Activity-Aware Sensor Networks for Smart Environments

The efficient designs of Wireless Sensor Network protocols and intelligent Machine Learning algorithms, together have led to the advancements of various systems and applications for Smart Environments. By definition, Smart Environments are the typical physical worlds used in human daily life, those are seamlessly embedded with smart tiny devices equipped with sensors, actuators and computational elements. Since human user is a key component in Smart Environments, human motion activity patterns have key importance in building sensor network systems and applications for Smart Environments. Motivated by this, in this thesis my work is focused on human motion activity-aware sensor networks for Smart Environments. The main contributions of this thesis are in two important aspects: (i) Designing event activity context-aware sensor networks for efficient performance optimization as well as resource usage; and (ii) Using binary motion sensing sensor networks\u27 collective data for device-free real-time tracking of multiple users. Firstly, I describe the design of our proposed event activity context-aware sensor network protocols and system design for Smart Environments. The main motivation behind this work is as follows. A sensor network, unlike a traditional communication network, provides high degree of visibility into the environmental physical processes. Therefore its operation is driven by the activities in the environment. In long-term operations, these activities usually show certain patterns which can be learned and effectively utilized to optimize network design. In this thesis I have designed several novel protocols: (i) ActSee for activity-aware radio duty-cycling, (ii) EAR for activity-aware and energy balanced routing, and (iii) ActiSen complete working system with protocol suites for activity-aware sensing/ duty-cycling/ routing. Secondly, I have proposed and designed FindingHuMo (Finding Human Motion), a Machine Learning based real-time user tracking algorithm for Smart Environments using Sensor Networks. This work has been motivated by increasing adoption of sensor network enabled Ubiquitous Computing in key Smart Environment applications, like Smart Healthcare. Our proposed FindingHuMo protocol and system can perform device-free tracking of multiple (unknown and variable number of) users in the hallway environments, just from non-invasive and anonymous binary motion sensor data

Spontaneous magnetization of quantum XYXY spin model in joint presence of quenched and annealed disorder

We investigate equilibrium statistical properties of the quantum XY spin-1/2 model in an external magnetic field when the interaction and field parts are subjected to quenched or/and annealed disorder. The randomness present in the system are termed annealed or quenched depending on the relation between two different time scales - the time scale associated with the equilibriation of the randomness and the time of observation. Within a mean-field framework, we study the effects of disorders on spontaneous magnetization, both by perturbative and numerical techniques. Our primary interest is to understand the differences between quenched and annealed cases, and also to investigate the interplay when both of them are present in a system. We observe in particular that when interaction and field terms are respectively quenched and annealed, critical temperature for the system to magnetize in the direction parallel to the applied field does not depend on any of the disorders. Further, an annealed disordered interaction neither affects the magnetizations nor the critical temperatures. We carry out a comparative study of the different combinations of the disorders in the interaction and field terms, and point out their generic features.Comment: 9 pages, 2 figures, 1 tabl

Adiabatic freezing of long-range quantum correlations in spin chains

We consider a process to create quasi long-range quantum discord between the non-interacting end spins of a quantum spin chain, with the end spins weakly coupled to the bulk of the chain. The process is not only capable of creating long-range quantum correlation but the latter remains frozen, when certain weak end-couplings are adiabatically varied below certain thresholds. We term this phenomenon as adiabatic freezing of quantum correlation. We observe that the freezing is robust to moderate thermal fluctuations and is intrinsically related to the cooperative properties of the quantum spin chain. In particular, we find that the energy gap of the system remains frozen for these adiabatic variations, and moreover, considering the end spins as probes, we show that the interval of freezing can detect the anisotropy transition in quantum XY spin chains. Importantly, the adiabatic freezing of long-range quantum correlations can be simulated with contemporary experimental techniques.Comment: Main text (6 pages, 6 figures) and Supplemental material (4 pages, 4 figures), REVTeX 4-

Beating no-go theorems by engineering defects in quantum spin models

There exist diverse no-go theorems, ranging from no-cloning to monogamies of quantum correlations and Bell inequality violations, which restrict the processing of information in the quantum world. In a multipartite scenario, monogamy of Bell inequality violation and exclusion principle of dense coding are such theorems, which impede the ability of the system to have quantum advantage between all its parts. In ordered spin systems, the twin restrictions of translation invariance and monogamy of quantum correlations, in general, enforce the bipartite states to be neither Bell inequality violating nor dense-codeable. We show that these quantum characteristics, viz. Bell inequality violation and dense-codeability, can be resurrected, and thereby the no-go theorems overcome, by having quenched disorder in the system parameters leading to quantum spin glass or quantum random field models. We show that the quantum characteristics are regained even though the quenched averaging keeps the disordered spin chains translationally invariant at the physically relevant level of observables. The results show that it is possible to conquer constraints imposed by quantum mechanics in ordered systems by introducing impurities.Comment: 9 pages, 6 figures, RevTeX 4.

Productivity Response to a Contract Change

This paper studies the productivity impact of a contract change for tea pluckers in an Indian plantation. The contract, implemented at the end of a three-year cycle in which contracts are generally revised, was (a) the joint outcome of negotiations between twenty unions and plantations, (b) mandated to respect a state government notification stipulating a new minimum wage for plantation workers statewide, and (c) applicable equally to all the plantations in the local region. The contract raised the baseline wage by 30% but lowered marginal incentives, by shifting the existing piece rates to higher minimum thresholds and eliminating an existing penalty per unit for low output. In the one month following the contract change, output increased by a factor between 30-60%, the exact number depending on the choice of counterfactual and the set of controls applied. This large and contrarian response to a flattening of marginal incentives is at odds with the standard model, including one that incorporates dynamic incentives, and it can only be partly accounted for by higher supervisory effort. We conclude that the increase is a "behavioral" response. Yet in subsequent months, the increase is comprehensively reversed. In fact, an entirely standard model with no behavioral or dynamic features that we estimate off the pre-change data, fits the observations four months after the contract change remarkably well. While not an unequivocal indictment of the recent emphasis on "behavioral economics," the findings suggest that non-standard responses may be ephemeral, especially in employment contexts in which the baseline relationship is delineated by financial considerations in the first place. From an empirical perspective, therefore, it is ideal to examine responses to a contract change over an substantial period of time