Conjoined piezoelectric harvesters and carbon supercapacitors for powering intelligent wireless sensors

To achieve total freedom of location for intelligent wireless sensors (IWS), these need to be autonomous. To achivethis today there is a need of broadband piezoelectric energy harvesting and a long-lasting energy. The Harvester needto be able to provide sufficient amount of energy for the intelligent wireless sensor to perform its task. The energystorage needs to fulfill the requirement of a large number of charge discharge cycles and contain sufficient power forthe intelligent wireless sensor.The biggest issue with piezoelectric energy harvesting today is the bandwidth limitation. Solutions today to achievelarger bandwidth make a tradeoff where the output is decreased. The biggest issue for energy storage today is thelimitation of energy density for supercapacitors and the lack of sufficient life cycles for batteries.This thesis aims to realize piezoelectric energy harvesters with broad bandwidth and maintained power output.Moreover, for energy storage in the form of supercapacitors realize an electrode material that has a high effectivesurface area, good conductivity not dependent on a conductive agent and can be used without a binder. This thesiscover background and history of the two fields, discussion of technologies used and presents solutions for piezoelectricenergy harvesting and carbon based supercapacitor storage.A Backfolded piezoelectric harvester was made of two conjoined piezoelectric cantilevers, one placed on top of abottom cantilever. By the backfolded design this thesis show that by utilizing the extended stress distribution of thebottom cantilever a maintained power output is achieved for both output peaks. By introducing asymmetry where thetop cantilever have 80% length compared with the bottom cantilever the bandwidth was increased. An effectivebandwidth of 70 Hz with voltage output above 2,75 V for 1 g is achieved.To achieve further enhanced bandwidth a piezoelectric energy harvester with selftuning was designed. Theselftuning was achieved by a sliding mass on a beam, which is conjoined, to two piezoelectric cantilevers in abackfolded structure. By introducing length asymmetry, the effective bandwidth was enhanced to 38 Hz with a poweroutput above 15 mW, for 1 g, which is sufficient for an intelligent wireless sensor to start up and transmit data.To utilize the positive output effect from conjoined cantielvers a micro harvester was fabricated. The design wasbased on the same principle as for the backfolded, but for fabrication reasons the design was made in one plane. Theharvester contain two outer cantilevers conjoined to a backfolded middle cantilever. Due to fabrication difficulties,only a mechanical characterization of the harvester was possible. The result from the characterization looks promisingfrom a harvesting point of view, by showing a clear peak that seems to be somewhat broadband.Energy storage for an autonomous wireless intelligent sensor (IWS) needs to be able to charge and discharge duringthe lifetime of the IWS. Therefor the choice fell on supercapacitors instead of batteries. Over time the supercapacitordue to its superior amount of charge and discharge cycles, outperform a battery when energy density is compared.Increasing the energy density for supercapacitors gives the advantage to prolong the providing of power to theIWS. One such electrode material is conjoined carbon nanofibers and carbon nanotubes. The material is not dependenton conductive agents or binders. The effective surface area can be expanded through a denser structure of CNF, wheremore CNT can grow. In combination with activation, which will yield more micropores, hence an increasedcapacitance for the presented synthesized material yielded 91 F/g with an effective surface area of 131 m2.There is many challenges to power an IWS on a gasturbine. This thesis cover challenges like vibrations on cables,placement issues and the charge of a supercapacitor by harvested energy that comes in small chunks. Solutions forthese challenges are offered.The presented work in this thesis shows how the bandwidth for piezoelectric energy harvesters can be broader byasymmetric implementation of conjoined resonators. In addition, the advantages of conjoined carbon electrodematerials to be implemented as electrode material in supercapacitors. Both harvester and storage are intended to beused as energy sources for intelligent wireless sensors

What do we learn from HER2-positive breast cancer genomic profiles?

Patients with a tumor presenting amplification of the HER2 gene are currently proposed trastuzumab (herceptin) and this has greatly changed their outcome. However, a number of HER2-positive cancers show intrinsic or acquired resistance to trastuzumab and there are clear indications that they form a heterogeneous group of tumors. A paper in this issue of Breast Cancer Research addresses this heterogeneity at the genomic level

Agency Shops and the Public Sector: An Economic Analysis

Traditionally, legislators and jurists have justified union and agency shops by resorting to the twin spectors of unequal bargaining power and free riders. Recently, the Supreme Court of the United States upheld the constitutionality of a state statute requiring an exclusive agency shop in the public educational labor market. Using this decision as a reference point, the authors present a Critical economic analysis of exclusive agency shops in the public sector labor market utilizing both a competitive and monopoly labor market model. They argue that the social and economic costs of a labor monopoly, the exclusive agency shop, may outweigh any possible benefits. Furthermore, they argue that the free rider hypothesis does not have an empirical foundation. Thus, they conclude that the arguments in favor of intervention in the competitive labor market are not persuasive

Agency Shops and the Public Sector: An Economic Analysis

Traditionally, legislators and jurists have justified union and agency shops by resorting to the twin spectors of unequal bargaining power and free riders. Recently, the Supreme Court of the United States upheld the constitutionality of a state statute requiring an exclusive agency shop in the public educational labor market. Using this decision as a reference point, the authors present a Critical economic analysis of exclusive agency shops in the public sector labor market utilizing both a competitive and monopoly labor market model. They argue that the social and economic costs of a labor monopoly, the exclusive agency shop, may outweigh any possible benefits. Furthermore, they argue that the free rider hypothesis does not have an empirical foundation. Thus, they conclude that the arguments in favor of intervention in the competitive labor market are not persuasive

Analytic modeling of a high temperature thermoelectric module for wireless sensors

A novel high temperature thermoelectric module with thermoelectric materials never before combined in a module is currently researched. The module placement in the cooling channels of a jet engine where the cold side will be cooled by high flow cooling air (550 degrees C) and the hot side will be at the wall (800 degrees C). The aim of the project is to drastically reduce the length of the wires by replacing wired sensors with wireless sensors and power these (3-10mW) with thermoelectric harvesters. To optimize the design for the temperature range and the environment an analytic model was constructed. Using known models for this purpose was not possible for this project, as many of the models have too many assumptions, e.g. that the temperature gradient is relatively low, that thick electrodes with very low resistance can be used, that the heat transfer through the base plates are perfect or that the aim of the design is to maximize the efficiency. The analytical model in this paper is a combination of several known models with the aim to examine what materials to use in this specific environment to achieve the highest possible specific power (mW/g)