Determination of Chromium and Zinc in Soil by Microwave Digestion and Flame Atomic Absorption Spectrometry

[Objective] The aim was to develop a rapid, simple method for determination of chromium and zinc in soil samples by flame atomic absorption spectrometry.[Method] The method for determination of Cr and Zn in soil by combined flame atomic absorption spectrometry and microwave digestion was used. [Result] The concentration curve was linear within the range of 0-0.8 mg/L for Cr and 0-0.8 mg/L for Zn, the detection limits of Cr and Zn was 0.0025 mg/L and 0.002 3 mg/L, respectively. Recoveries of 102.4%-103.2% for Cr and 97.7%-98.3% for Zn were obtained for there soil samples. [Conclusion] The proposed method has the advantages of simple operation, high sensitivity, and high efficiency; it was successfully used for determination of Cr and Zn in soil samples.

Determination of Mg Content in Crayfishby Microwave Digestion-Flame Atomic Absorption Spectrometry

[Objective] This study was conducted to investigate the Mg level in cray- fish. [Method] Microwave digestion was applied to treat crayfish sample, Mg content in which was then determined by flame atomic absorption spectrometry, and recov- ery test and the determination of standards were also performed. [Result] This method was used for the detection of Mg in crayfish, obtaining satisfactory effect. The sample recoveries were in the range of 90.0%-110%, and the detection limit was 0.8 mg/kg. [Conclusion] The method is rapid, simple, accurate and reliable, worth extending.

抽油机自锁式可解卡刹车保险装置

抽油机刹车保险装置的保险爪放入卡槽后会出现2种异常情况:卡死在槽中或因受到冲击而从卡槽中弹出,安全性、可靠性不尽如人意。现在设计、制造了可解卡刹车保险装置,在一定程度上提高了刹车保险的安全性和可靠性,而且操作简便。

TVD SCHEME WITH CHEMICAL REACTION FLOW AND ITS APPLICATION IN COMBUSTION GAS JETTING FLOW

By conjugating features of combustion gas jetting flows of the solid-rocket and using mathematical methods, a numerical scheme is systematically derived based on Harten′s standard TVD scheme, which fits for the flow with high temperature, pressure and velocity. The rational calculation formula of pressure partial derivation is also given out. By using the chemical kinetics knowledge, problems of multi-component and finite rate chemical reaction contained in combustion gas of the rocket flow field are discussed. The method for solving the mass source term of chemical reaction is clarified. Taking 9 reaction equations with 12 components as an example and utilizing the established calculation program, the free jetting flow field of the rocket is simulated. Numerical results show the correctness of the numerical scheme.

Regional metallogenic structure based on aeromagnetic data in northern Chile

Chile is a very important country that forms part of the Andean metallogenic belts. The Atacama and Domeyko fault systems in northern Chile control the tectonic- magmatic activities that migrate eastward and the types of mineral resources. In this paper, we processed and interpreted aeromagnetic data from northern Chile using reduction to pole, upward field continuation, the second derivative calculation in the vertical direction, inclination angle calculation, and analytical signal amplitude analysis. We revealed the locations and planar distribution characteristics of the regional deep faults along the NNE and NS directions. Furthermore, we observed that the major reasons for the formation of the tectonic-magmatic rocks belts were the nearly parallel deep faults distributed from west to east and multiple magmatic activities along these faults. We ascertained the locations of volcanic mechanisms and the relationships between them using these regional deep faults. We deduced the spatial distributions of the basic-intermediate, basic, and acidic igneous rocks, intrusive rocks, and sedimentary sequences. We showed the linear positive magnetic anomalies and magnetic anomaly gradient zones by slowly varying the background, negative magnetic anomaly field, which indicated the presence of strong magmatic activities in these regional deep faults; it also revealed the favorable areas of copper and polymetallic mineralization. This study provides some basic information for further research on the geology, structural characteristics, and mineral resource prospecting in northern Chile.

狐惑病验案举隅

狐惑病作为一类病因不明的炎症性疾病,其治疗一直被视为医学上的难题。本文针对辨证颇难,症状繁杂的狐惑病,提出以甘草泻心汤为主方,滋阴降火为原则治疗阴虚火旺型狐惑病,辅以疏肝解郁,养血健脾,临床疗效确切。

Ethanol sensing properties of Bi_(3.15)Nd_(0.85)Ti_3O_(12) films at low operating temperatures

Bi3.15Nd0.85Ti3O12 (BNdT) films were deposited on Pt/Ti/SiO2/Si(100) substrates by a metal organic decomposition (MOD)method, and annealed by a rapid thermal annealing process in oxygen atmosphere and in air, respectively. The crystalline structuresand morphologies of BNdT films were characterized by X-ray diffraction and field-emission scanning electron microscopy, and thegas sensing properties were measured by monitoring its resistance at different gas concentrations. The results indicate that the BNdTfilms annealed in air are of porous microstructure and rough surface, and the annealing atmosphere has great influence on gas sensingproperties. At an operating temperature of 100 °C, the BNdT films annealed in air are of high response value to 1×10?6 gaseousethanol, and the detecting limit is as low as 0.1×10?6. The corresponding response and recovery time is about 10 and 6 s, respectively.The results can offer useful guidelines for fabricating high performance ethanol sensors.

Combustion characteristics of semicokes derived from pyrolysis of low rank bituminous coal

Various semicokes were obtained from medium-low temperature pyrolysis of Dongrong long flame coal.The proximate analysis,calorific value and Hardgrove grindability index(HGI) of semicokes were determined,and the ignition temperature,burnout temperature,ignition index,burnout index,burnout ratio,combustion characteristic index of semicokes were measured and analyzed using thermogravimetry analysis(TGA).The effects of pyrolysis temperature,heating rate,and pyrolysis time on yield,composition and calorific value of long flame coal derived semicokes were investigated,especially the influence of pyrolysis temperature on combustion characteristics and grindability of the semicokes was studied combined with X-ray diffraction(XRD) analysis of semicokes.The results show that the volatile content,ash content and calorific value of semicokes pyrolyzed at all process parameters studied meet the technical specifications of the pulverized coal-fired furnaces(PCFF) referring to China Standards GB/T 7562-1998.The pyrolysis temperature is the most influential factor among pyrolysis process parameters.As pyrolysis temperature increases,the yield,ignition index,combustion reactivity and burnout index of semicokes show a decreasing tend,but the ash content increases.In the range of 400 and 450 °C,the grindability of semicokes is rational,especially the grindability of semicokes pyrolyzed at 450 °C is suitable.Except for the decrease of volatile content and increase of ash content,the decrease of combustion performance of semicokes pyrolyzed at higher temperature should be attributed to the improvement of the degree of structural ordering and the increase of aromaticity and average crystallite size of char.It is concluded that the semicokes pyrolyzed at the temperature of 450 °C is the proper fuel for PCFF.

Experimental Study of Kinetic Properties of Pyrolysis for Conveyor Belt in Coal Mine

The combustion of conveyor belt is a leading factor of mine fire. In this paper, the pyrolysis properties of ordinary conveyor belt and fire-resistant belt were studied experimentally with thermo-gravimetric analysis and derivative thermo-gravimetric analysis, and the curves of pyrolysis properties were achieved. On this basis, the activation energy and reaction order of pyrolysis were obtained in combination with theoretical analysis, aiming to provide data for further numerical simulation and simulating experiment of mine fire.

Dielectric and Thermal Analysis of a Shrub Leaf for the Modeling of Forest Fire

Most Mediterranean regions face a high risk to forest fires, estimation and anticipation of this risk modeled as a stochastic propagation process reproduces well some fire properties. This model needs information on the behavior of the bio-physical properties of vegetation associated to combustion. An experimental study to analyze the structure of a leaf of Laurel shrub at different biological stages is presented; it allows following the structural exchanges induced on the leaf by the effect of increasing temperature. For this purpose, both dielectric and TGA （Thermogravimetric Analysis）/DTA （Differentialthermal Analysis） was performed to a better understanding of the pyrolysis phenomenon. The results obtained provide information on the process of thermal degradation caused by fire. The evolution of the leaf impedance as a function of the applied frequency characterizes the moisture loss in plant species during pyrolysis. The dielectric response confirms the proposition to the equivalent circuit of the leaf as a composite of liquid and solid parts. The TGA/DTA results detected the behaviour of the solid parts in the fire under a constant heating rate, and were able to show all the transformation subjected by the Laurel leaf until ignition and all the gases released during it.

Sources of dissolved inorganic carbon in rivers from the Changbaishan area, an active volcanic zone in North Eastern China

Major elements and carbon isotopes of dissolved inorganic carbon(DIC)have been measured in the waters of Changbaishan mountain,a volcanic area in northeastern China,between June and September 2016 to decipher the origin of the CO_2 involved in chemical weathering reactions.Spatial variations of major elements ratios measured in water samples can be explained by a change of the chemical composition of the volcanic rocks between the volcanic cone(trachytes)and the basaltic shield as evidenced by the variations in the composition of these rocks.Hence,DIC results from the neutralization of CO_2 by silicate rocks.DIC concentrations vary from 0.3 to 2.5 mmol/L and carbon isotopic compositions of DIC measured in rivers vary from-14.2‰to 3.5‰.At a first order,the DIC transported by rivers is derived from the chemical weathering’s consumption of CO_2 with a magmatic origin,enriched in^(13)C(-5%)and biogenic soil CO_2 with lower isotopic compositions.The highest δ^(13)C values likely result from C isotopes fractionation during CO_2 degassing in rivers.A mass balance based on carbon isotopes suggest that the contribution of magmatic CO_2 varied from less than 20%to more than 70%.Uncertainties in this calculation associated with CO_2 degassing in rivers are difficult to quantify,and the consequence of CO_2 degassing would be an overestimation of the contribution of DIC derived from the neutralization of magmatic CO_2 by silicate rocks.

Study on Technology for Quenching Catalytic Pyrolysis Gas

This article describes the application of technology for quenching catalytic pyrolysis gas at the Daqing commercial CPP test unit and the Shenyang commercial CPP production unit.On the basis of results for application of the Shenyang CPP unit this paper puts forward an improved process flow scheme for quenching the pyrolysis gas and made calculations using the process flowsheet software.Case Ⅰ of the process flow scheme,which is designed for full circulation of slurry,intends to use the pyrolysis light oil and fresh feed oil as the quenching media with the product slurry oil and fresh feedstock being discharged from the quench cooler bottom and routed directly to the reactor so that the fresh feed oil can be preheated prior to pyrolysis.Case Ⅱ of the process flow scheme intends to adopt recycle oil as the quenching medium with the product slurry and recycle oil being discharged from the quench cooler bottom to the fractionator,which then delivers the slurry from the bottom.These two cases for improving the process flow diagram can all effectively control the density and viscosity of the quenching medium to secure the smooth operation of quench cooler.

Study on the crustal stress fi eld of the Tengchong volcanic area using composite focal mechanism method

We calculated the crustal stress field using the composite focal mechanism method based on the P-wave initial motion polarity data of the Tengchong volcanic area from January 2011 to April 2019 obtained from the Bulletin of Seismological Observations of Chinese stations.The magnitude range of earthquakes used in this study is 0–4,and their magnitudes are mainly approximately 1.0.To investigate the infl uence of the source location on the stress fi eld and obtain reliable stress fi elds of the study area,we applied the double-diff erence algorithm to relocate the seismic events,obtaining more accurate and reliable relative positions of seismic events with a clearer seismic belt.On the basis of relocation results,the study on the stress fi eld along the fault zone was conducted,and the infl uence of seismic event position on the stress fi eld was analyzed.Results show that,fi rst,the current stress regime in the shallow crust of the Tengchong volcanic area is strike-slip faulting,the orientation of the principal compressive stress axis is NE–SW,the orientation of the principal extension stress axis is SE–NW,the principal compressive and extension stress axes are nearly horizontal,and the dip angle of intermediate principal stress axis is relatively large.This reflects that the volcanic and seismic activities in the Tengchong volcanic area are mainly controlled by the collision and squeezing eff ect of the Indian–Eurasian plate.It also refl ects that the current tensile action caused by deep magma activity has little infl uence on the shallow crustal stress field.Second,the stress field along fault zones reveals that there exist local stress fi elds,such as the thrust stress regime at the strike-slip fault terminal area,which is consistent with the compressional area at the intersection of conjugate strike-slip faults indicated by previous study.Third,the stress fi eld results are consistent,regardless of using the original location in the bulletin or the relocated location,indicating that the infl uence of the event location error can be neglected when there are suffi cient data and refl ecting the stability of the composite focal mechanism method.The findings can serve as a reference for investigating geological structure movement,seismic activities,and volcanic activities in the Tengchong volcanic area.

Surface Fires： No Wind, No Slope, Marginal Burning

The first aim of this work is to provide an analytical expression to calculate the rate of spread of surface fires under no wind and no slope conditions. A previous simplified model was improved for this particular case of fire propagation. The test of this proposed model was performed by using two complete sets of experimental results with several fuel beds and variable parameters such as moisture content or bulk density. The second aim of this article is to highlight two conditions that allow stopping a fire： the low leaf area and the high value of the moisture content.

Effect of PLA/ZnO Packaging and Gamma Radiation on the Content of Listeria innocua, Escherichia coil and Salmonella enterica on Ham during Storage at 4℃

The effect of ZnO and low y-radiation on PLA based-films was investigated to be used for food packaging application. Ham slices were inoculated with E. coli, L. innocua and S. enterica and then covered with PLA and PLA/5% ZnO films. The samples were irradiated with a y-radiation dose of 0.3 kGy at dose rate of 13.5 kGy/h. Microbiological analysis was performed at 0, 1 and 5 days on samples stored at 4 ℃. Results showed that no consistent reduction of bacteria was obtained, even at the fifth day of storage, when the ham was covered with PLA/5% ZnO film and no γ-radiation was performed. The use of γ-radiation results necessary to reduce the bacteria growth. In fact E. coli and S. enterica were not detected after 5 days of storage; whereas in the case of test with L. innocua a reduction of 1.3 log CFU/g was observed after 5 days of storage. The antibacterial results indicate that the presence of ZnO in PLA film is effective only for E. coll. The differences of the results obtained here with those reported in literature （where ZnO particles are reported to be very effective as antimicrobial material） are accounted for the different methodologies used. In conclusion considering the positive results, even if small, obtained here at least only for the E. Coli and considering that PLA/5% ZnO film shows, compared to plain PLA film, good tensile properties （especially Young＇s modulus and stress at yielding） and good permeability （to O2 and CO2） induce to consider the PLA/5% ZnO composite film usable for food packaging when long shelf life and food safety are required, considering also that it is biodegradable and compostable.

清热解感方联合祛火散穴位贴敷治疗小儿疱疹性咽峡炎风热乘脾型32例临床观察

目的观察清热解感方联合祛火散穴位贴敷治疗小儿疱疹性咽峡炎风热乘脾型的临床疗效。方法选取2020年6月至2021年10月于福州市中医院儿科治疗的64例疱疹性咽峡炎风热乘脾型患儿,按照随机数字表法分为对照组和治疗组,各32例。对照组予四季抗病毒合剂口服,治疗组予中药口服联合穴位贴敷治疗,2组均连续治疗5 d后统计疗效。结果治疗组的总有效率为93.75%(30/32),明显高于对照组的84.38%(27/32),2组比较,差异有统计学意义(P<0.05)。治疗组服用退热药的次数明显少于对照组,且治疗组热退时间及疱疹消失时间均明显短于对照组,2组比较,差异均有统计学意义(P<0.05或P<0.01)。结论清热解感方联合祛火散穴位贴敷治疗小儿疱疹性咽峡炎风热乘脾型,不仅疗效显著,且可减少服用退热药次数,明显缩短热退及疱疹消失时间,值得临床推广应用。

夏季多吃四类菜

夏日气候酷热潮湿，各种疾病易乘虚而入，多吃下列四类蔬菜，对人体健康大有好处。

Entire solution in an ignition nonlocal dispersal equation:Asymmetric kernel

This paper mainly focuses on the front-like entire solution of a classical nonlocal dispersal equation with ignition nonlinearity. Especially, the dispersal kernel function J may not be symmetric here. The asymmetry of J has a great influence on the profile of the traveling waves and the sign of the wave speeds, which further makes the properties of the entire solution more diverse. We first investigate the asymptotic behavior of the traveling wave solutions since it plays an essential role in obtaining the front-like entire solution. Due to the impact of f′(0) = 0, we can no longer use the common method which mainly depends on Ikehara theorem and bilateral Laplace transform to study the asymptotic rates of the nondecreasing traveling wave and the nonincreasing one tending to 0, respectively, so we adopt another method to investigate them. Afterwards, we establish a new entire solution and obtain its qualitative properties by constructing proper supersolution and subsolution and by classifying the sign and size of the wave speeds.

The influence of abiotic and spatial variables on woody and herbaceous species abundances in a woodland-grassland system in the Eastern Terai of India

The environmental factors that influence tree-grass abundances in tropical savanna and grasslands are not well understood,particularly for woodland-grassland mosaics in humid zones.We studied the effects of abiotic and spatial variables on woody and herbaceous species distributions in a Terai ecosystem of northeastern India.We evaluated the importance of climatic and non-climatic factors that maintain variable tree-grass ratios across the landscape,and also accounted for spatial connectivity and dispersal.We measured species abundances of woody and herbaceous plant species in 134 plots with each 30 m×30 m in a 519 km^(2)protected Terai habitat,and derived several climatic and non-climatic environmental factors.We constructed variables based on different models of spatial connectivity among sites,to test their influence on species abundances.We then used redundancy analyses and variation partitioning to quantify the importance of environmental variables and spatial structure on variation in tree-grass abundances.We found that environmental variables including rainfall,fire,water stress,topography and soil nutrients had statistically significant effects on species abundance and tree-grass ratios.Spatial structure was significant,and the best spatial model was an inverse distance-weighted model with linkage extending to 23.5 km,indicating weak dispersal limitation.About 21%of the variation in species abundance was explained by the selected environmental and spatial factors.The results indicate that dynamic plant communities in which spatial-temporal variation in environmental factors may drive stochasticity in species distribution and abundance,thus dominantly influencing on the vegetation mosaic.

BLOW-UP OF SOLUTIONS OF THE IGNITION MODEL

By use of maximum principle and auxiliary function method,the paper discusses the blow-up sets of the solutions of the ignition model in two cases,It is obtained that the solutions blow up in single point in nonsymmetric case and that the solutions blow up totally or at a couple of points in symmetric case.