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Early warning systems and emergency management for disasters, environmental pollution, and illegal development require timely and accurate Earth surface anomaly detection (ESAD). Remote sensing, which uses satellites to observe the Earth’s surface, is an emerging approach to address this need. However, current remote sensing methods for ESAD are limited by their focus on specific anomalies, reliance on high-level satellite data, and the demand for significant computational and storage resources. In this article, we present a novel framework for general and on-orbit ESAD, which combines large vision models and lightweight priors. Our method characterizes images with a large vision model that is highly generalizable, reducing the dependency on high-level data, and compressing the prior base with sampling techniques, facilitating transmission and on-orbit storage. For on-orbit detection, we use a dictionary look-up style method for efficient anomaly prediction, enabling detection on satellites with limited computation resources. We evaluate our framework on typical scenarios and compare it with popular change detection (CD)-based and anomaly detection (AD)-based methods. Our results show that our framework achieves good performance while reducing the prior size by at least 95.56 times. Moreover, our framework can handle unpaired data, providing a chance to detect anomalies in the absence of near-term and paired images. Our framework has the potential to support the development and applications of general, on-orbit ESAD. The code and dataset are available at the following site: https://github.com/YummyWaffle/ESAD.

Land surface temperature (LST) is an important variable in Earth science research and can be measured using various thermal infrared (TIR) observations. Due to variations in data sources and inversion algorithms, LST products yield inconsistent results, further affecting subsequent applications (e.g., drought and vegetation monitoring). Although many evaluation studies have been conducted, most of them have focused on product validation or differences between inversion algorithms. There is a lack of analysis of the data sources, which is important for the data fusion. Therefore, a consistency analysis was conducted herein. Mainstream polar-orbiting satellite data were selected, including data from the Moderate Resolution Imaging Spectroradiometer (MODIS), Sea and LST Radiometer (SLSTR), and Visible Infrared Imaging Radiometer Suite (VIIRS). The same inversion algorithm (split window, SW) for LST was employed across all datasets, thereby ensuring that differences in satellite data were the primary factor. Following validation based on in situ measurements, the polar-orbiting LST results were intercompared and analyzed with the LST results derived from the Himawari-8 Advanced Himawari Imager (AHI) observations. The results indicated the following: 1) similar conclusions were obtained from the intercomparison results and the ground-based validation results, with root mean square errors (RMSEs) for intercomparison results ranging from 2.9 to 3.3 K; 2) based on the intercomparison results, regression analysis revealed that surface temperature status, land cover and vegetation information, and angular factors had a significant impact on the evaluation results, with t tests yielding p values less than 0.05 for all of these factors; and 3) based on a decision tree analysis, the contributions of angular factor, surface temperature status, and land surface structure were 50.9%, 31.3%, and 17.8%, respectively. These findings enhance knowledge regarding the impact of different satellite data on LST inversion results and emphasize the necessity of preprocessing before the joint application of satellite data, such as angle normalization and radiometric calibration.

Land surface temperature (LST) is an important parameter in many research fields. As a temperature characteristic, thermal radiation has an obvious directionality. In urban areas, the directional anisotropy (DA) in surface temperatures can reach 10 K during airborne measurements, limiting the applicability of urban surface temperature products. Notably, the intricate 3-D structures and heterogeneous temperature distributions in urban environments significantly influence this anisotropy. In recent decades, numerous models have been developed for urban thermal anisotropy (UTA) analysis; however, most of these models predominantly focus on horizontal surfaces, with little consideration of mountainous architectures. To balance the calculation efficiency and model complexity, this study introduces an analytical thermal anisotropy model applicable to urban areas. This model considers the effects of 3-D structures and slopes and is labeled as the AU3SM. The multiangle data used for the analysis are recorded by an unmanned aerial vehicle (UAV) with a multicircle observation scheme in Chongqing, China. Comparisons of the AU3SM simulated data with these measurement data yield root mean square error (RMSE) and coefficient of determination ( $R^{2}$ ) values of 0.57 K and 0.89, respectively. Furthermore, similar comparisons with the discrete anisotropic radiative transfer (DART) model yield $R^{2}$ and RMSE values of 0.98 and 0.12 K, respectively. Simulations reveal that slope influences the UTA, and the hotspot lies on the opposite side of the solar direction; ignoring slope values of 5°, 10°, 15°, and 25° results in UTA maximum biases of approximately 1.2, 3.5, 7, and 7.5 K, respectively, under certain conditions. These findings demonstrate that the proposed model can accomplish rapid UTA assessments in mountainous areas.

Land surface temperature (LST) is an essential parameter for geoscience studies, and the 1-km polar-orbiting satellite LST products are widely used due to their global coverage on a daily basis. Aimed to jointly utilize all 1-km LST products to thoroughly quantify the LST temporal tendency within one day, comprehensive evaluation of existing 1-km LST products over the same sites is meaningful. In this study, taking sparsely vegetated sites as an example, ten 1-km polar-orbiting LST products were evaluated against the in situ measurements of ten USCRN sites with high spatial representativeness (from December 2019 to November 2020 covering four seasons). The evaluated LST products included three Moderate Resolution Imaging Spectroradiometer (MODIS) LST products (i.e., MOD11, MYD11, and MYD21), two Sea and LST Radiometer (SLSTR) LST products (i.e., Sentinel-3A and Sentinel-3B), one LST product from Advanced Very High Resolution Radiometer (AVHRR) onboard Metop-B, three Visible Infrared Imaging Radiometer Suite (VIIRS) LST products (i.e., VNP21, S-NPP EDR, and NOAA-20 EDR), and one LST product from Visible and Infra-Red Radiometer (VIRR) onboard FY-3B. The results indicate that: 1) the RMSE is much higher in the daytime (2.5–4.0 K) than in the nighttime (1.7–2.5 K); 2) the daytime MBE is negative (from −0.3 to −2.8 K) and this underestimate trend is significantly slighter for nighttime MBE (from −1.7 to 0.2 K); and 3) the daytime RMSE varies from 2.7 to 4.6 K in summer, 2.7–4.5 K in spring, 2.5–3.7 K in winter, and 2.0–3.4 K in autumn. Furthermore, we found that the severe daytime RMSE is related to the thermal anisotropy amplitude, which is around 4 K in summer, 2 K in spring and autumn, and 1 K in winter. Correcting the thermal anisotropy of daytime LST is an essential step that needs to be taken seriously before conducting high-quality joint applications, such as diurnal temperature cycle (DTC) modeling.

Large Seebeck coefficients induced by high degeneracy of conduction band minimum, and low intrinsic lattice thermal conductivity originated from large lattice vibrational anharmonicity render Mg3Sb2as a promising n-type thermoelectric material. Herein, we demonstrated unique concentration-dependent occupation behaviors of Cu in Mg3.4Sb1.5Bi0.49Te0.01matrix, evidenced by structural characterization and transport property measurements. It is found that Cu atoms prefer to enter the interstitial lattice sites in Mg3Sb2host with low doping level (Mg3.4Sb1.5Bi0.49Te0.01 + x% Cu, x < 0.3%), acting as donors for providing additional electrons without deteriorating the carrier mobility. When xis larger than 0.3%, the excessive Cu atoms are inclined to substitute Mg atoms, yielding acceptors to decrease the electron concentration. As a result, the electrical conductivity of the Mg3.4Sb1.5Bi0.49Te0.01 + 0.3% Cu sample reaches 2.3 × 104 S/m at 300 K, increasing by 300% compared with that of the pristine sample. The figure of merit zTvalues in the whole measured temperature range are significantly improved by the synergetic improvement of power factor and reduction of thermal conductivity. An average zT∼1.07 from 323 K to 773 K has been achieved for the Mg3.4Sb1.5Bi0.49Te0.01 + 0.3% Cu sample, which is about 30% higher than that of the Mg3.4Sb1.5Bi0.49Te0.01sample.

A semi-empirical two-temperature (2-T) arc model is developed to study the near-electrode regions and thermal non-equilibrium characteristics of low-current arcs that employ pin-to-pin electrodes in micro‑tungsten inert gas (TIG) welding. Special emphasis is given to accurately depict the electrodes-arc attachment area and the spatial distributions of plasma temperature in 1–4 A argon arcs. The conditions of thermal non-equilibrium, as well as the coupling of the arc plasma and the cathode, are considered. The simulated electron temperature distributions are in good agreement with the arc appearances captured by the high-speed camera, and the predicted arc voltage is only 1.8 V lower than the experimental data. In contrast to TIG welding arcs that operate at higher currents, the temperature contours of the low-current arc column are parallel but slightly expanded in the vicinity of the electrodes. As the arc current decreases, the near-cathode voltage drop increases substantially. The electron temperature in the center of the arc column is almost constant, while the heavy particle temperature drops significantly, causing the arc column to contract. The heat flux at the center of the anode surface does not change as the arc current increases, but it increases significantly outside the 0.25 mm radius.

All-weather land surface temperature (LST) derived from passive microwave (PMW) sensors has significant implications for characterization on the physical processes of surface energy and water balance at local through global scales. However, the PMW sensors (e.g., the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E)] suffer from swath gaps cannot provide completely spatial-gapless observations. The existing multitemporal feature connection-convolutional neural network (MTFC-CNN) method caused obvious traces of “gaps” when the sample number is small or features are not rich. This article proposes a sample optimized-MTFC (SO-MTFC) seamless reconstruction method based on analyzing the periodicity and complementarity of AMSR-E swath gaps. Sample optimization includes two aspects: sample enhancement (SE) and single-cycle mask (SCM) strategy. Taking China’s landmass as the study area, experimental results show that the original AMSR-E LSTs and the reconstructed AMSR-E LSTs are basically connected seamlessly. Validation against with the MODIS LSTs shows that the daytime (nighttime) root-mean-squared errors (RMSEs) of the original and the reconstructed AMSR-E LSTs are 3.87 (2.57 K) and 4.76 K (2.96 K), respectively, while the corresponding daytime (nighttime) $R^{2}$ are 0.88 (0.94) and 0.73 (0.90), respectively. Validation against with the six in situ LSTs shows that the RMSEs and $R^{2}$ of reconstructed AMSR-E LSTs against in situ LSTs are almost consistent with those of the original AMSR-E LST. The ablation study proves the effectiveness of the sample optimization. These findings indicated that the SO-MTFC achieved a good reconstruction effect. Compared with the MTFC-CNN, the SO-MTFC got higher scores visually and quantitatively. The SO-MTFC can potentially be implemented with other satellite PMW sensors to produce completely spatial-seamless PMW LST records on a global scale.

Land surface temperature (LST) is an important parameter that characterizes the energy balance of the land surface, and it is widely used in various research fields. This article proposes an operational split-window (SW) algorithm for use with the Chinese Fengyun-3 (FY-3) series satellite data, with the purpose of generating long-term global LST products. The algorithm primarily involves three steps. First, the brightness temperatures of the FY-3 Visible and Infrared Radiometer (VIRR) were recalibrated using historical recalibration coefficients to improve the accuracy of the absolute radiometric calibration. Second, daily dynamic emissivity maps were estimated using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) global emissivity dataset (GED) and vegetation/snow cover products based on the vegetation cover method. Finally, the coefficients of the SW algorithm were simulated using MODTRAN 5 combined with the SeeBor V5.0 atmospheric profile library and ASTER spectral library, and then, the coefficients were stratified by the view zenith angle (VZA) and atmospheric water vapor content (WVC) to improve the fitting accuracy. The proposed SW algorithm was integrated into the MUlti-source data SYnergized Quantitative (MUSYQ) remote sensing production system to then generate FY-3 VIRR LST products. Ten land surface sites from the Heihe Watershed Allied Telemetry Experimental Research (HiWATER), Surface Radiation Budget (SURFRAD) networks, and nine water surface sites from the National Data Buoy Center (NDBC) were used to evaluate the accuracy of the FY-3 VIRR LST products. The results demonstrated that the accuracy of the historical recalibration coefficients of the FY-3A/B VIRR is higher than that of the operational calibration coefficients for LST retrieval. The evaluation results revealed that the FY-3A VIRR LST products (2009–2013) had a bias of 0.13 K and an RMSE of 2.77 K, and the FY-3B VIRR LST products (2011–2020) had a bias of −0.07 K and an RMSE of 2.83 K. These results demonstrate that the proposed operational SW algorithm has reasonable accuracy and can be used to produce global LST products from the FY-3 VIRR data.

Land surface temperature (LST) is a vital parameter for studying global ecological, climatic, and environmental changes. Although various LST retrieval algorithms have been proposed, including split-window (SW), dual-window (DW), three-channel (TC), and dual-angle (DA) algorithms, few studies have compared these algorithms using the same satellite observations. The Sea and Land Surface Temperature Radiometer (SLSTR) onboard Sentinel-3A provides a unique opportunity to conduct this comparison due to its DA viewing capability and multiple thermal infrared (TIR) and mid-infrared (MIR) channels. Here, we implemented two SW algorithms, one DW algorithm, two TC algorithms, and one DA algorithm for the SLSTR data. The LST retrievals from these six algorithms were validated, along with the SLSTR operational LST product based on an emissivity-implicit SW algorithm. Temperature- and radiance-based validation methods were used to evaluate different LST retrievals across different land cover types (LCTs). The results indicated that the proposed SW algorithm had the highest accuracy, followed by the Pérez-Planells SW and the official algorithms. The overall root-mean-square errors (RMSEs) of these three SW algorithms were 1.42, 1.79, and 2.05 K. The three algorithms involving the MIR channel (one DW and two TC algorithms) were more suitable for nighttime LST retrieval and had similar performances to the three SW algorithms, with a nighttime RMSE of approximately 1.36 K. The LST retrieval accuracy of the DA algorithm had the highest uncertainty and was closely related to the angular variation in surface emissivity and brightness temperature (BT). The findings of this study contribute to a better understanding of the different LST retrieval algorithms and facilitate potential improvements in the official LST retrieval algorithm for SLSTR.

Optical canopy models that connect land surface properties and satellite-observed radiance must be validated before being used. These models include the bidirectional reflectance distribution function (BRDF) models in the visible and near-infrared domains, and directional brightness temperature (DBT) models in the thermal infrared domain. Near-surface experiments have been extensively conducted to evaluate the modeling accuracy, including ground-, tower-, and aircraft-based measurements. Indeed, it should be noted that in situ measured BRDF/DBT results are sensitive to the experiment protocol, such as sensor moving orientation, flight height, and sampling frequency. A practical tool for optimizing the in situ measurement protocols is needed in the community of remote sensing modeling. For that, we devised a virtual experiment framework based on the discrete anisotropic radiative transfer (DART) 3-D radiative transfer model that is capable of simultaneously simulating both the BRDF/DBT pattern and the images acquired by in situ cameras. Here, as an optimization case, we use it to determine the optimal sensor flight orientation over heterogeneous vegetated canopies (a row-planted scene with three solar angles and a discrete scene with three solar angles) for measuring their DBT distribution. Results showed considerable errors (i.e., image-extracted DBT minus DART-simulated DBT) exist for sensor flight orientation along the canopy rows ( $R^{2}$ = 0.24 and root mean square error (RMSE) = 4.32 K), and they become much smaller ( $R^{2}$ = 0.94 ~ 0.98 and RMSE = 0.82 ~ 1.03 K) in other typical orientations (e.g., cross row plane, solar principal plane, and cross solar principal plane). The critical azimuth offset relative to the row direction that can ensure an acceptable RMSE < 1 K is quantified as atan(3*Unitwidth/Scenesize) based on a series of intensive simulations by this new tool. However, the RMSE of the discrete scene is not sensitive to the flight orientation. Such accuracy differences in various protocols were experimentally verified over row-planted maize using a 4-D tower in Huailai, Hebei, China. The result highlights the great potential of this newly designed DART-based virtual experiment to optimize near-surface experiment protocols.

The single-sided micro resistance spot welding (MRSW) of enameled copper wire to pad is widely applied in electronics manufacturing. The welding quality is significantly influenced by the process of heat generation and transfer which are gradually changing and quite uncertain in production. This work is to investigate the thermal process variation under the common influence factors of electrode wear and thermal contact conductance (TCC). Multi signals such as dynamic resistance and electrode temperature were detected to analyze the welding process. A finite element model of electrical-thermal-mechanical coupling was established to simulate the heat generation and transfer in MRSW. The coupled model was validated by comparing the simulated results of temperature and voltage with the experimental measurement. The results show that the electrode wear in single-sided MRSW of enameled wire to pad causes an increase in the resistance and temperature of electrode tip rather than decrease, and it requires reducing the welding parameters instead of increasing. In case of electrode wear, maintaining a consistent temperature rise of electrode tip helps to ensure welding quality. Due to the insulation coating of enameled wire, the normal TCC between electrode tip and workpieces significantly changes in the MRSW process and rapidly rises after the decomposition of insulation coating. TCC needs to be controlled within a reasonable range to prevent insufficient or excessive heat transfer in production.

Micro‑tungsten inert gas (TIG) welding is widely used in electronic component manufacturing. Arc ignition under low current should be employed to avoid burning the micro-component. However, it is relatively complex to manipulate. To improve the stability and reliability of the arc ignition under low current, the effect of the ignition method, cathode spot motion (CSM), and welding circuit inductance is investigated. High voltage arc ignition (HVAI) experiments are carried out with different inductances under various CSM amplitudes. A high-speed digital camera is employed to record the arc image, while a digital oscilloscope is used to simultaneously detect the arc voltage and current waveforms. The results show that HVAI can achieve smooth arc ignition with the low current in a relatively long discharge gap. The inductance in the welding circuit plays an effective role in maintaining the burning of the micro-arc. However, overly high inductance prevents arc formation just after the breakdown of the gap. When a traditional TIG welding torch is used, cathode spots move violently at the beginning of the low current arc ignition. This results in arc oscillation in the space or even rapid extinguishing. By placing an insulating ceramic tube on the tungsten electrode, the emission of electrons can be limited to the electrode tip. This, in turn, restricts the range of motion of the cathode spots to the tip region. Consequently, low-current arc ignition performance is improved.

To solve the serious loss problem for central energy of the Cassegrain antenna, this paper designs a beam-shaping system, named E-A system, to convert the elliptical divergent beam with astigmatism from a laser diode into an annular collimation beam. This E-A system, comprised only of lenses with quadratic surfaces, can simultaneously realize four functions, i.e., aberration correction, beam circularization, beam collimation, and dark hollow beam generation. By adjusting the parameters, the E-A system can be used to shape elliptical astigmatic beams with different parameters. Further, the E-A system can maintain good performance at wavelengths from 500 to 1647 nm. After considering various practical factors, the transmission efficiency of the entire transmitting system can be increased to 93.91% at a wavelength of 1550 nm.

Analyzing optical antenna systems through geometrical optics is quite popular for its convenience, which, however, may cause remarkable errors. This paper uses both geometrical optics and diffraction theory to analyze the performance of a traditional optical antenna system, and the results calculated through the two methods are carefully compared. Based on the comparison, it shows the situations in which geometric optics will cause significant errors. In addition, a parameter γ is defined to quickly determine whether geometrical optics is suitable for analyzing optical antenna systems under some situations. This paper can help engineers quickly choose the proper method for designing and analyzing optical antenna systems.

ABSTRACTSurface upward longwave radiation (SULR) is one of the four components of the surface radiation budget, which is defined as the total surface upward radiative flux in the spectral domain of 4-100 μm. The SULR is an indicator of surface thermal conditions and greatly impacts weather, climate, and phenology. Big Earth data derived from satellite remote sensing have been an important tool for studying earth science. The Advanced Baseline Imager (ABI) onboard the Geostationary Operational Environmental Satellite (GOES-16) has greatly improved temporal and spectral resolution compared to the imager sensor of the previous GOES series and is a good data source for the generation of high spatiotemporal resolution SULR. In this study, based on the hybrid SULR estimation method and an upper hemisphere correction method for the SULR dataset, we developed a regional clear-sky land SULR dataset for GOES-16 with a half-hourly resolution for the period from 1stJanuary 2018 to 30thJune 2020. The dataset was validated against surface measurements collected at 65 Ameriflux radiation network sites. Compared with the SULR dataset of the Global LAnd Surface Satellite (GLASS) longwave radiation product that is generated from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the polar-orbiting Terra and Aqua satellites, the ABI/GOES-16 SULR dataset has commensurate accuracy (an RMSE of 15.9 W/m2vs 19.02 W/m2and an MBE of −4.4 W/m2vs −2.57 W/m2), coarser spatial resolution (2 km at nadir vs 1 km resolution), less spatial coverage (most of the Americas vs global), fewer weather conditions (clear-sky vs all-weather conditions) and a greatly improved temporal resolution (48 vs 4 observations a day). The published data are available at http://www.dx.doi.org/10.11922/sciencedb.j00076.00062.

In this paper, a reflector antenna design method is proposed to improve transmission efficiency and control output intensity distribution. Primary and secondary mirrors are constructed segment by segment using a numerical method according to the law of energy conservation, the vector theory of reflection, and Fermat’s principle that the optical path length of each ray must be equal. To verify the effectiveness and practicability of this method, an example of an antenna with the prescribed intensity distribution of the output beam is given. The transmission efficiency of the antenna system designed by this method reaches 100% in theory. The effects of output intensity distribution and deviation on transmission efficiency were also analyzed. We believe that the results show that the proposed method is a highly efficient approach to the design of a freeform reflector antenna to improve transmission efficiency and control the output intensity distribution.

With the improvement of the transmission efficiency, the Cassegrain antenna can be widely used in space optical communication. In this paper, the Bessel–Gaussian (BG) beam is used to avoid the central energy loss of a Cassegrain antenna system. The intensity distribution and the phase distribution of the BG beam passing through a Cassegrain antenna are theoretically derived and simulated. At a wavelength of 1550 nm, this method can theoretically improve the transmission efficiency to approach 100% under the situation in which the obscuration ratio is nonzero, and the transmission efficiency can reach more than 80% when obscuration ratio is in the range of from 0 to 0.1252 with $l=4$l=4. The effects of on-axial defocusing on the light field and the transmission efficiency are studied. The method proposed in this paper can remarkably improve the transmission efficiency of a Cassegrain antenna in a practical and uncomplicated approach.

Central energy loss is a critical factor decreasing the transmission efficiency of a Cassegrain antenna. In this paper, a pair of conic lenses are designed and set in front of a Cassegrain antenna to improve the transmission efficiency of the antenna instead of designing a complicated antenna structure. On the basis of the analysis, the optimized conic lens pair can theoretically improve the transmission efficiency up to 100% at a wavelength of 1550 nm under ideal conditions. After several practical factors are considered, such as the dispersion of the material, the transmissivity and chamfering of the conic lens, and the reflectivity of the mirrors composing the Cassegrain antenna, the conic lens pair can still increase the transmission efficiency of the Cassegrain antenna up to 92.37% at a wavelength of 1550 nm. Compared with designing a complicated antenna, the method proposed here provides a more practical approach to improve the transmission efficiency of a Cassegrain antenna.

We propose a novel annular focus antenna with an off-axial parabolic primary mirror and slanting hyperbolic secondary mirror. Ray tracing based on three-dimensional vector reflection theory is utilized to design and analyze the structural parameters of the antenna. In ideal conditions, there is no geometric loss in theory and the transmitting efficiency increases by 24.54% compared with the conventional Cassegrain optical antenna. The transmitting efficiency is also calculated in the conditions of off-axial and on-axial defocus. The simulated results demonstrate that this design can increase transmission efficiency of the optical antenna effectively.

An analytical model was developed to understand the rapid growth mechanism of intermetallic compounds (IMC) interlayer in high-power ultrasonic welding process. The analytic solution was derived for the relationships among welding time, interface temperature and vacancy concentration. The effectiveness of this model was tested by comparing the predicted thickness with the experimental value for high-power ultrasonic welding of copper and aluminium at various amplitudes. The consistency of the comparison demonstrates the accuracy of the model has been improved by considering the dynamic change process of vacancy concentration. Besides, the effects of vibration amplitude and resistance heat on the increasing of the intermetallic thickness have been investigated independently. The results show that the additional heat source could significantly promote the process of ultrasonic welding.

In this paper, an asymmetric large-mode-area photonic crystal fiber (LMA-PCF) with low bending loss at a smaller bending radius is designed. The finite-element method with a perfectly matched layer boundary is used to analyze the performance of the PCF. To achieve LMA-PCF with low bending loss, the air holes with double lattice constants and different sizes at the core are designed. Numerical results show that this structure can achieve low bending loss and LMA with a smaller bending radius at the wavelength of 1.55 μm. The effective mode area of the fundamental mode is larger than 1000  μm^2 when the bending radius is ≥10  cm. The bending loss of the fundamental mode is just 0.0113 dB/m, and the difference between the fundamental and high-order modes of the bending loss is larger than 10^3 when the bending radius is 10 cm. Simulation results show this novel PCF can achieve LMA and have effective single-mode operation when the bending orientation angle ranges in ±110°. This novel photonic crystal has potential application in high-power fiber lasers.

During the resistance spot welding quality control process, the traditional quality control methods can’t compensate all the affecting factors effectively. By welding 316LVM stainless steel wire to the surface of sheet of the same material, three kinds of process parameters, including electrode voltage, dynamic resistance and electrode displacement which affected by many affecting factors during the spot welding process were measured and analyzed. The results show that, by comparing with the process parameters during the normal situation, the dynamic change of the these process parameters during different stage appears distinguishable characteristics, these characteristics would supply a research basis for recognizing whether the affecting factors exist.

The cracking for the faucet valve made from HPb59-1 brass was investigated by SEM and EDS, metallographic microscope, optical spectrum. The results show that it was a kind of stress corrosion cracking caused by machining stress and corrosive environment (such as sulfur, chlorine etc).

The giant magnetostrictive material (GMM) is a novel smart material based on magnetostrictive effect, and it is well suited to power ultrasonic transducer. Based on electromagnetic theory and vibration theory, the design and working principle of the magnetostrictive power ultrasonic transducer has been explained. This paper analyzed the dynamic characteristics of giant magnetostrictive materials under the outside magnetic field and deduced the wave equation of Terfenol-D rod, and the steady-state solution to the equation was obtained under given excitation. The speed and acceleration expressions of Terfenol-D were deduced by differentiating with respect to displacement equation. Based on developing mathematical models, computer imitation was made, and the result of modulation was analyzed from external conditions of transducer and inner structure of magnetostrictive material.

The welded joints of copper (Cu) to aluminum (Al) were increasingly being used for electric vehicle battery applications. To better understanding the interface connection mechanism of the Cu/Al joints produced by high power ultrasonic welding (HUSW), the texture and intermetallic compound of Cu/Al HUSW joints were systematically investigated. The grain morphology and size of pure copper along welding interface had little change with the increasing welding time, whereas the microstructure of aluminum alloy changed from elongated grains to equiaxed grains and the grain size increased rapidly at the welding time from 0.3 s to 0.5 s. The texture intensity of both copper and aluminum alloy decreased at first owing to ultrasonic softening and then increased due to the shear work hardening. The texture type of the copper had little change, whereas the gaussian texture {110}〈110〉 and the cubic rotation texture{001}〈110〉 were formed in aluminum alloy owing to the occurrence of recrystallization driven by the severe shear deformation. The formation mechanism and accelerated growth behavior of intermetallic compound at the welding interface during HUSW were discussed based on the atom rapid diffusion and the effective thermal formation model.