Novel Rat-race Hybrid Coupler for RF Front-end Module

In this paper, a novel compact rat-race hybrid coupler incorporating an improved beeline compact microstrip resonant cell(IB-CMRC) is presented firstly. The size of the coupler is reduced by 46.5% than conventional one due to IB-CMRC’s excellent slow-wave effect. The novel coupler possesses strong ability of high-order harmonic suppression (above 30 dB) in addition. The measured insertion loss is comparable to that of a conventional microstrip hybrid coupler. Great potential applications of this IB-CMRC can be explored in MICs and MMICs to reduce the circuits size, suppress harmonics and improve the overall performance of the RF front-end module.     

卫生职业教育为什么要上物理课

2004年，联合国大会在关于确定2005年为“国际物理年”的决议中指出：物理学是认识自然的基础，物理学是当今众多技术发展的基础，物理教育为人类发展提供了必要的科学基础．决议高度评价了物理学在人类认识世界、改变人类社会、提高公众的科学文化素质等方面所起的重大作用．     

聚酰亚胺薄膜表面粗糙度的影响因素

 采用热蒸发气相沉积聚合方法（VDP）制备了聚酰亚胺(PI)薄膜,研究了设备、衬底温度、升温过程和单体配比因素对PI薄膜表面形貌的影响。利用干涉显微镜和扫描电镜对薄膜表面形貌进行了分析;利用原子力显微镜测定了薄膜表面粗糙度。结果表明：设定蒸发源-衬底距离为74 cm时可成连续膜;蒸发源采用一段升温和多段升温时,膜表面均方根粗糙度分别为291.23 nm和61.99 nm;采用细筛网可防止原料的喷溅;均苯四甲酸二酐和4,4′-二氨基二苯醚（PMDA和ODA）单体沉积速率比值为0.9∶1时,膜表面均方根粗糙度值可减小至3.30 nm;沉积衬底温度保持30 ℃左右时,膜表面均方根粗糙度为4.01 nm, 随温度的上升,膜表面质量会逐渐变差。     

Optical multi-image encryption based on frequency shift

We present a novel multi-image encryption and decryption algorithm based on Fourier transform and fractional Fourier transforms. Lower frequency parts of the original images are selected, frequency shifted and encrypted by using double phase encoding in fractional Fourier domains. Multiple images are encrypted together into a single one. A simple optical setup is given to implement the proposed algorithm. This scheme has features of enhancement in decryption accuracy and high optical efficiency. Numerical results have been given to verify the validity and efficiency of the proposed scheme.     

Dual-beam coaxial amplification system of stimulated Brillouin scattering based on polarization control technology

In the field of Brillouin lidar, it has very important significance to find one method that can amplify the Brillouin scattering signal in real time. One new-type Brillouin lidar detection system based on Nd:YAG pulsed laser and polarization control device is designed in this paper. The key point of this detection system is to have two pulsed coherent lights with same frequency, same polarization and same initial phase, of which one beam is taken as the detection wave for generating stimulated Brillouin scattering signal and the other beam is taken as pumping wave for real time and effective amplification of stimulated Brillouin scattering signal. This detection system mainly includes two pulsed lasers and one electro-optical polarization controller. The laser is mainly used to obtain the pulsed lights with same frequency and same phase, and the polarization controller is mainly used to change the polarization state of two coaxial beams to make them change into same polarization state from orthogonal polarization state thus to enable the pumping wave to amplify the backward stimulated Brillouin scattering signal. It is shown from the experimental results that the adoption of this new system can realize the effect of pumping amplification and can increase the signal to noise ratio to a certain extent.     

The comparison of ZnO nanowire detectors working under two wavelengths of ultraviolet

Schottky-barrier ultraviolet (UV) detectors based on ZnO-nanowires (NWs) were fabricated with Pt as electrodes in this investigation. The ZnO NWs synthesized by the hydrothermal method were characterized by field-emission scanning electron microscopy (FE-SEM), Raman and PL spectroscopy. Photoelectric properties under 254 and 365 nm UV light were investigated. It is found that the photo-response properties of the devices under 365 nm UV light are better than those under 254 nm UV light, which is further illustrated by light transmission theory, energy-band diagram and absorption spectra. The results demonstrate that ZnO NWs detectors with selectivity to near-UV (NUV) light are promising candidates in photoelectric devices.     

The secondary structure of heated whey protein and its hydrolysates antigenicity

Fourier transform infrared spectroscopy(FTIR) and circular dichroism(CD) were used to investigate the conformational changes of heated whey protein(WP) and the corresponding changes in the hydrolysates immunoreactivity were determined by competitive enzyme-linked immunosorbent assay(ELISA).Results showed that the contents of α-helix and β-sheet of WP did not decrease much under mild heating conditions and the antigenicity was relatively high;when the heating intensity increased(70 ℃ for 25 min or 75 ℃ for 2...     

Study of diode-pumped Yb:YAG disk lasers at low temperature

A Yb:YAG disk laser with V-shaped stable resonator and active-mirror configuration,end-pumped by a 940-nm InGaAs laser diode array,is demonstrated.Performances and optimization of the disk laser at low temperature over a range of 130-200 K are investigated theoretically and experimentally.Laser output energy of 1.46 J/pulse operating at 10-Hz repetition rate is obtained with the optimum output coupler transmission of 30%,and the corresponding optical-to-optical efficiency is 48.7%.     

Electromagnetic interactions in a cluster of cylinders

We present a rigorous multiple-scattering method to calculate the interaction energies due to electromagnetic field fluctuations in a cluster of parallel cylinders. Various kinds of cluster structure with both isotropic and anisotropic materials are considered. It is shown that Casimir interactions are sensitive to the positions of the cylinders in the cluster or the structure of the system. The sign of the interaction energy cannot only be changed by tuning the parameters of anisotropic materials, it can also be caused by changing the cylinders configuration of the system.     

Study of magnetotransport properties of interacting quantum dot systems using the ECA method

We study the magnetotransport of the interacting QD system in a magnetic field using the numerical method of embedded-cluster approximation (ECA). The spin-resolved conductances display different magnetic field dependences for different transport regimes. Through comparison of conductance polarization, the mixed-valence regime shows the largest polarization. The spin-resolved conductance as a function of the ratio between the magnetic field and Kondo temperature H/TK is found to exhibit an approximate universal behavior in the Kondo regime. We also investigate conductance dependence on interaction strength and find interesting inversion of sign of polarization in some cases.