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The study of fast response nematic liquid crystal display material mixture and synthesis about compounds has always been an important subject in recent years. In this article, one type of high bire...

Because of the special needs for nanosecond double pulse applications in micromachining and material processing, we demonstrated a stable nanosecond dual-pulse erbium-doped fiber laser based on nonlinear polarization rotation technology. The fiber laser operates in a normal dispersion regime with a length of 256 m OFS-980 fiber. With the pump power of 1120 mW, the laser generates a highly stable dual-pulse train with the pulse widths of 6.2 ns and 1.2 ns respectively. By simply changing the pump power, the pulse width of one of dual-pulse can be tuned from 2.1 to 6.2 ns while the other pulse keeping almost the same duration of 1.2 ns. The maximum dual-pulse energy is about 72.5 nJ with a repetition rate of 783.3 kHz. The formation of such nanosecond dual-pulse is attributed to the pulse splitting and depends on the parameters of the laser cavity, such as the cavity-length and the state of polarization controller. The experiment of a single square pulse splitting into different shapes of nanosecond dual-pulse was demonstrated.

Nowadays, with the increasing use of high-power laser, research and development of laser-damage prevention materials with multifunctional features and wideband wavelengths are urgent and indispensa...

In order to obtain liquid crystals with high birefringence (Δn), four azobenzene compounds based on lateral fluorinated bistolane moieties with trifluoromethyl terminal groups were synthesized with...

Wavelength switchable and dual-wavelength soliton operations are demonstrated in an erbium-doped fiber laser with three pieces of TI Bi2Se3 polyvinyl alcohol (Bi2Se3-PVA) film. Wavelength switchable operation from 1532 to 1557 nm could be achieved just by adjusting the pump power. With the appropriate settings of PC and pump power, a novel dual-wavelength soliton operation was observed. The dual-wavelength pulses operate at different mode-locked states. One is the single pulse mode-locking operation at 1532 nm, and the other one is the bound-soliton states at 1557 nm. However, the dual-wavelength soliton operation cannot be stable for a long time. The numerical results demonstrate that the separations of bound pulses have small variation and that the phase difference of bound pulses appear jumping change of π.

For the classical Shiryaev--Roberts martingale diffusion considered on the interval $[0,A]$, where $A>0$ is a given absorbing boundary, it is shown that the rate of convergence of the diffusion's quasi-stationary cumulative distribution function (cdf), $Q_{A}(x)$, to its stationary cdf, $H(x)$, as $A\to+\infty$, is no worse than $O(\log(A)/A)$, uniformly in $x\ge0$. The result is established explicitly, by constructing new tight lower- and upper-bounds for $Q_{A}(x)$ using certain latest monotonicity properties of the modified Bessel $K$ function involved in the exact closed-form formula for $Q_{A}(x)$ recently obtained by Polunchenko (2017)., 15 pages

An all-normal-dispersion WS2 mode-locked Yb-doped fiber laser was demonstrated. The saturable absorber (SA) is a piece of WS2-PVA film which is sandwiched between two fiber connectors. The modulation depth and saturation intensity of the WS2-PVA film were 1.78% and 81 MW/cm2 , respectively. When the WS2-PVA film was utilized in the laser cavity, stable mode locking occurred with the pump power of 140 mW. The maximum single pulse energy was estimated to be more than 2.82 nJ. Besides, in order to know more about the influence of the SA on the generation of ultrashort pulses, the dynamic evolution of mode-locked lasers with the parameters of SAs was studied by solving the Ginzburg-Landau equation. Thus the high pulse energy could be reached.

We consider the quasi-stationary distribution of the classical Shiryaev diffusion restricted to the interval $[0,A]$ with absorption at a fixed $A>0$. We derive analytically a closed-form formula for the distribution's fractional moment of an {\em arbitrary} given order $s\in\mathbb{R}$; the formula is consistent with that previously found by Polunchenko and Pepelyshev (2018) for the case of $s\in\mathbb{N}$. We also show by virtue of the formula that, if $s, Accepted for publication in Communications in Statistics - Simulation and Computation. arXiv admin note: text overlap with arXiv:1805.07580

To clarify the judicial practice of environmental pollution crime in the field of soil, this article will combine the research of environmental criminal law and soil field, and allow a method of empirical analysis for cases of environmental pollution crime in the soil field through categorical integration. Results showed that environmental pollution crime of soil field was mainly committed by the natural person; the term of fixed-term imprisonment and the amount of criminal fine were low; the defendant had a good attitude to plead guilty; the application of penal auxiliary measures was mainly focused on confiscatory auxiliary measures.

Novel porous sphere-like Mn3O4/β-Bi2O3 heterojunction photocatalysts were successfully synthesized by a heat treatment technique for photocatalytic degradation of organic pollutants (Rhodamine B (RhB), Bisphenol-A (BPA) and Methyl Blue (MB)) and oxidation removal of nitric oxide (NO). The XRD pattern results reveal that the β-Bi2O3 phase exists in all as-prepared samples. The UV–Vis spectra show that the optical adsorption ability of β-Bi2O3 has been greatly enhanced by loading with Mn3O4. The HRTEM results show that the Mn3O4/β-Bi2O3 heterostructures were successfully formed in the composite photocatalyst (S2 sample). The photocatalytic experiments reveal that 2 wt% Mn3O4/β-Bi2O3 heterojunction photocatalyst (S2) exhibited the most superior photocatalytic performance for NO removal and organic pollutants (RhB, MB and BPA) degradation. The experimental and DFT calculation results show that a type-II heterojunction can be formed at the interface between the Mn3O4 and β-Bi2O3 phases, which is very beneficial to promote the rapid separation of photogenerated carriers, thus producing excellent photocatalytic performances. This work provides insights into preparation of highly efficient visible light driven photocatalysts for pollutants removal.

A wide pitch gradient covering the near infrared region (750.0–2500.0 nm) were facilely obtained by simple controlling temperature difference to LC mixtures with a twist grain boundary (TGB)–N* phase transition. After the pitch gradient formed, the structure of broad reflective bandwidth was fixed through polymerisation of monomers in mixtures by UV irradiation. It was found that the temperature difference between the up and down side of the samples was critical to form wide-pitch gradient distribution. Additionally, the reflection wavelength and bandwidth of films could be adjusted by the applied temperature difference with the widest bandwidth up to 1750 nm. This simple method for the preparation of broad reflective films was expected to be used in the fields like architectural energy conservation or infrared shield.

BACKGROUND Limited information is concerned on the structure changes of liposomal delivery system under infant conditions. Positively charged lactoferrin (LF)-loaded liposomes, with the entrapment efficiency (EE) of 52.3 ± 6.3%, were prepared from soybean-derived phospholipids using a thin-layer dispersion method. The structure changes and digestibility of LF-loaded liposomes under infant conditions, including simulated gastric fluid (SGF) and simulated small intestinal fluid (SIF), were characterized in terms of the average particle size, zeta potential, turbidity, fourier transform infrared, transmission electron microscopy, lipolysis and protein hydrolysis. RESULTS This study showed that the functional groups, favorable membrane structure and the EE of liposomes were slightly changed as a function of time when the liposome digested under SGF conditions. However, the intact bilayer structures were damaged and the EE of LF-loaded liposomes decreased to 28.5% after digestion in infant SIF. CONCLUSION These results suggested that liposomal membrane could prevent the gastric degradation and the structure of liposomes was not completely destroyed with a low concentration of pancreatin and bile salts under infant conditions. Present study provided information on the insight into the characteristics of liposomes during infant gastrointestinal digestion, which was useful for the development of microcapsule systems in infant diet. © 2018 Society of Chemical Industry.

In the harsh application environment, improving the mechanical properties of liquid crystal materials is a fundamental and important problem in the design of anti-counterfeit materials. In this paper, by a stepwise polymerization of first, photo-polymerization and subsequently thermal-polymerization, a coexistent polymer dispersed network was first constructed in cholesteric liquid crystal materials containing a photo-polymerizable system of urethane acrylate and a thermo-polymerizable system of isocyanate. Results revealed that the coexistent polymer dispersed network exhibited largely enhanced mechanical performance, and the networks obtained by different methods had different contributions to the enhancement of the peel strength and toughness of the composite films. Then an angular photochromic anti-fake label based on a coexistent polymer dispersed network with enhanced mechanical and apparent angular discoloration characteristics, suitable for practical applications, was successfully achieved.

Halogen bonding interactions in the formation of liquid crystalline phases have been recognised in recent years. Here, we report a novel series of iodine-bonded liquid crystals using 1,2-diiodotetrafluorobenzene (1,2-DITFB) and azopyridine derivatives (AnAzPy), showing a smectic A phase and concurrent photoresponsive behaviour. These were characterised by using a polarising optical microscope, differential scanning calorimetry and UV-vis absorption spectroscopy. The formation of iodine bonding in the complexes was confirmed by X-ray photoelectron spectroscopy and Raman spectroscopy. Importantly, these iodine-bonded complexes demonstrated a low liquid crystal temperature range (30–50°C) among those reported for photoresponsive halogen-bonded liquid crystals. The molar ratio of the iodine-bonded donor and acceptor was 1:1 upon the self-assembly of the supramolecular complex molecule, as indicated by 1D-WAXD experiments of mixed samples of 1,2-DITFB and AnAzPy with different molar ratios. This study offers a new family of photoresponsive halogen-bonded liquid crystals and broadens the potential applications in their associated systems.

Novel mesogenic [60]fullerenes have been synthesized and doped into cholesteric liquid crystals (CLCs) to achieve a dual-mechanism laser protection system that is effective for both pulsed and broadband cw lasers, simultaneously. It was found that this system integrated a good OPL response, broadband protection range, and high practicability with great potentials in flexible and even wearable protection devices.

Precision machining has been claimed to be the backbone to modern industry. It has been widely applied to the key parts’ production in the aerospace, medical and automotive industries. One of the main problems related to precision machining productivity and safety is the machining condition. By utilizing the acquired information from sensory measurements to direct the further actions, the signal processing bridges the gap between human instruction and full automation. Traditional signal acquisition and processing methods are mainly based on Shannon’s Sampling theory, Fourier methods or wavelet analysis. While these techniques meet challenges in precision machining environment, such as machining at high speed, low signal to noise ratio, and high sampling rate. These factors limit their applications especially the online monitoring implementation. The newly developed compressive sensing theory and sparse decomposition techniques provide a possible solution to these problems, while limited studies have been investigated. This paper serves as an introduction to the theory and shows the theory’s potentials in machining condition monitoring by reviewing related literatures and demonstrating case studies from real experiments.

We experimentally demonstrate a kind of simplified Yb-doped mode-locked fiber laser with a nonlinear polarization rotation technique. In the oscillator, there are no waveplates, physical bandpass filters, or polarization controlling devices except for one polarized beam splitter and a polarization-independent isolator. In the experiment, self-started stable mode locking pulse trains are obtained with four different cavity lengths: 110 m, 66 m, 50 m, and 26 m. To make clear the mechanism of pulse formation of this kind of simplified fiber laser, the characteristics of which are called an artificial saturable absorber, are discussed and the influences of these parameters on mode locking are also analyzed.

Polymer-dispersed liquid crystal (PDLC) films were prepared by the ultraviolet-light-induced polymerization of photopolymerizable monomers in nematic liquid crystal/chiral dopant/thiol-acrylate reaction monomer composites. The effects of the chiral dopant and crosslinking agents on the electro-optical properties of the PDLC films were systematically investigate. While added the chiral dopant S811 into the PDLC films, the initial off-state transmittance of the films was decreased. It was found that the weight ratio among acrylate monomers, thiol monomer PETMP and the polymercaptan Capcure 3-800 showed great influence on the properties of the fabricated PDLC films because of the existence of competition between thiol-acrylate reaction and acrylate monomer polymerization reaction. While adding polymercaptans curing agent Capcure 3-800 with appropriate concentration into the PDLC system, lower driven voltage and higher contrast ratio were achieved. This made the polymer network and electro-optical properties of the PDLC films easily tunable by the introduction of the thiol monomers.

A method to prepare wide-band reflection cholesteric liquid crystals (CLCs) films by thermally induced diffusion of dye was proposed. Due to the greatly enhanced UV intensity gradient formed by thermal diffusion of dye, the pitch gradient was formed and fixed after the process of photoinduced polymerization and diffusion of CLC monomers. Using this method, the prepared CLCs film can reflect circularly polarized light over a broad wavelength range of 750–2400 nm. The pitch gradient of the CLC film was observed by scanning electron microscopy (SEM). In addition, the influence of dye concentration, thermal diffusion time and thermal diffusion temperature on the consequent pitch gradient was systemically studied.

A controllable and reversible broad-band reflector can be obtained by virtue of the response of one-dimensional (1-D) nanomaterials in chiral nematic liquid crystalline media to an external electric field. The colour switching originated from the electro-responsive 1-D nanomaterials and the responsive mechanism was discussed based on the relationship between the pitch distribution and the alignment of nanomaterials.

The high energy noise-like pulses (NLPs) were experimentally investigated in a passively mode-locked erbium-doped fiber laser with a long ring cavity by using nonlinear polarization rotation technique. Large net normal group-velocity dispersion of the cavity is estimated as high as 6.46 ps2, which is beneficial to formation of high-energy pulses. With the total pump power of 970 mW (the pump powers of forward pump and backward pump are set at the value of 455 mW and 515 mW, respectively), a stable ultrahigh energy rectangular-shape pulse emission with the pulse duration of 35 ns was observed. The energy of square packet with a fundamental repetition rate of 141.6 kHz is as high as 840 nJ. The signal-to-noise is higher than 60 dB in RF spectrum. The feature of NLPs is confirmed by the coherent spike of autocorrelation trace. When the pump power is beyond 970 mW, the mode locking operation with fundamental repetition rate cannot be achieved despite of the large range variation of polarization controller (PC) settings. However, the forthorder harmonic mode locking can be observed, the square pulse packet duration still remains at ∼ 35 ns. The experimental results demonstrated that the ultrahigh energy NLPs is only realized at the condition of special physical parameters and it is restricted by the number and intensity of ultra short pulses within the envelope to some extent.

Perylene diimide derivatives were used as probes to investigate the effect of the molecular structures on the fluorescence quenching mechanism in a perylene diimide/graphene oxide system. The electrons transferred from the excited state of dyes to the conductive band of graphene oxide with different concentrations were determined by fluorescence spectra. The results indicated that the quenching efficiency of perylene diimides by graphene oxide was not only dependent on the difference between the lowest unoccupied molecular orbital level of dyes and the conduction band of the graphene oxide, but also mainly on the difference in the molecular structures.

High-performance and cost-effective laser protection system is of crucial importance for the rapid advance of lasers in military and civilian fields leading to severe damages of human eyes and sensitive optical devices. However, it is crucially hindered by the angle-dependent protective effect and the complex preparation process. Here we demonstrate that angle-independence, good processibility, wavelength tunability, high optical density and good visibility can be effectuated simultaneously, by embedding dichroic anthraquinone dyes in a cholesteric liquid crystal matrix. More significantly, unconventional two-dimensional parabolic protection behavior is reported for the first time that in stark contrast to the existing protection systems, the overall parabolic protection behavior enables protective effect to increase with incident angles, hence providing omnibearing high-performance protection. The protective effect is controllable by dye concentration, LC cell thickness and CLC reflection efficiency, and the system can be made flexible enabling applications in flexible and even wearable protection devices. This research creates a promising avenue for the high-performance and cost-effective laser protection, and may foster the development of optical applications such as solar concentrators, car explosion-proof membrane, smart windows and polarizers.

This study indicated that the smectic-like short-range order (SSO) provided an opportunity to improve the planar orientation of chiral nematic liquid crystal (N*-LC) molecules while increasing the light transmittance of the N*-LC cells. The SSO formed between N*-smectic A (SmA) transition was first introduced into N*-LC compositions and then applied a specific thermal process at the temperature of SSO (TSSO). Finally, the uniform alignment of the N*-LC molecules was obtained. Decreasing the heating rate and extending the holding time at TSSO were effective at reducing the oily streak and perfecting the planar texture of the N*-LC cells. And this method was also resultful for N*-LC composites exhibited different pitches.

When a certain range of frequencies of AC electric fields are applied to a chiral nematic (N*) liquid crystal (LC) with negative dielectric anisotropy ((N*-LCN), usually prepared from a nematic LC with negative dielectric anisotropy (N-LCN) doped with a chiral dopant (CD), the long axes of the LC molecules will be oriented perpendicular to the electric field, which will be helpful to improve the orientation degree compared with the orientation induced by rubbing on the inner surfaces of the substrates sandwiching the LC. After a photopolymerisable N*-LC monomer/N-LCN/CD/an ultraviolet (UV) absorber/a photoinitiator mixture with an appropriate composition is irradiated with UV light, while an electric field with an appropriate frequency and intensity is being applied to it during the UV curing, not only the planar orientation of a high degree but also a pitch gradient of the helical structure of the LC molecules are formed in the resulted polymer network/N*-LCN composite.

A series of side-chain polysiloxane liquid crystalline elastomers, E-Cm (where m is the number of carbon atoms in the interim alkyl groups, and m = 4, 6, 8, 10), with binaphthalene derivatives as crosslinkings, were designed and synthesized. The mesophase structures of these elastomers were dependent on the value of m. The elastomers with m ≤ 8 could form cholesteric (Ch) phases, while both smectic A and Ch phases could be formed for the elastomer with m = 10. Blue phases can be achieved when m ≥ 8. Besides, the helical twisting power (HTP) of all the elastomers exhibits a turning point with changing temperature. Both the turning temperature and HTP have an apparent dependence on the value of m. By adjusting the interim alkyl chain length in the elastomers, both visible and near-infrared light wide-band reflective films can be obtained. The broadband reflection mechanism was confirmed by SEM investigations.

A series of novel side-chain cholesteric liquid-crystalline elastomers based on polysiloxane and cholesterol derivate monomer were prepared by adopting a crosslinking agent containing binaphthalene group. The chemical structures and mesomorphic properties of the monomers and elastomers were confirmed by FT-IR, 1 H NMR, DSC and POM measurements. Worthily, the elastomers exhibited unusual temperature dependence of the helical twisting power (HTP) which is demonstrated resulting from coordination of the crosslinking agent and the mesogenic units. With increase in temperature, the HTP of elastomers containing small quantity of the crosslinking unit exhibited a turning point, while that of elastomers comprising much more crosslinking unit shifted straight. Furthermore, a single layer wide-band reflective film with non-uniform pitch distribution was prepared by utilizing the HTP variety of elastomers with change in temperature. From scanning electron microscopy (SEM) investigations, the mechanism of the broadband reflection was verified.

Three series of cholesteryl esters with different linkages and terminal groups have been synthesised and characterised. All the esters except cholesteryl 6-bromohexanoate can exhibit thermotropic liquid crystalline phases in certain temperature regions. The insertion of a 4-phenoxyl and a 4-biphenylyloxy group in the ester can increase the molecular length, broaden the whole mesophase width and heighten the clearing temperature. The increasing molecular length can enforce the layered arrangement in series A and B (resulting in a monolayer smectic A phase), while destroying the layer stacking in series C (resulting in a suppressed or absent interdigitated smectic A phase). Meanwhile, the molecular structure played an important role in the molar helical twisting power and its temperature dependence.

In order to reveal the nature of the formation of a broadband reflection property for polymer stabilised cholesteric liquid crystal, the spatially periodic helix structure of epoxy cholesteric liquid crystal is ‘frozen’ by cationic polymerisation following the formation of a polymer network induced by ultraviolet radical polymerisation of acrylate monomer. The fracture of the helix structure is observed by scanning electron microscopy, which reveals the presence of pitch gradient. Since the liquid crystal monomers have a UV absorption characteristic, a polymer network concentration gradient is formed after ultraviolet radical polymerisation. Using an attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrum, the concentration gradient of the polymer network and that of the chiral dopant, with the opposite trends, are confirmed. The existence of both gradients, resulting in the formation of the pitch gradient, are considered as the natural mechanism for the formation of the broadband refle...

A new liquid crystal, cholesteryl (S)-4′-(2-methylbutyl)biphenyl-4-carboxylate (CB15-COOChol*), has been designed, synthesised and characterised. CB15-COOChol* exhibits multiple liquid crystalline phases: smectic A (SmA), nematic (N) and chiral nematic (N*). When CB15-COOChol* is heated, two N* phases exhibiting opposite handedness (NR* and NL*) and opposite temperature dependence of the helical pitch separated by an N phase are observed above the SmA phase. The entire rare phase transition sequence can be described as crystalline Cr→SmA→NR*→N→NL*→I isotropic. The helix inversion behaviour occurs mainly due to the temperature-dependent intramolecular chiral conflict between the (S)-4′-2-methylbutyl and cholesteryl ester moieties with opposite handedness and opposite temperature dependence of the helical twisting power value.

In this study, we demonstrate a new method for obtaining a binary chiral mixture (BCM) which exhibits an unprecedented temperature-dependent helical twisting power (HTP) by utilising the chiral conflict between two chiral dopants with opposite handedness and HTP temperature dependence. Different from the common chiral dopant reported before, the addition of such a BCM could increase the clearing temperature of the host liquid crystal (LC). Due to the sufficiently large HTP value of the BCM, the three primary colours (blue, green and red) can be easily reflected by the nematic liquid crystal (N-LC)/BCM mixture at different temperatures. Moreover, the large HTP temperature dependence could be maintained and even enhanced in the longer wavelength region by adjusting the content of the BCM. Finally, based on the large HTP temperature dependence and the positive affect on the host LC of the BCM, a thermally bandwidth-controllable reflective polariser that could work in the visible region (400–750 nm) was prepa...

Carbon nanotubes in heavy water (deuteroxide, D2O) dispersion was fabricated and used as a saturable absorber for mode locking in a fiber laser. Such liquid absorber has the virtues of good optical transparency, high heat dissipation, and high damage threshold. A passively mode locked fiber laser with it was demonstrated. The pulsewidth is 306 fs with the maximum average output power of 20 mW. The center of the wavelength is 1560 nm with 15.2-nm spectral width.

In this study, we demonstrate a novel method for fabricating a single layer cholesteric liquid crystal (CLC) film with non-uniform pitch distribution by utilizing the chiral polynetworks. A chiral monomer, the helical twist power (HTP) of which decreases with the increase of temperature, was synthesized. The temperature dependence of the pitch of the mixtures before and after polymerization was investigated. To broaden the reflection band, the experimental processes of thermally induced pitch variation were presented. The results suggest that the chirality of the polymer network plays an integral role in the reflection spectra. Additionally, scanning electron microscopy (SEM) was used to examine the role of the polymer network induced by polymerization temperature. These wide-band reflection optical properties make the CLC gels interesting for their potential applications in many fields, such as colour filters, brightness enhancement films, smart switchable reflective windows etc.

The three-point bending experiment of sandstone from a coal mine roof under different loading rates based on acoustic emission was carried out. Through analyzing the AE phenomenon, found that the sandstone fracture is brittle fracture. The number of AE counts under low loading speed is more than it under high loading speed, indicated that internal crack is more fully occurred and expanded at low loading speed. The AE energy presents as solitary earthquake type. The flexural strength of sandstone is not high, the failure load and flexural strength increase with the increasing of loading speed, and then decline gradually after reaching the extreme value.

We demonstrated the noise-like pulse (NLP) generation in an ytterbium-doped fiber (YDF) laser with tungsten disulphide (WS2). Stable fundamental mode locking and second-order harmonic mode locking were observed. The saturable absorber (SA) was a WS2-polyvinyl alcohol film. The modulation depth of the WS2 film was 2.4%, and the saturable optical intensity was 155 MW cm−2. Based on this SA, the fundamental NLP with a pulse width of 20 ns and repetition rate of 7 MHz were observed. The autocorrelation trace of output pulses had a coherent spike, which came from NLP. The average pulse width of the spike was 550 fs on the top of a broad pedestal. The second-order harmonic NLP had a spectral bandwidth of 1.3 nm and pulse width of 10 ns. With the pump power of 400 mW, the maximum output power was 22.2 mW. To the best of our knowledge, this is the first time a noise-like mode locking in an YDF laser based on WS2-SA in an all normal dispersion regime was obtained.

An unsticking technique was applied for the fabrication of a polymer-stabilised cholesteric liquid crystal (PSCLC) cell. The template of polymer matrix in the planarly aligned cholesteric liquid crystal (Ch-LC) was perfectly preserved by lifting off the hydrophilic antisticking substrate. The desired PSCLC cell could then be obtained by injecting a third Ch-LC sample between two designed templates of PSCLC layer. By adjusting the pitch distribution in the two stacking templates, a reflectivity of nearly 50% incident light could be yielded and the bandwidth of the reflection spectrum could be controlled accurately in the PSCLC cell. Thus, a method to modulate the wide-band reflection of 50% visible light flux range was offered.

The preparation is reported of particles of photopolymerisable monomer/chiral dopant composites with a crystalline (Cr)‐chiral nematic (N*) phase transition. By mixing particles with different pitches of the N* phase in the Cr phase and crosslinking the liquid crystal (LC) monomer molecules by photopolymerisation in the planarly oriented N* phase, an N*‐LC composite film with a non‐uniform pitch distribution was obtained. Experimental results show that the bandwidth of the reflection spectrum and the location of reflection band of the composite films can be controlled accurately by controlling the pitch lengths of the N* phase of the particles. Effects of polymerisation temperature and UV intensity on the non‐uniform pitch distribution of N*‐LC composite films were investigated.

In this paper, we describe the synthesis of cholesteryl compounds of different functionality. A series of polymer‐stabilised cholesteric liquid crystal (PSCLC) cells are prepared by photo‐polymerisation of a cholesteric liquid crystal (Ch‐LC) mixture containing a non‐reactive liquid crystal, a nematic diacrylate and the above cholesteryl compounds. The effect of cholesteryl compound functionality on the morphology and the reflectance properties of PSCLC cells is evaluated, as are parameters such as the polymerisation temperature. The results indicate that the higher functional cholesteryl compound is more effective for broadening the reflection band of the Ch‐LC composites, which is speculated to be a result of the pitch differences in the local network environment. Scanning electron microscopy is used to examine the morphologies of the polymer network of the PSCLC cells. We have found that the morphologies of the polymer network are determined by the functionality of the cholesteryl compounds as well as ...

Mask exchange system is an important part of the Multi-Object Broadband Imaging Echellette (MOBIE) on the Thirty Meter Telescope (TMT). To solve the problem of stiffness changing with the gravity vector of the mask exchange system in the MOBIE, the hybrid parallel mechanism design method was introduced into the whole research. By using the characteristics of high stiffness and precision of parallel structure, combined with large moving range of serial structure, a conceptual design of a hybrid parallel mask exchange system based on 3-RPS parallel mechanism was presented. According to the position requirements of the MOBIE, the SolidWorks structure model of the hybrid parallel mask exchange robot was established and the appropriate installation position without interfering with the related components and light path in the MOBIE of TMT was analyzed. Simulation results in SolidWorks suggested that 3-RPS parallel platform had good stiffness property in different gravity vector directions. Furthermore, through the research of the mechanism theory, the inverse kinematics solution of the 3-RPS parallel platform was calculated and the mathematical relationship between the attitude angle of moving platform and the angle of ball-hinges on the moving platform was established, in order to analyze the attitude adjustment ability of the hybrid parallel mask exchange robot. The proposed conceptual design has some guiding significance for the design of mask exchange system of the MOBIE on TMT.

A 359fs erbium-doped fiber laser using topological insulator Bi 2 Se 3 /Polyvinyl alcohol (PVA) composite film as a saturable absorber was demonstrated. When changing the length of the erbium-doped fiber, a mode-locking pulse ranging from 1557nm to 1600nm could be generated.

This article proposes a new design of a 3D unfolded/tightened mechanism based on the spine structure of golden tree snake, which can realize torsion and bending. Inspired by golden tree snake vertebrae space deformation characteristics, analyzing the anatomy characteristics of the golden tree snake spine bone and muscle distribution characteristics, The bionic mechanism and drive unit can drive the 3D unfolded/tightened mechanism and meet the demand of unfolded/tightened mechanism pose and adjustment, compared with the traditional unfolded/tightened mechanism. In this paper, dynamics model of this robot established by Lagrange method is represented.