[en] Many studies of critical current density (Jc) from the point of view of application in liquid nitrogen have been made since the discovery of 90K YBa₂Cu₃O_y (YBCO) superconductor. It is believed that the weak links between grains are responsible for the low Jc of sintered YBCO at magnetic fields. In this work, the authors propose a new approach -- the powder melting process (PMP) -- through which high Jc YBCO conductor have been fabricated using precursor powders of 211 and Ba-Cu-O phase, instead of 123 phase, as starting materials. The current density of PMP YBCO sample has been over 71000A/cm² at 1T, 77K without quench. The SEM and TEM study revealed the microstructural characteristics of PMP YBCO sample, well distributed fine 211 phase particles, microcracks-free, very clean grain boundaries and high density of crystal defects, which are believed to be responsible for its high Jc(B) values. Another direction to develop PMP is to reduce the melting temperature, which is essential for the fabrication of YBCO tape with metal substrate. A discussion is given of effects of processing parameters and microstructure on the technological advantages of this method. The YBCO conductors were fabricated via the continuously partial melting and unidirectional resolidification steps of the process using precursor powders of Y₂BaCuO₅ and Ba-Cu-O phase as starting materials. Since the process enables the liquid phase to react fully with the fine 211 particles during the peritectic, no CuO and BaCuO₂ phase remained in 123 matrix. Strong flux pinning effect was introduced by the fine well-dispersive 211 particles via the very dense crystal defects induced around them. This new approach has potential for the fabrication of oxide conductor with metal substrates since its melting temperature is lower than that of other melting process by 50-70 degrees C. The authors have fabricated YBCO/Ag tape via PMP in N₂ atmosphere

[en] The authors have prepared the flexible Ag-sheated Bi(Pb)-Sr-Ca-Cu-O superconducting composites by the powder-in-tube process. The critical current density Jc has reached 5000 A/cm² (77K,OT), and the dependence of Jc on magnetic field is reduced to some extent. The improvement of the critical current density is considered due to the grain alignment and well connection between grains. Using these composites the authors succeeded in making gradient coils of magnetic flux transformers. Some results of bending test are also presented in this paper. (author). 14 refs., 6 figs., 1 tab

[en] We reported a planar waveguide structure on an Nd"3"+:Li_6Y(BO_3)_3 sample fabricated using 6 MeV C ion irradiation at a fluence of 2.5 × 10"1"5 ions/cm"2. Guided modes were detected in the visible and near-infrared wavelength regions. The refractive index profiles were reconstructed based on the effective refractive index functions. The near-field light intensity files in the visible and near-infrared bands were measured using the end-face coupling method with different light sources.

[en] A measurement-device-independent quantum key distribution (MDI-QKD) scheme with passive heralded single-photon sources has previously been published [1], while the two-intensity MDI-QKD scheme with a two-mode source proposed in our paper can been regarded as the extension and further research of the work [1].

[en] We propose a new scheme for measurement-device-independent quantum key distribution (MDI-QKD) with a two-mode state source. In this scheme, the trigger state is split into different paths and detected at both senders; thus, four types of detection events can be obtained. Based on these events, the signal state is divided into four non-empty sets that can be used for parameter estimation and key extraction. Additionally, we carry out a performance analysis on the scheme with two-intensity (vacuum state and signal state) heralded single-photon sources. We also numerically study the statistical fluctuation in the actual system. Our simulations show that the error rate and the secure transmission distance of our two-intensity scheme are better than those of existing three- and four-intensity MDI-QKD schemes with different light sources. Considering statistical fluctuations, the maximum secure distance of our scheme can reach 344 km when the data length is 10¹³ and remains as long as 250 km when the data length is 10¹⁰. Moreover, our scheme improves the system performance and reduces the challenges of implementing the system.

[en] Under the approximation of small birefringence, the properties of circularly polarized vortex beams tightly focused through a uniaxial birefringent crystal are studied. With the proper combination of the topological charge and the birefringence, the small focus, the small bottle beam and the inverse c-shaped intensity profile can be obtained. The effects of the focal shift and the Strehl ratio on the birefringence are analysed. A relation between angular momentum (included spin and orbital) and topological Pancharatnam charge is also presented. (fundamental areas of phenomenology (including applications))

[en] Titanium aluminides (Ti₃Al and TiAl) have received considerable attention as potential low density, high strength and creep resistant materials for high-temperature applications. For years, significant progress in improving the ambient temperature properties have been made, but the application temperature of these alloys is limited to less than 1,000 C for their relatively low high-temperature strength and poor oxidation resistance. Additions of niobium are known to increase the liquidus temperature and improve the properties of TiAl alloys. The needs for improving the limiting temperature of high-temperature structural materials are widespread. With a view to possible development of advanced intermetallic alloy for use above 1,000 C, a systematic study has been performed in the authors research group on the phase diagram, crystallographic structures, and oxidation and mechanical behavior of Ti-Al-Nb ternary alloys. The present paper is primarily concerned with the development of new Ti-Al-Nb intermetallic alloys based on their fundamental studies, which will be briefly reviewed here

[en] Acidic, alkaline, salty and hot oily water originated from industrial oily wastewater, petroleum spills and meal oily waste sewage have caused heavy environmental pollutions and energy waste. Underwater superoleophobic stainless steel mesh (SSM) is one kind of promising materials to purify above oily wastewater; however, it is still a challenge to prepare durable underwater superoleophobic SSM towards acid, base, salt, high temperature or abrasion. Herein, a durable underwater superoleophobic SSM (TA-PF-SSM) was prepared using tannic acid (TA) and paraformaldehyde (PF) via a simple and mild wet chemical immersion method. Surface morphologies show a few differences compared with those of pristine SSM. The underwater superoleophobic TA-PF-SSM can be utilized to separate various kinds of oil/water mixtures that water phase can be acidic/alkaline (pH = 1, 4, 10 and 13), salty and even hot. Separation efficiencies can reach 99.98% without any obvious declines after tens of cyclic separations, and also do not decrease after sand paper abrasion with a load of 200 g for 10 cycles. In addition, the TA-PF-SSM can also be applied to separate meal waste oily water at 80°C and crude oil/water at 50°C. And it shows excellent self-cleaning property towards crude oil. This study not only provides a simple surface modification method to prepare durable underwater superoleophobic material, but also proposes a TA-PF-SSM that can be applied to purify oily wastewater from industry, meal wastes and petroleum spills. (author)

[en] Planar and channel waveguides were fabricated in periodically poled lithium niobate crystals by 6 MeV O-ion implantation. Single-pass second harmonic generation was carried out. A conversion efficiency of 34.5%/(W . cm²) was achieved in the channel waveguide, and 1.11 mW second harmonic light at 492.5 nm was generated. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] Highlights: • Elevated concentrations of heavy metals were observed in the soil and crop locally. • Risk assessment of heavy metal contamination was significant for local inhabitants. • IR via ingesting rice, wheat, water and soil was high, especially for children. • Consumption of rice and wheat was the major contribution to risk. • The spatial distribution pattern of IR was predicted using geostatistical analysis. Environmental pollution by heavy metals resulting from rapid economic development is a major concern. Soil, water, wheat, and rice samples were collected from the Lihe River Watershed in the Taihu Region (east China). In this study area, many types of industrial plants, including ceramics factories, plants working with refractory materials, and chemical plants are densely distributed and cause serious heavy metal pollution. In addition, well-developed transportation and agricultural activities are also important sources of heavy metals. Thus, the concentrations of selected heavy metals including cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in the samples were analyzed to evaluate their potential integral risk (IR) to the health of the local population. Accordingly, the spatial distribution pattern of the IR values was determined in the study. The soil in the study area showed heavy Cd pollution, whereas the pollution by other elements was relatively slight. When the proportions of grain samples in which the concentrations exceeded the tolerance limits were examined, the grains were primarily contaminated with Pb, Ni, Cd, and Zn; and less contaminated with Cu and Cr. The drinking water of the local inhabitants was safe. The average IR value was 3.53 for adults and 3.91 for children, indicating that both adults and children may experience adverse health effects. The spatial distribution pattern of the IR values among the exposed populations in the study area showed high values in the eastern and middle parts, with maximum values > 5, and low values in the western part, with minimum values < 2. This is consistent with the distributions of the industries and the population. The study may provide a basis for comparison to other regions both in China and worldwide.