Strontium optical lattice clock at the National Time Service Center

We report the ~(87)Sr optical lattice clock developed at the National Time Service Center. We achieved a closed-loop operation of the optical lattice clock based on ~(87)Sr atoms. The linewidth of the spin-polarized clock peak is 3.9 Hz with a clock laser pulse length of 300 ms, which corresponds to a Fourier-limited linewidth of 3 Hz. The fitting of the in-loop error signal data shows that the instability is approximately 5 × 10~(-15)τ~(-1/2), affected primarily by the white noise. The fractional frequency difference averages down to 5.7 × 10~(-17) for an averaging time of 3000 s.     

Gaussian 03软件在染料化学教学中的应用

讨论了Gaussian 03在染整课程中的具体应用,尤其对结构的稳定性、振动频率、染料颜色和结构的关系、分子的电荷布局在化学反应中的应用进行具体介绍.这些应用极大的丰富了课堂教学内容,提高教学质量.     

Implementation of an 8-bit bit-slice AES S-box with rapid single flux quantum circuits

Rapid single flux quantum (RSFQ) circuits are a kind of superconducting digital circuits, having properties of a natural gate-level pipelining synchronous sequential circuit, which demonstrates high energy efficiency and high throughput advantage. We find that the high-throughput and high-speed performance of RSFQ circuits can take the advantage of a hardware implementation of the encryption algorithm, whereas these are rarely applied to this field. Among the available encryption algorithms, the advanced encryption standard (AES) algorithm is an advanced encryption standard algorithm. It is currently the most widely used symmetric cryptography algorithm. In this work, we aim to demonstrate the SubByte operation of an AES-128 algorithm using RSFQ circuits based on the SIMIT Nb03 process. We design an AES S-bbox circuit in the RSFQ logic, and compare its operational frequency, power dissipation, and throughput with those of the CMOS-based circuit post-simulated in the same structure. The complete RSFQ S-bbox circuit costs a total of 42237 Josephson junctions with nearly 130 Gbps throughput under the maximum simulated frequency of 16.28 GHz. Our analysis shows that the frequency and throughput of the RSFQ-based S-bbox are about four times higher than those of the CMOS-based S-bbox. Further, we design and fabricate a few typical modules of the S-box. Subsequent measurements demonstrate the correct functioning of the modules in both low and high frequencies up to 28.8 GHz.     

气相色谱-质谱联用法在火药剖析中的应用

采用固液萃取的方法对火药样品进行处理,用气相色谱-质谱联用法对某未知火药进行成分剖析,以选择离子质谱法进行定量。目标化合物浓度在20-50mg／L范围内与色谱峰面积呈良好的线性关系,相关系数在0．9940～0．9996之间。方法加标回收率为96．9％～104.3％,测定结果的相对标准偏差为2．4％-4．9％（n=5）.气相色谱-质谱联用法可用于火药剖析研究。     

求解多目标优化问题的邻近牛顿法

针对一类特殊的多目标优化问题,其每个目标函数为一个二阶连续可微凸函数与一个真凸但不必可微函数之和,提出了邻近牛顿法.我们引入了带线搜索的邻近牛顿法和不带线搜索的邻近牛顿法.在适当的条件下,我们证明了由这两类算法产生的序列的每个聚点是多目标优化问题的Pareto平稳点.此外,我们给出了它们在约束多目标优化和鲁棒多目标优化...     

Photon number resolvability of multi-pixel superconducting nanowire single photon detectors using a single flux quantum circuit

Superconducting nanowire single-photon detectors (SNSPDs) are typical switching devices capable of detecting single photons with almost 100% detection efficiency. However, they cannot determine the exact number of incident photons during a detection event. Multi-pixel SNSPDs employing multiple read-out channels can provide photon number resolvability (PNR), but they require increased cooling power and costly multi-channel electronic systems. In this work, a single-flux quantum (SFQ) circuit is employed, and PNR based on multi-pixel SNSPDs is successfully demonstrated. A multi-input magnetically coupled DC/SFQ converter (MMD2Q) circuit with a mutual inductance M is used to combine and record signals from a multi-pixel SNSPD device. The designed circuit is capable of discriminating the amplitude of the combined signals in accuracy of Φ₀/M with Φ₀ being a single magnetic flux quantum. By employing the MMD2Q circuit, the discrimination of up to 40 photons can be simulated. A 4-parallel-input MMD2Q circuit is fabricated, and a PNR of 3 is successfully demonstrated for an SNSPD array with one channel reserved for the functional verification. The results confirm that an MMD2Q circuit is an effective tool for implementing PNR with multi-pixel SNSPDs.     

C14H3自由基和C14H3+阳离子的结构和热力学稳定性理论研究

采用密度泛函理论B3LYP/6-31G方法对C14H3中性和阳离子所有可能的构型、振动频率及热力学稳定性进行研究。基于目前的计算结果,C14H3和C14H3+最稳定的构型都是具有Cs对称的十四元环构型。如果构型里具有单叁键相互交替的聚炔烃结构,这个异构体就具有≈20cm-1的低频振动。C14通过加氢反应可以减小环内张力,使得十四元环能量降低,结构变得更加稳定。C14H3在温度低于1556K存在的可能性较大。     

新疆蓝刺头中一个新的过氧环状化合物

从新疆蓝刺头中分离出一个新的含六元过氧环的二联噻吩类化合物(3R,4R,5S)-3-[(2,2′-bithiophen)-5-yl]-1,2-dioxane-4,5-diol, 命名为Echinobithiophene A(1). 通过2D NMR谱、旋光和13C NMR谱等计算方法确定该化合物的绝对构型为3R, 4R, 5S. 活性测试结果表明,  该化合物对S.  aureus ATCC2592, E. coli ATCC25922和C. albicans ATCC2002等3种菌株具有较强的抗菌活性, 其最小抑菌浓度(MIC)值分别为75, 37.5和75 μg/mL.     

一种基于单磁通量子的超导纳米线单光子探测器阵列的读出电路

超导纳米线单光子探测(Superconducting Nanowire Single Photon Detector, SNSPD)阵列可以实现单光子成像或高速单光子探测，如何有效对SNSPD阵列进行信号读出是实现SNSPD阵列的关键技术之一，本工作设计了一种基于超导单磁通量子(Single Flux Quantum, SFQ)的SNSPD阵列读出电路，该读出电路能够实现对阵列中SNSPD的地址分频，实验采用的核心编码电路利用4位二进制码对包含8个SNSPD的阵列进行编码，使用了基于SFQ的异或逻辑单元、D触发器、分路器和约瑟夫森传输线等标准单元，总计使用191个约瑟夫森结，采用两级流水线设计，仿真中最高可在19.4GH2的时钟频率下工作，功耗为42.1μW,在液氦环境下完成了编码电路的功能测试，验证了编码功能的正确性。     

计算化学在手性化合物结构分析中的应用

对有机化学研究中的手性化合物, 尤其是天然产物分子的立体构型的鉴定, 日益受到研究人员的重视. 然而, 在化合物不能结晶或其它条件影响到不能用实验来直接解析其立体构型的情况下, 计算化学是一个比较有效的手段. 目前可供利用的计算方法有旋光计算, 如利用量子力学方法或矩阵模型及13C NMR计算等. 本文对这些不同的计算方法进行介绍.