Systematic mechanical behaviors were investigated in a Ti-based metallic glass matrix (MGM) composite containing the in-situ β-dendrite phase at 100 K–298 K. We found that the yielding strength ...increased but the plastic strain decreased with a decrease temperature. The sharp ductile to brittle transition occurred at 100 K. The MGM composite exhibits the large work-hardening behavior at 298 K, but all sample display the work-softening behavior below 298 K. The nominal work-hardening parameter was employed to express the dependence of mechanical properties on temperatures including the brittle failure, the work-hardening and work softening behaviors. It may provide a useful way to evaluate the dependence of mechanical properties on temperatures of MGM composite.
•The yielding strength increased but the strain decreased with a decrease temperature.•The sharp ductile to brittle transition occurred at 100 K.•The MGM composite exhibits the large work-hardening behavior at 298 K.•All sample display the work-softening behavior below 298 K.•The nominal work-hardening parameter was employed to express the dependence.
Highly porous silicon carbide ceramic with a woodlike microstructure has been prepared by carbothermal reduction reaction of charcoal /silica composites in static argon atmosphere, which were ...fabricated by infiltrating silica sol into a porous biocarbon template from tilia amurensis wood using a vacuum/pressure infiltration process. The morphology of resulting porous SiC ceramic, as well as the conversion mechanism of wood to porous SiC ceramic, have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Experimental results show that the biomorphic cellular morphology of tilia amurensis wood charcoal tissue is remained in the porous SiC ceramic with high precision which consists of *b-SiC with traces of *a-SiC. The strut thickness of resulting SiC ceramic becomes thinner, even partially disappears with the increase of silica amount contained in the charcoal/silica composites. The morphology of the SiC ceramic reveals that solid-solid, gas-solid and gas-gas reactions occurred during the charcoal-to-ceramic conversion.
Analysis of helicon wave heating and current drive capability in EXL-50 spherical torus plasmas has been conducted. It is found that the driven current increases with the launched parallel refractive ...index
n
|
|
and peaks around
n
|
|
=
4.0
when the frequency of the helicon wave is between 300 and 380 MHz. The helicon wave current drive efficiency shows a relatively stable upward trend with increasing plasma temperature. Moreover, the driven current decreases as the plasma density increases. We also analyzed the current drive with helicon waves of 150 MHz and 170 MHz and found that the driven current at a lower frequency was lower than that at a higher frequency. A positive proportional relationship exists between the driven current and
n
|
|
. Besides, as
n
|
|
increases, the profile of the driven current becomes wider. Finally, the effect of the scrape-off layer (SOL) region on the helicon wave current drive was also investigated.
The compression behaviors of Ti-based metallic glass matrix composites with dendrites scale were tested at different loading rates. It was found that the composites exhibited not only high strength, ...but also large plasticity under quasi-static compression. Under the dynamic loading, however, the TZ1 alloy with fine dendrites demonstrated a catastrophic failure. Although both the strength and plasticity decreased for the TZ2 composite sample with coarse dendrite, the total strain is over 7%. Discussions on the strain rates and dendrite scale are provided by analyzing the effects of dendrite, which can present the possible deformation mechanism of the composites.
The Vela pulsar represents a distinct group of Delta *g-ray pulsars. Fermi Delta *g-ray observations reveal that it has two sharp peaks (P1 and P2) in the light curve, with a phase separation of 0.42 ...and a third peak (P3) in the bridge. The location and intensity of P3 are energy dependent. We use the three-dimensional magnetospheric model for the annular and core gaps to simulate the Delta *g-ray light curves and the phase-averaged and phase-resolved spectra. We found that the acceleration electric field along a field line in the annular gap region decreases with height. Emission at the high-energy GeV band originates from the synchro-curvature radiation (mainly curvature radiation) of accelerated primary particles, while the synchrotron radiation from secondary particles contributes somewhat to the low-energy Delta *g-ray band (0.1-0.3 GeV). The Delta *g-ray light curve peaks P1 and P2 are generated in the annular gap region near the altitude of null charge surface, whereas P3 and the bridge emission are generated in the core gap region. The intensity and location of P3 at different energy bands depend on the emission altitudes. The radio emission from the Vela pulsar should be generated in a high-altitude narrow region of the annular gap, which leads to a radio phase lag of ~0.13 prior to the first Delta *g-ray peak.
Pulsars have been recognized to be normal neutron stars, but sometimes have been argued to be quark stars. Submillisecond pulsars, if detected, would play an essential and important role in ...distinguishing quark stars from neutron stars. We focus on the formation of such submillisecond pulsars in this paper. A new approach to the formation of a submillisecond pulsar (quark star) by means of the accretion-induced collapse (AIC) of a white dwarf is investigated. Under this AIC process, we found that: (i) almost all newborn quark stars could have an initial spin period of ∼0.1 ms; (ii) nascent quark stars (even with a low mass) have a sufficiently high spin-down luminosity and satisfy the conditions for pair production and sparking process and appear as submillisecond radio pulsars; (iii) in most cases, the times of newborn quark stars in the phase with spin period <1 (or <0.5) ms are long enough for the stars to be detected. As a comparison, an accretion spin-up process (for both neutron and quark stars) is also investigated. It is found that quark stars formed through the AIC process can have shorter periods (≤0.5 ms), whereas the periods of neutron stars formed in accretion spin-up processes must be longer than 0.5 ms. Thus, if a pulsar with a period shorter than 0.5 ms is identified in the future, it could be a quark star.
Covalency in oxidized uranium Tobin, J. G.; Yu, S.-W.; Qiao, R. ...
Physical review. B, Condensed matter and materials physics,
07/2015, Letnik:
92, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Using x-ray emission spectroscopy and absorption spectroscopy, it has been possible to directly access the states in the unoccupied conduction bands that are involved with 5f and 6f covalency in ...oxidized uranium. By varying the oxidizing agent, the degree of 5f covalency can be manipulated and monitored, clearly and irrevocably establishing the importance of 5f covalency in the electronic structure of the key nuclear fuel, uranium dioxide.
Reaction with hydroxyl radicals (˙OH) is an important removal pathway for organic pollutants in the aquatic environment. The aqueous reaction rate constant (k
) is therefore an important parameter ...for fate assessment of aquatic pollutants. Since experimental determination fails to meet the requirement of being able to efficiently handle numerous organic chemicals at limited cost and within a relatively short period of time, in silico methods such as quantitative structure-activity relationship (QSAR) models are needed to predict k
. In this study, a QSAR model with a larger and wider applicability domain as compared with existing models was developed. Following the guidelines for the development and validation of QSAR models proposed by the Organization for Economic Co-operation and Development (OECD), the model shows satisfactory performance. The applicability domain of the model has been extended and contained chemicals that have rarely been covered in most previous studies. The chemicals covered in the current model contain functional groups including double bond splayed leftCdouble bond, length as m-dashCdouble bond splayed right, -Ctriple bond, length as m-dashC-, -C
H
, -OH, -CHO, -O-, double bond splayed leftCdouble bond, length as m-dashO, -Cdouble bond, length as m-dashO(O)-, -COOH, -Ctriple bond, length as m-dashN, double bond splayed leftN-, -NH
, -NH-C(O)-, -NO
, -Ndouble bond, length as m-dashC-Ndouble bond splayed right, double bond splayed leftN-Ndouble bond splayed right, -Ndouble bond, length as m-dashN-, -S-, -S-S-, -SH, -SO
, -SO
, -PO
, and -X (F, Cl, Br, and I).
Background: During whole genome microarray-based comparative genomic hybridisation (array CGH) screening of subjects with idiopathic intellectual disability, we identified two unrelated individuals ...with a similar de novo interstitial microdeletion at 2p15-2p16.1. Both individuals share a similar clinical phenotype including moderate to severe intellectual disability, autism/autistic features, microcephaly, structural brain anomalies including cortical dysplasia/pachygyria, renal anomalies (multicystic kidney, hydronephrosis), digital camptodactyly, visual impairment, strabismus, neuromotor deficits, communication and attention impairments, and a distinctive pattern of craniofacial features. Dysmorphic craniofacial features include progressive microcephaly, flat occiput, widened inner canthal distance, small palpebral fissures, ptosis, long and straight eyelashes, broad and high nasal root extending to a widened, prominent nasal tip with elongated, smooth philtrum, rounding of the upper vermillion border and everted lower lips. Methods: Clinical assessments, and cytogenetic, array CGH and fluorescence in situ hybridisation (FISH) analyses were performed. Results: The microdeletions discovered in each individual measured 4.5 Mb and 5.7 Mb, spanning the chromosome 2p region from 57.2 to 61.7 Mb and from 56 to 61.7 Mb, respectively. Each deleted clone in this range demonstrated a dosage reduction from two to one copy in each proband except for clone RP11-79K21, which was present in three copies in each proband and in four copies in their respective parents (two per each chromosome 2 homologue). Discussion: The common constellation of features found in the two affected subjects indicates that they have a newly recognised microdeletion syndrome involving haploinsufficiency of one or more genes deleted within at least a 4.5-Mb segment of the 2p15-16.1 region.
PDF
