to solve the problem. Expressions of stresses, temperature distribution, and pressures in the transformed domain are obtained by introducing potential functions. The numerical inversion technique is used to obtain the solution in the physical domain. The frequency domain expressions for steady state are also obtained with appropriate change of variables. Graphic representations due to the response of different sources and changes of angle inclination are shown. Some particular cases are also discussed.

Fatigue Reliability Analysis of Aircraft Turbine Disc under Random Loads

Due to bad working conditions and complicated structure,kinds of complicated cycle loads work on turbine disc, and it's difficult to determine the stress distribution of their equivalent load.Based on the traditional stress-strength interference model and conditional reliability,the reliability models of turbine disc without the stress distribution are established in this paper. In the range of fatigue limit, by improving fatigue life curve, the relationship between turbine disc's life probability distribution and material GH4133B's is got,and so is the relationship between life and stress.Then,on the basis of test data of smooth material test-piece from references,the fatigue life probability distribution of material testpiece is found out,and then the fatigue life probability distribution of turbine disc is confirmed. The fatigue life probability distribution of turbine disc is taken into reliability model and the reliability of turbine is analyzed disc under random loads. And this analysis result confirms the variation trend of engine's reliability.

Design of Robust Controller for LFC of Interconnected Power System Considering Communication Delays

The usage of open communication infrastructure for transmitting the control signals in the Load Frequency Control (LFC) scheme of power system introduces time delays. These time delays may degrade the dynamic performance of the power system. This paper proposes a robust method to design a controller for multi-area LFC schemes considering communication delays. In existing literature, the controller values of LFC are designed using time domain approach which is less accurate than the proposed method. In proposed method, the controller values are determined by moving the rightmosteigenvalues of the system to the left half plane in a quasi-continuous way for a preset upper bound of time delay. Then the robustness of the proposed controller is assessed by estimating the maximumtolerable value of time delay for maintaining system stability. Simulation studies are carried out for multi-area LFC scheme equipped with the proposed controller using Matlab/simulink. From the results, it has been concluded that the proposed controller guarantees the tolerance for all time delays smaller than the preset upper bound and provides a bigger delay margin than the existing controllers.

Design of control algorithm for accelerator magnet power supply with large time constant load

Objective High Energy Photon Source-Test Facility(HEPS-TF)is a pre-research project for the construction of high energy synchrotron radiation source in the 12th five-year plan period.The purpose is to research the key technology and develop the key equipment of high energy synchrotron radiation source.Superconducting 3W1 magnet is the first self-developed superconducting wiggler magnet in China,and it is also one of the key research topics of HEPS.The author has completed a new digital closed-loop control algorithm for the superconducting 3W1 magnet with large load time constant and the nonlinear characteristics of inductance increasing with current,namely three-branch structure algorithm.In the face of the rapid development of high energy accelerator technology,the application of intelligent technology has become an inevitable development trend in the field of accelerator magnet power supply technology.Although the digital control of accelerator magnet power supply has been widely used,it is the first time to apply the new closed-loop control algorithm to realize fast adjustment and precision tracking in accelerator superconducting magnet power supply in China.Method According to the nonlinear characteristics of inductance and output current of superconducting magnet,a new digital closed-loop control algorithm for the load of superconducting magnet power supply with large time constant is proposed.Conclusion This algorithm is quite different from the traditional algorithm and can attain the independent tracking and adjust-ment of the control target.Finally,by testing the ripple,error and stability of superconducting 3W1 magnet power supply,the correctness,practicability and reliability of power supply system as well as the digital control algorithm are verified.The results provide a new idea for the control of accelerator magnet power supply.

Anti-fatigue Effect of Renshen Yangrong Decoction(人参养荣汤) in Mice

Objective： To explore the anti-fatigue effect of Renshen Yangrong Decoction （人参养荣汤 RYD） in mice. Methods： One hundred Kunming mice were randomly divided into 5 groups with 20 mice in each group. The negative control group was treated with distilled water, the positive control group was treated with Shiyiwei Shenqi Tablet （十一味参芪片 1.0 g/kg）, the high-, medium- and low-dose RYD groups were treated with 42.0, 21.0 and 10.5 g/kg of RYD daily, respectively, by gastric infusion. At the end of the 7-day treatment, loaded swimming time, organ wet weight and coefficient, serum glucose, urea nitrogen, and hepatic glycogen levels were determined. The outcomes were compared among groups. Results： As compared with the negative control group, the loaded swimming time was significantly increased in the positive control group, specifically the medium- and high-dose RYD groups （P〈0.01）. In addition, the wet weights and coefficients of the spleen and thymus, and the serum glucose and hepatic glycogen contents were increased, whereas serum urea nitrogen level was significantly decreased in the positive control group and the high dose RYD group （P〈0.05 or P=〈0.01）. Conclusion： RYD showed an anti-fatigue effect in mice.

Efficient contraflow algorithms for quickest evacuation planning

The optimization models and algorithms with their implementations on flow over time problems have been an emerging field of research because of largely increasing human-created and natural disasters worldwide.For an optimal use of transportation network to shift affected people and normalize the disastrous situation as quickly and efficiently as possible,contraflow configuration is one of the highly applicable operations research(OR)models.It increases the outbound road capacities by reversing the direction of arcs towards the safe destinations that not only minimize the congestion and increase the flow but also decrease the evacuation time significantly.In this paper,we sketch the state of quickest flow solutions and solve the quickest contraflow problem with constant transit times on arcs proving that the problem can be solved in strongly polynomial time O(nm^2(long n)~2)where n and m are number of nodes and number of arcs,respectively in the network.This contraflow solution has the same computational time bound as that of the best min-cost flow solution.Moreover,we also introduce the contraflow approach with load dependent transit times on arcs and present an efficient algorithm to solve the quickest contraflow problem approximately.Supporting the claim,our computational experiments on Kathmandu road network and on randomly generated instances perform very well matching the theoretical results.For a sufficiently large number of evacuees,about double flow can be shifted with the same evacuation time and about half time is sufficient to push the given flow value with contraflow reconfiguration.

Deviation of design air-conditioning load based on weather database of reference weather year and actual weather year

In Japan,in order to determine the capacity of air-conditioning equipment,designers usually use the weather database of Reference Weather Year(RWY)to obtain the design air-conditioning load by using software such as New HASP/ACLD and Building Energy Simulation Tool(BEST)that are often used in Japan.In recent years,with the global warming due to climate change,the weather database used to calculate air conditioning load also changes.Thus,in order to determine an appropriate capacity of air-conditioning equipment for energy conservation of buildings,the deviation of design air-conditioning load calculated using the weather database of RWY and Actual Weather Year(AWY)should be discussed.In this paper,New HASP/ACLD was used to calculate the building heat loads of eight major Japanese cities over 30 years(1981-2010)between RWY and AWY.The heat load at an exceedance probability of 2.5%is defined as the design air-conditioning load in this paper.Comparing the design air-conditioning load obtained from RWY and AWY,it is shown that it is not necessarily the most appropriate when using the RWY to calculate the design air-conditioning load,especially for heating load in winter.Additionally,it is also shown that the annual heating load time ratio has decreased and the annual cooling load time ratio has increased over the 30 years.