Chance constrained optimal power flow (OPF) has been recognized as a promising framework to manage the risk from variable renewable energy (VRE). In presence of VRE uncertainties, this paper discusses a distributionally robust chance constrained approximate AC-OPF. The power flow model employed in the proposed OPF formulation combines an exact AC power flow model at the nominal operation point and an approximate linear power flow model to reflect the system response under uncertainties. The ambiguity set employed in the distributionally robust formulation is the Wasserstein ball centered at the empirical distribution. The proposed OPF model minimizes the expectation of the quadratic cost function w.r.t. the worst-case probability distribution and guarantees the chance constraints satisfied for any distribution in the ambiguity set. The whole method is data-driven in the sense that the ambiguity set is constructed from historical data without any presumption on the type of the probability distribution, and more data leads to smaller ambiguity set and less conservative strategy. Moreover, special problem structures of the proposed problem formulation are exploited to develop an efficient and scalable solution approach. Case studies are carried out on IEEE 14 and 118 bus systems to show the accuracy and necessity of the approximate AC model and the attractive features of the distributionally robust optimization approach compared with other methods to deal with uncertainties.

Chromatographic media with synchronously large protein adsorption capacity and high processing flux are highly desired in protein separation; however, the creation of such materials still faces enormous challenges. Herein, a robust strategy to develop highly carboxylated monolithic media by combining nanofibrous aerogels' forming technique and an in situ modification approach is reported. The obtained ion-exchange nanofibrous aerogels (IENFAs) exhibit a unique cellular structure consisting of flexible ceramic nanofibers and a functional polymer wrapping layer, endowing them with outstanding underwater superelasticity and compressive fatigue resistance (nearly no plastic deformation after 1000 compressive cycles). Benefiting from the interconnected nanofibrous cellular structure, good hydrophilicity, high carboxylation, and excellent mechanical properties, the IENFAs exhibit synchronously promoted static (2.9 × 10 3 mg g −1 ) and dynamic (1.7 × 10 3 mg g −1 ) lysozyme adsorption capacities and improved buffer flux (2.17 × 10 4 L m −2 h −1 , gravity driven), which are superior to these reported nanofibrous materials and commercial ion-exchange membranes. The IENFAs also possess outstanding performance stability, easy operation, and excellent regenerability. Moreover, the IENFA-packed column could directly and continuously separate lysozyme from egg white solely driven by gravity, highlighting their excellent practical application performance. This work may provide a new avenue to design and develop next-generation high-performance chromatographic media for bioseparation.

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Photoluminescence properties of Tb3+ and Ce3+ singly doped and Ce3+/Tb3+-codoped RE2Si4N6C (RE = Lu, Y, and Gd) phosphors were investigated. Tb3+ shows similar luminescence properties in RE2Si4N6C (RE = Lu, Y, and Gd) host lattices and emits bright green light under UV excitation around 300 nm. The luminescence properties of Ce3+ in RE2Si4N6C host lattices are influenced by the size of the RE3+ ions (Lu2Si4N6C and Y2Si4N6C vs Gd2Si4N6C). Both Ce3+-activated Lu2Si4N6C and Y2Si4N6C phosphors exhibit a broad band emission in the wavelength range of 450−750 nm with peak center at about 540 nm, while Ce3+-activated Gd2Si4N6C shows a broad emission band in the wavelength range of 500−800 nm with peak center at about 610 nm. This difference is ascribed to the different site occupations of Ce3+ on the two crystallographic sites in Gd2Si4N6C as compared to the Y and Lu compounds. In Ce3+/Tb3+-codoped RE2Si4N6C (RE = Lu, Y, and Gd) phosphors, it is observed that energy transfer takes place from Ce3+ to Tb3+ in Ce3+/Tb3+-codoped Lu2Si4N6C and Y2Si4N6C but in the reversed direction from Tb3+ to Ce3+ in Ce3+/Tb3+-codoped Gd2Si4N6C, depending on the position of the 5d level of Ce3+ versus the 5D4 level of Tb3+. The potential applications of these phosphors are pointed out.

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Although there are vast potential locations to install FACTS devices in a power system, the actual installation number is very limited due to economical consideration. Therefore the allocation strategy exhibits strong sparsity. This paper formulates FACTS device allocation problem as a general sparsity-constrained OPF problem and employs norms to enforce sparsity on FACTS devices setting values to achieve solutions with desirable device numbers and sites. An algorithm based on alternating direction method of multipliers is proposed to solve the sparsity-constrained OPF problem. The algorithm exploits the separability structure and decomposes the original problem into an NLP subproblem, an regularization subproblem, and a simple dual variable update step. The NLP subproblem is solved by the interior point method. The regularization subproblem has a closed-form solution expressed by shrinkage-threholding operators. The convergence of the proposed method is theoretically analyzed and discussed. The proposed method is successfully tested on allocation of SVC, TCSC, and TCPS on IEEE 30-, 118-, and 300-bus systems. Case studies are presented and discussed for both single-type and multiple-type FACTS devices allocation problems, which demonstrates the effectiveness and efficiency of the proposed formulation and algorithm.Index Terms-Alternating direction method of multipliers, flexible AC transmission system, norm, optimal power flow, sparse optimization.

Single crystals of the newly discovered borate YBa3B9O18 with dimensions up to 13 × 8 × 4 mm3 were successfully grown by the Czochralski pulling method. X-ray excited luminescence measurements of the YBa3B9O18 showed a broad emission band in the wavelength range from 350 to 500 nm with a peak center at 400 nm. The light yield is about 6−7 times larger than that of PbWO4 measured at nearly the same conditions. The results show that borate can also exhibit attracting scintillation properties. A narrow temperature range for growth and drastic anisotropy of the growth rates are the main difficulties in growing large crystals. The crystal growth and properties of denser isostructural REBa3B9O18 series (RE = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) deserve further investigation.