Synthesis, thermal expansion and high-temperature electrical conductivity of Co-doped (Y,Ca)FeO{sub 3−δ} with orthorhombic perovskite structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalyuzhnaya, A.S.; Drozhzhin, O.A.; Istomin, S.Ya., E-mail: istomin@icr.chem.msu.ru

Highlights: • (Y,Ca)(Fe,Co)O{sub 3−δ} was prepared via citrate-based route with annealing at 1150–1200 °C. • Y{sub 0.9}Ca{sub 0.1}Fe{sub 0.8}Co{sub 0.2}O{sub 3−δ} demonstrates low thermal expansion coefficient of 11.9 ppm K{sup −1}. • Oxides do not react with YSZ and GDC up to 1000 °C and 1100 °C, respectively. • Compounds demonstrate higher electrical conductivity in comparison with Y{sub 0.9}Ca{sub 0.1}FeO{sub 3}. • Pr-doped (Y,Ca)(Fe,Co)O{sub 3−δ} demonstrate both higher electrical conductivity and TEC. - Abstract: Orthorhombic perovskites Y{sub 1−x}Ca{sub x}Fe{sub 1−y}Co{sub y}O{sub 3−δ} (0.1 ≤ x ≤ 0.2, 0.1 ≤ y ≤ 0.2 and x = 0.1, y = 0.3) weremore » synthesized in air by the citrate route at 1150–1300 °C. High-temperature X-ray powder diffraction (HT XRPD) data for Y{sub 0.9}Ca{sub 0.1}Fe{sub 0.8}Co{sub 0.2}O{sub 3−δ} at 25–800 °C showed no phase transition with calculated thermal expansion coefficient (TEC) of 11.9 ppm K{sup −1}. High-temperature electrical conductivity measurements revealed almost composition independent conductivity values of 22–27 S/cm at 900 °C. No chemical interaction of Y{sub 0.8}Ca{sub 0.2}Fe{sub 0.9}Co{sub 0.1}O{sub 3−δ} with (Zr,Y)O{sub 2−x} (YSZ) or (Ce,Gd)O{sub 2−x} (GDC) was observed up to 1000 °C and 1100 °C, respectively. Partial replacement of Y by Pr according to formula Y{sub 0.8−z}Pr{sub z}Ca{sub 0.2}Fe{sub 0.7}Co{sub 0.3}O{sub 3−δ}, 0.1 ≤ z ≤ 0.35, leads to an increase of both electrical conductivity up to 50 S/cm (z = 0.3) at 900 °C and dilatometry measured TEC up to 15.1 ppm K{sup −1}. Moderate values of electrical conductivity in combination with low TEC and stability towards chemical interaction with typical SOFC electrolytes make Co-doped Y{sub 1−x}Ca{sub x}FeO{sub 3−δ} promissing cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFC)« less

Comparison of GPS derived TEC with the TEC predicted by IRI 2012 model in the southern Equatorial Ionization Anomaly crest within the Eastern Africa region

NASA Astrophysics Data System (ADS)

Sulungu, Emmanuel D.; Uiso, Christian B. S.; Sibanda, Patrick

2018-04-01

We have compared the TEC obtained from the IRI-2012 model with the GPS derived TEC data recorded within southern crest of the EIA in the Eastern Africa region using the monthly means of the 5 international quiet days for equinoxes and solstices months for the period of 2012 - 2013. GPS-derived TEC data have been obtained from the Africa array and IGS network of ground based dual-frequency GPS receivers from four stations (Kigali (1.95°S, 30.09°E; Geom. Lat. 11.63°S), Malindi (2.99°S, 40.19°E; Geom. Lat. 12.42°S), Mbarara (0.60°S, 30.74°E; Geom. Lat. 10.22°S) and Nairobi (1.22°S, 36.89°E; Geom. Lat. 10.69°S)) located within the EIA crest in this region. All the three options for topside Ne of IRI-2012 model and ABT-2009 for bottomside thickness have been used to compute the IRI TEC. Also URSI coefficients were considered in this study. These results are compared with the TEC estimated from GPS measurements. Correlation Coefficients between the two sets of data, the Root-Mean Square Errors (RMSE) of the IRI-TEC from the GPS-TEC, and the percentage RMSE of the IRI-TEC from the GPS-TEC have been computed. Our general results show that IRI-2012 model with all three options overestimates the GPS-TEC for all seasons and at all stations, and IRI-2001 overestimates GPS-TEC more compared with other options. IRI-Neq and IRI-01-corr are closely matching in most of the time. The observation also shows that, GPS TEC are underestimated by TEC from IRI model during noon hours, especially during equinoctial months. Further, GPS-TEC values and IRI-TEC values using all the three topside Ne options show very good correlation (above 0.8). On the other hand, the TEC using IRI-Neq and IRI-01- corr had smaller deviations from the GPS-TEC compared to the IRI-2001.

Analysis of FORTE data to extract ionospheric parameters

NASA Astrophysics Data System (ADS)

Roussel-Dupré, Robert A.; Jacobson, Abram R.; Triplett, Laurie A.

2001-01-01

The ionospheric transfer function is derived for a spherically symmetric ionosphere with an arbitrary radial electron density profile in the limit where the radio frequencies of interest ω are much larger than the plasma frequency ωpe. An expansion of the transfer function to second order in the parameter X (= ω2pe/ω2) is carried out. In this limit the dispersive properties of the ionosphere are manifested as a frequency-dependent time of arrival that includes quadratic, cubic, and quartic terms in 1/ω. The coefficients of these terms are related to the total electron content (TEC) along the slant path from transmitter to receiver, the product of TEC and the longitudinal magnetic field strength along the slant path, and refractive bending and higher-order electron density profile effects, respectively. By fitting the time of arrival versus frequency of a transionospheric signal to a polynomial in 1/ω it is possible to extract the TEC, the longitudinal magnetic field strength, the peak electron density, and an effective thickness for the ionosphere. This exercise was carried out for a number of transionospheric pulses measured in the VHF by the FORTE satellite receiver and generated by the Los Alamos Portable Pulser. The results are compared with predictions derived from the International Reference Ionosphere and the United States Geological Survey geomagnetic field model.

Potentialities of TEC topping: A simplified view of parametric effects

NASA Technical Reports Server (NTRS)

Morris, J. F.

1980-01-01

An examination of the benefits of thermionic-energy-conversion (TEC)-topped power plants and methods of increasing conversion efficiency are discussed. Reductions in the cost of TEC modules yield direct decreases in the cost of electricity (COE) from TEC-topped central station power plants. Simplified COE, overall-efficiency charts presented illustrate this trend. Additional capital-cost diminution results from designing more compact furnaces with considerably increased heat transfer rates allowable and desirable for high temperature TEC and heat pipes. Such improvements can evolve of the protection from hot corrosion and slag as well as the thermal expansion compatibilities offered by silicon-carbide clads on TEC-heating surfaces. Greater efficiencies and far fewer modules are possible with high-temperature, high-power-density TEC: This decreases capital and fuel costs much more and substantially increases electric power outputs for fixed fuel inputs. In addition to more electricity, less pollution, and lower costs, TEC topping used directly in coal-combustion products contributes balance-of-payment gains.

High-temperature properties of (La,Ca)(Fe,Mg,Mo)O3-δ perovskites as prospective electrode materials for symmetrical SOFC

NASA Astrophysics Data System (ADS)

Istomin, S. Ya.; Morozov, A. V.; Abdullayev, M. M.; Batuk, M.; Hadermann, J.; Kazakov, S. M.; Sobolev, A. V.; Presniakov, I. A.; Antipov, E. V.

2018-02-01

La1-yCayFe0.5+x(Mg,Mo)0.5-xO3-δ oxides with the orthorhombic GdFeO3-type perovskite structure have been synthesized at 1573 K. Transmission electron microscopy study for selected samples shows the coexistence of domains of perovskite phases with ordered and disordered B-cations. Mössbauer spectroscopy studies performed at 300 K and 573 K show that while compositions with low Ca-content (La0.55Ca0.45Fe0.5Mg0.2625Mo0.2375O3-δ and La0.5Ca0.5Fe0.6Mg0.175Mo0.225O3-δ) are nearly oxygen stoichiometric, La0.2Ca0.8Fe0.5Mg0.2625Mo0.2375O3-δ is oxygen deficient with δ ≈ 0.15. Oxides are stable in reducing atmosphere (Ar/H2, 8%) at 1173 K for 12 h. No additional phases have been observed at XRPD patterns of all studied perovskites and Ce1-xGdxO2-x/2 electrolyte mixtures treated at 1173-1373K, while Fe-rich compositions (x≥0.1) react with Zr1-xYxO2-x/2 electrolyte above 1273 K. Dilatometry studies reveal that all samples show rather low thermal expansion coefficients (TECs) in air of 11.4-12.7 ppm K-1. In reducing atmosphere their TECs were found to increase up to 12.1-15.4 ppm K-1 due to chemical expansion effect. High-temperature electrical conductivity measurements in air and Ar/H2 atmosphere show that the highest conductivity is observed for Fe- and Ca-rich compositions. Moderate values of electrical conductivity and TEC together with stability towards chemical interaction with typical SOFC electrolytes make novel Fe-containing perovskites promising electrode materials for symmetrical solid oxide fuel cell.

Molecular checkpoint decisions made by subverted vascular niche transform indolent tumor cells into chemoresistant cancer stem cells

PubMed Central

Cao, Zhongwei; Scandura, Joseph M; Inghirami, Giorgio G.; Shido, Koji; Ding, Bi-Sen; Rafii, Shahin

2017-01-01

Summary Tumor-associated endothelial cells (TECs) regulate tumor cell aggressiveness. However, the “core” mechanism by which TECs confer stem cell-like activity to indolent tumors is unknown. Here, we used in vivo murine and human tumor models to identify tumor-suppressive checkpoint role of TEC-expressed insulin growth factor (IGF) binding protein-7 (IGFBP7/angiomodulin). During tumorigenesis, IGFBP7 blocks IGF1 and inhibits expansion and engraftment of tumor stem-like cells (TSCs) expressing IGF1-receptor (IGF1R). However, chemotherapy triggers TECs to suppress IGFBP7, and this stimulates IGF1R+ TSCs to express FGF4, inducing a feed-forward FGFR1-ETS2 angiocrine cascade that obviates TEC IGFBP7. Thus, loss of IGFBP7 and upregulation of IGF1 activates the FGF4-FGFR1-ETS2 pathway in TECs and converts naive tumor cells to chemoresistant TSCs, thereby facilitating their engraftment and progression. PMID:27989801

Molecular Checkpoint Decisions Made by Subverted Vascular Niche Transform Indolent Tumor Cells into Chemoresistant Cancer Stem Cells.

PubMed

Cao, Zhongwei; Scandura, Joseph M; Inghirami, Giorgio G; Shido, Koji; Ding, Bi-Sen; Rafii, Shahin

2017-01-09

Tumor-associated endothelial cells (TECs) regulate tumor cell aggressiveness. However, the core mechanism by which TECs confer stem cell-like activity to indolent tumors is unknown. Here, we used in vivo murine and human tumor models to identify the tumor-suppressive checkpoint role of TEC-expressed insulin growth factor (IGF) binding protein-7 (IGFBP7/angiomodulin). During tumorigenesis, IGFBP7 blocks IGF1 and inhibits expansion and aggresiveness of tumor stem-like cells (TSCs) expressing IGF1 receptor (IGF1R). However, chemotherapy triggers TECs to suppress IGFBP7, and this stimulates IGF1R + TSCs to express FGF4, inducing a feedforward FGFR1-ETS2 angiocrine cascade that obviates TEC IGFBP7. Thus, loss of IGFBP7 and upregulation of IGF1 activates the FGF4-FGFR1-ETS2 pathway in TECs and converts naive tumor cells to chemoresistant TSCs, thereby facilitating their invasiveness and progression. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of colouring green stage zirconia on the adhesion of veneering ceramics with different thermal expansion coefficients

PubMed Central

Aktas, Guliz; Sahin, Erdal; Vallittu, Pekka; Özcan, Mutlu; Lassila, Lippo

2013-01-01

This study evaluated the adhesion of zirconia core ceramics with their corresponding veneering ceramics, having different thermal expansion coefficients (TECs), when zirconia ceramics were coloured at green stage. Zirconia blocks (N=240; 6 mm×7 mm×7 mm) were manufactured from two materials namely, ICE Zirconia (Group 1) and Prettau Zirconia (Group 2). In their green stage, they were randomly divided into two groups. Half of the specimens were coloured with colouring liquid (shade A2). Three different veneering ceramics with different TEC (ICE Ceramic, GC Initial Zr and IPS e.max Ceram) were fired on both coloured and non-coloured zirconia cores. Specimens of high noble alloys (Esteticor Plus) veneered with ceramic (VM 13) (n=16) acted as the control group. Core–veneer interface of the specimens were subjected to shear force in the Universal Testing Machine (0.5 mm⋅min−1). Neither the zirconia core material (P=0.318) nor colouring (P=0.188) significantly affected the results (three-way analysis of variance, Tukey's test). But the results were significantly affected by the veneering ceramic (P=0.000). Control group exhibited significantly higher mean bond strength values (45.7±8) MPa than all other tested groups ((27.1±4.1)−(39.7±4.7) and (27.4±5.6)−(35.9±4.7) MPa with and without colouring, respectively) (P<0.001). While in zirconia–veneer test groups, predominantly mixed type of failures were observed with the veneering ceramic covering <1/3 of the substrate surface, in the metal–ceramic group, veneering ceramic was left adhered >1/3 of the metal surface. Colouring zirconia did not impair adhesion of veneering ceramic, but veneering ceramic had a significant influence on the core–veneer adhesion. Metal–ceramic adhesion was more reliable than all zirconia–veneer ceramics tested. PMID:24158142

Effect of colouring green stage zirconia on the adhesion of veneering ceramics with different thermal expansion coefficients.

PubMed

Aktas, Guliz; Sahin, Erdal; Vallittu, Pekka; Ozcan, Mutlu; Lassila, Lippo

2013-12-01

This study evaluated the adhesion of zirconia core ceramics with their corresponding veneering ceramics, having different thermal expansion coefficients (TECs), when zirconia ceramics were coloured at green stage. Zirconia blocks (N=240; 6 mm×7 mm×7 mm) were manufactured from two materials namely, ICE Zirconia (Group 1) and Prettau Zirconia (Group 2). In their green stage, they were randomly divided into two groups. Half of the specimens were coloured with colouring liquid (shade A2). Three different veneering ceramics with different TEC (ICE Ceramic, GC Initial Zr and IPS e.max Ceram) were fired on both coloured and non-coloured zirconia cores. Specimens of high noble alloys (Esteticor Plus) veneered with ceramic (VM 13) (n=16) acted as the control group. Core-veneer interface of the specimens were subjected to shear force in the Universal Testing Machine (0.5 mm⋅min(-1)). Neither the zirconia core material (P=0.318) nor colouring (P=0.188) significantly affected the results (three-way analysis of variance, Tukey's test). But the results were significantly affected by the veneering ceramic (P=0.000). Control group exhibited significantly higher mean bond strength values (45.7±8) MPa than all other tested groups ((27.1±4.1)-(39.7±4.7) and (27.4±5.6)-(35.9±4.7) MPa with and without colouring, respectively) (P<0.001). While in zirconia-veneer test groups, predominantly mixed type of failures were observed with the veneering ceramic covering <1/3 of the substrate surface, in the metal-ceramic group, veneering ceramic was left adhered >1/3 of the metal surface. Colouring zirconia did not impair adhesion of veneering ceramic, but veneering ceramic had a significant influence on the core-veneer adhesion. Metal-ceramic adhesion was more reliable than all zirconia-veneer ceramics tested.

Validation of the technique for absolute total electron content and differential code biases estimation

NASA Astrophysics Data System (ADS)

Mylnikova, Anna; Yasyukevich, Yury; Yasyukevich, Anna

2017-04-01

We have developed a technique for vertical total electron content (TEC) and differential code biases (DCBs) estimation using data from a single GPS/GLONASS station. The algorithm is based on TEC expansion into Taylor series in space and time (TayAbsTEC). We perform the validation of the technique using Global Ionospheric Maps (GIM) computed by Center for Orbit Determination in Europe (CODE) and Jet Propulsion Laboratory (JPL). We compared differences between absolute vertical TEC (VTEC) from GIM and VTEC evaluated by TayAbsTEC for 2009 year (solar activity minimum - sunspot number about 0), and for 2014 year (solar activity maximum - sunspot number 110). Since there is difference between VTEC from CODE and VTEC from JPL, we compare TayAbsTEC VTEC with both of them. We found that TayAbsTEC VTEC is closer to CODE VTEC than to JPL VTEC. The difference between TayAbsTEC VTEC and GIM VTEC is more noticeable for solar activity maximum (2014) than for solar activity minimum (2009) for both CODE and JPL. The distribution of VTEC differences is close to Gaussian distribution, so we conclude that results of TayAbsTEC are in the agreement with GIM VTEC. We also compared DCBs evaluated by TayAbsTEC and DCBs from GIM, computed by CODE. The TayAbsTEC DCBs are in good agreement with CODE DCBs for GPS satellites, but differ noticeable for GLONASS. We used DCBs to correct slant TEC to find out which DCBs give better results. Slant TEC correction with CODE DCBs produces negative and nonphysical TEC values. Slant TEC correction with TayAbsTEC DCBs doesn't produce such artifacts. The technique we developed is used for VTEC and DCBs calculation given only local GPS/GLONASS networks data. The evaluated VTEC data are in GIM framework which is handy when various data analyses are made.

Method for thermoelectric cooler utilization using manufacturer's technical information

NASA Astrophysics Data System (ADS)

Ajiwiguna, Tri Ayodha; Nugroho, Rio; Ismardi, Abrar

2018-03-01

Thermoelectric cooler (TEC) module has been widely used for many applications. In this study, a procedure to use TEC module for specific requirement is developed based on manufacturer's technical data. For study case, the cooling system using TEC module is designed and tested to maintain 6.6 liter of water at 24 °C while surrounding temperature is 26 °C. First, cooling load estimation is performed empirically by observing the temperature change when cold water is inside the container. Second, the working temperature on hot side and cold side of TEC are determined. Third, the parameters of Seebeck coefficient, thermal resistance and electrical resistance are predicted by using information from the manufacturer. Fourth, the operating current is determined by the assumption the voltage across the TEC is 12V. Fifth, cooling capacity of TEC module is calculated by using energy balance equation of TEC. Sixth, the cooling load and cooling capacity are compared to determine the number of TEC module needed. The result of these calculations showed that one TEC module is enough for cooling system since the cooling load is 17.5 W while the cooling capacity is 18.87 W. From the experimental result, the set point temperature was achieved using one TEC module as predicted in calculations steps.

Detection of Seismic Precursors Using Distance Metrics Between GPS-TEC and IRI-Plas

NASA Astrophysics Data System (ADS)

Necat Deviren, M.; Gulyaeva, Tamara; Sezen, Umut; Arikan, Feza; Arikan, Orhan

Ionosphere is an important layer of atmosphere that varies under solar, geomagnetic, gravitational and seismic activities. Total Electron Content (TEC) is one of the main observables of ionosphere. International Reference Ionosphere Extended to Plasmasphere (IRI-Plas) is accepted by International Organization for Standardization (ISO) as the standard climatic model. IRI-Plas provides TEC up to GPS satellite height. TEC can be estimated using Global Positioning System (GPS) Networks. In this study, TEC is computed using both IRI-Plas and Turkish National Permanent GPS Network as IONOLAB-TEC. In order to detect seismic precursors, three different distance metrics, namely Symmetric Kullback-Liebler Distance (SKLD), Cross-Correlation Coefficient (CC), and L2-Norm (L2N), are implemented between IONOLAB-TEC and IRI-Plas-TEC values. SKLD is also computed between IONOLAB-TEC Maps and IRI-Plas-TEC Maps over Turkey. Between May 2009 and September 2012, it is observed that SKLD metric indicates a disturbance within the period prior to 10 days of earthquake day. The disturbance in SKLD increases for the range of stations in the neighborhood of the epicenter. For strong earthquakes all of the three distance metrics indicate a disturbance before the earthquake, yet SKLD behaves as a more sensitive precursor for earthquakes larger than magnitude 4. This study is supported by the joint grant of TUBITAK 112E568 and RFBR 13-02-91370-CT_a.

Performance evaluation of linear time-series ionospheric Total Electron Content model over low latitude Indian GPS stations

NASA Astrophysics Data System (ADS)

Dabbakuti, J. R. K. Kumar; Venkata Ratnam, D.

2017-10-01

Precise modeling of the ionospheric Total Electron Content (TEC) is a critical aspect of Positioning, Navigation, and Timing (PNT) services intended for the Global Navigation Satellite Systems (GNSS) applications as well as Earth Observation System (EOS), satellite communication, and space weather forecasting applications. In this paper, linear time series modeling has been carried out on ionospheric TEC at two different locations at Koneru Lakshmaiah University (KLU), Guntur (geographic 16.44° N, 80.62° E; geomagnetic 7.55° N) and Bangalore (geographic 12.97° N, 77.59° E; geomagnetic 4.53° N) at the northern low-latitude region, for the year 2013 in the 24th solar cycle. The impact of the solar and geomagnetic activity on periodic oscillations of TEC has been investigated. Results confirm that the correlation coefficient of the estimated TEC from the linear model TEC and the observed GPS-TEC is around 93%. Solar activity is the key component that influences ionospheric daily averaged TEC while periodic component reveals the seasonal dependency of TEC. Furthermore, it is observed that the influence of geomagnetic activity component on TEC is different at both the latitudes. The accuracy of the model has been assessed by comparing the International Reference Ionosphere (IRI) 2012 model TEC and TEC measurements. Moreover, the absence of winter anomaly is remarkable, as determined by the Root Mean Square Error (RMSE) between the linear model TEC and GPS-TEC. On the contrary, the IRI2012 model TEC evidently failed to predict the absence of winter anomaly in the Equatorial Ionization Anomaly (EIA) crest region. The outcome of this work will be useful for improving the ionospheric now-casting models under various geophysical conditions.

Short term variations of total electron content (TEC) fitting to a regional GPS network over the Kingdom of Saudi Arabia (KSA)

NASA Astrophysics Data System (ADS)

Alothman, A. O.; Alsubaie, M. A.; Ayhan, M. E.

2011-09-01

The ionosphere is a dispersive medium for radio waves with the refractive index which is a function of frequency and total electron content (TEC). TEC has a strong diurnal variation in addition to monthly, seasonal and solar cycle variations and small and large scale irregularities. Dual frequency GPS observations can be utilized to obtain TEC and investigate its spatial and temporal variations. We here studied short term TEC variations over the Kingdom of Saudi Arabia (KSA). A regional GPS network is formed consisting of 16 sites in and around KSA. GPS observations, acquired between 1st and 11th February 2009, were processed on a daily basis by using the Bernese v5.0 software and IGS final products. The geometry-free zero difference smoothed code observables were used to obtain two hour interval snapshots of TEC and their RMS errors at 0.5 × 0.5 degree grid nodes and regional ionosphere models in a spherical harmonics expansion to degree and order six. The equatorial ionized anomaly (EIA) is recovered in the south of 20°N from 08:00 to 12:00 UT. We found that day-by-day TEC variation is more stable than the night time variation.

Taguchi optimization of bismuth-telluride based thermoelectric cooler

NASA Astrophysics Data System (ADS)

Anant Kishore, Ravi; Kumar, Prashant; Sanghadasa, Mohan; Priya, Shashank

2017-07-01

In the last few decades, considerable effort has been made to enhance the figure-of-merit (ZT) of thermoelectric (TE) materials. However, the performance of commercial TE devices still remains low due to the fact that the module figure-of-merit not only depends on the material ZT, but also on the operating conditions and configuration of TE modules. This study takes into account comprehensive set of parameters to conduct the numerical performance analysis of the thermoelectric cooler (TEC) using a Taguchi optimization method. The Taguchi method is a statistical tool that predicts the optimal performance with a far less number of experimental runs than the conventional experimental techniques. Taguchi results are also compared with the optimized parameters obtained by a full factorial optimization method, which reveals that the Taguchi method provides optimum or near-optimum TEC configuration using only 25 experiments against 3125 experiments needed by the conventional optimization method. This study also shows that the environmental factors such as ambient temperature and cooling coefficient do not significantly affect the optimum geometry and optimum operating temperature of TECs. The optimum TEC configuration for simultaneous optimization of cooling capacity and coefficient of performance is also provided.

Evaluation of Ca3Co2O6 as cathode material for high-performance solid-oxide fuel cell

PubMed Central

Wei, Tao; Huang, Yun-Hui; Zeng, Rui; Yuan, Li-Xia; Hu, Xian-Luo; Zhang, Wu-Xing; Jiang, Long; Yang, Jun-You; Zhang, Zhao-Liang

2013-01-01

A cobalt-based thermoelectric compound Ca3Co2O6 (CCO) has been developed as new cathode material with superior performance for intermediate-temperature (IT) solid-oxide fuel cell (SOFC). Systematic evaluation has been carried out. Measurement of thermal expansion coefficient (TEC), thermal-stress (σ) and interfacial shearing stress (τ) with the electrolyte show that CCO matches well with several commonly-used IT electrolytes. Maximum power density as high as 1.47 W cm−2 is attained at 800°C, and an additional thermoelectric voltage of 11.7 mV is detected. The superior electrochemical performance, thermoelectric effect, and comparable thermal and mechanical behaviors with the electrolytes make CCO to be a promising cathode material for SOFC. PMID:23350032

Derivation of GPS TEC and receiver bias for Langkawi station in Malaysia

NASA Astrophysics Data System (ADS)

Teh, W. L.; Chen, W. S.; Abdullah, M.

2017-05-01

This paper presents the polynomial-type TEC model to derive total electron content (TEC) and receiver bias for Langkawi (LGKW) station in Malaysia at geographic latitude of 6.32° and longitude of 99.85°. The model uses a polynomial function of coordinates of the ionospheric piercing point to describe the TEC distribution in space. In the model, six polynomial coefficients and a receiver bias are unknown which can be solved by the least squares method. A reasonable agreement is achieved for the derivation of TEC and receiver bias for IENG station in Italy, as compared with that derived by the IGS analysis center, CODE. We process one year of LGKW data in 2010 and show the monthly receiver bias and the seasonal TEC variation. The monthly receiver bias varies between -48 and -24 TECu (1016 electrons/m2), with the mean value at -37 TECu. Large variations happen in the monthly receiver biases due to the low data coverage of high satellite elevation angle (60° < α ≤ 90°). Post-processing TEC approach is implemented which can resolve the wavy pattern of the monthly TEC baseline resulted from the large variation of the receiver bias. The seasonal TEC variation at LGKW exhibits a semi-annual variation, where the peak occurs during equinoctial months, and the trough during summer and winter months.

Ionospheric earthquake effects detection based on Total Electron Content (TEC) GPS Correlation

NASA Astrophysics Data System (ADS)

Sunardi, Bambang; Muslim, Buldan; Eka Sakya, Andi; Rohadi, Supriyanto; Sulastri; Murjaya, Jaya

2018-03-01

Advances in science and technology showed that ground-based GPS receiver was able to detect ionospheric Total Electron Content (TEC) disturbances caused by various natural phenomena such as earthquakes. One study of Tohoku (Japan) earthquake, March 11, 2011, magnitude M 9.0 showed TEC fluctuations observed from GPS observation network spread around the disaster area. This paper discussed the ionospheric earthquake effects detection using TEC GPS data. The case studies taken were Kebumen earthquake, January 25, 2014, magnitude M 6.2, Sumba earthquake, February 12, 2016, M 6.2 and Halmahera earthquake, February 17, 2016, M 6.1. TEC-GIM (Global Ionosphere Map) correlation methods for 31 days were used to monitor TEC anomaly in ionosphere. To ensure the geomagnetic disturbances due to solar activity, we also compare with Dst index in the same time window. The results showed anomalous ratio of correlation coefficient deviation to its standard deviation upon occurrences of Kebumen and Sumba earthquake, but not detected a similar anomaly for the Halmahera earthquake. It was needed a continous monitoring of TEC GPS data to detect the earthquake effects in ionosphere. This study giving hope in strengthening the earthquake effect early warning system using TEC GPS data. The method development of continuous TEC GPS observation derived from GPS observation network that already exists in Indonesia is needed to support earthquake effects early warning systems.

DKK1 mediated inhibition of Wnt signaling in postnatal mice leads to loss of TEC progenitors and thymic degeneration.

PubMed

Osada, Masako; Jardine, Logan; Misir, Ruth; Andl, Thomas; Millar, Sarah E; Pezzano, Mark

2010-02-08

Thymic epithelial cell (TEC) microenvironments are essential for the recruitment of T cell precursors from the bone marrow, as well as the subsequent expansion and selection of thymocytes resulting in a mature self-tolerant T cell repertoire. The molecular mechanisms, which control both the initial development and subsequent maintenance of these critical microenvironments, are poorly defined. Wnt signaling has been shown to be important to the development of several epithelial tissues and organs. Regulation of Wnt signaling has also been shown to impact both early thymocyte and thymic epithelial development. However, early blocks in thymic organogenesis or death of the mice have prevented analysis of a role of canonical Wnt signaling in the maintenance of TECs in the postnatal thymus. Here we demonstrate that tetracycline-regulated expression of the canonical Wnt inhibitor DKK1 in TECs localized in both the cortex and medulla of adult mice, results in rapid thymic degeneration characterized by a loss of DeltaNP63(+) Foxn1(+) and Aire(+) TECs, loss of K5K8DP TECs thought to represent or contain an immature TEC progenitor, decreased TEC proliferation and the development of cystic structures, similar to an aged thymus. Removal of DKK1 from DKK1-involuted mice results in full recovery, suggesting that canonical Wnt signaling is required for the differentiation or proliferation of TEC populations needed for maintenance of properly organized adult thymic epithelial microenvironments. Taken together, the results of this study demonstrate that canonical Wnt signaling within TECs is required for the maintenance of epithelial microenvironments in the postnatal thymus, possibly through effects on TEC progenitor/stem cell populations. Downstream targets of Wnt signaling, which are responsible for maintenance of these TEC progenitors may provide useful targets for therapies aimed at counteracting age associated thymic involution or the premature thymic degeneration associated with cancer therapy and bone marrow transplants.

THERMAL AND ELECTRICAL PROPERTIES OF Ba0.5Sr0.5CoxFe1-x-yNiyO3-δ (x = 0.4, 0 ≤ y ≤ 0.25) AS CATHODE MATERIAL FOR IT-SOFCs

NASA Astrophysics Data System (ADS)

Burnwal, Suman Kumar; Kistaiah, P.

2015-03-01

Ba0.5Sr0.5CoxFe1-x-yNiyO3-δ (BSCFNi; x = 0.4, 0 ≤ y ≤ 0.25) were studied in relation to their potential use as intermediate temperature solid oxide fuel cell (IT-SOFC) cathode. An emphasis is made on the effect of Ni-doping on crystal structure, thermal expansion coefficient (TEC) and dc electrical conductivity. A cubic perovskite structure was observed in the X-ray diffraction (XRD) measurement. The TEC of BSCFNi obtained for 0 ≤ y ≤ 0.25, varies in the range of (12.38-18.81) × 10-6 K-1, measured in the temperature range of 30°C to 800°C. The electrical conductivity which is a major defect of Ba0.5Sr0.5CoxFe1-xO3-δ (BSCF) was improved by Ni-doping. The compound with y = 0.20 and 0.25 demonstrated a conductivity of σ = 62.59 S-cm-1 and 72.64 S-cm-1 at 400°C and 77.01 S-cm-1 and 89.68 S-cm-1 at 500°C.

Inactivation of the RB family prevents thymus involution and promotes thymic function by direct control of Foxn1 expression

PubMed Central

Garfin, Phillip M.; Min, Dullei; Bryson, Jerrod L.; Serwold, Thomas; Edris, Badreddin; Blackburn, Clare C.; Richie, Ellen R.; Weinberg, Kenneth I.; Manley, Nancy R.; Viatour, Patrick

2013-01-01

Thymic involution during aging is a major cause of decreased production of T cells and reduced immunity. Here we show that inactivation of Rb family genes in young mice prevents thymic involution and results in an enlarged thymus competent for increased production of naive T cells. This phenotype originates from the expansion of functional thymic epithelial cells (TECs). In RB family mutant TECs, increased activity of E2F transcription factors drives increased expression of Foxn1, a central regulator of the thymic epithelium. Increased Foxn1 expression is required for the thymic expansion observed in Rb family mutant mice. Thus, the RB family promotes thymic involution and controls T cell production via a bone marrow–independent mechanism, identifying a novel pathway to target to increase thymic function in patients. PMID:23669396

Space Weather Activities of IONOLAB Group: TEC Mapping

NASA Astrophysics Data System (ADS)

Arikan, F.; Yilmaz, A.; Arikan, O.; Sayin, I.; Gurun, M.; Akdogan, K. E.; Yildirim, S. A.

2009-04-01

Being a key player in Space Weather, ionospheric variability affects the performance of both communication and navigation systems. To improve the performance of these systems, ionosphere has to be monitored. Total Electron Content (TEC), line integral of the electron density along a ray path, is an important parameter to investigate the ionospheric variability. A cost-effective way of obtaining TEC is by using dual-frequency GPS receivers. Since these measurements are sparse in space, accurate and robust interpolation techniques are needed to interpolate (or map) the TEC distribution for a given region in space. However, the TEC data derived from GPS measurements contain measurement noise, model and computational errors. Thus, it is necessary to analyze the interpolation performance of the techniques on synthetic data sets that can represent various ionospheric states. By this way, interpolation performance of the techniques can be compared over many parameters that can be controlled to represent the desired ionospheric states. In this study, Multiquadrics, Inverse Distance Weighting (IDW), Cubic Splines, Ordinary and Universal Kriging, Random Field Priors (RFP), Multi-Layer Perceptron Neural Network (MLP-NN), and Radial Basis Function Neural Network (RBF-NN) are employed as the spatial interpolation algorithms. These mapping techniques are initially tried on synthetic TEC surfaces for parameter and coefficient optimization and determination of error bounds. Interpolation performance of these methods are compared on synthetic TEC surfaces over the parameters of sampling pattern, number of samples, the variability of the surface and the trend type in the TEC surfaces. By examining the performance of the interpolation methods, it is observed that both Kriging, RFP and NN have important advantages and possible disadvantages depending on the given constraints. It is also observed that the determining parameter in the error performance is the trend in the Ionosphere. Optimization of the algorithms in terms of their performance parameters (like the choice of the semivariogram function for Kriging algorithms and the hidden layer and neuron numbers for MLP-NN) mostly depend on the behavior of the ionosphere at that given time instant for the desired region. The sampling pattern and number of samples are the other important parameters that may contribute to the higher errors in reconstruction. For example, for all of the above listed algorithms, hexagonal regular sampling of the ionosphere provides the lowest reconstruction error and the performance significantly degrades as the samples in the region become sparse and clustered. The optimized models and coefficients are applied to regional GPS-TEC mapping using the IONOLAB-TEC data (www.ionolab.org). Both Kriging combined with Kalman Filter and dynamic modeling of NN are also implemented as first trials of TEC and space weather predictions.

Thermodynamic Analysis of TEG-TEC Device Including Influence of Thomson Effect

NASA Astrophysics Data System (ADS)

Feng, Yuanli; Chen, Lingen; Meng, Fankai; Sun, Fengrui

2018-01-01

A thermodynamic model of a thermoelectric cooler driven by thermoelectric generator (TEG-TEC) device is established considering Thomson effect. The performance is analyzed and optimized using numerical calculation based on non-equilibrium thermodynamic theory. The influence characteristics of Thomson effect on the optimal performance and variable selection are investigated by comparing the condition with and without Thomson effect. The results show that Thomson effect degrades the performance of TEG-TEC device, it decreases the cooling capacity by 27 %, decreases the coefficient of performance (COP) by 19 %, decreases the maximum cooling temperature difference by 11 % when the ratio of thermoelectric elements number is 0.6, the cold junction temperature of thermoelectric cooler (TEC) is 285 K and the hot junction temperature of thermoelectric generator (TEG) is 450 K. Thomson effect degrades the optimal performance of TEG-TEC device, it decreases the maximum cooling capacity by 28 % and decreases the maximum COP by 28 % under the same junction temperatures. Thomson effect narrows the optimal variable range and optimal working range. In the design of the devices, limited-number thermoelectric elements should be more allocated appropriately to TEG when consider Thomson effect. The results may provide some guidelines for the design of TEG-TEC devices.

An empirical model of ionospheric total electron content (TEC) near the crest of the equatorial ionization anomaly (EIA)

NASA Astrophysics Data System (ADS)

Hajra, Rajkumar; Chakraborty, Shyamal Kumar; Tsurutani, Bruce T.; DasGupta, Ashish; Echer, Ezequiel; Brum, Christiano G. M.; Gonzalez, Walter D.; Sobral, José Humberto Andrade

2016-07-01

We present a geomagnetic quiet time (Dst > -50 nT) empirical model of ionospheric total electron content (TEC) for the northern equatorial ionization anomaly (EIA) crest over Calcutta, India. The model is based on the 1980-1990 TEC measurements from the geostationary Engineering Test Satellite-2 (ETS-2) at the Haringhata (University of Calcutta, India: 22.58° N, 88.38° E geographic; 12.09° N, 160.46° E geomagnetic) ionospheric field station using the technique of Faraday rotation of plane polarized VHF (136.11 MHz) signals. The ground station is situated virtually underneath the northern EIA crest. The monthly mean TEC increases linearly with F10.7 solar ionizing flux, with a significantly high correlation coefficient (r = 0.89-0.99) between the two. For the same solar flux level, the TEC values are found to be significantly different between the descending and ascending phases of the solar cycle. This ionospheric hysteresis effect depends on the local time as well as on the solar flux level. On an annual scale, TEC exhibits semiannual variations with maximum TEC values occurring during the two equinoxes and minimum at summer solstice. The semiannual variation is strongest during local noon with a summer-to-equinox variability of ~50-100 TEC units. The diurnal pattern of TEC is characterized by a pre-sunrise (0400-0500 LT) minimum and near-noon (1300-1400 LT) maximum. Equatorial electrodynamics is dominated by the equatorial electrojet which in turn controls the daytime TEC variation and its maximum. We combine these long-term analyses to develop an empirical model of monthly mean TEC. The model is validated using both ETS-2 measurements and recent GNSS measurements. It is found that the present model efficiently estimates the TEC values within a 1-σ range from the observed mean values.

Linear time series modeling of GPS-derived TEC observations over the Indo-Thailand region

NASA Astrophysics Data System (ADS)

Suraj, Puram Sai; Kumar Dabbakuti, J. R. K.; Chowdhary, V. Rajesh; Tripathi, Nitin K.; Ratnam, D. Venkata

2017-12-01

This paper proposes a linear time series model to represent the climatology of the ionosphere and to investigate the characteristics of hourly averaged total electron content (TEC). The GPS-TEC observation data at the Bengaluru international global navigation satellite system (GNSS) service (IGS) station (geographic 13.02°N , 77.57°E ; geomagnetic latitude 4.4°N ) have been utilized for processing the TEC data during an extended period (2009-2016) in the 24{th} solar cycle. Solar flux F10.7p index, geomagnetic Ap index, and periodic oscillation factors have been considered to construct a linear TEC model. It is evident from the results that solar activity effect on TEC is high. It reaches the maximum value (˜ 40 TECU) during the high solar activity (HSA) year (2014) and minimum value (˜ 15 TECU) during the low solar activity (LSA) year (2009). The larger magnitudes of semiannual variations are observed during the HSA periods. The geomagnetic effect on TEC is relatively low, with the highest being ˜ 4 TECU (March 2015). The magnitude of periodic variations can be seen more significantly during HSA periods (2013-2015) and less during LSA periods (2009-2011). The correlation coefficient of 0.89 between the observations and model-based estimations has been found. The RMSE between the observed TEC and model TEC values is 4.0 TECU (linear model) and 4.21 TECU (IRI2016 Model). Further, the linear TEC model has been validated at different latitudes over the northern low-latitude region. The solar component (F10.7p index) value decreases with an increase in latitude. The magnitudes of the periodic component become less significant with the increase in latitude. The influence of geomagnetic component becomes less significant at Lucknow GNSS station (26.76°N, 80.88°E) when compared to other GNSS stations. The hourly averaged TEC values have been considered and ionospheric features are well recovered with linear TEC model.

A high-performance, cobalt-free cathode for intermediate-temperature solid oxide fuel cells with excellent CO2 tolerance

NASA Astrophysics Data System (ADS)

Bu, Yun-fei; Zhong, Qin; Chen, Dong-Chang; Chen, Yu; Lai, Samson Yuxiu; Wei, Tao; Sun, Hai-bin; Ding, Dong; Liu, Meilin

2016-07-01

Compared with some cobalt-rich cathodes which have been proven to yield high performance in SOFCs, interest in cobalt-free cathodes has increased due to their reduced thermal expansion coefficients (TECs), high structural stability, and CO2 tolerance. In this report, a new robust Co-free complex perovskite oxide PrLa0.4Ba0.6Fe0.8Zn0.2O5+δ (PLBFZ) has been synthesized and evaluated. The TEC is 14.4 × 10-6 K-1. With the introduction of Sm0.2Ce0.8O2 (SDC), the composite cathode PLBFZ-SDC with a mass ratio of 7:3 (PLBFZ-SDC 73) exhibited the best electrocatalytic activity for oxygen reduction under OCV conditions, with polarization values of 0.044, 0.079, 0.124, 0.251, 0.572, and 1.297 Ω cm-2 at 800, 750, 700, 650, 600, and 550 °C, respectively. The power densities of the cell were 1309, 1079, 788 and 586 mW cm-2 at 750, 700, 650, and 600 °C, respectively. Moreover, it appears to have good stability in air containing 1% CO2 (volume ratio) for 150 h based on Raman and polarization resistance (Rp) analysis. These results suggest that PLBFZ and its SDC composite are promising cathodes for IT-SOFCs.

Empirical forecast of the quiet time Ionosphere over Europe: a comparative model investigation

NASA Astrophysics Data System (ADS)

Badeke, R.; Borries, C.; Hoque, M. M.; Minkwitz, D.

2016-12-01

The purpose of this work is to find the best empirical model for a reliable 24 hour forecast of the ionospheric Total Electron Content (TEC) over Europe under geomagnetically quiet conditions. It will be used as an improved reference for the description of storm-induced perturbations in the ionosphere. The observational TEC-data were obtained from the International GNSS Service (IGS). Four different forecast model approaches were validated with observational IGS TEC-data: a 27 day median model (27d), a Fourier Analysis (FA) approach, the Neustrelitz TEC global model (NTCM-GL) and NeQuick 2. Two years were investigated depending on the solar activity: 2015 (high activity) and 2008 (low avtivity) The time periods of magnetic storms, which were identified with the Dst index, were excluded from the validation. For both years the two models 27d and FA show better results than NTCM-GL and NeQuick 2. For example for the year 2015 and 15° E / 50° N the difference between the IGS data and the predicted 27d model shows a mean value of 0.413 TEC units (TECU), a standard deviation of 3.307 TECU and a correlation coefficient of 0.921, while NTCM-GL and NeQuick 2 have mean differences of around 2-3 TECU, standard deviations of 4.5-5 TECU and correlation coefficients below 0.85. Since 27d and FA predictions strongly depend on observational data, the results confirm that data driven forecasts perform better than the climatological models NTCM-GL and NeQuick 2. However, the benefits of NTCM-GL and NeQuick 2 are actually the lower data dependency, i.e. they do not lack on precision when observational IGS TEC data are unavailable. Hence a combination of the different models is recommended reacting accordingly to the different data availabilities.

Performance Evaluation of a Novel Chemiluminescence Assay Detecting Treponema Pallidum Antibody as a Syphilis Screening Method.

PubMed

Chen, Qixia; An, Jingna; Rao, Chenli; Wang, Tingting; Li, Dongdong; Feng, Shu; Tao, Chuanmin

2016-01-01

Syphilis is a major concern to global public health with increasing incidence. So its screening test should have sufficient sensitivity and specificity. We evaluated the performance of the Lumipulse G TP-N assay detection for syphilis screening and compared it with the InTec ELISA test kit for TP, which is widely used. Samples of several patient groups including 133 clinical and serologically characterized syphilitic sera, 175 samples containing potentially interfering agents, and 2290 unselected samples submitted for routine screening were detected by both the Lumipulse G TP-N assay and the InTec ELISA test kit for TP. Inconsistent samples were confirmed by RecomLine Treponema IgG, IgM immunoblot. Coefficient of variations of the Lumipulseo G TP-N assay at both levels were below 5% and of the InTec ELISA test kit for TP both over 5%. The sensitivity of the Lumipulse G TP-N assay and the InTec ELISA test kit for TP were 100% for all stages of syphilis. The two methods had consistent analytical specificity of 100% (95% CI: 97.21 - 100.00), while the clinical specificity was 100% (95% CI: 99.79 - 100.00) and 99.82% (95% CI: 99.51 - 99.94), respectively. Between them, Spearman's correlation coefficient was 0.455 and kappa value was 0.986. The overall sensitivity and specificity of the Lumipulse G TP-N assay was higher than the InTec ELISA test kit for TP (sensitivity: 100.0 versus 99.5, specificity: 100.0 versus 99.8). The automated Lumipulse G TP-N assay demonstrated excellent diagnostic sensitivity and specificity when evaluated as a screening test for syphilis. Thus, it can be an alternative to the treponemal screening test.

Solar activity indices as a proxy for the variation of ionospheric Total Electron Content (TEC) over Bahir Dar, Ethiopia during the year 2010-2014

NASA Astrophysics Data System (ADS)

Kassa, Tsegaye; Tilahun, Samson; Damtie, Baylie

2017-09-01

This paper was aimed at investigating the solar variations of vTEC as a function of solar activity parameters, EUV and F10.7 radio flux. The daily values of ionospheric vertical Total Electron Content (vTEC) were observed using a dual frequency GPS receiver deployed at Bahir Dar (11.6°N and 37.36°E), Ethiopia. Measurements were taken during the period of 2010-2014 for successive five years and analysis was done on only quiet day observations. A quadratic fit was used as a model to describe the daily variation of vTEC in relation to solar parameters. Linear and non-linear coefficients of the vTEC variations were calculated in order to capture the trend of the variation. The variation of vTEC have showed good agreement with the trend of solar parameters in almost all of the days we consider during the period of our observations. We have explicitly observed days with insignificant TECU deviation (eg. modeling with respect to EUV, DOY = 49 in 2010 and modeling with respect to F10.7, DOY = 125 in 2012 and the like) and days with maximum deviation (about 50 TECU). A maximum deviation were observed, on average, during months of equinox whereas minimum during solstice months. This implies that there is a need to consider more parameters, including EUV and F10.7, that can affect the variation of vTEC during equinox seasons. Relatively, small deviations was observed in modeling vTEC as a function of EUV compared to that of the variation due to F10.7 cm flux. This may also tell us that EUV can be more suitable in modeling the solar variation of vTEC especially for longterm trends. Even though, the linear trend of solar variations of vTEC was frequently observed, significant saturation and amplification trends of the solar variations of vTEC were also observed to some extent across the months of the years we have analyzed. This mixed trend of the solar variation of vTEC implies the need for thorough investigation on the effect of solar parameters on TEC. However, based on long-term dataset, we came to conclude that the solar variations of vTEC is dominated by its linear pattern.

Comparative analysis of GPS-derived TEC estimates and foF2 observations during storm conditions towards the expansion of ionospheric forecasting capabilities over Europe

NASA Astrophysics Data System (ADS)

Tsagouri, Ioanna; Belehaki, Anna; Elias, Panagiotis

2017-04-01

This paper builts the discussion on the comparative analysis of the variations in the peak electron density at F2 layer and the TEC parameter during a significant number of geomagnetic storm events that occurred in the present solar cycle 24. The ionospheric disturbances are determined through the comparison of actual observations of the foF2 critical frequency and GPS-TEC estimates obtained over European locations with the corresponding median estimates, and they are analysed in conjunction to the solar wind conditions at L1 point that are monitored by the ACE spacecraft. The quantification of the storm impact on the TEC parameter in terms of possible limitations introduced by different TEC derivation methods is carefully addressed.The results reveal similarities and differences in the response of the two parameters with respect to the solar wind drivers of the storms, as well as the local time and the latitude of the observation point. The aforementioned dependences drive the storm-time forecasts of the SWIF model (Solar Wind driven autorgressive model for Ionospheric short-term Forecast), which is operationally implemented in the DIAS system (http://dias.space.noa.gr) and extensively tested in performance at several occassions. In its present version, the model provides alerts and warnings for upcoming ionospheric disturbances, as well as single site and regional forecasts of the foF2 characteristic over Europe up to 24 hours ahead based on the assesment of the solar wind conditions at ACE location. In that respect, the results obtained above support the upgrade of the SWIF's modeling technique in forecasting the storm-time TEC variation within an operational environment several hours in advance. Preliminary results on the evaluation of the model's efficiency in TEC prediction are also discussed, giving special attention in the assesment of the capabilities through the TEC-derivation uncertanties for future discussions.

The First Use of Coordinated Ionospheric Radio and Optical Observations Over Italy: Convergence of High-and Low-Latitude Storm-Induced Effects

NASA Astrophysics Data System (ADS)

Cesaroni, C.; Alfonsi, L.; Pezzopane, M.; Martinis, C.; Baumgardner, J.; Wroten, J.; Mendillo, M.; Musicò, E.; Lazzarin, M.; Umbriaco, G.

2017-11-01

Ionospheric storm effects at midlatitudes were analyzed using different ground-based instruments distributed in Italy during the 13-15 November 2012 geomagnetic storm. These included an all-sky imager (ASI) in Asiago (45.8°N, 11.5°E), a network of dual-frequeny Global Navigation Satellite Systems receivers (Rete Integrata Nazionale GPS network), and ionosondes in Rome (41.8°N, 12.5°E) and San Vito (40.6°N, 17.8°E). GPS measurements showed an unusual enhancement of total electron content (TEC) in southern Italy, during the nights of 14 and 15 November. The ASI observed colocated enhancements of 630 nm airglow at the same time, as did variations in NmF2 measured by the ionosondes. Moreover, wave-like perturbations were identified propagating from the north. The Ensemble Empirical Mode Decomposition, applied to TEC values revealed the presence of traveling ionospheric disturbances (TIDs) propagating southward between 01:30 UT and 03:00 UT on 15 November. These TIDs were characterized by weak TEC oscillations ( ±0.5 TEC unit), period of 45 min, and velocity of 500 m/s typical of large-scale TIDs. Optical images showed enhanced airglow entering the field of view of the ASI from the N-NE at 02:00 UT and propagating to the S-SW, reaching the region covered by the GPS stations after 03:00 UT, when TEC fluctuations are very small ( ±0.2 TEC unit). The enhancement of TEC and airglow observed in southern Italy could be a consequence of a poleward expansion of the northern crest of the equatorial ionization anomaly. The enhanced airglow propagating from the north and the TEC waves resulted from energy injected at auroral latitudes as confirmed by magnetometer observations in Scandinavia.

Characterization and damage evaluation of advanced materials

NASA Astrophysics Data System (ADS)

Mitrovic, Milan

Mechanical characterization of advanced materials, namely magnetostrictive and graphite/epoxy composite materials, is studied in this dissertation, with an emphasis on damage evaluation of composite materials. Consequently, the work in this dissertation is divided into two parts, with the first part focusing on characterization of the magneto-elastic response of magnetostrictlve materials, while the second part of this dissertation describes methods for evaluating the fatigue damage in composite materials. The objective of the first part of this dissertation is to evaluate a nonlinear constitutive relation which more closely depict the magneto-elastic response of magnetostrictive materials. Correlation between experimental and theoretical values indicate that the model adequately predicts the nonlinear strain/field relations in specific regimes, and that the currently employed linear approaches are inappropriate for modeling the response of this material in a structure. The objective of the second part of this dissertation is to unravel the complexities associated with damage events associated with polymeric composite materials. The intent is to characterize and understand the influence of impact and fatigue induced damage on the residual thermo-mechanical properties and compressive strength of composite systems. The influence of fatigue generated matrix cracking and micro-delaminations on thermal expansion coefficient (TEC) and compressive strength is investigated for woven graphite/epoxy composite system. Experimental results indicate that a strong correlation exists between TEC and compressive strength measurements, indicating that TEC measurements can be used as a damage metric for this material systems. The influence of delaminations on the natural frequencies and mode shapes of a composite laminate is also investigated. Based on the changes of these parameters as a function of damage, a methodology for determining the size and location of damage is suggested. Finally, the influence of loading parameters on impact damage growth is investigated experimentally though constant amplitude and spectrum loading fatigue tests. Based on observed impact damage growth during these tests it is suggested that the low load levels can be deleted from the standardized test sequence without significant influence on impact damage propagation.

Performances of YBaCo 1.4Cu 0.6O 5+δ–Ce 0.8Sm 0.2O 1.9 composite cathodes for intermediate-temperature solid oxide fuel cells

DOE PAGES

Wang, Lizhong; Peng, Lu; Hu, Michael Z.; ...

2015-08-20

In this paper, the electrochemical properties of YBaCo 1.4Cu 0.6O 5+δ–xCe 0.8Sm 0.2O 1.9 (YBCC–xSDC, x=20, 30, 40, 50 wt%) have been investigated for the potential application in intermediate-temperature solid oxide fuel cells (IT-SOFCs). No chemical reactions between YBCC cathode and SDC electrolyte, and YBCC and La 0.9Sr 0.1Ga 0.8Mg 0.2O 3-δ (LSGM) occur. The thermal expansion coefficient (TEC) of YBCC cathode decreases with SDC addition. The TEC of YBCC–30SDC cathode is 13.60×10 –6 K -1 from 30 to 850 °C in air and it exhibits the best electrochemical performance among the YBCC–xSDC cathodes. The polarization resistance (R p) ofmore » YBCC–30SDC is 0.027 Ω cm 2 at 850 °C, 0.044 Ω cm 2 at 800 °C and 0.075 Ω cm 2 at 750 °C. The maximum power density value of electrolyte-based cell with YBCC–30SDC cathode is 662, 483 and 319 mW cm -2 at 850, 800 and 750 °C, respectively. Finally, preliminary results indicate that YBCC–30SDC is especially promising as a cathode for IT-SOFCs.« less

TECHNICAL NOTE: System for monitoring the evolution of the thermal expansion coefficient and autogenous deformation of hardening materials

NASA Astrophysics Data System (ADS)

Viviani, M.; Glisic, B.; Smith, I. F. C.

2006-12-01

This article presents an experimental system developed to determine the kinetic parameters of hardening materials. Kinetic parameters allow computation of the degree of reaction indices (DRIs). DRIs are used in predictive formulae for strength and are used to decouple the autogenous deformation (AD) and thermal deformation (TD). Although there are several methods to determine values for kinetic reaction parameters, most require extensive testing and large databases. A measurement system has been developed in order to determine kinetic parameters. The measurement system consists of optical fiber sensors embedded in specimens that are cured at varying temperatures and conditions. Sensors are used in pairs inside each specimen, and each pair has two deformation sensors that, aside from their axial stiffness, have the same characteristics. The study of the interaction between sensors and hardening material leads to establishment of a link between the deformations measured and the degree of reaction, by means of the newly developed concept of the equivalency point. The equivalency point is assumed to be an indicator of the degree of reaction and it allows the determination of the apparent activation energy (Ea) which defines the equivalent time. Equivalent time is a degree of reaction index (DRI) and it accounts for the combined effect of time and temperature in concrete. This new methodology has been used to predict the compressive strength and separate the AD and thermal expansion coefficient (TEC) in seven types of concrete. The measurement system allows gathering of data necessary for fast and efficient predictions. Due to its robustness and reduced dimensions it also has potential for in situ application.

Investigation of Ionospheric Precursors of 23 October 2011, Mw=7.2 Earthquake in Van, Turkey

NASA Astrophysics Data System (ADS)

Deviren, M. N.; Arikan, F.; Sezen, U.; Arikan, O.

2012-04-01

In recent years, a strong coupling between ionospheric disturbances and seismic activity has been observed through the increase of ion temperatures, critical frequencies of ionospheric layers and Total Electron Content (TEC) before high magnitude earthquakes. TEC is defined as total number of electrons over a ray path through the ionosphere. TEC can be estimated in a cost-effective way with dual-frequency Global Positioning Satellite (GPS) System receivers. The unit of TEC is given by TECU where 1 TECU = 1016 el/m2. In this study, the disturbances in daily TEC values before 23 October 2011, Mw=7.2 Earthquake in Van, Turkey are investigated using Turkish National Permanent GPS Network (TNPGN-Active). Earthquake Day Period (EDP) is chosen between October 1 and 31, 2011. Daily TEC values, for each station and each day, are estimated as IONOLAB-TEC (www.ionolab.org ) with 30 s time resolution. EDP-TEC values are compared with an Average Quiet Day TEC (AQDT) which is obtained by averaging the TEC values between 25 and 28 March, 2011. Statistical comparison is accomplished using Symmetric Kullback-Leibler Divergence (SKLD), which is also a method for measuring entropy of a system. It has been previously observed that SKLD is a better method for measuring the amount of disturbances compared to L2 norm and cross-correlation coefficient. AQDT is also compared with magnetically Quiet Day Period (QDP) from 25 to 28 April, 2011, during which Kp and Dst indices indicate a very quiet ionospheric and magnetospheric period. Also, in order to measure the variability between the consecutive days, TEC values for each day during EDP and QDP are compared with the TEC values of the following day. A third measure of W-index is also applied to identify the local disturbances in the ionosphere, where TEC of a given day is compared to the median of seven days prior to the day of investigation logarithmically. Since W-index is obtained for each epoch, the within-the-day variability can also be monitored. It has been observed that peak TEC values for all stations in TNPGN increase 10 to 15 TECU two days prior to the earthquake. The SKLD values for comparison of EDP and AQDT also peak on 21st of October, 2011, two days prior to the earthquake. Since ionospheric disturbance can be observed on all days prior to the earthquake, comparison of TEC for consecutive days for each station using SKLD does not provide extra information. The W-index values indicate that there may be small scale variability for stations closer to the earthquake epicenter. When compared with previous earthquakes that occurred in Turkey with magnitudes 4.5 and 5.2 on Richter scale, this 7.2 magnitude earthquake has been felt as an ionospheric disturbance for stations especially on Northern Anatolian Fault. The results also indicate the need for constant monitoring and statistical decision theory for detection of earthquake precursors. This study is supported by TUBITAK EEEAG Grant 109E055.

Prediction of global ionospheric VTEC maps using an adaptive autoregressive model

NASA Astrophysics Data System (ADS)

Wang, Cheng; Xin, Shaoming; Liu, Xiaolu; Shi, Chuang; Fan, Lei

2018-02-01

In this contribution, an adaptive autoregressive model is proposed and developed to predict global ionospheric vertical total electron content maps (VTEC). Specifically, the spherical harmonic (SH) coefficients are predicted based on the autoregressive model, and the order of the autoregressive model is determined adaptively using the F-test method. To test our method, final CODE and IGS global ionospheric map (GIM) products, as well as altimeter TEC data during low and mid-to-high solar activity period collected by JASON, are used to evaluate the precision of our forecasting products. Results indicate that the predicted products derived from the model proposed in this paper have good consistency with the final GIMs in low solar activity, where the annual mean of the root-mean-square value is approximately 1.5 TECU. However, the performance of predicted vertical TEC in periods of mid-to-high solar activity has less accuracy than that during low solar activity periods, especially in the equatorial ionization anomaly region and the Southern Hemisphere. Additionally, in comparison with forecasting products, the final IGS GIMs have the best consistency with altimeter TEC data. Future work is needed to investigate the performance of forecasting products using the proposed method in an operational environment, rather than using the SH coefficients from the final CODE products, to understand the real-time applicability of the method.

Some properties of lithium aluminium silicate (LAS) glass-ceramics used in glass-ceramic to metal compressive seal for vacuum applications

NASA Astrophysics Data System (ADS)

Ananthanarayanan, A.; Kumar, R.; Bhattacharya, S.; Shrikhande, V. K.; Kothiyal, G. P.

2008-05-01

We report here the preparation of LAS glass-ceramics and some studies on their thermo-physical properties and microstructure, for compressive seals in vacuum applications. Glass of composition 12.6Li2O-71.7SiO2-5.1Al2O3-4.9K2O-3.2B2O3-2.5P2O5 was prepared by the conventional melt quench technique. Based on differential thermal analysis (DTA) data, glass samples were nucleated at 600°C for 2hr and were then crystallized at 800°C for 2-5hr. X-ray diffraction (XRD) spectra showed lithium disilicate to be the major phase. A dwell time of 3hr yielded a sample of good crystallinity. Dilatometric measurements of this sample on a thermo-mechanical analyzer (TMA) measured a thermal expansion coefficient (TEC) of 94.61×10-7°C-1. Glass transition temperature (Tg), and dilatometric softening temperature (Tds) of the sample was recorded as 585°C and 830°C respectively. Considering TEC and Tds compression type seals were prepared with SS304 (TEC = 172×10-7°C-1) housing of length 15mm, outer diameter 30mm and inner diameter 15mm. After pre-heat treatment of the metal components, sealing was carried out under a protective atmosphere of flowing Argon gas. The finished seal was tested for leak tightness on a He leak detector. The seal was capable of withstanding a vacuum of 10-6 Torr; at a leak rate of 10-9 Torr lit s-1. Scanning electron microscopy (SEM) was carried out on LAS before and after fabrication of compressive seal to elucidate the effect of compressive stress and the presence of metal near the interface. We observe a significant difference in microstructure due to compressive stresses of sealing and due to the presence of metal. Energy dispersive analysis of X-rays (EDAX) revealed no interdiffusion of species from glass-ceramic to metal or vice-versa.

Case study of ISWI in Vietnam: A comparison of ionospheric parameters observed over Ho Chi Minh with IRI predictions

NASA Astrophysics Data System (ADS)

Lan, Hoang Thai; Tam, Dao Ngoc Hanh

2014-01-01

For the contribution of Vietnam to ISWI activities, there are 3 GPS receivers, 3 Ionosondes, 1 AWESOME and 1 MAGDAS operating in Vietnam. With a special geographical position stretching from the north tropic to the magnetic equator, Vietnam is an interesting area to supplement the data for the Global Space Weather Model. The Ionosphere is an important indicator of Space Weather and the International Reference Ionosphere (IRI) model has become widely accepted. The first task of ionospheric science in a new location is often comparing the observed data with IRI. This paper presents the results of comparisons of the foF2 and TEC observed over Ho Chi Minh City (10.51 N, 106.33 E) with the values calculated according to the IRI-2007 in order to evaluate the applicability of the model in forecasting for the equatorial region of Vietnam. We compare the critical frequency of layer F (foF2) and Total Electron Content (TEC) values for two phases of solar activity. The results show very good diurnal correlations between the observed foF2 and TEC with IRI values in the decreasing solar activity period 2003 ± 2006 (the deviation < 15%). In the increasing period 2009 ± 2012, good correlation was in the morning time before the foF2 peak at about 10 LT, with a deviation about 10% (except 2012). However, after 10 LT, the IRI-foF2 values rose up and the deviations were about 25% to 30%, especially during evening. In the years with low solar activity (SSN < 40), the IRI-foF2 are almost always higher than the observed foF2 data and vice versa for the years with SSN > 40. This is a note for correction IRI model applying for Vietnam. The comparison of the TEC shows that the correlation between GPS-TEC and IRI-TEC generally was good with coefficients k > 0.8 and R > 0.9 for the period 2006 - 2010. The worst relationship were March, April, September, October, November and December 2011, corresponding to periods when the TEC gradients are highest. The phenomenon of decline in the TEC at noon over Ho Chi Minh City observed pretty weak. This phenomenon appeared only in a few months from April to September, when the ionization is high. In the period from 0 to 5 am local time, the average minimum GPS-TEC observed over Ho Chi Minh City is about 3 tecu, while the IRI-TEC value is ~ 0.3. Thus, the IRI-TEC values should be recalibrated.

Monolithically Integrated Fiber Optic Coupler

DTIC Science & Technology

2013-01-14

tilted Bragg gratings 24 are thermoelectric coolers (TECs) 30 that can modify the pitch of the tilted Bragg gratings 24, thereby changing their...reflective properties at specific wavelengths to provide tunability. Heating or cooling by thermoelectric coolers 30 causes expansion or contraction of...of a different wavelength of light. While thermoelectric coolers are preferred, devices 30 can be any reversible cooling/heating device that is

Controlled ripple texturing of suspended graphene and ultrathin graphite membranes.

PubMed

Bao, Wenzhong; Miao, Feng; Chen, Zhen; Zhang, Hang; Jang, Wanyoung; Dames, Chris; Lau, Chun Ning

2009-09-01

Graphene is nature's thinnest elastic material and displays exceptional mechanical and electronic properties. Ripples are an intrinsic feature of graphene sheets and are expected to strongly influence electronic properties by inducing effective magnetic fields and changing local potentials. The ability to control ripple structure in graphene could allow device design based on local strain and selective bandgap engineering. Here, we report the first direct observation and controlled creation of one- and two-dimensional periodic ripples in suspended graphene sheets, using both spontaneously and thermally generated strains. We are able to control ripple orientation, wavelength and amplitude by controlling boundary conditions and making use of graphene's negative thermal expansion coefficient (TEC), which we measure to be much larger than that of graphite. These results elucidate the ripple formation process, which can be understood in terms of classical thin-film elasticity theory. This should lead to an improved understanding of suspended graphene devices, a controlled engineering of thermal stress in large-scale graphene electronics, and a systematic investigation of the effect of ripples on the electronic properties of graphene.

Nonlinear effects on composite laminate thermal expansion

NASA Technical Reports Server (NTRS)

Hashin, Z.; Rosen, B. W.; Pipes, R. B.

1979-01-01

Analyses of Graphite/Polyimide laminates shown that the thermomechanical strains cannot be separated into mechanical strain and free thermal expansion strain. Elastic properties and thermal expansion coefficients of unidirectional Graphite/Polyimide specimens were measured as a function of temperature to provide inputs for the analysis. The + or - 45 degrees symmetric Graphite/Polyimide laminates were tested to obtain free thermal expansion coefficients and thermal expansion coefficients under various uniaxial loads. The experimental results demonstrated the effects predicted by the analysis, namely dependence of thermal expansion coefficients on load, and anisotropy of thermal expansion under load. The significance of time dependence on thermal expansion was demonstrated by comparison of measured laminate free expansion coefficients with and without 15 day delay at intermediate temperature.

GPS, BDS and Galileo ionospheric correction models: An evaluation in range delay and position domain

NASA Astrophysics Data System (ADS)

Wang, Ningbo; Li, Zishen; Li, Min; Yuan, Yunbin; Huo, Xingliang

2018-05-01

The performance of GPS Klobuchar (GPSKlob), BDS Klobuchar (BDSKlob) and NeQuick Galileo (NeQuickG) ionospheric correction models are evaluated in the range delay and position domains over China. The post-processed Klobuchar-style (CODKlob) coefficients provided by the Center for Orbit Determination in Europe (CODE) and our own fitted NeQuick coefficients (NeQuickC) are also included for comparison. In the range delay domain, BDS total electrons contents (TEC) derived from 20 international GNSS Monitoring and Assessment System (iGMAS) stations and GPS TEC obtained from 35 Crust Movement Observation Network of China (CMONC) stations are used as references. Compared to BDS TEC during the short period (doy 010-020, 2015), GPSKlob, BDSKlob and NeQuickG can correct 58.4, 66.7 and 54.7% of the ionospheric delay. Compared to GPS TEC for the long period (doy 001-180, 2015), the three ionospheric models can mitigate the ionospheric delay by 64.8, 65.4 and 68.1%, respectively. For the two comparison cases, CODKlob shows the worst performance, which only reduces 57.9% of the ionospheric range errors. NeQuickC exhibits the best performance, which outperforms GPSKlob, BDSKlob and NeQuickG by 6.7, 2.1 and 6.9%, respectively. In the position domain, single-frequency stand point positioning (SPP) was conducted at the selected 35 CMONC sites using GPS C/A pseudorange with and without ionospheric corrections. The vertical position error of the uncorrected case drops significantly from 10.3 m to 4.8, 4.6, 4.4 and 4.2 m for GPSKlob, CODKlob, BDSKlob and NeQuickG, however, the horizontal position error (3.2) merely decreases to 3.1, 2.7, 2.4 and 2.3 m, respectively. NeQuickG outperforms GPSKlob and BDSKlob by 5.8 and 1.9% in vertical component, and by 25.0 and 3.2% in horizontal component.

Mapping the total electron content over Malaysia using Spherical Cap Harmonic Analysis

NASA Astrophysics Data System (ADS)

Bahari, S.; Abdullah, M.; Bouya, Z.; Musa, T. A.

2017-12-01

The ionosphere over Malaysia is unique because of her location which is in close proximity to the geomagnetic equator and is in the equatorial regions. In this region, the magnetic field is horizontally oriented from south to north and field aligned direction is in the meridional plane (ExB) which becomes the source of equatorial ionospheric anomaly occurrence such as plasma bubble, fountain effects and others. Until today, there is no model that has been developed over Malaysia to study the ionosphere. Due to that, the main objective of this paper is to develop a new technique for mapping the total electron content (TEC) from GPS measurements. Data by myRTKnet network of GPS receiver over Malaysia were used in this study. A new methodology, based on modified spherical cap harmonic analysis (SCHA), was developed to estimate diurnal vertical TEC over the region using GPS observations. The SCHA model is based on longitudinal expansion in Fourier series and fractional Legendre co-latitudinal functions over a spherical cap-like region. The TEC map with spatial resolution of 0.15 ° x 0.15 ° in latitude and longitude with the time resolution of 30 seconds are derived. TEC maps from the SCHA model were compared with the global ionospheric map and other regional models. Result shows that during low solar activity, SCHA model had a better mapping with the accuracy of less than 1 TECU compared to other regional models.

Solar eclipses at high latitudes: ionospheric effects in the lower ionosphere

NASA Astrophysics Data System (ADS)

Cherniakov, S.

2017-12-01

The partial reflection facility of the Polar Geophysical Institute (the Tumanny observatory, 69.0N, 35.7E) has observed behavior of the high-latitude lower ionosphere during the 20 March 2015 total solar eclipse. There were several effects during the eclipse. At the heights of 60-80 km the ionosphere has shown the effect of a "short night", but at the higher altitudes local enhanced electron concentration had a wave-like form. Data received by the riometer of the Tumanny observatory have also shown wave-like behavior. The behavior can be explained by influence of acoustic-gravity waves which originated after cooling of the atmosphere during the lunar shadow supersonic movement, and transport processes during the eclipse. During the 21 August 2017 solar eclipse there was a substorm at the high latitudes. But after the end of the substorm in the region of the Tumanny observatory the observed amplitudes of the reflected waves had wave effects which could be connected with the coming waves from the region of the eclipse. The wave features were also shown in the behavior of the total electron content (TEC) of the lower ionosphere. During several solar eclipses it was implemented observations of lower ionosphere behavior by the partial reflection facility of the Tumanny observatory. The consideration of the lower ionosphere TEC had revealed common features in the TEC behavior during the eclipses. The photochemical theory of processes in the lower ionosphere is very complicated and up to now it is not completely developed. Therefore introduction of the effective coefficients determining the total speed of several important reactions has been widely adopted when modeling the D-region of the ionosphere. However, experimental opportunities for obtaining effective recombination coefficients are rather limited. One of the methods to estimate effective recombination coefficients uses the phenomenon of a solar eclipse. During solar eclipses at the partial reflection facility of the Tumanny observatory observations were carried out. It gave possibility to obtain the behavior of the electron concentration in time at the selected heights. Using the obtained experimental profiles, the effective recombination coefficients at the D-region heights of the ionosphere have been evaluated.

SynTec Final Technical Report: Synthetic biology for Tailored Enzyme cocktails

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Janine; Teter, Sarah

Using a novel enzyme screening method inspired by synthetic biology, Novozymes developed new technology under SynTec which allows for more rapidly tailoring of enzyme cocktails. The methodology can be applied to specific feedstocks, and or coupled to address a specific hydrolytic conversion process context. Using combinatorial high throughput screening of libraries of enzyme domains, we can quickly assess which combination of catalytic modules delivers the best performance for a specific condition. To demonstrate the effectiveness of the screening process, we measured performance of the output catalytic cocktail compared to CTec3/HTec3. SynTec benchmark cocktail - blend of Cellic® CTec3 and HTec3.more » The test substrate was - ammonia fiber expansion pretreated corn stover (AFEX™ PCS).CTec3/HTec3 was assayed at the optimal pH and temperature, and also in the absence of any pH adjustment. The new enzyme cocktail discovered under SynTec was assayed in the absence of any pH adjustment and at the optimal temperature. Conversion is delivered by SynTec enzyme at significant dose reduction relative to CTec3/HTec3 at the controlled pH optimum, and without titrant required to maintain pH, which delivers additional cost savings relative to current state of the art process. In this 2.5 year $4M project, the team delivered an experimental cocktail that significantly outperformed CTec3/HTec3 for a specific substrate, and for specific hydrolysis conditions. As a means of comparing performance improvement delivered per research dollar spent, we note that SynTec delivered a similar performance improvement to the previous award, in a shorter time and with fewer resources than for the previously successful DOE project DECREASE, a 3.5 year, $25M project, though this project focused on a different substrate and used different hydrolysis conditions. The newly implemented technology for rapid sourcing of new cellulases and hemicellulases from nature is an example of Novozymes' continued innovation that results in more effective products for the advanced biofuel market.« less

With respect to coefficient of linear thermal expansion, bacterial vegetative cells and spores resemble plastics and metals, respectively.

PubMed

Nakanishi, Koichi; Kogure, Akinori; Fujii, Takenao; Kokawa, Ryohei; Deuchi, Keiji; Kuwana, Ritsuko; Takamatsu, Hiromu

2013-10-09

If a fixed stress is applied to the three-dimensional z-axis of a solid material, followed by heating, the amount of thermal expansion increases according to a fixed coefficient of thermal expansion. When expansion is plotted against temperature, the transition temperature at which the physical properties of the material change is at the apex of the curve. The composition of a microbial cell depends on the species and condition of the cell; consequently, the rate of thermal expansion and the transition temperature also depend on the species and condition of the cell. We have developed a method for measuring the coefficient of thermal expansion and the transition temperature of cells using a nano thermal analysis system in order to study the physical nature of the cells. The tendency was seen that among vegetative cells, the Gram-negative Escherichia coli and Pseudomonas aeruginosa have higher coefficients of linear expansion and lower transition temperatures than the Gram-positive Staphylococcus aureus and Bacillus subtilis. On the other hand, spores, which have low water content, overall showed lower coefficients of linear expansion and higher transition temperatures than vegetative cells. Comparing these trends to non-microbial materials, vegetative cells showed phenomenon similar to plastics and spores showed behaviour similar to metals with regards to the coefficient of liner thermal expansion. We show that vegetative cells occur phenomenon of similar to plastics and spores to metals with regard to the coefficient of liner thermal expansion. Cells may be characterized by the coefficient of linear expansion as a physical index; the coefficient of linear expansion may also characterize cells structurally since it relates to volumetric changes, surface area changes, the degree of expansion of water contained within the cell, and the intensity of the internal stress on the cellular membrane. The coefficient of linear expansion holds promise as a new index for furthering the understanding of the characteristics of cells. It is likely to be a powerful tool for investigating changes in the rate of expansion and also in understanding the physical properties of cells.

With respect to coefficient of linear thermal expansion, bacterial vegetative cells and spores resemble plastics and metals, respectively

PubMed Central

2013-01-01

Background If a fixed stress is applied to the three-dimensional z-axis of a solid material, followed by heating, the amount of thermal expansion increases according to a fixed coefficient of thermal expansion. When expansion is plotted against temperature, the transition temperature at which the physical properties of the material change is at the apex of the curve. The composition of a microbial cell depends on the species and condition of the cell; consequently, the rate of thermal expansion and the transition temperature also depend on the species and condition of the cell. We have developed a method for measuring the coefficient of thermal expansion and the transition temperature of cells using a nano thermal analysis system in order to study the physical nature of the cells. Results The tendency was seen that among vegetative cells, the Gram-negative Escherichia coli and Pseudomonas aeruginosa have higher coefficients of linear expansion and lower transition temperatures than the Gram-positive Staphylococcus aureus and Bacillus subtilis. On the other hand, spores, which have low water content, overall showed lower coefficients of linear expansion and higher transition temperatures than vegetative cells. Comparing these trends to non-microbial materials, vegetative cells showed phenomenon similar to plastics and spores showed behaviour similar to metals with regards to the coefficient of liner thermal expansion. Conclusions We show that vegetative cells occur phenomenon of similar to plastics and spores to metals with regard to the coefficient of liner thermal expansion. Cells may be characterized by the coefficient of linear expansion as a physical index; the coefficient of linear expansion may also characterize cells structurally since it relates to volumetric changes, surface area changes, the degree of expansion of water contained within the cell, and the intensity of the internal stress on the cellular membrane. The coefficient of linear expansion holds promise as a new index for furthering the understanding of the characteristics of cells. It is likely to be a powerful tool for investigating changes in the rate of expansion and also in understanding the physical properties of cells. PMID:24107328

Hoberman-sphere-inspired lattice metamaterials with tunable negative thermal expansion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yangbo; Chen, Yanyu; Li, Tiantian

Materials with engineered thermal expansion coefficients, capable of avoiding failure or irreversible destruction of structures and devices, are important for aerospace, civil, biomedical, optics, and semiconductor applications. In natural materials, thermal expansion usually cannot be adjusted easily and a negative thermal expansion coefficient is still uncommon. Here we propose a novel architected lattice bi-material system, inspired by the Hoberman sphere, showing a wide range of tunable thermal expansion coefficient from negative to positive, -1.04 x 10 -3 degrees C-1 to 1.0 x 10 -5 degrees C-1. Numerical simulations and analytical formulations are implemented to quantify the evolution of the thermalmore » expansion coefficients and reveal the underlying mechanisms responsible for this unusual behavior. We show that the thermal expansion coefficient of the proposed metamaterials depends on the thermal expansion coefficient ratio and the axial stiffness ratio of the constituent materials, as well as the bending stiffness and the topological arrangement of the constitutive elements. The finding reported here provides a new routine to design architected metamaterial systems with tunable negative thermal expansion for a wide range of potential applications.« less

Hoberman-sphere-inspired lattice metamaterials with tunable negative thermal expansion

DOE PAGES

Li, Yangbo; Chen, Yanyu; Li, Tiantian; ...

2018-02-02

Materials with engineered thermal expansion coefficients, capable of avoiding failure or irreversible destruction of structures and devices, are important for aerospace, civil, biomedical, optics, and semiconductor applications. In natural materials, thermal expansion usually cannot be adjusted easily and a negative thermal expansion coefficient is still uncommon. Here we propose a novel architected lattice bi-material system, inspired by the Hoberman sphere, showing a wide range of tunable thermal expansion coefficient from negative to positive, -1.04 x 10 -3 degrees C-1 to 1.0 x 10 -5 degrees C-1. Numerical simulations and analytical formulations are implemented to quantify the evolution of the thermalmore » expansion coefficients and reveal the underlying mechanisms responsible for this unusual behavior. We show that the thermal expansion coefficient of the proposed metamaterials depends on the thermal expansion coefficient ratio and the axial stiffness ratio of the constituent materials, as well as the bending stiffness and the topological arrangement of the constitutive elements. The finding reported here provides a new routine to design architected metamaterial systems with tunable negative thermal expansion for a wide range of potential applications.« less

Characterization of Ionospheric Dynamics Over The East African Dip Equatorial Region Using GPS-Derived Total Electron Content.

NASA Astrophysics Data System (ADS)

Olwendo, J. O.

2016-12-01

Through a linear combination of GPS satellite range and phase measurement observed on two carrier frequencies by terrestrial based GPS receivers, the ionospheric total electron content (TEC) along oblique GPS signal path can be quantified. Using Adjusted Spherical Harmonic (ASHA) expansion, regional TEC maps over the East Africa sector has been achieved. The observed TEC has been used to evaluate the performance of IRI2007 and NeQuick 2 models over the region. Ionospheric irregularities have been measured and the plasma drift velocity and the East-West extent of the irregularities have also been analyzed by using a Very High Frequency (VHF) receiver system that is closely spaced. The hourly TEC images developed have shown that the Southern Equatorial Ionization Anomaly (EIA) crest over the East African sector lies within the Kenyan region, and the occurrence of scintillation is dependent on how well the anomaly crest forms. Scintillation occurrences are intense at and around the edges of EIA crest due to the presence of high ambient electron densities and sharp TEC depletions. Simultaneous recording of amplitude scintillations at VHF and L-band frequencies reveal two distinct types of scintillation namely; the Plasma Bubble Induced (PBI) and the Bottom Side Sinusoidal (BSS). The PBI scintillations are characterized by high intensity during the post-sunset hours of the equinoctial months and appear at both VHF and L-band frequencies. The BSS type are associated with VHF scintillation and are characterized by long duration patches and often exhibit Fresnel oscillation on the roll portion of the power spectrum, which suggest a weak scattering from thin screen irregularities. The occurrence of post-midnight L-band scintillation events which are not linked to pre-midnight scintillation observations raises fundamental question on the mechanism and source of electric fields driving the plasma depletion under conditions of very low background electron density.

Temporal evolution of the EIA along 95°E as obtained from GNSS TEC measurements and SAMI3 model

NASA Astrophysics Data System (ADS)

Kakoti, Geetashree; Kalita, Bitap Raj; Hazarika, Rumajyoti; Bhuyan, Pradip Kumar; Sharma, Sanjay; Tiwari, Ramesh Chandra

2018-06-01

The total electron content (TEC) derived from GNSS measurements at a trans-hemispheric meridional chain of ground stations around 95°E longitude are used to study the quiet time inter-hemispheric structure and dynamics of the equatorial ionization anomaly (EIA) during the period March 2015 to February 2016. The stations are Dibrugarh (27.5°N, 95°E, 43° dip), Kohima (25.6°N, 94.1°E, 39° dip), Aizawl (23.7°N, 92.8°E, 36° dip), Port Blair (11.63°N, 92.71°E, 9° dip) and Cocos Islands (12.2°S, 96.8°E, 43° dip). The observation shows that the northern crest of the EIA lies in the south of 23°N (Aizawl) in all seasons but recedes further south towards the equator during December solstice. The largest poleward expansion of the northern (southern) EIA is observed in the March equinox (December solstice). The equinoctial and hemispherical asymmetry of TEC is noted. The winter anomaly is observed in the northern hemisphere but not in the southern hemisphere. The highest midday TEC over any station is observed in the March equinox. The TEC in southern summer (December solstice) is significantly higher than that in the northern summer (June solstice). The observed northern EIA contracts equatorward in the postsunset period of solstice but the southern EIA persists late into the midnight in the December solstice. The asymmetry may be attributed to the different geographic location of the magnetically conjugate stations. The SAMI3 simulations broadly capture the EIA structure and the inter-hemispheric asymmetry during solstices. The difference between observations and the SAMI3 is higher in March equinox and December solstice. The higher E × B vertical drift in the 90-100°E sector and the large geographic-geomagnetic offset in observing stations may have contributed to the observed differences.

Hybrid Exhaust Component

NASA Technical Reports Server (NTRS)

Pelletier, Gerard D. (Inventor); Logan, Charles P. (Inventor); McEnerney, Bryan William (Inventor); Haynes, Jeffrey D. (Inventor)

2015-01-01

An exhaust includes a wall that has a first composite material having a first coefficient of thermal expansion and a second composite material having a second coefficient of the thermal expansion that is less than the first coefficient of thermal expansion.

Ceramic matrix composite turbine engine vane

NASA Technical Reports Server (NTRS)

Prill, Lisa A. (Inventor); Schaff, Jeffery R. (Inventor); Shi, Jun (Inventor)

2012-01-01

A vane has an airfoil shell and a spar within the shell. The vane has an outboard shroud at an outboard end of the shell and an inboard platform at an inboard end of the shell. The shell includes a region having a depth-wise coefficient of thermal expansion and a second coefficient of thermal expansion transverse thereto, the depth-wise coefficient of thermal expansion being greater than the second coefficient of thermal expansion.

Performance of MIDAS Over East African Longitude Sector: Case Study During 4-14 March 2012 Quiet to Disturbed Geomagnetic Conditions

NASA Astrophysics Data System (ADS)

Giday, Nigussie M.; Katamzi-Joseph, Zama T.

2018-02-01

This study investigates the performance of a tomographic algorithm, Multi-Instrument and Data Analysis System (MIDAS), during an extended period of 4-14 March 2012, containing moderate and strong geomagnetic storms conditions, over an understudied and data scarce Eastern African longitude sector. Nonetheless, a relatively better distribution of Global Navigation Satellite Systems stations exists along a narrow longitude sector between 30°E and 44°E and latitude range of 30°S and 36°N that spans the equatorial, middle-, and low-latitude ionosphere. Then results are compared with independent global models such as International Reference Ionosphere 2012 (IRI-2012) and global ionosphere map (GIM). MIDAS performance was better than that of the IRI-2012 and GIM models in terms of capturing the diurnal trends as well as the short temporal total electron content (TEC) structures, with least root-mean-square errors (RMSEs). Overall, MIDAS results showed better agreement with the observation vertical TEC (VTEC) with computed maximum correlation coefficient (r) of 0.99 and minimum root-mean-square error (RMSE) of 2.91 TEC unit (1 TECU = 1,016 el m-2 over all the test stations and the validation days. Conversely, for the IRI-2012 and GIM TEC estimates, the corresponding maximum computed r values were 0.93 and 0.99, respectively, while the minimum RMSEs were 13.03 TECU and 6.52 TECU, respectively, for all the test stations and the validation days.

Conformal expansions and renormalons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rathsman, J.

2000-02-07

The coefficients in perturbative expansions in gauge theories are factorially increasing, predominantly due to renormalons. This type of factorial increase is not expected in conformal theories. In QCD conformal relations between observables can be defined in the presence of a perturbative infrared fixed-point. Using the Banks-Zaks expansion the authors study the effect of the large-order behavior of the perturbative series on the conformal coefficients. The authors find that in general these coefficients become factorially increasing. However, when the factorial behavior genuinely originates in a renormalon integral, as implied by a postulated skeleton expansion, it does not affect the conformal coefficients.more » As a consequence, the conformal coefficients will indeed be free of renormalon divergence, in accordance with previous observations concerning the smallness of these coefficients for specific observables. The authors further show that the correspondence of the BLM method with the skeleton expansion implies a unique scale-setting procedure. The BLM coefficients can be interpreted as the conformal coefficients in the series relating the fixed-point value of the observable with that of the skeleton effective charge. Through the skeleton expansion the relevance of renormalon-free conformal coefficients extends to real-world QCD.« less

Partial-fraction expansion and inverse Laplace transform of a rational function with real coefficients

NASA Technical Reports Server (NTRS)

Chang, F.-C.; Mott, H.

1974-01-01

This paper presents a technique for the partial-fraction expansion of functions which are ratios of polynomials with real coefficients. The expansion coefficients are determined by writing the polynomials as Taylor's series and obtaining the Laurent series expansion of the function. The general formula for the inverse Laplace transform is also derived.

A new electron density model of the plasmasphere for operational applications and services

NASA Astrophysics Data System (ADS)

Jakowski, Norbert; Hoque, Mohammed Mainul

2018-03-01

The Earth's plasmasphere contributes essentially to total electron content (TEC) measurements from ground or satellite platforms. Furthermore, as an integral part of space weather, associated plasmaspheric phenomena must be addressed in conjunction with ionosphere weather monitoring by operational space weather services. For supporting space weather services and mitigation of propagation errors in Global Navigation Satellite Systems (GNSS) applications we have developed the empirical Neustrelitz plasmasphere model (NPSM). The model consists of an upper L shell dependent part and a lower altitude dependent part, both described by specific exponential decays. Here the McIllwain parameter L defines the geomagnetic field lines in a centered dipole model for the geomagnetic field. The coefficients of the developed approaches are successfully fitted to numerous electron density data derived from dual frequency GPS measurements on-board the CHAMP satellite mission from 2000 to 2005. The data are utilized for fitting up to the L shell L = 3 because a previous validation has shown a good agreement with IMAGE/RPI measurements up to this value. Using the solar radio flux index F10.7 as the only external parameter, the operation of the model is robust, with 40 coefficients fast and sufficiently accurate to be used as a background model for estimating TEC or electron density profiles in near real time GNSS applications and services. In addition to this, the model approach is sensitive to ionospheric coupling resulting in anomalies such as the Nighttime Winter Anomaly and the related Mid-Summer Nighttime Anomaly and even shows a slight plasmasphere compression of the dayside plasmasphere due to solar wind pressure. Modelled electron density and TEC values agree with estimates reported in the literature in similar cases.

TEC protein tyrosine kinase is involved in the Erk signaling pathway induced by HGF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Feifei; Jiang, Yinan; Zheng, Qiping

Research highlights: {yields} TEC is rapidly tyrosine-phosphorylated and activated by HGF-stimulation in vivo or after partial hepatectomy in mice. {yields} TEC enhances the activity of Elk and serum response element (SRE) in HGF signaling pathway in hepatocyte. {yields} TEC promotes hepatocyte proliferation through the Erk-MAPK pathway. -- Abstract: Background/aims: TEC, a member of the TEC family of non-receptor type protein tyrosine kinases, has recently been suggested to play a role in hepatocyte proliferation and liver regeneration. This study aims to investigate the putative mechanisms of TEC kinase regulation of hepatocyte differentiation, i.e. to explore which signaling pathway TEC is involvedmore » in, and how TEC is activated in hepatocyte after hepatectomy and hepatocyte growth factor (HGF) stimulation. Methods: We performed immunoprecipitation (IP) and immunoblotting (IB) to examine TEC tyrosine phosphorylation after partial hepatectomy in mice and HGF stimulation in WB F-344 hepatic cells. The TEC kinase activity was determined by in vitro kinase assay. Reporter gene assay, antisense oligonucleotide and TEC dominant negative mutant (TEC{sup KM}) were used to examine the possible signaling pathways in which TEC is involved. The cell proliferation rate was evaluated by {sup 3}H-TdR incorporation. Results: TEC phosphorylation and kinase activity were increased in 1 h after hepatectomy or HGF treatment. TEC enhanced the activity of Elk and serum response element (SRE). Inhibition of MEK1 suppressed TEC phosphorylation. Blocking TEC activity dramatically decreased the activation of Erk. Reduced TEC kinase activity also suppressed the proliferation of WB F-344 cells. These results suggest TEC is involved in the Ras-MAPK pathway and acts between MEK1 and Erk. Conclusions: TEC promotes hepatocyte proliferation and regeneration and is involved in HGF-induced Erk signaling pathway.« less

A novel family of Nb-doped Bi0.5Sr0.5FeO3-δ perovskite as cathode material for intermediate-temperature solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Gao, Lei; Li, Qiang; Sun, Liping; Zhang, Xianfa; Huo, Lihua; Zhao, Hui; Grenier, Jean-Claude

2017-12-01

Cobalt-free provskite oxides Bi0.5Sr0.5Fe1-xNbxO3-δ (BSFNx, x = 0.05, 0.10 and 0.15) were prepared and evaluated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). In particular, the effects of Nb substitution on phase evolution, thermal expansion behavior and electrochemical performance were systematically investigated. The average thermal expansion coefficient (TEC) of BSFNx decreases from 13.3 × 10-6 K-1 at x = 0.05 to 12.6 × 10-6 K-1 at x = 0.15 within a temperature range of 50-800 °C. Among the BSFNx materials, Bi0.5Sr0.5Fe0.9Nb0.1O3-δ (BSFN0.10) oxide shows the best electrochemical performance. The polarization resistances (Rp) of BSFN0.10 cathode on CGO electrolyte are 0.038, 0.075 and 0.156 Ω cm2 at 700, 650 and 600 °C, respectively. Meanwhile the maximum power densities of the anode-supported single cells are 1.28, 1.54 and 1.34 W cm-2 at 700 °C for BSFNx cathodes with x = 0.05, 0.10, and 0.15, respectively. Furthermore, the relationship study of oxygen partial pressure dependence on Rp indicates that the oxygen reduction reaction (ORR) rate-limiting step is the oxygen adsorption-dissociation on the electrode surface. The desirable electrochemical performance demonstrates that BSFNx oxides are potential cathode materials for IT-SOFCs.

Improvement of Klobuchar model for GNSS single-frequency ionospheric delay corrections

NASA Astrophysics Data System (ADS)

Wang, Ningbo; Yuan, Yunbin; Li, Zishen; Huo, Xingliang

2016-04-01

Broadcast ionospheric model is currently an effective approach to mitigate the ionospheric time delay for real-time Global Navigation Satellite System (GNSS) single-frequency users. Klobuchar coefficients transmitted in Global Positioning System (GPS) navigation message have been widely used in various GNSS positioning and navigation applications; however, this model can only reduce the ionospheric error by approximately 50% in mid-latitudes. With the emerging BeiDou and Galileo, as well as the modernization of GPS and GLONASS, more precise ionospheric correction models or algorithms are required by GNSS single-frequency users. Numerical analysis of the initial phase and nighttime term in Klobuchar algorithm demonstrates that more parameters should be introduced to better describe the variation of nighttime ionospheric total electron content (TEC). In view of this, several schemes are proposed for the improvement of Klobuchar algorithm. Performance of these improved Klobuchar-like models are validated over the continental and oceanic regions during high (2002) and low (2006) levels of solar activities, respectively. Over the continental region, GPS TEC generated from 35 International GNSS Service (IGS) and the Crust Movement Observation Network of China (CMONOC) stations are used as references. Over the oceanic region, TEC data from TOPEX/Poseidon and JASON-1 altimeters are used for comparison. A ten-parameter Klobuchar-like model, which describes the nighttime term as a linear function of geomagnetic latitude, is finally proposed for GNSS single-frequency ionospheric corrections. Compared to GPS TEC, while GPS broadcast model can correct for 55.0% and 49.5% of the ionospheric delay for the year 2002 and 2006, respectively, the proposed ten-parameter Klobuchar-like model can reduce the ionospheric error by 68.4% and 64.7% for the same period. Compared to TOPEX/Poseidon and JASON-1 TEC, the improved ten-parameter Klobuchar-like model can mitigate the ionospheric delay by 61.1% and 64.3% in 2002 and 2006, respectively.

Comparison with IRI-PLUS and IRI-2012-TEC values of GPS-TEC values

NASA Astrophysics Data System (ADS)

Atıcı, Ramazan; Saǧır, Selçuk

2016-07-01

This study presents a comparison with IRI-PLUS and IRI-2012 Total Electron Content (TEC) values of Total Electron Content (TEC) values obtained from Ankara station (39,7 N; 32,76 E) of Global Position System (GPS) of Turkey on equinox and solstice days of 2009 year. For all days, it is observed that GPS-TEC values are greater than IRI-2012-TEC values, while IRI-PLUS-TEC values are very close to GPS-TEC values. When GPS-TEC values for both equinoxes are compared, it is seen that TEC values on September equinox are greater than one on March equinox. However, it is observed that GPS-TEC values on June solstice are greater than one on December solstice. Also, the relationship between GPS-TEC values and geomagnetic indexes is investigated.

Research on global plasmaspheric electron content by using LEO occultation and GPS data

NASA Astrophysics Data System (ADS)

Chen, Peng; Yao, Yibin

2015-05-01

This paper investigates the characteristics of global plasmaspheric electron content (pTEC) using COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) occultation and GPS (Global Positioning System) data. The ionospheric electron content (iTEC) within 100-1000 km was obtained by fitting the COSMIC occultation electron density profiles, and the pTEC was obtained by subtracting the iTEC from CODE (Center for Orbit Determination in Europe) GIM (global ionosphere maps) TEC provided by University of Bern. This paper also investigates the characteristics of pTEC variations with local time, latitude and season. The results show that in 2011, the worldwide average of pTEC was 4.02 TECu, which is consistent with the findings of other studies. The pTEC shows significant diurnal variation characteristics, that is, pTEC is higher during daytime than during nighttime, but the percentage contribution of pTEC to GPS TEC is higher during nighttime than during daytime. The pTEC varies with the seasons, pTEC hemispheres symmetrically during spring and autumn, while pTEC in the summer hemisphere is higher than that in the winter hemisphere. Moreover, the percentage contribution of pTEC to GPS TEC (total electron content) is higher in winter hemisphere than in summer hemisphere.

Ceramic joints

DOEpatents

Miller, Bradley J.; Patten, Jr., Donald O.

1991-01-01

Butt joints between materials having different coefficients of thermal expansion are prepared having a reduced probability of failure of stress facture. This is accomplished by narrowing/tapering the material having the lower coefficient of thermal expansion in a direction away from the joint interface and not joining the narrow-tapered surface to the material having the higher coefficient of thermal expansion.

Seal assembly for materials with different coefficients of thermal expansion

DOEpatents

Minford, Eric [Laurys Station, PA

2009-09-01

Seal assembly comprising (a) two or more seal elements, each element having having a coefficient of thermal expansion; and (b) a clamping element having a first segment, a second segment, and a connecting segment between and attached to the first and second segments, wherein the two or more seal elements are disposed between the first and second segments of the clamping element. The connecting segment has a central portion extending between the first segment of the clamping element and the second segment of the clamping element, and the connecting segment is made of a material having a coefficient of thermal expansion. The coefficient of thermal expansion of the material of the connecting segment is intermediate the largest and smallest of the coefficients of thermal expansion of the materials of the two or more seal elements.

Thermal Expansion of Ferromagnetic Superconductors:. Possible Application to UGe2

NASA Astrophysics Data System (ADS)

Hatayama, Nobukuni; Konno, Rikio

2011-03-01

We investigate the temperature dependence of thermal expansion of the ferromagnetic triplet superconductors and their thermal expansion coefficients below the superconducting transition temperature of a majority spin conduction band. The free energy of the ferromagnetic superconductors derived by Linder et al. is used. The superconducting gaps in the A2 phase of 3He and with a node in UGe2 are considered. By applying Takahashi's method to the free energy, i.e. by taking into account the volume dependence of the free energy explicitly, the temperature dependence of the thermal expansion and the thermal expansion coefficients is studied below the superconducting transition temperature of the majority spin conduction band. We find that we have anomalies of the thermal expansion in the vicinity of the superconducting transition temperatures and that we have divergence of the thermal expansion coefficients are divergent at the superconducting transition temperatures. The Grüneisen's relation between the temperature dependence of the thermal expansion coefficients and the temperature dependence of the specific heat at low temperatures is satisfied.

Thermal Expansion of Ferromagnetic Superconductors:. Possible Application to UGe2

NASA Astrophysics Data System (ADS)

Hatayama, Nobukuni; Konno, Rikio

We investigate the temperature dependence of thermal expansion of the ferromagnetic triplet superconductors and their thermal expansion coefficients below the superconducting transition temperature of a majority spin conduction band. The free energy of the ferromagnetic superconductors derived by Linder et al. is used. The superconducting gaps in the A2 phase of 3He and with a node in UGe2 are considered. By applying Takahashi's method to the free energy, i.e. by taking into account the volume dependence of the free energy explicitly, the temperature dependence of the thermal expansion and the thermal expansion coefficients is studied below the superconducting transition temperature of the majority spin conduction band. We find that we have anomalies of the thermal expansion in the vicinity of the superconducting transition temperatures and that we have divergence of the thermal expansion coefficients are divergent at the superconducting transition temperatures. The Grüneisen's relation between the temperature dependence of the thermal expansion coefficients and the temperature dependence of the specific heat at low temperatures is satisfied.

Ionospheric Correction Based on Ingestion of Global Ionospheric Maps into the NeQuick 2 Model

PubMed Central

Yu, Xiao; She, Chengli; Zhen, Weimin; Bruno, Nava; Liu, Dun; Yue, Xinan; Ou, Ming; Xu, Jisheng

2015-01-01

The global ionospheric maps (GIMs), generated by Jet Propulsion Laboratory (JPL) and Center for Orbit Determination in Europe (CODE) during a period over 13 years, have been adopted as the primary source of data to provide global ionospheric correction for possible single frequency positioning applications. The investigation aims to assess the performance of new NeQuick model, NeQuick 2, in predicting global total electron content (TEC) through ingesting the GIMs data from the previous day(s). The results show good performance of the GIMs-driven-NeQuick model with average 86% of vertical TEC error less than 10 TECU, when the global daily effective ionization indices (Az) versus modified dip latitude (MODIP) are constructed as a second order polynomial. The performance of GIMs-driven-NeQuick model presents variability with solar activity and behaves better during low solar activity years. The accuracy of TEC prediction can be improved further through performing a four-coefficient function expression of Az versus MODIP. As more measurements from earlier days are involved in the Az optimization procedure, the accuracy may decrease. The results also reveal that more efforts are needed to improve the NeQuick 2 model capabilities to represent the ionosphere in the equatorial and high-latitude regions. PMID:25815369

Lattice-structures and constructs with designed thermal expansion coefficients

DOEpatents

Spadaccini, Christopher; Hopkins, Jonathan

2014-10-28

A thermal expansion-managed lattice structure having a plurality of unit cells each having flexure bearing-mounted tabs supported on a base and actuated by thermal expansion of an actuator having a thermal expansion coefficient greater than the base and arranged so that the tab is inwardly displaced into a base cavity. The flexure bearing-mounted tabs are connected to other flexure-bearing-mounted tabs of adjacent unit cells so that the adjacent unit cells are spaced from each other to accommodate thermal expansion of individual unit cells while maintaining a desired bulk thermal expansion coefficient of the lattice structure as a whole.

Transparent athermal glass-ceramics in Li2O-Al2O3-SiO2 system

NASA Astrophysics Data System (ADS)

Himei, Yusuke; Nagakane, Tomohiro; Sakamoto, Akihiko; Kitamura, Naoyuki; Fukumi, Kohei; Nishii, Junji; Hirao, Kazuyuki

2005-04-01

An attempt has been conducted to develop multicomponent transparent glass-ceramics which have athermal property better than silica glass. Transparent Li2O-Al2O3-SiO2 (LAS) glass-ceramics with small thermal expansion coefficient was chosen as a candidate. Athermal property of the glass-ceramics was improved by the independent control of temperature coefficients of electronic polarizability and thermal expansion coefficient, both of which govern the temperature coefficient of optical path length. It was found that temperature coefficient of electronic polarizability and thermal expansion coefficient of the LAS glass-ceramics were controllable by the additives and crystallization conditions. The doping of B2O3 and the crystallization under a hydrostatic pressure of 196 MPa were very effective to reduce temperature coefficient of electronic polarizability without a remarkable increase in thermal expansion coefficient. It was deduced that the reduction in temperature coefficient of electronic polarizability by the crystallization under 196 MPa resulted from the inhibition of the precipitation of beta-spodumene solid solution. The relative temperature coefficients of optical path length of B2O3-doped glass-ceramic crystallized under 196 MPa was 11.7 x 10-6/°C, which was slightly larger than that of silica glass. Nevertheless, the thermal expansion coefficient of this glass-ceramic was smaller than that of silica glass.

Bus electrode having same thermal expansion coefficient as crystalline silicon solar cell

NASA Astrophysics Data System (ADS)

Kato, T.; Morita, H.; Nakano, H.; Washida, H.; Onoe, A.; Inomata, K.; Mori, F.; Sugai, S.

1982-01-01

It is well known that the bus electrode plays a main role in series resistance of solar cells. Bus electrodes composed of bare leads, were investigated for which thermal expansion coefficients are less than those of the cell and which are coated with highly conducting metals. These leads exhibited the lower expansion coefficient than expected by empirical law, and the origins of these phenomena were explained. Work hardening effect on the expansion coefficient was then measured. Solar cell fabrication with these leads and rigid solders rationalized assembly processing. Cell characteristics proved to be excellent compared with conventional ones. Finally, lead costs were compared for various materials.

Identification of embryonic precursor cells that differentiate into thymic epithelial cells expressing autoimmune regulator

PubMed Central

Takizawa, Nobukazu; Miyauchi, Maki; Yanai, Hiromi; Tateishi, Ryosuke; Shinzawa, Miho; Yoshinaga, Riko; Kurihara, Masaaki; Yasuda, Hisataka; Sakamoto, Reiko; Yoshida, Nobuaki

2016-01-01

Medullary thymic epithelial cells (mTECs) expressing autoimmune regulator (Aire) are critical for preventing the onset of autoimmunity. However, the differentiation program of Aire-expressing mTECs (Aire+ mTECs) is unclear. Here, we describe novel embryonic precursors of Aire+ mTECs. We found the candidate precursors of Aire+ mTECs (pMECs) by monitoring the expression of receptor activator of nuclear factor-κB (RANK), which is required for Aire+ mTEC differentiation. pMECs unexpectedly expressed cortical TEC molecules in addition to the mTEC markers UEA-1 ligand and RANK and differentiated into mTECs in reaggregation thymic organ culture. Introduction of pMECs in the embryonic thymus permitted long-term maintenance of Aire+ mTECs and efficiently suppressed the onset of autoimmunity induced by Aire+ mTEC deficiency. Mechanistically, pMECs differentiated into Aire+ mTECs by tumor necrosis factor receptor-associated factor 6-dependent RANK signaling. Moreover, nonclassical nuclear factor-κB activation triggered by RANK and lymphotoxin-β receptor signaling promoted pMEC induction from progenitors exhibiting lower RANK expression and higher CD24 expression. Thus, our findings identified two novel stages in the differentiation program of Aire+ mTECs. PMID:27401343

On the coefficients of integrated expansions of Bessel polynomials

NASA Astrophysics Data System (ADS)

Doha, E. H.; Ahmed, H. M.

2006-03-01

A new formula expressing explicitly the integrals of Bessel polynomials of any degree and for any order in terms of the Bessel polynomials themselves is proved. Another new explicit formula relating the Bessel coefficients of an expansion for infinitely differentiable function that has been integrated an arbitrary number of times in terms of the coefficients of the original expansion of the function is also established. An application of these formulae for solving ordinary differential equations with varying coefficients is discussed.

Measurements of LGS, LGN, and LGT thermal coefficients of expansion and density.

PubMed

Malocha, Donald C; François-Saint-Cyr, Hugues; Richardson, Kathleen; Helmbold, Robert

2002-03-01

This paper will report on the measurements of the thermal coefficients of expansion and density of langasite (LGS), langanite (LGN), and langatate (LGT). The data were obtained by fabricating cubes with X, Y, and Z faces with nominal dimensions of 1 cm on a side for each material under test. The techniques used for measurement of density and thermal coefficients of expansion (TCE) of the materials are discussed. The data sets obtained and the extracted coefficients are presented.

Total electron content (TEC) variability at Los Alamos, New Mexico: A comparative study: FORTE-derived TEC analysis

NASA Astrophysics Data System (ADS)

Huang, Zhen; Roussel-Dupré, Robert

2005-12-01

Data collected from Fast On-Orbit Recording of Transient Events (FORTE) satellite-received Los Alamos Portable Pulser (LAPP) signals during 1997-2002 are used to derive the total electron content (TEC) at Los Alamos, New Mexico. The LAPP-derived TECs at Los Alamos are analyzed for diurnal, seasonal, interannual, and 27-day solar cycle variations. Several aspects in deriving TEC are analyzed, including slant to vertical TEC conversion, quartic effects on transionosperic signals, and geomagnetic storm effects on the TEC variance superimposed on the averaged TEC values.

Efficient algorithms for construction of recurrence relations for the expansion and connection coefficients in series of Al-Salam Carlitz I polynomials

NASA Astrophysics Data System (ADS)

Doha, E. H.; Ahmed, H. M.

2005-12-01

Two formulae expressing explicitly the derivatives and moments of Al-Salam-Carlitz I polynomials of any degree and for any order in terms of Al-Salam-Carlitz I themselves are proved. Two other formulae for the expansion coefficients of general-order derivatives Dpqf(x), and for the moments xellDpqf(x), of an arbitrary function f(x) in terms of its original expansion coefficients are also obtained. Application of these formulae for solving q-difference equations with varying coefficients, by reducing them to recurrence relations in the expansion coefficients of the solution, is explained. An algebraic symbolic approach (using Mathematica) in order to build and solve recursively for the connection coefficients between Al-Salam-Carlitz I polynomials and any system of basic hypergeometric orthogonal polynomials, belonging to the q-Hahn class, is described.

Electrochemical characterization of B-site cation-excess Pr 2Ni 0.75Cu 0.25Ga 0.05O 4+δ cathode for IT-SOFCs

DOE PAGES

Meng, Xiangwei; Lü, Shiquan; Liu, Shouxiu; ...

2015-06-15

In this paper, the B-site cation-excess K 2NiF 4-type structure oxide, Pr 2Ni 0.75Cu 0.25Ga 0.05O 4+δ (PNCG) is investigated as a cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). XRD result shows that PNCG cathode is chemically compatible with the electrolyte Gd 0.1Ce 0.9O 2-δ (GDC) at 900 °C for 5 h. The PNCG material exhibits a semiconductor to metal transition around 425 °C. The thermal expansion coefficient (TEC) of the PNCG sample is 12.72×10 -6 K -1 between 30 and 850 °C in air. The polarization resistance (R p) of PNCG cathode on GDC electrolyte is 0.105, 0.197more » and 0.300 Ω cm 2 at 800, 750, 700 °C, respectively. A maximum power density of 371 mW cm -2 is obtained at 800 °C for single-cell with 300 μm thick GDC electrolyte and PNCG cathode. Finally, the results of this study demonstrate that PNCG can be a promising cathode material for IT-SOFCs.« less

The coefficient of bond thermal expansion measured by extended x-ray absorption fine structure.

PubMed

Fornasini, P; Grisenti, R

2014-10-28

The bond thermal expansion is in principle different from the lattice expansion and can be measured by correlation sensitive probes such as extended x-ray absorption fine structure (EXAFS) and diffuse scattering. The temperature dependence of the coefficient α(bond)(T) of bond thermal expansion has been obtained from EXAFS for CdTe and for Cu. A coefficient α(tens)(T) of negative expansion due to tension effects has been calculated from the comparison of bond and lattice expansions. Negative lattice expansion is present in temperature intervals where α(bond) prevails over α(tens); this real-space approach is complementary but not equivalent to the Grüneisen theory. The relevance of taking into account the asymmetry of the nearest-neighbours distribution of distances in order to get reliable bond expansion values and the physical meaning of the third cumulant are thoroughly discussed.

Progressive Failure Analysis of Advanced Composites

DTIC Science & Technology

2008-07-25

Fracture angle. αii Coefficients of thermal expansion . βii Coefficients of hygroscopic expansion . β Shear response factor. ηL Coefficient of... thermal expansion in the longitudinal and transverse direc- tions. To enable the calculation of the thermal stresses, the user should define in the...development of this second VUMAT subroutine was planned for the second year of this project). 4.2 Input into Abaqus explicit 4.2.1 Shell elements

The relationship between bond ionicity, lattice energy, coefficient of thermal expansion and microwave dielectric properties of Nd(Nb(1-x)Sb(x))O4 ceramics.

PubMed

Zhang, Ping; Zhao, Yonggui; Wang, Xiuyu

2015-06-28

The crystalline structure refinement, chemical bond ionicity, lattice energy and coefficient of thermal expansion were carried out for Nd(Nb(1-x)Sb(x))O4 ceramics with a monoclinic fergusonite structure to investigate the correlations between the crystalline structure, phase stability, bond ionicity, lattice energy, coefficient of thermal expansion, and microwave dielectric properties. The bond ionicity, lattice energy, and coefficient of thermal expansion of Nd(Nb(1-x)Sb(x))O4 ceramics were calculated using a semiempirical method based on the complex bond theory. The phase structure stability varied with the lattice energy which was resulted by the substitution constant of Sb(5+). With the increasing of the Sb(5+) contents, the decrease of Nb/Sb-O bond ionicity was observed, which could be contributed to the electric polarization. The ε(r) had a close relationship with the Nb/Sb-O bond ionicity. The increase of the Q×f and |τ(f)| values could be attributed to the lattice energy and the coefficient of thermal expansion. The microwave dielectric properties of Nd(Nb(1-x)Sb(x))O4 ceramics with the monoclinic fergusonite structure were strongly dependent on the chemical bond ionicity, lattice energy and coefficient of thermal expansion.

Short Term Single Station GNSS TEC Prediction Using Radial Basis Function Neural Network

NASA Astrophysics Data System (ADS)

Muslim, Buldan; Husin, Asnawi; Efendy, Joni

2018-04-01

TEC prediction models for 24 hours ahead have been developed from JOG2 GPS TEC data during 2016. Eleven month of TEC data were used as a training model of the radial basis function neural network (RBFNN) and 1 month of last data (December 2016) is used for the RBFNN model testing. The RBFNN inputs are the previous 24 hour TEC data and the minimum of Dst index during the previous 24 hours. Outputs of the model are 24 ahead TEC prediction. Comparison of model prediction show that the RBFNN model is able to predict the next 24 hours TEC is more accurate than the TEC GIM model.

The Response of Mid-Latitude Ionospheric TEC to Geomagnetic Storms and Solar Flares

NASA Astrophysics Data System (ADS)

Huang, Z.; Roussel-Dupre, R.

2004-12-01

The effects of geomagnetic storms and solar flares on the ionosphere are manifested as large magnitude sudden fluctuations in the Total Electron Content (TEC). In this study, the broadband VHF signal (30-100MHz) data from the Los Alamos Portable Pulser (LAPP) received by the FORTE (Fast Onboard Recording of Transient Events) satellite during the period of 1997-2002 are used to investigate the mean TEC variation response to geomagnetic storm. A total of 14 geomagnetic storms are selected where FORTE-LAPP data are available to derive average TECs during extended storm-time and non-storm time for a given storm. The variations in the ionospheric TECs at Los Alamos, New Mexico are investigated for the 14 selected geomagnetic storms. In most cases (12 out of 14), we see overall enhancements in TEC as a result of geomagnetic storm impact at Los Alamos. The relative enhancements in TEC at Los Alamos due to a geomagnetic storm can reach as high as 3-fold of the normal TEC values. The overall absolute enhancements in TEC at Los Alamos are up to about 30 TECU. The magnitude of TEC enhancements is diversified over all storm categories without a clean-cut relationship between the storm intensity and the TEC enhancement. The mean TEC variation response to geomagnetic storm can be complicated when several consecutive storms occurred in a row and a net TEC reduction may be seen. Data of continuous GPS TEC measurements are collected at a 1-minute time resolution during July 2004 when 5 X-class solar flares occurred from two Allen Osborne Associates ICS-4000Z GPS receivers mounted at the Physics Building at Los Alamos National Laboratory. In detecting effects of solar flares on the ionospheric TEC, we apply appropriate filtering to remove the linear trend of TEC and a coherent processing of TEC variations simultaneously for all the visible GPS satellites in a given time interval. The responses of ionospheric TEC at minute time scale to these powerful impulsive solar flares are investigated. The onset time of the ionospheric response and the magnitude of the TEC fluctuations and its time derivative are examined along with their relationships with the solar flux characteristics, duration of the flare and location of the flare on the Sun, X-ray emission variations during the flares, and local time of the flare occurrence.

Exact Solutions of Atmospheric (2+1)-Dimensional Nonlinear Incompressible Non-hydrostatic Boussinesq Equations

NASA Astrophysics Data System (ADS)

Liu, Ping; Wang, Ya-Xiong; Ren, Bo; Li, Jin-Hua

2016-12-01

Exact solutions of the atmospheric (2+1)-dimensional nonlinear incompressible non-hydrostatic Boussinesq (INHB) equations are researched by Combining function expansion and symmetry method. By function expansion, several expansion coefficient equations are derived. Symmetries and similarity solutions are researched in order to obtain exact solutions of the INHB equations. Three types of symmetry reduction equations and similarity solutions for the expansion coefficient equations are proposed. Non-traveling wave solutions for the INHB equations are obtained by symmetries of the expansion coefficient equations. Making traveling wave transformations on expansion coefficient equations, we demonstrate some traveling wave solutions of the INHB equations. The evolutions on the wind velocities, temperature perturbation and pressure perturbation are demonstrated by figures, which demonstrate the periodic evolutions with time and space. Supported by the National Natural Science Foundation of China under Grant Nos. 11305031 and 11305106, and Training Programme Foundation for Outstanding Young Teachers in Higher Education Institutions of Guangdong Province under Grant No. Yq2013205

Micro-Structured Two-Component 3D Metamaterials with Negative Thermal-Expansion Coefficient from Positive Constituents

PubMed Central

Qu, Jingyuan; Kadic, Muamer; Naber, Andreas; Wegener, Martin

2017-01-01

Controlling the thermal expansion of materials is of great technological importance. Uncontrolled thermal expansion can lead to failure or irreversible destruction of structures and devices. In ordinary crystals, thermal expansion is governed by the asymmetry of the microscopic binding potential, which cannot be adjusted easily. In artificial crystals called metamaterials, thermal expansion can be controlled by structure. Here, following previous theoretical work, we fabricate three-dimensional (3D) two-component polymer micro-lattices by using gray-tone laser lithography. We perform cross-correlation analysis of optical microscopy images taken at different sample temperatures. The derived displacement-vector field reveals that the thermal expansion and resulting bending of the bi-material beams leads to a rotation of the 3D chiral crosses arranged onto a 3D checkerboard pattern within one metamaterial unit cell. These rotations can compensate the expansion of the all positive constituents, leading to an effectively near-zero thermal length-expansion coefficient, or over-compensate the expansion, leading to an effectively negative thermal length-expansion coefficient. This evidences a striking level of thermal-expansion control. PMID:28079161

On the coefficients of differentiated expansions of ultraspherical polynomials

NASA Technical Reports Server (NTRS)

Karageorghis, Andreas; Phillips, Timothy N.

1989-01-01

A formula expressing the coefficients of an expression of ultraspherical polynomials which has been differentiated an arbitrary number of times in terms of the coefficients of the original expansion is proved. The particular examples of Chebyshev and Legendre polynomials are considered.

The proangiogenic phenotype of tumor-derived endothelial cells is reverted by the overexpression of platelet-activating factor acetylhydrolase.

PubMed

Doublier, Sophie; Ceretto, Monica; Lupia, Enrico; Bravo, Stefania; Bussolati, Benedetta; Camussi, Giovanni

2007-10-01

We previously reported that human tumor-derived endothelial cells (TEC) have an angiogenic phenotype related to the autocrine production of several angiogenic factors. The purpose of the present study was to evaluate whether an enhanced synthesis of platelet-activating factor (PAF) might contribute to the proangiogenic characteristics of TEC and whether its inactivation might inhibit angiogenesis. To address the potential role of PAF in the proangiogenic characteristics of TEC, we engineered TEC to stably overexpress human plasma PAF-acetylhydrolase (PAF-AH), the major PAF-inactivating enzyme, and we evaluated in vitro and in vivo angiogenesis. TECs were able to synthesize a significantly enhanced amount of PAF compared with normal human microvascular endothelial cells when stimulated with thrombin, vascular endothelial growth factor, or soluble CD154. Transfection of TEC with PAF-AH (TEC-PAF-AH) significantly inhibited apoptosis resistance and spontaneous motility of TEC. In addition, PAF and vascular endothelial growth factor stimulation enhanced the motility and adhesion of TEC but not of TEC-PAF-AH. In vitro, TEC-PAF-AH lost the characteristic ability of TEC to form vessel-like structures when plated on Matrigel. Finally, when cells were injected s.c. within Matrigel in severe combined immunodeficiency mice or coimplanted with a renal carcinoma cell line, the overexpression of PAF-AH induced a significant reduction of functional vessel formation. These results suggest that inactivation of PAF, produced by TEC, by the overexpression of plasma PAF-AH affects survival, migration, and the angiogenic response of TEC both in vitro and in vivo.

On the coefficients of integrated expansions and integrals of ultraspherical polynomials and their applications for solving differential equations

NASA Astrophysics Data System (ADS)

Doha, E. H.

2002-02-01

An analytical formula expressing the ultraspherical coefficients of an expansion for an infinitely differentiable function that has been integrated an arbitrary number of times in terms of the coefficients of the original expansion of the function is stated in a more compact form and proved in a simpler way than the formula suggested by Phillips and Karageorghis (27 (1990) 823). A new formula expressing explicitly the integrals of ultraspherical polynomials of any degree that has been integrated an arbitrary number of times of ultraspherical polynomials is given. The tensor product of ultraspherical polynomials is used to approximate a function of more than one variable. Formulae expressing the coefficients of differentiated expansions of double and triple ultraspherical polynomials in terms of the original expansion are stated and proved. Some applications of how to use ultraspherical polynomials for solving ordinary and partial differential equations are described.

Targeted deletion of c-Met in thymic epithelial cells leads to an autoimmune phenotype

PubMed Central

Su, Min; Hu, Rong; Song, Yinhong; Liu, Yalan; Lai, Laijun

2017-01-01

Hepatocyte growth factor (HGF) and its receptor c-Met signaling have been implicated in regulating various types of cells including epithelial cells. We have previously reported that c-Met is expressed by thymic epithelial cells (TECs), and that in vivo administration of hybrid cytokines containing IL-7 and the beta- or alpha-chain of HGF significantly increase the number of TECs. In order to study the role of c-Met signaling in TECs, we generated conditional knockout (cKO) mice in which c-Met was specifically deleted in TECs using a Foxn1-Cre transgene. We show here that c-Met deficiency in TECs results in age-progressive reduction in TEC number and reduced number of regulatory T cells. Consequently, c-Met TEC cKO mice displayed an autoimmune phenotype. Thus, c-Met signaling in TECs is important for the maintenance of TECs and immune self-tolerance. PMID:29363160

High-resolution station-based diurnal ionospheric total electron content (TEC) from dual-frequency GPS observations

NASA Astrophysics Data System (ADS)

ćepni, Murat S.; Potts, Laramie V.; Miima, John B.

2013-09-01

electron content (TEC) estimates derived from Global Navigation Satellite System (GNSS) signal delays provide a rich source of information about the Earth's ionosphere. Networks of Global Positioning System (GPS) receivers data can be used to represent the ionosphere by a Global Ionospheric Map (GIM). Data input for GIMs is dual-frequency GNSS-only or a mixture of GNSS and altimetry observations. Parameterization of GNSS-only GIMs approaches the ionosphere as a single-layer model (SLM) to determine GPS TEC models over a region. Limitations in GNSS-only GIM TEC are due largely to the nonhomogenous global distribution of GPS tracking stations with large data gaps over the oceans. The utility of slant GPS ionospheric-induced path delays for high temporal resolution from a single-station data rate offers better representation of TEC over a small region. A station-based vertical TEC (TECV) approach modifies the traditional single-layer model (SLM) GPS TEC method by introducing a zenith angle weighting (ZAW) filter to capture signal delays from mostly near-zenith satellite passes. Comparison with GIMs shows the station-dependent TEC (SD-TEC) model exhibits robust performance under variable space weather conditions. The SD-TEC model was applied to investigate ionospheric TEC variability during the geomagnetic storm event of 9 March 2012 at midlatitude station NJJJ located in New Jersey, USA. The high temporal resolution TEC results suggest TEC production and loss rate differences before, during, and after the storm.

Pressurized electrolysis stack with thermal expansion capability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bourgeois, Richard Scott

The present techniques provide systems and methods for mounting an electrolyzer stack in an outer shell so as to allow for differential thermal expansion of the electrolyzer stack and shell. Generally, an electrolyzer stack may be formed from a material with a high coefficient of thermal expansion, while the shell may be formed from a material having a lower coefficient of thermal expansion. The differences between the coefficients of thermal expansion may lead to damage to the electrolyzer stack as the shell may restrain the thermal expansion of the electrolyzer stack. To allow for the differences in thermal expansion, themore » electrolyzer stack may be mounted within the shell leaving a space between the electrolyzer stack and shell. The space between the electrolyzer stack and the shell may be filled with a non-conductive fluid to further equalize pressure inside and outside of the electrolyzer stack.« less

Comparison of GPS-derived TEC with IRI-2012 and IRI-2007 TEC predictions at Surat, a location around the EIA crest in the Indian sector, during the ascending phase of solar cycle 24

NASA Astrophysics Data System (ADS)

Patel, N. C.; Karia, S. P.; Pathak, K. N.

2017-07-01

This paper presents a comparison of GPS-derived TEC with IRI-2012 and IRI-2007 TEC Predictions at Surat (21.16°N Geographic latitude, 72.78°E Geographic longitude, 12.90°N Geomagnetic latitude) a location around the Equatorial Ionisation Anomaly (EIA) crest in the Indian sector, during the Ascending Phase of Solar Cycle 24, for a period of three years (January 2010-December 2012). In this comparison, plasmaspheric electron content (PEC) contribution to the GPS-TEC has been removed. It is observed that percentage PEC contribution to the GPS-TEC varies from about ∼15% (at the noon local time) to about ∼30% (at the morning local time). From the monthly comparison of GPS-TEC with IRI-TEC, it is observed that, TEC predicted by both the models overestimates in June-2012 and underestimates TEC in November-2011, December-2011 and March-2011. For all other months IRI estimates the TEC well. From the seasonal comparison, it is observed that the peak time appears ∼1-h later than the actual peak time in Winter 2010, Summer 2011, and Equinox 2010 and 2012 (the result suggest that it may be due to discrepancies/disagreement of both the versions of the IRI model in estimating the peak density as well as the thickness and shape parameters of the electron density profiles). For the Summer season, the IRI-TEC estimates the TEC well for all the years. Further, the seasonal variation of the GPS-TEC for all the three years matches well with IRI-2012 model compared to IRI-2007 model. Also, the mean annual TEC is predicted well by both the versions of the IRI model.

Radiation detector system having heat pipe based cooling

DOEpatents

Iwanczyk, Jan S.; Saveliev, Valeri D.; Barkan, Shaul

2006-10-31

A radiation detector system having a heat pipe based cooling. The radiation detector system includes a radiation detector thermally coupled to a thermo electric cooler (TEC). The TEC cools down the radiation detector, whereby heat is generated by the TEC. A heat removal device dissipates the heat generated by the TEC to surrounding environment. A heat pipe has a first end thermally coupled to the TEC to receive the heat generated by the TEC, and a second end thermally coupled to the heat removal device. The heat pipe transfers the heat generated by the TEC from the first end to the second end to be removed by the heat removal device.

Autofrettage to Counteract Coefficient of Thermal Expansion Mismatch in Cryogenic Pressurized Pipes with Metallic Liners

NASA Technical Reports Server (NTRS)

Wen, Ed; Barbero, Ever; Tygielski, Phlip; Turner, James E. (Technical Monitor)

2001-01-01

Composite feedlines with metal liners have the potential to reduce weight/cost while providing the same level of permeation resistance and material compatibility of all-metal feedlines carrying cryogenic propellants in spacecraft. The major technical challenges are the large difference in Coefficient of Thermal Expansion between the liner and the composite, and the manufacturing method required to make a very thin liner with the required strength and dimensional tolerance. This study investigates the use of autofrettage (compressive preload) to counteract Coefficient of Thermal Expansion when pre-pressurization procedures cannot be used to solve this problem. Promising materials (aluminum 2219, Inconel 718, nickel, nickel alloy) and manufacturing techniques (chemical milling, electroplating) are evaluated to determine the best liner candidates. Robust, autofrettaged feedlines with a low Coefficient of Thermal Expansion liner (Inconel 718 or nickel alloy) are shown to successfully counteract mismatch at LOX temperature. A new concept, autofrettage by temperature, is introduced for high Coefficient of Thermal Expansion materials (aluminum and pure nickel) where pressure cannot be used to add compressive preload.

CEDAR-GEM Challenge for Systematic Assessment of Ionosphere/Thermosphere Models in Predicting TEC During the 2006 December Storm Event

NASA Astrophysics Data System (ADS)

Shim, J. S.; Rastätter, L.; Kuznetsova, M.; Bilitza, D.; Codrescu, M.; Coster, A. J.; Emery, B. A.; Fedrizzi, M.; Förster, M.; Fuller-Rowell, T. J.; Gardner, L. C.; Goncharenko, L.; Huba, J.; McDonald, S. E.; Mannucci, A. J.; Namgaladze, A. A.; Pi, X.; Prokhorov, B. E.; Ridley, A. J.; Scherliess, L.; Schunk, R. W.; Sojka, J. J.; Zhu, L.

2017-10-01

In order to assess current modeling capability of reproducing storm impacts on total electron content (TEC), we considered quantities such as TEC, TEC changes compared to quiet time values, and the maximum value of the TEC and TEC changes during a storm. We compared the quantities obtained from ionospheric models against ground-based GPS TEC measurements during the 2006 AGU storm event (14-15 December 2006) in the selected eight longitude sectors. We used 15 simulations obtained from eight ionospheric models, including empirical, physics-based, coupled ionosphere-thermosphere, and data assimilation models. To quantitatively evaluate performance of the models in TEC prediction during the storm, we calculated skill scores such as RMS error, Normalized RMS error (NRMSE), ratio of the modeled to observed maximum increase (Yield), and the difference between the modeled peak time and observed peak time. Furthermore, to investigate latitudinal dependence of the performance of the models, the skill scores were calculated for five latitude regions. Our study shows that RMSE of TEC and TEC changes of the model simulations range from about 3 TECU (total electron content unit, 1 TECU = 1016 el m-2) (in high latitudes) to about 13 TECU (in low latitudes), which is larger than latitudinal average GPS TEC error of about 2 TECU. Most model simulations predict TEC better than TEC changes in terms of NRMSE and the difference in peak time, while the opposite holds true in terms of Yield. Model performance strongly depends on the quantities considered, the type of metrics used, and the latitude considered.

Temporal-Spatial Variation of Global GPS-Derived Total Electron Content, 1999–2013

PubMed Central

Guo, Jinyun; Li, Wang; Liu, Xin; Kong, Qiaoli; Zhao, Chunmei; Guo, Bin

2015-01-01

To investigate the temporal-spatial distribution and evolutions of global Total Electron Content (TEC), we estimate the global TEC data from 1999 to 2013 by processing the GPS data collected by the International Global Navigation Satellite System (GNSS) Service (IGS) stations, and robustly constructed the TEC time series at each of the global 5°×2.5° grids. We found that the spatial distribution of the global TEC has a pattern where the number of TECs diminishes gradually from a low-latitude region to high-latitude region, and anomalies appear in the equatorial crest and Greenland. Temporal variations show that the peak TEC appears in equinoctial months, and this corresponds to the semiannual variation of TEC. Furthermore, the winter anomaly is also observed in the equatorial area of the northern hemisphere and high latitudes of the southern hemisphere. Morlet wavelet analysis is used to determine periods of TEC variations and results indicate that the 1-day, 26.5-day, semi-annual and annual cycles are the major significant periods. The fitting results of a quadratic polynomial show that the effect of solar activity on TEC is stronger in low latitudes than in mid-high latitudes, and stronger in the southern hemisphere than in the northern hemisphere. But the effect in low latitudes in the northern hemisphere is stronger than that in low latitudes in the southern hemisphere. The effect of solar activity on TECs was analyzed with the cross wavelet analysis and the wavelet coherence transformation, and we found that there appears to be a strong coherence in the period of about 27 days. So the sunspot as one index of solar activity seriously affects the TEC variations with the sun’s rotation. We fit the TEC data with the least squares spectral analysis to study the periodic variations of TEC. The changing trend of TEC is generally -0.08 TECu per year from 1999 to 2013. So TECs decrease over most areas year by year, but TECs over the Arctic around Greenland maintained a rising trend during these 15 years. PMID:26193101

Thermal expansion coefficients of obliquely deposited MgF2 thin films and their intrinsic stress.

PubMed

Jaing, Cheng-Chung

2011-03-20

This study elucidates the effects of columnar angles and deposition angles on the thermal expansion coefficients and intrinsic stress behaviors of MgF2 films with columnar microstructures. The behaviors associated with temperature-dependent stresses in the MgF2 films are measured using a phase-shifting Twyman-Green interferometer with a heating stage and the application of a phase reduction algorithm. The thermal expansion coefficients of MgF2 films at various columnar angles were larger than those of glass substrates. The intrinsic stress in the MgF2 films with columnar microstructures was compressive, while the thermal stress was tensile. The thermal expansion coefficients of MgF2 films with columnar microstructures and their intrinsic stress evidently depended on the deposition angle and the columnar angle.

Total electron content anomalies associated with global VEI4 + volcanic eruptions during 2002-2015

NASA Astrophysics Data System (ADS)

Li, Wang; Guo, Jinyun; Yue, Jianping; Shen, Yi; Yang, Yang

2016-10-01

In previous studies, little attention has been paid to the total electron content (TEC) anomalies preceding the volcanic eruption. We analyze the coupling relationship between volcanic eruption and TEC anomalies, and discuss the spatial distribution of TEC anomalies associated with volcanic geographical location. We utilize the global ionosphere map (GIM) data from the Center for Orbit Determination in Europe (CODE) to analyze TEC variations before the global volcanic eruptions indicated by VEI (Volcanic Explosivity Index) 4 + from 2002 to 2015 with the sliding interquartile range method. The results indicate the occurrence rate of TEC anomalies before great volcanic eruptions is related with the volcanic type and geographical position. The occurrence rate of TEC anomalies before stratovolcano and caldera eruptions is higher than that before shield and pyroclastic shield eruptions, and the occurrence rate of TEC anomalies has a descending trend from low latitudes to high latitudes. The TEC anomalies before the volcanic eruptions in low-mid latitudes are within the volcanic affected areas, but do not coincide with the volcanic foci. The corresponding TEC anomalies could be observed in the conjugated region, and all the TEC anomalies in the volcanic affected areas are usually close to bounds of equatorial anomaly zones. However, the TEC anomalies preceding these eruptions in high latitudes usually surround the volcano, and no TEC anomalies appear in the conjugated region. These conclusions have potential applications to the prediction of great volcanic eruptions in the future.

Anamolous ionospheric TEC variations prior to the Indonesian earthquake (M 7.1) of November 15, 2014

NASA Astrophysics Data System (ADS)

Alcay, Salih

2017-05-01

This paper investigates preearthquake ionospheric variations with the use of TEC of Global Ionospheric Maps (GIMs) and regional maps based on Precise Point Positioning (PPP) during the 7.1-M Indonesian earthquake that occurred on November 15, 2014. TEC maps corresponding to 10 days before to 4 days after the event were examined. In addition, a time series of TEC values according to the PPP maps were also evaluated. In addition to GIMs, it was possible to detect TEC variations with PPP maps. The results showed that ionospheric TEC decreased strikingly 4 days prior to the earthquake. This TEC variation was highly likely related to seismic activity.

Distinct and Overlapping Functions of TEC Kinase and BTK in B Cell Receptor Signaling.

PubMed

de Bruijn, Marjolein J W; Rip, Jasper; van der Ploeg, Esmee K; van Greuningen, Lars W; Ta, Van T B; Kil, Laurens P; Langerak, Anton W; Rimmelzwaan, Guus F; Ellmeier, Wilfried; Hendriks, Rudi W; Corneth, Odilia B J

2017-04-15

The Tec tyrosine kinase is expressed in many cell types, including hematopoietic cells, and is a member of the Tec kinase family that also includes Btk. Although the role of Btk in B cells has been extensively studied, the role of Tec kinase in B cells remains largely unclear. It was previously shown that Tec kinase has the ability to partly compensate for loss of Btk activity in B cell differentiation, although the underlying mechanism is unknown. In this study, we confirm that Tec kinase is not essential for normal B cell development when Btk is present, but we also found that Tec-deficient mature B cells showed increased activation, proliferation, and survival upon BCR stimulation, even in the presence of Btk. Whereas Tec deficiency did not affect phosphorylation of phospholipase Cγ or Ca 2+ influx, it was associated with significantly increased activation of the intracellular Akt/S6 kinase signaling pathway upon BCR and CD40 stimulation. The increased S6 kinase phosphorylation in Tec-deficient B cells was dependent on Btk kinase activity, as ibrutinib treatment restored pS6 to wild-type levels, although Btk protein and phosphorylation levels were comparable to controls. In Tec-deficient mice in vivo, B cell responses to model Ags and humoral immunity upon influenza infection were enhanced. Moreover, aged mice lacking Tec kinase developed a mild autoimmune phenotype. Taken together, these data indicate that in mature B cells, Tec and Btk may compete for activation of the Akt signaling pathway, whereby the activating capacity of Btk is limited by the presence of Tec kinase. Copyright © 2017 by The American Association of Immunologists, Inc.

Observing Traveling Ionospheric Disturbances Caused by Tsunamis Using GPS TEC Measurements

NASA Technical Reports Server (NTRS)

Galvan, David A.; Komjathy, Attila; Hickey, Michael; Foster, James; Mannucci, Anthony J.

2010-01-01

Ground-based Global Positioning System (GPS) measurements of ionospheric Total Electron Content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events: the American Samoa earthquake of September 29, 2009, and the Chile earthquake of February 27, 2010. Fluctuations in TEC correlated in time, space, and wave properties with these tsunamis were observed in TEC estimates processed using JPL's Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove ionospheric TEC variations with wavelengths and periods outside the typical range of internal gravity waves caused by tsunamis. Observable variations in TEC appear correlated with the tsunamis in certain locations, but not in others. Where variations are observed, the typical amplitude tends to be on the order of 1% of the background TEC value. Variations with amplitudes 0.1 - 0.2 TECU are observable with periods and timing affiliated with the tsunami. These observations are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in good agreement in some locations, though there are cases when the model predicts an observable tsunami-driven signature and none is observed. These TEC variations are not always seen when a tsunami is present, but in these two events the regions where a strong ocean tsunami was observed did coincide with clear TEC observations, while a lack of clear TEC observations coincided with smaller tsunami amplitudes. There exists the potential to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for early warning systems.

Comparison of Ionospheric TEC Derived from GPS and IRI 2012 Model during Geomagnetic Storms at Indonesia

NASA Astrophysics Data System (ADS)

Marlia, Dessi; Wu, Falin

2016-07-01

This paper investigates the variations of vertical Total Electron Content (VTEC) at Manado, Indonesia (geographic coordinates : lat 1.34 ° S and long 124.82 ° E) for period 2013. The GPS measured TEC is compared with the TEC derived from the IRI (International Reference Ionosphere) 2012 model. Vertical TEC measurements obtained from dual frequency GPS receiver that is GISTM (GPS Ionospheric Scintillations and TEC monitor). Variation of TEC validate to IRI 2012 model at Manado station has been compared with the model for three different topside of electron density namely NeQuick, IRI-01-Corr and IRI2001.There is a need to investigation on diurnal, seasonal variations, solar activity dependence of TEC and including effects of space weather related events to TEC and modeling of TEC. In this paper, diurnal and seasonal variations of VTEC and the effect of VTEC due to space weather events like Geomagnetic storms are analyzed. The result show that the TEC prediction using IRI-2001 model overestimated the GPS TEC measurements, while IRI-NeQuick and IRI-01-corr show a tendency to underestimates the observed TEC during the day time particularly in low latitude region in the maximum solar activity period (2013). The variations of VTEC during 17th March, 2013, 29th June, 2013 storms are analyzed. During 17th March,2013 storm enhancement in VTEC with Kp value 6 and Disturbance storm index (DST) -132 nT. During 29th June, 2013 storm VTEC depletion with value 7 and DST -98 nT. Significant deviations in VTEC during the main phase of the storms are observed. It is found that the response of ionospheric TEC consist of effects of both enhancement and depletions in ionospheric structures (positive and negative storm). Keywords: TEC ionosphere, GPS, GISTM, IRI 2012 model, solar activity, geomagnetic storm

Regional TEC model under quiet geomagnetic conditions and low-to-moderate solar activity based on CODE GIMs

NASA Astrophysics Data System (ADS)

Feng, Jiandi; Jiang, Weiping; Wang, Zhengtao; Zhao, Zhenzhen; Nie, Linjuan

2017-08-01

Global empirical total electron content (TEC) models based on TEC maps effectively describe the average behavior of the ionosphere. However, the accuracy of these global models for a certain region may not be ideal. Due to the number and distribution of the International GNSS Service (IGS) stations, the accuracy of TEC maps is geographically different. The modeling database derived from the global TEC maps with different accuracy is likely one of the main reasons that limits the accuracy of the new models. Moreover, many anomalies in the ionosphere are geographic or geomagnetic dependent, and as such the accuracy of global models can deteriorate if these anomalies are not fully incorporated into the modeling approach. For regional models built in small areas, these influences on modeling are immensely weakened. Thus, the regional TEC models may better reflect the temporal and spatial variations of TEC. In our previous work (Feng et al., 2016), a regional TEC model TECM-NEC is proposed for northeast China. However, this model is only directed against the typical region of Mid-latitude Summer Nighttime Anomaly (MSNA) occurrence, which is meaningless in other regions without MSNA. Following the technique of TECM-NEC model, this study proposes another regional empirical TEC model for other regions in mid-latitudes. Taking a small area BeiJing-TianJin-Tangshan (JJT) region (37.5°-42.5° N, 115°-120° E) in China as an example, a regional empirical TEC model (TECM-JJT) is proposed using the TEC grid data from January 1, 1999 to June 30, 2015 provided by the Center for Orbit Determination in Europe (CODE) under quiet geomagnetic conditions. The TECM-JJT model fits the input CODE TEC data with a bias of 0.11TECU and a root mean square error of 3.26TECU. Result shows that the regional model TECM-JJT is consistent with CODE TEC data and GPS-TEC data.

Cooling Device for Combat Vehicle Crew Drinking Water. Phase 1.

DTIC Science & Technology

1988-03-21

stainless steel . A third concept, in which the water container is plastic and the vacuum space is replaced by plastic foam, was also considered. The glass...Btu/ftO/=F/hr Glass Thermos 0.0905 Stainless Steel Thermos 0.1724 Foam Insulated Thermos 0.527 16 5.2. Thermal Electric Cooler Evaluation The TEC is... stainless steel thermos, which has a heat transfer coefficient approximately twice that of the glass thermos, is preferred for the vehicular use because it

Controllable rectification of the axial expansion in the thermally driven artificial muscle

NASA Astrophysics Data System (ADS)

Yue, Donghua; Zhang, Xingyi; Yong, Huadong; Zhou, Jun; Zhou, You-He

2015-09-01

At present, the concept of artificial muscle twisted by polymers or fibers has become a hot issue in the field of intelligent material research according to its distinguishing advantages, e.g., high energy density, large-stroke, non-hysteresis, and inexpensive. The axial thermal expansion coefficient is an important parameter which can affect its demanding applications. In this letter, a device with high accuracy capacitive sensor is constructed to measure the axial thermal expansion coefficient of the twisted carbon fibers and yarns of Kevlar, and a theoretical model based on the thermal elasticity and the geometrical features of the twisted structure are also presented to predict the axial expansion coefficient. It is found that the calculated results take good agreements with the experimental data. According to the present experiment and analyses, a method to control the axial thermal expansion coefficient of artificial muscle is proposed. Moreover, the mechanism of this kind of thermally driven artificial muscle is discussed.

Dynamics of total electron content distribution during strong geomagnetic storms

NASA Astrophysics Data System (ADS)

Astafyeva, E. I.; Afraimovich, E. L.; Kosogorov, E. A.

We worked out a new method of mapping of total electron content TEC equal lines displacement velocity The method is based on the technique of global absolute vertical TEC value mapping Global Ionospheric Maps technique GIM GIM with 2-hours time resolution are available from Internet underline ftp cddisa gsfc nasa gov in standard IONEX-files format We determine the displacement velocity absolute value as well as its wave vector orientation from increments of TEC x y derivatives and TEC time derivative for each standard GIM cell 5 in longitude to 2 5 in latitude Thus we observe global traveling of TEC equal lines but we also can estimate the velocity of these line traveling Using the new method we observed anomalous rapid accumulation of the ionosphere plasma at some confined area due to the depletion of the ionization at the other spacious territories During the main phase of the geomagnetic storm on 29-30 October 2003 very large TEC enhancements appeared in the southwest of North America TEC value in that area reached up to 200 TECU 1 TECU 10 16 m -2 It was found that maximal velocity of TEC equal lines motion exceeded 1500 m s and the mean value of the velocity was about 400 m s Azimuth of wave vectors of TEC equal lines were orientated toward the center of region with anomaly high values of TEC the southwest of North America It should be noted that maximal TEC values during geomagnetically quiet conditions is about 60-80 TECU the value of TEC equal lines

Ultrastructural and mechanical changes in tubular epithelial cells by angiotensin II and aldosterone as observed with atomic force microscopy.

PubMed

Quan, Fu-Shi; Jeong, Kyung Hwan; Lee, Gi-Ja

2018-07-01

Tubular epithelial cells (TECs) play an important pathophysiological role in the promotion of renal fibrosis. Quantitative analysis of the mechanical changes in TECs may be helpful in evaluating novel pharmacological strategies. Atomic force microscopy (AFM) is a common nanotechnology tool used for imaging and measuring interaction forces in biological systems. In this study, we used AFM to study ultrastructural and mechanical changes in TECs mediated by the renin-angiotensin-aldosterone system. We quantitatively analyzed changes in the mechanical properties of TECs using three extrinsic factors, namely, chemical fixation, angiotensin II (AT II), and aldosterone (AD). Fixed TECs were 11 times stiffer at the cell body and 3 times stiffer at the cell-cell junction compared to live TECs. After stimulation with AT II, live TECs were four times stiffer at the junctional area than at the cell body, while fixed TECs after AT II stimulation were approximately two times stiffer at the both cell body and cell-cell junction compared to fixed unstimulated TECs. Fixed TECs also reflected changes in the mechanical properties of TECs at the cell body region after AD stimulation. Together, our results suggest that cell stiffness at the cell body region may serve as an effective index for evaluating drugs and stimulation, regardless of whether the cells are live or fixed at the time of analysis. In addition, studying the changes to the intrinsic mechanical property of TECs after application of external stimuli may be useful for investigating pathophysiologic mechanisms and effective therapeutic strategies for renal injury. Copyright © 2018 Elsevier Ltd. All rights reserved.

Method of fabricating composite structures

NASA Technical Reports Server (NTRS)

Sigur, W. A. (Inventor)

1990-01-01

A method of fabricating structures formed from composite materials by positioning the structure about a high coefficient of thermal expansion material, wrapping a graphite fiber overwrap about the structure, and thereafter heating the assembly to expand the high coefficient of thermal expansion material to forcibly compress the composite structure against the restraint provided by the graphite overwrap. The high coefficient of thermal expansion material is disposed about a mandrel with a release system therebetween, and with a release system between the material having the high coefficient of thermal expansion and the composite material, and between the graphite fibers and the composite structure. The heating may occur by inducing heat into the assembly by a magnetic field created by coils disposed about the assembly through which alternating current flows. The method permits structures to be formed without the use of an autoclave.

Method of fabricating composite structures

NASA Technical Reports Server (NTRS)

Sigur, Wanda A. (Inventor)

1992-01-01

A method of fabricating structures formed from composite materials by positioning the structure about a high coefficient of thermal expansion material, wrapping a graphite fiber overwrap about the structure, and thereafter heating the assembly to expand the high coefficient of thermal expansion material to forcibly compress the composite structure against the restraint provided by the graphite overwrap. The high coefficient of thermal expansion material is disposed about a mandrel with a release system therebetween, and with a release system between the material having the high coefficient of thermal expansion and the composite material, and between the graphite fibers and the composite structure. The heating may occur by inducing heat into the assembly by a magnetic field created by coils disposed about the assembly through which alternating current flows. The method permits structures to be formed without the use of an autoclave.

High temperature XRD of Cu2GeSe3

NASA Astrophysics Data System (ADS)

Premkumar D., S.; Chetty, Raju; Malar, P.; Mallik, Ramesh Chandra

2015-06-01

The Cu2GeSe3 is prepared by solid state synthesis method. The high temperature XRD has been done at different temperature from 30 °C to 450 °C. The reitveld refinement confirms Cu2GeSe3 phase and orthorhombic crystal structure. The lattice constants are increasing with increase in the temperature and their rate of increase with respect to temperature are used for finding the thermal expansion coefficient. The calculation of the linear and volume coefficient of thermal expansion is done from 30 °C to 400 °C. Decrease in the values of linear expansion coefficients with temperature are observed along a and c axis. Since thermal expansion coefficient is the consequence of the distortion of atoms in the lattice; this can be further used to find the minimum lattice thermal conductivity at given temperature.

Method of Minimizing Size of Heat Rejection Systems for Thermoelectric Coolers to Cool Detectors in Space

NASA Technical Reports Server (NTRS)

Choi, Michael K.

2014-01-01

A thermal design concept of attaching the thermoelectric cooler (TEC) hot side directly to the radiator and maximizing the number of TECs to cool multiple detectors in space is presented. It minimizes the temperature drop between the TECs and radiator. An ethane constant conductance heat pipe transfers heat from the detectors to a TEC cold plate which the cold side of the TECs is attached to. This thermal design concept minimizes the size of TEC heat rejection systems. Hence it reduces the problem of accommodating the radiator within a required envelope. It also reduces the mass of the TEC heat rejection system. Thermal testing of a demonstration unit in vacuum verified the thermal performance of the thermal design concept.

Curriculum Change Part 2a. Programme Development in Colleges. Part 2a: The Work Activities of Teachers on TEC Certificate Programmes.

ERIC Educational Resources Information Center

Dodd, S.; And Others

A study examined the day-to-day work activities of teachers of Technician Education Council (TEC) certificate programs in Great Britain. During the study, a detailed questionnaire dealing with the tasks performed by TEC teachers, the amount of time spent on TEC teachers on individual activities, and the impact of the TEC programs on teacher…

Scattering of electromagnetic plane wave from a perfect electric conducting strip placed at interface of topological insulator-chiral medium

NASA Astrophysics Data System (ADS)

Shoukat, Sobia; Naqvi, Qaisar A.

2016-12-01

In this manuscript, scattering from a perfect electric conducting strip located at planar interface of topological insulator (TI)-chiral medium is investigated using the Kobayashi Potential method. Longitudinal components of electric and magnetic vector potential in terms of unknown weighting function are considered. Use of related set of boundary conditions yields two algebraic equations and four dual integral equations (DIEs). Integrand of two DIEs are expanded in terms of the characteristic functions with expansion coefficients which must satisfy, simultaneously, the discontinuous property of the Weber-Schafheitlin integrals, required edge and boundary conditions. The resulting expressions are then combined with algebraic equations to express the weighting function in terms of expansion coefficients, these expansion coefficients are then substituted in remaining DIEs. The projection is applied using the Jacobi polynomials. This treatment yields matrix equation for expansion coefficients which is solved numerically. These unknown expansion coefficients are used to find the scattered field. The far zone scattering width is investigated with respect to different parameters of the geometry, i.e, chirality of chiral medium, angle of incidence, size of the strip. Significant effects of different parameters including TI parameter on the scattering width are noted.

TEXTURES IN EXTRUDED URANIUM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, R.B.

The preferred orientation or texture of alpha-extruded, cold-swaged, recrystallized, and beta-quenched uranium has been determined. An attempt is made to predict the mean thermal expansion coefficients from the texture and principal crystallographic thermal expansion coefficients. (auth)

Quantitative Evaluation of Ionosphere Models for Reproducing Regional TEC During Geomagnetic Storms

NASA Astrophysics Data System (ADS)

Shim, J. S.; Kuznetsova, M.; Rastaetter, L.; Bilitza, D.; Codrescu, M.; Coster, A. J.; Emery, B.; Foster, B.; Fuller-Rowell, T. J.; Goncharenko, L. P.; Huba, J.; Mitchell, C. N.; Ridley, A. J.; Fedrizzi, M.; Scherliess, L.; Schunk, R. W.; Sojka, J. J.; Zhu, L.

2015-12-01

TEC (Total Electron Content) is one of the key parameters in description of the ionospheric variability that has influence on the accuracy of navigation and communication systems. To assess current TEC modeling capability of ionospheric models during geomagnetic storms and to establish a baseline against which future improvement can be compared, we quantified the ionospheric models' performance by comparing modeled vertical TEC values with ground-based GPS TEC measurements and Multi-Instrument Data Analysis System (MIDAS) TEC. The comparison focused on North America and Europe sectors during selected two storm events: 2006 AGU storm (14-15 Dec. 2006) and 2013 March storm (17-19 Mar. 2013). The ionospheric models used for this study range from empirical to physics-based, and physics-based data assimilation models. We investigated spatial and temporal variations of TEC during the storms. In addition, we considered several parameters to quantify storm impacts on TEC: TEC changes compared to quiet time, rate of TEC change, and maximum increase/decrease during the storms. In this presentation, we focus on preliminary results of the comparison of the models performance in reproducing the storm-time TEC variations using the parameters and skill scores. This study has been supported by the Community Coordinated Modeling Center (CCMC) at the Goddard Space Flight Center. Model outputs and observational data used for the study will be permanently posted at the CCMC website (http://ccmc.gsfc.nasa.gov) for the space science communities to use.

Influence of additives on melt viscosity, surface tension, and film formation of dry powder coatings.

PubMed

Sauer, Dorothea; McGinity, James W

2009-06-01

Limited information on thermally cured dry-powder coatings used for solid dosage forms has been available in the literature. The aim of this study was to characterize the film formation process of Eudragit L 100-55 dry-powder coatings and to investigate the influence of film additives on melt viscosity and surface tension. The coating process employed no liquids and the plasticizer was combined with the polymer using hot melt extrusion. Thermoanalytical methods including differential scanning calorimetry and thermogravimetric analysis (TGA) were used to investigate the thermal properties of the dry-coating formulations. The rheological behavior of the coating formulations were characterized with the extrusion torque, and the surface energy parameters were determined from contact angle measurements. The influence of the level of triethyl citrate (TEC) as plasticizer and polyethylene glycol (PEG) 3350 in the polymer film on film formation was investigated using a digital force tester. TGA confirmed thermal stability of all coating excipients at the investigated curing conditions. Increasing TEC levels and the addition of PEG 3350 as a low melting excipient in the coating reduced the viscosity of the polymer. Plasticization of the polymer with TEC increased the surface free energy, whereas the admixture of 10% PEG 3350 did not affect the surface free energy of Eudragit L 100-55. The spreading coefficient of the polymers over two sample tablet formulations was reduced with increasing surface free energy. During the curing process, puncture strength, and elongation of powder-cast films increased. The effect of curing time on the mechanical properties was dependent on the plasticizer content. The incorporation of TEC and PEG 3350 into the Eudragit L 100-55 powder coating formulation improved film formation. Mechanical testing of powder-cast films showed an increase of both elongation and puncture strength over the curing process as criterion for polymer particle fusion, where film formation progressed faster at high plasticizer levels.

Cryogenic fiber optic temperature sensor and method of manufacturing the same

NASA Technical Reports Server (NTRS)

Kochergin, Vladimir (Inventor)

2012-01-01

This invention teaches the fiber optic sensors temperature sensors for cryogenic temperature range with improved sensitivity and resolution, and method of making said sensors. In more detail, the present invention is related to enhancement of temperature sensitivity of fiber optic temperature sensors at cryogenic temperatures by utilizing nanomaterials with a thermal expansion coefficient that is smaller than the thermal expansion coefficient of the optical fiber but larger in absolute value than the thermal expansion coefficient of the optical fiber at least over a range of temperatures.

CoLiTec software - detection of the near-zero apparent motion

NASA Astrophysics Data System (ADS)

Khlamov, Sergii V.; Savanevych, Vadym E.; Briukhovetskyi, Olexandr B.; Pohorelov, Artem V.

2017-06-01

In this article we described CoLiTec software for full automated frames processing. CoLiTec software allows processing the Big Data of observation results as well as processing of data that is continuously formed during observation. The scope of solving tasks includes frames brightness equalization, moving objects detection, astrometry, photometry, etc. Along with the high efficiency of Big Data processing CoLiTec software also ensures high accuracy of data measurements. A comparative analysis of the functional characteristics and positional accuracy was performed between CoLiTec and Astrometrica software. The benefits of CoLiTec used with wide field and low quality frames were observed. The efficiency of the CoLiTec software was proved by about 700.000 observations and over 1.500 preliminary discoveries.

Receiver DCB estimation and GPS vTEC study at a low latitude station in the South Pacific

NASA Astrophysics Data System (ADS)

Prasad, Ramendra; Kumar, Sushil; Jayachandran, P. T.

2016-11-01

The statistical estimation of receiver differential code bias (DCB) of the GSV4004B receiver at a low latitude station, Suva (lat. 18.15°S, long. 178.45°E, Geomag. Lat. 21.07°S), Fiji, and the subsequent behaviour of vTEC, are presented. By means of least squares linear regression fitting technique, the receiver DCB was determined using the GPS vTEC data recorded during the year 2010, CODE TEC and IRI-2012 model for 2010. To substantiate the results, minimization of the standard deviation (SD) method was also used for GPS vTEC data. The overall monthly DCB was estimated to be in the range of 62.6 TECU. The vTEC after removing the resultant monthly DCB was consistent with other low latitude observations. The GPS vTEC 2010 data after eliminating the resultant DCB were lower in comparison to Faraday rotation vTEC measurements at Suva during 1984 primarily due to higher solar activity during 1984 as compared to 2010. Seasonally, vTEC was maximum during summer and minimum during winter. The winter showed least vTEC variability whereas equinox showed the largest daytime variability. The geomagnetic disturbances effect showed that both vTEC and its variability were higher on magnetically disturbed days as compared to quiet days with maximum variability in the daytime. Two geomagnetic storms of moderate strengths with main phases in the local daytime showed long duration (∼52 h) increase in vTEC by 33-67% which can be accounted by changes in E×B drifts due to prompt penetration of storm-time auroral electric field in the daytime and disturbance dynamo electric field in the nighttime to low latitudes.

Salient features of the dayside low latitude ionospheric response to the main phase step-I of the 17 March 2015 geomagnetic storm

NASA Astrophysics Data System (ADS)

Bagiya, Mala S.; Sunil, A. S.; Chakrabarty, D.; Sunda, Surendra

2017-10-01

Based on TEC observations by India's GPS Aided GEO Augmented Navigation (GAGAN) GPS network, we report the dayside low latitude ionospheric variations over the Indian region during the moderate main phase step-I of the 17 March 2015 geomagnetic storm. In addition, we assess the efficacy of GPS inferred TEC maps by International GNSS service (IGS) in capturing large scale diurnal features of equatorial ionization anomaly (EIA) over the Indian region during this period. Following the prompt penetration electric field (PPE) at ∼0605 UT, equatorial electrojet (EEJ) enhances by ∼55 nT over 75 ± 3oE longitudes where main phase step-I is coincided with local noon. Initial moderate EIA gradually strengthens with the storm commencement. Although GAGAN TEC exhibits more intense EIA evolution compare to IGS TEC maps, latitudinal extent of EIA are comparable in both. The enhanced EEJ reverses by ∼0918 UT under the effect of overshielding electric field, the later is accompanied by northward turning of interplanetary magnetic field (IMF) Bz. The weakening of well evolved EIA reflects in IGS TEC maps after ∼45 min of the overshielding occurrence. In contrary, GAGAN TEC shows the corresponding feature after ∼0115 h. Resurgence of EIA, following the PPE ∼1115 UT, shows up in GAGAN TEC but IGS TEC maps fails in capturing this feature. The observed low latitude TEC variations and EIA modulations are explained in terms of the varying storm time disturbance electric fields. The anomalies between the GAGAN TEC and IGS TEC maps are discussed in terms of the possible limitations of the IGS TEC maps in capturing storm time EIA variability over the Indian region.

Parametric performance analysis of steam-injected gas turbine with a thermionic-energy-converter-lined combustor

NASA Technical Reports Server (NTRS)

Choo, Y. K.; Burns, R. K.

1982-01-01

The performance of steam-injected gas turbines having combustors lined with thermionic energy converters (STIG/TEC systems) was analyzed and compared with that of two baseline systems; a steam-injected gas turbine (without a TEC-lined combustor) and a conventional combined gas turbine/steam turbine cycle. Common gas turbine parameters were assumed for all of the systems. Two configurations of the STIG/TEC system were investigated. In both cases, steam produced in an exhaust-heat-recovery boiler cools the TEC collectors. It is then injected into the gas combustion stream and expanded through the gas turbine. The STIG/TEC system combines the advantage of gas turbine steam injection with the conversion of high-temperature combustion heat by TEC's. The addition of TEC's to the baseline steam-injected gas turbine improves both its efficiency and specific power. Depending on system configuration and design parameters, the STIG/TEC system can also achieve higher efficiency and specific power than the baseline combined cycle.

Thermal expansion coefficient determination of polylactic acid using digital image correlation

NASA Astrophysics Data System (ADS)

Botean, Adrian-Ioan

2018-02-01

This paper aims determining the linear thermal expansion coefficient (CTE) of polylactic acid (PLA) using an optical method for measuring deformations called digital image correlation method (DIC). Because PLA is often used in making many pieces with 3D printing technology, it is opportune to know this coefficient to obtain a higher degree of precision in the construction of parts and to monitor deformations when these parts are subjected to a thermal gradient. Are used two PLA discs with 20 and 40% degree of filling. In parallel with this approach was determined the linear thermal expansion coefficient (CTE) for the copper cylinder on the surface of which are placed the two discs of PLA.

Recurrences and explicit formulae for the expansion and connection coefficients in series of Bessel polynomials

NASA Astrophysics Data System (ADS)

Doha, E. H.; Ahmed, H. M.

2004-08-01

A formula expressing explicitly the derivatives of Bessel polynomials of any degree and for any order in terms of the Bessel polynomials themselves is proved. Another explicit formula, which expresses the Bessel expansion coefficients of a general-order derivative of an infinitely differentiable function in terms of its original Bessel coefficients, is also given. A formula for the Bessel coefficients of the moments of one single Bessel polynomial of certain degree is proved. A formula for the Bessel coefficients of the moments of a general-order derivative of an infinitely differentiable function in terms of its Bessel coefficients is also obtained. Application of these formulae for solving ordinary differential equations with varying coefficients, by reducing them to recurrence relations in the expansion coefficients of the solution, is explained. An algebraic symbolic approach (using Mathematica) in order to build and solve recursively for the connection coefficients between Bessel-Bessel polynomials is described. An explicit formula for these coefficients between Jacobi and Bessel polynomials is given, of which the ultraspherical polynomial and its consequences are important special cases. Two analytical formulae for the connection coefficients between Laguerre-Bessel and Hermite-Bessel are also developed.

High temperature XRD of Cu{sub 2}GeSe{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Premkumar, D. S.; Malar, P.; Chetty, Raju

2015-06-24

The Cu{sub 2}GeSe{sub 3} is prepared by solid state synthesis method. The high temperature XRD has been done at different temperature from 30 °C to 450 °C. The reitveld refinement confirms Cu{sub 2}GeSe{sub 3} phase and orthorhombic crystal structure. The lattice constants are increasing with increase in the temperature and their rate of increase with respect to temperature are used for finding the thermal expansion coefficient. The calculation of the linear and volume coefficient of thermal expansion is done from 30 °C to 400 °C. Decrease in the values of linear expansion coefficients with temperature are observed along a andmore » c axis. Since thermal expansion coefficient is the consequence of the distortion of atoms in the lattice; this can be further used to find the minimum lattice thermal conductivity at given temperature.« less

Numerical investigation of multi-beam laser heterodyne measurement with ultra-precision for linear expansion coefficient of metal based on oscillating mirror modulation

NASA Astrophysics Data System (ADS)

Li, Yan-Chao; Wang, Chun-Hui; Qu, Yang; Gao, Long; Cong, Hai-Fang; Yang, Yan-Ling; Gao, Jie; Wang, Ao-You

2011-01-01

This paper proposes a novel method of multi-beam laser heterodyne measurement for metal linear expansion coefficient. Based on the Doppler effect and heterodyne technology, the information is loaded of length variation to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain many values of length variation caused by temperature variation after the multi-beam laser heterodyne signal demodulation simultaneously. Processing these values by weighted-average, it can obtain length variation accurately, and eventually obtain the value of linear expansion coefficient of metal by the calculation. This novel method is used to simulate measurement for linear expansion coefficient of metal rod under different temperatures by MATLAB, the obtained result shows that the relative measurement error of this method is just 0.4%.

Structures, thermal expansion properties and phase transitions of Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (0.0 {le} x {le} 2.0).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Y. Z.; Wu, M. M.; Peng, J.

2007-05-03

Structures, thermal expansion properties and phase transitions of Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (0.0 {le} x {le} 2.0) have been investigated by X-ray diffraction and differential thermal analysis. The partial substitution of Er{sup 3+} for Fe{sup 3+} induces pronounced decreases in the phase transition temperature from monoclinic to orthorhombic structure. Rietveld analysis of the XRD data shows that both the monoclinic and orthorhombic Fe{sub 2}(MoO{sub 4}){sub 3}, as well as the orthorhombic Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (x {le} 0.8) have positive thermal expansion coefficients. However, the linear thermal expansion coefficients of Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (x = 0.6-2.0)more » decrease with increasing content of Er{sup 3+} and for x {ge} 1.0, compounds Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} show negative thermal expansion properties. Attempts for making zero thermal expansion coefficient materials result in that very low negative thermal expansion coefficient of -0.60 x 10{sup -6} C in Er{sub 1.0}Fe{sub 1.0}(MoO{sub 4}){sub 3} is observed in the temperature range of 180-400 C, and zero thermal expansion is observed in Er{sub 0.8}Fe{sub 1.2}(MoO{sub 4}){sub 3} in the temperature range of 350-450 C. In addition, anisotropic thermal expansions are found for all the orthorhombic Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} compounds, with negative thermal expansion coefficients along the a axes.« less

Long-Term Prediction of the Arctic Ionospheric TEC Based on Time-Varying Periodograms

PubMed Central

Liu, Jingbin; Chen, Ruizhi; Wang, Zemin; An, Jiachun; Hyyppä, Juha

2014-01-01

Knowledge of the polar ionospheric total electron content (TEC) and its future variations is of scientific and engineering relevance. In this study, a new method is developed to predict Arctic mean TEC on the scale of a solar cycle using previous data covering 14 years. The Arctic TEC is derived from global positioning system measurements using the spherical cap harmonic analysis mapping method. The study indicates that the variability of the Arctic TEC results in highly time-varying periodograms, which are utilized for prediction in the proposed method. The TEC time series is divided into two components of periodic oscillations and the average TEC. The newly developed method of TEC prediction is based on an extrapolation method that requires no input of physical observations of the time interval of prediction, and it is performed in both temporally backward and forward directions by summing the extrapolation of the two components. The backward prediction indicates that the Arctic TEC variability includes a 9 years period for the study duration, in addition to the well-established periods. The long-term prediction has an uncertainty of 4.8–5.6 TECU for different period sets. PMID:25369066

Global empirical model of TEC response to geomagnetic activity

NASA Astrophysics Data System (ADS)

Mukhtarov, P.; Andonov, B.; Pancheva, D.

2013-10-01

global total electron content (TEC) model response to geomagnetic activity described by the Kp index is built by using the Center for Orbit Determination of Europe (CODE) TEC data for a full 13 years, January 1999 to December 2011. The model describes the most probable spatial distribution and temporal variability of the geomagnetically forced TEC anomalies assuming that these anomalies at a given modified dip latitude depend mainly on the Kp index, local time (LT), and longitude. The geomagnetic anomalies are expressed by the relative deviation of TEC from its 15 day median and are denoted as rTEC. The rTEC response to the geomagnetic activity is presented by a sum of two responses with different time delay constants and different signs of the cross-correlation function. It has been found that the mean dependence of rTEC on Kp index can be expressed by a cubic function. The LT dependence of rTEC is described by Fourier time series which includes the contribution of four diurnal components with periods 24, 12, 8, and 6 h. The rTEC dependence on longitude is presented by Fourier series which includes the contribution of zonal waves with zonal wave numbers up to 6. In order to demonstrate how the model is able to reproduce the rTEC response to geomagnetic activity, three geomagnetic storms at different seasons and solar activity conditions are presented. The model residuals clearly reveal two types of the model deviation from the data: some underestimation of the largest TEC response to the geomagnetic activity and randomly distributed errors which are the data noise or anomalies generated by other sources. The presented TEC model fits to the CODE TEC input data with small negative bias of -0.204, root mean squares error RMSE = 4.592, and standard deviation error STDE = 4.588. The model offers TEC maps which depend on geographic coordinates (5° × 5° in latitude and longitude) and universal time (UT) at given geomagnetic activity and day of the year. It could be used for both science and possible service (nowcasting and short-term prediction); for the latter, a detailed validation of the model at different geophysical conditions has to be performed in order to clarify the model predicting quality.

Clouds and troughs of total electron content detected with the ionospheric weather index

NASA Astrophysics Data System (ADS)

Gulyaeva, Tamara

2016-07-01

The ionospheric weather W index has been developed with the different thresholds of change in the F2 layer peak electron density NmF2 (proportional to foF2 critical frequency) or total electron content TEC relative their quiet reference for quantifying the ionosphere variability. The thresholds of DTEC=log(TEC/TECq) are selected for the positive and negative logarithm of TEC ratio to the quiet reference median, TECq, at any given location on the Earth. The global W-index maps are produced from Global Ionospheric Maps of Total Electron Content, GIM-TEC, and provided online at http://www.izmiran.ru/services/iweather/ and http://www.iololab.org/. Based on W-index maps, Catalogues of the ionospheric storms and sub-storms are produced available for the users. The second generation of the ionospheric weather indices, designated V index, is recently introduced and applied for the retrospective study of GIM-TEC variability during 1999-2015. Using sliding-window statistical analysis, moving daily-hourly TEC median TECq for 15 preceding days with estimated variance bounds are obtained at cells of GIM-TEC. The ionosphere variability index, V, is expressed in terms of ΔTEC deviation from the median normalized by the standard deviation STD. V index segmentation is introduced from Vn=-4 in step of 1 to Vp=4 specifying TEC storm if an instant TEC is outside of TECq+-1STD. The global maps of V index allow distinguish the clouds of enhanced TEC (positive storm signatures) and troughs of TEC depletion (negative storm signatures) as compared to the background quiet reference TECq map. It is found that the large-scale TEC clouds and troughs are observed in space all over the world constituting up to 20-50 percent of cells of GIM-TEC. The time variation of these plasma patches is partly following to geomagnetic SSC storm onset. As concerns the interplanetary and the solar wind, SW, sources of the ionospheric storms the TEC storms are observed both with IMF and SW precursors and without the IMF and SW storm signatures. Results of the ionospheric storm studies with the ionospheric weather indices are discussed in the paper. This study is supported by TUBITAK EEEAG 115E915.

Application of Geostationary GNSS and SBAS Satellites for Studying Ionospheric TEC Disturbances of Geomagnetic and Meteorological Origin

NASA Astrophysics Data System (ADS)

Padokhin, A. M.; Kurbatov, G. A.; Yasyukevich, Y.; Yasyukevich, A.

2017-12-01

With the development of GNSS and SBAS constellations, the coherent multi-frequency L band transmissions are now available from a number of geostationary satellites. These signals can be used for ionospheric TEC estimations in the same way as widely used GPS/GLONASS signals. In this work, we compare noise patterns in TEC estimations based on different geostationary satellites data: augmentation systems (Indian GAGAN, European EGNOS and American WAAS), and Chinese COMPASS/Beidou navigation system. We show that noise level in geostationary COMPASS/Beidou TEC estimations is times smaller than noise in SBAS TEC estimation and corresponds to those of GPS/GLONASS at the same elevation angles. We discuss the capabilities of geostationary TEC data for studying ionospheric variability driven by space weather and meteorological sources at different time scales. Analyzing data from IGS/MGEX receivers we present geostationary TEC response on X-class Solar flares of current cycle, moderate and strong geomagnetic storms, including G4 St. Patrick's day Storm 2015 and recent G3 storm of the end of May 2017. We also discuss geostationary TEC disturbances in near equatorial ionosphere caused by two SSW events (minor and major final warming of 2015-2016 winter season) as well as geostationary TEC response on typhoons activity near Taiwan in autumn 2016. Our results show large potential of geostationary TEC estimations with GNSS and SBAS signals for continuous ionospheric monitoring.

Transformation of Chlorinated Benzenes and Toluenes by Ralstonia sp. Strain PS12 tecA (Tetrachlorobenzene Dioxygenase) and tecB (Chlorobenzene Dihydrodiol Dehydrogenase) Gene Products

PubMed Central

Pollmann, Katrin; Beil, Stefan; Pieper, Dietmar H.

2001-01-01

The tecB gene, located downstream of tecA and encoding tetrachlorobenzene dioxygenase, in Ralstonia sp. strain PS12 was cloned into Escherichia coli DH5α together with the tecA gene. The identity of the tecB gene product as a chlorobenzene dihydrodiol dehydrogenase was verified by transformation into the respective catechols of chlorobenzene, the three isomeric dichlorobenzenes, as well as 1,2,3- and 1,2,4-trichlorobenzenes, all of which are transformed by TecA into the respective dihydrodihydroxy derivatives. Di- and trichlorotoluenes were either subject to TecA-mediated dioxygenation (the major or sole reaction observed for the 1,2,4-substituted 2,4-, 2,5-, and 3,4-dichlorotoluenes), resulting in the formation of the dihydrodihydroxy derivatives, or to monooxygenation of the methyl substituent (the major or sole reaction observed for 2,3-, 2,6-, and 3,5-dichloro- and 2,4,5-trichlorotoluenes), resulting in formation of the respective benzyl alcohols. All of the chlorotoluenes subject to dioxygenation by TecA were transformed, without intermediate accumulation of dihydrodihydroxy derivatives, into the respective catechols by TecAB, indicating that dehydrogenation is no bottleneck for chlorobenzene or chlorotoluene degradation. However, only those chlorotoluenes subject to a predominant dioxygenation were growth substrates for PS12, confirming that monooxygenation is an unproductive pathway in PS12. PMID:11526005

GPS receiver CODE bias estimation: A comparison of two methods

NASA Astrophysics Data System (ADS)

McCaffrey, Anthony M.; Jayachandran, P. T.; Themens, D. R.; Langley, R. B.

2017-04-01

The Global Positioning System (GPS) is a valuable tool in the measurement and monitoring of ionospheric total electron content (TEC). To obtain accurate GPS-derived TEC, satellite and receiver hardware biases, known as differential code biases (DCBs), must be estimated and removed. The Center for Orbit Determination in Europe (CODE) provides monthly averages of receiver DCBs for a significant number of stations in the International Global Navigation Satellite Systems Service (IGS) network. A comparison of the monthly receiver DCBs provided by CODE with DCBs estimated using the minimization of standard deviations (MSD) method on both daily and monthly time intervals, is presented. Calibrated TEC obtained using CODE-derived DCBs, is accurate to within 0.74 TEC units (TECU) in differenced slant TEC (sTEC), while calibrated sTEC using MSD-derived DCBs results in an accuracy of 1.48 TECU.

Simultaneous total electron content and all-sky camera measurements of an auroral arc

NASA Astrophysics Data System (ADS)

Kintner, P. M.; Kil, H.; Deehr, C.; Schuck, P.

2002-07-01

We present an example of Global Positioning System (GPS) derived total electron content (TEC) and all-sky camera (ASC) images that show increases of TEC by ~10 × 1016 electrons m-2 (10 TEC units) occurring simultaneously with auroral light in ASC images. The TEC example appears to be an E region density enhancement produced by two discrete auroral arcs occurring in the late morning auroral oval at 1000 LT. This suggests that GPS signal TEC measurements can be used to detect individual auroral arcs and that individual discrete auroral arcs are responsible for some high-latitude phase scintillations. The specific auroral feature detected was a poleward moving auroral form believed to occur in the polar cap where the ionosphere is convecting antisunward. The magnitude of the rate of change of TEC (dTEC/dt) is comparable to that previously reported. However, the timescales associated with the event, the order of 1 min, suggest that the data sampling technique commonly used by chain GPS TEC receivers (averaging and time decimation) will undersample E region TEC perturbations produced by active auroral displays. The localized nature of this example implies that L1 ranging errors of at least 1.6 m will be introduced by auroral arcs into systems relying on differential GPS for navigation or augmentation. Although the TEC and auroral arcs presented herein occurred in the late morning auroral oval, we expect that the effects of discrete auroral arcs on GPS TEC and subsequent ranging errors should occur at all local times. Furthermore, GPS receivers can be used to detect individual discrete arcs.

Phase equilibria, crystal structure and oxygen content of intermediate phases in the Y-Ba-Co-O system

NASA Astrophysics Data System (ADS)

Urusova, A. S.; Cherepanov, V. A.; Aksenova, T. V.; Gavrilova, L. Ya.; Kiselev, E. A.

2013-06-01

The phase equilibria in the Y-Ba-Co-O system were systematically studied at 1373 K in air. The intermediate phases formed in the Y-Ba-Co-O system at 1373 K in air were: YBaCo2O5+δ, YBaCo4O7 and BaCo1-yYyO3-δ (0.09≤y≤0.42). It was shown that YBaCo2O5+δ possesses tetragonal structure with the 3ap×3ap×2ap superstructure (sp. gr. P4/mmm). High-temperature X-ray diffraction analysis of the YBaCo2O5+δ in the temperature range from 298 K up to 1073 K under Po2=0.21 аtm has not shown any phase transformations. The value of oxygen content for the YBaCo2O5+δ at room temperature was estimated as 5.40 and at 1323 K it was equal to 5.04. Thermal expansion of sample shows a linear characteristics and the average thermal expansion coefficient (TEC) is about 13.8×10-6, K-1 in the temperature range 298-1273 K. The homogeneity range and crystal structure of the BaCo1-yYyO3-δ (0.09≤y≤0.42) solid solutions were determined by X-ray diffraction of quenched samples. All BaCo1-yYyO3-δ solid solutions were found to have cubic structure (sp. gr. Pm3m). The unit cell parameters were refined using Rietveld full-profile analysis. Oxygen nonstoichiometry of BaCo1-yYyO3-δ solid solutions with 0.1≤y≤0.4 was measured by means of thermogravimetric technique within the temperature range 298-1373 K in air. Thermal expansion of BaCo1-yYyO3-δ (у=0.0; 0.1; 0.2; 0.3) samples was studied within the temperature range 298-1200 K in air. The projection of isothermal-isobaric phase diagram for the Y-Ba-Co-O system to the compositional triangle of metallic components was presented.

78 FR 64207 - Application To Export Electric Energy; TEC Energy Inc.

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-28

... DEPARTMENT OF ENERGY [OE Docket No. EA-388] Application To Export Electric Energy; TEC Energy Inc. AGENCY: Office of Electricity Delivery and Energy Reliability, DOE. ACTION: Notice of Application. SUMMARY: TEC Energy Inc. (TEC) has applied for authority to transmit electric energy from the United...

Thermal expansion and elastic anisotropy in single crystal Al2O3 and SiC reinforcements

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Li, Zhuang; Bradt, Richard C.

1994-01-01

In single crystal form, SiC and Al2O3 are attractive reinforcing components for high temperature composites. In this study, the axial coefficients of thermal expansion and single crystal elastic constants of SiC and Al2O3 were used to determine their coefficients of thermal expansion and Young's moduli as a function of crystallographic orientation and temperature. SiC and Al2O3 exhibit a strong variation of Young's modulus with orientation; however, their moduli and anisotropies are weak functions of temperature below 1000 C. The coefficients of thermal expansion exhibit significant temperature dependence, and that of the non-cubic Al2O3 is also a function of crystallographic orientation.

Modeling of the Earth's gravity field using the New Global Earth Model (NEWGEM)

NASA Technical Reports Server (NTRS)

Kim, Yeong E.; Braswell, W. Danny

1989-01-01

Traditionally, the global gravity field was described by representations based on the spherical harmonics (SH) expansion of the geopotential. The SH expansion coefficients were determined by fitting the Earth's gravity data as measured by many different methods including the use of artificial satellites. As gravity data have accumulated with increasingly better accuracies, more of the higher order SH expansion coefficients were determined. The SH representation is useful for describing the gravity field exterior to the Earth but is theoretically invalid on the Earth's surface and in the Earth's interior. A new global Earth model (NEWGEM) (KIM, 1987 and 1988a) was recently proposed to provide a unified description of the Earth's gravity field inside, on, and outside the Earth's surface using the Earth's mass density profile as deduced from seismic studies, elevation and bathymetric information, and local and global gravity data. Using NEWGEM, it is possible to determine the constraints on the mass distribution of the Earth imposed by gravity, topography, and seismic data. NEWGEM is useful in investigating a variety of geophysical phenomena. It is currently being utilized to develop a geophysical interpretation of Kaula's rule. The zeroth order NEWGEM is being used to numerically integrate spherical harmonic expansion coefficients and simultaneously determine the contribution of each layer in the model to a given coefficient. The numerically determined SH expansion coefficients are also being used to test the validity of SH expansions at the surface of the Earth by comparing the resulting SH expansion gravity model with exact calculations of the gravity at the Earth's surface.

Local Displacements and Load Transfer of Shape Memory Alloys in Polymeric Matrices

DTIC Science & Technology

1997-01-01

plane displacements of room temperature cured SMA ribbon composites were obtained using moiré interferometry. Displacements due to thermal expansion ...141 Figure 6.10 Displacement profiles along SMA ribbon or different values of the coefficient of thermal expansion ...greater importance in polymer composites, which can have large coefficients of thermal expansion . Further, there is also a lack of experimental data

Rectangular rotation of spherical harmonic expansion of arbitrary high degree and order

NASA Astrophysics Data System (ADS)

Fukushima, Toshio

2017-08-01

In order to move the polar singularity of arbitrary spherical harmonic expansion to a point on the equator, we rotate the expansion around the y-axis by 90° such that the x-axis becomes a new pole. The expansion coefficients are transformed by multiplying a special value of Wigner D-matrix and a normalization factor. The transformation matrix is unchanged whether the coefficients are 4 π fully normalized or Schmidt quasi-normalized. The matrix is recursively computed by the so-called X-number formulation (Fukushima in J Geodesy 86: 271-285, 2012a). As an example, we obtained 2190× 2190 coefficients of the rectangular rotated spherical harmonic expansion of EGM2008. A proper combination of the original and the rotated expansions will be useful in (i) integrating the polar orbits of artificial satellites precisely and (ii) synthesizing/analyzing the gravitational/geomagnetic potentials and their derivatives accurately in the high latitude regions including the arctic and antarctic area.

Determination of coefficient of thermal expansion effects on Louisiana's PCC pavement design.

DOT National Transportation Integrated Search

2011-12-01

With the development of the Mechanistic Empirical Pavement Design Guide (MEPDG) as a new pavement design tool, the : coefficient of thermal expansion (CTE) is now considered a more important design parameter in estimating pavement : performance inclu...

Nonlinear Finite Element Analysis of Metals and Metal Matrix Composites: A Local-Global Investigation

DTIC Science & Technology

1992-10-01

and SiC/Al [47] possess good chemical bonding and experience mechanical clamping due to the differences in thermal expansion coefficients between...Coefficient of Thermal 2.70 x 10.6 *F-1 4.09 x 10-6 *C-1 Expansion (ca) Poisson’s Ratio (v) 0.25 0.25 Fiber Diameter (d) 0.0056 in 0.014224 cm...Properties of the matrix (as fabricated) Coefficient of Thermal 5.4 x 10-6 "F1 9.72 x 10-6 "C-1 Expansion (a) Poisson’s Ratio (v) 0.351 0.351 Longitudinal

Observing Tsunamis in the Ionosphere Using Ground Based GPS Measurements

NASA Technical Reports Server (NTRS)

Galvan, D. A.; Komjathy, A.; Song, Y. Tony; Stephens, P.; Hickey, M. P.; Foster, J.

2011-01-01

Ground-based Global Positioning System (GPS) measurements of ionospheric Total Electron Content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following recent seismic events, including the Tohoku tsunami of March 11, 2011. We observe fluctuations correlated in time, space, and wave properties with this tsunami in TEC estimates processed using JPL's Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove ionospheric TEC variations with periods outside the typical range of internal gravity waves caused by tsunamis. Observable variations in TEC appear correlated with the Tohoku tsunami near the epicenter, at Hawaii, and near the west coast of North America. Disturbance magnitudes are 1-10% of the background TEC value. Observations near the epicenter are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in good agreement. The potential exists to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for future early warning systems.

Effects of treadmill training with the eyes closed on gait and balance ability of chronic stroke patients.

PubMed

Kim, Yong-Wook; Moon, Sung-Jun

2015-09-01

[Purpose] The purpose of this study was to compare the effect of treadmill walking with the eyes closed and open on the gait and balance abilities of chronic stroke patients. [Subjects and Methods] Thirty patients with chronic stroke participated in this study. The treadmill gait training for each group lasted 40 minutes, and sessions were held 3 times a week for 4 weeks. Gait ability was measured using a Biodex Gait Trainer Treadmill System. Balance ability was measured using a Biodex Balance System. [Results] After the treadmill training' the treadmill training with eyes closed (TEC) group showed significant improvements in walking distance' step length' coefficient of variation' and limit of stability (overall' lateral affected' forward lateral unaffected) compared to the treadmill training with eyes open (TEO) group. [Conclusion] The walking and balance abilities of the TEC participants showed more improvement after the treadmill walking sessions than those of the TEO participants. Therefore' treadmill walking with visual deprivation may be useful for the rehabilitation of patients with chronic stroke.

A single-station empirical model for TEC over the Antarctic Peninsula using GPS-TEC data

NASA Astrophysics Data System (ADS)

Feng, Jiandi; Wang, Zhengtao; Jiang, Weiping; Zhao, Zhenzhen; Zhang, Bingbing

2017-02-01

Compared with regional or global total electron content (TEC) empirical models, single-station TEC empirical models may exhibit higher accuracy in describing TEC spatial and temporal variations for a single station. In this paper, a new single-station empirical total electron content (TEC) model, called SSM-month, for the O'Higgins Station in the Antarctic Peninsula is proposed by using Global Positioning System (GPS)-TEC data from 01 January 2004 to 30 June 2015. The diurnal variation of TEC in the O'Higgins Station may have changing features in different months, sometimes even in opposite forms, because of ionospheric phenomena, such as the Mid-latitude Summer Nighttime Anomaly (MSNA). To avoid the influence of different diurnal variations, the concept of monthly modeling is proposed in this study. The SSM-month model, which is established by month (including 12 submodels that correspond to the 12 months), can effectively describe the diurnal variation of TEC in different months. Each submodel of the SSM-month model exhibits good agreement with GPS-TEC input data. Overall, the SSM-month model fits the input data with a bias of 0.03 TECU (total electron content unit, 1 TECU = 1016 el m-2) and a standard deviation of 2.78 TECU. This model, which benefits from the modeling method, can effectively describe the MSNA phenomenon without implementing any modeling correction. TEC data derived from Center for Orbit Determination in Europe global ionosphere maps (CODE GIMs), International Reference Ionosphere 2012 (IRI2012), and NeQuick are compared with the SSM-month model in the years of 2001 and 2015-2016. Result shows that the SSM-month model exhibits good consistency with CODE GIMs, which is better than that of IRI2012 and NeQuick, in the O'Higgins Station on the test days.

Ionospheric reaction on sudden stratospheric warming events in Russiás Asia region

NASA Astrophysics Data System (ADS)

Polyakova, Anna; Perevalova, Natalya; Chernigovskaya, Marina

2015-12-01

The response of the ionosphere to sudden stratospheric warmings (SSWs) in the Asian region of Russia is studied. Two SSW events observed in 2008-2009 and 2012-2013 winter periods of extreme solar minimum and moderate solar maximum are considered. To detect the ionospheric effects caused by SSWs, we carried out a joint analysis of global ionospheric maps (GIM) of the total electron content (TEC), MLS (Microwave Limb Sounder, EOS Aura) measurements of temperature vertical profiles, as well as NCEP/NCAR and UKMO Reanalysis data. For the first time, it was found that during strong SSWs, in the mid-latitude ionosphere the amplitude of diurnal TEC variation decreases nearly half compared to quiet days. At the same time, the intensity of TEC deviations from the background level increases. It was also found that at SSW peak the midday TEC maximum decreases, and night/morning TEC values increase compared to quiet days. It was shown that during SSWs, TEC dynamics was identical for different geophysical conditions.The response of the ionosphere to sudden stratospheric warmings (SSWs) in the Asian region of Russia is studied. Two SSW events observed in 2008-2009 and 2012-2013 winter periods of extreme solar minimum and moderate solar maximum are considered. To detect the ionospheric effects caused by SSWs, we carried out a joint analysis of global ionospheric maps (GIM) of the total electron content (TEC), MLS (Microwave Limb Sounder, EOS Aura) measurements of temperature vertical profiles, as well as NCEP/NCAR and UKMO Reanalysis data. For the first time, it was found that during strong SSWs, in the mid-latitude ionosphere the amplitude of diurnal TEC variation decreases nearly half compared to quiet days. At the same time, the intensity of TEC deviations from the background level increases. It was also found that at SSW peak the midday TEC maximum decreases, and night/morning TEC values increase compared to quiet days. It was shown that during SSWs, TEC dynamics was identical for different geophysical conditions.

Where does the plasmasphere begin? Revisit to topside ionospheric profiles in comparison with plasmaspheric TEC from Jason-1

NASA Astrophysics Data System (ADS)

Lee, Han-Byul; Kim, Yong Ha; Kim, Eunsol; Hong, Junseok; Kwak, Young-Sil

2016-10-01

Topside ionospheric profiles have been measured by Alouette 1 and ISIS 1/2 in the periods of 1962-1972 and 1972-1979, respectively. The profiles cover from the orbital altitude of 1000 km to the F2 peak and show large variations over local time, latitude, and seasons. We here analyze these variations in comparison with plasmaspheric total electron contents (pTECs) that were measured by Jason-1 satellite from the altitude of 1336 km to 20,200 km (GPS orbit). The scale heights of the profiles are generally smaller in the daytime than nighttime but show large day-to-day variations, implying that the ionospheric profiles at 1000 km are changing dynamically, rather than being in diffusive equilibrium. We also derived transition heights between O+ and H+, which show a clear minimum at dawn for low-latitude profiles due to decreasing O+ density at night. To compare with pTEC, we compute topside ionospheric total electron content (tiTEC) by integrating over 800-1336 km using the slope of the profiles. The tiTEC varies in a clear diurnal pattern from 0.3 to 1 and 3 total electron content unit (TECU, 1 TECU = 1016 el m-2) for low and high solar activity, respectively, whereas Jason-1 pTEC values are distributed over 2-6 TECU and 4-8 TECU for low and high solar activity, respectively, with no apparent diurnal modulation. Latitudinal variations of tiTEC show distinctive hemispheric asymmetry while that of Jason-1 pTEC is closely symmetric about the magnetic equator. The local time and latitudinal variations of tiTEC basically resemble those of the ionosphere but are characteristically different from those of Jason-1 pTEC. Based on the difference between tiTEC and pTEC variations, we propose that the region above 1300 km should be considered as the plasmasphere. Lower altitudes for the base of "plasmaspheric TEC," as used in some studies, would cause contamination of ionospheric influence.

Determinations of ionosphere and plasmasphere electron content for an African chain of GPS stations

NASA Astrophysics Data System (ADS)

Mazzella, Andrew J., Jr.; Bosco Habarulema, John; Yizengaw, Endawoke

2017-05-01

The confluence of recent instrumentation deployments in Africa with developments for the determination of plasmasphere electron content using Global Positioning System (GPS) receivers has provided new opportunities for investigations in that region. This investigation, using a selected chain of GPS stations, extends the method (SCORPION) previously applied to a chain of GPS stations in North America in order to separate the ionosphere and plasmasphere contributions to the total electron content (TEC) during a day (24 July) in 2011. The results span latitudes from the southern tip of Africa, across the Equator, to the southern Arabian Peninsula, providing a continuous latitudinal profile for both the ionosphere and plasmasphere during this day.The peak diurnal vertical ionosphere electron content (IEC) increases from about 14 TEC units (1 TEC unit = 1016 electrons m-2) at the southernmost station to about 32 TEC units near the geographic equator, then decreases to about 28 TEC units at the Arabian Peninsula. The peak diurnal slant plasmasphere electron content (PEC) varies between about 4 and 7 TEC units among the stations, with a local latitudinal profile that is significantly influenced by the viewing geometry at the station location, relative to the magnetic field configuration. In contrast, the peak vertical PEC varies between about 1 and 6 TEC units among the stations, with a more uniform latitudinal variation.Comparisons to other GPS data analyses are also presented for TEC, indicating the influence of the PEC on the determination of latitudinal TEC variations and also on the absolute TEC levels, by inducing an overestimate of the receiver bias. The derived TEC latitudinal profiles, in comparison to global map profiles, tend to differ from the map results only about as much as the map results differ among themselves. A combination of ionosonde IEC and alternative GPS TEC measurements, which in principle permits a PEC determination through their difference, was compared to the composite and separate ionosphere and plasmasphere contributions derived solely by the SCORPION method for one station. Although there is considerably more scatter in the PEC values derived from the difference of the GPS TEC and ionosonde IEC measurements compared to the PEC values derived by the SCORPION method, the average overhead values for this day are comparable for the two methods, near 2 TEC units, at the South African site examined.This initial investigation provides a basis for day-to-day TEC monitoring for Africa, with separate ionosphere and plasmasphere electron content determinations.

Development of TEC fluctuations in northern and southern hemispheres on the base of GPS observations

NASA Astrophysics Data System (ADS)

Shagimuratov, Irk; Krankowski, Andrzej; Sieradzki, Rafal; Ephishov, I. I.

GPS technique is widely used to study the global structure and dynamics of the ionosphere. In this paper GPS observations carried out at Arctic and Antarctic stations belonging to the IGS network were used to study TEC fluctuations in the high-latitude ionosphere during the ionospheric storms. Dual-frequency GPS phase measurements along individual satellite passes served as raw data. It was shown that ionospheric irregularities of a different scale were devel-oped in the auroral and polar ionosphere. It is a common phenomenon caused phase fluctuations of GPS signals. In November 2009, West Department of IZMIRAN in Kaliningrad (Russia) and University of Warmia and Mazury in Olsztyn (Poland) established computer server for automatic monitoring of these irregularities. The rate of TEC index (ROTI) expressed in TECU/min was used as a measure of TEC fluctuations. During its operation TEC variations related to ionospheric structures of a spatial scale more than 200-300 km were detected. Large-scale ionospheric structures cause an increase in horizontal gradients and difficulties with the carrier phase ambiguity resolution in GPS positioning. In turn, the phase fluctuations can cause cycle-slip effects. At the polar stations, ionospheric structures with TEC enhanced by a factor of 3-5 relative to the background were detected, whereas TEC increased to 5-8 TECU in about 10-15 min. These structures were observed during a storm, as well as during a moderate geomagnetic activity. It can be probably attributed to the polar cap patches. In this study are presented the extended and more detailed analyses of TEC fluctuations in both the northern and southern hemispheres and compare the winter and summer events (November and July 2004 storms). A special attention is given to the features related to TEC fluctuations occur-rence in both hemispheres for conjugated GPS stations. The temporal development of both storms was rather similar. During storms the intensity of irregularities essentially increases and its location expands to equator. Maximal activity of TEC fluctuations took place when IMF Bz component was negative. Storm-time development of TEC fluctuations caused by ionospheric irregularities was controlled by UT. At polar stations TEC fluctuations were more expressed at southern (winter) hemisphere. Over auroral stations the difference of TEC fluctuations oc-currence was less expressed. During storm the strong TEC fluctuations can be registered at subauroral ionosphere (on latitudes lower than 55 CGL). The seasonal effect in this area also took place. Differences and similarities of these storms occurrence of TEC fluctuations with dependence on season are discussed.

Seasonal and solar cycle effects on TEC at 95°E in the ascending half (2009-2014) of the subdued solar cycle 24: Consistent underestimation by IRI 2012

NASA Astrophysics Data System (ADS)

Kakoti, Geetashree; Bhuyan, Pradip Kumar; Hazarika, Rumajyoti

2017-07-01

TEC measured at Dibrugarh (27.5°N, 94.9°E, 17.5°N Geomag.) from 2009 to 2014 is used to study its temporal characteristics during the ascending half of solar cycle 24. The measurements provide an opportunity to assess the diurnal, seasonal and longterm predictability of the IRI 2012 (with IRI Nequick, IRI01-corr, IRI 2001topside options) during this solar cycle which is distinctively low in magnitude compared to the previous cycles. The low latitude station Dibrugarh is normally located at the poleward edge of the northern EIA. A semi-annual variation in GPS TEC is observed with the peaks occurring in the equinoxes. The peak in spring (March, April) is higher than that in autumn (September, October) irrespective of the year of observation. The spring autumn asymmetry is also observed in IRI TEC. In contrast, the winter (November, December, January, February) anomaly is evident only in high activity years. TEC bears a distinct nonlinear relationship with 10.7 cm solar flux (F10.7). TEC increases linearly with F10.7 up to about 125 sfu beyond which it tends to saturate. The correlation between TEC and solar flux is found to be a function of local time and peaks at 10:00 LT. TEC varies nonlinearly with solar EUV flux similar to its variation with F10.7. The nonlinearity is well captured by the IRI. The saturation of TEC at high solar activity is attributed to the inability of the ionosphere to accommodate more ionization after it reaches the level of saturation ion pressure. Annual mean TEC increased from the minimum in 2009 almost linearly till 2012, remains at the same level in 2013 and then increased again in 2014. IRI TEC shows a linear increase from 2009 to 2014. IRI01-corr and IRI-NeQuick TEC are nearly equal at all local times, season and year of observation while IRI-2001 simulated TEC are always higher than that simulated by the other two versions. The IRI 2012 underestimates the TEC at about all local times except for a few hours in the midday in all season or year of observation. The discrepancy between model and measured TEC is high in spring and in the evening hours. The consistent underestimation of the TEC at this longitude by the IRI may be attributed to the inadequate ingestion of F region data from this longitude sector into the model and exclusion of the plasmaspheric content.

Recursive formulas for the partial fraction expansion of a rational function with multiple poles.

NASA Technical Reports Server (NTRS)

Chang, F.-C.

1973-01-01

The coefficients in the partial fraction expansion considered are given by Heaviside's formula. The evaluation of the coefficients involves the differential of a quotient of two polynomials. A simplified approach for the evaluation of the coefficients is discussed. Leibniz rule is applied and a recurrence formula is derived. A coefficient can also be determined from a system of simultaneous equations. Practical methods for the performance of the computational operations involved in both approaches are considered.

Determination of coefficient of thermal expansion for Portland Cement Concrete pavements for MEPDG Implementation

DOT National Transportation Integrated Search

2012-10-01

The Coefficient of Thermal Expansion (CTE) is an important parameter in Portland Cement Concrete (PCC) pavement analysis and design as it is directly proportional to the magnitude of temperature-related pavement deformations throughout the pavement s...

Determination of coefficient of thermal expansion For Portland Cement Concrete pavements for MEPDG Implementation

DOT National Transportation Integrated Search

2012-10-01

The Coefficient of Thermal Expansion (CTE) is an important parameter in Portland Cement Concrete (PCC) pavement analysis and design as it is directly proportional to the magnitude of temperature-related pavement deformations throughout the pavement s...

Development of New Generation of Perspireable Skin

DTIC Science & Technology

2015-02-20

Coefficient of Thermal Expansion (CTE) material simulating Reinforced Carbon - Carbon Composites (RCC). These tiles made of different materials...Very low thermal expansion coefficient materials, Annu. Rev. Mater. Sci., 1989, 19, 59-81 3. Mittal, R. and Chaplot S.L., Lattice dynamical...thermal expansion from0.3 to 1050 Kelvin in ZrW2O8, Science, 1996, 272, 90-92 6. G. Savage, Carbon - carbon composites, New York: Chapman & Hall, pp

Precision Composite Space Structures

DTIC Science & Technology

2007-10-15

large structures. 15. SUBJECT TERMS Composite materials, dimensional stability, microcracking, thermal expansion , space structures, degradation...Figure 32. Variation of normalized coefficients of thermal expansion α11(n), α22(n), and α33(n) with normalized crack density of an AS4/3501-6...coefficients of thermal expansion α11(n), α22(n), and α33(n) with normalized crack density of an AS4/3501-6 composite lamina with a fiber volume

Composite fastener for use in high temperature environments

NASA Technical Reports Server (NTRS)

Miller, Robert J. (Inventor); Palusis, Mark E. (Inventor); Jarmon, David C. (Inventor)

2000-01-01

A fastener includes a composite body and a metal coupling attached to the body. The metal coupling includes an attachment structure to connect the fastener to an external structure. An assembly of components includes a first metallic component having a first coefficient of thermal expansion, a second non-metallic component having a second coefficient of thermal expansion different from the first thermal expansion and having a groove that receives a fastener that extends between the groove and the second component, the fastener slidably engaging the groove to accommodate relative expansion between the components.

Synthesis and characterization of La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} oxide as cathode for Intermediate Temperature Solid Oxide Fuel Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vázquez, Santiago; Davyt, Sebastián; Basbus, Juan F.

2015-08-15

Nanocrystalline La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} (LSFCu) material was synthetized by combustion method using EDTA as fuel/chelating agent and NH{sub 4}NO{sub 3} as combustion promoter. Structural characterization using thermodiffraction data allowed to determine a reversible phase transition at 425 °C from a low temperature R-3c phase to a high temperature Pm-3m phase and to calculate the thermal expansion coefficient (TEC) of both phases. Important characteristics for cathode application as electronic conductivity and chemical compatibility with Ce{sub 0.9}Gd{sub 0.1}O{sub 2−δ} (CGO) electrolyte were evaluated. LSFCu presented a p-type conductor behavior with maximum conductivity of 135 S cm{sup −1} at 275more » °C and showed a good stability with CGO electrolyte at high temperatures. This work confirmed that as prepared LSFCu has excellent microstructural characteristics and an electrical conductivity between 100 and 60 S cm{sup −1} in the 500–700 °C range which is sufficiently high to work as intermediate temperature Solid Oxide Fuel Cells (IT-SOFCs) cathode. However a change in the thermal expansion coefficient consistent with a small oxygen loss process may affect the electrode-electrolyte interface during fabrication and operation of a SOFC. - Graphical abstract: Nanocrystalline La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} was prepared by gel combustion and characterized by X-ray thermodiffraction and its conductivity was determined. The phase shows a reversible rhombohedral to cubic structural phase transition at 425 °C and a semiconductor to metallic phase transition at 275 °C. - Highlights: • LSFCu was prepared by gel combustion route using EDTA and NH{sub 4}NO{sub 3}. • LSFCu shows a reversible phase transition at 425 °C from R-3c to Pm-3m phase. • The sample has a maximum conductivity value of 135 S cm{sup −1} at 275 °C. • LSFCu shows a good chemical compatibility with CGO at 900 °C.« less

Expansion of Tabulated Scattering Matrices in Generalized Spherical Functions

NASA Technical Reports Server (NTRS)

Mishchenko, Michael I.; Geogdzhayev, Igor V.; Yang, Ping

2016-01-01

An efficient way to solve the vector radiative transfer equation for plane-parallel turbid media is to Fourier-decompose it in azimuth. This methodology is typically based on the analytical computation of the Fourier components of the phase matrix and is predicated on the knowledge of the coefficients appearing in the expansion of the normalized scattering matrix in generalized spherical functions. Quite often the expansion coefficients have to be determined from tabulated values of the scattering matrix obtained from measurements or calculated by solving the Maxwell equations. In such cases one needs an efficient and accurate computer procedure converting a tabulated scattering matrix into the corresponding set of expansion coefficients. This short communication summarizes the theoretical basis of this procedure and serves as the user guide to a simple public-domain FORTRAN program.

A conforming spectral collocation strategy for Stokes flow through a channel contraction

NASA Technical Reports Server (NTRS)

Phillips, Timothy N.; Karageorghis, Andreas

1989-01-01

A formula expressing the coefficients of an expansion of ultraspherical polynomials which has been differentiated an arbitrary number of times in terms of the coefficients of the original expansion is proved. The particular examples of Chebyshev and Legendre polynomials are considered.

Measurement of Linear Coefficient of Thermal Expansion and Temperature-Dependent Refractive Index Using Interferometric System

NASA Technical Reports Server (NTRS)

Corsetti, James A.; Green, William E.; Ellis, Jonathan D.; Schmidt, Greg R.; Moore, Duncan T.

2017-01-01

A system combining an interferometer with an environmental chamber for measuring both coefficient of thermal expansion (CTE) and temperature-dependent refractive index (dn/dT) simultaneously is presented. The operation and measurement results of this instrument are discussed.

Determination of coefficient of thermal expansion effects on Louisiana's PCC pavement design : research project capsule.

DOT National Transportation Integrated Search

2009-01-01

PROBLEM: The coefficient of thermal expansion (CTE) is a fundamental property of construction : materials such as steel and concrete. Although the CTE of steel is a well-defined : constant, the CTE of concrete varies substantially with aggregate type...

Determination of coefficient of thermal expansion effects on Louisiana's PCC pavement design : technical summary report.

DOT National Transportation Integrated Search

2011-12-01

The coefficient of thermal expansion (CTE) has been widely considered as a fundamental property of : Portland cement concrete (PCC) pavement but has never played an important role in the thickness design : procedure for PCC pavement until recently. I...

Assessment of Modeling Capability for Reproducing Storm Impacts on TEC

NASA Astrophysics Data System (ADS)

Shim, J. S.; Kuznetsova, M. M.; Rastaetter, L.; Bilitza, D.; Codrescu, M.; Coster, A. J.; Emery, B. A.; Foerster, M.; Foster, B.; Fuller-Rowell, T. J.; Huba, J. D.; Goncharenko, L. P.; Mannucci, A. J.; Namgaladze, A. A.; Pi, X.; Prokhorov, B. E.; Ridley, A. J.; Scherliess, L.; Schunk, R. W.; Sojka, J. J.; Zhu, L.

2014-12-01

During geomagnetic storm, the energy transfer from solar wind to magnetosphere-ionosphere system adversely affects the communication and navigation systems. Quantifying storm impacts on TEC (Total Electron Content) and assessment of modeling capability of reproducing storm impacts on TEC are of importance to specifying and forecasting space weather. In order to quantify storm impacts on TEC, we considered several parameters: TEC changes compared to quiet time (the day before storm), TEC difference between 24-hour intervals, and maximum increase/decrease during the storm. We investigated the spatial and temporal variations of the parameters during the 2006 AGU storm event (14-15 Dec. 2006) using ground-based GPS TEC measurements in the selected 5 degree eight longitude sectors. The latitudinal variations were also studied in two longitude sectors among the eight sectors where data coverage is relatively better. We obtained modeled TEC from various ionosphere/thermosphere (IT) models. The parameters from the models were compared with each other and with the observed values. We quantified performance of the models in reproducing the TEC variations during the storm using skill scores. This study has been supported by the Community Coordinated Modeling Center (CCMC) at the Goddard Space Flight Center. Model outputs and observational data used for the study will be permanently posted at the CCMC website (http://ccmc.gsfc.nasa.gov) for the space science communities to use.

Total Electron Content Retrieved From L-Band Radiometers and Potential Improvements to the IGS Model

NASA Astrophysics Data System (ADS)

Soldo, Yan; Hong, Liang; El-Nimri, Salem; Le Vine, David M.

2018-04-01

In recent years, several L-band microwave instruments have been launched into Earth's orbit to measure soil moisture and ocean salinity (e.g., Soil Moisture and Ocean Salinity [SMOS], Aquarius, and Soil Moisture Active/Passive [SMAP]). As the microwave signal travels through the ionosphere, the polarization vector rotates (Faraday rotation) and it is possible to estimate the total electron content (TEC) along the path by measuring this change. A comparison is presented of the TEC retrieved from Aquarius and SMAP over the ocean with the values provided by the IGS (International Global Navigation Satellite System Service (GNSS)). The TEC retrieved from Aquarius and SMAP measurements show good agreement with each other and, on a global scale, are in agreement with the TEC provided by the IGS. However, there are cases in which the TEC from the two satellite sensors are in good agreement with each other but differ significantly from the IGS TEC. The comparison suggests that the L-band instruments are a reliable source of TEC over the ocean and could be a valuable supplementary source of TEC values that could be assimilated in the IGS models, especially over the ocean, where GNSS ground stations are sparse.

Improving Sprint Performance in Soccer: Effectiveness of Jump Squat and Olympic Push Press Exercises

PubMed Central

Loturco, Irineu; Pereira, Lucas Adriano; Kobal, Ronaldo; Maldonado, Thiago; Piazzi, Alessandro Fromer; Bottino, Altamiro; Kitamura, Katia; Cal Abad, Cesar Cavinato; de Arruda, Miguel; Nakamura, Fabio Yuzo

2016-01-01

Training at the optimum power load (OPL) is an effective way to improve neuromuscular abilities of highly trained athletes. The purpose of this study was to test the effects of training using the jump squat (JS) or Olympic push-press (OPP) exercises at the OPL during a short-term preseason on speed-power related abilities in high-level under-20 soccer players. The players were divided into two training groups: JS group (JSG) and OPP group (OPPG). Both groups undertook 12 power-oriented sessions, using solely JS or OPP exercises. Pre- and post-6 weeks of training, athletes performed squat jump (SJ), countermovement jump (CMJ), sprinting speed (5, 10, 20 and 30 m), change of direction (COD) and speed tests. To calculate the transfer effect coefficient (TEC) between JS and MPP OPP and the speed in 5, 10, 20, and 30 m, the ratio between the result gain (effect size [ES]) in the untrained exercise and result gain in the trained exercise was calculated. Magnitude based inference and ES were used to test the meaningful effects. The TEC between JS and VEL 5, 10, 20, and 30 m ranged from 0.77 to 1.29, while the only TEC which could be calculated between OPP and VEL 5 was rather low (0.2). In addition, the training effects of JS on jumping and speed related abilities were superior (ES ranging from small to large) to those caused by OPP (trivial ES). To conclude, the JS exercise is superior to the OPP for improving speed-power abilities in elite young soccer players. PMID:27100085

Improving Sprint Performance in Soccer: Effectiveness of Jump Squat and Olympic Push Press Exercises.

PubMed

Loturco, Irineu; Pereira, Lucas Adriano; Kobal, Ronaldo; Maldonado, Thiago; Piazzi, Alessandro Fromer; Bottino, Altamiro; Kitamura, Katia; Cal Abad, Cesar Cavinato; de Arruda, Miguel; Nakamura, Fabio Yuzo

2016-01-01

Training at the optimum power load (OPL) is an effective way to improve neuromuscular abilities of highly trained athletes. The purpose of this study was to test the effects of training using the jump squat (JS) or Olympic push-press (OPP) exercises at the OPL during a short-term preseason on speed-power related abilities in high-level under-20 soccer players. The players were divided into two training groups: JS group (JSG) and OPP group (OPPG). Both groups undertook 12 power-oriented sessions, using solely JS or OPP exercises. Pre- and post-6 weeks of training, athletes performed squat jump (SJ), countermovement jump (CMJ), sprinting speed (5, 10, 20 and 30 m), change of direction (COD) and speed tests. To calculate the transfer effect coefficient (TEC) between JS and MPP OPP and the speed in 5, 10, 20, and 30 m, the ratio between the result gain (effect size [ES]) in the untrained exercise and result gain in the trained exercise was calculated. Magnitude based inference and ES were used to test the meaningful effects. The TEC between JS and VEL 5, 10, 20, and 30 m ranged from 0.77 to 1.29, while the only TEC which could be calculated between OPP and VEL 5 was rather low (0.2). In addition, the training effects of JS on jumping and speed related abilities were superior (ES ranging from small to large) to those caused by OPP (trivial ES). To conclude, the JS exercise is superior to the OPP for improving speed-power abilities in elite young soccer players.

Investigation of TEC Variations over Mid-Latitude during Quit and Disturbed Days of March 2015

NASA Astrophysics Data System (ADS)

Atıcı, Ramazan; Saǧır, Selçuk; Güzel, Esat

2016-07-01

The variations during 09-14-March-2015 quit days and 15-20 March 2015 disturbed days of Total Electron Content (TEC) values (provided by IONOLAB group) obtained by analysis the data from Ankara Global Position System (GPS) station of Turkey located at mid-latitude, IRI -2012 model the and IRI-PLUS model are investigated. Also, the variations of the geomagnetic, interplanetary and solar wind parameters are examined. As a result of investigations, TEC values from all three models are not change too much at quit days. Unlike, at the disturbed days, although IRI-2012 and IRI-PLUS TEC values are not change too much, a noticeable change in GPS-TEC values is occurred. GPS-TEC values are rapidly increased on 17-March 2015 to be severe magnetic storm (Dst = -124 nT). Then, on following days it was observed to significantly decrease. Thus, it is said that GPS-TEC values are more sensitive than IRI-2012 and IRI-PLUS models to variations occurred on disturbed days.

Short-time self-diffusion coefficient of a particle in a colloidal suspension bounded by a microchannel: Virial expansions and simulation

NASA Astrophysics Data System (ADS)

Kȩdzierski, Marcin; Wajnryb, Eligiusz

2011-10-01

Self-diffusion of colloidal particles confined to a cylindrical microchannel is considered theoretically and numerically. Virial expansion of the self-diffusion coefficient is performed. Two-body and three-body hydrodynamic interactions are evaluated with high precision using the multipole method. The multipole expansion algorithm is also used to perform numerical simulations of the self-diffusion coefficient, valid for all possible particle packing fractions. Comparison with earlier results shows that the widely used method of reflections is insufficient for calculations of hydrodynamic interactions even for small packing fractions and small particles radii, contrary to the prevalent opinion.

High temperature XRD of Cu2.1Zn0.9SnSe4

NASA Astrophysics Data System (ADS)

Chetty, Raju; Mallik, Ramesh Chandra

2014-04-01

Quaternary compound with chemical composition Cu2.1Zn0.9SnSe4 is prepared by solid state synthesis. High temperature XRD (X-Ray Diffraction) of this compound is used in studying the effect of temperature on lattice parameters and thermal expansion coefficients. Thermal expansion coefficient is one of the important quantities in evaluating the Grüneisen parameter which further useful in determining the lattice thermal conductivity of the material. The high temperature XRD of the material revealed that the lattice parameters as well as thermal expansion coefficients of the material increased with increase in temperature which confirms the presence of anharmonicty.

Space Weather Activities of IONOLAB Group: IONOLAB-TEC

NASA Astrophysics Data System (ADS)

Arikan, F.; Sezen, U.; Arikan, O.; Ugurlu, O.; Nayir, H.

2009-04-01

Space Weather (SW) is the concept of changing environmental conditions in outer space and affect Earth and its technological systems. SW is a consequence of the solar activities and the coupling of solar energy on Earth's atmosphere due to the Earth's magnetic field. The monitoring and prediction of SW has utmost importance for HF communication, Satellite communication, navigation and guidance systems, Low Earth Orbit (LEO) satellite systems, Space Craft exit and entry into the atmosphere. Ionosphere is the plasma layer of the atmosphere that is ionized by solar radiation and it is a key player of SW. Ionosphere is a temporally and spatially varying, dispersive, anisotropic and inhomogeneous medium that is characterized primarily by its electron density distribution. IONOLAB is a group of researchers of various disciplines, getting together to handle challenges of the Earth's ionosphere. The team has researchers from Hacettepe University and Bilkent University, Department of Electrical and Electronics Engineering and General Command of Mapping of Turkish Army. One of the most important contributions of IONOLAB group is the automated web-based computation service for Total Electron Content (TEC). TEC corresponds to the line integral of electron density distribution on a given path. TEC can also be expressed as the amount of free electrons within 1 m2 cross-sectional area of the cylinder on the ray path. Global Position System (GPS) provides a cost-effective medium for monitoring of ionosphere using the signals recorded by stationary GPS receivers in estimating TEC. IONOLAB group has developed IONOLAB-TEC for reliable and robust estimates for all latitudes and both calm and disturbed days by using RINEX, IONEX and satellite ephemeris data provided from the IGS centers. IONOLAB-TEC consists of a regularized signal estimation algorithm which combines signals from all GPS satellites for a given instant and a given receiver, for a desired time period or for 24 hours, with 30 s time resolution. IONOLAB-TEC values also include the receiver differential code bias (DCB) for each GPS station estimated uniquely by the IONOLAB-BIAS algorithm. The web based computation program is written in JAVA and it is provided both in Turkish and English at www.ionolab.org. The IONOLAB-TEC computation requires no installation or licensing on the client side. The application has a layered design. Developed components are modular that allows possible changes regarding the estimation method can be easily adapted. Same flexibility is also provided for the data access. Also, presentation of estimation data is architected to support different client types. Currently, the user can login to the IONOLAB-TEC web site and choose the desired location and dates on-line for TEC estimation. The carrier phase leveled TEC estimates of IONOLAB-TEC are provided for the chosen station/s and for the chosen day/s along with two-hourly GIM-TEC estimates of IGS centers. The output is provided in the user designated form either in graphs or an excel data sheet. The IONOLAB-TEC provides robust, reliable, and high resolution TEC estimates and provides a medium for comparison of the GIM-TEC values from the IGS centers.

Final Shape of Precision Molded Optics: Part 1 - Computational Approach, Material Definitions and the Effect of Lens Shape

DTIC Science & Technology

2012-05-15

subroutine by adding time-dependence to the thermal expansion coefficient. The user subroutine was written in Intel Visual Fortran that is compatible...temperature history dependent expansion and contraction, and the molds were modeled as elastic taking into account both mechanical and thermal strain. In...behavior was approximated by assuming the thermal coefficient of expansion to be a fourth order polynomial function of temperature. The authors

Voigt equivalent widths and spectral-bin single-line transmittances: Exact expansions and the MODTRAN®5 implementation

NASA Astrophysics Data System (ADS)

Berk, Alexander

2013-03-01

Exact expansions for Voigt line-shape total, line-tail and spectral bin equivalent widths and for Voigt finite spectral bin single-line transmittances have been derived in terms of optical depth dependent exponentially-scaled modified Bessel functions of integer order and optical depth independent Fourier integral coefficients. The series are convergent for the full range of Voigt line-shapes, from pure Doppler to pure Lorentzian. In the Lorentz limit, the expansion reduces to the Ladenburg and Reiche function for the total equivalent width. Analytic expressions are derived for the first 8 Fourier coefficients for pure Lorentzian lines, for pure Doppler lines and for Voigt lines with at most moderate Doppler dependence. A strong-line limit sum rule on the Fourier coefficients is enforced to define an additional Fourier coefficient and to optimize convergence of the truncated expansion. The moderate Doppler dependence scenario is applicable to and has been implemented in the MODTRAN5 atmospheric band model radiative transfer software. Finite-bin transmittances computed with the truncated expansions reduce transmittance residuals compared to the former Rodgers-Williams equivalent width based approach by ∼2 orders of magnitude.

Generalized approach to cooling charge-coupled devices using thermoelectric coolers

NASA Technical Reports Server (NTRS)

Petrick, S. Walter

1987-01-01

This paper is concerned with the use of thermoelectric coolers (TECs) to cool charge-coupled devices (CCDs). Heat inputs to the CCD from the warmer environment are identified, and generalized graphs are used to approximate the major heat inputs. A method of choosing and estimating the power consumption of the TEC is discussed. This method includes the use of TEC performance information supplied by the manufacturer and equations derived from this information. Parameters of the equations are tabulated to enable the reader to use the TEC performance equations for choosing and estimating the power needed for specific TEC applications.

Comparison of plasmaspheric electron content over sea and land using Jason-2 observations

NASA Astrophysics Data System (ADS)

Gulyaeva, Tamara; Cherniak, Iurii; Zakharenkova, Irina

2016-07-01

The Global Ionospheric Maps of Total Electron Content, GIM-TEC, may suffer from model assumptions, in particular, over the oceans where relatively few measurements are available due to a scarcity of ground-based GPS receivers network only on seashores and islands which involve more assumptions or interpolations imposed on GIM mapping techniques. The GPS-derived TEC represents the total electron content integrated through the ionosphere, iTEC, and the plasmasphere, pTEC. The sea/land differences in the F2 layer peak electron density, NmF2, and the peak height, hmF2, gathered with topside sounding data exhibit tilted ionosphere along the seashores with denser electron population at greater peak heights over the sea. Derivation of a sea/land proportion of total electron content from the new source of the satellite-based measurements would allow improve the mapping GIM-TEC products and their assimilation by the ionosphere-plasmasphere IRI-Plas model. In this context the data of Jason-2 mission provided through the NOAA CLASS Website (http://www.nsof.class.noaa.gov/saa/products/catSearch) present a unique database of pTEC measured through the plasmasphere over the Jason-2 orbit (1335 km) to GPS orbit (20,200 km) which become possible from GPS receivers placed onboard of Jason-2 with a zenith looking antenna that can be used not only for precise orbit determination (POD), but can also provide new data on the plasma density distribution in the plasmasphere. Special interest represents possibility of the potential increase of the data volume in two times due to the successful launch of the Jason-3 mission on 17 January 2016. The present study is focused on a comparison of plasmasphere electron content, pTEC, over the sea and land with a unique data base of the plasmasphere electron content, pTEC, using measurements onboard Jason-2 satellite during the solar minimum (2009) and solar maximum (2014). Slant TEC values were scaled to estimate vertical pTEC using a geometric factor derived by assuming the plasma occupies a spherical thin shell at 1400 km. The elevation angle cut-off was selected as 40 deg. Global distribution of POD TEC values has been presented in the form of pTEC maps, that were made by projecting the pTEC values on the Earth from the ionosphere pierce point at the shell altitude. Along the satellite pass for each epoch we have pTEC values for several linked LEO-GPS simultaneously, that can be binned and averaged into map cells. Results of pTEC maps analysis in terms of local time, season and solar activity are presented in the paper.

Review of variations in Mw < 7 earthquake motions on position and TEC (Mw = 6.5 Aegean Sea earthquake sample)

NASA Astrophysics Data System (ADS)

Yildirim, Omer; Inyurt, Samed; Mekik, Cetin

2016-02-01

Turkey is a country located in the middle latitude zone, where tectonic activity is intensive. Recently, an earthquake of magnitude 6.5 Mw occurred offshore in the Aegean Sea on 24 May 2014 at 09:25 UTC, which lasted about 40 s. The earthquake was also felt in Greece, Romania, and Bulgaria in addition to Turkey. In recent years, ionospheric anomaly detection studies have been carried out because of seismicity with total electron content (TEC) computed from the global navigation satellite system's (GNSS) signal delays and several interesting findings have been published. In this study, both TEC and positional variations have been examined separately following a moderate size earthquake in the Aegean Sea. The correlation of the aforementioned ionospheric variation with the positional variation has also been investigated. For this purpose, a total of 15 stations was used, including four continuously operating reference stations in Turkey (CORS-TR) and stations in the seismic zone (AYVL, CANA, IPSA, and YENC), as well as international GNSS service (IGS) and European reference frame permanent network (EPN) stations. The ionospheric and positional variations of the AYVL, CANA, IPSA, and YENC stations were examined using Bernese v5.0 software. When the precise point positioning TEC (PPP-TEC) values were examined, it was observed that the TEC values were approximately 4 TECU (total electron content unit) above the upper-limit TEC value at four stations located in Turkey, 3 days before the earthquake at 08:00 and 10:00 UTC. At the same stations, on the day before the earthquake at 06:00, 08:00, and 10:00 UTC, the TEC values were approximately 5 TECU below the lower-limit TEC value. The global ionosphere model TEC (GIM-TEC) values published by the Centre for Orbit Determination in Europe (CODE) were also examined. Three days before the earthquake, at all stations, it was observed that the TEC values in the time period between 08:00 and 10:00 UTC were approximately 2 TECU above the upper-limit TEC value; 1 day before the earthquake at 06:00, 08:00, and 10:00 UTC, the TEC values were approximately 4 TECU below the lower-limit TEC value. Again, by using the same 15 stations, positional variation investigation for before and after the earthquake was undertaken for the AYVL, CANA, IPSA, and YENC stations. As a result of the conducted analysis, positional displacements were seen before and after the earthquake at the CANA station, which is the nearest station to the earthquake centre. Before and after the earthquake, positional displacements were observed as 10 and 3 cm respectively.

Effect of moisture content on the coefficient of thermal expansion of concrete.

DOT National Transportation Integrated Search

2007-09-01

The purpose of this report is to discuss a study conducted on twenty separate mix designs of concrete and the effects of : the aggregate type, moisture content, and temperature on the coefficient of thermal expansion(CTE). These results are to be use...

Analysis of ionosphere variability over low-latitude GNSS stations during 24th solar maximum period

NASA Astrophysics Data System (ADS)

Venkata Ratnam, D.; Sivavaraprasad, G.; Latha Devi, N. S. M. P.

2017-07-01

Global Positioning System (GPS) is a remote sensing tool of space weather and ionospheric variations. However, the interplanetary space-dependent drifts in the ionospheric irregularities cause predominant ranging errors in the GPS signals. The dynamic variability of the low-latitude ionosphere is an imperative threat to the satellite-based radio communication and navigation ranging systems. The study of temporal and spatial variations in the ionosphere has triggered new investigations in modelling, nowcasting and forecasting the ionospheric variations. Hence, in this paper, the dynamism in the day-to-day, month-to-month and seasonal variability of the ionospheric Total Electron Content (TEC) has been explored during the solar maximum period, January-December 2013, of the 24th solar cycle. The spatial and temporal variations of the ionosphere are analysed using the TEC values derived from three Indian low-latitude GPS stations, namely, Bengaluru, Guntur and Hyderabad, separated by 13-18° in latitude and 77-81° in longitude. The observed regional GPS-TEC variations are compared with the predicted TEC values of the International Reference Ionosphere (IRI-2012 and 2007) models. Ionospheric parameters such as Vertical TEC (VTEC), relative TEC deviation index and monthly variations in the grand-mean of ionosphere TEC and TEC intensity, along with the upper and lower quartiles, are adopted to investigate the ionosphere TEC variability during quiet and disturbed days. The maximum ionospheric TEC variability is found during March and September equinoxes, followed by December solstice while the minimum variability is observed during June solstice. IRI models are in reasonable agreement with GPS TEC but are overestimating during dawn hours (01:00-06:00 LT) as compared to the dusk hours. Higher percentage deviations are observed during equinoctial months than summer over EIA stations, Guntur and Hyderabad. GPS TEC variations are overestimated during dawn hours for all the seasons over Bengaluru. It has also been observed that positive storm effect (enhancement of TEC) is observed during the main phase of the March storm, 2013 (March 16-18, 2013) while both positive and negative storm effects (depletion of TEC) are registered during the main phase of the June storm, 2013 (June 28-30, 2013) at Bengaluru and Guntur, respectively. IRI-2012 model has slightly large discrepancies with the GPS-VTEC compared with the IRI-2007 model during the June storm, 2013 over Guntur station. This analysis highlights the importance of upgrading the IRI models due to their discrepancies during quiet and disturbed states of the ionosphere and developing an early warning forecast system to alert about ionosphere variability.

Determination of Ionospheric Total Electron Content Derived from Gnss Measurements

NASA Astrophysics Data System (ADS)

Inyurt, S.; Mekik, C.; Yildirim, O.

2014-12-01

Global Navigation Satellite System (GNSS) has been used in numerous fields especially related to satellite- based radio navigation system for a long time. Ionosphere, one of the upper atmosphere layers ranges from 60 km to 1500 km, is a dispersive medium and it includes a number of free electrons and ions. The ionization is mainly subject to the sun and its activity. Ionospheric activity depends also on seasonal, diurnal variations and geographical location. Total Electron Content (TEC), which is also called Slant Total Electron Content (STEC), is a parameter that changes according to ionospheric conditions and has highly variable structure. Furthermore, Vertical TEC (VTEC) can be explained as TEC value in the direction of zenith. Thanks to VTEC, TEC values can be modelled. TEC is measured in units of TECU and 1TECU= 1016 electrons/m2. Ionospheric modelling has a great importance for improving the accuracies of positioning and understanding the ionosphere. Thus, various models have been developed to detect TEC value in the last years. Single Layer Model (SLM) which provides determining TEC value and GPS positioning in the ionosphere accurately is one of the most commonly used models. SLM assumes that all free electrons are concentrated in a shell of infinitesimal thickness. In this paper SLM model was used to derive TEC values by means of Bernese 5.0 program developed by the University of Bern, Sweden. In this study, we have used regional ionosphere model to derive TEC value. First of all, GPS data have been collected from 10 stations in Turkey and 13 IGS stations for 7 days from 06.03.2010 to 12.03.2010. Then, Regional Ionosphere Model (RIM) is created with the reference of the GPS data. At the end of the process, the result files are stored as IONEX format. TEC results for those days are obtained with two hours interval. TEC variation related to the research area ranges from nearly 6 TECU to approximately 20 TECU. The obtained results show that TEC values start increasing until mid-days and reach peak value at 12:00 UT. After 12:00 UT it begins decreasing gradually towards night because of recombination of the ions. As a result, SLM is an effective model for mapping TEC values and determination of TEC variation can be used to identify many studies such as precursor of earthquakes, volcanic eruptions and launching site determination etc.

GPS TEC near the crest of the EIA at 95°E during the ascending half of solar cycle 24 and comparison with IRI simulations

NASA Astrophysics Data System (ADS)

Bhuyan, Pradip Kumar; Hazarika, Rumajyoti

2013-10-01

Total electron content (TEC) data obtained from GPS dual frequency measurements during the ascending half of the solar cycle 24 from 2009 to 2012 over Dibrugarh (27.5°N, 94.9°E; 17.6°N MLAT) have been used to study the diurnal, seasonal, annual and solar cycle variation of TEC. The measurements reported here are for the first time from the location situated at the poleward edge of the northern equatorial ionization anomaly (EIA) and within the peak region of the longitudinal wave number 4 (WN4) structure in EIA crest TEC. TEC exhibits a minimum around 0600 LT and diurnal maximum around 1300-1600 LT. In the low and moderate solar activity years 2009-2010 and 2010-2011, average daytime (1000-1600 LT) TEC in summer was higher (25.4 and 36.6 TECU) compared to that in winter (21.5 and 26.1 TECU). However, at the peak of the solar cycle in 2011-2012, reversal in the level of ionization between winter and summer takes place and winter TEC becomes higher (50.6 TECU) than that in summer (45.0 TECU). Further, TEC in spring (34.1, 49.9 and 63.3 TECU respectively in 2009-10, 2010-11 and 2011-12) is higher than that in autumn (24.2, 32.3 and 51.9 TECU respectively) thus showing equinoctial asymmetry in all the years of observation. The winter anomaly in high solar activity years and equinoctial asymmetry all throughout may be largely attributed to changes in the thermospheric O/N2 density ratio. A winter to summer delay of ˜1 h in the time of occurrence of the diurnal maximum has also been observed. Daytime maximum TEC bears a nonlinear relationship with F10.7 cm solar flux. TEC increases linearly with F10.7 cm solar flux initially up to about 140 sfu (1 sfu = 10-22 W m-2 Hz-1) after which it tends to saturate. On the contrary, TEC increases linearly with solar EUV flux (photons cm-2 s-1, 0.5-50 nm) during the same period. TEC predicted by the IRI 2012 are lower than the measured TEC for nearly 90% of the time.

Optimize out-of-core thermionic energy conversion for nuclear electric propulsion

NASA Technical Reports Server (NTRS)

Morris, J. F.

1977-01-01

Current designs for out of core thermionic energy conversion (TEC) to power nuclear electric propulsion (NEP) were evaluated. Approaches to improve out of core TEC are emphasized and probabilities for success are indicated. TEC gains are available with higher emitter temperatures and greater power densities. Good potentialities for accommodating external high temperature, high power density TEC with heat pipe cooled reactors exist.

Imperfect coupling between northern and southern ionospheres: asymmetry in TEC anomalies before earthquakes

NASA Astrophysics Data System (ADS)

Jhuang, Hau-Kun; Ho, Yi-Ying; Lee, Lou-Chuang

2016-04-01

The northern ionosphere is coupled to the conjugate southern ionosphere through the highly conducting geomagenetic field lines. The coupling is very strong or "perfect" if the geomagnetic field lines are equipotential (the parallel electric field E||=0) and hence the perpendicular electric field (E⊥) at the conjugate sites of both ionospheres are equal. The coupling is "imperfect" if some of the geomagnetic field lines are non-equipotential (E||≠0). The field-aligned electric field E|| can be associated with electron inertia, pressure gradient and collisions appearing in the form of double layer, kinetic Alfvén waves and finite field-aligned conductivity σ||. We use the Global Ionospheric Maps (GIM) data to examine the conjugate effect of total electron content (TEC) for six significant earthquakes. The anomalous (ΔTEC)source in the source ionosphere and (ΔTEC)conjugate in the conjugate ionosphere are obtained for 85 events before the six earthquakes. The ΔTEC ratio β = (ΔTEC)conjugate / (ΔTEC)source is calculated for each anomaly. For a "perfect" coupling, β=1. There are 85 anomalous events before the six significant earthquakes, with 62 events occurring in the daytime (07-18 LT) and 23 events in the nighttime (19-06 LT). The average value of daytime (07-18 LT) TEC variations in the source ionosphere is |ΔTEC|source =20.13 TECu, while the average value in the nighttime (19-06 LT) ionosphere is |ΔTEC|source=14.43 TECu. The value of ΔTEC ratio β ranges from 0.05 (very weak coupling) to 0.98 (nearly perfect coupling) with an average of 0.52. There are 14 strong coupling cases with β ≥0.8, which take place from 11 LT to 19 LT. The daytime (07-18 LT) β average value is 0.57 and the nighttime (19-06 LT) β average is 0.37. The south-north ionosphere coupling is stronger (weaker) in the daytime (nighttime).

Validation of foF2 and TEC Modeling During Geomagnetic Disturbed Times: Preliminary Outcomes of International Forum for Space Weather Modeling Capabilities Assessment

NASA Astrophysics Data System (ADS)

Shim, J. S.; Tsagouri, I.; Goncharenko, L. P.; Kuznetsova, M. M.

2017-12-01

To address challenges of assessment of space weather modeling capabilities, the CCMC (Community Coordinated Modeling Center) is leading the newly established "International Forum for Space Weather Modeling Capabilities Assessment." This presentation will focus on preliminary outcomes of the International Forum on validation of modeled foF2 and TEC during geomagnetic storms. We investigate the ionospheric response to 2013 Mar. geomagnetic storm event using ionosonde and GPS TEC observations in North American and European sectors. To quantify storm impacts on foF2 and TEC, we first quantify quiet-time variations of foF2 and TEC (e.g., the median and the average of the five quietest days for the 30 days during quiet conditions). It appears that the quiet time variation of foF2 and TEC are about 10% and 20-30%, respectively. Therefore, to quantify storm impact, we focus on foF2 and TEC changes during the storm main phase larger than 20% and 50%, respectively, compared to 30-day median. We find that in European sector, both foF2 and TEC response to the storm are mainly positive phase with foF2 increase of up to 100% and TEC increase of 150%. In North America sector, however, foF2 shows negative effects (up to about 50% decrease), while TEC shows positive response (the largest increase is about 200%). To assess modeling capability of reproducing the changes of foF2 and TEC due to the storm, we use various model simulations, which are obtained from empirical, physics-based, and data assimilation models. The performance of each model depends on the selected metrics, therefore, only one metrics is not enough to evaluate the models' predictive capabilities in capturing the storm impact. The performance of the model also varies with latitude and longitude.

Passive athermalization: required accuracy of the thermo-optical coefficients

NASA Astrophysics Data System (ADS)

Rogers, John R.

2014-12-01

Passive athermalization requires that the materials (both optical and mechanical) and optical powers be carefully selected in order for the image to stay adequately in focus at the plane of the detector as the various materials change in physical dimension and refractive index. For a large operational temperature range, the accuracy of the thermo-optical coefficients (dn/dT coefficients and the Coefficients of Thermal Expansion) can limit the performance of the final system. Based on an example lens designed to be passively athermalized over a 200°C temperature range, and using a Monte Carlo analysis technique, we examine the accuracy to which the expansion coefficients and dn/dT coefficients of the system must be known.

Variations of total electron content in the equatorial anomaly region in Thailand

NASA Astrophysics Data System (ADS)

Chowdhary, V. Rajesh; Tripathi, N. K.; Arunpold, Sanit; Raju, Durairaju Kumaran

2015-01-01

This paper presents the first results of total electron content (TEC), derived by analyzing dual frequency Novatel GSV4004 GPS receiver's data which were installed by the SCINDA project, located at the Asian Institute of Technology, Bangkok (AITB, 14.079N, 100.612E) and Chiang Mai University, Chiang Mai (CHGM, 18.480N, 98.570E) with magnetic latitude of 4.13°N and 8.61°N respectively in Thailand, for the year 2011. These two stations are separated by 657 km in the equatorial anomaly region. The highest TEC values occurred from 1500 to 1900 LT throughout the study period. The diurnal, monthly and seasonal GPS-TEC have been plotted and analyzed. The diurnal peaks in GPS-TEC is observed to be maximum during equinoctial months (March, April, September and October) and minimum in solstice months (January, February, June, July and December). These high TEC values have been attributed to the solar extreme ultra-violet ionization coupled with the upward vertical E × B drift. A comparison of both station's TEC has been carried out and found that CHGM station experiences higher values of TEC than AITB station, due to formation of ionization crest over the CHGM station. Also, TEC values have shown increasing trend due to approaching solar maximum. These results from both stations were also compared with the TEC derived from the International Reference Ionosphere's (IRI) recently released, IRI-2012 model. Results have shown positive correlation with IRI-2012 model. Although, IRI-model does not show any response to geomagnetic activity, the IRI model normally remains smooth and underestimates TEC during a storm.

Space shuttle SRM plume expansion sensitivity analysis. [flow characteristics of exhaust gases from solid propellant rocket engines

NASA Technical Reports Server (NTRS)

Smith, S. D.; Tevepaugh, J. A.; Penny, M. M.

1975-01-01

The exhaust plumes of the space shuttle solid rocket motors can have a significant effect on the base pressure and base drag of the shuttle vehicle. A parametric analysis was conducted to assess the sensitivity of the initial plume expansion angle of analytical solid rocket motor flow fields to various analytical input parameters and operating conditions. The results of the analysis are presented and conclusions reached regarding the sensitivity of the initial plume expansion angle to each parameter investigated. Operating conditions parametrically varied were chamber pressure, nozzle inlet angle, nozzle throat radius of curvature ratio and propellant particle loading. Empirical particle parameters investigated were mean size, local drag coefficient and local heat transfer coefficient. Sensitivity of the initial plume expansion angle to gas thermochemistry model and local drag coefficient model assumptions were determined.

Isolated tumor endothelial cells maintain specific character during long-term culture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuda, Kohei; Oral Pathology and Biology, Hokkaido University Graduate School of Dental Medicine, N13 W7, Kita-ku, Sapporo 060-8586; Oral and Maxillofacial Surgery, Hokkaido University Graduate School of Dental Medicine, N13 W7, Kita-ku, Sapporo 060-8586

Tumor angiogenesis is necessary for solid tumor progression and metastasis. Increasing evidence indicates that tumor endothelial cells (TECs) are more relevant to the study of tumor angiogenesis than normal endothelial cells (NECs) because their morphologies and gene expression are different from NECs. However, it is challenging to isolate and culture large numbers of pure ECs from tumor tissue since the percentage of ECs is only about 1-2% and tumor cells and fibroblasts easily overgrow them. In addition, there has been concern that isolated TECs may lose their special phenotype once they are dissociated from tumor cells. In this study, wemore » have successfully purified murine TECs from four different human tumor xenografts and NECs from murine dermal tissue. Isolated ECs expressed endothelial markers, such as CD31, VE-cadherin (CD144), and endoglin (CD105), for more than 3 months after isolation. TECs maintained tumor endothelial-specific markers, such as tumor endothelial marker 8 (TEM8) and aminopeptidase N (APN), as in tumor blood vessels in vivo. In addition, TECs were more proliferative and motile than NECs. TECs showed a higher response to VEGF and higher expression of VEGF receptors-1 and -2 than NECs did. Stem cell antigen-1 was up-regulated in all four TECs, suggesting that they have a kind of stemness. Cultured TECs maintain distinct biological differences from NECs as in vivo. In conclusion, it was suggested that TECs are relevant material for tumor angiogenesis research.« less

TEC Variations Over Korean Peninsula During Magnetic Storm

NASA Astrophysics Data System (ADS)

Ji, E.-Y.; Choi, B.-K.; Kim, K.-H.; Lee, D.-H.; Cho, J.-H.; Chung, J.-K.; Park, J.-U.

2008-03-01

By analyzing the observations from a number of ground- and space-based instruments, including ionosonde, magnetometers, and ACE interplanetary data, we examine the response of the ionospheric TEC over Korea during 2003 magnetic storms. We found that the variation of vertical TEC is correlated with the southward turning of the interplanetary magnetic field B_z. It is suggested that the electric fields produced by the dynamo process in the high-latitude region and the prompt penetration in the low-latitude region are responsible for TEC increases. During the June 16 event, dayside TEC values increase more than 15%. And the ionospheric F2-layer peak height (hmF2) was ˜300km higher and the vertical E×B drift (estimated from ground-based magnetometer equatorial electrojet delta H) showed downward drift, which may be due to the ionospheric disturbance dynamo electric field produced by the large amount of energy dissipation into high-latitude regions. In contr! ast, during November 20 event, the nightside TEC increases may be due to the prompt penetration westward electric field. The ionospheric F2-layer peak height was below 200km and the vertical E×B drift showed downward drift. Also, a strong correlation is observed between enhanced vertical TEC and enhanced interplanetary electric field. It is shown that, even though TEC increases are caused by the different processes, the electric field disturbances in the ionosphere play an important role in the variation of TEC over Korea.

Thermal expansion behavior study of Co nanowire array with in situ x-ray diffraction and x-ray absorption fine structure techniques

NASA Astrophysics Data System (ADS)

Mo, Guang; Cai, Quan; Jiang, Longsheng; Wang, Wei; Zhang, Kunhao; Cheng, Weidong; Xing, Xueqing; Chen, Zhongjun; Wu, Zhonghua

2008-10-01

In situ x-ray diffraction and x-ray absorption fine structure techniques were used to study the structural change of ordered Co nanowire array with temperature. The results show that the Co nanowires are polycrystalline with hexagonal close packed structure without phase change up until 700 °C. A nonlinear thermal expansion behavior has been found and can be well described by a quadratic equation with the first-order thermal expansion coefficient of 4.3×10-6/°C and the second-order thermal expansion coefficient of 5.9×10-9/°C. The mechanism of this nonlinear thermal expansion behavior is discussed.

Novel quantum criticality in CeRu2Si2 near absolute zero observed by thermal expansion and magnetostriction.

PubMed

Yoshida, J; Abe, S; Takahashi, D; Segawa, Y; Komai, Y; Tsujii, H; Matsumoto, K; Suzuki, H; Onuki, Y

2008-12-19

We report linear thermal expansion and magnetostriction measurements for CeRu2Si2 in magnetic fields up to 52.6 mT and at temperatures down to 1 mK. At high temperatures, this compound showed Landau-Fermi-liquid behavior: The linear thermal expansion coefficient and the magnetostriction coefficient were proportional to the temperature and magnetic field, respectively. In contrast, a pronounced non-Fermi-liquid effect was found below 50 mK. The negative contribution of thermal expansion and magnetostriction suggests the existence of an additional quantum critical point.

Investigation of Thermal Expansion of a Glass Ceramic Material with an Extra-Low Thermal Linear Expansion Coefficient

NASA Astrophysics Data System (ADS)

Kompan, T. A.; Korenev, A. S.; Lukin, A. Ya.

2008-10-01

The artificial material sitall CO-115M was developed purposely as a material with an extra-low thermal expansion. The controlled crystallization of an aluminosilicate glass melt leads to the formation of a mixture of β-spodumen, β-eucryptite, and β-silica anisotropic microcrystals in a matrix of residual glass. Due to the small size of the microcrystals, the material is homogeneous and transparent. Specific lattice anharmonism of these microcrystal materials results in close to zero average thermal linear expansion coefficient (TLEC) of the sitall material. The thermal expansion coefficient of this material was measured using an interferometric method in line with the classical approach of Fizeau. To obtain the highest accuracy, the registration of light intensity of the total interference field was used. Then, the parameters of the interference pattern were calculated. Due to the large amount of information in the interference pattern, the error of the calculated fringe position was less than the size of a pixel of the optical registration system. The thermal expansion coefficient of the sitall CO-115M and its temperature dependence were measured. The TLEC value of about 3 × 10-8 K-1 to 5 × 10-8 K-1 in the temperature interval from -20 °C to +60 °C was obtained. A special investigation was carried out to show the homogeneity of the material.

Real-Time Detection of Tsunami Ionospheric Disturbances with a Stand-Alone GNSS Receiver: A Preliminary Feasibility Demonstration

NASA Astrophysics Data System (ADS)

Savastano, Giorgio; Komjathy, Attila; Verkhoglyadova, Olga; Mazzoni, Augusto; Crespi, Mattia; Wei, Yong; Mannucci, Anthony J.

2017-04-01

It is well known that tsunamis can produce gravity waves that propagate up to the ionosphere generating disturbed electron densities in the E and F regions. These ionospheric disturbances can be studied in detail using ionospheric total electron content (TEC) measurements collected by continuously operating ground-based receivers from the Global Navigation Satellite Systems (GNSS). Here, we present results using a new approach, named VARION (Variometric Approach for Real-Time Ionosphere Observation), and estimate slant TEC (sTEC) variations in a real-time scenario. Using the VARION algorithm we compute TEC variations at 56 GPS receivers in Hawaii as induced by the 2012 Haida Gwaii tsunami event. We observe TEC perturbations with amplitudes of up to 0.25 TEC units and traveling ionospheric perturbations (TIDs) moving away from the earthquake epicenter at an approximate speed of 316 m/s. We perform a wavelet analysis to analyze localized variations of power in the TEC time series and we find perturbation periods consistent with a tsunami typical deep ocean period. Finally, we present comparisons with the real-time tsunami MOST (Method of Splitting Tsunami) model produced by the NOAA Center for Tsunami Research and we observe variations in TEC that correlate in time and space with the tsunami waves.

Latitudinal and Seasonal Investigations of Storm-Time TEC Variation

NASA Astrophysics Data System (ADS)

Adimula, I. A.; Oladipo, O. A.; Adebiyi, S. J.

2016-07-01

The ionosphere responds markedly and unpredictably to varying magnetospheric energy inputs caused by solar disturbances on the geospace. Knowledge of the impact of the space weather events on the ionosphere is important to assess the environmental effect on the operations of ground- and space-based technologies. Thus, global positioning system (GPS) measurements from the international GNSS service (IGS) database were used to investigate the ionospheric response to 56 geomagnetic storm events at six different latitudes comprising the northern and southern hemispheres in the Afro-European sector. Statistical distributions of total electron content (TEC) response show that during the main phase of the storms, enhancement of TEC is more pronounced in most of the seasons, regardless of the latitude and hemisphere. However, a strong seasonal dependence appears in the TEC response during the recovery phase. Depletion of TEC is majorly observed at the high latitude stations, and its appearance at lower latitudes is seasonally dependent. In summer hemisphere, the depletion of TEC is more pronounced in nearly all the latitudinal bands. In winter hemisphere, enhancement as well as depletion of TEC is observed over the high latitude, while enhancement is majorly observed over the mid and low latitudes. In equinoxes, the storm-time TEC distribution shows a fairly consistent characteristic with the summer distribution, particularly in the northern hemisphere.

Real-Time Detection of Tsunami Ionospheric Disturbances with a Stand-Alone GNSS Receiver: A Preliminary Feasibility Demonstration

PubMed Central

Savastano, Giorgio; Komjathy, Attila; Verkhoglyadova, Olga; Mazzoni, Augusto; Crespi, Mattia; Wei, Yong; Mannucci, Anthony J.

2017-01-01

It is well known that tsunamis can produce gravity waves that propagate up to the ionosphere generating disturbed electron densities in the E and F regions. These ionospheric disturbances can be studied in detail using ionospheric total electron content (TEC) measurements collected by continuously operating ground-based receivers from the Global Navigation Satellite Systems (GNSS). Here, we present results using a new approach, named VARION (Variometric Approach for Real-Time Ionosphere Observation), and estimate slant TEC (sTEC) variations in a real-time scenario. Using the VARION algorithm we compute TEC variations at 56 GPS receivers in Hawaii as induced by the 2012 Haida Gwaii tsunami event. We observe TEC perturbations with amplitudes of up to 0.25 TEC units and traveling ionospheric perturbations (TIDs) moving away from the earthquake epicenter at an approximate speed of 316 m/s. We perform a wavelet analysis to analyze localized variations of power in the TEC time series and we find perturbation periods consistent with a tsunami typical deep ocean period. Finally, we present comparisons with the real-time tsunami MOST (Method of Splitting Tsunami) model produced by the NOAA Center for Tsunami Research and we observe variations in TEC that correlate in time and space with the tsunami waves. PMID:28429754

Statistical Analysis of TEC Anomalies Prior to M6.0+ Earthquakes During 2003-2014

NASA Astrophysics Data System (ADS)

Zhu, Fuying; Su, Fanfan; Lin, Jian

2018-04-01

There are many studies on the anomalous variations of the ionospheric TEC prior to large earthquakes. However, whether or not the morphological characteristics of the TEC anomalies in the daytime and at night are different is rarely studied. In the present paper, based on the total electron content (TEC) data from the global ionosphere map (GIM), we carry out a statistical survey on the spatial-temporal distribution of TEC anomalies before 1339 global M6.0+ earthquakes during 2003-2014. After excluding the interference of geomagnetic disturbance, the temporal and spatial distributions of ionospheric TEC anomalies prior to the earthquakes in the daytime and at night are investigated and compared. Except that the nighttime occurrence rates of the pre-earthquake ionospheric anomalies (PEIAs) are higher than those in the daytime, our analysis has not found any statistically significant difference in the spatial-temporal distribution of PEIAs in the daytime and at night. Moreover, the occurrence rates of pre-earthquake ionospheric TEC both positive anomalies and negative anomalies at night tend to increase slightly with the earthquake magnitude. Thus, we suggest that monitoring the ionospheric TEC changes at night might be a clue to reveal the relation between ionospheric disturbances and seismic activities.

Real-Time Detection of Tsunami Ionospheric Disturbances with a Stand-Alone GNSS Receiver: A Preliminary Feasibility Demonstration.

PubMed

Savastano, Giorgio; Komjathy, Attila; Verkhoglyadova, Olga; Mazzoni, Augusto; Crespi, Mattia; Wei, Yong; Mannucci, Anthony J

2017-04-21

It is well known that tsunamis can produce gravity waves that propagate up to the ionosphere generating disturbed electron densities in the E and F regions. These ionospheric disturbances can be studied in detail using ionospheric total electron content (TEC) measurements collected by continuously operating ground-based receivers from the Global Navigation Satellite Systems (GNSS). Here, we present results using a new approach, named VARION (Variometric Approach for Real-Time Ionosphere Observation), and estimate slant TEC (sTEC) variations in a real-time scenario. Using the VARION algorithm we compute TEC variations at 56 GPS receivers in Hawaii as induced by the 2012 Haida Gwaii tsunami event. We observe TEC perturbations with amplitudes of up to 0.25 TEC units and traveling ionospheric perturbations (TIDs) moving away from the earthquake epicenter at an approximate speed of 316 m/s. We perform a wavelet analysis to analyze localized variations of power in the TEC time series and we find perturbation periods consistent with a tsunami typical deep ocean period. Finally, we present comparisons with the real-time tsunami MOST (Method of Splitting Tsunami) model produced by the NOAA Center for Tsunami Research and we observe variations in TEC that correlate in time and space with the tsunami waves.

The NASA thermionic-conversion (TEC-ART) program

NASA Technical Reports Server (NTRS)

Morris, J. F.

1977-01-01

The current emphasis is on out-of-core thermionic conversion (TEC). The additional degrees of freedom offer new potentialities, but high-temperature material effects determine the level and lifetime of TEC performance: New electrodes not only raise power outputs but also maintain them regardless of emitter-vapor deposition on collectors. In addition, effective electrodes serve compatibly with hot-shell alloys. Space TEC withstands external and internal high-temperature vaporization problems, and terrestrial TEC tolerates hot corrosive atmospheres outside and near-vacuum inside. Finally, reduction of losses between converter electrodes is essential even though rather demanding geometries appear to be required for some modes of enhanced operation.

Joint Analysis of the Full AzTEC Sub-Millimeter Galaxy Data Set

NASA Astrophysics Data System (ADS)

Wilson, Grant; Ade, P.; Aretxaga, I.; Austermann, J.; Bock, J.; Hughes, D.; Kang, Y.; Kim, S.; Lowenthal, J.; Mauskopf, P.; Perera, T.; Scott, K.; Yun, M.

2006-12-01

Using the new AzTEC millimeter-wave camera on the James Clerk Maxwell Telescope (JCMT) in winter 2005/06, we conducted several surveys of the submm galaxy (SMG) population. The AzTEC 1.1 millimeter surveys include both blank-fields (no significant bias or foreground contamination) and regions of known over-densities, and are both large (100-1000 sq. arcmin.) and sensitive ( 1 mJy rms). The unique power of the AzTEC data set lies not only in the size and depth of the individual fields, but in the combined surveyed area that totals over 1 square degree. Hundreds of new sub-millimeter sources have been detected. A joint analysis of all AzTEC surveys will provide important new constraints on many characteristics of the SMG population, including number counts, clustering, and variance. In particular, the large area of the full AzTEC data set provides the first significant measurement of the brightest and most rare of the SMG population. Herein we present the initial combined results and explore the future potential of a complete joint analysis of the full AzTEC SMG data set.

Comparing GNSS Total Electron Content of Sonmiani, Pakistan with NeQuick-2 & IRI-2012 during July 2014 - June 2015

NASA Astrophysics Data System (ADS)

Ayyaz Ameen, Muhammad; Ghafoor, Memoona; Weimin, Zhen

2016-07-01

Total Electron Content (TEC) data acquired by an in-house fabricated GNSS receiver (by China Research Institute of Radiowave Propagation, CRIRP) working with NovaTel antenna installed at Sonmiani (geograph. 24.95°N, 67.14°E) is being reported for the first time. The period under study is one year (July 2014 to June 2015) which is based upon the hourly instantaneous TEC values of 120 days (10 international quietest days, IQD per month). The data confirms the annual variation of TEC at the station which lies at the northern crest of equatorial ionization anomaly (EIA) region. GNSS TEC values in general are then compared with NeQuick-2 and IRI-2012. Model comparison shows that NeQuick-2 predicts the TEC with greater confidence whereas IRI-2012 shows larger discrepancies with respect to the data. Seasonal variation shows the highest TEC values during equinox months. December solstice values of TEC are higher than the June solstice values, this confirms that the seasonal anomaly is dominating in the region during the course of study.

GNSS Observations of Ionospheric Variations During the 21 August 2017 Solar Eclipse

NASA Astrophysics Data System (ADS)

Coster, Anthea J.; Goncharenko, Larisa; Zhang, Shun-Rong; Erickson, Philip J.; Rideout, William; Vierinen, Juha

2017-12-01

On 21 August 2017, during daytime hours, a total solar eclipse with a narrow ˜160 km wide umbral shadow occurred across the continental United States. Totality was observed from the Oregon coast at ˜9:15 local standard time (LST) (17:20 UT) to the South Carolina coast at ˜13:27 LST (18:47 UT). A dense network of Global Navigation Satellite Systems (GNSS) receivers was utilized to produce total electron content (TEC) and differential TEC. These data were analyzed for the latitudinal and longitudinal response of the TEC and for the presence of traveling ionospheric disturbances (TIDs) during eclipse passage. A significant TEC depletion, in some cases greater than 60%, was observed associated with the eclipse shadow, exceeding initial model predictions of 35%. Evidence of enhanced large-scale TID activity was detected over the United States prior to and following the large TEC depletion observed near the time of totality. Signatures of enhanced TEC structures were observed over the Rocky Mountain chain during the main period of TEC depletion.

Near-Real Time Monitoring of TEC Over Japan at NICT (RWC Tokyo OF ISES)

NASA Astrophysics Data System (ADS)

Miyake, W.; Jin, H.

2010-05-01

The world wide use of global navigation satellite systems such as GPS offers unique opportunities for a permanent monitoring of the total electron content (TEC) of the ionosphere. We have developed a system of the rapid derivation of TEC from GEONET (a dense GPS receiver network in Japan). In addition to a previous plot of TEC temporal variation over Japan, we have recently developed a near-real-time two-dimensional TEC map and have used it for the daily operation of Space Weather Forecast Center at NICT (Regional Warning Center Tokyo of International Space Environment Service). The TEC map can be used to continuously monitor the ionospheric disturbances over Japan, including spatial and temporal development of ionospheric storms, large-amplitude traveling ionospheric disturbances, and plasma bubbles intruding over Japan, with high time resolution. The development of the real-time monitoring system of TEC enables us to monitor large ionospheric disturbances, ranging from global- to small-scale disturbances, expected in the next solar maximum. The plot and maps are open to the public and are available on http://wdc.nict.go.jp/IONO/index_E.html.

Positive and Negative Regulatory Mechanisms for Fine-Tuning Cellularity and Functions of Medullary Thymic Epithelial Cells.

PubMed

Akiyama, Taishin; Tateishi, Ryosuke; Akiyama, Nobuko; Yoshinaga, Riko; Kobayashi, Tetsuya J

2015-01-01

Self-tolerant T cells and regulatory T cells develop in the thymus. A wide variety of cell-cell interactions in the thymus is required for the differentiation, proliferation, and repertoire selection of T cells. Various secreted and cell surface molecules expressed in thymic epithelial cells (TECs) mediate these processes. Moreover, cytokines expressed by cells of hematopoietic origin regulate the cellularity of TECs. Tumor necrosis factor (TNF) family RANK ligand, lymphotoxin, and CD40 ligand, expressed in T cells and innate lymphoid cells (ILCs), promote the differentiation and proliferation of medullary TECs (mTECs) that play critical roles in the induction of immune tolerance. A recent study suggests that interleukin-22 (IL-22) produced by ILCs promotes regeneration of TECs after irradiation. Intriguingly, tumor growth factor-β and osteoprotegerin limit cellularity of mTECs, thereby attenuating regulatory T cell generation. We will review recent insights into the molecular basis for cell-cell interactions regulating differentiation and proliferation of mTECs and also discuss about a perspective on use of mathematical models for understanding this complicated system.

High temperature XRD of Cu{sub 2.1}Zn{sub 0.9}SnSe{sub 4}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chetty, Raju, E-mail: rcmallik@physics.iisc.ernet.in; Mallik, Ramesh Chandra, E-mail: rcmallik@physics.iisc.ernet.in

2014-04-24

Quaternary compound with chemical composition Cu{sub 2.1}Zn{sub 0.9}SnSe{sub 4} is prepared by solid state synthesis. High temperature XRD (X-Ray Diffraction) of this compound is used in studying the effect of temperature on lattice parameters and thermal expansion coefficients. Thermal expansion coefficient is one of the important quantities in evaluating the Grüneisen parameter which further useful in determining the lattice thermal conductivity of the material. The high temperature XRD of the material revealed that the lattice parameters as well as thermal expansion coefficients of the material increased with increase in temperature which confirms the presence of anharmonicty.

The JPL Cryogenic Dilatometer: Measuring the Thermal Expansion Coefficient of Aerospace Materials

NASA Technical Reports Server (NTRS)

Halverson, Peter G.; Dudick, Matthew J.; Karlmann, Paul; Klein, Kerry J.; Levine, Marie; Marcin, Martin; Parker, Tyler J.; Peters, Robert D.; Shaklan, Stuart; VanBuren, David

2007-01-01

This slide presentation details the cryogenic dilatometer, which is used by JPL to measure the thermal expansion coefficient of materials used in Aerospace. Included is a system diagram, a picture of the dilatometer chamber and the laser source, a description of the laser source, pictures of the interferometer, block diagrams of the electronics and software and a picture of the electronics, and software. Also there is a brief review of the accurace.error budget. The materials tested are also described, and the results are shown in strain curves, JPL measured strain fits are described, and the coefficient of thermal expansion (CTE) is also shown for the materials tested.

A possible space-based tsunami early warning system using observations of the tsunami ionospheric hole.

PubMed

Kamogawa, Masashi; Orihara, Yoshiaki; Tsurudome, Chiaki; Tomida, Yuto; Kanaya, Tatsuya; Ikeda, Daiki; Gusman, Aditya Riadi; Kakinami, Yoshihiro; Liu, Jann-Yenq; Toyoda, Atsushi

2016-12-01

Ionospheric plasma disturbances after a large tsunami can be detected by measurement of the total electron content (TEC) between a Global Positioning System (GPS) satellite and its ground-based receivers. TEC depression lasting for a few minutes to tens of minutes termed as tsunami ionospheric hole (TIH) is formed above the tsunami source area. Here we describe the quantitative relationship between initial tsunami height and the TEC depression rate caused by a TIH from seven tsunamigenic earthquakes in Japan and Chile. We found that the percentage of TEC depression and initial tsunami height are correlated and the largest TEC depressions appear 10 to 20 minutes after the main shocks. Our findings imply that Ionospheric TEC measurement using the existing ground receiver networks could be used in an early warning system for near-field tsunamis that take more than 20 minutes to arrive in coastal areas.

Nighttime Medium-Scale Traveling Ionospheric Disturbances From Airglow Imager and Global Navigation Satellite Systems Observations

NASA Astrophysics Data System (ADS)

Huang, Fuqing; Lei, Jiuhou; Dou, Xiankang; Luan, Xiaoli; Zhong, Jiahao

2018-01-01

In this study, coordinated airglow imager, GPS total electron content (TEC), and Beidou geostationary orbit (GEO) TEC observations for the first time are used to investigate the characteristics of nighttime medium-scale traveling ionospheric disturbances (MSTIDs) over central China. The results indicated that the features of nighttime MSTIDs from three types of observations are generally consistent, whereas the nighttime MSTID features from the Beidou GEO TEC are in better agreement with those from airglow images as compared with the GPS TEC, given that the nighttime MSTID characteristics from GPS TEC are significantly affected by Doppler effect due to satellite movement. It is also found that there are three peaks in the seasonal variations of the occurrence rate of nighttime MSTIDs in 2016. Our study revealed that the Beidou GEO satellites provided fidelity TEC observations to study the ionospheric variability.

A possible space-based tsunami early warning system using observations of the tsunami ionospheric hole

PubMed Central

Kamogawa, Masashi; Orihara, Yoshiaki; Tsurudome, Chiaki; Tomida, Yuto; Kanaya, Tatsuya; Ikeda, Daiki; Gusman, Aditya Riadi; Kakinami, Yoshihiro; Liu, Jann-Yenq; Toyoda, Atsushi

2016-01-01

Ionospheric plasma disturbances after a large tsunami can be detected by measurement of the total electron content (TEC) between a Global Positioning System (GPS) satellite and its ground-based receivers. TEC depression lasting for a few minutes to tens of minutes termed as tsunami ionospheric hole (TIH) is formed above the tsunami source area. Here we describe the quantitative relationship between initial tsunami height and the TEC depression rate caused by a TIH from seven tsunamigenic earthquakes in Japan and Chile. We found that the percentage of TEC depression and initial tsunami height are correlated and the largest TEC depressions appear 10 to 20 minutes after the main shocks. Our findings imply that Ionospheric TEC measurement using the existing ground receiver networks could be used in an early warning system for near-field tsunamis that take more than 20 minutes to arrive in coastal areas. PMID:27905487

Characterizing Interplanetary Structures of Long-Lasting Ionospheric Storm Events

NASA Astrophysics Data System (ADS)

Tandoi, C.; Dong, Y.; Ngwira, C. M.; Damas, M. C.

2015-12-01

Geomagnetic storms can result in periods of heightened TEC (Total Electron Content) in Earth's ionosphere. These periods of change in TEC (dTEC) can have adverse impacts on a technological society, such as scintillation of radio signals used by communication and navigation satellites. However, it is unknown which exact properties of a given storm cause dTEC. We are comparing different solar wind properties that result in a significant long-lasting dTEC to see if there are any patterns that remain constant in these storms. These properties, among others, include the interplanetary magnetic field By and Bz components, the proton density, and the flow speed. As a preliminary investigation, we have studied 15 solar storms. Preliminary results will be presented. In the future, we hope to increase our sample size and analyze over 80 different solar storms, which result in significant dTEC.

Theoretical modelling on thermal expansion of Al, Ag and Cu nanomaterials

NASA Astrophysics Data System (ADS)

Manu, Mehul; Dubey, Vikash

2018-05-01

A simple theoretical model is developed for the calculating the coefficient of volume thermal expansion (CTE) and volume thermal expansion (VTE) of Al, Ag and Cu nanomaterials by considering the cubo-octahedral structure with the change of temperature and the cluster size. At the room temperature, the coefficient of volume thermal expansion decreases sharply below 20-25 nm and the decrement of the coefficient of volume thermal expansion becomes slower above 20-25 nm. We also saw a variation in the volume thermal expansion with the variation of temperature and cluster size. At a fixed cluster size, the volume thermal expansion increases with an increase of temperature at below the melting temperature and show a linear relation of volume thermal expansion with the temperature. At a constant temperature, the volume thermal expansion decreases rapidly with an increase in cluster size below 20-25 nm and after 20-25 nm the decrement of volume thermal expansion becomes slower with the increase of the size of the cluster. Thermal expansion is due to the anharmonicity of the atom interaction. As the temperature rises the amplitude of crystal lattice vibration increases, but the equilibrium distance shifts as the atom spend more time at distance greater than the original spacing due as the repulsion at short distance greater than the corresponding attraction at farther distance. In considering the cubo- octahedral structure with the cluster order, the model prediction on the CTE and the VTE are in good agreement with the available experimental data which demonstrate the validity of our work.

Monitoring of ionospheric irregularities with multi-GNSS observations: a new ionosphere activity index and product services

NASA Astrophysics Data System (ADS)

Wang, Ningbo; Li, Zishen; Yuan, Yunbin; Yuan, Hong

2017-04-01

Key words: Ionospheric irregularity, Rate of TEC (ROT), Rate of ROT index (RROT), GPS and GLONASS The ionospheric irregularities have a strong impact on many applications of Global Navigation Satellite Systems (GNSS) and other space-based radio systems. The rate of ionospheric total electron content (TEC) change index (ROTI, TECu/min), defined as the standard deviation of rate of TEC change (ROT) within a short time (e.g. 5 minutes), has been developed to describe the ionospheric irregularities and associated scintillations. However, ROT parameter may still contain the trend term of ionospheric TEC in spite of small-scale fluctuations. On the basis of single-differenced ROT (dROT) values, we develop a new ionosphere activity index, rate of ROT change index (RROT, TECu/min), to characterize the irregularity degree of the ionosphere. To illustrate the use of the index, we investigated the consistency between ROTI and RROT indexes, through the analysis of GPS data and S4 observations collected at two high-latitude stations of the northern hemisphere. It is confirmed that the correlation coefficients between RROT and S4 are higher than those between ROTI and S4 for the test period, meaning that the proposed RROT index is applicable to monitor the ionospheric irregularities and associated scintillations. RROT index can be easily calculated from dual-frequency GNSS signals (like GPS L1 and L2 carrier phase measurements). On the basis of GPS and GLONASS data provided by the IGS, ARGN, EPN and USCORS tracking networks (more than 1500 stations per day), absolute ROT (AROT), gradient of TEC index (GOTI), ROTI and RROT maps are generated to reflect the ionospheric irregularity activities. These maps are provided in an IONEX-like format on a global scale with a temporal resolution of 15 minutes and a spatial resolution of 5 and 2.5 degrees in longitude and latitude, respectively, and the maps with high spatial resolution (2x2 degrees) are also generated for European, Australia and North American regions. The product files are produced on a daily basis with a latency of 3 days. Users now can access these products from the ftp archive of the Chinese Academy of Sciences (CAS, ftp://ftp.gipp.org.cn/product/). These maps can be used for ionospheric weather services, ionospheric irregularity modeling and foresting, as well as other GNSS applications. Although they are provided in a post-processing mode at present, it is expected that the near real-time services will be available since the availability of real-time data streams from the IGS.

Detection of Traveling Ionospheric Disturbances Induced by 2010 Mindanao Earthquakes

NASA Astrophysics Data System (ADS)

Shahbazi, A.; Park, J.; Huang, C.

2017-12-01

Earthquakes precipitate anomalous variations in the concentration of free electrons/ions in the ionosphere being known as the Traveling Ionospheric Disturbance (TID). The TIDs can be detected from the Total Electron Content (TEC), which can be extracted from the ionospheric delay along the ray path of the GNSS signal between a satellite and a receiver. In this study, we utilized the GNSS-derived TEC observed by Communication/Navigation Outage Forecasting System (C/NOFS), which is a Low Earth Orbit (LEO) satellite. As a case study, we detected the ionospheric perturbations triggered by 2010 Mindanao earthquakes in the Moro Gulf, southern Philippines. Since this sequence of the earthquakes was occurred in depths of about 600 km, the low detectability of TID signature was expected while the magnitude of the foreshock, primary shock and aftershock were of 7.3, 7.6, and 7.5 Mb, respectively. Hence, we introduced a novel filtering scheme to assess the performance of space-based TEC observations in identification of earthquake-induced TIDs as well as to cope with the challenge of investigating deep subsequent earthquakes. The proposed approach suppresses the dominant trend of TEC by Hodrick-Prescott (H-P) Filter, which identifies the extremums of the remained signal as the potential TIDs and associates them to the seismic waves. Considering the propagation mechanism of the seismic waves given in the literatures that the wave propagates upward from the earthquake epicenter to the upper atmosphere, and then, moves horizontally through the ionosphere, we applied the first order linear regression model to estimate the propagation velocity of TIDs. Our experimental result demonstrated the vertical propagation velocity of 0.980 km/s and the horizontal propagation velocity through the ionosphere of 1.066 km/s with the std. of 0.364 km/s. The correlation coefficient of the detected TIDs in this model is 0.78 that illustrates the detected TIDs are well correlated with the event under consideration. Also, the average (vertical and horizontal) velocities of wave were matched with the literatures which reveal the 2010 Mindanao earthquakes with near 600km of depth generated the TIDs being detectable by GNSS receivers on a LEO satellite.

Application of the laguerre deconvolution method for time-resolved fluorescence spectroscopy to the characterization of atherosclerotic plaques.

PubMed

Jo, J A; Fang, Q; Papaioannou, T; Qiao, J H; Fishbein, M C; Beseth, B; Dorafshar, A H; Reil, T; Baker, D; Freischlag, J; Marcu, L

2005-01-01

This study investigates the ability of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) to detect inflammation in atherosclerotic lesion, a key feature of plaque vulnerability. A total of 348 TR-LIFS measurements were taken from carotid plaques of 30 patients, and subsequently analyzed using the Laguerre deconvolution technique. The investigated spots were classified as Early, Fibrotic/Calcified or Inflamed lesions. A stepwise linear discriminant analysis algorithm was developed using spectral and TR features (normalized intensity values and Laguerre expansion coefficients at discrete emission wavelengths, respectively). Features from only three emission wavelengths (390, 450 and 500 nm) were used in the classifier. The Inflamed lesions were discriminated with sensitivity > 80% and specificity > 90 %, when the Laguerre expansion coefficients were included in the feature space. These results indicate that TR-LIFS information derived from the Laguerre expansion coefficients at few selected emission wavelengths can discriminate inflammation in atherosclerotic plaques. We believe that TR-LIFS derived Laguerre expansion coefficients can provide a valuable additional dimension for the detection of vulnerable plaques.

Mechanical properties of several neat polymer matrix materials and unidirectional carbon fiber-reinforced composites

NASA Technical Reports Server (NTRS)

Coguill, Scott L.; Adams, Donald F.

1989-01-01

The mechanical and physical properties of three neat matrix materials, i.e., PEEK (polyetheretherketone) thermoplastic, Hexcel F155 rubber-toughened epoxy and Hercules 8551-7 rubber-toughened epoxy, were experimentally determined. Twelve unidirectional carbon fiber composites, incorporating matrix materials characterized in this or earlier studies (with one exception; the PISO(sub 2)-TPI matrix itself was not characterized), were also tested. These composite systems included AS4/2220-1, AS4/2220-3, T500/R914, IM6/HX1504, T300/4901A (MDA), T700/4901A (MDA), T300/4901B (MPDA), T700/4901B (MPDA), APC2 (AS4/PEEK, ICI), APC2 (AS4/PEEK, Langley Research Center), AS4/8551-7, and AS4/PISO(sub 2)-TPI. For the neat matrix materials, the tensile, shear, fracture toughness, coefficient of thermal expansion, and coefficient of moisture expansion properties were measured as a function of both temperature and moisture content. For the unidirectional composites, axial and transverse tensile, longitudinal shear, coefficient of thermal expansion, and coefficient of moisture expansion properties were determined, at room temperature and 100 C.

Auxiliary basis expansions for large-scale electronic structure calculations.

PubMed

Jung, Yousung; Sodt, Alex; Gill, Peter M W; Head-Gordon, Martin

2005-05-10

One way to reduce the computational cost of electronic structure calculations is to use auxiliary basis expansions to approximate four-center integrals in terms of two- and three-center integrals, usually by using the variationally optimum Coulomb metric to determine the expansion coefficients. However, the long-range decay behavior of the auxiliary basis expansion coefficients has not been characterized. We find that this decay can be surprisingly slow. Numerical experiments on linear alkanes and a toy model both show that the decay can be as slow as 1/r in the distance between the auxiliary function and the fitted charge distribution. The Coulomb metric fitting equations also involve divergent matrix elements for extended systems treated with periodic boundary conditions. An attenuated Coulomb metric that is short-range can eliminate these oddities without substantially degrading calculated relative energies. The sparsity of the fit coefficients is assessed on simple hydrocarbon molecules and shows quite early onset of linear growth in the number of significant coefficients with system size using the attenuated Coulomb metric. Hence it is possible to design linear scaling auxiliary basis methods without additional approximations to treat large systems.

Detection of abnormalities in the superficial zone of cartilage repaired using a tissue engineered construct derived from synovial stem cells.

PubMed

Ando, Wataru; Fujie, Hiromichi; Moriguchi, Yu; Nansai, Ryosuke; Shimomura, Kazunori; Hart, David A; Yoshikawa, Hideki; Nakamura, Norimasa

2012-09-28

The present study investigated the surface structure and mechanical properties of repair cartilage generated from a tissue engineered construct (TEC) derived from synovial mesenchymal stem cells at six months post-implantation compared to those of uninjured cartilage. TEC-mediated repair tissue was cartilaginous with Safranin O staining, and had comparable macro-scale compressive properties with uninjured cartilage. However, morphological assessments revealed that the superficial zone of TEC-mediated tissue was more fibrocartilage-like, in contrast to the middle or deep zones that were more hyaline cartilage-like with Safranin O staining. Histological scoring of the TEC-mediated tissue was significantly lower in the superficial zone than in the middle and deep zones. Scanning electron microscopy showed a thick tangential bundle of collagen fibres at the most superficial layer of uninjured cartilage, while no corresponding structure was detected at the surface of TEC-mediated tissue. Immunohistochemical analysis revealed that PRG4 was localised in the superficial area of uninjured cartilage, as well as the TEC-mediated tissue. Friction testing showed that the lubrication properties of the two tissues was similar, however, micro-indentation analysis revealed that the surface stiffness of the TEC-repair tissue was significantly lower than that of uninjured cartilage. Permeability testing indicated that the TEC-mediated tissue exhibited lower water retaining capacity than did uninjured cartilage, specifically at the superficial zone. Thus, TEC-mediated tissue exhibited compromised mechanical properties at the superficial zone, properties which need improvement in the future for maintenance of long term repair cartilage integrity.

Preparing technicians for photonics industries and organizations

NASA Astrophysics Data System (ADS)

Souders, John; Hull, Dan

2012-10-01

U.S. photonics organizations need about 800 new photonics technicians each year. Thirty-one community and technical colleges have approximately 700 students enrolled in photonics related programs; about 275 of them complete their coursework and enter the workforce each year. A disparity exists between the demand and supply of qualified photonics technicians in the U.S. OP-TEC, the National Center for Optics and Photonics Education is a consortium of seven colleges, under the leadership of the University of Central Florida, and sponsored by NSF. OP-TEC's mission is to increase the quantity and quality of photonics technicians prepared at two-year colleges. OP-TEC maintains the National Photonics Skill Standards for Technicians, provides curriculum models, teaching materials, faculty training/professional development and planning services to strengthen existing college photonics programs and to attract and support new ones. OP-TEC is converting its text materials to E-Books to support students in technical programs. Through OP-TEC's recruitment efforts 84 additional colleges are interested in initiating new photonics programs. The OP-TEC Photonics College Network (OPCN) consists of 28 colleges that are currently providing photonics education. This fall OPCN will lead an additional national effort to further educate employed photonics technicians through on-line courses, complemented by lab experiences at nearby colleges. OP-TEC is expanding its outreach to photonics employers and colleges by regionalizing its approach to offering its services. OP-TEC is also planning to develop new curricula and instructional materials for AAS programs to prepare Precision Optics Technicians. This paper will detail OP-TEC's work with particular emphases on its materials and services.

The Effect of Compositional Tailoring on the Thermal Expansion and Tribological Properties of PS300: A Solid Lubricant Composite Coating

NASA Technical Reports Server (NTRS)

DellaCorte, C.; Fellenstein, J. A.

1996-01-01

This paper describes a research program in which the goal is to alter the thermal expansion coefficient of a composite solid lubricant coating, PS300, by compositional tailoring. PS300 is a plasma sprayed coating consisting of chrome oxide, silver and barium fluoride/calcium fluoride eutectic in NiCr binder. By adjusting the composition, the thermal expansion coefficient can be altered, and hence chosen, to more closely match a selected substrate preventing coating spallation at extreme temperatures. Thermal expansion coefficients (CTE) for a variety of compositions were measured from 25 to 800 C using a commercial dilatometer. The CTE's ranged from 7.0 to 13 x lO(exp -6)/deg C depending on the binder content. Subsequent tribological testing of a modified composition indicated that friction and wear properties were relatively insensitive to compositional tailoring.

Ionospheric storms—A challenge for empirical forecast of the total electron content

NASA Astrophysics Data System (ADS)

Borries, C.; Berdermann, J.; Jakowski, N.; Wilken, V.

2015-04-01

Since the last decades, the functioning of society depends more and more on well-functioning communication and navigation systems. As the availability and reliability of most of these satellite-based systems can be severely impacted by ionospheric storms, the accurate forecast of these events becomes a required task for mitigating social and economic risks. Here we aim to make initial steps toward an empirical model for ionospheric perturbations related to space weather events that are observable in the total electron content (TEC). The perturbation TEC forecast model will be a fast and robust approach, improving TEC forecasts based on climatological models during storm conditions. The derivation of such a model is a challenging task, because although a general dependence of the storm features (enhancement or depletion of electron density) on the storm onset time, local time, season and geomagnetic latitude is well known, there is a large deviation from the mean behavior. For a better understanding of storm conditions, this paper presents analyses of ionospheric storms observed in the TEC, broken down into diverse classes of storms. It provides a detailed characterization of the typical ionospheric storm behavior over Europe from high to midlatitudes, beyond case studies. Generally, the typical clear strong TEC enhancement starting in high latitudes and propagating equatorward is found to be strongest for storms starting in the morning hours independent of the season. In midlatitudes, it is strongest during noon. In addition, a clear difference between summer and winter storms is reported. While only winter storms develop high-latitude TEC enhancements, only summer storms typically exhibit TEC depletions during the storm recovery phase. During winter storms TEC enhancements can also occur the day following the storm onset, in contrast to summer storms. Strong correlation of TEC perturbation amplitudes to the Bz component of the interplanetary magnetic field and to a proxy of the polar cap potential are shown especially for summer midlatitude TEC enhancements during storms with and onset in the morning hours (6 to 12 UT over Europe) and for winter high-latitude TEC enhancements (around 60∘N). The results indicate the potential to derive improved predictions of maximum TEC deviations during space weather events, based on solar wind measurements.

Effect of ZrO(2) additions on the crystallization, mechanical and biological properties of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics.

PubMed

Li, H C; Wang, D G; Meng, X G; Chen, C Z

2014-06-01

A series of ZrO(2) doped MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics were obtained by sintering method. The crystallization behavior, phase composition, morphology and structure of glass-ceramics were characterized. The bending strength, elastic modulus, fracture toughness, micro-hardness and thermal expansion coefficient (TEC) of glass-ceramics were investigated. The in vitro bioactivity and cytotoxicity tests were used to evaluate the bioactivity and biocompatibility of glass-ceramics. The sedimentation mechanism and growth process of apatites on sample surface were discussed. The results showed that the mainly crystalline phases of glass-ceramics were Ca(5)(PO4)3F (fluorapatite) and β-CaSiO(3). (β-wollastonite). m-ZrO(2) (monoclinic zirconia) declined the crystallization temperatures of glasses. t-ZrO(2) (tetragonal zirconia) increased the crystallization temperature of Ca(5)(PO4)(3)F and declined the crystallization temperature of β-CaSiO(3). t-ZrO(2) greatly increased the fracture toughness, bending strength and micro-hardness of glass-ceramics. The nanometer apatites were induced on the surface of glass-ceramic after soaking 28 days in SBF (simulated body fluid), indicating the glass-ceramic has good bioactivity. The in vitro cytotoxicity test demonstrated the glass-ceramic has no toxicity to cell. Copyright © 2014 Elsevier B.V. All rights reserved.

Finding Coefficients of the Full Array of Motion-Independent N-Body Potentials of Metric Gravity from Gravity's Exterior and Interior Effacement Algebra

NASA Astrophysics Data System (ADS)

Nordtvedt, Kenneth

2018-01-01

In the author's previous publications, a recursive linear algebraic method was introduced for obtaining (without gravitational radiation) the full potential expansions for the gravitational metric field components and the Lagrangian for a general N-body system. Two apparent properties of gravity— Exterior Effacement and Interior Effacement—were defined and fully enforced to obtain the recursive algebra, especially for the motion-independent potential expansions of the general N-body situation. The linear algebraic equations of this method determine the potential coefficients at any order n of the expansions in terms of the lower-order coefficients. Then, enforcing Exterior and Interior Effacement on a selecedt few potential series of the full motion-independent potential expansions, the complete exterior metric field for a single, spherically-symmetric mass source was obtained, producing the Schwarzschild metric field of general relativity. In this fourth paper of this series, the complete spatial metric's motion-independent potentials for N bodies are obtained using enforcement of Interior Effacement and knowledge of the Schwarzschild potentials. From the full spatial metric, the complete set of temporal metric potentials and Lagrangian potentials in the motion-independent case can then be found by transfer equations among the coefficients κ( n, α) → λ( n, ɛ) → ξ( n, α) with κ( n, α), λ( n, ɛ), ξ( n, α) being the numerical coefficients in the spatial metric, the Lagrangian, and the temporal metric potential expansions, respectively.

An Analysis on the TEC Variability and Ionospheric Scintillation at Los Alamos, New Mexico Derived from FORTE-Received LAPP Signals

NASA Astrophysics Data System (ADS)

Huang, Z.; Roussel-Dupre, R.

2003-12-01

The total electron content (TEC) of ionosphere and its electron density irregularities (scintillation) have effects of degradation and disruption on radio signals passed between ground stations and orbiting man-made satellites. With the rapid increase in operational reliance on UHF/VHF satellite communication, it is desirable to obtain understandings of ionosphere TEC variability and scintillation characteristics to improve our ability of predicting satellite communication outages. In this work, data collected from FORTE satellite received LAPP (Los Alamos Portable Pulser) signals during 1998-2002 are used to derive TEC and ionospheric scintillation index at Los Alamos, New Mexico. To characterize in-situ TEC variability at Los Alamos, the FORTE-LAPP derived TECs are analyzed against diurnal, seasonal, solar activity, magnetic storm, and stratospheric warming. The results are also compared with the TEC estimates from the Los Alamos ionospheric transfer function (ITF) implemented with the global ionospheric models (IRI, PIM), and GPS -derived TEC maps. The FORTE-LAPP signals are also analyzed against two important measures of the effect of scintillation on broadband signals, the mean time delay and the time delay jitter. The results are used to examine coherence frequency bandwidth and compared with the predictions from a global scintillation model (WBMOD). The FORTE-LAPP analyzed and WBMOD predicted scintillation characteristics are used to investigate temporal and seasonal behavior of scintillation at Los Alamos.

A pilot study comparing the use of Thiel- and formalin-embalmed cadavers in the teaching of human anatomy.

PubMed

Balta, Joy Y; Lamb, Clare; Soames, Roger W

2015-01-01

Formalin had traditionally been used to preserve human material to teach gross anatomy. In 2008 the Centre for Anatomy and Human Identification (CAHID) at the University of Dundee embarked on the use of the Thiel method of embalming. The aim of this pilot study was to assess the difference between formalin-embalmed cadavers (FEC) and Thiel-embalmed cadavers (TEC) used for teaching and surgical training. Three different questionnaires were prepared for data collection from undergraduate and postgraduate students and clinical staff. All undergraduate and postgraduate students as well as clinical staff commented on the appearance of the TEC. There was no overall consensus concerning the use of TEC, some respondents preferred TEC for the entire dissection, some only for certain areas such as the musculoskeletal system. On a technical level TEC were considered less hazardous then FEC by one-third of participants with fewer than 10% regarding TEC as more irritating than FEC. Psychologically, 32.7% of undergraduate students expressed the view that TEC made them feel more uncomfortable compared with FEC because of their life-like appearance. However, 57.1% of undergraduate students encountered the same uncomfortable feelings when viewing both TEC and FEC. The use of Thiel-embalmed cadavers to teach anatomy has an added value, though further research is required over longer periods of time to identify its best usage. © 2014 American Association of Anatomists.

Statistical analysis of ionospheric TEC anomalies before global M w ≥ 7.0 earthquakes using data of CODE GIM

NASA Astrophysics Data System (ADS)

Liu, Wenjing; Xu, Liang

2017-07-01

Based on Center of Orbit Determination in Europe (CODE) global ionospheric map (GIM) data, a statistical analysis of local total electron content (TEC) anomalies before 121 low-depth ( D ≤ 100 km) strong ( M w ≥ 7.0) earthquakes has been made using the sliding median differential calculation method combining with a new approach of image processing technique. The results show that significant local TEC anomalies could be observed 0-6 days before 80 earthquakes, about 66.1% out of the total. The positive anomalies occur more often than negative ones. For 26 cases, both positive and negative anomalies are observed before the shock. The pre-earthquake TEC anomalies show local time recurrence for 38 earthquakes, which occur around the same local time on different days. The local time distribution of the pre-earthquake TEC anomalies mainly concentrates between 19 and 06 LT, roughly from the sunset to sunrise. Most of the pre-earthquake TEC anomalies do not locate above the epicenter but shift to the south. The pre-earthquake TEC anomalies could be extracted near the magnetic conjugate point of the epicenter for 40 events, which is 50% out of the total 80 cases with significant local TEC anomalies. In general, the signs of the anomalies around epicenter and its conjugate point are the same, but the abnormal magnitude and lasting time are not.

Observations of the Weddell Sea Anomaly in the ground-based and space-borne TEC measurements

NASA Astrophysics Data System (ADS)

Zakharenkova, Irina; Cherniak, Iurii; Shagimuratov, Irk

2017-08-01

The Weddell Sea Anomaly (WSA) is a summer ionospheric anomaly, which is characterized by a greater nighttime ionospheric density than that in daytime in the region near the Weddell Sea. We investigate the WSA signatures in the ground-based TEC (vertical total electron content) by using GPS and GLONASS measurements of the dense regional GNSS networks in South America. We constructed the high-resolution regional TEC maps for December 2014-January 2015. The WSA effects of the TEC exceed the noontime values are registered starting from 17 LT, it reaches its maximum at 01-05 LT and starts to disappear after 09 LT. Maximal TEC enhancements were as large as a factor of 2.5-3.5 and were registered at 03-04 LT. This effect was mainly localized in the geographical region of 55°S-75°S latitude and 80°W-30°W longitude, close to the Antarctic Peninsula. Further, we examined the WSA occurrence in the topside ionosphere by using GPS measurements from a zenith-looking GPS antenna on board three Swarm satellites to determine topside TEC (above ∼500 km altitude) at the topside ionosphere-plasmasphere system. Global maps of the topside TEC indicated that the zone with significant WSA effect in the topside TEC (TEC increase ∼2-4 times the noontime level) had a large spatial extent over southern Pacific and Atlantic Ocean. It was observed around 150°W-20°W and between 40°S and 70°S during 23 LT - 06 LT. For the first time, the WSA signatures were shown in the topside TEC data derived from the GPS measurements onboard the Swarm constellation. Independently, two other instruments - FORMOSAT-3/COSMIC radio occultation electron density profiles and in situ measurements by the Langmuir Probe instrument onboard Swarm satellites - were able to confirm: (1) the same location of the WSA zone as revealed in Swarm TEC; (2) the most-pronounced WSA effect, as a maximal electron density exceed over the noontime values, corresponds to altitudes above 400-500 km.

Long-term trends in the total electron content (TEC)

NASA Astrophysics Data System (ADS)

Laštovička, Jan

2017-04-01

The long-term trends in the total electron content (TEC) have very little been studied. Lean et al. (2011; J. Geophys. Res., 116, A00H04, doi:10.1029/2010JA016378) studied trends in TEC globally based on JPL maps for 1995-2010. However, their trends appear to be too positive, which is not plausible taking into account the trends in other ionospheric parameters. Therefore they prefer the less positive trends calculated under the assumption of the same level of solar activity in solar cycle minima 22/23 and 23/24. However, as it is now clear, this is not a correct assumption. Lastovicka (2013; J. Geophys. Res. Space Phys., 118, 3831-3835, doi:10.1002/jgra.50261) selected a region around Florence, Italy, as a region with available historical TEC data based on Faraday rotation measurements and remarkably larger than average trends in TEC by Lean et al. (2011). Historical data from Florence provide no trend in TEC. However, foF2 from Juliusruh provide slight negative trends for 1976-1996 but no trends for 1995-2010. Thus the question of reality of trends by Lean et al. (2011) remained open. Here we use TEC from GIM and JPL data for two European regions with high Lean's trends, regions around Florence and around Prague, using 10-14 LT medians, 1998-2015, yearly average values. A classical approach is applied. First a model of solar activity dependence of TEC is constructed separately for each region from all data. Then model data are subtracted from experimental data and analysis is made with residuals. This analysis shows that early data (1998-2001) are by several TECU lower than they should be according to solar activity, the year 2002 is intermediate and in 2003-2015 the data fit well a weak or rather no trend of TEC. The change in TEC data does not seem to be jump-like, it lasted at least a year, if not longer. Thus the positive TEC trends reported by Lean et al. (2011) appear to be affected by data problem; real trends are evidently less positive if any.

Performance evaluation of GNSS-TEC estimation techniques at the grid point in middle and low latitudes during different geomagnetic conditions

NASA Astrophysics Data System (ADS)

Abe, O. E.; Otero Villamide, X.; Paparini, C.; Radicella, S. M.; Nava, B.; Rodríguez-Bouza, M.

2017-04-01

Global Navigation Satellite Systems (GNSS) have become a powerful tool use in surveying and mapping, air and maritime navigation, ionospheric/space weather research and other applications. However, in some cases, its maximum efficiency could not be attained due to some uncorrelated errors associated with the system measurements, which is caused mainly by the dispersive nature of the ionosphere. Ionosphere has been represented using the total number of electrons along the signal path at a particular height known as Total Electron Content (TEC). However, there are many methods to estimate TEC but the outputs are not uniform, which could be due to the peculiarity in characterizing the biases inside the observables (measurements), and sometimes could be associated to the influence of mapping function. The errors in TEC estimation could lead to wrong conclusion and this could be more critical in case of safety-of-life application. This work investigated the performance of Ciraolo's and Gopi's GNSS-TEC calibration techniques, during 5 geomagnetic quiet and disturbed conditions in the month of October 2013, at the grid points located in low and middle latitudes. The data used are obtained from the GNSS ground-based receivers located at Borriana in Spain (40°N, 0°E; mid latitude) and Accra in Ghana (5.50°N, -0.20°E; low latitude). The results of the calibrated TEC are compared with the TEC obtained from European Geostationary Navigation Overlay System Processing Set (EGNOS PS) TEC algorithm, which is considered as a reference data. The TEC derived from Global Ionospheric Maps (GIM) through International GNSS service (IGS) was also examined at the same grid points. The results obtained in this work showed that Ciraolo's calibration technique (a calibration technique based on carrier-phase measurements only) estimates TEC better at middle latitude in comparison to Gopi's technique (a calibration technique based on code and carrier-phase measurements). At the same time, Gopi's calibration was also found more reliable in low latitude than Ciraolo's technique. In addition, the TEC derived from IGS GIM seems to be much reliable in middle-latitude than in low-latitude region.

Modeling laser beam diffraction and propagation by the mode-expansion method.

PubMed

Snyder, James J

2007-08-01

In the mode-expansion method for modeling propagation of a diffracted beam, the beam at the aperture can be expanded as a weighted set of orthogonal modes. The parameters of the expansion modes are chosen to maximize the weighting coefficient of the lowest-order mode. As the beam propagates, its field distribution can be reconstructed from the set of weighting coefficients and the Gouy phase of the lowest-order mode. We have developed a simple procedure to implement the mode-expansion method for propagation through an arbitrary ABCD matrix, and we have demonstrated that it is accurate in comparison with direct calculations of diffraction integrals and much faster.

ZERODUR TAILORED for cryogenic application

NASA Astrophysics Data System (ADS)

Jedamzik, R.; Westerhoff, T.

2014-07-01

ZERODUR® glass ceramic from SCHOTT is known for its very low thermal expansion coefficient (CTE) at room temperature and its excellent CTE homogeneity. It is widely used for ground-based astronomical mirrors but also for satellite applications. Many reference application demonstrate the excellent and long lasting performance of ZERODUR® components in orbit. For space application a low CTE of the mirror material is required at cryogenic temperatures together with a good match of the thermal expansion to the supporting structure material. It is possible to optimize the coefficient of thermal expansion of ZERODUR® for cryogenic applications. This paper reports on measurements of thermal expansion of ZERODUR® down to cryogenic temperatures of 10 K performed by the PTB (Physikalisch Technische Bundesanstallt, Braunschweig, Germany, the national metrology laboratory). The ZERODUR® TAILORED CRYO presented in this paper has a very low coefficient of thermal expansion down to 70 K. The maximum absolute integrated thermal expansion down to 10 K is only about 20 ppm. Mirror blanks made from ZERODUR® TAILORED CRYO can be light weighted to almost 90% with our modern processing technologies. With ZERODUR® TAILORED CRYO, SCHOTT offers the mirror blank material for the next generation of space telescope applications.

LISN: Measurement of TEC values, and TID characteristics over South and Central America (Invited)

NASA Astrophysics Data System (ADS)

Valladares, C. E.

2013-12-01

The Low-latitude Ionospheric Sensor Network (LISN) is a distributed observatory designed to provide the climatology and weather of the low latitude ionosphere over the South American continent. Presently, the LISN observatory consists of 47 GPS receivers able to transmit TEC and scintillation values to a central server in a real-time basis. Historical TEC values from these receivers and from about 300 other GPSs that operated in South and Central America between 2008 and 2012 were used to derive regional maps of TEC and TIDs. A prominent feature of the TEC maps is the intense day-to-day variability that is observed during all seasons and under quiet and active magnetic conditions. To assess the TEC dependencies a non-linear least-square fit was conducted to simultaneously extract the solar flux, magnetic and seasonal variability for each square cell of the TEC maps and for each 30-min local time sector. It was found that TEC values and the anomaly intensity increase as a function of the solar flux. The latitudinal separation increases with magnetic activity, and TEC values in Central America become the largest when Kp is equal to 5o or more. TIDs are seen quite frequently over the Caribbean region and in the northern part of South America. To calculate the TIDs travel velocities, their propagation direction, and the scale-size of the disturbances a multi-site multi-dimension cross-correlation method was applied to the TEC database. Phase velocities of order 150 m/s and scale sizes between 100 and 400 km were typically observed. This paper will present the morphology and statistics of TIDs as a function of latitude, longitude, local time and season. It is also introduced the results of an investigation to correlate the appearance, phase velocity and angle of propagation of TIDs and tropospheric phenomena observed with the TRMM satellite.

Purified enzymes improve isolation and characterization of the adult thymic epithelium.

PubMed

Seach, Natalie; Wong, Kahlia; Hammett, Maree; Boyd, Richard L; Chidgey, Ann P

2012-11-30

The reproducible isolation and accurate characterization of thymic epithelial cell (TEC) subsets is of critical importance to the ongoing study of thymopoiesis and its functional decline with age. The study of adult TEC, however, is significantly hampered due to the severely low stromal to hematopoietic cell ratio. Non-biased digestion and enrichment protocols are thus essential to ensure optimal cell yield and accurate representation of stromal subsets, as close as possible to their in vivo representation. Current digestion protocols predominantly involve diverse, relatively impure enzymatic variants of crude collagenase and collagenase/dispase (col/disp) preparations, which have variable efficacy and are often suboptimal in their ability to mediate complete digestion of thymus tissue. To address these issues we compared traditional col/disp preparations with the latest panel of Liberase products that contain a blend of highly purified collagenase and neutral protease enzymes. Liberase enzymes revealed a more rapid, complete dissociation of thymus tissue; minimizing loss of viability and increasing recovery of thymic stromal cell (TSC) elements. In particular, the recovery and viability of TEC, notably the rare cortical subsets, were significantly enhanced with Liberase products containing medium to high levels of thermolysin. The improved stromal dissociation led to numerically increased TEC yield and total TEC RNA isolated from pooled digests of adult thymus. Furthermore, the increased recovery of TEC enhanced resolution and quantification of TEC subsets in both adult and aged mice, facilitating flow cytometric analysis on a per thymus basis. We further refined the adult TEC phenotype by correlating surface expression of known TEC markers, with expression of intracellular epithelial lineage markers, Keratin 5 and Keratin 8. The data reveal more extensive expression of K8 than previously recognized and indicates considerable heterogeneity still exists within currently defined adult TEC subsets. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

US-TEC: A new data assimilation product from the Space Environment Center characterizing the ionospheric total electron content using real-time GPS data

NASA Astrophysics Data System (ADS)

Fuller-Rowell, Tim; Araujo-Pradere, Eduardo; Minter, Cliff; Codrescu, Mihail; Spencer, Paul; Robertson, Doug; Jacobson, Abram R.

2006-12-01

The potential of data assimilation for operational numerical weather forecasting has been appreciated for many years. For space weather it is a new path that we are just beginning to explore. With the emergence of satellite constellations and the networks of ground-based observations, sufficient data sources are now available to make the application of data assimilation techniques a viable option. The first space weather product at Space Environment Center (SEC) utilizing data assimilation techniques, US-TEC, was launched as a test operational product in November 2004. US-TEC characterizes the ionospheric total electron content (TEC) over the continental United States (CONUS) every 15 min with about a 15-min latency. US-TEC is based on a Kalman filter data assimilation scheme driven by a ground-based network of real-time GPS stations. The product includes a map of the vertical TEC, an estimate of the uncertainty in the map, and the departure of the TEC from a 10-day average at that particular universal time. In addition, data files are provided for vertical TEC and the line-of-sight electron content to all GPS satellites in view over the CONUS at that time. The information can be used to improve single-frequency GPS positioning by providing more accurate corrections for the ionospheric signal delay, or it can be used to initialize rapid integer ambiguity resolution schemes for dual-frequency GPS systems. Validation of US-TEC indicates an accuracy of the line-of-sight electron content of between 2 and 3 TEC units (1 TECU = 1016 el m-2), equivalent to less than 50 cm signal delay at L1 frequencies, which promises value for GPS users. This is the first step along a path that will likely lead to major improvement in space weather forecasting, paralleling the advances achieved in meteorological weather forecasting.

Thermoelectric Converter for Loop Heat Pipe Temperature Control: Experience and Lessons Learned

NASA Technical Reports Server (NTRS)

Ku, Jentung; Ottenstein, Laura

2010-01-01

This paper describes the theoretical background and implementation methodology of using a thermoelectric converter (TEC) for operating temperature control of a loop heat pipe (LHP). In particular, experimental results from ambient and thermal vacuum tests of an LHP are presented for illustrations. The most commonly used state-of-the-art method to control the LHP operating temperature is to cold bias its compensation chamber (CC) and use an electrical heater to maintain the CC at the desired set point temperature. Although effective, this approach has its shortcomings in that the electrical heater can only provide heating to the CC, and the required power can be large under certain conditions. An alternative method is to use a TEC, which is capable of providing both heating and cooling to the CC. In this method, one side of the TEC is attached to the CC, and the other side is connected to the evaporator via a thermal strap. Using a bipolar power supply and a control algorithm, a TEC can function as a heater or a cooler, depending on the direction of the current flow. Extensive ground tests of several LHPs have demonstrated that a TEC can provide very tight temperature control for the CC. It also offers several additional advantages: (1) The LHP can operate at temperatures below its natural operating temperature at low heat loads; (2) The required heater power for a TEC is much less than that for an electrical heater; and (3) It enhances the LHP start-up success. Although the concept of using a TEC for LHP temperature control is simple, there are many factors to be considered in its implementation for space applications because the TEC is susceptible to the shear stress and yet has to sustain the dynamic load under the spacecraft launch environment. The added features that help the TEC to withstand the dynamic load will inevitably affect the TEC thermal performance. Some experiences and lessons learned are addressed in this paper.

Was Magnetic Storm the Only Driver of the Long-Duration Enhancements of Daytime Total Electron Content in the Asian-Australian Sector Between 7 and 12 September 2017?

NASA Astrophysics Data System (ADS)

Lei, Jiuhou; Huang, Fuqing; Chen, Xuetao; Zhong, Jiahao; Ren, Dexin; Wang, Wenbin; Yue, Xinan; Luan, Xiaoli; Jia, Mingjiao; Dou, Xiankang; Hu, Lianhuan; Ning, Baiqi; Owolabi, Charles; Chen, Jinsong; Li, Guozhu; Xue, Xianghui

2018-04-01

In this study, multiple data sets from Beidou geostationary orbit satellites total electron contents (TECs), ionosonde, meteor radar, magnetometer, and model simulations have been used to investigate the ionospheric responses in the Asian-Australian sector during the September 2017 geomagnetic storm. It was found that long-duration daytime TEC enhancements that lasted from 7 to 12 September 2017 were observed by the Beidou geostationary orbit satellite constellation. This is a unique event as the prominent TEC enhancements persisted during the storm recovery phase when geomagnetic activity became quiet. The Thermosphere-Ionosphere Electrodynamics Global Circulation Model predicted that the TEC enhancements on 7-9 September were associated with the geomagnetic activity, but it showed significant electron density depletions on 10 and 11 September in contrast to the observed TEC enhancements. Our results suggested that the observed long-duration TEC enhancements from 7 to 12 September are mainly associated with the interplay of ionospheric dynamics and electrodynamics. Nevertheless, the root causes for the observed TEC enhancements seen in the storm recovery phase are unknown and require further observations and model studies.

CFD Extraction Tool for TecPlot From DPLR Solutions

NASA Technical Reports Server (NTRS)

Norman, David

2013-01-01

This invention is a TecPlot macro of a computer program in the TecPlot programming language that processes data from DPLR solutions in TecPlot format. DPLR (Data-Parallel Line Relaxation) is a NASA computational fluid dynamics (CFD) code, and TecPlot is a commercial CFD post-processing tool. The Tec- Plot data is in SI units (same as DPLR output). The invention converts the SI units into British units. The macro modifies the TecPlot data with unit conversions, and adds some extra calculations. After unit conversions, the macro cuts a slice, and adds vectors on the current plot for output format. The macro can also process surface solutions. Existing solutions use manual conversion and superposition. The conversion is complicated because it must be applied to a range of inter-related scalars and vectors to describe a 2D or 3D flow field. It processes the CFD solution to create superposition/comparison of scalars and vectors. The existing manual solution is cumbersome, open to errors, slow, and cannot be inserted into an automated process. This invention is quick and easy to use, and can be inserted into an automated data-processing algorithm.

RB inactivation in keratin 18 positive thymic epithelial cells promotes non-cell autonomous T cell hyperproliferation in genetically engineered mice.

PubMed

Song, Yurong; Sullivan, Teresa; Klarmann, Kimberly; Gilbert, Debra; O'Sullivan, T Norene; Lu, Lucy; Wang, Sophie; Haines, Diana C; Van Dyke, Terry; Keller, Jonathan R

2017-01-01

Thymic epithelial cells (TEC), as part of thymic stroma, provide essential growth factors/cytokines and self-antigens to support T cell development and selection. Deletion of Rb family proteins in adult thymic stroma leads to T cell hyperplasia in vivo. To determine whether deletion of Rb specifically in keratin (K) 18 positive TEC was sufficient for thymocyte hyperplasia, we conditionally inactivated Rb and its family members p107 and p130 in K18+ TEC in genetically engineered mice (TgK18GT121; K18 mice). We found that thymocyte hyperproliferation was induced in mice with Rb inactivation in K18+ TEC, while normal T cell development was maintained; suggesting that inactivation of Rb specifically in K18+ TEC was sufficient and responsible for the phenotype. Transplantation of wild type bone marrow cells into mice with Rb inactivation in K18+ TEC resulted in donor T lymphocyte hyperplasia confirming the non-cell autonomous requirement for Rb proteins in K18+ TEC in regulating T cell proliferation. Our data suggests that thymic epithelial cells play an important role in regulating lymphoid proliferation and thymus size.

Short-Term TEC Perturbations Associated With Planetary Waves Occurrence in the Ionosphere

NASA Astrophysics Data System (ADS)

Shagimuratov, I. I.; Karpov, I.; Krankowski, A.

2008-12-01

Analysis of TEC response to storm showed short-term perturbations which were observed after initial phase of geomagnetic storms. The perturbations demonstrated very well expressed latitudinal structure and were recognized on diurnal variations as surges of TEC enhancement of TEC. Ordinary such storm-time positive effect was associated with TAD. Duration of the perturbations was about 2-4 hours and their amplitude increased toward low latitudes. Such TEC perturbations have the longitudinal dependence. It is important that time location of surges have week dependence on latitude. The observed structure appeared to arrive from high latitudes, but at middle latitudes it was represented as a standing wave. It is assumed that such TEC perturbations can be produced due to superposition of the eastward and westward propagating planetary Poincare waves. The periods of these waves are usually several hours. Poincare waves can be excited at the atmosphere in storm time. At middle latitudes their superposition is as standing wave that forms observing TEC perturbations. In the report, the possibilities of application Poincare waves to the ionosphere dynamics studies are discussed and an explanation of the observed ionospheric effects is given.

Long time series analysis of ionospheric TEC disturbance over seismically region in southwest China during low solar activity

NASA Astrophysics Data System (ADS)

Yan, Xiangxiang; Yu, Tao; Shan, Xinjian; Liu, Zhan; Wang, Zhenjie

2016-04-01

Recently, there are growing interests in studying the seismo-ionospheric disturbance prior to earthquakes, mainly including the anomalies in the electric field, magnetic field and plasma parameters. However, there are still some controversies over this topic, mainly because of strong day-to-day variability of the ionosphere itself. It is hard to determine whether the different forms of ionospheric disturbances are associated with earthquakes or not. Using data of Crustal Movement Observation Network of China (CMONC) and IGS (International GNSS Service), we attempt to give a statistical investigation about the total electron content (TEC) perturbation before 30 Mw6.0+ earthquakes during January 2000 to December 2010 in China. To determine the abnormal TEC signals, a quartile-based process is performed. At each time point we calculated the median M using the TEC values at the same local time for the preceding 15 days. In addition, we calculated the maps of differential TEC from global ionosphere maps (GIM) in the above period. It is shown that TEC anomalies were detected before 20 earthquakes, nearly 67%. The anomalies represent positive before most events and occurred mostly within 2-6 days before the shocks, significantly during the afternoon period, 1200-2000LT. Part of perturbations appeared more than one time. Moreover, the affected area of TEC is not coincide with the vertical projection of the epicenter but shifts equatorward and is controlled by equatorial ionization anomaly (EIA) crest. On the other hand, we analyzed variations of TEC over southwest China during a period of low solar and geomagnetic activity in April-October 2008, based on the data of CMONC. During that time, six large earthquakes with magnitude M≧6.0 occurred around the southwest region of China. The method to detect abnormal TEC signals is same with above statistical study. Known that the decisive role in the ionosphere state is performed by space weather effects, we compared the TEC variations with time series of EUV solar radiation, Bz component of the interplanetary magnetic field (IMF), index of geomagnetic activity Dst and planetary index Kp, respectively. It is found that the observed anomalies in the regional TEC were in good correlation with the variations of above solar and geomagnetic activities. We have not detected obvious TEC disturbance before five earthquakes expect for Wenchuan earthquake. In order to additionally check the spatial occurrence of the observed anomalies, we chose a 'check-region' with the same geomagnetic latitudes as the epicentral area of the six considered earthquakes, and analyzed the TEC changes. The result shows that the time series of anomalous TEC in 'check-region' is similar to the epicentral area, which was dominated by space weather. Therefore, we are suspicious of the results of statistical investigation showed here or other similar papers, which indicates the difficulties in identifying earthquake precursors in the ionosphere TEC. The seismo-ionospheric coupling process is complex, and it is necessary to strengthen the observation of multi-parameters on the ground, in the atmosphere and ionosphere synchronously.

Texture formation in FePt thin films via thermal stress management

NASA Astrophysics Data System (ADS)

Rasmussen, P.; Rui, X.; Shield, J. E.

2005-05-01

The transformation variant of the fcc to fct transformation in FePt thin films was tailored by controlling the stresses in the thin films, thereby allowing selection of in- or out-of-plane c-axis orientation. FePt thin films were deposited at ambient temperature on several substrates with differing coefficients of thermal expansion relative to the FePt, which generated thermal stresses during the ordering heat treatment. X-ray diffraction analysis revealed preferential out-of-plane c-axis orientation for FePt films deposited on substrates with a similar coefficients of thermal expansion, and random orientation for FePt films deposited on substrates with a very low coefficient of thermal expansion, which is consistent with theoretical analysis when considering residual stresses.

Loop Heat Pipe Operation with Thermoelectric Converters and Coupling Blocks

NASA Technical Reports Server (NTRS)

Ku, Jentung; Nagano, Hosei

2007-01-01

This paper presents theoretical and experimental studies on using thermoelectric converters (TECs) and coupling blocks to control the operating temperature of a miniature loop heat pipes (MLHP). The MLHP has two parallel evaporators and two parallel condensers, and each evaporator has its own integral compensation chamber (CC). A TEC is attached to each CC, and connected to the evaporator via a copper thermal strap. The TEC can provide both heating and cooling to the CC, therefore extending the LHP operating temperature over a larger range of the evaporator heat load. A bi-polar power supply is used for the TEC operation. The bipolar power supply automatically changes the direction of the current to the TEC, depending on whether the CC requires heating or cooling, to maintain the CC temperature at the desired set point. The TEC can also enhance the startup success by maintaining a constant CC temperature during the start-up transient. Several aluminum coupling blocks are installed between the vapor line and liquid line. The coupling blocks serve as a heat exchanger which preheats the cold returning liquid so as to reduce the amount of liquid subcooling, and hence the power required to maintain the CC at the desired set point temperature. This paper focuses on the savings of the CC control heater power afforded by the TECs when compared to traditional electric heaters. Tests were conducted by varying the evaporator power, the condenser sink temperature, the CC set point temperature, the number of coupling blocks, and the thermal conductance of the thermal strap. Test results show that the TECs are able to control the CC temperature within k0.5K under all test conditions, and the required TEC heater power is only a fraction of the required electric heater power.

Real-Time Detection of Tsunami Ionospheric Disturbances with a Stand-Alone GNSS Receiver: An Integration of GPS and Galileo Systems

NASA Astrophysics Data System (ADS)

Savastano, Giorgio; Komjathy, Attila; Verkhoglyadova, Olga; Wei, Yong; Mazzoni, Augusto; Crespi, Mattia

2017-04-01

Tsunamis can produce gravity waves that propagate up to the ionosphere generating disturbed electron densities in the E and F regions. These ionospheric disturbances are studied in detail using ionospheric total electron content (TEC) measurements collected by continuously operating ground-based receivers from the Global Navigation Satellite Systems (GNSS). Here, we present results using a new approach, named VARION (Variometric Approach for Real-Time Ionosphere Observation), and for the first time, we estimate slant TEC (sTEC) variations in a real-time scenario from GPS and Galileo constellations. Specifically, we study the 2016 New Zealand tsunami event using GNSS receivers with multi-constellation tracking capabilities located in the Pacific region. We compare sTEC estimates obtained using GPS and Galileo constellations. The efficiency of the real-time sTEC estimation using the VARION algorithm has been demonstrated for the 2012 Haida Gwaii tsunami event. TEC variations induced by the tsunami event are computed using 56 GPS receivers in Hawai'i. We observe TEC perturbations with amplitudes up to 0.25 TEC units and traveling ionospheric disturbances moving away from the epicenter at a speed of about 316 m/s. We present comparisons with the real-time tsunami model MOST (Method of Splitting Tsunami) provided by the NOAA Center for Tsunami Research. We observe variations in TEC that correlate well in time and space with the propagating tsunami waves. We conclude that the integration of different satellite constellations is a crucial step forward to increasing the reliability of real-time tsunami detection systems using ground-based GNSS receivers as an augmentation to existing tsunami early warning systems.

Simultaneous Global Positioning System observations of equatorial scintillations and total electron content fluctuations

NASA Astrophysics Data System (ADS)

Beach, Theodore L.; Kintner, Paul M.

1999-10-01

One aspect of the Global Positioning System (GPS) is the potential to conduct geophysical research, and worldwide networks of GPS receivers have been established to exploit this potential. Several research groups have begun using this global GPS data to study ionospheric total electron content (TEC) variations, also referred to as GPS phase fluctuations, as surrogates for ionospheric scintillations. This paper investigates the relationship between GPS amplitude scintillations and TEC variations for the same line of sight using observations from Ancón, Peru. These observations were taken under equatorial spread F conditions for three nights in April 1997. As expected, only when the spectrum of TEC fluctuations includes significant power at the Fresnel scale do scintillations appear. We also find that when the TEC fluctuation spectrum includes the Fresnel scale, the S4 scintillation index is roughly proportional to measures of TEC fluctuation for the weak scintillations observed. The proportionality constant varies from night to night, however, casting doubt on the ability to predict GPS S4 successfully from TEC fluctuation data alone. We also present a simple theoretical phase screen model and show that if a relationship between TEC fluctuation measures and S4 exists, that relationship depends on the power spectrum of phase variations at the screen. Unfortunately, the available TEC data, at 30 s per sample (with some aliasing apparently permitted), offer limited spectral information. A preliminary comparison of 1 s/sample data with the same data decimated to a 30 s/sample interval suggests, however, that the level of successful S4 prediction, based on TEC fluctuation measures alone, is comparable at either sample rate.

Empirical model of TEC response to geomagnetic and solar forcing over Balkan Peninsula

NASA Astrophysics Data System (ADS)

Mukhtarov, P.; Andonov, B.; Pancheva, D.

2018-01-01

An empirical total electron content (TEC) model response to external forcing over Balkan Peninsula (35°N-50°N; 15°E-30°E) is built by using the Center for Orbit Determination of Europe (CODE) TEC data for full 17 years, January 1999 - December 2015. The external forcing includes geomagnetic activity described by the Kp-index and solar activity described by the solar radio flux F10.7. The model describes the most probable spatial distribution and temporal variability of the externally forced TEC anomalies assuming that they depend mainly on latitude, Kp-index, F10.7 and LT. The anomalies are expressed by the relative deviation of the TEC from its 15-day mean, rTEC, as the mean value is calculated from the 15 preceding days. The approach for building this regional model is similar to that of the global TEC model reported by Mukhtarov et al. (2013a) however it includes two important improvements related to short-term variability of the solar activity and amended geomagnetic forcing by using a "modified" Kp index. The quality assessment of the new constructing model procedure in terms of modeling error calculated for the period of 1999-2015 indicates significant improvement in accordance with the global TEC model (Mukhtarov et al., 2013a). The short-term prediction capabilities of the model based on the error calculations for 2016 are improved as well. In order to demonstrate how the model is able to reproduce the rTEC response to external forcing three geomagnetic storms, accompanied also with short-term solar activity variations, which occur at different seasons and solar activity conditions are presented.

Preliminary study of TEC application in cooling system

NASA Astrophysics Data System (ADS)

Sulaiman, A. C.; Amin, N. A. M.; Saidon, M. S.; Majid, M. S. A.; Rahman, M. T. A.; Kazim, M. N. F. M.

2017-10-01

Integration of thermoelectric cooling (TEC) within a space cooling system in the lecturer room is studied. The studied area (air conditioned surrounding) is encapsulated with wall, floor, roof, and glass window. TEC module is placed on the glass window. The prototype of the studied compartment is designed using cabin container. The type and number of TEC module are studied and the effects on the cooling performance are analyzed as it is assumed to be tested within an air conditioned lecturer room. The experimental and mathematical modeling of the cooling system developed. It is expected that the mathematical modeling derived from this study will be used to estimate the use of the number of TEC module to be integrated with air conditioner unit where possible.

Comparison of Two IRI plasmasphere Extensions with GPS-TEC Observations

NASA Technical Reports Server (NTRS)

Gulyaeva, T. L.; Gallagher, Dennis L.

2006-01-01

Comparisons of two model results with Global Positioning System GPS-TEC measurements have been carried out for different latitudinal, solar activity, magnetic activity, diurnal and seasonal conditions. The models evaluated are the Global Core Plasma Model (GCPM-2000) and the IRI extension with Russian plasmasphere model (IRI*).Data of 23 observatories providing GPS-TEC and ionosonde data have been used. It is shown that IRI* plasmasphere electron density is greater than GCPM results by an order of magnitude at 6370 km altitude (one Earth's radius) with this excess growing to 2-3 orders of magnitude towards the GPS satellite altitude of 20000 km. Another source of model and GPS-TEC differences is a way of selection of the F2 layer peak parameters driving the models either with ITU-R (former CCIR) maps or ionosonde observations. Plasmasphere amendment to IRI improves accuracy of TEC model predictions because the plasmasphere contribution to the total TEC varies from 10% by daytime under quiet magnetic conditions to more than 50% by night under stormy conditions.

Observation of subsecond variations in auroral region total electron content using 100 Hz sampling of GPS observables

NASA Astrophysics Data System (ADS)

McCaffrey, A. M.; Jayachandran, P. T.

2017-06-01

First ever auroral region total electron content (TEC) measurements at 100 Hz using a Septentrio PolaRxS Pro receiver are analyzed to discover ionospheric signatures which would otherwise be unobtainable with the frequently used lower sampling rates. Two types of variations are observed: small-magnitude (amplitude) variations, which are present consistently throughout the data set, and larger-magnitude (amplitude) variations, which are less frequent. Small-amplitude TEC fluctuations are accounted for by the receiver phase jitter. However, estimated secondary ionospheric effects in the calculation of TEC and the receiver phase jitter were unable to account for the larger-amplitude TEC fluctuations. These variations are also accompanied by fluctuations in the magnetic field, which seems to indicate that these fluctuations are real and of geophysical significance. This paper presents a technique and the capability of high-rate TEC measurements in the study of auroral dynamics. Further detailed study is needed to identify the cause of these subsecond TEC fluctuations and associated magnetic field fluctuations.

The synthesis of ternary acetylides with tellurium: Li 2 TeC 2 and Na 2 TeC 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Németh, Károly; Unni, Aditya K.; Kalnmals, Christopher

The synthesis of ternary acetylides Li 2TeC 2 and Na 2TeC 2 is presented as the first example of ternary acetylides with metalloid elements instead of transition metals. The synthesis was carried out by the direct reaction of the corresponding bialkali acetylides with tellurium powder in liquid ammonia. Alternatively, the synthesis of Na 2TeC 2 was also carried out by the direct reaction of tellurium powder and two equivalents of NaC 2H in liquid ammonia leading to Na 2TeC 2 and acetylene gas through an equilibrium containing the assumed NaTeC 2H molecules besides the reactants and the products. The resultingmore » disordered crystalline materials were characterized by X-ray diffraction and Raman spectroscopy. Implications of these new syntheses on the synthesis of other ternary acetylides with metalloid elements and transition metals are also discussed.« less

A statistical study of global ionospheric map total electron content changes prior to occurrences of M ≥ 6.0 earthquakes during 2000-2014

NASA Astrophysics Data System (ADS)

Thomas, J. N.; Huard, J.; Masci, F.

2017-02-01

There are many reports on the occurrence of anomalous changes in the ionosphere prior to large earthquakes. However, whether or not these changes are reliable precursors that could be useful for earthquake prediction is controversial within the scientific community. To test a possible statistical relationship between ionospheric disturbances and earthquakes, we compare changes in the total electron content (TEC) of the ionosphere with occurrences of M ≥ 6.0 earthquakes globally for 2000-2014. We use TEC data from the global ionosphere map (GIM) and an earthquake list declustered for aftershocks. For each earthquake, we look for anomalous changes in GIM-TEC within 2.5° latitude and 5.0° longitude of the earthquake location (the spatial resolution of GIM-TEC). Our analysis has not found any statistically significant changes in GIM-TEC prior to earthquakes. Thus, we have found no evidence that would suggest that monitoring changes in GIM-TEC might be useful for predicting earthquakes.

Seismo-Ionospheric Precursor in the GIM TEC of the 24 August 2014 M6 Napa Earthquake

NASA Astrophysics Data System (ADS)

Wu, T. Y.; Liu, T. J. Y.; Liu, J. Y.

2015-12-01

This study examines seismo-ionospheric precursors (SIPs) in the global ionosphere map (GIM) of the total electron content (TEC) associated with the 24 August 2014 M6 South Napa earthquake and statistical evidence of SIPs of the GPS TEC in western USA during 2000-2014. The temporal SIP in the GIM TEC around the epicenter significantly decreasing (negative anomaly) on 22 August. To discriminate the global effect, such as solar flares, magnetic storms, etc., and the local effect, such as earthquakes, 5183 lattices on the GIM are employed to conduct a global search of the SIP distribution. Anomalies of both GIM TEC and associated gradients specifically and continuously appearing over the epicenter suggest that the SIP relate to the 2014 South Napa earthquake. A simulation is further carried out to produce the SIP in GIM TEC before the earthquake. Results indicate that the eastward electric field generated over the epicenter area during the earthquake preparation period to be essential.

Ionospheric effects of sudden stratospheric warmings in eastern Siberia region

NASA Astrophysics Data System (ADS)

Polyakova, A. S.; Chernigovskaya, M. A.; Perevalova, N. P.

2014-12-01

Ionospheric effects observed in Russia's Asia region during sudden stratospheric warmings (SSWs) in the winters 2008/2009 and 2012/2013 corresponding to both extreme solar minimum and moderate solar maximum conditions have been examined. To detect the ionospheric effects which must have been induced by the SSWs, we have carried out a joint analysis of total electron content (TEC) global ionospheric maps (GIM), MLS (Microwave Limb Sounder, EOS Aura) measurements of vertical temperature profiles, as well as NCEP/NCAR and UKMO Reanalysis data. It has been revealed for the first time that during strong SSWs the amplitude of diurnal variation of TEC decreases nearly by half in the mid-latitude ionosphere. Besides, the intensity of TEC deviations from the background level increases during SSWs. It has also revealed that during SSW peak the midday TEC maximum considerably decreases, and the night/morning TEC increases compared to quiet days. The pattern of TEC response to SSW is shown to be identical for both quiet and disturbed geophysical conditions.

Local TEC modelling and forecasting using neural networks

NASA Astrophysics Data System (ADS)

Tebabal, A.; Radicella, S. M.; Nigussie, M.; Damtie, B.; Nava, B.; Yizengaw, E.

2018-07-01

Modelling the Earth's ionospheric characteristics is the focal task for the ionospheric community to mitigate its effect on the radio communication, and satellite navigation. However, several aspects of modelling are still challenging, for example, the storm time characteristics. This paper presents modelling efforts of TEC taking into account solar and geomagnetic activity, time of the day and day of the year using neural networks (NNs) modelling technique. The NNs have been designed with GPS-TEC measured data from low and mid-latitude GPS stations. The training was conducted using the data obtained for the period from 2011 to 2014. The model prediction accuracy was evaluated using data of year 2015. The model results show that diurnal and seasonal trend of the GPS-TEC is well reproduced by the model for the two stations. The seasonal characteristics of GPS-TEC is compared with NN and NeQuick 2 models prediction when the latter one is driven by the monthly average value of solar flux. It is found that NN model performs better than the corresponding NeQuick 2 model for low latitude region. For the mid-latitude both NN and NeQuick 2 models reproduce the average characteristics of TEC variability quite successfully. An attempt of one day ahead forecast of TEC at the two locations has been made by introducing as drivers previous day solar flux and geomagnetic index values. The results show that a reasonable day ahead forecast of local TEC can be achieved.

Local TEC Modelling and Forecasting using Neural Networks

NASA Astrophysics Data System (ADS)

Tebabal, A.; Radicella, S. M.; Nigussie, M.; Damtie, B.; Nava, B.; Yizengaw, E.

2017-12-01

Abstract Modelling the Earth's ionospheric characteristics is the focal task for the ionospheric community to mitigate its effect on the radio communication, satellite navigation and technologies. However, several aspects of modelling are still challenging, for example, the storm time characteristics. This paper presents modelling efforts of TEC taking into account solar and geomagnetic activity, time of the day and day of the year using neural networks (NNs) modelling technique. The NNs have been designed with GPS-TEC measured data from low and mid-latitude GPS stations. The training was conducted using the data obtained for the period from 2011 to 2014. The model prediction accuracy was evaluated using data of year 2015. The model results show that diurnal and seasonal trend of the GPS-TEC is well reproduced by the model for the two stations. The seasonal characteristics of GPS-TEC is compared with NN and NeQuick 2 models prediction when the latter one is driven by the monthly average value of solar flux. It is found that NN model performs better than the corresponding NeQuick 2 model for low latitude region. For the mid-latitude both NN and NeQuick 2 models reproduce the average characteristics of TEC variability quite successfully. An attempt of one day ahead forecast of TEC at the two locations has been made by introducing as driver previous day solar flux and geomagnetic index values. The results show that a reasonable day ahead forecast of local TEC can be achieved.

A Statistical Study of Total Electron Content Changes in the Ionosphere Prior to Earthquake Occurrences

NASA Astrophysics Data System (ADS)

Thomas, J. N.; Huard, J.; Masci, F.

2015-12-01

There are many published reports of anomalous changes in the ionosphere prior to large earthquakes. However, whether or not these ionospheric changes are reliable precursors that could be useful for earthquake prediction is controversial within the scientific community. To test a possible statistical relationship between the ionosphere and earthquakes, we compare changes in the total electron content (TEC) of the ionosphere with occurrences of M≥6.0 earthquakes globally for a multiyear period. We use TEC data from a global ionosphere map (GIM) and an earthquake list declustered for aftershocks. For each earthquake, we look for anomalous changes in TEC within ±30 days of the earthquake time and within 2.5° latitude and 5.0° longitude of the earthquake location (the spatial resolution of GIM). Our preliminary analysis, using global TEC and earthquake data for 2002-2010, has not found any statistically significant changes in TEC prior to earthquakes. Thus, we have found no evidence that would suggest that TEC changes are useful for earthquake prediction. Our results are discussed in the context of prior statistical and case studies. Namely, our results agree with Dautermann et al. (2007) who found no relationship between TEC changes and earthquakes in the San Andreas fault region. Whereas, our results disagree with Le et al. (2011) who found an increased rate in TEC anomalies within a few days before global earthquakes M≥6.0.

Long Duration Enhancement And Depletion Observed In The Topside Ionospheric Electron Content During The March 2015 Strong Storm

NASA Astrophysics Data System (ADS)

Zhong, J.; Wang, W.; Yue, X.; Burns, A. G.; Dou, X.; Lei, J.

2015-12-01

Up-looking total electron content (TEC) measurements from multiple low Earth orbit (LEO) satellites have been utilized to study the topside ionospheric response to the 17 March 2015 great storm. The combined up-looking TEC observations from these LEO satellites are valuable in addressing the local time and altitudinal dependences of the topside ionospheric response to geomagnetic storms from a global perspective, especially over the southern hemisphere and oceans. In the evening sector, the up-looking TEC showed an obvious long-duration of positive storm effect during the main phase and a long duration of negative storm effect during the recovery phase of this storm. The increases of the topside TEC during the main phase were symmetric with respect to the magnetic equator, which was probably associated with penetration electric fields. Additionally, the up-looking TEC from different orbital altitudes suggested that the negative storm effect at higher altitudes was stronger in the evening sector. In the morning sector, the up-looking TEC also showed increases at low and middle latitudes during the storm main phase. Obvious TEC enhancement can be also seen over the Pacific Ocean in the topside ionosphere during the storm recovery phase. These results imply that the topside ionospheric responses significantly depend on local time. Thus, the LEO-based up-looking TEC provides an important database to study the possible physical mechanisms of the topside ionospheric response to storms.

Relationships between elastic anisotropy and thermal expansion in A 2Mo 3O 12 materials

DOE PAGES

Romao, Carl P.; Donegan, S. P.; Zwanziger, J. W.; ...

2016-10-24

Here, we report calculated elastic tensors, axial Grüneisen parameters, and thermal stress distributions in Al 2Mo 3O 12, ZrMgMo 3O 12, Sc 2Mo 3O 12, and Y 2Mo 3O 12, a series of isomorphic materials for which the coefficients of thermal expansion range from low-positive to negative. Thermal stress in polycrystalline materials arises from interactions between thermal expansion and mechanical properties, and both can be highly anisotropic. Thermal expansion anisotropy was found to be correlated with elastic anisotropy: axes with negative thermal expansion were less compliant. Calculations of axial Grüneisen parameters revealed that the thermal expansion anisotropy in these materialsmore » is in part due to the Poisson effect. Models of thermal stress due to thermal expansion anisotropy in polycrystals following cooling showed thermal stresses of sufficient magnitude to cause microcracking in all cases. The thermal expansion anisotropy was found to couple to elastic anisotropy, decreasing the bulk coefficient of thermal expansion and leading to lognormal extremes of the thermal stress distributions.« less

Relationships between elastic anisotropy and thermal expansion in A 2Mo 3O 12 materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romao, Carl P.; Donegan, S. P.; Zwanziger, J. W.

Here, we report calculated elastic tensors, axial Grüneisen parameters, and thermal stress distributions in Al 2Mo 3O 12, ZrMgMo 3O 12, Sc 2Mo 3O 12, and Y 2Mo 3O 12, a series of isomorphic materials for which the coefficients of thermal expansion range from low-positive to negative. Thermal stress in polycrystalline materials arises from interactions between thermal expansion and mechanical properties, and both can be highly anisotropic. Thermal expansion anisotropy was found to be correlated with elastic anisotropy: axes with negative thermal expansion were less compliant. Calculations of axial Grüneisen parameters revealed that the thermal expansion anisotropy in these materialsmore » is in part due to the Poisson effect. Models of thermal stress due to thermal expansion anisotropy in polycrystals following cooling showed thermal stresses of sufficient magnitude to cause microcracking in all cases. The thermal expansion anisotropy was found to couple to elastic anisotropy, decreasing the bulk coefficient of thermal expansion and leading to lognormal extremes of the thermal stress distributions.« less

Lightweight Mechanical Metamaterials with Tunable Negative Thermal Expansion

NASA Astrophysics Data System (ADS)

Wang, Qiming; Jackson, Julie A.; Ge, Qi; Hopkins, Jonathan B.; Spadaccini, Christopher M.; Fang, Nicholas X.

2016-10-01

Ice floating on water is a great manifestation of negative thermal expansion (NTE) in nature. The limited examples of natural materials possessing NTE have stimulated research on engineered structures. Previous studies on NTE structures were mostly focused on theoretical design with limited experimental demonstration in two-dimensional planar geometries. In this work, aided with multimaterial projection microstereolithography, we experimentally fabricate lightweight multimaterial lattices that exhibit significant negative thermal expansion in three directions and over a temperature range of 170 degrees. Such NTE is induced by the structural interaction of material components with distinct thermal expansion coefficients. The NTE can be tuned over a large range by varying the thermal expansion coefficient difference between constituent beams and geometrical arrangements. Our experimental results match qualitatively with a simple scaling law and quantitatively with computational models.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biendicho, J.J.; The ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot, OX11 0QX Oxfordshire; Shafeie, S.

Oxygen-deficient ferrates with the cubic perovskite structure Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} were prepared in air (0.71≤x≤0.91) as well as in N{sub 2} (x=0.75 and 0.79) at 1573 K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3−δ=2.79(2) for x=0.75 to 3−δ=2.83(2) for x=0.91. Refinement of the crystal structure of Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} using TOF neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and high-resolution electron microscopy (HREM) studies of Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}more » reveal a modulation along 〈1 0 0〉{sub p} with G± ∼0.4〈1 0 0〉{sub p} indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5–390 K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm/K in air at 298–673 K. At 773–1173 K TEC increases up to 17.2 ppm/K due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673 K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr{sub 0.75}Y{sub 0.25}Fe{sub 1−y}M{sub y}O{sub 3−δ} (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}. Only M=Ni has increased electrical conductivity compared to un-doped Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79}. - Graphical abstract: Oxygen-deficient ferrates with the cubic perovskite structure Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} were prepared both in air (0.71≤x≤0.91) and N{sub 2} (x=0.75 and 0.79) at 1573 K. Refinement of the crystal structure of Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} using TOF neutron powder diffraction (NPD) data (S.G. Pm-3m, a=3.86455(3) Å; χ{sup 2}=6.71, R{sub p}=0.03; R{sub wp}=0.04) confirmed the cubic perovskite structure. The observed high anisotropic atomic displacement parameter for the oxygen atom indicates a substantial anion sublattice disorder. Electron diffraction (ED) and high-resolution electron microscopy (HREM) studies of Sr{sub 0.75}Y{sub 0.25}FeO{sub 2.79} show compositional modulation along 〈1 0 0〉{sub p} with G± ∼0.4〈1 0 0〉{sub p} indicating ordering of oxygen vacancies at the local scale. Highlights: ► Cubic perovskites Sr{sub x}Y{sub 1−x}FeO{sub 3−δ} (0.71≤x<0.91) were synthesized. ► Sr{sub 0.75}Y{sub 0.25}Fe{sub 1−y}M{sub y}O{sub 3−δ}, M=Cr, Mn, Ni were prepared. ► High-temperature conductivity properties and crystal structure were studied. ► High-temperature thermal expansion behavior was investigated.« less

Analysis of ionospheric TEC from GNSS observables over the Turkish region and predictability of IRI and SPIM models

NASA Astrophysics Data System (ADS)

Ansari, Kutubuddin; Corumluoglu, Ozsen; Panda, Sampad Kumar

2017-04-01

The present study investigates the ionospheric Total Electron Content (TEC) variations in the lower mid-latitude Turkish region from the Turkish Permanent GNSS Network (TPGN) and International GNSS Services (IGS) observations during the period from January 2015 to December 2015. The corresponding TEC predicted by the International Reference Ionosphere (IRI 2012) and Standard Plasmasphere-Ionosphere Model (SPIM), and interpolated from Global Ionosphere Maps (GIMs) are evaluated to realize their reliability over the region. We studied the diurnal and monthly behavior of TEC and the relative TEC deviations along with the upper and lower quartiles to represent its spatio-temporal variability. The diurnal variation of GNSS-derived TEC indicates its maximum peak value around 10.00 UT which decreases gradually to attain minimum value after midnight. The monthly maximum value of TEC is observed in March followed by May and August, and the lowest value is seen during September. Studies show that the monthly relative deviation of TEC variability lies in the range of -1 to 4 units for all stations with the maximum difference between positive and negative variability remaining around 5. The studies also cover seasonal variation, grand-mean of ionospheric TEC and TEC intensity from the TPGN. The seasonal ionospheric VTEC pattern over all stations depicts slight increment in VTEC distribution during March equinox compared to September equinox. The December solstice perceived relatively higher VTEC than June solstice. The overall of VTEC values enhanced at all stations towards end of the year 2015 compare to mid of year due the high solar activity. The maximum grand-mean of VTEC is registered in March equinox while the lowest value is seen in September irrespective of all stations. The measured grand-mean intensity variations of VTEC values are in ascending phase during March, May, August and November months, but in descending phase during February, April, June and September months. The latitudinal study shows daytime TEC slowly decreasing with latitudes with a latitudinal gradient range of 0.1-0.2 TECU/degree. Additionally, the TEC analysis during the strong geomagnetic storm period (07-11 September 2015; SYM-H -120 nT) infers relatively better predictability of the SPIM model compared to the IRI 2012 model. The outputs of this study would complement towards a complete understanding of the lower mid-latitude ionospheric dynamics and its effects on radio propagations, particularly over the Turkish region.

Review of variations in Mw < 7 earthquake motions on position and tec (Mw = 6.5 aegean sea earthquake sample)

NASA Astrophysics Data System (ADS)

Yildirim, O.; Inyurt, S.; Mekik, C.

2015-10-01

Turkey is a country located in Middle Latitude zone and in which tectonic activity is intensive. Lastly, an earthquake of magnitude 6.5Mw occurred at Aegean Sea offshore on date 24 May 2014 at 12:25 UTC and it lasted approximately 40 s. The said earthquake was felt also in Greece, Romania and Bulgaria in addition to Turkey. In recent years seismic origin ionospheric anomaly detection studies have been done with TEC (Total Electron Contents) generated from GNSS (Global Navigation Satellite System) signals and the findings obtained have been revealed. In this study, TEC and positional variations have been examined seperately regarding the earthquake which occurred in the Aegean Sea. Then The correlation of the said ionospheric variation with the positional variation has been investigated. For this purpose, total fifteen stations have been used among which the data of four numbers of CORS-TR stations in the seismic zone (AYVL, CANA, IPSA, YENC) and IGS and EUREF stations are used. The ionospheric and positional variations of AYVL, CANA, IPSA and YENC stations have been examined by Bernese 5.0v software. When the (PPP-TEC) values produced as result of the analysis are examined, it has been understood that in the four stations located in Turkey, three days before the earthquake at 08:00 and 10:00 UTC, the TEC values were approximately 4 TECU above the upper limit TEC value. Still in the same stations, one day before the earthquake at 06:00, 08:00 and 10:00 UTC, it is being shown that the TEC values were approximately 5 TECU below the lower limit TEC value. On the other hand, the GIM-TEC values published by the CODE center have been examined. Still in all stations, it has been observed that three days before the earthquake the TEC values in the time portions of 08:00 and 10:00 UTC were approximately 2 TECU above, one day before the earthquake at 06:00, 08:00 and 10:00 UTC, the TEC values were approximately 4 TECU below the lower limit TEC value. Again, by using the same fifteen numbers of stations, positional variation investigation before and after the earthquake has been made for AYVL, CANA, IPSA and YENC stations. As result of the analysis made, positional displacements has been seen before and after earthquake at CANA station which is the nearest station to earthquake center. It is about 10 and 3 cm before three days and one day earthquake.

Ceramic sealants prepared by polymer pyrolysis

NASA Astrophysics Data System (ADS)

Hong, Sung Jin; Kim, Deug Joong; Yoo, Young Sung

2011-02-01

The formation and properties of ceramic seals for SOFC applications prepared by polymer pyrolysis are investigated. A mixture with polymethylsiloxane and fillers are pyrolyzed in a N2 atmosphere. The coefficient of thermal expansion of the ceramic composites was controlled by fillers with a high coefficient of thermal expansion such as AlCo. The morphology of the ceramic composites derived from the mixture with polymethylsiloxane and fillers is composed of fillers embedded in a Si-O-C glass matrix. The thermal expansion behavior and sealing characteristics are measured and discussed

Ultraprecise thermal expansion measurements of seven low expansion materials

NASA Technical Reports Server (NTRS)

Berthold, J. W., III; Jacobs, S. F.

1976-01-01

We summarize a large number of ultraprecise thermal expansion measurements made on seven different low expansivity materials. Expansion coefficients in the -150-300 C temperature range are shown for Owens-Illinois Cer-Vit C-101, Corning ULE 7971 (titanium silicate) and fused silica 7940, Heraeus-Schott Zerodur low-expansion material and Homosil fused silica, Universal Cyclops Invar LR-35, and Simonds Saw and Steel Super Invar.

The thermal expansion of hard magnetic materials of the Nd-Fe-B system

NASA Astrophysics Data System (ADS)

Savchenko, Igor; Kozlovskii, Yurii; Samoshkin, Dmitriy; Yatsuk, Oleg

2017-10-01

The results of dilatometric measurement of the thermal expansion of hard magnetic materials brands N35M, N35H and N35SH containing as a main component the crystalline phase of Nd2Fe14B type are presented. The temperature range from 200 to 750 K has been investigated by the method of dilatometry with an error of 1.5-2×10-7 K-1. The approximation dependences of the linear thermal expansion coefficient have been obtained. The character of changes of the thermal coefficient of linear expansion in the region of the Curie point has been specified, its critical indices and critical amplitudes have been defined.

Thermal expansion of quaternary nitride coatings

NASA Astrophysics Data System (ADS)

Tasnádi, Ferenc; Wang, Fei; Odén, Magnus; Abrikosov, Igor A.

2018-04-01

The thermal expansion coefficient of technologically relevant multicomponent cubic nitride alloys are predicted using the Debye model with ab initio elastic constants calculated at 0 K and an isotropic approximation for the Grüneisen parameter. Our method is benchmarked against measured thermal expansion of TiN and Ti(1-x)Al x N as well as against results of molecular dynamics simulations. We show that the thermal expansion coefficients of Ti(1-x-y)X y Al x N (X  =  Zr, Hf, Nb, V, Ta) solid solutions monotonously increase with the amount of alloying element X at all temperatures except for Zr and Hf, for which they instead decrease for y≳ 0.5 .

Thermal expansion of boron subnitrides

NASA Astrophysics Data System (ADS)

Cherednichenko, Kirill A.; Gigli, Lara; Solozhenko, Vladimir L.

2018-07-01

The lattice parameters of two boron subnitrides, B13N2 and B50N2, have been measured as a function of temperature between 298 and 1273 K, and the corresponding thermal expansion coefficients have been determined. Thermal expansion of both boron subnitrides was found to be quasi-linear, and the volume thermal expansion coefficients of B50N2 (15.7 (2) × 10-6 K-1) and B13N2 (21.3 (2) × 10-6 K-1) are of the same order of magnitude as those of boron-rich compounds with structure related to α-rhombohedral boron. For both boron subnitrides no temperature-induced phase transitions have been observed in the temperature range under study.

Optimize out-of-core thermionic energy conversion for nuclear electric propulsion

NASA Technical Reports Server (NTRS)

Morris, J. F.

1978-01-01

Thermionic energy conversion (TEC) potentialities for nuclear electric propulsion (NEP) are examined. Considering current designs, their limitations, and risks raises critical questions about the use of TEC for NEP. Apparently a reactor cooled by hotter-than-1675 K heat pipes has good potentialities. TEC with higher temperatures and greater power densities than the currently proposed 1650 K, 5-to-6 W/sq cm version offers substantial gains. Other approaches to high-temperature electric isolation appear also promising. A high-power-density, high-temperature TEC for NEP appears, therefore, attainable. It is recommended to optimize out-of-core thermionic energy conversion for nuclear electric propulsion. Although current TEC designs for NEP seem unnecessary compared with Brayton versions, large gains are apparently possible with increased temperatures and greater power densities.

Coliphage HK022 Nun protein inhibits RNA polymerase translocation

PubMed Central

Vitiello, Christal L.; Kireeva, Maria L.; Lubkowska, Lucyna; Kashlev, Mikhail; Gottesman, Max

2014-01-01

The Nun protein of coliphage HK022 arrests RNA polymerase (RNAP) in vivo and in vitro at pause sites distal to phage λ N-Utilization (nut) site RNA sequences. We tested the activity of Nun on ternary elongation complexes (TECs) assembled with templates lacking the λ nut sequence. We report that Nun stabilizes both translocation states of RNAP by restricting lateral movement of TEC along the DNA register. When Nun stabilized TEC in a pretranslocated register, immediately after NMP incorporation, it prevented binding of the next NTP and stimulated pyrophosphorolysis of the nascent transcript. In contrast, stabilization of TEC by Nun in a posttranslocated register allowed NTP binding and nucleotidyl transfer but inhibited pyrophosphorolysis and the next round of forward translocation. Nun binding to and action on the TEC requires a 9-bp RNA–DNA hybrid. We observed a Nun-dependent toe print upstream to the TEC. In addition, mutations in the RNAP β′ subunit near the upstream end of the transcription bubble suppress Nun binding and arrest. These results suggest that Nun interacts with RNAP near the 5′ edge of the RNA–DNA hybrid. By stabilizing translocation states through restriction of TEC lateral mobility, Nun represents a novel class of transcription arrest factors. PMID:24853501

Total electron content responses to HILDCAAs and geomagnetic storms over South America

NASA Astrophysics Data System (ADS)

Mara de Siqueira Negreti, Patricia; Rodrigues de Paula, Eurico; Nicoli Candido, Claudia Maria

2017-12-01

Total electron content (TEC) is extensively used to monitor the ionospheric behavior under geomagnetically quiet and disturbed conditions. This subject is of greatest importance for space weather applications. Under disturbed conditions the two main sources of electric fields, which are responsible for changes in the plasma drifts and for current perturbations, are the short-lived prompt penetration electric fields (PPEFs) and the longer-lasting ionospheric disturbance dynamo (DD) electric fields. Both mechanisms modulate the TEC around the globe and the equatorial ionization anomaly (EIA) at low latitudes. In this work we computed vertical absolute TEC over the low latitude of South America. The analysis was performed considering HILDCAA (high-intensity, long-duration, continuous auroral electrojet (AE) activity) events and geomagnetic storms. The characteristics of storm-time TEC and HILDCAA-associated TEC will be presented and discussed. For both case studies presented in this work (March and August 2013) the HILDCAA event follows a geomagnetic storm, and then a global scenario of geomagnetic disturbances will be discussed. Solar wind parameters, geomagnetic indices, O / N2 ratios retrieved by GUVI instrument onboard the TIMED satellite and TEC observations will be analyzed and discussed. Data from the RBMC/IBGE (Brazil) and IGS GNSS networks were used to calculate TEC over South America. We show that a HILDCAA event may generate larger TEC differences compared to the TEC observed during the main phase of the precedent geomagnetic storm; thus, a HILDCAA event may be more effective for ionospheric response in comparison to moderate geomagnetic storms, considering the seasonal conditions. During the August HILDCAA event, TEC enhancements from ˜ 25 to 80 % (compared to quiet time) were observed. These enhancements are much higher than the quiet-time variability observed in the ionosphere. We show that ionosphere is quite sensitive to solar wind forcing and considering the events studied here, this was the most important source of ionospheric responses. Furthermore, the most important source of TEC changes were the long-lasting PPEFs observed on August 2013, during the HILDCAA event. The importance of this study relies on the peculiarity of the region analyzed characterized by high declination angle and ionospheric gradients which are responsible for creating a complex response during disturbed periods.

Validation of measured poleward TEC gradient using multi-station GPS with Artificial Neural Network based TEC model in low latitude region for developing predictive capability of ionospheric scintillation

NASA Astrophysics Data System (ADS)

Sur, D.; Paul, A.

2017-12-01

The equatorial ionosphere shows sharp diurnal and latitudinal Total Electron Content (TEC) variations over a major part of the day. Equatorial ionosphere also exhibits intense post-sunset ionospheric irregularities. Accurate prediction of TEC in these low latitudes is not possible from standard ionospheric models. An Artificial Neural Network (ANN) based Vertical TEC (VTEC) model has been designed using TEC data in low latitude Indian longitude sector for accurate prediction of VTEC. GPS TEC data from the stations Calcutta (22.58°N, 88.38°E geographic, magnetic dip 32°), Baharampore (24.09°N, 88.25°E geographic, magnetic dip 35°) and Siliguri (26.72°N, 88.39°E geographic; magnetic dip 40°) are used as training dataset for the duration of January 2007-September 2011. Poleward VTEC gradients from northern EIA crest to region beyond EIA crest have been calculated from measured VTEC and compared with that obtained from ANN based VTEC model. TEC data from Calcutta and Siliguri are used to compute VTEC gradients during April 2013 and August-September 2013. It has been observed that poleward VTEC gradient computed from ANN based TEC model has shown good correlation with measured values during vernal and autumnal equinoxes of high solar activity periods of 2013. Possible correlation between measured poleward TEC gradients and post-sunset scintillations (S4 ≥ 0.4) from northern crest of EIA has been observed in this paper. From the observation, a suitable threshold poleward VTEC gradient has been proposed for possible occurrence of post-sunset scintillations at northern crest of EIA along 88°E longitude. Poleward VTEC gradients obtained from ANN based VTEC model are used to forecast possible ionospheric scintillation after post-sunset period using the threshold value. It has been observed that these predicted VTEC gradients obtained from ANN based VTEC model can forecast post-sunset L-band scintillation with an accuracy of 67% to 82% in this dynamic low latitude region. The use of VTEC gradients from ANN based VTEC model removes the necessity of continuous operation of multi-station ground based TEC receivers in this low latitude region.

Thermoelastic characteristics testing on kevlar samples for spacecraft structures

NASA Astrophysics Data System (ADS)

Crema, L. Balis; Barboni, R.; Castellani, A.; Peroni, I.

The tensile properties, the thermal expansion coefficient and the thermal conductivity of woven roving (WR) reinforced Kevlar fabrics were experimentally determined. Theoretical values for tensile Young's modulus were calculated by simulating a fabric as an equivalent cross-ply laminate. As thermal expansion coefficient concerns the fabrics have shown an isotropic behaviour. The thermal conductivity normal to fabric plane has also been determined.

Auxiliary basis expansions for large-scale electronic structure calculations

PubMed Central

Jung, Yousung; Sodt, Alex; Gill, Peter M. W.; Head-Gordon, Martin

2005-01-01

One way to reduce the computational cost of electronic structure calculations is to use auxiliary basis expansions to approximate four-center integrals in terms of two- and three-center integrals, usually by using the variationally optimum Coulomb metric to determine the expansion coefficients. However, the long-range decay behavior of the auxiliary basis expansion coefficients has not been characterized. We find that this decay can be surprisingly slow. Numerical experiments on linear alkanes and a toy model both show that the decay can be as slow as 1/r in the distance between the auxiliary function and the fitted charge distribution. The Coulomb metric fitting equations also involve divergent matrix elements for extended systems treated with periodic boundary conditions. An attenuated Coulomb metric that is short-range can eliminate these oddities without substantially degrading calculated relative energies. The sparsity of the fit coefficients is assessed on simple hydrocarbon molecules and shows quite early onset of linear growth in the number of significant coefficients with system size using the attenuated Coulomb metric. Hence it is possible to design linear scaling auxiliary basis methods without additional approximations to treat large systems. PMID:15845767

On the construction of recurrence relations for the expansion and connection coefficients in series of Jacobi polynomials

NASA Astrophysics Data System (ADS)

Doha, E. H.

2004-01-01

Formulae expressing explicitly the Jacobi coefficients of a general-order derivative (integral) of an infinitely differentiable function in terms of its original expansion coefficients, and formulae for the derivatives (integrals) of Jacobi polynomials in terms of Jacobi polynomials themselves are stated. A formula for the Jacobi coefficients of the moments of one single Jacobi polynomial of certain degree is proved. Another formula for the Jacobi coefficients of the moments of a general-order derivative of an infinitely differentiable function in terms of its original expanded coefficients is also given. A simple approach in order to construct and solve recursively for the connection coefficients between Jacobi-Jacobi polynomials is described. Explicit formulae for these coefficients between ultraspherical and Jacobi polynomials are deduced, of which the Chebyshev polynomials of the first and second kinds and Legendre polynomials are important special cases. Two analytical formulae for the connection coefficients between Laguerre-Jacobi and Hermite-Jacobi are developed.

Boson expansion based on the extended commutator method in the Tamm-Dancoff representation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pedrocchi, V.G.; Tamura, T.

1983-07-01

Formal aspects of boson expansions in the Tamm-Dancoff representation are investigated in detail. This is carried out in the framework of the extended commutator method by solving in complete generality the coefficient equations, searching for Hermitian as well as non-Hermitian boson expansions. The solutions for the expansion coefficients are obtained in a new form, called the square root realization, which is then applied to carry out an analysis of the relationship between the type of expansion and the boson space in which the expansion is defined. It is shown that this new realization is reduced to various well-known boson theoriesmore » when the boson space is chosen in an appropriate manner. Further discussed, still on the basis of the square root realization, is the equivalence, on a practical level, of a few boson expansion approaches when the Tamm-Dancoff space is truncated to a single quadrupole collective component.« less

Interbasis expansions in the Zernike system

NASA Astrophysics Data System (ADS)

Atakishiyev, Natig M.; Pogosyan, George S.; Wolf, Kurt Bernardo; Yakhno, Alexander

2017-10-01

The differential equation with free boundary conditions on the unit disk that was proposed by Frits Zernike in 1934 to find Jacobi polynomial solutions (indicated as I) serves to define a classical system and a quantum system which have been found to be superintegrable. We have determined two new orthogonal polynomial solutions (indicated as II and III) that are separable and involve Legendre and Gegenbauer polynomials. Here we report on their three interbasis expansion coefficients: between the I-II and I-III bases, they are given by F32(⋯|1 ) polynomials that are also special su(2) Clebsch-Gordan coefficients and Hahn polynomials. Between the II-III bases, we find an expansion expressed by F43(⋯|1 ) 's and Racah polynomials that are related to the Wigner 6j coefficients.

Dual-band beacon experiment over Southeast Asia for ionospheric irregularity analysis

NASA Astrophysics Data System (ADS)

Watthanasangmechai, K.; Yamamoto, M.; Saito, A.; Saito, S.; Maruyama, T.; Tsugawa, T.; Nishioka, M.

2013-12-01

An experiment of dual-band beacon over Southeast Asia was started in March 2012 in order to capture and analyze ionospheric irregularities in equatorial region. Five GNU Radio Beacon Receivers (GRBRs) were aligned along 100 degree geographic longitude. The distances between the stations reach more than 500 km. The field of view of this observational network covers +/- 20 degree geomagnetic latitude including the geomagnetic equator. To capture ionospheric irregularities, the absolute TEC estimation technique was developed. The two-station method (Leitinger et al., 1975) is generally accepted as a suitable method to estimate TEC offsets of dual-band beacon experiment. However, the distances between the stations directly affect on the robustness of the technique. In Southeast Asia, the observational network is too sparse to attain a benefit of the classic two-station method. Moreover, the least-squares approch used in the two-station method tries too much to adjust the small scales of the TEC distribution which are the local minima. We thus propose a new technique to estimate the TEC offsets with the supporting data from absolute GPS-TEC from local GPS receivers and the ionospheric height from local ionosondes. The key of the proposed technique is to utilize the brute-force technique with weighting function to find the TEC offset set that yields a global minimum of RMSE in whole parameter space. The weight is not necessary when the TEC distribution is smooth, while it significantly improves the TEC estimation during the ESF events. As a result, the latitudinal TEC shows double-hump distribution because of the Equatorial Ionization Anomaly (EIA). In additions, the 100km-scale fluctuations from an Equatorial Spread F (ESF) are captured at night time in equinox seasons. The plausible linkage of the meridional wind with triggering of ESF is under invatigating and will be presented. The proposed method is successful to estimate the latitudinal TEC distribution from dual-band frequency beacon data for the sparse observational network in Southeast Asia which may be useful for other equatorial sectors like Affrican region as well.

Comparison of GPS TEC variations with Holt-Winter method and IRI-2012 over Langkawi, Malaysia

NASA Astrophysics Data System (ADS)

Elmunim, N. A.; Abdullah, M.; Hasbi, A. M.; Bahari, S. A.

2017-07-01

The Total Electron Content (TEC) is the ionospheric parameter that has the main effect on radio wave propagation. Therefore, it is crucial to evaluate the performance of the TEC models for the further improvement of the ionospheric modelling in equatorial regions. This work presents an analysis of the TEC, derived from the GPS Ionospheric Scintillation and TEC Monitor (GISTM) receiver at the Langkawi station, Malaysia, located at the geographic coordinates of 6.19°N, 99.51°E and the geomagnetic coordinates of 3.39°S, 172.42°E. The diurnal, monthly and seasonal variations in 2014 of the observed GPS-TEC were compared with the statistical Holt-Winter method and a recent version of the International Reference Ionosphere model (IRI-2012), using three different topside options of an electron density, which are the IRI-2001, IRI01-corr and NeQuick. The maximum peaks of the GPS-TEC were observed in the post-noon time and the minimum was observed during the early morning time. In addition, in monthly variations the Holt-Winter and the IRI-2012 topside options showed an underestimation that was in agreement with the GPS-TEC, except for the IRI-2001 model which showed an overestimation in June, July and August. Regarding the seasonal variation of the GPS-TEC, the lowest values were observed during summer and it reached its maximum value during the equinox season. The IRI-2001 showed the highest value of percentage deviation compared to the IRI01-corr, NeQuick and Holt-Winter method. Therefore, the accuracy of the models was found to be approximately 95% in the Holt-Winter method, 75% in the IRI01-corr, 73% in the NeQuick and 66% in the IRI-2001 model. Hence, it can be inferred that the Holt-Winter method showed a higher performance and better estimates of the TEC compared to the IRI01-corr and NeQuick, while the IRI-2001 showed a poor predictive performance in the equatorial region over Malaysia.

Ultraprecise thermal expansion measurements of seven low expansion materials.

PubMed

Berthold Iii, J W; Jacobs, S F

1976-10-01

We summarize a large number of ultraprecise thermal expansion measurements made on seven different low expansivity materials. Expansion coefficients in the -150-300 degrees C temperature range are shown for Owens-Illinois Cer-Vit C-101, Corning ULE 7971 (titanium silicate) and fused silica 7940, Heraeus-Schott Zerodur low-expansion material and Homosil fused silica, Universal Cyclops Invar LR-35, and Simonds Saw and Steel Super Invar.

Correction of Single Frequency Altimeter Measurements for Ionosphere Delay

NASA Technical Reports Server (NTRS)

Schreiner, William S.; Markin, Robert E.; Born, George H.

1997-01-01

This study is a preliminary analysis of the accuracy of various ionosphere models to correct single frequency altimeter height measurements for Ionospheric path delay. In particular, research focused on adjusting empirical and parameterized ionosphere models in the parameterized real-time ionospheric specification model (PRISM) 1.2 using total electron content (TEC) data from the global positioning system (GPS). The types of GPS data used to adjust PRISM included GPS line-of-sight (LOS) TEC data mapped to the vertical, and a grid of GPS derived TEC data in a sun-fixed longitude frame. The adjusted PRISM TEC values, as well as predictions by IRI-90, a climatotogical model, were compared to TOPEX/Poseidon (T/P) TEC measurements from the dual-frequency altimeter for a number of T/P tracks. When adjusted with GPS LOS data, the PRISM empirical model predicted TEC over 24 1 h data sets for a given local time to with in a global error of 8.60 TECU rms during a midnight centered ionosphere and 9.74 TECU rms during a noon centered ionosphere. Using GPS derived sun-fixed TEC data, the PRISM parameterized model predicted TEC within an error of 8.47 TECU rms centered at midnight and 12.83 TECU rms centered at noon. From these best results, it is clear that the proposed requirement of 3-4 TECU global rms for TOPEX/Poseidon Follow-On will be very difficult to meet, even with a substantial increase in the number of GPS ground stations, with any realizable combination of the aforementioned models or data assimilation schemes.

V-TECS Guide for Medical Assistant.

ERIC Educational Resources Information Center

South Carolina State Dept. of Education, Columbia. Office of Vocational Education.

This V-TECS (Vocational-Technical Consortium of States) Guide is an extension or continuation of the V-TECS catalog for the occupation of medical assistant. The guide is designed to help South Carolina teachers to promote the art of learning while teaching subject matter. The guide addresses the three domains of learning: psychomotor, cognitive,…

NMobTec-EnvEdu: M-Learning System for Environmental Education

ERIC Educational Resources Information Center

Cavus, Nadire

2008-01-01

This paper introduced the implementation of a New Mobile Technologies and Environmental Education System (NMobTec-EnvEdu) designed for m-learning environments. The NMobTec-EnvEdu system has been developed to provide environmental education in a collaborative framework to undergraduate students through the Internet using mobile phones. The study…

Culture promotes transfer of thyroid epithelial cell hyperplasia and proliferation by reducing regulatory T cell numbers.

PubMed

Kayes, Timothy D; Braley-Mullen, Helen

2013-01-01

IFN-γ(-/-) NOD.H-2h4 mice develop a spontaneous autoimmune thyroid disease, thyroid epithelial cell hyperplasia and proliferation (TEC H/P) when given NaI in their water for 7+ mo. TEC H/P can be transferred to IFN-γ(-/-) SCID mice by splenocytes from mice with severe (4-5+) disease, and transfer of TEC H/P is improved when splenocytes are cultured prior to transfer. Older (9+ mo) IFN-γ(-/-) NOD.H-2h4 mice have elevated numbers of FoxP3(+) T reg cells, up to 2-fold greater than younger (2 mo) mice. During culture, the number of T reg decreases and this allows the improved transfer of TEC H/P. Co-culture with IL-2 prior to transfer prevents the decrease of T reg and improves their in vitro suppressive ability resulting in reduced TEC H/P in recipient mice. Therefore, culturing splenocytes improves transfer of TEC H/P by reducing the number of T reg and IL-2 inhibits transfer by preserving T reg number and function. Copyright © 2013 Elsevier Inc. All rights reserved.

Vertical and Lateral Electron Content in the Martian Ionosphere

NASA Astrophysics Data System (ADS)

Paetzold, M. P.; Peter, K.; Bird, M. K.; Häusler, B.; Tellmann, S.

2016-12-01

The radio-science experiment MaRS (Mars Express Radio Science) on the Mars Express spacecraft sounds the neutral atmosphere and ionosphere of Mars since 2004. Approximately 800 vertical profiles of the ionospheric electron density have been acquired until today. The vertical electron content (TEC) is easily computed from the vertical electron density profile by integrating along the altitude. The TEC is typically a fraction of a TEC unit (1E16 m^-2) and depends on the solar zenith angle. The magnitude of the TEC is however fully dominated by the electron density contained in the main layer M2. The contributions by the M1 layer below M2 or the topside is marginal. MaRS is using two radio frequencies for the sounding of the ionosphere. The directly observed differential Doppler from the two received frequencies is a measure of the lateral electron content that means along the ray path and perpendicular to the vertical electron density profile. Combining both the vertical electron density profile, the vertical TEC and the directly observed lateral TEC describes the lateral electron density distribution in the ionosphere.

A regional ionospheric TEC mapping technique over China and adjacent areas on the basis of data assimilation

NASA Astrophysics Data System (ADS)

Aa, Ercha; Huang, Wengeng; Yu, Shimei; Liu, Siqing; Shi, Liqin; Gong, Jiancun; Chen, Yanhong; Shen, Hua

2015-06-01

In this paper, a regional total electron content (TEC) mapping technique over China and adjacent areas (70°E-140°E and 15°N-55°N) is developed on the basis of a Kalman filter data assimilation scheme driven by Global Navigation Satellite Systems (GNSS) data from the Crustal Movement Observation Network of China and International GNSS Service. The regional TEC maps can be generated accordingly with the spatial and temporal resolution being 1°×1° and 5 min, respectively. The accuracy and quality of the TEC mapping technique have been validated through the comparison with GNSS observations, the International Reference Ionosphere model values, the global ionosphere maps from Center for Orbit Determination of Europe, and the Massachusetts Institute of Technology Automated Processing of GPS TEC data from Madrigal database. The verification results indicate that great systematic improvements can be obtained when data are assimilated into the background model, which demonstrates the effectiveness of this technique in providing accurate regional specification of the ionospheric TEC over China and adjacent areas.

A Year-Long Comparison of GPS TEC and Global Ionosphere-Thermosphere Models

NASA Astrophysics Data System (ADS)

Perlongo, N. J.; Ridley, A. J.; Cnossen, I.; Wu, C.

2018-02-01

The prevalence of GPS total electron content (TEC) observations has provided an opportunity for extensive global ionosphere-thermosphere model validation efforts. This study presents a year-long data-model comparison using the Global Ionosphere-Thermosphere Model (GITM) and the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). For the entire year of 2010, each model was run and compared to GPS TEC observations. The results were binned according to season, latitude, local time, and magnetic local time. GITM was found to overestimate the TEC everywhere, except on the midlatitude nightside, due to high O/N2 ratios. TIE-GCM produced much less TEC and had lower O/N2 ratios and neutral wind speeds. Seasonal and regional biases in the models are discussed along with ideas for model improvements and further validation efforts.

Secular variation and fluctuation of GPS Total Electron Content over Antarctica

NASA Astrophysics Data System (ADS)

Jin, Rui; Jin, Shuanggen

2013-01-01

The total electron content (TEC) is an important parameters in the Earth's ionosphere, related to various space weather and solar activities. However, understanding of the complex ionospheric environments is still a challenge due to the lack of direct observations, particularly in the polar areas, e.g., Antarctica. Now the Global Positioning System (GPS) can be used to retrieve total electron content (TEC) from dual-frequency observations. The continuous GPS observations in Antarctica provide a good opportunity to investigate ionospheric climatology. In this paper, the long-term variations and fluctuations of TEC over Antarctica are investigated from CODE global ionospheric maps (GIM) with a resolution of 2.5°×5° every two hours since 1998. The analysis shows significant seasonal and secular variations in the GPS TEC. Furthermore, the effects of TEC fluctuations are discussed.

Comparison of Plateletpheresis on the Fenwal Amicus and Fresenius Com.Tec Cell Separators.

PubMed

Altuntas, Fevzi; Sari, Ismail; Kocyigit, Ismail; Kaynar, Leylagul; Hacioglu, Sibel; Ozturk, Ahmet; Oztekin, Mehmet; Solmaz, Musa; Eser, Bulent; Cetin, Mustafa; Unal, Ali

2008-01-01

SUMMARY: BACKGROUND: A variety of apheresis devices are now available on the market for plateletapheresis. We compared two apheresis instruments (Fenwal Amicus and Fresenius COM.TEC) with regard to processing time, platelet (PLT) yield and efficiency, and white blood cell (WBC) content. MATERIAL AND METHODS: Donors undergoing plateletpheresis were randomly separated into two groups (either the Amicus or the COM.TEC cell separator). RESULTS: In the pre-apheresis setting, 32 plateletpheresis procedures performed with each instrument revealed no significant differences in donors' sex, age, weight, height and total blood volume between the two groups. However, the pre-apheresis PLT count was higher with the COM.TEC than with the Amicus (198 × 10(3)/μl vs. 223 × 10(3)/μl; p = 0.035). The blood volume processed to reach a target PLT yield of ≥3.3 × 10(11) was higher in the COM.TEC compared to the Amicus (3,481 vs. 2,850 ml; p < 0.001). The median separation time was also significantly longer in the COM.TEC than in the Amicus (61 vs. 44 min; p < 0.001). 91 and 88% of the PLT products collected with the Amicus and the COM.TEC, respectively, had a PLT count of >3.3 × 10(11) (p = 0.325). All products obtained with both instruments had WBC counts lower than 5 ↔ 10(6), as required. There was no statistical difference with regard to collection efficiency between the devices (55 ± 15 vs. 57 ± 15%; p = 0.477). However, the collection rate was significantly higher with the Amicus compared to the COM.TEC instrument (0.077 ± 0.012 × 10(11) vs. 0.057 ± 0.008 × 10(11) PLT/min; p < 0.001). CONCLUSION: Both instruments collected platelets efficiently. Additionally, consistent leukoreduction was obtained with both instruments; however, compared with the COM.TEC instrument, the Amicus reached the PLT target yield more quickly.

Durable solar mirror films

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Neill, Mark B.; Henderson, Andrew J.; Hebrink, Timothy J.

The present disclosure generally relates to durable solar mirror films, methods of making durable solar mirror films, and constructions including durable solar mirror films. In one embodiment, the present disclosure relates to a solar mirror film comprising: a multilayer optical film layer including having a coefficient of hygroscopic expansion of less than about 30 ppm per percent relative humidity; and a reflective layer having a coefficient of hygroscopic expansion.

A Stress Gradient Failure Theory for Textile Structural Composites

DTIC Science & Technology

2006-05-01

additional element failures occur. Incorporation of thermal stresses and investigation of the coefficient of thermal expansion is another potential...avenue for further development of the failure modeling. Due to mismatches between the coefficient of thermal expansion of constituent materials...directly from ABAQUS software, which yields element volumes as outputs, thus the volume of all matrix elements can be compared to the volume of all

Multiscale Modeling and Multifunctional Composites

DTIC Science & Technology

2013-07-17

dλ α µ α= − − = +E Eθ θ (9) 6 where α is the coefficient of thermal expansion , and ,e d...longitudinal and transverse coefficient of thermal expansion , respectively. The piezoelectric constants are related by (Bahei-El-Din, 2009) 31 31 33 33 31...is coded into the user defined subroutine UEXPAN of the ABAQUS finite element program. This serves as the interface between the global finite element

Durable solar mirror films

DOEpatents

O'Neill, Mark B.; Henderson, Andrew J.; Hebrink, Timothy J.; Katare, Rajesh K.; Jing, Naiyong; North, Diane; Peterson, Eric M.

2017-02-14

The present disclosure generally relates to durable solar mirror films, methods of making durable solar mirror films, and constructions including durable solar mirror films. In one embodiment, the present disclosure relates to a solar mirror film comprising: a multilayer optical film layer including having a coefficient of hygroscopic expansion of less than about 30 ppm per percent relative humidity; and a reflective layer having a coefficient of hygroscopic expansion.

Thermionic Energy Conversion (TEC) topping thermoelectrics

NASA Technical Reports Server (NTRS)

Morris, J. F.

1981-01-01

Performance expectations for thermionic and thermoelectric energy conversion systems are reviewed. It is noted that internal radiation effects diminish thermoelectric figures of merit significantly at 1000 K and substantially at 2000 K; the effective thermal conductivity contribution of intrathermoelectric radiative dissipation increases with the third power of temperature. It is argued that a consideration of thermoelectric power generation with high temperature heat sources should include utilization of thermionic energy conversion (TEC) topping thermoelectrics. However TEC alone or TEC topping more efficient conversion systems like steam or gas turbines, combined cycles, or Stirling engines would be more desirable generally.

Dust Storm Signatures in Global Ionosphere Map of GPS Total Electron Content

NASA Astrophysics Data System (ADS)

Lin, Fang-Tse; Shih, Ai-Ling; Liu, Jann-Yenq; Kuo, Cheng-Ling; Lin, Tang-Huang; Lien, Wei-Hung

2016-04-01

In this paper both MODIS data and GIM (global ionosphere map) TEC (total electron content) as well as numerical simulations are used to study ionospheric dust storm effects in May 2008. The aerosol optical depth (AOD) and the LTT (latitude-time-TEC) along the Sahara longitude simultaneously reach their maximum values on 28 May 2008. The LLT (latitude-longitude-TEC) map specifically and significantly increases over the Sahara region on 28 May 2008. The simulation suggests that the dust storm may change the atmospheric conductivity, which in turn modifies the GIM TEC over the Sahara area.

Comparison of GPS-TEC measurements with NeQuick2 and IRI model predictions in the low latitude East African region during varying solar activity period (1998 and 2008-2015)

NASA Astrophysics Data System (ADS)

Mengistu, E.; Damtie, B.; Moldwin, M. B.; Nigussie, M.

2018-03-01

This paper examines the performances of NeQuick2, the latest available IRI-2016, IRI-2012 and IRI-2007 models in describing the monthly and seasonal mean total electron content (TEC) over the East African region. This is to gain insight into the success of the various model types and versions at characterizing the ionosphere within the equatorial ionization anomaly. TEC derived from five Global Positioning System (GPS) receivers installed at Addis Ababa (ADD, 5.33°N, 111.99°E Geog.), Asab (ASAB, 8.67°N, 116.44°E Geog.), Ambo (ABOO, 5.43°N, 111.05°E Geog.), Nairobi (RCMN, -4.48°N, 108.46°E Geog.) and Nazret (NAZR, 4.78°N, 112.43°E Geog.), are compared with the corresponding values computed using those models during varying solar activity period (1998 and 2008-2015). We found that different models describe the equatorial and anomaly region ionosphere best depending on solar cycle, season and geomagnetic activity levels. Our results show that IRI-2016 is the best model (compared to others in terms of discrepancy range) in estimating the monthly mean GPS-TEC at NAZR, ADD and RCMN stations except at ADD during 2008 and 2012. It is also found that IRI-2012 is the best model in estimating the monthly mean TEC at ABOO station in 2014. IRI show better agreement with observations during June solstice for all the years studied at ADD except in 2012 where NeQuick2 better performs. At NAZR, NeQuick2 better performs in estimating seasonal mean GPS-TEC during 2011, while IRI models are best during 2008-2009. Both NeQuick2 and IRI models underestimate measured TEC for all the seasons at ADD in 2010 but overestimate at NAZR in 2009 and RCMN in 2008. The periodic variations of experimental and modeled TEC have been compared with solar and geomagnetic indices at ABOO and ASAB in 2014 and results indicate that the F10.7 and sunspot number as indices of solar activity seriously affects the TEC variations with periods of 16-32 days followed by the geomagnetic activity on shorter timescales (roughly periods of less than 16 days). In this case, NeQuick2 derived TEC shows better agreement with a long term period variations of GPS-TEC, while IRI-2016 and IRI-2007 show better agreement with observations during short term periodic variations. This indicates that the dependence of NeQuick2 derived TEC on F10.7 is seasonal. Hence, we suggest that representation of geomagnetic activity indices is required for better performance over the low latitude region.

Risk-adapted, treosulfan-based therapy with auto- and allo-SCT for relapsed/refractory aggressive NHL: a prospective phase-II trial.

PubMed

Koenigsmann, M; Casper, J; Kahl, C; Basara, N; Sayer, H G; Behre, G; Theurich, S; Christopeit, M; Mohren, M; Reichle, A; Metzner, B; Ganser, A; Stadler, M; Uharek, L; Balleisen, L; Hinke, A; Hinke, R; Niederwieser, D

2014-03-01

Since the outcome of relapsed/refractory aggressive non-Hodgkin's lymphoma (NHL) is highly variable, a risk-adapted treatment approach was evaluated. After two cycles of DHAP, patients received high-dose treosulfan/etoposide/carboplatinum (TEC) and autologous stem cell rescue. After TEC, low-risk patients with late relapse (>1 year after first CR who achieved CR after DHAP received no further treatment. Patients with late relapse who achieved CR or PR only after TEC underwent a second cycle of TEC. High-risk patients with early relapse/refractory disease received treosulfan/fludarabine followed by allogeneic transplantation. Rituximab was added in patients with B-cell lymphoma (86%). At entry, 36% of all 57 patients had refractory disease, 32% early and 32% late relapse. During DHAP treatment, progression occurred in 32% of patients. Of 33 patients who received TEC, 5 received second TEC and 15 allogeneic transplantation. Main toxicity after TEC was oral mucositis (CTC grades 3 and 4 in 50% and 13%, respectively). In total, 42% patients achieved CR. Median OS was 21.4 months for all patients and 32.6 for those who underwent allogeneic transplantation. International prognostic index (IPI) at study entry was highly discriminative at predicting OS (P<0.0001). Risk-adapted, treosulfan-based therapy with auto- and allo-SCT is feasible. Long-term survival is possible with allogeneic transplantation.

FSP1+ fibroblast subpopulation is essential for the maintenance and regeneration of medullary thymic epithelial cells

PubMed Central

Sun, Lina; Sun, Chenming; Liang, Zhanfeng; Li, Hongran; Chen, Lin; Luo, Haiying; Zhang, Hongmei; Ding, Pengbo; Sun, Xiaoning; Qin, Zhihai; Zhao, Yong

2015-01-01

Thymic epithelial cells (TECs) form a 3-dimentional network supporting thymocyte development and maturation. Besides epithelium and thymocytes, heterogeneous fibroblasts are essential components in maintaining thymic microenvironments. However, thymic fibroblast characteristics, development and function remain to be determined. We herein found that thymic non-hematopoietic CD45-FSP1+ cells represent a unique Fibroblast specific protein 1 (FSP1)—fibroblast-derived cell subset. Deletion of these cells in FSP1-TK transgenic mice caused thymus atrophy due to the loss of TECs, especially mature medullary TECs (MHCIIhigh, CD80+ and Aire+). In a cyclophosphamide-induced thymus injury and regeneration model, lack of non-hematopoietic CD45-FSP1+ fibroblast subpopulation significantly delayed thymus regeneration. In fact, thymic FSP1+ fibroblasts released more IL-6, FGF7 and FSP1 in the culture medium than their FSP1- counterparts. Further experiments showed that the FSP1 protein could directly enhance the proliferation and maturation of TECs in the in vitro culture systems. FSP1 knockout mice had significantly smaller thymus size and less TECs than their control. Collectively, our studies reveal that thymic CD45-FSP1+ cells are a subpopulation of fibroblasts, which is crucial for the maintenance and regeneration of TECs especially medullary TECs through providing IL-6, FGF7 and FSP1. PMID:26445893

Response of data-driven artificial neural network-based TEC models to neutral wind for different locations, seasons, and solar activity levels from the Indian longitude sector

NASA Astrophysics Data System (ADS)

Sur, D.; Haldar, S.; Ray, S.; Paul, A.

2017-07-01

The perturbations imposed on transionospheric signals by the ionosphere are a major concern for navigation. The dynamic nature of the ionosphere in the low-latitude equatorial region and the Indian longitude sector has some specific characteristics such as sharp temporal and latitudinal variation of total electron content (TEC). TEC in the Indian longitude sector also undergoes seasonal variations. The large magnitude and sharp variation of TEC cause large and variable range errors for satellite-based navigation system such as Global Positioning System (GPS) throughout the day. For accurate navigation using satellite-based augmentation systems, proper prediction of TEC under certain geophysical conditions is necessary in the equatorial region. It has been reported in the literature that prediction accuracy of TEC has been improved using measured data-driven artificial neural network (ANN)-based vertical TEC (VTEC) models, compared to standard ionospheric models. A set of observations carried out in the Indian longitude sector have been reported in this paper in order to find the amount of improvement in performance accuracy of an ANN-based VTEC model after incorporation of neutral wind as model input. The variations of this improvement in prediction accuracy with respect to latitude, longitude, season, and solar activity have also been reported in this paper.

Thymus medulla under construction: Time and space oddities.

PubMed

Alves, Nuno L; Ribeiro, Ana R

2016-04-01

The development of effective T-cell-based immunotherapies to treat infection, cancer, and autoimmunity should incorporate the ground rules that control differentiation of T cells in the thymus. Within the thymus, thymic epithelial cells (TECs) provide microenvironments supportive of the generation and selection of T cells that are responsive to pathogen-derived antigens, and yet tolerant to self-determinants. Defects in TEC differentiation cause syndromes that range from immunodeficiency to autoimmunity, which makes the study of TECs of fundamental and clinical importance to comprehend how immunity and tolerance are balanced. Critical to tolerance induction are medullary thymic epithelial cells (mTECs), which purge autoreactive T cells, or redirect them to a regulatory T-cell lineage. In this issue of the European Journal of Immunology, studies by Baik et al. and Mayer et al. [Eur. J. Immunol. 2016. 46: XXXX-XXXX and 46: XXXX-XXXX]) document novel spatial-temporal singularities in the lineage specification and maintenance of mTECs. While Baik et al. define a developmental checkpoint during mTEC specification in the embryo, Mayer et al. reveal that the generation and maintenance of the adult mTEC compartment is temporally controlled in vivo. The two reports described new developmentally related, but temporally distinct principles that underlie the homeostasis of the thymic medulla across life. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A nonlinear background removal method for seismo-ionospheric anomaly analysis under a complex solar activity scenario: A case study of the M9.0 Tohoku earthquake

NASA Astrophysics Data System (ADS)

He, Liming; Wu, Lixin; Pulinets, Sergey; Liu, Shanjun; Yang, Fan

2012-07-01

A precise determination of ionospheric total electron content (TEC) anomaly variations that are likely associated with large earthquakes as observed by global positioning system (GPS) requires the elimination of the ionospheric effect from irregular solar electromagnetic radiation. In particular, revealing the seismo-ionospheric anomalies when earthquakes occurred during periods of high solar activity is of utmost importance. To overcome this constraint, a multiresolution time series processing technique based on wavelet transform applicable to global ionosphere map (GIM) TEC data was used to remove the nonlinear effect from solar radiation for the earthquake that struck Tohoku, Japan, on 11 March, 2011. As a result, it was found that the extracted TEC have a good correlation with the measured solar extreme ultraviolet flux in 26-34 nm (EUV26-34) and the 10.7 cm solar radio flux (F10.7). After removing the influence of solar radiation origin in GIM TEC, the analysis results show that the TEC around the forthcoming epicenter and its conjugate were significantly enhanced in the afternoon period of 8 March 2011, 3 days before the earthquake. The spatial distributions of the TEC anomalous and extreme enhancements indicate that the earthquake preparation process had brought with a TEC anomaly area of size approximately 1650 and 5700 km in the latitudinal and longitudinal directions, respectively.

Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites

NASA Technical Reports Server (NTRS)

Wei, Chengyu; Srivastava, Deepak; Cho, Kyeongjae; Biegel, Bryan (Technical Monitor)

2001-01-01

Classical molecular dynamics (MD) simulations employing Brenner potential for intra-nanotube interactions and van der Waals forces for polymer-nanotube interface have been used to investigate thermal expansion and diffusion characteristics of carbon nanotube-polyethylene composites. Addition of carbon nanotubes to polymer matrix is found to significantly increase the glass transition temperature Tg, and thermal expansion and diffusion coefficients in the composite above Tg. The increase has been attributed to the temperature dependent increase of the excluded volume for the polymer chains, and the findings could have implications in the composite processing, coating and painting applications.

Origami structures for tunable thermal expansion

NASA Astrophysics Data System (ADS)

Boatti, Elisa; Bertoldi, Katia

Materials with engineered thermal expansion, capable of achieving targeted and extreme area/volume changes in response to variations in temperature, are important for a number of aerospace, optical, energy, and microelectronic applications. While most of the proposed structures with tunable coefficient of thermal expansion consist of bi-material 2D or 3D lattices, here we propose a periodic metastructure based on a bilayer Miura-Ori origami fold. We combine experiments and simulations to demonstrate that by tuning the geometrical and mechanical parameters an extremely broad range of thermal expansion coefficients can be obtained, spanning both negative and positive values. Additionally, the thermal properties along different directions can be adjusted independently. Differently from all previously reported systems, the proposed structure is non-porous.

Expansion in chickpea (Cicer arietinum L.) seed during soaking and cooking

NASA Astrophysics Data System (ADS)

Sayar, Sedat; Turhan, Mahir; Köksel, Hamit

2016-01-01

The linear and volumetric expansion of chickpea seeds during water absorption at 20, 30, 50, 70, 85 and 100°C was studied. Length, width and thickness of chickpea seeds linearly increased with the increase in moisture content at all temperatures studied, where the greatest increase was found in length. Two different mathematical approaches were used for the determination of the expansion coefficients. The plots of the both linear and volumetric expansion coefficients versus temperature exhibited two linear lines, the first one was through 20, 30 and 50ºC and the second one was trough 70, 85 and 100ºC. The crossing point (58ºC) of these lines was very close to the gelatinisation temperature (60ºC) of chickpea starch.

StarTEC: A Technology Project in Education Reform.

ERIC Educational Resources Information Center

Hawley, Helen; Benavides, Otto; Duffy, Sharon; Georgi, David; Guay, Diane; Redmond, Pamela; Richmond, James

StarTEC (Staff, Teacher, and Restructured Technology Education Consortium) was a 3-year technology catalyst program funded by the U.S. Department of Education, and continued for a third year to complete its activities. The goal of StarTEC was to ensure that all teachers prepared by partners in the Consortium would meet the new California standard…

Temperature-assisted solute focusing with sequential trap/release zones in isocratic and gradient capillary liquid chromatography: Simulation and experiment

PubMed Central

Groskreutz, Stephen R.; Weber, Stephen G.

2016-01-01

In this work we characterize the development of a method to enhance temperature-assisted on-column solute focusing (TASF) called two-stage TASF. A new instrument was built to implement two-stage TASF consisting of a linear array of three independent, electronically controlled Peltier devices (thermoelectric coolers, TECs). Samples are loaded onto the chromatographic column with the first two TECs, TEC A and TEC B, cold. In the two-stage TASF approach TECs A and B are cooled during injection. TEC A is heated following sample loading. At some time following TEC A’s temperature rise, TEC B’s temperature is increased from the focusing temperature to a temperature matching that of TEC A. Injection bands are focused twice on-column, first on the initial TEC, e.g. single-stage TASF, then refocused on the second, cold TEC. Our goal is to understand the two-stage TASF approach in detail. We have developed a simple yet powerful digital simulation procedure to model the effect of changing temperature in the two focusing zones on retention, band shape and band spreading. The simulation can predict experimental chromatograms resulting from spatial and temporal temperature programs in combination with isocratic and solvent gradient elution. To assess the two-stage TASF method and the accuracy of the simulation well characterized solutes are needed. Thus, retention factors were measured at six temperatures (25–75 °C) at each of twelve mobile phases compositions (0.05–0.60 acetonitrile/water) for homologs of n-alkyl hydroxylbenzoate esters and n-alkyl p-hydroxyphenones. Simulations accurately reflect experimental results in showing that the two-stage approach improves separation quality. For example, two-stage TASF increased sensitivity for a low retention solute by a factor of 2.2 relative to single-stage TASF and 8.8 relative to isothermal conditions using isocratic elution. Gradient elution results for two-stage TASF were more encouraging. Application of two-stage TASF increased peak height for the least retained solute in the test mixture by a factor of 3.2 relative to single-stage TASF and 22.3 compared to isothermal conditions for an injection four-times the column volume. TASF improved resolution and increased peak capacity; for a 12-minute separation peak capacity increased from 75 under isothermal conditions to 146 using single-stage TASF, and 185 for two-stage TASF. PMID:27836226

Comparison of double dose plateletpheresis on the Fenwal Amicus, Fresenius COM.TEC and Trima Accel cell separators.

PubMed

Keklik, Muzaffer; Eser, Bulent; Kaynar, Leylagul; Solmaz, Musa; Ozturk, Ahmet; Yay, Mehmet; Birekul, Ayse; Oztekin, Mehmet; Sivgin, Serdar; Cetin, Mustafa; Unal, Ali

2014-10-01

A variety of apheresis instruments are now available on the market for double dose plateletpheresis. We compared three apheresis devices (Fenwal Amicus, Fresenius COM.TEC and Trima Accel) with regard to processing time, platelet (PLT) yield, collection efficiency (CE) and collection rate (CR). The single-needle or double-needle double plateletpheresis procedures of the three instruments were compared in a retrospective, randomized study in 135 donors. In the pre-apheresis setting, 45 double plateletpheresis procedures performed with each instrument revealed no significant differences in donor's age, sex, weight, hemoglobin, white blood cell and PLT count between three groups. The blood volume processed to reach a target PLT yield of ≥ 6 × 10(11) was higher in the COM.TEC compared with the Amicus and Trima (4394 vs. 3780 and 3340 ml, respectively; p < 0.001). Also there was a significantly higher median volume of ACD used in collections on the COM.TEC compared with the Amicus and Trima (426 vs. 387 and 329 ml, respectively; p < 0.001). There was a significantly higher median time needed for the procedures on the COM.TEC compared with the Amicus and Trima (66 vs. 62 and 63 min, respectively; p = 0.024). The CE was significantly higher with the Trima compared with the Amicus and COM.TEC (83.57 ± 17.19 vs. 66.71 ± 3.47 and 58.79 ± 5.14%, respectively; p < 0.001). Also, there was a significantly higher product volume on the Trima compared with the Amicus and COM.TEC (395.56 vs. 363.11 and 386.4 ml, respectively; p = 0.008). Additionally, the CR was significantly lower with the COM.TEC compared with the Amicus and Trima (0.092 ± 0.011 vs. 0.099 ± 0.013 and 0.097 ± 0.013 plt × 10(11)/min, respectively; p = 0.039). There was no significant differences in PLT yield between the three groups (p = 0.636). Trima single-needle device collected double dose platelets more efficiently than Amicus and COM.TEC double-needle devices. Blood volume processed, ACD-A volume, and median separation time was significantly higher with the COM.TEC. Also, the CR was significantly lower with the COM.TEC. Copyright © 2014 Elsevier Ltd. All rights reserved.

Temperature-assisted solute focusing with sequential trap/release zones in isocratic and gradient capillary liquid chromatography: Simulation and experiment.

PubMed

Groskreutz, Stephen R; Weber, Stephen G

2016-11-25

In this work we characterize the development of a method to enhance temperature-assisted on-column solute focusing (TASF) called two-stage TASF. A new instrument was built to implement two-stage TASF consisting of a linear array of three independent, electronically controlled Peltier devices (thermoelectric coolers, TECs). Samples are loaded onto the chromatographic column with the first two TECs, TEC A and TEC B, cold. In the two-stage TASF approach TECs A and B are cooled during injection. TEC A is heated following sample loading. At some time following TEC A's temperature rise, TEC B's temperature is increased from the focusing temperature to a temperature matching that of TEC A. Injection bands are focused twice on-column, first on the initial TEC, e.g. single-stage TASF, then refocused on the second, cold TEC. Our goal is to understand the two-stage TASF approach in detail. We have developed a simple yet powerful digital simulation procedure to model the effect of changing temperature in the two focusing zones on retention, band shape and band spreading. The simulation can predict experimental chromatograms resulting from spatial and temporal temperature programs in combination with isocratic and solvent gradient elution. To assess the two-stage TASF method and the accuracy of the simulation well characterized solutes are needed. Thus, retention factors were measured at six temperatures (25-75°C) at each of twelve mobile phases compositions (0.05-0.60 acetonitrile/water) for homologs of n-alkyl hydroxylbenzoate esters and n-alkyl p-hydroxyphenones. Simulations accurately reflect experimental results in showing that the two-stage approach improves separation quality. For example, two-stage TASF increased sensitivity for a low retention solute by a factor of 2.2 relative to single-stage TASF and 8.8 relative to isothermal conditions using isocratic elution. Gradient elution results for two-stage TASF were more encouraging. Application of two-stage TASF increased peak height for the least retained solute in the test mixture by a factor of 3.2 relative to single-stage TASF and 22.3 compared to isothermal conditions for an injection four-times the column volume. TASF improved resolution and increased peak capacity; for a 12-min separation peak capacity increased from 75 under isothermal conditions to 146 using single-stage TASF, and 185 for two-stage TASF. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparison of Borate Bioactive Glass and Calcium Sulfate as Implants for the Local Delivery of Teicoplanin in the Treatment of Methicillin-Resistant Staphylococcus aureus-Induced Osteomyelitis in a Rabbit Model

PubMed Central

Jia, Wei-Tao; Fu, Qiang; Huang, Wen-Hai

2015-01-01

There is growing interest in biomaterials that can cure bone infection and also regenerate bone. In this study, two groups of implants composed of 10% (wt/wt) teicoplanin (TEC)-loaded borate bioactive glass (designated TBG) or calcium sulfate (TCS) were created and evaluated for their ability to release TEC in vitro and to cure methicillin-resistant Staphylococcus aureus (MRSA)-induced osteomyelitis in a rabbit model. When immersed in phosphate-buffered saline (PBS), both groups of implants provided a sustained release of TEC at a therapeutic level for up to 3 to 4 weeks while they were gradually degraded and converted to hydroxyapatite. The TBG implants showed a longer duration of TEC release and better retention of strength as a function of immersion time in PBS. Infected rabbit tibiae were treated by debridement, followed by implantation of TBG or TCS pellets or intravenous injection with TEC, or were left untreated. Evaluation at 6 weeks postimplantation showed that the animals implanted with TBG or TCS pellets had significantly lower radiological and histological scores, lower rates of MRSA-positive cultures, and lower bacterial loads than those preoperatively and those of animals treated intravenously. The level of bone regeneration was also higher in the defects treated with the TBG pellets. The results showed that local TEC delivery was more effective than intravenous administration for the treatment of MRSA-induced osteomyelitis. Borate glass has the advantages of better mechanical strength, more desirable kinetics of release of TEC, and a higher osteogenic capacity and thus could be an effective alternative to calcium sulfate for local delivery of TEC. PMID:26416858

Comparison of Borate Bioactive Glass and Calcium Sulfate as Implants for the Local Delivery of Teicoplanin in the Treatment of Methicillin-Resistant Staphylococcus aureus-Induced Osteomyelitis in a Rabbit Model.

PubMed

Jia, Wei-Tao; Fu, Qiang; Huang, Wen-Hai; Zhang, Chang-Qing; Rahaman, Mohamed N

2015-12-01

There is growing interest in biomaterials that can cure bone infection and also regenerate bone. In this study, two groups of implants composed of 10% (wt/wt) teicoplanin (TEC)-loaded borate bioactive glass (designated TBG) or calcium sulfate (TCS) were created and evaluated for their ability to release TEC in vitro and to cure methicillin-resistant Staphylococcus aureus (MRSA)-induced osteomyelitis in a rabbit model. When immersed in phosphate-buffered saline (PBS), both groups of implants provided a sustained release of TEC at a therapeutic level for up to 3 to 4 weeks while they were gradually degraded and converted to hydroxyapatite. The TBG implants showed a longer duration of TEC release and better retention of strength as a function of immersion time in PBS. Infected rabbit tibiae were treated by debridement, followed by implantation of TBG or TCS pellets or intravenous injection with TEC, or were left untreated. Evaluation at 6 weeks postimplantation showed that the animals implanted with TBG or TCS pellets had significantly lower radiological and histological scores, lower rates of MRSA-positive cultures, and lower bacterial loads than those preoperatively and those of animals treated intravenously. The level of bone regeneration was also higher in the defects treated with the TBG pellets. The results showed that local TEC delivery was more effective than intravenous administration for the treatment of MRSA-induced osteomyelitis. Borate glass has the advantages of better mechanical strength, more desirable kinetics of release of TEC, and a higher osteogenic capacity and thus could be an effective alternative to calcium sulfate for local delivery of TEC. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

GNSS Derived Ionospheric TEC Observed Through Different TEC Calibration Techniques in the Brazilian Sector

NASA Astrophysics Data System (ADS)

Becker-Guedes, F.; Carmo, C. S.; Camargo, P. O.; Monico, J. F. G.; Nicoli Candido, C. M.

2017-12-01

Global Navigation Satellite System (GNSS) is becoming a reliable tool for use in air navigation systems. Its use as the main technology for determination of airplanes positioning has various economic and logistic benefits but it depends strongly on the ionospheric layer influences. The Brazilian sector ionosphere, mainly over the equatorial ionization anomaly (EIA), presents remarkable errors in the GNSS signal as compared to North America and Europe. In order to study the total electron content latitudinal variation of the Brazilian ionosphere we used a pair of GNSS receivers on the ground, one located in the equatorial region (Sao Luis) and other in the southern crest of the EIA (Cachoeira Paulista), to collect the GNSS observables and calculate the vertical TEC using different methods that has proven to work well to describe the ionospheric behavior in the North America and in Europe. We compared this results with a modified Nagoya TEC calculation method used by the EMBRACE (Estudo e Monitoramento BRAsileiro do Clima Espacial - Brazilian Study and Monitoring of Space Weather) program. This work intends to follow the performance of different TEC tuning methods to evaluate the spurious effects of the ionospheric EIA gradients in the TEC determination under typical conditions of the low-latitudes ionosphere in the Brazilian sector. The calculated TEC under different solar cycle conditions, geomagnetic activity, and seasonal variations show deviations in the performance of each method and stress the importance of well adjust the GNSS observations to local conditions in order to optimize the TEC evaluation. This study contributes to a better understanding of local GNSS signal errors in the global intent of offering conditions to improve the accuracy, integrity, availability, and continuity requirements for the use of GNSS for air navigation in South America.

Comparison of plateletpheresis on the Fenwal Amicus, Fresenius COM.TEC, and Trima Accel Cell separators.

PubMed

Keklik, Muzaffer; Eser, Bulent; Kaynar, Leylagul; Sivgin, Serdar; Keklik, Ertugrul; Solmaz, Musa; Ozturk, Ahmet; Buyukoglan, Ruksan; Yay, Mehmet; Cetin, Mustafa; Unal, Ali

2015-06-01

Blood component donations by apheresis have become more common in modern blood transfusion practices. We compared three apheresis instruments (Fenwal Amicus, Fresenius COM.TEC, and Trima Accel) with regard to platelet (PLT) yield, collection efficiency (CE), and collection rate (CR). The single-needle or double-needle plateletpheresis procedures of the three instruments were compared in a retrospective, randomized study in 270 donors. The blood volume processed was higher in the COM.TEC compared with the Amicus and Trima. Also there was a significantly higher median volume of ACD used in collections on the COM.TEC compared with the Amicus and Trima. The PLT yield was significantly lower with the COM.TEC compared with the Amicus and Trima. Additionally, the CE was significantly lower with the COM.TEC compared with the Amicus and Trima. There was no significant difference in median separation time and CR between the three groups. When procedures were compared regarding CE by using Amicus device, it was significantly higher in single-needle than double-needle plateletpheresis. When double-needle Amicus system was compared with double-needle COM.TEC system, CE and PLT yield were significantly higher with Amicus system. When single-needle Amicus system was compared with single-needle Trima system, CE and PLT yield were significantly higher with Trima system. All instruments collected PLTs efficiently. However, the CE was lower with the COM.TEC compared with the Amicus and Trima. Also, we found Amicus single-needle system collected PLTs more efficiently compared with the double-needle system. CE and PLT yields were significantly higher with the single-needle Trima instrument compared with the single-needle Amicus device. © 2014 Wiley Periodicals, Inc.

A IR-Femtosecond Laser Hybrid Sensor to Measure the Thermal Expansion and Thermo-Optical Coefficient of Silica-Based FBG at High Temperatures.

PubMed

Li, Litong; Lv, Dajuan; Yang, Minghong; Xiong, Liangming; Luo, Jie

2018-01-26

In this paper, a hybrid sensor was fabricated using a IR-femtosecond laser to measure the thermal expansion and thermo-optical coefficient of silica-based fiber Bragg gratings (FBGs). The hybrid sensor was composed of an inline fiber Fabry-Perot interferometer (FFPI) cavity and a type-II FBG. Experiment results showed that the type-II FBG had three high reflectivity resonances in the wavelength ranging from 1100 to 1600 nm, showing the peaks in 1.1, 1.3 and 1.5 μm, respectively. The thermal expansion and thermo-optical coefficient (1.3 μm, 1.5 μm) of silica-based FBG, under temperatures ranging from 30 to 1100 °C, had been simultaneously calculated by measuring the wavelength of the type-II FBG and FFPI cavity length.

Thermodynamic properties and diffusion of water + methane binary mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shvab, I.; Sadus, Richard J., E-mail: rsadus@swin.edu.au

2014-03-14

Thermodynamic and diffusion properties of water + methane mixtures in a single liquid phase are studied using NVT molecular dynamics. An extensive comparison is reported for the thermal pressure coefficient, compressibilities, expansion coefficients, heat capacities, Joule-Thomson coefficient, zero frequency speed of sound, and diffusion coefficient at methane concentrations up to 15% in the temperature range of 298–650 K. The simulations reveal a complex concentration dependence of the thermodynamic properties of water + methane mixtures. The compressibilities, heat capacities, and diffusion coefficients decrease with increasing methane concentration, whereas values of the thermal expansion coefficients and speed of sound increase. Increasing methanemore » concentration considerably retards the self-diffusion of both water and methane in the mixture. These effects are caused by changes in hydrogen bond network, solvation shell structure, and dynamics of water molecules induced by the solvation of methane at constant volume conditions.« less

Seismo-ionospheric Precursors in the GPS Total Electron Content of the 16 October 1999 Mw7.1 Hector Mine Earthquake

NASA Astrophysics Data System (ADS)

Tsai, H.; Su, Y.; Liu, J. G.; Chen, S.; Chen, M.

2013-12-01

In this paper, temporal and spatial analyses are employed to detect seismo-ionospheric precursors (SIPs) in the ionospheric total electron content (TEC) during 16 October 1999 Mw7.1 Hector Mine earthquake. To discriminate anomalies caused by global effects, such as solar radiations, magnetic storms, etc., and local effects, such as earthquake, we cross-examine the GPS TECs and their gradients in the eastward and northward directions at epicenter/centers of the Hector Mine area and the other two reference areas at similar magnetic latitudes in Europe and Japan. Temporal variations of the northward TEC gradient suggest SIPs most likely appearing day 6-5 before the earthquake. A global search by using the TEC of GIM (global ionosphere map) shows that the TEC increase and decrease anomalies continuously and specifically appear around the epicenter day 5 before the earthquake.

Ionospheric responses during equinox and solstice periods over Turkey

NASA Astrophysics Data System (ADS)

Karatay, Secil; Cinar, Ali; Arikan, Feza

2017-11-01

Ionospheric electron density is the determining variable for investigation of the spatial and temporal variations in the ionosphere. Total Electron Content (TEC) is the integral of the electron density along a ray path that indicates the total variability through the ionosphere. Global Positioning System (GPS) recordings can be utilized to estimate the TEC, thus GPS proves itself as a useful tool in monitoring the total variability of electron distribution within the ionosphere. This study focuses on the analysis of the variations of ionosphere over Turkey that can be grouped into anomalies during equinox and solstice periods using TEC estimates obtained by a regional GPS network. It is observed that noon time depletions in TEC distributions predominantly occur in winter for minimum Sun Spots Numbers (SSN) in the central regions of Turkey which also exhibit high variability due to midlatitude winter anomaly. TEC values and ionospheric variations at solstice periods demonstrate significant enhancements compared to those at equinox periods.

A hybrid-perturbation-Galerkin technique which combines multiple expansions

NASA Technical Reports Server (NTRS)

Geer, James F.; Andersen, Carl M.

1989-01-01

A two-step hybrid perturbation-Galerkin method for the solution of a variety of differential equations type problems is found to give better results when multiple perturbation expansions are employed. The method assumes that there is parameter in the problem formulation and that a perturbation method can be sued to construct one or more expansions in this perturbation coefficient functions multiplied by computed amplitudes. In step one, regular and/or singular perturbation methods are used to determine the perturbation coefficient functions. The results of step one are in the form of one or more expansions each expressed as a sum of perturbation coefficient functions multiplied by a priori known gauge functions. In step two the classical Bubnov-Galerkin method uses the perturbation coefficient functions computed in step one to determine a set of amplitudes which replace and improve upon the gauge functions. The hybrid method has the potential of overcoming some of the drawbacks of the perturbation and Galerkin methods as applied separately, while combining some of their better features. The proposed method is applied, with two perturbation expansions in each case, to a variety of model ordinary differential equations problems including: a family of linear two-boundary-value problems, a nonlinear two-point boundary-value problem, a quantum mechanical eigenvalue problem and a nonlinear free oscillation problem. The results obtained from the hybrid methods are compared with approximate solutions obtained by other methods, and the applicability of the hybrid method to broader problem areas is discussed.

Synthesis of Zr2WP2O12/ZrO2 Composites with Adjustable Thermal Expansion.

PubMed

Zhang, Zhiping; Sun, Weikang; Liu, Hongfei; Xie, Guanhua; Chen, Xiaobing; Zeng, Xianghua

2017-01-01

Zr 2 WP 2 O 12 /ZrO 2 composites were fabricated by solid state reaction with the goal of tailoring the thermal expansion coefficient. XRD, SEM and TMA were used to investigate the composition, microstructure, and thermal expansion behavior of Zr 2 WP 2 O 12 /ZrO 2 composites with different mass ratio. Relative densities of all the resulting Zr 2 WP 2 O 12 /ZrO 2 samples were also tested by Archimedes' methods. The obtained Zr 2 WP 2 O 12 /ZrO 2 composites were comprised of orthorhombic Zr 2 WP 2 O 12 and monoclinic ZrO 2 . As the increase of the Zr 2 WP 2 O 12 , the relative densities of Zr 2 WP 2 O 12 /ZrO 2 ceramic composites increased gradually. The coefficient of thermal expansion of the Zr 2 WP 2 O 12 /ZrO 2 composites can be tailored from 4.1 × 10 -6 K -1 to -3.3 × 10 -6 K -1 by changing the content of Zr 2 WP 2 O 12 . The 2:1 Zr 2 WP 2 O 12 /ZrO 2 specimen shows close to zero thermal expansion from 25 to 700°C with an average linear thermal expansion coefficient of -0.09 × 10 -6 K -1 . These adjustable and near zero expansion ceramic composites will have great potential application in many fields.

Midwest Structural Sciences Center 2009 Annual Report

DTIC Science & Technology

2010-08-01

simulations. Numerical simulations were carried with a single edge notch beam using an ABAQUS user-element subroutine in conjunction with bilinear and...this effort Digital Image Correlation (DIC) has been applied to measure the coefficient of thermal expansion of the nickel-based super alloy...between 30 and 650°C, the thermal expansion coefficient of Hastelloy X was measured over this entire range and found to be in good agreement with

Multimodal method for scattering of sound at a sudden area expansion in a duct with subsonic flow

NASA Astrophysics Data System (ADS)

Kooijman, G.; Testud, P.; Aurégan, Y.; Hirschberg, A.

2008-03-01

The scattering of sound at a sudden area expansion in a duct with subsonic mean flow has been modelled with a multimodal method. Technological applications are for instance internal combustion engine exhaust silencers and silencers in industrial duct systems. Both two-dimensional (2D) rectangular and 2D cylindrical geometry and uniform mean flow as well as non-uniform mean flow profiles are considered. Model results for the scattering of plane waves in case of uniform flow, in which case an infinitely thin shear layer is formed downstream of the area expansion, are compared to results obtained by other models in literature. Generally good agreement is found. Furthermore, model results for the scattering are compared to experimental data found in literature. Also here fairly good correspondence is observed. When employing a turbulent pipe flow profile in the model, instead of a uniform flow profile, the prediction for the downstream transmission- and upstream reflection coefficient is improved. However, worse agreement is observed for the upstream transmission and downstream reflection coefficient. On the contrary, employing a non-uniform jet flow profile, which represents a typical shear layer flow downstream of the expansion, gives worse agreement for the downstream transmission- and the upstream reflection coefficient, whereas prediction for the upstream transmission and downstream reflection coefficient improves.

Pressure-induced reversal between thermal contraction and expansion in ferroelectric PbTiO3.

PubMed

Zhu, Jinlong; Zhang, Jianzhong; Xu, Hongwu; Vogel, Sven C; Jin, Changqing; Frantti, Johannes; Zhao, Yusheng

2014-01-15

Materials with zero/near zero thermal expansion coefficients are technologically important for applications in thermal management and engineering. To date, this class of materials can only be produced by chemical routes, either by changing chemical compositions or by composting materials with positive and negative thermal expansion. Here, we report for the first time a physical route to achieve near zero thermal expansion through application of pressure. In the stability field of tetragonal PbTiO3 we observed pressure-induced reversals between thermal contraction and expansion between ambient pressure and 0.9 GPa. This hybrid behavior leads to a mathematically infinite number of crossover points in the pressure-volume-temperature space and near-zero thermal expansion coefficients comparable to or even smaller than those attained by chemical routes. The observed pressures for this unusual phenomenon are within a small range of 0.1-0.9 GPa, potentially feasible for designing stress-engineered materials, such as thin films and nano-crystals, for thermal management applications.

Analysis of the compressibility of a finite symmetrical nucleus in terms of a simple, analytically tractable model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maheswari, V.S.U.; Ramamurthy, V.S.; Satpathy, L.

1992-12-01

The liquid-drop model type expansion of the finite nuclear compressibility coefficients {ital K}{sub {ital A}} is studied in an energy density formalism, using a leptodermous expansion of the energies. It is found that the effective curvature compressibility coefficient {ital K}{sub {ital c}} is always negative for Skyrme type forces. It is also shown that the unexpectedly large value of about {minus}800 MeV of the surface compressibility coefficient {ital K}{sub {ital s}} found by Sharma {ital et} {ital al}. is an artifact of their analysis procedure.

Analytic integration of real-virtual counterterms in NNLO jet cross sections II

NASA Astrophysics Data System (ADS)

Bolzoni, Paolo; Moch, Sven-Olaf; Somogyi, Gábor; Trócsányi, Zoltán

2009-08-01

We present analytic expressions of all integrals required to complete the explicit evaluation of the real-virtual integrated counterterms needed to define a recently proposed subtraction scheme for jet cross sections at next-to-next-to-leading order in QCD. We use the Mellin-Barnes representation of these integrals in 4 - 2epsilon dimensions to obtain the coefficients of their Laurent expansions around epsilon = 0. These coefficients are given by linear combinations of multidimensional Mellin-Barnes integrals. We compute the coefficients of such expansions in epsilon both numerically and analytically by complex integration over the Mellin-Barnes contours.

Giant Thermal Expansion in 2D and 3D Cellular Materials.

PubMed

Zhu, Hanxing; Fan, Tongxiang; Peng, Qing; Zhang, Di

2018-05-01

When temperature increases, the volume of an object changes. This property was quantified as the coefficient of thermal expansion only a few hundred years ago. Part of the reason is that the change of volume due to the variation of temperature is in general extremely small and imperceptible. Here, abnormal giant linear thermal expansions in different types of two-ingredient microstructured hierarchical and self-similar cellular materials are reported. The cellular materials can be 2D or 3D, and isotropic or anisotropic, with a positive or negative thermal expansion due to the convex or/and concave shape in their representative volume elements respectively. The magnitude of the thermal expansion coefficient can be several times larger than the highest value reported in the literature. This study suggests an innovative approach to develop temperature-sensitive functional materials and devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Curriculum Change. An Evaluation of TEC Programme Development in Colleges. The Main Findings.

ERIC Educational Resources Information Center

Parkin, Christopher; And Others

An evaluation was made of the adoption of curriculum changes mandated by the Technician Education Council (TEC) by 78 colleges in England. The study concentrated on the processes of adaptation that occurred in the colleges in order to cope with the degree of change required by TEC. Data were collected via questionnaires, interviews, case studies,…

A program-management plan with critical-path definition for Combustion Augmentation with Thermionic Energy Conversion (CATEC)

NASA Technical Reports Server (NTRS)

Morris, J. F.; Merrill, O. S.; Reddy, H. K.

1981-01-01

Thermionic energy conversion (TEC) is discussed. In recent TEC-topping analyses, overall plant efficiency (OPE) and cost of electricity (COE) improved slightly with current capabilities and substantially with fully matured technologies. Enhanced credibility derives from proven hot-corrosion protection for TEC by silicon-carbide clads in fossil fuel combustion products. Combustion augmentation with TEC (CATEC) affords minimal cost and plant perturbation, but with smaller OPE and COE improvements than more conventional topping applications. Risk minimization as well as comparative simplicity and convenience, favor CATEC for early market penetration. A program-management plan is proposed. Inputs, characteristics, outputs and capabilities are discussed.

A program-management plan with critical-path definition for Combustion Augmentation with Thermionic Energy Conversion (CATEC)

NASA Astrophysics Data System (ADS)

Morris, J. F.; Merrill, O. S.; Reddy, H. K.

Thermionic energy conversion (TEC) is discussed. In recent TEC-topping analyses, overall plant efficiency (OPE) and cost of electricity (COE) improved slightly with current capabilities and substantially with fully matured technologies. Enhanced credibility derives from proven hot-corrosion protection for TEC by silicon-carbide clads in fossil fuel combustion products. Combustion augmentation with TEC (CATEC) affords minimal cost and plant perturbation, but with smaller OPE and COE improvements than more conventional topping applications. Risk minimization as well as comparative simplicity and convenience, favor CATEC for early market penetration. A program-management plan is proposed. Inputs, characteristics, outputs and capabilities are discussed.

A comparison of mapped and measured total ionospheric electron content using global positioning system and beacon satellite observations

NASA Technical Reports Server (NTRS)

Lanyi, Gabor E.; Roth, Titus

1988-01-01

Total ionospheric electron contents (TEC) were measured by global positioning system (GPS) dual-frequency receivers developed by the Jet Propulsion Laboratory. The measurements included P-code (precise ranging code) and carrier phase data for six GPS satellites during multiple five-hour observing sessions. A set of these GPS TEC measurements were mapped from the GPS lines of sight to the line of sight of a Faraday beacon satellite by statistically fitting the TEC data to a simple model of the ionosphere. The mapped GPS TEC values were compared with the Faraday rotation measurements. Because GPS transmitter offsets are different for each satellite and because some GPS receiver offsets were uncalibrated, the sums of the satellite and receiver offsets were estimated simultaneously with the TEC in a least squares procedure. The accuracy of this estimation procedure is evaluated indicating that the error of the GPS-determined line of sight TEC can be at or below 1 x 10 to the 16th el/sq cm. Consequently, the current level of accuracy is comparable to the Faraday rotation technique; however, GPS provides superior sky coverage.

Analysis of rocket beacon transmissions for computerized reconstruction of ionospheric densities

NASA Technical Reports Server (NTRS)

Bernhardt, P. A.; Huba, J. D.; Chaturvedi, P. K.; Fulford, J. A.; Forsyth, P. A.; Anderson, D. N.; Zalesak, S. T.

1993-01-01

Three methods are described to obtain ionospheric electron densities from transionospheric, rocket-beacon TEC data. First, when the line-of-sight from a ground receiver to the rocket beacon is tangent to the flight trajectory, the electron concentration can be obtained by differentiating the TEC with respect to the distance to the rocket. A similar method may be used to obtain the electron-density profile if the layer is horizontally stratified. Second, TEC data obtained during chemical release experiments may be interpreted with the aid of physical models of the disturbed ionosphere to yield spatial maps of the modified regions. Third, computerized tomography (CT) can be used to analyze TEC data obtained along a chain of ground-based receivers aligned along the plane of the rocket trajectory. CT analysis of TEC data is used to reconstruct a 2D image of a simulated equatorial plume. TEC data is computed for a linear chain of nine receivers with adjacent spacings of either 100 or 200 km. The simulation data are analyzed to provide an F region reconstruction on a grid with 15 x 15 km pixels. Ionospheric rocket tomography may also be applied to rocket-assisted measurements of amplitude and phase scintillations and airglow intensities.

Contribution of tumor endothelial cells to drug resistance: anti-angiogenic tyrosine kinase inhibitors act as p-glycoprotein antagonists.

PubMed

Bani, MariaRosa; Decio, Alessandra; Giavazzi, Raffaella; Ghilardi, Carmen

2017-05-01

Tumor endothelial cells (TEC) differ from the normal counterpart, in both gene expression and functionality. TEC may acquire drug resistance, a characteristic that is maintained in vitro. There is evidence that TEC are more resistant to chemotherapeutic drugs, substrates of ATP-binding cassette (ABC) transporters. TEC express p-glycoprotein (encoded by ABCB1), while no difference in other ABC transporters was revealed compared to normal endothelia. A class of tyrosine kinase inhibitors (TKI), used as angiostatic compounds, interferes with the ATPase activity of p-glycoprotein, thus impairing its functionality. The exposure of ovarian adenocarcinoma TEC to the TKIs sunitinib or sorafenib was found to abrogate resistance (proliferation and motility) to doxorubicin and paclitaxel in vitro, increasing intracellular drug accumulation. A similar effect has been reported by the p-glycoprotein inhibitor verapamil. No beneficial effect was observed in combination with cytotoxic drugs that are not p-glycoprotein substrates. The current paper reviews the mechanisms of TEC chemoresistance and shows the role of p-glycoprotein in mediating such resistance. Inhibition of p-glycoprotein by anti-angiogenic TKI might contribute to the beneficial effect of these small molecules, when combined with chemotherapy, in counteracting acquired drug resistance.

A novel binary Pt 3Te x/C nanocatalyst for ethanol electro-oxidation

NASA Astrophysics Data System (ADS)

Huang, Meihua; Wang, Fei; Li, Lirong; Guo, Yonglang

The Pt 3Te x/C nanocatalyst was prepared and its catalytic performance for ethanol oxidation was investigated for the first time. The Pt 3Te/C nanoparticles were characterized by an X-ray diffractometer (XRD), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy equipped with TEM (TEM-EDX). The Pt 3Te/C catalyst has a typical fcc structure of platinum alloys with the presence of Te. Its particle size is about 2.8 nm. Among the synthesized catalysts with different atomic ratios, the Pt 3Te/C catalyst has the highest anodic peak current density. The cyclic voltammograms (CV) show that the anodic peak current density for the Pt 3Te/C, commercial PtRu/C and Pt/C catalysts reaches 1002, 832 and 533 A g -1, respectively. On the current-time curve, the anodic current on the Pt 3Te/C catalyst was higher than those for the catalysts reported. So, these findings show that the Pt 3Te/C catalyst has uniform nanoparticles and the best activity among the synthesized catalysts, and it is better than commercial PtRu/C and Pt/C catalysts for ethanol oxidation at room temperature.

AzTEC/ASTE 1.1 mm Deep Surveys: Number Counts and Clustering of Millimeter-bright Galaxies

NASA Astrophysics Data System (ADS)

Hatsukade, B.

2011-11-01

We present results of a 1.1 mm deep survey of the AKARI Deep Field South (ADF-S) with AzTEC mounted on the Atacama Submillimetre Telescope Experiment (ASTE). We obtained a map of 0.25 deg2 area with an rms noise level of 0.32-0.71 mJy. This is one of the deepest and widest maps thus far at millimetre and submillimetre wavelengths. We uncovered 198 sources with a significance of 3.5-15.6σ, providing the largest catalog of 1.1 mm sources in a contiguous region. Most of the sources are not detected in the far-infrared bands of the AKARI satellite, suggesting that they are mostly at z ≥ 1.5 given the detection limits. We construct differential and cumulative number counts of the ADF-S, the Subaru/XMM Newton Deep Field (SXDF), and the SSA 22 field surveyed by AzTEC/ASTE, which provide currently the tightest constraints on the faint end. The integration of the differential number counts of the ADF-S find that the contribution of 1.1 mm sources with ≥1 mJy to the cosmic infrared background (CIB) at 1.1 mm is 12-16%, suggesting that the large fraction of the CIB originates from faint sources of which number counts are not yet constrained. We estimate the cosmic star-formation rate density contributed by 1.1 mm sources with ≥1 mJy using the differential number counts and find that it is lower by about a factor of 5-10 compared to those derived from UV/optically-selected galaxies at z ~ 2-3. Clustering analyses of AzTEC sources in the ADF-S and the SXDF find that bright (>3 mJy) AzTEC sources are more strongly clustered than faint (< 3 mJy) AzTEC sources and the average mass of dark halos hosting bright AzTEC sources was calculated to be 1013-1014M⊙. Comparison of correlation length of AzTEC sources with other populations and with a bias evolution model suggests that dark halos hosting bright AzTEC sources evolve into systems of clusters at present universe and the AzTEC sources residing the dark halos evolve into massive elliptical galaxies located in the center of clusters.

Real-Time Three-Dimensional Echocardiography of the Left Ventricle-Pediatric Percentiles and Head-to-Head Comparison of Different Contour-Finding Algorithms: A Multicenter Study.

PubMed

Krell, Kristina; Laser, Kai Thorsten; Dalla-Pozza, Robert; Winkler, Christian; Hildebrandt, Ursula; Kececioglu, Deniz; Breuer, Johannes; Herberg, Ulrike

2018-03-28

Real-time three-dimensional echocardiography (RT3DE) is a promising method for accurate assessment of left ventricular (LV) volumes and function, however, pediatric reference values are scarce. The aim of the study was to establish pediatric percentiles in a large population and to compare the inherent influence of different evaluation software on the resulting measurements. In a multicenter prospective-design study, 497 healthy children (ages 1 day to 219 months) underwent RT3DE imaging of the LV (ie33, Philips, Andover, MA). Volume analysis was performed using QLab 9.0 (Philips) and TomTec 4DLV2.7 (vendor-independent; testing high (TomTec 75 ) and low (TomTec 30 ) contour-finding activity). Reference percentiles were computed using Cole's LMS method. In 22 subjects, cardiovascular magnetic resonance imaging (CMR) was used as the reference. A total of 370/497 (74.4%) of the subjects provided adequate data sets. LV volumes had a significant association with age, body size, and gender; therefore, sex-specific percentiles were indexed to body surface area. Intra- and interobserver variability for both workstations was good (relative bias ± SD for end-diastolic volume [EDV] in %: intraobserver: QLab = -0.8 ± 2.4; TomTec 30  = -0.7 ± 7.2; TomTec 75  = -1.9 ± 6.7; interobserver: QLab = 2.4 ± 7.5; TomTec 30  = 1.2 ± 5.1; TomTec 75  = 1.3 ± 4.5). Intervendor agreement between QLab and TomTec 30 showed larger bias and wider limits of agreement (bias: QLab vs TomTec 30 : end-systolic volume [ESV] = 0.8% ± 23.6%; EDV = -2.2% ± 17.0%) with notable individual differences in small children. QLab and TomTec underestimated CMR values, with the highest agreement between CMR and QLab. RT3DE allows reproducible noninvasive assessment of LV volumes and function. However, intertechnique variability is relevant. Therefore, our software-specific percentiles, based on a large pediatric population, serve as a reference for both commonly used quantification programs. Copyright © 2018 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

About a global model of the equivalent slab thickness of the ionosphere

NASA Astrophysics Data System (ADS)

Maltseva, Olga; Mozhaeva, Natalya

2016-07-01

Use of a median of an equivalent slab thickness of the ionosphere τ(med) is the simplest case of assimilation of the total electron content TEC. To use τ(med) on a global scale it is necessary to have its model. Some variants are possible: (1) construction of superficial function of kriging type using values of τ(med) in several points, (2) the NGM model which can be constructed on the basis of two empirical Neustrelitz models for TEC and NmF2, (3) the IRI-Plas model. Construction of a model with use of τ(med) values is difficult because of the large variability of values (in particular, a strong pre-sunrise peak at some latitudes). Testing of models NGM and IRI-Plas shows that they not always provide satisfactory results in that or another region of globe. Besides, they are not pure empirical models. In the present work, an attempt is done to use two-parameter model on a basis of hyperbolic dependence of τ(med) from NmF2 (τ(hyp) =b0+b1/NmF2) and approximation of coefficient K(τ) = τ(med)/τ(IRI) in a latitudinal course. On an example of March 2015 when there was a great number of ionosonde data, coefficients b0 and b1 were modeled. Results are presented for two regions Lat1 and Lat2. Area Lat1 contains 13 stations, basically, on the American continent of northern and southern hemispheres. Area Lat2 contains 20 stations of the European, Siberian and Southeast regions. Certain advantage of use of coefficients K(τ) can be that in its numerator there is a magnitude of τ(IRI), having a global character, and a small variation of K(τ) in zones with close longitudes. Difference is a model construction at each hour. Degree of coincidence is better to illustrate on circular diagrams. Models were tested by elimination of one of stations and definition of deviations of calculated foF2 from experimental values. Authors thank Southern Federal University for support by grant #213.01-11/2014-22.

Simultaneous response of NmF2 and GPS-TEC to storm events at Ilorin

NASA Astrophysics Data System (ADS)

Joshua, B. W.; Adeniyi, J. O.; Oladipo, O. A.; Doherty, P. H.; Adimula, I. A.; Olawepo, A. O.; Adebiyi, S. J.

2018-06-01

A comparative study of both TEC and NmF2 variations during quiet and disturbed conditions has been investigated using simultaneous measurements from dual frequency Global Positioning System (GPS) receiver and a DPS-4 Digisonde co-located at Ilorin (Geog. Lat. 8.50°N, Long. 4.50°E, dip. - 7.9°). The results of the quiet time variations of the two parameters show some similarities as well as differences in their structures. The values of both parameters generally increase during the sunrise period attaining a peak around the noon and then decaying towards the night time. The onset time of the sunrise growth is observed to be earlier in TEC than in NmF2. The rate of decay of TEC was observed to be faster than that of the NmF2 in most cases. Also, the noon 'bite-outs', leading to the formation of pre-noon and post-noon peaks, are prominent in the NmF2 structure and was hardly noticed in TEC. Results of the variations of both TEC and NmF2 during the 5 April, 10 May and 3 August 2010 geomagnetic storm events showed a simultaneous deviations of both parameters from the quiet time behavior. The magnitude of the deviations is however most pronounced in NmF2 structure than in TEC. We also found that the enhancement observed in the two parameters during the storm events generally corresponds to decrease in hmF2.

Comparison of the Fenwal Amicus and Fresenius Com.Tec cell separators for autologous peripheral blood progenitor cell collection.

PubMed

Altuntas, Fevzi; Kocyigit, Ismail; Ozturk, Ahmet; Kaynar, Leylagul; Sari, Ismail; Oztekin, Mehmet; Solmaz, Musa; Eser, Bulent; Cetin, Mustafa; Unal, Ali

2007-04-01

Peripheral blood progenitor cells (PBPC) are commonly used as a stem cell source for autologous transplantation. This study was undertaken to evaluate blood cell separators with respect to separation results and content of the harvest. Forty autologous PBPC collections in patients with hematological malignancies were performed with either the Amicus or the COM.TEC cell separators. The median product volume was lower with the Amicus compared to the COM.TEC (125 mL vs. 300 mL; p < 0.001). There was no statistically significant difference in the median number of CD34+ cell/kg in product between the Amicus and the COM.TEC (3.0 x 10(6) vs. 4.1 x 10(6); p = 0.129). There was a statistically higher mean volume of ACD used in collections on the Amicus compared to the COM.TEC (1040 +/- 241 mL vs. 868 +/- 176 mL; p = 0.019). There was a statistical difference in platelet (PLT) contamination of the products between the Amicus and the COM.TEC (0.3 x 10(11) vs. 1.1 x 10(11); p < 0.001). The median % decrease in PB PLT count was statistically higher in the COM.TEC compared to the Amicus instruments (18.5% vs. 9.5%; p = 0.028). In conclusion, both instruments collected PBPCs efficiently. However, Amicus has the advantage of lower PLT contamination in the product, and less decrease in PB platelet count with lower product volume in autologous setting.

Thermodiffusion Coefficient Analysis of n-Dodecane /n-Hexane Mixture at Different Mass Fractions and Pressure Conditions

NASA Astrophysics Data System (ADS)

Lizarraga, Ion; Bou-Ali, M. Mounir; Santamaría, C.

2018-03-01

In this study, the thermodiffusion coefficient of n-dodecane/n-hexane binary mixture at 25 ∘C mean temperature was determined for several pressure conditions and mass fractions. The experimental technique used to determine the thermodiffusion coefficient was the thermograviational column of cylindrical configuration. In turn, thermophysical properties, such as density, thermal expansion, mass expansion and dynamic viscosity up to 10 MPa were also determined. The results obtained in this work showed a linear relation between the thermophysical properties and the pressure. Thermodiffusion coefficient values confirm a linear effect when the pressure increases. Additionally, a new correlation based on the thermodiffusion coefficient for n C12/n C6 binary mixture at 25 ∘C temperature for any mass fraction and pressures, which reproduces the data within the experimental error, was proposed.

THERMAL PROPERTIES AND HEATING AND COOLING DURABILITY OF REACTOR SHIELDING CONCRETE (in Japanese)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hosoi, J.; Chujo, K.; Saji, K.

1959-01-01

A study was made of the thermal properties of various concretes made of domestic raw materials for radiation shields of a power reactor and of a high- flux research reactor. The results of measurements of thermal expansion coefficient, specific heat, thermal diffusivity, thermal conductivity, cyclical heating, and cooling durability are described. Relationships between thermal properties and durability are discussed and several photographs of the concretes are given. It is shown that the heating and cooling durability of such a concrete which has a large thermal expansion coefficient or a considerable difference between the thermal expansion of coarse aggregate and themore » one of cement mortar part or aggregates of lower strength is very poor. The decreasing rates of bending strength and dynamical modulus of elasticity and the residual elongation of the concrete tested show interesting relations with the modified thermal stress resistance factor containing a ratio of bending strength and thermal expansion coefficient. The thermal stress resistance factor seems to depend on the conditions of heat transfer on the surface and on heat release in the concrete. (auth)« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beaucage, Timothy R; Beenfeldt, Eric P; Speakman, Scott A

Among the langasite family of crystals (LGX), the three most popular materials are langasite (LGS, La3Ga5SiO14), langatate (LGT, La3Ga5.5Ta0.5O14) and langanite (LGN, La3Ga5.5Nb0.5O14). The LGX crystals have received significant attention for acoustic wave (AW) device applications due to several properties, which include: (1) piezoelectric constants about two and a half times those of quartz, thus allowing the design of larger bandwidth filters; (2) existence of temperature compensated orientations; (3) high density, with potential for reduced vibration and acceleration sensitivity; and (4) possibility of operation at high temperatures, since the LGX crystals do not present phase changes up to their meltingmore » point above 1400degC. The LGX crystals' capability to operate at elevated temperatures calls for an investigation on the growth quality and the consistency of these materials' properties at high temperature. One of the fundamental crystal properties is the thermal expansion coefficients in the entire temperature range where the material is operational. This work focuses on the measurement of the LGT thermal expansion coefficients from room temperature (25degC) to 1200degC. Two methods of extracting the thermal expansion coefficients have been used and compared: (a) dual push-rod dilatometry, which provides the bulk expansion; and (b) x-ray powder diffraction, which provides the lattice expansion. Both methods were performed over the entire temperature range and considered multiple samples taken from <001> Czochralski grown LGT material. The thermal coefficients of expansion were extracted by approximating each expansion data set to a third order polynomial fit over three temperature ranges reported in this work: 25degC to 400degC, 400degC to 900degC, 900degC to 1200degC. An accuracy of fit better than 35ppm for the bulk expansion and better than 10ppm for the lattice expansion have been obtained with the aforementioned polynomial fitting. The percentage difference between the bulk and the lattice fitted expansion responses over the entire temperature range of 25degC to 1200degC is less than 2% for the three crystalline axes, which indicates the high quality and growth consistency of the LGT crystal measured« less

Early Experience with Technology-Based Eye Care Services (TECS): A Novel Ophthalmologic Telemedicine Initiative.

PubMed

Maa, April Y; Wojciechowski, Barbara; Hunt, Kelly J; Dismuke, Clara; Shyu, Jason; Janjua, Rabeea; Lu, Xiaoqin; Medert, Charles M; Lynch, Mary G

2017-04-01

The aging population is at risk of common eye diseases, and routine eye examinations are recommended to prevent visual impairment. Unfortunately, patients are less likely to seek care as they age, which may be the result of significant travel and time burdens associated with going to an eye clinic in person. A new method of eye-care delivery that mitigates distance barriers and improves access was developed to improve screening for potentially blinding conditions. We present the quality data from the early experience (first 13 months) of Technology-Based Eye Care Services (TECS), a novel ophthalmologic telemedicine program. With TECS, a trained ophthalmology technician is stationed in a primary care clinic away from the main hospital. The ophthalmology technician follows a detailed protocol that collects information about the patient's eyes. The information then is interpreted remotely. Patients with possible abnormal findings are scheduled for a face-to-face examination in the eye clinic. Any patient with no known ocular disease who desires a routine eye screening examination is eligible. Technology-Based Eye Care Services was established in 5 primary care clinics in Georgia surrounding the Atlanta Veterans Affairs hospital. Four program operation metrics (patient satisfaction, eyeglass remakes, disease detection, and visit length) and 2 access-to-care metrics (appointment wait time and no-show rate) were tracked. Care was rendered to 2690 patients over the first 13 months of TECS. The program has been met with high patient satisfaction (4.95 of 5). Eyeglass remake rate was 0.59%. Abnormal findings were noted in 36.8% of patients and there was >90% agreement between the TECS reading and the face-to-face findings of the physician. TECS saved both patient (25% less) and physician time (50% less), and access to care substantially improved with 99% of patients seen within 14 days of contacting the eye clinic, with a TECS no-show rate of 5.2%. The early experience with TECS has been promising. Tele-ophthalmology has the potential to improve operational efficiency, reduce cost, and significantly improve access to care. Although further study is necessary, TECS shows potential to help prevent avoidable vision loss. Published by Elsevier Inc.

Regulation of tumorigenesis and metastasis of hepatocellular carcinoma tumor endothelial cells by microRNA-3178 and underlying mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Wei; Shen, Shiqiang, E-mail: shenshiqiang2014@hotmail.com; Wu, Shanmin

2015-08-28

This study explored the effects of microRNA-3178 (miR-3178) on hepatocellular carcinoma (HCC) tumor endothelial cells (TECs) and on the target mRNA. Real-time polymerase chain reaction (PCR) was performed to detect the differential expression of miR-3178 in hepatic sinusoidal endothelial cells (HSECs) and HCC TECs. Furthermore, HCC TECs were transfected with miR-3178 mimic/inhibitor or their respective negative controls. The expression of miR-3178 before and after transfection was confirmed through RT-PCR. The effects of miR-3178 on the proliferation, apoptosis, cell cycle, invasion, migration, and angiogenesis of HCC TECs were also investigated through methyl thiazol tetrazolium assay, flow cytometry, matrigel invasion assay, transwellmore » migration assay, and tube formation assay. Early growth responsive gene 3 (EGR3), as the putative target of miR-3178, was detected through RT-PCR and Western blot. Compared with HSECs, HCC TECs had lower miR-3178 expression levels (P < 0.001). MiR-3178 mimic inhibited proliferation, arrested cell cycle in G1 phase, and increased apoptosis. The numbers of migrated and invaded cells and capillary-like structures were significantly less in the mimic group than in the other groups. MiR-3178 mimic significantly decreased the mRNA and protein expression levels of EGR3. By contrast, miR-3178 inhibitor induced opposite effects. We conclude that miR-3178 was lowly expressed in HCC TECs, and miR-3178 mimic specifically inhibited the proliferation, migration, invasion, and angiogenesis and promoted the apoptosis and G1 phase arrest of HCC TECs in vitro through the inhibition of EGR3 expression. Thus, miR-3178 might be a critical target in HCC therapy. - Highlights: • MiR-3178 is significantly low-expression in HCC TECs. • MiR-3178 acts as a tumor suppressor to inhibit tumorigenesis and metastasis. • MiR-3178 inhibit angiogenesis of HCC TECs. • EGR3 may be a target gene of miR-3178. • MiR-3178 may have therapeutic application for treatment of HCC.« less

Computer Modeling of Ceramic Boride Composites

DTIC Science & Technology

2014-11-01

the reinforcer deform elastically, for the theoretical strength of the composite it can be written [46] BBBAAABBAAK EE δεδεσδσδσ +=+= (51) where...coefficients of thermal expansion. Approximately linear expansion coefficient of the composite is determined by the relation [52] EEE BBBAAAk...1 δαδαα ⋅+⋅= , (58) where AE and BE are Young moduli of components, and E – average modulus for composition BBAA EEE δδ

Additivity of the coefficient of thermal expansion in silicate optical fibers.

PubMed

Cavillon, M; Dragic, P D; Ballato, J

2017-09-15

A model that predicts the material additivity of the thermal expansion coefficient in the binary silicate glasses most commonly used for present (GeO 2 -SiO 2 , P 2 O 5 -SiO 2 , B 2 O 3 -SiO 2 , and Al 2 O 3 -SiO 2 ) and emerging (BaO-SiO 2 ) optical fibers is proposed. This model is based on a derivation of the expression for the coefficient of thermal expansion in isotropic solids, and gives direct insight on the parameters that govern its additivity in silicate glasses. Furthermore, a consideration of the local structural environment of the glass system is necessary to fully describe its additivity behavior in the investigated systems. This Letter is important for better characterizing and understanding of the impact of temperature and internal stresses on the behavior of optical fibers.

Design, fabrication and test of graphite/epoxy metering truss structure components, phase 3

NASA Technical Reports Server (NTRS)

1974-01-01

The design, materials, tooling, manufacturing processes, quality control, test procedures, and results associated with the fabrication and test of graphite/epoxy metering truss structure components exhibiting a near zero coefficient of thermal expansion are described. Analytical methods were utilized, with the aid of a computer program, to define the most efficient laminate configurations in terms of thermal behavior and structural requirements. This was followed by an extensive material characterization and selection program, conducted for several graphite/graphite/hybrid laminate systems to obtain experimental data in support of the analytical predictions. Mechanical property tests as well as the coefficient of thermal expansion tests were run on each laminate under study, the results of which were used as the selection criteria for the single most promising laminate. Further coefficient of thermal expansion measurement was successfully performed on three subcomponent tubes utilizing the selected laminate.

The mapping of ionospheric TEC for central Russian and European regions on the base of GPS and GLONASS measurements

NASA Astrophysics Data System (ADS)

Shagimuratov, Irk; Cherniak, Iurii; Zakharenkova, Irina; Ephishov, Ivan; Krankowski, Andrzej; Radievsky, Alexander

2014-05-01

The total electron content (TEC) is a key parameter not only for space radio communication but also for addressing the fundamental problems of the ionosphere physics and near Earth space. Currently, the main sources of information on the TEC in the global scale are GNSS signals measurements. The spatial-temporal behavior of the ionosphere can be most effectively analyzed using TEC maps. To date, global IGS global ionospheric maps with a resolution of 2.5 degree in latitude and 5 in longitude and a time resolution of 2 h are most widely used. To study the detailed structure of the ionospheric gradients and rapid process as well as for precise positioning task it is necessary to use more precise regional TEC maps. The Regional TEC maps are currently constructed by different research groups for different regions: USA, Europe, Japan etc. The West Department of IZMIRAN research group is a one in Russia who works on the task of regional ionosphere mapping since 2000. It was developed the methodology for obtaining information on the spatial TEC distribution, TEC maps of the ionosphere on the basis of the algorithm for multi-station processing of GNSS observations. Using a set of algorithms and programs, regional TEC maps with a spatial resolution of 1° and a time resolution up to 15 min can be produced. Here is developed the approach to establish the regular online internet service for regional ionosphere mapping of the Western Russia and Eastern Europe. Nowadays the development of GLONASS navigation system is completely finished and it consists of a constellation of more than 24 satellites. It is good perspective for investigations of the ionosphere structure and dynamics on the base of the simultaneous observations of GPS and GLONASS systems. The GLONASS satellites have the inclination about 64 degrees as against GPS satellites with 56. So the GLONASS provides opportunity to study the high latitude ionosphere. The different scale electron density irregularities, presented in high latitude ionosphere, can complicate phase ambiguity resolution. As known the strong gradients are observed in polar ionosphere near equator and polar walls of the main ionospheric trough. At high latitudes GLONASS satellites are observed on higher elevations that decrease the influence of horizontal ionospheric gradients and as consequence enable represent with more true Total Electron Content over individual high latitude station. In the report we discuss the features determining TEC from GLONASS observations and demonstrate its advantages for the high latitude ionosphere's studies. A comparison with TEC measurements from GPS/GLONASS for quiet and disturbed geomagnetic conditions is also presented. This work is supported by RFBR grant 14-07-00512.

Short-term estimation of GNSS TEC using a neural network model in Brazil

NASA Astrophysics Data System (ADS)

Ferreira, Arthur Amaral; Borges, Renato Alves; Paparini, Claudia; Ciraolo, Luigi; Radicella, Sandro M.

2017-10-01

This work presents a novel Neural Network (NN) model to estimate Total Electron Content (TEC) from Global Navigation Satellite Systems (GNSS) measurements in three distinct sectors in Brazil. The purpose of this work is to start the investigations on the development of a regional model that can be used to determine the vertical TEC over Brazil, aiming future applications on a near real-time frame estimations and short-term forecasting. The NN is used to estimate the GNSS TEC values at void locations, where no dual-frequency GNSS receiver that may be used as a source of data to GNSS TEC estimation is available. This approach is particularly useful for GNSS single-frequency users that rely on corrections of ionospheric range errors by TEC models. GNSS data from the first GLONASS network for research and development (GLONASS R&D network) installed in Latin America, and from the Brazilian Network for Continuous Monitoring of the GNSS (RMBC) were used on TEC calibration. The input parameters of the NN model are based on features known to influence TEC values, such as geographic location of the GNSS receiver, magnetic activity, seasonal and diurnal variations, and solar activity. Data from two ten-days periods (from DoY 154 to 163 and from 282 to 291) are used to train the network. Three distinct analyses have been carried out in order to assess time-varying and spatial performance of the model. At the spatial performance analysis, for each region, a set of stations is chosen to provide training data to the NN, and after the training procedure, the NN is used to estimate vTEC behavior for the test station which data were not presented to the NN in training process. An analysis is done by comparing, for each testing station, the estimated NN vTEC delivered by the NN and reference calibrated vTEC. Also, as a second analysis, the network ability to forecast one day after the time interval (DoY 292) based on information of the second period of investigation is also assessed in order to verify the feasibility on using low amount of data for short-term forecasting. In a third analysis, the spatial performance of the NN model is assessed and compared against CODE Global Ionospheric Maps during the geomagnetic storm registered on 13th and 14th October 2016. The results obtained from the three described analyses indicate that even using a ten-days period of data to train the network, the proposed NN model provides good spatial performance and presents to be a promising tool for short-term forecasting. The results obtained in the analysis presented a root mean squared error less than 7.9 TECU in all scenarios under investigation.

Design of a three-dimensional scramjet nozzle considering lateral expansion and geometric constraints

NASA Astrophysics Data System (ADS)

Lv, Zheng; Xu, Jinglei; Mo, Jianwei

2017-12-01

A new method based on quasi two-dimensional supersonic flow and maximum thrust theory to design a three-dimensional nozzle while considering lateral expansion and geometric constraints is presented in this paper. To generate the configuration of the three-dimensional nozzle, the inviscid flowfield is calculated through the method of characteristics, and the reference temperature method is applied to correct the boundary layer thickness. The computational fluid dynamics approach is used to obtain the aerodynamic performance of the nozzle. Results show that the initial arc radius slightly influences the axial thrust coefficient, whereas the variations in the lateral expansion contour, the length and initial expansion angle of the lower cowl significantly affect the axial thrust coefficient. The three-dimensional nozzle designed by streamline tracing technique is also investigated for comparison to verify the superiority of the new method. The proposed nozzle shows increases in the axial thrust coefficient, lift, and pitching moment of 6.86%, 203.15%, and 642.86%, respectively, at the design point, compared with the nozzle designed by streamline tracing approach. In addition, the lateral expansion accounts for 22.46% of the entire axial thrust, while it has no contribution to the lift and pitching moment in the proposed nozzle.

Anomalous variation in GPS based TEC measurements prior to the 30 September 2009 Sumatra Earthquake

NASA Astrophysics Data System (ADS)

Karia, Sheetal; Pathak, Kamlesh

This paper investigates the features of pre-earthquake ionospheric anomalies in the total elec-tron content (TEC) data obtained on the basis of regular GPS observations from the GPS receiver at SVNIT Surat (21.16 N, 72.78 E Geog) located at the northern crest of equatorial anomaly region. The data has been analysed for 5 different earthquakes that occurred during 2009 in India and its neighbouring regions. Our observation shows that for the cases of the earthquake, in which the preparation area lies between the crests of the equatorial anomaly close to the geomagnetic equator the enhancement in TEC was followed by a depletion in TEC on the day of earthquake, which may be connected to the equatorial anomaly shape distortions. For the analysis of the ionospheric effects of one of such case-the 30 September 2009 Sumatra earthquake, Global Ionospheric Maps of TEC were used. The possible influence of the earth-quake preparation processes on the main low-latitude ionosphere peculiarity—the equatorial anomaly—is discussed.

Ionospheric Response to the Magnetic Storm of 22 June 2015

NASA Astrophysics Data System (ADS)

Mansilla, Gustavo A.

2018-03-01

A global study is made of the response of the total electron content of the ionosphere (TEC) to the geomagnetic storm occurred on 22 June 2015 (one of the strongest geomagnetic storms of the current Solar Cycle 24). Using data from 44 sites, a hemispheric comparison is made by considering high latitudes (> 50°), middle latitudes (30°-50°) and low latitudes (30°N-30°S). The main features observed were: increases in TEC at high latitudes prior to the storm main phase, a considerable asymmetry of TEC response at middle and low latitudes of the Northern Hemisphere and the Southern Hemisphere and decreases at equatorial latitudes. The long duration enhancements in TEC were well correlated with increases in the O/N2 ratio but decreases in TEC had not associated decreases in the O/N2 ratio as occur with the decreases in the electron density. Besides, prompt penetration electric fields can play an important role in the equatorial and low-latitude ionosphere during main phase of the storm.

Assessment of Ionospheric Anomaly Prior to the Large Earthquake: 2D and 3D Analysis in Space and Time for the 2011 Tohoku Earthquake (Mw9.0)

NASA Astrophysics Data System (ADS)

Hattori, Katsumi; Hirooka, Shinji; Han, Peng

2016-04-01

The ionospheric anomalies possibly associated with large earthquakes have been reported by many researchers. In this paper, Total Electron Content (TEC) and tomography analyses have been applied to investigate the spatial and temporal distributions of ionospheric electron density prior to the 2011 Off the Pacific Coast of Tohoku earthquake (Mw9.0). Results show significant TEC enhancements and an interesting three dimensional structure prior to the main shock. As for temporal TEC changes, the TEC value increases 3－4 days before the earthquake remarkably, when the geomagnetic condition was relatively quiet. In addition, the abnormal TEC enhancement area in space was stalled above Japan during the period. Tomographic results show that three dimensional distribution of electron density decreases around 250 km altitude above the epicenter (peak is located just the east-region of the epicenter) and increases the mostly entire region between 300 and 400 km.

Ionospheric total electron content seismo-perturbation after Japan's March 11, 2011, M=9.0 Tohoku earthquake under a geomagnetic storm; a nonlinear principal component analysis

NASA Astrophysics Data System (ADS)

Lin, Jyh-Woei

2012-10-01

Nonlinear principal component analysis (NLPCA) is implemented to analyze the spatial pattern of total electron content (TEC) anomalies 3 hours after Japan's Tohoku earthquake that occurred at 05:46:23 on 11 March, 2011 (UTC) ( M w =9). A geomagnetic storm was in progress at the time of the earthquake. NLPCA and TEC data processing were conducted on the global ionospheric map (GIM) for the time between 08:30 to 09:30 UTC, about 3 hours after this devastating earthquake and ensuing tsunami. Analysis results show stark earthquake-associated TEC anomalies that are widespread, and appear to have been induced by two acoustic gravity waves due to strong shaking (vertical acoustic wave) and the generation of the tsunami (horizontal Rayleigh mode gravity wave). The TEC anomalies roughly fit the initial mainshock and movement of the tsunami. Observation of the earthquake-associated TEC anomalies does not appear to be affected by a contemporaneous geomagnetic storm.

Earthquake Related Variation of Total Electron Content in Ionosphere over Chinese Mainland Derived from Observations of a Nationwide GNSS Network

NASA Astrophysics Data System (ADS)

Gan, Weijun

2016-07-01

Crustal Movement Observation Network of China (CMONOC) is a key national scientific infrastructure project carried out during 1997-2012 with 2 phases. The network is composed of 260 continuously observed GNSS stations (CORS) and 2081 campaign mode GNSS stations, with the main purpose to monitor the crustal movement, perceptible water vapor (PWV), total electron content (TEC), and many other tectonic and environmental elements around mainland China, by mainly using the Global Navigation Satellite System (GNSS) technology. Here, based on the GNSS data of 260 CORS of COMNOC for about 5 years, we investigated the characteristics of TEC in ionosphere over Chinese Mainland and discussed if there was any abnormal change of TEC before and after a big earthquake. our preliminary results show that it is hard to see any convincing precursor of TEC before a big earthquake. However, the huge energy released by a big earthquake can obviously disturb the TEC over meizoseismal area.

Investigation of the Effects of Solar and Geomagnetic Changes on the Total Electron Content: Mid-Latitude Region

NASA Astrophysics Data System (ADS)

Ulukavak, Mustafa; Yalcinkaya, Mualla

2016-04-01

The Global Positioning System (GPS) is used as an important tool for ionosphere monitoring and obtaining the Total Electron Content (TEC). GPS satellites, positioned in the Earth's orbit, are used as sensors to investigate the space weather conditions. In this study, solar and geomagnetic activity variations were investigated between the dates 1 March-30 June 2015 for the mid-latitude region. GPS-TEC variations were calculated for each selected International GNSS Service (IGS) station in Europe. GNSS data was obtained from Crustal Dynamics Data and Information System (CDDIS) archive. Solar and geomagnetic activity indices (Kp, F10.7 ve Dst) were obtained from the Oceanic and Atmospheric Administration (NOAA), the Canadian Space Weather Forecast Centre (CSWFC) and Data Analysis Center for geomagnetism and Space Magnetism Graduate School of Science, Kyoto University (WDC) archives. GPS-TEC variations were determined for the quiet periods of the solar and geomagnetic activities. GPS-TEC changes were then compared with respect to the quiet periods of the solar and geomagnetic activities. Global Ionosphere Maps (GIM) IONEX files, obtained from the IGS analysis center, was used to check the robustness of the GPS-TEC variations. The investigations revealed that it is possible to use the GPS-TEC data for monitoring the ionospheric disturbances.

Quantifications of Geomagnetic Storm Impact on TEC and NmF2 during 2013 Mar. event

NASA Astrophysics Data System (ADS)

Shim, J. S.; Tsagouri, I.; Goncharenko, L. P.; Mays, M. L.; Taktakishvili, A.; Rastaetter, L.; Kuznetsova, M. M.

2016-12-01

We investigate the ionospheric response to 2013 Mar. geomagnetic storm event using GPS TEC, ISR and ionosonde observations in North American sector. In order to quantify variations of TEC and NmF2 (or foF2) due to the storm, we remove the background quiet-time values (e.g., TEC of one day prior to the storm, NmF2 median and average of five quietest days for 30 days prior to the storm). In addition, in order to assess modeling capability of reproducing storm impacts on TEC and NmF2, we compare the observations with various model simulations, which are obtained from empirical, physics-based, and data assimilation models. Further, we investigate how uncertainty in the interplanetary magnetic field (IMF) impacts on TEC and NmF2 during the geomagnetic storm event. For this uncertainty study, we use a physics-based coupled ionosphere-thermosphere model, CTIPe, and solar wind parameters obtained from ensemble of WSA-ENLIL+Cone model simulations. This study has been supported by the Community Coordinated Modeling Center (CCMC) at the Goddard Space Flight Center. Model outputs and observational data used for the study will be permanently posted at the CCMC website (http://ccmc.gsfc.nasa.gov) for the space science communities to use.

Statistical seismo-ionospheric precursors of M7.0+ earthquakes in Circum-Pacific seismic belt by GPS TEC measurements

NASA Astrophysics Data System (ADS)

Li, Wang; Yue, Jianping; Guo, Jinyun; Yang, Yang; Zou, Bin; Shen, Yi; Zhang, Kefei

2018-03-01

The Circum-Pacific seismic belt is the region heavily affected by earthquakes in the world. The relationship between earthquake (e.g., the geographic location, occurrence time, magnitude, and focal depth) and ionospheric anomalies in the belt was investigated using 100 M7.0+ earthquakes during 2006-2015. The ground-based GPS measurements and global ionosphere map (GIM) data were used for the analyses of the ionospheric variations preceding the earthquakes. The results indicated that the occurrence rate of total electron content (TEC) anomalies was proportional to the magnitude and inversely proportional to the focal depth to a certain degree, and the occurrence frequency of anomalies had a rising trend with the days getting close to the main shock. The occurrence rate of TEC anomalies in the Southern hemisphere was larger than that in the Northern hemisphere. Besides, the spatial characteristics of TEC anomalies showed that the anomalies in low-middle latitudes did not coincide with the epicenter, sometimes the anomalies were also observed in the corresponding conjugated region. However, the TEC anomalies in the high latitude usually appeared around the epicenter and within the seismogenic zone while no TEC anomalies appeared in the conjugated area. These results may have potential applications to the earthquake prediction in the Circum-Pacific seismic belt.

Thermal Expansion Coefficient of Cold-Pressed Silicon Carbide

NASA Astrophysics Data System (ADS)

Olivieri, E.; Pasca, E.; Ventura, G.; Barucci, M.; Risegari, L.

2004-07-01

The measurement of the thermal linear expansion coefficient of a cold sintered SiC has been carried out in the 4.2 - 293 K temperature range. The properties of silicon carbide are specially suitable to realise high quality mirrors and complete optomechanical structures for space astronomy. The thermal contraction of the material used for the realization of the mirror is, of course, of primary interest. We present here both a plot and smoothed data of SiC thermal contraction coefficient. Details of the dilatometric interferometer used to carry out the measurements are also reported together with a control test of the measuring bench on a material (brass) of known thermal contraction.

Low expansion superalloy with improved toughness

DOEpatents

Smith, Darrell F.; Stein, Larry I.; Hwang, Il S.

1995-01-01

A high strength, low coefficient of thermal expansion superalloy exhibiting improved toughness over a broad temperature range down to about 4.degree. K. The composition is adapted for use with wrought superconducting sheathing.

Interphase ribosomal RNA cistron staining in thyroid epithelial cells in Grave's disease, Hashimoto's thyroiditis and benign and malignant tumours of the thyroid gland

PubMed Central

Mamaev, N N; Grynyeva, E N; Blagosklonnaya, Y V

1996-01-01

Aim—To evaluate the expression of ribosomal cistrons in human thyroid epithelial cells (TECs) of patients with Grave's disease, Hashimoto's thyroiditis and benign and malignant tumours of the thyroid gland. Methods—TEC nucleoli were investigated in fine needle biopsy specimens from 10 controls, 39 patients with Grave's disease, 15 with Hashimoto's thyroiditis, 56 with benign, and 15 with malignant tumours of the thyroid. A one step silver staining method was applied. In most cases serum concentrations of thyroxine and triiodothyronine as well as goitre size were determined. In every case 100 TECs were evaluated for the mean numbers of nucleoli and for the average number of argyrophilic nucleolar organiser regions (AgNORs) per nucleus. Results—NORs were activated in all patients, but not in controls. The numbers of AgNORs in patients with Grave's disease were closely correlated with thyroxine or triiodothyronine, or both, concentrations and with the size of the thyroid. In patients with Hashimoto's thyroiditis about 30% of TECs nucleoli did not contain AgNORs, whereas others were heavily impregnated with silver. Compared with controls and benign tumours, the nucleoli of carcinomatous TECs were larger and irregular in shape. The mean number of AgNORs per nucleus in malignant cells was higher than that in their benign counterparts. Conclusions—The mechanism by which NORs are activated in TECs varies depending on the type of lesion. The higher AgNOR score in TECs from malignant tumours can be used to distinguish them from their benign counterparts. Images PMID:16696083

Complex analysis of the ionospheric response to operation of ``Progress'' cargo spacecraft according to the data of GNSS receivers in Baikal region

NASA Astrophysics Data System (ADS)

Ishin, Artem; Voeykov, Sergey; Perevalova, Natalia; Khakhinov, Vitaliy

2017-12-01

As a part of the Plasma-Progress and Radar-Progress space experiments conducted from 2006 to 2014, effects of the Progress spacecraft engines on the ionosphere have been studied using data from Global Navigation Satellite System (GNSS) receivers. 72 experiments have been carried out. All these experiments were based on data from the International GNSS Service (IGS) to record ionospheric plasma irregularities caused by engine operation. 35 experiments used data from the ISTP SB RAS network SibNet. The analysis of the spatio-temporal structure of total electron content (TEC) variations has shown that the problem of identifying the TEC response to engine operation is complicated by a number of factors: 1) the engine effect on ionospheric plasma is strongly localized in space and has a relatively low intensity; 2) a small number of satellite-receiver radio rays due to the limited number of GNSS stations, particularly before 2013; 3) a potential TEC response is masked with background ionospheric disturbances of various intensities. However, TEC responses are identified with certainty when a satellite-receiver radio ray crosses a disturbed region within minutes after the impact. TEC responses have been registered in 7 experiments (10 % of cases). The amplitude of ionospheric response (0.3-0.16 TECU) exceeded the background TEC variations (~0.25 TECU) several times. The TEC data indicate that the ionospheric irregularity lifetime is from 4 to 10 minutes. According to the estimates we made, the transverse size of irregularities is from 12 to 30 km.

Synovial mesenchymal stem cells from osteo- or rheumatoid arthritis joints exhibit good potential for cartilage repair using a scaffold-free tissue engineering approach.

PubMed

Koizumi, K; Ebina, K; Hart, D A; Hirao, M; Noguchi, T; Sugita, N; Yasui, Y; Chijimatsu, R; Yoshikawa, H; Nakamura, N

2016-08-01

To assess whether synovial mesenchymal stem cells (SMSCs) from patients with osteoarthritis (OA) or rheumatoid arthritis (RA) can be used as an alternative cell source for cartilage repair using allogenic tissue engineered construct (TEC). Twenty-five patients (17 female, average age 61.8 years) were divided according to their pathology (control trauma group; N = 6, OA group; N = 6) and RA patients were subdivided into two groups to evaluate the impact of biologics in accordance with whether treated with biologics [Bio(+)RA; N = 7] or not [Bio(-)RA; N = 6]. We compared the following characteristics among these groups: (1) The cell proliferation capacity of SMSCs; (2) The influence of passage number on features of SMSCs; (3) The weight and volume of TEC from the same number of SMSCs; (4) Inflammatory cytokine gene expressions levels of TEC; (5) The chondrogenic potential of TEC; and (6) Osteochondral repair using TEC in athymic nude rats. SMSCs from the four groups exhibited equivalent features in the above evaluation items. In in vivo studies, the TEC-treated repair tissues for all groups exhibited significantly better outcomes than those for the untreated group and no significant differences among the four TEC groups. SMSCs from OA or RA patients are no less appropriate for repairing cartilage than those from trauma patients and thus, may be an effective source for allogenic cell-based cartilage repair. Copyright © 2016 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Imaging the topside ionosphere and plasmasphere with ionospheric tomography using COSMIC GPS TEC

NASA Astrophysics Data System (ADS)

Pinto Jayawardena, Talini S.; Chartier, Alex T.; Spencer, Paul; Mitchell, Cathryn N.

2016-01-01

GPS-based ionospheric tomography is a well-known technique for imaging the total electron content (TEC) between GPS satellites and receivers. However, as an integral measurement of electron concentration, TEC typically encompasses both the ionosphere and plasmasphere, masking signatures from the topside ionosphere-plasmasphere due to the dominant ionosphere. Imaging these regions requires a technique that isolates TEC in the topside ionosphere-plasmasphere. Multi-Instrument Data Analysis System (MIDAS) employs tomography to image the electron distribution in the ionosphere. Its implementation for regions beyond is yet to be seen due to the different dynamics present above the ionosphere. This paper discusses the extension of MIDAS to image these altitudes using GPS phase-based TEC measurements and follows the work by Spencer and Mitchell (2011). Plasma is constrained to dipole field lines described by Euler potentials, resulting in a distribution symmetrical about the geomagnetic equator. A simulation of an empirical plasmaspheric model by Gallagher et al. (1988) is used to verify the technique by comparing reconstructions of the simulation with the empirical model. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) is used as GPS receiver locations. The verification is followed by a validation of the modified MIDAS algorithm, where the regions' TEC is reconstructed from COSMIC GPS phase measurements and qualitatively compared with previous studies using Jason-1 and COSMIC data. Results show that MIDAS can successfully image features/trends of the topside ionosphere-plasmasphere observed in other studies, with deviations in absolute TEC attributed to differences in data set properties and the resolution of the images.

Equatorial ionization anomaly development as studied by GPS TEC and foF2 over Brazil: A comparison of observations with model results from SUPIM and IRI-2012

NASA Astrophysics Data System (ADS)

Nogueira, P. A. B.; Abdu, M. A.; Souza, J. R.; Batista, I. S.; Bailey, G. J.; Santos, A. M.; Takahashi, H.

2013-11-01

The equatorial ionization anomaly (EIA) development is studied using the total electron content (TEC) observed by the Global Positioning System (GPS) satellites, the F2-layer critical frequency (foF2) as measured by digisondes operated in the Brazilian sector, and by model simulation using the SUPIM (Sheffield University Plasmasphere Ionosphere Model). We have used two indices based on foF2 and TEC to represent the strength of the EIA Southern Anomaly Crest (SAC), which are denoted, respectively, by SAC(foF2) and SAC(TEC). Significant differences in the local time variations of the EIA intensity, as represented by these two indices, are investigated. The observed SAC indices are compared with their values modeled by the SUPIM and also by the International Reference Ionosphere (IRI)-2012. The SUPIM simulations that use the standard E×B plasma drift and neutral air wind models are found to provide acceptable representations of the observed foF2 and TEC, and hence the indices SAC(foF2) and SAC(TEC) during daytime, whereas the IRI-2012 model is not, except during the post-midnight/sunrise hours. It is found that the differences in the local time variations between the SAC(foF2) and SAC(TEC) can be reduced by limiting the TEC integrations in height up to an altitude of 630 km in the SUPIM calculations. It is also found that when the EIA intensity is calculated for an intermediate dip latitude (12°S) the difference between the local time variation patterns of the two corresponding indices in the experimental data and in the SUPIM results is reduced. For the IRI-2012 values, the subequatorial station modification does not appear to have any effect.

Regional And Seasonal Aspects Of Within-The-Hour Tec Statistics

NASA Astrophysics Data System (ADS)

Koroglu, Ozan; Arikan, Feza; Koroglu, Meltem

2015-04-01

Ionosphere is one of the atmosphere layers which has a plasma structure. Several mechanisms originating from both space and earth itself governs this plasma layer such as solar radiation and geomagnetic effects. Ionosphere plays important role for HF and satellite communication, and space based positioning systems. Therefore, the determination of statistical behavior of ionosphere has utmost importance. The variability of the ionosphere has complex spatio-temporal characteristics, which depends on solar, geomagnetic, gravitational and seismic activities. Total Electron Content (TEC) is one of the major observables for investigating and determining this variability. In this study, spatio-temporal within-the-hour statistical behavior of TEC is determined for Turkey, which is located in mid-latitude, using the TEC estimates from Turkish National Permanent GPS Network (TNPGN)-Active between the years 2009 and 2012. TEC estimates are obtained as IONOLAB-TEC which is developed by IONOLAB group (www.ionolab.org) from Hacettepe University. IONOLAB-TEC for each station in TNPGN-Active is organized in a database and grouped with respect to years, ionospheric seasons, hours and regions 2 degree by 3 degree, in latitude and longitude, respectively. The data sets are used to calculate within-the-hour parametric Probability Density Functions (PDF). For every year, every region and every hour, a representative PDF is determined. It is observed that TEC values have a strong hourly, seasonal and positional dependence on east-west direction, and the growing trend shifts according to sunrise and sunset times. It is observed that the data are distributed predominantly as Lognormal and Weibull. The averages and standard deviations of the chosen distributions follow the trends in 24 hour diurnal and 11 year solar cycle periods. The regional and seasonal behavior of PDFs are investigated using a representative GPS station within each region. Within-the-hour PDF estimates are grouped into ionospheric seasons as Winter, Summer, March equinox and September equinox. In winter and summer seasons, Lognormal distribution is observed. During equinox seasons, Weibull distribution is observed more frequently. Furthermore, all hourly TEC values in same region are combined in order to improve the reliability and accuracy of the probability density function estimates. It is observed that as being in mid-latitude region, the ionosphere over Turkey has robust characteristics that are distributed as Lognormal and Weibull. Statistical observations on PDF estimates of TEC of the ionosphere over Turkey will contribute to developing a regional and seasonal random field model, which will further contribute to HF channel characterization. This study is supported by a joint grant of TUBITAK 112E568 and RFBR 13-02-91370-CT_a.

New comparisons of ISR and RO data with the model IRI-Plas

NASA Astrophysics Data System (ADS)

Maltseva, Olga; Mozhaeva, Natalya; Zhbankov, Gennadii

2012-07-01

Space Weather events lead to strong changes in peak parameters of the ionosphere. These parameters, foF2 and hmF2, define the N(h)-profile, which is known to include bottom side and topside parts. Numerous studies have shown that adaptation of the IRI model to the experimental values of foF2 and hmF2 gave a good agreement between experimental and model N(h)-profiles of the bottom side ionosphere. This is not about the topside N(h)-profile. To improve the situation measurements of the total electron content TEC are involved. This work is devoted to the use of peak parameters with the TEC during Space Weather events for the evaluation of propagation conditions in both the bottom side and the topside ionosphere, based on the model IRI-Plas. To assess how well the model N(h)-profile matches the experimental one, the model IRI-Plas is tested according to the Incoherent Scatter Radars and the Radio Occultation measurements in various parts of the globe and at different levels of solar activity. The experimental N(h)-profiles are compared with profiles for the original model, the model adapted to the foF2 and hmF2, and for a model with full adaptation (including the TEC). The best fit is obtained in the European region, so the SW variations of peak parameters and N(h)-profiles are studied on the example of the European area. The IRI-Plas model allows to estimate the relative contributions of each region (bottom side BOT, topside TOP and plasmaspheric PL parts) in the value of the TEC. As the analysis of two W- and Wp-indexes (Gulyaeva, 2008; Gulyaeva and Stanislawska, 2008) is shown, TEC-storms occur in 2 times more likely than foF2-storms. This testifies that the variations of parts BOT, TOP and PL in the TEC are different. It determines different variations of N(h)-profiles. Results are given for several types of SW-events, in particular, for the strong positive and negative disturbances, when the variations of TEC and foF2 are of the same sign and the corresponding perturbation covers all regions of the ionosphere. Particular attention is paid to variations of peak parameters and N(h)-profiles during weak and moderate disturbances and bursts of TEC in long period of low activity, when the TEC and foF2 variations and variations of different parts of TEC are in the opposite phase.

Braze material for joining ceramic to metal and ceramic to ceramic surfaces and joined ceramic to metal and ceramic to ceramic article

DOEpatents

Hunt, T.K.; Novak, R.F.

1991-05-07

An improved active metal braze filler material is provided in which the coefficient of thermal expansion of the braze filler is more closely matched with that of the ceramic and metal, or two ceramics, to provide ceramic to metal, or ceramic to ceramic, sealed joints and articles which can withstand both high temperatures and repeated thermal cycling without failing. The braze filler material comprises a mixture of a material, preferably in the form of a powder, selected from the group consisting of molybdenum, tungsten, silicon carbide and mixtures thereof, and an active metal filler material selected from the group consisting of alloys or mixtures of nickel and titanium, alloys or mixtures of nickel and zirconium, alloys or mixtures of nickel, titanium, and copper, alloys or mixtures of nickel, titanium, and zirconium, alloys or mixtures of niobium and nickel, alloys or mixtures of niobium and zirconium, alloys or mixtures of niobium and titanium, alloys or mixtures of niobium, titanium, and nickel, alloys or mixtures of niobium, zirconium, and nickel, and alloys or mixtures of niobium, titanium, zirconium, and nickel. The powder component is selected such that its coefficient of thermal expansion will effect the overall coefficient of thermal expansion of the braze material so that it more closely matches the coefficients of thermal expansion of the ceramic and metal parts to be joined. 3 figures.

Braze material for joining ceramic to metal and ceramic to ceramic surfaces and joined ceramic to metal and ceramic to ceramic article

DOEpatents

Hunt, Thomas K.; Novak, Robert F.

1991-01-01

An improved active metal braze filler material is provided in which the coefficient of thermal expansion of the braze filler is more closely matched with that of the ceramic and metal, or two ceramics, to provide ceramic to metal, or ceramic to ceramic, sealed joints and articles which can withstand both high temperatures and repeated thermal cycling without failing. The braze filler material comprises a mixture of a material, preferably in the form of a powder, selected from the group consisting of molybdenum, tungsten, silicon carbide and mixtures thereof, and an active metal filler material selected from the group consisting of alloys or mixtures of nickel and titanium, alloys or mixtures of nickel and zirconium, alloys or mixtures of nickel, titanium, and copper, alloys or mixtures of nickel, titanium, and zirconium, alloys or mixtures of niobium and nickel, alloys or mixtures of niobium and zirconium, alloys or mixtures of niobium and titanium, alloys or mixtures of niobium, titanium, and nickel, alloys or mixtures of niobium, zirconium, and nickel, and alloys or mixtures of niobium, titanium, zirconium, and nickel. The powder component is selected such that its coefficient of thermal expansion will effect the overall coefficient of thermal expansion of the braze material so that it more closely matches the coefficients of thermal expansion of the ceramic and metal parts to be joined.

Linear thermal expansion coefficient determination using in situ curvature and temperature dependent X-ray diffraction measurements applied to metalorganic vapor phase epitaxy-grown AlGaAs

NASA Astrophysics Data System (ADS)

Maaßdorf, A.; Zeimer, U.; Grenzer, J.; Weyers, M.

2013-07-01

AlxGa1-xAs grown on GaAs is known to be almost perfectly lattice matched with a maximum lattice mismatch of 0.14% at room temperature and even less at temperatures of 700 °C-800 °C. However, as layer structures for edge-emitting diode lasers exhibit an increasing overall thickness of several microns of AlxGa1-xAs, e.g., diode lasers comprising a super-large optical cavity, the accumulated elastic strain energy increases as well. Depending on the growth temperature the formation energy of dislocations can be reached, which is limiting the pseudomorphic growth. In this regard, the thermal expansion coefficient difference between layer and substrate is an important parameter. We utilize in situ curvature measurements during growth of AlxGa1-xAs by metal-organic vapour phase epitaxy to determine the thermal expansion coefficient α. The curvature change with increasing layer thickness, as well as with wafer temperature at constant layer thickness is used to assess α. This is compared to ex situ temperature dependent X-ray diffraction measurements to obtain α. All determined values for α are in good agreement, yielding αAlAs=4.1×10-6 K-1 for a given GaAs linear thermal expansion coefficient of αGaAs=5.73×10-6 K-1.

Ionospheric Anomalies on the day of the Devastating Earthquakes during 2000-2012

NASA Astrophysics Data System (ADS)

Su, Fanfan; Zhou, Yiyan; Zhu, Fuying

2013-04-01

The study of the ionospheric abnormal changes during the large earthquakes has attracted much attention for many years. Many papers have reported the deviations of Total Electron Content (TEC) around the epicenter. The statistical analysis concludes that the anomalous behavior of TEC is related with the earthquakes with high probability[1]. But the special cases have different features[2][3]. In this study, we carry out a new statistical analysis to investigate the nature of the ionospheric anomalies during the devastating earthquakes. To demonstrate the abnormal changes of the ionospheric TEC, we have examined the TEC database from the Global Ionosphere Map (GIM). The GIM ( ftp://cddisa.gsfc.nasa.gov/pub/gps/products/ionex) includes about 200 of worldwide ground-based receivers of the GPS. The TEC data with resolution of 5° longitude and 2.5° latitude are routinely published in a 2-h time interval. The information of earthquakes is obtained from the USGS ( http://earthquake.usgs.gov/earthquakes/eqarchives/epic/). To avoid the interference of the magnetic storm, the days with Dst≤-20 nT are excluded. Finally, a total of 13 M≥8.0 earthquakes in the global area during 2000-2012 are selected. The 27 days before the main shock are treated as the background days. Here, 27-day TEC median (Me) and the standard deviation (σ) are used to detect the variation of TEC. We set the upper bound BU = Me + 3*σ, and the lower bound BL = Me - 3*σ. Therefore the probability of a new TEC in the interval (BL, BU) is approximately 99.7%. If TEC varies between BU and BL, the deviation (DTEC) equals zero. Otherwise, the deviations between TEC and bounds are calculated as DTEC = BU/BL - TEC. From the deviations, the positive and negative abnormal changes of TEC can be evaluated. We investigate temporal and spatial signatures of the ionospheric anomalies on the day of the devastating earthquakes(M≥8.0). The results show that the occurrence rates of positive anomaly and negative anomaly are almost equal. The most significant anomaly on the day may occur at the time very close to the main shock, but sometimes it is not the case. The positions of the maximal deviations always deviate from the epicenter. The direction may be southeast, southwest, northeast or northwest with the almost equal probability. The anomalies may move to the epicenter, deviate to any direction, or stay at the same position and gradually fade out. There is no significant feature, such as occurrence time, position, or motion, and so on, which can indicate the source of the anomalies. References: [1].Le, H., J. Y. Liu, et al. (2011). "A statistical analysis of ionospheric anomalies before 736 M6.0+earthquakes during 2002-2010." J. Geophys. Res. 116. [2].Liu, J. Y., Y. I. Chen, et al. (2009). "Seismoionospheric GPS total electron content anomalies observed before the 12 May 2008 Mw7.9 Wenchuan earthquake." J. Geophys. Res. 114. [3].Rolland, L. M., P. Lognonne, et al. (2011). "Detection and modeling of Rayleigh wave induced patterns in the ionosphere." J. Geophys. Res. 116.

Low expansion superalloy with improved toughness

DOEpatents

Smith, D.F.; Stein, L.I.; Hwang, I.S.

1995-06-20

A high strength, low coefficient of thermal expansion superalloy exhibiting improved toughness over a broad temperature range down to about 4 K is disclosed. The composition is adapted for use with wrought superconducting sheathing.

Elastic and thermal expansion asymmetry in dense molecular materials.

PubMed

Burg, Joseph A; Dauskardt, Reinhold H

2016-09-01

The elastic modulus and coefficient of thermal expansion are fundamental properties of elastically stiff molecular materials and are assumed to be the same (symmetric) under both tension and compression loading. We show that molecular materials can have a marked asymmetric elastic modulus and coefficient of thermal expansion that are inherently related to terminal chemical groups that limit molecular network connectivity. In compression, terminal groups sterically interact to stiffen the network, whereas in tension they interact less and disconnect the network. The existence of asymmetric elastic and thermal expansion behaviour has fundamental implications for computational approaches to molecular materials modelling and practical implications on the thermomechanical strains and associated elastic stresses. We develop a design space to control the degree of elastic asymmetry in molecular materials, a vital step towards understanding their integration into device technologies.

Using a Michelson Interferometer to Measure Coefficient of Thermal Expansion of Copper

ERIC Educational Resources Information Center

Scholl, Ryan; Liby, Bruce W.

2009-01-01

When most materials are heated they expand. This concept is usually demonstrated using some type of mechanical measurement of the linear expansion of a metal rod. We have developed an alternative laboratory method for measuring thermal expansion by using a Michelson interferometer. Using the method presented, interference, interferometry, and the…

On Partial Fraction Expansion with Multiple Poles. Classroom Notes

ERIC Educational Resources Information Center

Hou, Shui-Hung; Hou, Edwin Sui-Hoi

2004-01-01

A simple and novel method for evaluating the partial fraction expansion of proper rational functions is presented. The technique involves simultaneous determination of the partial fraction coefficients associated with each of the multiple poles in the expansion in turn. Only synthetic division is required, which makes the process very suitable for…

Spherical-wave expansions of piston-radiator fields.

PubMed

Wittmann, R C; Yaghjian, A D

1991-09-01

Simple spherical-wave expansions of the continuous-wave fields of a circular piston radiator in a rigid baffle are derived. These expansions are valid throughout the illuminated half-space and are useful for efficient numerical computation in the near-field region. Multipole coefficients are given by closed-form expressions which can be evaluated recursively.

Ab-initio study of thermal expansion in pure graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mann, Sarita; Kumar, Ranjan; Jindal, V. K., E-mail: jindal@pu.ac.in

Graphene is a zero band gap semiconductor with exceptionally high thermal conductivity. The electronic properties having been studied, therole of phonon in contributing to thermal expansion, thermal conductivity and other thermodynamic properties, is required to be investigated. This paper focuses more on thermal expansion. Some others results like phonon dispersion, Grüneisenparameters and bulk modulus,which are essential to estimation of thermal expansion, are also presented. The dynamical matrix was calculated using VASP code using both DFT and DFPT and the phonon frequencies were calculated using phonopy code under harmonic approximation. The linear thermal expansion coefficient of graphene is found to bemore » strongly dependent on temperature but remains negative upto 470 K and positive thereafter, with a room temperature value of −1.44×10{sup −6}. The negative expansion coefficient is very interesting and is found to be in conformity with experimental as well as with recent theoretical estimates. There is only qualitative agreement of our results with experimental data and motivates further investigation, primarily on the high negative values of Grüneisen parameters.« less

Operation and Maintenance Manual, TECS 18.

DTIC Science & Technology

1978-11-01

width modulated variable output voltage and frequency using a three-phase transistor bridge circuit . Reduced power line electromagnetic interference...Description 3-1 Section II. Circuit Fundamentals 3-1 Section III. System Description 3-2 CHAPTER 4. Protection and Maintenance 4-1 Section I. Internal...Number I-la TECS 18 Electronic Module Location-Evaporator Side 1-3 1-lb TECS 18 Electronic Module Location-Condenser Side 1-4 1-2 Remote Control Panel 1-5

Regional ionospheric model for improvement of navigation position with EGNOS

NASA Astrophysics Data System (ADS)

Swiatek, Anna; Tomasik, Lukasz; Jaworski, Leszek

The problem of insufficient accuracy of EGNOS correction for the territory of Poland, located at the edge of EGNOS range is well known. The EEI PECS project (EGNOS EUPOS Integration) assumed improving the EGNOS correction by using the GPS observations from Polish ASG-EUPOS stations. A ionospheric delay parameter is a part of EGNOS correction. The comparative analysis of TEC values obtained from EGNOS and regional permanent GNSS stations showed the systematic shift. The TEC from EGNOS correction is underestimated related to computed regional TEC value. The new-‘improved’ corrections computed based on regional model were substituted for the EGNOS correction for suitable message. Dynamic measurements managed using the Mobile GPS Laboratory (MGL), showed the improvement of navigation position with TEC regional model.

The National Network forTechnology Entrepreneurship and Commercialization (N2TEC): Bringing New Technologies to Market

NASA Astrophysics Data System (ADS)

Allen, Kathleen

2003-03-01

N2TEC, the National Network for Technology Entrepreneurship and Commercialization, is a National Science Foundation "Partnerships for Innovation" initiative designed to raise the level of innovation and technology commercialization in colleges, universities, and communities across the nation. N2TEC is creating a network of people and institutions, and a set of technology tools that will facilitate the pooling of resources and knowledge and enable faculty and students to share those resources and collaborate without regard to geographic boundaries. N2TEC will become the backbone by which educational institutions across the nation can move their technologies into new venture startups. The ultimate goal is to create new wealth and strengthen local, regional and national economies.

Optimal Integration of Cascade Thermoelectric Cooler into Electronic Housing: Experimental Approach

NASA Astrophysics Data System (ADS)

Semeniuk, V.; Protsenko, D.

2018-06-01

The problem of the optimal integration of thermoelectrically cooled optoelectronic components into an electronic housing is studied with the emphasis on practical implementation. The lines of 2-stage and 3-stage thermoelectric coolers (TECs) compatible with TO8 housing have been developed, and their parameters are measured in a wide range of heat sink temperatures. The TECs are optimized to receive a temperature difference of 100-110 K under a heat load from 70 mW to 100 mW with minimal power consumption. To fit into a standard housing interior, all the TECs have the same overall dimensions, regardless of the number of stages. Details of the TEC configurations and their performance characteristics are presented and discussed.

Optimal Integration of Cascade Thermoelectric Cooler into Electronic Housing: Experimental Approach

NASA Astrophysics Data System (ADS)

Semeniuk, V.; Protsenko, D.

2018-03-01

The problem of the optimal integration of thermoelectrically cooled optoelectronic components into an electronic housing is studied with the emphasis on practical implementation. The lines of 2-stage and 3-stage thermoelectric coolers (TECs) compatible with TO8 housing have been developed, and their parameters are measured in a wide range of heat sink temperatures. The TECs are optimized to receive a temperature difference of 100-110 K under a heat load from 70 mW to 100 mW with minimal power consumption. To fit into a standard housing interior, all the TECs have the same overall dimensions, regardless of the number of stages. Details of the TEC configurations and their performance characteristics are presented and discussed.

High Temporal and Spatial Resolution Global GPS TEC Observations of the 2015 St. Patrick Day Storm

NASA Astrophysics Data System (ADS)

Vierinen, J.

2015-12-01

High spatiotemperal resolution global GPS TEC measurements of the 2015 St. Patrick's day storm are presented. The high resolution data is useful, as it clearly shows the high latitude convection patterns, the equatorward progression of the auroral region, the tongue of ionization, as well as the increased electron density in the equatorial anomaly region. The measurements are compared with high power large aperture radar and passive radar measurements of coherent and incoherent scatter at Millstone Hill. Regions of fast convection identified in the GPS TEC data are found to coincide with coherent scatter in both radar data. Convection velocities determined from GPS TEC are compared with those obtained from incoherent scatter radar measurements.

Analysis of the stress field in a wedge using the fast expansions with pointwise determined coefficients

NASA Astrophysics Data System (ADS)

Chernyshov, A. D.; Goryainov, V. V.; Danshin, A. A.

2018-03-01

The stress problem for the elastic wedge-shaped cutter of finite dimensions with mixed boundary conditions is considered. The differential problem is reduced to the system of linear algebraic equations by applying twice the fast expansions with respect to the angular and radial coordinate. In order to determine the unknown coefficients of fast expansions, the pointwise method is utilized. The problem solution derived has explicit analytical form and it’s valid for the entire domain including its boundary. The computed profiles of the displacements and stresses in a cross-section of the cutter are provided. The stress field is investigated for various values of opening angle and cusp’s radius.

Study of Ionospheric TEC from GPS observations and comparisons with IRI and SPIM model predictions in the low latitude anomaly Indian subcontinental region

NASA Astrophysics Data System (ADS)

Panda, S. K.; Gedam, S. S.; Rajaram, G.

2015-04-01

The present study investigates variation of the ionospheric total electron content (TEC) in the low latitude Indian sub-continental region from the GPS observations and its comparison with the global ionosphere maps (GIMs), standard international reference ionosphere (IRI 2012), and the standard plasmasphere-ionosphere model (SPIM) for the period from November 2011 to October 2012 that corresponds to the progressive phase towards the midst of the solar cycle-24. Observations during quiet period show diurnal maximum of TEC occurring around 14:00-16:00 IST, with relatively broader and longer duration of local maximum at Bangalore and behave reversely towards Delhi. The secondary maximum of TEC was markedly noticeable at Bangalore during the months of March and September, and only in the month of September at Hyderabad and Mumbai. However, the relatively higher TEC during December month than the June is ascribed to the winter anomaly which is more prevalent during the high solar activity periods. The prevailing instability in latitudes of anomaly crest during January 2012 is possibly due to the seasonal variation of lunar tidal effects, modulating the EEJ strength at the equator. The studies covered the period of a strong geomagnetic storm during 6-11 March 2012 (SYM-H: -149 nT) which resulted in positive deviation of GPS-TEC at Bangalore (↑ 20%), Hyderabad (↑ 22%), and Lucknow (↑ 94%) compared to the mean quiet days level. The relatively large deviation of TEC at Lucknow could be attributed to the poleward shifting of the anomaly crest, manifested by enhanced fountain effect at the equator. Studies confirm excellent agreement (80-85%) of GPS-TEC with IGS-GIM at Bangalore and Hyderabad with the exception of the night-time hours (Deviations >50%). However relatively larger deviation of GPS-TEC from GIM-TEC at Delhi could be due to the unavailability of IGS stations in the proximity of the position. Predictions of the SPIM model (extension of IRI up to GPS altitude) exhibit much higher deviation from the in situ GPS observations as well as GIM and IRI outputs during quiet periods. Correspondingly, either of the models (IRI and SPIM) did not respond well to the arrival of the sudden storm commencements (SSCs) during the storm period (6-11 March 2012). When SPIM is used instead of IRI, the overestimation from GPS-TECs are further exaggerated by 13-18% (December solstice), 27-37% (March equinox), 15-31% (June solstice), and 20-32% (September equinox) during peak hours of the period. We attribute the relatively more deviation of the SPIM than the IRI model possibly due to its plasmaspheric extension to the IRI model by adding the Russian SMI model of high latitude characteristics. Hence, we emphasize the further improvement in the model with due consideration of the driving forces at play in the region, for reliable predictions of the low latitude ionosphere.

Application of Modified Particle Swarm Optimization Method for Parameter Extraction of 2-D TEC Mapping

NASA Astrophysics Data System (ADS)

Toker, C.; Gokdag, Y. E.; Arikan, F.; Arikan, O.

2012-04-01

Ionosphere is a very important part of Space Weather. Modeling and monitoring of ionospheric variability is a major part of satellite communication, navigation and positioning systems. Total Electron Content (TEC), which is defined as the line integral of the electron density along a ray path, is one of the parameters to investigate the ionospheric variability. Dual-frequency GPS receivers, with their world wide availability and efficiency in TEC estimation, have become a major source of global and regional TEC modeling. When Global Ionospheric Maps (GIM) of International GPS Service (IGS) centers (http://iono.jpl.nasa.gov/gim.html) are investigated, it can be observed that regional ionosphere along the midlatitude regions can be modeled as a constant, linear or a quadratic surface. Globally, especially around the magnetic equator, the TEC surfaces resemble twisted and dispersed single centered or double centered Gaussian functions. Particle Swarm Optimization (PSO) proved itself as a fast converging and an effective optimization tool in various diverse fields. Yet, in order to apply this optimization technique into TEC modeling, the method has to be modified for higher efficiency and accuracy in extraction of geophysical parameters such as model parameters of TEC surfaces. In this study, a modified PSO (mPSO) method is applied to regional and global synthetic TEC surfaces. The synthetic surfaces that represent the trend and small scale variability of various ionospheric states are necessary to compare the performance of mPSO over number of iterations, accuracy in parameter estimation and overall surface reconstruction. The Cramer-Rao bounds for each surface type and model are also investigated and performance of mPSO are tested with respect to these bounds. For global models, the sample points that are used in optimization are obtained using IGS receiver network. For regional TEC models, regional networks such as Turkish National Permanent GPS Network (TNPGN-Active) receiver sites are used. The regional TEC models are grouped into constant (one parameter), linear (two parameters), and quadratic (six parameters) surfaces which are functions of latitude and longitude. Global models require seven parameters for single centered Gaussian and 13 parameters for double centered Gaussian function. The error criterion is the normalized percentage error for both the surface and the parameters. It is observed that mPSO is very successful in parameter extraction of various regional and global models. The normalized reconstruction error varies from 10-4 for constant surfaces to 10-3 for quadratic surfaces in regional models, sampled with regional networks. Even for the cases of a severe geomagnetic storm that affects measurements globally, with IGS network, the reconstruction error is on the order of 10-1 even though individual parameters have higher normalized errors. The modified PSO technique proved itself to be a useful tool for parameter extraction of more complicated TEC models. This study is supported by TUBITAK EEEAG under Grant No: 109E055.

A Combined Experimental and Numerical Technique to Estimate Interfacial Bond Strength in MMC-Encapsulated Ceramic Systems

DTIC Science & Technology

2013-03-01

with density, Young’s modulus, coefficient of thermal expansion , and Poisson’s ratio, of 3.2 cm 3 , 449 GPa, 4.0 × 10 –6 o C –1 , and 0.16...considers the effect of hydrostatic pressure (confinement) on the strength of ceramics and was implemented using a user subroutine in ABAQUS . The...Due to the high temperature of the encapsulation casting process and the large differential in coefficients of thermal expansion (CTE) between the MMC

Densities of Pb-Sn alloys during solidification

NASA Technical Reports Server (NTRS)

Poirier, D. R.

1988-01-01

Data for the densities and expansion coefficients of solid and liquid alloys of the Pb-Sn system are consolidated in this paper. More importantly, the data are analyzed with the purpose of expressing either the density of the solid or of the liquid as a function of its composition and temperature. In particular, the densities of the solid and of the liquid during dendritic solidification are derived. Finally, the solutal and thermal coefficients of volume expansion for the liquid are given as functions of temperature and composition.

Reduction of thermal stresses in continuous fiber reinforced metal matrix composites with interface layers

NASA Technical Reports Server (NTRS)

Jansson, S.; Leckie, F. A.

1990-01-01

The potential of using an interface layer to reduce thermal stresses in the matrix of composites with a mismatch in coefficients of thermal expansion of fiber and matrix was investigated. It was found that compliant layers, with properties of readily available materials, do not have the potential to reduce thermal stresses significantly. However, interface layers with high coefficient of thermal expansion can compensate for the mismatch and reduce thermal stresses in the matrix significantly.

Investigation of the TEC Changes in the vicinity of the Earthquake Preparation Zone

NASA Astrophysics Data System (ADS)

Ulukavak, Mustafa; Yalcinkaya, Mualla

2016-04-01

Recently, investigation of the anomalies in the ionosphere before the earthquake has taken too much attention. The Total Electron Content (TEC) data has been used to monitor the changes in the ionosphere. Hence, researchers use the TEC changes before the strong earthquakes to monitor the anomalies in the ionosphere. In this study, the GPS-TEC variations, obtained from the GNSS stations in the vicinity of the earthquake preparation zone, was investigated. Nidra earthquake (M6.5), which was occurred on the north-west of Greece on November 17th, 2015 (38.755°N, 20.552°E), was selected for this study. First, the equation proposed by Dobrovolsky et al. (1979) was used to calculate the radius of the earthquake preparation zone. International GNSS Service (IGS) stations in the region were classified with respect to the radius of the earthquake preparation zone. The observation data of each station was obtained from the Crustal Dynamics Data and Information System (CDDIS) archive to estimate GPS-TEC variations between 16 October 2015 and 16 December 2015. Global Ionosphere Maps (GIM) products, obtained from the IGS, was used to check the robustness of the GPS-TEC variations. Possible anomalies were analyzed for each GNSS station by using the 15-day moving median method. In order to analyze these pre-earthquake ionospheric anomalies, we investigated three indices (Kp, F10.7 and Dst) related to the space weather conditions between 16 October 2015 and 16 December 2015. Solar and geomagnetic indices were obtained from The Oceanic and Atmospheric Administration (NOAA), The Canadian Space Weather Forecast Centre (CSWFC), and the Data Analysis Center for Geomagnetism and Space Magnetism Graduate School of Science, Kyoto University (WDC). This study aims at investigating the possible effects of the earthquake on the TEC variations.

Are There Gender Differences in Emotion Comprehension? Analysis of the Test of Emotion Comprehension.

PubMed

Fidalgo, Angel M; Tenenbaum, Harriet R; Aznar, Ana

2018-01-01

This article examines whether there are gender differences in understanding the emotions evaluated by the Test of Emotion Comprehension (TEC). The TEC provides a global index of emotion comprehension in children 3-11 years of age, which is the sum of the nine components that constitute emotion comprehension: (1) recognition of facial expressions, (2) understanding of external causes of emotions, (3) understanding of desire-based emotions, (4) understanding of belief-based emotions, (5) understanding of the influence of a reminder on present emotional states, (6) understanding of the possibility to regulate emotional states, (7) understanding of the possibility of hiding emotional states, (8) understanding of mixed emotions, and (9) understanding of moral emotions. We used the answers to the TEC given by 172 English girls and 181 boys from 3 to 8 years of age. First, the nine components into which the TEC is subdivided were analysed for differential item functioning (DIF), taking gender as the grouping variable. To evaluate DIF, the Mantel-Haenszel method and logistic regression analysis were used applying the Educational Testing Service DIF classification criteria. The results show that the TEC did not display gender DIF. Second, when absence of DIF had been corroborated, it was analysed for differences between boys and girls in the total TEC score and its components controlling for age. Our data are compatible with the hypothesis of independence between gender and level of comprehension in 8 of the 9 components of the TEC. Several hypotheses are discussed that could explain the differences found between boys and girls in the belief component. Given that the Belief component is basically a false belief task, the differences found seem to support findings in the literature indicating that girls perform better on this task.

GIM-TEC adaptive ionospheric weather assessment and forecast system

NASA Astrophysics Data System (ADS)

Gulyaeva, T. L.; Arikan, F.; Hernandez-Pajares, M.; Stanislawska, I.

2013-09-01

The Ionospheric Weather Assessment and Forecast (IWAF) system is a computer software package designed to assess and predict the world-wide representation of 3-D electron density profiles from the Global Ionospheric Maps of Total Electron Content (GIM-TEC). The unique system products include daily-hourly numerical global maps of the F2 layer critical frequency (foF2) and the peak height (hmF2) generated with the International Reference Ionosphere extended to the plasmasphere, IRI-Plas, upgraded by importing the daily-hourly GIM-TEC as a new model driving parameter. Since GIM-TEC maps are provided with 1- or 2-days latency, the global maps forecast for 1 day and 2 days ahead are derived using an harmonic analysis applied to the temporal changes of TEC, foF2 and hmF2 at 5112 grid points of a map encapsulated in IONEX format (-87.5°:2.5°:87.5°N in latitude, -180°:5°:180°E in longitude). The system provides online the ionospheric disturbance warnings in the global W-index map establishing categories of the ionospheric weather from the quiet state (W=±1) to intense storm (W=±4) according to the thresholds set for instant TEC perturbations regarding quiet reference median for the preceding 7 days. The accuracy of IWAF system predictions of TEC, foF2 and hmF2 maps is superior to the standard persistence model with prediction equal to the most recent ‘true’ map. The paper presents outcomes of the new service expressed by the global ionospheric foF2, hmF2 and W-index maps demonstrating the process of origin and propagation of positive and negative ionosphere disturbances in space and time and their forecast under different scenarios.

Investigating the performance of neural network backpropagation algorithms for TEC estimations using South African GPS data

NASA Astrophysics Data System (ADS)

Habarulema, J. B.; McKinnell, L.-A.

2012-05-01

In this work, results obtained by investigating the application of different neural network backpropagation training algorithms are presented. This was done to assess the performance accuracy of each training algorithm in total electron content (TEC) estimations using identical datasets in models development and verification processes. Investigated training algorithms are standard backpropagation (SBP), backpropagation with weight delay (BPWD), backpropagation with momentum (BPM) term, backpropagation with chunkwise weight update (BPC) and backpropagation for batch (BPB) training. These five algorithms are inbuilt functions within the Stuttgart Neural Network Simulator (SNNS) and the main objective was to find out the training algorithm that generates the minimum error between the TEC derived from Global Positioning System (GPS) observations and the modelled TEC data. Another investigated algorithm is the MatLab based Levenberg-Marquardt backpropagation (L-MBP), which achieves convergence after the least number of iterations during training. In this paper, neural network (NN) models were developed using hourly TEC data (for 8 years: 2000-2007) derived from GPS observations over a receiver station located at Sutherland (SUTH) (32.38° S, 20.81° E), South Africa. Verification of the NN models for all algorithms considered was performed on both "seen" and "unseen" data. Hourly TEC values over SUTH for 2003 formed the "seen" dataset. The "unseen" dataset consisted of hourly TEC data for 2002 and 2008 over Cape Town (CPTN) (33.95° S, 18.47° E) and SUTH, respectively. The models' verification showed that all algorithms investigated provide comparable results statistically, but differ significantly in terms of time required to achieve convergence during input-output data training/learning. This paper therefore provides a guide to neural network users for choosing appropriate algorithms based on the availability of computation capabilities used for research.

Detection of Geomagnetic Pulsations of the Earth Using GPS-TEC Data

NASA Astrophysics Data System (ADS)

Koroglu, Ozan; Arikan, Feza; Köroǧlu, Meltem; Sabri Ozkazanc, Yakup

2016-07-01

The magnetosphere of the Earth is made up of both magnetic fields and plasma. In this layer, plasma waves propagate as Ultra Low Frequency (ULF) waves having mHz scale frequencies. ULF waves are produced due to complicated solar-geomagnetic interactions. In the literature, these ULF waves are defined as pulsations. The geomagnetic pulsations are classified into main two groups as continuous pulsations (Pc) and irregular pulsations (Pi). These pulsations can be determined by ionospheric parameters due to the complex lithosphere-ionosphere-magnetosphere coupling processes. Total Electron Content (TEC) is one of the most important parameters for investigating the variability of ionosphere. Global Positioning System (GPS) provides a cost-effective means for estimating TEC from GPS satellite orbital height of 20,000 km to the ground based receivers. Therefore, the time series of GPS-TEC inherently contains the above mentioned ULF waves. In this study, time series analysis of GPS-TEC is carried out by applying periodogram method to the mid-latitude annual TEC data. After the analysis of GPS-TEC data obtained for GPS stations located in Central Europe and Turkey for 2011, it is observed that some of the fundamental frequencies that are indicators of Pc waves, diurnal and semi-diurnal periodicity and earth-free oscillations can be identified. These results will be used in determination of low frequency trend structure of magnetosphere and ionosphere. Further investigation of remaining relatively low magnitude frequencies, all Pi and Pc can be identified by using time and frequency domain techniques such as wavelet analysis. This study is supported by the joint TUBITAK 115E915 and joint TUBITAK114E092 and AS CR 14/001 projects.

Ionospheric variation observed in Oregon Real-time GNSS network during the total eclipse of 21 August 2017

NASA Astrophysics Data System (ADS)

Shahbazi, A.; Park, J.; Kim, S.; Oberg, R.

2017-12-01

As the ionospheric behavior is highly related to the solar activity, the total eclipse passing across the North America on 21 August 2017 is expected to significantly affect the electron density in the ionosphere along the path. Taking advantage of GNSS capability for observing total electron content (TEC), this study demonstrates the impact of the total eclipse not only on the TEC variation during the period of the event but also on GNSS positioning. Oregon Department of Transportation (ODOT) runs a dense real time GNSS network, referred to as Oregon Real-time GNSS network (ORGN). From the dual frequency GPS and GLONASS observations in ORGN, the TEC over the network area can be extracted. We observe the vertical TEC (VTEC) from the ORGN for analyzing the ionospheric condition in the local area affected by the eclipse. To observe the temporal variation, we also observe the slant TEC (STEC) in each ray path and analyze the short term variation in different geometry of each ray path. Although the STEC is dependent quantity upon the changing geometry of a satellite, this approach provides insight to the ionospheric behavior of the total eclipse because the STEC does not involve the projection error, which is generated by VTEC computation. During the period of eclipse, the abnormal variations on VTEC and STEC are expected. The experimental results will be presented in time series plots for selected stations as well as the regional TEC map in Oregon. In addition to the TEC monitoring, we also test the positioning result of ORGN stations through Precise Point Positioning (PPP) and relative positioning. The expected result is that the both positioning results are degraded during the solar eclipse due to the instable ionospheric condition over short time.

Safe Gene Therapy for Type 1 Diabetes

DTIC Science & Technology

2012-10-01

by transplanting these cells, either alone or together with FoxP3+eGFP+ T-regulatory cells into prediabetic ID-TEC pups. Diabetes incidence and...transplanting these cells, either alone or together with FoxP3+eGFP+ T-regulatory cells into prediabetic ID-TEC pups. Diabetes incidence and progression will...progression of islet-autoimmunity in prediabetic ID-TEC pups. 38 In the fourth quarterly scientific progress report (06/28/11 - 09/27/11) of year 02

Plasma density irregularities and Total Electron Content gradients over Europe

NASA Astrophysics Data System (ADS)

Zakharenkova, I.; Kotulak, K.; Cherniak, I.; Krankowski, A.; Froń, A.

2017-12-01

Perturbations of the ionospheric plasma density are crucial from the scientific and application points of view, as they can severe affect radio signals used in the Global Navigation Satellite Systems (GNSS) and low frequency radio astronomy. For several decades the ionospheric irregularities have been extensively studied by different techniques, including ground-based GNSS observations. Spatial distribution of ionospheric disturbances can be specified by horizontal gradients of the ionospheric density (total electron content, TEC). Another, widely used tool in irregularities monitoring is the rate of TEC index (ROTI). Recently, the Northern Hemisphere ROTI product has been implemented to the International GNSS Service (IGS) and available for community. In this study, we present climatology of the spatial TEC gradients occurred over European region at high to middle latitudes. We developed the TEC gradient maps based on the high-resolution (0.5 degree in latitude and longitude) regional TEC maps covering Europe. The obtained climatological characteristics of the spatial TEC gradients are superimposed and analyzed with the global and regional ROTI product in order to reveal development of highly intense plasma irregularities occurred at high and middle latitudes. During geomagnetic storm the complex of physical processes at auroal zone leads to development of intnse ionospheric irregularities and travelling ionospheric disturbances (TIDs). We presents results of the geomagnetic storm analysis including the 2013 and 2015 St. Patrick's Day geomagnetic storms.

In situ structures of the segmented genome and RNA polymerase complex inside a dsRNA virus

NASA Astrophysics Data System (ADS)

Zhang, Xing; Ding, Ke; Yu, Xuekui; Chang, Winston; Sun, Jingchen; Hong Zhou, Z.

2015-11-01

Viruses in the Reoviridae, like the triple-shelled human rotavirus and the single-shelled insect cytoplasmic polyhedrosis virus (CPV), all package a genome of segmented double-stranded RNAs (dsRNAs) inside the viral capsid and carry out endogenous messenger RNA synthesis through a transcriptional enzyme complex (TEC). By direct electron-counting cryoelectron microscopy and asymmetric reconstruction, we have determined the organization of the dsRNA genome inside quiescent CPV (q-CPV) and the in situ atomic structures of TEC within CPV in both quiescent and transcribing (t-CPV) states. We show that the ten segmented dsRNAs in CPV are organized with ten TECs in a specific, non-symmetric manner, with each dsRNA segment attached directly to a TEC. The TEC consists of two extensively interacting subunits: an RNA-dependent RNA polymerase (RdRP) and an NTPase VP4. We find that the bracelet domain of RdRP undergoes marked conformational change when q-CPV is converted to t-CPV, leading to formation of the RNA template entry channel and access to the polymerase active site. An amino-terminal helix from each of two subunits of the capsid shell protein (CSP) interacts with VP4 and RdRP. These findings establish the link between sensing of environmental cues by the external proteins and activation of endogenous RNA transcription by the TEC inside the virus.

STAT6 deficiency ameliorates Graves' disease severity by suppressing thyroid epithelial cell hyperplasia.

PubMed

Jiang, Xuechao; Zha, Bingbing; Liu, Xiaoming; Liu, Ronghua; Liu, Jun; Huang, Enyu; Qian, Tingting; Liu, Jiajing; Wang, Zhiming; Zhang, Dan; Wang, Luman; Chu, Yiwei

2016-12-01

Signal transducer and activator of transcription 6 (STAT6) is involved in epithelial cell growth. However, little is known regarding the STAT6 phosphorylation status in Graves' disease (GD) and its role in thyroid epithelial cells (TECs). In this study, we found that STAT6 phosphorylation (p-STAT6) was significantly increased in TECs from both GD patients and experimental autoimmune Graves' disease mice and that STAT6 deficiency ameliorated GD symptoms. Autocrine IL-4 signalling in TECs activated the phosphorylation of STAT6 via IL-4 R engagement, and the downstream targets of STAT6 were Bcl-xL and cyclin D1. Thus, the IL-4-STAT6-Bcl-xL/cyclin D1 pathway is crucial for TEC hyperplasia, which aggravates GD. More importantly, in vitro and in vivo experiments demonstrated that STAT6 phosphorylation inhibited by AS1517499 decreased TEC hyperplasia, thereby reducing serum T3 and T4 and ameliorating GD. Thus, our study reveals that in addition to the traditional pathogenesis of GD, in which autoantibody TRAb stimulates thyroid-stimulating hormone receptors and consequently produces T3, T4, TRAb could also trigger TECs producing IL-4, and IL-4 then acts in an autocrine manner to activate p-STAT6 signalling and stimulate unrestricted cell growth, thus aggravating GD. These findings suggest that STAT6 inhibitors could be potent therapeutics for treating GD.

STAT6 deficiency ameliorates Graves' disease severity by suppressing thyroid epithelial cell hyperplasia

PubMed Central

Jiang, Xuechao; Zha, Bingbing; Liu, Xiaoming; Liu, Ronghua; Liu, Jun; Huang, Enyu; Qian, Tingting; Liu, Jiajing; Wang, Zhiming; Zhang, Dan; Wang, Luman; Chu, Yiwei

2016-01-01

Signal transducer and activator of transcription 6 (STAT6) is involved in epithelial cell growth. However, little is known regarding the STAT6 phosphorylation status in Graves' disease (GD) and its role in thyroid epithelial cells (TECs). In this study, we found that STAT6 phosphorylation (p-STAT6) was significantly increased in TECs from both GD patients and experimental autoimmune Graves' disease mice and that STAT6 deficiency ameliorated GD symptoms. Autocrine IL-4 signalling in TECs activated the phosphorylation of STAT6 via IL-4 R engagement, and the downstream targets of STAT6 were Bcl-xL and cyclin D1. Thus, the IL-4-STAT6-Bcl-xL/cyclin D1 pathway is crucial for TEC hyperplasia, which aggravates GD. More importantly, in vitro and in vivo experiments demonstrated that STAT6 phosphorylation inhibited by AS1517499 decreased TEC hyperplasia, thereby reducing serum T3 and T4 and ameliorating GD. Thus, our study reveals that in addition to the traditional pathogenesis of GD, in which autoantibody TRAb stimulates thyroid-stimulating hormone receptors and consequently produces T3, T4, TRAb could also trigger TECs producing IL-4, and IL-4 then acts in an autocrine manner to activate p-STAT6 signalling and stimulate unrestricted cell growth, thus aggravating GD. These findings suggest that STAT6 inhibitors could be potent therapeutics for treating GD. PMID:27906181

Medium Calcium Concentration Determines Keratin Intermediate Filament Density and Distribution in Immortalized Cultured Thymic Epithelial Cells (TECs)

NASA Astrophysics Data System (ADS)

Sands, Sandra S.; Meek, William D.; Hayashi, Jun; Ketchum, Robert J.

2005-08-01

Isolation and culture of thymic epithelial cells (TECs) using conventional primary tissue culture techniques under conditions employing supplemented low calcium medium yielded an immortalized cell line derived from the LDA rat (Lewis [Rt1l] cross DA [Rt1a]) that could be manipulated in vitro. Thymi were harvested from 4 5-day-old neonates, enzymically digested using collagenase (1 mg/ml, 37°C, 1 h) and cultured in low calcium WAJC404A medium containing cholera toxin (20 ng/ml), dexamethasone (10 nM), epidermal growth factor (10 ng/ml), insulin (10 [mu]g/ml), transferrin (10 [mu]g/ml), 2% calf serum, 2.5% Dulbecco's Modified Eagle's Medium (DMEM), and 1% antibiotic/antimycotic. TECs cultured in low calcium displayed round to spindle-shaped morphology, distinct intercellular spaces (even at confluence), and dense reticular-like keratin patterns. In high calcium (0.188 mM), TECs formed cobblestone-like confluent monolayers that were resistant to trypsinization (0.05%) and displayed keratin intermediate filaments concentrated at desmosomal junctions between contiguous cells. Changes in cultured TEC morphology were quantified by an analysis of desmosome/membrane relationships in high and low calcium media. Desmosomes were significantly increased in the high calcium medium. These studies may have value when considering the growth conditions of cultured primary cell lines like TECs.

Behaviour of Electron Content in the Ionospheric D-Region During Solar X-Ray Flares

NASA Astrophysics Data System (ADS)

Todorović Drakul, M.; Čadež, V. M.; Bajčetić, J.; Popović, L. Č.; Blagojević, D.; Nina, A.

2016-12-01

One of the most important parameters in ionospheric plasma research, also having a wide practical application in wireless satellite telecommunications, is the total electron content (TEC) representing the columnal electron number density. The F-region with high electron density provides the biggest contribution to TEC while the relatively weakly ionized plasma of the D-region (60 km - 90 km above Earth's surface) is often considered as a negligible cause of satellite signal disturbances. However, sudden intensive ionization processes, like those induced by solar X-ray flares, can cause relative increases of electron density that are significantly larger in the D-region than in regions at higher altitudes. Therefore, one cannot exclude a priori the D-region from investigations of ionospheric influences on propagation of electromagnetic signals emitted by satellites. We discuss here this problem which has not been sufficiently treated in literature so far. The obtained results are based on data collected from the D-region monitoring by very low frequency radio waves and on vertical TEC calculations from the Global Navigation Satellite System (GNSS) signal analyses, and they show noticeable variations in the D-region's electron content (TEC_{D) during activity of a solar X-ray flare (it rises by a factor of 136 in the considered case) when TEC_{D} contribution to TEC can reach several percent and which cannot be neglected in practical applications like global positioning procedures by satellites.

ROS enhance angiogenic properties via regulation of NRF2 in tumor endothelial cells

PubMed Central

Towfik, Alam Mohammad; Akiyama, Kosuke; Ohga, Noritaka; Shindoh, Masanobu; Hida, Yasuhiro; Minowa, Kazuyuki; Fujisawa, Toshiaki; Hida, Kyoko

2017-01-01

Reactive oxygen species (ROS) are unstable molecules that activate oxidative stress. Because of the insufficient blood flow in tumors, the tumor microenvironment is often exposed to hypoxic condition and nutrient deprivation, which induces ROS accumulation. We isolated tumor endothelial cells (TECs) and found that they have various abnormalities, although the underlying mechanisms are not fully understood. Here we showed that ROS were accumulated in tumor blood vessels and ROS enhanced TEC migration with upregulation of several angiogenesis related gene expressions. It was also demonstrated that these genes were upregulated by regulation of Nuclear factor erythroid 2-related factor 2 (NRF2). Among these genes, we focused on Biglycan, a small leucine-rich proteoglycan. Inhibition of Toll-like receptors 2 and 4, known BIGLYCAN (BGN) receptors, cancelled the TEC motility stimulated by ROS. ROS inhibited NRF2 expression in TECs but not in NECs, and NRF2 inhibited phosphorylation of SMAD2/3, which activates transcription of BGN. These results indicated that ROS-induced BGN caused the pro-angiogenic phenotype in TECs via NRF2 dysregulation. PMID:28525375

On the reported ionospheric precursor of the 1999 Hector Mine, California earthquake

USGS Publications Warehouse

Thomas, Jeremy N.; Love, Jeffrey J.; Komjathy, Attila; Verkhoglyadova, Olga P.; Butala, Mark; Rivera, Nicholas

2012-01-01

Using Global Positioning System (GPS) data from sites near the 16 Oct. 1999 Hector Mine, California earthquake, Pulinets et al. (2007) identified anomalous changes in the ionospheric total electron content (TEC) starting one week prior to the earthquake. Pulinets (2007) suggested that precursory phenomena of this type could be useful for predicting earthquakes. On the other hand, and in a separate analysis, Afraimovich et al. (2004) concluded that TEC variations near the epicenter were controlled by solar and geomagnetic activity that were unrelated to the earthquake. In an investigation of these very different results, we examine TEC time series of long duration from GPS stations near and far from the epicenter of the Hector Mine earthquake, and long before and long after the earthquake. While we can reproduce the essential time series results of Pulinets et al., we find that the signal they identify as anomalous is not actually anomalous. Instead, it is just part of normal global-scale TEC variation. We conclude that the TEC anomaly reported by Pulinets et al. is unrelated to the Hector Mine earthquake.

On the reported ionospheric precursor of the Hector Mine, California earthquake

USGS Publications Warehouse

Thomas, J.N.; Love, J.J.; Komjathy, A.; Verkhoglyadova, O.P.; Butala, M.; Rivera, N.

2012-01-01

Using Global Positioning System (GPS) data from sites near the 16 Oct. 1999 Hector Mine, California earthquake, Pulinets et al. (2007) identified anomalous changes in the ionospheric total electron content (TEC) starting one week prior to the earthquake. Pulinets (2007) suggested that precursory phenomena of this type could be useful for predicting earthquakes. On the other hand, and in a separate analysis, Afraimovich et al. (2004) concluded that TEC variations near the epicenter were controlled by solar and geomagnetic activity that were unrelated to the earthquake. In an investigation of these very different results, we examine TEC time series of long duration from GPS stations near and far from the epicenter of the Hector Mine earthquake, and long before and long after the earthquake. While we can reproduce the essential time series results of Pulinets et al., we find that the signal they identified as being anomalous is not actually anomalous. Instead, it is just part of normal global-scale TEC variation. We conclude that the TEC anomaly reported by Pulinets et al. is unrelated to the Hector Mine earthquake.

Statistical evidence of seismo-ionospheric precursors of the GPS total electron content in China

NASA Astrophysics Data System (ADS)

Chen, Yuh-Ing; Huang, Chi-Shen; Liu, Jann-Yenq

2015-04-01

Evidence of the seismo-ionospheric precursor (SIP) is reported by statistically investigating the relationship between the total electron content (TEC) in global ionosphere map (GIM) and 56 M≥6.0 earthquakes during 1998-2013 in China. A median-based method together with the z test is employed to examine the TEC variations 30 days before and after the earthquake. It is found that the TEC significantly decreases 0600-1000 LT 1-6 days before the earthquake, and anomalously increases in 3 time periods of 1300-1700 LT 12-15 days; 0000-0500 LT 15-17 days; and 0500-0900 LT 22-28 days before the earthquake. The receiver operating characteristic (ROC) curve is then used to evaluate the efficiency of TEC for predicting M≥6.0 earthquakes in China during a specified time period. Statistical results suggest that the SIP is the significant TEC reduction in the morning period of 0600-1000 LT. The SIP is further confirmed since the area under the ROC curve is positively associated with the earthquake magnitude.

Statistical evidences of seismo-ionospheric precursors applying receiver operating characteristic (ROC) curve on the GPS total electron content in China

NASA Astrophysics Data System (ADS)

Chen, Yuh-Ing; Huang, Chi-Shen; Liu, Jann-Yenq

2015-12-01

Evidence of the seismo-ionospheric precursor (SIP) is reported by statistically investigating the relationship between the total electron content (TEC) in global ionosphere map (GIM) and 56 M ⩾ 6.0 earthquakes during 1998-2013 in China. A median-based method together with the z test is employed to examine the TEC variations 30 days before and after the earthquake. It is found that the TEC significantly decreases 0600-1000 LT 1-6 days before the earthquake, and anomalously increases in 3 time periods of 1300-1700 LT 12-15 days; 0000-0500 LT 15-17 days; and 0500-0900 LT 22-28 days before the earthquake. The receiver operating characteristic (ROC) curve is then used to evaluate the efficiency of TEC for predicting M ⩾ 6.0 earthquakes in China during a specified time period. Statistical results suggest that the SIP is the significant TEC reduction in the morning period of 0600-1000 LT. The SIP is further confirmed since the area under the ROC curve is positively associated with the earthquake magnitude.

Structures of human Bruton's tyrosine kinase in active and inactive conformations suggest a mechanism of activation for TEC family kinases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marcotte, Douglas J.; Liu, Yu-Ting; Arduini, Robert M.

Bruton's tyrosine kinase (BTK), a member of the TEC family of kinases, plays a crucial role in B-cell maturation and mast cell activation. Although the structures of the unphosphorylated mouse BTK kinase domain and the unphosphorylated and phosphorylated kinase domains of human ITK are known, understanding the kinase selectivity profiles of BTK inhibitors has been hampered by the lack of availability of a high resolution, ligand-bound BTK structure. Here, we report the crystal structures of the human BTK kinase domain bound to either Dasatinib (BMS-354825) at 1.9 {angstrom} resolution or to 4-amino-5-(4-phenoxyphenyl)-7H-pyrrolospyrimidin- 7-yl-cyclopentane at 1.6 {angstrom} resolution. This data providesmore » information relevant to the development of small molecule inhibitors targeting BTK and the TEC family of nonreceptor tyrosine kinases. Analysis of the structural differences between the TEC and Src families of kinases near the Trp-Glu-Ile motif in the N-terminal region of the kinase domain suggests a mechanism of regulation of the TEC family members.« less

Te/C nanocomposites for Li-Te Secondary Batteries

NASA Astrophysics Data System (ADS)

Seo, Jeong-Uk; Seong, Gun-Kyu; Park, Cheol-Min

2015-01-01

New battery systems having high energy density are actively being researched in order to satisfy the rapidly developing market for longer-lasting mobile electronics and hybrid electric vehicles. Here, we report a new Li-Te secondary battery system with a redox potential of ~1.7 V (vs. Li+/Li) adapted on a Li metal anode and an advanced Te/C nanocomposite cathode. Using a simple concept of transforming TeO2 into nanocrystalline Te by mechanical reduction, we designed an advanced, mechanically reduced Te/C nanocomposite electrode material with high energy density (initial discharge/charge: 1088/740 mA h cm-3), excellent cyclability (ca. 705 mA h cm-3 over 100 cycles), and fast rate capability (ca. 550 mA h cm-3 at 5C rate). The mechanically reduced Te/C nanocomposite electrodes were found to be suitable for use as either the cathode in Li-Te secondary batteries or a high-potential anode in rechargeable Li-ion batteries. We firmly believe that the mechanically reduced Te/C nanocomposite constitutes a breakthrough for the realization and mass production of excellent energy storage systems.

In situ X-ray and neutron diffraction of the Ruddlesden–Popper compounds (RE 2–xSr x)₀.₉₈(Fe₀.₈Co₀.₂) 1–yMg yO 4–δ (RE=La, Pr): Structure and CO₂ stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatzichristodoulou, C., E-mail: ccha@dtu.dk; Hauback, B.C.; Hendriksen, P.V.

2013-05-01

The crystal structure of the Ruddlesden–Popper compounds (La₁.₀Sr₁.₀)₀.₈Fe₁.₀Co₀.₂O 4–δ and (La₁.₂Sr₀.₈)₀.₉₈(Fe₀.₈Co₀.₂)₀.₈Mg₀.₂O 4–δ was investigated at 1000 °C in N₂ (a O₂=1×10₋₄ by in-situ powder neutron diffraction. In-situ powder X-ray diffraction (PXD) was also employed to investigate the temperature dependence of the lattice parameters of the compounds in air and the oxygen activity dependence of the lattice parameters at 800 °C and 1000 °C. The thermal and chemical expansion coefficients, determined along the two crystallographic directions of the tetragonal unit cell, are highly anisotropic. The equivalent pseudo-cubic thermal and chemical expansion coefficients are in agreement with values determined by dilatometry. Themore » chemical stability in CO₂ containing environments of various Ruddlesden–Popper compounds with chemical formula (RE 2-xSr x)₀.₉₈(Fe₀.₈Co₀.₂) 1-yMg yO 4–δ (RE=La, Pr), as well as their stability limit in H₂/H₂O=4.5 were also determined by in-situ PXD for x=0.9, 1.0 and y=0, 0.2. - Graphical abstract: Influence of electronic configuration on bond length, lattice parameters and anisotropic thermal and chemical expansion. Highlights: • The thermal and chemical expansion coefficients are largely anisotropic. • The expansion of the perovskite layers is constrained along the a direction. • The studied compositions show remarkable thermodynamic stability upon reduction. • The thermal and chemical expansion coefficients are lower than related perovskites. • The investigated materials decompose in CO₂ containing atmospheres.« less

Caustics, counting maps and semi-classical asymptotics

NASA Astrophysics Data System (ADS)

Ercolani, N. M.

2011-02-01

This paper develops a deeper understanding of the structure and combinatorial significance of the partition function for Hermitian random matrices. The coefficients of the large N expansion of the logarithm of this partition function, also known as the genus expansion (and its derivatives), are generating functions for a variety of graphical enumeration problems. The main results are to prove that these generating functions are, in fact, specific rational functions of a distinguished irrational (algebraic) function, z0(t). This distinguished function is itself the generating function for the Catalan numbers (or generalized Catalan numbers, depending on the choice of weight of the parameter t). It is also a solution of the inviscid Burgers equation for certain initial data. The shock formation, or caustic, of the Burgers characteristic solution is directly related to the poles of the rational forms of the generating functions. As an intriguing application, one gains new insights into the relation between certain derivatives of the genus expansion, in a double-scaling limit, and the asymptotic expansion of the first Painlevé transcendent. This provides a precise expression of the Painlevé asymptotic coefficients directly in terms of the coefficients of the partial fractions expansion of the rational form of the generating functions established in this paper. Moreover, these insights point towards a more general program relating the first Painlevé hierarchy to the higher order structure of the double-scaling limit through the specific rational structure of generating functions in the genus expansion. The paper closes with a discussion of the relation of this work to recent developments in understanding the asymptotics of graphical enumeration. As a by-product, these results also yield new information about the asymptotics of recurrence coefficients for orthogonal polynomials with respect to exponential weights, the calculation of correlation functions for certain tied random walks on a 1D lattice, and the large time asymptotics of random matrix partition functions.

Theoretical performance of liquid hydrogen and liquid fluorine as a rocket propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Huff, Vearl N

1953-01-01

Theoretical values of performance parameters for liquid hydrogen and liquid fluorine as a rocket propellant were calculated on the assumption of equilibrium composition during the expansion process for a wide range of fuel-oxidant and expansion ratios. The parameters included were specific impulse, combustion-chamber temperature, nozzle-exit temperature, equilibrium composition, mean molecular weight, characteristic velocity, coefficient of thrust, ration of nozzle-exit area to throat area, specific heat at constant pressure, coefficient of viscosity, and coefficient of thermal conductivity. The maximum value of specific impulse was 364.6 pound-seconds per pound for a chamber pressure of 300 pounds per square inch absolute (20.41 atm) and an exit pressure of 1 atmosphere.

Theoretical performance of liquid ammonia and liquid fluorine as a rocket propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Huff, Vearl N

1953-01-01

Theoretical values of performance parameters for liquid ammonia and liquid fluorine as a rocket propellant were calculated on the assumption of equilibrium composition during the expansion process for a wide range of fuel-oxidant and expansion ratios. The parameters included were specific impulse, combustion chamber temperature, nozzle-exit temperature, equilibrium composition, mean molecular weight, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, coefficient of viscosity, and coefficient of thermal conductivity. The maximum value of specific impulse was 311.5 pound-seconds per pound for a chamber pressure of 300 pounds per square inch absolute (20.41 atm) and an exit pressure of 1 atmosphere.

Translation of Bernstein Coefficients Under an Affine Mapping of the Unit Interval

NASA Technical Reports Server (NTRS)

Alford, John A., II

2012-01-01

We derive an expression connecting the coefficients of a polynomial expanded in the Bernstein basis to the coefficients of an equivalent expansion of the polynomial under an affine mapping of the domain. The expression may be useful in the calculation of bounds for multi-variate polynomials.

On the modular structure of the genus-one Type II superstring low energy expansion

NASA Astrophysics Data System (ADS)

D'Hoker, Eric; Green, Michael B.; Vanhove, Pierre

2015-08-01

The analytic contribution to the low energy expansion of Type II string amplitudes at genus-one is a power series in space-time derivatives with coefficients that are determined by integrals of modular functions over the complex structure modulus of the world-sheet torus. These modular functions are associated with world-sheet vacuum Feynman diagrams and given by multiple sums over the discrete momenta on the torus. In this paper we exhibit exact differential and algebraic relations for a certain infinite class of such modular functions by showing that they satisfy Laplace eigenvalue equations with inhomogeneous terms that are polynomial in non-holomorphic Eisenstein series. Furthermore, we argue that the set of modular functions that contribute to the coefficients of interactions up to order are linear sums of functions in this class and quadratic polynomials in Eisenstein series and odd Riemann zeta values. Integration over the complex structure results in coefficients of the low energy expansion that are rational numbers multiplying monomials in odd Riemann zeta values.

Measurement of Rapid Protein Diffusion in the Cytoplasm by Photo-Converted Intensity Profile Expansion.

PubMed

Gura Sadovsky, Rotem; Brielle, Shlomi; Kaganovich, Daniel; England, Jeremy L

2017-03-14

The fluorescence microscopy methods presently used to characterize protein motion in cells infer protein motion from indirect observables, rather than measuring protein motion directly. Operationalizing these methods requires expertise that can constitute a barrier to their broad utilization. Here, we have developed PIPE (photo-converted intensity profile expansion) to directly measure the motion of tagged proteins and quantify it using an effective diffusion coefficient. PIPE works by pulsing photo-convertible fluorescent proteins, generating a peaked fluorescence signal at the pulsed region, and analyzing the spatial expansion of the signal. We demonstrate PIPE's success in measuring accurate diffusion coefficients in silico and in vitro and compare effective diffusion coefficients of native cellular proteins and free fluorophores in vivo. We apply PIPE to measure diffusion anomality in the cell and use it to distinguish free fluorophores from native cellular proteins. PIPE's direct measurement and ease of use make it appealing for cell biologists. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Characteristic eddy decomposition of turbulence in a channel

NASA Technical Reports Server (NTRS)

Moin, Parviz; Moser, Robert D.

1991-01-01

The proper orthogonal decomposition technique (Lumley's decomposition) is applied to the turbulent flow in a channel to extract coherent structures by decomposing the velocity field into characteristic eddies with random coefficients. In the homogeneous spatial directions, a generaliztion of the shot-noise expansion is used to determine the characteristic eddies. In this expansion, the Fourier coefficients of the characteristic eddy cannot be obtained from the second-order statistics. Three different techniques are used to determine the phases of these coefficients. They are based on: (1) the bispectrum, (2) a spatial compactness requirement, and (3) a functional continuity argument. Results from these three techniques are found to be similar in most respects. The implications of these techniques and the shot-noise expansion are discussed. The dominant eddy is found to contribute as much as 76 percent to the turbulent kinetic energy. In both 2D and 3D, the characteristic eddies consist of an ejection region straddled by streamwise vortices that leave the wall in the very short streamwise distance of about 100 wall units.

(Sub)millimetre interferometric imaging of a sample of COSMOS/AzTEC submillimetre galaxies. I. Multiwavelength identifications and redshift distribution

NASA Astrophysics Data System (ADS)

Miettinen, O.; Smolčić, V.; Novak, M.; Aravena, M.; Karim, A.; Masters, D.; Riechers, D. A.; Bussmann, R. S.; McCracken, H. J.; Ilbert, O.; Bertoldi, F.; Capak, P.; Feruglio, C.; Halliday, C.; Kartaltepe, J. S.; Navarrete, F.; Salvato, M.; Sanders, D.; Schinnerer, E.; Sheth, K.

2015-05-01

We used the Plateau de Bure Interferometer (PdBI) to map a sample of 15 submillimetre galaxies (SMGs) in the COSMOS field at the wavelength of 1.3 mm. The target SMGs were originally discovered in the James Clerk Maxwell Telescope (JCMT)/AzTEC 1.1 mm continuum survey at S/N1.1 mm = 4-4.5. This paper presents, for the first time, interferometric millimetre-wavelength observations of these sources. The angular resolution of our observations, 1''&dotbelow;8, allowed us to accurately determine the positions of the target SMGs. Using a detection threshold of S/N1.3 mm> 4.5 regardless of multiwavelength counterpart association, and 4