A new process chain for ultra-precision machining potassium dihydrogen phosphate (KDP) crystal parts

Potassium dihydrogen phosphate (KDP) crystal parts used in high power laser systems require high figure accuracy and high laser induced damage threshold (LIDT). However KDP crystal is extremely soft, hygroscopic, brittle and thermally sensitive, which make it difficult to meet the requirements via conventional processing methods. This paper puts forward a new process chain for ultra-precision machining KDP crystals, including single point diamond turning (SPDT), magnetorheological finishing (MRF) polishing and ion beam figuring (IBF) polishing processes. A compensation SPDT process is developed as the first step of the process chain to reduce machining errors (due to vacuum suction force, spindle unbalance, etc.). As a result high shape accuracy and fine surface roughness is obtained with high machining efficiency Non-aqueous and abrasive-free MRF polishing process is then employed to remove the diamond turning marks and further improve shape accuracy and increase the LIDT. Ion beam figuring (IBF) polishing is introduced as the final step of the process chain to remove the impurity layer. Experiments are carried out to evaluate the effectiveness of the proposed ultra-precision process chain

Existence and stability of mild solutions to parabolic stochastic partial differential equations driven by Lévy space-time noise

This paper is concerned with well-posedness and stability of parabolic stochastic partial differential equations. Firstly, we obtain some sufficient conditions ensuring the existence and uniqueness of mild solutions, and some $\mathcal{H}$-stability criteria for a class of parabolic stochastic partial differential equations driven by Lévy space-time noise under the local/non-Lipschitz condition. Secondly, we establish some existence-uniqueness theorems and present sufficient conditions ensuring the $\mathcal{H}'$-stability of mild solutions for a class of parabolic stochastic partial functional differential equations driven by Lévy space-time noise under the local/non-Lipschitz condition. These theoretical results generalize and improve some existing results. Finally, two examples are given to illustrate the effectiveness of our main results

Existence of positive ground state solutions for Kirchhoff type equation with general critical growth

We study the existence of positive ground state solutions for the nonlinear Kirchhoff type equation \begin{cases} \displaystyle -\bigg(a+b\int_{\mathbb R^3}|\nabla u|^2\bigg)\Delta {u}+V(x)u =f(u) & \mbox{in }\mathbb R^3, \\ \noalign{\medskip} u\in H^1(\mathbb R^3), \quad u> 0 & \mbox{in } \mathbb R^3, \end{cases} % where a,b> 0 are constants, $f\in C(\mathbb R,\mathbb R)$ has general critical growth. We generalize a Berestycki-Lions theorem about the critical case of Schrödinger equation to Kirchhoff type equation via variational methods. Moreover, some subcritical works on Kirchhoff type equation are extended to the current critical case

Turbulence-resistant self-focusing vortex beams

We consider recently introduced self-focusing fields that carry orbital angular momentum (OAM) [Opt. Lett. $\textbf{46}$, 2384$-$2387 (2021)] and in particular, their propagation properties through a turbulent ocean. We show that this type of field is especially robust against turbulence induced degradation, when compared to a completely coherent beam. In moderately strong oceanic turbulence, the self-focusing OAM beam features over five orders of magnitude higher peak intensities at the receiver plane, an $\sim$80 $\%$ detection probability for the signal mode, as well as an energy transmission efficiency in excess of 70 $\%$ over a link of $\sim$100 m. Counter-intuitively, the focusing properties of such fields may be enhanced with increasing turbulence, causing the mean squared waist to become smaller with greater turbulence strength. Our results demonstrate that certain types of partial coherence may be highly desirable for optical telecommunication employing OAM

Triangular Ag–Pd alloy nanoprisms : rational synthesis with high-efficiency for electrocatalytic oxygen reduction

We report the generation of triangular Ag–Pd alloy nanoprisms through a rationally designed synthetic strategy based on silver nanoprisms as sacrificial templates. The galvanic replacement between Ag nanoprisms and H2PdCl4 along with co-reduction of Ag+/Pd2+ is responsible for the formation of final prismatic Ag–Pd alloy nanostructures. Significantly, these Ag–Pd alloy nanoprisms exhibited superior electrocatalytic activity for the oxygen reduction reaction (ORR) as compared with the commercial Pd/C catalyst. Such a high catalytic activity is attributed to not only the alloyed Ag–Pd composition but also the dominant {111} facets of the triangular Ag–Pd nanoprisms. This work demonstrates the rational design of bimetallic alloy nanostructures with control of selective crystal facets that are critical to achieve high catalytic activity for fuel cell systems.Accepted versio

Liquid-phase epitaxial growth of two-dimensional semiconductor hetero-nanostructures

Although many two-dimensional (2D) hybrid nanostructures are being prepared, the engineering of epitaxial 2D semiconductor hetero-nanostructures in the liquid phase still remains a challenge. The preparation of 2D semiconductor hetero-nanostructures by epitaxial growth of metal sulfide nanocrystals, including CuS, ZnS and Ni3S2, is achieved on ultrathin TiS2 nanosheets by a simple electrochemical approach by using the TiS2 crystal and metal foils. Ultrathin CuS nanoplates 50–120 nm in size and with a triangular/hexagonal shape are epitaxially grown on TiS2 nanosheets with perfect epitaxial alignment. ZnS and Ni3S2 nanoplates can be also epitaxially grown on TiS2 nanosheets. As a proof-of-concept application, the obtained 2D CuS–TiS2 composite is used as the anode in a lithium ion battery, which exhibits a high capacity and excellent cycling stability

Preparation of Cobalt Sulfide Nanoparticle-Decorated Nitrogen and Sulfur Co-Doped Reduced Graphene Oxide Aerogel Used as a Highly Efficient Electrocatalyst for Oxygen Reduction Reaction

A novel 3D cobalt sulfide (CoS) nanoparticle-decorated nitrogen and sulfur co-doped reduced graphene oxide aerogel (NSGA), referred to as CoS/NSGA, is prepared via three sequential processes, i.e., freeze-drying, annealing, and sulfidization. The obtained CoS/NSGA exhibits excellent electrocatalytic performance in the alkaline solution.ASTAR (Agency for Sci., Tech. and Research, S’pore)MOE (Min. of Education, S’pore

Black phosphorus quantum dots

10.1002/anie.201409400Angewandte Chemie - International Edition54123653-365