An Efficient Framework For Fast Computer Aided Design of Microwave Circuits Based on the Higher-Order 3D Finite-Element Method

In this paper, an efficient computational framework for the full-wave design by optimization of complex microwave passive devices, such as antennas, filters, and multiplexers, is described. The framework consists of a computational engine, a 3D object modeler, and a graphical user interface. The computational engine, which is based on a finite element method with curvilinear higher-order tetrahedral elements, is coupled with built-in or external gradient-based optimization procedures. For speed, a model order reduction technique is used and the gradient computation is achieved by perturbation with geometry deformation, processed on the level of the individual mesh nodes. To maximize performance, the framework is targeted to multicore CPU architectures and its extended version can also use multiple GPUs. To illustrate the accuracy and high efficiency of the framework, we provide examples of simulations of a dielectric resonator antenna and full-wave design by optimization of two diplexers involving tens of unknowns, and show that the design can be completed within the duration of a few simulations using industry-standard FEM solvers. The accuracy of the design is confirmed by measurements

A Search for N2+ in Spectra of Comet C/2002C1 (Ikeya-Zhang)

We report low- and high-resolution spectra of comet C/2002 C1 (Ikeya-Zhang) from McDonald Observatory. The comet had a well-developed ion tail including CO+, CO2+, CH+, and H2O+. We used our high-resolution spectra to search for N2+. None was detected and we placed upper limits on N2+/CO+ of 5.4 times 10^{-4}. N2+ was detected in the low-resolution spectra but we show that this emission was probably telluric in origin (if cometary, we derive N2+/CO+ = 5.5 times 10^{-3}, still very low). We discuss the implications for the conditions in the early solar nebula of the non-detection of N2+. These depend on whether the H2O ice was deposited in the amorphous or crystalline form. If H2O was deposited in its crystalline form, the detection of CO+ but not N2+ has implications for H2O/H2 in the early solar nebula.Comment: Accepted for publication in ApJ (Letters) - 10 Sept 200

Continuity of Lithic Practice from the Eighteenth to the Nineteenth Centuries at the Nipmuc Homestead of Sarah Boston, Grafton, Massachusetts

Stone tools have been found at all Nipmuc-related house sites in central Massachusetts dating from the 17th through 20th centuries. This article explores in detail the lithic assemblage recovered from the kitchen midden of the late 18th and early 19th century Sarah Burnee/Sarah Boston farmstead in Grafton, Massachusetts. Quartz and quartzite lithics were found in similar concentrations as historic ceramics within the midden suggesting that these tools were in active use within the household. Ground-stone tools of ancient origin indicate curation and reuse of older materials, and knapped glass and re-worked gunflints suggest knowledge of flintknapping. This article argues that despite colonial rules forbidding traditional Native practices, this and other Nipmuc families continued to practice the production and use of lithics for at least 300 years after the arrival of Europeans

Ultra-low noise, bi-polar, programmable current sources

We present the design process and implementation of fully open-source, ultra-low noise programmable current source systems in two configurations. Although originally designed as coil drivers for Optically Pumped Magnetometers (OPMs), the device specifications make them potentially useful in a range of applications. The devices feature a bi-directional current range of $\pm$~10~mA and $\pm$~250~mA respectively on three independent channels with 16-bit resolution. Both devices feature narrow 1/f noise bandwidth of 1~Hz, enabling magnetic field manipulation for high-performance OPMs. They exhibit low noise of 146.3~pA/$\sqrt{\mathrm{Hz}}$ and 4114~pA/$\sqrt{\mathrm{Hz}}$ which translates to 14.57~ppb/$\sqrt{\mathrm{Hz}}$ and 16.46~ppb/$\sqrt{\mathrm{Hz}}$ noise relative to full scale.Comment: 9 pages, 9 figure

High-efficiency coupled-cavity optical frequency comb generation

We present a high efficiency source of picosecond pulses derived from a dual cavity optical frequency comb generator. This approach overcomes the limitations of single cavity comb generators that are restricted to efficiencies of a few percent. We achieve picosecond pulses with GHz repetition rates offering over a hundred times higher output efficiency than a single cavity design and demonstrate tuning of pulse width by varying the modulation depth of the intra-cavity electro-optic modulator. These results provide a wavelength-agnostic design with a compact footprint for the development of portable picosecond pulsed laser systems for timing, metrology, and LIDAR applications

The Archaeology of Hassanamesit Woods: The Sarah Burnee/Sarah Boston Farmstead

Between 2003 and 2013 the Fiske Center for Archaeological Research at the University of Massachusetts Boston conducted an intensive investigation of the Sarah Burnee/Sarah Boston Farmstead on Keith Hill in Grafton, Massachusetts. The project employed a collaborative method that involved working closely with the Town of Grafton, through the Hassanmesit Woods Management Committee, and the Nipmuc Nation, the state recognized government of the Nipmuc people. Yearly excavation and research plans were decided through consultation with both the Nipmuc Tribal Council, their designated representative, Dr. D. Rae Gould, and the Hassanamesit Woods Management Committee. Dr. Gould also played a continuous and active role in reviewing and collaborating on research activities including scholarly presentations at national and international academic meetings and public presentations at the community level. Large scale excavation between 2006 and 2013 focused on the Sarah Burnee/Sarah Boston farmstead that was occupied intensively between 1750 and 1840. Sarah Burnee and Sarah Boston were two of four Nipmuc women to own and possibly reside on the 206 acre parcel that today comprises Hassanamesit Woods. The other two, Sarah Robins and Sarah Muckamaug, were Sarah Burnee’s grandmother and mother respectively. Excavation, archaeogeophysical survey, soil chemistry, and micromorphological and macrobotanical analysis were combined with the analysis of material culture and faunal material to generate a detailed picture of Nipmuc life during the 18th and 19th centuries. Excavation also found evidence of earlier indigenous occupations spanning some 6,000 years. The most intensive period of occupation covered the period 1750 to 1840, but with a significant spike the period 1790 to 1830. This appears to coincide with the coming of age of Sarah Boston who continues to live in the household with her mother Sarah Burnee Philips. Based on a combination of the documentary, architectural and archaeological data, it seems that an addition was made the structure between 1799 and 1802. A rich material assemblage of more than 120,000 artifacts was recovered from the site that provides detailed information on cultural practices including foodways, exchange networks, agricultural activities and other work-related activities such as basket making. A wealth of foodways related artifacts as well as faunal and floral remains provide ample evidence of daily meals and feasting. The latter conclusion is particularly important because of the implications is has for demonstrating that the Hassanamisco Nipmuc were regularly engaged in political activities. We believe the findings of the project provide empirical evidence that counters arguments made by the Bureau of Indian Affairs that the Hassanamisco Nipmuc did not persist as a politically and culturally continuous community

GPU-Accelerated 3D Mesh Deformation for Optimization Based on the Finite Element Method

This paper discusses a strategy for speeding up the mesh deformation process in the design-by-optimization of high-frequency components involving electromagnetic field simulations using the 3D finite element method (FEM). The mesh deformation is assumed to be described by a linear elasticity model of a rigid body; therefore, each time the shape of the device is changed, an auxiliary elasticity finite-element problem must be solved. In order to accomplish this in a very short time numerical integration and the solution of the resulting system of equations are performed using a graphics processing unit (GPU). The performance of the proposed algorithm is illustrated are verified using a complex example involving 3D FEM analysis of a dielectric-resonator filter

Demonstration of quantum-enhanced rangefinding robust against classical jamming

We demonstrate a quantum-enhanced lidar capable of performing confident target detection and rangefinding in the presence of strong, time-varying classical noise whilst operating with over five orders of magnitude separation between signal and background levels and target reflectivities down to -52 dB. We use a log-likelihood-based framework to introduce a new protocol for dynamic background tracking, verifying resilience of our system to both fast- and slow-modulation jamming in regimes where a classical illumination-based system fails to find a target. These results demonstrate the advantage of exploiting quantum correlations for lidar applications, providing a clear route to implementation in real-world scenarios

Ultra-low noise, bi-polar, programmable current sources

We present the design process and implementation of fully open-source, ultra-low noise programmable current source systems in two configurations. Although originally designed as coil drivers for Optically Pumped Magnetometers (OPMs), the device specifications make them potentially useful in a range of applications. The devices feature a bi-directional current range of ±10 and ±250 mA on three independent channels with 16-bit resolution. Both devices feature a narrow 1/f noise bandwidth of 1 Hz, enabling magnetic field manipulation for high-performance OPMs. They exhibit a low noise of 146 pA/√Hz and 4.1 nA/√Hz, which translates to 15 and 16 ppb/√Hz noise relative to full scale

Modal Analysis and Coupling in Metal-Insulator-Metal Waveguides

This paper shows how to analyze plasmonic metal-insulator-metal waveguides using the full modal structure of these guides. The analysis applies to all frequencies, particularly including the near infrared and visible spectrum, and to a wide range of sizes, including nanometallic structures. We use the approach here specifically to analyze waveguide junctions. We show that the full modal structure of the metal-insulator-metal (MIM) waveguides--which consists of real and complex discrete eigenvalue spectra, as well as the continuous spectrum--forms a complete basis set. We provide the derivation of these modes using the techniques developed for Sturm-Liouville and generalized eigenvalue equations. We demonstrate the need to include all parts of the spectrum to have a complete set of basis vectors to describe scattering within MIM waveguides with the mode-matching technique. We numerically compare the mode-matching formulation with finite-difference frequency-domain analysis and find very good agreement between the two for modal scattering at symmetric MIM waveguide junctions. We touch upon the similarities between the underlying mathematical structure of the MIM waveguide and the PT symmetric quantum mechanical pseudo-Hermitian Hamiltonians. The rich set of modes that the MIM waveguide supports forms a canonical example against which other more complicated geometries can be compared. Our work here encompasses the microwave results, but extends also to waveguides with real metals even at infrared and optical frequencies.Comment: 17 pages, 13 figures, 2 tables, references expanded, typos fixed, figures slightly modifie