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Locally repairable codes (LRCs), which can recover any symbol of a codeword by reading only a small number of other symbols, have been widely used in real-world distributed storage systems, such as Microsoft Azure Storage and Ceph Storage Cluster. Since the binary linear LRCs can significantly reduce the coding and decoding complexity, the construction of binary LRCs is of particular interest. To date, all the known optimal binary linear LRCs with the locality $2^b$ ($b\geq 3$) are based on the so-called partial spread which is a collection of the same dimensional subspaces with pairwise trivial, i.e., zero-dimensional intersection. In this paper, we concentrate on binary linear LRCs with disjoint local repair groups. We construct dimensional optimal binary linear LRCs with locality $2^b$ ($b\geq 3$) and minimum distance $d\geq 6$ by employing intersection subspaces deduced from the direct sum vs. the traditional partial spread construction. This method will increase the number of possible repair groups of LRCs as many as possible, and thus efficiently enlarge the range of the construction parameters while keeping the largest code rates compared with all known binary linear LRCs with minimum distance $d\geq 6$ and locality $2^b$ ($b\geq 3$).

The ceramic-polymer nanocomposites consisting of Ba0.6Sr0.4TiO3 nanofibers (BST60 NF) with a large aspect ratio prepared via electrospinning and employing surface hydroxylated as fillers and poly(vinylidene fluoride) (PVDF) as matrix have been fabricated by a solution casting method. The nanocomposites exhibit enhanced permittivity, reduced loss tangents and improved breakdown electric field strength at a low volume fraction of hydroxylated BST60 NF. The energy density of the nanocomposites is significantly enhanced, and the maximal energy density of 6.4 J/cm(3) is obtained in the composite material with 2.5 wt % hydroxylated BST60 NF, which is more than doubled as compared with the pure PVDF. Such significant enhancements result from combined effect of the large aspect ratio, the surface modification and the improved crystallinity of the nanocomposites induced by the hydroxylated BST60 NF. This work may provide a route for using the hydroxylated ceramic nanofibers to enhance the dielectric energy density in ceramic-polymer nanocomposites.

A high performance liquid chromatography with post-column photochemical derivatization method has been developed for the simultaneous determination of aflatoxins B1,B2,G1 and G2 in feed and feed stuffs.The samples were extracted with methanol-water solution (80:20,V/V),and were cleaned up by immunoaffinity columns.The separation of aflatoxins B1,B2,G1 and G2 were conducted by HPLC,the determination was carried out by fluorescence detector after photochemical derivatization and quantified by external standard method.Under the optimal conditions,the linear range was 0.38 ～ 20.00 μg/L,and that of the correlation coefficients were 0.999 6 ～ 0.999 9,the average recovery rates of aflatoxins B1,B2,G1 and G2 in feed and feed stuffs samples were in the range of 81.9% ～ 98.7% when spiked 0.75 ～ 20.00 μg/kg,inner-day RSD ranged from 1.57% to 3.87%,inter-day RSD ranged from 3.01% to 6.87%,the detection limits (S/N=3) of aflatoxins B1,B2,G1 and G2 were 0.05,0.02,0.05 and 0.08 μg/kg,respectively.The method is simple,high in sensitivity and good in repeatability,which had produced satisfactory results in determination of aflatoxins in feed and feed stuffs.