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DZ245电热恒温箱的微机控制系统,毕业设计
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ABSTRACT Chapter 1 Introduction Near zone magnetic source transient EM was developed on base metal exploration at the 50s,both in the west and Russian. As TEM was establishing its predominance in mineral exploration, TEM systems were gaining an enormously expanded role in general geological mapping, such as, shallow geothermal sources, ground water aquifers, ground water contamination and saline intrusion, depth of bedrock, overburden thickness, civil engineering and environment investigation, cave detecting and other applications. In China TEM was developed initially in 70s, however it is a subject mainly of researching investing and applying merely in Institute and university instead to be as a conventional method applied by Geophysical prospecting group of provinces till now Because of its complexity, besides financial difficulties there are technical problems. The imported TEM system is too expensive and the quality of native TEM system is unstable. Fortunately in recent seven years, a lot of good results was obtained and several better anomalies had been verified to be caused by ore body. On the other hand, the stability of native TEM system had been improved successfully and TEM could be developed with expanding application. For introduce TEM to Chinese readers, last thirty years, we had translated paper and literatures, such as kamenetskiis handbook(1976),edited by Buselli McCraken and Rutters manual(1985),Kaufman and kelles literature, Sidorovs Writings(1987),edited by Nabighians writings(1988),textbook(in Chinese) wrote by Piao Huarong(1900),and Niu Zhilian(1992),and soon. TEM developed (and developing)in China which had been attributed to these materials. But for expanding application to be promoted, some of it are rather theoretical, or else rather simple, is some what unsuitable for Chinese field geophysicist and for the need of workshop in nowadays. I prefer only to its realm of near zone and confine it to magnetic sources which proper for field geophysicist, because of near zone magnetic sources TEM having natural advantages and easy be carried out in the field due to the native TEM system adaptable for that of course the such discussion is in this book should be systematic comprehensive and applicable. I hope that readers would benefit with some useful and new knowledge from here and ntswill have a jump on their competition as well. Of course you will find many faults even mistakes in this book at meantime. I hope you wont spare your comments. Chapter 2 Basic theory of TEM In this Chapter, we describe and illustrate the character of electromagnetic wave diffusion in the ground and the distribution of eddy current within the sphere in early time, intermediate time and late time, then by beginning of explanation of vauyans(1960) practical criterion of near zone. middle zone and far zone at first, accompanying with give some formulas of different configuration to different targets and explanation of what premise condition is necessary. As well know, one of TEM advantages isnt topographical effect excited, relative to FEM. Topographical effect could be divided into two parts, one is due to the different elevations between Tx and Rx. Tx and target and Rx to target, other is due to the conductive and the shape of the materials of relief portion. By logic inference, the former is main factor due to topographical effect, and it was proved by scale modeling and field results of tiltdip angle method(FEM)and dipoledipole TEM especially. On the basis of that, we assume a conductive sphere under different topographic relief and high resistively host rock then calculate the responses of coincident loop and central loop configuration and find that the responses having to be distorted relative to typical response for some position of the peaks are shifted or being a unsymmetrical about center line, even only one peak originally to be distorted to three peaks. So we would like to say that topographic effect is still a serious problem and attention should be paid to data interpretation. Chapter 3 Scale Modeling Scale modeling is still a very important tool for research or interpretation, although numerical modeling applications are widely used nowadays. Because some couldnt be solved with numerical modeling and some numerical modeling data should be proved by scale modeling yet. For Scale modeling there two criteria should be obeyed. Therefore we shall analysis the criteria in detail and introduce some modeling materials, equipment, by drawing up different sketch of borehole TEM scale model, borehole holder and conductor mount etc. Finally we introduced a practical scale modeling data of Elura deposit. ntsChapter 4 Signal detection and TEM system introduction This chapter is written but for operating the TEM instruments correctly and flexibility rather than designing it. Here we introduced three imported and four native TEM systems. The imported TEM system are SIROTEM , Digital PEM and PORTEM except UTEM .Although UTEM system is one of excellent systems, but with triangle waveform current that means primary field exist in whole sampling time, then topographical effect in mountain area would be serious. However such effect could be reduced by correct program as Lamontagne. Y. L. answered (personal com ),but there is still more successive troublesome problem at all. Maybe it is the reason without importation in China , and that is why we neglect it in this book. Four native TEM systems are WDC-2B,SD -1,LCTEM and TEMS-3S.The transmitting current wave form of the first two are same as SIROTEM system, the later two are transmitting single pulse with very high currents of 100200 amperes single pulse supplied by condensers discharge. Of course discharge current form would accompany with lots of problems. The designer of TEMS-3S thoroughly realized, these problems have been solved with harmonic analysis and designed corresponding hard ward and programming soft ward equipped in the systems (). The characters of transient response due to target is what we desire to detect and research for and any other transient phenomenon should be omitted or minimized. The receiver coil transient or coil delay is one of the problems. A. A. Vakulskiy and A. S. Fedchishin published their analytic results about this problem in 1995.They assumed that the transmitting current is in step form , but all of the commercial TEM system are in ramp form. It was solved by Jiang-Bang Yuan in 1976. According Jings studies we could know which receive coil is available and how to design a coil for special case and the sign rule about it. It is defined as that when the direction secondary flux is same as primary one in a component, it is plus, if opposite to each other, it is minus. So that a response signs to a vertical thin conductive plate is plus, minus and plus in FEM, and minus plus and minus in TEM. This is reasonable, but some authors had drawn response curve with same sign both to FEM and TEM. It is would be confused in interpretation. Chapter 5 Field procedure for surface survey ntsAt first, in this chapter we introduce some conventional configurations and its type curves, such as single loop coincident loop , central (or in loop),separate loop and large fixed transmitter loop with roving receiver, which within or out off the loop ,Besides, we suggest a new configuration as that lay out two same size large fixed transmitter loop separated about 10001500meters;the currents flowing in two loops with same amplitude(10-20A)but opposite direction, and with the roving receiver surveying in the middle. Therefore the total flux attitude benefits very helpful advantages for deep ore body detection, because the total flux at shallow deep are weaker and at depth are relative uniform than one fixed loop. The only one disadvantage is that two transmitters are necessary. At last we named the new configuration as two fixed Tx loop with homogenous field configuration or two fixed large separate loop configuration. Another new configuration is to do relative measurement, such as horizontal or ignored from 50s till now, In fact, it the vertical is better than the absolute measurement, because the serifs noise and the power noise can be minimized or to be avoided. By the way, we point out that in-loop is not central loop in any case .For the analytical solution of a sphere in free space is exactly for fixed loop and roving receiver in the loop to do the measurement station by station, but this configuration was called in-loop in Busllis(1985)and there is no optimum delay time in this case, but in kamenetskii and Busllis books showing the optimum decay time equate to Chapter 6 Data proceeding and figuring There are three correction procedures, Levys(1984),Spies(1985)and Fittermans(1987)to be discussed in detail .By the field tests, data measure under same conditions and in one day, but with different turn-off time, 0.5ms, 1.0ms and (Crone Digital PEM),then corrected it with three different procedures. The results show that only Fitters gave three apparent resistively curves agree with each other with the relative error less than 10%.But the relative error of raw data would approximate to 100%(data of turn-off time 0.5ms vs1.5ms) Chapter 7 Data Interpretation Data interpretation in this chapter is expressed for profile and sounding but excluding borehole. In part of profile do my best only to collect useful interpretation expressions and ntsmonograms completely. Buy my opinion, I favor of the vector intersection method, for its simple and adaptability for different shape confined targets. Otherwise, it is emphasized that interpreter should pay attention to analyze the nature of response with delay time and estimate the apparent time constant. That is the key for TEM profile interpretation. Part of sounding is for inversion to TEM. At first we initiated by introducing the exact apparent resistively formula derived by Raiche and spies (1981).It is simple and can cover middle zone. That is to say that should cover all most field situation, if loop size is selected correctly. Then we introduce two inversion techniques to TEM sounding. One is called to be “apparent longitudinal conductance method” .It is based on floating tinplate theory, and is used widely in Russia. The second is rapid inversion technique as Eaton and Hohmann called (1989).Which is based on smoking ring theory, or the behavior of vortex current diffusing into a layered earth. However we derived a more simple formula and can be calculated only with a calculator. By the former we could obtain the depths of every layers, and the depth value should correct with a correcting coefficient which depended on the type of layer, other than a constant. By the latter, we can obtain exact apparent resistively and corresponding apparent depth only. With these data a pseudo-section can be drawn up .So that the interface between two layer is obscure. A new apparent longitudinal conductance formula and apparent depth which we derived in this book are very simple and the later is unnecessary to do correction by any coefficient. Numerical modeling and field data processing show good match with two methods and the new one is better. They are adaptable not only for layer earth but also for some conductive ore body. Chapter 8 Bore-hole TEM Bore-hole TEM can be broadly defined including different configurations that either the source or the receiver (or both)is put into drill hole. In this chapter, however, only a conventional BHTEM is introduced such configuration is that the large transmitter lay out on the surface, and the receiver coil(coaxial with the drill hole)is lowered down the drill hole, taking readings at regular intervals, so it is rather to be called as surface-hole TEM(SHTEM). SHTEM is used to detect missed ore body nearby or under a drill hole, so it is a ntsexploration method. For interpretation D. V. Woods had studied a lot of borehole TEM scale-modeling to tabular conductive body(1975),and Dyck accomplished numerical estimates with PLATE and SPHERE program. These results showed the capability of SHTEM for geophysical exploration in drill hole and could be used directly as type curves for the interpretation to field results. However these curves should be
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