Nonadiabatic charge pumping across two superconductors connected through a normal metal region by periodically driven potentials

Periodically driven systems exhibit resonance when the difference between an excited state energy and the ground state energy is an integer multiple of $\hbar$ times the driving frequency. On the other hand, when a superconducting phase difference is maintained between two superconductors, subgap states appear which carry a Josephson current. A driven Josephson junction therefore opens up an interesting avenue where the excitations due to applied driving affect the current flowing from one superconductor to the other. Motivated by this, we study charge transport in a superconductor-normal metal-superconductor (SNS) junction where oscillating potentials are applied to the normal metal region. We find that for small amplitudes of the oscillating potential, driving at one site reverses the direction of current at the superconducting phase differences when difference between the subgap eigenenergies of the undriven Hamiltonian is integer multiple of $\hbar$ times the driving frequency. For larger amplitudes of oscillating potential, driving at one site exhibits richer features. We show that even when the two superconductors are maintained at same superconducting phase, a current can be driven by applying oscillating potentials to two sites in the normal metal differing by a phase. We find that when there is a nonzero Josephson current in the undriven system, the local peaks and valleys in current of the system driven with an amplitude of oscillating potential smaller than the superconducting gap indicates sharp excitations in the system. In the adiabatic limit, we find that charge transferred in one time period diverges as a powerlaw with pumping frequency when a Josephson current flows in the undriven system. Our calculations are exact and can be applied to finite systems. We discuss possible experimental setups where our predictions can be tested.Comment: 9 pages, 9 figures. Published versio

Experimental and numerical investigation into effect of elevated temperature on fretting fatigue behavior

Fretting fatigue damage occurs in contacting parts when they are subjected to fluctuating loadings and sliding movements at the same time. This phenomenon may occur in many applications such as bearings/ shafts, bolted and riveted connections, steel cables, and steam and gas turbines. In this paper, the effect of elevated temperature on fretting fatigue life of Al7075-T6 is investigated using a new device for fretting fatigue tests with variable crank shaft mechanism. Also a finite element modeling method was used to estimate crack propagation lifetime in aluminum alloy, Al7075-T6 specimens at elevated temperature under fretting condition. In this method, shear and normal stresses that are caused by contact load are updated at each crack growth increment. Finally, a comparison between the experimental and numerical results is done in order to evaluate the FE simulation. Department of mechanical engineering, Islamic Azad University, Takestan Branch, Takestan, Iran The experimental results show that: (i) fretting fatigue life of the material increases with temperature up to 350°C by 180% for low stresses and decreases by 40% for high stresses, (ii) this fashion of variation of fretting fatigue life versus temperature is believed to be due to degradation of material properties which occurs by overaging and wear resistance increase due to oxidation of aluminum alloy. While overaging gives rise to degradation of mechanical strength of material and hence the reduction of its fretting fatigue life, surface oxidation of the specimens brings some improvement of fatigue behavior of the material. Metallurgical examination of the specimens reveals that temperature results in precipitation of impurities of al-7075-T6. The size of precipitated impurities and their distances gets bigger as temperature increases. This could be a reason for material degradation of specimens which are exposed to heating for longer time duration

Cost Estimation of Road Traffic Injuries Among Iranian Motorcyclists Using the Willingness to Pay Method

Background: Motorcycle riders are amongst some of the most vulnerable road users. The burden of motorcycles injuries from low and middle income countries is under-reported. Objectives: In this study, the cost of traffic injuries among motorcyclists was calculated using the willingness to pay (WTP) method in Iran in 2013. Patients and Methods: In a cross-sectional study, 143 motorcyclists were randomly selected. The research questionnaire was prepared based on the standard WTP method [stated preference (SP), contingent value (CV) and revealed preference (RP) models] taking into consideration perceived risks, especially those in Iran. Data were collected by a scenario for motorcyclists. The criteria for inclusion in the study consisted of having at least a high school education and being in the age range of 18 - 65 years. The final analysis of the WTP data was performed using the Weibull model. Results: The mean WTP was 888,110 IRR (Iranian Rial) among motorcyclists. The statistical value of life was estimated according to 4694 death cases as 3,146,225,350,943 IRR, which was equivalent to USD 104,874,178 based on the dollar free market rate of 30,000 IRR (purchasing power parity). The cost of injury was 6,903,839,551,000 IRR, equivalent to USD 230,127,985 (based upon 73,325 injured motorcyclists in 2013, a daily traffic volume of 311, and a daily payment of 12,110 IRR for 250 working days). In total, injury and death cases came to 10,050,094,901,943 IRR, equivalent to USD 335,003,163. Willingness to pay had a significant relationship with having experienced an accident, the length of the daily trip (in km), and helmet use (P < 0.001). Conclusions: Willingness to pay can be affected by experiencing an accident, the distance of the daily trip, and helmet use. The cost of traffic injuries among motorcyclists shows that this rate is much higher than the global average. Thus, expenditure should be made on effective initiatives such as the safety of motorcyclists

Epidemiology of Accidents and Traumas in Qom Province in 2010

Background: Accidents are the most important public health challenges in our society. To prevent\n the accidents, the identification of their epidemiological features seems necessary. Objectives: This study was conducted to reveal the epidemiological features of accidents and their\n casualties in Qom province in 2010. Patients and Methods: A cross–sectional study was conducted on 29426 injured people referred to Qom\n province hospitals in 2010. Information about place, time, type of accidents and traumas\n and demographic variables had been collected in a veteran hospital. Data were analyzed\n by SPSS (version 16) software, using chi-square test and logistic regression. Results: The incidence of accidents was about 27/1000 per year. The incidences of traffic\n accidents, motorcycle accidents, violence, burns, poisoning and suicides were 3, 1.6,\n 1.2, 0.3, 0.8, 0.37 cases per 1000 people respectively. Strikes (65%) and falls (12%)\n were the main causes of traumas. Forty-six percent of all injuries had occurred in 16 -\n 30 years groups. Most frequent accidents were as follows: fall (97%) and strike (50%) in\n < 12, violence (46%) in 20 - 29, suicide (71%) in 15 - 29, poisoning (34%) and burns\n (20%) among < 5 years old. Pedestrian and motorcycle accidents among +60 years old\n people were significantly higher than other (P = 0.000). Odds ratio for suicide among\n female was about 3.36 and in 16 - 30 age-group was 15.7 more than +60 years old group (P\n = 0.000). Conclusions: Most traumas in Qom province occurred among younger age-groups and strikes and falls\n are the main causes of such traumas. Therefore, safeties to prevent falls and traffic\n regulations to reduce strikes can be effective strategies

Estimation of the population attributable fraction of road-related injuries due to speeding and passing in Iran

OBJECTIVES: Speeding and passing are considered to be the main human factors resulting in road traffic injuries (RTIs). This study aimed to estimate the population attributeable fraction (PAF) of speeding and passing in RTIs in rural Iran during 2012. METHODS: The contribution of speeding and passing to RTI-related morbidity and mortality was estimated using the PAF method. The prevalence of speeding and passing was obtained from the national traffic police data registry. A logistic regression model was used to measure the association between the above risk factors and RTIs. RESULTS: Speeding accounted for 20.96 and 16.61 of rural road-related deaths and injuries, respectively. The corresponding values for passing were 13.50 and 13.44, respectively. Jointly, the PAF of these factors was 31.63 for road-related deaths and 27.81 for injuries. CONCLUSIONS: This study illustrates the importance of controlling speeding and passing as a high-priority aspect of public-health approaches to RTIs in Iran. It is recommended that laws restricting speeding and passing be enforced more strictly

Comparative noise performance of a coded aperture spectral imager

Novel types of spectral sensors using coded apertures may offer various advantages over conventional designs, especially the possibility of compressive measurements that could exceed the expected spatial, temporal or spectral resolution of the system. However, the nature of the measurement process imposes certain limitations, especially on the noise performance of the sensor. This paper considers a particular type of coded-aperture spectral imager and uses analytical and numerical modelling to compare its expected noise performance with conventional hyperspectral sensors. It is shown that conventional sensors may have an advantage in conditions where signal levels are high, such as bright light or slow scanning, but that coded-aperture sensors may be advantageous in low-signal condition

Conductance of Tomonaga-Luttinger liquid wires and junctions with resistances

We study the effect that resistive regions have on the conductance of a quantum wire with interacting electrons which is connected to Fermi liquid leads. Using the bosonization formalism and a Rayleigh dissipation function to model the power dissipation, we use both scattering theory and Green's function techniques to derive the DC conductance. The resistive regions are generally found to lead to incoherent transport. For a single wire, we find that the resistance adds in series to the contact resistance of h/e^2 for spinless electrons, and the total resistance is independent of the Luttinger parameter K_W of the wire. We numerically solve the bosonic equations to illustrate what happens when a charge density pulse is incident on the wire; the results depend on the parameters of the resistive and interacting regions in interesting ways. For a junction of Tomonaga-Luttinger liquid wires, we use a dissipationless current splitting matrix to model the junction. For a junction of three wires connected to Fermi liquid leads, there are two families of such matrices; we find that the conductance matrix generally depends on K_W for one family but is independent of K_W for the other family, regardless of the resistances present in the system.Comment: 6 pages, 3 figures; added a discussion of time reversal invariance; this is the published versio