Multiple structure graphite stabilized stearic acid as composite phase change materials for thermal energy storage

This paper used 3 types of graphite with different physical structures as the porous matrix to prepare composite phase change materials(PCMs),and investigated their photo-thermal conversion performance and application in battery thermal management.Multiple structure graphite minerals,including microcrystalline graphite(MG),scale graphite(SG),and expanded graphite(EG)were used as porous matrix,while stearic acid(SA)acts as the phase change material.The vacuum impregnation method was applied to prepare SA/MG,SA/SG,SA/EG,and SA/MG1,and SA/EG1was/were prepared by the ethyl alcohol method.Results show that the thermal conductivities of all composite phase change materials were 10.82 to 22.06 times higher than that of the pure SA.Thermogravimetric(TG)analysis showed that the loadages of SA were 43.61%,18.74%,and 92.66%for SA/MG,SA/SG,and SA/EG respectively.The load rates of SA were 18.98%and 18.88%for SA/MG1 and SA/EG1,respectively.For the 3 types of graphite materials of different dimensions,the BET(Brunauer,Emmett,and Teller)surface area determines the maximum load of SA.The Fourier-transform infrared(FTIR)and X-ray diffraction(XRD)results indicated that there was good compatibility between the SA and the supports.The SA/EG1 has better thermophysical properties in heat energy storage and release process.The thermal infrared images show that SA/EG1 has higher sensitivity to the temperature changes.SA/EG1 has better photo-heat conversion performance than SA/SG and SA/MG1 attributed to the multilayer structure of EG.SA/EG has better thermal management performance in the Li-ion batteries discharge process.

Cnoidal waves and their soliton limits in single mode fiber lasers

Cnoidal waves are a type of nonlinear periodic wave solutions of the nonlinear dynamic equations.They are well known in fluid dynamics,but it is not the case in optics.In this paper we show both experimentally and numerically that cnoidal waves could be formed in a fiber laser either in the net normal or net anomalous cavity dispersion regime,especially because,as the pump power is increased,the formed cnoidal waves could eventually evolve into a train of bright(in the net anomalous cavity dispersion regime)or dark(in the net normal cavity dispersion regime)solitons.Numerical simulations of the laser operation based on the extended nonlinear Schrödinger equation(NLSE)have well reproduced the experimental observations.The result not only explains why solitons can still be formed in a fiber laser even without mode locking but also suggests a new effective way of automatic stable periodic pulse train generation in lasers with a nonlinear cavity.

Novel optical soliton molecules formed in a fiber laser with near-zero net cavity dispersion

Soliton molecules(SMs)are stable bound states between solitons.SMs in fiber lasers are intensively investigated and embody analogies with matter molecules.Recent experimental studies on SMs formed by bright solitons,including soliton-pair,soliton-triplet or even soliton-quartet molecules,are intensive.However,study on soliton-binding states between bright and dark solitons is limited.In this work,the formation of such novel SMs in a fber laser with near-zero group velocity dispersion(ZGVD)is reported.Physically,these SMs are formed because of the incoherent cross-phase modulation of light and constitute a new form of SMs that are conceptually analog to the multi-atom molecules in chemistry.Our research results could assist the understanding of the dynamics of large SM complexes.These findings may also motivate potential applications in large-capacity transmission and all-optical information storage.

In-Fiber Thermally Diffused Coupler and Fiber Bragg Grating Inscribed in Twin-Core Fiber for Sensitivity-Enhanced Vector Bending Sensing

A vector bending fiber sensor based on core-by-core inscribed fiber Bragg gratings in a twin-core fiber has been proposed and experimentally demonstrated.An in-fiber integrated vector bending sensor is realized by using the thermal diffusion technique to fabricate the coupler.The characteristics of the coupler fabricated by thermal diffusion are simulated and experimented.By inscribing fiber Bragg gratings with different reflection wavelengths in the two cores of a symmetrical twin-core fiber,the curvature sensitivity can be enhanced by tracking the wavelength difference between the fiber Bragg gratings of the two cores.The measured bending sensitivity of the fiber Bragg grating ranges from–161.6 pm/m^(−1) to+165.5 pm/m^(−1).The differential sensitivity of the two cores is twice that of a conventional single grating,and the temperature-induced crosstalk is also reduced.The bending sensor proposed in this paper has the advantages of high integration,enhancing the sensitivity and two-dimensional orientation recognizability,and reducing temperature crosstalk,which can be a promising candidate for structural health monitoring or wearable artificial electronics applications.