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David R. Smith

Bio: David R. Smith is an academic researcher from Duke University. The author has contributed to research in topics: Metamaterial & Antenna (radio). The author has an hindex of 110, co-authored 881 publications receiving 91683 citations. Previous affiliations of David R. Smith include Brunel University London & Princeton University.


Papers
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Journal ArticleDOI
TL;DR: Ono et al. as mentioned in this paper measured electron temperature gradient (ETG) turbulence in National Spherical Torus Experiment (NSTE) and reported the toroidal field scaling of fluctuation amplitudes.
Abstract: A collective scattering system has measured electron gyroscale fluctuations in National Spherical Torus Experiment [M Ono et al, Nucl Fusion 40, 557 (2000)] H-mode plasmas to investigate electron temperature gradient (ETG) turbulence Observations and results pertaining to fluctuation measurements in ETG-stable regimes, the toroidal field scaling of fluctuation amplitudes, the relation between fluctuation amplitudes and transport quantities, and fluctuation magnitudes and k-spectra are presented Collectively, the measurements provide insight and guidance for understanding ETG turbulence and anomalous electron thermal transport

10 citations

Proceedings ArticleDOI
01 Jul 2017
TL;DR: In this article, a software correction technique was proposed to eliminate the misalignment errors in the measurement of antenna radiated fields for frequency-diverse imaging using RF fiducials integrated into the antennas.
Abstract: In this paper, we propose a software correction technique to eliminate the misalignment errors in the measurement of antenna radiated fields for frequency-diverse imaging. It is shown that by using RF fiducials integrated into the antennas, the effect of rotation (range and cross-range) and offset misalignment errors can be corrected to a good accuracy, holding significant potential for applications where precise alignment is required for antenna field measurements.

10 citations

Proceedings ArticleDOI
17 Jun 2005
TL;DR: In this paper, a symmetric realization for a predistorted bandpass filter using a general cross-coupled resonator structure was presented, which enables much simpler conversion from an existing filter design without predistortion.
Abstract: This paper presents a symmetric realization for a predistorted bandpass filter using a general cross-coupled resonator structure. The new method enables much simpler conversion from an existing filter design without predistortion. Hence both design and tuning efforts are reduced. A 10-4-4 dielectric resonator filter was built to verify the validity of the new method. The filter, coupled with an input circulator and output isolator was tested over temperature to validate the suitability for practical applications such as satellite transponder input multiplexers.

10 citations

Journal ArticleDOI
TL;DR: In this paper, the high-energy feature (HEF) is observed on the NB-injected energetic-ion spectrum only in discharges where tearing or kink-type modes (f 1000 kHz) is usually sporadic or absent during the HEF event.
Abstract: In the National Spherical Torus Experiment (NSTX), a large increase in the charge exchange neutral flux localized around the neutral beam (NB) injection full energy is measured using a neutral particle analyser. Termed the high-energy feature (HEF), it appears on the NB-injected energetic-ion spectrum only in discharges where tearing or kink-type modes (f 1000 kHz) is usually sporadic or absent during the HEF event. The HEF exhibits growth times of Δt ~ 20–80 ms, durations spanning 100–600 ms and peak-to-base flux ratios up to H = Fmax/Fmin ~ 10. In infrequent cases, a slowing-down distribution below the HEF energy can develop that continues to evolve over periods of order 100 ms, a time scale long compared with the typical fast-ion equilibration times. HEFs are observed only in H-mode (not L-mode) discharges with injected power Pb ≥ 4 MW and in the pitch range χ ≡ v||/v ~ 0.7–0.9; i.e. only for passing particles. Increases of order 10–30% in the measured neutron yield and total stored energy that are observed to coincide with the feature appear to be driven by concomitant broadening of measured Te(r), Ti(r) and ne(r) profiles and not the HEF itself. While the HEF has minimal impact on plasma performance, it nevertheless poses a challenging wave–particle interaction phenomenon to understand. Candidate mechanisms for HEF formation are developed based on quasilinear (QL) theory of wave–particle interaction. The only mechanism found to lead to the large NPA flux ratios, H = Fmax/Fmin, observed in NSTX is the QL evolution of the energetic-ion distribution, Fb(E, χ, r), in phase space. A concomitant loss of some particles is observed due to interaction through cyclotron resonance of the particles with destabilized modes having sufficiently high frequencies, f ~ 700–1000 kHz, in the plasma frame that are tentatively identified as GAEs.

9 citations

Journal ArticleDOI
David R. Smith1
TL;DR: In this paper, a collimated beam of light passes through a small aperture in an opaque barrier, and if the size of the aperture is similar to the wavelength of the incident light, the emerging light flares out from the aperture and forms a diffraction pattern whereby the intensity of the transmitted light has a broad central peak.
Abstract: One of the best known properties of light is that it diffracts, bending or spreading around objects that lie in its path. A familiar example is when a collimated beam of light passes through a small aperture in an opaque barrier. If the aperture is large, the light emerges as a beam with the same radius as that of the aperture. But if the size of the aperture is similar to the wavelength of the incident light, the emerging light flares out from the aperture and forms a diffraction pattern whereby the intensity of the transmitted light has a broad central peak.

9 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: A review of gold nanoparticles can be found in this article, where the most stable metal nanoparticles, called gold colloids (AuNPs), have been used for catalysis and biology applications.
Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

11,752 citations

Journal ArticleDOI
14 Aug 2003-Nature
TL;DR: By altering the structure of a metal's surface, the properties of surface plasmons—in particular their interaction with light—can be tailored, which could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved.
Abstract: Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons--in particular their interaction with light--can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.

10,689 citations

Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations