建筑土木系探地雷達(dá)外文中英對(duì)照翻譯

1、<p><b>　　外文文獻(xiàn)</b></p><p>　　3 PHYSICAL PROPERTIES I</p><p>　　3.1 WHY ARE PHYSICAL PROPERTIES IMPORTANT?</p><p>　　GPR investigates the subsurface by makinguse of elec

2、tromagnetic fields which propagate into the subsurface. EM fields which are time varying consist of coupled electric (E) and magnetic (H) fields. As discussed in section 2 the fields interact with the surrounding media.

3、This interaction is macroscopically described by the constitutive equations 2.5 to 2.7. The manner in which the electromagnetic fields interact with natural materials controls how electro-magnetic fields spread into the

4、medium a</p><p>　　In most geological and NDT (non-destructive testing) applications of GPR, electrical properties tend to be the domi-nant factor controlling GPR responses. Magnetic variations are usually we

5、ak. Occasionally magnetic properties can affect radar responses and GPR users should be cognizant of magnetic effects.</p><p>　　An electric field in a material gives riseto the movement of electric charge, (

6、i.e., electric current). The current flow depends on the nature of the material. There are two types of charge in a material, namely bound and free, which give rise to two types of current flow, namely displacement and c

7、onduction. In the following, we will provide a simple overview of the two types of current flow. An in-depth discussion of electrical properties can be found in the text by</p><p>　　Von Hippel,(1954).</p&

8、gt;<p>　　Magnetic properties are controlled by the electric charge circulation character at the atomic and molecular level. Macroscopic magnetic properties are addressed briefly in these notes. Von Hippel (1954) a

9、ddresses some of the basic concepts.</p><p>　　3.2 CONDUCTION CURRENTS</p><p>　　Most people are very familiar with electrical conduction currents. Conduction currents are created when unbound(fre

10、e) charges move in a material. The electrons which flowin a metal wire are an example of conduction current. In a metal, electrons move through the metallic matrix to transfer charge from one point to another. Another co

11、mmon conduction mechanism is the movement of ions in a water solution. The later is much more important in most GPR applications. </p><p>　　Conduction currents arise whenfree charge accelerates to a terminal

12、 velocity (basically instantaneously) when an electric field (E) is applied. As long as the electric field is applied, the charge moves; when the electric field is removed, the charge decelerates and stops moving Figure

13、3-1 illustrates these concepts.</p><p>　　Figure: 3-1 Conceptual illustration of charge movement for conduction currents.</p><p>　　a) Charge velocity versus time after E field applied.</p>

14、<p>　　b) Energy is extractedfrom the applied electric field versus time.</p><p>　　Figure: 3-2 When an electric field is applied, unbound electrical charges accelerate to a terminal velocity. After init

15、ial acceleration, velocity becomes constant and a continual transfer of energy to the surrounding material in the form of heat occurs</p><p>　　All the time that charge is moving, the moving charge is working

16、 against its surroundings dissipating energy in the form of heat. The moving charge bumps into 'non-moving'objects and transfers mechanical energy which appears in the form of heat in the medium. Conduction curre

17、nts represent an energy dissipating mechanism for an electromag-netic field. Energy is extracted from the electromagnetic field and transferred irreversibly into the medium as heat. </p><p>　　Mathematically

18、one describes the relationship between conduction current and the applied electric field as indicated</p><p>　　in Equation 3-1.</p><p><b>　?。?-1）</b></p><p>　　In simple

19、materials, the relationship is linear and the proportionality constant is referred to as the electrical conductiv-ity. Electrical conductivity has units ofSiemens per meter (S/m). For many applications, however, it is mo

20、re useful to work with units of milliSiemens per meter (mS/m). Conductivity is dependent on the charge density and the inter-nal statistical mechanical interaction ofthe charge with its surroundings. These details are be

21、yond the scope of this discussion.</p><p>　　It should be noted that electrical conductivity and resistivity are directly related. Refer toFigure 3-3 for the relation-ship and the expression of Ohm's law.

22、 Electrical resistivity is the inverse of electrical conductivity.</p><p>　　Figure: 3-3 Relationship between current and applied field as well as the relationship will Ohm's law and resis-tively.</p&g

23、t;<p>　　It is important to note that there are simplifications in the above discussion from the general form shown in Chapter 2.</p><p>　　The conductivity is shown as being a constant. In fact it can

24、be a function of the rate of change of the electric field,the amplitude of electric field itself, as well as temperature, pressure and many other factors. As a result, one should not be surprised to see both non-linearit

25、y and frequency dependent conductivity in real materials. Generally these are second order effects but they must be considered when advanced use of GPR is contemplated. For this basic GPR overview, they will be treated&l

26、t;/p><p>　　3.3 DISPLACEMENT (POLARIZATION) CURRENTS</p><p>　　Displacement currents are associated with bound charges which are constrained to limited distance of movement. Examples of this are the

27、electron cloud around an atomic nucleus, the electricalcharge in a small metal object imbed-ded in an insulating environment, and the redistribution ofthe molecular dipole moment intrinsic to some molecules. Figure 3-4 d

28、epicts the concept. When an electric field is applied, bound charge moves to another static configuration.This transition occurs virtually insta</p><p>　　is extracted from the electric field and the energy i

29、s stored in the material. When the field is removed, the charge moves back to the original equilibrium distribution and energy is released. This type of behavior is typical of what happens in a capacitor in an electric c

30、ircuit. Energy is stored by the buildup of charge in the capacitor and then</p><p>　　energy is extracted by the release ofthat charge from the device.</p><p>　　Figure: 3-4 Conceptual illustratio

31、n of charge movement associated with displacement currents.</p><p>　　Figure 3-5 depicts the characterization of charge separation in a material. When an electrical field is applied, dis-placement of charge i

32、n a bulk material gives rise to a dipole moment distribution in the material. The charge separa-tion is described in terms of a dipole moment density, D.In a more formal derivation, D is called the electric displacement

33、field (see chapter 2). In simple materials, the induced dipole moment densityis directly proportional to the applied electric field and the pr</p><p>　　Figure: 3-5 Dipole moment density induced by applied el

34、ectric field and relation to displacement current.</p><p>　　The creation of a dipole moment distribution in the material is associated with charge movement. The electric current associated with this charge m

35、ovement is referred to as displacement current. The displacement current is mathemati-cally defined as the time rate of change of the dipole moment density. </p><p>　　The electric permittivity is never zero.

36、 Even in a vacuum, the permittivity, takes on a finite value of 8.85 x 10-12F/m (Farads per meter). The explanation for this lies in the field of quantum electrodynamics and is far beyond the scope of this discussion.<

37、;/p><p>　　It is often more convenient to deal with a dimensionless term called relative permittivity or dielectric constant, K. As depicted in Figure 3-6 , the relative permittivity is the ratio of material per

38、mittivity to the permittivity of a vacuum.</p><p>　　Figure: 3-6 Dielectric constant or relative permittivity is the ratio of permittivity of material to that of free space.</p><p>　　3.4 TOTAL CU

39、RRENT FLOW</p><p>　　In any natural material, the current which flows in response to the application of an electric field is a mixture of con-duction and displacement currents. Depending on the rate of change

40、 of the electric field, one or other of the two types of current may dominate the response. Mathematically, the total current consists of two terms; one which depends on the electric field itself and one which depends on

41、the rate of change of the electric field.</p><p><b>　　(3-2)</b></p><p><b>　　(3-3)</b></p><p>　　Quite often it is useful to deal with sinusoidally time varyin

42、g excitation fields. In this situation, one finds that the dis-placement currents are proportional to the angular frequency.</p><p><b>　　(3-4)</b></p><p>　　where is the angular frequ

43、ency.</p><p>　　The displacement currents are out of phase with the conductioncurrents by 90° which is what ascribing an imaginary aspect to the displacement component implies. Those familiar with elect

44、rical engineering circuitry termi-nology will realize that there is a phase shift between the conduction currents and the displacement currents which indicates that one term is an energy dissipation mechanism and the oth

45、er one is an energy storage mechanism .A simplified plot of displacement current and conducti</p><p>　　Figure: 3-7 Conduction, displacement and total current versus frequency.</p><p>　　Mathemati

46、cally the transitionfrequency is defined.</p><p><b>　?。?-5）</b></p><p>　　In addition, another term called the loss tangent is defined. The loss tangent is the ratio of conduction to

47、displace-ment currents in a material.</p><p><b>　?。?-6）</b></p><p>　　The term loss target tends to be most common in electrical engineering contexts.</p><p>　　Conductivi

48、ty and permittivity are not independent of the excitation frequency. There is always some variation. This topic is beyond the scope of this chapter of the notes but there is considerable literature (i.e., Olhoeft, 1975)

49、on fre-quency dependent electric</p><p>　　3.5 MAGNETICPERMEABILITY</p><p>　　Magnetic permeability is seldom of major importance for GPR applications. For completeness and to address those except

50、ional situations where permeabilitymay become important, we review some of the basic aspects of magnetic permeability. </p><p>　　Magnetic permeability is actually related to the intrinsic electrical characte

51、ristics of the basic building blocks of phys-ical materials. In simple terms, charged particles, which form atoms , which in turn make molecules, have a quantum mechanical property referred toas spin. When combined with

52、the charge on the particle, spin results in the particle having a magnetic dipole moment. When an electron moves around an atomic nucleus, the charge motion can also create a magnetic moment. </p><p>　　The s

53、imple analogy is to have electrical charge uniformly distributed on a spherical ball and then spin ball. The resulting rotating charge appears to be a circular loop of current, which in turn gives on rise to a magnetic d

54、ipole.</p><p>　　Magnetic properties are essentially the properties of an electrical change moving around a closed path.al properties which can be referred to.</p><p><b>　　a）</b></

55、p><p><b>　　b）</b></p><p>　　Figure: 3-8 a) A simple picture suggesting the origin of electron spin movement; b) relating the magnetic moment induced in an electron cloud by a change in m

56、agnetic field</p><p>　　Figure: 3-9 Relating the magnetic moment to a simple electron orbit.</p><p>　　The details are obviously more complex but this provides a simple pictorial model to use.Atom

57、s are formed of elec-trons and protons plus neutrons. The electrically changed components have intrinsic and orbital spin when they form molecules of a given type of material. The particular orientation of the spin axes

58、of the individual particles can be aligned in random or structured ways and may be altered by an ambient magnetic field. If the molecular structure does not accept random spin orientation</p><p>　　Magnetic p

59、ermeability measures the degree to which individual dipole moments of the building blocks can be aligned or moved from their normal orientation by an externally applied magnetic field. The more of the individual moments

60、that can be moved into alignment, the more magnetically polarizable the material. The magnetic properties of materi-als are quantified by magnetic dipole moment density. When an electrical current flows in a closed loop,

61、 the mag-netic moments is.</p><p><b>　　（3-7）</b></p><p>　　where M is the dipole moment, I is the current and A is the area of the loop enclosed by the current filament. M has units o

62、f Am2 For bulk materials, the material is characterized by dipole moment density</p><p><b>　　（3-8）</b></p><p>　　which has units of A/m. V is volume. When a magnetic field, H, induces

63、 a magnetic moment, the amount of moment is expressed as</p><p><b>　?。?-9）</b></p><p>　　where k is the magnetic susceptibility (and is a dimensionless quantity). There is considerabl

64、e similarity between induced magnetic moment and induced electric dipole momentdiscussed previously in the displacement current sec-tion.</p><p>　　In the material, the magnetic flux is expressed as </

65、p><p><b>　　（3-10）</b></p><p>　　and magnetic permeability is expressed as</p><p><b>　?。?-11）</b></p><p><b>　　where</b></p><p&

66、gt;<b>　?。?-12）</b></p><p>　　The term relative magnetic permeability is expressed as</p><p><b>　?。?-13）</b></p><p>　　in an analogous fashion to relative permi

67、ttivity. When both magnetic and electric properties vary, relative permittiv-ity is usually expressed as Ke to avoid confusion.</p><p>　　The presence of a magnetic field induces the individual dipole moment

68、to change orientation and line up with the applied field. In some materials the alignment is in the same direction as the applied field, whereas in other materials the alignment maybe anti-parallel to the applied field.

69、These two types of behavior referred to as paramagnetism and diamagnetism. Generally these responses are very weak and give rise to small variations in magnetic permeability. Typical values of magnetic suscepti</p>

70、<p>　　In some situations, however, the magnetic moments can be aligned in large sections (called domains) of the crystal structure of a material. The moment ofdomains can be changed by the molecules in the crystal

71、 structure behaving in a sympathetic fashion and moving from one domain to another. Such materials are known as ferromagnetic materi-als. </p><p>　　In ferromagnetic materials, the polarization can be quite l

72、arge and high values of Kmin the range of tens or even hun-dreds may be observed in materials such as iron, cobalt, and nickel. With ferromagnetic materials, the behavior is more complex in that the dipole moments when m

73、oved, or aligned, remain aligned. This is known as permanent magnetization. In such materials the permeability is very high and the dynamic behavior of the material complex. Such materials seldom form a large volume frac

74、t</p><p>　　Behavior can be very complex. The behavior of dipolemoment density is controlled by how domains move, grow and change orientation which can be field dependent, frequency dependent and temperature

75、dependent. The subjects are well beyond the scope of these notes.</p><p>　　Figure: 3-10 Ferromagnetic domain structures: a) single crystal, b) polycrystalline specimen. Arrows represent the direction of mag

76、netization.</p><p>　　Figure: 3-11 Magnetization of a ferromatic material: a) unmagnetized, b) magnetization by domain wall motion, c) magnetization by domain rotation.</p><p>　　In soils and rock

77、s, magnetic behavior is dictated by the amount of magnetite (or similar minerals such as meghemite or ilmenite). The graph (from Grant & West (1965)) in Figure 3-14 shows how susceptibility varies with magnetite volu

78、me fraction. The simple approximate formula is</p><p><b>　?。?-14）</b></p><p>　　where q is the volume fraction of magnetite in the material. To put this result in perspective, 1% by v

79、olume magnetite (which is very high in most cases) content yields Km=1.038. Only in rare cases will Kmbe significantly different from unity.</p><p>　　Figure: 3-12 Data from which the emperial formula for sus

80、ceptibility k=2.89 x 10-3V1.01 was derived. [Mooney and Bleifuss (7).]</p><p><b>　　中文翻譯</b></p><p><b>　　3 物理性質(zhì)I</b></p><p>　　3.1 為什么物理性質(zhì)重要</p><p&g

81、t;　　探地雷達(dá)是利用電磁場(chǎng)的傳播來(lái)研究地下空間。電磁場(chǎng)是隨時(shí)間變化的一對(duì)耦合的電場(chǎng)（E）和磁場(chǎng)（H）。在第2節(jié)中討論了場(chǎng)與周?chē)橘|(zhì)的相互作用。本文方程2.5到2.7的宏觀描述了這種相互作用。而電磁場(chǎng)的天然材料，互動(dòng)的方式，控制電磁場(chǎng)在基質(zhì)中的擴(kuò)散、衰減。此外，在地下反射與雷達(dá)系統(tǒng)獲得觀測(cè)物理性能的產(chǎn)生到變化。</p><p>　　在大多數(shù)探地雷達(dá)的地質(zhì)和NDT（無(wú)損檢測(cè)）應(yīng)用中，電氣性能往往是主要控制探地雷達(dá)響

82、應(yīng)的因素。磁場(chǎng)的變化通常是弱的。磁性能偶爾的影響雷達(dá)的反應(yīng)，探地雷達(dá)用戶應(yīng)該認(rèn)識(shí)到磁效應(yīng)。</p><p>　　電場(chǎng)在材料中產(chǎn)生電荷的運(yùn)動(dòng)，（即，電流）。當(dāng)前的流動(dòng)取決于材料的性質(zhì)。材料中有兩種類(lèi)型的電荷，即束縛和自由，其產(chǎn)生兩種類(lèi)型的束流，即位移和傳導(dǎo)。下面，我們將提供一個(gè)簡(jiǎn)單的的電流流動(dòng)的兩種類(lèi)型的概述。在希佩爾文本（1954）可以看到關(guān)于電氣特性的深入探討。</p><p>　　原子

83、和分子水平上的電荷循環(huán)特性控制著磁性。希佩爾（1954）的筆記提出宏觀磁特性簡(jiǎn)要討論和基本概念。</p><p><b>　　3.2、傳導(dǎo)電流</b></p><p>　　大多數(shù)人都非常熟悉電流的傳導(dǎo)。材料中未束縛的（自由）電荷運(yùn)動(dòng)創(chuàng)造出傳導(dǎo)電流。金屬絲的電子流是傳導(dǎo)電流的一個(gè)例子。在一種金屬，電子通過(guò)金屬基體的電荷從一點(diǎn)傳輸?shù)搅硪粋€(gè)。另一個(gè)常見(jiàn)的傳導(dǎo)機(jī)制是在水溶液中

84、的離子的運(yùn)動(dòng)，是探地雷達(dá)中更重要應(yīng)用。</p><p>　　自由電荷加速到終端速度（基本上瞬間）時(shí)應(yīng)用電場(chǎng)（E）產(chǎn)生傳導(dǎo)電流。圖3-1展示了僅利用電場(chǎng)使電荷運(yùn)動(dòng)拆下，減速和停止移動(dòng)的這些理念。</p><p>　　圖3-1：傳導(dǎo)電流電荷運(yùn)動(dòng)的概念圖。</p><p>　　a）應(yīng)用E場(chǎng)后電荷的速度與時(shí)間。</p><p>　　b）施加的電場(chǎng)隨時(shí)

85、間提取的電能。</p><p>　　圖3-2：當(dāng)施加電場(chǎng)時(shí)，自由的電荷在初始加速度后，加速到終端速度。速度常數(shù)和在對(duì)周?chē)牧系哪芰窟B續(xù)轉(zhuǎn)移為以熱的形式出現(xiàn)。</p><p>　　運(yùn)動(dòng)消耗所有的時(shí)間，運(yùn)動(dòng)的電荷能量耗散是在其周?chē)詿岬男问?。運(yùn)動(dòng)電荷碰到的靜止物質(zhì)并以熱的形式在介質(zhì)中傳送機(jī)械能。傳導(dǎo)電流電磁場(chǎng)的能量耗散的機(jī)制。從電磁場(chǎng)的能量轉(zhuǎn)移到基質(zhì)中提取和不可逆熱。</p>&

86、lt;p>　　數(shù)學(xué)描述傳導(dǎo)電流和電場(chǎng)之間的關(guān)系表示公式。</p><p><b>　?。?-1）</b></p><p>　　對(duì)簡(jiǎn)單的材料，導(dǎo)電性比例常數(shù)為線性關(guān)系。電導(dǎo)率的單位為西門(mén)子/米（S / M）。但是，對(duì)于許多應(yīng)用程序，單位毫西門(mén)子每米（MS /米），它是更有用的。導(dǎo)電性電荷密度和內(nèi)部統(tǒng)計(jì)力學(xué)是依賴(lài)于電荷與周?chē)沫h(huán)境的相互作用。這些細(xì)節(jié)超出了本文討論的

87、范圍。值得注意的是，電導(dǎo)率和電阻率有直接的關(guān)系。引用3-3歐姆定律的表達(dá)的關(guān)系。</p><p>　　圖3-3：電流和外加磁場(chǎng)的關(guān)系以及將歐姆定律，電阻性能之間的關(guān)系。</p><p>　　根據(jù)上文第二章所討論的關(guān)于簡(jiǎn)化的重要性需重視。電導(dǎo)率顯示為一常數(shù)。事實(shí)上，它可以對(duì)電場(chǎng)的變化率，電場(chǎng)振幅本身，以及溫度，壓力和許多其他因素的函數(shù)。其結(jié)果，應(yīng)不要對(duì)兩個(gè)非線性和頻率所依據(jù)的真實(shí)材料感到驚奇

88、。。通常這些都是二階效應(yīng)，但他們必須考慮使用探地雷達(dá)先進(jìn)設(shè)想。這個(gè)基本的探地雷達(dá)概述，他們視其為次要的問(wèn)題。</p><p>　　3.3 位移（極化）的電流</p><p>　　位移電流與電荷的運(yùn)動(dòng)有限距離的約束有關(guān)。這樣的例子如原子核周?chē)碾娮釉?，在一個(gè)小的金屬物體在絕緣環(huán)境嵌入的一個(gè)電荷，且再分配的分子偶極矩的一些分子特性。圖3-4所描繪了這樣的概念：當(dāng)施加電場(chǎng)時(shí)，束縛電荷移動(dòng)到另一個(gè)

89、靜態(tài)狀態(tài)。這種轉(zhuǎn)變發(fā)生幾乎瞬間之后，不再動(dòng)彈受指控。在過(guò)渡期間，</p><p>　　能源從電場(chǎng)和能量提取并存儲(chǔ)在材料中。場(chǎng)被消除時(shí)，電荷回到原來(lái)的平衡分布且釋放能量。這種發(fā)生在電子電路中的電容器行為是典型的。能量是由電容器中存儲(chǔ)的電荷的積累，然后能源是由從器件釋放的該電荷中提取。</p><p>　　圖3-4：位移電流與電荷運(yùn)動(dòng)的有關(guān)概念圖。</p><p>　　

90、圖3-5描述材料中電荷的分離表征。當(dāng)一個(gè)電場(chǎng)，在散裝材料的電荷位移引起材料中的偶極矩分布。電荷分離效果是用一個(gè)偶極矩密度來(lái)描述，根據(jù)一個(gè)更正式的推導(dǎo)，D.被稱(chēng)為電位移場(chǎng)（見(jiàn)第二章）。在簡(jiǎn)單的材料，誘導(dǎo)偶極矩密度成正比外加電場(chǎng)和比例常數(shù)稱(chēng)為材料的介電常數(shù)，單位為法拉/ 米（F / M）。</p><p>　　圖3-5：偶極矩密度和電場(chǎng)誘導(dǎo)的位移電流的關(guān)系。</p><p>　　材料中創(chuàng)造的偶

91、極矩的分布與電荷的運(yùn)動(dòng)有關(guān)。電流與此相關(guān)的電荷運(yùn)動(dòng)被稱(chēng)為位移電流。位移電流是數(shù)學(xué)上定義的時(shí)間變化率的偶極矩密度。</p><p>　　介電常數(shù)不會(huì)是零。即使在真空，介電常數(shù)，為8.85×10-12 F / M（法拉每米）的有限值。在量子電動(dòng)力學(xué)方面對(duì)此的解釋?zhuān)h(yuǎn)遠(yuǎn)超出了本文的討論范圍。</p><p>　　它往往是更方便的處理的一個(gè)無(wú)量綱的術(shù)語(yǔ)稱(chēng)為相對(duì)介電常數(shù)和介電常數(shù)，K。圖3

92、-6所示，相對(duì)介電常數(shù)是材料介電常數(shù)與真空介電常數(shù)的比率</p><p>　　圖3-6：介電常數(shù)或相對(duì)介電常數(shù)材料的介電常數(shù)，自由空間的比率</p><p><b>　　3.4 總電流</b></p><p>　　任何的天然材料，電場(chǎng)的應(yīng)用電流是一種混合的傳導(dǎo)和位移電流。根據(jù)電場(chǎng)的變化率，目前可能會(huì)占主導(dǎo)地位的有一個(gè)或其他的兩種類(lèi)型。在數(shù)學(xué)上，

93、總電流包括兩個(gè)方面；一個(gè)取決于電場(chǎng)本身和一個(gè)取決于電場(chǎng)的變化對(duì)率。</p><p><b>　　(3-2)</b></p><p><b>　　(3-3)</b></p><p>　　通常是處理正弦時(shí)對(duì)變化激發(fā)場(chǎng)有用。在這種情況下，人們發(fā)現(xiàn)，位移電流與角頻率成正比。</p><p><b>

94、;　　(3-4)</b></p><p><b>　　角頻率w</b></p><p>　　虛構(gòu)方面的位移分量位移電流和傳導(dǎo)電流的相位相差90°。熟悉電氣工程電路專(zhuān)門(mén)名詞會(huì)意識(shí)到有一個(gè)相移之間的傳導(dǎo)電流和位移電流是表示一個(gè)一個(gè)能量耗散機(jī)制術(shù)語(yǔ)，另一個(gè)是能量存儲(chǔ)機(jī)構(gòu)。一個(gè)簡(jiǎn)化的位移電流和傳導(dǎo)電流和總電流與頻率圖3-7。通常有一些頻率以上的位移電流超

95、過(guò)傳導(dǎo)電流。一個(gè)簡(jiǎn)單的材料的電導(dǎo)率和介電常數(shù)是恒定的，有一個(gè)過(guò)渡頻率，和傳導(dǎo)電流的位移電流是相等的。高于這個(gè)頻率，位移電流占主導(dǎo)地位；低于這個(gè)頻率，傳導(dǎo)電流控制。這個(gè)因素很重要，當(dāng)我們處理采用電磁波的傳播。對(duì)探地雷達(dá)來(lái)說(shuō)頻</p><p>　　率是重要的定義上的低損耗。</p><p>　　圖3-7：傳導(dǎo)，位移和總電流頻率。</p><p>　　數(shù)學(xué)上過(guò)度頻率的定義

96、</p><p><b>　　（3-5）</b></p><p>　　此外，另一項(xiàng)定義稱(chēng)為損耗角正切。傳導(dǎo)材料中位移電流的損耗角正切比例。</p><p><b>　?。?-6）</b></p><p>　　該種損失往往在電氣工程中是最常見(jiàn)的。</p><p>　　電導(dǎo)率和介

97、電常數(shù)不是獨(dú)立的激發(fā)頻率?？傆幸恍┳兓?。這主題超出了本章的論述范圍，但有相當(dāng)多的文獻(xiàn)（即，奧爾霍夫特，1975）涉及到電氣性能對(duì)頻率的依賴(lài)性的主題。</p><p><b>　　3.5導(dǎo)磁率</b></p><p>　　導(dǎo)磁率在探地雷達(dá)的重要應(yīng)用中用的很少。常在解決一些特殊情況下，滲透率可能變得非常重要，我們回顧一些滲透性的基本磁性。</p><p

98、>　　物理材料的基本構(gòu)建塊的內(nèi)在相關(guān)與電氣特性實(shí)際上是導(dǎo)磁率。簡(jiǎn)單來(lái)說(shuō)，帶電粒子，形成原子，從而使分子，有一個(gè)量子機(jī)械性能被稱(chēng)為自旋。結(jié)合顆粒上的電荷，在粒子的自旋結(jié)果具有磁偶極矩。當(dāng)一個(gè)電荷的電子繞著原子核運(yùn)動(dòng)，也可以創(chuàng)建一個(gè)磁矩。</p><p>　　簡(jiǎn)單電荷均勻分布類(lèi)比在球后旋繞。由此產(chǎn)生的旋轉(zhuǎn)電荷似乎是圓電流，從而給一個(gè)磁偶極子上升。電的磁性能變化基本上在一個(gè)封閉的路徑。</p>&l

99、t;p><b>　　a）</b></p><p><b>　　b）</b></p><p>　　圖3-8：a）一個(gè)簡(jiǎn)單的圖片顯示的電子自旋運(yùn)動(dòng)的起源；b）有關(guān)在磁場(chǎng)中電子云的變化引起的磁矩。</p><p>　　圖3-9：一個(gè)簡(jiǎn)單磁矩的電子軌道。</p><p>　　詳細(xì)的顯然更復(fù)雜，所以使用

100、一個(gè)簡(jiǎn)單的圖形模型。原子由電子、質(zhì)子和中子構(gòu)成。自旋形成的時(shí)候電子改變組件的固有的軌道一個(gè)給定類(lèi)型的物質(zhì)分子。對(duì)單個(gè)粒子的自旋軸特定方向可隨機(jī)或結(jié)構(gòu)化的方式排列，可能是通過(guò)周?chē)艌?chǎng)的改變。如果分子結(jié)構(gòu)不接受隨機(jī)自旋取向而需要一個(gè)結(jié)構(gòu)化的結(jié)晶結(jié)構(gòu)，該材料可以有一個(gè)永久磁化。如果部件可以對(duì)齊平行或反平行的磁場(chǎng)，感應(yīng)將產(chǎn)生的磁化響應(yīng)。</p><p>　　導(dǎo)磁率具有可以排列的特征，單個(gè)的偶極矩的積累或從其正常的方向施加

101、外部的磁場(chǎng)。更多可移動(dòng)到互動(dòng)位置，材料的磁性極化。當(dāng)電流在一個(gè)閉合回路，材料的磁特性的磁偶極矩密度量化。磁矩</p><p><b>　　（3-7）</b></p><p>　　其中M是偶極矩，I是電流，是由電流絲封閉的環(huán)路面積。M的單位是Am2 對(duì)于散裝材料，該材料在通過(guò)偶極矩密度的特征。</p><p><b>　?。?-8）&l

102、t;/b></p><p>　　這單位的A / m。V是體積。當(dāng)一個(gè)磁場(chǎng),H,誘使一個(gè)磁矩,瞬時(shí)量表示為</p><p><b>　?。?-9）</b></p><p>　　其中K是磁化率（是一個(gè)無(wú)量綱的量）。有較大的相似性的導(dǎo)磁矩和誘導(dǎo)的電偶極矩的電流截面位移在之前討論過(guò)。</p><p>　　在材料中，磁通量表

103、示為</p><p><b>　?。?-10）</b></p><p><b>　　導(dǎo)磁率表示為</b></p><p><b>　?。?-11）</b></p><p><b>　　其中</b></p><p><b>

104、　?。?-12）</b></p><p>　　穩(wěn)定的相對(duì)導(dǎo)磁率表示為</p><p><b>　?。?-13）</b></p><p>　　為了避免混亂當(dāng)磁場(chǎng)和電場(chǎng)的性質(zhì)不同，以類(lèi)似通常的方式的相對(duì)介電常數(shù)表示為K</p><p>　　磁場(chǎng)的存在下誘導(dǎo)偶極矩的取向和個(gè)體改變符合此應(yīng)用場(chǎng)。某些材料排列在同一方向