158,645 research outputs found
Electronic and phonon contributions to the Thermoelectric properties of newly discovered half-Heusler alloys XHfPb (X= Ni, Pd, and Pt)
No full textIn this work we calculate the thermoelectric figure of merit of XHfPb (X= Ni, Pd, and Pt) by computing the both the power factor and the lattice thermal conductivity by first principles. We make reasonable approximations: we use the Constant Relaxation Time Approximation (CRTA) to compute the electron transport contribution and the modified Debye-Callaway model to calculate the thermal lattice conductivity. We also report the dielectric properties of these semiconductors and the mode Gruneisen parameters. Not surprisingly we find that the average Gruneisen coefficient correlates with the thermal conductivity. Next, we consider a realistic relaxation timer-and carrier concentration n from experimental data on ZrHfPb and obtain the figure of merit ZT as a function of temperature. Our main finding is that despite the Pt is isoelectronic with Ni and Pd, the ZT of PtHfPb is larger and behaves differently from the other two materials, suggesting that PtHfPb is better suited for high temperature thermoelectric generators
Radiological Assessment of Primordial Radionuclides in Crab Species from Igbokoda River in Southwest of Nigeria
No full textOlusegun Sowole* and Adesoji A. R. Adebambo
Primordial radionuclides are natural radionuclides of specific half-lives that are capable of disintegrating with the release of ionizing radiations along with huge amount of energy which can be so harmful to living organisms. Activity concentrations and radiological indices of 40K, 226Ra and 228Ra in crab species from Igbokoda River in the coastal area of South Western Nigeria, have been determined using gamma spectrometry method. Twenty (20) samples of three different species (Callinectes latimanus, Callinectes amnicola and Cadiosoma armatum) of crabs were collected from the River. The results obtained indicated that the highest dose rates of 40K, 226Ra and 228Ra were associated with Callinectes latimanus while the highest annual committed effective dose of 40K to man was 0.0026mSvyr-1 and was associated with Callinectes latimanus for 226Ra (0.0068mSvyr-1) and 228Ra (0.0208mSvyr-1). The highest excess lifetime cancer risk associated with 40K, 226Ra and 228Ra 0.0237 x 10-3 0.0728 x 10-3. All the values obtained were within the limits recommended globally; indicating that there was no significant radiological health implication to the aquatic animals and man the consumer
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
A new subcontinuum of β R\R.
No full textAbstract. We present a method for describing all indecomposable subcontinua of beta_R \ R. This method enables us to construct in ZFC a new subcontinuum of beta_R \ R. We also show that the nontrivial layers of standard subcontinua can be described by our method. This allows us to construct a layer with a proper dense F_-subset and bring the number of (known) nonhomeomorphic subcontinua of beta_R \ R to 14
Letter from R. R. Zellick, Assistant Trust Officer, Anglo California National Bank of San Francisco, to Joseph R. Goodman, October 2, 1942
No full textLetter from R. R. Zellick, Assistant Trust Officer at The Anglo California National Bank of San Francisco, to Joseph R. Goodman, regarding property owned by Dave Tatsuno. Zellick mentions a dispute between current tenants and Tatsuno, and that Tatsuno has asked Goodman to help locate trustworthy tenants.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
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