栎类林对火的适应和响应研究进展

近年来,由于人类活动的影响,加之极端天气常现,森林火灾呈现持续多发且频发的趋势,火格局(发生季节、频率、强度等)也发生相应改变。尽管栎类林出现了各种不同频率和强度的火灾,但大多数栎类已经进化出能够在周期性火灾中生存的能力。需要明确栎类对森林火灾的响应,进而揭示栎类对火的适应性策略。本文从栎类林特征、燃烧性、栎类植物自然更新以及个体和种群对火干扰的适应与响应等方面入手,论述了栎类林对火的适应与响应,对其现存研究问题进行了分析,并对未来的研究方向进行了展望。研究结果能够为生态恢复树种选择、防火树种筛选、生物防火林带营建等提供科学依据,有利于我国栎类的适地适树造林和管护,特别有利于火灾频发多发区域选择抗火性强的栎类树种;有利于对栎类的分类经营和管理,提高生产力;有利于栎类的高效综合利用,发挥生态、经济和社会效益。

The Model of Thermal Response of Liquefied Petroleum Gas Tanks Partially Exposed to Jet Fire

This paper describes a mathematical model developed to study the behavior of liquefied petroleum gas (LPG) tanks when subjected to jet fire. The model consists of a number of field and zone sub-models which are used to simulate the various physical phenomena taking place during the tank engulfment period. The model can be used to predict the pressure and temperature of the LPG in the tank, the temperature of the wall of tank, and the time of tank explosion. The comparisons between the model predicted results and the test data show good agreement. The results show that the jet fire partially impinging on tank wall led to higher wall temperature and the time to failure was shorter than that in engulfing pool fire. And the exposure of the upper wall in the vapor zone to the fire is more dangerous than that of the LPG contacted wall.

Removal of AlN from secondary aluminum dross by pyrometallurgical treatment

A new process of AlN removal from secondary aluminum dross(SAD)by pyrometallurgical treatment with added cryolite was applied for solving the problem of recycling the secondary aluminum dross.The response surface methodology(RSM)was used to design experiments and optimize parameters.The results show that adding the appropriate amount of cryolite can effectively promote the oxidation of AlN in the SAD,and too much cryolite will reduce the promotion effect.The effects of roasting temperature and cryolite on the denitrification rate are the most significant(p<0.0001)followed by holding time.Predicted values of the denitrification rate are found to be in good agreement with experimental values(R^(2)=0.9894 and R_(adj)^(2)=0.9775),which confirms the validity of the model employed.The optimum conditions of roasting temperature of 750°C,holding time of 194 min,mass fraction of cryolite of 17.7%are obtained according to the quadratic model.Under these conditions,the maximum actual denitrification rate reaches 94.71%and the AlN content in the SAD is only 0.55 wt%.The unfired brick with compressive strength of 18.62 MPa(GB/T 2542−2012)was prepared based on the roasted SAD.

Optimization of electrical discharge machining process parameters for Al6061/cenosphere composite using grey-based hybrid approach

Fly ash has congregated considerable attention as a potential reinforcement for aluminum matrix composites(AMCs)to enhance selective properties and reduce the cost of fabrication.However,poor machinability of such AMCs limits their application.The present study focuses on the preparation of cenosphere fly ash reinforced Al6061alloys by compo casting method.X-ray diffraction analysis of the prepared AMCs exposes the presence of cenosphere particles without any formation of other intermetallic compounds.In this study,electrical discharge machining(EDM)was engaged to examine the machinability of the prepared metal matrix composite(MMCs).The measured performance characteristics for the various combinations of input process parameters were considered to be MRR,EWR and SR.Face centered central composite design(CCD)of response surface method(RSM)was employed to design the number of experimental trials required and a hybrid approach of grey-based response surface methodology(GRSM)was imposed for predicting the optimal combination of processing parameter in EDM process.Generous improvement was observed in the performance characteristics obtained by employing both the optimal setting of machining parameters.The optical3D surface profile graphs of the ED machined surface also revealed the improvement in surface quality and texture employing the optimal processing conditions proposed by hybrid GRSM approach.

Sedimentary response to volcanic activity in the Okinawa Trough since the last deglaciation

To investigate the relationship between volcanic activity and sediment record on regional and temporal scales,158 surface sediment samples were collected from the East China Sea Shelf to the northern Okinawa Trough (OT),and two cores recovered in the northern and southern OT,respectively.Mineralogy,grain-size,and geochemical analyses of those samples show that:1) volcanic glass,volcanic-type pyroxene,hypersthenes,and magnetite increase in sediment influenced by volcanic activity;2) sediment grain sizes (and also silt content) increase in ash layers;and 3) the contents of Na2O and Zr are higher,while terrigenous elements,e.g.,TFe2O3 and K2O,and biogenous compositions,e.g.,CaO and Sr,are relatively lower in ash layers than those of non-ash layers.The distribution of volcanic ash has three distinguishing characteristics:1) volcanic ash is more abundant in the northern and central OT than the southern OT;2) volcanic ash increases from continental shelf to the trough;3) the sediment during the last 12 000 a suggests stronger volcanic events than during 15 000-12 000 a.The eruptive locations,frequency,and volume of calderas are among the most important factors controlling the distributions of volcanic ash.In addition,the main Kuroshio warm current that extends northward probably impeded the diffusion of volcanic ash to the west and south in the OT.However,a southward current probably carried some volcanic ash toward southern OT.

Solution of false alarm and slow response in flame detector

A new flame detector with one ultraviolet and two infrared detectors is designed. The ultraviolet detector is of rapid response(≤10 μs) while the two infrared detectors usually have a response time of more than 5 ms. The ultraviolet detector is applied to deal with the flame of large scales. When facing the flame of mid or small scales, the three detectors cooperate. Employing the high-order derivatives of the sample data of the infrared circuits to improve the sensitivity, the response speed is greatly improved. The data of the temperature sensor is used to adjust circuit parameters in real time, thus reducing the effect of temperature drift. The flame detectors are tested at different distances and the response time is as rapid as 0.65 ms. The test results show that the new flame detector has the characteristics of high speed and a low rate of false alarms.

A Study on Modelling Surface Finish in Electrical Discharge Machining Tablet Shape Punches Using Response Surface Methodology

This paper introduces a study on modelling surface finish in EDM （Electrical Discharge Machining） of tablet shape punches when using copper as electrode material. In this study, 27 experiments were performed based on BBD （Box-Behnken Design） and the work-piece material was 9CrSi steel. The input process parameters were the current, the pulse on time, the pulse off time and the voltage. The effects of the input parameters on the surface finish were evaluated by analysing variance. Besides, from the results of the experiments, a regression equation for determining the surface roughness is introduced. Also, the optimum input parameter values were found in order to get the minimum surface roughness.

The Fire Danger Rating Index ＂FMA＂ as Control of Remote Sensoring System

Recent remote monitoring surveys of smoke produced by burning and forest fires using weather radar equipment showed excellent preliminary results, but their progress is hindered due to the high operating cost of radar systems. The fire danger rating index is a good indicator of the event occurrence probability, what contributes to the monitoring areas and adds value to the alert degree information. The application of FMA fire danger index ＂Formula de Monte Alegre＂ for areas in radar coverage radius of the S-band weather radar operated by the Meteorological Research Institute, IPMet, S^fo Paulo State University, efficiently optimize the use of the radar equipment, significantly reduce operational costs, enable new research and promise results which have already reduced the average response time between ignition and detection for less than 5 minutes. It reduces more than 50% response time considered optimal for conventional detection systems. Thus, the ＂FMA＂ values act as a trigger （on-off） in the remote monitoring system of forest fires, optimizing its use at low cost, avoiding the possible stress of equipment and enabling the advance of research monitoring, detection of burnings and forest fires using weather radar.