Piecewise principal comodule algebras

A comodule algebra P over a Hopf algebra H with bijective antipode is called principal if the coaction of H is Galois and P is H-equivariantly projective (faithfully flat) over the coaction-invariant subalgebra PcoH. We prove that principality is a piecewise property: given N comodule-algebra surjections P → P_i whose kernels intersect to zero, P is principal if and only if all P_i’s are principal. Furthermore, assuming the principality of P, we show that the lattice these kernels generate is distributive if and only if so is the lattice obtained by intersection with PcoH. Finally, assuming the above distributivity property, we obtain a flabby sheaf of principal comodule algebras over a certain space that is universal for all such N-families of surjections P → P_i and such that the comodule algebra of global sections is P

A Fully Parameterized Fem Model for Electromagnetic Optimization of an RF Mems Wafer Level Package

In this work, we present a fully parameterized capped transmission line model for electromagnetic optimization of a wafer level package (WLP) for RF MEMS applications using the Ansoft HFSS-TM electromagnetic simulator. All the degrees of freedom (DoF's) in the package fabrication can be modified within the model in order to optimize for losses and mismatch (capacitive and inductive couplings) introduced by the cap affecting the MEMS RF behaviour. Ansoft HFSS-TM was also validated for the simulation of capped RF MEMS devices by comparison against experimental data. A test run of capped 50 transmission lines and shorts was fabricated and tested.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

THE RHETORIC OF DESTRUCTION: RACIAL IDENTITY AND NONCOMBATANT IMMUNITY IN THE CIVIL WAR ERA

This study explores how Americans chose to conduct war in the mid-nineteenth century and the relationship between race and the onset of “total war” policies. It is my argument that enlisted soldiers in the Civil War era selectively waged total war using race and cultural standards as determining factors. A comparative analysis of the treatment of noncombatants throughout the United States between 1861 and 1865 demonstrates that nonwhites invariably suffered greater depredations at the hands of military forces than did whites. Five types of encounters are examined: 1) the treatment of white noncombatants by regular Union and Confederate forces; 2) the fate of noncombatants caught up in the guerrilla wars of the border regions; 3) the relationship between native New Mexicans, Anglo Union troops and Confederate Texans; 4) the relationship between African American noncombatants and Union and Confederate forces; and 5) the conflict between various Indian tribes and Union and Confederate forces apart from the Civil War. By moving away from a narrow focus of white involvement in a single conflict and instead speaking of a “Civil War era,” new comparisons can be drawn that illuminate the multi-faceted nature of American warfare in the mid-nineteenth century. Such a comparison, advances the notion that there has been not one “American way of war,” but two – the first waged against whites, and the second against all others. A thorough study of the language soldiers employed to stereotype explains how the process of dehumanization functioned and why similar groups of men behaved with restraint in one instance and committed atrocity in another. Though the fates of Hispanic, black, and Indian noncombatants have generally been obscured by the “greater” aspects of the Civil War, they are integral to understanding both the capacity of mid-nineteenth century Americans to inflict destruction and the importance of race in shaping military responses. Ultimately, the racialist assumptions of white soldiers served to prevent atrocities against white noncombatants, while the desire to maintain white privilege virtually guaranteed the implementation of harsh tactics against nonwhites

Parasitic Effects Reduction for Wafer-Level Packaging of RF-Mems

In RF-MEMS packaging, next to the protection of movable structures, optimization of package electrical performance plays a very important role. In this work, a wafer-level packaging process has been investigated and optimized in order to minimize electrical parasitic effects. The RF-MEMS package concept used is based on a wafer-level bonding of a capping silicon substrate to an RF-MEMS wafer. The capping silicon substrate resistivity, substrate thickness and the geometry of through-substrate electrical interconnect vias have been optimized using finite-element electromagnetic simulations (Ansoft HFSS). Test structures for electrical characterization have been designed and after their fabrication, measurement results will be compared with simulations.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Bulk-micromachined tunable fabry–perot microinterferometer for the visible spectral range

The design, fabrication and measured characteristics of a bulk-micromachined tunable Fabry–Perot microinterferometer (FPMI) for the visible spectral range are presented. The FPMI is formed by two parallel 40 nm thick silver mirrors supported by a 300 nm low tensile stress silicon nitride membrane with a square aperture (side length of 2 mm) and initial cavity gap of 1.2 µm. One of the mirrors is fixed, the other is under tension on a movable Si frame, which is electrostatically deflected, using several distributed electrodes, to control cavity spacing and mirror parallelism. Performance achieved is: high flatness of the mirrors (λ/10 for the visible part of the spectrum), low control voltages (<21 V for 450 nm deflection) and simple fabrication.Fundação para a Ciência e Tecnologia (FCT

Efficiency improvement of a chip-size antenna for wireless microsystems

This work reports on the use of bulk-micromachining technology to increase the efficiency of a folded shorted-patch antenna. This antenna was designed on two stacked wafers (glass bonded on high-resistivity silicon). The analysis was carried out using the HFSS FEM tool. It was shown that bulk-micromachining technology could be used together with HRS to increase the antenna efficiency by ~20 %. Also, it can be used to allow the use of low-resistivity silicon for antenna substrate. Furthermore, bulk-micromachining technology can be used as an option to tune or to select the antenna operating frequency.Fundação para a Ciência e Tecnologia (FCT) -SFRH/BD/4717/2001, POCTI/ESE/38468/2001

Micromachined fabry-perot optical filters

The design, fabrication and measured characteristics of micromachined Fabry- Perot (F-P) optical filters for the visible spectral range are presented. Silver films of 40-50 nm thickness, evaporated on a 300 nm thick low-stress silicon nitride membrane, are used as high-quality mirrors. Two parallel mirrors, with a square aperture of up to 2x2 mm2 and initial cavity gap of 1.2 µm, form a tunable Fabry- Perot optical filter. One of the mirrors is fixed the other is under tension on a movable Si frame, which is electrostatically deflected to control the mirror spacing and parallelism. Results are compared with non-tunable F-P filters that are composed of an Ag/SiN/Ag or Ag/SiO2/Al layer stack. The FWHM of 40 nm (tunable filter) and 16 nm (non-tunable filter) have been achieved.STW - Project DEL 55.3733. Junta Nacional de Investigação Científica e Tecnológica - PRAXIS XXI-BD/5181/95

High-selectivity single-chip spectrometer in silicon for operation at visible part of the spectrum

A microspectrometer has been realized based on an array of Fabry–Perot optical thin-film filters. The 16-channel microspectrometer is compatible with IC fabrication methods and operates in the visible spectral range with an interchannel shift of 6 nm. Each of the channels is sensitive in a single peak with full-width-half-maximum (FWHM) of 16 nm. Also aFWHMbelow 2 nm and finesse of 40 for narrow band operation is demonstrated. The device can easily be tuned during fabrication to cover a different spectral band only by adjusting the etching times without affecting the device layout. Such a device is extremely suitable for applications in microsystems because of its small size, high spectral selectivity, and low cost. Microspectrometers for the UV and IR regions are also feasible using this technique.Fundação para a Ciência e a Tecnologia (FCT

Silver-based reflective coatings for micromachined optical filters

Silver films of 40 nm thickness, evaporated on a 300 nm thick low-stress silicon nitride layer, are used as high-quality mirrors operating in the visible and near IR spectral range. Application of a silicon nitride membrane under tension, placed within a square Si frame after bulk micromachining, improves the initial mirror flatness. Two parallel mirrors, each with square aperture of up to 2x2 mm2 and an electrostatically controlled spacing, form a tunable Fabry–P´erot optical filter. Investigation of the silver-based reflective coatings, and mirror characterization, including influence of bulk micromachining, are presentedFundação para a Ciência e a Tecnologia FC

High-selectivity single-chip spectrometer for operation at visible wavelengths

A micro-spectrometer has been realized based on an array of Fabry-Perot thin-film optical resonators. The 16 channel micro-spectrometer is IC fabrication compatible and operates in the visible spectral range with an inter-channel shift of 6 nm. Each of the channels is sensitive in a single peak with FWHM of 16 nm. A FWHM < 2 nm and finesse of 40 for narrowband operation is demonstrated.STW - Project DEL 55.3733. TUDelft. Fundação para a Ciência e Tecnologia - Praxis XXI-BD/5181/95