Irreversibility-to-reversibility crossover in transient response of an optically trapped particle

We study the transient response of a colloidal bead which is released from different heights and allowed to relax in the potential well of an optical trap. Depending on the initial potential energy, the system's time evolution shows dramatically different behaviors. Starting from the short-time reversible to long-time irreversible transition, a stationary reversible state with zero net dissipation can be achieved as the release point energy is decreased. If the system starts with even lower energy, it progressively extracts useful work from thermal noise and exhibits an anomalous irreversibility. In addition, we have verified the Transient Fluctuation Theorem and the Integrated Transient Fluctuation Theorem even for the non-ergodic descriptions of our system. Copyright (C) EPLA, 2011

Phase relations in the Fe Ni Cr S system and the sulfidation of an austenitic stainless steel

The stability fields of various sulfide phases that form on Fe-Cr, Fe-Ni, Ni-Cr, and Fe-Cr-Ni alloys have been developed as a function of temperature and the partial pressure of sulfur. The calculated stability fields in the ternary A-B-S system are displayed on plots of log \textpS2 pS2 vs. the conjugate extensive variable (nA/nA–nB), which provides a better framework for following the sulfidation of Fe-Cr-Ni alloys at high temperatures. Experimental and estimated thermodynamic data were used in developing the sulfur potential diagrams. Current models and correlations were employed to estimate the unknown thermodynamic behavior of solid solutions of sulfides and to supplement the incomplete phase-diagram data of geophysical literature. These constructed stability field diagrams are in excellent agreement with the sulfide phases and compositions determined experimentally during the sulfidation of SAE 310 stainless steel. The sulfur potential plots appear to be very useful in predicting and correlating the sulfidation of commercial alloys.

On numerical prediction of the acoustic source characteristics of an engine exhaust system

The contemporary methods for source characterization rely mainly on experiments. These methods produce inaccurate results in the low‐frequency band, where the characteristics are all the more important. Moreover, the experimental methods cannot be used at the design stage. Hence, a numerical technique to obtain the source characteristics is desirable. In this paper, the pressure‐time history and the mass‐flux‐time history obtained by means of the time‐domain analysis have been used, along with the two‐load method to compute the source characteristics. Two new computational methods for obtaining the source characteristics have been described. These are much simpler, and computationally more economical than the complete time‐domain simulation, which makes use of the method of characteristics.

Scalable Preference Aggregation in Social Networks

In social choice theory, preference aggregation refers to computing an aggregate preference over a set of alternatives given individual preferences of all the agents. In real-world scenarios, it may not be feasible to gather preferences from all the agents. Moreover, determining the aggregate preference is computationally intensive. In this paper, we show that the aggregate preference of the agents in a social network can be computed efficiently and with sufficient accuracy using preferences elicited from a small subset of critical nodes in the network. Our methodology uses a model developed based on real-world data obtained using a survey on human subjects, and exploits network structure and homophily of relationships. Our approach guarantees good performance for aggregation rules that satisfy a property which we call expected weak insensitivity. We demonstrate empirically that many practically relevant aggregation rules satisfy this property. We also show that two natural objective functions in this context satisfy certain properties, which makes our methodology attractive for scalable preference aggregation over large scale social networks. We conclude that our approach is superior to random polling while aggregating preferences related to individualistic metrics, whereas random polling is acceptable in the case of social metrics.

Evidence of an intermediate phase in a quaternary Ag bearing telluride glass system using alternating DSC

Alternating Differential Scanning Calorimetric (ADSC) studies on quaternary Ge15Te80-xIn5Agx glasses show the non-reversing enthalpy (Delta H-NR) at T-g to exhibit a broad global minimum in the 8% <= x <= 16% range of Ag, an observation that is taken evidence for existence of an Intermediate Phase (IP) in that range. Glasses at x < 8% are in the flexible phase while those at x > 16% in the stressed-rigid phase. The nature of crystalline phases formed upon crystallization of bulk glasses are elucidated by XRD studies, and reveal presence of Te, GeTe, Ag8GeTe6, AgTe, In2Te3 and In4Te3 phases. These experiments also reveal that the fraction of Ag- bearing phases increases while those of Te- bearing ones decreases with increasing x, suggesting progressive replacement of Te-Te bonds by Ag-Te bonds. (C) 2013 Elsevier Ltd. All rights reserved.

Efficient simulation of unitary operators by combining two numerical algorithms: An NMR simulation of the mirror-inversion propagator of an XY spin chain

Precise experimental implementation of unitary operators is one of the most important tasks for quantum information processing. Numerical optimization techniques are widely used to find optimized control fields to realize a desired unitary operator. However, finding high-fidelity control pulses to realize an arbitrary unitary operator in larger spin systems is still a difficult task. In this work, we demonstrate that a combination of the GRAPE algorithm, which is a numerical pulse optimization technique, and a unitary operator decomposition algorithm Ajoy et al., Phys. Rev. A 85, 030303 (2012)] can realize unitary operators with high experimental fidelity. This is illustrated by simulating the mirror-inversion propagator of an XY spin chain in a five-spin dipolar coupled nuclear spin system. Further, this simulation has been used to demonstrate the transfer of entangled states from one end of the spin chain to the other end.

Design of an Automated Dispenser Unit

This paper presents our work on developing an automated micro positioner and a low cost disposable dispenser module having a disposable dispenser core. The dispenser core is made up of Polydimethylsiloxane (PDMS). Once the user specifies the dispensing location in the Graphical User Interface (GUI), the movement of the micropositioner is automatic. The design, fabrication and characterization results of the dispenser module are also presented. The dispensing experiments are performed with Di-Ethanol Amine as the working reagent. The minimum dispensed volume achieved is about 4 nL.