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The design flexibility of photonic crystal fiber (PCF) is convenient for sensor design. In this paper, we propose a high sensitivity surface plasmon resonance (SPR) sensor based on indium tin oxide (ITO)-coated PCF with simple structure. A structure consisting of four square air holes is used for the sensing of bio-analytes.To supports the SPR, we use a novel conductor material for ITO and a continuous metal film to help improve the sensing performance. According to numerical results, the maximum wavelength sensitivity of the sensor can reach 28500 nm/RIU. It has high wavelength resolution of 3.5×10− 6 RIU and the refractive index detection range of the sensor is 1.33–1.40. Besides, the sensor has a highly linear sensing performance. Considering the simple structure and competitive sensing performance,the sensor can detect the refractive index of liquid in a wide range and accurately detect the refractive index of liquid in a small range such as plasma, hemoglobin,etc.

A tunable and switchable multi-wavelength random distributed feedback fiber laser based on cascaded Sagnac loops is proposed and experimentally demonstrated. The random distribution feedback of the laser is provided by the Rayleigh scattering generated by the single-mode fiber (SMF). The cascaded Sagnac loops act as a filter and a reflector in the half-open cavity laser. The single-, dual-, three-, and four-wavelength channels can be realized by adjusting the angle of the polarization controller at the pump power of 300 mW. In the single-, dual-, and three-wavelength channels, the wavelength spacing can be maintained, and the laser wavelength position can be changed at the same time. The maximum wavelength tuning ranges of single-, dual-, and three-wavelength outputs are about 4.5 nm, 2.6 nm, and 1 nm, respectively. The proposed multi-wavelength random fiber laser has the advantages of simple structure and low threshold, and it has good application prospects in remote sensing and imaging systems.

A multi-wavelength switchable random fibre laser based on a double Sagnac-loop filter is proposed. The threshold of laser is 27 mW and the slope efficiency of the total power output to pump power i...

Purpose An accurate and fast dynamic analysis innovative approach for vehicle parts is provided for engineering practice. Design/methodology/approach This paper presents an innovative dynamic analysis approach for vehicle parts based on parallel optimization algorithm with CUDA. Findings This project is supported by the National Science Foundation of China (No. 51805076, No. U1708255 and No. 51775093), the Fundamental Research Funds for the Central Universities (No. N170503011) and the Natural Science Foundation of Liaoning Province, China (No. 20180551058). Originality/value This paper presents an innovative approach for vehicle parts using parallel optimization algorithm based on CUDA, which can improve the computing accuracy and speed effectively.

Transparent synaptic devices remain great prospects for a future comprehensive simulation of artificial synapses with the combination of photoelectric coupling characteristics in the neuromorphic system. In this article, one type of memristors based on a stack structure of ITO/TiO y /TiO x /TiN with high transmittance ( ${T}>81$ %) is fabricated, in which an oxygen-deficient TiO y layer between TiO x and ITO top electrode is introduced to adjust the gradual current characteristics during the SET/RESET process. Furthermore, the devices with different thickness ratios (1:4, 1:2, 1:1, 2:1) of oxygen-deficient TiO y active layers are designed to realize the adjustability of the multilevel resistance state and the analog resistive switching (RS) behavior and improve electrical performances and synaptic simulation characteristics. Meantime, the device based on optimum thickness ratio (1:2) offers excellent uniformity for 1000 cycles and better nonlinearity (0.69) at a low programming power consumption, which reveals further simulation of essential synaptic functions, including paired-pulse facilitation (PPF), and spike-timing-dependent plasticity (STDP) as well as learning–relearning characteristics. In addition, oxygen concentration gradient could be regulated by controlling the thickness ratio to drive oxygen vacancy redistribution at the interfacial layer, which are also demonstrated by high-resolution transmission electron microscopy (HRTEM) and improve electronic properties and analog modulation characteristics.

This paper investigated the modeling and free vibration characteristics of a spinning graphene nanoplatelet (GPL) reinforced porous nanocomposite blade. The blade is made of porous foam metal matrix reinforced with graphene nanoplatelets (GPLs). Several different GPL distributions and porosity distributions in the blade are taken into account. The effective material properties of the blade, determined via the open-cell scheme, the Halpin-Tsai model, and the rule of mixture, are assumed to be varying continuously along the its thickness direction. According to the Kirchhoff’s plate theory, the governing equations of the spinning blade are derived by adopting the Hamilton principle. On the other hand, the non-uniform spinning blade is modeled by the finite element method which is compared with the theoretical method. The theoretical results match very well with the finite element ones obtained from ANSYS. Particular focus is given to the effects of the spinning speed, porosity coefficient, distribution pattern of GPLs and porosities, GPL weight fraction, length-to-thickness ratio and length-to-width ratio of GPLs, blade length, and spinning radius on the free vibration performance of the blade rotor.

Targeted at the poor heat transfer effect of the phase change thermal storage heat exchanger due to the low thermal conductivity of the phase change material, a fin-tube type phase change thermal storage heat exchanger has been proposed in the study. A 2-D model of the phase-change heat storage unit was established, and the dynamic heat transfer law of the melting and solidification of the phase change material, and the influence of the fin structure size on the heat storage/release performance of the heat exchanger were numerically analyzed. The results show that in the area close to the tube wall, the smaller the fin spacing, the larger the thickness, the faster the phase change heat storage/release speed, and the better heat transfer effect. In the central area of the phase change material, the greater the fin spacing and thickness, and the better the heat transfer effect of the phase change heat storage/release. The area close to the outer wall has the smallest temperature change, and the heat storage/release effect is the worst. Therefore, the use of energy storage heat exchangers with gradual fin thickness and spacing is an effective method to improve the heat transfer efficiency of existing equipment. In addition, in order to improve the heat exchange effect of the edge area of the phase change, its structure could be changed or the heat exchange form can be increased.

We propose a surface plasmon resonance (SPR) refractive index (RI) sensor based on a novel D-shaped photonic crystal fiber. We used an open air hole coated with gold film to improve SPR effect. The effects of structural parameters on resonance spectrum were analyzed by finite element method (FEM). Three SPR peaks were obtained in the wavelength range of 800nm-1300nm. The simulation results show that the refractive index detection range of the sensor is 1.26-1.38. The maximum sensitivity is 5626.86 nm/RIU and the maximum resolution is 1.78×10-5 RIU at the refractive index of 1.38. The sensor uses photonic crystal fiber with the same air holes diameter. Compared with other D-shaped structures, our sensor can measure larger RI ranges of the analyte.

Plates are commonly used in many engineering disciplines, including aerospace. With the continuous improvement in the capacity of high value-added airplanes, large transport aircrafts, and fighter planes that have high strength, high toughness, and corrosion resistance have gradually become the development direction of airplane plate structure production and research. The strength and stability of metal plate structures can be improved by adding reinforced materials. This paper studies graphene platelets (GPLs) reinforced with a free vibration porous composite plate. The porous plate is constructed with a multi-layer model in a metal matrix containing uniform or non-uniformly distributed open-cell internal pores. Considering the random and directional arrangement of graphene platelets in the matrix, the elastic modulus of graphene composites was estimated using the Halpin–Tsai micromechanical model, and the vibration frequencies of graphene composite were calculated using the differential quadrature method. The effects of the total number of layers, GPL distribution pattern, porosity coefficient, GPL weight fraction, and boundary conditions on the free vibration frequency of GPLs reinforced porous composite plates are studied, and the accuracy of the conclusions are verified by the finite element software.

The rotor critical speed of turbine generator unit when the amplitude of the rotor increases sharply, bring to unit certain harm, rotor critical speed calculation method often results with the actual error is bigger. Through Bode diagram method and frequency spectrum analysis method, the rotor critical speed measurement was carried out. Through the experimental results it was concluded that two methods the test results are basically identical, and bode diagram was determined the selection method of measuring rotor critical speed more accurate. By changing the rotor on the quality of the wheel and position change, the use of Bode diagram method for rotor critical speed measurement. It was concluded that with the increase of the quality of the rotor critical speed decreased, the impact is not big in the center of the deviation from the rotor position far; The same quality case, the farther wheel deviating from the center of rotor, the rotor critical speed increases faster. The test results can guide the engineering practice, for the calculation of the rotor critical speed, the simulation and experiment have certain reference function.

With the rapid development of modern information, resistance random access memory (RRAM) has been a continuous research hotspot because of its large storage capacity, high reading speed, and excellent low-power performance. In this paper, in order to improve switching ratio of single-layer TiOx structure and uniformity of device, the double-layer TaOx/TiOx-based RRAM was fabricated and characterized by a semiconductor device analyzer (Agilent B1500A). The results showed that the uniformity was improved, and the window was enlarged from 33 to 100 by adding the TaOx layer in ITO/TiOx/TiN structure. And the devices with double-layer TaOx/TiOx had lower operating voltage and more consistent SET/RESET voltage distribution compared with the single-layer TiOx structure. In addition, the position of TaOx insertion layer was further discussed and it was found that the insertion layer could effectively increase the oxygen vacancy concentration in the resistive layer. A possible switching mechanism of TaOx/TiOx-based RRAM was inferred. It was believed that TaOx/TiOx double-layer structure can reduce the randomness of the filament's formation/fracture position to some extent, thereby making the uniformity better.

Based on the gas turbine blade disc system, the finite element model of the blade disc is established and the modal analysis is carried out. The vibration characteristics of the system under the working load are studied, and the fatigue life of the blade disc system is calculated. Combined with the analysis results to evaluate the blade disc life. The results show that the blade vibration is dominated by blade vibration, and excessive blade vibration causes damage. The magnitude of the amplitude is related to the position of the disc and the blade node. The life of the disc is inversely proportional to the load and is proportional to the surface roughness.

In this paper, pulse regulation by the combination of actively Q-switched and passively Q-switched mechanisms in a random erbium-doped fiber laser is demonstrated. Pulse shape is regulated from square wave to quasi passively Q-switched pulse by changing pump power and loss in laser cavity. Pulse shape similar to external modulation signal on electro-optic modulator (EOM) is achieved when the pump power is low. When the pump power is increased and an additional attenuation is inserted, a regular and stable output pulse is generated by the combination of EOM and stimulated Brillouin scattering (SBS) in fiber. The frequency irregular and intensity fluctuation of pulse shown in passively Q-switched random fiber lasers reported previously are greatly eliminated. Not only pulse amplitude and pulse width are controlled by pump power and additional attenuation in the cavity, but also the repetition rate of output pulse is controlled by the external modulation signal on EOM, which has great potential applications in high-resolution imaging, and next-generation laser medical treatment.

We proposed a passively Q-switched fiber laser with switchable wavelength based on two parallel fiber Bragg gratings. By increasing the input power, a single wavelength with a center wavelength of 1545.63 nm and dual wavelengths with a center wavelength of 1545.63 nm and 1553.60 nm can be obtained respectively. The wavelength spacing of the dual wavelengths is 8.17 nm, and the maximum repetition frequency of Q-switching is 24.27 kHz, and the narrowest pulse width is 5.48 ms. The combination of parallel fiber grating and erbium-ytterbium co-doped fiber (EYDF) saturable absorber provides a simple and feasible method to obtain stable (single and double wavelength switching) passively Q-switched pulses.

This paper presents a test method to measure vibration characteristics of mistuned bladed disk system. Modal analysis for the disk is to verify the precision of test bench. Further mistuned parameter identification method is proposed to introduce stiffness detuning. From this the samples can be obtained. On the other hand, the joint optimization analysis system is applied which consists of iterative response surface method and particle swarm optimization algorithm. At the same time, it is proved to have higher accuracy and better generalization ability than standard polynomial response surface method for the problem in this paper. The research results indicate that the amplitudes of optimal solution are smaller than that with random arrangement. The vibration response can be improved obviously, especially for resonance region. So, this paper has a certain universality and application value for blade arrangement based on iterative response surface joint algorithm.

A Mach-Zehnder interferometer (MZI) fiber sensing and positioning system based on common optical path technology that combines the advantages of the positioning method of the conventional MZI and the common optical path technology is proposed to improve the performance of the system in this paper. The feasibility of the interferometer has been proved by simulation and experiment. In the conventional MZI, the temperature and environment have an effect on the system performance due to the interference light transmitted through different optical fibers. The system proposed in this paper overcomes the disadvantages of the conventional MZI.

In this paper, a multi-wavelength fiber laser based on electro-optical Q-switching is proposed to achieve stable dual-pulse output. The addition of a tunable filter outside the cavity to filter out different wavelengths separately proves that the dual-pulse is generated due to the time delay between different wavelengths. When the input power is 160 mW, we observed single pulses with pulse widths of 28.94 μs and 23.25 μs were obtained at 1544.11 nm and 1546.77 nm, respectively. We changed the average output power and pulse width by changing the input power or frequency of the external modulated signal, and simultaneously discussed the effect of the modulation amplitude of the electro-optical modulator (EOM) on the output of dual-pulse.

In order to study the rubbing of the mistuned bladed disk system with variable thickness blades, an elastically supported shaft-variable thickness blades coupled finite element model is established in this paper. A new rubbing force model is proposed considering the variable thickness section characteristics and rotation effect of the variable thickness blade. A method of mistuned parameter identification is introduced which consists of static frequency testing of blades, dichotomy, and finite element analysis. Based on the finite element method, the mistuned bladed disk system is made dynamic analysis in full rubbing by applying the judgment load method. The dynamic response of the mistuned bladed disk system is discussed under different conditions. The results show that increasing the amount of mistuning will increase the system vibration. At high speeds, the impact force will be partially offset by centrifugal force. And the rubbing gap affects the form of rubbing. With the gap decreases, the system will change from intermittent rubbing to continuous rubbing. In addition, when the system is rubbed, due to energy dissipation and blade damping, the stress is transferred from the blade tip to the blade root and attenuated. In general, rubbing is a random complex nonlinear vibration process.

In this paper, we present a simple compact and low threshold laser that has characteristics of Q-switched and multi-wavelength oscillation simultaneously. Multi-wavelength Q-switched oscillation is realized by inserting a Sagnac filter as a multi-wavelength filter and a section of unpumped erbium-ytterbium co-doped fiber (EYDF) into the laser cavity as a saturable absorber (SA). The characteristics of multi-wavelength Q-switched fiber laser affected by wavelength separation of filter and pump power are investigated. The number of Q-switched wavelengths increases and the wavelength separation of the laser reduces with wavelength separation of the filter decreasing. Stable multi-wavelength oscillations at wavelength separation of 0.4–0.8 nm were obtained by increasing the length of polarization maintaining fiber (PMF) in the Sagnac filter. Moreover, the number of wavelengths and wavelength separation are increased by increasing the pump power when the filter is fixed. Further, the multi-wavelength laser is verified to have Q-switched properties at each wavelength, which is filtered from laser output through a narrow-band tunable filter outside of the cavity.