United States
United States

Time filter

Source Type

Jiang Y.,CA Technologies | Wang H.,University of California at Davis | Daneshrad B.,UCLACA | Fette B.,CA Technologies
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2014

This paper studies physical (PHY) and MAC layer design for multi-antenna based mobile ad hoc networks (MANET). The central piece of the PHY layer design is a distributed transmit-receive (Tx-Rx) beam forming algorithm named the minimum interference leakage (MIL) beam former. With this algorithm, each pair of Tx-Rx nodes aims at maximizing the throughput of their own link while minimizing the interference leakage to the unintended ones. Besides the beam forming algorithm are other PHY functions, such as link selection and adaptation, and closed-loop power control (CLPC). To enable such a PHY design, we propose a slotted ALOHA-like MAC frame structure, based on which the PHY functional blocks can work in synergy to dramatically improve the network spectral efficiency. The simulation results show that the proposed design has nearly 100x gain over the single antenna baseline system using TDMA with QPSK rate 1/2, measured by the network area spectral efficiency. © 2014 IEEE.

Smith E.C.,NASA | Miles J.W.,Universities Space Research Association | Helton L.A.,Universities Space Research Association | Sankrit R.,Universities Space Research Association | And 24 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is the world's largest airborne observatory, featuring a 2.5 meter effective aperture telescope housed in the aft section of a Boeing 747SP aircraft. SOFIA's current instrument suite includes: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), a 5-40 μm dual band imager/grism spectrometer developed at Cornell University; HIPO (High-speed Imaging Photometer for Occultations), a 0.3-1.1μm imager built by Lowell Observatory; GREAT (German Receiver for Astronomy at Terahertz Frequencies), a multichannel heterodyne spectrometer from 60-240 μm, developed by a consortium led by the Max Planck Institute for Radio Astronomy; FLITECAM (First Light Infrared Test Experiment CAMera), a 1-5 μm wide-field imager/grism spectrometer developed at UCLA; FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), a 42-200 μm IFU grating spectrograph completed by University Stuttgart; and EXES (Echelon-Cross-Echelle Spectrograph), a 5-28 μm highresolution spectrometer designed at the University of Texas and being completed by UC Davis and NASA Ames Research Center. HAWC+ (High-resolution Airborne Wideband Camera) is a 50-240 μm imager that was originally developed at the University of Chicago as a first-generation instrument (HAWC), and is being upgraded at JPL to add polarimetry and new detectors developed at Goddard Space Flight Center (GSFC). SOFIA will continually update its instrument suite with new instrumentation, technology demonstration experiments and upgrades to the existing instrument suite. This paper details the current instrument capabilities and status, as well as the plans for future instrumentation. © 2014 SPIE.

Katsavrias C.,National and Kapodistrian University of Athens | Katsavrias C.,Aristotle University of Thessaloniki | Daglis I.A.,National and Kapodistrian University of Athens | Li W.,UCLACA | And 4 more authors.
Annales Geophysicae | Year: 2015

We present electron phase space density (PSD) calculations as well as concurrent Pc5 and chorus wave activity observations during two intense geomagnetic storms caused by interplanetary coronal mass ejections (ICMEs) resulting in contradicting net effect. We show that, during the 17 March 2013 storm, the coincident observation of chorus and relativistic electron enhancements suggests that the prolonged chorus wave activity seems to be responsible for the enhancement of the electron population in the outer radiation belt even in the presence of pronounced outward diffusion. On the other hand, the significant depletion of electrons, during the 12 September 2014 storm, coincides with long-lasting outward diffusion driven by the continuous enhanced Pc5 activity since chorus wave activity was limited both in space and time. © 2015 Author(s).

Yingst R.A.,Planetary Science Institute | Mest S.C.,Planetary Science Institute | Berman D.C.,Planetary Science Institute | Garry W.B.,Planetary Science Institute | And 13 more authors.
Planetary and Space Science | Year: 2014

We report on a preliminary global geologic map of Vesta, based on data from the Dawn spacecraft's High-Altitude Mapping Orbit (HAMO) and informed by Low-Altitude Mapping Orbit (LAMO) data. This map is part of an iterative mapping effort; the geologic map has been refined with each improvement in resolution. Vesta has a heavily-cratered surface, with large craters evident in numerous locations. The south pole is dominated by an impact structure identified before Dawn's arrival. Two large impact structures have been resolved: the younger, larger Rheasilvia structure, and the older, more degraded Veneneia structure. The surface is also characterized by a system of deep, globe-girdling equatorial troughs and ridges, as well as an older system of troughs and ridges to the north. Troughs and ridges are also evident cutting across, and spiraling arcuately from, the Rheasilvia central mound. However, no volcanic features have been unequivocally identified. Vesta can be divided very broadly into three terrains: heavily-cratered terrain; ridge-and-trough terrain (equatorial and northern); and terrain associated with the Rheasilvia crater. Localized features include bright and dark material and ejecta (some defined specifically by color); lobate deposits; and mass-wasting materials. No obvious volcanic features are evident. Stratigraphy of Vesta's geologic units suggests a history in which formation of a primary crust was followed by the formation of impact craters, including Veneneia and the associated Saturnalia Fossae unit. Formation of Rheasilvia followed, along with associated structural deformation that shaped the Divalia Fossae ridge-and-trough unit at the equator. Subsequent impacts and mass wasting events subdued impact craters, rims and portions of ridge-and-trough sets, and formed slumps and landslides, especially within crater floors and along crater rims and scarps. Subsequent to the formation of Rheasilvia, discontinuous low-albedo deposits formed or were emplaced; these lie stratigraphically above the equatorial ridges that likely were formed by Rheasilvia. The last features to be formed were craters with bright rays and other surface mantling deposits. Executed progressively throughout data acquisition, the iterative mapping process provided the team with geologic proto-units in a timely manner. However, interpretation of the resulting map was hampered by the necessity to provide the team with a standard nomenclature and symbology early in the process. With regard to mapping and interpreting units, the mapping process was hindered by the lack of calibrated mineralogic information. Topography and shadow played an important role in discriminating features and terrains, especially in the early stages of data acquisition. © 2013 Elsevier Ltd. All rights reserved.

Liang J.,University of Calgary | Donovan E.,University of Calgary | Nishimura Y.,UCLACA | Yang B.,University of Calgary | And 5 more authors.
Journal of Geophysical Research A: Space Physics | Year: 2015

Pulsating auroras often appear in forms of geo-stable or slowly convecting "patches." These patches can maintain their rough shape and size over many sequences of luminosity pulsations, yet they slowly drift with ionospheric E × B convection. Because of these characteristics, there has long been a speculation that the pulsating auroral patch (PAP) is connected to flux tubes filled with enhanced cold plasma. In this study, we perform a survey on pulsating auroral events when the footprints of low-Earth-orbit satellites traversed the PAPs, with a focus on the low-energy particle signatures associated with the PAPs. As a result, we identified, in a majority (∼2/3) of events, the existence of a low-energy ion precipitation structure that is collocated with the PAP, with core energies ranging from several tens of eV up to a few hundred eV. This result supports the hypothesis that a PAP connects to flux tubes filled with enhanced cold plasma. We further propose that the plasma outflows from the ionosphere are the origin of such cold plasma flux tubes. We suggest that the PAP is formed by a combination of high-energy electrons of a magnetospheric origin, the low-energy plasma structure of an ionospheric origin, and certain ELF/VLF waves that are intensified and modulated in interactions with both the hot and cold plasma populations. ©2015. American Geophysical Union. All Rights Reserved.

Tien N.,China Medical University at Taichung | Sung Y.-J.,China Medical University at Taichung | Chang Y.-C.,China Medical University at Taichung | You B.-J.,China Medical University at Taichung | And 11 more authors.
BioMedicine (Netherlands) | Year: 2015

Brucellosis is a bacterial zoonotic disease which can be easy to misdiagnose in clinical microbiology laboratories. In the present study, we have tried to improve the current clinical method for detecting Brucella spp. and its antibiotic characteristics. Our method begins with detecting the clinical isolate through traditional biochemical methods and automatic identification systems. Then, we move on to editing the sequence for BLAST allows us to compare 16s rRNA sequences with sequences from other species, allowing the gene level to be determined. Next, the phylogenetic analysis of multiple genetic loci is able to determine the evolutionary relationships between our bacteria strain and those from other locations. Finally, an anti-microbial susceptibility test hones in on the level of antibacterial activity that the bacteria displays. Employing these four steps in concert is extremely effective in identifying rare bacteria. Thus, when attempting to determine the identity of rare bacteria such as Brucella, utilizing these four steps from our research should be highly effective and ultimately prevent further identification errors and misdiagnoses. The standards we have suggested to identify rare bacteria strains is applicable not only to Brucella, but also to other rarely encountered bacteria. © Author(s) 2015.

Wang H.,UC DavisCA | Jiang Y.,CA Technologies | Daneshrad B.,UCLACA | Fette B.,UC DavisCA
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2014

This paper presents a solution for improving the network spectral efficiency (NSE) of a MIMO ad hoc network by simultaneously increasing the number of concurrent links in the network while maximizing the spectral efficiency of each. Our approach combines multiple physical layer techniques and balances the trade-offs of them. Assuming only the channel state information to the intended receiver, a two-level iterative algorithm is designed and presented. The inner loop uses an algorithm, which we refer to as the 'greedy MCS packing'(GMP), generates the generalized (eigen-) beam forming, performs power allocation and chooses proper modulation and coding scheme (MCS). The GMP attempts to maximize the rate while packing them in as few eigen-channels as possible. The outer loop is used for frequency sub-band selection. It uses a heuristic algorithm to choose the number of 'spectral segments' used by each TX-RX pair to further reduce overall network interference. Simulation results show that our algorithm yields as much as 71% improvement over a related previous work, which also combines multiple MIMO techniques and considers finite MCS rate with imperfect channel information. We further investigate the improvements in network spectral efficiency (NSE) when our baseline GMP approach is augmented by nonlinear Successive Interference Cancellation (SIC) at the receiver. While the NSE gain brought by this SIC-enhanced receiver is quite limited, our simulation shows that more concurrent links can be supported compared with GMP scheme using an MMSE receiver. © 2014 IEEE.

Jiang Y.,UCLACA | Daneshrad B.,UCLACA | Pottie G.,UCLACA
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2015

As the next generation mobile ad hoc network (MANET) evolves to allow for multiple simultaneous transmissions within one-hop for higher spectral efficiency, the interferences from the peer nodes will pose a challenge to the initial acquisition in the MANET. In this paper, we propose a maximum likelihood (ML) method of initial acquisition of the preamble sequences. Simulations show that this proposed method is robust against the interferences. We also propose to use a pair of Zadoff-Chu (Z-C) sequences as the preamble. By exploiting the unique structure of the Z-C sequences, we can estimate both timing and frequency offsets through two fast Fourier transforms (FFT). The estimation of the channel response and the interference covariance is also obtained as a by-product. Simulation results verified that the presented method is efficient in interference suppression and may allow for dozens of simultaneous transmissions. © 2015 IEEE.

Gahm J.K.,UCLACA | Wisniewski N.,UCLACA | Kindlmann G.,University of Chicago | Kung G.L.,UCLACA | And 3 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

Purpose: Various methods exist for interpolating diffusion tensor fields, but none of them linearly interpolate tensor shape attributes. Linear interpolation is expected not to introduce spurious changes in tensor shape. Methods: Herein we define a new linear invariant (LI) tensor interpolation method that linearly interpolates components of tensor shape (tensor invariants) and recapitulates the interpolated tensor from the linearly interpolated tensor invariants and the eigenvectors of a linearly interpolated tensor. The LI tensor interpolation method is compared to the Euclidean (EU), affine-invariant Riemannian (AI), log-Euclidean (LE) and geodesic-loxodrome (GL) interpolation methods using both a synthetic tensor field and three experimentally measured cardiac DT-MRI datasets. Results: EU, AI, and LE introduce significant microstructural bias, which can be avoided through the use of GL or LI. Conclusion: GL introduces the least microstructural bias, but LI tensor interpolation performs very similarly and at substantially reduced computational cost. © Springer-Verlag Berlin Heidelberg 2012.

Loading UCLACA collaborators
Loading UCLACA collaborators