Enhanced cold mercury atom production with two-dimensional magneto-optical trap

A cold atom source is important for quantum metrology and precision measurement. To reduce the quantum projection noise limit in optical lattice clock, one can increase the number of cold atoms and reduce the dead time by enhancing the loading rate. In this work, we realize an enhanced cold mercury atom source based on a two-dimensional (2D) magneto-optical trap (MOT). The vacuum system is composed of two titanium chambers connected with a differential pumping tube. Two stable cooling laser systems are adopted for the 2D-MOT and the three-dimensional (3D)-MOT, respectively. Using an optimized 2D-MOT and push beam, about 1.3×10⁶ atoms, which are almost an order of magnitude higher than using a pure 3D-MOT, are loaded into the 3D-MOT for ²⁰²Hg atoms. This enhanced cold mercury atom source is helpful in increasing the frequency stability of a neutral mercury lattice clock.     

基于改进的隐马尔可夫和神经网络混合模型的语音识别

研究了一种非齐次隐马尔可夫模型（Inhomogeneous Hidden Markov Model），然后将自组织特征映射神经网络与这种非齐次隐马尔可夫模型相结合，训练出抗噪声的HMM模型，并应用该混合模型进行语音识别。实验结果表明，该模型适合于对噪声背景下的语音进行识别。该模型具有更好的抗噪鲁棒性，在信噪比较低的情况下（5dB-10dB），识别率可以提高5％左右。     

臭氧处理生活污水的应用

臭氧是国际公认的绿色环保型杀菌消毒剂，消毒效率高，对各种病毒、细菌均有很强的杀灭能力，它还能除味、脱色，改善水质，而且没有二次污染。臭氧处理技术被认为是未来水处理领域的新兴技术     

微孔-介孔复合SiO2-Al2O3分子筛的水热合成研究

结合介孔和微孔分子筛的合成,采用十六烷基三甲基溴化铵(CTAB)和ZSM-5引导剂分别作为介孔和微孔结构的导向剂,在水热条件下合成了具有微孔-中孔复合结构的SiO2-Al2O3分子筛,并采用XRD和N2吸附对分子筛的结构进行了表征.结果表明,分子筛的XRD图谱在大角度区和小角度区同时出现较强的衍射峰,分别对应于四方晶型和MCM-41的结构.样品的N2吸附曲线亦在P/P0<0.1和P/P0＝0.25～0.4出现两个突跃,其DFT孔径则主要集中在1.2nm和3.4nm.     

纯硅MCM-48的合成研究

以正硅酸乙酯为硅源,非离子型表面活性剂聚乙二醇辛基苯基醚和阳离子型表面活性剂十六烷基三甲基溴化铵为共模板水热法合成了纯硅MCM-48分子筛。利用范德华力和氢键,聚乙二醇辛基苯基醚不仅可降低合成MCM-48所需阳离子表面活性剂的用量,而且有利于制备有序性好和稳定性高的MCM-48;并与单一阳离子表面活性剂制备的MCM-48的稳定性进行比较。     

具有强酸性位的高水热稳定介孔分子筛的合成

在强酸性介质中,以预先制备的β沸石纳米簇作为前驱体,通过S＋X－I＋路线及氨水热后处理步骤合成具有强酸性位的高水热稳定性介孔分子筛.XRD、氮气吸附、HRTEM和SEM分析表明所得样品具有普通MCM-41的典型介孔结构和表观形貌.较短的组装周期和室温的组装条件减弱了脱铝效应,27Al MAS NMR表明铝元素主要以四配位状态存在于介孔分子筛骨架中.采用NH3-TPD和水热老化方法分别考察了其固体酸性和水热稳定性,结果表明此介孔分子筛相对于普通MCM-41分子筛具有较强酸性位和较高的水热稳定性.沸石纳米簇的引入提高了分子筛骨架的聚合度和孔壁的厚度,是水热稳定性提高的主要原因.     

STUDY OF MESOPOROUS SILICA MATERIALS BY SMALL ANGLE X-RAY SCATTERING

Small angle X-ray scattering experiments have been performed to study the microstructure of mesoporous silica materials prepared by condensation of tetraethylorthosilicate using non-ionic alkylpolyethyleneoxide (AEO₉) and ionic cetyltrimethylammonium bromide (CTAB) surfactant as templates. It is the pores within the nanometre range that produce the main scattering. The scattering of the pure silica systems obey Porod's law. The scattering of the systems with templates remaining in the pores show positive deviations from Porod's law. This may be because the templates produce some additional scattering background and then make the scattering of pores distorted. The results show that the full removal of templates from the pores of the materials by Soxhlet extraction is very easy for AEO₉, but it is difficult for CTAB. The positive deviation correction is also performed.     

An application of a combined gradient system to stabilize a mechanical system

A gradient system and a skew-gradient system can be merged into a combined gradient system. The differential equations of the combined gradient system are established and its property is studied. If a mechanical system can be represented as a combined gradient system, the stability of the mechanical system can be studied by using the property of the combined gradient system. Some examples are given to illustrate the applications of the results.     

基于量子级联激光器中红外光谱技术的幽门螺旋杆菌呼气诊断的可行性研究

幽门螺旋杆菌(Hp)与胃、十二指肠疾病密切相关,被证明是胃癌的Ⅰ类致癌因子。碳13尿素呼气试验(¹³C-UBT)因具有准确、简单、无放射性和非侵入性的优势,已成为检测Hp感染的初步诊断和治愈确认的首选测试方法。但是,因测试仪器昂贵且¹³C尿素试剂全球产量有限导致其价格不菲,使得¹³C-UBT仍是一种成本较高的Hp感染检测方法。为实现¹³C-UBT对Hp的高灵敏、低成本的实时检测,本研究探究了高分辨率、高灵敏度的中红外量子级联激光光谱技术替代传统基于质谱和近红外光谱技术作为Hp检测仪器的可行性。选择纳入Hp感染阳性、阴性、治疗中的受试者,考察了呼气采样方式(口呼气和鼻呼气)、¹³C尿素服用剂量(5、 10、 20和75 mg)对Hp感染诊断结果的影响。结果表明,中红外量子级联激光光谱技术具有实时原位测量、准确度高的特点,最大测量误差约为0.1‰～0.3‰。呼气采样方式结果表明,口呼气和鼻呼气两种采样方式得到的测量值一致(p>0.05),表明鼻呼气有望替代口呼气为Hp呼气检测...     

合成高产率分子筛MCM-48

以十六烷基三甲基溴化铵（CTAB）和Triton X-100（TX-100）混合表面活性剂为模板剂,正硅酸乙酯（TEOS）为硅源,采用水热法合成了MCM-48分子筛.实验中发现,晶化3 d后用醋酸调节溶液pH值的方法可有效提高MCM-48分子筛的产率；同时采用混合表面活性剂使模板剂的利用效率达到了6.0 TEOS/1.0 Surf (摩尔比）,并通过XRD、N2-吸附/脱附和TG-DSC等测试手段对产物的结构性能进行了表征.