Design of a reentrant double staggered ladder circuit for V-band coupled-cavity traveling-wave tube

The reentrant double staggered ladder slow-wave structure is employed in a high-power V-band coupled-cavity traveling-wave tube. This structure has a wide bandwidth, a moderate interaction impedance, and excellent thermal dissipation properties, besides the easy fabrication. A well-matched waveguide coupler is proposed for the structure. Combining the design of attenuators, a full-scale three-dimensional circuit model for the V-band coupled-cavity traveling-wave tube is constructed. The electromagnetic characteristics and the beam--wave interaction of this structure are investigated. The beam current is set to be 100 mA, and the cathode voltage is tuned from 16.8 kV to 15.8 kV. The calculation results show that this tube can produce a saturated average output power over 100 W with an instantaneous bandwidth greater than 1.25 GHz in the frequency ranging from 58 GHz to 62 GHz. The corresponding gain and electronic efficiency can reach over 32 dB and 6.5%, respectively.     

Effect of radiation-induced mean wavelength shift in optical fibers on the scale factor of interferometric fiber optic gyroscope at a wavelength of 1300 nm

In order to analyze the effect of wavelength-dependent radiation-induced attenuation (RIA) on the mean transmission wavelength in optical fiber and the scale factor of interferometric fiber optic gyroscopes (IFOGs), three types of polarization-maintaining (PM) fibers is tested by using a ⁶⁰Co γ -radiation source. The observed different mean wavelength shift (MWS) behaviors for different fibers are interpreted by color-center theory involving dose rate-dependent absorption bands in ultraviolet and visible range and total dose-dependent near infrared absorption bands. To evaluate the mean wavelength variation in fiber coil and the induced scale factor change for space-borne IFOG under low radiation dose in space environment, the influence of dose rate on the mean wavelength is investigated by testing four germanium (Ge) doped fibers and two germanium-phosphorus (Ge-P) codoped fibers irradiated at different dose rates. Experimental results indicate that the Ge-doped fibers show the least mean wavelength shift during irradiation and their mean wavelength of optical signal transmitting in fibers will shift to shorter wavelength in low-dose-rate radiation environment. Finally, the change in the scale factor of IFOG resulting from the mean wavelength shift is estimated and tested, and it is found that the significant radiation-induced scale factor variation must be considered during the design of space-borne IFOG.     

硝酸处理的活性碳催化苯一步合成苯酚

将市售的煤质活性炭用不同浓度的硝酸处理后,在乙腈体系下催化苯一步羟化成苯酚. 并对处理过的活性炭进行Boehm滴定、XPS/EDX、BET等方法表征,发现活性炭表面羧基的数量是影响其催化活性的主要因素. 得到苯酚的最高收率为15.7%,选择性为87.2%.     

Lateral IBIC characterization of single crystal synthetic diamond detectors

In order to evaluate the charge collection efficiency (CCE) profile of single‐crystal diamond devices based on a p‐type/intrinsic/metal configuration, a lateral Ion Beam Induced Charge (IBIC) analysis was performed over their cleaved cross sections using a 2 MeV proton microbeam. CCE profiles in the depth direction were extracted from the cross‐sectional maps at variable bias voltage. IBIC spectra relevant to the depletion region extending beneath the frontal Schottky electrode show a 100% CCE, with a spectral resolution of about 1.5%. The dependence of the width of the high efficiency region from applied bias voltage allows the constant residual doping concentration of the active region to be evaluated. The region where the electric field is absent shows an exponentially decreasing CCE profile, from which it is possible to estimate the diffusion length of the minority carriers by means of a drift–diffusion model. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Substituent effect investigation of 3‐(2, 4‐dichlorophenyl)‐1‐(4′‐X‐phenyl)‐2‐propen‐1‐one. Part 1. Correlation analysis of 13C NMR chemical shifts

A series of substituted chlorinated chalcones namely, 3‐(2,4‐dichlorophenyl)‐1‐(4′‐X‐phenyl)‐2‐propen‐1‐one, have been synthesized, X being H, NH₂, OMe, Me, F, Cl, CO₂Et, CN, and NO₂. Dual substituent parameter (DSP) models of ¹³C NMR chemical shift (CS) have revealed that π‐polarization concept could be utilized to explain the reverse field effect at CO, the enhanced substituent field effect at CO, C‐2, and C‐5, and the decreased sensitivity of substituent field effect at C‐6. Chlorine atoms dipole direction at the benzylidene ring either enhances or reduces substituent effect depending on how they couple with the substituent dipole at the probe site. The correlation of ¹³C NMR CS of C‐2, C‐5, and C‐6 with σ and σ indicates that chlorine atoms in the benzylidine ring deplete the ring from charges. Both MSP of Hammett and DSP of Taft ¹³C NMR CS models give similar trends of substituent effects at C‐2, C‐5, and C‐6. However, the former fail to give a significant correlation for CO and C‐6 ¹³C NMR CS. MSP of σ_q and DSP of Taft and Reynolds models significantly correlated ¹³C NMR CS of C_β. MSP of σ_q fails to correlate C‐1′ ¹³C NMR CS. Investigation of ¹³C NMR CS of non‐chlorinated chalcones series: 3‐phenyl‐1‐(4′‐X‐phenyl)‐2‐propen‐1‐one has revealed similar trends of substituent effects as in the chlorinated chalcones series for C‐1′, CO, C_α, and C_β. In contrast, the substituent effect of the non‐chlorinated chalcone series at C‐2, C‐5, and C‐6 did not correlate with any substituent constant. Copyright © 2010 John Wiley & Sons, Ltd.     

Local dimming algorithm and color gamut calibration for RGB LED backlight LCD display

A 32 in RGB LED backlight unit is developed. A local dimming algorithm is designed for the backlight, and grid-noise artifacts in the LC driving signal are successfully removed with consideration of the backlight distribution to provide identical intensity from each LED block. The 32 in RGB LED backlight LCD display has achieved a static display contrast of over 20000:1 and an average power reduction of 30%. We have also obtained the color gamut transformation matrix for transferring a cold cathode fluorescent lamp BLU LCD display gamut system to our RGB LED BLU LCD display gamut system, and extended the color saturation by suppositional color expansion method. As a result, the color has been accurately reproduced in RGB LED BLU LCD display with more richness and more saturation.     

中国散裂中子源直线射频低电平远程控制软件研制

中国散裂中子源一期工程的直线加速器,共有8套数字化射频低电平控制单元,射频低电平的本地控制属于EPICS的异构系统,无法直接与EPICS客户端进行通信。通过在射频低电平本地控制上位机程序中嵌入一个C#类型的EPICS服务器程序,实现了使用EPICS客户端对射频低电平系统的远程控制, 从而把射频低电平控制系统接入基于EPICS框架的控制系统中。直线射频低电平远程控制投入在线运行以来,运行稳定可靠。     

Phase transition characteristics of Ge–Sb–Te pseudobinary alloys in laser irradiation measurement

Optical switching and structural transformation of GeTe–Sb₂Te₃ pseudobinary alloys, Ge₂Sb₂Te₅, Ge₁Sb₂Te₄, and Ge₁Sb₄Te₇, were studied for data storage application. As-deposited Ge₂Sb₂Te₅, Ge₁Sb₂Te₄, and Ge₁Sb₄Te₇ thin films were amorphous and they crystallized to FCC and HCP upon heat treatment. Crystallization was accelerated by increasing the proportion of Sb₂Te₃ rather than GeTe in Ge–Sb–Te compounds; this was observed by reflectivity changes under nanosecond laser irradiation in static tester. The different crystallization kinetics according to composition might be affected by the structural incompatibility of GeTe under the ‘Umbrella Flip’ theory.     

Measurements of excess loss of the crossed waveguide using optical waveguide ring resonators

Crossed waveguide is widely used in optical devices, whose excess loss has a strong impact on multi-turn optical waveguide ring resonator and resonator integrated optic gyro. The resonance curve of the ring resonator is sharply dependent on the loss within the resonator. This paper presents how to get excess loss of the crossed waveguides nondestructively through the comparison of the resonance characteristics between one-turn and multi-turn optical waveguide ring resonators.