用于自适应波束形成语音增强的球谐域掩蔽函数估计方法

提出一种用于球形阵列自适应波束形成的掩蔽函数估计方法。该方法利用包含空间信息的球谐系数提取低维空间向量,并采用复高斯混合模型和深度学习两种方案来估计掩蔽函数,最终利用估计的掩蔽函数设计最小方差无失真响应波束形成器,以达到空域滤波的效果。理论分析和仿真实验证明,对于相同时长的声信号,球谐域掩蔽函数估计方法的计算复杂度比传统阵元域估计方法低了一个数量级。并且在大部分声场环境中,尤其在低信噪比情况下,所提方法的语音质量感知评估测度得分、分段信噪比和短时客观可懂度明显高于阵元域方法,三者最高分别可提升1.31 dB,4.54 dB和35%。另外,实际声学环境的测量实验也验证了所提方法在不影响可懂度的条件下比传统阵元域方法具备更高的降噪量。      

Two-dimensional Janus van der Waals heterojunctions: A review of recent research progresses

Two-dimensional Jamus van der Waals(vdW)heterojunctions,referring to the junction containing at least one Janus material,are found to exhibit tuneable electronic structures,wide light adsorption spectra,controllable contact resistance,and sufficient redox potential due to the intrinsic polarization and unique interlayer coupling.These novel structures and properties are promising for the potential applications in eleetronics and energy conversion devices.To provide a comprehensive picture about the research progress and guide the following investigations,here we summarize their fundamental properties of different types of two-dimensional Janus vdW heterostruct ures including electronic struc-ture,interface contact and optical properties,and discuss the potential applications in electronics and energy conversion devices.The further challenges and possible research directions of the novel heterojunctions are discussed at the end of this review.     

Distribution and source identification of dissolved sulfate by dual isotopes in waters of the Babu subterranean river basin,SW China

Sulfur and oxygen isotopes were employed to identify SO₄ ^2? sources in surface water and groundwater in the Babu subterranean river basin (BSRB). Our study revealed SO₄ ^2? enrichment in the BSRB waters compared with adjacent areas. The SO₄ ^2? in some samples originated mainly from precipitation; in others, it was derived mainly from sulfide dissolution in coal seams or from gypsum dissolution. In the water at the subterranean river exit, 13% of SO₄ ^2? originated from precipitation, 40% from sulfide oxidation in coal seams, and 47% from gypsum dissolution.     

Enhancement of the efficiency and stability of planar p-i-n perovskite solar cells via incorporation of an amine-modified fullerene derivative as a cathode buffer layer

A methanol-soluble diamine-modified fullerene derivative (denoted as PCBDANI) was applied as an efficient cathode buffer layer (CBL) in planar p-i-n perovskite solar cells (pero-SCs) based on the CH₃NH₃PbI_3–x Cl _x absorber. The device with PCBDANI single CBL exhibited significantly improved performance with a power conversion efficiency (PCE) of 15.45%, which is approximately 17% higher than that of the control device without the CBL. The dramatic improvement in PCE can be attributed to the formation of an interfacial dipole at the PCBM/Al interface originating from the amine functional group and the suppression of interfacial recombination by the PCBDANI interlayer. To further improve the PCE of pero-SCs, PCBDANI/LiF double CBLs were introduced between PCBM and the top Al electrode. An impressive PCE of 15.71% was achieved, which is somewhat higher than that of the devices with LiF or PCBDANI single CBL. Besides the PCE, the long-term stability of the device with PCBDANI/LiF double CBLs is also superior to that of the device with LiF single CBL.     

A note on the almost-one-half holomorphic pinching

Motivated by a previous work by Zheng and the second-named author, we study pinching constants of compact Kähler manifolds with positive holomorphic sectional curvature. In particular, we prove a gap theorem on Kähler manifolds with almost-one-half pinched holomophic sectional curvature. The proof is motivated by the work of Petersen and Tao on Riemannian manifolds with almost-quarter-pinched sectional curvature.     

Synthesis of sulfonamides from azoles and sodium sulfinates at ambient temperature

NBS or NIS mediated direct SN bond formation between azoles and sodium sulfinates is described. The reaction shows good substrate scope and tolerates a wide range of functionalities in both azoles and sodium sulfinate substrates. Pyrazoles are also suitable for this method, various 4-halopyrazoles derivatives were obtained by using N-halosuccinimide (NXS) as the halogen source.     

A selective and cost-effective method for the reductive deuteration of activated alkenes

A new single electron transfer reaction for the reductive deuteration of activated alkenes has been developed for the selective synthesis of α,β-dideuterio compounds. A cheap, stable and commercially-available sodium dispersion with high specific surface area is employed as the electron donor to replace the traditionally used sodium/liquid ammonium system. Deuterium source is provided by EtOD-d₁. Excellent yields and deuterium incorporations were obtained across a broad range of activated alkenes with good functional group tolerance. This method provided a cheap, efficient and operationally-simple method for the synthesis of deuterium labeled compounds.     

气相色谱–质谱法测定棉花中苯氧羧酸类除草剂

采用气相色谱–质谱联用法检测棉花中3种苯氧羧酸类除草剂[2,4-D,2,4,5-T,2-甲-4-氯丁酸(MCPB)]的残留量。样品用甲酸酸化的丙酮提取,硫酸催化甲酯化反应,用气相色谱–质谱联用仪测定。采用HPLC法与GC–MS法对提取与衍生化步骤进行优化。2,4-D,2,4,5-T,MCPB 3种化合物在0.075~7.5 mg/kg范围内线性均良好,检出限分别为0.5,0.5,0.8μg/kg,测定结果的相对标准偏差分别为4.1%,4.3%,4.0%(n=5),方法回收率分别为93.6%,95.5%,93.9%。该方法各项指标均可满足检测要求。     

Resonant terahertz generation from InN thin films

Highly efficient conversion from ultrafast optical pulses to their terahertz (THz) counterparts has been achieved with InN thin films. An average THz output power as high as 0.931 microW has been obtained for an average pump power of 1 W, corresponding to a normalized conversion efficiency of 190% mm(-2). Based on our measured dependences of the THz output power on pump polarization, incident angle, pump power, and InN film thickness, resonance-enhanced optical rectification is one of the most plausible mechanisms for the THz generation in the InN films.     

Model of fluorescence intermittency in single enzymes

The intermittent emission of fluorescent light from single enzymes, quantum dots, and other nanoscale systems is often characterized by statistical correlations in the emitted signal. A one-dimensional model of such correlations in enzymes, based on a model of protein conformational fluctuations developed by Kou and Xie (Phys. Rev. Lett. 2004, 93, 180603), is formulated in the present paper in terms of the dynamics of a particle moving stochastically between "on" and "off" states under the action of fractional Gaussian noise. The model yields predictions for the short and long time behavior of the following quantities: the time correlation function, C(t), of the fluctuations of the signal intensity, the distribution, f(t), of time intervals between intensity fluctuations, and the Mandel parameter, Q(t), describing the extent of bunching or anti-bunching in the signal. At short times, C(t) and f(t) are found to decay exponentially, while, at long times, they are found to decay as power laws, the exponents being functions solely of the nature of the temporal correlations in the noise. The results are in good qualitative agreement with results from single-molecule experiments on fluorescence intermittency in the enzyme cholesterol oxidase carried out by Xie and co-workers (Science 1998, 282, 1877). The Mandel parameter, Q(t), for this model is positive at short and long times, indicating super-Poisson statistics in these limits, consistent with bunching of the fluorescent signal.