Current in nanojunctions : Effects of reservoir coupling

We study the effect of system reservoir coupling on currents flowing through quantum junctions. We consider two simple double-quantum dot configurations coupled to two external fermionic reservoirs and study the net current flowing between the two reservoirs. The net current is partitioned into currents carried by the eigenstates of the system and by the coherences between the eigenstates induced due to coupling with the reservoirs. We find that current carried by populations is always positive whereas current carried by coherences are negative for large couplings. This results in a non-monotonic dependence of the net current on the coupling strength. We find that in certain cases, the net current can vanish at large couplings due to cancellation between currents carried by the eigenstates and by the coherences. These results provide new insights into the non-trivial role of system-reservoir couplings on electron transport through quantum dot junctions. In the presence of weak coulomb interactions, net current as a function of system reservoir coupling strength shows similar trends as for the non-interacting case.Comment: 9 pages, 12 figure

Statistics of an adiabatic charge pump

We investigate the effect of time-dependent cyclic-adiabatic driving on the charge transport in quantum junction. We propose a nonequilibrium Greens function formalism to study statistics of the charge pumped (at zero bias) through the junction. The formulation is used to demonstrate charge pumping in a single electronic level coupled to two (electronic) reservoirs with time dependent couplings. Analytical expression for the average pumped current for a general cyclic driving is derived. It is found that for zero bias, for a certain class of driving, the Berry phase contributes only to the odd cumulants. To contrast, a quantum master equation formulation does not show Berry-phase effect at all

Statistics of heat transport across capacitively coupled double quantum dot circuit

We study heat current and the full statistics of heat fluctuations in a capacitively-coupled double quantum dot system. This work is motivated by recent theoretical studies and experimental works on heat currents in quantum dot circuits. As expected intuitively, within the (static) mean-field approximation, the system at steady-state decouples into two single-dot equilibrium systems with renormalized dot energies, leading to zero average heat flux and fluctuations. This reveals that dynamic correlations induced between electrons on the dots is solely responsible for the heat transport between the two reservoirs. To study heat current fluctuations, we compute steady-state cumulant generating function for heat exchanged between reservoirs using two approaches : Lindblad quantum master equation approach, which is valid for arbitrary coulomb interaction strength but weak system-reservoir coupling strength, and the saddle point approximation for Schwinger-Keldysh coherent state path integral, which is valid for arbitrary system-reservoir coupling strength but weak coulomb interaction strength. Using thus obtained generating functions, we verify steady-state fluctuation theorem for stochastic heat flux and study the average heat current and its fluctuations. We find that the heat current and its fluctuations change non-monotonically with the coulomb interaction strength ($U$) and system-reservoir coupling strength ($\Gamma$) and are suppressed for large values of $U$ and $\Gamma$.Comment: 14 pages, 6 figure

Statistics of work done in degenerate parametric amplification process

We study statistics of work done by two classical electric field pumps (two-photon and one-photon resonant pumps) on a quantum optical oscillator. We compute moment generating function for the energy change of the oscillator, interpreted as work done by the classical drives on the quantum oscillator starting out in a thermalized Boltzmann state. The moment generating function is inverted, analytically when only one of the pumps is turned on and numerically when both the pumps are turned on, to get the probability function for the work. The resulting probability function for the work done by the classical drive is shown to satisfy transient detailed and integral work fluctuation theorems. Interestingly, we find that, in order for the work distribution function to satisfy the fluctuation theorem in presence of both the drivings, relative phase of drivings need to be shifted by $\pi$, this is related to the broken time reversal symmetry of the Hamiltonian.Comment: 10 pages, 8 figur

Designing of Pick and Place Robotic Arm

The project is designed to developed a pick and place vehicle for picking and placing objects. Robotic vehicle is based on Bluetooth technology as we have already seen mobile controlled robot using dtmf technology and wireless controlled robots using rf modules having their own limitations. At the transmitting end robot is controlled by android device with an application installed in it working as a remote control to move forward backward left or right. At the receiving end five motors are used where two motors are used for body movement and remaining three motors are used for arm and gripper movement Bluetooth receiver receives the commands and gives it to the microcontroller circuit to drive the motors.This project is not limited to picking and placing but it can be enhanced to pick sensitive objects like bomb and can also be interfaced with camera so that user can view and control the operation from distance

Pan-sharpening Using Spatial-frequency Method

Over the years, researchers have formulated various techniques for pan sharpening that attempt to minimize the spectral distortion, i.e., retain the maximum spectral fidelity of the MS images. On the other hand, if the use of the PAN-sharpened image is just to produce maps for better visual interpretation, then the spectral distortion is not of much concern, as the goal is to produce images with high contrast. To solve the color distortion problem, methods based on spatial frequency domain have been introduced and have demonstrated superior performance in terms of producing high spectral fidelity pan-sharpened images over spatial-scale methods

The Networks of Social Infrastructure Linked with Jamaat–e-Islami in Bangladesh

This paper claims that Bangladesh Jamaat-e-Islami heavily invests in building social infrastructure in the country. Indeed, building social infrastructure by religion based political party like Bangladesh Jamaat-e-Islami has a deep implication in terms of social and political sphere. Through the facilitation of various social services and welfare works, the party aspires to garner support of the people for its political legitimacy and accessibility in the society of Bangladesh. The social infrastructure provides a legitimate space in which the party tries to expand its popular base and change the secular characters of the country into Islamic state. In the first half of the paper, a short description of the party and discourse on building social infrastructure, resources etc. are delineated, and in the second half, the party linked organisations, institutions and programmes are given in detail. In this paper, primary sources such as government and organisational reports, and secondary sources have been used. Moreover, online newspapers and various websites of the concerning organisations and institutions have been accessed to prepare this paper. Keywords: Bangladesh Jamaat-e-Islami, Bangladesh, Social infrastructure, Sharia Law, Fundamentalism, Islamism, Welfare work, Islami Bank Foundation, Ibn Sina Trust, Islamic State

A Review on Applications of Peltier Devices

This paper presents a study on the recovery of waste thermal energy using thermoelectric modules for application in vehicles that could benefit from the generation of a small amount of electric current. A large amount of energy is wasted within the engine and in car cooling, energy that could otherwise be recovered by thermoelectric effect. Thermoelectric device is a solid-state active heat pump which transfers heat from one side of the device to the other side against the temperature gradient (from cold to hot), with consumption of electrical energy, also known as Peltier device. The conclusion appears really attractive economically and energy cogeneration using thermoelectric modules is totally clean