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Light-weight and high-strength aluminum alloy drill pipes are potential and promising to replace traditional steel drill pipes. In this study, the grain size and mechanical properties of aluminum alloy drilling pipe materials reinforced by in-situ TiB2 particles were studied. The results showed when reinforced by in-situ TiB2 particles the grain size of aluminum alloy materials was refined from 155 m to 57 m and ultimate tensile strength was increased from 590 MPa to 720 MPa. Besides, the results also indicated that the friction coefficient was reduced from 0.99 to 0.50 and thus the abrasion resistance of 7075 aluminum alloy was enhanced by 34 %. This study provided theoretical basis for the application of light-weight and high-strength aluminum alloy drill pipes in directional drilling and ultra-deep wells.

Lüscher's formula relates the elastic scattering phase shifts to the two-particle energy levels in a finite cubic box. The original formula was obtained for elastic scattering of two massive spinless particles in the center-of-mass frame. In this paper, we consider the case for the scattering of a spin 1 /2 particle with a spinless particle in a multichannel scattering. A generalized relation between the energy of the twoparticle system and the scattering matrix elements is established. We first obtain this relation using quantum mechanics in both the center-of-mass frame and in a general moving frame. The result is then generalized to quantum field theory, using methods outlined by Hansen and Sharpe [Phys. Rev. D 86, 016007 (2012)]. We verify that the results obtained using both methods are equivalent up to terms that are exponentially suppressed in the box size. [ABSTRACT FROM AUTHOR]

In this paper, we propose a theoretical scheme of many-ghost imaging in terms of Nth-order correlated thermal light. We obtain the Gaussian thin lens equations in the many-ghost imaging protocol. We show that it is possible to produce N-1 ghost images of an object at different places in a nonlocal fashion by means of a higher order correlated imaging process with an Nth-order correlated thermal source and correlation measurements. We investigate the visibility of the ghost images in the scheme and obtain the upper bounds of the visibility for the Nth-order correlated thermal-light ghost imaging. It is found that the visibility of the ghost images can be dramatically enhanced when the order of correlation becomes larger. It is pointed out that the many-ghost imaging phenomenon is an observable physical effect induced by higher order coherence or higher order correlations of optical fields. [ABSTRACT FROM AUTHOR]

Using the path integral representation, bulk thermodynamic properties of the two-dimensional Hubbard model on a square lattice are studied numerically using the hybrid Monte Carlo simulation algorithm. Results for averaged energy, spin-spin correlation functions and Cooper pair correlation functions are presented. All these results suggest that the system exhibits an anti-ferromagnetic correlation at half-filling for a wide range of temperature.

Glueball spectrum is studied using an improved gluonic action on asymmetric lattices in the pure gauge theory. The smallest spatial lattice spacing is about 0.08 fm which makes the extrapolation to the continuum limit more reliable. In particular, attention is paid to the scalar glueball mass which is known to have problems in the extrapolation. Converting our lattice results to physical units using the scale set by the static quark potential, we obtain the following results for the glueball masses: for the scalar glueball mass and for the tensor glueball.

Using a Hamiltonian approach and the adiabatic approximation, the low-lying spectrum of the lattice model in the broken phase is analyzed to the next to leading order. It is seen that these corrections appear as a systematic expansion in the inverse power of the lattice size L in the large volume limit.

Spontaneous symmetry breaking plays a crucial role in quantum field theories and it occurs only for systems with infinite degrees of freedom. For a system in a large but finite volume, although the symmetry is not broken spontaneously, an adiabatic approximation can be applied to study the would-be broken symmetry. Lattice O(N) model is studied within the Hamiltonian approach. It is shown that the low-lying spectrum of the system can be explained using an adiabatic, or Born-Oppenheimer approximation, which turns out to become 1 an expansion in the inverse power of volume. In the infinite volume limit, the symmetry is broken while in the finite volume the slow rotation of the zero-momentum mode restores the symmetry and gives rise to the rotator spectrum, which has been observed in real Monte Carlo simulations.

The lattice O(N) model, defined on a large but finite three-dimensional cubic lattice, is studied using the Hamiltonian approach in bare perturbation theory in the broken phase. Renormalization is carried out to O(?0) and the results are compared with those obtained using the conventional Lagrangian approach in the infinite volume limit. Complete agreement is found between the two methods.

Abstract: A new matrix perturbation analysis method is presented for efficient approximate solution of the complex modal quadratic generalized eigenvalue problem of viscously damped linear vibration systems. First, the damping matrix is decomposed into the sum of a proportional- and a nonproportional-damping parts, and the solutions of the real modal eigenproblem with the proportional dampings are determined, which are a set of initial approximate solutions of the complex modal eigenproblem. Second, by taking the nonproportional-damping part as a small modification to the proportional one and using the matrix perturbation analysis method, a set of approximate solutions of the complex modal eigenvalue problem can be obtained analytically. The result is quite simple. The new method is applicable to the systems with viscous dampings which do not deviate far away from the proportional- damping case. It is particularly important that the solution technique be also effective to the systems with heavy, but not over, dampings. The solution formulas of complex modal eigenvlaues and eigenvectors are derived up to second- order perturbation terms. The effectiveness of the perturbation algorithm is illustrated by an exemplar numerical problem with heavy dampings. In addition, the practicability of approximately estimating the complex modal eigenvalues, under the proportional-damping hypothesis, of damped vibration systems is discussed by several numerical examples.

Abstract: LetKbe a class of spaces which are eigher a pseudo-opens-image of a metric space or ak-space having a compact-countable closedk-network. LetK′ be a class of spaces which are either a Frchet space with a point-countablek-network or a point-Gδk-space having a compact-countablek-network. In this paper, we obtain some sufficient and necessary conditions that the products of finitely or countably many spaces in the classKorK′ are ak-space. The main results are that

Abstract: In this paper internal characterization on certain quotient images of locally separable metric spaces are discussed. We obtain some descriptions of quotients-images, pseudo-opens-images, quotient compact images and closed images of locally separable metric spaces, and establish some relations between these and certain quotient images of metric spaces by the local separability of suitable subspaces.

[C15H6Cl6O4], monoclinic, Cc(no. 9), a= 12.0980(11) Å, b= 10.0628(9) Å, c= 15.1518(14) Å, β= 104.231(1)°, V= 1788.0(3) Å3, Z= 4, Rgt(F) = 0.0214, wRref(F2) = 0.0568, T= 296(2) K.

The three-photon decay rate of J/ψ is studied using two Nf=2 twisted-mass gauge ensembles with lattice spacings a≃0.085 and 0.067 fm. Using a new method, only the correlation functions directly related to the physical decay width are computed with all polarizations of the initial and final states summed over. The final result can be obtained after a naive extrapolation to the continuum limit. To be specific, the result for such rare decay is given as B(J/ψ→3γ)=(2.13±0.14±0.29)×10-5, where the first error is statistical and the second is an estimate of the systematics. We also propose a method to analyze the Dalitz plot of the corresponding process based on the lattice data which can provide direct information for the relevant experiments. [ABSTRACT FROM AUTHOR]

Using a recently proposed method [Y. Meng, C. Liu, and K. L. Zhang, arXiv:1910.11597v3], we study the two-photon decay rate of ηc using two Nf=2 twisted mass gauge ensembles with lattice spacings 0.067 fm and 0.085 fm. The results obtained from these two ensembles can be extrapolated in a naive fashion to the continuum limit, yielding a result that is consistent with the experimental one within two standard deviations. To be specific, we obtain the results for two-photon decay of ηc as B(ηc→2γ)=1.29(3)(18)×10-4 where the first error is statistical and the second is our estimate for the systematic error caused by the finite lattice spacing. It turns out that Ward identity for the vector current is of vital importance within this new method. We verify that the Ward identity is violated for local current with a finite lattice spacing, however it will be restored after the continuum limit is taken. [ABSTRACT FROM AUTHOR]

Within the framework of three-channel Ross-Shaw effective range theory, we derive the constraints among different parameters of the theory in the case of a narrow resonance close to the threshold of the third channel, which is relevant for the resonancelike structure Zc(3900). The usage of these constraint relations, together with the multichannel Lüscher formula in lattice QCD calculations are also discussed and the strategies are outlined. [ABSTRACT FROM AUTHOR]

An explicit expression for the finite-volume energy shift of shallow three-body bound states for nonidentical particles is obtained in the unitary limit. The inclusion of the higher partial waves is considered. To this end, the method of Meißner, Rìos, and Rusetsky [Phys. Rev. Lett. 114, 091602 (2015)] is generalized for the case of unequal masses and arbitrary angular momenta. It is shown that in the S-wave and in the equal-mass limit, the result from Meißner, Rìos, and Rusetsky is reproduced. [ABSTRACT FROM AUTHOR]

In this paper, Ltischer's formula is generalized to the case of two spin-| particles in two-channel scattering based on our previous work [Phys. Rev. D 87, 014502 (2013)]. This is first done in a nonrelativistic quantum mechanics model and then generalized to the quantum field theory. We show that Liischer's formulas obtained from these two different methods are equivalent up to terms that are exponentially suppressed in the box size. This formalism can be readily applied to future lattice QCD calculations in nucleon-nucleon or nucleon-hyperon scattering processes. [ABSTRACT FROM AUTHOR]

In this paper, low-energy scattering of the (D*...*)± meson system is studied within Liischer's finite-size formalism using Nf = 2 twisted-mass gauge field configurations. With three different pion mass values, the 5-wave threshold scattering parameters--namely the scattering length a0 and the effective range r0--are extracted in the JPC = l+- channel. Our results indicate that, in this particular channel, the interaction between the two vector charmed mesons is weakly repulsive in nature and hence it does not support the possibility of a shallow bound state for the two mesons, at least for the pion mass values being studied. However, these results might suffer from undetermined systematic errors due to low-lying states ignored in this exploratory study. Still, it provides some useful information on the nature of the newly discovered resonance-like structure Zc(4025) observed in various experiments. [ABSTRACT FROM AUTHOR]

We present an exploratory study for charmonium radiative transitions: J/ψ → ηcγ χc0 → J/ψγ, and hc → ηcγ using Nf = 2 twisted-mass lattice QCD gauge configurations. The single-quark vector form factors for ηc and χc0 are also determined. The simulation is performed at a lattice spacing of α = 0.067(2) fm and the lattice size is 32³ x 64 with a pion mass of about 485 MeV. Alter extrapolation of lattice data at nonzero Q² to 0, we compare our results with previous quenched lattice results and the available experimental values. [ABSTRACT FROM AUTHOR]

Two field-sparsening methods, namely the sparse-grid method and the random field selection method, are used in this paper for the construction of the 2-point and 3-point correlation functions in lattice QCD. We argue that, due to the high correlation among the lattice correlators at different field points associated with source, current, and sink locations, one can save a lot of computational time by performing the summation over a subset of the lattice sites. Furthermore, with this strategy, one only needs to store a small fraction of the full quark propagators. It is found that the number of field points can be reduced by a factor of ∼100 for the point-source operator and a factor of ∼1000 for the Gaussian-smeared operator, while the uncertainties of the correlators only increase by ∼15%. Therefore, with a modest cost of the computational resources, one can approach the precision of the all-to-all correlators using the field-sparsening methods. [ABSTRACT FROM AUTHOR]

We perform a first calculation for the unpolarized parton distribution function of the Δ+ baryon using lattice QCD simulations within the framework of large momentum effective theory. Two ensembles of Nf = 2 + 1 + 1 twisted mass fermions are utilized with a pion mass of 270 and 360 MeV, respectively. The baryon, which is treated as a stable single-particle state, is boosted with momentum P3 with values {0.42, 0.83, 1.25} GeV, and we utilize momentum smearing to improve the signal. The unpolarized parton distribution function of Δ+ is obtained using a nonperturbative renormalization and a one-loop formula for the matching, with encouraging precision. In particular, we compute the d̅(x) - u̅(x) asymmetry and compare it with the same quantity in the nucleon, in a first attempt towards resolving the physical mechanism responsible for generating such asymmetry. [ABSTRACT FROM AUTHOR]