Search

Purpose This study aimed to evaluate the clinical value of the fractional flow reserve derived from coronary computed tomography angiography (CT-FFR) and fat attenuation index (FAI) in predicting coronary revascularization. Methods Patients with known or suspected CAD who underwent coronary computed tomography angiography (CCTA) and subsequent invasive coronary angiography were screened. All CCTA data were calculated by a cloud workstation in standard Digital Imaging and Communications in Medicine format. Lesion-specific CT-FFR, distal-tip CT-FFR, and FAI were analyzed by core laboratories blinded to patient management. Results A total of 94 patients who received CCTA followed by invasive coronary angiography were identified and analyzed; 282 vessels were included for analysis. Overall, 54 (57.4%) patients with 72(25.5%) vessels demonstrated revascularization. In the multivariate model, FAI (odds ratio [OR]: 1.19; p

Femtosecond laser pump-probe method is a useful tool to study the transient reflection phenomenon on metal films. Using double pump beams in femtosecond laser pump-probe system can both increase the electron non-equilibrium heat transport time and degrade the noise by adjust the experimental optical path. In this paper, the transient non-equilibrium heat transport processes of the copper-silver alloy films were studied by using femtosecond laser pump-probe method of double pump beams. The electron-lattice interactions were analysed and the electron non-equilibrium heat transport time was measured. The transient reflection phenomenons on copper-silver alloy films with the diverse film thickness were different, and the non-equilibrium heat transport time was inversely proportional to the film thickness. Two sudden changes which ascend abruptly appeared in the transient reflection signals, that is, twice electron non-equilibrium heat transport occurred in the copper-silver alloy films. With this method, the non-equilibrium heat transport time can be extend more than two times, which is expected to reduce the influence of thermal barrier and improve production efficiency.

High drainage roadway horizon parameters not only influence goaf drainage effect, but also have effect on the air leakage field and spontaneous combustion three zones’ distribution in the goaf. Combined with mine fire-prevention and goaf spontaneous combustion three zones recognition, it was put forward to stimulate the distribution law of goaf air leakage field and spontaneous combustion three zones with fluid mechanics software FLUENT. The results showed that the width of goaf oxidization and heat accumulation zone increased with high drainage roadway vertically. Through stimulation study, it supplies a certain method to reasonablely optimizatate high drainage roadway vertical parameters, which to a great extent ensures mine safety production, fire and gas prevention.

Surface soil moisture (SSM) is one of the key parameters in the study of global climate change, water, and energy exchanges at both the land surface and atmospheric interface and drought and acidif...

To investigate the application value of spectral computed tomography (CT)quantitative parameters for preoperative diagnosis of metastatic lymph nodes in patients with non-small cell lung cancer (NSLC).84 patients with suspected lung cancer who underwent chest dual-phase enhanced scan with gemstone spectral CT imaging (GSI) mode were selected. GSI quantitative parameters including normalized iodine concentrations (NIC), water concentration, slope of the spectral Hounsfield unit curve (λHU) were measured. The two-sample t test was used to statistically compare these quantitative parameters. Receiver operating characteristic (ROC) curves were drawn to establish the optimal threshold values.A total of 144 lymph nodes were included, with 48 metastatic lymph nodes and 96 non-metastatic lymph nodes. The slope of the spectral Hounsfeld unit curve (λHU) measured during both arterial and venous phases were signifcantly higher in metastatic than in benign lymph nodes (P0.05). The area under the ROC curve (AUC=0.951) of λHU of the arterial phase (AP) was the largest. When the optimal threshold values of λHU was 2.75, the sensitivity, specificity, and overall accuracy in the diagnosis of metastatic lymph nodes were 88.2%, 88.4%, 87.0%, respectively.Conventional CT diagnostic criteria established in accordance with size (lymph node maximal short axis diameter ≥10mm) as the basis for judging metastatic lymph node. In quantitative assessment using spectral CT imaging, quantitative parameters showed higher accuracy than qualitative assessment of conventional CT based on the size for preoperative diagnosis of metastatic lymph nodes.

In order to protect the power electronic equipment and make the output current amplitude of distributed generation (DG) maintain a stable value for different short-circuit faults, this paper proposed a current-limiting strategy based on proportional-resonant controller (PR), filtering inductance reference current (FIRC), and shunt active power filter (APF) for droop controlled microgrid. First, the relationship is discussed in detail among the output current of DG, the output voltage of DG and FIRC, theoretical derivation demonstrates that the error between output current of DG and FIRC can be decreased through adjusting the value of PR parameters, filtering capacitance and the compensation current obtained by APF. Moreover, some advantages of proposed strategy for microgrid protection are discussed. Then, when the fault is detected, the current-limiting strategy is implemented by setting the FIRC value. Finally, the experiments prove that the proposed strategy can precisely limit the maximum phase current to the given value which cannot be influenced by the short-circuit fault type, grounding resistance, fault initial phase, non-linear load, and so on.

After the mechanization upgrade of Yongjing Coal Mine, the original extraction method cannot solve the problem of gas. According to the actual production conditions of the mine, the source and composition ratio of gas emission are analyzed.By combining with the gas extraction method before upgrading and transformation, it is of great importance to determine the appropriate comprehensive gas extraction method and optimize the gas extraction parameters for improving the gas extraction effect and eliminating the risk of gas outburst.

In order to solve the problem of gas overrun during the mining of large mining height working face in high process mine, based on the gas emission prediction, the source and composition of gas emission are analyzed, gas extraction method of combining the grossmeasures boreholes with borehole along the seam are put forwarded, the reasonable arrangement of the gas extraction parameter are designed, comprehensive control of gas in working face, heading face and goaf was carried out, and the new scheme of high concentration gas and low concentration gas clean utilization is proposed. It has been proved by practice that the coal and gas co-mining and clean utilization scheme of ‘gas pre-extraction + gas civil-oriented + gas power generation + waste heat utilization’ is of great significance to ensure coal mine safety production and environmental protection.

BACKGROUND The aim of this study was to evaluate the accuracy of transluminal attenuation gradient (TAG) in diagnosing the stenosis degree of difficult lesions to accurately assess the degree of luminal stenosis using coronary computed tomography angiography (CCTA). METHODS A total of 130 patients consecutively received CCTA and coronary angiography (CAG). The average transluminal Hounsfield units (HU) of the regions of interest were consecutively measured at an interval of 5 mm from the ostium to the distal level, followed by the calculation of TAG. The diagnostic performance of CCTA, TAG and CCTA+TAG for the stenosis degree of coronary calcified lesions and their reclassification for stenosis degree were analyzed, especially for calcified lesions. RESULTS Compared with CAG, the TAG in CCTA was consistent with the largest stenosis degree of each blood vessel. TAG improved the accuracy of CCTA in the diagnosis of calcified lesions (P

The statistics and analysis of mine gas extraction is very important for mine gas control, which provides a basis for the formulation of mine gas extraction plan. Because of its simple and convenient characteristics, it is favored by the engineering and technical personnel in the coal mine field, and has been widely used, and achieved good results. Based on the statistics of gas drainage in Weijiadi Coal Mine from 2008 to 2018, the characteristics and quantity of gas emission are analyzed according to the statistical results of gas drainage in Weijiadi Coal Mine, and the characteristics of gas emission in the process of driving in the main mining seam are predicted, and the mathematics relations of the length of driving roadway and the quantity of gas emission is obtained.

In view of the coupling problem of gas and coal spontaneous combustion in goaf of 2302 coal mining face in Weijiadi Coal Mine in Jingyuan Coal Area, if the control is not in place, it may cause serious accidents such as gas explosion. By means of fluent simulation, the spontaneous combustion period and oxygen distribution of residual coal in goaf are obtained, and the minimum advancing speed of coal mining face to prevent spontaneous combustion in goaf is calculated to be 1.43m/d. By implementing fire prevention measures such as blocking air leakage in upper and lower corners, grouting and nitrogen injection in goaf, the oxygen concentration in goaf is controlled within 11%, and the spontaneous combustion zone of oxidation is fast. Transferring to asphyxiation zone and preventing the residual coal from firing in goaf are of great significance for ensuring the safety of mine production.

Taking 1302 fully mechanized caving face of Weijiadi Coal Mine as the research object, aiming at the characteristics of large gas emission and frequent gas exceeding limit during mining, this paper analyzed the difficult problems of gas control in working face, determined the theoretical height of caving zone and fissure zone of working face according to the gas cascade control mode formulated by Weijiadi Coal Mine and the principle of pressure relief gas, and inspected the “three zones”. The reasonable horizon and arrangement of drilling holes along the strike of large diameter and high position rocks are determined. The field practice results show that the gas extraction technology of large diameter and high rock trending borehole has good extraction effect, the maximum gas concentration is 26.5% and the maximum gas extraction volume is 14000 m3. It effectively solves the problem of return air flow and upper corner gas exceeding the limit. The gas concentration of return air flow is basically kept at 0.2%∼0.25%, which ensures the safety of mine production.

China is rich in coal resources, especially in Northwest China. However, due to the complex geological conditions, some low permeability and high gas seams often accompany abnormal gas emission during mining, which poses a serious threat to the safety of coal mine. This paper takes East 102 working face of Weijiadi Coal Mine in Jingyuan mining area of Gansu Province as the research object. Aiming at the abnormal gas emission phenomenon during the initial discharge period of working face, the causes of abnormal gas emission are analyzed. The prevention of abnormal gas emission should be carried out from five aspects: strengthening ventilation management, perfecting gas extraction system, perfecting safety monitoring and control system, strengthening power supply management and emergency management on site.

The division of gas geological units in coal mine is the basis of studying the occurrence law of gas geology in coal mine field, which is of great significance to the prediction of regional gas content and gas emission. Taking Weijiadi coalfield in Jingyuan mining area of Gansu Province as an object, this paper divides the coalfield into gas geological units, according to the gas content of coal seams in different regions, targeted gas extraction measures are implemented, gas cascade control is implemented, regional gas abnormal emission is strictly prevented, and mine safety production is ensured.

Abnormal gas emission is a common gas phenomenon in coal mining face of gas mine. In order to prevent gas accidents, on the one hand, gas extraction measures are adopted to reduce or avoid abnormal gas emission; on the other hand, when abnormal gas emission is unavoidable, in order to prevent abnormal gas emission from occurring gas explosion accident by electric spark, non-cost cutting is adopted. Emergency measures such as power supply for quality and safety electrical equipment are taken as the second line of defense. Aiming at the abnormal gas emission phenomenon in East 102 coal face of Weijiadi Coal Mine, in order to avoid the gas explosion accident during the abnormal gas gushing period, the emergency measures for gas abnormal emission were expounded from the aspects of gas electric blockade, power cut and evacuation.

At present, 53% of reserves buried under 1 kilometers in China and the amount of green coal resources is less than 500 billion tons. Ningzheng Mining Area is a newly developed large-scale coal mining area in Western China, and is the main succession area of coal resources in Gansu Province in the future. The coal seams are generally buried more than 1 kilometres. Taking the newly built mines in Ningzheng Mining Area as an example, this paper carried out a geological analysis of thermal environment and analysis of the main influencing factors of thermal hazards, established the model of mine production system, and explored several comprehensive utilization technologies of thermal hazards such as HEMS (High Temperature Exchange Machinery System) cooling technology model and gas, the cooling modes of power generation combined heat, power and cooling system and the artificial ice-making. The cooling technology can effectively guide the development of new mines in Western China in mines and the efficient utilization of resources.

Emergency command system is the hub of dealing with emergencies, which is of great significance to emergency rescue. In order to establish a more perfect emergency command system, considering the characteristics of strong subjectivity and large error in qualitative evaluation of information security system, based on AHP (Analytic Hierarchy Process) and Fuzzy (Fuzzy Analysis) evaluation method, this paper uses AHP-Fuzzy comprehensive evaluation model to quantitatively evaluate the information security of emergency command system of a hazardous chemical production enterprise in Qingyang, and calculates the risk. The validity of the discriminant model is verified.

Chemical plants usually store hazardous chemicals in high-pressure or low-pressure storage tanks in the form of pressurization, liquefaction, and low temperature. The poisonous gas in the tank is easily diffused. If a leakage accident occurs, it will cause personal injury and environmental pollution. In this paper, based on the propane acrylonitrile project in an industrial park, Major hazard identifications were identified for the tank area (risk level is Level 1), then PHAST software was used to simulate the leakage and diffusion of acrylonitrile storage tanks. It was concluded that the greater the wind speed, the leakage pore and the more stable atmosphere, the greater the leakage and diffusion of hazardous areas. And timely and intuitive prediction of the diffusion process and scope of toxic gases provide a scientific reference for taking corresponding countermeasures and on-site control after the accident.

Coal seam waterflooding hydraulic wetting has been widely used in coal mines, and plays an increasingly important role in coal and gas outburst prevention, dust prevention, and rock burst prevention. In order to explore the mechanism of coal and gas outburst prevention and control by hydraulic wetting, this paper analyses the three stages of hydraulic wetting through Gibbs function: wetting, soaking and spreading; explains the solution of the three stages through Young's equation, and finally discusses the release and stress of coal gas potential caused by water movement in coal. The centralized influence provides a theoretical basis for the application of coal and gas outburst prevention and control technology in mines.

In Weijiadi Coal Mine, the No.2 coal seam is uncovered by the Donger return air shaft. According to the concept of “regional measures first, local measures supplement”, the measures are taken strictly in the outburst seam, the gas pressure P=0.2MPa and the gas content W=1.4729m3/t in the coal seam are determined by preconstruction prediction drilling, and there are no gas dynamic phenomena such as drilling jam and sticking in the drilling process. It is proved that there is no outburst danger, and then it is implemented according to the local “four in one” outburst prevention measures. The maximum gas pressure determined is 0.2 MPa in the working face, and the validity check is still no outburst danger. Finally, safety protection devices are installed in the working face to ensure the No.2 coal seam to be uncovered smoothly by return air shaft.

Hazardous chemical leakage accidents occur frequently, and once it appears, it will create a great effect. If a more accurate risk assessment impact area can be made in advance, the preventions and controls will play an invaluable role. A propylene storage tank in an industrial park was taken to identify the lying accidents and the risk ranks with the method of Preliminary Risk Analysis. It was found that the propylene poisoning accident and the steam cloud explosion accident have a great threat to the surrounding. With the inputs of relevant parameters, ALOHA software was used to simulate each accident, and the propylene poisoning accident and the vapour cloud explosion accident threat areas were obtained. The simulation provides effective information for the prevention and control of leakage accidents in the propylene storage tank leaking, and provides a scientific guideline for its ordinary safety management.

The analysis found that the coal mining process in the western mining area has the mining loss and disaster effect of the water-rich aquifer of the coal seam roof, which is mainly manifested by the overburden water in the roof. On this basis, the formation and development of the separation water of the roof is proposed, and the mechanism of the water inrush from the layer is revealed. It is found that there is hydrostatic pressure and hydrodynamic pressure in the separated water, under the combined action of bed separation water pressure, the mining-induced fracture and water-isolation layer tension fracture are connected, which causes water inrushing in the coal working face of the mine, and provides a theoretical guarantee for the large-scale development of coal resources in western mining areas.

In view of the frequent occurrence of roof collapse and chipping accidents in the broken surrounding rock roadway in the goaf, grouting reinforcement is applied to the surrounding rock of the ro ent ratio. The field test proves that the selected grouting parameters are reasonable and achieve the purpose of controlling the deformation of the surrounding rock of the roadway.

A evaluation system was constructed and each weight of the indexes was calculated based on the principle of AHP (Analytic Hierarchy Process), which were benefit of safety and sustainable development of chemical enterprise, emergency response capacity, accidents numbers and property losses The results show that emergency prevention capability and emergency preparedness capability are the key elements in the first-level indicator system. The plan initiation, drill, hazard source control and monitoring and early warning, emergency command, coordination and rapid response capability are the key elements in the secondary indicators.

Stratigraphic sequence contrast and sequence stratigraphic framework are of great significance for the sedimentary phase and sedimentary systems of coal-accumulating basin. In the coal-bearing basin, the variation of the flooding surface controls the migration law of the coal-concentrating centres within the range. Therefore, the sequence comparison work is crucial to find favorable coal-collecting areas. In addition, studying the position of the coal seam in the sequence stratigraphic framework and carrying out the sequence comparison work in the lateral direction can effectively track the change of the position of the coal seam in the sequence stratum and summarize the law of coal seam accumulation and occurrence, which can be better to plan and guide the exploration and development of coal resources in Longdong coalfield.

A new series of zinc(II) phthalocyanine derivatives have been synthesized and characterized. These macrocycles exhibited a sharp absorption band in the red visible region in DMF, which indicated that they were dissolved well and almost did not aggregate in this solvent. Compared with the unsubstituted zinc(II) phthalocyanine, all these phthalocyanines have a red-shifted Q-band (at 678-699 vs 670 nm) and exhibit a relatively weaker fluorescence emission and a higher efficiency at generating singlet oxygen. The monosubstituted photosensitizers also exhibit high photocytotoxicity toward HepG2 human hepatocarcinoma cells with IC50 values as low as 0.02-0.05 μM (λ = 670 nm, 80 mW·cm(-2), 1.5 J·cm(-2)). The high photodynamic activities of these compounds are in accordance with their low aggregation tendency and high cellular uptake. Their structure-activity relationship was assessed by determining the photophysical properties, cellular uptake, and in vitro photodynamic activities of this series of compounds. As shown by confocal microscopy, monosubstituted phthalocyanines can target the mitochondria and lysosomes of the cells, and tetrasubstituted phthalocyanines tend to target the lysosomes of the cells.

This paper investigates data processing approaches to detect and locate ground moving targets using distributed spaceborne SAR systems with long cross-track baselines. In particular, it investigates the performance of ground moving target detection for two typical satellite formations: Cartwheel and Pendulum. An approach based on SAR images and a space-time adaptive processing (STAP) algorithm is proposed in order to overcome the effects of the ground terrain on the clutter suppression. The key idea of the approach is firstly to reduce the clutter degrees of freedom greatly by using conventional SAR imaging processing. Then the ground terrain clutter within each SAR pixel can be effectively cancelled by using the very limited spatial degrees of freedom. Finally, constant-false-alarm-rate (CFAR) techniques can be used to detect the remaining target SAR pixels after clutter cancellation. An approach to relocate the detected targets is also proposed, which is based on the estimation of the Doppler spectrum shifts of ground moving targets relative to the clutter Doppler spectrum. The proposed approaches in this paper have the advantages of simplicity and high efficiency.