关于“智能化工”背景下物理化学教学改革的思考

在当前“智能化工”迅速发展的大背景下,作为化工专业的核心课程之一,物理化学的教学不仅要因应智能化工的发展对化工专业人才的知识和能力需求,同时也应积极探索教学方法和手段的创新,吸收智能化工发展的最新技术成果并应用于教学过程中。通过对课程体系内容的进一步优化、引入先进的计算机辅助教学以及模拟实验手段等,提升教学效果,增强学生的实践能力和创新意识,培养他们适应智能化工发展的能力。

Litter decomposition and the degradation of recalcitrant components in Pinus massoniana plantations with various canopy densities

To understand the decomposition characteristics of Pinus massoniana foliar litter and the degradation of its refractory compounds in plantations under five canopy densities,a litter bag experiment over a decomposition time of 392 days was carried out.The results show that canopy density significantly affected decomposition rates of litter and degradation rate of lignin and cellulose.Litter decomposition rates decreased significantly with decreasing canopy density.Both lignin and cellulose degradation rates were lower with canopy densities of 0.62 and 0.74 as compared with the three other densities.Lignin and cellulose losses were more rapid in the first 118 days.Soil fauna had significant impacts on litter decomposition and the degradation of refractory compounds.Canopy density had significant effects on factors such as soil properties and soil fauna community structure,which could be conducive to the decomposition of litter and the degradation of litter recalcitrant components.Canopy density between 0.6 and 0.7 might be a favorable management practice promoting litter decomposition and beneficial for the sustainable development of P.massoniana plantations.

Insulation Design Rule for a Spacer in SF_(6)/N_(2)-filled DC Gas Insulated Apparatus

A recurring challenge of a DC SF_(6)/N_(2)-filled GIS/GIL apparatus is the charge accumulation at DC stress.The conventional design rules and knowledge of AC spacers may not be applicable for this new type of apparatus.A novel design rule is proposed considering the effect of accumulated charge on the threshold of electric field strength being resistant to the superposed voltage.A surface charge accumulation simulation model is introduced,and the key parameters in the simulation model are measured.In addition,an experimental platform for a 100 kV spacer flashover test is established.Spacer flashover tests under superimposed voltage with opposing polarities are carried out,and the withstanding voltage of the spacer is obtained.Finally,based on the proposed model,the threshold of the surface electric field strength(tangential component)on the DC spacer in SF_(6)/N_(2) mixed gases is discussed.For a reliable insulation design of a DC GIS/GIL apparatus filled with 0.7 MPa SF_(6)/N_(2),the threshold of surface electric field strength on the DC spacer is 12 kV/mm.The insulation design rule can be referenced in the design of a high-voltage DC SF_(6)/N_(2)-filled GIS/GIL apparatus.

Optical sensors for power transformer monitoring:A review

Power transformers play a vital role in power transmission systems from the energy source to the consumption center.In situ diagnostics of the performance of power transformers provides a variety of benefits to ensure reliable electricity transmission.Immunity to electromagnetic interference,high sensitivity,high insulation as well as small dimensions of optical sensing make it very attractive for applications in power transformer monitoring.This paper presents a critical review of various diagnostic methods for power transformers such as partial discharge,dissolved gases,temperature and other important sensing,and optical detection.The advantages and disadvantages of different monitoring methods are carefully discussed and assessed.Finally,the existing technical barriers and future prospects of optical monitoring methods for power transformers are presented.

Flashover Behavior of Cone-type Spacers with Inhomogeneous Temperature Distribution in SF_(6)/N_(2)-filled DC-GIL Under Lightning Impulse with DC Voltage Superimposed

Before designing DC gas insulated transmission lines(GIL),the insulation characteristics of spacers under a lightning impulse(LI)voltage with a superimposed DC voltage must be clarified.Many experiments have been performed to guide the development of the DC spacer.However,the impacts of thermal stresses on their insulation performance under combined voltage are always neglected,and little attention has been given to the insulation characteristics of spacers in an eco-friendly gas filled DC-GIL.To solve these problems,an experiment setup with the abilities to load the thermal field and the DC voltage with LI voltage superimposed on the cone-type spacer are built.After that,the insulation characteristics of spacers under the combined voltage of DC with lightning impulse at 0.1 MPa SF_(6)/N_(2) gas mixtures are investigated,under different thermal stress conditions.The experiment’s results indicate that:1)The flashover voltage of spacers under the same polarity superimposed voltages is slightly higher than that under LI alone.Conversely,the flashover voltage under reverse polarity superimposed voltages is lower than that under LI alone.2)The longer the duration of the foregoing DC voltage,the differences between the flashover voltage under superposed voltage and that under LI alone are larger.3)The combined flashover voltages are reduced under thermal stress.To ensure the insulation performance of newly designed DC spacers,the insulation test is suggested to be applied under thermal stress and combined voltage of the DC with lightning impulse,especially for superimposed reverse polarity.

High‐performance ZnO varistor ceramics prepared by arc‐induced flash sintering with low energy consumption at room temperature

The development of ultra‐high voltage transmission lines requires a ZnO arrester with excellent electrical response and high voltage gradient.Compared with conventional preparation methods,flash sintering allows fast production of novel high‐performance ZnO varistor ceramics with low energy consumption and controlled grain growth.Herein,ZnO varistor ceramics were prepared using the flash sintering method at an air pressure of 21 kPa for 60 s at 25℃.The results showed that the flash‐sintered samples had fine grains and reduced loss of volatile elements.Moreover,the voltage gradient,leakage current density,and non‐linear coefficient of the flash‐sintered varistor ceramics were significantly improved compared with those of conventionally sintered samples.Owing to the short preparation time and absence of a heating process,the energy consumption of the proposed flash sintering method was significantly reduced to 10%of that by conventional sintering.The proposed method is a promising approach for the preparation of ZnO arresters with excellent electrical properties and serves as an effective method that realises energy saving and emission reduction.

Gas-discharge induced flash sintering of YSZ ceramics at room temperature

This is the first study to conduct the flash sintering of 3 mol%yttria-stabilized zirconia(3YSZ)ceramics at room temperature(25℃)under a strong electric field,larger than 1 kV/cm.At the standard atmospheric pressure(101 kPa),the probability of successful sintering is approximately half of that at low atmospheric pressure,lower than 80 kPa.The success of the proposed flash sintering process was determined based on the high electric arc performance at different atmospheric pressures ranging from 20 to 100 kPa.The 3YSZ samples achieved a maximum relative density of 99.5%with a grain size of~200 nm.The results showed that as the atmospheric pressure decreases,the onset electric field of flash sintering decreases,corresponding to the empirical formula of the flashover voltage.Moreover,flash sintering was found to be triggered by the surface flashover of ceramic samples,and the electric arc on the sample surfaces floated upward before complete flash sintering at overly high pressures,resulting in the failure of flash sintering.This study reveals a new method for the facile preparation of flash-sintered ceramics at room temperature,which will promote the application of flash sintering in the ceramic industry.

Review of flash sintering with strong electric field

Flash sintering is a novel field‐assisted sintering technology for ceramics that allows a dramatic reduction in processing time and temperature.Since 2010,when flash sintering was first reported,it has been a focus of research interest in the field of materials science.Recent study results have confirmed that the sintering temperature decreases with the strength of the applied electric field;for some ceramics,the sintering temperature can be lowered even to room temperature.This represents an innovative breakthrough for ceramic sintering at ultra‐low temperatures.However,once the electric field strength in flash sintering is increased,new questions and challenges arise,such as whether or not partial discharge occurs in the green body if under electro‐thermal coupling stress,how to quantitatively analyse the impact of discharge on sintering,and,moreover,whether the sintering mechanism under a strong electric field is consistent with that under a weak electric field.These research questions require knowledge of partial discharge detection,dielectric theory,and other topics that are beyond the scope of materials science.To address this need,this review summarises the work carried out in flash sintering with a strong electric field from the perspective of high voltage and insulation technology.First,the flash sintering process and mechanism are briefly introduced.Then,the published literature on flash sintering with a strong electric field for various ceramic materials is summarised in depth.In addition,experimental phenomena that are observed in flash sintering with a strong electric field,such as flash and blackening,are discussed.Finally,some suggestions for future work are presented.It is anticipated that the knowledge gap between different areas of study can be filled by this review.

Review of Charge Accumulation on Spacers of Gas Insulated Equipment at DC Stress

Charge accumulation on the spacer surface in gas insulated equipment is very severe in the DC field,leading to easy flashover,which restricts the application of DC GIS/GIL.Therefore,knowledge about the charge accumulation characteristics of gas insulated equipment at DC stress is essential.In this paper,we reviewed the research methods and the characteristics of charge accumulation on spacers.A summary of charge measurement methods and setups are presented.And the surface charge inversion algorithms are introduced.Then the simulation model for charge accumulation in the DC field is reviewed.Subsequently,the charge accumulation mechanisms and phenomenon,the influence factor of surface charge accumulation and the influence of accumulated charge on spacer insulation characteristics are summarized.In addition,some suppression methods of surface charge accumulation are discussed.Finally,based on the understanding of charge accumulation on spacers,some suggestions on further studies are presented to aid in the design of a better spacer free from surface charges.