New data of the electronic properties of liquid helium and liquid neon are discussed with respect to their relevance for the initiation of electric breakdown. It is concluded that under ideal conditions the cathode plays a decisive role in the initiation of the breakdown process. It is speculated that a Townsend type breakdown mechanism is absent in the liquid phase of these elements. 相似文献
We report the two- and three-dimensional quantum lattice-gas automata simulation for one-particle electronic wave propagation in nanostructures. The transmission coefficient of the electronic wave through the two-dimensional quantum point contact is investigated taking account of the surface roughness of the confinement wall. It is demonstrated that the electron transmission is significantly affected by the surface roughness pattern even if the same roughness parameter is assumed. We also perform the three-dimensional simulation, and the wave propagation in the structure like an ultrathin-body MOSFET is visualized. 相似文献
Amorphous silicon is the most popular material in the field of semiconductors. However, little is known about its microstructures. To understand the dependence of these microstructures on the fabrication process and on structural relaxation, amorphous silicon samples fabricated by various simulated processes are classified according to structural parameters within the molecular dynamics method.
The results show that the amorphous structures fabricated by the melt-quench method have many odd-membered rings and large bond-angle deviation. The structures fabricated by the molecular-beam epitaxy method involve fewer floating bonds, smaller bond-angle deviations, and fewer six-membered rings in comparison with the melt-quenched structure. Through long-term annealing, both structures are transformed to the most stable structure as described by the Tersoff potential. It is also found that the continuous random network structure does not meet the Tersoff potential. Verification of the results through first-principle calculations shows that well-relaxed amorphous structure can be described by classical molecular dynamics despite the slightly large number of the floating bond and the overestimation of amorphous-phase energy. 相似文献
Thermoplastic resins are typically used without any kind of physical aging treatment. For such materials, creep behavior and physical aging, which depend on time and temperature, occur simultaneously. The effects of these processes are evident after quenching and are recorded in the material as a thermal history. This history strongly influences mechanical properties and creep behavior in particular. Thus, a more thorough understanding of the physical aging process is desirable. We examined the creep deformation of polycarbonate (PC) to reveal the effects of physical aging on creep behavior. The effects were dependent on both time and temperature. The relationship between physical aging and creep behavior exemplified superposition principles with regard to time and both pre-test aging time and pre-test aging temperature. The superposition principles allowed the calculation of creep deformations at a given temperature; the calculated results were corroborated by experimental data. 相似文献
Abstract Cell transformation in vitro is a model of carcinogenesis in vivo. Two-stage transformation assay increases the sensitivity of cells to chemicals and permits detection of carcinogens acting as initiating agents. [60]Fullerene (C60) was cytotoxic in BALB/3T3 cells when it was irradiated by visible light, but not without light irradiation. Under conditions when C60 was cytotoxic, it acted as an initiating agent for cell transformation, but it did not act as a complete transforming agent. the initiating activity of visible-light-irradiated C60 was statistically significant in a modified two-stage transformation assay including a procedure for replating cells treated by C60 and light, but it was equivocal in the standard two-stage transformation assay. 相似文献
Uranium concentrations in drainage water are typically determined by α-spectrometry. However, due to the low specific radioactivity of uranium, the evaporation of large volumes of drainage water, followed by several hours of measurements, is required. Thus, the development of a rapid and simple detection method for uranium in drainage water would enhance the operation efficiency of radiation control workers. We herein propose a novel methodology based on total reflection X-ray fluorescence (TXRF) for the measurement of uranium in contaminated water. TXRF is a particularly desirable method for the rapid and simple evaluation of uranium in contaminated water, as chemical pretreatment of the sample solution is not necessary, measurement times are typically several seconds, and the required sample volume is low. We herein employed sample solutions containing several different concentrations of uranyl acetate with yttrium as an internal standard. The solutions were placed onto sample holders, and were dried prior to TXRF measurements. The relative intensity, otherwise defined as the net intensity ratio of the Lα peak of uranium to the Kα peak of yttrium, was directly proportional to the uranium concentration. Using this method, a TXRF detection limit for uranium in contaminated water of 0.30 µg/g was achieved. 相似文献
Mesostructured zirconia particles having monoclinic-type crystalline walls were prepared using a low-temperature crystallization
technique. Crystalline zirconia particles with highly-ordered mesostructures were obtained through the sol–gel process of
zirconium sulfate tetrahydrate at 333 K in the presence of molecular self-assemblies of cetyltrimethylammonium bromide (CTAB)
or mixtures of CTAB and anionic molecules such as sodium dodecyl sulfate and sodium p-toluenesulfonate. Variations in the molar ratios of CTAB and the chemical species of anionic molecules led to the variations
in the periods of highly-ordered zirconia having crystalline walls. Calcination of the mesostructured zirconia particles prepared
using templates consisting solely of CTAB yielded crystalline mesoporous zirconia particles. 相似文献
Olivine lithium manganese phosphate (LiMnPO4) becomes research focus because of its high energy density and improved thermal stability. However, its application in lithium ion batteries suffers severely from poor electrochemical activity due to low conductivity and structural instability upon the charge and discharge process. By applying a high-energy ball-milling method we succeed in improving the capacity delivery and rate capability. LiMnPO4 materials ball-milled without or with acetylene black are able to deliver a high capacity of 135 and 127 mAh g−1, respectively, more than 50% greater than the pristine one. Particularly, the latter also shows an improved discharge plateau and stable cyclability. High-energy synchrotron radiation X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, laser particle analysis, and galvanostatic charge and discharge are employed to understand the effect of ball-milling on the LiMnPO4 material. 相似文献