Radiation effect of neutrons produced by D–D side reactions on a D–3He fusion reactor

One of the most important characteristics in D–³He fusion reactors is neutron production via D–D side reactions. The neutrons can activate structural material, degrading them and ultimately converting them into high-level radioactive waste, while it is really costly and difficult to remove them. The neutrons from a fusion reactor could also be used to make weapons-grade nuclear material, rendering such types of fusion reactors a serious proliferation hazard. A related problem is the presence of radioactive elements such as tritium in D–³He plasma, either as fuel for or as products of the nuclear reactions; substantial quantities of radioactive elements would not only pose a general health risk, but tritium in particular would also be another proliferation hazard. The problems of neutron radiation and radioactive element production are especially interconnected because both would result from the D–D side reaction. Therefore, the presentation approach for reducing neutrons via D–D nuclear side reactions in a D–³He fusion reactor is very important. For doing this research, energy losses and neutron power fraction in D–³He fusion reactors are investigated. Calculations show neutrons produced by the D–D nuclear side reaction could be reduced by changing to a more ³He-rich fuel mixture, but then the bremsstrahlung power loss fraction would increase in the D–³He fusion reactor.     

Infrared spectra of acetylene–water complexes: C2D2–H2O,C2D2–HDO,and C2D2–D2O

Infrared spectra of C₂D₂–water complexes are studied in the 4.1 μm region of the C₂D₂ ν₃ fundamental band using a tunable diode laser source to probe a pulsed supersonic slit jet. Relatively large vibrational red shifts (?27.7 to ?28.0 cm^?1) are observed which are more easily interpretable than for the analogous C₂H₂ vibration thanks to the absence of Fermi resonance effects for C₂D₂. Noticeable homogeneous line broadening leads to estimates of upper state predissociation lifetimes of about 0.5, 0.9 and 1.1 ns for C₂D₂–H₂O, –HDO, and –D₂O, respectively. Transitions involving K_a = 0 and 1 levels are observed for C₂D₂–HDO, but there is a puzzling absence of K_a = 1 for C₂D₂–H₂O and C₂D₂–D₂O.     

Momentum-carrying waves on D1–D5 microstate geometries

If one attempts to add momentum-carrying waves to a black string then the solution develops a singularity at the horizon; this is a manifestation of the ‘no hair theorem’ for black objects. However individual microstates of a black string do not have a horizon, and so the above theorem does not apply. We construct a perturbation that adds momentum to a family of microstates of the extremal D1–D5 string. This perturbation is analogous to the ‘singleton’ mode localized at the boundary of AdS; to leading order it is pure gauge in the AdS interior of the geometry.     

D0–D6 States Counting and GW Invariants

We describe a correspondence between the Donaldson?CThomas invariants enumerating D0?CD6 bound states on a Calabi?CYau 3-fold and certain Gromov?CWitten invariants counting rational curves in a family of blowups of weighted projective planes. This is a variation on a correspondence found by Gross?CPandharipande, with D0?CD6 bound states replacing representations of generalised Kronecker quivers. We build on a small part of the theories developed by Joyce?CSong and Kontsevich?CSoibelman for wall-crossing formulae and by Gross?CPandharipande?CSiebert for factorisations in the tropical vertex group. Along the way we write down an explicit formula for the BPS state counts which arise up to rank 3 and prove their integrality. We also compare with previous ??noncommutative DT invariants?? computations in the physics literature.     

The 2D Kramers–Dirac oscillator

The Dirac oscillator was initially introduced as a Dirac operator which is linear in momentum and coordinate variables. In contrast to the usual 2D Dirac oscillator, the 2D Kramers–Dirac oscillator admits the time-reversal symmetry, which is a reason for the present nomenclature. It is shown that there exists a family of eigenstates associated with an eigenvalue linear in the control parameter, and the eigenvalue in question goes down from positive values to negative values as the parameter varies in the positive direction. The other eigenvalues are broken up into two bands, positive and negative. The 2D Dirac and the 2D Kramers–Dirac oscillators are compared in their physical grounds and in their spectral structure from the viewpoint of the time-reversal symmetry.     

Evaluation of the neutron production rate using D–D and D–T fuel in an inertial electrostatic confinement fusion device

The correlation between the neutron production rate and fuel species in a spherical inertial electrostatic confinement fusion (IECF) device is investigated by solving the Poisson equation for various ion and electron distribution functions. The fuel ion energy distribution function is determined at each radial point. The fusion reaction rate is evaluated from the energy distribution function. The dependence of the neutron production rate (NPR) on some important parameters, like the ion convergence, the broadening of the distributions in the energy space, working pressure and fuel species, are also investigated. Compared with the IECF device with D–D, numerical calculations show that by increasing the percentage of tritium in the D–T mixture fuel the neutron production rate grows significantly.     

Waveguiding effect in 2D metal–dielectric–metal grating structure

We have studied the waveguiding effect in a 2D metal–dielectric–metal (MDM) grating structure formed on a quartz substrate. The grating was first formed via e-beam lithography and subsequently covered by Ag/MgF₂/Ag MDM films. At a pitch of 300 nm in both x- and y-directions, low reflectance and transmittance were observed in the UV–VIS range, indicating efficient coupling of normal incident light into waveguiding modes. As evidence, we measured the spectrum of the waveguide from the edge, and the bandwidth of the spectrum was as narrow as ∼74 nm. The bandwidth of the waveguide can be further improved by increasing the MDM stack number. In addition, the bandwidth can also be widened by increasing the pitch of the structure. The physical mechanism underlying the phenomena was analyzed and experimentally confirmed. Such effect could be useful in many applications, such as DFB lasers, solar cells, waveguides, and light emitting devices.     

4D Einstein equations in a 5D general Kaluza–Klein space

Based on the new point of view on space–time–matter theory developed in our paper (Bejancu, Gen Rel Grav, 2013), we obtain the $4D$ 4 D Einstein equations in a general $5D$ 5 D Kaluza–Klein space with electromagnetic potentials. In particular, we recover the $4D$ 4 D Einstein equations obtained by Wesson and Ponce de Leon (J Math Phys 33:3883, 1992) in case the electromagnetic potentials vanish identically on $\bar{M}$ M ¯ . The Riemannian horizontal connection and the $4D$ 4 D tensor calculus on $\bar{M}$ M ¯ , are the main tools in the study.     

Fermions tunnelling from GHS and non-extremal D1–D5 black holes

Recent research shows that fermions tunnelling can result in correct Hawking temperature of a black hole. In this letter, choosing a set of appropriate matrices γμ${\gamma }^{\mu }$, we attempt to study Hawking radiation of Dirac particles across the horizons of the GHS and non-extremal five-dimensional D1–D5 black holes in string theory by using fermions tunnelling method. Finally, the expected Hawking temperatures of the GHS and non-extremal D1–D5 black holes are correctly recovered.     

Collimation of Acoustic Radiation via Zero–Refraction–Index 2D Periodic Structures

Acoustical Physics - The experimental study results of acoustic radiation generation via zero–refraction–index periodic structures are presented. The frequency dependences of refraction...     

Numerical solutions to 2D Maxwell–Bloch equations

Rare-earth-doped crystals contain inhomogeneously broadened two-level atoms. Optical propagation and nonlinear interaction in the crystals can be described by the Maxwell–Bloch equations. We show a consistent numerical approach that solves Maxwell’s equations by using the FFT-finite difference beam propagation method and the Bloch equations by using the finite difference method. Numerical simulation results are given for an off-axis 3-pulse photon echo.     

Electron–Hole Dimers in the Parent Phase of Quasi–2D Cuprates

Physics of the Solid State - The key feature of parent cuprates of the La2CuO4 type, in addition to their high ionic polarizability and closeness to polarization catastrophe, is identified as their...     

An Algebraic Proof on the Finiteness of Yang–Mills–Chern–Simons Theory in D=3

A rigorous algebraic proof of the full finiteness in all orders of perturbation theory is given for the Yang–Mills–Chern–Simons theory in a general three-dimensional Riemannian manifold. We show the validity of a trace identity, playing the role of a local form of the Callan–Symanzik equation, in all loop orders, which yields the vanishing of the -functions associated to the topological mass and gauge coupling constant as well as the anomalous dimensions of the fields.     

Applications of a Cole–Hopf transform to the 3D Navier–Stokes equations

The Navier–Stokes equations written in the vector potential can be recast as non-linear Schrödinger equations at imaginary times, i.e. heat equations with a potential term, using the Cole–Hopf transform. On this basis, we study two kinds of Navier–Stokes flows by means of direct numerical simulations. In an experiment on vortex reconnection, it is found that the potential term takes large negative values in regions where intensive reconnection takes place, whereas the signature of the non-linear term is more broadly spread. For decaying turbulence starting from a random initial condition, such a correspondence is also observed in the early stage when the flow is dominated by vorticity layers. At later times, when the flow features several tubular vortices, this correspondence becomes weaker. Finally, a similar set of transformations is presented for the magneto–hydrodynamic equations, which reduces them to a set of heat equations with suitable potential terms, thereby obtaining new criteria for the regularity of their solutions.     

Rovibrational spectra of the Ar–D2O and Kr–D2O van der Waals complexes in the v2 bend region of D2O

Rovibrational spectra of Ar–D₂O and Kr–D₂O complexes are measured in the v₂ bend region of D₂O monomer using a tunable mid-infrared diode laser spectrometer. One para and two ortho bands for both complexes are identified and then analyzed in terms of a nearly free internal rotor model. Molecular constants for the excited vibrational states, including band-origin, rotational and centrifugal distortion constants, and Coriolis coupling constant, are determined accurately. A comparison of the observed band-origins of Ar–D₂O and Kr–D₂O with the previous results of Ne–D₂O shows regular trends of shift from Kr–D₂O to Ne–D₂O.     

4+2D维Einstein–Maxwell量子宇宙

利用推广的Hartle-Hawking假设,研究了4+2D维Einstein-Maxwell量子宇宙,计算了微超空间波函数的近似解.发现当D≤2时存在与观测宇宙相符合的暴胀解.     

The effect of twisted D–D–π–A configuration on electron transfer and photo-physics characteristics

Two D–D–π–A organic dyes (M45, M46) with dithieno[3,2-b:2′,3′-d]pyrrole (DTP) units as election donors in two perpendicular directions, were investigated using density functional theory (DFT) and time-dependent DFT. The ground-state geometries, the absorption, the electronic structures, the charge density difference and molecular electrostatic potential were obtained. To simulate a more realistic performance, all calculations were based on gas condition and dichloromethane solvent. Photoelectric parameters were evaluated by the following factors: the light harvesting efficiency, electron injection driving force, the excited lifetime and vertical dipole moment. Meanwhile, the polarisability and hyperpolarisability were investigated to further explain the relationship between non-linear optical properties and efficiency. The direction of the DTP obviously affects the twisted degree of molecule, forming a better coplanarity on the donor 2 of M45, which results in stronger charge transfer interactions. Furthermore, M45 possesses significant advantages in geometric structure, absorption band and intramolecular charge transfer mechanism. These critical parameters supported the higher performance of M45 in comparison with M46. Moreover, four dyes were designed by the substitution of donor 2, which further verify the influence of the twisted donor 2 on electron transfer and photoelectric properties of D–D–π–A configuration.     

A modified Euler–Maclaurin formula in 1D and 2D with applications in statistical physics

The Euler–Maclaurin summation formula is generalized to a modified form by expanding the periodic Bernoulli polynomials as its Fourier series and taking cuts, which includes both the Euler–Maclaurin summation formula and the Poisson summation formula as special cases. By making use of the modified formula, a possible numerical summation method is obtained and the remainder can be controlled. The modified formula is also generalized from one dimension to two dimensions. Approximate expressions of partition functions of a classical particle in square well in 1D and 2D and that of a quantum rotator are obtained with error estimation.