An efficient model for capturing gas transients in the energy flow of integrated electricity–gas systems

Gas-fired units provide great flexibility to accommodate the intermittent nature of renewable energy sources and are also considered to be an ideal substitute for retiring coal-fired generations. However, the increasing deployment of gas-fired units deepens interdependency between electric power and natural gas, calling for efficient modeling of the heterogeneous energy flow in the integrated electricity–gas systems (IEGS). Plenty of research works show the necessity of considering gas flow transients in the IEGS, which can be described by a set of partial differential equations (PDEs). To ensure a tractable optimization, the PDEs are often discretized using the finite/infinite difference method, which may result in a large computational scale for achieving good precision. To this end, this paper proposes an efficient model for capturing gas flow transients in the IEGS, which can be taken as the operational constraints in the optimal energy flow model for IEGS coordinated planning, scheduling, and control. For improving the computational efficiency, the PDE-based transient gas flow model is discretized using a space–time orthogonal collocation (OC) method, which provides high-quality results using fewer spatial–temporal discrete points than differential methods. Further, aiming at the difficulty in the determination of the number of space–time collocation points, an adaptive strategy is proposed and embedded in the proposed model utilizing the local fitting errors of state variables related to pipelines. Case studies show the superiority in computational accuracy and efficiency of the proposed model over the existing models based on Wendorff difference and global OC. And an illustrative case based on the modified IEGS benchmark system composed of the IEEE 118-bus power system and the Belgian 20-node gas network exhibits the application value of the proposed model in the optimization and control of the IEGS

4-Dimethylamino-N′-(4-nitrobenzylidene)benzohydrazide methanol monosolvate

In the title compound, C16H16N4O3·CH3OH, the aromatic rings form a dihedral angle of 0.4 (2)°. The nitro group is twisted from the attached benzene ring by 7.5 (2)°. In the crystal, N—H...O and O—H...O hydrogen bonds link alternating hydrazone and methanol molecules into chains in [100]. The crystal packing exhibits π–π interactions between aromatic rings from neighbouring chains [centroid–centroid distances = 3.734 (3) and 3.903 (3) Å]

Optimizing the Spatial Location of Street Lights in Belle Isle, Michigan

Improved street lighting can provide better use of public space and helps to promote safety while driving or walking. In terms of balancing benefits and impacts, on the basis of cost saving, this research adopts two prominent mathematical models, the maximal coverage location problem and the location set covering problem, to optimize street light locations. By comparing with the currently installed lights following the rule of thumb, the mathematical models in this research achieve the effect of saving electric energy while meeting residents’ traffic safety needs and living conditions. Furthermore, the models can provide greater coverage of illumination using the same amount of energy

Optimizing the Spatial Location of Street Lights in Belle Isle, Michigan

Improved street lighting can provide better use of public space and helps to promote safety while driving or walking. In terms of balancing benefits and impacts, on the basis of cost saving, this research adopts two prominent mathematical models, the maximal coverage location problem and the location set covering problem, to optimize street light locations. By comparing with the currently installed lights following the rule of thumb, the mathematical models in this research achieve the effect of saving electric energy while meeting residents’ traffic safety needs and living conditions. Furthermore, the models can provide greater coverage of illumination using the same amount of energy

Transient voltage stability emergency control strategy for HVDC receiving end power grid based on global orthogonal collocation

When asynchronous motors, especially double-fed asynchronous motors in large capacity pump storage are the main loads in the high voltage direct current (HVDC) receiving end power grid, the increase of the equivalent slip of asynchronous motor load may cause transient voltage instability. In order to recover the voltage rapidly in the grid, the emergency reactive power support needs to be quick and accurate. A method for transient voltage stability emergency control by temporarily reducing DC current is proposed, the inverter station is used as emergency reactive power source for the HVDC receiving end power grid. In detail, firstly, aiming at the quantitative calculation of DC current, a nonlinear optimization model with the optimization variable of DC current and the objective of minimizing energy transmission reduction of HVDC is established. Further, in order to achieve fast solution and meet the accuracy requirements, global orthogonal collocation (GOC) is incorporated into the optimization model to transform the differential equations of both objective function and constraints into algebraic equations, thus the optimization is transformed into a nonlinear programming (NLP) problem, by which the emergency control strategy, in specific, the optimal DC current control scheme is obtained. Finally, the modified IEEE 14 benchmark is used to verify the effectiveness and superiority of the proposed strategy

Characteristics and Discrimination of the Commercial Chinese Four Famous Vinegars Based on Flavor Compositions

Shanxi aged vinegar (SAV), Zhenjiang aromatic vinegar (ZAV), Sichuan bran vinegar (SBV), and Fujian monascus vinegar (FMV) are the representative Chinese traditional vinegars. However, the basic differential compositions between the four vinegars are unknown. In this study, compositions of commercial vinegar were investigated to evaluate the influence of diverse technologies on their distinct flavor. Unlike amino acids and organic acids which were mostly shared, only five volatiles were detected in all vinegars, whereas a dozen volatiles were common to each type of vinegar. The four vinegars could only be classified well with all compositions, and difference analysis suggested the most significant difference between FMV and SBV. However, SAV, ZAV, and SBV possessed similar volatile characteristics due to their common heating treatments. Further, the correlation of identification markers with vinegars stressed the contributions of the smoking process, raw materials, and Monascus inoculum to SAV, SBV, and FMV clustering, respectively. Therefore, regardless of the technology modification, this basic process supported the uniqueness of the vinegars. This study contributes to improving the standards of defining the characteristics of types of vinegar

A Pectic Polysaccharide from Sijunzi Decoction Promotes the Antioxidant Defenses of SW480 Cells

Sijunzi Decoction (SJZD) is a formula used for the treatment of spleen deficiency and gastrointestinal diseases in Traditional Chinese Medicine. Polysaccharides are reported to be the main components of SJZD responsible for its bio-functions. However, highly purified and clearly characterized polysaccharides from SJZD are not well described. Here we obtained a purified polysaccharide (SJZDP-II-I) from SJZD using ion exchange chromatography and gel filtration. Structure analysis by FT-IR and NMR identified SJZDP-II-I as a typical pectic polysaccharide with homogalacturonan and rhamnogalacturonan type I regions and arabinogalactan type I and II as side chains. In vitro studies indicated that SJZDP-II-I treatment could significantly enhance the total antioxidant capacity of SW480 cells, resulting from the promoted expressions of antioxidant enzymes and their master regulator PGC-1α, which would be valuable for further research and applications

Spacer Engineering for 2D Ruddlesden–Popper Perovskites with an Ultralong Carrier Lifetime of Over 18 μs Enable Efficient Solar Cells

2D Ruddlesden–Popper (RP) perovskites have become emerging photovoltaic materials due to their outstanding optoelectronic properties and intrinsic structure stability. Here, two structurally similar organic spacers with conjugated and unconjugated unites, namely FuMA and THFMA, were developed to study their effects on the photophysical properties of 2D RP perovskites. A very important finding is that the 2D perovskite film (n = 4) based on FuMA with a conjugated furan unit exhibits an ultralong average carrier lifetime of 18.03 μs, which could be attributed to the enlarged dielectric constant, reduced exciton binding energy, and decreased electron–phonon coupling coefficients of the FuMA-based 2D RP perovskites. The optimized device based on the FuMA spacer achieves a high PCE of 18.00% with negligible hysteresis, much higher than that of the THFMA-based device (PCE = 13.79%). This work opens a new avenue for developing 2D RP perovskite films with ultralong carrier lifetimes for photovoltaic and other optoelectronic applications

Alteration of endocannabinoid system in human gliomas

Fujian Health-Education Research Grant, china [WKJ2008-2-45]; Xiamen Science and Technology Key Program Grant, China [3502Z20100006]Endocannabinoids are neuromodulatory lipids that mediate the central and peripheral neural functions. Endocannabinoids have demonstrated their anti-proliferative, anti-angiogenic and pro-apoptotic properties in a series of studies. In the present study, we investigated the levels of two major endocannabinoids, anandamide and 2-arachidonylglycerol (2-AG), and their receptors, CB1 and CB2, in human low grade glioma (WHO grade I-II) tissues, high grade glioma (WHO grade III-IV) tissues, and non-tumor brain tissue controls. We also measured the expressions and activities of the enzymes responsible for anandamide and 2-AG biosynthesis and degradation, that is, N-acylphosphatidylethanolamine-hydrolysing phospholipase D (NAPE-PLD), fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MGL), and diacylglycerol lipase-alpha (DGL), in the same samples. Liquid chromatographymass spectometry analysis showed that the levels of anandamide decreased, whereas the levels of 2-AG increased in glioma tissues, comparing to the non-tumor controls. The expression levels and activities of NAPE-PLD, FAAH and MGL also decreased in glioma tissues. Furthermore, quantitative-PCR analysis and western-blot analysis revealed that the expression levels of cananbinoid receptors, CB1 and CB2, were elevated in human glioma tissues. The changes of anandamide and 2-AG contents in different stages of gliomas may qualify them as the potential endogenous biomarkers for glial tumor malignancy