The Static Stability Region of an Integrated Electricity-Gas System Considering Voltage and Gas Pressure

In an integrated electricity-gas system(IEGS),load fluctuations affect not only the voltage in the power system but also the gas pressure in the natural gas system.The static voltage stability region(SVSR)method is a tool for analyzing the overall static voltage stability in a power system.However,in an IEGS,the SVSR boundary may be overly optimistic because the gas pressure may collapse before the voltage collapses.Thus,the SVSR method cannot be directly applied to an IEGS.In this paper,the concept of the SVSR is extended to the IEGS-static stability region(SSR)while considering voltage and gas pressure.First,criteria for static gas pressure stability in a natural gas system are proposed,based on the static voltage stability criteria in a power system.Then,the IEGS-SSR is defined as a set of active power injections that satisfies multi-energy flow(MEF)equations and static voltage and gas pressure stability constraints in the active power injection space of natural gas-fired generator units(NGUs).To determine the IEGSSSR,a continuation MEF(CMEF)method is employed to trace the boundary point in one specific NGU scheduling direction.A multidimensional hyperplane sampling method is also proposed to sample the NGU scheduling directions evenly.The obtained boundary points are further used to form the IEGSSSR in three-dimensional(3D)space via a Delaunay triangulation hypersurface fitting method.Finally,the numerical results of typical case studies are presented to demonstrate that the proposed method can effectively form the IEGS-SSR,providing a tool for IEGS online monitoring and dispatching.

Application of Risk-based Flexibility Assessment Methods to Evaluate System Expansion Plans

This paper proposed a flexibility assessment approach based on and risk assessment methodology. System planners prioritize each planning scheme with consideration of three aspects: reliability, economics, and flexibility. In the past, there is lack of quantitative indices to measure flexibility of a power system. This paper proposes applying probabilistic risk assessment method to quantify system flexibility. The proposed approach is demonstrated to compare two transmission planning schemes during Guangdong expansion planning process.

Support vector regression constraint to remove fault shadows-A case study of an oil field in the pearl river estuary basin,South China Sea

The main reservoirs in different fields in the YP oil region of the eastern Pearl River Estuary Basin are all fault-locked reservoirs.A large amount of seismic data in this area has fault-influenced distortion imaging zones,which poses a challenge to the tectonic evaluation of the area.Traditional solutions to fault shadows generally use reacquisition of multi-directional seismic data or targeted processing for fault imaging,which involves the acquisition of high cost and long processing cycle.In this paper,we propose to quantitatively depict the shadow zone range of faults using 3D stratigraphic dip attributes,and then combine it with the lateral distribution of marine stratigraphy features in the YP oil region,we introduced a support vector regression algorithm to calculate a high-precision nonlinear tectonic trend surface in the area.Under the constraint of this trend surface,we completed the prediction of distortion area structure of the fault shadow zone.The theoretical model test calculations and the production application of an oil field in the YP oil region show that the method has a great potential for application.

The Application of BIM Technology in Architectural Lighting Design

With the continuous development of science technology,Building Information Modeling(BIM)technology has slowly garnered wider attention from designers and architecture professionals.BIM,the 3D model-based process that allows for efficient planning,designing,constructing and managing buildings and infrastructure,could potentially revolutionize the building architectural discipline.This paper analyses the significance of the application of BIM technology in architectural lighting design,as well as the application points and the trends.

Distributionally robust optimization configuration method for island microgrid considering extreme scenarios

The marine climate conditions are intricate and variable. In scenarios characterized by high proportions of wind and solar energy access, the uncertainty regarding the energy sources for island microgrid is significantly exacerbated, presenting challenges to both the economic viability and reliability of the capacity configuration for island microgrids. To address this issue, this paper proposes a distributionally robust optimization (DRO) method for island microgrids, considering extreme scenarios of wind and solar conditions. Firstly, to address the challenge of determining the probability distribution functions of wind and solar in complex island climates, a conditional generative adversarial network (CGAN) is employed to generate a scenario set for wind and solar conditions. Then, by combining k-means clustering with an extreme scenario selection method, typical scenarios and extreme scenarios are selected from the generated scenario set, forming the scenario set for the DRO model of island microgrids. On this basis, a DRO model based on multiple discrete scenarios is constructed with the objective of minimizing the sum of investment costs, operation and maintenance costs, fuel purchase costs, penalty costs of wind and solar curtailment, and penalty costs of load loss. The model is subjected to equipment operation and power balance constraints, and solved using the columns and constraints generation (CCG) algorithm. Finally, through typical examples, the effectiveness of this paper’s method in balancing the economic viability and robustness of the configuration scheme for the island microgrid, as well as reducing wind and solar curtailment and load loss, is verified.

Temperature‑Gated Light‑Guiding Hydrogel Fiber for Thermoregulation During Optogenetic Neuromodulation

With the rise of optogenetic manipulation of neurons,the effects of optogenetic heating on temperature-sensitive physi-ological processes,and the damage to surrounding tissues have been neglected.This manuscript reports the fabrication of a highly temperature-sensitive semi-interpenetrating optical hydrogel fiber(TSOHF)using the integrated dynamic wet-spinning technique.TSOHF exhibits a structural tunable diameter,clear core/sheath structure,tunable temperature-sensitivity,excellent light propagation property(0.35 dB cm^(-1),650 nm laser light),and good biocompatibility(including tissue-like Young’s modulus,stable dimensional stability,and low cytotoxicity).Based on these properties,a potential application of optogenetic regulation of neural tissue(hypoglossal nerve),with controllable temperature using TSOHF was designed and performed.Further,this work provides new insight into molecular design and a practical approach to continually manufacture a temperature-sensitive hydrogel optical fiber for applications in intelligent photomedicine.

A Modified Impact-increment-based State Enumeration Method and Its Application in Power Distribution Systems

Reliable planning and operation of power distribution systems are of great significance. In this paper, the impactincrement based state enumeration(IIBSE) method is modified to adapt to the features of distribution systems. With the proposed method, the expectation, probabilistic, and duration reliability indices can be accurately obtained with a lower enumerated order of contingency states. In addition, the time-consuming optimal power flow(OPF) calculation can be replaced by a simple matrix operation for both independent and radial series failure states. Therefore, the accuracy and efficiency of the assessment process are improved comprehensively. The case of RBTS bus 6 system and IEEE 123 node test feeder system are utilized to test the performance of the modified IIBSE. The results show the superiority of the proposed method over Monte Carlo(MC) sampling and state enumeration(SE) methods in distribution systems.

Effect of radical scavenger on electrical tree in cross-linked polyethylene with large harmonic superimposed DC voltage

In this study,three kinds of radical scavenger Chimassorb 944,Tinuvin 622,and Tinuvin 770 are used to suppress the growth of electrical trees in cross-linked polyethylene(XLPE)with transient superimposed voltage under the temperature gradient.The tree morphology,tree length,accumulated damage,and time to breakdown are used to investigate the effect of radical scavenger on the electrical treeing process.It is found that under the temperature gradient caused by the temperature rise on the high voltage side,only Tinuvin 622 can always suppress the electrical tree as the temperature gradient rises.Under the temperature gradient caused by the temperature rise on the ground side,the three radical scavengers can all suppress the electrical tree.The breakdown of electrical tree exhibits the strong DC polarity dependence.Meanwhile,energy levels of these three radical scavengers are calculated through quantum chemistry,and the results indicate that radical scavengers have greater electron affinity,smaller ionisation energy,and smaller energy gap than XLPE.According to the surface potential decay test results at 60℃,it is found that all three radical scavengers can introduce deep traps.The different performances of radical scavengers under different temperature gradients and voltages are determined by the trap distribution characteristics,the molecular structure and chemical reaction of the additives themselves.It is concluded that Tinuvin 622 has potential for use in high voltage direct current XLPE cable application.

Load curve smoothing strategy based on unified state model of different demand side resources

Renewable energy based distributed generation(DG) has the potential to reach high penetration levels in the residential region. However, its integration at the demand side will cause rapid power fluctuations of the tieline in the residential region. The traditional generators are generally difficult to manage rapid power fluctuations due to their insufficient efficiency requirements and low responding speed. With an effective control strategy, the demand side resources(DSRs) including DGs, electric vehicles and thermostatically-controlled loads at thedemand side, are able to serve as the energy storage system to smooth the load fluctuations. However, it is a challenge to properly model different types of DSRs. To solve this problem, a unified state model is first developed to describe the characteristics of different DSRs. Then a load curve smoothing strategy is proposed to offset the load fluctuations of the tie-line of the residential region, where a control matrix deduced from the unified state model is introduced to manage the power outputs of different DSRs,considering the response order and the comfort levels.Finally, a residential region with households is used to validate the load curve smoothing strategy based on the unified state model, and the results show that the power fluctuation rate of the tie-line is significantly decreased.Meanwhile, comparative study results are shown to demonstrate the advantages of the unified state model based load curve smoothing strategy.

Maximum entropy based probabilistic load flow calculation for power system integrated with wind power generation

Distributed generation including wind turbine(WT) and photovoltaic panel increases very fast in recent years around the world, challenging the conventional way of probabilistic load flow(PLF) calculation. Reliable and efficient PLF method is required to take this chage into account.This paper studies the maximum entropy probabilistic density function reconstruction method based on cumulant arithmetic of linearized load flow formulation,and then develops a maximum entropy based PLF(MEPLF) calculation algorithm for power system integrated with wind power generation(WPG). Compared with traditional Gram–Charlier expansion based PLF(GC-PLF)calculation method, the proposed ME-PLF calculation algorithm can obtain more reliable and accurate probabilistic density functions(PDFs) of bus voltages and branch flows in various WT parameter scenarios. It can solve thelimitation of GC-PLF calculation method that mistakenly gains negative values in tail regions of PDFs. Linear dependence between active and reactive power injections of WPG can also be effectively considered by the modified cumulant calculation framework. Accuracy and efficiency of the proposed approach are validated with some test systems. Uncertainties yielded by the wind speed variations, WT locations, power factor fluctuations are considered.

Impact Increment Based Hybrid Reliability Assessment Method for Transmission Systems

This paper proposes an impact-increment-based hybrid(IIHybrid)reliability assessment approach for power transmission systems.The proposed approach integrates the advantages of the impact-increment-based state enumeration method(IISE)and impact-increment-based Monte Carlo simulation(IIMC)to improve computational efficiency and accuracy.The IISE can efficiently assess the impacts of low-order contingencies.The accuracy is,however,sacrificed as highorder contingencies are usually neglected.The IIMC is more suitable for large-scale contingency spaces compared with IISE,although the calculation process is time-consuming.In this paper,the proposed IIHybrid takes advantage of its strengths while avoiding its shortcomings.The IISE and the IIMC are applied to lower and higher contingency spaces respectively.The high-order contingencies elimination technique proposed in our previous studies is still applicable to the IIHybrid.In addition,efficiency can be controlled by modifying the preset parameters to adapt to various scenarios.Case studies are performed on the IEEE 118-bus test system and PEGASE System.The results show that the proposed approach is more efficient and practicable than traditional methods.

Scalable carbon black deposited fabric/hydrogel composites for affordable solar-driven water purification

Interfacial solar-driven evaporators have presented great potential for water purification owing to their low energy consumption and high steam generation efficiency. However, their further applications are hindered by the high costs and complicated fabrication processes. Here, a scalable bilayer interfacial evaporator was constructed via an affordable technique, in which carbon black deposited nonwoven fabric(CB@NF) was employed as the upper photothermal layer, as well as PVA/starch hybrid hydrogel for selffloating and water transport. Under simulated one sun irradiation, CB@NF layer displayed excellent photothermal conversion performance, whose temperature could increase 30.4 ℃ within 15 min. Moreover,the introduction of starch into PVA endowed the hybrid hydrogels with considerable water-absorption capability on the premise of ensuring mechanical properties. The resultant CB@NF/PVA/starch composites achieved superior interfacial adhesion performance with interfacial toughness at about 200 J m.Combining with good evaporation performance, salt-rejection property and high purification efficiency on pollutants, this evaporation system would become a promising candidate to alleviate water shortage.

Improve the Thermal and Mechanical Properties of Poly(L-lactide) by Forming Nanocomposites with Pristine Vermiculite

Poly（L-lactide）（PLLA）/pristine vermiculite nanocomposites were prepared by melt blending in a twin-screw extruder, and the detailed information of vermiculite dispersion state and effect of vermiculite on thermal and mechanical properties were systematically studied. The results show that the dispersion of vermiculite in the matrix is quite well when the loading content does not exceed 3 wt%. Pristine vermiculite can obviously improve the melt-crystallization temperature during the nonisothermal crystallization. Both crystallization time span and spherulitic size of PLLA decrease with the increasing amount of vermiculite under isothermal crystallization condition by enhancing the primary nucleation of PLLA. And the adding vermiculite can also improve the tensile modulus and Izod impact strength of PLLA. The intrinsic mechanism for the nucleating effect of vermiculite on PLLA is proposed to be the epitaxial crystallization and specific interaction between vermiculite and PLLA.

Transcriptome changes in Polygonum multiflorum Thunb. roots induced by methyl jasmonate

Transcriptome profiling has been widely used to analyze transcdptomic variation in plants subjected to abiotic or biotic stresses. Although gene expression changes induced by methyl jasmonate （MeJA） have been profiled in several plant species, no information is available on the MeJA-triggered transcriptome response of Polygonum multiflorum Thunb., a species with highly valuable medicinal properties. In this study, we used transcriptome profiling to investigate transcdptome changes in roots of P. mu/tiflorum seedlings subjected to a 0.25 mmol/L-MeJA rootirrigation treatment. A total of 18 677 differentially expressed genes （DEGs） were induced by MeJA treatment, of which 4535 were up-regulated and 14 142 were down-ragulated compared with controls. These DEGs were associated with 125 metabolic pathways. In addition to various common primary and secondary metabolic pathways, several sec- ondary metabolic pathways related to components with significant pharmacological effects were enriched by MeJA, including arachidonic acid metabolism, linoleic acid metabolism, and stilbenoid biosynthesis. The MeJA-induced transcdptome changes uncovered in this study provide a solid foundation for future study of functional genes controlling effective components in secondary metabolic pathways of P. multiflorum.

Homogeneous intercalated graphene/manganic oxide hybrid fiber electrode assembly by non-liquid-crystal spinning for wearable energy storage

Reduced graphene oxide(rGO)-based fibers with high electrochemical performance have recently showed great potential in the field of flexible energy storage devices.However,they still suffer from low capacitance due to the severe stacking of graphene sheets.Hybrids with nanofillers are an efficient way to improve the electrochemical performance of rGO fibers.Nevertheless,controlling the distribution of nanoparticles in the matrix is still an enormous challenge due to the strong attraction among these nanoparticles which results into agglomeration.Here,we continually prepared rGO hybrid fibers via nonliquid-crystal spinning,accompanied by chemical reduction.Manganic oxide(Mn OX)nanoparticles remained well-dispersed in GO dispersion during the continuous spinning of rGO/Mn OXhybrid fibers.Results showed that rGO/Mn OX-20 hybrid fibers possessed the best capacitance of 123.3 F g^(-1)(87.6 F cm^(-3))and 97.1 F g^(-1)(68.9 F cm^(-3))at the current density of 0.2 A g^(-1),and 0.5 A g^(-1)respectively.Furthermore,a fiber-shaped all-solid-state supercapacitor assembly from the optimized hybrid fibers demonstrated an energy density of 2.67 m Wh cm^(-3)(3.76 m Wh g^(-1))at the power density of 24.76 m Wh cm^(-3)(34.89 m Wh g^(-1)).These fiber-based devices show great potential for application in the fields of wearable electronics and energy storage devices.