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991.
A novel and practical preparation of 2-pyridone-containing tricyclic alkaloid derivatives was developed. By regioselective intramolecular N- and C-acylation of 2-(4-aryl-2-pyridon-6-yl)benzoic acid, a pair of structural isomers 2-aryl pyrido[2,1-a]isoindole-4,6-diones and 4-aryl 1-methyl-1H-indeno[1,2-b]-pyridine-2,5-diones, as potential inhibitors of tumor cell proliferation, were prepared respectively. 相似文献
992.
The structures and energies of hydrated oxalate clusters, C2O4(2-)(H2O)n, n = 6-12, are obtained by density functional theory (DFT) calculations and compared to SO4(2-)(H2O)n. Although the evolution of the cluster structure with size is similar to that of SO4(2-)(H2O)n, there are a number of important and distinctive futures in C2O4(2-)(H2O)n, including the separation of the two charges due to the C-C bond in C2O4(2-), the lower symmetry around C2O4(2-), and the torsion along the C-C bond, that affect both the structure and the solvation energy. The solvation dynamics for the isomers of C2O4(2-)(H2O)12 are also examined by DFT based ab initio molecular dynamics. 相似文献
993.
994.
995.
基于FPGA的控制器局部网(CAN)总线控制器设计 总被引:1,自引:0,他引:1
提出一种基于FPGA的CAN总线控制器的实现方案,给出其结构框图,并对内部各模块进行较为详细的介绍.最后给出控制器在Altera公司的系列FPGA上实现时的资源利用情况及其性能,并参照CAN协议规范对其进行仿真验证. 相似文献
996.
997.
Tzung-Lin Li Wu-Lin Ho Hung-Bin Chen Wang H.C.-H. Chun-Yen Chang Chenming Hu 《Electron Devices, IEEE Transactions on》2006,53(6):1420-1426
A novel dual-metal gate technology that uses a combination of Mo-MoSi/sub x/ gate electrodes is proposed. An amorphous-Si/Mo stack was fabricated as a gate electrode for the n-channel device. It was thermally annealed to form MoSi/sub x/. Pure Mo served as the gate electrode for the p-channel device. The work functions of MoSi/sub x/ and pure Mo gates on SiO/sub 2/ are 4.38 and 4.94 eV, respectively, which are appropriate for devices with advanced transistor structures. The small increase in the work function (< 20 meV) and the negligible equivalent oxide thickness variation (< 0.08 nm) after rapid thermal annealing at 950 /spl deg/C for 30 s also demonstrate the excellent thermal stabilities of Mo and MoSi/sub x/ on SiO/sub 2/. Additional arsenic ion implantation prior to silicidation was demonstrated further to lower the work function of MoSi/sub x/ to 4.07 eV. This approach for modulating the work function makes the proposed combination of Mo-MoSi/sub x/ gate electrodes appropriate for conventional bulk devices. The developed dual-metal-gate technology on HfO/sub 2/ gate dielectric was also evaluated. The effective work functions of pure Mo and undoped MoSi/sub x/ gates on HfO/sub 2/ are 4.89 and 4.34 eV, respectively. A considerable work-function shift was observed on the high-/spl kappa/ gate dielectric. The effect of arsenic preimplantation upon the work function of the metal silicide on HfO/sub 2/ was also demonstrated, even though the range of modulation was a little reduced. 相似文献
998.
A.W.M. Lee B.S. Williams S. Kumar Qing Hu J.L. Reno 《Photonics Technology Letters, IEEE》2006,18(13):1415-1417
We report the use of a /spl sim/50-mW peak power 4.3-THz quantum cascade laser (QCL) as an illumination source for real-time imaging with a 320 /spl times/ 240 element room-temperature microbolometer focal-plane array detector. The QCL is modulated synchronously with the focal-plane array for differential imaging. Signal-to-noise ratios of /spl sim/340 are achieved at a 20-frame/s acquisition rate, and the optical noise equivalent power of the detector array at 4.3 THz is estimated to be /spl sim/320 pW//spl radic/Hz. Both reflection and transmission mode imaging are demonstrated. 相似文献
999.
Performance and optimization of multistage partial parallel interference cancellation for wideband CDMA systems in multipath fading channels 总被引:2,自引:0,他引:2
Hu Cheng-hua Li Shao-qian Tang You-xi Li Zhong-ling 《Vehicular Technology, IEEE Transactions on》2006,55(4):1137-1158
In this paper, a closed-form bit error rate (BER) of hard-decision multistage partial parallel interference cancellation (PPIC) having perfect and imperfect channel estimation for complex spreading code-division multiple access (CDMA) over multipath Rayleigh channels was derived. The effects of receiving BER, power ratio of pilot to data channels, multiple-access interference (MAI) and multipath interference, additive white Gaussian noise, and other factors affecting channel estimation error are analyzed. The expression determining the optimal interference cancellation weight at path level for PPIC is first derived. Then, the oscillatory behavior of user-level-optimized PIC and the convergence of perfect channel estimation PIC and path-level-optimized PIC are validated. Results indicate that all factors determining the optimal weight certainly affect the BER performance of PPIC and that the lower BER limit of multistage PPIC depends on the adjustable factors, which include power ratio, observation length, and signal-to-noise ratio, and an unchangeable factor, i.e., number of users. In addition, the variance of MAI for complex spreading sequence is obtained, and the analytical expression can also be employed to predict the performance of multicode CDMA. 相似文献
1000.
为集成调谐器接收机芯片系统设计了一个带自动幅度控制回路的差分结构电容电感压控振荡器.通过采用pMOS管作为有源负阻使振荡器谐振回路可以直接接地电平,减小了寄生效应,扩大了频率调谐的线性及其范围.采用的自动幅度控制AAC回路具有元件少,噪声低,控制灵敏,调节容易,结构简单及设计方便的优点,并保证振荡器电路的性能最小地依赖于环境和制造工艺参数的变化.所设计的压控振荡器采用新加坡特许50GHz 0.35μm SiGe BiCMOS工艺流片,经测试在1MHz频率偏移处达到了-127.27dBc/Hz的相位噪声性能,具有宽的(990~1140MHz)和线性(调谐增益32.4MHz/V)的频率调谐曲线.整个振荡器电路在5V的供电电压下仅消耗6.6mA的电流,可以满足调谐器的应用需要. 相似文献