near-field aperture probes

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NEAR-FIELD OPTICAL MICROSCOPY AND SPECTROSCOPY WITH POINTED PROBES

NEAR-FIELD OPTICAL MICROSCOPY AND SPECTROSCOPY WITH POINTED PROBES

In near-field optical microscopy, the resolution x no longer depends onλ but on a characteristic length d (e.g., aperture diameter or tip diameter) of a local probe. Near-field optical microscopy relies on a confined photon flux between a local probe and the sample surface. The probe is raster-scanned over the sample surface, and for predefined positions (x,y) of the probe, a remote detector acquires the optical response. In this way an optical contrast image can be recorded. In Synge’s original concept, the local probe consisted of a tiny aperture in a perfectly reflecting metal screen (11) (see Figure 2b). Immediately behind the irradiated screen, the light field is spatially confined to the size of the aperture (d ). Only if a scatterer is within a distance d from the aperture will it interact with the radiation field. Synge’s idea was soon forgotten after its inception because nanofabrication techniques were not then available. In the following decades, however, the idea was reinvented several times. The first experimental results performed at optical frequencies were published by Pohl et al. at the IBM Research Laboratory in Switzerland followed shortly by Lewis et al. at Cornell University (1, 2). A reproduction of the first near-field optical measurement is shown in Figure 3.
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Comparative scanning near-field optical microscopy studies of plasmonic nanoparticle concepts

Comparative scanning near-field optical microscopy studies of plasmonic nanoparticle concepts

Classical SNOM technology can be found in many applications and analytical processes. The field is covered from opto- magnetics up to Raman spectroscopy or two-color fluorescence imaging [30-32]. Commercial SNOM setups show limitations for the space and the detector one can use [3] and the number of light sources is limited. For this reason, here a homebuilt aperture scanning near-field optical microscope with commercial probes is used to investigate nanoparticles on glass substrates. The scheme of the setup is shown in Figure 3. The light source is selected by a fiber splice from a 532 nm LASER with10 mW. This light couples into an Al coated HSPC10 (Lovalite, multimode Fiber, 0.1 NA, 10 µm core) fiber probe with an aperture of 100 nm that is glued at the tuning fork. The distance control is done by a shear force mode with an amplitude of less than approximately 1 nm. The sample is moved by an (x,y,z)-stage and due to the
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Near-field optical microscopy based on microfabricated probes

Near-field optical microscopy based on microfabricated probes

The mechanism of light coupling through the metalized tip and light confinement at the tip apex is not yet understood. The far-field transmission through the thin metal layer could be because of the finite conductivity of aluminium. However, a different effect must be responsible for the light confinement necessary for the subdiffraction limited resolution. A potential explanation relies on modes propagating along the air±metal interface in combination with field localization at the tip apex. The possibility that the tip is modified during approach is exceedingly small, given the small and defined aperture that had to be produced in a reproducible way. This is supported by the fact that the tip does not alter during scanning. Additionally, from other experiments we would expect that rather high forces would be necessary to break up a continuous metal layer as it is found at the apex.
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X-Band Aperture Antenna with Hybrid Dielectric Inserts

X-Band Aperture Antenna with Hybrid Dielectric Inserts

Aperture radiators based on rectangular waveguides are widely used in microwave technology, both as individual antennas and phased arrays with close packing of elements and wide-angle scanning when operating at high levels of microwave power. In this respect, there is a need to reduce the cross-section of the elements. Open-ended waveguides filled with a dielectric are commonly used as transceiver probes or antennas. The problem of waveguide matching with the free space becomes the main design problem for this type of antennas. Different techniques for matching the antenna to its feeding line have been reported in the literature [1–3]. In particular, in [1] good matching is achieved by using an additional matching layer with lower permittivity. An alternative technique is the use of air gaps between dielectric filling elements in the waveguide to achieve high performance of both the individual radiator and the array itself; this technique has been used in the frequency range 1–3 GHz [2, 3]. There are also several types of probe design [4–7] for measuring the near-field distribution in the microwave and millimeter wave ranges. Near-field microwave probes have been extensively used in non-destructive testing. For example, in [8] a layered medium at the end of an open-ended waveguide was used for improved sensitivity. In [9] the original approach to the problem of antenna-probe miniaturization for the precision EM field measurements is presented. Recently, metamaterials have been used to achieve improved near-field properties [10, 11]. The used metamaterials consist of split ring resonators or similar metallic structures. Similar metamaterials have also been used to achieve improved directivity of the far field properties of the open-ended antennae [12, 13].
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A SRR-Based Near Field RFID Antenna

A SRR-Based Near Field RFID Antenna

which is one of the smallest dimension of RFID reader antenna in the world. The measured result of prototype shows good impedance matching over 13 MHz (914.5–927.5 MHz) with reflection coefficient less than −10 dB, which covers the China RFID band II (920– 925 MHz). Simulation shows that the antenna features a strong and uniform magnetic field distribution, and agrees well with the reading range of 42 mm. The antenna also operates different UHF RFID bands (Europe band, China band I&II) by modifying the SRR parameters.

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Vol 11, No 6 (2020)

Vol 11, No 6 (2020)

In this paper we together introduced a maiden effort to bring the two probable existing applications in PART III some applications of Fuzzy Kalangi non-associative Γ-semi sub near-field spaces of a Γ-near-field space over near-field. We are not widely speaking about the applications of Fuzzy Kalangi non-associative Γ-semi sub near-field spaces of a Γ-near-field space we only discuss here the two applications one in automatons and the other in the construction of error correcting codes.

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Photographic surface photometry of galaxies in the Virgo cluster

Photographic surface photometry of galaxies in the Virgo cluster

techniques with the IDT tracing of NG-C 4261 illustrated in figure 13, it is apparent that the outermost isophote runs near to, or even intersects the two stars located closest to the galaxy. This dramatic agreement between figures 13, 18, 1 9 , 21 and 22 illustrates the advantages of the smoothing of data. There is, however, a case against smoothing of data based on the view that some important information is lost in the process. For this reason, it would be preferable to preserve all the

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Aperture Field Estimation in Waveguide for Non Sinusoidal Periodic Excitation

Aperture Field Estimation in Waveguide for Non Sinusoidal Periodic Excitation

In this paper an attempt has been made to find the aperture field distribution in a rectangular waveguide for non-sinu- soidal, periodic excitations using Multiple Cavity Modeling Technique. The excitation functions, considered, are square, trapezoidal and clipped sine wave in nature. In the present analysis these time domain excitation functions have been represented in terms of a truncated Fourier series consisting of the fundamental frequency and its higher harmonics. Within the waveguide the fundamental frequency will give rise to a dominant mode excitation whereas the higher order modes will excite dominant and higher order modes. If the higher harmonics are assumed suppressed then the waveguide is subjected only to a dominant mode excitation. Results for dominant mode reflection coefficient (magni- tude), VSWR and complex transmission coefficient have been computed and compared with theoretical data. The ex- cellent agreement between them validates the analysis.
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Vol 11, No 2 (2020)

Vol 11, No 2 (2020)

Here in this section, Here also we once again mention loop Γ-semi sub near-field spaces and near loop Γ-semi sub near- field spaces are different for the former has ‘+’ to be non associative where as in the later ‘+’ is associative but ‘.’ Happens to be non associative and the near loop Γ-semi sub near-field spaces are built using a loop and a Γ-semi near- field space over a near-field. Finally we also introduce the identities newly to be the near-field space which are non associative Γ-semi sub near-field space. We introduce the concept of Thurumella right loop – half groupoid near-field space which is the most generalized concept of loop Γ-semi sub near-field space over near-field.
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Evaluation of Polymethine Dyes as Potential Probes for Near Infrared Fluorescence Imaging of Tumors: Part - 1

Evaluation of Polymethine Dyes as Potential Probes for Near Infrared Fluorescence Imaging of Tumors: Part - 1

in vivo characterization of tumors, significantly ad- vancing tumor visualization [4, 11], enable detection and identification of small pre-neoplastic lesions, and metastasis [4]. In vivo fluorescence imaging is usually conducted within the “tissue transmission window” which corresponds to a near- infrared (NIR) spectral range of 700 – 900 nm. For this spectral range, scat- tering of the excitation light and tissue autofluores- cence is minimal, resulting in facilitated deep tissue imaging due to substantially increased signal/noise ratio [12]. A great number of polymethine cya- nine-based fluorophores are being used as exogenous probes for NIR fluorescence imaging. These com- pounds usually are not tumor-avid (therefore, tumor targeting becomes essential). Their excita- tion/emission wavelengths can be tuned to the de- sired spectral range by altering the indolenine or benzindolenine heterocyclic nucleus and the number of double bonds in the polymethine chain [13]. Some of these cyanine dyes have sulfonate groups directly attached to the aromatic benzindolenium or indole- nium nucleus. These groups shield the fluorophores from non-specific hydrophobic interaction with other molecules , a process known to affect the emission of many fluorophores in aqueous media [13]. Addition- ally, dyes containing sulfonate or sulfonatoalkyl groups attached to the heterocyclic nucleus, tend to aggregate less [14]. Various structural modifications have been made to the polymethine chromophores to enhance its light and chemical stability [14]. These modifications usually include rigidization of the polymethine chain in order to inhibit radiationless internal conversion (IC) and subsequent isomeriza- tion [14]. The stability of the polymethine chain is lowered as the chain lengthens. However, incorpora- tion of a central ring system such as a cyclohexenyl group enhances the rigidity of the polymethine chain, decreases the efficiency of IC and increases the fluo- rescence quantum yield.
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Near field/far field interface of a near surface low level radioactive waste site

Near field/far field interface of a near surface low level radioactive waste site

In order to model the processes occurring at the interface it is essential to understand the properties and evolution of the near-field leachates that are ingressing into the far-field. Trench wastes comprise large quantities of cellulosic material (paper, cotton, and wood) and ferrous metals. The decomposition of these materials by microbial hydrolysis and corrosion [3] results in the development of anaerobic conditions within the waste.

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A fully probe corrected near-field far-field transformation technique employing plane-wave synthesis

A fully probe corrected near-field far-field transformation technique employing plane-wave synthesis

Abstract. The far-field behavior of an antenna under test (AUT) can be obtained by exciting the AUT with a plane wave. In a measurement, it is sufficient if the plane wave is artificially generated in the vicinity of the AUT. This can be achieved by using a virtual antenna array formed by a probe antenna which is sequentially sampling the radiating near- field of the AUT at different positions. For this purpose, an optimal filter for the virtual antenna array is computed in a preprocessing step. Applying this filter to the near-field mea- surements, the far-field of the AUT is obtained according to the propagation direction and polarization of the synthesized plane wave. This means that the near-field far-field transfor- mation (NFFFT) is achieved simply by filtering the near-field measurement data. Taking the radiation characteristic of the probe antenna into account during the synthesis process, its influence on the NFFFT is compensated.
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Horn Antenna with a Specific Radiation Pattern

Horn Antenna with a Specific Radiation Pattern

Abstract— This document deals with a horn antenna deigned to heat objects. Horn antenna is one of the simplest and frequently used antennas in telecommunications technology. When using these antennas, maximum directivity is in most cases required – the narrowest directivity pattern is desired. The described antenna however, serves as the heating for material that is placed near the antenna aperture; so that it requires the widest directivity pattern – the smallest directivity is desired. This article describes the process of testing and individual possibilities of gaining the widest possible directivity pattern. Designed antennas were simulated in the CST microwave studio.
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Near-field measurement of continuously modulated fields employing the time-harmonic near- to far-field transformation

Near-field measurement of continuously modulated fields employing the time-harmonic near- to far-field transformation

tion (NFFFT) (Yaghjian, 1986), where advanced algorithms such as the fast irregular antenna field transformation algo- rithm (FIAFTA) offer various source representations and ad- ditional diagnostic capabilities (Schmidt et al., 2008; Eibert et al., 2015). NF measurements are usually performed in ane- choic chambers, since they provide an echo free measure- ment environment, which forms a defined and acceptable ap- proximation of free space. However, it is sometimes neces- sary to perform in-situ measurements, especially if an an- tenna is too large to be mounted in available anechoic cham- bers or if an antenna shall be measured in its real environ- ment. In such more natural environments, the FIAFTA offers modelling capabilities suitable for in-situ measurements, like handling a reflective ground (Mauermayer and Eibert, 2018; Eibert and Mauermayer, 2018) as well as echo suppression of known and unknown scatterers (Yinusa and Eibert, 2013). In-situ measurements can be, for example, perfomed with unmanned aerial vehicles (UAVs), where a large problem is that common receiver equipment can easily measure only the magnitudes of the fields (Virone et al., 2014; Fritzel et al., 2016; García-Fernández et al., 2017). Since available algo- rithms for phaseless NFFFT are not yet completely reliable (Paulus et al., 2017), we assume an in-situ measurement sce- nario where magnitude and phase are available.
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Near Field Communication and Its Applications in Various Fields

Near Field Communication and Its Applications in Various Fields

NFC provides speed and secure way of communication in hospitals. Doctors equipped with NFC-capable tablet computers can call up all the information on a patient within seconds, without any chance of data getting mixed up. A quick check of the patient’s records before the required treatment or prescription of medicines ensures that the recommendations are just right for the patient in question. Chemists and pharmacists can also quickly check medicines in order to further diminish the risk of side-effects or to identify counterfeits if any doubt arises. In particular, those patients who are frequently in hospitals or doctors' clinics due to long-term or chronic illnesses will greatly appreciate the fact that NFC can also give them insights into the details of the medical procedures which they are undergoing, since there is nothing to stop information on patients' treatments or prescriptions being stored on a chip. Hence, NFC becomes the natural choice for wireless communicating between two medical devices. Medical devices using Near Field Communication can transmit data without any delay, since the data generated by medical devices are within the range of NFC. Devices, that resides in the body for long years are called implanted devices. Those devices should be highly energy efficient and conserve as much power as possible. For such applications NFC protocols are well suited as the reader can operate the tag when necessary. NFC is very easy to understand for old patients.NFC works similar to RFID tag in its passive form. NFC can be used to keep tabs on blisters and other drug
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Near Field Communication In Mobile Technology

Near Field Communication In Mobile Technology

One of the most popular systems for RFID based mobile ticketing is operating in London. The so-called Oyster Card works as contactless smartcard for prepaid mobile ticketing and can be used on all public transport services within the London area. All buses as well as entrance and departure gates of subway and train stations are equipped with RFID readers which the customers have touch with their Oyster cards when starting and ending their journey. Altogether more than 20.000 reading devices are installed in the field. In either case, the readers are able to read and write the cards in less than 300ms allowing a quick and straightforward access control and ticketing procedure. This form of system thus not only prevents travellers from using the transport systems without a valid ticket, but also can automatically debit the appropriate fare from the card depending on the travelling type and duration. As a matter of course the card needs to be topped up in advance. This is usually done via cash or credit card at kiosks or at certain vending machines placed at the stations. Flat rate tickets, e.g. based on monthly subscriptions, can of course also be linked to the Oyster Card. As being technically compatible, this immense RFID based ticketing system can be extended for NFC support without much effort. This means that the smartcard could be replaced by a NFC enabled mobile phone. Tickets could be either bought online and disposed directly to the phone in advance or - combined with NFC payment - debited from a bank account automatically.
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Experimentation and modelling of near field explosions

Experimentation and modelling of near field explosions

Finally, the results and comparisons presented in this paper show that repeatable experimental measurements of reflected pressure are possible at very small scaled distances, that turbulent instabilities grow with the expansion of the detonation products and that the JWL EOS for PE4 will significantly over predict pressure and impulse in the extreme near field. These finding are in keeping with the hypothesis that the JWL EOS releases the energy associated with secondary combustion upon detonation; rather than over a timescale as a result of mixing with free oxygen in the air.
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VIABILITY OF NEAR  FIELD COMMUNICATION TECHNOLOGY

VIABILITY OF NEAR FIELD COMMUNICATION TECHNOLOGY

Essentially, the advances Radio Frequency Identification and Near Field Communication utilize the same working gauges. Notwithstanding, the key augmentation of RFID is the correspondence mode between two dynamic gadgets. Notwithstanding contactless savvy cards (ISO 14443), which just bolster correspondence between controlled gadgets and inactive labels, NFC likewise gives distributed correspondence .Thus, NFC joins the component to peruse out and copy RFID labels, and moreover, to share information between electronic gadgets that both have dynamic force. NFCIP-1 is a NFC-particular correspondence mode, characterized in the ECMA-340 standard. This mode is proposed for distributed information correspondence between gadgets. In this mode, NFC is tantamount to other short-run correspondence advances, for example, IrDA, in spite of the fact that the physical information exchange component is diverse. The NFCIP-1 mode is isolated into two variations: dynamic mode and aloof mode. In dynamic mode, both members create their own transporter while transmitting information. In uninvolved mode, just the initiator produces a transporter amid interchanges, and the objective gadget uses load adjustment when imparting back to the initiator, in a manner like latent RFID label conduct. This makes it conceivable to spare force in the objective gadget, which is a helpful component if the objective gadget has an exceptionally confined vitality source, for example, a little battery
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NEAR FIELD COMMUNICATIONS Neha Katkamwar

NEAR FIELD COMMUNICATIONS Neha Katkamwar

The voltage generated at the receiving resonator © changing magnetic field is used to energize the electronic cirtuits in a passive NFC tag. The energizing signal for NFC is a 13.56 MHz carrier that is allowed for transmission in all regulatory regions. The sam Erf energizing signal is also used to send the data. The amplitude of the energizing signal is modulated by the NFC reader, then the receiving circuits in the NFC tag strip off a baseband waveform that is detected and demodulated. After sending its message to the tag, the reader continues to send the RF signal without any modulations so that tag can remain ereergized and waits for a response. The tag responnds by modulating the load it presents to the reader. Since any energy transmitted to the load in the tag must be generated in the source at the reader, a change in tag load is seen as a change in current in the reader inductor. The tag data stream does this modulation by driving a circuit that switches the load across its inductor. The reader detects this change in current and as a result can demodulate the data from the tag. This method for the tag to communicate to the reader while still being energized by it is called load modulation. Care must be taken in the placement of the NFC antenna in the phone package as the magnetic field has the potential of disrupting the operation of the phone circuits, and the structure around the antenna can pull its resonant frequency.
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USER FRIENDLINESS OF NEAR-FIELD COMMUNICATION

USER FRIENDLINESS OF NEAR-FIELD COMMUNICATION

Over the last few years, one of the emerging communication technology introduced within mobile devices is the Near Field Communication (NFC) technology. Most of the devices in the current market such as smart phones, tablets, and even cameras have been embedded with the NFC functionality. NFC is a newly introduced wireless technology that evolved from the Radio Frequency Identification (RFID) technology Both NFC and RFID are bidirectional short-range communication tools. The contactless interaction between two NFC-enabled devices is approximately 5-10 cm [1]. The technology uses radio waves to identify, track devices and send data in a near-field approach. The technology is widely used as a contactless payment in some grocery shops, food outlets and as a ticketing method for public transportation [1]. The NFC technology is also implemented in library systems in Japan. The Saitama Prefecture in Hanno, Japan has utilized the NFC technology [2] within their local library. Around 100 tags, or known as “Tatchitagu” is placed on the shelves where the tags contain the necessary information about the specific books. The users are able to review the books or recommend it to another user via the tags.
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