1. What Two Characteristics Can Be Used to Classify Electromagnetic Rays?

RFID+ Physics, Math, and RFID: Mind the Gap

Dr. Paul Sanghera , in RFID+ Report Guide and Exercise Exams, 2007

Types of Electromagnetic Waves

Electromagnetic waves tin can be grouped according to the direction of disturbance in them and according to the range of their frequency. Remember that a wave transfers free energy from one point to another point in infinite. That means there are two things going on: the disturbance that defines a wave, and the propagation of moving ridge. In this context the waves are grouped into the post-obit two categories:

▪

Longitudinal waves A wave is called a longitudinal moving ridge when the disturbances in the wave are parallel to the direction of propagation of the moving ridge. For instance, sound waves are longitudinal waves because the alter of pressure occurs parallel to the management of wave propagation.

▪

Transverse waves A wave is called a transverse wave when the disturbances in the wave are perpendicular (at right angles) to the direction of propagation of the moving ridge.

Electromagnetic waves are transverse waves. That means the electrical and magnetic fields change (oscillate) in a plane that is perpendicular to the direction of propagation of the wave. Also notation that electrical and magnetic fields in an EM moving ridge are besides perpendicular to each other.

NOTE

Electric fields and magnetic fields (Eastward and B) in an EM wave are perpendicular to each other and are also perpendicular to the direction of propagation of the wave.

Considering electric and magnetic fields change in a plane (perpendicular to the management of wave propagation), the management of change still has some freedom. Different means of using this freedom provide another criterion to classify electromagnetic waves into the following:

▪

Linearly polarized waves If the electric field (and hence the magnetic field) changes in such a style that its management remains parallel to a line in infinite as the wave travels, the wave is chosen linearly polarized.

▪

Circularly polarized waves If the change in electrical field occurs in a circumvolve or in an ellipse, the wave is called circularly or elliptically polarized. Therefore, the polarization of a transverse wave determines the direction of disturbance (oscillation) in a plane perpendicular to the direction of wave propagation.

CAUTION

Only transverse waves can be polarized, considering in a longitudinal moving ridge, the disturbance is always parallel to the direction of wave propagation.

And so, you can classify electromagnetic waves based on the direction of disturbance in them (polarization). The other criterion to classify EM waves is the frequency.

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Presence, detection, and persistence of SARS-CoV-ii in wastewater and the sustainable remedial measures

Bashir Adelodun , ... Kyung Sook Choi , in Environmental and Health Management of Novel Coronavirus Disease (COVID-19 ), 2021

4.5.5 Ultraviolet irradiation

Ultraviolet light (UV) is an electromagnetic wave with a length between 200 and 400   nm. The outset UV application dated back to 1910 in the disinfection of drinking water. ¹⁴ Ultraviolet light can exist divided into four types: ultraviolet A, UV-A (320–400   nm; 315–400   nm), ultraviolet B, UV-B (280–320   nm; 280–315   nm), ultraviolet C, UV-C (200–280   nm), and vacuum ultraviolet (100–200   nm). However, the utilize of vacuum ultraviolet as a disinfectant is express due to its assimilation by the wastewater. ^{14 , 62}

Ghernaout and Elboughdiri ⁶⁰ posited that the wavelength range value of 200–300   nm is enough to disinfect or destroy the Deoxyribonucleic acid and ribonucleic acid (RNA) structure of bacteria, viruses, and single-celled microorganisms, which can thereby cake the synthesis of poly peptide. The inactivation of coronaviruses was reviewed for the food industry using UV radiation by Quevedo-León et al. ⁶² It was reported that for effective inactivation of the viruses using UV-A and UV-B, the exposure fourth dimension needs to be extended, while the types of microorganisms affecting the effectiveness of UV-C and the exposure limit to UV-C by a human should be maintained at 2.5   J/m² in ten–15   min; otherwise, there is a risk of erythema (the redness of the peel or mucous membranes). Exposure to UV-A is safe at a maximum level of x   W   yard^two for viii   h, at the eye level.

Simmons et al. ⁶³ studied the deactivation of SARS-CoV-2 on surfaces (environmental surfaces and personal protective equipment) using a pulsed-xenon UV light. The authors obtained remarkable success in the disinfection charge per unit for hard surfaces at 1, two, and five   min with 3.53 log₁₀, >iv.54 log₁₀, and >iv.12 log_ten viral load reduction, respectively, and a viral load reduction of >4.79 log_ten in 5   min for N95 respirators. Therefore, it was concluded that using a pulsed-xenon UV light, SARS-CoV-2 was significantly reduced, and this can be replicated on other mediums where the virus may persist.

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Industrial boilers

E Walker CEng, BSc, MIMechE , R J Blaen , in Plant Engineer's Reference Book (Second Edition), 2002

10.two.ii Radiation

Thermal radiation takes identify by the emission of electromagnetic waves, at the velocity of low-cal, from all bodies at temperatures in a higher place absolute zero. The heat flux from an ideal or 'black body' radiating surface is proportional to the quaternary ability of the accented temperature of the surface. The abiding of proportionality is the Stefan–Boltzmann abiding, which has a value of v.6696 × 108 (W/thousand ²Chiliad^four).

The heat flux radiated from a real surface is less than that from an ideal 'black body' surface at the same temperature. The ratio of real to 'black body' flux is the normal full emissivity. Emissivity, similar thermal conductivity, is a belongings which must exist determined experimentally.

Although the rate of emission from a surface is independent of the status of the environs, the internet overall exchange of radiant heat between surfaces at unlike temperatures depends on a number of factors. The continuous interchange of energy is a result of the reciprocal processes of radiation and assimilation, and these are dependent on geometrical relationships, emissivity differences and the presence of any arresting and emitting gases in the intervening space.

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THERMAL PROCESSES | Pasteurization

F.V.M. Silva , ... R. Simpson , in Encyclopedia of Food Microbiology (Second Edition), 2014

Microwave Heating

Microwave processing is divers as the utilize of electromagnetic waves of certain frequencies to generate rut in a material. Because information technology is an electrothermal process, microbial devastation by microwaves occurs through heat. The application of microwave pasteurization has been applied largely applied to fluid foods, such equally the continuous pasteurization processing of milk and juices, and the pasteurization of solid food materials, such as intact beat eggs and pickled asparagus. Bacterial pathogens whose inactivation has been demonstrated using microwave applied science include the following: B. cereus, Campylobacter jejuni, C. perfringens, pathogenic E. coli, Enterococcus spp., L. monocytogenes, Southward. aureus, and Salmonella spp. Parasitic pathogens (Trichinella spiralis, Toxoplasma gondii, and Anisakis simplex) all have been found to survive diverse microwave treatments, but this well-nigh probable is due to the unevenness of the temperature distribution during the process.

Microwave technology achieves an issue equivalent to thermal pasteurization. However, the major disadvantage is the nonuniform temperature distribution, resulting in hot and common cold spots in microwave-heated products (Vadivambal and Jayas, 2010). Traditional thermal destruction parameters class the basis for microwave inactivation, and time and temperature parameters are disquisitional. Accordingly, the criteria that should be used to blueprint microwave processes include the blazon of food and its characteristics, the backdrop associated with the process (power level, cycling, equilibration fourth dimension, and the presence of hot water or air surrounding the food), the properties associated with the equipment (dimensions, shape, electromagnetic characteristics of the oven, agitation, presence of stirrers and turntables, frequency (2450 or 915 MHz), and historic period of the magnetron), the effect of packaging fabric on procedure delivery, and a reliable means past which to monitor the temperature to prevent significant process deviations.

Table 6 shows examples of applications in pasteurization.

Tabular array 6. Examples of applications in microwave pasteurization

Microorganism	Food	Comments	Reference
Eastward. coli	Apple tree juice	E. coli populations were lower in apple juice at 900 and 720 W ability levels for threescore and xc s, respectively. At these levels, no pregnant differences were found between conventional pasteurization and microwave treatment. The population reductions were more often than not inside the range of 2–four logs.	Cañumir et al. (2002)
E. coli	Apple cider	The purpose was to blueprint a continuous catamenia microwave pasteurization arrangement and to evaluate the following process parameters: Volume load size (0.5 and 1.38 l), input power (900–2000 W), and inlet temperature (3, 21, and 40 °C). The pasteurization process resulted in a 5-log10 reduction of leaner.	Gentry and Roberts (2005)
Salmonella typhimurium	Yolk of shell eggs	A 22% reduction in microbes was attained for microwave irradiation of xv s, whereas a 36% reduction was achieved by moist heat treatment of 15 min.	Shenga et al. (2010)
Yersinia enterocolitica, C. jejuni, L. monocytogenes	Milk	Batches were processed at 71.1 °C (160 °F) for various time periods. Complete inactivation (viii–ix logx) of Y. enterocolitica was accomplished after 8 min, of C. jejuni afterward iii min, and of Fifty. monocytogenes afterwards 10 min.	Choi et al. (1993a,b)
Alicyclobacillus acidoterrestris spores	Cream of asparagus	Microwave pasteurization achieved a twofold reduction compared to conventional treatment at the following process conditions: 100% microwave power for five min, 90% microwave power for six min, and 80% microwave ability for 7 min.	Giuliani et al. (2010)

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RFID+ The Physics of RFID

Dr. Paul Sanghera , in RFID+ Study Guide and Practice Exams, 2007

Impedance

Impedance is divers as resistance to the flow of electric current in a circuit element and is measured as a ratio of voltage, say 5, across the element and current, say I, through the element:

Z= V/I

The antenna receives power (in terms of electric current) from the source through the manual line. The input impedance, Z_i, for the antenna is the following:

Z_i = V_i/l

Vi is the antenna input voltage, and I ⁱ is the antenna input current.

To realize how impedance affects functioning, annotation that the electromagnetic wave (power) travels through dissimilar parts of the antenna system, which can have different values for impedance. The parts to be considered here are the source that produces the power, the transmission line that brings the power to the antenna, and the antenna transmitter that transmits the power. The following are the different kinds of impedance divers in this case:

▪

Characteristic impedance This is the impedance of the transmission line, which is assumed to be lossless and of infinite length:

Z₀= (μ/ɛ)^½

where μ is the magnetic permeability of the medium that makes the manual line and/ɛ is the electrical permeability of the medium. An example of transmission line is the antenna cablevision.

▪

Antenna input impedance The ratio of the input antenna voltage to the input antenna electric current.

▪

Transmitter output impedance The impedance used by the antenna's transmitter to transmit the ability into the free space.

To go the all-time operation, it is important that all these impedances belonging to the different parts of an RFID organisation match with each other. If the antenna input impedance and the transmitter output impedance match the characteristic impedance of the transmission line, the antenna volition radiate maximum power. However, there is always some impedance mismatch-for instance, due to discontinuities in the manual line or if the transmission line is terminated with other than its characteristic impedance. The impedance mismatch results in reflecting part of the moving ridge energy back to the source and thereby impeding the functioning. This phenomenon can be understood in terms of the voltage standing moving ridge ratio.

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Lengthened Optical Imaging

S.A. Carp , Q. Fang , in Pathobiology of Human Affliction, 2014

Invisible Waves

Physics tells united states that the visible light is a form of electromagnetic (EM) wave. However, nigh EM waves are not at all visible. For a very long time, people have been seeking for means to look through visually opaque objects without cutting the object open up. This is obviously important for medical purposes because noninvasive imaging does not require i to perform an performance to see what is going on inside someone'due south body. The use of EM and/or its sibling, audio-visual, wave phenomena constitutes the foundation of modern medical imaging modalities due primarily to their unique ability to penetrate through domains beyond direct inspection. Over the by several decades, novel medical imaging systems take proliferated through both research and clinical applications equally we continue to gain insight into the nature of the EM and mechanical waves and their interactions with human tissue. Many of these advances allow clinicians to inspect not merely the morphological structures in human anatomy just as well the tissue functions and interaction in an unprecedented level.

EM wave interacts with homo tissue at various levels, from macroscopic thermal event all the way down to the molecular and diminutive effects. In Figure 1 , we testify the EM spectrum and a range of medical imaging modalities, each one associated with a particular wavelength range. At the brusque wavelength end, powerful gamma-ray radiation can be created from the annihilation of an electron and a positron (a basic particle that is almost identical to an electron but has a positive charge), commonly used in nuclear medicine and positron emission tomography (PET). ten-Ray, the 'mysterious' ray that had opened the new era of modernistic medical imaging, is another form of loftier-energy EM radiation, generated by bombarding sure metal with high-speed electrons. A rich set of modern medical imaging techniques take been built upon ten-ray, including computed tomography (CT), micro-CT, mammography, and digital breast tomosynthesis. Both x-rays and gamma-rays interact with tissue in the molecular and atomic level. In some rare cases, they can impairment the cell and chromosome and cause problems; therefore, the dose command of x-ray and gamma-ray radiation is critically important when used in medicine.

Effigy 1. Electromagnetic moving ridge spectrum and the associated medical imaging modalities.

Reproduced from http://en.wikipedia.org/wiki/File:EM_Spectrum_Properties_edit.svg.

Abundant imaging methods tin can exist found in the visible light range. These include diverse microscopy techniques and fluorescence and molecular imaging methods, amid others. Thermal cameras, ordinarily used in the security systems, house inspections, and medical applications, tin can capture thermal-infrared (wavelength betwixt three.v and 20   μm) photons radiated from a heated surface. If we keep moving upwardly in wavelength, equally we approach the radio-frequency (RF) domain, there are a number of novel techniques that permit noninvasive and nondestructive evaluations of opaque structures. Terahertz imaging techniques can provide loftier-resolution subsurface images that tin can easily 'see through' thin fabrics. For this reason, terahertz imaging is widely used for security scans in the airport. Microwave tomography and electrical impedance tomography, operated at an even lower frequency range, are both emerging technologies for noninvasively generating three-dimensional (3D) tomographic images of tissue dielectric properties, known to be markers for diagnosing malignant tumors. We should likewise mention that the widely used magnetic resonance imaging (MRI) technique uses RF pulses to measure diverse molecular backdrop, including proton density, in the man trunk and provides high-resolution structure and functional images.

Virtually-infrared (NIR) photons have some favorable properties that no other EM moving ridge can supplant. In this commodity, we desire to peculiarly focus on a set of novel imaging techniques utilizing the near-infrared radiation. These techniques include nearly-infrared spectroscopy (NIRS), diffuse optical tomography (DOT), diffuse correlation spectroscopy (DCS), and diverse related techniques. In the following sections, nosotros will discuss the fundamentals backside these techniques, the fundamental components of instrumentation and imaging analysis, and various medical applications associated with these techniques that are currently explored past the scientific enquiry community.

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Handbook of Media Economics

Gregory Due south. Crawford , in Handbook of Media Economic science, 2015

seven.2.1.1 Broadcast (Gratis) Television set

"Broadcasting" conventionally covers the distribution of both radio and television signals via electromagnetic waves, but my focus is on the boob tube portion of this clarification. ⁶ Broadcast television in the The states began in the 1930s, simply gained widespread popularity and household penetration in the 1950s. ^seven While the specifics vary across countries, diffusion in Western Europe followed a similar pattern, with Africa and parts of Asia starting roughly 10 years later. Television stations are by and large licensed by a national regulatory authority because the electromagnetic spectrum used by broadcasters is a national resource and licensing is required to prevent interference among broadcasters. In the US, circulate stations are licensed by the Federal Communications Committee (FCC).

At that place are a wide multifariousness of station types in the US (with similar patterns internationally), but the about important distinctions are between commercial and non-commercial stations, full- and low-power stations, and analog and digital stations. The vast majority of commercial stations support themselves through the sale of advert, while not-commercial stations rely on donations from viewers or similar sources of funding other than advertising (FCC, 2008). ^eight The number of broadcast Tv set stations in the Usa has been stable over time at roughly 1400 full-ability stations, 28 per state, and simply under vii per TV market place (FCC, 2013a).

Depression-power stations are smaller, local, and are oft community-oriented. They are considered a secondary service and are not permitted to interfere with full-power broadcasters and are at risk of interference from them. Analog stations transmit programming using the continuous modulation of an uninterrupted audio wave, with different channels allocated to different portions of the electromagnetic spectrum, while digital signals digitally process and multiplex programming. Digital broadcasting is more efficient in its use of spectrum, freeing up spectrum previously used for analog broadcasting for other, higher-value uses.

In the US, at that place is often a separation of ownership between content providers (broadcast networks) and distributors (broadcast stations). Since the early on days of the industry, the production of commercial broadcast programming has been organized and managed by "tv set networks," of which the largest are ABC, NBC, CBS, and Flim-flam. ^nine The left side of the left panel of Effigy 7.1 shows the vertical construction associated with the circulate television manufacture.

Figure 7.1. The 2-sided TV market. Notes: Depicted is the two-sided nature of Idiot box markets. In the left console is the costless-to-air broadcasting market and in the right console the pay-boob tube market. In both markets, there is a wholesale marketplace for programming, in which content providers (broadcaster networks, pay-Telly networks) negotiate with distributors (broadcast stations, pay-Television receiver distributors) for the right to carry their content, and a retail market for distribution, in which distributors either circulate or set prices for access to that content to households. The majority of commercial broadcasters only earn money through the sale of audiences to advertisers. Funding for Public Service Broadcasters (PSBs) comes from mandatory household license fees, sales of advertising, and/or donations from viewers. Funding for pay-tv channels and distributors comes from a mix of advertising sales and subscriber payments (see Tables vii.i–7.iii).

Table seven.i reports aggregate statistics for United states broadcast networks in 2012. Reported are measures of network costs (programming expenditure), quantity (viewership), price (advertising price per thousand viewers, or CPM), and advertising acquirement. I split up US broadcast networks into two groups: the so-chosen "Big Four" broadcast networks mentioned above and "minor" circulate networks. Circulate networks simply earn advertising revenue, with the Big 4 receiving between 83% and 89% of the full broadcast viewing (ratings) and revenue.

Table seven.1. Us broadcast television networks, 2012

	Program expenditure ($ 1000000)	Boilerplate prime time rating	Average 24-h rating	Cost per thousand (CPM) ($)	Net advert revenue ($ one thousand thousand)
Big-iv B/C networks
ABC	2763	3.9	2.4	17.6	3177
CBS	3303	5.2	2.8	16.2	4124
NBC	4041	iv.7	2.6	18.v	3955
Fox	2120	three.5	3.viii	33.eight	2634
Total Big-iv	12,226	17.four	11.half-dozen	21.5	13,891
Pocket-size B/C networks
The CW	439	0.vii	0.6	44.i	418
Univision	234	one.7	0.7	−	641
Telemundo	204	0.6	0.3	−	374
UniMás	83	0.iii	0.two	−	160
Total minor	1129	3.6	2.0	−	1752
Full B/C networks	13,355	21.0	thirteen.vi	−	15,642
Weighted average B/C networks	−	−	−	21.six	−
Large-four share	91.5%	83.0%	85.5%	−	88.8%

Notes: Reported are aggregate statistics for US broadcast networks in 2012 (SNL Kagan, 2014a). Measures of network costs (programming expenditure), quantity (viewership), price (advertizement cost per k, or CPM), and net advertising acquirement are given. "Rating" is the average percentage of US households watching that channel across a set time interval. U.s. broadcast networks are divided into two groups: the "Large-Four" circulate networks (ABC, NBC, CBS, and Fox) and "minor" broadcast networks. Weighted average broadcast networks are weighted by the average 24-h rating. Big-4 share is the share of the column spent/watched/earned by the Big-4 broadcast networks.

In the US, FCC regulations limit the number of stations television networks tin own; the remaining stations are owned by independent firms (that typically own many stations) that negotiate with television networks to be the exclusive provider of that network'due south programming in a TV market. Television set markets are based on geography: The Nielsen Company has divided the US into 210 mutually exclusive and exhaustive markets chosen Designated Market place Areas that are widely used in the auction of advertising. Nigh network programming is shown during "prime time" (seven:00 p.m. to eleven:00 p.m.). News local to the station's principal community is produced by private stations and programming in other parts of the day is either provided past the network or programmed independently with syndicators or independent program producers.

7.2.1.one.1 Public Service Broadcasters

In many countries, some portion of broadcast television service is provided by "Public Service Broadcasters" (PSBs). PSBs compete with commercial broadcasters in providing content free over the air. In the U.s.a., "the mission of public broadcasting is to advance a well-educated, well-informed society capable of cocky-governing the world's greatest commonwealth" (CPB, 2012). In the Uk, the mission of the British Broadcasting Corporation (BBC) is famously to "inform, educate and entertain." In the broadest terms this captures the role of public service broadcasting in many countries; information technology is hard to come upward with a more precise definition. ¹⁰ In exercise, mutual aims of PSB policy are to ensure that diverse and high-quality programming is supplied which caters to all interests and communities. In add-on, programs that yield educational and other social benefits are to be encouraged, including programs that might make the population more tolerant, and likewise more than enlightened of their regional and national identity. And in a related vein, there is oft intervention to ensure that sufficient locally produced content is available, and that the domestic "environmental" of program product is protected. ^xi These values and examples of the types and providers of programming that back up these values in the U.k. are shown in Effigy vii.two. ¹²

Figure 7.2. Cadre purposes of Great britain PSBs. Notes: Depicted are the core purposes of the UK's Public Service Broadcasters, including the BBC, and examples of the types of programming that back up these purposes, as indicated by the UK media regulator, Ofcom (2004, p. 26).

Funding for PSBs comes from a diversity of sources that differ beyond countries and across PSBs within countries, including mandatory household license fees, sales of advertising, and/or donations from viewers. The right side of the left console of Figure 7.1 shows the vertical structure and payment flows associated with PSBs. In the Britain, the oldest and largest PSB, the BBC, is the beneficiary of an almanac license fee of £145.50 (approx. $20/month) and sells no advertising, while the other commercial PSBs in the market—ITV, Channel 4, and Channel five—receive no license fee and simply sell advertising. In the US, public service dissemination is provided by public (not-commercial) idiot box stations that provide a mix of locally and nationally produced programming. The majority of the national programming is provided by the Public Broadcasting Service, a non-turn a profit public broadcaster jointly endemic past over 350 member television stations. Funding for public broadcasting comes from a mix of sources, with contributions from individuals most important (22% on average across public television stations), followed by federal government support (eighteen%), land and local government back up (17%), university and foundation support (15%), and underwriting by businesses (13%) (CPB, 2012).

Figure 7.3 reports the aggregate corporeality of public (government) funding for telly along with the per-household-per-calendar month TV license paid for a pick of major world economies. ^xiii It shows that most developed country governments provide betwixt $6 and $15 per household per month in public back up for television. The United states, despite being the largest television set market in the globe, provides only $0.40 per household per calendar month in government support for PSBs.

Effigy 7.three. Public funding for tv set, 2011. Notes: Reported is the corporeality of public (regime) funding for television in a range of countries in the twelvemonth 2011. The top panel reports aggregate funding (in $ billion) and per-household funding (in $ per household per month). Amounts accept been converted to USD using World Banking concern average 2011 exchange rates. Ofcom (2012), figure 3.1, author calculations.

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Antennas, Variety, and Link Analysis

Vijay 1000. Garg , in Wireless Communications & Networking, 2007

10.3 Antenna Gain

The job of a transmitting antenna is to convert the electrical energy travelling along a transmission path into electromagnetic waves in space. The antennas are passive devices, the power radiated by the transmitting antenna cannot be greater than the power entering from the transmitter. It is ever less because of losses. Antenna gain in one direction results from a concentration of power in that direction and is accompanied past a loss in other directions. Antenna gain [ vii] is the nigh important parameter in the pattern of an antenna system. A loftier gain is achieved by increasing the aperture area, A, of the antenna. Antennas obey reciprocity; the transmit proceeds and receive gain are the same, and the antenna can be analyzed by examining information technology as either a receive or transmit antenna. The amount of ability captured by an antenna is given as:

(10.1) $P=pA$

where:

p = ability density (power per unit area)

A = aperture surface area

Antenna gain can be defined either with respect to an isotropic antenna or with respect to a one-half-moving ridge dipole and is usually analyzed every bit a transmit antenna. An isotropic antenna is an idealized system that radiates equally in all directions. The half-wave dipole antenna is a simple, practical antenna which is in mutual use.

The gain of an antenna in a given direction is the ratio of power density produced by information technology in that direction divided by the power density that would be produced past an isotropic antenna. The term dBi is used to refer to the antenna proceeds with respect to the isotropic antenna. The term dBd is used to refer to the antenna proceeds with respect to a one-half-moving ridge dipole (0 dBd = 2.1 dBi). While nearly analyses of organization performance use a half-wave dipole as the reference, many times antenna gain figures are quoted in dBi to give a falsely inflated proceeds figure. The system designer must carefully read information sheets on antennas to utilize the right gain effigy. As a dominion of pollex, if the gain is not quoted in either dBd or dBi, the gain is in dBi, with the dBi left out to inflate the gain figures.

For an isotropic antenna in free space, the received ability density is given as

(x.2a) $p_R=\frac{P_T}{\mathrm{four}\pi d^2}$

where:

P_T = transmitter power

p_R = receiver power density

d = distance betwixt transmitter and receiver

When a directional transmitting antenna with power gain cistron, Chiliad_T , is used, the power density at the receiver antenna is Yard_T times Equation 10.2a, i.e.,

(10.2b) $p_R={\mathrm{1000}}_T\frac{P_T}{4\pi d^2}$

The amount of power captured past the receiver is p_R times the aperture area, A_R , of the receiving antenna. The aperture area is related to the proceeds of the receiving antenna by

(10.iii) $G_R=\frac{\mathrm{iv}\pi A_R}{{\lambda }^{\mathrm{two}}}$

where:

$\lambda =\frac{c}{f}$

f = the transmission frequency in Hz

c = 3 × 10⁸ thou/s is the free-infinite speed of propagation for electromagnetic waves

A_R = the effective area of aperture, which is less than the concrete area by an efficiency gene ρ _R ; typical value for ρ _R ranges from sixty to 80%

The full received power, P_R is given as:

(x.4) $P_R=A_R{p}_R$

Substituting the value of P_R and A_R from Equations ten.2b and x.3 into Equation 10.4, together with the transmitting antenna gain G_T , we go

(10.5) $P_R={\left[\frac{\lambda }{4\pi d}\right]}^2{P}_T{\mathrm{Yard}}_T{G}_R$

Equation 10.five includes the power loss only from the spreading of the transmitted wave. If other losses are also present, such as atmospheric absorption or ohm losses of the waveguides leading to antennas, Equation 10.5 can be modified as [4]:

(10.6) $\frac{P_R}{P_T}={\left[\frac{\lambda }{4\pi d}\right]}^2\cdot \frac{G_T{M}_R}{L_0}$

(ten.7) $\frac{P_R}{P_T}=\frac{G_T{G}_R}{{\mathrm{Fifty}}_0{\mathrm{50}}_p}$

where:

$L_p={\left[\frac{4\pi d}{\lambda }\right]}^2$ denotes the loss associated with propagation of electromagnetic waves from the transmitter to the receiver as discussed in Chapter 3.

L_p depends on carrier frequency and separation distance d. This loss is e'er nowadays. L ₀ is the loss gene for additional losses.

When nosotros limited Equation 10.7 in terms of decibels, we go

(10.8) $P_R=20log\left[\frac{\lambda }{\mathrm{four}\pi d}\right]+P_T+G_T+G_R-{\mathrm{Fifty}}_0\text{dB}$

The product P_TG_T is chosen the effective isotropic radiated ability (EIRP) and term $20log\left[\frac{\lambda }{4\pi d}\right]$ refers to costless space path loss (L_p ) in dB. Another term, effective radiated power (ERP), is as well used. It is the power input multiplied by the antenna gain measured with respect to a one-half-wave dipole antenna. The EIRP is related to ERP as

(ten.9) $\text{EIRP}=\text{ERP}+2.14\text{dB}$

In the costless space, the path between ii antennas has no obstruction (see Figure 10.1) and there is no object where reflection can occur. Thus, the received betoken is composed of only one component. When the two antennas are located on the earth, then in that location are multiple paths from the transmitter to the receiver. The event of multiple paths is to modify the path loss between two points. The simplest case occurs when the antenna heights h_T and h_R are pocket-size compared to their separation distance d and the reflecting earth surface is assumed to be apartment (see Chapter 3). The received signal can then exist represented by a field that is approximated by a combination of a direct moving ridge and a reflected wave equally shown in Figure x.ii. In this case the received power, P_R , and transmitted ability, P_T , are related as (see Chapter 3 and Appendix B for derivation):

Figure ten.1. Gratuitous-space path-loss model.

Figure x.2. Path-loss model with reflection.

(ten.ten) $\frac{P_R}{P_T}={\left[\frac{h_T{h}_R}{d^{\mathrm{ii}}}\right]}^2\cdot \frac{G_T{G}_R}{L_0}$

Expressing Equation 10.9 in decibels, we get

(10.11) $P_R=20log\left[\frac{h_T{h}_R}{d^{\mathrm{two}}}\right]+P_T+G_T+G_R-{\mathrm{Fifty}}_0\text{dB}$

comparing it with Equation ten.8 we note that Equation 10.10 is independent of transmitting frequency.

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Radiation

Bruce Busby , in Information Resource in Toxicology (Quaternary Edition), 2009

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In the simplest terms, radiations is energy in transit in the form of high-speed particles or electromagnetic waves. In typical usage, the word radiation means the ionizing radiation, i.e. radiation with enough energy to release electrons in the textile it interacts with, such as gamma rays and beta particles. Non-ionizing radiations sources such as microwaves or radio waves can too be a hazard though. Radioactive materials, substances that give off radiation, are constitute naturally in everything nosotros touch, eat, and inhale. The Earth's atmosphere is continually bombarded with cosmic radiation, some of which reaches the surface. Radiation is a known carcinogen and mutagen to which every human on the planet is exposed to every 2nd of every day. Radiation is a natural part of our environment and it plays important roles in medicine, industry, and academic enquiry.

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Hybrid polymer composites for electromagnetic absorption in electronic industry

Charalampos A. Stergiou , ... Konstantin N. Rozanov , in Hybrid Polymer Blended Materials, Book 4, 2017

3.5.ii.two Mixed-blazon filler materials

On account of their diluted magnetic properties, pure ferrite-loaded composites can inappreciably produce sufficient attenuation of the travelling EM waves. To this finish, for such applications, ferrite particles basically class hybrid composites in combination with conductive inclusions. In diverse conductive composites, the incorporation of particles with nonzero magnetic losses (Mn–Zn ferrite, Atomic number 26₃O₄, Ba₃Co_iiIron₂₃O₄₁ and Ba_twoZn_twoFe_11.5O₂₂ hexaferrites) has led to ameliorate impedance matching, which is later displayed past the diminishing RL in the range up to 12   GHz (Phan et al., 2016; Al-Ghamdi et al., 2016b; Li et al., 2006). Therefore, at low ferrite content, SE is maximized following the maximization of total EM losses. Further, increase of the depression-conductivity magnetic filler corporeality yields the respective decrease of captivated ability. On the same principle, polystyrene composites loaded with ii.24   vol.% of Fe₃O₄-busy graphene nanosheets possess increased SE past v   dB (SE>25   dB in the 10-band), while maintaining similar return loss with the pristine graphene composite (Chen et al., 2015b). By employing a polymer cream filled with 10   vol.% of Fe₃O₄-coated graphene, Shen et al. (2013) recorded an excellent combination of shielding properties (SE>15   dB and RL<0.5   dB) in the whole 10-band for t=two.5   mm.

Except for the ferromagnetic oxides, metallic magnetic particulates accept been used in conjunction with different C-based fillers. Wang et al. (2013c) accept shown that SE of a MWCNT epoxy blended in the 26.5–40   GHz region is increased by 10   dB by the inclusion of 1   wt% of Iron nanoparticles, in upshot of raised ε _r ″. Huang et al. (2015) also investigated CoNi alloy-coated carbon fiber composites for dissimilar alloy compositions and recorded the maximum SE in the 10-band (SE>25   dB) for the composite with higher ε _r ″. According to Labunov et al. (2012), in composites with these bifiller systems, reflection is the dominant shielding machinery in the 8–12   GHz region, whereas absorption dominates in the 26.5–xl   GHz. Notwithstanding, a low reflectance shield for the 10-band (RL<two.5   dB and SE>30   dB for t=4   mm) was prepared by Chen et al. (2015a) past blending thirty   wt% of CI microparticles and 3   wt% of rGO nanosheets in epoxy medium. For even higher CI content (75   wt%) in MWCNT resin composite, inferior shielding characteristics are reported compared to the previous case (RL<five.v   dB and SE<28   dB for t=ane.4   mm) (Wang et al., 2015a).

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