In order to evaluate thermal hazards of aromatic dinitro compoullds,thermal decompositions of dinitrobenzene(DNB)and dillitrotoluene(DNT)isomers were carried out with heating rate of 10℃/min,and the products of themal decomposi-tions were identified by gas-chromatography(GC)and/or gas-chromatography/mass spectrometer(GC/MS).Teir heats of decomposition weYe also studied by using diffeTential scanning calorimetry(DSC). There was remarkable difference in thermal decomposition mechanism between o-DNB and m一DNB,also between3, 4-DNT and2,4-DNT.The initlal step of the thermal decompositions seems to be initiated with dissociation of either ortho substituents of the benzene rlng.Th1s resulted in that decompositjon temperature of o-DNB observed by DSC was lower than that of m一DNB.Namely,the initlal step of decomposition was affected by an ortho effect. On the other hand,nnal decomposltion products of all tested compounds were similar,i.e. N2,CO,CO2,H20 and carbonaceous products.Estimated heats of decomposition fmm amounts of these products showed very close values with those obtahled by DSC measurements.
The occurrence of various kinds of phellomena in materials gives rise to the emission of elastic waves、These waves are cailed acoustic emission(AE)or stress wave emission(SWE).Wave forms and the velocity of AE will change whlle it propagates in a non 1inear medium、So,wave forms and changes of arrival times are conskiered to contain informations on the source phenomena and informations on the path where AE travels、 In this paper,therefore,in order to get the informations on the path between AE source and AE detector and aound the AE source caused by the uni-axial compression test,deterlorated concrete is used as a specimen、 AE wave forms are measured by 12 AE detectors with three transient recorders with 1 M words memory which were designed for AE measurement(see Fig.3).The rise times of AE waves are decided automatlcally,and then AE source is calculated by the method of successive approximation of which variables are(x,y,z),t,V(see Fig、2). Three dimensional AE tomography of which generator is AE is simulated by SIRT(Simultaneous Interactive Reconstruc- tion Technique)method.The deteriorated part of the concrete specimen is visualized by means of computer graphics(see Fig、7and Fig.8).