Array designs for amplitude and phase control of millimeter-wave beams

New array design concepts are described for the phase and amplitude control of millimeter and submillimeter-wave beams. Phase shifter array designs providing increased phase range and wider bandwidth are described. Techniques involving the integration of gain-producing elements as well as tuning elements on a single array are proposed for application to high-performance beam control and beam shaping. These concepts should facilitate the further development of quasi-optical solid state device-based arrays for application to millimeter-wave electronic systems.     

Optical Design of ECEI Diagnostic System for HT-T Tokamak

Electron cyclotron emission imaging system in the frequency range of 95 GHz -125 GHz is going to be constructed for a two-dimensional diagnosis of the electron temperature profiles and fluctuations on the HT-7 Tokamak. The optical design for the ECEI diagnostic system is completed. Because of the superconducting technology used in HT-7, the vacuum chamber is rather thick (630 mm), the height of the horizontal windows is limited (maximum 450 mm), which constrains greatly the ECE imaging Gaussian beam that passing through the windows. We here comes to make a design compromise between the number of the beams that can pass through the windows and the spatial resolution (around 1.1 cm). We also find that due to the field curvature of the optical system, the gaussian beams of edge channels are always overlapped. To flatten the field curvature, it is needed to insert a concave made of a material with a low refractive index (compared with the one used in the convex). But the suitable material has not been avail     

Symptomatic talocalcaneal coalition resection: indications and results

We report our results of talocalcaneal coalition (TCC) resection in 25 feet after failed nonoperative treatment. Preoperative computed tomography (CT) scans were used to quantify the amount of heel valgus and the size of the coalition relative to the posterior facet. The ratio of mean TCC cross-sectional area to the surface area of the posterior facet was 53.4%. Mean hindfoot valgus was 17.8 degrees. The mean AOFAS (American Orthopaedic Foot and Ankle Society) hindfoot score was 81.9, at an average of 2.5 years after surgery. Statistical analysis determined a significant association between TCC > 50% the size of the posterior facet and poor outcome (p = 0.014). Similarly, heel valgus > 21 degrees was associated with poor outcome (p = 0.014). However, there were good postoperative results in feet with heel valgus > 21 degrees and in those whose TCC was > 50% of the posterior facet. Therefore we advocate using these CT-scan criteria for preoperative discussions with patients and families and not for determination of the index operative procedure (resection vs. arthrodesis). Hindfoot arthrodesis should only be used as a salvage procedure. We recommend those feet with heel valgus > 21 degrees use an orthosis postoperatively to stabilize the hindfoot or a secondary calcaneal procedure should nonoperative management fail.     

A high-power CH3F laser for plasma diagnostics

A high-power, optically pumped, methyl fluoride laser operating at 496 μm has been developed for plasma diagnostic applications. An output power of 100 mW has been measured directly on a calorimeter. The high-pump power utilized in this experiment has also allowed the first observation of saturation in far-infrared output power resulting from severe vibrational bottlenecking. The effect of buffer gases in relieving this bottlenecking is described and compared to a simple rate-equation model     

Monolithic watt-level millimeter-wave diode-grid frequency tripler array

Thousands of solid-state diodes are monolithically integrated by a metal grid as a highly efficient frequency multiplier which promises watt-level CW output power throughout the millimeter and submillimeter wave region. Different devices such as GaAs Schottky diode, thin MOS diode, and GaAs Barrier-Intrinsic-N⁺ diode are employed in this study. The approach also results in low-cost fabication and small-size realization.     

Expectations and interpretations during causal learning.

In existing models of causal induction, 4 types of covariation information (i.e., presence/absence of an event followed by presence/absence of another event) always exert identical influences on causal strength judgments (e.g., joint presence of events always suggests a generative causal relationship). In contrast, we suggest that, due to expectations developed during causal learning, learners give varied interpretations to covariation information as it is encountered and that these interpretations influence the resulting causal beliefs. In Experiments 1A–1C, participants' interpretations of observations during a causal learning task were dynamic, expectation based, and, furthermore, strongly tied to subsequent causal judgments. Experiment 2 demonstrated that adding trials of joint absence or joint presence of events, whose roles have been traditionally interpreted as increasing causal strengths, could result in decreased overall causal judgments and that adding trials where one event occurs in the absence of another, whose roles have been traditionally interpreted as decreasing causal strengths, could result in increased overall causal judgments. We discuss implications for traditional models of causal learning and how a more top-down approach (e.g., Bayesian) would be more compatible with the current findings. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Fatigue and extreme load reduction on two‐bladed wind turbines using the flexible hub connection

The load reduction potential in regular operation and the design drivers of a flexible hub connection on two‐bladed turbines are presented in this paper. Developed for the two‐bladed Skywind 3.4 MW wind turbine, the flexible hub connection integrates an additional, multidirectional elasticity between the hub mount and the nacelle carrier to reduce the load transfer into the support structure. The stiffness and damping properties of the interface connection determine the load amplitudes of the system and influence the overall turbine dynamics. Consequently, the design relevant operating scenarios change due to a potential dynamic instability, resonance, or violation of deflection margins in comparison with a nonflexible hub connection. The system's capability to reduce fatigue and ultimate loads is assessed in several turbulent inflow conditions and transient operating states, while taking into account the operating limits of displacements. A permutation of the dynamic coupling parameters is conducted to characterize the sensitivity of load characteristics to the design variables. By identifying the critical operating conditions, it is possible to provide design guidelines for an effective optimization strategy.     

Development of KSTAR ECE imaging system for measurement of temperature fluctuations and edge density fluctuations

The ECE imaging (ECEI) diagnostic tested on the TEXTOR tokamak revealed the sawtooth reconnection physics in unprecedented detail, including the first observation of high-field-side crash and collective heat transport [H. K. Park, N. C. Luhmann, Jr., A. J. H. Donne? et al., Phys. Rev. Lett. 96, 195003 (2006)]. An improved ECEI system capable of visualizing both high- and low-field sides simultaneously with considerably better spatial coverage has been developed for the KSTAR tokamak in order to capture the full picture of core MHD dynamics. Direct 2D imaging of other MHD phenomena such as tearing modes, edge localized modes, and even Alfve?n eigenmodes is expected to be feasible. Use of ECE images of the optically thin edge region to recover 2D electron density changes during L/H mode transitions is also envisioned, providing powerful information about the underlying physics. The influence of density fluctuations on optically thin ECE is discussed.     

NSTX far infrared tangential interferometer/polarimeter electronics upgrade

New electronics for the multichannel far infrared tangential interferometer/polarimeter system employed on the National Spherical Torus Experiment (NSTX) have greatly extended its capability to monitor high frequency density fluctuations. Such measurements are essential in understanding transport physics issues in NSTX as well as for the coming ITER device. The electronics, which were previously limited to ～250?kHz, have been upgraded with a video bandwidth that extends to 4 MHz when operating as an interferometry-only configuration, and to ～500?kHz when operating as a simultaneous interferometer/polarimeter system. Experimental details and test results of the new electronics are presented.