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Nuclear magnetic resonance (NMR) technology can directly detect hydrogen signals in hydrogen-containing fluids, such as water and hydrocarbon. It can provide quantitative characterization of the fluid content and surrounding environment, thus finding extensive application in oil and gas exploration field. However, when measured samples containing ultra-fast relaxation components, such as shale oil and gas, the reliability of measurement results tends to be very low because only a small number of front-end signals in Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence can be obtained for the fast relaxation components. To address this problem, a multiple micro echo interval measurement (MCTEM) method was proposed in this research. In the measurement stage, the proposed method acquired more NMR front-end signals. In the inversion stage, multiple echo data were adopted for the joint inversion. It contributed to forming an accurate fast relaxation T2 spectrum. MCTEM method was validated through numerical simulations and rock physics experiments. It was concluded from the results that MCTEM method could improve the problem of peak disappearance for fast relaxation components in T2 spectrum caused by long echo interval. MCTEM method could enhance the measurement accuracy of fast relaxation signals effectively.

In order to improve the reliability of two-dimensional nuclear magnetic resonance (2D NMR) measurement in shale oil reservoirs, the T2-T1 2D NMR response characteristics and influencing factors of shale oil reservoirs were analyzed in three scenarios: laboratory core analysis, wellsite mobile full-diameter core scanning and logging. For different application scenarios, the optimization method of T2-T1 NMR measurement parameters for shale oil reservoirs were proposed. Laboratory core measurements require attention to the choice of echo interval time (TE) and number of echo groups, in addition to the different magnetic field strengths and measurement sequences. When scanning full-diameter cores at the well site, it is necessary to focus on TE and minimum waiting time (Tw). To ensure the convergence in T1 dimension of quickly relaxed component, the minimum Tw should be set to at least 1 ms. NMR logging is limited by the acquisition conditions. It is necessary to focus on the distribution range and smoothing factor in data processing to interpret and modify data with different signal-to-noise ratios. A poor shale oil reservoir with NMR porosity less than 5% is difficult to ensure the accuracy of NMR results for its low signal-to-noise ratio. The systematic analysis of T2-T1 2D NMR measurement parameters provides a reference for the optimization of 2D NMR detection methods for shale oil reservoirs, which helps to improve the accuracy of NMR measurements and obtain more reliable reservoir information.

Multi Core Fiber (MCF) is an important transmission medium of Space Division Multiplexing (SDM) technology, which can significantly enhance the communication capacity of existing optical fiber. However, MCF has the problems of high structural complexity, difficult to test, and no test standard for parameters. According to the structural characteristics, combined with the technical experience in the development, this paper standardize the splicing method and the parameters testing method of MCF, which lays the foundation for the large-scale commercialization of MCF in the future.

At present, resonance demodulation and data envelopment analysis, etc are usually used for health evaluation and remaining life prediction of bearings, but there are some problems such as difficulty in extracting health degree, single fault prediction type, and lack of reliable models. Aiming at these deficiencies, this paper proposes a method which realizes bearing health assessment and remaining life prediction through two-stage cascaded long short term memory neural network. In this paper, the bearing data set of Xi'an Jiaotong University is used for experimental comparison. The results show that, compared with the resonance demodulation method, the monotonicity, robustness and trend of the health degree curve are comprehensive in the health degree evaluation of single fault data using this method. The evaluation indicators increase by 12%, 24.8% and 5% respectively, and the comprehensive evaluation index in the composite fault data increases by 15.1%, and the remaining service life can be predicted according to the health evaluation curve, which proves that the method is effective in health evaluation and remaining life.

In order to study the effect of echo time (TE) on nuclear magnetic resonance (NMR) porosity in tight oil (gas) and shale reservoir, multi-TE NMR experiments and NMR numerical simulations were performed on CuSO4 solutions with specific transversal relaxation time (T2). The results showed that the normalization NMR porosity of different T2 relaxation components remained 100% in the low TE region, and rapidly decreased with increasing TE. When TE was greater than certain value, the normalization NMR porosity dropped to zero. However, the TE value at which the normalization NMR porosity began to decrease and the TE value at which the normalization NMR porosity dropped to zero were different for different NMR relaxation component. Moreover, the whole NMR measurement was divided into lossless zone, fast decay zone, invalid parameter zone and instrument blind zone, based on the relationships between the normalization NMR porosity of different relaxation component and TE. For each specific relaxation component, a logarithmic relationship was demonstrated between the loss of relaxation component and TE in the fast decay zone. A method for NMR porosity correction was given.

Microporosity in the body and platform of the three different compositions complex nickel-based single crystal castings solidified by high rate solidification (HRS) process was investigated by the X-ray tomography (XRT). The results show that the solidification range and the dendrite tortuosity have a strong effect on the formation of microporosity. In the body of the casting, the arrangement mode of dendrites among three different compositions castings is the same. Due to the largest solidification range of the first generation single crystal SX1, its porosity volume fraction is the largest. The difference of solidification range in the second generation single crystal SX2 and the third generation single crystal SX3 is not obvious, thus, their porosity volume fraction is mostly influenced by the eutectic volume fraction. With the increase of single crystal generation, the level of refractory elements will be increased, also the eutectic fraction of the body increases. Therefore, the size of interdendritic zone in the final solidification stage is increased, and the pressure drop in liquid phase is reduced, leading to the decrease of porosity volume fraction. The porosity in the platform is mostly decided by the dendrite tortuosity compared with that in the body. In the platform of the first generation single crystal SX1, there is no obvious difference in the dendrite tortuosity, thus, the volume fraction of porosity is similar to that in the body. Due to the larger dendrite tortuosity in the second generation single crystal SX2 and the third generation single crystal SX3, the corresponding porosity volume fraction is increased.

Two-dimensional (2D) NMR logging activation sets are acquisition means aiming at obtaining specific formation information, affecting the adaptability of NMR instruments to different types of reservoirs and the reliability of the original data. In this work, a software with the visualization function for designing 2D NMR logging activation sets was developed using the C# language, based on the component elements and working mechanism of activation. The software supported the design of activation sets for 2D NMR logging and NMR core analyzer. Meanwhile, the software provided three kinds of parameter editing methods, observation mode optimization and graphical display functions, and thus realized flexible adjustment of the activation sets. It solved the problems in the former mainstream 2D NMR logging activation sets, such as low signal-to-noise ratio of the raw data, incomplete loading of fluid relaxation characteristics due to inadequately fixed acquisition parameters and inflexible adjustment etc. In addition, the software also provided outputs for acquisition parameters and acquisition timing.

Microporosity in the body and platform of the three different compositions complex nickel-based single crystal castings solidified by high rate solidification (HRS) process was investigated by the X-ray tomography (XRT). The results show that the solidification range and the dendrite tortuosity have a strong effect on the formation of microporosity. In the body of the casting, the arrangement mode of dendrites among three different compositions castings is the same. Due to the largest solidification range of the first generation single crystal SX1, its porosity volume fraction is the largest. The difference of solidification range in the second generation single crystal SX2 and the third generation single crystal SX3 is not obvious, thus, their porosity volume fraction is mostly influenced by the eutectic volume fraction. With the increase of single crystal generation, the level of refractory elements will be increased, also the eutectic fraction of the body increases. Therefore, the size of interdendritic zone in the final solidification stage is increased, and the pressure drop in liquid phase is reduced, leading to the decrease of porosity volume fraction. The porosity in the platform is mostly decided by the dendrite tortuosity compared with that in the body. In the platform of the first generation single crystal SX1, there is no obvious difference in the dendrite tortuosity, thus, the volume fraction of porosity is similar to that in the body. Due to the larger dendrite tortuosity in the second generation single crystal SX2 and the third generation single crystal SX3, the corresponding porosity volume fraction is increased.

The effect of different process parameters on solidification of industrial gas turbine hollow blades via HRS (High Rate Solidification) and LMC (Liquid Metal Cooling) was studied by ProCAST software. The results show that the paste zone via LMC process is much narrower than that by HRS process and the shape of the S/L (solid/liquid) interface is more flat. The axial thermal gradient of the blade by LMC process is about three times higher than that by HRS process. The cooling rate of the blade is 0.3-2.00℃/s by LMC process, which is far higher than that by HRS process (0.05-0.16℃/s). In LMC process, low holding temperature can still ensure high temperature gradient and cooling rate of the blade; while in order to avoid blocking of stray grains to the initial grains at the platform of the blade, HRS process should adopt high holding temperature and lower withdrawal rate. The calculated and the measured results show that compared with the blade prepared by HRS process, the PDAS (primary dendrite arm spacing) is much finer in the blade prepared by LMC process.

Objective A titanium personalized orthodontic bracket is designed and manufactured using the technol⁃ ogy of computed tomography (CT), computer aided design (CAD), finite element analysis (FEA), and selective laser melt⁃ ing (SLM) to well match the patient tooth so as to realize mold ⁃free manufacturing. Methods A model of a titanium personalized orthodontic bracket which is built by CT scanning machine and Pro/E software, is imported into Ansys soft⁃ ware to carry out finite element simulation analysis with nonlinear contact method. Then, the titanium personalized orth⁃ odontic bracket is proposed after the model data above is imported to SLM molding equipment via titanium powder melt⁃ ed with layer by layer using a high⁃speed scanning galvanometer. Results The maximum equivalent stress of the titani⁃ um personalized orthodontic bracket is distributed uniformly and reasonably, the titanium personalized orthodontic bracket formed by SLM molding equipment can provide high accuracy and there is a high similarity between the bottom of the orthodontic bracket and the tooth surface shape. Conclusion The combination of CT, CAD, FEA, SLM technolo⁃ gy can fulfill model⁃free manufacturing of the personalized orthodontic bracket and thus shorten the manufacturing cycle.

The rock mechanism under frozen condition has played down the significance on the design of frozen wall thickness and section height of the ultra-deep shaft in Western of China.This paper investigated the particle size and voids distribution principles using magnified image technique, which is on the typical medium size sandstone within the deep water-rich stratum during a coal mining construction with artificial freezing skill in Ordos of China.The frozen medium size sandstone have been studied with triaxial compression test under the temperature of-5℃,-10℃,-15℃, and Brazilian Split test at 26℃,-10℃ and-20℃.The test results indicated that the compressive strength improved linearly up to maximum of 27.29%when temperature dropped down, and this effect was weakened with the increase of the confining pressure.So did the internal frictional angle and cohesion, which ended up with the biggest rise of 12.54%and 18.69%.The tensile strength jumped from 0.73 MPa at 26℃ up to 1.59 MPa at-10℃, as of 118.18%extra, followed with declining when the temperature reduced more.The strength property of medium sandstones have been further improved with only cer-tain extent during lowering the temperature, therefore the design criteria of frozen wall thickness should rather be governed by the purpose of sealing water than over cooling control.

A new method is proposed to evaluate the process parameters by the solid-liquid interface position, thermal gradient angle and the axial thermal gradient. The effects of the process parameters on the solid-liquid interface position, thermal gradient angle and the axial thermal gradient were simulated by ProCAST using LMC(Liquid Metal Cooling) and HRS(High Rate Solidification) processes. The results show that HRS process is little affected by the mold thickness, the dominant heat transfer factor in HRS is radiation from the mold surface, and the dominant heat transfer factor in LMC either mold thermal conductivity or mold-metal interface heat transfer; increasing furnace temperature is beneficial to increase the axial thermal gradient; the withdrawal rate is the most important process parameter which significantly affects the thermal field during solidification, as the withdrawal rate increases, the axial thermal gradient first increases and then decreases, therefore, it is necessary to apply different withdrawal rates for different alloys. After holding 10min at different pouring temperatures, a uniform temperature is achieved, and it has slight influence on the subsequent solidification. It has been put forward that the solid-liquid interface position, thermal gradient angle and the axial thermal gradient can be utilized as a serial of efficient analysis standards for optimization of process conditions independent of casting geometry.

The complex reconstructed structure of materials can be revealed by global optimization. This paper describes a hybrid evolutionary algorithm (HEA) that combines differential evolution and genetic algorithms with a multi-tribe framework. An on-the-fly machine learning calculator is adopted to expedite the identification of low-lying structures. With a superior performance to other well-established methods, we further demonstrate its efficacy by optimizing the complex oxidized surface of Pt/Pd/Cu with different facets under (4 × 4) periodicity. The obtained structures are consistent with experimental results and are energetically lower than the previously presented model.

The grain boundaries (GBs) in copper (Cu) electrocatalysts have been suggested as active sites for CO2 electroreduction to ethanol. Nevertheless, the mechanisms are still elusive. Herein, we describe how GBs tune the activity and selectivity for ethanol on two representative Cu-GB models, namely Cu∑3/(111) GB and Cu∑5/(100) GB, using joint first-principles calculations and experiments. The unique geometric structures on the GBs facilitate the adsorption of bidentate intermediates, *COOH and *CHO, which are crucial for CO2 activation and CO protonation. The decreased CO-CHO coupling barriers on the GBs can be rationalized via kinetics analysis. Furthermore, when introducing GBs into Cu (100), the product is selectively switched from ethylene to ethanol, due to the stabilization effect for *CH3CHO and inapposite geometric structure for *O adsorption, which are validated by experimental trends. An overall 12.5 A current and a single-pass conversion of 5.18% for ethanol can be achieved over the synthesized Cu-GB catalyst by scaling up the electrode into a 25 cm2 membrane electrode assembly system.

This paper illustrates the full use of an orthogonal decoupling signal model to describe the 3-D construction of polarized electromagnetic waves. The maximum likelihood method and MUSIC algorithm were introduced into the parameter estimation of partially polarized waves. Attitude reference information for an aircraft that was calibrated by an information base station was delivered by polarized electromagnetic waves. Through receiving and processing the information of the aircraft, a single electromagnetic vector sensor can acquire the aircraft attitude in a geographic coordinate system. Differing from the triangle calculation method which relies on a multi-point measurement, the proposed method only needs a base station signal and a single receiver on the motion platform to realize the posture perception of aircraft. It can therefore serve as a substitute for aircraft attitude navigation and aircraft heading navigation. The introduction of the motion platform attitude estimation algorithm provides a technology support for engineering applications.

How to obtain high-resolution images of ship targets is an active research area in radar field due to the complexity of the ship motion. At the same time, multi-platform based surveillance and combat mode is gaining more and more interests in recent years. Based on the above situation, in this paper, a multistatic Inverse Synthetic Aperture Radar (ISAR) ship imaging method is presented, the method is capable of increasing the integration time for stationary imaging by deploying the multiple platforms with appropriate altitudes and aspect angles and coherently integrating the echoes received by each platform. Combined with the optimal imaging time selection scheme, this method can obtain side-view or top-view ship images with higher-resolution as compared to the monostatic radar. Simulations are performed to verify the effectiveness of our multistatic ISAR ship imaging method.