975 research outputs found
Development of Aluminum LEKIDs for Balloon-Borne Far-IR Spectroscopy
We are developing lumped-element kinetic inductance detectors (LEKIDs)
designed to achieve background-limited sensitivity for far-infrared (FIR)
spectroscopy on a stratospheric balloon. The Spectroscopic Terahertz Airborne
Receiver for Far-InfraRed Exploration (STARFIRE) will study the evolution of
dusty galaxies with observations of the [CII] 158 m and other atomic
fine-structure transitions at , both through direct observations of
individual luminous infrared galaxies, and in blind surveys using the technique
of line intensity mapping. The spectrometer will require large format
(1800 detectors) arrays of dual-polarization sensitive detectors with
NEPs of W Hz. The low-volume LEKIDs are fabricated
with a single layer of aluminum (20 nm thick) deposited on a crystalline
silicon wafer, with resonance frequencies of MHz. The inductor is a
single meander with a linewidth of 0.4 m, patterned in a grid to absorb
optical power in both polarizations. The meander is coupled to a circular
waveguide, fed by a conical feedhorn. Initial testing of a small array
prototype has demonstrated good yield, and a median NEP of
W Hz.Comment: accepted for publication in Journal of Low Temperature Physic
Experiential learning and cognitive tools:The impact of simulations on conceptual change in continuing healthcare education
Conceptual change involves the acquisition of new cognitive resources (e.g., mental models) for thinking, problem solving, and decision making. Conceptual change, especially the development of robust mental models related to complex phenomena, is essential in continuing healthcare education (including medicine, nursing, public health, and social work). Jonassen’s work related to mindtools (also known as cognitive tools) and conceptual change has been influential in the development of interactive simulations designed to foster experiential learning opportunities for healthcare professionals. Experiential learning results when people engage in purposeful reflection about their experiences. The experiences that foster the kind of reflection and meaning making necessary for new conceptual change can occur in the real world (e.g., stitching a wound) or in a virtual world (managing a cancer patient within an interactive multimedia simulation). Cognitive tools are ‘‘technologies that enhance the cognitive powers of human beings during thinking, problem solving, and learning’’ (Jonassen & Reeves, 1996, p. 693). This chapter reviews the literature on simulations as cognitive tools that enable experiential learning in support of conceptual change in continuing healthcare education. In addition, the chapter prescribes an educational design research agenda to advance the state-of-the-art of simulation development and theory in this area
Microwave Dielectric Loss at Single Photon Energies and milliKelvin Temperatures
The microwave performance of amorphous dielectric materials at very low
temperatures and very low excitation strengths displays significant excess
loss. Here, we present the loss tangents of some common amorphous and
crystalline dielectrics, measured at low temperatures (T < 100 mK) with near
single-photon excitation energies, using both coplanar waveguide (CPW) and
lumped LC resonators. The loss can be understood using a two-level state (TLS)
defect model. A circuit analysis of the half-wavelength resonators we used is
outlined, and the energy dissipation of such a resonator on a multilayered
dielectric substrate is considered theoretically.Comment: 4 pages, 3 figures, submitted to Applied Physics Letter
Status of SuperSpec: A Broadband, On-Chip Millimeter-Wave Spectrometer
SuperSpec is a novel on-chip spectrometer we are developing for multi-object,
moderate resolution (R = 100 - 500), large bandwidth (~1.65:1) submillimeter
and millimeter survey spectroscopy of high-redshift galaxies. The spectrometer
employs a filter bank architecture, and consists of a series of half-wave
resonators formed by lithographically-patterned superconducting transmission
lines. The signal power admitted by each resonator is detected by a lumped
element titanium nitride (TiN) kinetic inductance detector (KID) operating at
100-200 MHz. We have tested a new prototype device that is more sensitive than
previous devices, and easier to fabricate. We present a characterization of a
representative R=282 channel at f = 236 GHz, including measurements of the
spectrometer detection efficiency, the detector responsivity over a large range
of optical loading, and the full system optical efficiency. We outline future
improvements to the current system that we expect will enable construction of a
photon-noise-limited R=100 filter bank, appropriate for a line intensity
mapping experiment targeting the [CII] 158 micron transition during the Epoch
of ReionizationComment: 16 pages, 10 figures, Proceedings of the SPIE Astronomical Telescopes
+ Instrumentation 2014 Conference, Vol 9153, Millimeter, Submillimeter, and
Far-Infrared Detectors and Instrumentation for Astronomy VI
Revisiting Old Friends: Is CoDel Really Achieving What RED Cannot?
We use ns-2 simulations to compare RED's gentle mode to CoDel in terms of their ability to reduce the latency for various TCP variants. We use a common dumbbell topology with Pareto background traffic, and measure the packet delays and transmission time of a 10MB FTP transfer.
In our scenarios, we find that CoDel reduces the latency by 87%, but RED still manages to reduce it by 75%. However, the use of CoDel results in a transmission time 42% longer than when using RED. In light of its maturity, we therefore argue that RED could be considered as a good candidate to tackle Bufferbloat
- …