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The evolution of wooden bridge trusses to 1850
Published in David T. Yeomans, The Development of Timber as a Structural Material, 2017
To meet the railway boom Town effectively extended his patent by obtaining a new one April 3, 1835 for ‘improvements’. This covered the use of close-coupled pairs of lattices in place of single ones and additional stringers. For very long spans Town also envisaged triple and quadruple lattices but no examples of these are known. The double lattice (the joints in one being out of phase with the other) became standard for railway use (Fig 69) when spans over about 120 ft were needed. In a new edition of his pamphlet in 1839132 Town listed some sizable railway bridges, largely drawing on an article which had appeared in the New Haven Daily Herald in September 1838.
Theory of photon detectors
Published in Antoni Rogalski, Infrared and Terahertz Detectors, 2019
At present the following materials have proved to be appropriate for the fabrication of high-performance APDs: Silicon (for wavelengths of 0.4 to 1.1 μm). The electron ionization rate is much higher than the hole ionization rate (αe>>αh);Germanium (for wavelengths of up to 1.65μm). Since the bandgap in Ge is lower than in Si and the ionization rates for electrons and holes are approximately equal (αe≈αh), the noise is considerably higher and this limits the applications of Ge-based APDs;GaAs-based devices. Most compound materials have αe≈αh and so designers usually use heterostructures like GaAs/Al0.45Ga0.55As, for which αe(GaAs)>>αe(AlGaAs). The large increase in gain occurs due to the avalanche effect that occurs in GaAs layers. GaAs/Al0.45Ga0.55As heterostructures are in spectral range below 0.9 μm. Applying InGaAs layers allows the sensitivity to extend to≈1.4 μm;InP-based devices are used in the wavelength range of 1.2–1.6 μm. In double lattice–matched heterostructure n+-InP/n-GaInAsP/p-GaInAsP/p+-InP, either of the carriers are injected into the high field region—this structure is essential for low-noise operation. The second structure, p+-InP/n-InP/n-InGaAsP/n+-InP, is similar to the Si reach through devices. The absorption occurs in the relatively wide InGaAsP layers and avalanche multiplication of the minority carriers proceeds in the n-InP layer.Hg1–xCdxTe APDs. These devices are electron-initiated ones and their operation has been demonstrated for a broad range of compositions from x = 0.7 to 0.21 corresponding to cut-off wavelengths from 1.3 μm to 11 μm. Thus, HgCdTe APD at gain = 100 provides 10 to 20 times less noise than InGaAs or InAlAs APDs and 4 times less noise than Si APDs.
Fundamentals of Optical Detection
Published in Antoni Rogalski, Zbigniew Bielecki, Detection of Optical Signals, 2022
Antoni Rogalski, Zbigniew Bielecki
At present the following materials have proved to be appropriate for the fabrication of high-performance avalanche photodiodes (APDs): Silicon (for wavelengths of 0.4 to 1.1 μm). The electron ionisation rate is much higher than the hole ionisation rate (αe >> αh);Germanium (for the wavelengths of up to 1.65 μm). Since the bandgap in Ge is lower than in Si, and the ionisation rates for electrons and holes are approximately equal (αe ≈ αh), the noise is considerably higher, and this limits the applications of Ge-based APDs;GaAs based devices. Most compound materials have αe ≈ αh, so designers usually use heterostructures like GaAs/Al0.45Ga0.55As, for which αe(GaAs) >> αe(AlGaAs). The large increase in gain occurs due to the avalanche effect that occurs in GaAs layers. GaAs/Al0.45Ga0.55As heterostructures are in spectral range below 0.9 μm. Applying InGaAs layers allows the sensitivity to extend to ≈ 1.4 μm;InP-based devices are used in the wavelength range of 1.2–1.6 μm. In double lattice-matched heterostructure n+-InP/n-GaInAsP/p-GaInAsP/p+-InP either of carriers are injected into the high field region – this structure is essential for low-noise operation. The second structure, p+-InP/n-InP/n-InGaAsP/n+-InP, is similar to the Si reach through devices. The absorption occurs in the relatively wide InGaAsP layers and avalanche multiplication of the minority carriers proceeds in the n-InP layer.Hg1-xCdxTe APDs. These devices are electron-initiated, and their operation has been demonstrated for a broad range of compositions from x = 0.7 to 0.21 corresponding to cut-off wavelengths from 1.3 μm to 11 μm. Thus, HgCdTe APD at gain = 100 provides 10 to 20 times less noise than InGaAs or InAlAs APDs and 4 time less noise than Si APDs.
Prediction of the Bain spin memory materials (BSMM) revealed by Kaneyoshi theory
Published in Philosophical Magazine Letters, 2020
Buket Saatçi, Numan Şarlı, Yılmaz Dağdemir, Yasin Göktürk Yıldız, Hamza Yaşar Ocak
In the 1.4% carbon steel alloy, the orientation relationship between martensite and austenite was first determined by Kurdjumov and Sachs and the researchers suggested that the conversion mechanism could be determined by this correlation [5]. Following this study, Nishiyama found a new rotational correlation in Fe-30% Ni alloy, which was slightly different from the rotational correlation determined by Kurdjumov and Sachs, and proposed the mechanism of this transformation [5]. Classical theories were successfully applied to martensitic transformations having a habit plane in steel {225}. However, parallel to the theoretical calculations, {225} martensites were determined by a transmission electron microscope which contained different cutting elements. To explain these issues in classical theories, Ross and Crocker [12] and Acton and Bevis [13] developed new theories known as double lattice invariant shear crystallographic martensite theories at approximately the same time and independently of each other. In addition, in the study of the crystallography of the martensite structure formed in Cu-15% Sn alloy, neither single shear theories nor double shear theories couldn’t explain the observed shape strain in this alloy. Therefore, the multiple-shear martensitic transformation model was developed by Wayman [14].
Controlling Rayleigh–Bénard convection via reinforcement learning
Published in Journal of Turbulence, 2020
Gerben Beintema, Alessandro Corbetta, Luca Biferale, Federico Toschi
We simulate the flow dynamics through the Lattice–Boltzmann method (LBM) [5] employing a double lattice, respectively for the velocity and for the temperature populations (with D2Q9 and D2Q4 schemes on a square lattice with sizes ; collisions are resolved via the standard BGK relaxation). We opt for the LBM since it allows for fast, extremely vectorizable, implementations which enables us to perform multiple (up to hundreds) simulations concurrently on a GPU architecture. See Table 1 for relevant simulation parameters; further implementation details are reported in Appendix 1.
Improving the emission intensity and broadening spectrum of borate NaSrBO3 blue phosphor by double ion doping
Published in Journal of Modern Optics, 2022
Qizheng Dong, Wenbo Zhang, Ling He, Xuefeng Lu, Binglong Tian
Since Ce has only one 4f orbital electron, it will transition to the 5d orbital after being excited. The excitation and emission of the 4f and 5d energy levels are parity and spin-allowed transitions, so it is suitable as an activator that produces efficient emission [6]. But its luminescence performance is affected by the host, therefore, the choice of the matrix also brings an important influence on the luminescent material. Some scholars have carried out research on Ce-doped phosphor host. such as β-Ca3(PO4)2 is a kind of whitlockite-type structure, the coordination polyhedron of Ca2+ itself has multiple crystal lattices, so Ce3+-doped β-Ca3(PO4)2 can be used as an excellent blue phosphor [7], as well owing to the special structure of Ba3Y2B2O15 host, phase BaO-Y2O3-B2O3 will be produced, realizing wide colour gamut illumination [8]. Borate has become a possible phosphor host candidate because of its low synthesis temperature, simple structure and good crystallization performance [9]. All of them have obtained good blue phosphors through Ce3+ doping due to their special structure. A family of efficient orthoborate phosphors with the general formula NaMBO3:Ce3+ (M = Ca, Sr, Ba) have attracted the attention of researchers [10–12]. Recently, Junpeng Xue et al. reported NaMgBO3:Ce3+, Tb3+ phosphor [13], and Zhong et al. studied NaBaBO3:Ce3+ blue phosphor through experiments and calculations [12]. In addition, A. K. Bedyal et al. studied NaSrBO3:Eu3+/Tb3+ phosphor and by changing the Eu3+/Tb3+ ratio, tunable photoluminescence was realized. The current research proves that NaMBO3 retain a special structure, and its luminous properties can be effectively improved by doping, thence this system has the potential to be a high-efficiency blue phosphor. However, current reports are limited to substitute on a single lattice site, and the doping substitution on double lattice sites co-doping is rarely reported.