Evolution of shear bands in bulk metallic glasses under dynamic loading

Shear band spacing in Zr-based bulk metallic glasses (BMGs) under dynamic loads is found to vary with position and local strain rate in the indented region. To investigate the dependence of shear band evolution characteristics on local strain rate and normal stress, a micromechanical model based on momentum diffusion is proposed. The thermo-mechanical model takes into account the normal stress dependence of yield stress, the free volume theory and the associated viscosity change within the shear band region. Temperature rise is obtained from the balance between the heat diffusion to the adjacent regions from a shear band and the heat generation due to the accumulated plastic work in a shear band. The parametric study has revealed that thermal effects play a minor role when the critical shear displacement is below 10 nm (as in nanoindentation) but become significant when the shear displacement accumulated in a shear band is of the order of hundreds of nanometers (as in uniaxial compression and in dynamic indentations). Finally, it is found that the normal stress plays a crucial role in the deformation behavior of BMGs by not only decreasing the time for shear band formation but also increasing the temperature rise significantly.     

Fabrication of Novel Reversible Photoswitchable Fluorescent Nanoparticles

Novel photoswitchable fluorescent nanoparticles were fabricated by a facile one-step mini-emulsion polymerization, in which fluorescence resonance energy transfer (FRET) donor, 9,10-diphenylanthracene (DPA), and photoswitchable acceptor, spiropyran derivate, were simultaneously embedded in polymer matrix during the polymerization process. The prepared fluorescent nanoparticles exhibit the typical absorption properties of both DPA dye and spiropyran moiety, indicating that the two chromophores have been incorporated into the polymer nanoparticles. The obtained fluorescent nanoparticles exhibited superior photoswitchable fluorescent performance due to the effective photoinduced interparticle FRET. Moreover, the novel photoswitchable fluorescent nanoparticles also revealed small size (ca. 60 nm), high intensity, relatively fast photoresponsive property and good photoreversibility in aqueous media.     

Relative calibration for a polarization interference imaging spectrometer

A polarization interference imaging spectrometer (PIIS) for remote sensing is developed. Its operation principle and typical configuration are introduced. A polarization beam-splitter is its key component. The principle of calibration for the PIIS is introduced. The results of relative calibration for the PIIS are given. After the calibration, the responding uniformity of the detector of the PIIS to an expanded uniform light source is largely improved and the quality of the pictures obtained by the PIIS is obviously clear and accurate to the aims. Some applications and expectations of a PIIS are put forward.     

Electro-optical properties of dielectric liquid microlens

We report the electro-optical properties of dielectric liquid droplets based on dielectrophoretic effect. Due to dielectric force, the surface of each droplet can be reshaped which in turn alters its focusing behaviors. Our experimental results show that a deformed droplet can recover to its original shape with a negligible hysteresis. Both amplitude and frequency of the applied voltage play important roles affecting the droplet's shape change. The rise time is mainly governed by the applied voltage: for a given frequency a higher voltage results in a faster rise time. On the other hand, the decay time is jointly determined by the interfacial surface tensions, droplet size, and viscosity of the employed liquids.     

In situ formed silver nanoparticles on glass fibers grafted with polyacrylamide and their antibacterial activity

In this paper, grafted polyacrylamide from the surface of glass fibers was prepared by surface initiated atom transfer radical polymerization in order to control the matrix surface structure and properties. The uniform and stable grafted polymer layer was utilized to prepare silver ions complexes, and then the silver ions were reduced by AlLiH₄ to form in situ silver nanoparticles. The structure, composition, properties and surface morphology of the modified glass fibers were characterized by X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, thermo gravimetric analysis and scanning electron microscopy. The antibacterial activities of modified glass fibers against E. coli, B. subtilis and S. cerevisiae had been studied respectively by Shake Flask Method. The results show that the antibacterial ratio of Ag nanoparticles loaded glass fibers is significantly improved than that of Ag⁺ loaded, and the highest antibacterial ratio is 72.2% against E. coli.     

苯甲亚氨酸乙酯及N—乙氧基羰基亚甲基苯甲亚氨酯乙酯的~1H和~(13)C NMR的研究

本文测定了苯甲亚氨酸乙酯(Ⅰ)和N-乙氧基羰基亚甲基苯甲亚氨酸乙酯(Ⅱ)的~1H和~(13)C NMR谱,归属了共振谱线,得到了这两类化合物的官能团在苯衍生物中的经验增量,讨论了化学位移与Hammett常数的相关性.     

选择双波长光度法测定环境水中微量成份

本文依据成份显色液在某一波长范围其吸收光谱与悬浊液光谱曲线的平行性研究测定微量成份新方法,称选择双波长光度法,该方法计算曲线稳定,基本不受环境条件影响。通过对NH_3-N,Fe、Cr(Ⅵ)、S~(2-)、NO_3~--N、PO_4~(3-)等成份测定,结果满意。该原理和方法适合于天然水,生活污水和工业废水等监测。     

氨基酸合成方法研究-(XI)N-取代亚氨酸酯与芳醛缩合产物-去氢氨基酸衍生物的构型及其NMR研究

通过¹H NMR、NOE差谱和门控去偶¹³C NMR等的研究确定了新合成的五对α-去氢氨基酸衍生物的构型,并利用部分弛豫、APT ¹³C NMR二维碳氢相关谱及¹³C-¹⁹F偶合常数等对NMR谱线进行了归属.     

Optical and magnetic properties of small-size core–shell Fe3O4@C nanoparticles

Core–shell Fe₃O₄@C magnetic nanoparticles which are of great interest for research have a widely applied prospect. However, people know little about the optical and magnetic properties of the small-size Fe₃O₄@C nanoparticles due to the difficulty of uniformly coating small size Fe₃O₄ nanoparticles. In this paper, the influence of carbon shell coating on the optical and magnetic properties of small size Fe₃O₄ nanoparticles was presented. Carbon coating can strengthen the absorption intensity in the UV–visible light region through the introduction of oxygen defects on the surface of the nanoparticles by nitric acid treatment. Fe₃O₄ and Fe₃O₄@C nanoparticles both display typical superparamagnetic behavior in the high-temperature regime and a blocked state at low temperature from hysteresis loop, zero-field cooled and field cooled curves. Carbon coating reduce the surface uniaxial anisotropy, thus the average blocking temperature <T_B> decreases from 59 K of Fe₃O₄ nanoparticles to 50 K of Fe₃O₄@C nanoparticles.     

Improving Log-Likelihood Ratio Estimation with Bi-Gaussian Approximation under Multiuser Interference Scenarios

Accurate estimation of channel log-likelihood ratio (LLR) is crucial to the decoding of modern channel codes like turbo, low-density parity-check (LDPC), and polar codes. Under an additive white Gaussian noise (AWGN) channel, the calculation of LLR is relatively straightforward since the closed-form expression for the channel likelihood function can be perfectly known to the receiver. However, it would be much more complicated for heterogeneous networks where the global noise (i.e., noise plus interference) may be dominated by non-Gaussian interference with an unknown distribution. Although the LLR can still be calculated by approximating the distribution of global noise as Gaussian, it will cause performance loss due to the non-Gaussian nature of global noise. To address this problem, we propose to use bi-Gaussian (BG) distribution to approximate the unknown distribution of global noise, for which the two parameters of BG distribution can easily be estimated from the second and fourth moments of the overall received signals without any knowledge of interfering channel state information (CSI) or signaling format information. Simulation results indicate that the proposed BG approximation can effectively improve the word error rate (WER) performance. The gain of BG approximation over Gaussian approximation depends heavily on the interference structure. For the scenario of a single BSPK interferer with a 5 dB interference-to-noise ratio (INR), we observed a gain of about 0.6 dB. The improved LLR estimation can also accelerate the convergence of iterative decoding, thus involving a lower overall decoding complexity. In general, the overall decoding complexity can be reduced by 25 to 50%.