Analysis of the Thermal Performance of External Insulation in Prefabricated Buildings Using Computational Fluid Dynamics

This paper investigates the thermal performance of prefabricated exterior walls using the Computational Fluid Dynamics method to reduce energy consumption.The thermal performance of the prefabricated exterior wall was numerically simulated using the software ANSYS Fluent.The composite wall containing the cavity is taken as the research object in this paper after analysis.The simulation suggests that when the cavity thickness is 20 mm and 30 mm,the heat transfer coefficient of the air-sandwich wall is 1.3 and 1.29,respectively.Therefore,the optimal width of the cavity is 20 mm,and the most suitable material is the aerated concrete block.In addition,a comparative analysis is conducted on the cavity temperature in the wall under different conditions.It is proven that an intelligent environment control system can significantly improve thermal efficiency and provide a solid theoretical basis for further research in the external insulation of prefabricated buildings.

Using Image Processing Technology and General Fluid Mechanics Principles to Model Smoke Diffusion in Forest Fires

In the present study,the laws of smoke diffusion during forest fires are determined using the general principles of fluid mechanics and dedicated data obtained experimentally using an“ad hoc”imaging technology.Experimental images mimicking smoke in a real scenario are used to extract some“statistics”.These in turn are used to obtain the“divergence”of the flow(this fluid-dynamic parameter describing the amount of air that converges to a certain place from the surroundings or vice versa).The results show that the divergence of the smoke depends on the outside airflow and finally tends to zero as time passes.Most remarkably,compared with clouds and fog,smoke has a unique dynamic time-evolution curve.The present study demonstrates that as long as image processing technology and intelligent monitoring technology are used to monitor the gas flow in a forest,the occurrence of forest fires can be quickly diagnosed.

Methane and nitrous oxide emissions in rice-crab culture systems of northeast China

Rice-crab integrated ecosystem has been confirmed to improve the ecological environment and brought greater economic benefits.In order to know greenhouse gases methane(CH_(4))and nitrous oxide(N_(2)O)emissions in ricecrab system,they were quantified from a flooding rice field in northeast China,as affected by integrated ricecrab cultivation.Three treatments with three replications each were given:(1)RC1-rice with crab(megalopa),(2)RC2-rice with crab(juvenile),(3)RM-rice only.Seasonal CH_(4) and N_(2)O fluxes were measured by closed chamber method.Compared with RM treatment,RC1 and RC2 treatments greatly enhanced the cumulative seasonal CH_(4) emissions(by 36.8%and 29.2%,respectively),and reduced the cumulative seasonal N_(2)O emissions(by 28.2%and 19.7%,respectively).Across treatments,CH_(4) represented over 97%of total global warming potential(GWP)and as a result,RC1 and RC2 treatments significantly increased the GWP than RM treatment.Although the GWP was highest in RC1 treatment,it provided highest rice yield(8780 kg/ha)and net ecosystem economic budget(NEEB,23,159 Yuan/ha)over RM(7668 kg/ha,15,130 Yuan/ha)and RC2(8042 kg/ha,18,713 Yuan/ha)treatments.To summarize,cultivation of megalopa in rice field is a better strategy to optimize the economic and environmental benefits in northeast China.

A novel power-on-reset circuit for passive UHF RFID tag chip

A novel power-on-reset(POR) circuit with simple architecture, small values of capacitances, ultralower power consumption, and self-adjustable delay time of reset pulse for passive UHF RFID tags is presented in this paper. A proposed delay element was adopted for the features of small capacitances and wide power supply rise time range. An inverter was used as a two-inputs logic device to simplify the architecture of the circuit. The technology used for design and simulation is SMIC 0.18 μm RF. Simulation results show that the circuit functions well under different process corners with different power supply rise time, and is able to generate a POR signal after the power supply is briefly powered off. The static power consumption is less than 30 pA. Moreover, the circuit operates properly along with other modules of analog front-end.

Current research status of tumor cell biomarker detection

With the annual increases in the morbidity and mortality rates of tumors,the use of biomarkers for early diagnosis and real-time monitoring of tumor cells is of great importance.Biomarkers used for tumor cell detection in body fluids include circulating tumor cells,nucleic acids,protein markers,and extracellular vesicles.Among them,circulating tumor cells,circulating tumor DNA,and exosomes have high potential for the prediction,diagnosis,and prognosis of tumor diseases due to the large amount of valuable information on tumor characteristics and evolution;in addition,in situ monitoring of telomerase and miRNA in living cells has been the topic of extensive research to understand tumor development in real time.Various techniques,such as enzyme-linked immunosorbent assays,immunoblotting,and mass spectrometry,have been widely used for the detection of these markers.Among them,the detection of tumor cell markers in body fluids based on electrochemical biosensors and fluorescence signal analysis is highly preferred because of its high sensitivity,rapid detection and portable operation.Herein,we summarize recent research progress in the detection of tumor cell biomarkers in body fluids using electrochemical and fluorescence biosensors,outline the current research status of in situ fluorescence monitoring and the analysis of tumor markers in living cells,and discuss the technical challenges for their practical clinical application to provide a reference for the development of new tumor marker detection methods.

Nitrogen uptake strategies of mature conifers in Northeastern China, illustrated by the ^(15)N natural abundance method

Background:Conifers partition different N forms from soil,including ammonium,nitrate,and dissolved organic N(DON),to sustain plant growth.Previous studies focused on inorganic N sources and specific amino acid forms using ^(15)N labelling,but knowledge of the contribution of DON to mature conifers’N uptake is still scarce.Here,we quantified the contribution of different N forms(DON vs.NH_(4)^(+)vs.NO_(3)^(−))to total N uptake,based on ^(15)N natural abundance of plant and soil available N,in four mature conifers(Pinus koraiensis,Pinus sylvestris,Picea koraiensis,and Larix olgensis).Results:DON contributed 31%,29%,28%,and 24%to total N uptake by Larix olgensis,Picea koraiensis,Pinus koraiensis,and Pinus sylvestris,respectively,whereas nitrate contributed 42 to 52%and ammonium contributed 19 to 29%of total N uptake for these four coniferous species.Conclusions:Our results suggested that all four conifers could take up a relatively large proportion of nitrate,while DON was also an important N source for the four conifers.Given that DON was the dominant N form in study soil,such uptake pattern of conifers could be an adaptive strategy for plants to compete for the limited available N sources from soil so as to promote conifer growth and maintain species coexistence.

Trajectories in nitrogen availability during forest secondary succession:illustrated by foliarδ^(15)N

Background:Forest succession is an important ecological process and has been studied for more than a century.However,changes in nitrogen(N)availability during succession remain unclear as they may lead to either N satura-tion or N limitation.Here,we propose a conceptual model to illustrate changes in N availability during four stages of secondary succession using the natural abundance of ^(15) N in plant leaves(foliarδ^(15)N).We predicted that N availability would decline in the early stages of succession and then increase in late stages,coinciding with the changes in foliarδ^(15)N,with the inflection point varying in different climate zones.Data on foliarδ^(15)N from 16 succession sequences were synthesized to explore changes in N availability during forest succession.Results:The compiled data were consistent with the proposed conceptual model.Foliarδ^(15)N in boreal and temperate forests decreased significantly in the first two stages of succession(estimated to last at least 66 years in temperate forests),at a rate of 0.18‰and 0.38‰per decade,respectively,and decreased slightly in tropical forests in the first 23 years.Foliarδ^(15)N is projected to increase in later stages in all forests,which is supported by observations in both temperate and tropical forests.The inflection points of N availability when N limitation peaked during succession were different in different climate zones,implying different ecosystem N turnovers.Conclusions:Our study reconciles the controversies regarding changes in N availability during forest secondary succession.Our findings are also useful for predicting the recovery of N and carbon accumulation during succession.Nonetheless,studies on forest secondary succession using foliarδ^(15)N have thus far been limited,and more research should be conducted to further verify the conceptual model proposed here.