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We proposed a silver-coated 45 radiated tilted fiber grating (45 RTFG) based interferometer, in which the 45 RTFG is working as a beam splitter and a coupler, and the light transmitting in the fiber core is radiated out and resonant in the cladding radial cavity formed by the fully coated silver film, which forms multiple beam interference. We have theoretically and experimentally investigated the proposed fiber interferometer in terms of polarization-dependent transmission spectra, the free spectral range (FSR), spectral visibility and sensing characteristics. Due to the single polarization radiation feature of 45 RTFG, only S-polarized light could form the multiple beam interference and P-polarized light would pass through the grating with low loss. And the FSR of the proposed fiber interferometer is around 6.8 nm, which is determined by the 125 m cladding diameter. The theoretical results show that the spectral visibility of interference is proportional to the coupling efficient of 45 RTFG and when the coupling efficient reaches 0.92, the spectral visibility is the maximum. In the experiment, the fiber interferometer formed by the 45 RTFG with 11 dB polarization extinction ratio has the spectral visibility of 26 dB. Moreover, we have also investigated the temperature, strain and twist characteristics of the proposed interferometer. The experimental results show that the transmission peak has a red shift with increasing temperature, with a sensitivity of 10 0.1 pm/C; The strain causes a blue shift for the transmission peak with -0.42 0.01 pm/ sensitivity, and the twist sensitivity reaches 22.408 0.2 dB/rad. The proposed silver-coated 45 RTFG based interferometer has an in-fiber and compact structure, which can be potentially used for optical fiber sensing.

In this Letter, we have proposed an in-fiber duplex optical antenna based on a 45° radiated titled fiber grating (RTFG), in which the 45° RTFG not only radiates the light from the fiber core to the free space, but also harvests the light from the free space back into the fiber core. Using the finite difference time domain method, we have theoretically analyzed the light recoupling efficiency of the RTFG. The simulated results have shown that the RTFG-based optical antennas have a maximum coupling efficiency of 10%. The recoupling wavelength and efficiency are related to the grating period and horizontal incidence angle. Furthermore, we demonstrate a programmable spectral filtering system based on the 45° RTFG antennas, which could achieve filtering with arbitrary spectral shapes. The spectral resolution is 0.4 nm and the insertion loss is around 20 dB. The proposed programmable spectral filtering system has a compact structure compared with the traditional filter.

We have experimentally demonstrated an all-fiber mode-locked laser by using a 45°-tilted fiber grating (45°-TFG) based in-fiber polarization beam splitter (PBS). Based on the nonlinear polarization rotation (NPR), the slanted refractive index modulation structure of the 45° TFG is able to tap the pluses out from the side face of the fiber. The central wavelength of the laser is 1559.9 nm and the period of pulse train is 156 ns, corresponding to the fundamental repetition rate of 6.79 MHz, the pulse energy of 0.26 nJ and the pulse duration of 1.06ps. Additionally, the laser shows a high degree of polarization (DOP) output of 99.8%. This mode-locked fiber laser with single polarization mode output is reliable during long-term operation and thus promising for many practical applications. As a proof of principle, the demonstrated laser can provide neat solution in designing compact mode-locked fiber laser.

A multi-switchable generation between dissipative solitons (DSs) and noise-like pulses (NLPs) in a fiber laser is demonstrated. A 45° tilted fiber grating is applied as an effective in-line all-fiber polarizer to realize the nonlinear polarization rotation (NPR) mechanism. With the fixed orientations of polarization controllers, the operation regimes of the fiber laser can be alternatively switched between DS and NLP by monotonically increasing pump power only. We observed five switching stages between DS/NLP regimes with the pump power elevating from 200 to 660 mW. Remarkably, the whole procedure could be precisely controlled forwardly and backwardly. This multi-shuttle behavior between the two distinct types of output pulse can be attributed to the transmission of NPR mechanism together with the gain filtering effect. To the best of our knowledge, this is the first report on the multi-shuttle behavior between DS and NLP in a fiber laser under monotonic change of pump power. Our findings may contribute to in-depth understanding of nonlinear dynamics and laser physics.

A wavelength-tunable noise-like pulse (NLP) erbium-doped fiber laser incorporating PbS quantum dot (QD) polystyrene (PS) composite film as a saturable absorber (SA) is experimentally demonstrated. The wavelength tuning is implemented via a Lyot filter consisting of a segment of polarization-maintaining fiber (PMF) and a 45° tilted fiber grating. By adjusting the polarization state of the ring cavity, the laser can deliver NLP with a continuous wavelength-tunable range from 1550.21 to 1560.64 nm. During continuous wavelength tuning, the output power varies between a range of 30.88–48.8 mW. Worthwhile noting is that the output power of 48.8 mW is the reported highest output power for wavelength-tunable NLP operation in an erbium-doped fiber laser using composite film as a saturable absorber.

We review the wavelength selective switch (WSS) for ultra-broadband transmission and spatial division multiplexing. We also discuss and present experimental results of WSS components with high spectral resolution and compactness.

The ocean is a natural link for economic, trade, and cultural exchanges between countries. The "21st Century Maritime Silk Road" is a new type of trade road proposed by China to connect the world under the changing situation of global politics and trade. Based on the AIS data of global dry bulk carriers in 2014, this paper selected and counted AIS data of 26 countries along the "21st Century Maritime Silk Road" to build a dry bulk shipping network with the number of routes and the number of trades. The two types of networks constructed are analyzed using primary flow analysis and multiple flow analysis, with a view to providing support and basis for the construction of the "21st Century Maritime Silk Road" and trade cooperation between countries. The results show that: Singapore is the most important node in both networks; the dry bulk shipping network hierarchy of the number of routes is more obvious; the multiple flow analysis results show that China is at the first level in the dry bulk shipping network with the number of routes.

With the increasing demand for oil in various countries, the study of the spatial pattern of maritime oil transportation become the new focus. Based on the AIS trajectory data of 2014, this paper constructs the oil transportation network of the MSR and analyzes the topological structure and spatial pattern of the oil transportation network of the MSR by applying the complex network theory. The study finds: The oil transportation network of the MSR exhibits the characteristics of the small-world and scale-free as a whole; The space difference of degree and degree distribution is large, and the network centrality shows a trend of decreasing scale and stratification; In the oil transport network, the ports who have the three largest centralities are all the Jurong Port, which has the highest overall centrality and is in the absolute core position; The top 10 ports of the three centralities are basically similar, with only a slight difference in the position order. Most of them are distributed in ASEAN, West Asia and Western Europe, which have strong maritime transportation strength, larger maritime transportation radiation range and superior geographical location.

This paper proposes a novel three-phase rectifier which combines the benefits of diode bridge and PWM rectifier with high efficiency and low THD, making it suitable for high power DC fast charging applications. It targets at achieving high efficiency and control simplicity compared to conventional PWM type rectifier. The operation principle, current compensation method at voltage zero-crossing point and power loss analysis are presented and analyzed. Besides, simulations were performed in Matlab/Simulink and a 60kW prototype using IGBT modules and fast recovery diode bridge rectifier was built and tested. The experiment results manifest the merits of proposed three-phase rectifier with 99.5% peak efficiency and 9.2% THD.

In this paper a novel phase-shift autotransformer is proposed to reduce the required kVA capacity in multi-pulse rectifier applications with utility interface. The structure and operation principle of proposed autotransformer are presented and analyzed in detail. Design criteria of turn ratio, phase-shift angle and equivalent capacity for the proposed autotransformer is illustrated. It can be shown that the proposed method can significantly lower the kVA rating of transformer to 9.38% of output power. Simulations in Matlab/Simulink and experimental results of a 40kW prototype further validate the proposed concept.

We have proposed a compact and distributed near infrared detecting system based on 45 ºtilted fiber gratings. The system has been applied to measure the moisture level of flour sample, which have shown linear response between moisture level and testing signal. (tel:18062120349, e-mail: yanzhijun@gmail.com).

We report the observation of second order Bragg resonance (2nd-OBG) produced by tilted fiber gratings (TFGs) fabricated using phase mask UV inscription. The theoretical analysis has revealed that the generation of high order Bragg resonance of gratings is induced by a square-shape refractive index profile, which is caused by over-saturated UV exposure. In the experiment, we have studied the TFGs with different tilt angles under over-saturated UV exposure, in which all gratings have showed the 2nd-OBR, and the larger tilt angle of the grating has the stronger 2nd-OBR. When the tilt angle of the grating is ∼45°, the Bragg resonance exhibits very strong polarization dependence, because the 2nd-OBR wavelength is located within the polarizing bandwidth of 45° TFG. Finally, we have demonstrated an erbium-doped fiber laser with >99.9% degree of polarization, and, by applying mechanical stretching on the grating, a wavelength tunable laser output has been achieved. The output laser shows ∼0.2 dB amplitude variation within 1 h continuous monitoring of the laser.

We demonstrate a fiber Bragg grating (FBG)-based oscillator-accelerometer in which the acceleration sensitivity can be tuned by controlling the location of the mass oscillator. We theoretically and experimentally investigated the performance of the proposed accelerometer. Theoretical analysis showed that both the mass and location of the oscillator affect the sensitivity and resonant frequency of the accelerometer. To simplify the analysis, a nondimensional parameter, P, was introduced to tune the sensitivity of the FBG-based oscillator-accelerometer, which is related to the location of the mass oscillator. Numerical analysis showed that the accelerometer sensitivity is linearly proportional to the P parameter. In the experiment, six FBG-based oscillator-accelerometers with different P parameters (0.125, 0.25, 0.375, 0.5, 0.625, 0.75) were fabricated and tested. The experimental results agree very well with the numerical analysis, in which the sensitivity of the proposed accelerometer linearly increased with the increase in parameter P (7.6 pm/g, 15.8 pm/g, 19.3 pm/g, 25.4 pm/g, 30.6 pm/g, 35.7 pm/g). The resonance frequency is quadratically proportional to parameter P, and the resonance frequency reaches the minimum of 440 Hz when P is equal to 0.5. The proposed oscillator-accelerometer showed very good orthogonal vibration isolation.

In this paper, we report a Surface Plasmon Resonance (SPR) Surrounding Refractive Index (SRI) sensing system based on a hybrid grating structure comprising of a 45o tilted fiber grating (TFG) and a silver coated small angle tilted fiber Bragg grating (TFBG) that have been inscribed into a single mode fiber in series. In this structure, the 45o-TFG is used as a polarizer (replacing a Polarizer Controller) to filter out the S-Polarization mode of the light, and enable the TFBG operating at the P-Polarization mode for SRI sensing. The experiment results show that the sensor covers a range between 1.33 and 1.40 refractive index units (RIU) with a sensitivity of 509.32 nm/RIU.

We demonstrate a multi-wavelength mode-locked Yb-doped fiber laser by incorporating a pair of polarization maintaining 45° tilted fiber gratings (PM-45°TFG) based Lyot filter. Thanks to the functions of the polarizer and the comb filtering introduced by the Lyot filter, dissipative soliton (DS) pulses centered at 1035.26 nm, 1044.93 nm, 1055.62 nm, 1066.11 nm and 1076.63 nm can be generated respectively by finely tuning the intracavity polarization controllers (PCs). Moreover, the laser also can operate in a multi-wavelength regime via appropriately adjusting the pump power and polarization orientation. The high nonlinearity induced by the long cavity length leads to the generation of h-shaped mode-locked pulse with a repetition rate of 566.27 kHz. In the absence of any disturbance, the laser can operate steadily, that can potentially be used in various fields including wavelength division multiplexing systems etc.

We demonstrate a pump-controlled wavelength switchable Yb-doped fiber laser (YDFL) by nonlinear polarization rotation (NPR) for the first time. The polarizer replaced by a 45° tilted fiber grating (45°-TFG) combines with a section of polarization maintaining fiber (PMF) to form a fiber-based birefringent filter. Stable dissipative soliton (DS) with center wavelength of 1068.39 nm is generated under the mode-locked threshold of 277 mW. The operating wavelength switching between 1046.51 nm and 1067.90 nm can be realized via increasing the pump power simply while keeping the polarization controllers (PCs) in a fixed state. The laser maintains stable mode-locking operation at each wavelength, which can be regarded as a type of multi-wavelength ultrafast light source with precise control and integration potential.

We experimentally demonstrate a harmonic-order controllable L-band Er-doped passively mode-locked fiber laser based on nonlinear polarization rotation (NPR). Distinct from all previous reports, we find that the intracavity birefringence is able to control the harmonic order of a passively mode-locked fiber laser. Experimentally, under a constant pump power of 704 mW, the harmonic order can be tuned from 113th to 39th monotonically by adjusting the polarization controller orientation only. The corresponding repetition rate changes from 2.21 to 0.77 GHz simultaneously. Remarkably, the super-mode suppression ratio of each harmonic order we observed is higher than 29 dB with a maximum of 36.5 dB. Simulated transmission spectra of NPR prove that the changed transmission plays an important role in controlling the harmonic order.

We proposed a hybrid tilted fiber gratings (polarizing grating and tilted fiber Bragg grating)-based surface plasmon resonance (SPR) sensor. The hybrid tilted fiber grating, consisting of a polarizing grating and tilted fiber Bragg grating (TFBG), is fabricated in a single-mode fiber in series by using a UV-inscription technique, in which the TFBG could generate a dense cladding mode resonance to excite SPR and the polarizing grating could filter out the S-polarization cladding mode of the TFBG. Such proposed hybrid tilted fiber gratings could greatly simplify the interrogation system of the TFBG-based SPR sensor. The experiment results showed that the hybrid tilted fiber gratings-based SPR sensor has the refractive index sensitivity of 522.8 nm/RIU. Finally, by using the proposed sensor, we have achieved the hemoglobin concentration detection within a sensing range from 0.1 mg/mL to 1.0 mg/mL and the sensitivity of 8.144 nm/(mg/mL).

A novel silica-based reversed-phase/weak anion-exchange mixed-mode chromatography (MMC) stationary phase referred to as OTAS was synthesized based on the horizontal polar-copolymerized approach using trichlorooctadecylsilane (ODS) and (3-glycidyloxypropyl)trimethoxysilane (GPS) as ligands, and then followed by the reaction of epoxy group with diethylamine to introduce the tertiary ammonium functional group. The new stationary phase was characterized by instrumental analysis, and evaluated by separating the mixture of alkylbenzene homologues in reversed-phase mode and acidic organic compounds in ion-exchange chromatography mode, respectively. The results indicate that not only the baseline separation of 11 kinds of neutral and acidic organic compounds can be achieved successfully, but also 5 kinds of inorganic anions can be separated completely. The chromatographic property of OTAS column can be controlled by adjusting the molar ratio of ODS to GPS. Moreover, the OTAS column was used successfully to analyze the inorganic anions in the actual water samples. The good separation and selectivity of OTAS column suggests that the new MMC stationary phase can be used for the analysis of complex samples containing of neutral and acidic organic compounds or inorganic anions.

China’s newly enacted Breakwater Design Specifications (JTS154-2011) explicitly state that breakwaters with water depths greater than 20 m are categorized as deep-water breakwaters, and emphasize that design principles, methods and construction requirements are different from those of common shallow water breakwaters. However, the specifications do not make any mention of how to choose wave force calculation methods of deep-water breakwaters. To study the feasibility of different formulae for wave force estimation of deep water combined breakwaters, the wave force calculated by the Sainflou’s, Goda’s, modified Goda’s and specifications’ methods are compared for various water depths and wave heights in this paper. The calculated results are also compared with experimental data. The total horizontal forcing and the pattern of pressure distributions are presented. Comparisons show that the wave pressure distributions by the four methods are similar, but the total horizontal forces are different. The results obtained by the Goda’s method and the specified formulae are much closer to the experimental data. As for the wave force estimation for the deepwater mixed embankment foundation bed parapet, the Goda’s formula is applied in the case with a water depth of less than 42 m. The Specifications method is suitable for standing waves. In the wave force estimates of breastworks, Sainflou’s and the modified Gaoda’s formulae are no longer applicable for the foundation bed of mixed embankment.

In this study, 3-diethylamino-1-propyne was covalently bonded to the azide-silica by a click reaction to obtain a novel dual-function mixed-mode chromatography stationary phase for protein separation with a ligand containing tertiary amine and two ethyl groups capable of electrostatic and hydrophobic interaction functionalities, which can display hydrophobic interaction chromatography character in a high-salt-concentration mobile phase and weak anion exchange character in a low-salt-concentration mobile phase employed for protein separation. As a result, it can be employed to separate proteins with weak anion exchange and hydrophobic interaction modes, respectively. The resolution and selectivity of the stationary phase were evaluated in both hydrophobic interaction and ion exchange modes with standard proteins, respectively, which can be comparable to that of conventional weak anion exchange and hydrophobic interaction chromatography columns. Therefore, the synthesized weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography column can be used to replace two corresponding conventional weak anion exchange and hydrophobic interaction chromatography columns to separate proteins. Based on this mixed-mode chromatography stationary phase, a new off-line two-dimensional liquid chromatography technology using only a single dual-function mixed-mode chromatography column was developed. Nine kinds of tested proteins can be separated completely using the developed method within 2.0 h.

High-density submicrometer-sized Ni0.5Zn0.5 Fe2O4 ferrite ceramics were prepared by spark plasma sintering in conjunction with sufficient high energy ball milling. They were evaluated by different characterization techniques such as X-ray diffraction, scanning electron microscopy, and dielectric and magnetic measurements. All samples prepared at sintering temperatures ranging from 850 to 925 0C exhibit a single spinel phase and their relative densities and grain sizes range from 90% to 99% and ~100 nm to ~300 nm, respectively. The dielectric constant increases with decreasing grain size until ~250 nm, and then decreases dramatically with further decreasing grain size. The saturation magnetization increases continuously with increasing grain size/density but the magnetic coercivity decreases. The highest dielectric constant and saturation magnetization at room temperature are approximately 1.0 x 105 and 84.4emu/g, respectively, while the lowest magnetic coercivity is only around 15 Oe. These outstanding properties may be associated with high density and uniform micro structure created by spark plasma sintering. Therefore, the spark plasma sintering is a promising technique for fabricating high-quality NiZn ferrites with high saturation magnetization and low coercivity.

In this study, 3-diethylamino-1-propyne was covalently bonded to the azide-silica by a click reaction to obtain a novel dual-function mixed-mode chromatography stationary phase for protein separation with a ligand containing tertiary amine and two ethyl groups capable of electrostatic and hydrophobic interaction functionalities, which can display hydrophobic interaction chromatography character in a high-salt-concentration mobile phase and weak anion exchange character in a low-salt-concentration mobile phase employed for protein separation. As a result, it can be employed to separate proteins with weak anion exchange and hydrophobic interaction modes, respectively. The resolution and selectivity of the stationary phase were evaluated in both hydrophobic interaction and ion exchange modes with standard proteins, respectively, which can be comparable to that of conventional weak anion exchange and hydrophobic interaction chromatography columns. Therefore, the synthesized weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography column can be used to replace two corresponding conventional weak anion exchange and hydrophobic interaction chromatography columns to separate proteins. Based on this mixed-mode chromatography stationary phase, a new off-line two-dimensional liquid chromatography technology using only a single dual-function mixed-mode chromatography column was developed. Nine kinds of tested proteins can be separated completely using the developed method within 2.0 h.

Besides effectively reducing the voltage stress of switches, the cascaded multilevel inverter could also improve the quality of output waveforms by addition of waveforms. The step waveform addition is a usual method. The addition could reduce the loss of switches, but the introduced angle of flow calculating methods of cascade inverters based on step waveform addition are only suitable for cascaded inverters with the same voltage step. To this situation, an angle of flow calculating method of inverters with the different voltage step is proposed in this paper. The method is very suitable for the application of solar battery cascaded inverters and fuel battery cascaded inverters. The method follows the equal area principle, and the online calculation is realized by some constraint conditions. Finally, the correctness of the method is validated by simulations.

According to the noise in the nonlinear systems and shortage of chaotic prediction method at present, this paper presents a local linear adaptive prediction algorithm based on the kernel function of wavelet decomposition. This method using wavelet transformation has a unique multi-scale analysis capability, decomposed the singular into low frequency part and high frequency part, thereby it can reduce the degree of nonlinear time series and make the issue easy to analyze and predict. Analysis of each part indicates that there exists a chaos feature. Then novel local linear predicting models based on kernel function are established, this model is equivalent to estimate high-complicated nonlinear chaotic series by high-complicated nonlinear function in the origin phase space, and can predict chaotic sequence more exactly. At last, forecasting results of the chaotic models are reconstructed which is based on wavelet theory, so as to forecast the system feature reference data series. The following simulation results show the effectiveness of the method described.

Aiming at five-phase permanent magnetism synchronous motor (PMSM), this paper sets up the variable-frequency variable-speed system supplied with three-level inverter and makes study about PWM control algorithm of five-phase three-level inverter. In multilevel inverter, switching frequency optimal PWM (SFOPWM) has many advantages such as high voltage usage and simple control, but the calculation of zero-sequence component in the five-phase three-level inverter need to be studied. This paper propose a calculation method of zero-sequence component in five-phase inverter, which is proved in SFOPWM. For multi-phase multi-level inverter, the numbers of voltage vector and switching state grow rapidly with the increment of phase and level. On the basis of profound analysis about characteristic and rule of five-phase three-level inverter's voltage vector, a simple and practical control algorithm of voltage space vector PWM (SVPWM) is put forward, and it is proved by simulation experiment

PWM control of multi-phase inverter is one of the key technologies in the ships electrical propulsion. In this paper, a novel discontinuous space vector PWM (DSVPWM) method of multiphase inverter is proposed by arranging the two zero vectors skillfully. Comparing with the continuous space vector PWM (CSVPWM) method the DSVPWM use only one zero vector in one switching period, so the switching loss is only four fifths of the CSVPWM. However, the output target line voltages of DSVPWM are still sine wave, the harmonic performance is excelled that of traditional SVPWM (TSVPWM) therefore. Several classic DSVPWM realization methods are given, and the operation characteristic, adapted load types and total harmonic distortion rate of them are analyzed and simulated

Aiming at five-phase permanent magnetism synchronous motor (PMSM), this paper sets up the variable-frequency variable-speed system supplied with three-level inverter and makes study about space vector PWM control algorithm of five-phase three-level inverter. In the control method of voltage space vector, the converter and machine is seen as a whole body, so it has the advantage of good control effect and high voltage usage. For multi-phase multi-level inverter, the numbers of voltage vector and switching state grow rapidly with the increment of phase and level. Firstly, the output voltage vector should be chosen appropriately when use the method of space vector PWM (SVPWM), and then the actuation duration of each in a control cycle can be figured out simply and quickly. Secondly, the output voltage vector should be optimized and the switching sequence be selected properly to decrease switching loss. On the basis of profound analysis about characteristic and rule of five-phase three-level inverter's voltage vector, a simple and practical control algorithm of voltage space vector PWM is put forward, and it is proved by simulation experiment