Proceedings of the Fourteenth NASA Propagation Experimenters Meeting (NAPEX 14) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. NAPEX XIV was held on May 11, 1990, at the Balcones Research Centers, University of Texas, Austin, Texas. The meeting was organized into two technical sessions: Satellite (ACTS) and the Olympus Spacecraft, while the second focused on the fixed and mobile satellite propagation studies and experiments. Following NAPEX XIV, the ACTS Miniworkshop was held at the Hotel Driskill, Austin, Texas, on May 12, 1990, to review ACTS propagation activities since the First ACTS Propagation Studies Workshop was held in Santa Monica, California, on November 28 and 29, 1989

Advanced Modulation and Coding Technology Conference

The objectives, approach, and status of all current LeRC-sponsored industry contracts and university grants are presented. The following topics are covered: (1) the LeRC Space Communications Program, and Advanced Modulation and Coding Projects; (2) the status of four contracts for development of proof-of-concept modems; (3) modulation and coding work done under three university grants, two small business innovation research contracts, and two demonstration model hardware development contracts; and (4) technology needs and opportunities for future missions

Simultaneous Multislice Functional Magnetic Resonance Imaging.

Functional magnetic resonance imaging (fMRI) is a valuable tool for mapping brain activity in many fields. Since functional activity is determined by temporal signal changes, undesired fluctuations from physiological motion are problematic. Simultaneous multislice (SMS) imaging can alleviate these issues by accelerating image acquisition, increasing the temporal resolution. Furthermore, some applications require a temporal resolution higher than what conventional fMRI will allow. Current research in SMS has focused on Cartesian readouts due to their ease in analysis and reconstruction. However, non-Cartesian readouts such as spirals have shorter readout times and better signal recovery. This work explores the acquisition and reconstruction of both spiral and concentric ring readouts in parallel SMS. The concentric ring readout retains most of the benefits of spirals, but also increases the usability of alternative reconstruction techniques for non-Cartesian SMS such as generalized autocalibrating partially parallel acquisitions (GRAPPA). To date, non-Cartesian SMS imaging has only been reconstructed with sensitivity encoding (SENSE), but results in this work indicate GRAPPA-based reconstructions have reduced root-mean-square-error compared to SENSE and good subjective image quality as well. Furthermore, using point spread function analysis, the concentric ring trajectory is found to have superior slice separation properties compared to a spiral one. Since parallel imaging greatly magnifies the amount of data used for reconstruction, a novel coil compression method is developed, which outperforms conventional coil compression in fMRI, substantially decreasing the amount of reconstruction time needed for sufficient detection of functional activation. Results indicate that the proposed method can compress 3 simultaneous slice data using a 32-channel coil down to only 10 virtual coils without any adverse effects in functional activation, noise, or image artifacts. Competing methods require substantially more coils for preservation of the data, resulting in large reconstruction time savings for the proposed method. This work also explores the use of Hadamard-encoded fMRI for increased temporal resolution. Because Hadamard-encoded SMS uses data from multiple time frames to separate slices, physiological noise correction is critical. However, even with physiological noise correction, results indicate Hadamard-encoded fMRI is not as reliable as conventional fMRI due to undesired temporal fluctuations, most notably from uncorrected physiological noise.PhDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120669/1/alanchu_1.pd

Mapping multiplexing technique (MMT): a novel intensity modulated transmission format for high-speed optical communication systems

There is a huge rapid growth in the deployment of data centers, mainly driven from the increasing demand of internet services as video streaming, e-commerce, Internet Of Things (IOT), social media, and cloud computing. This led data centers to experience an expeditious increase in the amount of network traffic that they have to sustain due to requirement of scaling with the processing speed of Complementary metal–oxide–semiconductor (CMOS) technology. On the other side, as more and more data centers and processing cores are on demand, as the power consumption is becoming a challenging issue. Unless novel power efficient methodologies are innovated, the information technology industry will be more liable to a future power crunch. As such, low complex novel transmission formats featuring both power efficiency and low cost are considered the major characteristics enabling large-scale, high performance data transmission environment for short-haul optical interconnects and metropolitan range data networks. In this thesis, a novel high-speed Intensity-Modulated Direct-Detection (IM/DD) transmission format named “Mapping Multiplexing Technique (MMT)” for high-speed optical fiber networks, is proposed and presented. Conceptually, MMT design challenges the high power consumption issue that exists in high-speed short and medium range networks. The proposed novel scheme provides low complex means for increasing the power efficiency of optical transceivers at an impactful tradeoff between power efficiency, spectral efficiency, and cost. The novel scheme has been registered as a patent (Malaysia PI2012700631) that can be employed for applications related but not limited to, short-haul optical interconnects in data centers and Metropolitan Area networks (MAN). A comprehensive mathematical model for N-channel MMT modulation format has been developed. In addition, a signal space model for the N-channel MMT has been presented to serve as a platform for comparison with other transmission formats under optical channel constraints. Especially, comparison with M-PAM, as meanwhile are of practical interest to expand the capacity for optical interconnects deployment which has been recently standardized for Ethernet IEEE 802.3bs 100Gb/s and in today ongoing investigation activities by IEEE 802.3 400Gb/s Ethernet Task Force. Performance metrics have been considered by the derivation of the average electrical and optical power for N-channel MMT symbols in comparison with Pulse Amplitude Modulation (M-PAM) format with respect to the information capacity. Asymptotic power efficiency evaluation in multi-dimensional signal space has been considered. For information capacity of 2, 3 and 4 bits/symbol, 2-channel, 3-channel and 4-channel MMT modulation formats can reduce the power penalty by 1.76 dB, 2.2 dB and 4 dB compared with 4-PAM, 8-PAM and 16-PAM, respectively. This enhancement is equivalent to 53%, 60% and 71% energy per bit reduction to the transmission of 2, 3 and 4 bits per symbol employing 2-, 3- and 4-channel MMT compared with 4-, 8- and 16-PAM format, respectively. One of the major dependable parameters that affect the immunity of a modulation format to fiber non-linearities, is the system baud rate. The propagation of pulses in fiber with bitrates in the order > 10G, is not only limited by the linear fiber impairments, however, it has strong proportionality with fiber intra-channel non-linearities (Self Phase Modulation (SPM), Intra-channel Cross-Phase Modulation (IXPM) and Intra-channel Four-Wave Mixing (IFWM)). Hence, in addition to the potential application of MMT in short-haul networks, the thesis validates the practicality of implementing N-channel MMT system accompanied by dispersion compensation methodologies to extend the reach of error free transmission (BER ≤ 10-12) for Metro-networks. N-Channel MMT has been validated by real environment simulation results to outperform the performance of M-PAM in tolerating fiber non-linearities. By the employment of pre-post compensation to tolerate both residual chromatic dispersion and non-linearity, performance above the error free transmission limit at 40Gb/s bit rate have been attained for 2-, 3- and 4-channel MMT over spans lengths of up to 1200Km, 320 Km and 320 Km, respectively. While, at an aggregated bit rate of 100 Gb/s, error free transmission can be achieved for 2-, 3- and 4-channel MMT over spans lengths of up to 480 Km, 80 Km and 160 Km, respectively. At the same spectral efficiency, 4-channel MMT has realized a single channel maximum error free transmission over span lengths up to 320 Km and 160 Km at 40Gb/s and 100Gb/s, respectively, in contrast with 4-PAM attaining 240 Km and 80 Km at 40Gb/s and 100Gb/s, respectively

Mapping multiplexing technique (MMT): a novel intensity modulated transmission format for high-speed optical communication systems

There is a huge rapid growth in the deployment of data centers, mainly driven from the increasing demand of internet services as video streaming, e-commerce, Internet Of Things (IOT), social media, and cloud computing. This led data centers to experience an expeditious increase in the amount of network traffic that they have to sustain due to requirement of scaling with the processing speed of Complementary metal–oxide–semiconductor (CMOS) technology. On the other side, as more and more data centers and processing cores are on demand, as the power consumption is becoming a challenging issue. Unless novel power efficient methodologies are innovated, the information technology industry will be more liable to a future power crunch. As such, low complex novel transmission formats featuring both power efficiency and low cost are considered the major characteristics enabling large-scale, high performance data transmission environment for short-haul optical interconnects and metropolitan range data networks. In this thesis, a novel high-speed Intensity-Modulated Direct-Detection (IM/DD) transmission format named “Mapping Multiplexing Technique (MMT)” for high-speed optical fiber networks, is proposed and presented. Conceptually, MMT design challenges the high power consumption issue that exists in high-speed short and medium range networks. The proposed novel scheme provides low complex means for increasing the power efficiency of optical transceivers at an impactful tradeoff between power efficiency, spectral efficiency, and cost. The novel scheme has been registered as a patent (Malaysia PI2012700631) that can be employed for applications related but not limited to, short-haul optical interconnects in data centers and Metropolitan Area networks (MAN). A comprehensive mathematical model for N-channel MMT modulation format has been developed. In addition, a signal space model for the N-channel MMT has been presented to serve as a platform for comparison with other transmission formats under optical channel constraints. Especially, comparison with M-PAM, as meanwhile are of practical interest to expand the capacity for optical interconnects deployment which has been recently standardized for Ethernet IEEE 802.3bs 100Gb/s and in today ongoing investigation activities by IEEE 802.3 400Gb/s Ethernet Task Force. Performance metrics have been considered by the derivation of the average electrical and optical power for N-channel MMT symbols in comparison with Pulse Amplitude Modulation (M-PAM) format with respect to the information capacity. Asymptotic power efficiency evaluation in multi-dimensional signal space has been considered. For information capacity of 2, 3 and 4 bits/symbol, 2-channel, 3-channel and 4-channel MMT modulation formats can reduce the power penalty by 1.76 dB, 2.2 dB and 4 dB compared with 4-PAM, 8-PAM and 16-PAM, respectively. This enhancement is equivalent to 53%, 60% and 71% energy per bit reduction to the transmission of 2, 3 and 4 bits per symbol employing 2-, 3- and 4-channel MMT compared with 4-, 8- and 16-PAM format, respectively. One of the major dependable parameters that affect the immunity of a modulation format to fiber non-linearities, is the system baud rate. The propagation of pulses in fiber with bitrates in the order > 10G, is not only limited by the linear fiber impairments, however, it has strong proportionality with fiber intra-channel non-linearities (Self Phase Modulation (SPM), Intra-channel Cross-Phase Modulation (IXPM) and Intra-channel Four-Wave Mixing (IFWM)). Hence, in addition to the potential application of MMT in short-haul networks, the thesis validates the practicality of implementing N-channel MMT system accompanied by dispersion compensation methodologies to extend the reach of error free transmission (BER ≤ 10-12) for Metro-networks. N-Channel MMT has been validated by real environment simulation results to outperform the performance of M-PAM in tolerating fiber non-linearities. By the employment of pre-post compensation to tolerate both residual chromatic dispersion and non-linearity, performance above the error free transmission limit at 40Gb/s bit rate have been attained for 2-, 3- and 4-channel MMT over spans lengths of up to 1200Km, 320 Km and 320 Km, respectively. While, at an aggregated bit rate of 100 Gb/s, error free transmission can be achieved for 2-, 3- and 4-channel MMT over spans lengths of up to 480 Km, 80 Km and 160 Km, respectively. At the same spectral efficiency, 4-channel MMT has realized a single channel maximum error free transmission over span lengths up to 320 Km and 160 Km at 40Gb/s and 100Gb/s, respectively, in contrast with 4-PAM attaining 240 Km and 80 Km at 40Gb/s and 100Gb/s, respectively

Emulation of Narrowband Powerline Data Transmission Channels and Evaluation of PLC Systems

This work proposes advanced emulation of the physical layer behavior of NB-PLC channels and the application of a channel emulator for the evaluation of NB-PLC systems. In addition, test procedures and reference channels are proposed to improve efficiency and accuracy in the system evaluation and classification. This work shows that the channel emulator-based solution opens new ways toward flexible, reliable and technology-independent performance assessment of PLC modems

Research and Technology 1995

This report selectively summarizes the NASA Lewis Research Center's research and technology accomplishments for fiscal year 1995. It comprises over 150 short articles submitted by the staff members of the technical directorates. The report is organized into six major sections: aeronautics, aerospace technology, space flight systems, engineering support, Lewis Research Academy, and technology transfer. A table of contents, an author index, and a list of NASA Headquarters program offices have been included to assist the reader in finding articles of special interest. This report is not intended to be a comprehensive summary of all research and technology work done over the past fiscal year. Most of the work is reported in Lewis-published technical reports, journal articles, and presentations prepared by Lewis staff members and contractors (for abstracts of these Lewis-authored reports, visit the Lewis Technical Report Server (LETRS) on the World Wide Web-http://letrs.lerc.nasa.gov/LeTRS/). In addition, university grants have enabled faculty members and graduate students to engage in sponsored research that is reported at technical meetings or in journal articles. For each article in this report, a Lewis contact person has been identified, and where possible, reference documents are listed so that additional information can be easily obtained. The diversity of topics attests to the breadth of research and technology being pursued and to the skill mix of the staff that makes it possible. For more information about Lewis' research, visit us on the World Wide web-http://www.lerc.nasa.gov

Research and Technology 1990

A brief but comprehensive review is given of the technical accomplishments of the NASA Lewis Research Center during the past year. Topics covered include instrumentation and controls technology; internal fluid dynamics; aerospace materials, structures, propulsion, and electronics; space flight systems; cryogenic fluids; Space Station Freedom systems engineering, photovoltaic power module, electrical systems, and operations; and engineering and computational support

Research and technology

The research and technology accomplishments of the NASA Lewis Research Center are summarized for the fiscal year 1986, the 45th anniversary year of the Center. Five major sections are presented covering: aeronautics, aerospace technology, space communications, space station systems, and computational technology support. A table of contents by subjects was developed to assist the reader in finding articles of special interest

Probing and Overcoming Extracellular Barriers to Inhaled Nanomedicine

Inhaled nanoparticles are a promising technology for delivering therapeutic molecules to the lungs to treat diseases such as cystic fibrosis (CF) and lung cancer. This dissertation focuses on characterizing and overcoming a critical extracellular barrier to inhaled nanomedicine: the mucus gel that coats the lung airway epithelium. Mucus is an adhesive meshwork that can trap particles and facilitate their removal from the lungs via mucociliary clearance. Although this defense mechanism protects the lungs from pathogens and particulate pollution, it can also prevent inhaled drug and gene nanoparticles from reaching their target. We therefore investigated strategies to improve particle penetration through human lung mucus. To measure nanoparticle transport, we used multiple particle tracking, a high resolution microscopy technique for quantifying movement of individual particles. First, we examined how particle size and surface chemistry affect mobility in respiratory mucus. We prepared polymeric nanoparticles densely coated with low molecular weight polyethylene glycol (PEG) to minimize muco-adhesion, and compared their transport to that of uncoated, muco-adhesive particles in respiratory mucus collected from endotracheal tubes of surgical patients without pulmonary comorbidities. We found that 100 and 200 nm diameter PEG-coated particles rapidly penetrated respiratory mucus, at rates exceeding their uncoated counterparts by more than one order of magnitude. In contrast, coated and uncoated particles 500 nm in diameter were sterically immobilized by the mucus mesh. These findings identify small size and adhesion-resistant surface as design criteria for therapeutic, respiratory-mucus-penetrating nanoparticles. Next, we studied viruses – nature’s nanoparticles – for CF lung gene therapy. We investigated whether CF sputum acts as a barrier to adeno-associated virus (AAV) gene vectors including AAV2, the serotype tested in CF clinical trials, and AAV1, a leading candidate for future trials. We found that sputum strongly impeded diffusion of AAV, regardless of serotype, and may thereby inhibit access to target cells. However, an AAV2 mutant engineered to have reduced heparin binding diffused twice as fast as AAV2 on average, presumably because of reduced adhesion to sputum. We also discovered that the mucolytic N-acetylcysteine could markedly enhance AAV diffusion. These studies offer strategies for increasing AAV penetration through sputum to improve clinical outcomes