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In order to calculate dynamic stability of the Mobile Elevating Work Platforms (MEWP) during driving across obstacles and operating on the slope, the analysis method based on mathematical models and simulation models of the MEWP was put forward, then the MEWP dynamic simulation models where the tires and booms were set as flexible bodies were made by ADAMS. Four kinds of the most dangerous working conditions were analyzed, and then the dynamic curves of tire loads and dynamic stability safety coefficient were obtained. Next, the dynamic stability of the MEWP during operating on the slope was verified by field experiments, and the results show that the minimum dynamic stability safety coefficient is 0.157. By comparison and analysis of dynamic stability safety coefficient between simulation analysis and field experiment, it can be seen that the deviations are all positive and less than 5%, therefore the results show that the dynamic stability of the MEWP during driving across obstacles are satisfied. At the same time, the analysis method combining dynamic simulation and some field experiments of the MEWP is proved reliability, accuracy and economy. In all, the dynamic stability of the MEWP can be calculated accurately by ADAMS, in the meantime, the overload operation test (1.5 times rated load) must be performed on the 5° cross slope before the MEWP are selled, and so long as the minimum dynamic stability safety coefficient is no less than 0.1, the MEWP are proved stability and safety.

With the deepening of people’s understanding of new energy, geothermal has become more and more "hot." The abundant geothermal resources of Henan Province will be an important resource pillar for the future economic growth of the Central Plains[1]. However, the vigorous development and utilization of geothermal resources will largely affect the soil structure. Through the data analysis of Luoyang A area, the influence of temperature change on soil structure was studied by using control variables and single factor experiment. The results showed that: with the continuous development of geothermal resources in Luoyang A area, the total amount of microbes, organic carbon and total nitrogen in the soil would chang with the increase of temperature.Among them, the number of microorganisms growed faster with the increase of temperature and reached the highest value up to 40 °C. As the temperature continuing to rise, the number of microbes growed slowly or on a downward trend.In order to avoid the influence of temperature changes on the soil structure, it is recommended to put insulation materials around the wellhead and the reservoir to prevent the lowest loss temperature from exceeding 30 °C or 3 wells alternating every other quarter[2].

An injection-seeded single-frequency Q-switched Nd:YAG laser is accomplished by using a phase modulated ramp-fire technique. A RbTiOPO4 (RTP) electro-optic crystal is selected for effective optical path length modulation of the slave self-filtering unstable resonator. This single-frequency laser is capable of producing 50 mJ pulse energy at 1 Hz repetition rate with a pulse width of 16 ns. The standard deviation of laser pulse intensity for consecutive 100 shots from the mean pulse intensity is less than 1.05%. A spectral linewidth of less than 0.5 pm with a frequency jitter of about 14 fm over 30 min is obtained.

We introduce PBGFs with the cladding made of our newly designed quasi-hexagonal air holes and demonstrate how it actually operates. This cladding structure is introduced for the first time to the best of our knowledge, and is realized by making use of the hydrofluoric acid's corrosive properties. The fibre corrosion can be accurately controlled, thus opening us the gate for the design and fabrication of new PBGFs with more complex and more efficient cladding structures. Numerical results and actual simulations indicate that PBGFs built with this cladding structure have improved bandgap properties and guiding bands as wide as 500 nm have been theoretically reached. Using the same method, we have also been able to design two other types of PBGFs with improved cladding structure.

Hollow core's inner surface coating in a photonic bandgap fibre (PBGF) is investigated by means of finite element method. The coat material and thickness-dependence dispersion curve and group velocity dispersion are numerically studied. The coating with materials of low index or small thickness will rise up the dispersion curve but will not induce surface modes. However, coating with materials of high index or big coat thickness will induce surface modes and avoided-crossings. By varying coat material's refractive index and thickness, the appearances of surface modes and avoided-crossings can be changed. It is found that the avoided-crossing can enormously enlarge the negative dispersion which can find applications in dispersion compensation. We numerically achieve a negative dispersion as large as -21416.15 ps/nm/km. The results give a physical insight into the propagation properties of PBGFs with the hollow core coated by a layer of material and are of crucial significance in the applications of PBGF coating.

Birefringence of a microstructure fibre with irregular structures is investigated using the finite element method. The birefringence of each sample is statistically analysed, and the relation between the birefringence and the irregular structure of the microstructure fibre is derived. The results indicate that the irregular structure of the symmetrical microstructure fibre result in the birefringence which is more strongly affected by disorder of air holes than the nonuniformity. Moreover, lower birefringence can be obtained with smaller air holes and larger pitch in the fibre structure.

Fibre Bragg gratings (FBGs) are inscribed in homemade microstructured fibres by the standard phase mask method. Enhanced couplings between the forward fundamental mode and backward cladding modes are obtained. The mode coupling and spectral characteristics are investigated experimentally. The cladding mode resonances can be affected by filling active materials into the air holes, which will be useful for the implementation of tunable photonic devices in optical fibre communication and sensing systems.

Enhancing coherent combining efficiency via choosing appropriate lasing wavelength in a Michelson compound cavity based on two 3?dB fibre loop mirrors and one fibre Bragg grating (FBG) has been experimentally demonstrated. The FBG with 4.5% reflectivity is replaced at the cleaved facet with 4% Fresnel reflection. A high coherent combining efficiency of 93.5% is obtained when the FBG with central wavelength at 1559.845?nm is introduced into the cavity, while it is only 90.1% combining efficiency with the FBG at central wavelength 1557.830?nm. In comparison with other reports, the proposed compound-cavity laser has the advantage of needless tuning FBG to obtain the coherent condition, and it is facile to ascertain the seemly wavelength lasing for a Michelson compound cavity.

We numerically investigate the mode exciting properties of photonic crystal fibres by using the beam propagation method when the optical field is input from a traditional single mode fibre. The results show that both the excited mode spectrum and the coupling-efficiency of each excited mode depend on the normalized pitch ?/? and the normalized hole-size ?/?. Furthermore, we obtain the boundary profile of the optimizing coupling-efficiency for the excited fundamental mode: the boundary (?/?)* is linear to the boundary (d/?)*. All of these will pave the way for smoothing applications of photonic-crystal fibres, such as splicing and designing photonic-crystal-fibre functional devices.

A dual-wavelength laser system with wideband tunable wavelength spacing and more than 2 W output power is proposed and demonstrated. The operation principle of the laser system is based on the saturation gain characteristic of a cladding-pumped Er3+/Yb3+ co-doped fibre amplifier combining with a wideband tunable fibre laser with flat power spectrum. The tuning range of the wavelength spacing is continuous within a 35 nm spectral range, and the power difference between both lasing wavelengths can be easily adjusted and controlled by a variable optical attenuator. The total output power can approximately keep unchangeable when the wavelength spacing and the power difference between both lasing wavelengths are continuously tuned and changed. The maximum total output power of the laser system is about 2.22 W.

Novel highly birefringent photonic bandgap fibres (PBGFs) are obtained by filling of a high index material in the air holes of total internal reflection birefringent photonic crystal fibres. The effect of the filling high index material on the transmission characteristics has been theoretically investigated. The photonic bandgap has been achieved by using plane-wave method. Moreover, the phase and group modal birefringence have been studied by a full-vector finite-element method. Numerical results show that very high group and phase modal birefringence with magnitude of order of 10−2 and 10−3 has been respectively acquired, which is much higher than those of the non-filled fibres. Furthermore, strong coupling between surface modes and the fundamental modes has been found in the bandgap of the birefringent PBGFs, whose effect on the birefringence and confinement loss has also been discussed.

In this paper, a novel output-power controllable erbium-doped fibre laser, based on a strain-applied high-birefringence fibre loop mirror (HBFLM), was proposed and demonstrated. The reflectivity of HBFLM could be changed from about 0.8% to 100% because the fibre length and birefringence of the high-birefringence fibre (HBF) were altered via bonding a part of HBF to the centric surface of an uniform-strength cantilever beam and applying different stress at end of the beam. As a result, the laser output power could be adjusted and controlled in a dynamic range of more than 33 dB. The laser is not only a controllable and adjustable output-power laser with simple configuration and low cost, but also can be used for optimizing the output characteristics of a linear cavity laser via easily finding out the optimized reflectivity of the reflectors.

A 2-μm composite Tm:YAG laser pumped with a narrow-band laser diode was presented. The temperature distribution and thermal lens in the Tm:YAG were numerically simulated by a finite element method and the results were used to design the special cavity, in order to achieve a high efficiency and stable output. With a 25-W incident pump power, we obtained a maximum output power of 11 W at 2018.5 nm, corresponding to a slope efficiency of 51.3% and an optical-to-optical efficiency of 44.5%, respectively. The beam quality was measured to be and .

We demonstrate a compact photonic device based on efficient and wavelength-tunable doubling of an all fibre-format source. Quasi-phase-matched second-harmonic generation in periodically poled lithium niobate is used to generate 90.6mW at 775.9nm with a single-pass conversion efficiency of 14.7%. A tuning bandwidth of 2.1nm and a tuning temperature range of 150.6 ± 1.7°C can be achieved. The Er-doped seed fibre source is amplified by a clad-pumped Er3+/Yb3+ -codoped fibre laser with a high output power up to 2.18 W over a tunable wavelength range from 1535 nm to 1570 nm.

We propose and demonstrate a new concept of stable narrow-line-width and close wavelength spacing dual-wavelength lasing in an Er-doped fibre ring laser (EDFRL) by cleaving the spectrum with a wavelength-selective component in the EDFRL. A fibre loop mirror (FLM) combining with a polarization controller (PC) acts as the cleaver. The cleaver can produce a fine pectinate spectrum. By adjusting the PC, the fine pectinate spectrum can be so changeable that cleaving the spectrum of a fibre Bragg grating (FBG) into two parts. As a result, we obtain the dual-wavelength fibre lasering with a bandwidth of only 0.03 nm and a wavelength spacing of only 0.07 nm. Furthermore, the laser can also perform stable switchable single wavelength or stable different-bandwidth dual-wavelength by carefully adjusting the PC at room temperature.

Giant magneto-impedance (GMI) effects in Fe73.5Cu1Mo3Si13.5B9 alloy ribbons have been measured under different external magnetic fields and different ac driving current frequencies. The results show that the longitudinal and the transverse GMI change with the annealing temperature. Based on the classical electromagnetic theory, the difference between the longitudinal and the transverse GMI (R,X,Z) has been discussed in this letter.

A polarization-independent all-fibre comb filter with dynamically halved channel spacing is proposed. The filter is based on high-birefringent fibre Sagnac interferometers and its channel spacing can be dynamically halved by turning on an optical switch. A good agreement between the numerical simulation and the experimental results is achieved.

A high-power Er3+/Yb3+-codoped double-cladding all-fibre amplifier was successfully demonstrated and experimentally investigated. The amplifier could be operated with a maximum output power of 2.18 W and 2.11 W at 1541 nm and 1550 nm wavelengths, respectively, when the maximum pump power was 6.07 W. The power conversion efficiency was up to 35.6% and 34.4% at the two wavelengths, respectively. The output power and the gain were greater than 2.00 W and 20.0 dB, respectively, in the wavelength range from 1539 nm to 1565 nm for 20.0 mW input signal power. The gain fluctuation and the noise figure around 1550 nm wavelength were less than 0.3 dB and 6.0 dB, respectively.

Multiwavelength operation of a linear cavity erbium-doped fibre laser (EDFL) is proposed and demonstrated. A 3-dB fibre loop mirror and a high birefringence (HiBi) fibre loop mirror are utilized as the cavity reflectors. By utilizing the wavelength-dependent polarization rotation induced by the HiBi fibre loop mirror and by using a fibre polarizer to control the intracavity polarization state, the polarization states of different wavelengths are diversified. Therefore, the polarization hole burning (PHB) effect has been greatly enhanced and the homogeneous broadening of erbium-doped fibre is suppressed to a large extent. By simply tuning a polarization controller, we experimentally obtained simultaneous lasing of four and five wavelengths with wavelength spacing of ~1.8 nm and less than 2 nm at room temperature, respectively. The repeated scans show that all of these lasers have good stability.

All-fibre high power erbium–ytterbium co-doped double clad fibre lasers are proposed and demonstrated. By using different back-cavity mirrors, the different double clad fibre lasers are constructed. It is experimentally found that the output behaviour of laser can be controlled by a back-cavity mirror. The lower the reflectivity of the back-cavity mirror, the higher the output power and the high the slop efficiency. The maximum output power is about 1.6 W and the slop efficiency is 27.6%.

A polarization controlled switchable multiwavelength erbium-doped fibre laser with overlapping cavities is proposed. The wavelengths are specified by two Bragg gratings in polarization-maintaining PANDA fibre. The proposed laser can be designed to be operated in stable four-wavelength or wavelength switching modes only by simple adjustment of two polarization controllers. For wavelength switching, four single-wavelength, six dual-wavelength, and four three-wavelength operations have been obtained. The minimum wavelength spacing is only about 0.4 nm.

A simple actively mode-locked fibre ring laser is proposed and successfully demonstrated to generate switchable dual-wavelength picosecond pulses using a Bragg grating in a polarization-maintaining fibre. The wavelength spacing specified by the grating is only 0.52 nm. The proposed laser can be made to operate in stable dual-wavelength or switch between wavelengths at room temperature, by simple adjustment of a polarization controller.

We first demonstrate a high-efficiency composite Tm-doped yttrium aluminum garnet laser end-pumped with a narrow-linewidth laser diode, which was locked at a wavelength of 784.9 nm with volume Bragg gratings. The locked pump wavelength was experimentally determined by the excitation peak, which was also the absorption peak of a 3.5 at.% Tm:YAG crystal around 785 nm, for the improvement of laser efficiency under high-intensity pumping. Under an absorbed pump power of 24.64 W, a maximum output power of 11.12 W at 2018 nm was obtained, corresponding to an optical to optical conversion efficiency of 45.1% and a slope efficiency of 52.4%.

La3Ga5SiO14 (LGS) has been designed and used successfully not only as an electro-optical (EO) Q-switch but also as the optically active crystal in an Nd:YAG (yttrium aluminum garnet) pulse-off laser cavity with two-rod birefringence compensation in this paper. A maximum average output power of 15.8 W with a pulse width of 21 ns was obtained at the maximum repetition rate of 1 kHz, and the dynamic–static ratio was 75%. Experimental results revealed that the spatial distribution of the laser intensity with the two LGS crystals inserted between two identical Nd:YAG rods was significantly better than the spatial distribution with no birefringence compensation or a KD P EO Q-switcher.

The iron-based superconductivity (IBSC) is a great challenge in correlated system. Angle-resolved photoemission spectroscopy (ARPES) provides electronic structure of the IBSCs, the pairing strength, and the order parameter symmetry. Here, we briefly review the recent progress in IBSCs and focus on the results from ARPES. The ARPES study shows the electronic structure of "122", "111", "11", and "122*" families of IBSCs. It has been agreed that the IBSCs are unconventional superconductors in strong coupling region. The order parameter symmetry basically follows s± form with considerable out-of-plane contribution.

We demonstrate an all-normal-dispersion mode-locked fiber laser based on a piece of large-core Yb-doped multi-mode fiber. High order modes are suppressed by coiling the gain fiber to produce large loss for the high modes but low loss for the fundamental mode. Mode-locking is self-starting by exploiting a combination of a grating-aperture based spectral filter with a nonlinear polarization evolution effect. The laser directly delivers 1.1 ps, 107 nJ pulses at a repetition rate of 76.7 MHz, with an average power of up to 8.2 W. The pulses can be compressed externally to 210 fs with a peak power of up to 350 kW.

Moire fibre Bragg gratings are made in a single mode fibre and a polarization-maintaining fibre respectively, using an excimer KrF laser and a phase mask. Two gratings are written at the same location of the optical fibre. The wavelength spacing can be finely tuned from 0 to 1.86 nm by straining the optical fibre during UV illumination.

A temperature tunable photonic bandgap fiber (PBGF) is demonstrated by an index-guiding photonic crystal fiber filled with high-index liquid. The temperature tunable characteristics of the fiber are experimentally and numerically investigated. Compression of transmission bandwidth of the PBGF is demonstrated by changing the temperature of part of the fiber. The tunable transmission bandwidth with a range of 250 nm is achieved by changing the temperature from 30°C to 90°C.