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《信息安全与通信保密》2002,(10)
北京中青联迪科技发展有限公司是团中央直属单位中青高新技术产业发展中心发起组建的高新技术企业,公司是3COM公司防火墙中国区独家总代理。 1.纯硬件设备、采用专业操作系统,高安全性、高性价比,获得国际国内多种认证。 2.操作方便简单,即插即用,全部采用Web图形管理界面,可以在3分钟内完成安装配置。 相似文献
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给出了一种基于2的补码的卷积运算算法及其硬件实现体系结构。该算法结构使用了一个特殊的移位累加单元代替并行补码乘法,降低了卷积系数为负数时的计算复杂度。 相似文献
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采用激光诱导荧光技术对InCl分子B3П1→X1∑+荧光光谱进行了分析和归属,并对
B3П1(v′=0)→X1∑+(v″=0)的时间分辨谱进行了观测.首次得到InCl分子B3П1态(v′=
0)无碰撞辐射寿命т0≈353ns,无辐射弛豫速率常数kQ≈1.985×10-10cm3molec-1s-1及
电子跃迁矩|Re|2=0.40D2. 相似文献
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Planar CH3NH3PbI3 perovskite based photodetectors are fabricated by a facile and low-cost one-step method. The devices show broad spectral photoresponse from the ultraviolet to whole visible region and the performance can be significantly improved by the introduction of a bipolar transporting MoO3 interface layer between CH3NH3PbI3 film and Au electrode. The photocurrent of the device with an optimized MoO3 layer is about twice that of the reference device without MoO3 layer, which results in a high ON/OFF current ratio of 5.9 × 103 at 5 V. Besides, slightly increased photoresponse speed is also found in the optimized device with rise time and decay time of 21.6 and 9.9 ms, respectively. The improvement can be attributed to the improved hole and electron collection efficiency and the quickly filled in or emptied trap states at the CH3NH3PbI3/Au interface due to the introduction of the bipolar transporting MoO3 layer. 相似文献
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采用固相反应法制备了Bi 3+ 、Eu3+ 、Tb3+ 掺杂的Lu3TaO7。测量了样品的X射线衍射谱、激发和发射光谱及荧光衰减曲线。三种离子掺杂的Lu3TaO7均呈现出强的荧光发射,其中Bi3+具有峰位在431 nm处的一强发射宽带,衰减寿命为16.8 μs,Eu 3+ 、Tb 3+ 则表现出稀土离子的特征锐发射峰,衰减寿命分别为1.26 ms和1.20 ms。因此,它们均是具有潜在应用前景的重闪烁体材料。 相似文献
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Tzu‐Chiao Wei Sudha Mokkapati Ting‐You Li Chun‐Ho Lin Gong‐Ru Lin Chennupati Jagadish Jr‐Hau He 《Advanced functional materials》2018,28(18)
Researchers have recently revealed that hybrid lead halide perovskites exhibit ferroelectricity, which is often associated with other physical characteristics, such as a large nonlinear optical response. In this work, the nonlinear optical properties of single crystal inorganic–organic hybrid perovskite CH3NH3PbBr3 are studied. By exciting the material with a 1044 nm laser, strong two‐photon absorption‐induced photoluminescence in the green spectral region is observed. Using the transmission open‐aperture Z‐scan technique, the values of the two‐photon absorption coefficient are observed to be 8.5 cm GW?1, which is much higher than that of standard two‐photon absorbing materials that are industrially used in nonlinear optical applications, such as lithium niobate (LiNbO3), LiTaO3, KTiOPO4, and KH2PO4. Such a strong two‐photon absorption effect in CH3NH3PbBr3 can be used to modulate the spectral and spatial profiles of laser pulses, as well as to reduce noise, and can be used to strongly control the intensity of incident light. In this study, the superior optical limiting, pulse reshaping, and stabilization properties of CH3NH3PbBr3 are demonstrated, opening new applications for perovskites in nonlinear optics. 相似文献
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钛酸钙对BZN-CaTiO3系统介电性能的影响 总被引:1,自引:0,他引:1
研究了利用电子陶瓷工艺制得的主晶相为Ba(Zn1/3Nb2/3)O3(BZN)和CaTiO3的新型陶瓷,BZN具有立方钙钛矿结构。通过烧结温度的改变得到不同介电性能的陶瓷材料,发现CaTiO3的添加量对系统介电性能有显著影响。在1 395℃烧结的BZN-CaTiO3陶瓷,当CaTiO3的添加量为60%(质量分数)时介电性能最佳,其εr为99.97,tgδ为0.54×10-4,αC为–13.05×10-6℃–1(25~85℃,1MHz下测量)。 相似文献
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Without adding feedback to modulate light path system, the dissymmetrical 3×3 coupled optical accelerometer reduces the complexity of the design of light path system. Experiments prove that it can attain good demodulation effects. As carrier is not needed in this system, the frequency range of input signal is diminished so as to decrease the sampling frequency of accelerometer. This makes for the system on programmable chip(SOPC) design of digital demodulating system. The upper limit of accelerometer working frequency can reach 3 500 Hz. But affected by the inherent frequency of sensitive components, its working frequency is 10 Hz~1 000 Hz, and the sensitivity is 8.718 0 V/(m·s-2). This accelerometer can detect the dynamic range of acceleration signal real-timely, steadily and accurately, solving the dissymmetrical problem of light path caused by circumstances and the complexity of process. 相似文献
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Without adding feedback to modulate light path system, the dissymmetrical 3×3 coupled optical accelerometer reduces the complexity of the design of light path system. Experiments prove that it can attain good demodulation effects. As carrier is not needed in this system, the frequency range of input signal is diminished so as to decrease the sampling frequency of accelerometer. This makes for the system on programmable chip(SOPC) design of digital demodulating system. The upper limit of accelerometer working frequency can reach 3 500 Hz. But affected by the inherent frequency of sensitive components, its working frequency is 10 Hz~1 000 Hz, and the sensitivity is 8.718 0 V/(m·s-2). This accelerometer can detect the dynamic range of acceleration signal real-timely, steadily and accurately, solving the dissymmetrical problem of light path caused by circumstances and the complexity of process. 相似文献
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Er3 /Yb3 共掺TeO2-WO3-Bi2O3玻璃的光谱性质 总被引:5,自引:4,他引:1
用高温熔融法制备了Er3+/Yb3+共掺的TeO2-WO3-Bi2O3玻璃,研究了该玻璃的吸收和荧光光谱性质.应用Judd-Ofelt(JO)理论计算了Er3+的谱线强度、自发辐射跃迁几率、荧光分支比和辐射寿命等光谱参数,并拟合了相应的强度参数Ωt(t=2,4,6).Er3+在该玻璃中4I13/2→4I15/2发射的荧光半高宽(FWHM)为77nm,应用McCumber理论计算的受激发射截面为1.03×10-20cm2.其带宽特性FWHM×σpeake乘积优于掺Er3+的硅酸盐、磷酸盐和铋酸盐玻璃,说明这是一种制备宽带光纤放大器的优良基质材料.Er3+在400~850nm波长范围存在着5个上转换发射峰,分别对应Er3+的激发态4I7/2、2H11/2、4S3/2、4F9/2和4I9/2到基态4I15/2的发射,分析了其可能存在的上转换过程. 相似文献
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研究了不同成分的BiYbO_3-BaTiO_3-LiNbO_3陶瓷的晶体结构、表面形貌与介电、铁电性能。研究结果表明,BiYbO_3-BaTiO_3-LiNbO_3预烧粉体均为纯相,烧结后试样中存在少量的Bi2O_3和Yb_2TiO_5第二相,其组织致密、多边形状晶粒中有少量细小的球状晶粒存在。0.25BY-0.7BT-0.05LN陶瓷的介电常数最大(ε_(rmax)=280),剩余极化强度相对较大,P_r=0.47μC/cm2,矫顽场强E_c=19.04kV/cm。0.1BY-0.8BT-0.1LN陶瓷的剩余极化强度最大(P_(rmax)=0.83μC/cm~2),矫顽场强E_c=17.86kV/cm。 相似文献
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Daehee Seol Ahreum Jeong Man Hyung Han Seongrok Seo Tae Sup Yoo Woo Seok Choi Hyun Suk Jung Hyunjung Shin Yunseok Kim 《Advanced functional materials》2017,27(37)
Organic–inorganic hybrid perovskite solar cells are attracting the attention of researchers owing to the high level of performance they exhibit in photovoltaic device applications. However, the attainment of an even higher level of performance is hindered by their anomalous current–voltage (I–V) hysteresis behavior. Even though experimental and theoretical studies have suggested that the perovskite materials may have a ferroelectric nature, it is still far from being fully understood. In this study, the origin of the hysteresis behavior in CH3NH3PbI3 perovskite thin films is investigated. The behavior of ferroelectricity using piezoresponse force microscopy is first examined. Then, by comparing the scan‐rate‐dependent nano/macroscopic I–V curves, it is found that ion migration assisted by the grain boundaries is a dominant origin of I–V hysteresis from a macroscopic viewpoint. Consequently, the observations suggest that, even though ferroelectricity exists in the CH3NH3PbI3 perovskite materials, ion migration primarily contributes to the macroscopic I–V hysteresis. The presented results can provide fundamental guidelines to the resolution of hysteresis issues in organic–inorganic hybrid perovskite materials. 相似文献
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Tian-Bo Deng 《International Journal of Electronics》2016,103(11):1804-1821
An interpolation kernel is required in a wide variety of signal processing applications such as image interpolation and timing adjustment in digital communications. This article presents a general-form interpolation kernel called 3-3-3 interpolation kernel and derives its frequency response in a closed-form by using a simple derivation method. This closed-form formula is preliminary to designing various 3-3-3 interpolation kernels subject to a set of design constraints. The 3-3-3 interpolation kernel is formed through utilising the third-degree piecewise polynomials, and it is an even-symmetric function. Thus, it will suffice to consider only its right-hand side when deriving its frequency response. Since the right-hand side of the interpolation kernel contains three piecewise polynomials of the third degree, i.e. the degrees of the three piecewise polynomials are (3,3,3), we call it the 3-3-3 interpolation kernel. Once the general-form frequency-response formula is derived, we can systematically formulate the design of various 3-3-3 interpolation kernels subject to a set of design constraints, which are targeted for different interpolation applications. Therefore, the closed-form frequency-response expression is preliminary to the optimal design of various 3-3-3 interpolation kernels. We will use an example to show the optimal design of a 3-3-3 interpolation kernel based on the closed-form frequency-response expression. 相似文献
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Cr3+,Yb3+,Er3+共掺磷酸盐铒玻璃中Ce3+和Cr3+离子对光谱性质的影响 总被引:3,自引:2,他引:3
研究了 Cr3+ ,Yb3+ ,Er3+共掺磷酸盐铒玻璃的吸收光谱和荧光光谱性质。通过测定和计算各种 Cr3+ ,Yb3+ ,Er3+ 共掺磷酸盐铒玻璃的光谱参数 ,初步探明了 Ce3+ 和 Cr3+ 离子浓度含量对 Cr3+ ,Yb3+ ,Er3+ 共掺磷酸盐铒玻璃光谱性质的影响。结果表明 ,Ce O2 含量为 2 .8mol- %,Cr2 O3含量为 0 .0 8wt.- %玻璃的光谱性质较好。Ce3+ 离子价态的变化也对玻璃的光谱性质有重要影响。 Ce3+ 离子的存在更有利于对抽运光的吸收和能量的传递。在 Cr3+ ,Yb3+ ,Er3+共掺磷酸盐铒玻璃中实现了 Er3+荧光寿命达 8m s,受激发射截面为 0 .8× 1 0 - 2 0 cm2的光谱特性 ,为今后该玻璃的激光实验提供了重要参数。 相似文献
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Amasev D. V. Mikhalevich V. G. Tameev A. R. Saitov Sh. R. Kazanskii A. G. 《Semiconductors》2020,54(6):654-657
Semiconductors - The effect of annealing of a CH3NH3PbI3 organometallic perovskite film on its electrical, photoelectrical, and optical properties is studied. It is shown that annealing at the... 相似文献
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许可证的拍卖炒作和世界电信业的下滑严重影响了原本领跑的欧洲3G的健康发展,曾经一度使3G变成了"3D"--债务、推迟、怀疑(Debt、Delay、Doubt).在欧洲受到挫折时,日本变成率先吃螃蟹的国家.NTT DoCoMo于2001年10月成为采用WCDMA正式开通3G业务的第一家运营商.此后,J-Phone和KDDI也相继投入这一行列.经过一年的摸索,日本对3G似乎更加坚定信心,三大3G运营商纷纷亮出自己的发展策略,意气风发,锐意奋进. 相似文献