医学硕士研究生论文参考文献肯定是越多越好，这样更能够支持你的观点，而且查重的时候不容易出问题。具体数目没有统一规定，各个学校自己掌握。我是山东大学的，我的毕业论文参考文献是41篇（含外文文献9篇，港台地区文献2篇）
Introduction vibrations of frequencies greater than the upper limit of the audible range for humans—that is, greater than about 20 The term sonic is applied to ultrasound waves of very high Hypersound, sometimes called praetersound or microsound, is sound waves of frequencies greater than 1013 At such high frequencies it is very difficult for a sound wave to propagate efficiently; indeed, above a frequency of about 25 × 1013 hertz, it is impossible for longitudinal waves to propagate at all, even in a liquid or a solid, because the molecules of the material in which the waves are traveling cannot pass the vibration along rapidly TableMany animals have the ability to hear sounds in the human ultrasonic frequency Some ranges of hearing for mammals and insects are compared with those of humans in the T A presumed sensitivity of roaches and rodents to frequencies in the 40 kilohertz region has led to the manufacture of “pest controllers” that emit loud sounds in that frequency range to drive the pests away, but they do not appear to work as Transducers An ultrasonic transducer is a device used to convert some other type of energy into an ultrasonic There are several basic types, classified by the energy source and by the medium into which the waves are being Mechanical devices include gas-driven, or pneumatic, transducers such as whistles as well as liquid-driven transducers such as hydrodynamic oscillators and vibrating These devices, limited to low ultrasonic frequencies, have a number of industrial applications, including drying, ultrasonic cleaning, and injection of fuel oil into Electromechanical transducers are far more versatile and include piezoelectric and magnetostrictive A magnetostrictive transducer makes use of a type of magnetic material in which an applied oscillating magnetic field squeezes the atoms of the material together, creating a periodic change in the length of the material and thus producing a high-frequency mechanical Magnetostrictive transducers are used primarily in the lower frequency ranges and are common in ultrasonic cleaners and ultrasonic machining By far the most popular and versatile type of ultrasonic transducer is the piezoelectric crystal, which converts an oscillating electric field applied to the crystal into a mechanical Piezoelectric crystals include quartz, Rochelle salt, and certain types of Piezoelectric transducers are readily employed over the entire frequency range and at all output Particular shapes can be chosen for particular For example, a disc shape provides a plane ultrasonic wave, while curving the radiating surface in a slightly concave or bowl shape creates an ultrasonic wave that will focus at a specific Piezoelectric and magnetostrictive transducers also are employed as ultrasonic receivers, picking up an ultrasonic vibration and converting it into an electrical Applications in research One of the important areas of scientific study in which ultrasonics has had an enormous impact is When water is boiled, bubbles form at the bottom of the container, rise in the water, and then collapse, leading to the sound of the boiling The boiling process and the resulting sounds have intrigued people since they were first observed, and they were the object of considerable research and calculation by the British physicists Osborne Reynolds and Lord Rayleigh, who applied the term cavitation to the process of formation of Because an ultrasonic wave can be used carefully to control cavitation, ultrasound has been a useful tool in the investigation of the The study of cavitation has also provided important information on intermolecular Research is being carried out on aspects of the cavitation process and its A contemporary subject of research involves emission of light as the cavity produced by a high-intensity ultrasonic wave This effect, called sonoluminescence, is believed to create instantaneous temperatures hotter than the surface of the S The speed of propagation of an ultrasonic wave is strongly dependent on the viscosity of the This property can be a useful tool in investigating the viscosity of Because the various parts of a living cell are distinguished by differing viscosities, acoustical microscopy can make use of this property of cells to “see” into living cells, as will be discussed below in Medical Ranging and navigating Sonar (sound navigation and ranging) has extensive marine By sending out pulses of sound or ultrasound and measuring the time required for the pulses to reflect off a distant object and return to the source, the location of that object can be ascertained and its motion This technique is used extensively to locate and track submarines at sea and to locate explosive mines below the surface of the Two boats at known locations can also use triangulation to locate and track a third boat or The distance over which these techniques can be used is limited by temperature gradients in the water, which bend the beam away from the surface and create shadow One of the advantages of ultrasonic waves over sound waves in underwater applications is that, because of their higher frequencies (or shorter wavelengths), the former will travel greater distances with less Ranging has also been used to map the bottom of the ocean, providing depth charts that are commonly used in navigation, particularly near coasts and in shallow Even small boats are now equipped with sonic ranging devices that determine and display the depth of the water so that the navigator can keep the boat from beaching on submerged sandbars or other shallow Modern fishing boats use ultrasonic ranging devices to locate schools of fish, substantially increasing their Even in the absence of visible light, bats can guide their flight and even locate flying insects (which they consume in flight) through the use of sonic Ultrasonic echolocation has also been used in traffic control applications and in counting and sorting items on an assembly Ultrasonic ranging provides the basis of the eye and vision systems for robots, and it has a number of important medical applications (see below) The Doppler effect If an ultrasonic wave is reflected off a moving obstacle, the frequency of the resulting wave will be changed, or Doppler- More specifically, if the obstacle is moving toward the source, the frequency of the reflected wave will be increased; and if the obstacle is moving away from the source, the frequency of the reflected wave will be The amount of the frequency shift can be used to determine the velocity of the moving Just as the Doppler shift for radar, an electromagnetic wave, can be used to determine the speed of a moving car, so can the speed of a moving submarine be determined by the Doppler shift of a sonar An important industrial application is the ultrasonic flow meter, in which reflecting ultrasound off a flowing liquid leads to a Doppler shift that is calibrated to provide the flow rate of the This technique also has been applied to blood flow in Many burglar alarms, both for home use and for use in commercial buildings, employ the ultrasonic Doppler shift Such alarms cannot be used where pets or moving curtains might activate Materials testing Nondestructive testing involves the use of ultrasonic echolocation to gather information on the integrity of mechanical Since changes in the material present an impedance mismatch from which an ultrasonic wave is reflected, ultrasonic testing can be used to identify faults, holes, cracks, or corrosion in materials, to inspect welds, to determine the quality of poured concrete, and to monitor metal Owing to the mechanism by which sound waves propagate in metals, ultrasound can be used to probe more deeply than any other form of Ultrasonic procedures are used to perform in-service inspection of structures in nuclear Structural flaws in materials can also be studied by subjecting the materials to stress and looking for acoustic emissions as the materials are Acoustic emission, the general name for this type of nondestructive study, has developed as a distinct field of High-intensity applications High-intensity ultrasound has achieved a variety of important Perhaps the most ubiquitous is ultrasonic cleaning, in which ultrasonic vibrations are set up in small liquid tanks in which objects are placed for Cavitation of the liquid by the ultrasound, as well as the vibration, create turbulence in the liquid and result in the cleaning Ultrasonic cleaning is very popular for jewelry and has also been used with such items as dentures, surgical instruments, and small Degreasing is often enhanced by ultrasonic Large-scale ultrasonic cleaners have also been developed for use in assembly Ultrasonic machining employs the high-intensity vibrations of a transducer to move a machine If necessary, a slurry containing carborundum grit may be used; diamond tools can also be A variation of this technique is ultrasonic drilling, which makes use of pneumatic vibrations at ultrasonic frequencies in place of the standard rotary drill Holes of virtually any shape can be drilled in hard or brittle materials such as glass, germanium, or Ultrasonic soldering has become important, especially for soldering unusual or difficult materials and for very clean The ultrasonic vibrations perform the function of cleaning the surface, even removing the oxide layer on aluminum so that the material can be Because the surfaces can be made extremely clean and free from the normal thin oxide layer, soldering flux becomes Chemical and electrical uses The chemical effects of ultrasound arise from an electrical discharge that accompanies the cavitation This forms a basis for ultrasound's acting as a catalyst in certain chemical reactions, including oxidation, reduction, hydrolysis, polymerization and depolymerization, and molecular With ultrasound, some chemical processes can be carried out more rapidly, at lower temperatures, or more The ultrasonic delay line is a thin layer of piezoelectric material used to produce a short, precise delay in an electrical The electrical signal creates a mechanical vibration in the piezoelectric crystal that passes through the crystal and is converted back to an electrical A very precise time delay can be achieved by constructing a crystal with the proper These devices are employed in fast electronic timing Medical applications Although ultrasound competes with other forms of medical imaging, such as X-ray techniques and magnetic resonance imaging, it has certain desirable features—for example, Doppler motion study—that the other techniques cannot In addition, among the various modern techniques for the imaging of internal organs, ultrasonic devices are by far the least Ultrasound is also used for treating joint pains and for treating certain types of tumours for which it is desirable to produce localized A very effective use of ultrasound deriving from its nature as a mechanical vibration is the elimination of kidney and bladder Diagnosis Much medical diagnostic imaging is carried out with X Because of the high photon energies of the X ray, this type of radiation is highly ionizing—that is, X rays are readily capable of destroying molecular bonds in the body tissue through which they This destruction can lead to changes in the function of the tissue involved or, in extreme cases, its One of the important advantages of ultrasound is that it is a mechanical vibration and is therefore a nonionizing form of Thus, it is usable in many sensitive circumstances where X rays might be Also, the resolution of X rays is limited owing to their great penetrating ability and the slight differences between soft Ultrasound, on the other hand, gives good contrast between various types of soft Ultrasonic scanning in medical diagnosis uses the same principle as Pulses of high-frequency ultrasound, generally above one megahertz, are created by a piezoelectric transducer and directed into the As the ultrasound traverses various internal organs, it encounters changes in acoustic impedance, which cause The amount and time delay of the various reflections can be analyzed to obtain information regarding the internal In the B-scan mode, a linear array of transducers is used to scan a plane in the body, and the resultant data is displayed on a television screen as a two-dimensional The A-scan technique uses a single transducer to scan along a line in the body, and the echoes are plotted as a function of This technique is used for measuring the distances or sizes of internal The M-scan mode is used to record the motion of internal organs, as in the study of heart Greater resolution is obtained in ultrasonic imaging by using higher frequencies—, shorter A limitation of this property of waves is that higher frequencies tend to be much more strongly Because it is nonionizing, ultrasound has become one of the staples of obstetric During the process of drawing amniotic fluid in testing for birth defects, ultrasonic imaging is used to guide the needle and thus avoid damage to the fetus or surrounding Ultrasonic imaging of the fetus can be used to determine the date of conception, to identify multiple births, and to diagnose abnormalities in the development of the Ultrasonic Doppler techniques have become very important in diagnosing problems in blood In one technique, a three-megahertz ultrasonic beam is reflected off typical oncoming arterial blood with a Doppler shift of a few kilohertz—a frequency difference that can be heard directly by a Using this technique, it is possible to monitor the heartbeat of a fetus long before a stethoscope can pick up the Arterial diseases such as arteriosclerosis can also be diagnosed, and the healing of arteries can be monitored following A combination of B-scan imaging and Doppler imaging, known as duplex scanning, can identify arteries and immediately measure their blood flow; this has been extensively used to diagnose heart valve Using ultrasound with frequencies up to 2,000 megahertz, which has a wavelength of 75 micrometre in soft tissues (as compared with a wavelength of about 55 micrometre for light), ultrasonic microscopes have been developed that rival light microscopes in their The distinct advantage of ultrasonic microscopes lies in their ability to distinguish various parts of a cell by their Also, because they require no artificial contrast mediums, which kill the cells, acoustic microscopy can study actual living Therapy and surgery Because ultrasound is a mechanical vibration and can be well focused at high frequencies, it can be used to create internal heating of localized tissue without harmful effects on nearby This technique can be employed to relieve pains in joints, particularly in the back and Also, research is now being carried out in the treatment of certain types of cancer by local heating, since focusing intense ultrasonic waves can heat the area of a tumour while not significantly affecting surrounding Trackless surgery—that is, surgery that does not require an incision or track from the skin to the affected area—has been developed for several Focused ultrasound has been used for the treatment of Parkinson's disease by creating brain lesions in areas that are inaccessible to traditional A common application of this technique is the destruction of kidney stones with shock waves formed by bursts of focused In some cases, a device called an ultrasonic lithotripter focuses the ultrasound with the help of X-ray guidance, but a more common technique for destruction of kidney stones, known as endoscopic ultrasonic disintegration, uses a small metal rod inserted through the skin to deliver ultrasound in the 22- to 30-kilohertz frequency Infrasonics The term infrasonics refers to waves of a frequency below the range of human hearing—, below about 20 Such waves occur in nature in earthquakes, waterfalls, ocean waves, volcanoes, and a variety of atmospheric phenomena such as wind, thunder, and weather Calculating the motion of these waves and predicting the weather using these calculations, among other information, is one of the great challenges for modern high-speed TableAircraft, automobiles, or other rapidly moving objects, as well as air handlers and blowers in buildings, also produce substantial amounts of infrasonic Studies have shown that many people experience adverse reactions to large intensities of infrasonic frequencies, developing headaches, nausea, blurred vision, and On the other hand, a number of animals are sensitive to infrasonic frequencies, as indicated in the T It is believed by many zoologists that this sensitivity in animals such as elephants may be helpful in providing them with early warning of earthquakes and weather It has been suggested that the sensitivity of birds to infrasound aids their navigation and even affects their One of the most important examples of infrasonic waves in nature is in Three principal types of earthquake wave exist: the S-wave, a transverse body wave; the P-wave, a longitudinal body wave; and the L-wave, which propagates along the boundary of stratified L-waves, which are of great importance in earthquake engineering, propagate in a similar way to water waves, at low velocities that are dependent on S-waves are transverse body waves and thus can only be propagated within solid bodies such as P-waves are longitudinal waves similar to sound waves; they propagate at the speed of sound and have large When P-waves propagating from the epicentre of an earthquake reach the surface of the Earth, they are converted into L-waves, which may then damage surface The great range of P-waves makes them useful in identifying earthquakes from observation points a great distance from the In many cases, the most severe shock from an earthquake is preceded by smaller shocks, which provide advance warning of the greater shock to Underground nuclear explosions also produce P-waves, allowing them to be monitored from any point in the world if they are of sufficient The reflection of man-made seismic shocks has helped to identify possible locations of oil and natural-gas Distinctive rock formations in which these minerals are likely to be found can be identified by sonic ranging, primarily at infrasonic
很显然如果前面那段没有符号的就是提名的话那么缺少了作者和来源根据我的猜测咱给你分割分割【1】HIMANISHDAS,UsefulByproductsfromCellulosicWastesofAgricultureandFoodIndustry-ACriticalAppraisalCriticalReviews[J]FoodScienceandNutritionBocaRaton,2004,44(2):77~90以上就是格式了算了我今天就吃亏点把咱学校论文中参考文献的格式和你说一下吧:参考文献A．正文中的参考文献格式：×××[3]，×××××××××[3，6]，××××××××××××××××××××××××××××××××××[3-6]。[5号TimesNewRoman，上标；[3]表示第三篇文献，[3，6]表示第三篇和第六篇文献，[3-6]表示第三，四，五，六篇连续的文献]B后面参考文献的格式：参考文献[宋体；五号；加粗；居中；段前段后各空一行][1]张毅铸造工艺CAD及其应用[M]北京:机械工业出版社，1994:14-15[2]HuangSC,HuangYM,ShiehSMVibrationandstabilityofarotatingshaftcontainingatransersecrack[J]JSoundandVibration,1993,162(3):387-401[3]陈金梅．氟石膏生产早强快硬水泥的试验研究[D]．西安：西安建筑科学大学，2000{五号字体，中文为楷体_GB2312，英文和数字为TimesNewRoman，3倍行距，两端对齐（不是分散对齐）。(1)专著格式：[序号]编著者书名[M]版本(第1版不标注),出版地:出版社，年代:起止页码(2)期刊论文格式：[序号]作者（不超过3人者全部列出，超过者只列前3名，后加“等”或“”）论文名称[J]期刊名称，年度，卷（期）：起止页码(3)学位论文格式：[序号]作者学位论文名称[D]发表地：学位授予单位，年度}__________________________________________________________________________________最后，西瓜，好评给我要不然明天烘了你实验室。。。哈哈哈哈
英文参考文献引用格式有两种：APA格式和MLA格式。1、APA格式：APA（American Psychological Association）是一种标明参考来源的格式，主要使用在社会科学领域及其他学术准则中，国内很多期刊也是采用的APA格式。APA文内注的参考文献格式是：“（作者姓氏，发表年份）”。APA文末的参考文献目录格式是：Reference List, 必须以姓（Family name）的字母顺序来排列，基本结构为：期刊类：【作者】【发表年份】【文章名】【期刊名】【卷号/期数：起止页码】Smith,J（2006）The title of the The title of Journal,1,101-105。非期刊类：【作者】【发表年份】【书籍名】【出版地：出版社】SG（2002）What computers can't New York:Harp&Row。2、MLA格式：MLA是美国现代语言协会（Modern Language Association）制定的论文指导格式，多用于人文学科（Liberal Arts）。MLA文内注的基本格式：“（作者姓氏，文献页码）”。MLA文末的参考文献目录格式：在MLA格式中称为Works Cited,同样是以姓（Family name）的字母顺序来排列，基本结构为：期刊类：【作者】【“文章名”】【期刊名】【卷号或期数】【发表年份】起止页码】Nwezeh,CE“The Comparative Approachto Modern African L”Year book of General and Comparative Literature 28(1979):22。非期刊类【作者】【书籍名】【出版地：出版社】【发表年份】Winfield,Richard DLaw in Civil SMadison:U of Wisconsin P,1995。文献引用不符合要求具体表现是：1、所列文献范围过宽，凡所参阅过的均列出其中，如教材、内部刊物、获奖过但并未公开发表的成果报告等。2、所列文献过多，如有些医生认为文献越多越好，将参阅过的文章书籍后的参考文献也悉数收录，有些文献作者并没有亲自阅读，只是认为跟自己的文章搭点边，也凑数其后。3、所列文献过少，有些医生怕自己文章引述别人东西太多，被人认为抄袭，故意将一些重要参考文献略去。4、对文献的理解偏面，以为只有引用文献原文才需要列出。5、大而不当，将整期刊物甚至连续几期杂志或整张报纸作为参考文献。
Introductionvibrations of frequencies greater than the upper limit of the audible range for humans—that is, greater than about 20 The term sonic is applied to ultrasound waves of very high Hypersound, sometimes called praetersound or microsound, is sound waves of frequencies greater than 1013 At such high frequencies it is very difficult for a sound wave to propagate efficiently; indeed, above a frequency of about 25 × 1013 hertz, it is impossible for longitudinal waves to propagate at all, even in a liquid or a solid, because the molecules of the material in which the waves are traveling cannot pass the vibration along rapidly TableMany animals have the ability to hear sounds in the human ultrasonic frequency Some ranges of hearing for mammals and insects are compared with those of humans in the T A presumed sensitivity of roaches and rodents to frequencies in the 40 kilohertz region has led to the manufacture of “pest controllers” that emit loud sounds in that frequency range to drive the pests away, but they do not appear to work as TransducersAn ultrasonic transducer is a device used to convert some other type of energy into an ultrasonic There are several basic types, classified by the energy source and by the medium into which the waves are being Mechanical devices include gas-driven, or pneumatic, transducers such as whistles as well as liquid-driven transducers such as hydrodynamic oscillators and vibrating These devices, limited to low ultrasonic frequencies, have a number of industrial applications, including drying, ultrasonic cleaning, and injection of fuel oil into Electromechanical transducers are far more versatile and include piezoelectric and magnetostrictive A magnetostrictive transducer makes use of a type of magnetic material in which an applied oscillating magnetic field squeezes the atoms of the material together, creating a periodic change in the length of the material and thus producing a high-frequency mechanical Magnetostrictive transducers are used primarily in the lower frequency ranges and are common in ultrasonic cleaners and ultrasonic machining By far the most popular and versatile type of ultrasonic transducer is the piezoelectric crystal, which converts an oscillating electric field applied to the crystal into a mechanical Piezoelectric crystals include quartz, Rochelle salt, and certain types of Piezoelectric transducers are readily employed over the entire frequency range and at all output Particular shapes can be chosen for particular For example, a disc shape provides a plane ultrasonic wave, while curving the radiating surface in a slightly concave or bowl shape creates an ultrasonic wave that will focus at a specific Piezoelectric and magnetostrictive transducers also are employed as ultrasonic receivers, picking up an ultrasonic vibration and converting it into an electrical Applications in researchOne of the important areas of scientific study in which ultrasonics has had an enormous impact is When water is boiled, bubbles form at the bottom of the container, rise in the water, and then collapse, leading to the sound of the boiling The boiling process and the resulting sounds have intrigued people since they were first observed, and they were the object of considerable research and calculation by the British physicists Osborne Reynolds and Lord Rayleigh, who applied the term cavitation to the process of formation of Because an ultrasonic wave can be used carefully to control cavitation, ultrasound has been a useful tool in the investigation of the The study of cavitation has also provided important information on intermolecular Research is being carried out on aspects of the cavitation process and its A contemporary subject of research involves emission of light as the cavity produced by a high-intensity ultrasonic wave This effect, called sonoluminescence, is believed to create instantaneous temperatures hotter than the surface of the SThe speed of propagation of an ultrasonic wave is strongly dependent on the viscosity of the This property can be a useful tool in investigating the viscosity of Because the various parts of a living cell are distinguished by differing viscosities, acoustical microscopy can make use of this property of cells to “see” into living cells, as will be discussed below in Medical Ranging and navigatingSonar (sound navigation and ranging) has extensive marine By sending out pulses of sound or ultrasound and measuring the time required for the pulses to reflect off a distant object and return to the source, the location of that object can be ascertained and its motion This technique is used extensively to locate and track submarines at sea and to locate explosive mines below the surface of the Two boats at known locations can also use triangulation to locate and track a third boat or The distance over which these techniques can be used is limited by temperature gradients in the water, which bend the beam away from the surface and create shadow One of the advantages of ultrasonic waves over sound waves in underwater applications is that, because of their higher frequencies (or shorter wavelengths), the former will travel greater distances with less Ranging has also been used to map the bottom of the ocean, providing depth charts that are commonly used in navigation, particularly near coasts and in shallow Even small boats are now equipped with sonic ranging devices that determine and display the depth of the water so that the navigator can keep the boat from beaching on submerged sandbars or other shallow Modern fishing boats use ultrasonic ranging devices to locate schools of fish, substantially increasing their Even in the absence of visible light, bats can guide their flight and even locate flying insects (which they consume in flight) through the use of sonic Ultrasonic echolocation has also been used in traffic control applications and in counting and sorting items on an assembly Ultrasonic ranging provides the basis of the eye and vision systems for robots, and it has a number of important medical applications (see below)The Doppler effectIf an ultrasonic wave is reflected off a moving obstacle, the frequency of the resulting wave will be changed, or Doppler- More specifically, if the obstacle is moving toward the source, the frequency of the reflected wave will be increased; and if the obstacle is moving away from the source, the frequency of the reflected wave will be The amount of the frequency shift can be used to determine the velocity of the moving Just as the Doppler shift for radar, an electromagnetic wave, can be used to determine the speed of a moving car, so can the speed of a moving submarine be determined by the Doppler shift of a sonar An important industrial application is the ultrasonic flow meter, in which reflecting ultrasound off a flowing liquid leads to a Doppler shift that is calibrated to provide the flow rate of the This technique also has been applied to blood flow in Many burglar alarms, both for home use and for use in commercial buildings, employ the ultrasonic Doppler shift Such alarms cannot be used where pets or moving curtains might activate Materials testingNondestructive testing involves the use of ultrasonic echolocation to gather information on the integrity of mechanical Since changes in the material present an impedance mismatch from which an ultrasonic wave is reflected, ultrasonic testing can be used to identify faults, holes, cracks, or corrosion in materials, to inspect welds, to determine the quality of poured concrete, and to monitor metal Owing to the mechanism by which sound waves propagate in metals, ultrasound can be used to probe more deeply than any other form of Ultrasonic procedures are used to perform in-service inspection of structures in nuclear Structural flaws in materials can also be studied by subjecting the materials to stress and looking for acoustic emissions as the materials are Acoustic emission, the general name for this type of nondestructive study, has developed as a distinct field of High-intensity applicationsHigh-intensity ultrasound has achieved a variety of important Perhaps the most ubiquitous is ultrasonic cleaning, in which ultrasonic vibrations are set up in small liquid tanks in which objects are placed for Cavitation of the liquid by the ultrasound, as well as the vibration, create turbulence in the liquid and result in the cleaning Ultrasonic cleaning is very popular for jewelry and has also been used with such items as dentures, surgical instruments, and small Degreasing is often enhanced by ultrasonic Large-scale ultrasonic cleaners have also been developed for use in assembly Ultrasonic machining employs the high-intensity vibrations of a transducer to move a machine If necessary, a slurry containing carborundum grit may be used; diamond tools can also be A variation of this technique is ultrasonic drilling, which makes use of pneumatic vibrations at ultrasonic frequencies in place of the standard rotary drill Holes of virtually any shape can be drilled in hard or brittle materials such as glass, germanium, or Ultrasonic soldering has become important, especially for soldering unusual or difficult materials and for very clean The ultrasonic vibrations perform the function of cleaning the surface, even removing the oxide layer on aluminum so that the material can be Because the surfaces can be made extremely clean and free from the normal thin oxide layer, soldering flux becomes Chemical and electrical usesThe chemical effects of ultrasound arise from an electrical discharge that accompanies the cavitation This forms a basis for ultrasound's acting as a catalyst in certain chemical reactions, including oxidation, reduction, hydrolysis, polymerization and depolymerization, and molecular With ultrasound, some chemical processes can be carried out more rapidly, at lower temperatures, or more The ultrasonic delay line is a thin layer of piezoelectric material used to produce a short, precise delay in an electrical The electrical signal creates a mechanical vibration in the piezoelectric crystal that passes through the crystal and is converted back to an electrical A very precise time delay can be achieved by constructing a crystal with the proper These devices are employed in fast electronic timing Medical applicationsAlthough ultrasound competes with other forms of medical imaging, such as X-ray techniques and magnetic resonance imaging, it has certain desirable features—for example, Doppler motion study—that the other techniques cannot In addition, among the various modern techniques for the imaging of internal organs, ultrasonic devices are by far the least Ultrasound is also used for treating joint pains and for treating certain types of tumours for which it is desirable to produce localized A very effective use of ultrasound deriving from its nature as a mechanical vibration is the elimination of kidney and bladder DiagnosisMuch medical diagnostic imaging is carried out with X Because of the high photon energies of the X ray, this type of radiation is highly ionizing—that is, X rays are readily capable of destroying molecular bonds in the body tissue through which they This destruction can lead to changes in the function of the tissue involved or, in extreme cases, its One of the important advantages of ultrasound is that it is a mechanical vibration and is therefore a nonionizing form of Thus, it is usable in many sensitive circumstances where X rays might be Also, the resolution of X rays is limited owing to their great penetrating ability and the slight differences between soft Ultrasound, on the other hand, gives good contrast between various types of soft Ultrasonic scanning in medical diagnosis uses the same principle as Pulses of high-frequency ultrasound, generally above one megahertz, are created by a piezoelectric transducer and directed into the As the ultrasound traverses various internal organs, it encounters changes in acoustic impedance, which cause The amount and time delay of the various reflections can be analyzed to obtain information regarding the internal In the B-scan mode, a linear array of transducers is used to scan a plane in the body, and the resultant data is displayed on a television screen as a two-dimensional The A-scan technique uses a single transducer to scan along a line in the body, and the echoes are plotted as a function of This technique is used for measuring the distances or sizes of internal The M-scan mode is used to record the motion of internal organs, as in the study of heart Greater resolution is obtained in ultrasonic imaging by using higher frequencies—, shorter A limitation of this property of waves is that higher frequencies tend to be much more strongly Because it is nonionizing, ultrasound has become one of the staples of obstetric During the process of drawing amniotic fluid in testing for birth defects, ultrasonic imaging is used to guide the needle and thus avoid damage to the fetus or surrounding Ultrasonic imaging of the fetus can be used to determine the date of conception, to identify multiple births, and to diagnose abnormalities in the development of the Ultrasonic Doppler techniques have become very important in diagnosing problems in blood In one technique, a three-megahertz ultrasonic beam is reflected off typical oncoming arterial blood with a Doppler shift of a few kilohertz—a frequency difference that can be heard directly by a Using this technique, it is possible to monitor the heartbeat of a fetus long before a stethoscope can pick up the Arterial diseases such as arteriosclerosis can also be diagnosed, and the healing of arteries can be monitored following A combination of B-scan imaging and Doppler imaging, known as duplex scanning, can identify arteries and immediately measure their blood flow; this has been extensively used to diagnose heart valve Using ultrasound with frequencies up to 2,000 megahertz, which has a wavelength of 75 micrometre in soft tissues (as compared with a wavelength of about 55 micrometre for light), ultrasonic microscopes have been developed that rival light microscopes in their The distinct advantage of ultrasonic microscopes lies in their ability to distinguish various parts of a cell by their Also, because they require no artificial contrast mediums, which kill the cells, acoustic microscopy can study actual living Therapy and surgeryBecause ultrasound is a mechanical vibration and can be well focused at high frequencies, it can be used to create internal heating of localized tissue without harmful effects on nearby This technique can be employed to relieve pains in joints, particularly in the back and Also, research is now being carried out in the treatment of certain types of cancer by local heating, since focusing intense ultrasonic waves can heat the area of a tumour while not significantly affecting surrounding Trackless surgery—that is, surgery that does not require an incision or track from the skin to the affected area—has been developed for several Focused ultrasound has been used for the treatment of Parkinson's disease by creating brain lesions in areas that are inaccessible to traditional A common application of this technique is the destruction of kidney stones with shock waves formed by bursts of focused In some cases, a device called an ultrasonic lithotripter focuses the ultrasound with the help of X-ray guidance, but a more common technique for destruction of kidney stones, known as endoscopic ultrasonic disintegration, uses a small metal rod inserted through the skin to deliver ultrasound in the 22- to 30-kilohertz frequency InfrasonicsThe term infrasonics refers to waves of a frequency below the range of human hearing—, below about 20 Such waves occur in nature in earthquakes, waterfalls, ocean waves, volcanoes, and a variety of atmospheric phenomena such as wind, thunder, and weather Calculating the motion of these waves and predicting the weather using these calculations, among other information, is one of the great challenges for modern high-speed TableAircraft, automobiles, or other rapidly moving objects, as well as air handlers and blowers in buildings, also produce substantial amounts of infrasonic Studies have shown that many people experience adverse reactions to large intensities of infrasonic frequencies, developing headaches, nausea, blurred vision, and On the other hand, a number of animals are sensitive to infrasonic frequencies, as indicated in the T It is believed by many zoologists that this sensitivity in animals such as elephants may be helpful in providing them with early warning of earthquakes and weather It has been suggested that the sensitivity of birds to infrasound aids their navigation and even affects their One of the most important examples of infrasonic waves in nature is in Three principal types of earthquake wave exist: the S-wave, a transverse body wave; the P-wave, a longitudinal body wave; and the L-wave, which propagates along the boundary of stratified L-waves, which are of great importance in earthquake engineering, propagate in a similar way to water waves, at low velocities that are dependent on S-waves are transverse body waves and thus can only be propagated within solid bodies such as P-waves are longitudinal waves similar to sound waves; they propagate at the speed of sound and have large When P-waves propagating from the epicentre of an earthquake reach the surface of the Earth, they are converted into L-waves, which may then damage surface The great range of P-waves makes them useful in identifying earthquakes from observation points a great distance from the In many cases, the most severe shock from an earthquake is preceded by smaller shocks, which provide advance warning of the greater shock to Underground nuclear explosions also produce P-waves, allowing them to be monitored from any point in the world if they are of sufficient The reflection of man-made seismic shocks has helped to identify possible locations of oil and natural-gas Distinctive rock formations in which these minerals are likely to be found can be identified by sonic ranging, primarily at infrasonic Environmental noiseMany forms of noise in the urban environment, including traffic and airplane noise, industrial noise, and noise from electronically amplified music performed at high audio levels in confined rooms, may contribute to hearing Even when t
希望这个超声波测距原理能帮助你。。 多给点分啊 下载这个找了很长时间This article described the three directions (before, left, right) ultrasonic ranging system is to understand the front of the robot, left and right environment to provide a movement away from the (Similar to GPS Positioning System) A principle of ultrasonic distance measurement 1, the principle of piezoelectric ultrasonic generator Piezoelectric ultrasonic generator is the use of piezoelectric crystal resonators to Ultrasonic generator, the internal structure as shown in Figure 1, it has two piezoelectric chip and a resonance When it's two plus pulse signal, the frequency equal to the intrinsic piezoelectric oscillation frequency chip, the chip will happen piezoelectric resonance, and promote the development of plate vibration resonance, ultrasound is Conversely, if the two are not inter-electrode voltage, when the board received ultrasonic resonance, it will be for vibration suppression of piezoelectric chip, the mechanical energy is converted to electrical signals, then it becomes the ultrasonic 2, the principle of ultrasonic distance measurement Ultrasonic transmitter in a direction to launch ultrasound, in the moment to launch the beginning of time at the same time, the spread of ultrasound in the air, obstacles on his way to return immediately, the ultrasonic reflected wave received by the receiver immediately stop the Ultrasound in the air as the propagation velocity of 340m / s, according to the timer records the time t, we can calculate the distance between the launch distance barrier (s), that is: s = 340t / 2 Ultrasonic Ranging System for the Second Circuit Design System is characterized by single-chip microcomputer to control the use of ultrasonic transmitter and ultrasonic receiver since the launch from time to time, single-chip selection of 8751, economic-to-use, and the chip has 4K of ROM, to facilitate Circuit schematic diagram shown in Figure Draw only the front range of the circuit wiring diagram, left and right in front of Ranging Ranging circuits and the same circuit, it is 1,40 kHz ultrasonic pulse generated with the launch Ranging system using the ultrasonic sensor of piezoelectric ceramic sensors UCM40, its operating voltage of the pulse signal is 40kHz, which by the single-chip implementation of the following procedures to puzel: mov 14h, # 12h; ultrasonic firing continued 200ms here: cpl 0; output 40kHz square wave nop; nop; nop; djnz 14h, here; ret Ranging in front of single-chip termination circuit P0 input port, single chip implementation of the above procedure, the P0 port in a 40kHz pulse output signal, after amplification transistor T, the drive to launch the first ultrasonic UCM40T, issued 40kHz ultrasonic pulse, and the continued launch of Ranging the right and the left side of the circuit, respectively, then input port P1 and P2, the working principle and circuit in front of the same 2, reception and processing of ultrasonic Used to receive the first launch of the first pair UCM40R, the ultrasonic pulse modulation signal into an alternating voltage, the op-amp amplification IC1A and after polarization IC1B to IC IC2 is locked loop with audio decoder chip LM567, internal voltage-controlled oscillator center frequency of f0 = 1/1R8C3, capacitor C4 determine their target R8-conditioning in the launch of the carrier frequency on the LM567 input signal is greater than 25mV, the output from the high jump 8 feet into a low-level, as interrupt request signals to the single-chip Ranging in front of single-chip termination circuit output port INT0 interrupt the highest priority, right or left location of the output circuit with output gate IC3A access INT1 port single-chip, while single-chip P3 and P 4 received input IC3A, interrupted by the process to identify the source of inquiry to deal with, interrupt priority level for the first left right Part of the source code is as follows: receive1: push psw push acc clr ex1; related external interrupt 1 jnb 1, right; P1 pin to 0, ranging from right to interrupt service routine circuit jnb 2, left; P2 pin to 0, to the left ranging circuit interrupt service routine return: SETB EX1; open external interrupt 1 pop? acc pop? psw reti right: ?; right location entrance circuit interrupt service routine ? Ajmp? Return left: ; left Ranging entrance circuit interrupt service routine ? Ajmp? Return 4, the calculation of ultrasonic propagation time When you start firing at the same time start the single-chip circuitry within the timer T0, the use of timer counting function records the time and the launch of ultrasonic reflected wave received When you receive the ultrasonic reflected wave, the receiver circuit outputs a negative jump in the end of INT0 or INT1 interrupt request generates a signal, single-chip microcomputer in response to external interrupt request, the implementation of the external interrupt service subroutine, read the time difference, calculating the distance Some of its source code is as follows: RECEIVE0: PUSH PSW PUSH ACC CLR EX0; related external interrupt 0 ? MOV R7, TH0; read the time value MOV R6, TL0? CLR C MOV A, R6 SUBB A, # 0BBH; calculate the time difference MOV 31H, A; storage results MOV A, R7 SUBB A, # 3CH MOV 30H, A? SETB EX0; open external interrupt 0 POP ACC? POP PSW RETI Fourth, the ultrasonic ranging system software design Software is divided into two parts, the main program and interrupt service routine, shown in Figure 3 (a) (b) (c) Completion of the work of the main program is initialized, each sequence of ultrasonic transmitting and receiving Interrupt service routines from time to time to complete three of the rotation direction of ultrasonic launch, the main external interrupt service subroutine to read the value of completion time, distance calculation, the results of the output and so V CONCLUSIONS Required measuring range of 30cm ~ 200cm objects inside the plane to do a number of measurements found that the maximum error is 5cm, and good Single-chip design can be seen on the ultrasonic ranging system has a hardware structure is simple, reliable, small features such as measurement Therefore, it can be used not only for mobile robot can be used in other detection Thoughts: As for why the receiver do not have the transistor amplifier circuit, because the magnification well, CX20106 integrated amplifier, but also with automatic gain control level, magnification to 76dB, the center frequency is 38k to 40k, is exactly resonant ultrasonic sensors frequency=====本文所介绍的三方向（前、左、右）超声波测距系统，就是为机器人了解其前方、左侧和右侧的环境而提供一个运动距离信息。（类似GPS定位系统） 一 超声波测距原理 1、压电式超声波发生器原理压电式超声波发生器实际上是利用压电晶体的谐振来工作的。超声波发生器内部结构如图1所示，它有两个压电晶片和一个共振板。当它的两极外加脉冲信号，其频率等于压电晶片的固有振荡频率时，压电晶片将会发生共振，并带动共振板振动，便产生超声波。反之，如果两电极间未外加电压，当共振板接收到超声波 时，将压迫压电晶片作振动，将机械能转换为电信号，这时它就成为超声波接收器了。 2、超声波测距原理超声波发射器向某一方向发射超声波，在发射时刻的同时开始计时，超声波在空气中传播，途中碰到障碍物就立即返回来，超声波接收器收到反射波就立即停止计时。超声波在空气中的传播速度为340m/s，根据计时器记录的时间t，就可以计算出发射点距障碍物的距离(s)，即：s=340t/2二 超声波测距系统的电路设计 系统的特点是利用单片机控制超声波的发射和对超声波自发射至接收往返时间的计时，单片机选用8751，经济易用，且片内有4K的ROM，便于编程。电路原理图如图2所示。其中只画出前方测距电路的接线图，左侧和右侧测距电路与前方测距电路相同，故省略之。1、40kHz 脉冲的产生与超声波发射测距系统中的超声波传感器采用UCM40的压电陶瓷传感器，它的工作电压是40kHz的脉冲信号，这由单片机执行下面程序来产生。puzel： mov 14h, #12h；超声波发射持续200mshere： cpl 0 ； 输出40kHz方波 nop ； nop ； nop ； djnz 14h，here； ret前方测距电路的输入端接单片机P0端口，单片机执行上面的程序后，在P0 端口输出一个40kHz的脉冲信号，经过三极管T放大，驱动超声波发射头UCM40T，发出40kHz的脉冲超声波，且持续发射200ms。右侧和左侧测 距电路的输入端分别接P1和P2端口，工作原理与前方测距电路相同。2、超声波的接收与处理接收头采用与发射头配对的UCM40R，将超声波调制脉冲变为交变电压信号，经运算放大器IC1A和IC1B两极放大后加至IC2。IC2是带有锁 定环的音频译码集成块LM567，内部的压控振荡器的中心频率f0=1/1R8C3，电容C4决定其锁定带宽。调节R8在发射的载频上，则LM567 输入信号大于25mV，输出端8脚由高电平跃变为低电平，作为中断请求信号，送至单片机处理前方测距电路的输出端接单片机INT0端口，中断优先级最高，左、右测距电路的输出通过与门IC3A的输出接单片机INT1端口，同时单片机P3和P4接到IC3A的输入端，中断源的识别由程序查询来处理，中断优先级为先右后左。部分源程序如下：receive1：push psw push acc clr ex1 ； 关外部中断1 jnb 1, right ； P1引脚为0,转至右测距电路中断服务程序 jnb 2, left ； P2引脚为0,转至左测距电路中断服务程序return： SETB EX1； 开外部中断1 pop? acc pop? psw retiright： ? ； 右测距电路中断服务程序入口 ? ajmp? returnleft： ； 左测距电路中断服务程序入口 ? ajmp? return4、计算超声波传播时间在启动发射电路的同时启动单片机内部的定时器T0，利用定时器的计数功能记录超声波发射的时间和收到反射波的时间。当收到超声波反射波时，接收电路 输出端产生一个负跳变，在INT0或INT1端产生一个中断请求信号，单片机响应外部中断请求，执行外部中断服务子程序，读取时间差，计算距离。其部分源程序如下：RECEIVE0： PUSH PSW PUSH ACC CLR EX0 ； 关外部中断0 ? MOV R7, TH0 ； 读取时间值 MOV R6, TL0? CLR C MOV A, R6 SUBB A, #0BBH； 计算时间差 MOV 31H, A ； 存储结果 MOV A, R7 SUBB A, #3CH MOV 30H, A? SETB EX0 ； 开外部中断0 POP ACC? POP PSW RETI四、超声波测距系统的软件设计 软件分为两部分，主程序和中断服务程序，如图3（a）（b）(c) 所示。主程序完成初始化工作、各路超声波发射和接收顺序的控制。定时中断服务子程序完成三方向超声波的轮流发射，外部中断服务子程序主要完成时间值的读取、距离计算、结果的输出等工作。五、结论对所要求测量范围30cm~200cm内的平面物体做了多次测量发现，其最大误差为5cm，且重复性好。可见基于单片机设计的超声波测距系统具有硬件结构简单、工作可靠、测量误差小等特点。因此，它不仅可用于移动机器人，还可用在其它检测系统中。思考：至于为什么接收不用晶体管做放大电路呢，因为放大倍数搞不好，CX20106集成放大电路，还带自动电平增益控制，放大倍数为76dB，中心频率是38k到40k，刚好是超声波传感器的谐振频率 。
可以这样说：Zhang D Basic Ultrasonic M Beijing: Science Publisher, 希望能帮到你，满意请采纳，别忘了点个赞!
自19世纪末到20世纪初，在物理学上发现了压电效应与反压电效应之后，人们解决了利用电子学技术产生超声波的办法，从此迅速揭开了发展与推广超声技术的历史篇章。1922年，德国出现了首例超声波治疗的发明专利；1939年发表了有关超声波治疗取得临床效果的文献报道。20世纪40年代末期超声治疗在欧美兴起，直到1949年召开的第一次国际医学超声波学术会议上，才有了超声治疗方面的论文交流，为超声治疗学的发展奠定了基础。1956年第二届国际超声医学学术会议上已有许多论文发表，超声治疗进入了实用成熟阶段。声波是物体机械振动状态（或能量）的传播形式。超声波是指振动频率大于20000Hz以上的，其每秒的振动次数（频率）甚高，超出了人耳听觉的一般上限（20000Hz），人们将这种听不见的声波叫做超声波。由于其频率高，因而具有许多特点：首先是能量集中，其波长比一般声波短得多，因而可以用来切削、焊接、钻孔等。再者由于它频率高，波长短，衍射不严重，具有良好的定向性，工业与医学上常用超声波进行超声探测。超声和可闻声本质上是一致的，它们的共同点都是一种机械振动模式，通常以纵波的方式在弹性介质内会传播，是一种能量的传播形式，其不同点是超声波频率高，波长短，在一定距离内沿直线传播具有良好的束射性和方向性，1MHz=10^6Hz，即每秒振动100万次，可闻声的频率在20~20000Hz之间）。
自19世纪末到20世纪初，在物理学上发现了压电效应与反压电效应之后，人们解决了利用电子学技术产生超声波的办法，从此迅速揭开了发展与推广超声技术的历史篇章。1922年，德国出现了首例超声波治疗的发明专利；1939年发表了有关超声波治疗取得临床效果的文献报道。20世纪40年代末期超声治疗在欧美兴起，直到1949年召开的第一次国际医学超声波学术会议上，才有了超声治疗方面的论文交流，为超声治疗学的发展奠定了基础。1956年第二届国际超声医学学术会议上已有许多论文发表，超声治疗进入了实用成熟阶段。声波是物体机械振动状态（或能量）的传播形式。超声波是指振动频率大于20000Hz以上的，其每秒的振动次数（频率）甚高，超出了人耳听觉的一般上限（20000Hz），人们将这种听不见的声波叫做超声波。由于其频率高，因而具有许多特点：首先是能量集中，其波长比一般声波短得多，因而可以用来切削、焊接、钻孔等。再者由于它频率高，波长短，衍射不严重，具有良好的定向性，工业与医学上常用超声波进行超声探测。超声和可闻声本质上是一致的，它们的共同点都是一种机械振动模式，通常以纵波的方式在弹性介质内会传播，是一种能量的传播形式，其不同点是超声波频率高，波长短，在一定距离内沿直线传播具有良好的束射性和方向性，1MHz=10^6Hz，即每秒振动100万次，可闻声的频率在20~20000Hz之间）。
可以这样说：Zhang D Basic Ultrasonic M Beijing: Science Publisher, 希望能帮到你，满意请采纳，别忘了点个赞!
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怎么长这个的话找的话他通过一个那个，文字的后缀就可以找到了。