Results 1 - 10 of 26899
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[en] The structure and properties of quasicrystals are discussed. The short-and long-range atomic orders and the effect of these factors on the physical characteristics are considered. It is noted that investigations of the physical properties of quasicrystals at temperatures above room temperature should be performed. Promising applications are briefly outlined
[en] This paper presents the design, fabrication and calibration of a novel two-dimension microforce sensor with nano-Newton resolution. The sensor, mainly composed of a clamped–clamped beam (horizontal detecting beam), an overhanging beam (vertical detecting beam) and a half-folded beam, is highly sensitive to microforces in the horizontal (parallel to the probe of the designed sensor) and vertical (perpendicular to the wafer surface) directions. The four vertical sidewall surface piezoresistors (horizontal piezoresistors) and two surface piezoresistors (vertical piezoresistors) were fabricated to achieve the requirements of two-dimension microforce measurements. Combining the sensor structure with Wheatstone bridge configurations, the microforce decoupling among the x , y , and z direction can be realized. Accordingly, the sensor is capable of detecting microforces in the horizontal and vertical directions independently. The calibration results verified that the sensor sensitivities at room temperature are 210.58 V N−1and 159.2 V N−1 in the horizontal and vertical directions, respectively. Additionally, the sensor’s corresponding force resolutions are estimated at 2 nN and 3 nN in theory, respectively. The sensor can be used to measure the contact force between manipulating tools and micro-objects, in fields such as microassembly and biological assays. (paper)
[en] We have carried out a high magnetic field study on single crystalline stoichiometric , a material discussed in terms quantum criticality in itinerant ferromagnets, by means of high field resistivity experiments. Our experiments have been performed at the Laboratoire National des Champs Magnétiques Intenses in Toulouse, France. The resistivity of single crystalline , has been investigated in external fields up to 15.5 T aligned along the c-axis in the temperature range of 1.4–55 K. The main focus of our study lies on the method to extract TN from the magnetoresistivity measurements, because TN could not be easily observed in temperature dependent resistivity for stoichiometric .
[en] Thermoacoustics in cryogenics continues to be a very interesting phenomenon which is still poorly understood but often experienced unexpectedly in experiments where it causes unacceptable heat leaks. The authors report on the appearance and onset of this unwanted occurrence at temperatures below 35 K. A number of physical experiments are presented, where the authors had the means to take quantitative measurements of the heat leak caused by these pressure oscillations in apparatus with bent tubes ranging from 4.55 and 4.7 mm inner diameter, with heat stationing links. The parameters which indicate the likelihood of inadvertently developing these thermoacoustic oscillations are presented and means developed to avoiding them in that instance are given. Furthermore, we had the rare opportunity to record and analyze 4 K TAOs experienced on a test setup and present the simple method that was used to eliminate them. (paper)
[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] We report experimental results on the free cooling power available at the level of the second stage regenerator of a 4K pulse tube cooler. By using two localised heat exchangers we obtained additional cooling power, in the range 400 and 600 mW at 4.8 K or between 500 and 700 mW at 18 K. We have investigated in detail the thermal behavior of the system. In this manuscript we report on the evolution of the temperature of the heat exchangers and the pulse tube stages under different distributions of the total heat load.
[en] We investigate one-dimensional arrays of small capacitance Josephson junctions fabricated by conventional e-beam lithography techniques. The arrays are designed to operate in the vicinity of the Coulomb blockade regime. It has been suggested that charges propagate though these arrays in a form similar to solitary waves, following the sine-Gordon model. This system is dual to a long Josephson junction, in which magnetic flux solitons have been thoroughly investigated in the past. Localized charge excitations are of metrological interest because they might offer access to very accurate frequency-to-current conversion. Although previous experiments appear consistent with the existence of solitary charge transport, conclusive evidence is still missing. We present our recent fabrication and measurement results obtained at millikelvin temperatures.
[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] Pressures up to a few 100 GPa and temperatures as high as a few 1000 K have been achieved with high dynamic pressures using a two-stage light-gas gun. Results are reviewed for molecular fluids, metallic hydrogen, solids, implications for planetary interiors, and structures and properties of materials recovered intact from high dynamic pressures