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[en] Results of studying stripe quantum cascade lasers emitting at room temperature in the spectral range of 4.8 µm are presented. Power characteristics and turn-on dynamics of the lasers upon pulse pumping are studied. The performed investigations demonstrate the presence of a significant heating of the active region during the pump pulse.
[en] Acoustic properties of alloys of Ge-Pb system have been studied. The temperature dependencies of ultrasound propagation velocity in alloys of Ge-Pb system were investigated in detail. It has been defined that the melting temperature of germanium is 1211 K and lead - 600 K. Based on conducted studies it has been shown that ultrasound propagation velocity depending on temperature decreases linearly.
[en] Ionized gas in low-temperature conditions, are in general characterized by the presence of molecular species, which can strongly affect the system properties and its evolution. In particular, when non-equilibrium conditions exists, the interactions occurring among the particles at a microscopic level, give rise to a complex collisional physics, largely dominated by molecules in different internal quantum states which act as different chemical species. So the modeling of these systems requires the characterization of a plethora of collisional processes, involving molecules, where exchanges of ro-vibronic energies, dissociation, ionization, reactive processes etc., may occur. In this frame, the availability of large sets of cross section data becomes a crucial prerequisite for a realistic simulation of plasma system.
[en] The effect of interfacial scattering on anomalous Hall effect (AHE) was studied in the multilayers. Field-dependent Hall resistivity was measured in the temperature range of 5–300 K with the magnetic field up to 50 kOe. The anomalous Hall resistivity () was enhanced by more than six times at 5 K from n = 1 to n = 12 due to the increased interfacial scattering, whereas the longitudinal resistivity () was increased nearly three times. A scaling relation with was obtained for and measured at 5 K, indicating that the dominant mechanism(s) of the AHE in these multilayers should be side-jump or/and intrinsic in nature. The new scaling relation (Tian et al 2009 Phys. Rev. Lett. 103 087206) has been applied to our data to identify the origin of the AHE in this type of multilayer. (paper)
[en] High-temperature micro-/nanomechanics has attracted much interest over the last decade, primarily because of the urgent need to understand the mechanical and tribological properties of advanced engineering materials at micro-/nanoscale and the underlying physics controlling such properties at operationally relevant conditions. Recent years have subsequently witnessed the swift growth and development of new high-temperature micro- and nanoscratching/tribology instruments. Here, we present an overview of fundamental principles and developments in these instruments, discuss pertinent findings on the topic in detail, and outline current challenges and promising future directions in the field.
[en] Nanostructure with an interior nanogap has received much attention in surface-enhanced Raman scattering (SERS). However, controllable synthesis of nanostructure with ultrasmall nanogap and innovative morphology still remains a challenge. Herein, we present a facile seed-mediated route to integrate uniform nanogap in novel Ag nano coix seeds and locate Raman molecules in the nanogap at room temperature. After 20-nm Ag nanoparticles (NPs) modified by Raman ligand 2-naphthalenethiol and coated by polymer shells as cores were obtained, outside Ag shells were formed by in situ reduction on the polymer surface. The SERS properties of these resulting Ag nano coix seeds were systematically explored. More importantly, the novel SERS active substrate exhibited ultrahigh homogeneity, reproducibility, stability, and even a reliable quantitative SERS analysis mediated by internal standard molecules. .
[en] Typical sources of ultracold atoms operate with a considerable delay between the delivery of ensembles due to sequential trapping and cooling schemes. Therefore, alternative schemes for the continuous generation of ultracold atoms are highly desirable. Here, we demonstrate the continuous loading of a magnetic trap from a quasi-continuous atom beam. We achieve a steady state with magnetically trapped atoms and a temperature of K. The ensemble is protected from laser light sources, a requirement for its application in metrological tasks or sympathetic cooling. The continuous scheme is robust and applicable to a wide range of particles and trapping potentials. (paper)
[en] This study investigates the risks of non-conservative piping design according to ASME B31.1 for high-temperature piping subjected to long-term operation at high temperature in a creep regime based on a sensitivity analysis of the hold time. Design evaluations of high-temperature piping were conducted over a range of hold times in the creep regime according to ASME B31.1, which implicitly considers the creep effects, and the French high-temperature design code of the RCC-MRx, which explicitly considers the creep effects. Conservatisms were quantified among the codes in terms of the hold times. In the case of B31.1, the design evaluation results do not change depending on the hold time at high temperature, whereas in the case of RCC-MRx, they do. It was shown that the design limits of RCC-MRx were exceeded when the hold time exceeded certain values, whereas those of B31.1 were satisfied regardless of the hold times. Thus, the design evaluations according to B31.1 did not consistently yield conservative results and might lead to non-conservative results in the case of long-term operations in the creep range.
[en] Lasing of quantum cascade lasers is demonstrated at a radiation wavelength of 8100 nm at room temperature. Analysis of oscillograms of optical pulses is used to determine dependence of mean and peak radiation intensities on current. A delay of turn-on of quantum cascade lasers is experimentally estimated at a level of two times higher than the lasing threshold to be greater than theoretically estimated delay by several orders of magnitude.
[en] Nanodroplet formation is a critical process in the development of 3D nano-inkjet printing. We show that many-body dissipative particle dynamics (MDPD) can be used to predict nanodroplet formation in nanosized nozzles with good accuracy. A conversion methodology is also introduced to overcome the problem of large coarse-graining factor, which results in unphysical results when the simulation is scaled up to real units. Using our MDPD model and the new conversion methodology, insights into possible trends of physical quantities in nanodroplet formation of polymeric ultraviolet ink can be gained. It was found that higher temperature and applied pressure reduce droplet break-up time. In addition, higher temperature increases the droplets’ diameter while higher effective pressure reduces it. These findings suggest that the physical environment can be tuned to achieve the desired droplet properties for 3D nano-inkjet printing. Due to the technical challenges that impedes experimental testing, this work demonstrates that MDPD provides a low-cost alternative to study nanodroplet formation in 3D nano-inkjet printing. (paper)