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1

Hard plastic cladding fiber (HPCF) based optical components for high speed short reach optical communications  

Microsoft Academic Search

We developed the primary components applicable to HPCF links for short reach (SR) and very short reach (VSR) data communication systems. We fabricated 4x4 HPCF fused taper splitter, HPCF pigtailed VCSEL and PIN photodiode for high speed short reach communications and characterized back to back transmission performance of the link composed of these components by measuring eye diagrams and jitters.

Jun Ki Kim; Dong Uk Kim; Tae Young Kim; Chang Soo Park; Kyunghwan Oh

2006-01-01

2

Hard plastic cladding fiber (HPCF) based optical components for high speed short reach optical communications  

NASA Astrophysics Data System (ADS)

We developed the primary components applicable to HPCF links for short reach (SR) and very short reach (VSR) data communication systems. We fabricated 4x4 HPCF fused taper splitter, HPCF pigtailed VCSEL and PIN photodiode for high speed short reach communications and characterized back to back transmission performance of the link composed of these components by measuring eye diagrams and jitters. Adapting the fusion-tapering technique for glass optical fiber, we successfully fabricated a 4x4 HPCF fused taper coupler. The HPCF with a core diameter of 200?m and an outer diameter of 230?m had step refractive index of 1.45 and 1.40 for the core and the clad. The optimized fusion length and tapering waist which make minimum insertion loss of about 7dB and uniform output power splitting ratio with less than 0.5dB are 13mm and 150µm, respectively. As a light source for VSR networks, we chose a vertical cavity surface emitting laser (VCSEL) and developed a package with a HPCF pigtail. After positioning VCSEL and HPCF that made a minimum coupling loss, we glued the HPCF inside ceramic ferrule housing. In HPCF-PIN PD packaging, we added a micro polymer lens tip onto the HPCF ends to match the mode field area to the sensitive area of GaAs or InGaAs PIN PD. Coupling between a PIN PD chip and the lensed HPCF was optimized with the radius of curvature of 156µm with a low coupling loss of 0.3dB, which is compatible to conventional MMF-PD packaging. For 1.25 Gbps data rate, the eyes adequate to eye mask in gigabit Ethernet were wide open after all HPCF transmission link and no significant power penalty was observed.

Kim, Jun Ki; Kim, Dong Uk; Kim, Tae Young; Park, Chang Soo; Oh, Kyunghwan

2006-10-01

3

High reliability optical interconnections for short range applications in high performance optical communication systems  

NASA Astrophysics Data System (ADS)

This paper has proposed a new progress of optical interconnections, taking into account the following items such as its ultimate device bandwidth, its available transmission bit rates based on soliton transmission technique, its ultimate transmission link bandwidth, and the product of the link bandwidth and its transmission length. Two items of special emphasis in the basic design of optical interconnection are polymethyl metha acrylate (PMMA) and barium fluoride (BaF2) waveguides, and the optical source cast as vertical cavity surface emitting laser diode (VCSELD), made of either AlGaAs at operating wavelength of 1.3 ?m or aluminum gallium indium phosphors (AlGaInP) at operating wavelength of 1.55 ?m; special emphasis is focused on both the above two items under different operating conditions including both thermal and electrical effects. The optical interconnect is built up on the bases of two VCSELD and one optical link where thermal effects of both diodes and links are included. The good performance of the optical interconnect is deeply and parametrically investigated under wide ranges of the affecting parameters. The high speed performance is processed through three different effects, namely the device 3-dB bandwidth, and the link dispersion characteristics.

Rashed, Ahmed Nabih Zaki

2013-06-01

4

Short-range communication system  

NASA Technical Reports Server (NTRS)

A short-range communication system includes an antenna, a transmitter, and a receiver. The antenna is an electrical conductor formed as a planar coil with rings thereof being uniformly spaced. The transmitter is spaced apart from the plane of the coil by a gap. An amplitude-modulated and asynchronous signal indicative of a data stream of known peak amplitude is transmitted into the gap. The receiver detects the coil's resonance and decodes same to recover the data stream.

Alhorn, Dean C. (Inventor); Howard, David E. (Inventor); Smith, Dennis A. (Inventor)

2012-01-01

5

Automatic short-pulse reshaping for high-speed optical communication systems  

NASA Astrophysics Data System (ADS)

For the next-generation ultra-high-speed TDM optical communication systems, we are developing a waveguide type digital optical pulse synthesizer based on the time-to-space conversion. Our digital optical synthesizer can produce arbitrary optical packets with high bit rate in the order of 100 Gbps and chirp-free pulses. In the early prototype, the signal for controlling the phase and the amplitude of optical signal was manually adjusted with trial and error. Recently, we have introduced a feedback system to this synthesizer for automatic generation of controlling signal, which makes it extremely easier to produce optical signal with arbitrary shape. In this paper, we demonstrate experimental generation of Fourier-transform limited optical pulses and arbitrary 8-bit RZ pulse packets with a bit rate of 100 Gbps.

Tanaka, Yosuke; Kurokawa, Takashi

2007-11-01

6

High prevalence of intestinal zoonotic parasites in dogs from Belgrade, Serbia--short communication.  

PubMed

To identify areas of risk for canine-related zoonoses in Serbia, the aim of this study was to provide baseline knowledge about intestinal parasites in 151 dogs (65 household pets, 75 stray and 11 military working dogs) from Belgrade. The following parasites, with their respective prevalences, were detected: Giardia duodenalis (14.6%), Ancylostomatidae (24.5%), Toxocara canis (30.5%), Trichuris vulpis (47.0%) and Taenia-type helminths (6.6%). Of all examined dogs, 75.5% (114/151) were found to harbour at least one parasite species. Of these, mixed infections with up to four species per dog occurred in 44.7% (51/114). Infections with all detected species were significantly higher (p < 0.05) in military working (100%) and stray dogs (93.3%) versus household pets (50.8%). Among all parasites, agents with zoonotic potential including Giardia, Ancylostomatidae and Toxocara were detected in 58.3% (88/151) of all examined dogs with a significant difference (p < 0.05) among the subgroups (100%, 62.7% and 46.2% for military working dogs, stray dogs and household pets, respectively). The high prevalence of zoonotic parasites registered in the dog population from a highly urban area in south-eastern Europe indicates a potential risk to human health. Thus, veterinarians should play an important role in helping to prevent or minimise zoonotic transmission. PMID:18828485

Nikoli?, Aleksandra; Dimitrijevi?, Sanda; Kati?-Radivojevi?, Sofija; Klun, Ivana; Bobr?, Branko; Djurkovi?-Djakovi?, Olgica

2008-09-01

7

Multichannel Medium Access Control for Dedicated Short-Range Communications  

Microsoft Academic Search

This paper describes a medium access control (MAC) protocol to enable multichannel operation for dedicated short-range communications (DSRCs). In particular, we focus on the challenge of supporting potentially high-bandwidth commercial or infotainment communications between vehicles and the roadside in hotspots over several service channels, while concurrently enabling time-critical vehicle-vehicle communications for safety in a separate channel. In our architecture, within

Tony K. Mak; Kenneth P. Laberteaux; Raja Sengupta; Mustafa Ergen

2009-01-01

8

Error statistics during the propagation of short optical pulses in a high-speed fibreoptic communication line  

SciTech Connect

Simple analytic expressions are derived to approximate the bit error rate for data transmission through fibreoptic communication lines. The propagation of optical pulses is directly numerically simulated. Analytic estimates are in good agreement with numerical calculations. (fibreoptic communication)

Shapiro, E G [Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

2008-09-30

9

Use of Ultra-Wideband (UWB) Technology for Designated Short Range Communications (DSRC) for Highway and High-Speed Rail ITS-IDEA Project 66.  

National Technical Information Service (NTIS)

MSSI has successfully completed the design and development of an Ultra Wideband (UBW) Electronic License Plate (ELP) that is capable of transmitting driver and vehicle information for Designated Short Range Communication (DSRC) applications. The ELP is al...

R. Fontana

2001-01-01

10

Short communication: Inactivation of microbial contaminants in raw milk La Serena cheese by high-pressure treatments.  

PubMed

La Serena cheese, a Spanish variety made from Merino ewes' raw milk, has a high pH value, low salt content, and high moisture, conditions that are all favorable for growth and survival of contaminating microorganisms, including pathogens. To improve its microbiological quality and safety, high-pressure treatments at 300 or 400 MPa for 10 min at 10 degrees C were applied to 2 batches of La Serena cheese on d 2 or 50 of ripening. Cheese treated on d 2 at 300 MPa showed viable aerobic counts that were 0.99 log units lower than those for control cheese on d 3 and showed counts of enterococci, coagulase-positive staphylococci, gram-negative bacteria, and coliforms that were 2.05, 0.49, 3.14, and 4.13 log units lower, respectively, than control cheese. For cheese treated on d 2 at 400 MPa, the respective reductions in counts were 2.02, 2.68, 1.45, 3.96, and 5.50 log units. On d 60, viable aerobic counts in cheese treated on d 50 at 300 MPa were 0.50 log units lower than those in control cheese, and counts of enterococci, gram-negative bacteria, and coliforms were 1.37, 2.30, and 4.85 log units lower, respectively. For cheese treated on d 50 at 400 MPa, the respective reductions in counts were 1.29, 1.98, 4.47, and > 5 log units. High-pressure treatments at 300 or 400 MPa on d 2 or 50 reduced significantly the counts of undesirable microorganisms, improving the microbiological quality and safety of La Serena cheese immediately after treatment and at the end of the ripening period. PMID:16507682

Arqués, J L; Garde, S; Gaya, P; Medina, M; Nuñez, M

2006-03-01

11

Short Communication Spatial variability of the Caribbean mid-summer drought and relation to north Atlantic high circulation  

Microsoft Academic Search

ABSTRACT: Annual rainfall in the Caribbean exhibits a bimodal,structure with two,rainfall maxima,(May–June and September–October) separated by what has been termed,a mid-summer,drought (MSD) (July–August). Despite general acceptance of the intensification and expansion,of the North Atlantic High Pressure (NAHP) as the cause of the Caribbean MSD, it has been noted in several studies that the influence of the NAHP may not be

Douglas W. Gamble; Darren B. Parnell; Scott Curtis

12

A Short History of Electrical Communication.  

ERIC Educational Resources Information Center

Electrical communication progressed rapidly after Samuel Morse demonstrated the telegraph in 1838. Western Union completed the first transcontinental telegraph line in 1861. Five years later the first transoceanic cable was laid. In 1875 A.G. Bell transmitted the first complete sentence heard over wire, and the first Bell telephone company was…

Federal Communications Commission, Washington, DC.

13

Islam and suicide: a short personal communication.  

PubMed

Islamic countries display lower suicide rates compared to the other countries of the world. Since most studies dealing with the relationships between Islam and suicide have focused on the extent of the problem and not the underlying mechanisms, the focus of this brief communication is to provide a rather more in-depth discussion regarding the mechanism of this relation. It also covers issues which may have an adverse effect on suicide within Islamic countries and consequently tries to sketch a path ahead in the area of suicide research within the Islamic countries. PMID:19112876

Rezaeian, Mohsen

14

MAC for dedicated short range communications in intelligent transport system  

Microsoft Academic Search

The need for critical improvements to the North American surface transportation infrastructure vis-a-vis alleviation of congestion while enhancing public safety has led to new intelligent transportation system (ITS) infrastructure based on vehicle-to-vehicle (v2v) wireless communications. The allocation of 75 MHz in the 5.9 GHz band for dedicated short-range communications (DSRC) may also enable future delivery of rich media content to

Jing Zhu; S. Roy

2003-01-01

15

Integrated Short Range, Low Bandwidth, Wearable Communications Networking Technologies.  

National Technical Information Service (NTIS)

This report provides a summary of research and development (R&D) activity and accomplishments, with respect to the development of SPARNET, for U.S. Army contract number W911QY-11-C-0012 - Integrated Short Range, Low Bandwidth, Wearable Communications Netw...

D. Barnett

2012-01-01

16

The Global System for Mobile Communications Short Message Service  

Microsoft Academic Search

This tutorial presents an overview of the Global System for Mobile Communications Short Message Service from the viewpoint of implementing new telematic services. The SMS offers the users of GSM networks the ability to exchange alphanumeric messages up to the limit of 160 characters. The tutorial is motivated by an acute absence of research publications in this field. The information

C. Peersman; S. Cvetkovic; P. Griffiths; H. Spear

2000-01-01

17

The relevance of short communication in scholarly journals: An empirical study  

Microsoft Academic Search

This study aims to examine whether rapid communications exert more influence\\/impact on subsequent research. Citation analysis\\u000a of Short Communications (SCs) and Main Articles (MAs) from 1983 and 1990 for 5 high impact biomedical journals was carried\\u000a out for a five year period following publication.\\u000a \\u000a The mean citations cumulated for the five year period showed no consistent trend. Some journals showed

K. Satyanarayana; D. Srivastava; V. Sreenivas

1999-01-01

18

M?ssbauer effect in the `super-reduced' form of the high-potential iron-sulphur protein from Chromatium (Short Communication)  

PubMed Central

Mössbauer-effect studies of the super-reduced form of Chromatium high-potential iron–sulphur protein indicate that the iron atoms are in a similar valency state to those in reduced ferredoxin from Clostridium pasteurianum, with possibly some inequivalence between the iron atoms within the four-iron centre. Mössbauer spectroscopy also shows magnetic differences between the four-iron centres in the two proteins.

Dickson, Dominic P. E.; Cammack, Richard

1974-01-01

19

Short Communication: HIV+ Viremic Slow Progressors Maintain Low Regulatory T Cell Numbers in Rectal Mucosa but Exhibit High T Cell Activation  

PubMed Central

Abstract Viremic slow progressors (VSP) are a rare subset of HIV-infected persons who exhibit slow immunologic progression despite high viremia. The mechanisms associated with this slow progression remain to be defined. Clinical characteristics of VSP are similar to those of natural hosts for simian immunodeficiency virus (SIV), such as sooty mangabeys (SM) and African green monkeys (AGM), who maintain near-normal CD4 counts despite high-level viremia but maintain low immune activation. Immune activation is a powerful predictor of disease progression, and we hypothesized that low immune activation might also explain the VSP phenotype. Using multiparameter flow cytometry, we assessed levels of T cell activation and regulatory T cells (Treg) in blood and rectal mucosa of VSP, typical progressors, virologic controllers, and seronegative controls. We also assessed Treg function and CD4 T cell proliferative capacity in VSP. Contrary to expectations, we found that VSP subjects have high levels of T cell activation in the gastrointestinal mucosa. The ratio of Treg to CD3+ T cells in the mucosa of VSP was relatively low, potentially contributing to increased immune activation. Nonetheless, CD4+CD25– T cells isolated from these individuals displayed a comparatively weak proliferative response to anti-CD3 stimulation. These data reveal that the VSP phenotype is associated with elevated markers of mucosal immune activation and low numbers of mucosal Treg, suggesting that factors other than immune activation account for this phenotype.

Shaw, Julia M.; Hunt, Peter W.; Critchfield, J. William; McConnell, Delandy H.; Garcia, Juan Carlos; Pollard, Richard B.; Somsouk, Ma; Deeks, Steven G.

2013-01-01

20

Design and analysis of highway safety communication protocol in 5.9 GHz dedicated short range communication spectrum  

Microsoft Academic Search

We study the wireless communication among highway vehicles in the newly-assigned 5.9 GHz dedicated short range communication (DSRC) spectrum. A vehicle-vehicle location-based broadcast (LBB) communication protocol is designed to meet highway safety applications' communication requirements. The analytical expressions of the performance of the protocol in terms of probability of transmission failure and channel occupancy are derived with commonly satisfied assumptions.

Qing Xu; R. Segupta; Daniel Jiang; D. Chrysler

2003-01-01

21

Short communication: Staphylococcus aureus isolated from colostrum of dairy heifers represent a closely related group exhibiting highly homogeneous genomic and antimicrobial resistance features.  

PubMed

In heifers, intramammary infections caused by Staphylococcus aureus affect milk production and udder health in the first and subsequent lactations, and can lead to premature culling. Not much is known about Staph. aureus isolated from heifers and it is also unclear whether or not these strains are readily transmitted between heifers and lactating herd mates. In this study, we compared phenotypic characteristics, spa types, and DNA microarray virulence and resistance gene profiles of Staph. aureus isolates obtained from colostrum samples of dairy heifers with isolates obtained from lactating cows. Our objective was to (1) characterize Staph. aureus strains associated with mastitis in heifers and (2) determine relatedness of Staph. aureus strains from heifers and lactating cows to provide data on transmission. We analyzed colostrum samples of 501 heifers and milk samples of 68 lactating cows within the same herd, isolating 48 and 9 Staph. aureus isolates, respectively. Staphylococcus aureus strains from heifers, lactating herd mates, and an unrelated collection of 78 strains from bovine mastitis milk of mature cows were compared. With 1 exception each, characterization of all strains from heifers and lactating cows in the same herd yielded highly similar phenotypic and genotypic results. The strains were Staphaurex latex agglutination test negative (Oxoid AG, Basel, Switzerland) and belonged to agr type II, CC705, and spa types tbl 2645 and t12926. They were susceptible to all antimicrobial agents tested. In contrast, the strains from mature cows in other herds were spread across different clonal complexes, spa types, and SplitsTree clusters (http://www.splitstree.org/), thus displaying a far higher degree of heterogeneity. We conclude that strains isolated from colostrum of heifers and mastitis milk of lactating cows in the same herd feature highly similar phenotypic and genomic characteristics, suggesting persistence of the organism during the first and potentially subsequent lactations or transmission between heifers and mature herd mates. PMID:24881795

Stalder, Ueli; Stephan, Roger; Corti, Sabrina; Bludau, Maren; Maeschli, Ariane; Klocke, Peter; Johler, Sophia

2014-08-01

22

Short communication: Effects of molasses products on productivity and milk fatty acid profile of cows fed diets high in dried distillers grains with solubles.  

PubMed

Previous research has shown that replacing up to 5% [of dietary dry matter (DM)] corn with cane molasses can partially alleviate milk fat depression when cows are fed high-concentrate, low-fiber rations containing dried distillers grains with solubles. The primary objective of this study was to determine whether dietary molasses alters milk fatty acid (FA) profile or improves solids-corrected milk yield in the context of a more typical lactation diet. A secondary objective was to assess production responses to increasing rumen-degradable protein supply when molasses was fed. Twelve primiparous and 28 multiparous Holstein cows (196±39 d in milk) were blocked by parity and assigned to 4 pens. Pens were randomly allocated to treatment sequence in a 4 × 4 Latin square design, balanced for carryover effects. Treatment periods were 21 d, with 17 d for diet adaptation and 4 d for sample and data collection. Treatments were a control diet, providing 20% dried distillers grains with solubles (DM basis), 35% neutral detergent fiber, 30% starch, and 5% ether extract; a diet with 4.4% cane molasses replacing a portion of the corn grain; a diet with 2.9% molasses supplement containing 32% crude protein on a DM basis; and a diet with 5.8% (DM basis) molasses supplement. Animal-level data were analyzed using mixed models, including the fixed effect of treatment and the random effects of period, pen, period × pen interaction, and cow within pen to recognize pen as the experimental unit. Diets did not alter DM intake, milk production, milk component concentration or yield, feed efficiency (DM intake/milk yield), body weight change, or milk somatic cell count. Milk stearic acid content was increased by the diet containing 5.8% molasses supplement compared with the control diet and the diet containing 2.9% molasses supplement, but the magnitude of the effect was small (12.27, 11.75, and 11.69±0.29 g/100g of FA). Production data revealed a dramatic effect of period on milk fat content and yield. Milk fat content decreased during the course of the experiment (least squares means = 3.16, 2.81, 2.93, and 2.64±0.09% for periods 1 to 4, respectively), as did milk fat yield (1.20, 1.03, 0.98, and 0.79±0.05 kg/d). Exchanging molasses-based products for corn at 2.9 to 5.8% of dietary DM did not influence productivity and had minute effects on milk FA profile. The limited responses in this study may have been influenced by dietary unsaturated FA content or the advancing stage of lactation of cows in the study. PMID:24746128

Siverson, A; Vargas-Rodriguez, C F; Bradford, B J

2014-06-01

23

High thermally conductive communications equipment panel module for communications satellite  

Microsoft Academic Search

A new communications equipment panel module for satellite use has been developed to obtain a high thermal conductivity across the thickness in transversal direction of the panel. As the conventional communications equipment panel has a sandwich structure with aluminum-alloy face sheets and a honeycomb core, the transversal thermal conductivity is relatively small, mainly due to epoxy resin adhesive layers between

Akio Iso; Mitsunobu Watanabe; Hiroaki Tsunoda

1986-01-01

24

ISS Update: High Rate Communications System  

NASA Video Gallery

ISS Update Commentator Pat Ryan interviews Diego Serna, Communications and Tracking Officer, about the High Rate Communications System. Questions? Ask us on Twitter @NASA_Johnson and include the ha...

25

High bandwidth underwater optical communication  

NASA Astrophysics Data System (ADS)

We report error-free underwater optical transmission measurements at 1 Gbit/s (109 bits/s) over a 2 m path in a laboratory water pipe with up to 36 dB of extinction. The source at 532 nm was derived from a 1064 nm continuous-wave laser diode that was intensity modulated, amplified, and frequency doubled in periodically poled lithium niobate. Measurements were made over a range of extinction by the addition of a Mg(OH)2 and Al(OH)3 suspension to the water path, and we were not able to observe any evidence of temporal pulse broadening. Results of Monte Carlo simulations over ocean water paths of several tens of meters indicate that optical communication data rates >1 Gbit/s can be supported and are compatible with high-capacity data transfer applications that require no physical contact.

Hanson, Frank; Radic, Stojan

2008-01-01

26

High current short pulse ion sources  

SciTech Connect

High current short pulse ion beams can be generated by using a multicusp source. This is accomplished by switching the arc or the RF induction discharge on and off. An alternative approach is to maintain a continuous plasma discharge and extraction voltage but control the plasma flow into the extraction aperture by a combination of magnetic and electric fields. Short beam pulses can be obtained by using a fast electronic switch and a dc bias power supply. It is also demonstrated that very short beam pulses ({approximately} 10 {micro}s) with high repetition rate can be formed by a laser-driven LaB{sub 6} or barium photo-cathode.

Leung, K.N. [Lawrence Berkeley National Lab., CA (United States). Accelerator and Fusion Research Div.

1996-08-01

27

A high temperature superconductivity communications flight experiment  

NASA Technical Reports Server (NTRS)

The proposed high temperature superconductivity (HTSC) millimeter-wave communications flight experiment from the payload bay of the Space Shuttle Orbiter to the Advanced Communications Technology Satellite (ACTS) in geosynchronous orbit is described. The experiment will use a Ka-band HTSC phased array antenna and front-end electronics to receive a downlink communications signal from the ACTS. The discussion covers the system configuration, a description of the ground equipment, the spacecraft receiver, link performance, thermal loading, and the superconducting antenna array.

Ngo, P.; Krishen, K.; Arndt, D.; Raffoul, G.; Karasack, V.; Bhasin, K.; Leonard, R.

1992-01-01

28

47 CFR Governing - 5925 MHz Band for Dedicated Short-Range Communications Service (DSRCS)  

Code of Federal Regulations, 2010 CFR

...Governing Regulations Governing the Licensing and Use of Frequencies in the 5850 Telecommunication FEDERAL COMMUNICATIONS...1998] Regulations Governing the Licensing and Use of Frequencies in the 5850-5925 MHz Band for Dedicated Short-Range...

2010-10-01

29

Data transmission characteristics in short range inter-vehicle communication system (IVCS)  

Microsoft Academic Search

The author deals with the data transmission characteristics of a previously presented short-range intervehicle communication system The quality of the microwave communication channel is characterized by the fact that both, sender and receiver are in motion. The communication link is modeled theoretically by the prediction of expected signal-to-noise ratio (SNR) which is determined by two factors, the sender-receiver distance and

W. Kremer

1992-01-01

30

Green Codes: Energy-Efficient Short-Range Communication  

Microsoft Academic Search

A green code attempts to minimize the total en- ergy per-bit required to communicate across a noisy channel. The classical information-theoretic approach neglects the energy expended in processing the data at the encoder and the decoder and only minimizes the energy required for transmissions. Since there is no cost associated with using more degrees of freedom, the traditionally optimal strategy

Pulkit Grover; Anant Sahai

2008-01-01

31

Radiation characteristics of short backfire antenna applicable to mobile communications  

Microsoft Academic Search

A numerical analysis of the short backfire antenna (SBA) is performed using the method of moments with the wire-grid model. The radiation characteristics of this antenna, including the radiation pattern and the antenna gain, are clarified. Comparisons with measured data were carried out, and good agreement was obtained. It is pointed out that the theoretical approach presented here can be

Kazunori Takeuchi; Takayasu Shiokawa; Masayuki Yasunaga

1991-01-01

32

Short-term outcome of psychogenic non-epileptic seizures after communication of the diagnosis.  

PubMed

We previously described a communication strategy for the delivery of the diagnosis of psychogenic non-epileptic seizures (PNES) that was acceptable and effective at communicating the psychological cause of PNES. This prospective multicenter study describes the short-term seizure and psychosocial outcomes after the communication of the diagnosis and with no additional treatment. Participants completed self-report measures at baseline, two and six months after the diagnosis (seizure frequency, HRQoL, health care utilization, activity levels, symptom attributions and levels of functioning). Thirty-six participants completed the self-report questionnaires. A further eight provided seizure frequency data. After six months, the median seizure frequency had dropped from 10 to 7.5 per month (p=0.9), 7/44 participants (16%) were seizure-free, and an additional 10/44 (23%) showed greater than 50% improvement in seizure frequency. Baseline questionnaire measures demonstrated high levels of impairment, which had not improved at follow-up. The lack of change in self-report measures illustrates the need for further interventions in this patient group. PMID:23168089

Mayor, R; Brown, R J; Cock, H; House, A; Howlett, S; Singhal, S; Smith, P; Reuber, M

2012-12-01

33

Performance of shorted microstrip patch antennas for mobile communications handsets at 1800 MHz  

Microsoft Academic Search

We have investigated the application of two different types of novel shorted-patch antennas for mobile communications handsets at 1800 MHz. A single shorted-patch and a stacked shorted-patch antenna offering improved bandwidth are compared with data for a ?\\/4 monopole. The finite-difference time-domain (FDTD) technique was used to calculate antenna characteristics such as impedance and radiation patterns for two cases: on

Jack T. Rowley; Rod B. Waterhouse

1999-01-01

34

Short pulse high power fiber laser systems  

Microsoft Academic Search

We review the rapid recent progress in the development of short pulse high-power fiber laser and amplifier devices. Use of cladding pump technology now provides a route to compact and efficient laser and amplifier systems with high beam quality and high output powers. A new Yb-fiber CPA system incorporating a CFBG stretcher with both 2nd and 3rd order dispersion is

A. Malinowski; A. Piper; J. H. V. Price; F. HE; M. Ibsen; J. Nilsson; D. J. Richardson

2005-01-01

35

Dedicated short-range communication mobile device for intelligent transport systems  

US Patent & Trademark Office Database

A dedicated short-range communication mobile device for Intelligent transport systems, including: an antenna; a data transmission/reception circuit for transmitting and receiving data to and from a ground device through the antenna; a first power supply circuit for supplying power to the data transmission/reception circuit; a received electric field strength detecting unit for measuring a power level of a radio wave transmitted from the ground device; a communication area detecting unit for recognizing a communication area based on an output of the received electric field strength detecting unit; a power supply starting unit for starting the first power supply circuit based on an output of the communication area detecting unit; and a second power supply circuit for supplying power to the received electric field strength detecting unit, the communication area detecting unit and the power supply starting unit. As a result of the above configuration, the mobile device can reduce dissipation and does not complicate communication control.

2002-01-08

36

Spacecraft design project: High latitude communications satellite  

NASA Technical Reports Server (NTRS)

The spacecraft design project was part of AE-4871, Advanced Spacecraft Design. The project was intended to provide experience in the design of all major components of a satellite. Each member of the class was given primary responsibility for a subsystem or design support function. Support was requested from the Naval Research Laboratory to augment the Naval Postgraduate School faculty. Analysis and design of each subsystem was done to the extent possible within the constraints of an eleven week quarter and the design facilities (hardware and software) available. The project team chose to evaluate the design of a high latitude communications satellite as representative of the design issues and tradeoffs necessary for a wide range of satellites. The High-Latitude Communications Satellite (HILACS) will provide a continuous UHF communications link between stations located north of the region covered by geosynchronous communications satellites, i.e., the area above approximately 60 N latitude. HILACS will also provide a communications link to stations below 60 N via a relay Net Control Station (NCS), which is located with access to both the HILACS and geosynchronous communications satellites. The communications payload will operate only for that portion of the orbit necessary to provide specified coverage.

Josefson, Carl; Myers, Jack; Cloutier, Mike; Paluszek, Steve; Michael, Gerry; Hunter, Dan; Sakoda, Dan; Walters, Wes; Johnson, Dennis; Bauer, Terry

1989-01-01

37

Short range RF communication for jet engine control  

NASA Technical Reports Server (NTRS)

A method transmitting a message over at least one of a plurality of radio frequency (RF) channels of an RF communications network is provided. The method comprises the steps of detecting a presence of jamming pulses in the at least one of the plurality of RF channels. The characteristics of the jamming pulses in the at least one of the plurality of RF channels is determined wherein the determined characteristics define at least interstices between the jamming pulses. The message is transmitted over the at least one of the plurality of RF channels wherein the message is transmitted within the interstices of the jamming pulse determined from the step of determining characteristics of the jamming pulses.

Sexton, Daniel White (Inventor); Hershey, John Erik (Inventor)

2007-01-01

38

Short signalling distances make plant communication a soliloquy  

PubMed Central

Plants respond to attack by herbivores or pathogens with the release of volatile organic compounds. Neighbouring plants can receive these volatiles and consecutively induce their own defence arsenal. This ‘plant communication’, however, appears counterintuitive when it benefits independent and genetically unrelated receivers, which may compete with the emitter. As a solution to this problem, a role for volatile compounds in within-plant signalling has been predicted. We used wild-type lima bean (Phaseolus lunatus) to quantify under field conditions the distances over which volatile signals move, and thereby determine whether these cues will mainly trigger resistance in other parts of the same plant or in independent plants. Independent receiver plants exhibited airborne resistance to herbivores or pathogens at maximum distances of 50 cm from a resistance-expressing emitter. In undisturbed clusters of lima bean, over 80 per cent of all leaves that were located around a single leaf at this distance were other leaves of the same plant, whereas this percentage dropped below 50 per cent at larger distances. Under natural conditions, resistance-inducing volatiles of lima bean move over distances at which most leaves that can receive the signal still belong to the same plant.

Heil, Martin; Adame-Alvarez, Rosa M.

2010-01-01

39

Short-Distance Wireless Voice Communication Technology Based on ZigBee  

Microsoft Academic Search

Unified the formidable signal processing function of microprocessor and the wireless communication technology based on ZigBee, this paper proposed one kind of short-distance wireless voice communication solution based on ZigBee which takes the low power MCU as core control unit, auxiliary by the wireless radio frequency transceiver as well as the audio codec. The character of voice signal is that

Li Wenfeng; Cao Guojun; Han Fei

2009-01-01

40

High accuracy deployable antenna for communications satellite  

Microsoft Academic Search

High frequency multi-beam satellite antennas have been studied to realize increased communication capacity, simplified earth stations, and multiple frequency reuse. The satellite antenna needs a highly accurate and large reflector. To overcome the launching vehicle's constraints in size and weight, a solid deployable antenna is under development. A petal antenna (PETAL), composed of solid shell elements, has been studied as

M. Watanabe; M. Misawa; M. Minomo; T. Yasaka

1982-01-01

41

Empirical Analysis on the Human Dynamics of a Large-Scale Short Message Communication System  

NASA Astrophysics Data System (ADS)

Research on human behavior has attracted increasing attention recently because of its scientific significance and potential applications. Some empirical results have indicated that the timing of many human activities follows non-Poisson statistics. We analyze a real-life huge dataset of short message communication with 6326713 users and 37577781 records during the 2006 Chinese New Year. The results show that the number of short message sendings, the interevent time between two consecutive short message sendings and the response time all follow heavy-tailed distribution. We further observe a strongly positive correlation between the activity and the power-law exponent of the interevent time distribution. In addition, the short message communication system displays a bursty property yet no memory effects, which is in particular different from some well-studied human-activited systems such as email-sending, library-loaning and file printing.

Zhao, Zhi-Dan; Xia, Hu; Shang, Ming-Sheng; Zhou, Tao

2011-06-01

42

Technology Development for High Efficiency Optical Communications  

NASA Technical Reports Server (NTRS)

Deep space optical communications is a significantly more challenging operational domain than near Earth space optical communications, primarily due to effects resulting from the vastly increased range between transmitter and receiver. The NASA Game Changing Development Program Deep Space Optical Communications Project is developing four key technologies for the implementation of a high efficiency telecommunications system that will enable greater than 10X the data rate of a state-of-the-art deep space RF system (Ka-band) for similar transceiver mass and power burden on the spacecraft. These technologies are a low mass spacecraft disturbance isolation assembly, a flight qualified photon counting detector array, a high efficiency flight laser amplifier and a high efficiency photon counting detector array for the ground-based receiver.

Farr, William H.

2012-01-01

43

Seed treatment with GA 3 or stratification enhances emergence of some strawberry tree genotypes - Short communication  

Microsoft Academic Search

Demirsoy L., Demirsoy H., Celikel G., Macit I., Ersoy B. , 2010: Seed treatment with GA 3 or stratification en - hances emergence of some strawberry tree genotypes - Short communication . Hort. Sci. (Prague), 37: 34-37. The strawberry tree is a valuable ornamental plant because of its attractive red fruits in the fall and winter, and pink - ish-white

L. Demirsoy; H. Demirsoy; G. Celikel; I. Macit; B. Ersoy

2010-01-01

44

Efficient High Performance Collective Communication for Distributed Memory Environments  

ERIC Educational Resources Information Center

Collective communication allows efficient communication and synchronization among a collection of processes, unlike point-to-point communication that only involves a pair of communicating processes. Achieving high performance for both kernels and full-scale applications running on a distributed memory system requires an efficient implementation of…

Ali, Qasim

2009-01-01

45

High-Capacity Communications from Martian Distances  

NASA Technical Reports Server (NTRS)

High capacity communications from Martian distances, required for the envisioned human exploration and desirable for data-intensive science missions, is challenging. NASA s Deep Space Network currently requires large antennas to close RF telemetry links operating at kilobit-per-second data rates. To accommodate higher rate communications, NASA is considering means to achieve greater effective aperture at its ground stations. This report, focusing on the return link from Mars to Earth, demonstrates that without excessive research and development expenditure, operational Mars-to-Earth RF communications systems can achieve data rates up to 1 Gbps by 2020 using technology that today is at technology readiness level (TRL) 4-5. Advanced technology to achieve the needed increase in spacecraft power and transmit aperture is feasible at an only moderate increase in spacecraft mass and technology risk. In addition, both power-efficient, near-capacity coding and modulation and greater aperture from the DSN array will be required. In accord with these results and conclusions, investment in the following technologies is recommended:(1) lightweight (1 kg/sq m density) spacecraft antenna systems; (2) a Ka-band receive ground array consisting of relatively small (10-15 m) antennas; (3) coding and modulation technology that reduces spacecraft power by at least 3 dB; and (4) efficient generation of kilowatt-level spacecraft RF power.

Williams, W. Dan; Collins, Michael; Hodges, Richard; Orr, Richard S.; Sands, O. Scott; Schuchman, Leonard; Vyas, Hemali

2007-01-01

46

Short-Range Ultra-Broadband Terahertz Communications: Concepts and Perspectives  

Microsoft Academic Search

We propose the concept of ultra-broadband terahertz communication, based on directed non-line-of-sight (NLOS) transmissions. Potential applications of such a system supporting multi-gigabit data rates are given, and put into the context of currently emerging WLANs\\/WPANs. The technology and propagation constraints serve as boundary conditions for the determination of the required antenna gain to support ultra-broadband communication. Resulting high-gain antenna requirements

Radoslaw Piesiewicz; Thomas Kleine-Ostmann; Norman Krumbholz; Daniel Mittleman; Martin Koch; J. Schoebel; Thomas Kurner

2007-01-01

47

High accuracy deployable antenna for communications satellite  

NASA Astrophysics Data System (ADS)

High frequency multi-beam satellite antennas have been studied to realize increased communication capacity, simplified earth stations, and multiple frequency reuse. The satellite antenna needs a highly accurate and large reflector. To overcome the launching vehicle's constraints in size and weight, a solid deployable antenna is under development. A petal antenna (PETAL), composed of solid shell elements, has been studied as a high frequency use deployable antenna. It is an axi-symmetric antenna composed of a fixed central shell and deployable triangular and square shells. During the launch phase, a restraining cable is bound around the periphery of deployable elements stowed in a hexagonal configuration. Deployment is initiated by pyrotechnic cable cutters, and the shells are deployed by spring action.

Watanabe, M.; Misawa, M.; Minomo, M.; Yasaka, T.

48

Gravitational Waves: A Means of Communication with Highly Developed Civilians.  

National Technical Information Service (NTIS)

Ways to communicate with highly developed alien (extraterrestrial) civilizations are presented. The gravitation-wave method is cited as being the most suitable, due to the inadequacies of radio-wave communications. (Author)

V. B. Kudrin

1973-01-01

49

Small Signaling Peptides in Arabidopsis Development: How Cells Communicate Over a Short Distance  

PubMed Central

To sustain plants’ postembryonic growth and development in a structure of cells fixed in cell walls, a tightly controlled short distance cell–cell communication is required. The focus on phytohormones, such as auxin, has historically overshadowed the importance of small peptide signals, but it is becoming clear that secreted peptide signals are important in cell–cell communication to coordinate and integrate cellular functions. However, of the more than 1000 potential secreted peptides, so far only very few have been functionally characterized or matched to a receptor. Here, we will describe our current knowledge on how small peptide signals can be identified, how they are modified and processed, which roles they play in Arabidopsis thaliana development, and through which receptors they act.

Murphy, Evan; Smith, Stephanie; De Smet, Ive

2012-01-01

50

Selective interaction between nonribosomal peptide synthetases is facilitated by short communication-mediating domains  

PubMed Central

Nonribosomal peptide synthetases (NRPSs) catalyze the formation of structurally diverse and biologically important peptides. Given their modular organization, NRPSs provide an enormous potential for biocombinatorial approaches to generate novel bioactive compounds. Crucial for the exploitation of this potential is a profound knowledge of the intermolecular communication between partner NRPSs. The overall goal of this study was to understand the basis of protein–protein communication that facilitates the selective interaction in these multienzyme complexes. On this account, we studied the relevance of short regions at the termini of the NRPSs tyrocidine (Tyc) synthetases TycA, TycB, and TycC, constituting the Tyc biosynthetic template. In vitro and in vivo investigations of C-terminal deletion mutants of the initiation module TycA provided evidence for the existence and impact of short communication-mediating (COM) domains. Their decisive role in protein–protein recognition was subsequently proven by means of COM domain-swapping experiments. Substitution of the terminal COM domains between the donor modules TycA and TycB3, as well as between the acceptor modules TycB1 and TycC1, clearly demonstrated that matching pairs of COM domains are both necessary and sufficient for the establishment of communication between partner NRPSs in trans. These results corroborated the generality of COM domains, which were subsequently exploited to induce crosstalk, even between NRPSs derived from different biosynthetic systems. In conclusion, COM domains represent interesting tools for biocombinatorial approaches, which, for example, could be used for the generation of innovative natural product derivatives.

Hahn, Martin; Stachelhaus, Torsten

2004-01-01

51

German Deaf People Using Text Communication: Short Message Service, TTY, Relay Services, Fax, and E-Mail  

ERIC Educational Resources Information Center

An online survey of German deaf people demonstrated that they use text communication through Short Message Service (SMS), e-mail, fax, and telephone typewriters (TTY) to communicate within communities of deaf and hearing people. SMS is used most, with more than 96% of respondents having access to a mobile phone. Most use is intrinsic and directed…

Power, Des; Power, Mary R.; Rehling, Bernd

2007-01-01

52

Beam divergence changing mechanism for short-range inter-unmanned aerial vehicle optical communications.  

PubMed

The problems associated with using a single fixed beam divergence for short-range inter-unmanned aerial vehicle free-space optical communications are discussed. To overcome the problems, a beam divergence changing mechanism is proposed. Four different methods are then proposed to implement the beam divergence changing mechanism. The performance of these methods is evaluated in terms of transmission distance under adverse weather conditions. The results show that the performance is greatly improved when the beam divergence changing mechanism is used. PMID:19277090

Heng, Kiang Huat; Zhong, Wen-De; Cheng, Tee Hiang; Liu, Ning; He, Yingjie

2009-03-10

53

High Average Power, High Energy Short Pulse Fiber Laser System  

SciTech Connect

Recently continuous wave fiber laser systems with output powers in excess of 500W with good beam quality have been demonstrated [1]. High energy, ultrafast, chirped pulsed fiber laser systems have achieved record output energies of 1mJ [2]. However, these high-energy systems have not been scaled beyond a few watts of average output power. Fiber laser systems are attractive for many applications because they offer the promise of high efficiency, compact, robust systems that are turn key. Applications such as cutting, drilling and materials processing, front end systems for high energy pulsed lasers (such as petawatts) and laser based sources of high spatial coherence, high flux x-rays all require high energy short pulses and two of the three of these applications also require high average power. The challenge in creating a high energy chirped pulse fiber laser system is to find a way to scale the output energy while avoiding nonlinear effects and maintaining good beam quality in the amplifier fiber. To this end, our 3-year LDRD program sought to demonstrate a high energy, high average power fiber laser system. This work included exploring designs of large mode area optical fiber amplifiers for high energy systems as well as understanding the issues associated chirped pulse amplification in optical fiber amplifier systems.

Messerly, M J

2007-11-13

54

Visible light communication in dynamic environment using image/high-speed communication hybrid sensor  

NASA Astrophysics Data System (ADS)

Visible Light Communication (VLC) is a wireless communication method using LEDs. LEDs can respond in high-speed and VLC uses this characteristics. In VLC researches, there are two types of receivers mainly, one is photodiode receiver and the other is high-speed camera. A photodiode receiver can communicate in high-speed and has high transmission rate because of its high-speed response. A high-speed camera can detect and track the transmitter easily because it is not necessary to move the camera. In this paper, we use a hybrid sensor designed for VLC which has advantages of both photodiode and high-speed camera, that is, high transmission rate and easy detecting of the transmitter. The light receiving section of the hybrid sensor consists of communication pixels and video pixels, which realizes the advantages. This hybrid sensor can communicate in static environment in previous research. However in dynamic environment, high-speed tracking of the transmitter is essential for communication. So, we realize the high-speed tracking of the transmitter by using the information of the communication pixels. Experimental results show the possibility of communication in dynamic environment.

Maeno, Keita; Panahpour Tehrani, Mehrdad; Fujii, Toshiaki; Okada, Hiraku; Yamazato, Takaya; Tanimoto, Masayuki; Yendo, Tomohiro

2012-01-01

55

Applications of High Technology to Communication Instruction.  

ERIC Educational Resources Information Center

Discusses classroom design and uses of interactive media. Covers the design of public speaking/interpersonal/small group communication classrooms, the simulation laboratory, the communication effectiveness trainer (ComET system), audience response systems, speech evaluation using computers, and system design considerations. (PD)

Behnke, Ralph R.; O'Hair, H. Dan

1984-01-01

56

High Altitude Satellite Communications, with Crosslinks.  

National Technical Information Service (NTIS)

Analysis and FORTRAN programs that quantitatively describe the uplink, crosslinks, and downlinks for a 10 satellite, two ground-station satellite communications system are described. The existence of each link (accounting for earth obstruction for crossli...

P. F. Christopher E. R. Edelman S. M. Maciorowski

1977-01-01

57

Design of the Radiation Pattern of Infrared Short-Range Communication Systems for Electronic-Toll-Collection Applications  

Microsoft Academic Search

This paper proposes a very simple method for enhancing the performance of infrared electronic-toll-collection systems. Using two typical low-cost commercial LEDs with different half-intensity angles Phi1\\/2 = 22deg and 10deg, the radiation pattern of the emitting module of an infrared short-range communication system for electronic-toll-collection applications is designed. This enables us to construct a system that has an extended communication

Wern-yarng Shieh; Ti-ho Wang; Yen-hsih Chou; Chi-chang Huang

2008-01-01

58

TDX: A high-bandwidth crossbar-switched communication paradigm  

SciTech Connect

Digital signal processing systems under development today require scalable and reconfigurable high bandwidth communication resources between processing elements. Shared memory architectures require the ability to transfer data from one processor node to another, as well as maintaining data coherency such as provided by the Scalable Coherent Interface (SCI). Signal processing systems that must move large amounts of data between processor nodes, are best served by a communication system that allows reconfigurable streams of data to flow at deterministic rates with minimal overhead. A Time Domain Crossbar (TDX) communication system providing scalable, programmable, high-bandwidth, streaming communication has been developed and is described in this paper.

Pierce, P.E.; Eilers, D.L.; Schreiber, A.L.

1994-08-01

59

Short pulse High Power Microwave surface flashover  

Microsoft Academic Search

High power microwave (HPM) induced surface flashover is investigated in order to gain a better understanding of this phenomenon and reduce the limitations it imposes on transmitted power levels. This work builds on previous testing using a magnetron producing 5 MW for 4 ¿s at 2.85 GHz. Both the previous and current experimental setups are designed to produce a flashover

J. Krile; L. McQuage; J. Walter; A. Neuber

2009-01-01

60

Short Pulse High Power Microwave Surface Flashover  

Microsoft Academic Search

Summary form only given. High power microwave (HPM) surface flashover is investigated in order to gain a better understanding of this phenomenon and reduce the limitations it imposes on transmitted power levels. The experimental setup is designed to produce window flashover without the influence of a triple point. The HPM source for this testing is an experimental virtual cathode oscillator

L. McQuage; G. Edmiston; J. Mankovvski; A. Neuber

2007-01-01

61

Short pulse High Power Microwave surface flashover  

Microsoft Academic Search

High Power Microwave (HPM) surface flashover is investigated in order to gain a better understanding of this phenomenon and reduce the limitations it imposes on transmitted power levels. The experimental setup is designed to produce window flashover without the influence of a triple point. The HPM source for this testing is an experimental virtual cathode oscillator (vircator) capable of producing

L. McQuage; G. Edmiston; J. Mankowski; A. Neuber

2007-01-01

62

Reliable Communication for Highly Mobile Agents  

Microsoft Academic Search

The provision of a reliable communication infrastructure for mobile agents is still an open research issue. The challenge to reliability we address in this work does not come from the possibility of faults, but rather from the mere presence of mobility, which complicates the problem of ensuring the delivery of information even in a fault-free network. For instance, the asynchronous

Amy L. Murphy; Gian Pietro Picco

1999-01-01

63

High accuracy in short ISS missions  

NASA Astrophysics Data System (ADS)

Traditionally Inertial Surveying Systems ( ISS) are used for missions of 30 km to 100 km length. Today, a new type of ISS application is emanating from an increased need for survey control densification in urban areas often in connection with land information systems or cadastral surveys. The accuracy requirements of urban surveys are usually high. The loss in accuracy caused by the coordinate transfer between IMU and ground marks is investigated and an offsetting system based on electronic tacheometers is proposed. An offsetting system based on a Hewlett-Packard HP 3820A electronic tacheometer has been tested in Sydney (Australia) in connection with a vehicle mounted LITTON Auto-Surveyor System II. On missions over 750 m ( 8 stations, 25 minutes duration, 3.5 minute ZUPT intervals, mean offset distances 9 metres) accuracies of 37 mm (one sigma) in position and 8 mm in elevation were achieved. Some improvements to the LITTON Auto-Surveyor System II are suggested which would improve the accuracies even further.

Rüeger, J. M.

1986-06-01

64

Highly survivable communications: complementary media packet switched networks  

Microsoft Academic Search

The requirement for reliable communications for many national security, crisis management and natural disaster related requirements is clear. The ability to communicate under extreme conditions including intense and\\/or sophisticated jamming and adverse propagation conditions (possibly induced by high altitude nuclear events) is a very important requirement. This paper presents complementary multi (propagation) media approach as the most cost-effective manner for

D. Yavuz; F. Eken; N. Karavassilis

1994-01-01

65

NASA high performance computing and communications program  

NASA Technical Reports Server (NTRS)

The National Aeronautics and Space Administration's HPCC program is part of a new Presidential initiative aimed at producing a 1000-fold increase in supercomputing speed and a 100-fold improvement in available communications capability by 1997. As more advanced technologies are developed under the HPCC program, they will be used to solve NASA's 'Grand Challenge' problems, which include improving the design and simulation of advanced aerospace vehicles, allowing people at remote locations to communicate more effectively and share information, increasing scientist's abilities to model the Earth's climate and forecast global environmental trends, and improving the development of advanced spacecraft. NASA's HPCC program is organized into three projects which are unique to the agency's mission: the Computational Aerosciences (CAS) project, the Earth and Space Sciences (ESS) project, and the Remote Exploration and Experimentation (REE) project. An additional project, the Basic Research and Human Resources (BRHR) project exists to promote long term research in computer science and engineering and to increase the pool of trained personnel in a variety of scientific disciplines. This document presents an overview of the objectives and organization of these projects as well as summaries of individual research and development programs within each project.

Holcomb, Lee; Smith, Paul; Hunter, Paul

1993-01-01

66

NASA High Performance Computing and Communications program  

NASA Technical Reports Server (NTRS)

The National Aeronautics and Space Administration's HPCC program is part of a new Presidential initiative aimed at producing a 1000-fold increase in supercomputing speed and a 1(X)-fold improvement in available communications capability by 1997. As more advanced technologies are developed under the HPCC program, they will be used to solve NASA's 'Grand Challenge' problems, which include improving the design and simulation of advanced aerospace vehicles, allowing people at remote locations to communicate more effectively and share information, increasing scientists' abilities to model the Earth's climate and forecast global environmental trends, and improving the development of advanced spacecraft. NASA's HPCC program is organized into three projects which are unique to the agency's mission: the Computational Aerosciences (CAS) project, the Earth and Space Sciences (ESS) project, and the Remote Exploration and Experimentation (REE) project. An additional project, the Basic Research and Human Resources (BRHR) project, exists to promote long term research in computer science and engineering and to increase the pool of trained personnel in a variety of scientific disciplines. This document presents an overview of the objectives and organization of these projects, as well as summaries of early accomplishments and the significance, status, and plans for individual research and development programs within each project. Areas of emphasis include benchmarking, testbeds, software and simulation methods.

Holcomb, Lee; Smith, Paul; Hunter, Paul

1994-01-01

67

Methods for UGV teleoperation with high latency communications  

NASA Astrophysics Data System (ADS)

In this project, we developed and demonstrated complementary UGV control methods for teleoperation with highlatency communications. The methods included latency protection, predictive displays, and supervisory control. Latency protection mitigate against typical types of high-latency teleoperation input errors. The Phase I latency protection methods included filtering the joysick commands, limiting the commanded rates as a function of latency, and emergency stop when the operator commands and OCU navigation video were out of phase. Predictive displays indicate to the operator the current state of the UGV, i.e., the state after all of the latent commands are executed (latent commands are those that have been issued but whose effects do not yet appear in the OCU display). We implemented two alternative predictive display methods: augmented reality using iconography to indicate the effects of the latent commands, and virtual reality which warps the image to show the view to reflect the latent commands. Supervisory control allows the operator to specify simple, short-range objectives that the UGV can accomplish on its own, without advanced sensing, path planning, etc. We implemented an effective "point-and-go" supervisory control system. We successfully implemented and demonstrated these methods on a Packbot© 510 EOD robot (made by iRobot Corporation), currently being used in-theater.

Witus, Gary; Hunt, Shawn; Janicki, Phil

2011-05-01

68

NASA satellite communications application research. Phase 2: Efficient high power, solid state amplifier for EFH communications  

NASA Technical Reports Server (NTRS)

The final report describes the work performed from 9 Jun. 1992 to 31 Jul. 1993 on the NASA Satellite Communications Application Research (SCAR) Phase 2 program, Efficient High Power, Solid State Amplifier for EHF Communications. The purpose of the program was to demonstrate the feasibility of high-efficiency, high-power, EHF solid state amplifiers that are smaller, lighter, more efficient, and less costly than existing traveling wave tube (TWT) amplifiers by combining the output power from up to several hundred solid state amplifiers using a unique orthomode spatial power combiner (OSPC).

Benet, James

1993-01-01

69

Fiber Laser Front Ends for High Energy, Short Pulse Lasers  

SciTech Connect

We are developing a fiber laser system for short pulse (1-10ps), high energy ({approx}1kJ) glass laser systems. Fiber lasers are ideal for these systems as they are highly reliable and enable long term stable operation.

Dawson, J; Messerly, M; Phan, H; Siders, C; Beach, R; Barty, C

2007-06-21

70

High capacity satellite communication system and key technologies  

NASA Astrophysics Data System (ADS)

A high-capacity satellite communication system for Japan, with multiple beams and key technologies for onboard equipment, is described. The system will provide trunk transmission, digital business communication, and mobile communication. Advantages of the multibeam system include increased transmission capacity, reduction in earth-station antenna diameter, and frequency reuse. Onboard technologies discussed include cluster-feed horn design, reflector deployment, antenna pointing control (accurate to 0.015 degree with 0.3-degree spot width for the 12 beams), satellite switch, and onboard receiver and transmitter.

Nagai, Y.; Okasaka, S.; Nakagawa, K.

71

Spontaneous Radiation Emission from Short, High Field Strength Insertion Devices  

SciTech Connect

Since the earliest papers on undulaters were published, it has been known how to calculate the spontaneous emission spectrum from ''short'' undulaters when the magnetic field strength parameter is small compared to unity, or in ''single'' frequency sinusoidal undulaters where the magnetic field strength parameter is comparable to or larger than unity, but where the magnetic field amplitude is constant throughout the undulater. Fewer general results have been obtained in the case where the insertion device is both short, i.e., the magnetic field strength parameter changes appreciably throughout the insertion device, and the magnetic field strength is high enough that ponderomotive effects, radiation retardation, and harmonic generation are important physical phenomena. In this paper a general method is presented for calculating the radiation spectrum for short, high-field insertion devices. It is used to calculate the emission from some insertion device designs of recent interest.

Geoffrey Krafft

2005-09-15

72

Review of high speed communications photomultiplier detectors  

NASA Technical Reports Server (NTRS)

Four types of newly developed high speed photomultipliers are discussed: all electrostatic; static crossed field; dynamic crossed field; and hybrid (EBS). Design, construction, and performance parameters of each class are presented along with limitations of each class of device and prognosis for its future in high speed light detection. The particular advantage of these devices lies in high speed applications using low photon flux, large cathode areas, and broadband optical detection.

Enck, R. S.; Abraham, W. G.

1978-01-01

73

Assessment of highly active dune mobility in the medium, short and very short term  

NASA Astrophysics Data System (ADS)

Dune activity or stability has usually been studied over long time periods; however, this may not reflect changes that occur in the short term, especially for highly active dunefields. Extreme wind conditions that are generated near the Strait of Gibraltar (SW Spain) have given rise to the transgressive Valdevaqueros dunefield. The current work focuses on analyzing the sand drift potential and the evolution of the dune profile in the medium term (months), the short term (days) and the very short term (hours). Topographic data, which were collected with a differential GPS, were interpreted from reconstructed empirical orthogonal functions (EOF). The results showed that generally the dune profile presented shifting morphologies, especially around the crest and brink, and a trend towards migration to a gentler steady state. As a result, the leeward side adopted continuous slope variations during the different survey periods, whereas the windward slope did not undergo any significant change. Lateral and vertical displacements were analyzed during a severe easterly sandstorm, when the dune brink experienced an advance migration rate of 1.75 m in 24 h. Sand transport rates of 25.5-36.5 m 3 m - 1 month - 1 , 22.52 m 3 m - 1 day - 1 and 0.93 m 3 m - 1 h - 1 were measured for the medium term, short term and very short term, respectively. These values were compared to the theoretical sand transport rate for Valdevaqueros dune, based on the classic Bagnold equation as well other more recent formulae, to obtain a ratio between the real and the theoretical rates for each study period. These results together with the sand drift potential (up to 10,000 vector units) demonstrate that Valdevaqueros (Tarifa) is a dunefield with one of the highest sand transport capacities in Europe.

Navarro, Marina; Muñoz-Pérez, Juan J.; Román-Sierra, Jorge; Tsoar, Haim; Rodríguez, Inmaculada; Gómez-Pina, Gregorio

2011-06-01

74

High-temperature-short-time thermal quarantine methods  

Microsoft Academic Search

In this paper, kinetic models are discussed with respect to their uses in describing the intrinsic thermal mortality of insect pests. A unique heating block system was used to obtain kinetic information for the thermal mortality of codling moth larvae. The kinetic data demonstrated the possibility to develop high-temperature-short-time thermal treatments to control codling moth and reduce thermal impact on

J. Tang; J. N. Ikediala; S. Wang; J. D. Hansen; R. P. Cavalieri

2000-01-01

75

High-altitude platforms for wireless communications  

Microsoft Academic Search

The demand for high-capacity wireless services is bringing increasing challenges, especially for delivery of the'last mile'. Terrestrially, the need for line-of-sight propagation paths represents a constraint unless very large numbers of base-station masts are deployed, while satellite systems have capacity limitations. An emerging solution is offered by high-altitude platforms (HAPs) operating in the stratosphere at altitudes of up to 22

T. C. Tozer; D. Grace

2001-01-01

76

Communicative Conference on High-Energy Materials.  

National Technical Information Service (NTIS)

A symposium on high-energy forming was held in the Peking Science Hall from July 26 to August 7, 1965, sponsored by the Aeronautical society of China and the New technology bureau, Chinese academy of sciences, and attended by 184 members and more than 100...

1967-01-01

77

High bandwidth electro-optic technology for intersatellite optical communications  

NASA Technical Reports Server (NTRS)

The research and development of electronic and electro-optic components for geosynchronous and low earth orbiting satellite optical high bandwidth communications at the NASA-Goddard Space Flight Center is reviewed. Intersatellite optical communications retains a strong reliance on microwave circuit technology in several areas - the microwave to optical interface, the laser transmitter modulation driver and the optical receiver. A microwave to optical interface is described requiring high bandwidth electronic downconverters and demodulators. Electrical bandwidth and current drive requirements for the laser modulation driver for three laser alternatives are discussed. Bandwidth and noise requirements are presented for optical receiver architectures.

Krainak, Michael A.

1992-01-01

78

Tissue reaction of the EndoREZ in root canal fillings short of or beyond an apical foramenlike communication.  

PubMed

This study evaluated the response of periapical tissues to the endodontic sealer EndoREZ in root canal fillings short of or beyond the apical foramenlike communication. Twenty root canals of premolars and incisors of 2 mongrel dogs were used. After coronal access and pulp extirpation, the canals were instrumented up to a size 55 K-file and the apical cemental barrier was penetrated with a size 15 K-file to create an apical foramenlike communication, which was widened to a size 25 K-file. The canals were irrigated with saline at each change of file. The root canals were obturated either short of or beyond the apical foramenlike opening by the lateral condensation of gutta-percha and EndoREZ, originating 2 experimental groups: G1, EndoREZ/short of the apical foramenlike opening, and G2, EndoREZ/beyond the apical foramenlike opening. The animals were killed by anesthetic overdose 90 days after endodontic treatment. The individual roots were obtained and serial histological sections were prepared for histomorphological analysis (H&E and Brown and Brenn techniques) under light microscopy. The following parameters were examined: closure of the apical foramenlike communication and apical opening of accessory canals, apical cementum resorptions, intensity of the inflammatory infiltrate, presence of giant cells, and thickness and organization of the apical periodontal ligament. Each parameter was scored 1 to 4, 1 being the best result and 4 the worst. Data were analyzed statistically by the Wilcoxon nonparametric tests (P = .05). Comparing the 2 groups, the best result (P = .05) was obtained with root canal filling with EndoREZ short of the apical foramenlike opening. In conclusion, limiting the filling material to the root canal space apically was important to determine the best treatment outcome when EndoREZ was used as the sealer. PMID:20416527

Suzuki, Patrícia; de Souza, Valdir; Holland, Roberto; Murata, Sueli Satomi; Gomes-Filho, João Eduardo; Dezan Junior, Eloi; Rodrigues Dos Passos, Thiago

2010-05-01

79

Ultra-Wideband Technology for Short or Medium-Range Wireless Communications  

Microsoft Academic Search

Ultra-Wideband (UWB) technology is loosely defined as any wireless transmission scheme that occupies a bandwidth of more than 25% of a center frequency, or more than 1.5GHz. The Federal Communications Commission (FCC) is currently working on setting emissions limits that would allow UWB communication systems to be deployed on an unlicensed basis following the Part 15.209 rules for radiated emissions

Jeff Foerster; Evan Green; Srinivasa Somayazulu; David Leeper

2001-01-01

80

Minimum energy per bit in high bit rate optical communications and quantum communications  

NASA Astrophysics Data System (ADS)

Optical direct detection usually operates far above the quantum limit, due to the high thermal noise level of PIN photodiodes. For signal energy at the quantum level, the thermal effects in photon counters are also a strong limitation. The optical amplification or the heterodyne detection of the 2 quadratures of the field, widely used in high bit rate and long haul optical systems, overcome this limitation at the expense of a minimum 3db noise figure. By allowing a noise free mixing gain, as well as single quadrature measurements, the balanced homodyne receiver is allowed to reach quantum noise limited operation. The aim of this paper is to review the different quantum receiver implementations and to compare the minimum signal energy required to achieve a given bit error rate, or a given bit erasure rate, in high bit rate communications and quantum communications. Application to quantum cryptography will be also addressed.

Gallion, P.; Mendieta, F. J.

2011-04-01

81

The research of high efficient optical fiber coupling technology in space laser communication  

NASA Astrophysics Data System (ADS)

With the development of optical fiber communications, especially the maturity of the optical amplifiers and the WDM technology, space optical communication at 1550 nm becomes a promising solution for future high speed satellite communication. Receiving technology with optical amplifiers and coupling space light into single mode fiber are key technologies in space optical communication at 1550 nm. Free-space-to-fiber coupling technique investigated in this paper is the first challenge of applying fiber communication techniques to free space optical communications. We analyzed the factors that affect the efficiency of free-space-to single-mode-fiber coupling based on mode-matching theory of electromagnetic fields. On this objective, in this paper, the theoretical analysis of the effect of atmospheric turbulence on the space light-single mode fiber coupling efficiency is discussed. On this basis, the short-distance experiment coupling space light into single mode fiber is carried out. 1. The main factors affecting the process coupling space light into single mode fiber are analyzed. This paper introduced the statistical theory of atmospheric turbulence and gave out the main turbulence parameters and meteyard based on the theory of the space light-single mode fiber coupling efficiency under ideal conditions. 2. The influence of atmospheric turbulence on the space light-single mode fiber coupling efficiency is analyzed and simulated. In the weak turbulence condition, mathematical model of the mean coupling efficiency and its fluctuation variance was given. And the fluctuation variance of coupling efficiency was simulated studied under the atmospheric conditions. The influences on the average coupling efficiency was theoretically studied, which were induced by the structure constant of atmospheric refractive index, the diameter of coupling lens and the single-mode fiber mode field radius. 3. Validating the theoretical model by a experiment under a short link coupling condition. The results of this paper lay the theoretical and experimental foundation for indeed establishing the efficient space light-single mode fiber coupling systems.

Wang, Hao-zeng; Tong, Shou-feng; Zhang, Lei; Yang, Hong-kun

2013-08-01

82

Short-backfire antenna - A highly efficient array element  

Microsoft Academic Search

A compact efficient directional radiator functioning as short-backfire (SBF) antenna is described. Two-element and four-element variants of the SBF array were investigated, and radiation patterns are displayed. Multielement high-gain broadside arrays comprising a multiplicity of SBF elements are envisaged. A single SBF element can replace 4-6 conventional elements without gain loss, and with concomitant advantages in reliability and simplicity. The

H. W. Ehrenspeck; J. A. Strom

1977-01-01

83

Overlapped Discrete Multitone Modulation for High Speed Copper Wire Communication  

Microsoft Academic Search

Multicarrier modulation possesses several properties which make it an attractive approach for high speed copper wire communications networks. Among these properties are the ability to efficiently access and distribute multiplexed data streams, and a reduced susceptibility to impulsive, as well as to narrowband channel disturbances. In digital implementations of multicarrier modulation, subcarrier generation and data modulation are accomplished digitally using

Stuart D. Sandberg; Michael A. Tzannes

1995-01-01

84

Overlapped discrete multitone modulation for high speed copper wire communications  

Microsoft Academic Search

Multicarrier modulation possesses several properties which make it an attractive approach for high speed copper wire communication networks. Among these properties are the ability to efficiently access and distribute multiplexed data streams, and a reduced susceptibility to impulsive, as well as to narrowband channel disturbances. In digital implementations of multicarrier modulation, subcarrier generation and data modulation are accomplished digitally using

Stuart D. Sandberg; Michael A. Tzannes

1995-01-01

85

Wireless communications from high altitude platforms: Applications, deployment and development  

Microsoft Academic Search

In this paper, an overview of the HAP concept development and HAP trails is introduced to show the worldwide interest and development in the emerging novel technology. A comparison of the HAP, terrestrial and satellite system characteristics is given. Main advantages of HAPs for wireless communication applications are large coverage area, high capacity and cost-effective deployment. Three applicable scenarios of

Z. Yang; A. Mohammed

2010-01-01

86

Broadband communications via high-altitude platforms: A survey  

Microsoft Academic Search

This article is a survey on communication aspects of High Altitude Platforms (HAPs), namely airships or aircraft positioned in the stratosphere between 17 and 22 km. HAPs can be considered as a novel solution for providing telecommunications services. This survey begins with an introduction to HAPs, that is, some historical information and advantages of HAPs compared to terrestrial and satellite

Stylianos Karapantazis; Fotini-niovi Pavlidou

2005-01-01

87

Verifying cell loss requirements in high-speed communication networks  

Microsoft Academic Search

In high-speed communication networks it is common to have requirements of very small cell lossprobabilities due to buffer overflow. Losses are measured to verify that the cell loss requirementsare being met, but it is not clear how to interpret such measurements. We propose methods fordetermining whether or not cell loss requirements are being met. A key idea is to look

Kerry W. Fendick; Ward Whitt

1998-01-01

88

Methods for UGV teleoperation with high latency communications  

Microsoft Academic Search

In this project, we developed and demonstrated complementary UGV control methods for teleoperation with highlatency communications. The methods included latency protection, predictive displays, and supervisory control. Latency protection mitigate against typical types of high-latency teleoperation input errors. The Phase I latency protection methods included filtering the joysick commands, limiting the commanded rates as a function of latency, and emergency stop

Gary Witus; Shawn Hunt; Phil Janicki

2011-01-01

89

An empirical study of short-term mass communication saturation and perception of population problems.  

PubMed

A 1-week population sensitivity campaign was held in the primarily university community of Boulder, Colorado, in November 1969. This 8-day campaign was conducted by running quarter-page advertisements in the newspaper and by braodcasting radio spots, which contained information on the population explosion. A control group of 175 people responded to a 1-minute telephone questionnaire immediately before the "population sensitivity" week began. A different sample of 185 people responded to the same questionnaire following the sensitivity week in order to test any increase in awareness that was not interviewer-induced. 96% of both the control and follow-up groups had heard of the population explosion, and 78% believed that "the population explosion applies to population growth in the United States." 55% of the respondents believed that the population explosion would have an effect on either their families or themselves. Older, less educated individuals who are lower in the occupational strata were found to be less likely to acknowledge that the U.S. has problems with population growth than were younger, better educated persons of high occupational status. Overall, there were no significant differences between the control and the experimental groups. Short-term saturation techniques conducted through the mass media are unlikely to affect attitudes concerning population growth, and this conclusion indicates the need for long-term education programs. PMID:12308778

Jobes, P

1977-01-01

90

Commercial optical inter-satellite communication at high data rates  

NASA Astrophysics Data System (ADS)

Laser communication terminals with data rates far above 1 Gbps have been in operation in orbit since January 2008, and the links established between two low Earth orbit (LEO) satellites have demonstrated error-free communication. Bit error rates better than 10-11 have been achieved without data encoding. Signal acquisition can be reproducibly achieved within a few seconds. After adaptation to larger link separation distances these laser communication terminals will be used in the low earth orbit-geosynchronous satellite (LEO-GEO) link of European data relay satellite (EDRS), the GEO European data relay system. LEO-to-ground and ground-to-LEO links have examined the impact of the atmosphere on such optical links. In the future, high data rate GEO-to-ground links will require ground stations equipped with adaptive optics, which are currently under development.

Gregory, Mark; Heine, Frank; Kämpfner, Hartmut; Lange, Robert; Lutzer, Michael; Meyer, Rolf

2012-03-01

91

A secure communications infrastructure for high-performance distributed computing  

SciTech Connect

Applications that use high-speed networks to connect geographically distributed supercomputers, databases, and scientific instruments may operate over open networks and access valuable resources. Hence, they can require mechanisms for ensuring integrity and confidentially of communications and for authenticating both users and resources. Security solutions developed for traditional client-server applications do not provide direct support for the program structures, programming tools, and performance requirements encountered in these applications. The authors address these requirements via a security-enhanced version of the Nexus communication library; which they use to provide secure versions of parallel libraries and languages, including the Message Passing Interface. These tools permit a fine degree of control over what, where, and when security mechanisms are applied. In particular, a single application can mix secure and nonsecure communication, allowing the programmer to make fine-grained security/performance tradeoffs. The authors present performance results that quantify the performance of their infrastructure.

Foster, I.; Koenig, G.; Tuecke, S. [and others

1997-08-01

92

System and method that suppresses intensity fluctuations for free space high-speed optical communication  

DOEpatents

A high-speed (Gbps), free space optical communication system is based on spectral encoding of radiation from a wide band light source, such as a laser. By using partially coherent laser beams in combination with a relatively slow photosensor, scintillations can be suppressed by orders of magnitude for distances of more than 10 km. To suppress the intensity fluctuations due to atmospheric turbulence, a source with partial transverse coherence in combination with slow response time photodetector is used. Information is encoded in the spectral domain of a wideband optical source by modulation of spectral amplitudes. A non-coherent light source with wide spectrum (an LED, for example) may be used for high-speed communication over short (less than about a mile) distances.

Berman, Gennady P. (Los Alamos, NM) [Los Alamos, NM; Bishop, Alan R. (Los Alamos, NM) [Los Alamos, NM; Nguyen, Dinh C. (Los Alamos, NM) [Los Alamos, NM; Chernobrod, Boris M. (Santa Fe, NM) [Santa Fe, NM; Gorshkov, Vacheslav N. (Kiev, UA) [Kiev, UA

2009-10-13

93

Short- and Long-Term Effectiveness of Two Communication Training Modalities with Distressed Couples.  

ERIC Educational Resources Information Center

Investigated the effectiveness of communication training in treating marital discord for conjoint and conjoint group modalities. Results showed that conjoint couples (N=16) improved on five of seven outcome variables, while conjoint group couples (N=13) improved on two. One-year follow-up showed substantial reduction in treatment gains. (WAS)

Schindler, Ludwig; And Others

1983-01-01

94

Solid state laser communications in space (SOLACOS) high data rate satellite communication system verification program  

NASA Astrophysics Data System (ADS)

This paper gives an overview on the current development status of the SOLACOS program and presents the highlights of the program. SOLACOS (Solid State Laser Communications in Space) is the national German program to develop a high performance laser communication system for high data rate transmission between LEO and GEO satellites (Inter Orbit Link, IOL). Two experimental demonstrator terminals are designed and developed in the SOLACOS program. The main development objectives are the Pointing Acquisition and Tracking subsystem (PAT) and the high data rate communication system. All key subsystems and components are straightway developed to be upgraded in follow- on projects to full space qualification. The main design objective for the system is a high degree of modularity which allows to easily upgrade the system with new upcoming technologies. Therefore, all main subsystems are interconnected via fibers to ease replacement of subsystems. The system implements an asymmetric data link with a 650 MBit/s return channel and a 10 MBit/s forward channel. The 650 MBit/s channel is based on a diode pumped Nd:YAG, Integrated Optics Modulator and uses the syncbit transmission scheme. In the syncbit system synchronization information which is necessary to maintain phase lock of the local oscillator of the coherent receiver is transmitted time multiplexed into the data stream. The PAT system comprises two beam detection sensors and three beam steering elements. For initial acquisition and tracking of the remote satellite a high speed CCD camera with an integrated image processing unit, the Acquisition and Tracking Sensor (ATS) is used. In the tacking mode the beam position is sensed via the Fibernutator sensor which is also used to couple the incoming signal into the receiver fiber. Incoming and outgoing beams are routed through the telescopes which are positioned with a 2 axis gimbal mechanism and a high speed beam steering mirror. The PAT system is controlled by a digital signal processor. For beam control advanced PAT algorithms are under development.

Pribil, Klaus; Flemmig, Joerg

1994-09-01

95

Analysis of SCTP and TCP based communication in high-speed clusters  

NASA Astrophysics Data System (ADS)

Performance and financial constraints are pushing modern DAQs (Data Acquisition Systems) to use distributed cluster environments instead of monolith one-box systems. Inside clusters application communication layers should support outstanding high performance requirements. We are currently investigating different network protocols that could meet the requirements of high speed/low latency peer-to-peer communication within DAQ clusters. We have carried out various performance measurements with TCP and SCTP over Fast and Gigabit Ethernet. We are focusing on Ethernet Technologies, because this transport medium is broad deployed, cost efficient and it has much better cost/throughput ratio than other available communication alternatives (e.g.: Myrinet, Infiniband). During this study, a protocol performance measurement application with different peer transport components has been developed. In the first part of the paper, we give a short comparison of the two protocols (SCTP and TCP), and an introduction of the transport layer structure developed. Later on we discuss the performance results of single/multi-stream peer-to-peer communication, give overview about application code transition possibilities from application developer point of view between the two protocols, and draw conclusions about usability.

Kozlovszky, M.; Berceli, T.; Kutor, L.

2006-04-01

96

Communication.  

ERIC Educational Resources Information Center

This theme issue on communication includes annotated listings of Web sites, CD-ROM and computer software, videos, books, and professional resources that deal with various methods of communication. Sidebars discuss mythology, photojournalism, sharing ideas on the Web, and songs of protest. Suggestions for class activities are also included. (LRW)

Online-Offline, 1998

1998-01-01

97

Photoemission spectroscopy with high-intensity short-wavelength lasers  

NASA Astrophysics Data System (ADS)

We theoretically study the process of photoelectron emission from the helium atom using a high-intensity short-wavelength laser at a resonance condition of the residual singly charged ion. Photoionization followed by strong resonance coupling in the ion leads to a change in the photoelectron spectrum due to Rabi oscillations in the residual ion. Similarly to resonance fluorescence at high laser intensity, the photoelectron spectrum at high intensities evolves into a multipeaked structure. The number of peaks in the photoelectron spectrum is related to the number of Rabi cycles following the photoionization process. Moreover, the strong laser-induced coupling to nonresonant states of the residual ion has an imprint on the photoelectron spectrum, leading to additional, isolated peaks at the lower- or higher-energy sides. The effect should be observable at current seeded extreme ultraviolet (XUV) free-electron lasers and persists after volume integration in a realistic experimental geometry.

Zhang, Song Bin; Rohringer, Nina

2014-01-01

98

High Temperature Wireless Communication And Electronics For Harsh Environment Applications  

NASA Technical Reports Server (NTRS)

In order for future aerospace propulsion systems to meet the increasing requirements for decreased maintenance, improved capability, and increased safety, the inclusion of intelligence into the propulsion system design and operation becomes necessary. These propulsion systems will have to incorporate technology that will monitor propulsion component conditions, analyze the incoming data, and modify operating parameters to optimize propulsion system operations. This implies the development of sensors, actuators, and electronics, with associated packaging, that will be able to operate under the harsh environments present in an engine. However, given the harsh environments inherent in propulsion systems, the development of engine-compatible electronics and sensors is not straightforward. The ability of a sensor system to operate in a given environment often depends as much on the technologies supporting the sensor element as the element itself. If the supporting technology cannot handle the application, then no matter how good the sensor is itself, the sensor system will fail. An example is high temperature environments where supporting technologies are often not capable of operation in engine conditions. Further, for every sensor going into an engine environment, i.e., for every new piece of hardware that improves the in-situ intelligence of the components, communication wires almost always must follow. The communication wires may be within or between parts, or from the engine to the controller. As more hardware is added, more wires, weight, complexity, and potential for unreliability is also introduced. Thus, wireless communication combined with in-situ processing of data would significantly improve the ability to include sensors into high temperature systems and thus lead toward more intelligent engine systems. NASA Glenn Research Center (GRC) is presently leading the development of electronics, communication systems, and sensors capable of prolonged stable operation in harsh 500C environments. This has included world record operation of SiC-based transistor technology (including packaging) that has demonstrated continuous electrical operation at 500C for over 2000 hours. Based on SiC electronics, development of high temperature wireless communication has been on-going. This work has concentrated on maturing the SiC electronic devices for communication purposes as well as the passive components such as resistors and capacitors needed to enable a high temperature wireless system. The objective is to eliminate wires associated with high temperature sensors which add weight to a vehicle and can be a cause of sensor unreliability. This paper discusses the development of SiC based electronics and wireless communications technology for harsh environment applications such as propulsion health management systems and in Venus missions. A brief overview of the future directions in sensor technology is given including maturing of near-room temperature "Lick and Stick" leak sensor technology for possible implementation in the Crew Launch Vehicle program. Then an overview of high temperature electronics and the development of high temperature communication systems is presented. The maturity of related technologies such as sensor and packaging will also be discussed. It is concluded that a significant component of efforts to improve the intelligence of harsh environment operating systems is the development and implementation of high temperature wireless technology

Hunter, G. W.; Neudeck, P. G.; Beheim, G. M.; Ponchak, G. E.; Chen, L.-Y

2007-01-01

99

Short communication: Automatic detection of social competition using an electronic feeding system.  

PubMed

The objective of this study was to determine if data derived from a system that electronically monitors feeding behavior could be used to identify competitive interactions of dairy cows at the feed bunk. A short interval between successive feeding events of 2 cows at 1 feed bin was predicted to be associated with a competitive replacement: when one cow displaced a feeding cow and then took her position at the bin. To identify the interval between feeding events that best predicted these replacement events, the feeding activity of 5 Holstein dairy cows was monitored using an electronic feeding system and video recordings. The number of times a cow was replaced at the feed bunk over 3 consecutive 24-h periods was determined using video analysis and these events were paired with the corresponding feeding events recorded by an electronic feeding system (Roughage Intake Control system; Insentec B.V., Marknesse, the Netherlands). A pooled analysis of all 5 cows showed that the optimal interval for predicting replacements at the feed bunk was 26s (sensitivity=86% and specificity=82%); this interval was termed the replacement criterion. This criterion was then applied to feeding data from a sample of 24 independent Holstein dairy cows, each observed for 3d during the week following calving. Video had previously been used to measure the number of times each cow was an actor and reactor of a displacement (when one cow displaced a feeding cow but did not necessarily take her position at the bin). Despite the differences in measures, the number of replacements (as estimated by our algorithm) was positively correlated with the number of displacements [as measured using video; correlation coefficient (r)=0.63 as actor, r=0.69 as reactor]. Estimates of an index of success in competitive interactions (number of times actor/number of times actor = number of times reactor) generated using the 2 methods were highly correlated (r=0.94). These results suggest that competitive behavior at the feed bunk can be automatically quantified using data derived from an electronic feeding system. PMID:24630661

Huzzey, J M; Weary, D M; Tiau, B Y F; von Keyserlingk, M A G

2014-05-01

100

Short communication Conodont index fossil Hindeodus changxingensis Wang fingers greatest mass extinction event  

Microsoft Academic Search

The marine conodont fossil species, Hindeodus changxingensis Wang, that has a distinctive morphology, is restricted to a very narrowstratigraphicintervalessentiallyfromthePermian-Triassicextinctioneventthroughtheinternationallyrecognizedboundary and into the very earliest Triassic. The species is geographically widespread in the Tethyan Region, from Italy to South China, and serves as a characteristic index fossil to reliably identify this short but critical interval that encompasses the greatest mass extinction

I. Metcalfe; R. S. Nicoll; B. R. Wardlaw

101

High Spectral Efficient and Flexible Next Generation Mobile Communications  

Microsoft Academic Search

In this paper we identify and describe the requirements and challenges of next generation mobile communications systems. The so-called fourth genera- tion (4G) aims at throughput rates of more than 100 MBit=s outdoors with high mobility and 1 GBit=s indoors. This requires new advanced techniques in the air interface of such a system. We outline new possible techniques and introduce

Simon Plass; Stephan Sand; Mikael Sternad; Arne Svensson

2007-01-01

102

High Spectral Efficient and Flexible Next Generation Mobile Communications  

Microsoft Academic Search

In this article we identify and describe the requirements and challenges of next generation mobile communications systems.\\u000a The so-called fourth generation (4G) aims at throughput rates of more than 100 MBit\\/s outdoors with high mobility and 1GBit\\/s\\u000a indoors. This requires new advanced techniques in the air interface of such a system. We outline new possible techniques and\\u000a introduce a future

Simon Plass; Stephan Sand; Mikael Sternad; Arne Svensson

2008-01-01

103

Highly survivable communications: Complementary media packet switched networks  

NASA Astrophysics Data System (ADS)

The requirement for highly survivable communications (HSC) for essential command functions in military operations does not need any justification. The ability to communicate under extreme jamming levels and adverse propagation conditions, including high altitude nuclear events, is a very important requirement. There are also many natural disaster related requirements that also need such highly survivable communications. The prevalent and in a sense classical, approach to provide highly assured connectivity can be summarized as follows: Take a particular propagation medium and try to obtain the ultimate performance from it. There are many examples of this philosophy some successful, most not. Our approach, on the other hand, is to use complementary multi-media or mixed-media where communication links utilizing essentially commercial-off-the-shelf (COTS) equipment are integrated using packet radio (PR) techniques. There is also, in our view, an even more fundamental, recently discovered consideration why the expectation of continuous incremental refinement of a system using a given single media may be be achievable. This is derived from the theory of 'deterministic uncertainty' or more popularly known as 'theory of CHAOS', systems whose state space behavior has fractal characteristics. We will elaborate on this novel argument. Complementary multi-media approach has been the focus for all HSC communications activities at STC since 1982. The original STC studies and prototypes were in response to requirements of broadcasting (i.e., one-way transmission) information. A high frequency (HF)/meteorburst (MB) system was developed/prototyped/tested demonstrating the cost effectiveness of the approach. These results are reviewed. More recently, in 1992 STC has completed the development/test of an Open Systems Interconnection (OSI) HF packet radio protocol as no such open or non-proprietary protocol exists. This protocol has been fully tested, documented and made available to all NATO nations/industries. These extensive results show that significant improvements in throughput of up to many times are obtained. A similar development for an OSI MB protocol has also been completed and combined with the HF protocol to obtain an OSI HF/MB link layer protocol with unique properties for HSC networks. Description of these protocols and the relevant results are presented. highly survivable connectivity, by providing the most important ingredient of survivability, media diversity.

Yavuz, D.; Eken, F.; Karavassilis, N.

1994-07-01

104

Iridium Short Burst Data: Two-Way, Robust, Reliable, Low Power Communications for Oceanographic Data Transmission Applications  

NASA Astrophysics Data System (ADS)

Over the past two hundred years, water level observations in coastal areas have been used to help mariners navigate oceans and estuaries, cartographers develop nautical charts, government agencies regulate boundaries, and scientists gain a better understanding of various physical processes in the ocean. As technology has progressed the latency in providing these data to the user has been reduced. The National Oceanic and Atmospheric Administration's (NOAA) Center for Operational Oceanographic Products and Services (CO-OPS) provides near real-time oceanographic and meteorological data to support navigation, coastal managers, and storm surge and tsunami warning programs. CO-OPS maintains the National Water Level Observation Network (NWLON), a system of over 200 stations for the coastal United States, Great Lakes, Caribbean islands, and Pacific island territories. CO-OPS also supports the NOAA Physical Oceanographic Real Time Systems° (PORTS), which are currently operating in 21 US ports. With an expanding role in Arctic and Alaska support, CO-OPS has identified a need for a robust and reliable data communications pathway to supplement the existing Geostationary Operational Environmental Systems (GOES) network, which has limitations at high latitudes. Iridium satellite Short Burst Data (SBD) services offer a global coverage, including remote Arctic regions outside of GOES coverage. Previous testing conducted by CO-OPS has shown a great potential for the SBD service including continuous near-real-time 6 minute data transmissions from two CO-OPS test water level stations located in Guam, with >99.9% data return. Also, successful transmissions of hourly wave statistics were demonstrated with a with a test system that employed a Nortek Acoustic Wave and Current (AWAC) instrument in Chesapeake Bay were accomplished. Data transmissions involved a buoy-mounted SIM-less SBD modem. Independent of location, data can be transmitted from a remote instrument platform to Iridium satellites with a latency of just 15 seconds. Successful test demonstrations have led to discussions regarding prospective work to integrate these small modems into CO-OPS current meters that are mounted on United States Coast Guard (USCG) Aid to Navigation (ATON) buoys, improving the reliability of the real-time transmission pathway between data collection and data reporting via PORTS °. Overall, this work has shown that with careful evaluation of data needs, commercial Iridium service can be economically used to accomplish telemetry requirements. It also shows potential for event-driven high frequency data transmission options, for applications such as marine warning systems. CO-OPS efforts to test and evaluate Iridium communications oceanographic observatories reported on here has been a collaborative endeavor with the United States Army Corp Engineers (USACE) Field Research Facility (FRF) in Duck, NC, the USACE Cold Regions Research Engineering Laboratory (CRREL) in Hanover, NH, NAL Research Inc, Sutron Corporation,and Nortek USA.

Roggenstein, E. B.; Hensley, W.

2011-12-01

105

Short communication Frequency and length-dependent effects of Botulinum toxin-induced muscle weakness  

Microsoft Academic Search

While the pathogenesis of Botulinum toxin type A (BTX-A)-induced muscle weakness has been systematically researched, little is known about the effects of motor fibre paralysis on the mechanical properties of skeletal muscle. Here, the long-term effect of BTX- A injection on the force-length and force-frequency properties of rabbit knee extensors is investigated. BTX-A-induced muscle weakness was greater at short comparedto

Timothy A. Butterfield; Walter Herzog

106

Communication  

Microsoft Academic Search

\\u000a Communication impairment is a core deficit associated with autism spectrum disorder (ASD). Therefore, it should not be surprising\\u000a that this topic has become a major thrust of assessment and treatment in applied behavior analysis (ABA). The types of communication\\u000a skills to target for intervention and the behavioral assessment methods that can be used to identify these target behaviors\\u000a are reviewed

Jeff Sigafoos; Mark F. O’Reilly; Giulio E. Lancioni

107

Rad-Hard high speed serial communication using Honeywell SerDes macros  

Microsoft Academic Search

SerDes (serializer\\/deserializer) is a key component of serial communication architecture for high-speed servers and communications networking systems and point to point communication links. It is a vital building block for space-based high-speed data communications. Honeywell is enabling optimized communication systems with a SerDes macro-cell as part of their HX5000 rad-hard ASIC design platform and a SerDes standard part for next-generation

G. Roosevelt; D. Bueno; J. Haque; W. Roper; T. Romanko

2009-01-01

108

High-power diode lasers for optical communications applications  

NASA Technical Reports Server (NTRS)

High-power, single-mode, double-heterojunction AlGaAs diode lasers are being developed to meet source requirements for both fiber optic local area network and free space communications systems. An individual device, based on the channeled-substrate-planar (CSP) structure, has yielded single spatial and longitudinal mode outputs of up to 90 mW CW, and has maintained a single spatial mode to 150 mW CW. Phase-locked arrays of closely spaced index-guided lasers have been designed and fabricated with the aim of multiplying the outputs of the individual devices to even higher power levels in a stable, single-lobe, anastigmatic beam. The optical modes of the lasers in such arrays can couple together in such a way that they appear to be emanating from a single source, and can therefore be efficiently coupled into optical communications systems. This paper will review the state of high-power laser technology and discuss the communication system implications of these devices.

Carlin, D. B.; Goldstein, B.; Channin, D. J.

1985-01-01

109

High temperature superconductor analog electronics for millimeter-wavelength communications  

NASA Technical Reports Server (NTRS)

The performance of high temperature superconductor (HTS) passive microwave circuits up to X-band was encouraging when compared to their metallic counterparts. The extremely low surface resistance of HTS films up to about 10 GHz enables a reduction in loss by as much as 100 times compared to copper when both materials are kept at about 77 K. However, a superconductor's surface resistance varies in proportion to the frequency squared. Consequently, the potential benefit of HTS materials to millimeter-wave communications requires careful analysis. A simple ring resonator was used to evaluate microstrip losses at Ka-band. Additional promising components were investigated such as antennas and phase shifters. Prospects for HTS to favorable impact millimeter-wave communications systems are discussed.

Romanofsky, R. R.; Bhasin, K. B.

1991-01-01

110

A new short-anoded IGBT with high emission efficiency  

NASA Astrophysics Data System (ADS)

A novel short-anoded insulated-gate bipolar transistor (SA-IGBT) with double emitters is proposed. At the on-state, the new structure shows extraordinarily high emission efficiency. Moreover, with a short-contacted anode, it further enhances the hole emission efficiency because of the crowding of the electrons. The forward voltage drop VF of this structure is 1.74 V at a current density 100 of A/cm2. Compared to the conventional NPT IGBT (1.94 V), segment-anode IGBT (SA-NPN 2.1 V), and conventional SA-IGBT (2.33 V), VF decreased by 10%, 17% and 30%, respectively. Furthermore, no NDR has been detected comparing to the SA-IGBT. At the off-state, there is a channel for extracting excessive carriers in the drift region. The turn-off loss Eoff of this proposed structure is 8.64 mJ/cm2. Compared to the conventional NPT IGBT (15.3 mJ/cm2), SA-NPN IGBT (12.8 mJ/cm2), and SA-IGBT (12.1 mJ/cm2), Eoff decreased by 43.7%, 32% and 28%, respectively.

Weizhong, Chen; Bo, Zhang; Zehong, Li; Min, Ren; Zhaoji, Li

2012-11-01

111

High performance computing and communications: FY 1997 implementation plan  

SciTech Connect

The High Performance Computing and Communications (HPCC) Program was formally authorized by passage, with bipartisan support, of the High-Performance Computing Act of 1991, signed on December 9, 1991. The original Program, in which eight Federal agencies participated, has now grown to twelve agencies. This Plan provides a detailed description of the agencies` FY 1996 HPCC accomplishments and FY 1997 HPCC plans. Section 3 of this Plan provides an overview of the HPCC Program. Section 4 contains more detailed definitions of the Program Component Areas, with an emphasis on the overall directions and milestones planned for each PCA. Appendix A provides a detailed look at HPCC Program activities within each agency.

NONE

1996-12-01

112

A wideband propagation simulator for high speed mobile radio communications  

NASA Astrophysics Data System (ADS)

Multipath, jamming, listening and detection are the main limitations for mobile radio communications. Spread spectrum techniques, especially frequency hopping, can be used to avoid these problems. Therefore, a wideband simulation for multipath mobile channels appeared the most appropriate evaluation technique. It also gives useful indications for system characteristic improvements. This paper presents the design and realization of a new UHF-VHF propagation simulator, which can be considered as an extended version of Bussgang's one. This frequency hopping simulator (up to 100,000 hops per second) is wideband thus capable to deal with spread spectrum signals. As it generates up to 16 paths, it can be used in almost all mobile radio propagation situations. Moreover, it is also able to simulate high mobile relative speeds up to 2000km/h such as air-air communication systems. This simulator can reproduce, in laboratory, 16 rays Rician or Rayleigh fading channels with a maximum time delay of about 15 ms. At the highest frequency of 1200 MHz, Doppler rates up to 2 kHz can be generated corresponding to vehicle speeds up to 2000 km/h. Let note that the Bussgang simulator was defined for narrowband and fixed radio communications. In both equipments, in-phase and quadrature signals are obtained using two numerical transversal filters. Simulation results were derived in various situations especially in terrestrial urban and suburban environments, where they could be compared with measurements. The main advantage of the simulator lies in its capacity to simulate the high speed and wideband mobile radio communication channels.

Busson, P.; Lejannic, J. C.; Elzein, G.; Citerne, J.

1994-07-01

113

Preliminary investigation of acoustic bar codes for short-range underwater communications  

NASA Astrophysics Data System (ADS)

In March 2005, underwater acoustic communications experiments were carried out from the DRDC Atlantic research vessel CFAV QUEST. A battery-operated BATS20 transmitter and a broadband barrel-stave flextensional transducer were used to broadcast noise containing acoustic bar code (ABC) information. The ABCs are silent frequency bands of fixed duration that resemble retail bar codes when viewed in a spectrogram. Two sites were selected for the experiments. The first was a shallow-water area west of the Berry Islands in the Bahamas, and the second was a deep-water site south of the Western Bank on the Scotian Shelf. Two receiver systems were deployed; autonomous, variable-buoyancy Stealth Buoys resting on the bottom at the shallow site, and drifting AN/SSQ-53F sonobuoys fitted with GPS at the deep site. Results from these experiments will be presented and future work will be discussed.

Jones, Dennis F.

2005-09-01

114

Communication: An exact short-time solver for the time-dependent Schro?dinger equation.  

PubMed

The short-time integrator for propagating the time-dependent Schro?dinger equation, which is exact to machine's round off accuracy when the Hamiltonian of the system is time-independent, was applied to solve dynamics processes. This integrator has the old Cayley's form [i.e., the Pade? (1,1) approximation], but is implemented in a spectrally transformed Hamiltonian which was first introduced by Chen and Guo. Two examples are presented for illustration, including calculations of the collision energy-dependent probability passing over a barrier, and interaction process between pulse laser and the I(2) diatomic molecule. PMID:21280676

Sun, Zhigang; Yang, Weitao

2011-01-28

115

Communication: An exact short-time solver for the time-dependent Schr?dinger equation  

PubMed Central

The short-time integrator for propagating the time-dependent Schrödinger equation, which is exact to machine’s round off accuracy when the Hamiltonian of the system is time-independent, was applied to solve dynamics processes. This integrator has the old Cayley’s form [i.e., the Padé (1,1) approximation], but is implemented in a spectrally transformed Hamiltonian which was first introduced by Chen and Guo. Two examples are presented for illustration, including calculations of the collision energy-dependent probability passing over a barrier, and interaction process between pulse laser and the I2 diatomic molecule.

Sun, Zhigang; Yang, Weitao

2011-01-01

116

HIGH-ENERGY EMISSION COMPONENTS IN THE SHORT GRB 090510  

SciTech Connect

We investigate the origin of the prompt and delayed emission observed in the short GRB 090510. We use the broadband data to test whether the most popular theoretical models for gamma-ray burst emission can accommodate the observations for this burst. We first attempt to explain the soft-to-hard spectral evolution associated with the delayed onset of a GeV tail with the hypothesis that the prompt burst and the high-energy tail both originate from a single process, namely, synchrotron emission from internal shocks (IS). Considerations on the compactness of the source imply that the high-energy tail should be produced in a late-emitted shell, characterized by a Lorentz factor greater than the one generating the prompt burst. However, in this hypothesis, the predicted evolution of the synchrotron peak frequency does not agree with the observed soft-to-hard evolution. Given the difficulties of a single-mechanism hypothesis, we test two alternative double-component scenarios. In the first, the prompt burst is explained as synchrotron radiation from IS and the high-energy emission (up to about 1 s following the trigger) as IS synchrotron-self-Compton. In the second scenario, in view of its long duration ({approx}100 s), the high-energy tail is decoupled from the prompt burst and has an external shock origin. In this case, we show that a reasonable choice of parameters does indeed exist to accommodate the optical-to-GeV data, provided the Lorentz factor of the shocked shell is sufficiently high. Finally, we attempt to explain the chromatic break observed around {approx}10{sup 3} s with a structured jet model. We find that this might be a viable explanation and that it lowers the high value of the burst energy derived by assuming isotropy, {approx}10{sup 53} erg, below {approx}10{sup 49} erg, which is more compatible with the energetics from a binary merger progenitor.

Corsi, Alessandra [Universita degli studi di Roma 'Sapienza' and INFN-Sezione di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy); Guetta, Dafne [INAF - Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone (Italy); Piro, Luigi, E-mail: alessandra.corsi@roma1.infn.i, E-mail: luigi.piro@iasf-roma.inaf.i, E-mail: guetta@oa-roma.inaf.i, E-mail: corsi@caltech.ed [INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica di Roma, Via Fosso del Cavaliere 100, 00133 Roma (Italy)

2010-09-10

117

Exposure caused by wireless technologies used for short-range indoor communication in homes and offices.  

PubMed

In order to estimate typical radio frequency exposures from indoor used wireless communication technologies applied in homes and offices, WLAN, Bluetooth and Digital Enhanced Cordless Telecommunications systems, as well as baby surveillance devices and wireless headphones for indoor usage, have been investigated by measurements and numerical computations. Based on optimised measurement methods, field distributions and resulting exposure were assessed on selected products and real exposure scenarios. Additionally, generic scenarios have been investigated on the basis of numerical computations. The obtained results demonstrate that under usual conditions the resulting spatially (over body dimensions) averaged and 6-min time-averaged exposure for persons in the radio frequency fields of the considered applications is below approximately 0.1% of the reference level for power density according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines published in 1998. Spatial and temporal peak values can be considerably higher by 2-3 orders of magnitude. In case of some transmitting devices operated in close proximity to the body (e.g. WLAN transmitters), local exposure can reach the same order of magnitude as the basic restriction; however, none of the devices considered in this study exceeded the limits according to the ICNIRP guidelines. PMID:17566000

Schmid, G; Lager, D; Preiner, P; Uberbacher, R; Cecil, S

2007-01-01

118

Communications.  

ERIC Educational Resources Information Center

Five articles discussing communications in vocational education include "The Golden Rule of Administration" by Ben Mortensen; "Vital Link with Parents" by Richard Sullivan; "An Interpersonal Exercise" by John Villiers; "Face to Face with Employers" by Gregg Bosak; and "Recruitment Strategies" by Susan Miller. (SK)

Mortensen, Ben F.; And Others

1981-01-01

119

A high current, short pulse electron source for wakefield accelerators  

SciTech Connect

Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

Ho, Ching-Hung

1992-12-31

120

A high current, short pulse electron source for wakefield accelerators  

SciTech Connect

Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

Ho, Ching-Hung.

1992-01-01

121

High power microwave components for space communications satellite  

NASA Technical Reports Server (NTRS)

Analyzed, developed, and tested were high power microwave components for communications satellites systems. Included were waveguide and flange configurations with venting, a harmonic filter, forward and reverse power monitors, electrical fault sensors, and a diplexer for two channel simultaneous transmission. The assembly of 8.36 GHz components was bench tested, and then operated for 60 hours at 3.5 kW CW in a high vacuum. The diplexer was omitted from this test pending a modification of its end irises. An RF leakage test showed only that care is required at flange junctions; all other components were RF tight. Designs were extrapolated for 12 GHz and 2.64 GHz high power satellite systems.

Jankowski, H.; Geia, A.

1972-01-01

122

Radio Synthesis Imaging - A High Performance Computing and Communications Project  

NASA Astrophysics Data System (ADS)

The National Science Foundation has funded a five-year High Performance Computing and Communications project at the National Center for Supercomputing Applications (NCSA) for the direct implementation of several of the computing recommendations of the Astronomy and Astrophysics Survey Committee (the "Bahcall report"). This paper is a summary of the project goals and a progress report. The project will implement a prototype of the next generation of astronomical telescope systems - remotely located telescopes connected by high-speed networks to very high performance, scalable architecture computers and on-line data archives, which are accessed by astronomers over Gbit/sec networks. Specifically, a data link has been installed between the BIMA millimeter-wave synthesis array at Hat Creek, California and NCSA at Urbana, Illinois for real-time transmission of data to NCSA. Data are automatically archived, and may be browsed and retrieved by astronomers using the NCSA Mosaic software. In addition, an on-line digital library of processed images will be established. BIMA data will be processed on a very high performance distributed computing system, with I/O, user interface, and most of the software system running on the NCSA Convex C3880 supercomputer or Silicon Graphics Onyx workstations connected by HiPPI to the high performance, massively parallel Thinking Machines Corporation CM-5. The very computationally intensive algorithms for calibration and imaging of radio synthesis array observations will be optimized for the CM-5 and new algorithms which utilize the massively parallel architecture will be developed. Code running simultaneously on the distributed computers will communicate using the Data Transport Mechanism developed by NCSA. The project will also use the BLANCA Gbit/s testbed network between Urbana and Madison, Wisconsin to connect an Onyx workstation in the University of Wisconsin Astronomy Department to the NCSA CM-5, for development of long-distance distributed computing. Finally, the project is developing 2D and 3D visualization software as part of the international AIPS++ project. This research and development project is being carried out by a team of experts in radio astronomy, algorithm development for massively parallel architectures, high-speed networking, database management, and Thinking Machines Corporation personnel. The development of this complete software, distributed computing, and data archive and library solution to the radio astronomy computing problem will advance our expertise in high performance computing and communications technology and the application of these techniques to astronomical data processing.

Crutcher, Richard M.

123

High-rate-long-distance fiber-optic communication based on advanced modulation techniques.  

PubMed

The presence of fiber attenuation and chromatic dispersion is one of the major design aspects of fiber-optic communication systems when one addresses high-rate and long-distance digital data transmission. Conventional digital communication systems implement a modulation technique that generates light pulses at the fiber input end and tries to detect them at the fiber output end. Here an advanced modulation transmission system is developed based on knowledge of the exact dispersion parameters of the fiber and the principles of space-time mathematical analogy. The information encodes the phase of the input light beam (a continuous laser beam). This phase is designed such that, when the signal is transmitted through a fiber with a given chromatic dispersion, high peak pulses emerge at the output, which follows a desired bit pattern. Thus the continuous input energy is concentrated into short time intervals in which the information needs to be represented at the output. The proposed method provides a high rate-distance product even for fibers with high dispersion parameters, high power at the output, and also unique protection properties. Theoretical analysis of the proposed method, computer simulations, and some design aspects are given. PMID:18324062

Ivankovski, Y; Mendlovic, D

1999-09-10

124

Short Communication: In Vitro Antimicrobial Susceptibility of Prototheca wickerhamii and Prototheca zopfii Isolated from Bovine Mastitis  

Microsoft Academic Search

Bovine mastitis caused by Prototheca spp. can as- sume high significance because of economic losses and the potential risk to public health. Studies on the sus- ceptibility of Prototheca spp. to antimicrobials have demonstrated its high level of resistance. We report the susceptibility of bovine isolates of Prototheca wick- erhamii and Prototheca zopfii to amphotericin B and nystatin, 2 antifungal

S. Marques; E. Silva; J. Carvalheira; G. Thompson

2006-01-01

125

High-dimensional modulation for coherent optical communications systems.  

PubMed

In this paper, we examine the performance of several modulation formats in more than four dimensions for coherent optical communications systems. We compare two high-dimensional modulation design methodologies based on spherical cutting of lattices and block coding of a 'base constellation' of binary phase shift keying (BPSK) on each dimension. The performances of modulation formats generated with these methodologies is analyzed in the asymptotic signal-to-noise ratio regime and for an additive white Gaussian noise (AWGN) channel. We then study the application of both types of high-dimensional modulation formats to standard single-mode fiber (SSMF) transmission systems. For modulation with spectral efficiencies comparable to dual-polarization (DP-) BPSK, polarization-switched quaternary phase shift keying (PS-QPSK) and DP-QPSK, we demonstrate SNR gains of up to 3 dB, 0.9 dB and 1 dB respectively, at a BER of 10(-3). PMID:24718249

Millar, David S; Koike-Akino, Toshiaki; Ar?k, Sercan Ö; Kojima, Keisuke; Parsons, Kieran; Yoshida, Tsuyoshi; Sugihara, Takashi

2014-04-01

126

SLIM, Short-pulse Technology for High Gradient Induction Accelerators  

SciTech Connect

A novel short-pulse concept (SLIM) suited to a new generation of a high gradient induction particle accelerators is described herein. It applies advanced solid state semiconductor technology and modern microfabrication techniques to a coreless induction method of charged particle acceleration first proven on a macro scale in the 1960's. Because this approach avoids use of magnetic materials there is the prospect of such an accelerator working efficiently with accelerating pulses in the nanosecond range and, potentially, at megahertz pulse rates. The principal accelerator section is envisioned as a stack of coreless induction cells, the only active element within each being a single, extremely fast (subnanosecond) solid state opening switch: a Drift Step Recovery Diode (DSRD). Each coreless induction cell incorporates an electromagnetic pulse compressor in which inductive energy developed within a transmission-line feed structure over a period of tens of nanoseconds is diverted to the acceleration of the passing charge packet for a few nanoseconds by the abrupt opening of the DSRD switch. The duration of this accelerating output pulse--typically two-to-four nanoseconds--is precisely determined by a microfabricated pulse forming line connected to the cell. Because the accelerating pulse is only nanoseconds in duration, longitudinal accelerating gradients approaching 100 MeV per meter are believed to be achievable without inciting breakdown. Further benefits of this approach are that, (1) only a low voltage power supply is required to produce the high accelerating gradient, and, (2) since the DSRD switch is normally closed, voltage stress is limited to a few nanoseconds per period, hence the susceptibility to hostile environment conditions such as ionizing radiation, mismatch (e.g. in medical applications the peak beam current may be low), strong electromagnetic noise levels, etc is expected to be minimal. Finally, we observe the SLIM concept is not limited to linac applications; for instance, it could be employed to both accelerate the beam and to stabilize the superbunch mode of operation in circular track machines.

Arntz, Floyd; /Diversified Tech., Bedford; Kardo-Sysoev, A.; /Ioffe Phys. Tech. Inst.; Krasnykh, A.; /SLAC

2008-12-16

127

Short communication: In vitro antimicrobial susceptibility of Prototheca wickerhamii and Prototheca zopfii isolated from bovine mastitis.  

PubMed

Bovine mastitis caused by Prototheca spp. can assume high significance because of economic losses and the potential risk to public health. Studies on the susceptibility of Prototheca spp. to antimicrobials have demonstrated its high level of resistance. We report the susceptibility of bovine isolates of Prototheca wickerhamii and Prototheca zopfii to amphotericin B and nystatin, 2 antifungal agents commonly used in the control of protothecosis, and discuss the results. After subculture, minimum inhibitory concentrations of both antifungal drugs were determined using macrodilution and agar diffusion methods. The inoculum concentration was standardized by determination of colony-forming units per milliliter. Nystatin showed more efficacy than amphotericin B in inhibiting P. wickerhamii growth. In contrast, growth inhibition of P. zopfii was similar for both antifungal agents. This study demonstrates different in vitro susceptibility patterns of P. wickerhamii and P. zopfii, reinforcing the necessity for more investigation into drugs that can be used with clinical efficacy. PMID:17033006

Marques, S; Silva, E; Carvalheira, J; Thompson, G

2006-11-01

128

Short Communication: Evidence That Microbial Translocation Occurs in HIV-Infected Children in the United Kingdom  

PubMed Central

Abstract Microbial translocation (MT) from the gut is implicated in driving immune activation, increasing morbidity and mortality in HIV. We used bacterial 16S rDNA PCR, Sanger sequencing, and high-throughput sequencing to identify microbial DNA in the bloodstream of HIV-infected children in London, United Kingdom. Blood samples were collected from sequential children attending the HIV clinic at Great Ormond Street Hospital, London. DNA extraction, broad range 16S rDNA PCR, and standard Sanger sequencing were carried out. A subset of positive samples was analyzed by high-throughput sequencing (Roche 454 platform). Of 105 samples collected from sequential children, nine were positive using broad range 16S rDNA PCR (8.6%; 95% CI 4.4–16%). From three amplicons, 16S rDNA sequences were identified as Streptococcus, Propionibacterium acnes, and coagulase-negative Staphylococcus. Four positive samples were analyzed by high-throughput sequencing. In the three samples in which organisms were identified by Sanger sequencing, the same species were identified. Further species, in differing proportions, were identified in all four samples. The identified organisms included known gut orders Bifidobacteriaceae, Lactobacillaceae, Bacteroidales, and Clostridiales. In immunocompetent children of equivalent age, no bacterial DNA was detected in blood using this approach. This is the first study to our knowledge using molecular techniques to identify MT in children in the developed world. Our data indicate that 16S rDNA is detectable in 8.6% of HIV-infected children. Levels of DNA were low and from multiple bacterial species. Further studies are needed to ascertain the importance of MT in HIV-infected children.

Fitzgerald, Felicity; Harris, Kathryn; Doyle, Ronan; Alber, Dagmar

2013-01-01

129

A self-adaptive method for creating high efficiency communication channels through random scattering media.  

PubMed

Controlling the propagation of electromagnetic waves is important to a broad range of applications. Recent advances in controlling wave propagation in random scattering media have enabled optical focusing and imaging inside random scattering media. In this work, we propose and demonstrate a new method to deliver optical power more efficiently through scattering media. Drastically different from the random matrix characterization approach, our method can rapidly establish high efficiency communication channels using just a few measurements, regardless of the number of optical modes, and provides a practical and robust solution to boost the signal levels in optical or short wave communications. We experimentally demonstrated analog and digital signal transmission through highly scattering media with greatly improved performance. Besides scattering, our method can also reduce the loss of signal due to absorption. Experimentally, we observed that our method forced light to go around absorbers, leading to even higher signal improvement than in the case of purely scattering media. Interestingly, the resulting signal improvement is highly directional, which provides a new means against eavesdropping. PMID:25070592

Hao, Xiang; Martin-Rouault, Laure; Cui, Meng

2014-01-01

130

Plasmas and Short-Pulse, High-Intensity Lasers  

NASA Astrophysics Data System (ADS)

Many of the applications of short-pulse, high-intensity laser systems, including coherent UV and X-ray generation, compact particle accelerators, and non-perturbative nonlinear optics as well as the study of laser-matter interaction physics, require large intensity-interaction length products. In recent years, plasma structures resulting from the hydrodynamic evolution of laser-produced plasma filaments have proven to be attractive media for guiding pulses with peak powers approaching the terawatt level over lengths many times the vacuum Rayleigh range. The hydrodynamics of plasma waveguides have been characterized using time- and space-resolved interferometry measurements of electron density profiles. The laser-driven ionization and heating phase of the plasma filament creation is followed by hot electron driven plasma expansion. Density profiles suitable for optical guiding develop within the first few hundred picoseconds after plasma creation, during which rapid cooling occurs. At longer times the plasma expansion closely follows that of a cylindrical blast wave, with further cooling due to expansion work. The observed guided intensity profiles of end-coupled and tunnel-coupled pulses compare favorably with calculations of the quasi-bound waveguide modes based on the measured electron density profiles. Time- and space-resolved electron density measurements of a laser-driven concentric implosion were also performed. The implosion is the result of the interaction of a second laser pulse with an existing plasma waveguide. The two-pulse absorption and ionization significantly exceed that due to a single pulse of the same total energy. The author would like to acknowledge the significant contributions of Prof. Howard M. Milchberg to the work being presented.

Clark, Thomas

1999-11-01

131

Short communication: Linear discriminant analysis and type of oil added to dairy goat diets.  

PubMed

Gas chromatography fatty acid (FA) analysis of 112 milk fat samples from dairy goats fed a basal diet with no added oil or the same diet with 1 of 3 vegetable oils added [high oleic sunflower oil (HOSFO), regular sunflower oil (RSFO), or linseed oil (LO)] was used to identify the type of diet consumed through linear discriminant analysis. Twenty variables (19 FA and 1 FA ratio) were selected as valid predictors out of 84 variables tested. The Mahalanobis squared distance was minimal between HOSFO and RSFO groups and maximal between control and LO groups. Cross-validation showed that only one observation from RSFO group was misclassified into the HOSFO group. We concluded that linear discriminant analysis is a useful method to classify milk fat samples from dairy goats according to the particular vegetable oil (of the 3 oils tested here) added to the basal diet. PMID:22720959

Martínez Marín, A L; Gómez-Cortés, P; Gómez Castro, A G; Juárez, M; Pérez Alba, L; Pérez Hernández, M; de la Fuente, M A

2012-07-01

132

Short communication: utilization of sheep's milk cheese whey in the manufacture of an alkylphenol flavor concentrate.  

PubMed

The recovery of species-related conjugated sheep-like flavored alkylphenols from Manchego-type cheese whey by ultrafiltration was investigated. Concentrations of conjugated alkylphenols were similar in the various fractions of whey permeate collected during ultrafiltration, and this was interpreted as a reflection of their high water solubility. About 49 and 62% of conjugated 3- and 4-ethylphenols and p- and m-cresols in sheep's milk cheese whey, respectively, were recovered in the permeate after ultrafiltration with a volume concentration factor of 5.4. Cheese whey retentate correspondingly contained 38 and 28% of conjugated 3- and 4-ethylphenols and p- and m-cresols from the original whey, respectively. Permeate fractions from sheep's milk cheese whey were combined, concentrated by vacuum evaporation, and lactose was partially removed by crystallization and filtration to obtain an aqueous sheep-like flavor precursor concentrate. PMID:15545359

Kilic, M; Lindsay, R C

2004-12-01

133

Short communication: Decrease in rumination time as an indicator of the onset of calving.  

PubMed

The aim of this study was to investigate whether rumination time (RT) is affected by the onset of calving. The relationship between both feeding time and dry matter intake (DMI) to the onset of calving was also examined. In addition, the correlation between feeding behavior characteristics, described here as RT, feeding time, and DMI, was evaluated. Under test conditions, the feeding behavior of pregnant Holstein cows was recorded from the time when they were moved into calving pens (usually 7 to 5d prepartum) until the onset of calving. Feeding time and DMI were recorded by automatic feed bins; RT was measured continuously by a measuring halter based on electromyography (DairyCheck; BITSz Engineering GmbH, Zwickau, Germany), which constitutes a new approach regarding feeding behavior detection. Data analysis related to the final 72h, before the onset of calving, which were divided into twelve 6-h blocks. The last 6h (one 6-h block) before calving were compared with the 72- to 7-h time frame (11 times 6-h blocks) before calving, which was defined as the reference period. For this time period, feeding behavior data for 17 cows was fully available, which was the precondition for data analysis. In the final 6h before imminent birth, RT was significantly reduced. During this time, it was found that the mean minimum RT was 69.9±28.5min/6h compared with the mean RT of 95.5±30.8min/6h in the reference period. The average decrease in RT was 27% (25.6min/6h). In addition, feeding time and DMI were significantly reduced. The average decrease in feeding time was 57% (20.8min/6h), and in DMI it was 56% (1.9kg/6h). High correlation coefficients between feeding behavior characteristics were only found between feeding time and DMI. Values of feeding behavior among cows were characterized by high variability. Recording RT can serve as a use ful tool for predicting the timing of birth for dairy cows, but further research is necessary. PMID:24612813

Büchel, S; Sundrum, A

2014-05-01

134

Short communication: Fractional milking distribution of immunoglobulin G and other constituents in colostrum.  

PubMed

The provision of quality colostrum with a high concentration of immunoglobulins is critical for newborn calf health. Because first colostrum may be low in overall concentration to effectively reduce the risk of newborn infections, we tested equivalent milking fractions of colostrum for possible IgG differences. The objective of this study was to determine if the fractional composition of colostrum changes during the course of milking with a focus on immunoglobulins. Twenty-four Holstein and Simmental cows were milked (first colostrum) within 4h after calving. The colostrum of 1 gland per animal was assembled into 4 percentage fractions over the course of milking: 0 to 25%, 25 to 50%, 50 to 75%, and 75 to 100%. The IgG concentration among the various fractions did not change in any significant pattern. Concentration of protein, casein, lactose and somatic cell count remained the same or exhibited only minor changes during the course of fractional milking colostrum. We determined that no benefit exists in feeding any particular fraction of colostrum to the newborn. PMID:23810595

Vetter, A; Argüello, A; Baumrucker, C; Bruckmaier, R M

2013-09-01

135

Short communication: Effect of milk and milk containing Lactobacillus casei on the intestinal microbiota of mice.  

PubMed

BALB/c mice were fed milk or Lactobacillus casei BL23 in milk for 14d and fecal samples were collected at d 0, 4, and 7 as well as 1 and 8d after the last administration. According to high-throughput DNA sequencing of the 16S rRNA genes extracted from the fecal microbiota, the bacterial diversity in the fecal samples of all mice increased over time. After 14d of administration, the consumption of milk and milk containing L. casei BL23 resulted in distinct effects on the microbial composition in the intestine. Specifically, the proportions of bacteria in the Lactobacillaceae, Porphyromonadaceae, and Comamonadaceae were significantly higher in mice fed the L. casei BL23-milk culture compared with one or more of the other groups of mice. The relative amounts of Lachnospiraceae were higher and Streptococcaceae were lower in mice fed milk alone. The changes were not found at d 4 and 7 during milk and L. casei feeding and were no longer detected 8d after administration was stopped. This study shows that consumption of milk or probiotic L. casei-containing milk results in non-overlapping, taxa-specific effects on the bacteria in the distal murine intestine. PMID:24508432

Yin, Xiaochen; Yan, Yinzhuo; Kim, Eun Bae; Lee, Bokyung; Marco, Maria L

2014-04-01

136

Short communication: new HIV infections at Southern New England academic institutions: implications for prevention.  

PubMed

New HIV infections among younger men who have sex with men (MSM) in the United States are escalating. Data on HIV infections in college students are limited. In 2010, three MSM college students presented to our clinic with primary HIV infection (PHI) in a single month. To determine the number of college students among new HIV diagnoses, we reviewed clinical characteristics and molecular epidemiology of HIV-diagnosed individuals from January to December 2010 at the largest HIV clinic in Southern New England. PHI was defined as acute HIV infection or seroconversion within the last 6 months. Of 66 individuals diagnosed with HIV in 2010, 62% were MSM and 17% were academic students (12% college or university, 5% other). Seventy-three percent of students were MSM. Compared to nonstudents, students were more likely to be younger (24 versus 39 years), born in the United States (91% versus 56%), have another sexually transmitted disease (45% versus 11%), and present with PHI (73% versus 16%, all p-values<0.05). Thirty percent of individuals formed eight transmission clusters including four students. MSM were more likely to be part of clusters. Department of Health contact tracing of cluster participants allowed further identification of epidemiological linkages. Given these high rates of PHI in recently diagnosed students, institutions of higher education should be aware of acute HIV presentation and the need for rapid diagnosis. Prevention strategies should focus on younger MSM, specifically college-age students who may be at increased risk of HIV infection. PMID:22724920

Chan, Philip A; Kazi, Shahzeb; Rana, Amaad; Blazar, Ilyse; Dejong, Colette C; Mayer, Kenneth H; Huard, Thomas K; Carleton, Kim; Gillani, Fizza; Alexander, Nicole; Parillo, Zoanne; Flanigan, Timothy P; Kantor, Rami

2013-01-01

137

Short communication: Occurrence of aflatoxin M1 in the Manchego cheese supply chain.  

PubMed

The importance of ewe milk lies in the production of high quality cheeses, such as Manchego cheese with a Protected Designation of Origin, whose safety must be guaranteed. In a 2-yr study, 407 bulk tank milk samples from farms and 82 silo milk and curd samples from cheese factories were collected from southeast Spain and tested for aflatoxin M1 (AFM1) using 2 commercial ELISA tests. Of these, 99.3% of the bulk tank samples had AFM1 levels below the European Union (EU) legal limit for milk (50 ng/kg), and well below the limit adopted by the Codex Alimentarius (500 ng/kg). Moreover, 98.8% of the silo milk and curd samples from cheese factories had AFM1 levels below the EU limit for milk. When considering median AFM1 concentrations, an average 4-fold increase was found in the final curd in relation to the corresponding silo milk. Control of AFM1 in Manchega ewe milk would enhance dairy product safety by the possible detection of faults in the manufacture of Manchego cheese. PMID:21605747

Rubio, R; Licón, C C; Berruga, M I; Molina, M P; Molina, A

2011-06-01

138

Short communication: Lymphoproliferative response to lipopolysaccharide and incidence of infections in periparturient dairy cows.  

PubMed

This preliminary study aimed at assessing whether the in vitro proliferation of peripheral blood mononuclear cells in response to lipopolysaccharide permits individual characterization of periparturient dairy cows, and whether this parameter may be associated with incidence of infections and with some of the single nucleotide polymorphisms located on the toll-like receptor 4 (TLR4) gene. Based on the average response of peripheral blood mononuclear cells to lipopolysaccharide over 7 time points during the transition period, 31 cows were categorized as low (LO), medium (MED), and high (HI) responders. This categorization identified 7 HI, 19 MED, and 5 LO cows, respectively. Genomic DNA was genotyped for P-226 C>G and E3+2021 C>T TLR4 single nucleotide polymorphisms. Monitoring of the health status revealed that 8 of the 31 cows suffered from clinical mastitis, metritis, or interdigital dermatitis during the first 60d in milk. The association study pointed out that none of the HI cows and all of the LO cows developed an infection; cows with the CCGT haplotype remained healthy and none of them belonged to the LO responder category. PMID:24054285

Catalani, Elisabetta; Amadori, Massimo; Vitali, Andrea; Lacetera, Nicola

2013-11-01

139

The Development and Validity Investigation of a Classroom Communication Apprehension Scale for Japanese High School Students.  

ERIC Educational Resources Information Center

The purpose of this study was to examine the construct validity of a classroom communication apprehension scale. Subjects were 196 high school students in Japan. The original English version of a classroom communication apprehension scale (M. R. Neer, 1987) consisted of 20 items representing 2 hypothesized dimensions of classroom communication

Anzai, Shinobu; Paik, Chie Matsuzawa

140

Short communication: renal tubular vacuolation in animals treated with polyethylene-glycol-conjugated proteins.  

PubMed

During toxicologic evaluation of a dimeric PEG-linked protein, tumor necrosis factor binding protein (TNF-bp), vacuolation of renal cortical tubular epithelium was seen in male and female Sprague-Dawley rats (200-300 g) given i.v. doses of 40, 20, or 10 mg/kg every other day for 3 months. Tubular lesions in rats treated with 20 or 40 mg/kg for 3 months were only partially reversible after a 2-month recovery period. Despite the presence of marked vacuolation, there were no changes in BUN, creatinine, urinalysis parameters, urinary NAG, urinary B2-microglobulin, or fractional sodium excretion. Single i.v. doses > or = 20 mg/kg TNF-bp caused similar but milder changes. However, equivalent doses of PEG alone or the non-PEG-linked TNF-bp did not cause light microscopic evidence of vacuolation. Treatment of rats with another PEG-linked protein of similar molecular weight resulted in similar changes. Immunostaining for TNF-bp revealed positivity in the apical cytoplasm of renal tubular epithelium within 1 h of i.v. dosing. Immunostaining of kidneys from chronically dosed rats indicated that protein was present in some vacuoles as long as dosing continued; however, kidneys from animals on a reversibility study had vacuoles but no immunostaining for TNF-bp. These results, along with a study that showed more severe lesions with PEG-linked proteins of lower molecular weight and minimal if any lesions with PEG-linked proteins > 70 kDa, suggest that TNF-bp is filtered through the glomerulus and that the protein with attached PEG is reabsorbed by the proximal tubules. Vacuolation may be a result of fluid distension of lysosomes due to the hygroscopic nature of PEG. These studies demonstrated that PEG-linked proteins have the capacity to induce renal tubular vacuolation at high doses. However, the change was not associated with alteration of clinical pathology or functional markers. PMID:9579027

Bendele, A; Seely, J; Richey, C; Sennello, G; Shopp, G

1998-04-01

141

Short communication: Prediction of intake in dairy cows under tropical conditions.  

PubMed

A meta-analysis was conducted to develop a model for predicting dry matter intake (DMI) in dairy cows under the tropical conditions of Brazil and to assess its adequacy compared with 5 currently available DMI prediction models: Agricultural and Food Research Council (AFRC); National Research Council (NRC); Cornell Net Carbohydrate and Protein System (CNCPS; version 6); and 2 other Brazilian models. The data set was created using 457 observations (n=1,655 cows) from 100 studies, and it was randomly divided into 2 subsets for statistical analysis. The first subset was used to develop a DMI prediction equation (60 studies; 309 treatment means) and the second subset was used to assess the adequacy of DMI predictive models (40 studies; 148 treatment means). The DMI prediction model proposed in the current study was developed using a nonlinear mixed model analysis after reparameterizing the NRC equation but including study as a random effect in the model. Body weight (mean=540±57.6kg), 4% fat-corrected milk (mean=21.3±7.7kg/d), and days in milk (mean=110±62d) were used as independent variables in the model. The adequacy of the DMI prediction models was evaluated based on coefficient of determination, mean square prediction error (MSPE), root MSPE (RMSPE), and concordance correlation coefficient (CCC). The observed DMI obtained from the data set used to evaluate the prediction models averaged 17.6±3.2kg/d. The following model was proposed: DMI (kg/d)=[0.4762 (±0.0358) × 4% fat-corrected milk + 0.07219 (±0.00605) × body weight(0.75)] × (1 - e(-0.03202 (±0.00615) × [days in milk + 24.9576 (±5.909)])). This model explained 93.0% of the variation in DMI, predicting it with the lowest mean bias (0.11kg/d) and RMSPE (4.9% of the observed DMI) and the highest precision [correlation coefficient estimate (?)=0.97] and accuracy [bias correction factor (Cb)=0.99]. The NRC model prediction equation explained 92.0% of the variation in DMI and had the second lowest mean bias (0.42kg/d) and RMSPE (5.8% of the observed DMI), as well as the second highest precision (?=0.94) and accuracy (Cb=0.98). The CNCPS and AFRC DMI prediction models explained 93.0 and 85.0% of the variation in DMI but underpredicted DMI by 1.8 and 1.4kg/d, respectively. These 2 models (CNCPS and AFRC) resulted, respectively, in RMSPE of 11.3 and 10.7% of the observed DMI, with moderate to high precision (?=0.81 and 0.82) and accuracy (Cb=0.84 and 0.89). The remaining 2 models resulted in the poorest results, underpredicting DMI by 2.3 and 1.9kg/d, with RMSPE of 22.8 and 14.9% of the observed DMI and moderate to low precision (?=0.49 and 0.76) and accuracy (Cb=0.81 and 0.86). The new model derived from the current meta-analytical approach provided the best accuracy and precision for predicting DMI in lactating dairy cows under Brazilian conditions. PMID:24731647

Souza, M C; Oliveira, A S; Araújo, C V; Brito, A F; Teixeira, R M A; Moares, E H B K; Moura, D C

2014-06-01

142

PM: An Operating System Coordinated High Performance Communication Library  

Microsoft Academic Search

. We have developed a new communication library, called PM,for the Myrinet gigabit LAN card, that has a dedicated processor andon-board memory to handle a communication protocol. In order to obtainhigh performance communication and support a multi-user environment,we have co-desgined PM, an operating system realized by adaemon process, and the run-time routine for a programming language.Several unique features, e.g., network

Hiroshi Tezuka; Atsushi Hori; Yutaka Ishikawa; Mitsuhisa Sato

1997-01-01

143

High-throughput measurement of gap junctional intercellular communication.  

PubMed

Gap junctional intercellular communication (GJIC) is a critical part of cellular activities and is necessary for electrical propagation among contacting cells. Disorders of gap junctions are a major cause for cardiac arrhythmias. Dye transfer through microinjection is a conventional technique for measuring GJIC. To overcome the limitations of manual microinjection and perform high-throughput GJIC measurement, here we present a new robotic microinjection system that is capable of injecting a large number of cells at a high speed. The highly automated system enables large-scale cell injection (thousands of cells vs. a few cells) without major operator training. GJIC of three cell lines of differing gap junction density, i.e., HeLa, HEK293, and HL-1, was evaluated. The effect of a GJIC inhibitor (18-?-glycyrrhetinic acid) was also quantified in the three cell lines. System operation speed, success rate, and cell viability rate were quantitatively evaluated based on robotic microinjection of over 4,000 cells. Injection speed was 22.7 cells per min, with 95% success for cell injection and >90% survival. Dye transfer cell counts and dye transfer distance correlated with the expected connexin expression of each cell type, and inhibition of dye transfer correlated with the concentration of GJIC inhibitor. Additionally, real-time monitoring of dye transfer enables the calculation of coefficients of molecular diffusion through gap junctions. This robotic microinjection dye transfer technique permits rapid assessment of gap junction function in confluent cell cultures. PMID:24778169

Liu, Jun; Siragam, Vinayakumar; Chen, Jun; Fridman, Michael D; Hamilton, Robert M; Sun, Yu

2014-06-15

144

High frequency sound attenuation in short flow ducts  

Microsoft Academic Search

A geometrical acoustics approach is proposed as a practical design tool for absorbent liners in such short flow ducts as may be found in turbofan engine nacelles. As an example, a detailed methodology is presented for three different types of sources in a parallel plate duct containing uniform ambient flow. A plane wave whose wavefronts are not normal to the

J. W. Posey

1978-01-01

145

High-speed magneto-optic switch for optical communication  

NASA Astrophysics Data System (ADS)

In this paper, an all fiber high-speed magneto-optic switch based on Faraday rotation in Bismuth-substituted Rare-earth Iron Garnet single crystal is proposed and investigated. It contains optical route, picosecond pulse generator and high-speed magnetic field structure. The optical route is designed with the function of switching the output optical signals in the networks. The biasing circuit for the magnetic field should be able to change the voltage rapidly in order to obtain fast operating time of the magneto-optic switch. Therefore, a kind of picosecond pulse generator based on the low-voltage avalanche characteristics of RF-BJT BFP450 is designed to drive a high-speed magnetic field. The experimental results indicate that the rise time of the output current pulse is only hundreds of picoseconds, which is satisfying for the high-speed magneto-optic switch. A current solenoid is used as high-speed magnetic field structure in this paper. It is noted that there is a time constant associated with the inductance of the current solenoid, which is an important factor determining the switching time. The switching time of the device also depends on the switching of the magnetic domains in the magneto-optic material. By controlling the magnetization of the magneto-optic material, the optical beam can be stably switched. The measured switching time of the device is only 134.2ns, so it can be widely used in the all-optical communication networks.

Ruan, Jianjian; Weng, Zihua; Lin, Shaohan

2009-11-01

146

Short Distance Wireless Communications  

Microsoft Academic Search

\\u000a Since the publication of the first biomedical swallowable telemetry device in 1957, an immense evolution has taken place in\\u000a biomedical monitoring, stimulation and instrumentation, that would have been impossible without the use of wireless information\\u000a transmission. The first section gives an overview of wireless methods for transmitting information to and from biomedical\\u000a implants, followed by a practical introduction on analog

Robert Puers; Jef Thoné

147

The Investigation of Teacher Communication Practices in Virtual High School  

ERIC Educational Resources Information Center

Virtual schooling is an increasing trend for secondary education. Research of the communication practices in virtual schools has provided a myriad of suggestions for virtual school policies. Although transactional distance has been investigated in relation to certain aspects of the communication process, a small-scale qualitative study has not…

Belair, Marley

2011-01-01

148

Toward High-Performance Communications Interfaces for Science Problem Solving  

NASA Astrophysics Data System (ADS)

From a theoretical viewpoint, educational interfaces that facilitate communicative actions involving representations central to a domain can maximize students' effort associated with constructing new schemas. In addition, interfaces that minimize working memory demands due to the interface per se, for example by mimicking existing non-digital work practice, can preserve students' attentional focus on their learning task. In this research, we asked the question: What type of interface input capabilities provide best support for science problem solving in both low- and high- performing students? High school students' ability to solve a diverse range of biology problems was compared over longitudinal sessions while they used: (1) hardcopy paper and pencil (2) a digital paper and pen interface (3) pen tablet interface, and (4) graphical tablet interface. Post-test evaluations revealed that time to solve problems, meta-cognitive control, solution correctness, and memory all were significantly enhanced when using the digital pen and paper interface, compared with tablet interfaces. The tangible pen and paper interface also was the only alternative that significantly facilitated skill acquisition in low-performing students. Paradoxically, all students nonetheless believed that the tablet interfaces provided best support for their performance, revealing a lack of self-awareness about how to use computational tools to best advantage. Implications are discussed for how pen interfaces can be optimized for future educational purposes, and for establishing technology fluency curricula to improve students' awareness of the impact of digital tools on their performance.

Oviatt, Sharon L.; Cohen, Adrienne O.

2010-12-01

149

High-energy x-ray source generation by short-pulse high-intensity lasers  

Microsoft Academic Search

We are studying the feasibility of utilizing Kalpha x-ray sources in the range of 20 to 100 keV as a backlighters for imaging various stages of implosions and high aerial density planar samples driven by the NIF laser facility. The hard x-ray Kalpha sources are created by relativistic electron plasma interactions in the target material after a radiation by short

Hye-Sook Park; Jeffrey A. Koch; Otto L. Landen; Thomas W. Phillips; Tim J. Goldsack; E. Clark; Richard Eagleton; Ray D. Edwards

2004-01-01

150

High Energy X-Ray Source Generation by Short Pulse High Intensity Lasers  

Microsoft Academic Search

We are studying the feasibility of utilizing K x-ray sources in the range of 20 to 100 keV as a backlighters for imaging various stages of implosions and high areal density planar samples driven by the NIF laser facility. The hard x-ray K sources are created by relativistic electron plasma interactions in the target material after a radiation by short

H-S Park; J A Koch; O L Landen; T W Phillips; T Goldsack; E Clark; R Eagleton; R Edwards

2003-01-01

151

Persuading Girls to Take Elective Physical Science Courses in High School: Who Are the Credible Communicators?  

ERIC Educational Resources Information Center

Identifies communicators whom eighth-grade girls perceive as credible regarding reasons for taking elective physical science courses in high school. Finds that father, woman science teacher, mother, and boy high school student are ranked highly. Attributes associated with the communicators were classified as prestige, trustworthiness, similarity,…

Koballa, Thomas R., Jr.

1988-01-01

152

High-speed quasi-balanced detection OFDM in visible light communication.  

PubMed

In this paper, we proposed and experimentally demonstrated a novel quasi-balanced detection (QBD) technique in orthogonal frequency division multiplexing (OFDM) visible light communication (VLC) system. By employing opposite signals to odd and even consecutive symbols, the nonlinearity distortion, and direct current can be eliminated efficiently. Additionally, the sensitivity of receiver can also be improved by 3dB, thus a longer transmission distance and high-order modulation formats can be received. We achieved physical data rate of 2.1-Gb/s enabled by wavelength-division-multiplexing (WDM), pre- and post-equalization, and the resulting bit error ratios (BERs) were below the FEC limit of 3.8x10(-3). The distance was above 2.5 meters that was long enough for indoor communication. Compared with conventional direct-detection optical (DDO-OFDM) and asymmetrically-clipped optical (ACO-OFDM), the BER can be enhanced by 22.2dB and 20.8dB, respectively, which shows great potential in short range and low cost access network. PMID:24514274

Wang, Yuanquan; Chi, Nan; Wang, Yiguang; Li, Rongling; Huang, Xingxing; Yang, Chao; Zhang, Ziran

2013-11-18

153

The effect of tobacco and alcohol and their reduction/cessation on mortality in oral cancer patients: short communication  

PubMed Central

Background The use of tobacco is known to increase the incidence of developing oral cancer by 6 times, while the additive effect of drinking alcohol further increases the risk leading to higher rate of morbidity and mortality. In this short communication, we prospectively assessed the effect of tobacco smoking and alcohol drinking in oral cancer patients on the overall mortality from the disease, as well as the effect of smoking and drinking reduction/cessation at time of diagnosis on mortality in the same group. Materials and methods A cohort, involved 67 male patients who were diagnosed with oral squamous cell carcinoma, was included in this study. The smoking and drinking habits of this group were recorded, in addition to reduction/cessation after diagnosis with the disease. Comparisons were made to disease mortality at 3 and 5 years. Results Follow-up resulted in a 3-year survival of 46.8% and a 5-year survival of 40.4%. Reduction of tobacco smoking and smoking cessation led to a significant reduction in mortality at 3 (P < 0.001) and 5 (P < 0.001) years. Reduction in drinking alcohol and drinking cessation led to a significant reduction in mortality at 3 (P < 0.001) and 5 (P < 0.001) years. Conclusion Chronic smoking and drinking does have an adverse effect on patients with oral cancer leading to increased mortality from cancer-related causes. Reduction/cessation of these habits tends to significantly reduce mortality in this group of patients. Smoking and drinking cessation counseling should be provided to all newly diagnosed oral cancer patients.

2012-01-01

154

Design of high sensitivity detector for underwater communication system  

NASA Astrophysics Data System (ADS)

Al0.52In0.48P is the largest bandgap material in III-V non-nitride semiconductors that is lattice matched to a readily available substrate (GaAs). Having a bandgap narrower than that of GaN enables it to detect wavelengths around 480 nm. Such wavelengths have the best transmittance underwater and may be used as a carrier in underwater communication systems. We present an Al0.52In0.48P homo-junction Separate-Absorption-Multiplication-Avalanche-Photodiode (SAMAPD) as a high sensitivity detector for such an application. By increasing the neutral and space-charge region thicknesses, the peak response wavelength can be tuned to longer wavelengths with a narrower full-width-half-maximum (FWHM). The quantum efficiency of the detector reduces with FWHM and this is compensated by having an avalanche gain. At room temperature, the SAM-APD has a dark current of <20 pA for a 210 ?m radius device up to 99.9% of breakdown voltage. The structure gives a narrow spectral FWHM of 22 nm with centre wavelength of 482 nm. An external quantum efficiency of 33% and 6410% at 482 nm is obtained at bias voltage of -19 V and -92.6 V respectively.

Cheong, J. S.; Ong, J. S. L.; Ng, J. S.; Krysa, A. B.; Bastiman, F.; David, J. P. R.

2013-11-01

155

Free space optical communications routing performance in highly dynamic airspace environments  

Microsoft Academic Search

Airborne networking environments utilizing high speed free space optical communications are being proposed as a method of providing immediate high speed network access and communications in a tactical environment where access is otherwise unavailable. Frequent link failures and recoveries due to wing obstruction and the dead zone produced by the wake vortex of the aircraft characterize the links. Many links

Bracha Epstein; Vineet Mehta

2004-01-01

156

Investigation of the Effect of Sport on Submissive Behavior and Communication Skills of High School Students  

ERIC Educational Resources Information Center

This study was carried out to detect the differences in submissive behaviors and communication skills of high school students in terms of sports activities and relationship between communication skills and properties of submissive behavior of high school students who are actively involved in sports activities. In this respect at the study, 728…

Abakay, Ugur

2013-01-01

157

High bandwidth specialty optical fibers for data communications  

NASA Astrophysics Data System (ADS)

Perhaps the most common specialty optical fiber is HCS hard polymer clad silica fiber. It was invented almost 30 years ago for transmitting laser light to initiate explosives in mining industry and later adapted to be used in a variety of new applications, such as data communications. The most typical HCS fiber typically consists of a 200 ?m pure silica glass core, a thin coating of low refractive index hard polymer as the cladding, and an ETFE buffer. This design enables the "crimp-and-cleave" technique of terminating and connectorizing fibers quickly and reliably. Its greater glass diameter also renders greater robustness allowing the fiber to endure greater forces during installation. Due to its larger core size and high numerical aperture (NA), the fiber can be used with a plastic connector and low cost LED transmitter that can greatly reduce the system cost. It can also be used at higher temperature and humidity conditions than standard optical fibers coated with telecommunications grade acrylate material. As applications evolve and require greater bandwidth and/or performance over a greater distance, the challenge now is to develop specialty optical fibers with significantly greater bandwidth-length product while maintaining all other characteristics critical to their ease of use and performance. As a response to the demand, two new fiber types have been designed and developed as higher bandwidth versions of the original HCS fiber. In this paper, we will discuss some of the main design requirements for the fibers, describe in detail the two designs, and present the results of fiber performance.

Li, Jie; Sun, Xiaoguang

2008-11-01

158

Design study for high performance optical communications satellite terminal with high power laser diode transmitter  

NASA Astrophysics Data System (ADS)

The present optical terminal design for a high data rate interorbit communications link with 500 Mbit/sec (or higher) transmission rate is based on high-power laser diode transmitters with 1 W peak power at 800 nm, in conjunction with a direct-detection receiver; two-channel wavelength-division multiplexing, together with the high transmission capability of the off-axis telescope used, contribute to the achievement of the requisite data rates. In order to minimize system mass, the only rotatable device is the telescope.

Hildebrand, U.; Seeliger, R.; Smutny, B.; Sand, R.

1991-05-01

159

Short and Long-Term Impacts of Biotechnology Education on Professionals Who Communicate Science to the Public  

ERIC Educational Resources Information Center

Consumer acceptance or rejection of biotechnology is often shaped by information prepared by communicators with varying levels of scientific knowledge, awareness, and acceptance. This study compared the prior, post-workshop, and sustained (1 year) biotechnology awareness, acceptance, and attitudes of professionals who communicate biotechnology to…

Fritz, Susan M.; Ward, Sarah M.; Byrne, Pat F.; Namuth, Deana M.; Egger, Valerie A.

2004-01-01

160

Spall due to short high-intensity impulses  

SciTech Connect

Spallation thresholds for (3)/(16) -- (3)/(8) -in. 6061-T6, 5456, and 1100 aluminum and 6A14V titanium alloys were determined for impulses from 5 to 30 ktap with a pulse duration of 0.15 ..mu..s. These experiments show that for aluminum alloys the spall fracture stress is nearly a constant but varies between 16 and 20 kbar in different batches of material and shows suggestion of a weak dependence on strain rate with strain rates from 0.04 to 0.4 ..mu..s/sup -1/. The impulse threshold for spall was 7.5 ktap. For 6A14V titanium the spall fracture stress was 60 kbar and the impulse threshold was 15 ktap. The stress pulses were produced by impacting target samples with a 0.012-in. (0.305 mm) thick by 3-in. (76 mm) square Kapton impactor projectile at velocities ranging from 0.13 to 0.44 cm/..mu..s. Data obtained include detailed records of the impactor and rear (spalled) surface velocity versus time measured with a dual-beam Fabry--Perot interferometer, as well as soft recovery of the target residual and spall fragments. From these we are able to determine the partitioning of impulse between the target residual and the spall fragment(s) and the critical spall fracture stress and strain rate. We have also made microphotographic inspections and measured the stress-strain properties of recovered target. The data show that the amount of impulse (momentum per unit area) absorbed by a structural wall by a short duration pulse is limited by the spall threshold. Increases in applied impulse above this spall threshold result in higher spall fragment velocities but no apparent increase in the impulse delivered to the residual structure. Spall is thus an effective damage limiting mechanism which must be considered when estimating the effectiveness of systems whose primary damage is structural collapse due to impulse generated by short duration pulses.

Froeschner, K.E.; Maiden, D.E.; Chau, H.H.

1989-04-15

161

High-power CW quantum cascade lasers: How short can we go?  

Microsoft Academic Search

Limiting factors for short-wavelength CW QCL designs are discussed. A model is used to predict the short-wavelength cutoff for strain-balanced QCL structures. High performance is predicted at wavelengths as short as 3.0 micron based on a conduction band offset of 0.9 eV in the GaInAs\\/AlInAs materials. Recent work is presented on the growth of strained materials using gas-source molecular beam

Manijeh Razeghi; Allan Evans; Steven Slivken; Jae-Su Yu

2005-01-01

162

Ultra high frequency follow-on communications satellite system  

NASA Astrophysics Data System (ADS)

The existing constellation of UHF communications satellites (LEASAT and FLTSAT) provide key command and control links for mobile forces of the DoD and other government agencies. The UHF Follow-On satellite program will provide for a new generation of communications satellites to replace the existing ones as they reach the end of their life cycle beginning in 1992. Continued coverage is required for both peacetime and crisis environments, and must be maintained indefinitely. An eight-satellite UFO constellation (two per coverage area) will replenish the existing FLTSATCOM constellation.

Hassien, Michael J.

1992-03-01

163

Model of Atmospheric Links on Optical Communications from High Altitude  

NASA Technical Reports Server (NTRS)

Optical communication links have the potential to solve many of the problems of current radio and microwave links to satellites and high-altitude aircraft. The higher frequency involved in optical systems allows for significantly greater signal bandwidth, and thus information transfer rate, in excess of 10 Gbps, and the highly directional nature of laser-based signals eliminates the need for frequency-division multiplexing seen in radio and microwave links today. The atmosphere, however, distorts an optical signal differently than a microwave signal. While the ionosphere is one of the most significant sources of noise and distortion in a microwave or radio signal, the lower atmosphere affects an optical signal more significantly. Refractive index fluctuations, primarily caused by changes in atmospheric temperature and density, distort the incoming signal in both deterministic and nondeterministic ways. Additionally, suspended particles, such as those in haze or rain, further corrupt the transmitted signal. To model many of the atmospheric effects on the propagating beam, we use simulations based on the beam-propagation method. This method, developed both for simulation of signals in waveguides and propagation in atmospheric turbulence, separates the propagation into a diffraction and refraction problem. The diffraction step is an exact solution, within the limits of numerical precision, to the problem of propagation in free space, and the refraction step models the refractive index variances over a segment of the propagation path. By applying refraction for a segment of the propagation path, then diffracting over that same segment, this method forms a good approximation to true propagation through the atmospheric medium. Iterating over small segments of the total propagation path gives a good approximation to the problem of propagation over the entire path. Parameters in this model, such as initial beam profile and atmospheric constants, are easily modified in a simulation such as this, which allows for the rapid analysis of different propagation scenarios. Therefore, this method allows the development of a near-optimal system design for a wide range of situations, typical of what would be seen in different atmospheric conditions over a receiving ground station. A simulation framework based upon this model was developed in FORTRAN, and for moderate grid sizes and propagation distances these simulations are computable in reasonable time on a standard workstation. This presentation will discuss results thus far.

Subich, Christopher

2004-01-01

164

LOTTERYBUS: a new high-performance communication architecture for system-on-chip designs  

Microsoft Academic Search

This paper presents Lotterybus, a novel high-performance communication architecture for system-on-chip (SoC) designs. The Lotterybus architecture was designed to address the following limitations of current communication architectures: (i) lack of control over the allocation of communication bandwidth to different system components or data flows (e.g., in static priority based shared buses), leading to starvation of lower priority components in some

Kanishka Lahiri; Anand Raghunathan; Ganesh Lakshminarayana

2001-01-01

165

High-Level Data Communication Optimization For Reconfigurable Systems  

Microsoft Academic Search

This paper describes methods for synthesizing the internal representation of a compiler into a hardware description language in order to program reconfigurable hardware devices. We demonstrate the usefulness of static single assignment (SSA) in reducing the amount of data communication in the hardware. However, the placement of ? -nodes by current SSA algorithms is not optimal in terms of minimizing

Adam Kaplan; Majid Sarrafzadeh; Ryan Kastner

166

High bandwidth specialty optical fibers for data communications  

Microsoft Academic Search

Perhaps the most common specialty optical fiber is HCS hard polymer clad silica fiber. It was invented almost 30 years ago for transmitting laser light to initiate explosives in mining industry and later adapted to be used in a variety of new applications, such as data communications. The most typical HCS fiber typically consists of a 200 mum pure silica

Jie Li; Xiaoguang Sun

2008-01-01

167

An Investigation of Communication in Virtual High Schools  

ERIC Educational Resources Information Center

Virtual schooling is an increasing trend for secondary education. Research of the communication practices in virtual schools has provided a myriad of suggestions for virtual school policies. The purpose of this qualitative study was to investigate the activities and processes involved in the daily rituals of virtual school teachers and learners…

Belair, Marley

2012-01-01

168

Toward High-Performance Communications Interfaces for Science Problem Solving  

ERIC Educational Resources Information Center

From a theoretical viewpoint, educational interfaces that facilitate communicative actions involving representations central to a domain can maximize students' effort associated with constructing new schemas. In addition, interfaces that minimize working memory demands due to the interface per se, for example by mimicking existing non-digital work…

Oviatt, Sharon L.; Cohen, Adrienne O.

2010-01-01

169

Integrating Multiple Communication Paradigms in High Performance Multiprocessors  

Microsoft Academic Search

In the design of FLASH, the successor to the Stanford DASH multiprocessor, we are exploring architectural mechanisms for efficiently supporting both the shared memory and message passing communication models in a single system. The unique feature in the FLASH (FLexible Architecture for SHared memory) system is the use of a programmablecontroller at each node that replaces the functionality of hardwired

John Heinlein; Kourosh Gharachorloo; Anoop Gupta

1994-01-01

170

High Performance Communication and Navigation Systems for Interplanetary Networks  

Microsoft Academic Search

The increasing development of technologies enabling efficient space exploration and data communications has recently fostered a number of scientific missions, aimed at supporting the research in the field of geology and astronomy. To this end, the design of an effective telecommunication infrastructure is the challenge offered to research scientists and space engineers. In particular, the definition of a network architecture

Tomaso de Cola; Mario Marchese

2008-01-01

171

High-Tech PR: Five Case Studies in Computerized Communication.  

ERIC Educational Resources Information Center

Use of computer technology for specialized communication networks at University of California (Oakland), Lafayette College (Pennsylvania), Carnegie Mellon University (Pennsylvania), the University of Wisconsin at Eau Claire, and the State University of New York at Stony Brook is described. The systems feature different forms of internal and…

Malaspina, Rick; And Others

1993-01-01

172

Building reliable, high-performance communication systems from components  

Microsoft Academic Search

Although building systems from components has attractions, this approach also has problems. Can we be sure that a certain configuration of components is correct? Can it perform as well as a monolithic system? Our paper answers these questions for the Ensemble communication architecture by showing how, with help of the Nuprl formal system, configurations may be checked against specifications, and

Xiaoming Liu; Christoph Kreitz; Robbert van Renesse; Jason Hickey; Mark Hayden; Kenneth P. Birman; Robert L. Constable

1999-01-01

173

Highly Efficient Amplifier for Ka-Band Communications  

NASA Technical Reports Server (NTRS)

An amplifier developed under a Small Business Innovation Research (SBIR) contract will have applications for both satellite and terrestrial communications. This power amplifier uses an innovative series bias arrangement of active devices to achieve over 40-percent efficiency at Ka-band frequencies with an output power of 0.66 W. The amplifier is fabricated on a 2.0- by 3.8-square millimeter chip through the use of Monolithic Microwave Integrated Circuit (MMIC) technology, and it uses state-of-the-art, Pseudomorphic High-Electron-Mobility Transistor (PHEMT) devices. Although the performance of the MMIC chip depends on these high-performance devices, the real innovations here are a unique series bias scheme, which results in a high-voltage chip supply, and careful design of the on-chip planar output stage combiner. This design concept has ramifications beyond the chip itself because it opens up the possibility of operation directly from a satellite power bus (usually 28 V) without a dc-dc converter. This will dramatically increase the overall system efficiency. Conventional microwave power amplifier designs utilize many devices all connected in parallel from the bias supply. This results in a low-bias voltage, typically 5 V, and a high bias current. With this configuration, substantial I(sup 2) R losses (current squared times resistance) may arise in the system bias-distribution network. By placing the devices in a series bias configuration, the total current is reduced, leading to reduced distribution losses. Careful design of the on-chip planar output stage power combiner is also important in minimizing losses. Using these concepts, a two-stage amplifier was designed for operation at 33 GHz and fabricated in a standard MMIC foundry process with 0.20-m PHEMT devices. Using a 20-V bias supply, the amplifier achieved efficiencies of over 40 percent with an output power of 0.66 W and a 16-dB gain over a 2-GHz bandwidth centered at 33 GHz. With a 28-V bias, a power level of 1.1 W was achieved with a 12-dB gain and a 36-percent efficiency. This represents the best reported combination of power and efficiency at this frequency. In addition to delivering excellent power and gain, this Ka-band MMIC power amplifier has an efficiency that is 10 percent greater than existing designs. The unique design offers an excellent match for spacecraft applications since the amplifier supply voltage is closely matched to the typical value of spacecraft bus voltage. These amplifiers may be used alone in applications of 1 W or less, or several may be combined or used in an array to produce moderate power, Ka-band transmitters with minimal power combining and less thermal stress owing to the combination of excellent efficiency and power output. The higher voltage operation of this design may also save mass and power because the dc-dc power converter is replaced with a simpler voltage regulator.

1996-01-01

174

Short Note: High Throughput Microsatellite Genotyping in Oak Species  

Microsoft Academic Search

Microsatellites are widely used markers for multiple purposes in oaks. We describe a complete procedure for cheap DNA extraction and fast microsatellites genotyp- ing by multiplex PCR. 10 loci were selected to form two multiplex kits including three loci that show a high dif- ferentiation between Quercus robur and Q. petraea. The loci were tested in three oak species and

V. LÉGER; S. GERBER

2006-01-01

175

Short communication: fasting increases serum concentrations of bilirubin in patients receiving atazanavir: results from a pilot study.  

PubMed

Unconjugated hyperbilirubinemia resulting from therapy with atazanavir is physiologically related to hyperbilirubinemia in Gilbert's syndrome (GS). In patients with GS, changes in diet have a significant impact on bilirubinemia. Our aim was to investigate whether changes in diet affect the level of serum bilirubin in patients receiving atazanavir. Thirty patients on stable therapy with ritonavir-boosted atazanavir without evidence of GS were enrolled. Hemolysis and chronic hepatitis were excluded. After a baseline period of normal intake of calories, the patients were randomized to follow a 24-h 400-calorie diet (fasting), then a 48-h period of normal calorie intake and, afterward, a 24-h period of a high-calorie diet, or the same interventions in inverse order. Serum bilirubin concentrations were measured before and after each intervention. A high adherence to the recommended diet was observed. The mean unconjugated bilirubin concentration before the high-calorie diet was 2.79±1.53 mg/dl and after such intervention it was 2.70±1.40 mg/dl. The mean difference between preintervention and postintervention was -0.08±0.69 mg/dl (p=NS). The mean unconjugated bilirubin concentration before the fasting diet was 2.31±1.23 mg/dl and it was 3.84±1.90 mg/dl after. The mean difference between prefasting and postfasting was 1.53±1.17 mg/dl (p=0.001). According to these results, short periods of fasting seem to increase the unconjugated bilirubin concentration in patients on atazanavir. A high-calorie diet did not have any impact in bilirubin probably because most patients follow similar diets in their everyday life. PMID:23113663

Lopardo, Gustavo; Bissio, Emiliano; Espinola, Lidia; Gallego, Paula; Stambullian, Marcela; Gadano, Adrián

2013-03-01

176

Short Communication: Fasting Increases Serum Concentrations of Bilirubin in Patients Receiving Atazanavir: Results from a Pilot Study  

PubMed Central

Abstract Unconjugated hyperbilirubinemia resulting from therapy with atazanavir is physiologically related to hyperbilirubinemia in Gilbert's syndrome (GS). In patients with GS, changes in diet have a significant impact on bilirubinemia. Our aim was to investigate whether changes in diet affect the level of serum bilirubin in patients receiving atazanavir. Thirty patients on stable therapy with ritonavir-boosted atazanavir without evidence of GS were enrolled. Hemolysis and chronic hepatitis were excluded. After a baseline period of normal intake of calories, the patients were randomized to follow a 24-h 400-calorie diet (fasting), then a 48-h period of normal calorie intake and, afterward, a 24-h period of a high-calorie diet, or the same interventions in inverse order. Serum bilirubin concentrations were measured before and after each intervention. A high adherence to the recommended diet was observed. The mean unconjugated bilirubin concentration before the high-calorie diet was 2.79±1.53?mg/dl and after such intervention it was 2.70±1.40?mg/dl. The mean difference between preintervention and postintervention was ?0.08±0.69?mg/dl (p=NS). The mean unconjugated bilirubin concentration before the fasting diet was 2.31±1.23?mg/dl and it was 3.84±1.90?mg/dl after. The mean difference between prefasting and postfasting was 1.53±1.17?mg/dl (p=0.001). According to these results, short periods of fasting seem to increase the unconjugated bilirubin concentration in patients on atazanavir. A high-calorie diet did not have any impact in bilirubin probably because most patients follow similar diets in their everyday life.

Bissio, Emiliano; Espinola, Lidia; Gallego, Paula; Stambullian, Marcela; Gadano, Adrian

2013-01-01

177

Computer Mediated Communication: Providing Pastoral Care to Youth in “A High Tech” World  

Microsoft Academic Search

This study used a hermeneutical methodology to explore how Computer Mediated Communication (CMC) can be used to provide pastoral care to youth in a high tech world. The research was motivated by the writers desire to find ways to be in communication with youth and provide pastoral care to them during their adolescent years. The thesis will explore computer mediated

Tanya L. Ramer

2008-01-01

178

Using Mobile Communication Technology in High School Education: Motivation, Pressure, and Learning Performance  

ERIC Educational Resources Information Center

Motivation and pressure are considered two factors impacting vocational senior high school student learning. New communication technology, especially mobile communication technology, is supposed to be effective in encouraging interaction between the student and the instructor and improving learning efficiency. Social presence and information…

Rau, Pei-Luen Patrick; Gao, Qin; Wu, Li-Mei

2008-01-01

179

LiMIC: Support for High-Performance MPI Intra-node Communication on Linux Cluster  

Microsoft Academic Search

High performance intra-node communication support for MPI applications is critical for achieving best perfor- mance from clusters of SMP workstations. Present day MPI stacks cannot make use of operating system kernel support for intra-node communication. This is primarily due to the lack of an efficient, portable, stable and MPI friendly inter- face to access the kernel functions. In this paper

Hyun-wook Jin; Sayantan Sur; Lei Chai; Dhabaleswar K. Panda

2005-01-01

180

High-bit-rate chaotic optical communication system using semiconductor lasers with optoelectronic feedback  

Microsoft Academic Search

A high-speed chaotic optical communication system using semiconductor lasers with optoelectronic feedback is investigated both experimentally and numerically. The nonlinear dynamics, synchronization, and communication property of the system are investigated, respectively. The lasers are found to generate different states including periodic pulsing, quasiperiodic pulsing, and chaotic pulsing with the variation in operating conditions. The system follows a quasiperiodic scenario to

Shuo Tang

2003-01-01

181

Quantum secure direct communication with high-dimension quantum superdense coding  

SciTech Connect

A protocol for quantum secure direct communication with quantum superdense coding is proposed. It combines the ideas of block transmission, the ping-pong quantum secure direct communication protocol, and quantum superdense coding. It has the advantage of being secure and of high source capacity.

Wang Chuan; Li Yansong; Liu Xiaoshu [Key Laboratory for Quantum Information and Measurements, and Department of Physics, Tsinghua University, Beijing 100084 (China); Deng Fuguo [Key Laboratory for Quantum Information and Measurements, and Department of Physics, Tsinghua University, Beijing 100084 (China); Key Laboratory of Beam Technology and Materials Modification of Ministry of Education, and Institute of Low Energy Nuclear Physics, Beijing Normal University, Beijing 100875 (China); Long Guilu [Key Laboratory for Quantum Information and Measurements, and Department of Physics, Tsinghua University, Beijing 100084 (China); Key Laboratory for Atomic and Molecular NanoSciences, Tsinghua University, Beijing 100084 (China)

2005-04-01

182

Short-pulse, high-intensity lasers at Los Alamos  

SciTech Connect

Advances in ultrafast lasers and optical amplifiers have spurred the development of terawatt-class laser systems capable of delivering focal spot intensities approaching 10{sup 20} W/cm{sup 2}. At these extremely high intensities, the optical field strength is more than twenty times larger than the Bohr electric field, permitting investigations of the optical properties of matter in a previously unexplored regime. The authors describe two laser systems for high intensity laser interaction experiments: The first is a terawatt system based on amplification of femtosecond pulses in XeCl which yields 250 mJ in 275 fs and routinely produces intensifies on target in excess of 10{sup 18} W/cm{sup 2}. The second system is based on chirped pulse amplification of 100-fs pulses in Ti:sapphire.

Taylor, A.J.; Roberts, J.P.; Rodriguez, G.; Fulton, R.D.; Kyrala, G.A.; Schappert, G.T.

1994-03-01

183

Short communication: Strengthening sub-national communicable disease surveillance in a remote Pacific Island country by adapting a successful African outbreak surveillance model.  

PubMed

Successful communicable disease surveillance depends on effective bidirectional information flow between clinicians at the periphery and communicable disease control units at regional, national and global levels. Resource-poor countries often struggle to establish and maintain the crucial link with the periphery. A simple syndrome-based outbreak surveillance system initially developed and evaluated in Mpumalanga Province, South Africa was adapted for the Pacific island nation of Tuvalu. Eight syndromes were identified for surveillance: acute flaccid paralysis (poliomyelitis), profuse watery diarrhoea (cholera), diarrhoea outbreak, dysentery outbreak, febrile disease with abdominal symptoms and headache (typhoid), febrile disease with generalized non-blistering rash (measles), febrile disease with intense headache and/or neck stiffness with or without haemorrhagic rash (meningococcal meningitis), and outbreaks of other febrile diseases of unknown origin. A user-oriented manual, the Tuvalu Outbreak Manual (http://www.wepi.org/books/tom/), was developed to support introduction of the surveillance system. Nurses working in seven outer island clinics and the hospital outpatient department on the main island rapidly report suspected outbreaks and submit weekly zero-reports to the central communicable disease control unit. An evaluation of the system after 12 months indicated that the Outbreak Manual was regarded as very useful by clinic nurses, and there was early evidence of improved surveillance and response to the disease syndromes under surveillance. PMID:16398751

Nelesone, Tekaai; Durrheim, David N; Speare, Richard; Kiedrzynski, Tom; Melrose, Wayne D

2006-01-01

184

Short Range Correlations, High-Momentum Components of Nuclei, and the EMC Effect; New Theoretical Insights  

NASA Astrophysics Data System (ADS)

Recent progress in studies of short-range correlations sheds new light on the host of nuclear phenomena ranging from hadronic modifications, quark-hadron transitions to the equation of state of superdense nuclear matter. We will first discuss the theoretical approaches in probing nuclear structure at short distances and high local densities. Then the question on how the nuclear interactions at short distances are related to the modification of the properties of bound nucleons will be addressed. The theoretical description of the recent observation of the relation between probabilities of 2N short range correlations and EMC effects will be presented. In the last part of the talk we will discuss the implications of the recent progress in studies of isospin structure of short-range correlations on the properties of the equation of state of high density asymmetric nuclear matter.

Sargsian, Misak

2011-04-01

185

High-performance multiqueue buffers for VLSI communication switches  

Microsoft Academic Search

A type of buffer called a dynamically allocated multiqueue (DAMQ) buffer, designed for use in n×n switches, is presented. This buffer provides efficient handling of variable-length packets and the forwarding of packets in non-FIFO (first-in-first-out) order. The microarchitecture of the DAMQ buffer and its controller is described in the context of the ComCoBB communication coprocessor for multicomputers. The DAMQ buffer

Y. Tamir; Gregory L. Frazier

1988-01-01

186

Intercellular Communication Amplifies Stressful Effects in High-Charge, High-Energy (HZE) Particle-Irradiated Human Cells  

PubMed Central

Understanding the mechanisms that underlay the biological effects of particulate radiations is essential for space exploration and for radiotherapy. Here, we investigated the role of gap junction intercellular communication (GJIC) in modulating harmful effects induced in confluent cultures wherein most cells are traversed by one or more radiation tracks. We focused on the effect of radiation quality (linear energy transfer; LET) on junctional propagation of DNA damage and cell death among the irradiated cells. Confluent normal human fibroblasts were exposed to graded doses of 1 GeV protons (LET ~0.2 keV/?m) or 1 GeV/u iron ions (LET ~151 keV/?m) and were assayed for clonogenic survival and for micronucleus formation, a reflection of DNA damage, shortly after irradiation and following longer incubation periods. Iron ions were ~2.7 fold more effective than protons at killing 90% of the cells in the exposed cultures when assayed within 5–10 minutes after irradiation. When cells were held in the confluent state for several hours after irradiation, substantial repair of potentially lethal damage (PLDR), coupled with a reduction in micronucleus formation, occurred in cells exposed to protons, but not in those exposed to iron ions. In fact, such confluent holding after exposure to a similarly toxic dose of iron ions enhanced the induced toxic effect. However, following iron ion irradiation, inhibition of GJIC by 18-?-glycyrrhetinic acid eliminated the enhanced toxicity and reduced micronucleus formation to levels below those detected in cells assayed shortly after irradiation. The data show that low LET radiation induces strong PLDR within hours, but that high LET radiation with similar immediate toxicity does not induce PLDR and its toxicity increases with time following irradiation. The results also show that GJIC among irradiated cells amplifies stressful effects following exposure to high, but not LET radiation, and that GJIC has only minimal effect on cellular recovery following low LET irradiation.

AUTSAVAPROMPORN, Narongchai; DE TOLEDO, Sonia M.; BUONANNO, Manuela; JAY-GERIN, Jean-Paul; HARRIS, Andrew L.; AZZAM, Edouard I.

2014-01-01

187

High Bandwidth Short Stroke Rotary Fast Tool Servo  

SciTech Connect

This paper presents the design and performance of a new rotary fast tool servo (FTS) capable of developing the 40 g's tool tip acceleration required to follow a 5 micron PV sinusoidal surface at 2 kHz with a planned accuracy of 50 nm, and having a full stroke of 50 micron PV at lower frequencies. Tests with de-rated power supplies have demonstrated a closed-loop unity-gain bandwidth of 2 kHz with 20 g's tool acceleration, and we expect to achieve 40 g's with supplies providing {+-} 16 Amp to the Lorentz force actuator. The use of a fast tool servo with a diamond turning machine for producing non-axisymmetric or textured surfaces on a workpiece is well known. Our new rotary FTS was designed to specifically accommodate fabricating prescription textured surfaces on 5 mm diameter spherical target components for High Energy Density Physics experiments on the National Ignition Facility Laser (NIF).

Montesanti, R C; Trumper, D L

2003-08-22

188

A low-complexity and high performance concatenated coding scheme for high-speed satellite communications  

NASA Technical Reports Server (NTRS)

This report presents a low-complexity and high performance concatenated coding scheme for high-speed satellite communications. In this proposed scheme, the NASA Standard Reed-Solomon (RS) code over GF(2(exp 8) is used as the outer code and the second-order Reed-Muller (RM) code of Hamming distance 8 is used as the inner code. The RM inner code has a very simple trellis structure and is decoded with the soft-decision Viterbi decoding algorithm. It is shown that the proposed concatenated coding scheme achieves an error performance which is comparable to that of the NASA TDRS concatenated coding scheme in which the NASA Standard rate-1/2 convolutional code of constraint length 7 and d sub free = 10 is used as the inner code. However, the proposed RM inner code has much smaller decoding complexity, less decoding delay, and much higher decoding speed. Consequently, the proposed concatenated coding scheme is suitable for reliable high-speed satellite communications, and it may be considered as an alternate coding scheme for the NASA TDRS system.

Lin, Shu; Rhee, Dojun; Rajpal, Sandeep

1993-01-01

189

Key Devices for High-Speed Optical Communication and Their Application to Transceiver Module  

NASA Astrophysics Data System (ADS)

High-speed semiconductor device technologies and optical device technologies are shown in this section. The integration technologies of these devices and their packaging technologies are also important to utilize them in communication equipments.

Matsuura, Hiroyuki

190

Electronic Components for High Speed Signal Processing in Fiber Optical Communication.  

National Technical Information Service (NTIS)

Progress in the development of electronic components for high speed signal processing in fiber optical communication is reported. For the transmitter, a transistor power stage (200 mA output current, 1 nsec ri time), step recovery diode amplifier (voltage...

P. Russer

1977-01-01

191

Simplified processing for high spectral efficiency wireless communication employing multi-element arrays  

Microsoft Academic Search

We investigate robust wireless communication in high-scattering propagation environments using multi-element antenna arrays (MEAs) at both transmit and receive sites. A simplified, but highly spectrally efficient space-time communication processing method is presented. The user's bit stream is mapped to a vector of independently modulated equal bit-rate signal components that are simultaneously transmitted in the same band. A detection algorithm similar

Gerard J. Foschini; Glen D. Golden; Reinaldo A. Valenzuela; Peter W. Wolniansky

1999-01-01

192

Analysis of SCTP and TCP based communication in high-speed clusters  

Microsoft Academic Search

Performance and financial constraints are pushing modern DAQs (Data Acquisition Systems) to use distributed cluster environments instead of monolith one-box systems. Inside clusters application communication layers should support outstanding high performance requirements. We are currently investigating different network protocols that could meet the requirements of high speed\\/low latency peer-to-peer communication within DAQ clusters. We have carried out various performance measurements

M. Kozlovszky; T. Berceli; L. Kutor

2006-01-01

193

Establishing wireless communications services via high-altitude aeronautical platforms: a concept whose time has come?  

Microsoft Academic Search

The focus of this article is high altitude aeronautical platforms (HAAPs) such as airships, planes, helicopters, or some hybrid salutions which could operate at stratospheric altitudes for significant periods of time, be low-cost, and be capable of carrying sizable, multipurpose communications payloads. Of particular interest are ways to implement cellular\\/PCS or high-speed data networks in airborne platforms. From a communications

Goran M. Djuknic; John Freidenfelds; Y. Okunev

1997-01-01

194

A Short Communication Course for Physicians Improves the Quality of Patient Information in a Clinical Trial | accrualnet.cancer.gov  

Cancer.gov

This article addresses the question of how to improve the informed consent process. The investigators tested a one-day communications course for physicians and research nurses that included lecture and role-play approaches for its ability to improve the quality of informed consent and the satisfaction of patients who enrolled in a randomized clinical trial of adjuvant treatment for breast cancer.

195

Framework and Research Methodology of Short-Timescale Pulsed Power Phenomena in High-Voltage and High-Power Converters  

Microsoft Academic Search

Various short-timescale transients exist in power electronic converters, particularly in high-voltage and high-power systems. The timescales of these transients are from nanoseconds to microseconds, including a switching transition of power semiconductor devices, commutating processes, and drive signal transmissions. These transient processes directly affect the performance and reliability of power electronic systems. Therefore, it is necessary to study these short-timescale processes.

Hua Bai; Zhengming Zhao; Chris Mi

2009-01-01

196

Communication architecture tuners: a methodology for the design of high-performance communication architectures for systems-on-chips  

Microsoft Academic Search

In this chapter, we present a general methodology for the design of custom system-on-chip communication architectures. Our technique is based on the addition of a layer of circuitry, called the Communication Architecture Tuner (CAT), around any existing communication architecture topology. The added layer enhances the ability of the system to adapt to changing communication needs of its constituent components. For

Kanishka Lahiri; Anand Raghunathan; Ganesh Lakshminarayana; Sujit Dey

2000-01-01

197

The impact of high fidelity human simulation on self-efficacy of communication skills.  

PubMed

Communication is a critical component of nursing education as well as a necessity in maintaining patient safety. Psychiatric nursing is a specialty that emphasizes utilization of communication skills to develop therapeutic relationships. Nursing students are frequently concerned and anxious about entering the mental health setting for their first clinical placement. High fidelity human simulation (HFHS) is one method that can be used to allow students to practice and become proficient with communication skills. The purpose of this study was to compare the effectiveness of two educational delivery methods, traditional lecture and HFHS, on senior level nursing student's self-efficacy with respect to communicating with patients experiencing mental illness. The results of this study support the use of HFHS to assist in enhancing undergraduate students' self-efficacy in communicating with patients who are experiencing mental illness. PMID:20394477

Kameg, Kirstyn; Howard, Valerie M; Clochesy, John; Mitchell, Ann M; Suresky, Jane M

2010-05-01

198

Generation of high-energy (>15 MeV) neutrons using short pulse high intensity lasers  

NASA Astrophysics Data System (ADS)

A roadmap is suggested and demonstrated experimentally for the production of high-energy (>15 MeV) neutrons using short pulse lasers. Investigation with a 3D Monte Carlo model has been employed to quantify the production of energetic neutrons. Numerical simulations have been performed for three nuclear reactions, d(d,n)3He, 7Li(d,n)8Be, and 7Li(p,n)7Be, driven by monoenergetic ion beams. Quantitative estimates for the driver ion beam energy and number have been made and the neutron spectra and yield in the ion propagation direction have been evaluated for various incident ion energies. In order to generate neutron fluence above a detection limit of 106 neutrons/sr, either ~1010 protons with energy 20-30 MeV or comparable amount of deuterons with energy 5-10 MeV are required. Experimental verification of the concept with deuterons driven by the Titan laser (peak intensity 2 × 1019 W/cm2, pulse duration of 9 ps, wavelength 1.05 ?m, and energy of 360 J) is provided with the generation of neutrons with energy of up to 18 MeV from 7Li(d,n)8Be reactions. Future research will focus on optimized schemes for ion acceleration for production of high-energy neutrons, which will involve efficient target design, laser parameter optimization, and converter material.

Petrov, G. M.; Higginson, D. P.; Davis, J.; Petrova, Tz. B.; McNaney, J. M.; McGuffey, C.; Qiao, B.; Beg, F. N.

2012-09-01

199

High Capacity Communications From Martian Distances. Part 1; Spacecraft Link Design Analysis  

NASA Technical Reports Server (NTRS)

High capacity space communications has been a desire for Human Exploration and Science missions. Current Mars missions operate at data rates of 120 kbps for telemetry downlink and it is desirable to study high rate communication links in the range of 100 Mbps to 1 Gbps data rates from Martian distances. This paper will present some assumed scenarios along with link design assumptions and link analysis for high capacity communications from Mars. The paper will focus on RF subsystems namely antenna and power for the downlink communication from a relay orbiter at Mars. The relay orbiter will communicate with the low orbit spacecrafts at Mars or any Martian surface elements such as robots, and relay the data back to the ground networks on Earth. The study will dive into the spacecraft downlink system design and communication link analysis between the relay orbiter and ground network on Earth for data rates ranging from 100 Mbps to 1 Gbps based on the assumed scenarios and link assumptions. With high rate links at larger distances, there will be a significant impact on the antenna and power requirements and the link design will make an attempt to minimize the mass of the RF subsystem on the spacecraft. The results of this study will be presented for three data rates 1 Gbps, 500 Mbps and 100 Mbps at maximum Mars to Earth distance of 2.67AU. The design will use a Ka-band downlink with 90% link availability, along with various ground network G/T assumptions and possible bandwidth efficient modulations. The paper will conclude with what types of high rate communication links are feasible from Martian distances and also identify a range of requirements for antenna and power technologies for these high capacity communications from Mars.

Vyas, Hemali N.; Schuchman, Leonard; Orr, Richard; Williams, Wallace Dan; Collins, Michael; Noreen, Gary

2006-01-01

200

Generation of Radiation from Interaction Between Ultra Short Pulse Ultra High Power Laser and Magnetized Plasma  

Microsoft Academic Search

Investigation on electro-magnetic (EM) radiation due to the interaction of ultra-short terra-watt laser is presented. When high power and short laser pulse is focused in the plasma, the plasma wake field can be generated. Characteristics of such wake field is modified in the presence of magnetic field and rotational components of plasma electron motion, consequently it can emit the radiation.

Hajime Noda; Parchamy Homaira; Kobayashi Kazuhiro; Yugami Noboru

2004-01-01

201

Short circuit current fundamentals: characteristics\\/magnitudes\\/definitions for high voltage circuit breaker duties  

Microsoft Academic Search

The ANSI\\/IEEE Standards C37 provide many sections identifying the characteristics, magnitudes and relationships for short circuit\\/fault currents. Also, these standards provide many sections defining the preferred ratings that circuit breakers and\\/or fuses are to be capable of. The goal for this paper is to provide a general\\/executive summary and clear definition for medium and high voltage short circuit (SC) current

C. E. McCoy

1995-01-01

202

3Dimensional thermal analysis and active cooling of short-length high-power fiber lasers  

Microsoft Academic Search

A fully 3-dimensional finite element model has been developed that simulates the internal temperature distribution of short-length high-power fiber lasers. We have validated the numerical model by building a short, cladding-pumped, Er-Yb-codoped fiber laser and measuring the core temperature during laser operation. A dual-end-pumped, actively cooled, fiber laser has generated >11 W CW output power at 1535 nm from only

L. Li; H. Li; T. Qiu; V. L. Temyanko; M. M. Morrell; A. Schülzgen; A. Mafi; J. V. Moloney; N. Peyghambarian

2005-01-01

203

Seamless Dual-Link Handover Scheme in Broadband Wireless Communication Systems for High-Speed Rail  

Microsoft Academic Search

Due to frequent handovers in broadband wireless communications in high-speed rail, communication interruption during handover could seriously degrade the experiences of passengers on the train. Aiming to reduce the interruption time, this paper proposes a seamless handover scheme based on a dual-layer and dual-link system architecture, where a Train Relay Station is employed to execute handover for all users in

Lin Tian; Juan Li; Yi Huang; Jinglin Shi; Jihua Zhou

2012-01-01

204

Standardization of a Communication Middleware for High-Performance Real-Time Systems  

Microsoft Academic Search

The last several years saw an emergence of standardization activities for real-time systems including standardization of operating systems (series of POSIX standards [1]), of communication for distributed (POSIX.21 [10]) and parallel systems (MPI\\/RT [5]) and real-time object management (realtime CORBA [9]). This article describes the ongoing standardization work and implementation of communication middleware for high performance real-time computing. The real-time

Arkady Kanevsky; Anthony Skjellum; Jerrell Watts

1997-01-01

205

Remotely-interrogated high data rate free space laser communications link  

DOEpatents

A system and method of remotely extracting information from a communications station by interrogation with a low power beam. Nonlinear phase conjugation of the low power beam results in a high power encoded return beam that automatically tracks the input beam and is corrected for atmospheric distortion. Intracavity nondegenerate four wave mixing is used in a broad area semiconductor laser in the communications station to produce the return beam.

Ruggiero, Anthony J. (Livermore, CA)

2007-05-29

206

Control System With High-Speed and Real-Time Communication Links  

Microsoft Academic Search

Recent technological advances have enabled distributed control systems to be implemented via networks. This allows feedback control loops to be closed over communication channels. This paper develops a control system with high-speed and real-time communication links. Two-degrees-of-freedom control is utilized in this servo control system, and sigma-delta modulation is employed to compress data and to transmit the signal over the

Tianjian Li; Yasutaka Fujimoto

2008-01-01

207

Generation of high-energy (>15 MeV) neutrons using short pulse high intensity lasers  

SciTech Connect

A roadmap is suggested and demonstrated experimentally for the production of high-energy (>15 MeV) neutrons using short pulse lasers. Investigation with a 3D Monte Carlo model has been employed to quantify the production of energetic neutrons. Numerical simulations have been performed for three nuclear reactions, d(d,n){sup 3}He, {sup 7}Li(d,n){sup 8}Be, and {sup 7}Li(p,n){sup 7}Be, driven by monoenergetic ion beams. Quantitative estimates for the driver ion beam energy and number have been made and the neutron spectra and yield in the ion propagation direction have been evaluated for various incident ion energies. In order to generate neutron fluence above a detection limit of 10{sup 6} neutrons/sr, either {approx}10{sup 10} protons with energy 20-30 MeV or comparable amount of deuterons with energy 5-10 MeV are required. Experimental verification of the concept with deuterons driven by the Titan laser (peak intensity 2 Multiplication-Sign 10{sup 19} W/cm{sup 2}, pulse duration of 9 ps, wavelength 1.05 {mu}m, and energy of 360 J) is provided with the generation of neutrons with energy of up to 18 MeV from {sup 7}Li(d,n){sup 8}Be reactions. Future research will focus on optimized schemes for ion acceleration for production of high-energy neutrons, which will involve efficient target design, laser parameter optimization, and converter material.

Petrov, G. M.; Davis, J.; Petrova, Tz. B. [Naval Research Laboratory, Plasma Physics Division, 4555 Overlook Ave. SW, Washington, DC 20375 (United States); Higginson, D. P. [Mechanical and Aerospace Engineering, University of California-San Diego, La Jolla, California 92093 (United States); Lawrence Livermore National Laboratory, Livermore, California 94440 (United States); McNaney, J. M. [Lawrence Livermore National Laboratory, Livermore, California 94440 (United States); McGuffey, C.; Qiao, B.; Beg, F. N. [Mechanical and Aerospace Engineering, University of California-San Diego, La Jolla, California 92093 (United States)

2012-09-15

208

Simple Short-Pulse CO2 Laser Excited by Longitudinal Discharge without High-Voltage Switch  

NASA Astrophysics Data System (ADS)

We have developed a longitudinally excited CO2 laser without a high-voltage switch. The laser produces a short laser pulse similar to those from TEA and Q-switched CO2 lasers. This system, which is the simplest short-pulse CO2 laser yet constructed, includes a pulsed power supply, a high-speed step-up transformer, a storage capacitor, and a laser tube. At high pressure (4.2 kPa and above), a rapid discharge produces a short laser pulse with a sharp spike pulse. In mixed gas (CO2: N2: He = 1: 1: 2) at a pressure of 9.0 kPa, the laser pulse contains a spike pulse of 218 ns and has a pulse tail length of 16.7 ?s.

Uno, Kazuyuki; Jitsuno, Takahisa; Akitsu, Tetsuya

2012-05-01

209

Communication architecture tuners: a methodology for the design of high-performance communication architectures for system-on-chips  

Microsoft Academic Search

In this paper, we present a general methodology for the design of custom system-on-chip communication architectures. Our technique is based on the addition of a layer of circuitry, called the Communica- tion Architecture Tuner (CAT), around any existing communication architecture topology. The added layer enhances the ability of the system to adapt to changing communication needs of its constituent components.

Kanishka Lahiri; Anand Raghunathan; Ganesh Lakshminarayana; Sujit Dey

2000-01-01

210

A high-power communications technology satellite for the 12 and 14 GHz bands.  

NASA Technical Reports Server (NTRS)

Description of the mission, subsystems and communication capabilities of a joint Communications Technology Satellite (CTS) scheduled for launch in 1975 by the Canadian Department of Communications in cooperation with NASA. The principal objectives of the mission are TV transmission at 12 GHz to low-cost ground terminals, up-link TV transmission at 14 GHz transportable terminals, and flight tests of spacecraft subsystems and components for future communications satellites. The major advanced spacecraft subsystems are a novel superefficiency TWT design, a 0.4 mlb Mercury Bombardment ion engine for north-south station keeping, a 3-axis stabilization system to maintain a high antenna boresight pointing accuracy, a liquid metal slip ring experiment, and a lightweight extendible solar array with an initial power output greater than 1 kW.

Franklin, C. A.; Davison, E. H.

1972-01-01

211

A high power TWT power processing system. [for communication satellites  

NASA Technical Reports Server (NTRS)

A power processing system (PPS) is designed for a space-type high power (200W RF) multi-collector traveling-wave tube (TWT). The basic power circuit is presented along with the simplified block diagram and the input, output, and general requirements for the PPS design are tabulated. The paper covers the PPS design as to critical TWT/PPS interface requirements, high voltage cathode/collector supply, high voltage components material, packaging, grounding and isolation, and electrical performance. The use of a single two loop control system for the regulation of cathode and collector voltages is shown to give high efficiency, excellent steady-state and transient performance characteristics, and complete protection for TWT and PPS components under transient conditions.

Farber, B. F.; Goldin, D. S.; Siegert, C.; Gourash, F.

1974-01-01

212

Single and repetitive short-pulse high-power microwave window breakdown  

SciTech Connect

The mechanisms of high-power microwave breakdown for single and repetitive short pulses are analyzed. By calculation, multipactor saturation with electron density much higher than the critical plasma density is found not to result in microwave cutoff. It is local high pressure about Torr class that rapid plasma avalanche and final breakdown are realized in a 10-20 ns short pulse. It is found by calculation that the power deposited by saturated multipactor and the rf loss of protrusions are sufficient to induce vaporizing surface material and enhancing the ambient pressure in a single short pulse. For repetitive pulses, the accumulation of heat and plasma may respectively carbonize the surface material and lower the repetitive breakdown threshold.

Chang, C.; Tang, C. X. [Department of Engineering Physics, Key Laboratory of Particle and Radiation Imaging, Ministry of Education, Tsinghua University, Beijing 100084 (China); Shao, H.; Chen, C. H.; Huang, W. H. [Northwest Institute of Nuclear Technology, Xi'an, Shannxi 710024 (China)

2010-05-15

213

RAPID COMMUNICATION: High performance superconducting wire in high applied magnetic fields via nanoscale defect engineering  

NASA Astrophysics Data System (ADS)

High temperature superconducting (HTS) wires capable of carrying large critical currents with low dissipation levels in high applied magnetic fields are needed for a wide range of applications. In particular, for electric power applications involving rotating machinery, such as large-scale motors and generators, a high critical current, Ic, and a high engineering critical current density, JE, in applied magnetic fields in the range of 3-5 Tesla (T) at 65 K are required. In addition, exceeding the minimum performance requirements needed for these applications results in a lower fabrication cost, which is regarded as crucial to realize or enable many large-scale bulk applications of HTS materials. Here we report the fabrication of short segments of a potential superconducting wire comprised of a 4 µm thick YBa2Cu3O7-? (YBCO) layer on a biaxially textured substrate with a 50% higher Ic and JE than the highest values reported previously. The YBCO film contained columns of self-assembled nanodots of BaZrO3 (BZO) roughly oriented along the c-axis of YBCO. Although the YBCO film was grown at a high deposition rate, three-dimensional self-assembly of the insulating BZO nanodots still occurred. For all magnetic field orientations, minimum Ic and JE at 65 K, 3 T for the wire were 353 A cm-1 and 65.4 kA cm-2, respectively.

Wee, Sung Hun; Goyal, Amit; Zuev, Yuri L.; Cantoni, Claudia

2008-09-01

214

Low profile, low cost and high efficiency phased array for automobile radar and communication systems  

Microsoft Academic Search

Large profile, high price, low efficiency in realization prevent phased array from being broadly used in automobile radar and communication systems, though phased array has high performance. The article puts forward a new kind of shifterless phased array based on coupled oscillators. The article studies the dynamics of nearest-neighbor coupled oscillators after reviewing the principles of electrical beam-scanning. According to

Tang Zhikai; Jiang Yonghua; Liu Longhe; Hao Yuan; Ling Xiang

2005-01-01

215

Radiation Hardened, Modulator ASIC for High Data Rate Communications  

NASA Technical Reports Server (NTRS)

Satellite-based telecommunication services are challenged by the need to generate down-link power levels adequate to support high quality (BER approx. equals 10(exp 12)) links required for modem broadband data services. Bandwidth-efficient Nyquist signaling, using low values of excess bandwidth (alpha), can exhibit large peak-to-average-power ratio (PAPR) values. High PAPR values necessitate high-power amplifier (HPA) backoff greater than the PAPR, resulting in unacceptably low HPA efficiency. Given the high cost of on-board prime power, this inefficiency represents both an economical burden, and a constraint on the rates and quality of data services supportable from satellite platforms. Constant-envelope signals offer improved power-efficiency, but only by imposing a severe bandwidth-efficiency penalty. This paper describes a radiation- hardened modulator which can improve satellite-based broadband data services by combining the bandwidth-efficiency of low-alpha Nyquist signals with high power-efficiency (negligible HPA backoff).

McCallister, Ron; Putnam, Robert; Andro, Monty; Fujikawa, Gene

2000-01-01

216

Use of a lateral offset short-leg walking cast before high tibial osteotomy.  

PubMed

The clinical results after high tibial osteotomy for the treatment of symptomatic varus gonarthrosis are unpredictable. Although preoperative gait analysis has been shown to be useful in predicting successful outcome after high tibial osteotomy, there are no readily available preoperative clinical tests for predicting success. The authors did a study to determine the effects of an offset short-leg walking cast as a potential predictor of clinical success after high tibial osteotomy. Specifically, the authors evaluated the effect of an offset short-leg walking cast on pain relief and changes in the peak external adduction moments in patients with symptomatic varus gonarthrosis indicated for high tibial osteotomy. Nineteen consecutive patients indicated for high tibial osteotomy were enrolled and completed the study. All patients had precast gait analysis to determine baseline parameters. Immediately after gait analysis, a short-leg lateral offset walking cast was applied and worn for 3 days to allow time for adaptation. Gait analysis then was repeated. Western Ontario and McMaster Universities Osteoarthritis Index pain scores were obtained before and after the cast was applied. The cast resulted in a mean reduction in pain of 53%, and a mean reduction in the peak external adduction moment of 36% in the 17 of 19 patients who tolerated the cast. The reduction in pain was correlated with the reduction in the peak adduction moment (r = 0.63). The authors conclude that an offset short-leg walking cast results in pain reduction that correlates with changes in external adduction moments about the knee. Therefore, an offset short-leg walking cast may prove to be an effective tool for predicting patients who ultimately will benefit from valgus high tibial osteotomy. PMID:12616061

Cole, Brian J; Freedman, Kevin B; Taksali, Sudeep; Hingtgen, Brooke; DiMasi, Michelle; Bach, Bernard R; Hurwitz, Debra E

2003-03-01

217

Short-Backfire Antenna as an Element for High-Gain Arrays.  

National Technical Information Service (NTIS)

The short backfire (SBF) antenna consisting of a large reflector illuminated by a dipole feed and smaller disk reflector produces a gain of 15 dB above isotropic. As an array element it has been effciently adapted for various configurations of high-gain a...

H. W. Ehrenspeck J. A. Strom

1971-01-01

218

Inversion Method Study on Short Wave Infrared Remote Sensing Data High Temperature Surface Feature Temperature  

Microsoft Academic Search

The short wave infrared remote sensing data element DN value is synthesis reflectance of surface features reflex and the emission energy that the emission energy can be ignored generally in terms of the normal temperature surface features, but emission energy of the high temperature surface feature is close or higher than its reflex energy value, based on this, using the

Pan Jun; Xing Li-xin; Wen Jiu-cheng; Meng Tao; Jiang Li-jun

2009-01-01

219

The Use of Short-Story in Teaching English to the Students of Public High Schools  

ERIC Educational Resources Information Center

Although the studies on the use of literature in teaching English have been increasing abroad, in our country, particularly in public high schools, only English grammar is being taught. The students who are expected to memorise these rules cannot use English. The aim of this study is to exhibit why and how short-story can be used in order to teach…

Eren, Zerrin

2004-01-01

220

Short Pulse High Brightness X-ray Production with the PLEIADES Thomson Scattering Source  

SciTech Connect

We describe PLEIADES, a compact, tunable, high-brightness, ultra-short pulse, Thomson x-ray source. The peak brightness of the source is expected to exceed 10{sup 20} photons/s/0.1% bandwidth/mm{sup 2}/mrad{sup 2}. Initial results are reported and compared to theoretical calculations.

Anderson, S G; Barty, C P J; Betts, S M; Brown, W J; Crane, J K; Cross, R R; Fittinghoff, D N; Gibson, D J; Hartemann, F V; Kuba, J; LaSage, G P; Rosenzweig, J B; Slaughter, D R; Springer, P T; Tremaine, A M

2003-07-01

221

Short-pulse and high-frequency signal generation in semiconductor lasers  

Microsoft Academic Search

The application of high-speed semiconductors lasers in short-pulse generation by mode locking, gain\\/Q-switching, and microwave signal generation is reviewed. The underlying basic principles, current state of the art, and areas for further developments are discussed

KAM Y. LAU

1989-01-01

222

Validation of the Short Form of the Career Development Inventory with an Iranian High School Sample  

ERIC Educational Resources Information Center

A short 33-item form of the Career Development Inventory was validated on a sample of 310 Iranian high school students. Factor analysis indicated that attitude and cognitive subscale items loaded on their respective factors, and that internal reliability coefficients at all levels were satisfactory to good. Support for validity was demonstrated by…

Sadeghi, Ahmad; Baghban, Iran; Bahrami, Fatemeh; Ahmadi, Ahmad; Creed, Peter

2011-01-01

223

Temperature Rise of Optical Fiber Ground Wires Subjected to Short Duration-High Current Transients  

Microsoft Academic Search

A thermal model capable of predicting the local temperature history in an optical fiber ground wire (OFGW) when it is subjected to a short duration, high-current transient is discussed. The model is used to predict the temperature rise that can occur from typical lightning strikes and from contact with an energized phase conductor. The model is capable of predicting the

W. Z. Black; M. Glen Wells

1989-01-01

224

Efficient and scalable side pumping scheme for short high-power optical fiber lasers and amplifiers  

Microsoft Academic Search

A new and simple method of pumping short high-power optical fiber lasers and amplifiers is described. In our approach, several passive coreless optical fibers are brought into direct contact alongside a single rare-earth doped active fiber which constitutes the active medium of the laser (amplifier). Pump light is delivered through the passive coreless fibers and penetrates into the active fiber

Pavel Polynkin; Valery Temyanko; Masud Mansuripur; N. Peyghambarian

2004-01-01

225

Rubidium Recycling in a High Intensity Short Duration Pulsed Alkali Laser.  

National Technical Information Service (NTIS)

Laser induced fluorescence was used to study how pump pulse duration and alkali recycle time effects maximum power output in a Diode Pumped Alkali Laser (DPAL) system. A high intensity short pulsed pump source was used to excited rubidium atoms inside a D...

W. S. Miller

2010-01-01

226

Development of microlens arrays for high-speed optical communication  

Microsoft Academic Search

In this study, polymeric microlens arrays, well suited for high-volume and low-cost production, were developed for efficiently coupling the light from vertical-cavity surface emitting lasers (VCSELs) to multi-mode fiber ribbon. They were fabricated by microinjection molding with Ni-electroplated mold insert. Modified LIGA processes and the Ni-electroplating are used to make the master and the metallic mold insert, respectively. In this

Chih-Hsiang Ko; Chun-Hsu Lin; Bor-Chen Tsai; His-Hsin Shih; Chien-Tsung Wu; Yu-Lin Chao; Yu-Kon Chou; Chun-Hsun Chu; Yii-Tay Chiou; Rax Chen

2004-01-01

227

Improved performance of a cooled photoreceiver for high speed communication  

Microsoft Academic Search

An alternative method of improving photoreceiver sensitivity in a high-bit-rate optical transmission system is described. HEMTs have recently become commercially available and are known to generate mainly thermal noise and to exhibit transconductance enhancement at cryogenic temperatures. This suggests that a cooled photoreceiver with a HEMT in the first stage of the front-end amplifier could have an improved sensitivity with

D. Ronarc'h; M. Guibert

1988-01-01

228

On the super-Gaussian unstable resonator for high-gain short-pulse laser media  

SciTech Connect

High-mode-volume high-energy (70 mJ) high-brightness (1.6 [times] 10[sup 14] W cm[sup [minus]2] Sr[sup [minus]1]) laser beams have been extracted from a high gain short-pulse XeCl laser with a super-Gaussian unstable resonator. These results are obtained by increasing the cavity magnification factor to 6.6 and the output mirror peak reflectivity to 78%. The output beam divergence is seen to decrease from an initial value of [approximately]0.2 mrad down to nearly diffraction limited after 6 ns for the short gain build-up time of the active medium.

Perrone, M.R. (Dipartimento di Fisica, Via per Arnesano (Italy)); Piegari, A.; Scaglione, S. (Laboratorio Film Sottili, ENEA Casaccia (Italy))

1993-05-01

229

Three-phase short circuit testing of high-voltage circuit breakers using synthetic circuits  

Microsoft Academic Search

High-voltage circuit-breakers have reached such high short-circuit breaking capabilities that they must be tested in synthetic circuits with separate current and voltage sources. As the main performance to be verified by type tests is the interruption of three-phase faults, it is desirable whenever possible to perform three-phase tests. Three-phase synthetic testing is rather new and not covered by ANSI\\/IEEE and

D. Dufournet; G. Montillet

2000-01-01

230

High-voltage and short-rise-time pulse-transformer with amorphous cores  

Microsoft Academic Search

A short rise time pulsed power transformer using cobalt-based amorphous alloy cores, which operates at high voltage (~100 kV) and high repetition rate (~4000 pps), has been developed for application as a pulsed power modulator for copper vapor lasers. An output voltage of more than 80 kV, a rise time of 65 ns and a transformation efficiency of 83% were

N. Kobayashi; N. Aoki; H. Horie; Y. Baba; Y. Sano; H. Kimura; C. Konagal

1997-01-01

231

Short-range order in Au-Fe alloys studied by high-temperature Mössbauer spectroscopy  

NASA Astrophysics Data System (ADS)

Local atomic configurations of iron atoms in Au1-xFex alloys with x=0.01,0.05,0.15 are investigated from 300 up to 1100 K using high-temperature Mössbauer spectroscopy. In all alloys a short-range order (anticlustering) tendency is observed. Complementary x-ray small-angle scattering experiments reveal no Fe clusters of the Guinier-Preston-zone type in agreement with the result from Mössbauer experiments. The temperature dependence of the first short-range-order parameter, ?1, obtained from the Mössbauer spectra, is surprisingly weak. A computer simulation shows that, however, the short-range-order can be temperature dependent due to the effect of higher-order correlations, namely third-neighbor Fe-Fe pairs. These higher-order correlations may play an important role for the magnetic properties at low temperature.

Yoshida, Y.; Langmayr, F.; Fratzl, P.; Vogl, G.

1989-04-01

232

High Efficiency Power Combining of Ka-Band TWTs for High Data Rate Communications  

NASA Technical Reports Server (NTRS)

Future NASA deep space exploration missions are expected in some cases to require telecommunication systems capable of operating at very high data rates (potentially 1 Gbps or more) for the transmission back to Earth of large volumes of scientific data, which means high frequency transmitters with large bandwidth. Among the Ka band frequencies of interest are the present 500 MHz Deep Space Network (DSN) band of 31.8 to 32.3 GHz and a broader band at 37-38 GHz allocated for space science [1]. The large distances and use of practical antenna sizes dictate the need for high transmitter power of up to 1 kW or more. High electrical efficiency is also a requirement. The approach investigated by NASA GRC is a novel wave guide power combiner architecture based on a hybrid magic-T junction for combining the power output from multiple TWTs [1,2]. This architecture was successfully demonstrated and is capable of both high efficiency (90-95%, depending on frequency) and high data rate transmission (up to 622 Mbps) in a two-way power combiner circuit for two different pairs of Ka band TWTs at two different frequency bands. One pair of TWTs, tested over a frequency range of 29.1 to 29.6 GHz, consisted of two 110-115W TWTs previously used in uplink data transmission evaluation terminals in the NASA Advanced Communications Technology Satellite (ACTS) program [1,2]. The second pair was two 100W TWTs (Boeing 999H) designed for high efficiency operation (greater than 55%) over the DSN frequency band of 31.8 to 32.3 GHz [3]. The presentation will provide a qualitative description of the wave guide circuit, results for power combining and data transmission measurements, and results of computer modeling of the magic-T and alternative hybrid junctions for improvements in efficiency and power handling capability. The power combiner results presented here are relevant not only to NASA deep space exploration missions, but also to other U.S. Government agency programs.

Wintucky, E. G.; Simons, R. N.; Vaden, K. R.; Lesny, G. G.; Glass, J. L.

2006-01-01

233

Experimental error filtration for quantum communication over highly noisy channels.  

PubMed

Error filtration is a method for encoding the quantum state of a single particle into a higher dimensional Hilbert space in such a way that it becomes less sensitive to noise. We have realized a fiber optics demonstration of this method and illustrated its potentialities by carrying out the optical part of a quantum key distribution scheme over a line whose phase noise is too high for a standard implementation of BB84 to be secure. By filtering out the noise, a bit error rate of 15.3% +/- 0.1%, which is beyond the security limit, can be reduced to 10.6% +/- 0.1%, thereby guaranteeing the cryptographic security. PMID:16090449

Lamoureux, L-P; Brainis, E; Cerf, N J; Emplit, Ph; Haelterman, M; Massar, S

2005-06-17

234

Space Weather effects on airline communications in the high latitude regions  

NASA Astrophysics Data System (ADS)

Efficient air traffic management depends on reliable communications between aircraft and the air traffic control centres at all times. At high latitudes, and especially on polar routing, VHF ground infrastructure does not exist and the aircraft have to rely on HF radio for communications. HF relies on reflections from the ionosphere to achieve long distance communications. Unfortunately the high latitude ionosphere is affected by space weather events. During such events HF radio communication can be severely disrupted and aircraft are forced to use longer low latitude routes with consequent increased flight time, fuel consumption and cost. This presentation describes a new research programme at the University of Lancaster in collaboration with the University of Leicester, Solar Metrics Ltd and Natural Resources Canada for the development of a nowcasting and forecasting HF communications tool designed for the particular needs of civilian airlines. This project funded by EPSRC will access a wide variety of solar and interplanetary measurements to derive a complete picture of space weather disturbances affecting radio absorption and reflection

Honary, Farideh

2014-05-01

235

Properties and structure of high erbium doped phosphate glass for short optical fibers amplifiers  

SciTech Connect

New phosphate glasses have been developed in order to incorporate high rare-earth ions concentrations. These glasses present a great chemical stability and a high optical quality. The phosphate glass network is open, very flexible, with a linkage of the tetrahedrons very disordered and contains a larger number of non-bridging oxygens (66%). The great stability and resistance against crystallization associated with the possibility to incorporate high doping concentration of rare-earth ions in these phosphate glasses make them very good candidates for the realization of ultra short single mode amplifiers with a high gain at 1.55 {mu}m.

Seneschal, Karine [UMR CNRS 6512 Verres et Ceramiques, Institut de Chimie de Rennes, Universite de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex (France); Smektala, Frederic [UMR CNRS 6512 Verres et Ceramiques, Institut de Chimie de Rennes, Universite de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex (France)]. E-mail: Frederic.Smektala@univ-rennes1.fr; Bureau, Bruno [UMR CNRS 6512 Verres et Ceramiques, Institut de Chimie de Rennes, Universite de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex (France); Floch, Marie Le [UMR CNRS 6512 Verres et Ceramiques, Institut de Chimie de Rennes, Universite de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex (France); Jiang Shibin [NP Photonic Technologies, LLC, Tucson, AZ (United States); Luo, Tao [NP Photonic Technologies, LLC, Tucson, AZ (United States); Lucas, Jacques [UMR CNRS 6512 Verres et Ceramiques, Institut de Chimie de Rennes, Universite de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex (France); Peyghambarian, Nasser [Optical Sciences Center, Meinel Building, 1630 East University Boulevard, University of Arizona, Tucson, AZ 85721 (United States)

2005-09-01

236

K-band high power latching switch. [communication satellite system  

NASA Technical Reports Server (NTRS)

A 19 GHz waveguide latching switch with a bandwidth of 1400 MHz and an exceptionally low insertion loss of 0.25 dB was demonstrated. The RF and driver ferrites are separate structures and can be optimized individually. This analysis for each structure is separately detailed. Basically, the RF section features a dual turnstile junction. The circulator consists of a dielectric tube which contains two ferrite rods, and a dielectric spacer separating the ferrite parts along the center of symmetry of the waveguide to form two turnstiles. This subassembly is indexed and locked in the center of symmetry of a uniform junction of three waveguides by the metallic transformers installed in the top and bottom walls of the housing. The switching junction and its actuating circuitry met all RF performance objectives and all shock and vibration requirements with no physical damage or performance degradation. It exceeds thermal requirements by operating over a 100 C temperature range (-44 C to +56 C) and has a high power handling capability allowing up to 100 W of CW input power.

Mlinar, M. J.; Piotrowski, W. S.; Raue, J. E.

1980-01-01

237

Coherent DWDM technology for high speed optical communications  

NASA Astrophysics Data System (ADS)

The introduction of coherent digital optical transmission enables a new generation of high speed optical data transport and fiber impairment mitigation. An initial implementation of 40 Gb/s coherent systems using Dual Polarization Quadrature Phase Shift Keying (DP-QPSK) is already being installed in carrier networks. New systems running at 100 Gb/s DP-QPSK data rate are in development and early technology lab and field trial phase. Significant investment in the 100 Gb/s ecosystem (optical components, ASICs, transponders and systems) bodes well for commercial application in 2012 and beyond. Following in the footsteps of other telecommunications fields such as wireless and DSL, we can expect coherent optical transmission to evolve from QPSK to higher order modulations schemes such as Mary PSK and/or QAM. This will be an interesting area of research in coming years and poses significant challenges in terms of electro-optic, DSP, ADC/DAC design and fiber nonlinearity mitigation to reach practical implementation ready for real network deployments.

Saunders, Ross

2011-10-01

238

Ablation cleaning techniques for high-power short-pulse laser produced heavy ion targets  

NASA Astrophysics Data System (ADS)

It has become apparent in the last few years that the light ion surface contamination on short-pulse laser targets is a major impediment to the acceleration of heavier target ions. Mitigation strategies have been tested in experiments at the Los Alamos Trident Laser facility using one arm of the Trident laser at 150 ps to ablatively clean a large area of heated targets in a single short that are subsequently irradiated by the Trident 30 TW short-pulse arm to accelerate the bulk target ions to high energies. This process was used on targets consisting of 15 microns of vanadium. The 150 ps pulse rids the rear of the target of its omnipresent surface contamination layer, consisting mainly of water vapor and hydrocarbons, and allows the Trident 30 TW short-pulse arm to illuminate the target and accelerate ions via the Target Normal Sheath Acceleration (TNSA) mechanism. Because this mechanism relies on a laser generated electrostatic sheath, the ions with the lightest charge to mass ratio (i.e. protons) would be accelerated preferentially at the expense of heavier ions. However with the contamination layer removed, and hence the bulk of the available protons, the TNSA mechanism is able to accelerate the bulk material ions to high energies. Our experimental results are discussed and compared to the LASNEX rad-hydro code to validate and improve our predictive capabilities for future acceleration experiments.

Flippo, Kirk A.; Hegelich, B. Manuel; Schmitt, Mark J.; Gauthier, D. Cort; Meserole, Chad A.; Fisher, Gregory L.; Cobble, James A.; Johnson, Randall A.; Letzring, Samuel A.; Fernández, Juan C.; Schollmeier, Marius; Schreiber, Jörg

2006-05-01

239

The design of a linear L-band high power amplifier for mobile communication satellites  

NASA Technical Reports Server (NTRS)

A linear L-band solid state high power amplifier designed for the space segment of the Mobile Satellite (MSAT) mobile communication system is described. The amplifier is capable of producing 35 watts of RF power with multitone signal at an efficiency of 25 percent and with intermodulation products better than 16 dB below carrier.

Whittaker, N.; Brassard, G.; Li, E.; Goux, P.

1990-01-01

240

Implementation of the SNR High Speed Network Communication Protocol (Receiver Part).  

National Technical Information Service (NTIS)

This thesis work is to implement the receiver pan of the SNR high speed network transport protocol. The approach was to use the Systems of Communicating Machines (SCM) as the formal definition of the protocol. Programs were developed on top of the Unix sy...

W. J. Wan

1995-01-01

241

A High-Efficiency Ytterbium-Doped Fiber Amplifier Designed for Interplanetary Laser Communications  

Microsoft Academic Search

Design, performance, and environmental screening of flight prototype Ytterbium amplifiers designed for the Mars Laser Communications Demonstration are described. The high-reliability design delivered >8-W average power with low-duty-cycle PPM waveforms and >21% electrical-to-optical conversion efficiency.

Neal W. Spellmeyer; David O. Caplan; Bryan S. Robinson; David Sandberg; Mark L. Stevens; Matt M. Willis; Denis V. Gapontsev; Nikolai S. Platonov; Alexander Yusim

2007-01-01

242

High data rate ground-to-train free-space optical communication system  

NASA Astrophysics Data System (ADS)

We developed a new technology that does the acquisition, stable tracking, and fast handover for free space optical links to high-speed trains. Our prototype provided a stable communication link between a train and the ground at a data rate near 1 Gb/s with a handover time on the order of 100 ms.

Urabe, Hideki; Haruyama, Shinichiro; Shogenji, Tomohiro; Ishikawa, Shoichi; Hiruta, Masato; Teraoka, Fumio; Arita, Tetsuya; Matsubara, Hiroshi; Nakagawa, Shingo

2012-03-01

243

Observation of High School Students' Real-Life Communication during a Study Tour Abroad.  

ERIC Educational Resources Information Center

This study assessed various traits of two Japanese high school students' communicative performance by examining their interaction with native speakers of English while they were visiting the United States as part of a 5-day study tour. The study focused on the kind of student performance that should be considered a successful outcome of…

Iwami, Ichiro

2001-01-01

244

Recent advances in millimeter-wave photonic wireless links for very high data rate communication  

NASA Astrophysics Data System (ADS)

To provide integrated and high quality broadband services, higher carrier frequencies are required in wireless communications. Currently, there is a great deal of interests in wireless communications at sub-terahertz or terahertz frequencies, i.e., the millimeter-wave (MMW) or sub-millimeter-wave (sub-MMW). In this work, we will discuss our recent advances in millimeter-wave photonic wireless links for high data rate (10 - 20 Gb/s) communications. The concept of fiber-to-the-antenna (FTTA) system using radio-over-fiber (ROF) technologies will be given in the introduction. Then a design and the structure of the high speed MMW photonic transmitter, namely near-ballistic unitraveling- carrier photodiode (NBUTC-PD), will be discussed in section 2. In section 3, the operation principle of photonic mm-wave waveform generator (PMWG), which is used to produce the optical pulse train for the photonic transmitter at the antenna-site will be illustrated. We then demonstrate the use of the NBUTC-PD and the PMWG for the downstream and upstream high data rate communications in the W-band.

Pan, C.-L.; Chow, C. W.; Yeh, C. H.; Huang, C. B.; Shi, J. W.

2011-11-01

245

A survey of communications in the high noise environment of Army aircraft  

Microsoft Academic Search

In Army aircraft, the noise environment consists of a continuous noise level comprised of a mixture of random (broadband) and periodic frequencies (the aircraft noise signature or whine) and in the case of gunships, transient high-level noise bursts generated by the weapons systems. The noise environment reaching the aviator's ear is comprised of direct ambient noise penetration and communications systems

M. S. Mayer; A. W. Lindberg

1978-01-01

246

The constitution and characteristics of 20 GHz band high power transmitter for communications satellite  

Microsoft Academic Search

The paper describes the design and characteristics of two 20 GHz band high-power transmitters onboard a communication satellite. The type A transmitter is a lightweight model noted for its electrical performance, while the type B transmitter is an environmental test model designed to withstand severe launching and geostationary orbit conditions. Both transmitters consist of active and standby TWT amplifiers, single

M. Nakamura; F. Kawashima; A. Iso

1975-01-01

247

Nonlinear Compensation of High Power Amplifier Distortion for Communication Using a Histogram-Based Method  

Microsoft Academic Search

A probabilistic approach to compensate the nonlinear distortion caused by a high power amplifier (HPA) in a communication system is proposed here. This is a nonparametric method that involves estimating two probabilistic cumulative distribution functions without any explicit parameter estimation as in the conventional compensation techniques. It is shown analytically that the maximum compensation error of the proposed method is

Dongliang Huang; Xinping Huang; Henry Leung

2006-01-01

248

Synchronization and secure communication of chaotic systems via robust adaptive high-gain fuzzy observer  

Microsoft Academic Search

This paper proposes an alternative robust adaptive high-gain fuzzy observer design scheme and its application to synchronization and secure communication of chaotic systems. It is assumed that their states are immeasurable and their parameters are unknown. The structure of the proposed observer is represented by Takagi–Sugeno fuzzy model and has the integrator of the estimation error. It improves the performance

Chang-Ho Hyun; Chang-Woo Park; Jae-Hun Kim; Mignon Park

2009-01-01

249

Communication about Contraception and Knowledge of Oral Contraceptives amongst Norwegian High School Students.  

ERIC Educational Resources Information Center

Examines communication about contraception and specific knowledge of oral contraceptives (OCs) in a sample of Norwegian high school students. More females than males discussed contraception at least monthly. Discussions were predominantly held with peers and not adults. Females were far more knowledgeable about OCs than males. The most significant…

Hansen, Thomas; Skjeldestad, Finn Egil

2003-01-01

250

Federal High Performance Computing and Communications Program. The Department of Energy Component.  

ERIC Educational Resources Information Center

This report, profusely illustrated with color photographs and other graphics, elaborates on the Department of Energy (DOE) research program in High Performance Computing and Communications (HPCC). The DOE is one of seven agency programs within the Federal Research and Development Program working on HPCC. The DOE HPCC program emphasizes research in…

Department of Energy, Washington, DC. Office of Energy Research.

251

Prospects of CMOS technology for high-speed optical communication circuits  

Microsoft Academic Search

This paper describes the capabilities of deep-submi- cron CMOS technologies for the realization of highly integrated optical communication transceivers in the range of tens of gigabits per second. Following an overview of a CMOS process, the design of traditional and modern transceivers is presented and speed and integration issues are discussed. Next, the problem of equalization is addressed. Finally, the

Behzad Razavi

2002-01-01

252

Persuading girls to take elective physical science courses in high school: Who are the credible communicators?  

NASA Astrophysics Data System (ADS)

Eighth-grade girls (N=257) randomly selected from nine different public junior high schools in central Texas were questioned in order to identify the communicators whom they perceive as highly credible regarding reasons for taking elective physical science courses in high school and the attributes associated with these communicators. Four persons were each identified by better than 10 percent of the sample as the best person to try to convince junior high school girls to take elective physical science courses in high school. In order of perceived credibility, these persons are father, woman science teacher, mother, and boy high school student. Slight variations in the order of perceived credibility were found when the responses from girls of the different ethnic groups represented in the sample (Caucasian, Hispanic, Black, and Asian) were examined separately. Attributes listed by the respondents for father, woman science teacher, mother, and boy high school student were examined and classified into the categories of prestige, trustworthiness, similarity, attractiveness, and power. Prestige and trustworthiness are the attributes associates most frequently with communicators identified as highly credible. Implications of the present study and suggestions for further research are discussed.

Koballa, Thomas R., Jr.

253

[Psychological processes predicting the English communication behavior of Japanese high school students].  

PubMed

This study presents a new model of psychological processes to predict English communication behaviors of Japanese high school students. Various models have been proposed in Japan, based mainly on Canadian models, to predict second-language communication behaviors. This study shows problems with the previous models in Japan and introduces a new model from the perspective of "Expectancy-Value Theory". Questionnaire Survey 1 compared the previous model and the modified models which suggested that a new psychological variable, "Value in English Communication", was necessary to construct the new model. In Survey 2, the new model was further modified by incorporating into it various English learning values which the Japanese have. This study makes a significant contribution to studies and practices of teaching English as a foreign language in Japan. PMID:24505975

Ito, Takehiko

2013-12-01

254

Generation of ultra-short pulses from high-gain narrow-linewidth lasers  

Microsoft Academic Search

Modified type mode-locking with many passive-mode excitation has been proposed to generate ultra-short light pulses from high-gain narrow-linewidth lasers, The mode-locking with single-active-mode (MLSAM) which is the useful and practical case of the modified type mode-locking has been analyzed taking into account the effect of large locking signal and the variation of the saturated gain along the light path. An

T. Kobayashi; S. Konishi; T. Sueta

1975-01-01

255

The Propagation of Short-Pulse High-Intensity Lasers in Underdense Plasmas: Theory and Simulation  

Microsoft Academic Search

In this dissertation we examine several key issues relevant to the transport of short-pulse high-intensity lasers through underdense plasmas. First we re-examine the collisional absorption of intense lasers. We extend the collision model of Dawson and Oberman to the case in which the quiver velocity v_{o} = eE\\/momega_{o} is much larger than the thermal velocity v_{th } and compare it

Christopher Dean Decker

1994-01-01

256

Design of a capacitive-sensor signal processing system with high accuracy and short conversion time  

Microsoft Academic Search

This paper presents the design of a capacitive-sensor signal processing system, which is capable of converting the capacitance change into digital signal output with high accuracy and short conversion time. The system consists the current conveyors, analog switches, current source, A\\/D converter and 32-bit advanced RISC machine (ARM). The digital readout ranges from 0000 to FFFF corresponding to the capacitance

An Sang Hou; Susan Xiao-Ping Su

2005-01-01

257

Solution processed OTFTs for OLED backplanes: development of high performance short channel length devices  

Microsoft Academic Search

High performance short channel OTFTs with field effect mobilities greater than 1cm2V-1s-1 have been developed for OLED driver applications incorporating soluble crystalline semiconductor materials. We highlight the impact of contact resistance on the mobility in these devices and show by functionalising both the source and drain contacts and channel regions in a top gate bottom contact device architecture that the

Christopher J. Newsome; Richard J. Wilson; Thomas J. Kugler; Mohd K. Othman; Jeremy H. Burroughes

2010-01-01

258

PIC Simulations of Short-Pulse High-Intensity Laser-Plasma Interactions  

Microsoft Academic Search

We use our MPP PIC code, Z3, to model short-pulse high-intensity laser plasma interactions in 2D and 3D. The 3D modeling of the laser pulse through the underdense plasma produced by a prepulse is discussed and its impact on the laser plasma interaction in the overdense region is assessed. We also describe the production of charged particles for parameters associated

B. F. Lasinski; C. H. Still; A. B. Langdon; R. P. J. Town; M. Tabak; W. L. Kruer; S. C. Wilks

2003-01-01

259

Short communication A mammographic dilemma: calcification or haemosiderin as a cause of opacities? Validation of a new digital diagnostic tool  

Microsoft Academic Search

Core biopsies of an area of microcalcification demonstrated large collections of macrophages containing haemosiderin, with evidence of minimal microcalcification on H&E staining. Algorithms were developed that were capable of differentiating with high accuracy those signs due to calcification, using quantitative measurements such as the apparent volume composition of calcium. Using the linear attenuation coefficients of calcification and assuming an ellipsoid

M YAM; J TCHOU; R ENGLISH; R HIGHNAM; M GREENALL; M BRADY

2001-01-01

260

Short communication The impact of an air quality advisory program on voluntary mobile source air pollution reduction  

Microsoft Academic Search

Air pollution from mobile source emissions is a major cause of air quality degradation in the Denver, Colorado, metropolitan area. The projected increase in both population and vehicle miles driven, coupled with the high altitude, predominantly clear skies, and prevalent wintertime temperature inversions aid in the formation and retention of pollutants. The Colorado Department of Public Health issues an air

Peter D. Blanken; Jennifer Dillon; Genevieve Wismann

261

Short Communication: Hydroperoxides in Circulating Lipids from Dairy Cows: Implications for Bioactivity of Endogenous-Oxidized Lipids  

Microsoft Academic Search

This study was conducted to investigate the potential for increased oxidative stress of high- vs. average-pro- ducing dairy cows. Two experiments were performed using 11 and 13 Holstein cows (53 ± 2 d postpartum). Lipohydroperoxides (LHP) were determined in serum lipids (experiment 1) and low-density lipoprotein (ex- periment 2) via oxidation of ferrous to ferric ions through LHP using thiocyanate

B. Löhrke; T. Viergutz; W. Kanitz; B. Losand; D. G. Weiss; M. Simko

2005-01-01

262

High-power 0.87-micron channel substrate planar lasers for spaceborne communications  

NASA Technical Reports Server (NTRS)

High-power single-mode channeled-substrate planar AlGaAs diode lasers are being developed for reliable high-power operation for use as sources in spaceborne optical communication systems. The CSP laser structure has been optimized for operation at an emission wavelength of 870 nm. Such devices have exhibited output powers in excess of 80 mW CW at an operating temperature of 80 C.

Connolly, J. C.; Stewart, T. R.; Gilbert, D. B.; Slavin, S. E.; Carlin, D. B.

1988-01-01

263

Design of High-Speed CMOS ICs for 10 Gbit\\/s Optical Communication System  

Microsoft Academic Search

In this paper, the intrinsic disadvantages of the nowadays low-cost deep-submicron digital CMOS technologies in respect of the design of high-speed optical communication (OC) systems front-end integrated circuits (ICs) have been discussed. The critical passive components such as on-chip inductor and varactor, and the key high-speed circuits of clock and data re- covery circuit (CDR) such as voltage controlled oscillator

Zheng Gu; Andreas Thiede

264

Congestion control in high-speed communication networks using the Smith principle  

Microsoft Academic Search

High-speed communication networks are characterized by large bandwidth-delay products. This may have an adverse impact on the stability of closed-loop congestion control algorithms. In this paper, classical control theory and Smith's principle are proposed as key tools for designing an e!ective and simple congestion control law for high-speed data networks. Mathematical analysis shows that the proposed control law guarantees stability

Saverio Mascolo

1999-01-01

265

Improving communication and social support for caregivers of high-risk infants through mobile technologies  

Microsoft Academic Search

Upon leaving the hospital, parents of high-risk infants experience a variety of challenges in providing care at home. In this work, we present results from a qualitative study to understand the role of social interaction and information-sharing surrounding high-risk infants among both home caregivers and health professionals. These results demonstrate challenges in communication and social support for caregivers of these

Leslie S. Liu; Sen H. Hirano; Monica Tentori; Karen G. Cheng; Sheba George; Sun Young Park; Gillian R. Hayes

2011-01-01

266

Combining low-latency communication protocols with multithreading for high performance DSM systems on clusters  

Microsoft Academic Search

With the development of clusters based on high performance networks, it is now possible to design efficient Distributed Shared Memory systems. In this paper we present the approach we choose to implement a high performance DSM system on top of a cluster by combining the use of low-latency communication protocols (MPI-BIP on Myrinet networks) with multithreading approach (PM2). We present

Laurent Lefevre; Olivier Reymann

2000-01-01

267

Free-space high data rate communications technologies for near terrestrial space  

Microsoft Academic Search

Recent progress at the Applied Physics Laboratory in high data rate communications technology development is described in this paper. System issues for developing and implementing high data rate downlinks from geosynchronous earth orbit to the ground, either for CONUS or in-theater users is considered. Technology is described that supports a viable dual-band multi-channel system concept. Modeling and simulation of micro-electro-mechanical

C. L. Edwards; J. R. Bruzzi; B. G. Boone

2008-01-01

268

Characteristics of High Energy Ka and Bremsstrahlung Sources Generated by Short Pulse Petawatt Lasers  

SciTech Connect

We have measured the characteristics of high energy K{alpha} sources created with the Vulcan Petawatt laser at RAL and the JanUSP laser at LLNL. High energy x-ray backlighters will be essential for radiographing High-Energy-Density Experimental Science (HEDES) targets for NIF projects especially to probe implosions and high areal density planar samples. Hard K{alpha} x-ray photons are created through relativistic electron plasma interactions in the target material after irradiation by short pulse high intensity lasers. For our Vulcan experiment, we employed a CsI scintillator/CCD camera for imaging and a CCD camera for single photon counting. We measured the Ag K{alpha} source (22 keV) size using a pinhole array and the K{alpha} flux using a single photon counting method. We also radiographed a high Z target using the high energy broadband x-rays generated from these short pulse lasers. This paper will present results from these experiments.

Park, H; Izumi, N; Key, M H; Koch, J A; Landen, O L; Patel, P K; Phillips, T W; Zhang, B B

2004-04-13

269

Short communication: hydroperoxides in circulating lipids from dairy cows: implications for bioactivity of endogenous-oxidized lipids.  

PubMed

This study was conducted to investigate the potential for increased oxidative stress of high- vs. average-producing dairy cows. Two experiments were performed using 11 and 13 Holstein cows (53 +/- 2 d postpartum). Lipohydroperoxides (LHP) were determined in serum lipids (experiment 1) and low-density lipoprotein (experiment 2) via oxidation of ferrous to ferric ions through LHP using thiocyanate as chromogen. In experiment 1, differing milk yield and milk energy output corresponded to different concentrations of LHP. In experiment 2, analysis of regression resulted in a significant relationship between milk yield and LHP. Phospholipids isolated from lipids with 6.5 microM of LHP evoked in monocytic cells a transient increase in superoxide formation, indicating inflammatory potential. The results show that high milk productivity can associate with oxidative stress indicated by oxidative modifications of circulating lipids and their changed bioactivity. PMID:15829662

Löhrke, B; Viergutz, T; Kanitz, W; Losand, B; Weiss, D G; Simko, M

2005-05-01

270

Short communication An application of artificial reefs to reduce organic enrichment caused by net-cage fish farming: preliminary results  

Microsoft Academic Search

Two artificial reefs made of porous recycled high-density polyethylene fence material were moored on the sea floor (20-m depth) off the North Beach of Eilat (Gulf of Aqaba, Red Sea) in April 1999. One reef was situated below a commercial net-cage fish farm, and a control reef was deployed outside the area of direct influence of the farm. The objective

Dror L. Angel; Ehud Spanier

271

Development of a bidirectional data communication system using ultra high frequency radio wave for implantable artificial hearts  

Microsoft Academic Search

In order to minimize infection risks for patients with artificial hearts, wireless data transmission methods with electromagnetic or optical transcutaneous data transmission have been developed. However, using these methods, it tends to become difficult to transmit data if the external data transceiver moves from its proper position because the communication distance is short. To resolve this problem, the purpose of

Shinichi Tsujimura; Hiroto Yamagishi; Yoshiyuki Sankai

2010-01-01

272

BRIEF COMMUNICATIONS: Possibility of generation of short laser radiation pulses as a result of photolysis of a cooled H2-F2 mixture  

Microsoft Academic Search

It is shown theoretically that sufficiently strong optical initiation (pulse duration 1-4 musec) of a chain reaction in a cooled (to 100-150 °K) hydrogen-fluorine mixture ensures that the HF laser radiation energy is emitted mainly as a short pulse lasting a few tens of nanoseconds. The predicted reaction regime is characterized by a high yield of coherent radiation and is

A. S. Bashkin; Valerii I. Igoshin; V. Yu Nikitin; A. N. Oraevskii

1978-01-01

273

Short communication: expression of transporters and metabolizing enzymes in the female lower genital tract: implications for microbicide research.  

PubMed

Topical vaginal microbicides have been considered a promising option for preventing the male-to-female sexual transmission of HIV; however, clinical trials to date have not clearly demonstrated robust and reproducible effectiveness results. While multiple approaches may help enhance product effectiveness observed in clinical trials, increasing the drug exposure in lower genital tract tissues is a compelling option, given the difficulty in achieving sufficient drug exposure and positive correlation between tissue exposure and microbicide efficacy. Since many microbicide drug candidates are substrates of transporters and/or metabolizing enzymes, there is emerging interest in improving microbicide exposure and efficacy through local modulation of transporters and enzymes in the female lower genital tract. However, no systematic information on transporter/enzyme expression is available for ectocervical and vaginal tissues of premenopausal women, the genital sites most relevant to microbicide drug delivery. The current study utilized reverse transcriptase polymerase chain reaction (RT-PCR) to examine the mRNA expression profile of 22 transporters and 19 metabolizing enzymes in premenopausal normal human ectocervix and vagina. Efflux and uptake transporters important for antiretroviral drugs, such as P-gp, BCRP, OCT2, and ENT1, were found to be moderately or highly expressed in the lower genital tract as compared to liver. Among the metabolizing enzymes examined, most CYP isoforms were not detected while a number of UGTs such as UGT1A1 were highly expressed. Moderate to high expression of select transporters and enzymes was also observed in mouse cervix and vagina. The implications of this information on microbicide research is also discussed, including microbicide pharmacokinetics, the utilization of the mouse model in microbicide screening, as well as the in vivo functional studies of cervicovaginal transporters and enzymes. PMID:23607746

Zhou, Tian; Hu, Minlu; Cost, Marilyn; Poloyac, Samuel; Rohan, Lisa

2013-11-01

274

Dimming-discrete-multi-tone (DMT) for simultaneous color control and high speed visible light communication.  

PubMed

Visible light communication (VLC) using LEDs has attracted significant attention recently for the future secure, license-free and electromagnetic-interference (EMI)-free optical wireless communication. Dimming technique in LED lamp is advantageous for energy efficiency. Color control can be performed in the red-green-blue (RGB) LEDs by using dimming technique. It is highly desirable to employ dimming technique to provide simultaneous color and dimming control and high speed VLC. Here, we proposed and demonstrated a LED dimming control using dimming-discrete-multi-tone (DMT) modulation. High speed DMT-based VLC with simultaneous color and dimming control is demonstrated for the first time to the best of our knowledge. Demonstration and analyses for several modulation conditions and transmission distances are performed, for instance, demonstrating the data rate of 103.5 Mb/s (using RGB LED) with fast Fourier transform (FFT) size of 512. PMID:24718127

Sung, Jiun-Yu; Chow, Chi-Wai; Yeh, Chien-Hung

2014-04-01

275

Isolation and analysis of tetracycline-resistant Mycoplasma agalactiae strains from an infected goat herd in Cyprus - short communication.  

PubMed

A major concern with the use of tetracycline against mycoplasmas is the development of resistance. Infections in small ruminants due to tetracyclineresistant Mycoplasma agalactiae strains are becoming a frequent problem worldwide. In the present paper the detection and analysis of three tetracycline-resistant M. agalactiae strains, isolated from infected goats in Cyprus, are reported. The three field isolates were identified as M. agalactiae by polymerase chain reaction (PCR) showing 98% identity to the M. agalactiae PG2 reference strain. Furthermore, they were found sensitive to tylosin, enrofloxacin, spiramycin and lincomycin. In contrast, they were resistant to tetracycline. None of the putative genes [tet(M), tet(O) and tet(S)] that commonly contribute to high-level resistance to tetracycline could be amplified from their genome. Contrarily, the field isolates were found to carry ISMag1, an insertion sequence related to the IS30 family of mobile elements. Although ISMag1 is widely believed to induce high-frequency chromosomal rearrangements resulting in phenotypic changes of microorganisms, its potential role in tetracycline resistance of mycoplasmas requires further studies. PMID:23921341

Filioussis, George; Ioannou, Ioannis; Petridou, Evanthia; Avraam, Maria; Giadinis, Nektarios D; Kritas, Spyridon K

2013-09-01

276

High-frequency dynamics in delayed semiconductor lasers with short external cavity  

NASA Astrophysics Data System (ADS)

We analyze the dynamics of a laser diode subject to optical feedback from a short external cavity (EC), i.e. with an EC round-trip time much smaller than the period of the laser relaxation oscillations (RO). Our numerical simulations are based on the Lang-Kobayashi (LK) equations for single mode edge-emitting lasers subject to weak/moderate optical feedback. A new, detailed, Hopf bifurcation analysis shows that LK equations admist both supercritical and subcritical Hopf bifurcation points. Subcritical Hopf points lead to time-periodic pulsating intensity solutions with a frequency close to half the RO frequency. In contrast, from supercritical Hopf bifurcatiosn emerge harmonic intensity oscillations with a frequency either close to the RO frequency or to the EC frequency. Microwave oscillations are obtained, as a result of a beating between two EC modes. In general, these high frequency dynamics are stable only for a small range of feedback parameters. However, we find that decreasing the ? factor largely improves the stability of the microwave oscillations and makes it possible to observe pulsating intensity solutions for a larger range of EC length. The high frequency intensity solutions of laser diodes with short EC are thought to be of great interest for new applications in all optical signal handling. Our results motivate new theoretical studies of LK equations with short EC.

Sciamanna, Marc; Erneux, Thomas; Gavrielides, Athanasios; Kovanis, Vassilios; Megret, Patrice; Blondel, Michel

2003-07-01

277

Generating High-Power Short Terahertz Electromagnetic Pulses with a Multifoil Radiator  

NASA Astrophysics Data System (ADS)

We describe a multifoil cone radiator capable of generating high-field short terahertz pulses using short electron bunches. Round flat conducting foil plates with successively decreasing radii are stacked, forming a truncated cone with the z axis. The gaps between the foil plates are equal and filled with some dielectric (or vacuum). A short relativistic electron bunch propagates along the z axis. At sufficiently high particle energy, the energy losses and multiple scattering do not change the bunch shape significantly. When passing by each gap between the foil plates, the electron bunch emits some energy into the gap. Then, the radiation pulses propagate radially outward. For transverse electromagnetic waves with a longitudinal (along the z axis) electric field and an azimuthal magnetic field, there is no dispersion in these radial lines; therefore, the radiation pulses conserve their shapes (time dependence). At the outer surface of the cone, we have synchronous circular radiators. Their radiation field forms a conical wave. Ultrashort terahertz pulses with gigawatt-level peak power can be generated with this device.

Vinokurov, Nikolay A.; Jeong, Young Uk

2013-02-01

278

High-dose short-term chlorambucil for intractable sympathetic ophthalmia and Beh?et's disease.  

PubMed Central

We treated five patients with intractable sympathetic ophthalmia and six patients with severe Behçet's disease by high-dose, short-term chlorambucil therapy. We used a total dose ranging from 306 mg to 4.2 g and a duration of therapy no longer than 36 weeks and in most cases less than 24 weeks. After termination of therapy all 11 patients had a sustained remission of their eye disease. Unless subretinal neovascularisation was present, all had a final visual acuity of 20/50 or better. Malignancy has not developed in any of our cases, with a follow-up ranging from 6 months to 12 years (mean, 4.5 years). Although 30- and 40-year follow-ups and larger numbers of patients may be necessary fully to realise the risks of chlorambucil, we believe that our high-dose, short-term regimen (Behçet's disease: average duration, 23 weeks; average total dose 2.2 g; sympathetic ophthalmia: average duration, 11 weeks; total average dose, 0.9 g) may be safer than previously reported chlorambucil regimens of one to two years or longer. In addition we fulfilled our aim of discontinuing all concomitant systemic corticosteroids within a relatively short time (usually six to eight weeks).

Tessler, H H; Jennings, T

1990-01-01

279

Short Communication: Transmitted Drug Resistance and Molecular Epidemiology in Antiretroviral Naive HIV Type 1-Infected Patients in Rhode Island  

PubMed Central

Abstract Transmission of HIV-1 drug resistance has important clinical and epidemiological consequences including earlier treatment failure and forward transmission of resistance strains in high-risk groups. To evaluate the prevalence and molecular epidemiology of transmitted drug resistance in Rhode Island, we collected genotypic, demographic, clinical, and laboratory data from treatment-naive individuals presenting to the largest outpatient HIV clinic in the state from January 2007 to November 2007. Sequences from 35 treatment-naive individuals were available, 83% of whom were men who had sex with men (MSM). All sequences were HIV-1 subtype B. Drug resistance mutations were identified in 7/35 [20%; 95% confidence interval (CI), 0.08–0.37] patients, six of whom had K103N. Two phylogenetic transmission clusters were found, involving 17% (6/35) of individuals, three in each cluster. We did not find an association between belonging to a cluster and age, gender, AIDS-defining illness, CD4 cell count, or viral load. Drug resistance mutations were more commonly observed in transmission clusters (p?=?0.08). Individuals in one cluster all had K103N and were MSM who had attended local bathhouses. Individuals forming clusters were significantly more likely to have visited a bathhouse compared to nonclusters (p?=?0.02). The prevalence of transmitted drug resistance in Rhode Island is high, further justifying genotypic testing on presentation to care and prior to treatment initiation. Molecular epidemiological analysis and association of resistance with phylogenetic networks using data obtained for clinical purposes may serve as useful tools for the prevention of drug resistance transmission and for contact tracing.

Tashima, Karen; Cartwright, Charles P.; Gillani, Fizza S.; Mintz, Orli; Zeller, Kimberly; Kantor, Rami

2011-01-01

280

How high is visual short-term memory capacity for object layout?  

PubMed

Previous research measuring visual short-term memory (VSTM) suggests that the capacity for representing the layout of objects is fairly high. In four experiments, we further explored the capacity of VSTM for layout of objects, using the change detection method. In Experiment 1, participants retained most of the elements in displays of 4 to 8 elements. In Experiments 2 and 3, with up to 20 elements, participants retained many of them, reaching a capacity of 13.4 stimulus elements. In Experiment 4, participants retained much of a complex naturalistic scene. In most cases, increasing display size caused only modest reductions in performance, consistent with the idea of configural, variable-resolution grouping. The results indicate that participants can retain a substantial amount of scene layout information (objects and locations) in short-term memory. We propose that this is a case of remote visual understanding, where observers' ability to integrate information from a scene is paramount. PMID:20436203

Sanocki, Thomas; Sellers, Eric; Mittelstadt, Jeff; Sulman, Noah

2010-05-01

281

Short Communication: Synergism Between a CD4-Mimic Peptide and Antibodies Elicited by a Constrained V3 Peptide  

PubMed Central

Abstract Due to the different mechanisms HIV-1 has evolved to escape from a neutralizing antibody response it has been extremely challenging to develop an effective anti-HIV-1 vaccine. The V3 region of the gp120 HIV-1 envelope glycoprotein has been considered as one of the possible targets for an anti-HIV vaccine. It is well known that the V3 region of gp120 is at least partially masked in circulating strains and becomes exposed only after CD4 binding. However, when the virus is bound to surface CD4, steric hindrance prevents effective neutralization by V3-directed antibodies. Here we have used a 27-residue CD4-mimetic peptide in combination with immune sera elicited by an optimally constrained V3 peptide to enhance neutralization of a panel of clade B viruses. We observed strong synergism between the immune sera and the CD4-mimetic in the neutralization of tier 1 and a representative tier 2 clade B virus suggesting that the constrained V3 peptide immunogen correctly mimics the V3 conformation even in tier 2 clade B viruses. This synergy should improve the potential of CD4-mimetic compounds for preexposure prophylaxis and in the treatment of HIV-1-infected patients who usually manifest high titers of V3-directed antibodies. Moreover, constrained V3 immunogens elicit immune sera that may neutralize HIV in synergy with CD4 binding site antibodies that expose V3 and the coreceptor binding site.

Moseri, Adi; Tantry, Subramanyam; Ding, Fa-Xiang; Naider, Fred

2013-01-01

282

Design and evaluation of a 2-Mb/s GMSK modem for short-distance infrared wireless communications  

NASA Astrophysics Data System (ADS)

A carrier-based modem for an IR Wireless LAN (IR-WLAN) design is presented. It is based on GMSK modulation schemes. This modem is capable of operating at 2 Mb/s, but it can easily modify to work up to 4.8 Mb/s. GMSK Schemes are filtered modulation schemes with higher spectral efficiency and robustness against jitter than basic FSK. The emitter uses a pulse-conformation stage for full-digital gaussian pulse conformation. Transitions are codified and the resulting waveform is similar to the output of a gaussian filter. The main applications of the proposed GMSK modem are in the area of a full-duplex IR link. And can be applied either in point-to-point links or into a local area network. It can work without interference wither with IrDA systems (even with the proposed PPM 4.4 Mb/s link) or with IEEE 802.11-baseband link (1 or 2 Mb/s). It is also more spectral efficient and jitter resistant than PPM. Carrier-based systems can be used either in point-to-point links or in diffuse systems. For diffuse systems, this modem assumes a high level of use of the available IR spectrum, supporting at least 4 channels in a 30 MHz bandwidth. We also compare the performances of GMSK with other schemes (as can be OQPSK or FQPSK-2).

Perez-Jimenez, Rafael; Montelongo, Cesar; Rabadan Borges, Jose A.

1999-12-01

283

An impulse radio communications system  

NASA Astrophysics Data System (ADS)

Pulson Communications has built a prototype impulse radio. The transmitter has an average power of 450 microwatts as measured out of the antenna. This prototype, transmitting high quality audio, was tested to ranges in excess of 7 kilometers. The potential range of this type of system at this power level may exceed 20 kilometers. The prototype had a center frequency of 675 MHz and an approximately equal bandwidth. We used a small wideband omni-directional antenna. While Pulson's laboratory hardware has been optimized for short range, there is no theoretical reason it could not be used for longer range communications, e.g., satellite-to-ground communications or interplanetary probes.

Withington, Paul, II; Fullerton, Larry W.

1993-01-01

284

Short communication: HIV blips while on antiretroviral therapy can indicate consistently detectable viral levels due to assay underreporting.  

PubMed

Viral blips, where HIV RNA plasma viral load (pVL) intermittently increases above the lower limit of assay detection, are a cause for concern. We investigated a number of hypotheses for their cause. We assessed HIV RNA, and total and episomal HIV DNA from 16 individuals commencing antiretroviral therapy (ART) consisting of raltegravir and tenofovir/emtricitabine for 3 years, using two assays: a single-copy assay [SCA; lower limit of quantification (LLOQ), <1 copy/ml] and the Amplicor assay (LLOQ of 50 copies/ml). Two individuals exhibited viral blips. From week 20 onward, the period where ART had achieved its final suppressive levels, pVL ranged from <1 to 330 copies/ml, except for one individual at the final time. Both assays were 98% consistent (108/110) in assessing pVL <50 copies/ml, but the Amplicor assay registered 56% of samples (19/34) as below the LLOQ that were in the 50 to 1000 copy/ml range as quantified by SCA. pVL changes between successive time points did not correlate with changes in cellular infection as measured through either total or episomal HIV DNA. Changes in pVL were correlated (negatively) with changes in total CD4(+) T cell numbers (p=0.003), naive (CD45RO(-)CD62L(+)CD4(+)), natural regulatory (CD45RO(-)CD25(+)CD127(-)CD4(+)), activated effector (CD45RO(+)CD38(++)CCR5(+)CD8(+)), but not activated (CD38(+)HLA-DR(+)) CD4(+) T cells. Patients receiving stable, seemingly suppressive ART can have pVL near the 50 copy LLOQ at multiple time points. The high Amplicor assay error rate around this level implies that viral blips underrepresent pVL being more consistently above the LLOQ. Activation of latently infected cells is less likely to contribute to this phenomenon. PMID:23844947

Murray, John M; Zaunders, John J; Koelsch, Kersten K; Natarajan, Ven; Badralmaa, Yunden; McBride, Kristin; Carrera, Alexander; Cooper, David A; Emery, Sean; Kelleher, Anthony D

2013-12-01

285

Wireless infrared communications  

Microsoft Academic Search

The use of infrared radiation as a medium for high-speed short-range wireless digital communication is discussed. Available infrared links and local-area networks are described. Advantages and drawbacks of the infrared medium are compared to those of radio and microwave media. The physical characteristics of infrared channels using intensity modulation with direct detection (IM\\/DD) are presented including path losses and multipath

JOSEPH M. KAHN; JOHN R. BARRY

1997-01-01

286

Short communication: Maternal heat stress during the dry period alters postnatal whole-body insulin response of calves.  

PubMed

Heat stress during the dry period not only negatively affects a cow's performance but also affects her offspring. Previous studies indicate that calves born to cows heat-stressed during late gestation have lower birth weight but similar overall weight gain during the prepubertal period compared with those cooled in utero. However, it is unclear if whole-body insulin response, and thus metabolism, of calves is altered in their postnatal life after in utero heat stress. The aim of the present study was to examine the effects of maternal heat stress during the dry period on whole-body insulin response of calves after weaning. Calves (10/treatment) were born to cows exposed to heat stress (HT) or cooling (CL) when dry. Calves were immediately separated from their dams and fed 3.8L of high-quality colostrum within 1h after birth and then 1.9L 12h later. All calves were fed 1.9 to 3.8L of pasteurized milk in the morning and afternoon from 2 to 42 d of age and then only in the morning until weaning at 49 d. Calf starter and water were offered ad libitum starting at 2 d of age. All calves were managed in the same manner throughout the study. All calves were subjected to a glucose tolerance test (GTT) and an insulin challenge (IC) at 55 d of age. Calves heat-stressed in utero were born lighter (40±1.4 vs. 45±1.4kg) compared with CL calves. Both groups of calves had similar weaning weights (HT: 68±3.2kg; CL: 71±3.3kg) and body weight gain from birth to weaning (HT: 28±2.2kg; CL: 26±2.3kg). Compared with those cooled in utero, HT calves had a similar insulin response to GTT and insulin clearance during IC but faster glucose clearance during GTT and IC. In conclusion, in addition to impaired fetal growth, maternal heat stress during the dry period enhances the whole-body insulin response of calves after weaning, which suggests the possibility of accelerated lipogenesis and fat deposition in early life. PMID:24359830

Tao, S; Monteiro, A P A; Hayen, M J; Dahl, G E

2014-02-01

287

ScalaTrace: Scalable Compression and Replay of Communication Traces for High Performance Computing  

SciTech Connect

Characterizing the communication behavior of large-scale applications is a difficult and costly task due to code/system complexity and long execution times. While many tools to study this behavior have been developed, these approaches either aggregate information in a lossy way through high-level statistics or produce huge trace files that are hard to handle. We contribute an approach that provides orders of magnitude smaller, if not near-constant size, communication traces regardless of the number of nodes while preserving structural information. We introduce intra- and inter-node compression techniques of MPI events that are capable of extracting an application's communication structure. We further present a replay mechanism for the traces generated by our approach and discuss results of our implementation for BlueGene/L. Given this novel capability, we discuss its impact on communication tuning and beyond. To the best of our knowledge, such a concise representation of MPI traces in a scalable manner combined with deterministic MPI call replay are without any precedent.

Noeth, M; Ratn, P; Mueller, F; Schulz, M; de Supinski, B R

2008-05-16

288

High-energy K{alpha} radiography using high-intensity, short-pulse lasers  

SciTech Connect

The characteristics of 22-40 keV K{alpha} x-ray sources are measured. These high-energy sources are produced by 100 TW and petawatt high-intensity lasers and will be used to develop and implement workable radiography solutions to probe high-Z and dense materials for the high-energy density experiments. The measurements show that the K{alpha} source size from a simple foil target is larger than 60 {mu}m, too large for most radiography applications. The total K{alpha} yield is independent of target thicknesses, verifying that refluxing plays a major role in photon generation. Smaller radiating volumes emit brighter K{alpha} radiation. One-dimensional radiography experiments using small-edge-on foils resolved 10 {mu}m features with high contrast. Experiments were performed to test a variety of small volume two-dimensional point sources such as cones, wires, and embedded wires, measured photon yields, and compared the measurements with predictions from hybrid-particle-in-cell simulations. In addition to high-energy, high-resolution backlighters, future experiments will also need imaging detectors and diagnostic tools that are workable in the high-energy range. An initial look at some of these detector issues is also presented.

Park, H.-S.; Chung, H.-K.; Izumi, N.; Key, M.H.; King, J.A.; Koch, J.A.; Landen, O.L.; Patel, P.K.; Price, D.F.; Remington, B.A.; Robey, H.F.; Snavely, R.A.; Tabak, M.; Town, R.P.J.; Wickersham, J.E. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Chambers, D.M.; Eagleton, R.; Goldsack, T. [Atomic Weapons Establishment, Aldermaston, Reading, RG7 4PR (United Kingdom); Clarke, R.J.; Heathcote, R. [Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX (United Kingdom)] (and others)

2006-05-15

289

A novel high-gain wide-band omnidirectional antenna for satellite communication application  

NASA Astrophysics Data System (ADS)

A novel antenna is proposed in this article, which has simple structure, high gain, wide-band, omni direction and small physical size characteristics. Through optimized design, the maximum gain in omnidirectional plane is 5.0dB, the 3dB beam width in the normal plane >=40°, the absolute VSWR band width of this antenna is 22.2GHz, and the relative VSWR band width is about 73% (VSWR<2), so the antenna can cover the K/Ka band. Because of the merits of the high gain and wide band, this antenna is not just used in the satellite communication, but also in the other domain such as the mobile communication.

Wang, Yonggen

2009-12-01

290

Performance analysis of high altitude platform multi-hop optical communication with non-regenerative system  

NASA Astrophysics Data System (ADS)

Based on non-regenerative relays, the bit error probability expressions of CSI-assisted relay and fixed-gain relays for high altitude platform multi-hop optical communication is given. The effect of the factors, including atmospheric turbulence pointing error and relay node position, on the performance of multi-hop optical links is analyzed. The simulation results show that the influence of atmospheric turbulence on optical links is greater than that of pointing error. The improvement of average SNR per hop and transmit power on multi-hop optical communications may be restricted by pointing error. Compared to CSI-assisted relay, fixed-gain relay is suited to more hops links with the condition of high average SNR per hop.

Wang, Xiang; Zhao, Shang-hong; Shi, Lei; Li, Yong-jun; Zheng, Guang-wei; Zhao, Gu-hao; Zhu, Zi-hang

2013-08-01

291

High-frequency, short-latency disinhibition bursting of midbrain dopaminergic neurons  

PubMed Central

During reinforcement and sequence learning, dopaminergic neurons fire bursts of action potentials. Dopaminergic neurons in vivo receive strong background excitatory and inhibitory inputs, suggesting that one mechanism by which bursts may be produced is disinhibition. Unfortunately, these inputs are lost during slice preparation and are not precisely controlled during in vivo experiments. In the present study we show that dopaminergic neurons can be shifted into a balanced state in which constant synaptic N-methyl-d-aspartate (NMDA) and GABAA conductances are mimicked either pharmacologically or using dynamic clamp. From this state, a disinhibition burst can be evoked by removing the background inhibitory conductance. We demonstrate three functional characteristics of network-based disinhibition that promote high-frequency, short-latency bursting in dopaminergic neurons. First, we found that increasing the total background NMDA and GABAA synaptic conductances increased the intraburst firing frequency and reduced its latency. Second, we found that the disinhibition burst is sensitive to the proportion of background inhibitory input that is removed. In particular, we found that high-frequency, short-latency bursts were enhanced by increasing the degree of disinhibition. Third, the time course over which inhibition is removed had a large effect on the burst, namely, that synchronous removal of weak inhibitory inputs produces bursts of high intraburst frequency and shorter latency. Our results suggest that fast, more precisely timed bursts can be evoked by complete and synchronous disinhibition of dopaminergic neurons in a high-conductance state.

Lobb, Collin J.; Wilson, Charles J.

2011-01-01

292

Characterization of laser diodes under short-pulsed conditions with high pulse energies  

NASA Astrophysics Data System (ADS)

New applications require diode lasers to be driven with short pulses in the sub-micro second range. The goal is to minimize both the cost and size of the diode laser module by minimizing the number of laser bars required while maintaining the lifetime that is desired for the application. Products demanded by the market using such short pulses range from QCW stacks to fiber coupled modules. While many short pulsed applications use high fill factor bars, these bars are not suited for high brightness applications or coupling into small fiber cores. The focus of this work is the analysis of CW diode designs commonly used for high brightness fiber coupled modules under short pulsed conditions. Three key parameters need to be known in order to design a diode laser module that is suited for high peak powers. First is the damage threshold of the facet. The damage threshold determines the maximum power level at which the laser can be operated safely, considering a proper safety margin dependent on application. The damage threshold is a function of the input pulse width and amplitude. The second parameter which is influenced by the drive current is the slow axis divergence of the diode laser. Knowledge of this parameter is critical when designing the system optics. The third parameter is the effective emitter size which may increase with operating current. An increase in emitter size will lead to larger divergences after collimating optics for a given focal length lens and may result in a larger spot when coupling into an optical fiber. All these parameters have to be considered when designing a new product. Presented here is a study on these three critical parameters as a function of operating conditions. Results for different diode designs will be presented. The data presented includes damage thresholds, as well as near field and far field data at various operating currents. A design study for fiber coupled modules with high pulse energies based on the test results will be shown for various wavelengths.

Koenning, Tobias; Hale, Evan; Irwin, David; Alegria, Kim; Patterson, Steve

2013-02-01

293

Design of a high-bandwidth steering mirror for space-based optical communications  

Microsoft Academic Search

A space-based optical communications experiment, developed at Lincoln Laboratory, requires a fast steering mirror as part of its spatial pointing, tracking and acquisition system. The High Bandwidth Steering Mirror version C (HBSM-C), has been designed, built and tested. This device steers a small-aperture mirror of 6 mm about two axes, through an operating range of 25 milliradian and a small-signal

Gregory C. Loney

1992-01-01

294

A space-time coding modem for high-data-rate wireless communications  

Microsoft Academic Search

This paper presents the theory and practice of a new advanced modem technology suitable for high-data-rate wireless communications and presents its performance over a frequency-flat Rayleigh fading channel. The new technology is based on space-time coded modulation (STCM) with multiple transmit and\\/or multiple receive antennas and orthogonal pilot sequence insertion (O-PSI). In this approach, data is encoded by a space-time

Ayman F. Naguib; Vahid Tarokh; Nambirajan Seshadri; A. Robert Calderbank

1998-01-01

295

High-speed serial communication with error correction using 0.25 um CMOS technology  

Microsoft Academic Search

In this paper we propose a novel design for an autonomous high-speed serial off and on-chip communication system which incorporates impedance tuning, error correction with a packet transfer and a parallel asynchronous interface. The constructed transmitter-receiver pair has throughput of 5 Gbit\\/s. With error correction and packet transfer overhead accounted for this construct has bandwidth of 500

Teemu Suutari; Jouni Isoaho; Hannu Tenhunen

2001-01-01

296

A New Class of Block Turbo Code for High Speed Fiber Optic Communication  

NASA Astrophysics Data System (ADS)

In this study, a novel serial concatenated coding scheme (Block Turbo Codes-BTC)-Forward Error Correction (FEC) codes-to mitigate error in high speed (>10 GHz) fiber optic communication is proposed and analyzed through simulation results. With combination of Reed Solomon and Reed Muller component codes-RS (255,223)+RM(1,5) outperform ITU-T G.975 RS (255.239) FEC recommendation with coding gain 1.95-2.00 dB.

Balamuralithara, B.

297

Monolithic 40GHz Mode-Locked MQW DBR Lasers for High-Speed Optical Communication Systems  

Microsoft Academic Search

The state-of-the-art of the development and fabrication of advanced 1.55-mum\\/40-GHz pulse laser modules with a monolithic InP-based mode-locked distributed Bragg reflector (DBR) MQW laser chip inside is reported, with respect to the future applications in high-speed optical communications. We emphasize the latest improvements for hybrid mode-locked devices, which integrate a saturable absorber or an electroabsorption modulator. We further illustrate different

Ronald Kaiser; B. Huttl

2007-01-01

298

A 60 GHz Radio-Over-Fiber Network Architecture for Seamless Communication With High Mobility  

Microsoft Academic Search

We demonstrate a 60 GHz broadband picocellular Radio-over-Fiber network architecture that enables seamless connectivity for highly mobile end-users. Its seamless communication capabilities arise by the supported handover scheme that relies on a novel Moving Extended Cell (MEC) concept. MEC exploits user-centric virtual groups of adjacent cells that transmit the same data content to the user and utilizes a switch mechanism

Nikos Pleros; Konstantinos Vyrsokinos; Kostas Tsagkaris; Nikolaos D. Tselikas

2009-01-01

299

The Cluster File System: Integration of High Performance Communication and I\\/O in Clusters  

Microsoft Academic Search

In this paper, we report on the experiences in designing a portable parallel file system for clusters. The file system offers to the applications an interface compliant with MPI-IO, the I\\/O interface of the MPI-2 standard. The file system implementation relies upon MPI for internal coordination and communication. This guarantees high performance and portability over a wide range of hardware

Rosario Cristaldi; Giulio Iannello; Francesco Delfino

2002-01-01

300

InfoMall: an innovative strategy for high-performance computing and communications applications development  

Microsoft Academic Search

InfoMall is a program led by the Northeast Parallel Architectures Center featuring a partnership of approximately twenty-four organizations with a plan for accelerating development of the High-Performance Computing and Communications (HPCC) software and systems industry. HPCC is a critical technology where the United States has clear international leadership and which will have unprecedented impact on industry, education, society, and defense.

Kim Mills; Geoffrey Fox

1994-01-01

301

Ferroelectric and SiGe device development for high data rate communications  

Microsoft Academic Search

Future broadband wireless communication systems will require hardware that is capable of processing and tuning high RF power microwave signals K-band frequencies. Integration of ferroelectric and SiGe technologies is proposed for developing low-cost hardware that is capable of providing this functionality. Ferroelectric thin film phase shifters demonstrated 140° of analog tuning at 20 GHz, and computer simulations show the feasibility

C. H. Mueller; F. W. Van Keuls; R. R. Romanofsky; F. A. Miranda

2000-01-01

302

Small-angle stability analysis of a linear control system for a high power communication satellite  

NASA Technical Reports Server (NTRS)

A small angle stability analysis is presented for one particular configuration of a high power communication satellite having a linear control system. Both the central body and the solar array are treated as rigid bodies. The control system studied consists of three-axis control of the central body and one-axis control of the solar array rotation relative to the central body. The results yield preliminary indications of the relation of stability to satellite inertias and control gains.

Omalley, T. A.

1972-01-01

303

High-throughput sequencing of Medicago truncatula short RNAs identifies eight new miRNA families  

PubMed Central

Background High-throughput sequencing technology is capable to identify novel short RNAs in plant species. We used Solexa sequencing to find new microRNAs in one of the model legume species, barrel medic (Medicago truncatula). Results 3,948,871 reads were obtained from two separate short RNA libraries generated from total RNA extracted from M. truncatula leaves, representing 1,563,959 distinct sequences. 2,168,937 reads were mapped to the available M. truncatula genome corresponding to 619,175 distinct sequences. 174,504 reads representing 25 conserved miRNA families showed perfect matches to known miRNAs. We also identified 26 novel miRNA candidates that were potentially generated from 32 loci. Nine of these loci produced eight distinct sequences, for which the miRNA* sequences were also sequenced. These sequences were not described in other plant species and accumulation of these eight novel miRNAs was confirmed by Northern blot analysis. Potential target genes were predicted for most conserved and novel miRNAs. Conclusion Deep sequencing of short RNAs from M. truncatula leaves identified eight new miRNAs indicating that specific miRNAs exist in legume species.

Szittya, Gyorgy; Moxon, Simon; Santos, Dulce M; Jing, Runchun; Fevereiro, Manuel PS; Moulton, Vincent; Dalmay, Tamas

2008-01-01

304

Using UDP Datagram to Realize a Distributed Control Mode at High-Speed Data Communication  

NASA Astrophysics Data System (ADS)

This article presents a distributed control mode at high-speed data communication by using UDP datagram based on a dual-port RAM, with the purpose of exploring an efficient, low CPU occupancy, high-speed, reliable and large amounts of data exchange mode. One port of the proposed dual-port RAM mode is connected to local CPU, which can be easily read and write data and the other port is connected to the reading and writing and communication control dedicated logic, which is responsible for organizing, sending, receiving and analyzing UDP datagram and also for completing the tasks of reading and writing dual-port RAM and sending interrupt request to the local processor. This model not only realizes efficient data exchange, but also provides real-time interrupt response mechanism. In this article, it discusses the functional modules required for these functions, describes the composition of the system and the advantages of technical performance. It also analyzes the feasibility of its development, and demonstrates that this model is an advanced, high performance distributed control communication program with great promising.

Zhao, Lindi

305

Implementing Molecular Dynamics for Hybrid High Performance Computers - 1. Short Range Forces  

SciTech Connect

The use of accelerators such as general-purpose graphics processing units (GPGPUs) have become popular in scientific computing applications due to their low cost, impressive floating-point capabilities, high memory bandwidth, and low electrical power requirements. Hybrid high performance computers, machines with more than one type of floating-point processor, are now becoming more prevalent due to these advantages. In this work, we discuss several important issues in porting a large molecular dynamics code for use on parallel hybrid machines - 1) choosing a hybrid parallel decomposition that works on central processing units (CPUs) with distributed memory and accelerator cores with shared memory, 2) minimizing the amount of code that must be ported for efficient acceleration, 3) utilizing the available processing power from both many-core CPUs and accelerators, and 4) choosing a programming model for acceleration. We present our solution to each of these issues for short-range force calculation in the molecular dynamics package LAMMPS. We describe algorithms for efficient short range force calculation on hybrid high performance machines. We describe a new approach for dynamic load balancing of work between CPU and accelerator cores. We describe the Geryon library that allows a single code to compile with both CUDA and OpenCL for use on a variety of accelerators. Finally, we present results on a parallel test cluster containing 32 Fermi GPGPUs and 180 CPU cores.

Brown, W Michael [ORNL] [ORNL; Wang, Peng [NVIDIA, Santa Clara, CA] [NVIDIA, Santa Clara, CA; Plimpton, Steven J [ORNL] [ORNL; Tharrington, Arnold N [ORNL] [ORNL

2011-01-01

306

High nitrogen removal rate using ANAMMOX process at short hydraulic retention time.  

PubMed

The anaerobic ammonium oxidation (ANAMMOX) is a chemolithoautotrophic process, which converts NH(4)(+) to N(2) using nitrite (NO(2)(-)) as the electron acceptor. This process has very high nitrogen removal rates (NRRs) and is an alternative to classical nitrification/denitrification wastewater treatment. In the present work, a strategy for nitrogen removal using ANAMMOX process was tested evaluating their performance when submitted to high loading rates and very short hydraulic retention times (HRTs). An up-flow ANAMMOX column reactor was inoculated with 30% biomass (v v(-1)) fed from 100 to 200 mg L(-1) of total N (NO(2)(-)-N + NH(4)(+)-N) at 35 °C. After start-up and process stability the maximum NRR in the up-flow anaerobic sludge blanket (UASB) reactor was 18.3 g-N L(-1) d(-1) operated at 0.2 h of HRT. FISH (fluorescence in situ hybridization) analysis and process stoichiometry confirmed that ANAMMOX was the prevalent process for nitrogen removal during the experiments. The results point out that high NRRs can be obtained at very short HRTs using up-flow ANAMMOX column reactor configuration. PMID:23416586

Casagrande, C G; Kunz, A; De Prá, M C; Bressan, C R; Soares, H M

2013-01-01

307

High Energy K(alpha) Radiography Using High-intensity, Short-pulse Lasers  

SciTech Connect

We have performed experiments using Callisto, the Vulcan 100 TW and the Vulcan Petawatt high intensity lasers to understand the characteristics of high energy, K{alpha} x-ray sources and to implement workable radiography solutions at 20-100 keV. Our measurements show that the K{alpha} size from a simple foil target is larger than 60 {micro}m, far larger than the experiment resolution requirement. The total K{alpha} yield is independent of target thicknesses verifying that refluxing plays a major role in photon generation. Smaller radiating volumes emit brighter K{alpha} radiation. 1-D radiography experiments using small-edge-on foils resolved 10 {micro}m features with high contrast. We tested a variety of small volume 2-D point sources such as cones, wires, and embedded wires, measuring photon yields and comparing our measurements with predictions from hybrid-PIC LSP simulations. In addition to high-energy, high-resolution backlighters, future experiments will also need imaging detectors and diagnostic tools that are workable in the 20-100 keV energy range. An initial look at some of these detector issues is also presented.

Park, H; Izumi, N; Key, M H; King, J A; Koch, J A; Landen, O L; Patel, P K; Price, D F; Remington, B A; Robey, H F; Snavely, R A; Tabak, M; Town, R J; Wickersham, J E; Stoeckl, C; Storm, M; Theobald, W; Chambers, D M; Eagelton, R; Goldsack, T; Clarke, R J; Heathcote, R; Giraldez, E; Nikroo, A; Steinman, D A; Stephens, R B; Zhang, B B

2005-11-16

308

Development of data communication system with ultra high frequency radio wave for implantable artificial hearts.  

PubMed

In order to minimize infection risks of patients with artificial hearts, wireless data transmission methods with electromagnetic induction or light have been developed. However, these methods tend to become difficult to transmit data if the external data transmission unit moves from its proper position. To resolve this serious problem, the purpose of this study is to develop a prototype wireless data communication system with ultra high frequency radio wave and confirm its performance. Due to its high-speed communication rate, low power consumption, high tolerance to electromagnetic disturbances, and secure wireless communication, we adopted Bluetooth radio wave technology for our system. The system consists of an internal data transmission unit and an external data transmission unit (53 by 64 by 16 mm, each), and each has a Bluetooth module (radio field intensity: 4 dBm, receiver sensitivity: -80 dBm). The internal unit also has a micro controller with an 8-channel 10-bit A/D converter, and the external unit also has a RS-232C converter. We experimented with the internal unit implanted into pig meat, and carried out data transmission tests to evaluate the performance of this system in tissue thickness of up to 3 mm. As a result, data transfer speeds of about 20 kbps were achieved within the communication distance of 10 m. In conclusion, we confirmed that the system can wirelessly transmit the data from the inside of the body to the outside, and it promises to resolve unstable data transmission due to accidental movements of an external data transmission unit. PMID:19964616

Tsujimura, Shinichi; Yamagishi, Hiroto; Sankai, Yoshiyuki

2009-01-01

309

Improvement of short tandem repeat analysis of samples highly contaminated by humic acid.  

PubMed

We investigated several methods for obtaining successful short tandem repeat (STR) results from high-humic acid (HA)-content samples. DNA purification efficiency was tested for QIAquick(®) PCR Purification, QIAamp(®) DNA Investigator and Prepfiler™ Forensic DNA Extraction kits. HA-removal capacity of Inhibitor Remover and InhibitEX(®) Tablet was tested. Experiments on overcoming HA effects on STR amplification were conducted using an AmpliTaq Gold(®) DNA Polymerase and a TaKaRa Ex Taq™ Hot Start Version (Ex Taq HS) with BSA addition. QIAquick kit was most efficient in HA removal and Ex Taq HS showed high resistance to HA. Increasing the amounts of Taq polymerases and BSA addition were shown to be efficient in overcoming PCR inhibition, but BSA addition was superior to the former method. Inhibitor Remover and InhibitEX(®) Tablet did not positively affect the STR results. This study will help achieve better STR results with high-HA-content samples. PMID:24112347

Seo, Seung Bum; Jin, Hong Xuan; Lee, Hye Young; Ge, Jianye; King, Jonathan L; Lyoo, Sung Hee; Shin, Dong Hoon; Lee, Soong Deok

2013-10-01

310

High-energy laser-pulse self-compression in short gas-filled fibers  

NASA Astrophysics Data System (ADS)

We examine the spatiotemporal compression of energetic femtosecond laser pules within short gas-filled fibers. The study is undertaken using an advanced nonlinear pulse propagation model based on a multimode generalized nonlinear Schrödinger equation that has been modified to include plasma effects. Plasma defocusing and linear propagation effects are shown to be the dominant processes within a highly dynamical mechanism that enables 100-fs pulses to be compressed into the few-cycle regime after <50mm of propagation. Once the mechanism has been introduced, parameter spaces are explored and compressor designs suitable for performing high-field experiments in situ are presented. We finish by showing how these designs may be extended to novel wavelengths and driving pulses delivered by state-of-the-art high-repetition-rate lasers.

Anderson, P. N.; Horak, P.; Frey, J. G.; Brocklesby, W. S.

2014-01-01

311

Goal-Oriented Communication: A CBO Technique with High Management Payback.  

ERIC Educational Resources Information Center

Discusses communication by objectives, a strategy that extends management by objectives techniques into the area of communication to strengthen ties between decision making and decision communicating. Discusses its classroom application. (FL)

Myrsiades, Linda S.

1984-01-01

312

The Relative Importance of Selected Communication Skills for Adolescents' Interactions with Their Teachers: High School Teachers' Opinions.  

ERIC Educational Resources Information Center

High school teachers (n=143) ranked 14 communication skills according to the perceived order of importance for Grade 10 adolescents' communication with them as teachers. Teachers tended to perceive skills associated with discourse management strategies as relatively more important than other skills. Science teachers ranked turn taking higher than…

Reed, Vicki A.; Spicer, Lynette

2003-01-01

313

Performance analysis of the TCP\\/IP protocol under UNIX operating systems for high performance computing and communications  

Microsoft Academic Search

Among many protocols, the TCP\\/IP protocol suite is the most widely used form of networking computers. With the advent of high-speed communication paradigms such as asynchronous transfer mode (ATM) and the advances of transmission media technologies such as optical fibers, the physical transmission medium is no longer the performance bottleneck in communication systems. Thus, transport layers are currently receiving much

Kyok Kim; Hongki Sung; Hoonbock Lee

1997-01-01

314

Performance Analysis of the TCP\\/IP Protocol Under Unix Operating System for High Performance Computing and Communications  

Microsoft Academic Search

Among many protocols, the TCP\\/IP protocol suite is the most widely used form of networking comput- ers. With the advent of high speed communication paradigms such as asynchronous transfer mode, as well as with the advances of transmission medium technologies such as optical bers, the physical trans- mission medium is no longer the performance bottle- neck in communication systems. Thus,

Hyok Kim; Hongki Sung; Hoonbock Lee

2002-01-01

315

Feasibility study on radio communications using high altitude radio platform in the stratosphere - Applicability to mobile radio and coverage performance  

Microsoft Academic Search

It is possible that a platform, powered by microwaves beamed from the earth, carrying radio equipment and flying in the stratosphere, could be used for radio relay such as satellite communications, terrestrial microwave radio relay, land mobile base stations. In the Communication Research Laboratory, feasibility studies were started in 1989 on application of the high altitude radio platform (HARP) to

Taiji Saruwatari

1991-01-01

316

Improving Switching Performance of Power MOSFETs Used in High Rep-Rate, Short Pulse, High-Power Pulsers  

SciTech Connect

As their switching and power handling characteristics improve, solid-state devices are finding new applications in pulsed power. This is particularly true of applications that require fast trains of short duration pulses. High voltage (600-1200V) MOSFETs are especially well suited for use in these systems, as they can switch at significant peak power levels and are easily gated on and off very quickly. MOSFET operation at the shortest pulse durations is not constrained by the intrinsic capabilities of the MOSFET, but rather by the capabilities of the gate drive circuit and the system physical layout. This project sought to improve MOSFET operation in a pulsed power context by addressing these issues. The primary goal of this project is to improve the switching performance of power MOSFETs for use in high rep-rate, short pulse, high-power applications by improving the design of the gate drive circuits and the circuit layouts used in these systems. This requires evaluation of new commercial gate drive circuits and upgrading the designs of LLNL-developed circuits. In addition, these circuits must be tested with the fastest available high-voltage power MOSFETs.

Cook, E G

2006-09-19

317

Specification of minimum short circuit capacity for three-phase unbalance evaluation of high-speed railway power system  

Microsoft Academic Search

In the paper, firstly, we present an efficient computational algorithm to evaluate the short circuit capacity distribution at a substation bus, and on the basis of this distribution to specify the minimum short circuit capacity for the year under evaluation. Secondly, we estimate the maximum traction load at seven 161 kV substations of Taiwan high-speed railway system which is now

Shi-Lin Chen; Fu-Chien Kao; Tsung-Ming Lee

1995-01-01

318

Incorporating risk communication into highly pathogenic avian influenza preparedness and response efforts.  

PubMed

A highly pathogenic avian influenza (HPAI) outbreak in the United States will initiate a federal emergency response effort that will consist of disease control and eradication efforts, including quarantine and movement control measures. These movement control measures will not only apply to live animals but also to animal products. However, with current egg industry "just-in-time" production practices, limited storage is available to hold eggs. As a result, stop movement orders can have significant unintended negative consequences, including severe disruptions to the food supply chain. Because stakeholders' perceptions of risk vary, waiting to initiate communication efforts until an HPAI event occurs can hinder disease control efforts, including the willingness of producers to comply with the response, and also can affect consumers' demand for the product. A public-private-academic partnership was formed to assess actual risks involved in the movement of egg industry products during an HPAI event through product specific, proactive risk assessments. The risk analysis process engaged a broad representation of stakeholders and promoted effective risk management and communication strategies before an HPAI outbreak event. This multidisciplinary team used the risk assessments in the development of the United States Department of Agriculture, Highly Pathogenic Avian Influenza Secure Egg Supply Plan, a comprehensive response plan that strives to maintain continuity of business. The collaborative approach that was used demonstrates how a proactive risk communication strategy that involves many different stakeholders can be valuable in the development of a foreign animal disease response plan and build working relationships, trust, and understanding. PMID:23402134

Voss, Shauna J; Malladi, Sasidhar; Sampedro, Fernando; Snider, Tim; Goldsmith, Timothy; Hueston, William D; Lauer, Dale C; Halvorson, David A

2012-12-01

319

High speed QPPM direct detection optical communication receivers for FSDD intersatellite links  

NASA Technical Reports Server (NTRS)

This final report consists of four separate reports, one for each project involved in this contract. The first report is entitled '325 Mbps QPPM (quaternary pulse position modulation) Direct Detection Free Space Optical Communication Encoder and Receiver,' which was our primary work. The second report is entitled 'Test Results of the 325 Mbps QPPM High Speed Data Transmission GaAs ASICs,' which describes our work in connection with Galaxy Microsystems, Inc. who produced these ASICs for NASA. The third report, 'Receiver Performance Analysis of BPPM Optical Communication Systems Using 1.3 micron Wavelength Transmitter and InGaAs PIN Photodiodes,' was prepared at the request of the NASA/Photonics Branch for their efforts in upgrading the 1773 optical fiber data bus. The fourth report, 'Photomultiplier Tubes for Use at 1.064 micron Wavelength,' was also prepared at the request of the NASA/Photonics Branch as a research project.

Davidson, Frederic M.; Sun, Xiaoli

1993-01-01

320

An historical review of application of optical solitons for high speed communications.  

PubMed

The history of application of optical solitons for high speed communications presents an interesting example of how an abstract mathematical concept has been put into practical use. The historical development introduced in this manuscript is divided into five stages: (1) historical background and the discovery of the optical soliton, (2) the idea and demonstration of all optical soliton transmission systems, (3) identification of possible problems, (4) demonstration of soliton control and (5) discovery of dispersion managed optical solitons (DMS). Although there are many interesting related subjects such as modulational instability, dark solitons, and spatial solitons, the manuscript focuses only on the subject of primarily theoretical developments of soliton based communications in fibers. (c) 2000 American Institute of Physics. PMID:12779400

Hasegawa, Akira

2000-09-01

321

High energy, short pulse fiber laser front end for kilo-Joule class CPA systems  

NASA Astrophysics Data System (ADS)

We are developing an all fiber laser system optimized for providing input pulses for short pulse (1-10ps), high energy (~1kJ) glass laser systems. Fiber lasers are ideal solutions for these systems as they are highly reliable and enable long term stable operation. The design requirements for this application are very different than those commonly seen in fiber lasers. High-energy lasers often have low repetition rates (as low as one pulse every few hours), and thus high average power and efficiency are of little practical value. What is of high value is pulse energy, high signal to noise ratio (expressed as pre-pulse contrast), good beam quality, consistent output parameters and timing. Our system focuses on optimizing these parameters. Our prototype system consists of a mode-locked fiber laser, a compressed pulse fiber amplifier, a "pulse cleaner", a chirped fiber Bragg grating, pulse selectors, a transport fiber system and a large mode area fiber amplifier. We will review the system and present theoretical and experimental studies of critical aspects, in particular the requirement for high pre-pulse contrast.

Dawson, J. W.; Mitchell, S.; Beach, R. J.; Messerly, M. J.; Siders, C. W.; Phan, H.; Barty, C. P. J.

2006-03-01

322

Compensation performance of decision feedback equalizer in high speed optical communication system  

NASA Astrophysics Data System (ADS)

This paper discusses electronics dispersion compensation (EDC) by decision feedback equalizer (DFE) in high speed optical communication system using the LMS and the RLS algorithms, respectively. The theory of the decomposed DFE derived from basic concept of DFE in EDC is studied. Compared with the traditional DFE, the system complexity of new one has been reduced while it still keeps the high performance of DFE. Simulation results prove the validity of practicability and indicate that the decomposed DFE using RLS algorithm can more effectively eliminate intersymbol interference (ISI) after being transmitted long distance.

Lu, Li; Lei, Jianming; Bing, Linlin; Zou, Xuecheng

2008-11-01

323

Tissue integrity signals communicated by high-molecular weight hyaluronan and the resolution of inflammation  

PubMed Central

The extracellular matrix polysaccharide hyaluronan (HA) exerts size-dependent effects on leukocyte behavior. Low-molecular weight HA is abundant at sites of active tissue catabolism and promotes inflammation via effects on Toll-like receptor signaling. Conversely, high-molecular weight HA is prevalent in uninjured tissues and is anti-inflammatory. We propose that the ability of high-molecular weight but not low-molecular weight HA to cross-link CD44 functions as a novel form of pattern recognition that recognizes intact tissues and communicates “tissue integrity signals” that promote resolution of local immune responses.

Ruppert, S. M.; Hawn, T. R.; Arrigoni, A.; Wight, T. N.

2014-01-01

324

Noninvasive epileptic seizure localization from stochastic behavior of short duration interictal high density scalp EEG data.  

PubMed

The stochastic behavior of the phase synchronization index (SI) in different EEG bands was examined for noninvasive localization of the epileptogenic areas from the short duration (30-60 s), seizure-free and spike-free high density (256 channel) scalp EEG data. We also examined the cross-frequency and cross-electrode coupling in different EEG bands. EEG data of four subjects was used. The seizure areas were localized with subdural recordings with an 8×8 grid electrode array. It was found that the stochastic behavior of the SI in low gamma band (30-50 Hz) was higher in epileptogenic areas. The beta (12-30 Hz) band also showed similar tendencies. The stochastic behavior in theta (3-7 Hz) band was depressed in the seizure area while it was widespread in large areas over the scalp in the alpha (7-12 Hz) band. The stochastic behavior of the cross-frequency and cross-electrode couplings in theta-gamma, alpha-gamma and beta-gamma bands were decreased in the seizure areas for all four subjects. These findings suggest that it is possible to localize the epileptogenic areas from the short duration seizure-free and spike-free high density scalp EEG data. PMID:21644027

Ramon, Ceon; Holmes, Mark D

2012-01-01

325

High-Speed Imaging of Short Wind Waves by Shape from Refraction  

NASA Astrophysics Data System (ADS)

This paper introduces the first high-speed system for slope imaging of wind-induced short water waves. The imaging slope gauge method is used, which is based on the shape from refraction principle. The downward looking camera with a telecentric lens observes the refraction of light rays coming from a high power custom telecentric LED light source that is placed underneath the wind wave facility. The light source can be programmed to arbitrary intensity gradients in the x- and y-direction, so that the origin of a light ray is coded in intensity. Four gradient images (acquired at 6000 fps) are combined for one 2D slope image. By only using intensity ratios, the measurements become independent of lens effects from the curved water surface and inhomogeneities in the light source. Independence of wave height is guaranteed by using telecentric illumination and telecentric imaging. The system is capable to measure the slopes of a wind-driven water surface in the Heidelberg Aeolotron wind-wave facility on a footprint of 200 x 160 mm with a spatial resolution of 0.22 mm and a temporal resolution of more than 1500 fps. For the first time, it is now possible to investigate the structure of short wind-induced waves with sufficient spatial and temporal resolution to study their dynamic characteristics without aliasing effects. Example images and a video of a 3D reconstructed water surface are shown to illustrate the principle.

Kiefhaber, D.; Reith, S.; Rocholz, R.; Jähne, B.

2014-03-01

326

Directly draw highly nonlinear tellurite microstructured fiber with diameter varying sharply in a short fiber length.  

PubMed

We demonstrate theoretically and experimentally that it is feasible to draw the microstructured fiber with longitudinally varying diameter (FLVD) whose diameter varies sharply in a short fiber length. It is elucidated that during the fiber drawing process the tension is linearly proportional to the natural logarithm of the fiber drawing speed. As a result, the tension is not so sensitive to the fiber diameter. Moreover, this sensitivity can be decreased by using a large diameter ratio of preform to fiber. Owing to the low sensitivity the FLVD with diameter varying sharply in a short fiber length can be drawn directly from the preform. Additionally we show that the microstructural geometry of FLVD does not depend on the varying diameter. The deformation in microstructural geometry is determined by the fiber segment with the smallest diameter. We fabricate a FLVD of which the diameter decreases by 75% in a fiber length of 10 cm. By using this fiber we demonstrate the 600-1800 nm supercontinuum (SC) generation and the 532 nm second harmonic generation pumped by a picosecond fiber laser. The SC spectra by the conventional fibers with the largest and the smallest diameters of the FLVD are also shown, respectively. The comparisons show that the FLVD has the broadest SC spectrum due to its high nonlinearity, varying dispersion, and high damage threshold. PMID:22274459

Liao, Meisong; Gao, Weiqing; Duan, Zhongchao; Yan, Xin; Suzuki, Takenobu; Ohishi, Yasutake

2012-01-16

327

Laser driven proton beam for the applications: toward ultra-high intensity & short pulse proton beam  

NASA Astrophysics Data System (ADS)

As a benchmark experiment to realize a novel and compact laser driven proton accelerator whose significant features are high number density in a short pulse width (~ns), 2.4 MeV laser driven proton beam is stably focused at 1 Hz repetition rate by using a pair of permanent quadrupole magnets (PMQs) with large apertures whose diameters and field strengths are 3.5 cm and 55 T/m for the first and 2.3 cm and 60 T/m for the second magnets, respectively. The proton beam has been focused to a focal spot of 3×8 mm2 in horizontal and vertical direction (full width at half maximum) at 650~mm from the source, which is well reproduced by the simulation. The further optimization of the focusing system will sure to pave a way to the novel proton accelerator with which we can investigate the physics appeared in the short time scale as well as that in a high energy density matter, oncology, astrophysics, and so on.

Nishiuchi, M.; Daido, H.; Daito, I.; Ikegami, M.; Mori, M.; Orimo, S.; Ogura, K.; Sagisaka, A.; Yogo, A.; Pirozhkov, A. S.; Sugiyama, H.; Kiriyama, H.; Okada, H.; Kanazawa, S.; Kondo, S.; Shimomura, T.; Tanoue, M.; Nakai, Y.; Sasao, H.; Wakai, D.; Sakaki, H.; Hori, T.; Bolton, P.; Choi, I. W.; Sung, J. H.; Lee, J.; Oishi, Y.; Fujii, T.; Nemoto, K.; Souda, H.; Noda, A.; Iseki, Y.; Yoshiyuki, T.

2009-07-01

328

Short-read, high-throughput sequencing technology for STR genotyping.  

PubMed

DNA-based methods for human identification principally rely upon genotyping of short tandem repeat (STR) loci. Electrophoretic-based techniques for variable-length classification of STRs are universally utilized, but are limited in that they have relatively low throughput and do not yield nucleotide sequence information. High-throughput sequencing technology may provide a more powerful instrument for human identification, but is not currently validated for forensic casework. Here, we present a systematic method to perform high-throughput genotyping analysis of the Combined DNA Index System (CODIS) STR loci using short-read (150 bp) massively parallel sequencing technology. Open source reference alignment tools were optimized to evaluate PCR-amplified STR loci using a custom designed STR genome reference. Evaluation of this approach demonstrated that the 13 CODIS STR loci and amelogenin (AMEL) locus could be accurately called from individual and mixture samples. Sensitivity analysis showed that as few as 18,500 reads, aligned to an in silico referenced genome, were required to genotype an individual (>99% confidence) for the CODIS loci. The power of this technology was further demonstrated by identification of variant alleles containing single nucleotide polymorphisms (SNPs) and the development of quantitative measurements (reads) for resolving mixed samples. PMID:22668513

Bornman, Daniel M; Hester, Mark E; Schuetter, Jared M; Kasoji, Manjula D; Minard-Smith, Angela; Barden, Curt A; Nelson, Scott C; Godbold, Gene D; Baker, Christine H; Yang, Boyu; Walther, Jacquelyn E; Tornes, Ivan E; Yan, Pearlly S; Rodriguez, Benjamin; Bundschuh, Ralf; Dickens, Michael L; Young, Brian A; Faith, Seth A

2012-04-01

329

Method of high speed flow field influence and restrain on laser communication  

NASA Astrophysics Data System (ADS)

For laser communication performance which carried by airplane or airship, due to high-speed platform movement, the air has two influences in platform and laser communication terminal window. The first influence is that aerodynamic effect causes the deformation of the optical window; the second one is that a shock wave and boundary layer would be generated. For subsonic within the aircraft, the boundary layer is the main influence. The presence of a boundary layer could change the air density and the temperature of the optical window, which causes the light deflection and received beam spot flicker. Ultimately, the energy hunting of the beam spot which reaches receiving side increases, so that the error rate increases. In this paper, aerodynamic theory is used in analyzing the influence of the optical window deformation due to high speed air. Aero-optics theory is used to analyze the influence of the boundary layer in laser communication link. Based on this, we focused on working on exploring in aerodynamic and aero-optical effect suppression method in the perspective of the optical window design. Based on planning experimental aircraft types and equipment installation location, we optimized the design parameters of the shape and thickness of the optical window, the shape and size of air-management kit. Finally, deformation of the optical window and air flow distribution were simulated by fluid simulation software in the different mach and different altitude fly condition. The simulation results showed that the optical window can inhibit the aerodynamic influence after optimization. In addition, the boundary layer is smoothed; the turbulence influence is reduced, which meets the requirements of the airborne laser communication.

Meng, Li-xin; Wang, Chun-hui; Qian, Cun-zhu; Wang, Shuo; Zhang, Li-zhong

2013-08-01

330

Molecular communication: Harnessing biochemical materials to engineer biomimetic communication systems  

Microsoft Academic Search

Molecular communication uses molecules (i.e., biochemical signals) as an information medium and allows biologically and artificially created nano- or microscale entities to communicate over a short distance. It is a new communication paradigm; it is different from the traditional communication paradigm, which uses electromagnetic waves (i.e., electronic and optical signals) as an information medium. Key research challenges in molecular communication

Satoshi Hiyama; Yuki Moritani

2010-01-01

331

Core Communications  

ERIC Educational Resources Information Center

The website--it is where people go to find out anything and everything about a school, college, or university. In the relatively short life of the Internet, institutional websites have moved from the periphery to center stage and become strategically integral communications and marketing tools. As the flow of information accelerates and new…

Block, Greg; Ross, J. D.; Mulder, David

2011-01-01

332

Fiber Laser Front Ends for High-Energy Short Pulse Lasers  

SciTech Connect

We are developing an all fiber laser system optimized for providing input pulses for short pulse (1-10ps), high energy ({approx}1kJ) glass laser systems. Fiber lasers are ideal solutions for these systems as they are highly reliable and once constructed they can be operated with ease. Furthermore, they offer an additional benefit of significantly reduced footprint. In most labs containing equivalent bulk laser systems, the system occupies two 4'x8' tables and would consist of 10's if not a 100 of optics which would need to be individually aligned and maintained. The design requirements for this application are very different those commonly seen in fiber lasers. High energy lasers often have low repetition rates (as low as one pulse every few hours) and thus high average power and efficiency are of little practical value. What is of high value is pulse energy, high signal to noise ratio (expressed as pre-pulse contrast), good beam quality, consistent output parameters and timing. Our system focuses on maximizing these parameters sometimes at the expense of efficient operation or average power. Our prototype system consists of a mode-locked fiber laser, a compressed pulse fiber amplifier, a ''pulse cleaner'', a chirped fiber Bragg grating, pulse selectors, a transport fiber system and a large flattened mode fiber amplifier. In our talk we will review the system in detail and present theoretical and experimental studies of critical components. We will also present experimental results from the integrated system.

Dawson, J W; Liao, Z M; Mitchell, S; Messerly, M; Beach, R; Jovanovic, I; Brown, C; Payne, S A; Barty, C J

2005-01-18

333

High-quality detection in heavy-traffic avionic communication system using interference cancellation techniques  

NASA Astrophysics Data System (ADS)

This dissertation focuses on quantifying the effects of multi-user co-channel interference for an avionic communication system operating in a heavy-traffic aeronautical mobile environment and proposes advanced interference cancellation techniques to mitigate the interference. The dissertation consists of two parts. The first part of the work investigates the use of a visualization method to quantify and characterize the multi-user co-channel interference (multiple access interference) effects impinging on an avionic communication system. The interference is caused by complex interactions of thousands of RF signals transmitted from thousands of aircraft; each attempts to access a common communication channel, which is governed by a specific channel contention access protocol. The visualization method transforms the co-channel interference, which is specified in terms of signal-overlaps (signal collisions), from a visual representation to a matrix representation for further statistical analysis. It is found that the statistical Poisson and its cumulative distribution provide the best estimates of multi-user co-channel interference. It is shown, using Monte Carlo simulation, that the co-channel interference of a victim aircraft operating in the heavy-traffic environment could result in as high as eight signal-overlaps. This constitutes to approximately 83.4% of success rate in signal detection for the entire three thousand aircraft environment using conventional FSK receiver. One key finding shows that high-quality communications, up to 98.5% success rate, is achievable if only three overlapping signals can be decoded successfully. The interference results found in the first part set the stage for interference cancellation research in the second part. The second part of the work proposes the use of advanced interference cancellation techniques, namely sequential interference cancellation (SIC) and parallel interference cancellation (PIC), as potential solutions to mitigating the interference effects. These techniques can be implemented in radio receivers to perform multi-signal decoding functionality to remove the required interferers (three overlapping signals) so that high-quality communication, as described in the first part, can be achieved. Various performance graphs are shown for B-FSK and B-PSK for both SIC and PIC techniques. One key finding is that the system performance can be improved substantially to an additional 15% in signal reception success rate by using SIC or PIC. This means that critical information transmitted from 450 aircraft (out of approximately three thousand aircraft in the environment) is preserved and successfully decoded. Multi-signal decoding using these interference cancellation receivers comes at a small penalty of 2 - 4.5 dBs in Eb/No when sufficient signal-to-interference (SIR) ratio (7-12 dB) is provided.

Nguyen, Anh-Minh Ngoc

334

Induction and decay of short-term heat acclimation in moderately and highly trained athletes.  

PubMed

A rethinking of current heat-acclimation strategies is required as most research and advice for improving physiological strain in the heat includes maintaining hydration using long-term acclimation protocols (>10 days). Furthermore, these strategies have tended to use untrained and moderately trained participants. Therefore, the aims of this review were to (i) investigate the effectiveness of short-term heat acclimation (STHA) with moderately and highly trained athletes; (ii) determine the importance of fluid regulatory strain, which has a thermally independent role in heat adaptation; (iii) assess the impact of STHA on a marker of thermotolerance (inducible heat-shock protein 70 [HSP70]); and (iv) provide further information on the decay of acclimation to heat. The review suggests that 5-day STHA is effective, and adaptations may be more pronounced after fluid regulatory strain from a dehydration-acclimation regimen. Furthermore, highly trained athletes may have similar physiological gains to those who are less trained using STHA. However, research has tended to focus on untrained or moderately trained participants and more information is required for highly trained populations. HSP70 response is upregulated across STHA. This indicates increased thermotolerance and protective adaptive change that may indicate HSP70 response as a useful marker of heat acclimation. Physiological adaptations after heat acclimation are relatively short term and may vanish only a few days or weeks after removal from heat exposure. From a practical perspective 5-day STHA may be the preferred acclimation regimen for moderately and highly trained athletes as it has been shown to be effective, less expensive and less likely to disrupt the tapering for competition in elite performers. Furthermore, updated information on the time course of acclimation decay may allow a reliable estimate of how long individuals can be free from heat exposure before reacclimation is required. This is particularly pertinent in present times as many athletes, civilians and military personnel increasingly have to relocate to different climates of the world, often within a short period of time. PMID:21846164

Garrett, Andrew T; Rehrer, Nancy J; Patterson, Mark J

2011-09-01

335

A highly reliable, autonomous data communication subsystem for an advanced information processing system  

NASA Technical Reports Server (NTRS)

The need to meet the stringent performance and reliability requirements of advanced avionics systems has frequently led to implementations which are tailored to a specific application and are therefore difficult to modify or extend. Furthermore, many integrated flight critical systems are input/output intensive. By using a design methodology which customizes the input/output mechanism for each new application, the cost of implementing new systems becomes prohibitively expensive. One solution to this dilemma is to design computer systems and input/output subsystems which are general purpose, but which can be easily configured to support the needs of a specific application. The Advanced Information Processing System (AIPS), currently under development has these characteristics. The design and implementation of the prototype I/O communication system for AIPS is described. AIPS addresses reliability issues related to data communications by the use of reconfigurable I/O networks. When a fault or damage event occurs, communication is restored to functioning parts of the network and the failed or damage components are isolated. Performance issues are addressed by using a parallelized computer architecture which decouples Input/Output (I/O) redundancy management and I/O processing from the computational stream of an application. The autonomous nature of the system derives from the highly automated and independent manner in which I/O transactions are conducted for the application as well as from the fact that the hardware redundancy management is entirely transparent to the application.

Nagle, Gail; Masotto, Thomas; Alger, Linda

1990-01-01

336

A highly reliable, autonomous data communication subsystem for an advanced information processing system  

NASA Astrophysics Data System (ADS)

The need to meet the stringent performance and reliability requirements of advanced avionics systems has frequently led to implementations which are tailored to a specific application and are therefore difficult to modify or extend. Furthermore, many integrated flight critical systems are input/output intensive. By using a design methodology which customizes the input/output mechanism for each new application, the cost of implementing new systems becomes prohibitively expensive. One solution to this dilemma is to design computer systems and input/output subsystems which are general purpose, but which can be easily configured to support the needs of a specific application. The Advanced Information Processing System (AIPS), currently under development has these characteristics. The design and implementation of the prototype I/O communication system for AIPS is described. AIPS addresses reliability issues related to data communications by the use of reconfigurable I/O networks. When a fault or damage event occurs, communication is restored to functioning parts of the network and the failed or damage components are isolated. Performance issues are addressed by using a parallelized computer architecture which decouples Input/Output (I/O) redundancy management and I/O processing from the computational stream of an application. The autonomous nature of the system derives from the highly automated and independent manner in which I/O transactions are conducted for the application as well as from the fact that the hardware redundancy management is entirely transparent to the application.

Nagle, Gail; Masotto, Thomas; Alger, Linda

1990-04-01

337

Characteristics of high energy K{alpha} and Bremsstrahlung sources generated by short pulse petawatt lasers  

SciTech Connect

We have measured the characteristics of high energy K{alpha} sources created with the Vulcan Petawatt laser at RAL and the JanUSP laser at Lawrence Livermore National Laboratory. High energy x-ray backlighters will be essential for radiographing high energy-density experimental science targets for NIF projects especially to probe implosions and high areal density planar samples. Hard K{alpha} x-ray photons are created through relativistic electron plasma interactions in the target material after irradiated by short pulse high intensity lasers. For our Vulcan experiment, we employed a CsI scintillator charge coupled device (CCD) camera for imaging and a CCD camera for single photon counting. We have directly measured the 22 keV Ag K{alpha} source size using the RAL petawatt laser and performed knife-edge measurements of a 40 keV Sm K{alpha} source using the JanUSP laser. The measured source sizes are both {approx}60 {mu}m full width half maximum. We have also measured the Ag K{alpha} conversion efficiencies. At laser intensities of 1x10{sup 18} W/cm{sup 2} range, the conversion efficiency at 22 keV is {approx}1x10{sup -4}.

Park, H.-S.; Izumi, N.; Key, M.H.; Koch, J.A.; Landen, O.L.; Patel, P.K.; Phillips, T.W.; Zhang, B.B. [University of California, Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); University of California, Davis, California 95616 (United States)

2004-10-01

338

Sample stacking capillary electrophoretic microdevice for highly sensitive mini Y short tandem repeat genotyping.  

PubMed

Lab-on-a-chip provides an ideal platform for short tandem repeat (STR) genotyping due to its intrinsic low sample consumption, rapid analysis, and high-throughput capability. One of the challenges, however, in the forensic human identification on the microdevice is the detection sensitivity derived from the nanoliter volume sample handling. To overcome such a sensitivity issue, here we developed a sample stacking CE microdevice for mini Y STR genotyping. The mini Y STR includes redesigned primer sequences to generate smaller-sized PCR amplicons to enhance the PCR efficiency and the success rate for a low copy number and degraded DNA. The mini Y STR amplicons occupied in the 5- and 10-mm stacking microchannels are preconcentrated efficiently in a defined narrow region through the optimized sample stacking CE scheme, resulting in more than tenfold improved fluorescence peak intensities compared with that of a conventional cross-injection microcapillary electrophoresis method. Such signal enhancement allows us to successfully analyze the Y STR typing with only 25?pg of male genomic DNA, with high background of female genomic DNA, and with highly degraded male genomic DNA. The combination of the mini Y STR system with the novel sample stacking CE microdevice provides the highly sensitive Y STR typing on a chip, making it promising to perform high-performance on-site forensic human identification. PMID:20715129

Chen, Yuchao; Choi, Jong Young; Choi, Seok Jin; Seo, Tae Seok

2010-09-01

339

Reflectivity of plasmas created by high-intensity, ultra-short laser pulses  

SciTech Connect

Experiments were performed to characterize the creation and evolution of high-temperature (T{sub e}{approximately}100eV), high-density (n{sub e}>10{sup 22}cm{sup {minus}3}) plasmas created with intense ({approximately}10{sup 12}-10{sup 16}W/cm{sup 2}), ultra-short (130fs) laser pulses. The principle diagnostic was plasma reflectivity at optical wavelengths (614nm). An array of target materials (Al, Au, Si, SiO{sub 2}) with widely differing electronic properties tested plasma behavior over a large set of initial states. Time-integrated plasma reflectivity was measured as a function of laser intensity. Space- and time-resolved reflectivity, transmission and scatter were measured with a spatial resolution of {approximately}3{mu}m and a temporal resolution of 130fs. An amplified, mode-locked dye laser system was designed to produce {approximately}3.5mJ, {approximately}130fs laser pulses to create and nonintrusively probe the plasmas. Laser prepulse was carefully controlled to suppress preionization and give unambiguous, high-density plasma results. In metals (Al and Au), it is shown analytically that linear and nonlinear inverse Bremsstrahlung absorption, resonance absorption, and vacuum heating explain time-integrated reflectivity at intensities near 10{sup 16}W/cm{sup 2}. In the insulator, SiO{sub 2}, a non-equilibrium plasma reflectivity model using tunneling ionization, Helmholtz equations, and Drude conductivity agrees with time-integrated reflectivity measurements. Moreover, a comparison of ionization and Saha equilibration rates shows that plasma formed by intense, ultra-short pulses can exist with a transient, non-equilibrium distribution of ionization states. All targets are shown to approach a common reflectivity at intensities {approximately}10{sup 16}W/cm{sup 2}, indicating a material-independent state insensitive to atomic or solid-state details.

Gold, D.M.

1994-06-01

340

Measurements of plasma-wave generation using a short-pulse high-intensity laser beat wave  

Microsoft Academic Search

Experiments to examine the generation of relativistic plasma waves via a high-intensity short-pulse beat-wave scheme are described in detail. The pulse stretcher of the Vulcan chirped-pulse amplification (CPA) laser system was modified to produce two frequency, 3 ps pulses focusable to intensities up to 1018 W cm-2. Short high-intensity pulses were used to avoid limitations to the plasma-wave amplitude due

B. Walton; Z. Najmudin; M. S. Wei; C. Marle; R. J. Kingham; K. Krushelnick; A. E. Dangor; R. J. Clarke; M. J. Poulter; C. Hernandez-Gomez; S. Hawkes; D. Neely; J. L. Collier; C. N. Danson; S. Fritzler; V. Malka

2006-01-01

341

Development of a 1 J short pulse tunable TEA CO2 laser with high energy stability  

NASA Astrophysics Data System (ADS)

The design, development and operational characteristics of a 1 J, repetitively pulsed, line tunable TEA CO2 laser producing nearly tail free short pulses (~170 ns) suitable for laser isotope separation is discussed. Tail free short laser pulses were generated by employing a nitrogen lean gaseous active medium. Use of an indigenously developed stable pulsed power supply, uniform and intense UV spark pre-ionization and optimum gas purging with catalytic regeneration to control the deleterious oxygen accumulation helps generate laser pulses with high energy stability. Integration of a sensitive arc detection system allows long term arc-free operation of the laser and protects it from catastrophic failure. Laser pulses in more than 90 lines in 10.6 ?m and 9.6 ?m bands of CO2 laser spectrum with energy about 1 J in as many as 50 lines could be generated with a typical efficiency of about 4%. A typical pulse to pulse energy stability of ±1.4% was obtained during one hour of continuous operation of the TEA CO2 laser at 75 Hz.

Kumar, Manoj; Reghu, T.; Biswas, A. K.; Bhargav, Pankaj; Pakhare, J. S.; Kumar, Shailesh; Verma, Abrat; Mandloi, Vagesh; Kukreja, L. M.

2014-12-01

342

On the choice of electromagnetic model for short high-intensity arcs, applied to welding  

NASA Astrophysics Data System (ADS)

We have considered four different approaches for modelling the electromagnetic fields of high-intensity electric arcs: (i) three-dimensional, (ii) two-dimensional axi-symmetric, (iii) the electric potential formulation and (iv) the magnetic field formulation. The underlying assumptions and the differences between these models are described in detail. Models (i) to (iii) reduce to the same limit for an axi-symmetric configuration with negligible radial current density, contrary to model (iv). Models (i) to (iii) were retained and implemented in the open source CFD software OpenFOAM. The simulation results were first validated against the analytic solution of an infinite electric rod. Perfect agreement was obtained for all the models tested. The electromagnetic models (i) to (iii) were then coupled with thermal fluid mechanics, and applied to axi-symmetric gas tungsten arc welding test cases with short arc (2, 3 and 5 mm) and truncated conical electrode tip. Models (i) and (ii) lead to the same simulation results, but not model (iii). Model (iii) is suited in the specific limit of long axi-symmetric arc with negligible electrode tip effect, i.e. negligible radial current density. For short axi-symmetric arc with significant electrode tip effect, the more general axi-symmetric formulation of model (ii) should instead be used.

Choquet, Isabelle; Javidi Shirvan, Alireza; Nilsson, Håkan

2012-05-01

343

Advances in high-throughput speed, low-latency communication for embedded instrumentation ( 7th Annual SFAF Meeting, 2012)  

ScienceCinema

Scott Jordan on "Advances in high-throughput speed, low-latency communication for embedded instrumentation" at the 2012 Sequencing, Finishing, Analysis in the Future Meeting held June 5-7, 2012 in Santa Fe, New Mexico.

Jordan, Scott [Physik Instrumente

2013-02-11

344

Design of a High-Bandwidth Steering Mirror for Spacebased Optical Communications. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

A space-based optical communications experiment, developed at Lincoln Laboratory, requires a fast steering mirror as part of its spatial pointing, tracking and acquisition system. The High Bandwidth Steering Mirror version C (HBSM-C), has been designed, b...

G. L. Loney

1991-01-01

345

Wide-area technologies and services in the Trans-Pacific High Data Rate (HDR) satellite communications experiments  

NASA Technical Reports Server (NTRS)

This paper describes the technologies and services used in the experiments and demonstrations using the Trans-Pacific high data rate satellite communications infrastructure, and how the environment tasked protocol adaptability, scalability, efficiency, interoperability, and robustness.

Hsu, E.; Hung, C.; Kadowaki, N.; Yoshimura, N.; Takahashi, T.; Shopbell, P.; Walker, G.; Wellnitz, D.; Gary, P.; Clark, G.; Yoshikawa, M.; desJardins, R.; Gill, M.; Tatsumi, H.

2000-01-01

346

An integrated optical/acoustic communication system for seafloor observatories: A field test of high data rate communications at CORK 857D  

NASA Astrophysics Data System (ADS)

We report the successful deployment and testing of an underwater optical communication system that provides high data rate communications over a range of 100 meters from a deep sea borehole observatory located in the northeast Pacific. Optical underwater communications offers many advantages over acoustic or underwater wet mateable connections (UWMC). UMWCs requires periodic visits from a submersible or ROV to plug in and download data. Typically, these vehicles cannot perform any other tasks during these download periods - their time on station is limited, restricting the amount of data that can be downloaded. To eliminate the need for UWMCs requires the use of remote communication techniques such as acoustics or optical communications. Optical communications is capable of high data rates up to 10 mega bits per sec (Mbps) compared to acoustic data rates of 57 Kbps. We have developed an integrated optical/acoustic telemetry system (OTS) that uses an acoustic command system to control a high bandwidth, low latency optical communication system. In July 2010, we used the deep submersible ALVIN to install the Optical Telemetry System (OTS) at CORK 857D. The CORK is instrumented with a thermistor string and pressure sensors that record downhole formation pressures and temperatures within oceanic basement that is pressure sealed from the overlying water column. The seafloor OTS was plugged into the CORK’s existing UWMC to provide an optical and acoustic communication interface and additional data storage and battery power for the CORK to sample at 1 Hz data-rate, an increase over the normal 15 sec data sample rate. Using a CTD-mounted OTS lowered by wire from a surface ship, we established an optical communication link at 100 meters range at rates of 1, 5 and 10 Mbps with no bit errors. Tests were also done to establish the optical range of various data rates and the optical power of the system. After a week, we repeated the CTD-OTS experiment and downloaded 20 Mbytes of data over a 5 Mbps link at a range of 80 m. The OTS will remain installed at CORK 857D for a year. Our OTS enables faster data rates to be employed for in situ measurements that were previously limited by data download times from a submersible. The OTS also permits non submersible-equipped vessels to interrogate the CORK borehole observatory on a more frequent basis using a receiver lowered by wire from a ship of opportunity. In the future, autonomous vehicles could interrogate such seafloor observatories in a “data-mule” configuration and then dock at a seafloor cabled node to download data. While borehole observatories may ultimately be linked into undersea cables relaying real-time data back to shore they represent a superb opportunity to test free water optical communication methods. The lessons learned from our CORK development efforts will go a long way towards establishing the viability of underwater optical communications for a host of autonomous seafloor sensor systems in the future.

Tivey, M.; Farr, N.; Ware, J.; Pontbriand, C.

2010-12-01

347

A High Speed, Long-Range Mobile Communications Link for use in Polar Regions  

NASA Astrophysics Data System (ADS)

The Polar Radar for Ice Sheet Measurements (PRISM) project has developed a high bandwidth, wireless communications link between an autonomous rover and a manned vehicle deployed on a polar ice sheet to exchange real-time video, timing signals for a bistatic radar, and rover sensory data. The PRISM project is developing advanced intelligent remote sensing technology that involves radar systems, an autonomous rover, and communications systems to measure detailed ice sheet characteristics, and to determine bed conditions (frozen or wet) below active ice sheets in both Greenland and Antarctica. While this wireless communications link is being developed to fill a need within the PRISM Project, the same technology will allow polar researchers separated by moderate distances ( ˜10 km) to exchange data. The communications link is based on a high data rate 802.11b wireless technology, and a prototype system has been tested and evaluated during field experiments conducted at the NorthGRIP ice core drilling camp in Greenland (75° 06\\'\\ N, 42° 20\\'\\ W) from June 23-July 17, 2003. The IEEE 802.11b standard works in the 2.4-2.483 GHz band and has been widely used for high-speed data transfer in a WLAN (Wireless Local Area Network). It typically has a range of a few hundred meters and theoretical data rates on the order of 11 Mbps. It has been used for a number of applications in home and office environments. We modified a 802.11b system to operate up to a maximum distance of about 8 km and investigated the radio propagation environment over the flat terrain of the Greenland ice sheet. We evaluated its performance along three different tracks of 8 km in length, and made throughput measurements at intervals of 0.5 km. We measured the received signal strength and noise level in 2-s intervals along these 8 km tracks. Also we conducted experiments for four different antenna heights (1, 2, 3 and 5 m) for developing a radio propagation model for WLAN communication over the ice sheet. We found that peer-to-peer communication between nodes on the ice had data rates varying from 4.5 Mbps at close range to 2.5 Mbps at a distance of 8 km from the base station. The design, propagation model, throughput and coverage of this peer-to-peer communications system in Greenland are presented in this paper. This WLAN system has numerous applications in polar field camps. We tested the transfer of real-time video segments across this link for our educational outreach efforts in the field. These video segments were subsequently uploaded using an Iridium-based Internet link, and sent back to the University of Kansas. The wireless Internet connectivity was also made available to members of the North Grip camp, who were able to access e-mail and the Internet from their tents and common areas. However, throughput for wireless access to the Internet was limited by the Iridium-based Internet connection that had a maximum bandwidth of 9.6 Kbps.

Chalishazar, N.; Prescott, G.; Braaten, D.

2003-12-01

348

Free-space high data rate communications technologies for near terrestrial space  

NASA Astrophysics Data System (ADS)

Recent progress at the Applied Physics Laboratory in high data rate communications technology development is described in this paper. System issues for developing and implementing high data rate downlinks from geosynchronous earth orbit to the ground, either for CONUS or in-theater users is considered. Technology is described that supports a viable dual-band multi-channel system concept. Modeling and simulation of micro-electro-mechanical systems (MEMS) beamsteering mirrors has been accomplished to evaluate the potential for this technology to support multi-channel optical links with pointing accuracies approaching 10 microradians. These models were validated experimentally down to levels in which Brownian motion was detected and characterized for single mirror devices only 500 microns across. This multi-channel beamsteering technology can be designed to address environmental compromises to free-space optical links, which derive from turbulence, clouds, as well as spacecraft vibration. Another technology concept is being pursued that is designed to mitigate the adverse effects of weather. It consists of a dual-band (RF/optical) antenna that is optimally designed in both bands simultaneously (e.g., Ku-band and near infrared). This technology would enable optical communications hardware to be seamlessly integrated with existing RF communications hardware on spacecraft platforms, while saving on mass and power, and improving overall system performance. These technology initiatives have been pursued principally because of potential sponsor interest in upgrading existing systems to accommodate quick data recovery and decision support, particularly for the warfighter in future conflicts where the exchange of large data sets such as high resolution imagery would have significant tactical benefits.

Edwards, C. L.; Bruzzi, J. R.; Boone, B. G.

2008-08-01

349

Dispersive and nonlinear effects in high-speed reconfigurable WDM optical fiber communication systems  

NASA Astrophysics Data System (ADS)

Chromatic dispersion, polarization mode dispersion (PMD) and nonlinear effects are important issues on the physical layer of high-speed reconfigurable WDM optical fiber communication systems. For beyond 10 Gbit/s optical fiber transmission system, it is essential that chromatic dispersion and PMD be well managed by dispersion monitoring and compensation. One the other hand, dispersive and nonlinear effects in optical fiber systems can also be beneficial and has applications on pulse management, all-optical signal processing and network function, which will be essential for high bite-rate optical networks and replacing the expensive optical-electrical-optical (O/E/O) conversion. In this Ph.D. dissertation, we present a detailed research on dispersive and nonlinear effects in high-speed optical communication systems. We have demonstrated: (i) A novel technique for optically compensating the PMD-induced RF power fading that occurs in single-sideband (SSB) subcarrier-multiplexed systems. By aligning the polarization states of the optical carrier and the SSB, RF power fading due to all orders of PMD can be completely compensated. (ii) Chromatic-dispersion-insensitive PMD monitoring by using a narrowband FBG notch filter to recover the RF clock power for 10Gb/s NRZ data, and apply it as a control signal for PMD compensation. (iii) Chirp-free high-speed optical pulse generation with a repetition rate of 160 GHz (which is four times of the frequency of the electrical clock) using a phase modulator and polarization maintaining (PM) fiber. (iv) Polarization-insensitive all-optical wavelength conversion based on four-wave mixing in dispersion-shifted fiber (DSF) with a fiber Bragg grating and a Faraday rotator mirror. (v) Width-tunable optical RZ pulse train generation based on four-wave mixing in highly-nonlinear fiber. By electrically tuning the delay between two pump pulse trains, the pulse-width of a generated pulse train is continuously tuned. (vi) A high-speed all-optical XOR gate based on polarization rotation induced by Kerr effect in a single highly--nonlinear fiber. (vii) Wavelength-shift-free 3R-regeneration of 40-Gbit/s optical RZ signal by OPA with a clock-modulated pump in highly-nonlinear fiber. These techniques will play key roles in future high-speed dynamic WDM optical fiber communication systems and reconfigurable networks.

Yu, Changyuan

350

Combinatorial FSK modulation for power-efficient high-rate communications  

NASA Technical Reports Server (NTRS)

Deep-space and satellite communications systems must be capable of conveying high-rate data accurately with low transmitter power, often through dispersive channels. A class of noncoherent Combinatorial Frequency Shift Keying (CFSK) modulation schemes is investigated which address these needs. The bit error rate performance of this class of modulation formats is analyzed and compared to the more traditional modulation types. Candidate modulator, demodulator, and digital signal processing (DSP) hardware structures are examined in detail. System-level issues are also discussed.

Wagner, Paul K.; Budinger, James M.; Vanderaar, Mark J.

1991-01-01

351

A high-efficiency 59- to 64-GHz TWT for intersatellite communications  

NASA Technical Reports Server (NTRS)

The design of a 75-W, 59- to 64- GHz TWT with a predicted overall efficiency in excess of 40 percent is described. This intersatellite communications TWT, designated Model 961HA, employs a coupled-cavity slow-wave structure with a two-step velocity taper and an isotropic graphite multistage depressed collector (MDC). Because the RF efficiency of this TWT is less than 8 percent, an MDC design providing a very high collector efficiency was necessary to achieve the overall efficiency goal of 40 percent.

Wilson, Jeffrey D.; Ramins, Peter; Force, Dale A.; Limburg, Helen C.; Tammaru, Ivo

1991-01-01

352

High-speed communication detector characterization by bit error rate measurements  

NASA Technical Reports Server (NTRS)

Performance data taken on several candidate high data rate laser communications photodetectors is presented. Measurements of bit error rate versus signal level were made in both a 1064 nm system at 400 Mbps and a 532 nm system at 500 Mbps. RCA silicon avalanche photodiodes are superior at 1064 nm, but the Rockwell hybrid 3-5 avalanche photodiode preamplifiers offer potentially superior performance. Varian dynamic crossed field photomultipliers are superior at 532 nm, however, the RCA silicon avalanche photodiode is a close contender.

Green, S. I.

1978-01-01

353

Short pulse energetic electron production by high-intensity laser ionization of gases  

NASA Astrophysics Data System (ADS)

Electrons in tightly bound atomic states are an excellent means of investigating high field electron-photon interactions, since the atomic binding potential dresses the electrons in high energy states before release in a high-intensity laser focus. Following ionization, canonical momentum conservation and ponderomotive acceleration can result in electron ejection from the focus with kinetic energies of megavolts or higher. During ejection from the focus, electrons gain both transverse momentum (from ponderomotive forces due to radial intensity gradients) and longitudinal momentum (from vxB or field momentum effects). Higher energy electrons gain more longitudinal momentum and are ejected closer to the laser axis. This indicates a transition from a Thomson to multi-photon Compton scattering regime as field momentum effects become significant. This laser ionization and ponderomotive acceleration (LIPA) of tightly bound electrons from gases has been investigated experimentally and numerically. Utilizing the energy dependent angle of ejection as a means of energy selection, 600 keV electrons with a 100 keV energy spread have been produced experimentally. Simulations show that current short pulse lasers can produce femtosecond pulses of megavolt electrons with normalized emittances of approximately 0.1 mm-mrad using this mechanism. These novel laser produced high brightness electron beams are useful for ultrafast imaging and for injection into electron accelerators.

Moore, Christopher I.

2000-10-01

354

Short-pulse, high-energy radiation generation using a laser wakefield accelerator  

NASA Astrophysics Data System (ADS)

Recent experimental results of laser wakefield acceleration (LWFA) of electrons and their subsequent radiation generation driven by the HERCULES laser with up to 200TW are presented. In LWFA, the plasma ``bubble'' structure forces trapped, off-axis electrons to undergo transverse oscillatory motion during acceleration, resulting in synchrotron-like betatron radiation in the keV X-ray regime. Measurements indicate that the beam source size can be as small as 1 micron and that the radiation exhibits spatial coherence, allowing phase-contrast imaging. Data from Cu K-? generated using an identical geometry are presented to give yield and source size comparisons. Alternatively, the high energy (>200 MeV) electron beam can be subsequently converted via Bremsstrahlung into low-divergence beams of high-energy photons and positrons. These photons are spectrally resolved using a Compton scattering-based, high-energy (30-80 MeV) photon spectrometer. All of these subsequent beams are presumed to retain the short-pulse characteristic of the electron beam, resulting in high peak flux, making the source an excellent candidate for ultrafast pump-probe applications in the keV and MeV photon range.

Schumaker, W.; Vargas, M.; He, Z.; Chvykov, V.; Hou, B.; Yanovsky, V.; Maksimchuk, A.; Thomas, A. G. R.; Krushelnick, K.; Sarri, G.; Dromey, B.; Zepf, M.

2012-10-01

355

Epithermal Neutron Source for Neutron Resonance Spectroscopy (NRS) using High Intensity, Short Pulse Lasers  

SciTech Connect

A neutron source for neutron resonance spectroscopy (NRS) has been developed using high intensity, short pulse lasers. This measurement technique will allow for robust measurements of interior ion temperature of laser-shocked materials and provide insight into equation of state (EOS) measurements. The neutron generation technique uses protons accelerated by lasers off of Cu foils to create neutrons in LiF, through (p,n) reactions with {sup 7}Li and {sup 19}F. The distribution of the incident proton beam has been diagnosed using radiochromic film (RCF). This distribution is used as the input for a (p,n) neturon prediction code which is compared to experimentally measured neutron yields. From this calculation, a total fluence of 1.8 x 10{sup 9} neutrons is infered, which is shown to be a reasonable amount for NRS temperature measurement.

Higginson, D P; McNaney, J M; Swift, D C; Bartal, T; Hey, D S; Pape, S L; Mackinnon, A; Mariscal, D; Nakamura, H; Nakanii, N; Beg, F N

2010-04-22

356

Study of short haul high-density V/STOL transportation systems, volume 1  

NASA Technical Reports Server (NTRS)

The relative advantages of STOL aircraft concepts were examined by simulating the operations of a short haul high-density intercity STOL system set in two arenas, the California corridor and the Chicago-Detroit-Cleveland triangle, during the 1980 time period. The study was constrained to the use of three aircraft concepts designated as the deflected slipstream turboprop, externally blown flap, and augmentor wing turbofan configurations. The projected demographic, economic, travel demand, and travel characteristics of the representative arenas were identified. The STOL airline operating scenarios were then formulated and through the use of the aerospace modal split simulation program, the traveler modal choices involving alternative STOL concepts were estimated in the context of the total transportation environment for 1980. System combinations that presented the best potential for economic return and traveler acceptance were then identified for each STOL concept.

Solomon, H. L.

1972-01-01

357

Interplay of mulitphoton and tunneling ionization in short-wavelength-driven high-order harmonic generation  

NASA Astrophysics Data System (ADS)

High-order harmonic generation efficiency is theoretically modeled and compared with experiments using 400 and 800 nm driver pulses. It is shown that, for a short drive wavelength and a Keldysh parameter larger than 1, the Ammosov-Delone-Krainov (ADK) ionization model does not give a good agreement between theory and experiment. Since the ADK ionization model only accounts for tunnel ionization, it underestimates the yield of low-order harmonics from the wings of the driver pulse. In contrast, the Yudin-Ivanov ionization model [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.64.013409 64, 013409 (2001)], which accounts for both tunnel and multiphoton ionization, gives much better agreement with the experimental results.

Gkortsas, Vasileios-Marios; Bhardwaj, Siddharth; Lai, Chien-Jen; Hong, Kyung-Han; Falcão-Filho, Edilson L.; Kärtner, Franz X.

2011-07-01

358

High-speed asynchronous communication technique for MOS (metal-oxide-semiconductor) VLSI systems. Master's thesis  

SciTech Connect

As MOS technologies advance, the relative differences between on-chip and off-chip delays increase. Drivers and receivers can be designed that allow high-bit-rate communications (>100 Mbits/sec) between MOS chips at the expense of increased latency. Designing synchronous systems that couple a high clock frequency with large and variable delays is difficult and expensive due to the complexity of insuring that no delays violate the constraints imposed by synchronous operation. A circuit-based technique for automatically adjusting signal delays in an MOS system was developed. The Dynamic Delay Adjustment (DDA) technique provides reliable high-speed communications directly between MOS chips independent of the delay between the chips. The amount of phase jitter immunity provided by the synchronizer can be traded off against circuit complexity; the signal delays are adjusted continuously to track-temperature-induced delay variations. A 3-micron DDA synchronizer was fabricated to confirm the validity of the DDA approach; test results will be presented.

Bassett, P.D.

1985-12-01

359

Chaos-based communications at high bit rates using commercial fibre-optic links  

NASA Astrophysics Data System (ADS)

Chaotic signals have been proposed as broadband information carriers with the potential of providing a high level of robustness and privacy in data transmission. Laboratory demonstrations of chaos-based optical communications have already shown the potential of this technology, but a field experiment using commercial optical networks has not been undertaken so far. Here we demonstrate high-speed long-distance communication based on chaos synchronization over a commercial fibre-optic channel. An optical carrier wave generated by a chaotic laser is used to encode a message for transmission over 120km of optical fibre in the metropolitan area network of Athens, Greece. The message is decoded using an appropriate second laser which, by synchronizing with the chaotic carrier, allows for the separation of the carrier and the message. Transmission rates in the gigabit per second range are achieved, with corresponding bit-error rates below 10-7. The system uses matched pairs of semiconductor lasers as chaotic emitters and receivers, and off-the-shelf fibre-optic telecommunication components. Our results show that information can be transmitted at high bit rates using deterministic chaos in a manner that is robust to perturbations and channel disturbances unavoidable under real-world conditions.

Argyris, Apostolos; Syvridis, Dimitris; Larger, Laurent; Annovazzi-Lodi, Valerio; Colet, Pere; Fischer, Ingo; García-Ojalvo, Jordi; Mirasso, Claudio R.; Pesquera, Luis; Shore, K. Alan

2005-11-01

360

Integration and test of high-speed transmitter electronics for free-space laser communications  

NASA Technical Reports Server (NTRS)

The NASA Lewis Research Center in Cleveland, Ohio, has developed the electronics for a free-space, direct-detection laser communications system demonstration. Under the High-Speed Laser Integrated Terminal Electronics (Hi-LITE) Project, NASA Lewis has built a prototype full-duplex, dual-channel electronics transmitter and receiver operating at 325 megabit S per second (Mbps) per channel and using quaternary pulse-position modulation (QPPM). This paper describes the integration and testing of the transmitter portion for future application in free-space, direct-detection laser communications. A companion paper reviews the receiver portion of the prototype electronics. Minor modifications to the transmitter were made since the initial report on the entire system, and this paper addresses them. The digital electronics are implemented in gallium arsenide integrated circuits mounted on prototype boards. The fabrication and implementation issues related to these high-speed devices are discussed. The transmitter's test results are documented, and its functionality is verified by exercising all modes of operation. Various testing issues pertaining to high-speed circuits are addressed. A description of the transmitter electronics packaging concludes the paper.

Soni, Nitin J.; Lizanich, Paul J.

1994-01-01

361

A single-photon detector for high-speed telecom-band quantum communication applications  

NASA Astrophysics Data System (ADS)

We present the design and construction of a high-speed telecom-band (1.5 ?m) single-photon counting system based on an InGaAs/InP avalanche photodiode (APD) operating in the gated Geiger mode. The detector can be gated at high speeds (we examine its performance up to 25 MHz) to maximize the counting rate in long-distance, telecom-band, fiber-optic quantum communication applications. Narrow gate pulses (250 ps full width at half maximum) are used to reduce the dark-count and the after-pulse probability. In order to count the avalanche events, we employ a high-speed comparator to sample the unfiltered and unamplified avalanche photocurrent. The APD and all the associated electronics are integrated onto a printed circuit board with a computer interface. In addition, we cool the APD to -27°C to reduce the dark-count probability.

Liang, Chuang; Lee, Kim F.; Voss, Paul L.; Corndorf, Eric; Kanter, Gregory S.; Chen, Jun; Li, Xiaoying; Kumar, Prem

2005-08-01

362

Textured dysprosium and gadolinium poles for high-field, short-period hybrid undulators  

NASA Astrophysics Data System (ADS)

We discuss the feasibility of enhancement of the gap field in a short-period hybrid undulator by using pole inserts with the saturation inductance Bs, over that of iron, 2 T. Dysprosium metal, with the saturation inductance of 3.4 T below 90 K, and Gadolinium with Bs=2.7 T, appear as good candidates as the optimized pole material. However, due to the high magnetic anisotropy of Dy, such a high level of magnetization can only be realized when the external field lies in the basal plane. This implies that the pole has to be single-crystalline or highly textured. Considering that growing large, >10mm, Dy single crystals is difficult, we propose secondary recrystallization as a method to induce the required texture in thin Dy and Gd foils. The textured foils can be stacked to produce pole inserts of the desired geometry and orientation. Results of small-scale processing and magnetic measurements of thin (20-60 ?) foils provide evidence that the required texture quality can be achieved by a relatively simple sequence of heat-treatments and cold rolling. The advantage of textured Dy and Gd poles is demonstrated in a several period test undulator.

Murokh, Alex; Solovyov, Vyacheslav; Agustsson, Ron; O'Shea, Finn H.; Chubar, Oleg; Chen, Yung; Grandsaert, Thomas

2014-01-01

363

OPTICAL COMMUNICATION: Study of new modulation data-transmission formats for dispersion-controlled high-bit-rate fibreoptic communication lines  

Microsoft Academic Search

The results of simulation of the propagation of optical signals in a multichannel high-bit-rate fibreoptic communication line with a combined scheme for amplifying optical signals based on new modulation data-transmission formats are presented. A comparative characteristic of formats with the amplitude and phase modulations of the electromagnetic-wave carrier is presented. The results of numerical simulation show that phase-modulation formats have

O. V. Shtyrina; M. P. Fedoruk; S. K. Turitsyn

2007-01-01

364

Effect of Short-Term Acclimatization to High Altitude on Sleep and Nocturnal Breathing  

PubMed Central

Study Objective: Objective physiologic data on sleep and nocturnal breathing at initial exposure and during acclimatization to high altitude are scant. We tested the hypothesis that acute exposure to high altitude induces quantitative and qualitative changes in sleep and that these changes are partially reversed with acclimatization. Design: Prospective observation. Setting: One night in a sleep laboratory at 490 meters, the first and the third night in a mountain hut at 4559 meters. Participants: Sixteen healthy mountaineers. Intervention: Altitude exposure. Measurements: Polysomnography, questionnaire evaluation of sleep and acute mountain sickness. Results: Compared to 490 m, median nocturnal oxygen saturation decreased during the 1st night at 4559 m from 96% to 67%, minute ventilation increased from 4.4 to 6.3 L/min, and the apnea-hypopnea index increased from 0.1 to 60.9/h; correspondingly, sleep efficiency decreased from 93% to 69%, and slow wave sleep from 18% to 6% (P < 0.05, all instances). During the 3rd night at 4559 m, oxygen saturation was 71%, slow wave sleep 11% (P < 0.05 vs. 1st night, both instances) and the apnea/hypopnea index was 86.5/h (P = NS vs. 1st night). Symptoms of AMS and of disturbed sleep were significantly reduced in the morning after the 3rd vs. the 1st night at 4559 m. Conclusions: In healthy mountaineers ascending rapidly to high altitude, sleep quality is initially impaired but improves with acclimatization in association with improved oxygen saturation, while periodic breathing persists. Therefore, high altitude sleep disturbances seem to be related predominantly to hypoxemia rather than to periodic breathing. Citation: Nussbaumer-Ochsner Y; Ursprung J; Siebenmann C; Maggiorini M; Bloch KE. Effect of short-term acclimatization to high altitude on sleep and nocturnal breathing. SLEEP 2012;35(3):419-423.

Nussbaumer-Ochsner, Yvonne; Ursprung, Justyna; Siebenmann, Christoph; Maggiorini, Marco; Bloch, Konrad E.

2012-01-01

365

Speech Communication.  

ERIC Educational Resources Information Center

The communications approach to teaching speech to high school students views speech as the study of the communication process in order to develop an awareness of and a sensitivity to the variables that affect human interaction. In using this approach the student is encouraged to try out as many types of messages using as many techniques and…

Anderson, Betty

366

Communicator, 1998.  

ERIC Educational Resources Information Center

The CAG "Communicator" focuses on serving gifted students in California. This document consists of the four issues of "Communicator" issued during 1998. Featured articles include: (1) "Underachievement for Some--Dropping Out with Dignity for Others" (Sally Reis); (2) "When Gifted High School Students Fail" (Patty Bort); (3) "Choosing a College"…

Bortolussi, Vicki, Ed.

1998-01-01

367

Fire Safety for High-Rise Buildings: The Role of Communications.  

National Technical Information Service (NTIS)

This literature survey reviews the communications requirements for fire safety in buildings from the standpoint of the building occupant and the control operator. It traces the development of the problem of communications in buildings and the specialized ...

R. A. Glass A. I. Rubin

1979-01-01

368

Can High-resolution WRF Simulations Be Used for Short-term Forecasting of Lightning?  

NASA Technical Reports Server (NTRS)

A number of research teams have begun to make quasi-operational forecast simulations at high resolution with models such as the Weather Research and Forecast (WRF) model. These model runs have used horizontal meshes of 2-4 km grid spacing, and thus resolved convective storms explicitly. In the light of recent global satellite-based observational studies that reveal robust relationships between total lightning flash rates and integrated amounts of precipitation-size ice hydrometeors in storms, it is natural to inquire about the capabilities of these convection-resolving models in representing the ice hydrometeor fields faithfully. If they do, this might make operational short-term forecasts of lightning activity feasible. We examine high-resolution WRF simulations from several Southeastern cases for which either NLDN or LMA lightning data were available. All the WRF runs use a standard microphysics package that depicts only three ice species, cloud ice, snow and graupel. The realism of the WRF simulations is examined by comparisons with both lightning and radar observations and with additional even higher-resolution cloud-resolving model runs. Preliminary findings are encouraging in that they suggest that WRF often makes convective storms of the proper size in approximately the right location, but they also indicate that higher resolution and better hydrometeor microphysics would be helpful in improving the realism of the updraft strengths, reflectivity and ice hydrometeor fields.

Goodman, S. J.; Lapenta, W.; McCaul, E. W., Jr.; LaCasse, K.; Petersen, W.

2006-01-01

369

Development of a resonant laser ionization gas cell for high-energy, short-lived nuclei  

NASA Astrophysics Data System (ADS)

A new laser ion source configuration based on resonant photoionization in a gas cell has been developed at RIBF RIKEN. This system is intended for the future PArasitic RI-beam production by Laser Ion-Source (PALIS) project which will be installed at RIKEN's fragment separator, BigRIPS. A novel implementation of differential pumping, in combination with a sextupole ion beam guide (SPIG), has been developed. A few small scroll pumps create a pressure difference from 1000 hPa-10-3 Pa within a geometry drastically miniaturized compared to conventional systems. This system can utilize a large exit hole for fast evacuation times, minimizing the decay loss for short-lived nuclei during extraction from a buffer gas cell, while sufficient gas cell pressure is maintained for stopping high energy RI-beams. In spite of the motion in a dense pressure gradient, the photo-ionized ions inside the gas cell are ejected with an assisting force gas jet and successfully transported to a high-vacuum region via SPIG followed by a quadrupole mass separator. Observed behaviors agree with the results of gas flow and Monte Carlo simulations.

Sonoda, T.; Wada, M.; Tomita, H.; Sakamoto, C.; Takatsuka, T.; Furukawa, T.; Iimura, H.; Ito, Y.; Kubo, T.; Matsuo, Y.; Mita, H.; Naimi, S.; Nakamura, S.; Noto, T.; Schury, P.; Shinozuka, T.; Wakui, T.; Miyatake, H.; Jeong, S.; Ishiyama, H.; Watanabe, Y. X.; Hirayama, Y.; Okada, K.; Takamine, A.

2013-01-01

370

High Density Lipoproteins for the Systemic Delivery of short interfering RNA  

PubMed Central

Introduction RNA interference (RNAi) is a powerful mechanism for gene silencing with the potential to greatly impact the development of new therapies for many human diseases. Short interfering RNAs (siRNAs) may be the ideal molecules for therapeutic RNAi. However, therapeutic siRNAs face significant challenges that must be overcome prior to widespread clinical use. Many efforts have been made to overcome the hurdles associated with systemic administration of siRNA; however, current approaches are still limited. As such, there is an urgent need to develop new strategies for siRNA delivery that have the potential to impact a broad spectrum of systemic diseases. Areas covered This review focuses on the promise of siRNA therapies and highlights current siRNA delivery methods. With an eye toward new strategies, this review first introduces high density lipoproteins (HDL) and their natural functions, and then transitions into how HDLs may provide significant opportunities as next generation siRNA delivery vehicles. Importantly, this review describes how synthetic HDLs leverage the natural ability of HDL to stabilize and deliver siRNAs. Expert Opinion HDLs are natural nanoparticles that are critical to understanding the systemic delivery of therapeutic nucleic acids, like siRNA. Methods to synthesize biomimetic HDLs are being explored and data demonstrate that this type of delivery vehicle may be highly beneficial for targeted and efficacious systemic delivery of siRNAs.

McMahon, Kaylin M.; Thaxton, C. Shad

2014-01-01

371

Does visual short-term memory have a high-capacity stage?  

PubMed Central

Visual short-term memory (VSTM) has long been considered a durable, limited-capacity system for the brief retention of visual information. However, a recent work by Sligte, Scholte, and Lamme (2008) reported that, relatively early after the removal of a memory array, a cue allowed participants to access a fragile, high-capacity stage of VSTM that is distinct from iconic memory. In the present study, we examined whether this stage division is warranted by attempting to corroborate the existence of an early, high-capacity form of VSTM. The results of four experiments did not support Sligte et al.’s claim, as we did not obtain evidence for VSTM retention that exceeded traditional estimates of capacity. However, performance approaching that observed in Sligte et al. can be achieved through extensive practice, providing a clear explanation for their findings. Our evidence favors the standard view of VSTM as a limited-capacity system that maintains a few object representations in a relatively durable form.

Matsukura, Michi; Hollingworth, Andrew

2011-01-01

372

Managing Multiple Communication Methods in High-Performance Networked Computing Systems  

Microsoft Academic Search

Modern networked computing environments and applications often require---or canbenefit from---the use of multiple communication substrates, transport mechanisms, andprotocols, chosen according to where communication is directed, what is communicated,or when communication is performed. We propose techniques that allow multiple communicationmethods to be supported transparently in a single application, with eitherautomatic or user-specified selection criteria guiding the methods used...

Ian T. Foster; Jonathan Geisler; Carl Kesselman; Steven Tuecke

1997-01-01

373

Development of a medical record and radiographic image transmission system using a high-speed communication network.  

PubMed

A medical record and radiographic image transmission system has been developed using a high-speed communication network. The databases are designed to store and transmit the data acquired from the scanner. To maximally utilize the communication bandwidth, the medical records and radiographic images are compressed using the G3 facsimile and JPEG coding standard method, respectively. TCP/IP, OOP and Windows-based system software enable a modular design, future expandability, open system interconnectivity, and diverse image manipulation functions. PMID:10384462

Kim, N H; Yoo, S K; Kim, K M; Kang, Y T; Bae, S H; Kim, S R

1998-01-01

374

High Speed VSAT Network for Data Communication at Greater Mekong Subregion  

Microsoft Academic Search

Now a day, the reliable and faster communication system has become crucial requirement for the development of a region and so implementation of communication system backbone will be the essential requirement of the Mekong Subregion. Even though there are different types of communication medium, use of VSAT network is most appropriate one because of its flexibility and relatively easier to

Myo Tun

375

Laser Communications and Fiber Optics Lab Manual. High-Technology Training Module.  

ERIC Educational Resources Information Center

This laboratory training manual on laser communications and fiber optics may be used in a general technology-communications course for ninth graders. Upon completion of this exercise, students achieve the following goals: match concepts with laser communication system parts; explain advantages of fiber optic cable over conventional copper wire;…

Biddick, Robert

376

Teaching Communication Book Use to a High School Student Using a Milieu Approach.  

ERIC Educational Resources Information Center

A study combined communication book training, a milieu approach, and systematic vocabulary selection to teach a nonspeaking adolescent with mental retardation to communicate in three settings. Results indicated rapid learning of communication book use in meal preparation and employment training and more delayed increased in small group…

Rodi, Michael S.; Hughes, Carolyn

2000-01-01

377

Time-Varying Parameter Method with High Security Performance for Chaotic Synchronized Communication  

Microsoft Academic Search

A chaotic synchronized secure communication method based on time-varying parameter is presented. The method improves security performance of communication greatly, and can defeat all kinds of attacking methods at present. The parameter sensitivity of chaotic synchronization makes chaotic synchronization robust, but eavesdroppers can follow this way to attack and defeat communication system. Time-varying parameter method can solve this problem. In

Bin Chen; Zheng-Ou Zhou; Guang-Hu Liu; Yong Zhang; Jun Tang

2006-01-01

378

A Simple Semaphore Signaling Technique for Ultra-High Frequency Spacecraft Communications  

NASA Technical Reports Server (NTRS)

For planetary lander missions such as the upcoming Phoenix mission to Mars, the most challenging phase of the spacecraft-to-ground communications is during the critical phase termed entry, descent, and landing (EDL). At 8.4 GHz (X-band), the signals received by the largest Deep Space Network (DSN) antennas can be too weak for even 1 bit per second (bps) and therefore not able to communicate critical information to Earth. Fortunately, the lander s ultra-high frequency (UHF) link to an orbiting relay can meet the EDL requirements, but the data rate needs to be low enough to fit the capability of the UHF link during some or all of EDL. On Phoenix, the minimum data rate of the as-built UHF radio is 8 kbps and requires a signal level at the Odyssey orbiter of at least -120 dBm. For lower signaling levels, the effective data rate needs to be reduced, but without incurring the cost of rebuilding and requalifying the equipment. To address this scenario, a simple form of frequency-shift keying (FSK) has been devised by appropriately programming the data stream that is input to the UHF transceiver. This article describes this technique and provides performance estimates. Laboratory testing reveals that input signal levels at -140 dBm and lower can routinely be demodulated with the proposed signaling scheme, thereby providing a 20-dB and greater margin over the 8-kbps threshold.

Butman, S.; Satorius, E.; Ilott, P.

2005-01-01

379

A high capacity mobile communications satellite system for the first generation MSS  

NASA Astrophysics Data System (ADS)

A low-cost high-capacity dual-band mobile communications satellite system using existing equipment is proposed for the first generation MSS. Cost effectiveness and the requirements of beam optimization and passive intermodulation avoidance dictated the choice of two single band satellites for separate UHF and L-band coverage of North America. Similar designs for the two satellites, based on the Intelsat V and Insat/Arabsat configurations, will achieve over 6000 5-kHz SCPC, communications channels for the system. The 12 beam UHF and 17 beam L-band satellites achieve up to a three-fold frequency reuse of the FCC allocated MSS frequency spectrum. Spacecraft design features include separate 9.1 m antennas for sending and receiving, SAW filters for channel noise attenuation, an integrated bipropellant propulsion system, and a 3.8 kW 10-year electrical power subsystem with a solar array. The satellites are compatible with the STS, Ariane, and other expendable boosters.

Wiedeman, R. A.

380

A new circuit for synthetic autoreclosing test duties under short circuit conditions on high-power circuit-breakers  

Microsoft Academic Search

The need of fully proving high voltage and high power circuit breakers is brought into evidence; to achieve this objective suitable synthetic circuits have to be provided which not only can correctly simulate the breaking operations but also the making operation under short circuit, autoreclosing. Two new synthetic making circuits which can easily be combined with the existing widely known

S. Manganaro; S. Rovelli

1977-01-01

381

Effect of short fibers on residual permeability and mechanical properties of hybrid fibre reinforced high strength concrete after heat exposition  

Microsoft Academic Search

Mechanical and permeability performance of fibre reinforced high strength concrete after heat exposition were evaluated in the experimental study. Cylindrical concrete specimens were exposed to heat with the rate of 10 °C\\/min of up to 400 °C. In order to study the effect of short fibres on residual performance of heated high strength concrete, polypropylene and steel fibres had been added into

Sofren Leo Suhaendi; Takashi Horiguchi

2006-01-01

382

RF and Optical Communications: A Comparison of High Data Rate Returns From Deep Space in the 2020 Timeframe  

NASA Technical Reports Server (NTRS)

As NASA proceeds with plans for increased science data return and higher data transfer capacity for science missions, both RF and optical communications are viable candidates for significantly higher-rate communications from deep space to Earth. With the inherent advantages, smaller apertures and larger bandwidths, of optical communications, it is reasonable to expect that at some point in time and combination of increasing distance and data rate, the rapidly emerging optical capabilities would become more advantageous than the more mature and evolving RF techniques. This paper presents a comparison of the burden to a spacecraft by both RF and optical communications systems for data rates of 10, 100, and 1000 Mbps and large distances. Advanced technology for RF and optical communication systems have been considered for projecting capabilities in the 2020 timeframe. For the comparisons drawn, the optical and RF ground terminals were selected to be similar in cost. The RF system selected is composed of forty-five 12-meter antennas, whereas the selected optical system is equivalent to a 10-meter optical telescope. Potential differences in availability are disregarded since the focus of this study is on spacecraft mass and power burden for high-rate mission data, under the assumption that essential communications will be provided by low-rate, high availability RF. For both the RF and optical systems, the required EIRP, for a given data rate and a given distance, was achieved by a design that realized the lowest possible communications subsystem mass (power + aperture) consistent with achieving the lowest technology risk. A key conclusion of this paper is that optical communications has great potential for high data rates and distances of 2.67 AU and beyond, but requires R&D and flight demonstrations to prove out technologies.

Williams, W. Dan; Collins, Michael; Boroson, Don M.; Lesh, James; Biswas, Abihijit; Orr, Richard; Schuchman, Leonard; Sands, O. Scott

2007-01-01

383

The social construction of communication climate: An analysis of at-risk students in alternative high school  

NASA Astrophysics Data System (ADS)

Alternative high schools affect more potential high school dropouts than any other school or program and are designed to meet the needs of students who have had difficulty in conventional schools. This study examines the communication climate and constructions of caring in an alternative school for at-risk students by using a qualitative analysis grounded in the theoretical perspective of social constructionism. Observations and interviews were conducted over a six month time period. The first two chapters provide a review of literature and a detailed account of the methods used to conduct the study. Chapter Three describes the socially constructed nature of the school and the participants and the dialectical tensions of communication climate revealed from the analysis. The six dialectical tensions of communication climate are: (1) freedom/restraint, (2) disengagement/engagement, (3) personal communication/impersonal communication, (4) disconfirmation/confirmation, (5) equality/inequality, and (6) ambiguity/clarity. Although the school climate is comprised of each of these tensions, the data suggest that the interaction within the majority of classes created some common characteristics of the general communication climate at the school and can be characterized as one of freedom, disengagement, personal communication, disconfirmation, equality, and ambiguity. Chapter Four describes how caring was constructed and communicated. Although some students perceived some teachers as caring about students and about student learning, half of the students interviewed thought they were not learning or not learning much. Finally, Chapter Five provides a summary of the findings and a discussion of the results. The results of this study contribute to an understanding of the social construction of communication climate and caring in general, and within an alternative school for at-risk students, in specific. The results contribute to the understanding of the complexity of the jointly produced nature of communication climate and reveal the potential effect of communication climate and constructions of caring on teachers' instructional methods, teacher and student interaction, and student learning. Such information can aid pragmatically in the development or modification of programs designed to serve at-risk students, and theoretically in the understanding of the co-constructed nature of communication climate.

Souza, Tasha Jean

384

High speed ultra short pulse fiber ring laser using photonic crystal fiber nonlinear optical loop mirror  

NASA Astrophysics Data System (ADS)

A scheme to generate high speed optical pulse train with ultra short pulse width is proposed and experimentally studied. Two-step compression is used in the scheme: 20 GHz and 40 GHz pulse trains generated from a rational harmonic actively mode-locked fiber ring laser is compressed to a full width at half-maximum (FWHM) of ~ 1.5 ps using adiabatic soliton compression with dispersion shifted fibers (DSF). The pulse trains then undergo a pedestal removal process by transmission through a cascaded two photonic crystal fiber (PCF)-nonlinear optical loop mirrors (NOLM) realized using a double-ring structure. The shortest output pulse width obtained was ~ 610 fs for 20 GHz pulse train and ~ 570 fs for 40 GHz pulse train. The signal to noise ratio of the RF spectrum of the output pulse train is larger than 30 dB. Theoretical simulation of the NOLM transmission is conducted using split-step Fourier method. The results show that two cascaded NOLMs can improve the compression result compared to that for a single NOLM transmission.

Ma, Shaozhen; Li, Wenbo; Hu, Hongyu; Dutta, Niloy K.

2012-06-01

385

First spectral measurements of a cryogenic high-field short-period undulator  

NASA Astrophysics Data System (ADS)

Further development of synchrotron light sources and new concepts for free electron lasers require undulators with short periods and high magnetic fields. A promising approach is the cryogenic permanent magnet undulator concept based on an advanced magnet material. This new rare earth alloy (Pr,Nd)2Fe14B, shows an increasing remanent field of up to 1.7 T without the limits of spin reorientation transition. This work presents first spectral measurements of a prototype cryogenic permanent magnet undulator, consisting of 20 periods of 9 mm in length, cooled by a closed cycle cryo-cooler to temperatures below 30 K. The K parameter of 0.837 at RT is increased by more than 15% to 0.966, and an increase of the third harmonics photon flux of up to 66% was achieved. A possible degradation of the on-axis field quality due to thermally induced magnetic field errors, deduced from the measured bandwidth of the spectrum, is below the limits of the detector resolution of 2%.

Holy, F.; Maier, A. R.; Zeitler, B.; Weingartner, R.; Raith, S.; Kajumba, N.; Ghazaly, M. El; Lauth, W.; Krambrich, D.; Gaupp, A.; Scheer, M.; Bahrdt, J.; Grüner, F.

2014-05-01

386

Short-term nanostructural effects of high radiofrequency treatment on the skin tissues of rabbits.  

PubMed

The aim of this study is to quantitatively investigate the short-term effects of RF tissue-tightening treatment in in vivo rabbit dermal collagen fibrils. These effects were measured at different energy levels and at varying pass procedures on the nanostructural response level using histology and AFM analysis. Each rabbit was divided into one of seven experimental groups, which included the following: control group, and six RF group according to RF energy (20 W and 40 W) and three RF pass procedures. The progressive changes in the diameter and D-periodicity of rabbit dermal collagen fibrils were investigated in detail over a 7-day post-treatment period. The dermal tissues treated with the RF tissue-tightening device showed more prominent inflammatory responses with inflammatory cell ingrowth compared to the control. This effect showed more prominent with the passage of day after treatment. Although an increase in the diameter and D-periodicity of dermal collagen fibrils was identified immediately after the RF treatment, a decrease in the morphology of dermal collagen fibrils continued until post-operative day 7. Furthermore, RF treatment led to the loss of distinct borders. Increases in RF energy with the same pass procedure, as well as an increase in the number of RF passes, increased the occurrence of irreversible collagen fibril injury. A multiple-pass treatment at low energy rather than a single-pass treatment at high energy showed a large amount of collagen fibrils contraction at the nanostructural level. PMID:22037867

Choi, Samjin; Cheong, Youjin; Shin, Jae-Ho; Lee, Hui-Jae; Lee, Gi-Ja; Choi, Seok Keun; Jin, Kyung-Hyun; Park, Hun-Kuk

2012-09-01

387

Department of Energy Mathematical, Information, and Computational Sciences Division: High Performance Computing and Communications Program  

SciTech Connect

This document is intended to serve two purposes. Its first purpose is that of a program status report of the considerable progress that the Department of Energy (DOE) has made since 1993, the time of the last such report (DOE/ER-0536, The DOE Program in HPCC), toward achieving the goals of the High Performance Computing and Communications (HPCC) Program. The second purpose is that of a summary report of the many research programs administered by the Mathematical, Information, and Computational Sciences (MICS) Division of the Office of Energy Research under the auspices of the HPCC Program and to provide, wherever relevant, easy access to pertinent information about MICS-Division activities via universal resource locators (URLs) on the World Wide Web (WWW).

NONE

1996-11-01

388

Department of Energy: MICS (Mathematical Information, and Computational Sciences Division). High performance computing and communications program  

SciTech Connect

This document is intended to serve two purposes. Its first purpose is that of a program status report of the considerable progress that the Department of Energy (DOE) has made since 1993, the time of the last such report (DOE/ER-0536, {open_quotes}The DOE Program in HPCC{close_quotes}), toward achieving the goals of the High Performance Computing and Communications (HPCC) Program. The second purpose is that of a summary report of the many research programs administered by the Mathematical, Information, and Computational Sciences (MICS) Division of the Office of Energy Research under the auspices of the HPCC Program and to provide, wherever relevant, easy access to pertinent information about MICS-Division activities via universal resource locators (URLs) on the World Wide Web (WWW). The information pointed to by the URL is updated frequently, and the interested reader is urged to access the WWW for the latest information.

NONE

1996-06-01

389

Communication: High speed optical investigations of a character of boiling-up onset  

NASA Astrophysics Data System (ADS)

In this communication, we discuss the phenomenon of attainable superheat of liquid and the peculiarities of its release by spontaneous boiling-up. We have combined the apparatus for superheating, namely, bubble chamber, with a high speed micro-optical method for detailed monitoring of the initial stage of boiling-up. In experiments on the isothermal pressure drop, it was found that the boiling-up onset of n-hexane is accompanied by characteristic step signal. The signal has proved to be typical of the heterogeneous character of boiling-up onset in a whole range of superheating degrees. The performance of the method for investigation of the refractive index and density for superheated liquids as functions of temperature and pressure has been revealed. The experimental error is estimated to be 0.1%.

Gurashkin, A. L.; Starostin, A. A.; Ermakov, G. V.; Skripov, P. V.

2012-01-01

390

High phase noise tolerant pilot-tone-aided DP-QPSK optical communication systems.  

PubMed

In this paper we experimentally demonstrate a novel, high phase-noise tolerant, optical dual polarization (DP) quadrature phase-shift keying (QPSK) communication system based on pilot-tone-aided phase noise cancellation (PNC) algorithm. Vertical cavity surface emitting lasers (VCSELs) with approximate 300 MHz linewidth are used as transmitters and local oscillators for coherent detection of optical DP-QPSK signals. The proposed system, with central wavelength at 1540.68 nm, operates at 40 Gb/s over 80 km single mode fiber (SMF) as part of a passive optical network (PON). The deployment of pilot-tone-aided PNC algorithm guarantees a bit error rate (BER) performance below the forward error correction (FEC) threshold. Moreover, we also evaluate a novel digital signal processing (DSP) algorithm for adaptive pilot tone detection. PMID:23037051

Zhang, Xu; Pang, Xiaodan; Deng, Lei; Zibar, Darko; Monroy, Idelfonso Tafur; Younce, Richard

2012-08-27

391

A high performance communications and memory caching scheme for molecular dynamics on the CM-5  

SciTech Connect

In this paper, we provide a brief overview of our general molecular dynamics algorithm and focus on several performance enhancements that have allowed us to achieve high performance on the CM-5. Our use of the CM-5 vector units (VUs) to calculate forces is described along with a memory caching scheme that speeds up the force calculation by as much as 50%. In addition, we discuss a method used to speed up the communication aspects of our algorithm by more than 35%. Lastly, recent timing and scaling results are presented. Our code has been implemented in ANSI C with explicit calls to the CMMD message-passing library. To use the VUs we have written our force calculation in CDPEAC (a C interface to the VU assembler language, DPEAC). We also assume that particles interact according to the Lennard-Jones 6--12 (LJ) potential.

Beazley, D.M.; Lomdahl, P.S.; Gronbech-Jensen, N.; Tamayo, P.

1993-09-15

392

A Study of an Optical Lunar Surface Communications Network with High Bandwidth Direct to Earth Link  

NASA Technical Reports Server (NTRS)

A lunar surface systems study explores the application of optical communications to support a high bandwidth data link from a lunar relay satellite and from fixed lunar assets. The results show that existing 1-m ground stations could provide more than 99% coverage of the lunar terminal at 100Mb/s data rates from a lunar relay satellite and in excess of 200Mb/s from a fixed terminal on the lunar surface. We have looked at the effects of the lunar regolith and its removal on optical samples. Our results indicate that under repeated dust removal episodes sapphire rather than fused silica would be a more durable material for optical surfaces. Disruption tolerant network protocols can minimize the data loss due to link dropouts. We report on the preliminary results of the DTN protocol implemented over the optical carrier.

Wilson, K.; Biswas, A.; Schoolcraft, J.

2011-01-01

393

Short spatial filters with spherical lenses for high-power pulsed lasers  

NASA Astrophysics Data System (ADS)

We report possible employment of short spatial filters based on spherical lenses in a pulsed laser source (neodymium glass, 300 J, 1 ns). The influence of the spherical aberration on the quality of output radiation and coefficient of conversion to the second harmonics is studied. The ultra-short aberration spatial filter of length 1.9 m with an aperture of 122 mm is experimentally tested. A considerable shortening of multi-cascade pump lasers for modern petawatt laser systems is demonstrated by the employment of short spatial filters without expensive aspherical optics.

Burdonov, K. F.; Soloviev, A. A.; Egorov, A. S.; Shaikin, A. A.; Potemkin, A. K.

2013-11-01

394

Secure Communications in High Speed Fiber Optical Networks Using Code Division Multiple Access (CDMA) Transmission  

SciTech Connect

This project is focused on the development of advanced components and system technologies for secure data transmission on high-speed fiber optic data systems. This work capitalizes on (1) a strong relationship with outstanding faculty at the University of California-Davis who are experts in high speed fiber-optic networks, (2) the realization that code division multiple access (CDMA) is emerging as a bandwidth enhancing technique for fiber optic networks, (3) the realization that CDMA of sufficient complexity forms the basis for almost unbreakable one-time key transmissions, (4) our concepts for superior components for implementing CDMA, (5) our expertise in semiconductor device processing and (6) our Center for Nano and Microtechnology, which is where the majority of the experimental work was done. Here we present a novel device concept, which will push the limits of current technology, and will simultaneously solve system implementation issues by investigating new state-of-the-art fiber technologies. This will enable the development of secure communication systems for the transmission and reception of messages on deployed commercial fiber optic networks, through the CDMA phase encoding of broad bandwidth pulses. CDMA technology has been developed as a multiplexing technology, much like wavelength division multiplexing (WDM) or time division multiplexing (TDM), to increase the potential number of users on a given communication link. A novel application of the techniques created for CDMA is to generate secure communication through physical layer encoding. Physical layer encoding devices are developed which utilize semiconductor waveguides with fast carrier response times to phase encode spectral components of a secure signal. Current commercial technology, most commonly a spatial light modulator, allows phase codes to be changed at rates of only 10's of Hertz ({approx}25ms response). The use of fast (picosecond to nanosecond) carrier dynamics of semiconductors, as opposed to field dynamics of liquid crystal molecules, enable phase codes at GHz rates. The semiconductor arrayed waveguide grating (AWG) is the building block of the encoder/decoder device. A monolithically integrated AWG is developed in this LDRD. Using this building block, the AWG can be integrated with phase modulators to create temporally varying phase codes; this allows superior physical level encoding technology. The breadth of this project is wide, covering a free space optic demonstration (large optic at the meter scale) of the encoding system. This was done as a proof-of-principal exercise and to investigate the time varying phase codes (''locks'' and ''keys''). Then a monolithically integrated AWG implemented at the millimeter was investigated. The mono lithically integrated AWG has the same functionality as the table top free space optic but reduced down in size to be easily embedded in fiber optic networks.

Han, I; Bond, S; Welty, R; Du, Y; Yoo, S; Reinhardt, C; Behymer, E; Sperry, V; Kobayashi, N

2004-02-12

395

High speed GaN micro-light-emitting diode arrays for data communications  

NASA Astrophysics Data System (ADS)

Micro light-emitting diode (micro-LED) arrays based on an AlInGaN structure have attracted much interest recently as light sources for data communications. Visible light communication (VLC), over free space or plastic optical fibre (POF), has become a very important technique in the role of data transmission. The micro-LEDs which are reported here contain pixels ranging in diameter from 14 to 84?m and can be driven directly using a high speed probe or via complementary metal-oxide semiconductor (CMOS) technology. The CMOS arrays allow for easy, computer control of individual pixels within arrays containing up to 16×16 elements. The micro-LEDs best suited for data transmission have peak emissions of 450nm or 520nm, however various other wavelengths across the visible spectrum can also be used. Optical modulation bandwidths of over 400MHz have been achieved as well as error-free (defined as an error rate of <1x10-10) data transmission using on-off keying (OOK) non-return-to-zero (NRZ) modulation at data rates of over 500Mbit/s over free space. Also, as a step towards a more practical multi-emitter data transmitter, the frequency response of a micro-LED integrated with CMOS circuitry was measured and found to be up to 185MHz. Despite the reduction in bandwidth compared to the bare measurements using a high speed probe, a good compromise is achieved from the additional control available to select each pixel. It has been shown that modulating more than one pixel simultaneously can increase the data rate. As work continues in this area, the aim will be to further increase the data transmission rate by modulating more pixels on a single device to transmit multiple parallel data channels simultaneously.

Watson, Scott; McKendry, Jonathan J. D.; Zhang, Shuailong; Massoubre, David; Rae, Bruce R.; Green, Richard P.; Gu, Erdan; Henderson, Robert K.; Kelly, A. E.; Dawson, Martin D.

2012-10-01

396

Optical performance monitoring in high-speed optical fiber communication systems  

NASA Astrophysics Data System (ADS)

Optical performance monitoring (OPM) becomes an attractive topic as the rapid growth of data rate in optical communication networks. It provides improved operation of the high capacity optical transmission systems. Among the various impairments, chromatic dispersion (CD) is one of major factors limiting the transmission distance in high-speed communication systems. Polarization-mode dispersion (PMD) also becomes a degrading effect in the system with data rate larger than 40 Gbit/s. In this paper, we summarize several CD and PMD monitoring methods based on RF spectrum analysis and delay-tap sampling. By using a narrow band fiber Bragg grating (FBG) notch filter, centered at 10 GHz away from the optical carrier, 10-GHz RF power can be used as a CD-insensitive PMD monitoring signal. By taking the 10-GHz RF power ratio of non-filtered and filtered signal, PMD-insensitive CD monitoring can be achieved. If the FBG notch filter is placed at optical carrier, the RF clock power ratio between non-filtered and filtered signal is also a PMDinsensitive CD monitoring parameter, which has larger RF power dynamic range and better measurement resolution. Both simulation and experiment results show that the proposed methods are efficient on measuring CD and PMD values in 57-Gbit/s D8PSK systems. Delay-tap sampling is another efficient method of measuring residual CD. Amplitude ratio of asynchronous delay-tap sampling plot decreases with CD monotonously, and the amplitude ratio can be obtained by using low bandwidth balanced receiver. The simulated results show that our method is efficient on residual CD measurement in 50-Gbit/s 50% RZ DQPSK systems with a 12-GHz balanced receiver. Since no modification on the transmitter or receiver is required, the proposed scheme is simple and cost effective.

Yu, Changyuan; Yang, Jing; Hu, Junhao; Zhang, Banghong

2011-11-01

397

A Framework for Assessing High School Students' Intercultural Communicative Competence in a Computer-Mediated Language Learning Project  

ERIC Educational Resources Information Center

The purposes of this study were to identify the essential dimensions of intercultural communicative competence (ICC) and to establish a framework for assessing the ICC level of high school students that included a self-report inventory and scoring rubrics for online interaction in intercultural contexts. A total of 472 high school students from…

Peng, Hsinyi; Lu, Wei-Hsin; Wang, Chao-I

2009-01-01

398

Novel High-Voltage, High-Power Piezoelectric Transformer Developed and Demonstrated for Space Communications Applications  

NASA Technical Reports Server (NTRS)

Improvements in individual piezoelectric transformer (PT) performance and the combination of these PTs in a unique modular topology under a Phase I contract with the NASA Glenn Research Center have enabled for the first time the simultaneous achievement of both high voltage and high power at much higher levels than previously obtained with any PT. Feasibility was demonstrated by a prototype transformer (called a Tap-Soner), which is shown in the preceding photograph as part of a direct-current to direct-current (dc-dc) converter having two outputs rated at 1.5 kV/5 W and 4.5 kV/20 W. The power density of 3.5 W/cm3 is significantly lower than for magnetic transformers with the same voltage and power output. This development, which is being done under a Small Business Innovation Research (SBIR) contract by Face Electronics, LC (Norfolk, VA), is based on improvements in the materials and design of Face's basic patented Transoner-T3 PT, shown in the left in the following figure. The T3 PT is most simply described as a resonant multilayer transducer where electrical energy at the input section is efficiently mechanically coupled to the output section, which then vibrates in a fundamental longitudinal mode to generate a high gain in voltage. The piezoelectric material used is a modified lead-zirconium-titanate-based ceramic. One of the significant improvements in PT design was the incorporation of a symmetrical double input layer, shown on the right in the following figure, which eliminated the lossy bending vibration modes characteristic of a single input layer. The performance of the improved PT was optimized to 1.5 kV/5 W. The next step was devising a way to combine the individual PTs in a modular circuit topology needed to achieve the desired high voltage and power output. Since the optimum performance of the individual PT occurs at resonance, the most efficient operation of the modular transformer was achieved by using a separate drive circuit for each PT. The output section consists of a separate output rectifier for each PT connected in series.

Carazo, Alfredo V.; Wintucky, Edwin G.

2004-01-01

399

Large-amplitude plasma wave generation with a high-intensity short-pulse beat wave  

Microsoft Academic Search

A short-pulse laser beat wave scheme for advanced particle accelerator applications is examined. A short, intense (3-ps, >1018-W cm-2) two-frequency laser pulse is produced by use of a modified chirped-pulse amplification scheme and is shown to produce relativistic plasma waves during interactions with low-density plasmas. The generation of plasma waves was observed by measurement of forward Raman scattering. Resonance was

B. Walton; Z. Najmudin; M. S. Wei; C. Marle; R. J. Kingham; K. Krushelnick; A. E. Dangor; R. J. Clarke; M. J. Poulter; C. Hernandez-Gomez; S. Hawkes; D. Neely; J. L. Collier; C. N. Danson; S. Fritzler; V. Malka

2002-01-01

400

Acoustic Navigation and Communication forHigh-Latitude Ocean Research Workshop  

NASA Astrophysics Data System (ADS)

Recent community reports on autonomousplatforms and Arctic observing U.S. NationalScience Foundation, 2002; Proshutinsky et al.,2004; Rudnick and Perry, 2003 identify thedevelopment of under-ice navigation andtelemetry technologies as one of the criticalfactors limiting the scope of high-latitudemeasurement efforts. Advances in autonomousplatforms (profiling floats, drifters,long-range gliders, and propeller-driven vehicles)promise to revolutionize ocean observations,providing unprecedented spatialand temporal resolution for both short-durationprocess studies and multiyear effortsdesigned to quantify long-timescale environmentalchanges. This new generation of platformsfacilitates access to logistically difficultregions where weather and remotenesschallenge conventional techniques, makingthem attractive for polar regions. These platformscould provide persistent, high-resolution,basin-wide sampling in ice-coveredregions and operate near the critical icewaterinterface.

Lee, Craig M.; Gobat, Jason I.

2006-07-01

401

Innovative, High-Pressure, Cryogenic Control Valve: Short Face-to-Face, Reduced Cost  

NASA Technical Reports Server (NTRS)

A control valve that can throttle high-pressure cryogenic fluid embodies several design features that distinguish it over conventional valves designed for similar applications. Field and design engineers worked together to create a valve that would simplify installation, trim changes, and maintenance, thus reducing overall cost. The seals and plug stem packing were designed to perform optimally in cryogenic temperature ranges. Unlike conventional high-pressure cryogenic valves, the trim size can be changed independent of the body. The design feature that provides flexibility for changing the trim is a split body. The body is divided into an upper and a lower section with the seat ring sandwiched in between. In order to maintain the plug stem packing at an acceptable sealing temperature during cryogenic service, heat-exchanging fins were added to the upper body section. The body is made of stainless steel. The seat ring is made of a nickel-based alloy having a coefficient of thermal expansion less than that of the body material. Consequently, when the interior of the valve is cooled cryogenically, the body surrounding the seat ring contracts more than the seat ring. This feature prevents external leakage at the body-seat joint. The seat ring has been machined to have small, raised-face sealing surfaces on both sides of the seal groove. These sealing surfaces concentrate the body bolt load over a small area, thereby preventing external leakage. The design of the body bolt circle is different from that of conventional highpressure control valves. Half of the bolts clamp the split body together from the top, and half from the bottom side. This bolt-circle design allows a short, clean flow path, which minimizes frictional flow losses. This bolt-circle design also makes it possible to shorten the face-toface length of the valve, which is 25.5 in. (65 cm). In contrast, a conventional, high-pressure control valve face-to-face dimension may be greater than 40 in. (>1 m) long.

2002-01-01

402

Highly variable chemical signatures over short spatial distances among Scots pine (Pinus sylvestris) populations.  

PubMed

Understanding within-species variability in terpenoid content and composition is highly relevant for predicting species adaptive potential to biotic stresses, but there is still limited information on terpene variations even for widespread species. We studied the foliage content and composition of terpenoids, foliage structure, and carbon (C) and nitrogen (N) contents in Pinus sylvestris L. in four Estonian sites ranging from dry forest to raised bog. In the bogs, samples were taken along the environmental gradient from drier margins towards wetter central parts. A chiral column was used to gain insight into the variation in terpene composition. We hypothesized that terpene contents increase and the composition becomes more diverse in more strongly N-limited sites (greater C/N ratio) and that terpene signatures cluster together in sub-sites with similar conditions (drier/wetter). Altogether 37 terpenes were quantified across the sites. Extremely large variability of terpene contents, 48-62% for monoterpenes and 61-89% for sesquiterpenes, was observed. According to the amounts of ?-pinenes and (+)-3-carene, we distinguished two different 'pine chemotypes'. Contrary to the hypothesis, terpene contents and variability were the greatest in the dry site with the lowest C/N ratio. However, individual terpenoids correlated differently with C or N in different sites, indicating site effects on terpene composition. Moreover, correlations between the terpenoids and C or N depended on the pine chemotype. The sub-sites with different water regime were more strongly clustered together within the site than across the sites. The study demonstrates extensive variations in terpene contents and composition among the populations and over short spatial distances within the populations, suggesting a large among- and within-population adaptive capacity of P. sylvestris. PMID:23513034

Kännaste, Astrid; Copolovici, Lucian; Pazouki, Leila; Suhhorutšenko, Marina; Niinemets, Ülo

2013-04-01

403

Using Transmission Control Protocol in the Trans-Pacific High Definition Video Satellite Communication Experiment - the Next Test  

NASA Technical Reports Server (NTRS)

Ths paper describes a future Transmission Control Protocol (TCP) test which was planned as a part of the Trans-Pacific High Definition Video Satellite Communications Experiment. The TCP test portion of the Trans-Pacific High Definition Video Satellite Communications Experiment intends to examine the correlation between the underlying assumptions of come TCP algorithms and the performance shortfalls observed when the algorithms are used in a stellite-based environment, and to make experimental changes to existing TCP variants to study the effects of the modifications.

Hsu, E.

1998-01-01

404

Starbursts and high-redshift galaxies are radioactive: high abundances of 26Al and other short-lived radionuclides  

NASA Astrophysics Data System (ADS)

Short-lived radionuclides (SLRs) like 26Al are synthesized by massive stars and are a byproduct of star formation. The abundances of SLRs in the gas of a star-forming galaxy are inversely proportional to the gas consumption time. The rapid evolution of specific star formation rate (SSFR) of normal galaxies implies they had mean SLR abundances ˜3-10 times higher at z = 2. During the epoch of Solar system formation, the background SLR abundances of the Galaxy were up to twice as high as at present, if SLR yields from massive stars do not depend on metallicity. If SLRs are homogenized in the gas of galaxies, the high SSFRs of normal galaxies can partly explain the elevated abundance of SLRs like 60Fe and 26Al in the early Solar system. Starburst galaxies have much higher SSFRs still, and have enormous mean abundances of 26Al (26Al/27Al ?10-3 for solar metallicity gas). The main uncertainty is whether the SLRs are mixed with the star-forming molecular gas: they could be trapped in hot gas and decay before entering the colder phases, or be blown out by starburst winds. I consider how variability in star formation rate affects the SLR abundances, and I discuss how SLR transport may differ in these galaxies. The enhanced 26Al of starbursts might maintain moderate ionization rates (10-18-10-17 s-1), possibly dominating ionization in dense clouds not penetrated by cosmic rays. Similar ionization rates would be maintained in protoplanetary discs of starbursts, if the SLRs are well mixed, and the radiogenic heating of planetesimals would likewise be much higher. In this way, galaxy evolution can affect the geological history of planetary systems.

Lacki, Brian C.

2014-06-01

405

Effects of Various Physical Training Programs on Short Duration, High Intensity Load Bearing Performance and the Army Physical Fitness Test.  

National Technical Information Service (NTIS)

The purpose of this study was to contrast the effects of different physical training programs on short duration, high intensity load bearing performance and Army Physical Fitness Test (APFT) scores. Thirty-five soldiers were randomly assigned to one of fo...

J. A. Vogel J. E. Dziados J. F. Patton K. L. Reynolds W. J. Kraemer

1987-01-01

406

High resolution kinetic energy release spectra and angular distributions from double ionization of nitrogen and oxygen by short laser pulses  

Microsoft Academic Search

We have used momentum imaging techniques to measure in high resolution the kinetic energy release spectra and angular distributions of coincident O+ and N+ ion pairs produced by short laser pulses (8-35 fs) on targets of N2 and O2 at peak intensities between 1 and 12 × 1014 W cm-2. We record the full momentum vectors of both members of

S. Voss; A. S. Alnaser; X.-M. Tong; C. Maharjan; P. Ranitovic; B. Ulrich; B. Shan; Z. Chang; C. D. Lin; C. L. Cocke

2004-01-01

407

Visuospatial Short-Term Memory Explains Deficits in Tower Task Planning in High-Functioning Children with Autism Spectrum Disorder  

Microsoft Academic Search

Previous findings on planning abilities in individuals with high-functioning autism spectrum disorder (HFA) are inconsistent. Exploring possible reasons for these mixed findings, the current study investigated the involvement of memory in planning performance in 15 children with HFA and 17 typically developing controls. In addition to planning abilities (measured with the Tower of London), short-term memory and delayed recall for

Katharina Zinke; Eva Fries; Mareike Altgassen; Clemens Kirschbaum; Lucia Dettenborn; Matthias Kliegel

2010-01-01

408

Impact of background light induced shot noise in high-speed full-duplex indoor optical wireless communication systems.  

PubMed

The use of infrared radiation to provide high speed indoor wireless communication has attracted considerable attention for over a decade. In previous studies we proposed a novel full-duplex indoor optical wireless communication system with high-speed data transmission and limited mobility can be provided to users. When it is incorporated with localization function, gigabit mobile communication can be provided over the entire room. In this paper we theoretically analyze the limiting factor of our proposed system - background light induced shot noise. A theoretical model that allows the receiver sensitivity and the corresponding power penalty is proposed and the model is validated by experiments. Experimental results show that for both down-link and up-link transmission the background light will result in several dB power penalty and it is more dominant in lower speed links. As the bit rate increases, the preamplifier induced noise becomes larger and eventually dominates the noise process. PMID:22108983

Wang, Ke; Nirmalathas, Ampalavanapillai; Lim, Christina; Skafidas, Efstratios

2011-10-24

409

In-situ short circuit protection system and method for high-energy electrochemical cells  

DOEpatents

An in-situ thermal management system for an energy storage device. The energy storage device includes a plurality of energy storage cells each being coupled in parallel to common positive and negative connections. Each of the energy storage cells, in accordance with the cell's technology, dimensions, and thermal/electrical properties, is configured to have a ratio of energy content-to-contact surface area such that thermal energy produced by a short-circuit in a particular cell is conducted to a cell adjacent the particular cell so as to prevent the temperature of the particular cell from exceeding a breakdown temperature. In one embodiment, a fuse is coupled in series with each of a number of energy storage cells. The fuses are activated by a current spike capacitively produced by a cell upon occurrence of a short-circuit in the cell, thereby electrically isolating the short-circuited cell from the common positive and negative connections.

Gauthier, Michel (La Prairie, CA); Domroese, Michael K. (South St. Paul, MN); Hoffman, Joseph A. (Minneapolis, MN); Lindeman, David D. (Hudson, WI); Noel, Joseph-Robert-Gaetan (St-Hubert, CA); Radewald, Vern E. (Austin, TX); Rouillard, Jean (Saint-Luc, CA); Rouillard, Roger (Beloeil, CA); Shiota, Toshimi (St. Bruno, CA); Trice, Jennifer L. (Eagan, MN)

2000-01-01

410

In-situ short-circuit protection system and method for high-energy electrochemical cells  

DOEpatents

An in-situ thermal management system for an energy storage device. The energy storage device includes a plurality of energy storage cells each being coupled in parallel to common positive and negative connections. Each of the energy storage cells, in accordance with the cell's technology, dimensions, and thermal/electrical properties, is configured to have a ratio of energy content-to-contact surface area such that thermal energy produced by a short-circuit in a particular cell is conducted to a cell adjacent the particular cell so as to prevent the temperature of the particular cell from exceeding a breakdown temperature. In one embodiment, a fuse is coupled in series with each of a number of energy storage cells. The fuses are activated by a current spike capacitively produced by a cell upon occurrence of a short-circuit in the cell, thereby electrically isolating the short-circuited cell from the common positive and negative connections.

Gauthier, Michel (La Prairie, CA); Domroese, Michael K. (South St. Paul, MN); Hoffman, Joseph A. (Minneapolis, MN); Lindeman, David D. (Hudson, WI); Noel, Joseph-Robert-Gaetan (St-Hubert, CA); Radewald, Vern E. (Austin, TX); Rouillard, Jean (Saint-Luc, CA); Rouillard, Roger (Beloeil, CA); Shiota, Toshimi (St. Bruno, CA); Trice, Jennifer L. (Eagan, MN)

2003-04-15

411

Multipath Effects on High-Frequency Coherent Acoustic Communications in Shallow Water  

NASA Astrophysics Data System (ADS)

Shallow-water acoustic communication channel, referred to as a multipath-limited channel, produces inter-symbol interference that poses a significant obstacle to reliable communication. Accordingly, signal-to-multipath ratio (SMR), rather than signal-to-noise ratio (SNR), becomes an important factor affecting communication performance. However, it is difficult to estimate SMR from measured communication data, especially at higher frequency (>10 kHz) because many arrivals scattered from rough ocean boundaries produce a significant intrapath time spreading, which acts as random noise in communication. In this paper, the energy fraction of the channel impulse response existing in one symbol duration is proposed as a parameter for estimating the quality of shallow-water communication channels. This parameter is compared with the bit-error-rate performance for data acquired in shallow water off the south coast of Korea, where the water depth is 45 m and the bottom consists of sandy clay sediment. The results imply that the energy fraction in one symbol duration may be used as a parameter for describing shallow-water communication channels and applied to the quick decision of a symbol or bit rate in a shallow-water field for reliable underwater communication.

Son, Su-Uk; Kim, Hyeonsu; Joo, Jongmin; Choi, Jee Woong

2013-07-01

412

Annual Enrollment Report Number of Students Studying Journalism and Mass Communication at All-time High.  

ERIC Educational Resources Information Center

Finds that journalism and mass communication programs appear to be entering another period of rapid enrollment growth, swept up by overall increases in enrollments at United States universities. Finds that only about four in ten of the journalism and mass communication programs report enrollments by race, suggesting many administrators are not…

Becker, Lee B.; Vlad, Tudor; Huh, Jisu; Prine, Joelle

2001-01-01

413

High speed RS232 fibre optic communication system for underwater remotely operated vehicles  

Microsoft Academic Search

The design and implementation of a communication system for an underwater remotely operated vehicle (ROV) are presented. The system is assumed to be composed of a remotely operated vehicle driven by a set of seven thrusters, a tethering cable including power supply cables and two fibres for communication (the function of which is to transmit and monitor information) and a

J. N. Lygouras; A. Kapsopoulos; Ph. G. Tsalides

1995-01-01

414

High-Speed Visible Light Communications Using Multiple-Resonant Equalization  

Microsoft Academic Search

White light-emitting diodes (LEDs) are becoming widespread in commercial lighting applications, and there are predictions that they will be in common use in domestic applications in the future. There is also growing interest in using these devices for both illumination and communications. One of the major challenges in visible light communications is the low modulation bandwidth (BW) available from devices,

Hoa Le Minh; Dominic O'Brien; Grahame Faulkner; Lubin Zeng; Kyungwoo Lee; Daekwang Jung; Yunje Oh

2008-01-01

415

DYMAC communications system  

SciTech Connect

The DYMAC Communications System is part of a nuclear safeguards system called DYMAC - short for DYnamic Materials ACcountability - that gathers accountability information at the Los Alamos Scientific Laboratory (LASL) Plutonium Processing Facility. The communications system handles transmissions between data-entry terminals and nondestructive assay (NDA) instruments located in the facility, and a computer located in an adjacent building. System design emphasizes reliability rather than high speed to ensure the integrity of data transmissions. This manual is directed toward the person responsible for maintaining the DYMAC Communication System. It describes the components that make up the communications network, explains how they operate, and gives detailed information about all of the connections. Many of the system components are commercially available; some have been modified at LASL for DYMAC purposes; others were designed and fabricated at LASL. This manual provides circuit diagrams for all of the LASL modifications and LASL-fabricated equipment. In addition, it provides a series of procedures for tracing cables, reconfiguring various parts of the system, testing data transmissions, and troubleshooting malfunctions.

Lindsey, K.A.

1980-01-01

416

High-performance Optical Receivers Using Conventional Sub-micron CMOS Technology for Optical Communication Applications  

NASA Astrophysics Data System (ADS)

A novel sub-micron total-CMOS common-gate Transimpedance Amplifier (TIA) has been designed for high-speed optical communication applications. This total-CMOS approach has given a tremendous flexibility in optimizing the circuit for high performance. The new design shows superior performance compared to recent common-gate and common-base TIAs. Using conventional 0.8 µm CMOS process parameters, simulations showed a transimpedance gain of 69.0 dB over a 3.5 GHz bandwidth, approaching the technology fT of 10 GHz. The mean input referred noise current density was calculated to be 21.2 pA/Hz0.5 at 3.5 GHz, giving an input optical sensitivity of -20.4 dBm for a BER of 10-9. This allows a data transmission easily at 2.5 Gbps for a NRZ synchronous link. The power consumption is only 44 mW when AC coupled to a 50 ? load. In addition, the TIA was designed to tolerate a relatively wide variation in bias conditions while preserving stability. Moreover, simulations using a 0.6 µm CMOS process showed even lower noise and wider bandwidth now at 6.0 GHz. The new design approaches similar IC designs in Si-bipolar or GaAs technologies. The design is the first reported TIA, which combines such features and using conventional 0.8 µm CMOS transistors with fT = 10 GHz.

Touati, F.; Douss, S.; Elfadil, N.; Nadir, Z.; Suwailam, M. B.; Loulou, M.

417

Ground Radar Polarimetric Observations of High-Frequency Earth-Space Communication Links  

NASA Technical Reports Server (NTRS)

Strategic roadmaps for NASA's Human Exploration and Development of Space (REDS) enterprise support near-term high-frequency communication systems that provide moderate to high data rates with dependable service. Near-earth and human planetary exploration will baseline Ka-Band, but may ultimately require the use of even higher frequencies. Increased commercial demand on low-frequency earth-space bands has also led to increased interest in the use of higher frequencies in regions like K u - and K,- band. Data is taken from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR), which operates at 13.8 GHz, and the true radar reflectivity profile is determined along the PR beam via low-frequency ground based polarimetric observations. The specific differential phase (Kdp) is measured along the beam and a theoretical model is used to determine the expected specific attenuation (k). This technique, called the k-Kdp method, uses a Fuzzy-Logic model to determine the hydrometeor type along the PR beam from which the appropriate k-Kdp relationship is used to determine k and, ultimately, the total path-integrated attenuation (PIA) on PR measurements. Measurements from PR and the NCAR S-POL radar were made during the TEFLUN-B experiment that took place near Melbourne, FL in 1998, and the TRMM-LBA campaign near Ji-Parana, Brazil in 1999.

Bolen, Steve; Chandrasekar, V.; Benjamin, Andrew

2002-01-01

418

An implementation of the SNR high speed network communication protocol (Receiver part)  

NASA Astrophysics Data System (ADS)

This thesis work is to implement the receiver pan of the SNR high speed network transport protocol. The approach was to use the Systems of Communicating Machines (SCM) as the formal definition of the protocol. Programs were developed on top of the Unix system using C programming language. The Unix system features that were adopted for this implementation were multitasking, signals, shared memory, semaphores, sockets, timers and process control. The problems encountered, and solved, were signal loss, shared memory conflicts, process synchronization, scheduling, data alignment and errors in the SCM specification itself. The result was a correctly functioning program which implemented the SNR protocol. The system was tested using different connection modes, lost packets, duplicate packets and large data transfers. The contributions of this thesis are: (1) implementation of the receiver part of the SNR high speed transport protocol; (2) testing and integration with the transmitter part of the SNR transport protocol on an FDDI data link layered network; (3) demonstration of the functions of the SNR transport protocol such as connection management, sequenced delivery, flow control and error recovery using selective repeat methods of retransmission; and (4) modifications to the SNR transport protocol specification such as corrections for incorrect predicate conditions, defining of additional packet types formats, solutions for signal lost and processes contention problems etc.

Wan, Wen-Jyh

1995-03-01

419

Analysis of high-voltage generator stator windings sudden three-phase short-circuit and loss of excitation fault  

Microsoft Academic Search

Base on a prototype of the 130 kw\\/5 kv high voltage generator, the system simulation model is set up for the generator stator windings suddenly three-phase short-circuit failure and loss of excitation failures. The dynamic simulation compared with experiment on DJ18-1 synchronous generator, it reaches conclusion that the system simulation model is correct. The current of the high-voltage generator stator

Lv Yan-ling; Ge Bao-jun; Li Cui-cui; Tao Da-jun; Zhang Zhi-qiang

2009-01-01

420

Means and method for characterizing high power, ultra short laser pulses in a real time, on line manner  

DOEpatents

An ultra short (<10 ps), high power laser pulse is temporally characterized by a system that uses a physical measurement of a wavefront that has been altered in a known manner. The system includes a first reflection switch to remove a portion of a pulse from a beam of pulses, then includes a second reflection switch, operating in a mode that is opposite to the first reflection switch, to slice off a portion of that removed portion. The sliced portion is then directed to a measuring device for physical measurement. The two reflection switches are arranged with respect to each other and with respect to the beam of ultra short pulses such that physical measurement of the sliced portion is related to the temporal measurement of the ultra short pulse by a geometric or trigonometric relationship. The reflection switches are operated by a control pulse that is directed to impinge on each of the reflection switches at a 90.degree. angle of incidence.

Veligdan, James T. (Manorville, NY) [Manorville, NY

1994-01-01

421

Design of an Electro-Optic Modulator for High Speed Communications  

NASA Astrophysics Data System (ADS)

The telecommunications and computer technology industries have been requiring higher communications speeds at all levels for devices, components and interconnected systems. Optical devices and optical interconnections are a viable alternative over other traditional technologies such as copper-based interconnections. Latency reductions can be achieved through the use of optical interconnections. Currently, a particular architecture for optical interconnections is being studied at the University of Colorado at Boulder in the EMT/NANO project, called Broadcast Optical Interconnects for Global Communication in Many-Core Chip Multiprocessor. As with most types of networks, including optical networks, one of the most important components are modulators. Therefore adequate design and fabrication techniques for modulators contribute to higher modulation rates which lead to improve the efficiency and reductions in the latency of the optical network. Electro-optical modulators are presented in this study as an alternative to achieve this end. In recent years, nonlinear optical (NLO) materials have been used for the fabrication of high-speed electro-optical modulators. Polymers doped with chromophores are an alternative among NLO materials because they can develop large electro-optic coefficients and low dielectric constants. These two factors are critical for achieving high-speed modulation rates. These polymer-based electro-optical modulators can be fabricated using standard laboratory techniques, such as polymer spin-coating onto substrates, UV bleaching to achieve a refractive index variation and poling techniques to align the chromophores in cured polymers. The design of the electro-optic modulators require the use of the optical parameters of the materials to be used. Therefore the characterization of these materials is a required previous step. This characterization is performed by the fabrication of chromophores-doped polymer samples and conducting transmission and reflection measurements to obtain the optical density. Then, using the Kramer-Kronig analysis, the refractive index change can be calculated. Another measured parameter is the electro-optic coefficient. After obtaining these optical and electric parameters, they are used as inputs in the Computer Aid Design (CAD) software COMSOL Multiphysics to carry out the simulation of the modes of the waveguide. Finally, an analysis of nanotechnology and nanophotonics in telecommunications can show us how the design of optical devices using NLO materials fits in a much larger technological area. It is important to have an understanding of the industry that this technology is a part of. A roadmap for nanophotonics shows where this technology is going and what kind of technological constraints or needs it can solve.

Espinoza, David

422

Short-term outcomes of CyberKnife therapy for advanced high-risk tumors: A report of 160 cases  

PubMed Central

The objective of the present study was to evaluate short-term outcomes of CyberKnife therapy in patients with advanced high-risk tumors. A total of 201 target areas from 341 advanced high-risk tumor lesions in 160 patients were treated with CyberKnife. A prescribed dose of 18–60 Gy to the gross tumor volume was delivered in 1–6 fractions to complete the entire treatment in 1 week. Radiographic studies and clinical examinations were performed at 1- to 3-month follow-up intervals, and the results were compared to outcomes of 160 similar advanced high-risk tumor patients who were treated by conformal radiotherapy (CRT). After CyberKnife therapy, the short-term improvement in the quality of life was significant according to radiographic study, radioimmunoassay and ZPS scores of these patients. The total rates of objective efficacy and alleviation of ascities were as high as 66.88 and 67.90%. The short-term outcomes in our series of patients with advanced high-risk tumors treated with CyberKnife appeared to be better compared to conventional CRT. CyberKnife may be an option for patients with incurable advanced high-risk tumors, although further studies of the long-term outcomes are required to confirm the validity.

WANG, YI-SHAN; WANG, YUAN-YUAN; JIANG, PENG; MA, JIAN-JUN; QU, ZHEN; WANG, XI-LIN; LI, JUN-TI; JIA, XI-FENG

2012-01-01

423

A simple model for high fluence ultra-short pulsed laser metal ablation  

Microsoft Academic Search

The ultra-short laser metal ablation is a very complex process, the complete simulation of which requires applications of complicated hydrodynamics or molecular dynamics models, which, however, are often time-consuming and difficult to apply. For many practical applications, where the laser ablation depth is the main concern, a simplified model that is easy to apply but at the same time can

Benxin Wu; Yung C. Shin

2007-01-01

424

Short-circuit tests on a high-voltage, cable-wound hydropower generator  

Microsoft Academic Search

Data from measurements on the first Powerformer generator installed in Porjus, Sweden, will be presented. The generator has a rating of 45 kV and 11 MVA. In total, the machine has been running more than 13700 h (October 2001) and has been exposed to a number of different tests including short-circuit tests on the terminal at 100% magnetization. Experience and

Stefan G. Johansson; Bertil Larsson

2004-01-01

425

Study of short haul high-density V/STOL transportation systems. Volume 2: Appendices  

NASA Technical Reports Server (NTRS)

Essential supporting data to the short haul transportation study are presented. The specific appendices are arena characteristics, aerospace transportation analysis computer program, economics, model calibration, STOLport siting and services path selection, STOL schedule definition, tabulated California corridor results, and tabulated Midwest arena results.

Solomon, H. L.

1972-01-01

426

Quench performance of Fermilab high gradient quadrupole short models for the LHC Interaction Regions  

Microsoft Academic Search

Fermilab and LBNL are in the midst of superconducting magnet R&D program to test and optimize the design of quadrupoles to be used in the LHC Interaction Region inner triplets. The magnets are required to deliver a 215 T\\/m gradient across a 70 mm aperture. Five quadrupole short models have been fabricated and four of them have been tested. This

N. Andreev; T. Arkan; R. Bossert; J. Brandt; D. Chichili; J. DiMarco; S. Feher; J. Kerby; M. J. Lamm; P. J. Limon; F. Nobrega; D. Orris; I. Novitski; J. P. Ozelis; T. Peterson; G. Sabbi; P. Schlabach; J. Strait; M. Tartaglia; J. C. Tompkins; S. Yadav; A. V. Zlobin; S. Caspi; A. D. McInturff; R. M. Scanlan; A. Ghosh

1999-01-01

427

Rapid short-term rates of intraplate seismicity related to episodic release of high pore pressure  

Microsoft Academic Search

One puzzling characteristic of intraplate seismicity is that centers of intense seismic activity appear to be geologically short-lived. Comparison of earthquake focal mechanisms with independent stress orientation data indicate that faulting in these intraplate areas is occurring in response to a relatively uniform regional stress field derived from far-field sources that are unlikely to change rapidly with time. The authors

M. L. Zoback; M. D. Zoback

1992-01-01

428

High Speed Buffer Board A SAIL EIA-485 Communications Accelerator Card for the Vector Measuring Current Meter.  

National Technical Information Service (NTIS)

A High Speed Buffer Board )HSBB) has been developed for the Vector Measuring Current Meter(VMCM) to implement the transmission of data at 9600 baud over an EIA-485 link. The HSBB significantly extends the VMCM communication functionality, which was previo...

R. Singer D. M. Butler

1990-01-01

429

High-Frequency Wireless Communications System: 2.45-GHz Front-End Circuit and System Integration  

ERIC Educational Resources Information Center

In this article, a course on high-frequency wireless communications systems is presented. With the 145-MHz baseband subsystem available from a prerequisite course, the present course emphasizes the design and implementation of the 2.45-GHz front-end subsystem as well as system integration issues. In this curriculum, the 2.45-GHz front-end…

Chen, M.-H.; Huang, M.-C.; Ting, Y.-C.; Chen, H.-H.; Li, T.-L.

2010-01-01

430

InfoMall: A Scalable Organisation for the Development of High-Performance Computing and Communications - Software and Systems  

Microsoft Academic Search

InfoMall is a programme lead by the Northeast Parallel Architectures Center (NPAC) featuring a partnership of over twenty-five organisations and a plan for accelerating development of the High Performance Computing and Communications (HPCC) software and systems industry. HPCC (or HPCN as it is known in Europe) is a critical technology which will have unprecedented impact on industry, education, society, and

Geoffrey Fox; E. Bogucz; D. A. Jones; Kim Mills; Marek Podgorny; Kenneth A. Hawick

1994-01-01

431

When Asking Questions Is Not Enough: An Observational Study of Social Communication Differences in High Functioning Children with Autism  

ERIC Educational Resources Information Center

This investigation examined communication patterns between high functioning children with autism and their families and typically developing children and their families within traditional dinner time conversation. Twenty families with a child with autism (3.5-7 years.) and ten families with typically developing children (3.5-6 years) were video…

Jones, Christopher D.; Schwartz, Ilene S.

2009-01-01

432

Cryptanalysis and improvement of three-particle deterministic secure and high bit-rate direct quantum communication protocol  

NASA Astrophysics Data System (ADS)

The three-particle deterministic secure and high bit-rate direct quantum communication protocol and its improved version are analyzed. It shows that an eavesdropper can steal the sender's secret message by the intercept-resend attack and the entanglement attack. The original version is even fragile under denial-of-service attack. As a result, some suggestions to revise them are given.

Liu, Zhi-Hao; Chen, Han-Wu; Wang, Dong; Li, Wen-Qian

2014-06-01

433

Molecular Communication - A Biochemically-Engineered Communication System  

Microsoft Academic Search

Molecular communication uses molecules (i.e., chemical signals) as an information carrier and allows biological and artificially-created nano- or cell-scale devices to communicate over a short distance. It is a new communication paradigm and is different from the existing communication paradigm that uses electromagnetic waves (i.e., electronic and optical signals) as an information carrier. Key research challenges in molecular communication include

Yuki Moritani; Satoshi Hiyama; Tatsuya Suda

2007-01-01

434

Modelling single shot damage thresholds of multilayer optics for high-intensity short-wavelength radiation sources.  

PubMed

The single shot damage thresholds of multilayer optics for high-intensity short-wavelength radiation sources are theoretically investigated, using a model developed on the basis of experimental data obtained at the FLASH and LCLS free electron lasers. We compare the radiation hardness of commonly used multilayer optics and propose new material combinations selected for a high damage threshold. Our study demonstrates that the damage thresholds of multilayer optics can vary over a large range of incidence fluences and can be as high as several hundreds of mJ/cm(2). This strongly suggests that multilayer mirrors are serious candidates for damage resistant optics. Especially, multilayer optics based on Li(2)O spacers are very promising for use in current and future short-wavelength radiation sources. PMID:23263054

Loch, R A; Sobierajski, R; Louis, E; Bosgra, J; Bijkerk, F

2012-12-17

435

Final Report and Documentation for the Optical Backplane/Interconnect for High Speed Communication LDRD  

SciTech Connect

Current copper backplane technology has reached the technical limits of clock speed and width for systems requiring multiple boards. Currently, bus technology such as VME and PCI (types of buses) will face severe limitations are the bus speed approaches 100 MHz. At this speed, the physical length limit of an unterminated bus is barely three inches. Terminating the bus enables much higher clock rates but at drastically higher power cost. Sandia has developed high bandwidth parallel optical interconnects that can provide over 40 Gbps throughput between circuit boards in a system. Based on Sandia's unique VCSEL (Vertical Cavity Surface Emitting Laser) technology, these devices are compatible with CMOS (Complementary Metal Oxide Semiconductor) chips and have single channel bandwidth in excess of 20 GHz. In this project, we are researching the use of this interconnect scheme as the physical layer of a greater ATM (Asynchronous Transfer Mode) based backplane. There are several advantages to this technology including small board space, lower power and non-contact communication. This technology is also easily expandable to meet future bandwidth requirements in excess of 160 Gbps sometimes referred to as UTOPIA 6. ATM over optical backplane will enable automatic switching of wide high-speed circuits between boards in a system. In the first year we developed integrated VCSELs and receivers, identified fiber ribbon based interconnect scheme and a high level architecture. In the second year, we implemented the physical layer in the form of a PCI computer peripheral card. A description of future work including super computer networking deployment and protocol processing is included.

ROBERTSON, PERRY J.; CHEN, HELEN Y.; BRANDT, JAMES M.; SULLIVAN, CHARLES T.; PIERSON, LYNDON G.; WITZKE, EDWARD L.; GASS, KARL

2001-03-01

436

Low latency, high bandwidth data communications between compute nodes in a parallel computer  

DOEpatents

Methods, parallel computers, and computer program products are disclosed for low latency, high bandwidth data communications between compute nodes in a parallel computer. Embodiments include receiving, by an origin direct memory access (`DMA`) engine of an origin compute node, data for transfer to a target compute node; sending, by the origin DMA engine of the origin compute node to a target DMA engine on the target compute node, a request to send (`RTS`) message; transferring, by the origin DMA engine, a predetermined portion of the data to the target compute node using memory FIFO operation; determining, by the origin DMA engine whether an acknowledgement of the RTS message has been received from the target DMA engine; if the an acknowledgement of the RTS message has not been received, transferring, by the origin DMA engine, another predetermined portion of the data to the target compute node using a memory FIFO operation; and if the acknowledgement of the RTS message has been received by the origin DMA engine, transferring, by the origin DMA engine, any remaining portion of the data to the target compute node using a direct put operation.

Archer, Charles J. (Rochester, MN); Blocksome, Michael A. (Rochester, MN); Ratterman, Joseph D. (Rochester, MN); Smith, Brian E. (Rochester, MN)

2010-11-02

437

Communication Requirements and Interconnect Optimization forHigh-End Scientific Applications  

SciTech Connect

The path towards realizing peta-scale computing isincreasingly dependent on building supercomputers with unprecedentednumbers of processors. To prevent the interconnect from dominating theoverall cost of these ultra-scale systems, there is a critical need forhigh-performance network solutions whose costs scale linearly with systemsize. This work makes several unique contributions towards attaining thatgoal. First, we conduct one of the broadest studies to date of high-endapplication communication requirements, whose computational methodsinclude: finite-difference, lattice-bolzmann, particle in cell, sparselinear algebra, particle mesh ewald, and FFT-based solvers. Toefficiently collect this data, we use the IPM (Integrated PerformanceMonitoring) profiling layer to gather detailed messaging statistics withminimal impact to cod