Performance characteristics of an HTS linear synchronous motor with HTS bulk magnet secondary

A single-sided high-temperature superconducting (HTS) linear synchronous motor (HTSLSM) with an HTS bulk magnet array as its secondary has been developed, and a split pulse coil magnetization system is used to magnetize the secondary HTS bulks with alternating magnetic poles. The electromagnetic parameters of the HTSLSM have been calculated to verify its performance. The HTSLSM is incorporated with a developed control system based on the voltage space vector pulsewidth modulation strategy implemented by a computer-software-controlled platform. A compositive experimental testing system has also been developed to measure the thrust and normal force of the HTSLSM. The traits of the thrust and normal force have been comprehensively identified experimentally, and the results from the experiments and analysis would benefit the electromagnetic design and the control scheme development for the HTSLSM. © 2006 IEEE

THz quantum cascade lasers with output power over 1 W

Terahertz (THz) frequency radiation has many potential applications, ranging from imaging and chemical sensing through to telecommunications. However, one of the principal challenges is to develop compact, low-cost, efficient THz sources. In this respect, the development of the THz quantum cascade laser (QCL) has provided a potential solid-state solution. Nonetheless, for many remote sensing and imaging applications, high THz powers are desirable, in part owing to the significant attenuation of THz radiation by water vapour in the atmosphere. THz QCLs have been demonstrated with peak pulsed output powers (Ppeak) of up to 470 mW per facet, using a direct wafer-bonding technique to stack two separate THz QCLs together. This approach, however, requires the QCL to have a symmetric active region, limiting widespread applicability of the technique. In general, increased output powers in semiconductor lasers can be obtained by using longer and/or broader area cavities. Indeed, in long-cavity 4.7-THz QCLs, a Ppeak of up to 875 W (from both facets) was recently achieved. Here, we demonstrate THz QCLs with a Ppeak of 1.01 W from a single facet at 10 K by using a broader area device. The devices operate in pulsed mode with an emission frequency of around 3.4 THz. To the best of our knowledge, this is the first demonstration of THz QCLs with Ppeak exceeding 1 W

Silver-based surface plasmon waveguide for terahertz quantum cascade lasers

Terahertz quantum cascade lasers (THz QCLs) have undergone rapid developments since their first demonstration in 2002. Presently, the wide spectral range (1.2–5.2 THz) and high output power (1 W) make THz QCLs promising sources for applications in high-resolution spectroscopy and THz imaging. However, their maximum operating temperature is only 199.5 K and therefore cryogenic cooling is still needed. Improving the thermal performance of THz QCLs is a key challenge for their practical usage. The waveguide loss is closely related with the device thermal performance. To lower the loss, copper has been used to replace the gold in the standard metal–metal waveguide scheme, and around 10 K increase in the maximum lasing temperature has been achieved. Here, we employ silver as the waveguide metal and investigate its effects on devices with a single surface-plasmon waveguide configuration

Terahertz frequency quantum cascade lasers for use as waveguide-integrated local oscillators

Since their first demonstration in 2002, the performance of terahertz frequency quantum cascade lasers has developed extremely rapidly. We consider the potential use of terahertz frequency quantum cascade lasers as local oscillators in satellite-borne instrumentation for future Earth observation and planetary science missions. A specific focus will be on the development of compact, waveguide-integrated, heterodyne detection systems for the supra-terahertz range

Extraction-controlled terahertz frequency quantum cascade lasers with a diagonal LO-phonon extraction and injection stage

We report an extraction-controlled terahertz (THz)-frequency quantum cascade laser design in which a diagonal LO-phonon scattering process is used to achieve efficient current injection into the upper laser level of each period and simultaneously extract electrons from the adjacent period. The effects of the diagonality of the radiative transition are investigated, and a design with a scaled oscillator strength of 0.45 is shown experimentally to provide the highest temperature performance. A 3.3 THz device processed into a double-metal waveguide configuration operated up to 123 K in pulsed mode, with a threshold current density of 1.3 kA/cm2 at 10 K. The QCL structures are modeled using an extended density matrix approach, and the large threshold current is attributed to parasitic current paths associated with the upper laser levels. The simplicity of this design makes it an ideal platform to investigate the scattering injection process

Phase Locking Of A 2.5 THz Quantum Cascade Laser To A Microwave Reference Using THz Schottky Mixer

The frequency of a 2.5 THz QCL are stabilized to sub-hertz accuracy by phase-locking to a stable 100 MHz microwave reference, using a 2.3–3.2 THz room temperature Schottky diode based harmonic mixer. The down-converted phase locked beat note is stable over a long term test

Gating control of the cardiac sodium channel Nav1.5 by its β3-subunit involves distinct roles for a transmembrane glutamic acid and the extracellular domain.

The auxiliary β3-subunit is an important functional regulator of the cardiac sodium channel Nav1.5, and some β3 mutations predispose individuals to cardiac arrhythmias. The β3-subunit uses its transmembrane α-helix and extracellular domain to bind to Nav1.5. Here, we investigated the role of an unusually located and highly conserved glutamic acid (Glu-176) within the β3 transmembrane region and its potential for functionally synergizing with the β3 extracellular domain (ECD). We substituted Glu-176 with lysine (E176K) in the WT β3-subunit and in a β3-subunit lacking the ECD. Patch-clamp experiments indicated that the E176K substitution does not affect the previously observed β3-dependent depolarizing shift of V½ of steady-state inactivation but does attenuate the accelerated recovery from inactivation conferred by the WT β3-subunit. Removal of the β3-ECD abrogated both the depolarizing shift of steady-state inactivation and the accelerated recovery, irrespective of the presence or absence of the Glu-176 residue. We found that steady-state inactivation and recovery from inactivation involve movements of the S4 helices within the DIII and DIV voltage sensors in response to membrane potential changes. Voltage-clamp fluorometry revealed that the E176K substitution alters DIII voltage sensor dynamics without affecting DIV. In contrast, removal of the ECD significantly altered the dynamics of both DIII and DIV. These results imply distinct roles for the β3-Glu-176 residue and the β3-ECD in regulating the conformational changes of the voltage sensors that determine channel inactivation and recovery from inactivation

An invisibility cloak using silver nanowires

In this paper, we use the parameter retrieval method together with an analytical effective medium approach to design a well-performed invisible cloak, which is based on an empirical revised version of the reduced cloak. The designed cloak can be implemented by silver nanowires with elliptical cross-sections embedded in a polymethyl methacrylate host. This cloak is numerically proved to be robust for both the inner hidden object as well as incoming detecting waves, and is much simpler thus easier to manufacture when compared with the earlier proposed one [Nat. Photon. 1, 224 (2007)].Comment: 7 pages, 4 figures, 2 table

Use of moxibustion to treat primary dysmenorrhea at two interventional times: study protocol for a randomized controlled trial

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