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In coal mines, underground roadways are required to transport coal and personnel. Such tunnels can become unstable and hazardous. This study simulates deformation and damage in the rock surrounding a shallow coal seam roadway using particle flow code. A numerical model of particle flow in the surrounding rock was constructed based on field survey and drilling data. Microcharacteristic indices, including stress, displacement, and microcrack fields, were used to study deformation and damage characteristics and mechanisms in the surrounding rocks. The results show that the stress within the rock changed gradually from a vertical stress to a circumferential stress pattern. Stress release led to self-stabilizing diamond-shaped and X-shaped tensile stress distribution patterns after the excavation of the roadway. Cracking increased and eventually formed cut-through cracks as the concentrated stress transferred to greater depths at the sides, forming shear and triangular-shaped failure regions. Overall, the roof and floor were relatively stable, whereas the sidewalls gradually failed. These results provide a reference for the control of rock surrounding roadways in coal mines.

Since black silicon was discovered by coincidence, the special material was explored for many amazing material characteristics in optical, surface topography, and so on. Because of the material property, black silicon is applied in many spheres of a photodetector, photovoltaic cell, photo-electrocatalysis, antibacterial surfaces, and sensors. With the development of fabrication technology, black silicon has expanded in more and more applications and has become a research hotspot. Herein, this review systematically summarizes the fabricating method of black silicon, including nanosecond or femtosecond laser irradiation, metal-assisted chemical etching (MACE), reactive ion etching (RIE), wet chemical etching, electrochemical method, and plasma immersion ion implantation (PIII) methods. In addition, this review focuses on the progress in multiple black silicon applications in the past 10 years. Finally, the prospect of black silicon fabricating and various applications are outlined.

This paper presents a novel phase-shift arctangent (PSA) interpolation method to improve the measurement accuracy of a planar capacitive incremental displacement sensor. Signals of planar capacitive micro-sensors acquire waveform errors, including sensitivity differences and phase-shift errors, because of static errors and dynamic disturbances. In the proposed PSA scheme, such errors are removed completely by loading a particular arctangent function. Moreover, measuring efficiency of the proposed planar capacitive sensors is improved by combining coarse measurement and fine estimation. Experiments show unanimous results to model-based fitting. When electrode length is four times the gap distance, applying the PSA interpolation method decreases waveform errors from more than 4 % to 1.72 %.

Background: Several neoadjuvant treatments are available for patients with resectable gastroesophageal cancer. We did a Bayesian network meta-analysis (NMA) to compare available treatments, summarizing the direct and indirect evidence.Method: We searched relevant databases for randomized controlled trials of neoadjuvant treatments for resectable gastroesophageal cancer which compared two or more of the following treatments: surgery alone, perioperative docetaxel, oxaliplatin, leucovorin, and fluorouracil (FLOT), and neoadjuvant treatments listed in National Comprehensive Cancer Network guideline. Then we performed a NMA to summarize the direct and indirect evidence to estimate the relative efficacy for outcomes including overall survival (OS), progression-free survival and R0 resection rate. We calculated odds ratio (OR) and hazard ratio (HR) with 95% credible intervals (CrI) for dichotomous data and time-to-event data, respectively. We also calculated the surface under the cumulative ranking curve (SUCRA) value of each intervention to obtain a hierarchy of treatments.Result: Eight eligible trials (2434 patients) were included in our NMA. The treatment with the highest probability of benefit on OS as compared with surgery alone was perioperative FLOT [HR = 0.58 with 95% CrI: (0.43, 0.78), SUCRA = 93%], followed by preoperative radiotherapy, paclitaxel, and carboplatin (RT/PC) [HR = 0.68 with 95% CrI: (0.53, 0.87), SUCRA = 72%], perioperative cisplatin with fluorouracil (CF) [HR = 0.70 with 95% CrI: (0.51, 0.95), SUCRA = 68%], and perioperative epirubicin, cisplatin, and fluorouracil or capecitabine (ECF/ECX) [HR = 0.75 with 95% CrI: (0.60, 0.94), SUCRA = 56%].Conclusion: Compared with surgery alone, perioperative CF, perioperative ECF/ECX, perioperative FLOT, and preoperative RT/PC significantly improved survival. Perioperative FLOT is likely to be the most effective neoadjuvant treatment for the disease. Further clinical studies are needed and justified.

Guangdong has abundant kinds of rare earth element resources. The resource which could satisfy the industry exploitation is only the ion adsorption type of rare earth ores. According to previous survey, Guangdong possesses heavy rare earth element resource, which is about 1/3 of total ion adsorption type ore resource. Recently, there are only three companies owning mining rights (referred to as A, B, C mine quarry, respectively). Mining quota of REO (rare earth oxides) for 2013 was only 2200 tons, while Annual ionic rare earth separation capacity was more than 10000 tons. The contradiction between supply and demand is outstanding. In order to reveal the exploitation situation of the rare-earth ores in Guangdong, we collected samples from weathering crust profiles and tailings of A, B and C mining areas. Additionally, in order to study the geochemical characteristics and their resource potential, we analyzed the rare earth elements, trace elements and associated elements by ICP-MS. Our results show that: (1) Guangdong has quite rich resource in rare earth ore, and the resource we calculated is two more orders of magnitude than previous official calculation. (2) The LREEs/HREEs ratios from three weathering crust of rare earth ore areas all ranges from 1.8 to 6.6, implying these three ores are enriched in LREEs, rather than HREEs. However, only mining the LREE ore is incompatible with market demand and the enrichment of heavy rare earth resources in Guangdong. Furthermore, there is a great gap between the rare earth mining quota and smelting separation ability. Therefore, we suggest to raise more mining right licenses and quota for mining rare earth ore properly. (3) The rare earth content of the humus layer and semi-weathered layer was not high in A and C mining areas, which is surface magnetic type metallogenic model and mineralization zone was located in weathered layer. In contrast, the rare earth content of humic layer and completely weathered layer was high (more than 0.3%) in B mining area, which is shallow type metallogenic model. (4) We need to adjust the mining area of weathering crusts according to market demand to reduce the mining leakage and recycle tailings of rare earth resources. (5) The enrichment factors of trace element content in weathering crusts and tailings are less than 10, compared with continental crust abundance, even some elements are depleted. Accordingly, we suggest it is not useful for recycling the trace elements from weathering crusts and tailings.

As a basic building block in power systems, the three-phase voltage-source inverter (VSI) connects the distributed energy to the grid. For the inductor-capacitor-inductor (LCL)-filter three-phase VSI, according to different current sampling position and different reference frame, there mainly exist four control schemes. Different control schemes present different impedance characteristics in their corresponding determined frequency range. To analyze the existing resonance phenomena due to the variation of grid impedances, the sequence impedance models of LCL-type grid-connected three-phase inverters under different control schemes are presented using the harmonic linearization method. The impedance-based stability analysis approach is then applied to compare the relative stability issues due to the impedance differences at some frequencies and to choose the best control scheme and the better controller parameters regulating method for the LCL-type three-phase VSI. The simulation and experiments both validate the resonance analysis results.

This study is aimed to obtain fundamental data of transient heat transfer and clarify transient heat transfer process between the surface of solid and the neighboring helium gas in Very High Temperature Reactor (VHTR). Such studies are important for both of the academic knowledge on the complex transient phenomena and the safety assessment of severe nuclear reactor accidents such as power burst, rapid depressurization and withdraw of control rods. In this paper, a series of flat plates with different widths under different pressures inside a circular channel have been experimental tested and numerical analyzed for forced convection transient heat transfer for helium gas flowing over the plate. The heat generation rate of the plate was increased with a function of Q0exp(t/τ) (where t is time and τ is period of heat generation rate or e-fold time). The plates were made of platinum with a thickness of 0.1 mm and widths of 2 mm, 4 mm and 6 mm. Based on the experimental data and our previous research (Liu, et al. 2008a), we found that when the period τ is longer than around 1 second the heat transfer coefficients approach the quasi-steady-state values but when the period is shorter than around 1 second the heat transfer coefficients become higher as the period decreases. In this paper, we found that the conductive heat transfer becomes predominant for the period less than around 1 second and the heat transfer is mainly governed by convection heat transfer in the quasi-steady-state for the period larger than around 1 s. A semi-empirical correlation of surface temperature difference for plate heater was obtained based on the experimental data and analytic results. A 3-dimensional numerical simulation was carried out for the purpose of obtaining the plate temperature changes with time at various periods and velocities. The numerical solutions agree well with the experimental data within 6% differences.

Background . Single ventricle disease is treated by Glenn surgery. It is generally accompanied by stenosis on a pulmonary artery or its branches, which has great effect on hemodynamics. This study investigated the hemodynamic influence of different pulmonary stenosis degree in Glenn procedure. Materials . Four three-dimensional Glenn models with different left pulmonary artery stenosis rates as, respectively, 0% (model 1), 25% (model 2), 50% (model 3), and 75% (model 4) by the diameter were generated. Method . Geometric multiscale analysis method was used in the numerical simulations by coupling the lumped parameter model (LPM) and three-dimensional model. Results . During one cardiac cycle, the flow ratio between left pulmonary artery and superior vena cava was about 0.49 for models 1, 2, and 3, while the ratio decreased to 0.34 for model 4. On the other hand, hemodynamics parameters like power loss and oscillation shear index show complications of the stenosis to the postoperative development. Conclusion . When the stenosis rate is above 75%, it is suggested to treat stenosis before Glenn procedure, while when the stenosis rate is below 50%, there is no necessity to pay attention to it due to the little effect it makes.