Simulation and Analysis of Cascading Faults in Integrated Heat and Electricity Systems Considering Degradation Characteristics

Cascading faults have been identified as the primary cause of multiple power outages in recent years.With the emergence of integrated energy systems(IES),the conventional approach to analyzing power grid cascading faults is no longer appropriate.A cascading fault analysis method considering multi-energy coupling characteristics is of vital importance.In this study,an innovative analysis method for cascading faults in integrated heat and electricity systems(IHES)is proposed.It considers the degradation characteristics of transmission and energy supply com-ponents in the system to address the impact of component aging on cascading faults.Firstly,degradation models for the current carrying capacity of transmission lines,the water carrying capacity and insulation performance of thermal pipelines,as well as the performance of energy supply equipment during aging,are developed.Secondly,a simulation process for cascading faults in the IHES is proposed.It utilizes an overload-dominated development model to predict the propagation path of cascading faults while also considering network islanding,electric-heating rescheduling,and load shedding.The propagation of cascading faults is reflected in the form of fault chains.Finally,the results of cascading faults under different aging levels are analyzed through numerical examples,thereby verifying the effectiveness and rationality of the proposed model and method.

Effects of Heat Stress during Seed Filling Stage on Brassica napus Seed Oil Accumulation and Chlorophyll Fluorescence Characteristics

As global temperature rise,the threat of heat stress to rapeseed production is becoming more obvious.Exploring the response characteristics of two important biological pathways,oil accumulation and photosynthesis,to heat stress during B.napus seed filling is helpful in the genetic improvement of heat-tolerant rapeseed.The effects of heat stress on seed oil accumulation and chlorophyll fluorescence characteristics of 29 B.napus germplasms with different oil content and environmental sensitivity,including 6 rapeseed varieties which exhibited environmentsensitive/insensitive and with high,medium or low oil content,were tested by whole plant heat stress or the in vitro silique culture system.Both assay exhibited similar trend on oil content of the rapeseed germplasms.The heat effect on the chlorophyll fluorescence kinetic parameters F_(v)/F_(m),ETR and Y(Ⅱ)were also consistent.Heat stress significantly decreased oil content,although there was abundant genetic variation on heat tolerance among the genotypes.Correlation analysis showed that the decrease rate of F_(v)/F_(m) of silique heat-stressed B.napus developing seed was positive correlative to the decrease rate of mature seed oil content of the whole plant heat-stressed rapeseed(R=0.9214,P-value<0.01).Overall,the results indicated that heat stress inhibited oil accumulation and photosynthesis in B.napus developing seed.The decrease rate of chlorophyll fluorescence parameter F_(v)/F_(m) of heat-stressed developing seed could be used as the index of heat tolerant rapeseed identification.Further,two heat insensitive rapeseed varieties with high oil content were identified.

Effects of Heat Treatment on Processing Characteristics of Pork

[Objectives]This study was conducted to explore the effects of heat treatment on processing characteristics of pork.[Methods]The effects of low-temperature long-term cooking(LTLT),high-temperature vacuum cooking,high-temperature cooking and high-temperature steaming on some indexes of pork products were studied,and principal component analysis was carried out.[Results]LTLT had significant effects on the total sensory score,moisture content,cooking loss rate,a value,shear force,and TBARS of pork,and the corresponding optimal product indicators were 71.40 points,72.36%,14.20%,4.79,7089.87 g,and 0.05 mg/kg,respectively.The microstructure changes in the LTLT group were relatively small,as the muscle fiber structure was relatively dense and uniform,and the gaps between muscle fibers were small.A total of 30 volatile flavor compounds were detected in the four groups,mainly alcohols,alkenes,alkanes,lipids,ketones,and aldehydes,and the LTLT group had more types and high contents.PCA analysis showed that the sensory evaluation,moisture content,elasticity,a value and LTLT were positively correlated with principal component 1.[Conclusions]Various indexes comprehensively showed that the LTLT group had better meat color,flavor,texture characteristics and lower oxidation degree than traditional cooking and steaming methods,which provides a theoretical reference for its large-scale application in the processing of prepared meat products.

Research on Load Characteristic of Electrothermal Film Heating Community

In this paper, a case study of an electrothermal film heating community in Tianjin is carried out, in which the winter load characteristic and electricity use law are analyzed. In this community, every household installs two watt-hour meters, one of which is only used to measure the electrothermal heating power, so the interference factors are eliminated. The main factors influencing the residents’ power consumption are summarized, and a method for estimating the thermal load of the residents is given. The conclusions can provide important reference to generalize the electric heating technology.

Effect of Coat Characteristics on Physiological Traits and Heat Tolerance of West African Dwarf Sheep in Southern Nigeria

This experiment was conducted to investigate the effect of coat characteristics on physiological traits and heat tolerance of dwarf sheep in southern Nigeria. A total number of twenty West African dwarf male sheep with an average weight of 9.00 ± 0.52 kg and aged 10 months old were used for the experiment. The dwarf sheep were assigned to four treatment groups in a completely randomized design with five sheep per treatment group. The compared treatment groups were TA (black coat colour sheep with low coat depth and short hair length), TB (black coat colour sheep with high coat depth and long hair length), TC (light brown coat colour sheep with low coat depth and short hair length) and TD (light brown coat colour sheep with high coat depth and long hair length). The results obtained in the study showed that midday was significantly (P 0.05) affected by morning, midday and evening. Rectal temperature (40.09℃), respiratory rate (21.01 breaths/min), pulse rate (87.49 beats/min), heat tolerance coefficient (97.10%), haemoglobin (9.04 g/l), blood cell (10.84 × 106/μl), white blood cell (12.06 × 106/μl) and glucose (50.10 mg/dl) were significantly (P 0.05) did not occur in total protein, albumin and globulin among treatment groups. It is concluded that coat characteristics have significant effects on physiological indices and heat tolerance in Nigeria.

Characteristics of urban heat island effect in Lhasa City

This paper analyzes the Urban Heat Island （UHI） effect in Lhasa City of Tibet using meteorological observations, the Normalized Difference Vegetation Index （NDVI）, Land Surface Temperature （LST） data obtained from Earth Observing System/Moderate resolution Imaging Spectroradiometer （EOS/MODIS） information, and correlation and composite analyses. The results show： （1） Areas with high temperature are primarily located in the center of the city or nearby counties, while low temperature areas are in the suburbs of counties. The area with high temperature has expanded in recent years and some high-temperature centers have even migrated to certain other regions. （2） The UHI intensity tends to be stronger both in annual and seasonal variations, especially in winter. Also, LST is somewhat positively related to mean air temperature. （3） A negative correlation exists between the changes of LST and NDVI with the increase of vegetation from urban to rural areas in different seasons. （4） The UHI intensity is negatively correlated with precipitation while positively correlated with wind speed, and the relation between the UHI intensity and evaporation varies with the seasons, namely, the intensity is positively correlated with summer evaporation but negatively corre- lated with winter evaporation. （5） UHI intensity might be enhanced by intensified urbanization, wherein built-up areas expand, there is increased heat from human activity, and there is more artificial heat input to the atmosphere.

Expression Characteristics of AaHsp90 Gene in Antheraea assamensis under Different Temperature and Starvation Stress

[Objectives]To investigate the effects of different temperature and starvation stress on the expression of AaHsp90 and reveal the molecular mechanism of adaptation to environment in Antheraea assama.[Methods]Taking the normal feeding group at 26℃as the control,the expression change of AaHsp90 was detected by real-time PCR in midgut,fat body and hemlymph after high temperature stress at 38℃,low temperature stress at 4℃and starvation stress separately for different time on the third day of the fifth larvae.[Results]The expression of AaHsp90 in midgut,fat body and hemlymph of Antheraea assama were increased obviously at first and then decreased sharply with the prolongation of treatment time at 38℃.There has a certain inhibitory effect on the expression of AaHsp90 in midgut,fat body and hemolymph after treatment with 4℃for different time.After treatment with starvation,the AaHsp90 expression were increased at 12 and 18 h and decreased sharply at 24 h in midgut,fat body and hemolymph of A.assama.[Conclusions]Comprehensive analysis showed that high temperature and starvation stress can induce the expression of AaHsp90,while low temperature stress mainly suppressed its expression.It was suggested that the AaHsp90 protein may play an important role in the process of adaptation to high temperature and starvation stress in A.assama.

Effects of drought and heat on the productivity and photosynthetic characteristics of alpine meadow plants on the Qinghai-Tibetan Plateau

Alpine meadow plants,adapted to humid and cold environments,are highly sensitive to environmental factors such as drought and heat.However,the physiological responses of individual alpine meadow species to drought and heat stress remain unclear.In this study,four representative species of typical functional groups in an alpine meadow of the Qinghai-Tibet Plateau were selected as experimental materials.Heat(H1,H2),drought(D1,D2),and combined stress(D1H1,D2H2)treatments were implemented to reveal the biomass and physiological characteristics’response to a constant drought and heat environment.Our results showed that the leaf water content(LWC)of Kobresia humilis and Poa annua increased significantly under heat stress and the compound stress(P<0.05).The effect of a single factor on LWC was greater than that of multiple factors.The aboveground biomass(AGB)of Oxytropis ochrocephala and Saussurea pulchra decreased significantly under compound stress(P<0.05).The response patterns of the net photosynthetic rate(Pn)and transpiration rate(Tr)of K.humilis and P.annua under various stress treatments were similar;as were those of O.ochrocephala and S.pulchra.The stomatal conductance(Gs)variation in K.humilis,P.annua,O.ochrocephala,and S.pulchra were the same under three kinds of stress treatments.The photosynthetic characteristics were more sensitive to the effects of composite than those of single factors.The drought×heat×species treatment had a significant influence on various indexes except on height(Ht)and the belowground biomass(BGB)(P<0.01).Within a certain range,daytime temperature(DT)promoted the Ht and increased the LWC of the plants,while it inhibited their AGB and intercellular CO2 concentration(Ci).The Pn,Tr,and Gs were more sensitive to soil moisture than to DT.The results help improve understanding of the physiological response regularity of representative alpine meadow plant species to continuous drought and high temperature conditions at the species level,and provided experimental data and theoretical basis to identify the decisive factors of stress response.

Numerical Simulation on Subcooled Boiling Heat Transfer Characteristics of Water-Cooled W/Cu Divertors

In order to realize safe and stable operation of a water-cooled W/Cu divertor under high heating condition,the exact knowledge of its subcooled boiling heat transfer characteristics under different design parameters is crucial.In this paper,subcooled boiling heat transfer in a water-cooled W/Cu divertor was numerically investigated based on computational fluid dynamic（CFD）.The boiling heat transfer was simulated based on the Euler homogeneous phase model,and local differences of liquid physical properties were considered under one-sided high heating conditions.The calculated wall temperature was in good agreement with experimental results,with the maximum error of 5%only.On this basis,the void fraction distribution,flow field and heat transfer coefficient（HTC）distribution were obtained.The effects of heat flux,inlet velocity and inlet temperature on temperature distribution and pressure drop of a water-cooled W/Cu divertor were also investigated.These results provide a valuable reference for the thermal-hydraulic design of a water-cooled W/Cu divertor.

Variation characteristics of aquifer parameters induced by groundwater source heat pump operation under variable flow

The variation characteristics of aquifer parameters,induced by groundwater source heat pump(GWSHP) operation under variable flow,were theoretically analyzed through a case study,in which the characteristics of building air conditioning load were considered.The results,compared with the constant flow operation,indicate that the influence on the variations of porosity,hydraulic conductivity and confined water head is decreased by 48%,51% and 71%,respectively,under variable flow operation.The security of variable flow operation is superior to that of constant flow.It is also concluded that the climate region and function of the buildings are primary factors which affect the suitability of variable flow operation in GWSHP.

Effects of heat treatment on dynamic compressive properties and energy absorption characteristics of open-cell aluminum alloy foams

The effects of heat treatment on the dynamic compressive properties and energy absorption characteristics of open cell aluminum alloy foams (Al-Mg-Si alloy foam and Al-Cu-Mg alloy foam) produced by infiltrating process were studied. Two kinds of heat treatment were exploited: age-hardening and solution heat treating plus age-hardening (T6). The split Hopkinson pressure bar (SHPB) was used for high strain rate compression test. The results show that both age-hardened and T6-strengthened foams exhibit improved compression strength and shortened plateau region compared with that of foams in as-fabricated state under high strain rate compression, and the energy absorption capacity is also influenced significantly by heat treatment. It is worthy to note that omitting the solution treating can also improve the strength and energy absorbed much.

Heat transfer characteristics of nanofluid through circular tube

Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experiment was conducted aiming at investigating the forced heat transfer characteristics of aqueous copper (Cu) nanofluid at varying concentration of Cu nano-particles in different flow regimes (300<Re≤16 000). The forced convective heat transfer enhancement is available both in the laminar and turbulent flow with increasing the concentration. Especially, the enhancement rate increases dramatically in laminar flow regime, for instance, the heat transfer coefficient of Cu/water nanofluid increases by two times at around Re=2 000 compared with that of base fluid water, and averagely increases by 62% at 1% volume fraction. However, the heat transfer coefficient of Cu/water decreases sharply in the transition flow regime. Furthermore, it has the trend that the heat transfer coefficient displays worse with increasing the concentration.

Change Characteristics and Influencing Factors of Urban Heat Island Effect Intensity in Heyuan City

According to the data in the past nine years in Heyuan urban district and its adjacent five counties,annual,seasonal and monthly change characteristics of heat island effect in Heyuan City and its meteorological influence factors were analyzed. The results showed that the intensity of heat island effect in central urban district and suburb of Heyuan City overall showed an upward trend from 2007 to 2015. From 2007 to 2012,heat island effect showed a slow weakening trend; from 2012 to 2013,heat island effect significantly enhanced and then weakened; after 2013,heat island effect significantly reduced. Heat island effect of Heyuan was the strongest in winter,followed by autumn,and it was the weakest in summer.The strongest heat island effect occurred in October,while the weakest occurred in July. According to the grey correlation analysis,the main factors affecting urban heat island effect of Heyuan were analyzed,and the order of each influence factor was as follows: average wind speed > relative humidity > rainfall > sunshine hours.

Experimental investigation of bioheat transfer characteristics induced by pulsed-laser irradiation

An experimental study of bioheat transfer characteristics induced bypulsed-laser irradiation was presented. The heat transfer characteristics of bio-materials, and theinfluences of pulse duration, power density, species of bio-materials, thickness and initialmoisture content of bio-materials on heat transfer were studied in details. The experimental resultsindicate that the penetration and absorption of laser in bio-materials are considerable, the heattransfer inside the bio-materials should include the effects of volumetric absorption, pulseduration, power density, bio-materials thickness, and material species have a significant influenceon the temperature variation.

Heat Transfer and Flow Characteristics of Water Flow with Air Injection in Polyethylene Tube Placed over Metal Rods: Influence of Pitch Length and Tube Width

A polyethylene tube can be used as a heat exchanger for a low-running-cost?temperature control system. In this system, the flow of temperature-controlled?water in the tube is used as the heat source, and the tube is placed on the ceiling of a temperature-controlled space using a metal net. Owing to this structure, the tube is deformed by its weight. This deformation has a significant influence on heat transfer and flow characteristics. Therefore, an air injection method, in which air and water are injected simultaneously into the tube, is developed for preventing the deformation of the tube. In this study, bedding metal rods were used instead of a metal net. The influence of the pitch length of the metal rods (5 - 15 cm) and the width of the polyethylene tube 15, 20, 25, 30, and 35 cm was examined experimentally. The length of the polyethylene tube was 178 cm. The air flow rate was 9.5 × 10-5 m3/s. The water flow rates were 60, 80, 100, 120, and 140 mL/min. Results show that the thermal response improved because of air injection. In particular, the temperature at steady state increased, and steady state was attained approximately 1.2 - 3 times faster with air injection than without air injection. The optimum pitch length of the metal rods and the range of the optimum width of the polyethylene tube were 8 cm and 20 - 25 cm, respectively, with and without air injection.

Influence of heat treatment regimes on microstructures and fracture characteristics of 7055Al alloy containing Ag

Tensile properties, fracture characteristics and microstructures of 7055 aluminum-based alloy containing Ag after T6, T73 and RRA treatment were investigated. The results show that RRA treatment retains strength of 7055-T6 with higher electrical conductivity close to that of 7055-T73 alloy, but its elongation decreases greatly. SEM fractographs reveal that intergranular cracking and shear-type transgranular cracking are both presented on the fracture appearance of 7055-T6 specimen. After T73 treatment, the fractographs mainly consist of dimple-type transgranular cracking with minor intergranular cracking. For 7055-RRA specimen, intergranular cracking dominates with minor dimples on the fracture surface. The type and size of precipitates, width of grain boundary and the ability of precipitates to impede dislocation motion vary with heat treatment regimes. Three frature models were built on the basis of microstructural analyses.

Effect of Heat Treatment on the Corrosion Characteristics of Al-Li Alloys

Experiments were conducted to study the general room temperature corrosion characteristics of heat-treated and non-heat-treated Al-Li alloys with different Li compositions. Corrosion rate was measured using both the polarisation method and the weight-loss method. It was observed that the samples with higher Li content had lower corrosion resistance than those with lower Li content. Moreover, for all the specimens tested, it was fOund that heat treatment at 180℃ for 2 h (for the purpose of precipitation hardening) severely reduced the corrosion resistance,whereas heat treatment at 180℃ for 6 h significantly increased the corrosion resistance.

Heat Transfer Characteristics and Pressure Drop in a Horizontal Circulating Fluidized Bed Evaporator

A vapor-liquid-solid horizontal circulating fluidized bed evaporation setup was constructed to study the thermal-exchange properties and pressure change.The influences of the operating variables,including the amount of added particles,heat flux,and circulating flow velocity,were systematically inspected using resistance temperature detectors and pressure sensors.The results showed that the heat transfer eff ect was improved with the increase in the amount of added particles,circulating flow velocity,and particle diameter,but decreased with increasing heat flux.The pressure drop fluctuated with the increase in operating parameters,except circulating flow velocity.The enhancing factor reached up to 71.5%.The enhancing fac-tor initially increased and then decreased with the increase in the amount of added particles and circulating flow velocity,fluctuated with increasing particle diameter,and decreased with increasing heat flux.Phase diagrams showing the variation ranges of the operation variables for the enhancing factor were constructed.

Visual Study on Flow and Operational Characteristics of Flat Plate Closed Loop Pulsating Heat Pipes

This paper presents an experimental study including visualization on a flat plate closed loop pulsating heat pipes.It consists of a total of 40 channels with square cross section(2 mm×2 mm,165 mm long) machined directly on an aluminum plate(180 mm×120 mm×3 mm) covered by a transparent plate.The working fluid employed is ethanol.As a result,various flow patterns and their transitions are observed and found to be related to the fluid fill ratio,input heat load and the device orientation.Also the operational characteristics and working mechanism are discussed.

Estimations of Land Surface Characteristic Parameters and Turbulent Heat Fluxes over the Tibetan Plateau Based on FY-4A/AGRI Data

Accurate estimates of land surface characteristic parameters and turbulent heat fluxes play an important role in the understanding of land-atmosphere interaction. In this study, Fengyun-4A (FY-4A) Advanced Geostationary Radiation Imager (AGRI) satellite data and the China Land Data Assimilation System (CLDAS) meteorological forcing dataset CLDAS-V2.0 were applied for the retrieval of broadband albedo, land surface temperature (LST), radiation flux components, and turbulent heat fluxes over the Tibetan Plateau (TP). The FY-4A/AGRI and CLDAS-V2.0 data from 12 March 2018 to 30 April 2018 were first used to estimate the hourly turbulent heat fluxes over the TP. The time series data of in-situ measurements from the Tibetan Observation and Research Platform were divided into two halves-one for developing retrieval algorithms for broadband albedo and LST based on FY-4A, and the other for the cross validation. Results show the root-mean-square errors (RMSEs) of the FY-4A retrieved broadband albedo and LST were 0.0309 and 3.85 K, respectively, which verifies the applicability of the retrieval method. The RMSEs of the downwelling/upwelling shortwave radiation flux and downwelling/upwelling longwave radiation flux were 138.87/32.78 W m^(−2) and 51.55/17.92 W m^(−2), respectively, and the RMSEs of net radiation flux, sensible heat flux, and latent heat flux were 58.88 W m^(−2), 82.56 W m^(−2) and 72.46 W m^(−2), respectively. The spatial distributions and diurnal variations of LST and turbulent heat fluxes were further analyzed in detail.