A close look at teachers ́ lives : caring for the well-being of elementary teachers in the US

The purpose of this qualitative study is to shed light on elementary teachers’ perspectives on their sense of well-being, with emphasis on contextual factors that promote or block their sense of well-being. Data were collected through background questionnaires, teachers’ journal writings, and interviews with teachers. Findings reveal that teachers’ sense of well-being was fostered mainly by student growth and supportive colleagues. The major themes that emerged as negatively affecting teachers’ well-being were the influence of accountability testing, lack of power, sense of being scrutinized, student misbehavior, and heavy workload. The results of this study show the need for restructuring teaching contexts. When schools are places in which teachers feel valued, respected, empowered and involved in decision-making processes, they are likely to have a better sense of well-being.peer-reviewe

Conducting polymer coated fabrics for potential applications in microwave frequencies : a study of electromagnetic properties

The microwave reflection, transmission and complex permittivity of paratoluene-2-sulfonic acid doped conducting polypyrrole (PPy/pTSA) coated Nylon-Lycra textiles in the 1-18 GHz frequency were investigated. The real part of permittivity increased with polymerization time and dopant concentration, reaching a plateau at certain dopant concentration and polymerization time. The imaginary part of permittivity showed a frequency dependent change throughout the tested range. All the samples had higher values of absorption than reflection. The total electromagnetic shielding effectiveness exceeded 80% for the highly pTSA doped samples coated for 3 hours

A 77 GHz on-chip strip dipole antenna integrated with balun circuits for automotive radar

In this paper, design and implementation of a 77 GHz on-chip strip dipole antenna integrated with both lumped and transmission line based balun circuits are presented. The on-chip antenna is realized by using IHP’s 0.25 μm SiGe BiCMOS technology with localized back-side etch (LBE) module to decrease substrate loss. The strip dipole antenna is fed by both a lumped LC circuit and strip line tapered baluns integrated on the same substrate and occupies an area of 1x1.2 mm2 including the RF pads. For increased directivity, the antenna sits on a grounded silicon substrate. Experimental results show that antenna is well matched around the design frequency and achieves 7 GHz impedance bandwidth (minimum return loss of 17 dB) for the LC balun circuit. The antenna and its feeding structure are well suited for 77 GHz single chip automotive radar applications

SiGe process integrated on-chip dipole antenna on finite size ground plane

This letter investigates the effect of a finite-size ground plane on the radiation pattern and reflection coefficient of a SiGe process integrated on-chip antenna. A flat 77-GHz on-chip strip dipole antenna integrated with a lumped balun circuit is designed and implemented. For increased directivity, the etched silicon substrate is placed on a metal ground plate. The on-chip antenna with the balun circuit is connected to GSG pads for measurement purposes. The antenna is well matched at the original resonance frequency band with 7-12 GHz impedance bandwidth and 4 dBi measured gain at 85 GHz

Soluble poly-3-alkylpyrrole polymers on films and fabrics

Conductive textiles with specific properties can be produced by the chemical polymerisation of a range of 3-alkylpyrroles in the presence of textiles. The morphologies of these coatings are altered from the traditional conductive coatings. Comparison using a SEM reveals substantial differences.<br /

A77 GHz on-chip dipole antenna with etched silicon substrate

In this paper, a 77 GHz microstrip dipole antenna is integrated on a layered 11.4 m SiO2 and a silicon substrate with thickness of 670 m. The unbalanced microstrip line is balanced by using a lumped LC circuit balun to feed both of the dipole arms. To decrease the substrate loss and hence increase the antenna gain, Localized Backside Etch (LBE) module offered by IHP is utilized to etch the area under the dipole antenna. For mechanical robustness, two walls of silicon substrate are left at the end of the dipole arms inside the etched area. The simulation results show a 3.2 dBi gain and 15 GHz bandwidth at 77 GHz

Electromagnetic interference shielding and radiation absorption in thin polypyrrole films

Results of permittivity measurements, electromagnetic interference shielding effectiveness, and heat generation due to microwave absorption in conducting polymer coated textiles are reported and discussed. The intrinsically conducting polymer, polypyrrole, doped with anthraquinone-2-sulfonic acid (AQSA) or para-toluene-2-sulfonic acid (pTSA) was applied on textile substrates and the resulting materials were investigated in the frequency range 1&ndash;18 GHz. The 0.54 mm thick conducting textile/polypyrrole composites absorbed up to 49.5% of the incident 30&ndash;35 W microwave radiation. A thermography station was used to monitor the temperature of these composites during the irradiation process, where absorption was confirmed via visible heat losses. Samples with lower conductivity showed larger temperature increases caused by microwave absorption compared to samples with higher conductivity. A sample with an average sheet resistivity of 150 &Omega;/sq. showed a maximum temperature increase of 5.27 &deg;C, whilst a sample with a lower resistivity (105 &Omega;/sq.) rose by 3.85 &deg;C.<br /