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The presence of underlying mined-out layer and developed joints have an important impact on the fragmentation process of landslide collapse. In order to further explore the cutting and fragmentation effects and characteristics of joints on rock masses, based on UAV aerial photography and field investigations of debris flows in the Madaling landslide, the particle discrete element method was used to simulate the flow force crushing process of landslide debris with joints in the underlying layer. Changes in the quantity and particle size distribution of fragmented bodies were analyzed. The conclusions are as follows: 1. The development process of debris flow in the Madaling landslide can be summarized as the following: trailing edge tension fracture, stepped creeping tension fracture, shear deformation, slip surface connection, and overall failure of the sliding mass. The collapse of joints and underlying layer promotes the failure and fragmentation process of the sliding mass; 2. Fragmentation occurs during both the failure and movement deposition processes of the sliding mass, with fragmentation dominating during movement deposition; 3. Results fitted with the Weibull dual-parameter model show continuous increase in fine particle fragmentation within the sliding body, ultimately resulting in predominantly medium to small particle size fragmentation in the deposited mass, demonstrating the phenomenon of fragmentation and disintegration during the movement and deposition of the sliding body. This study provides new insights for the analysis of the fracture mechanism of the landslide debris flow with joints in such underlying layer, and proves that the effect of the caving and joint cutting of the underlying layer on the rock mass fracture has a certain guiding significance for the prevention and control of landslide debris flow disasters in areas with similar geological conditions. [ABSTRACT FROM AUTHOR]

In recent years, rock avalanche disasters have been occurring frequently in southwest China, which seriously affect the regional ecological environment and human activities. To understand the fragmentation characteristics of the avalanche masses during their movement, this study is based on the field investigation of the rock avalanche in Zongling Town, Nayong County. The dynamic fragmentation process of the rock avalanche during the failure and accumulation stages was simulated using the particle discrete element method. Additionally, the distribution characteristics of the maximum feret's diameter of the fragments within the rock avalanche mass were statistically analyzed. The results show that: (1) Under the effect of gravity, the internal structural joints of the rock avalanche rapidly interconnected, dividing the avalanche mass into numerous fragmented blocks that eventually slid along the down-dip joint surfaces. (2) The collapse exhibited significant fragmentation phenomena in the entire movement process, with extensive disintegration during the initial failure and friction-induced tearing and cracking fragmentation during the accumulation stage. (3) The feret's diameter distribution curves of the fragments at different time intervals were fitted using Weibull two-parameter distribution model and fractal geometry theory. The results showed that the fragmentation degree of the avalanche during the accumulation stage (t = 21.7 to 72.4 s) was weaker than that during the initial failure stage (t = 0 to 21.7 s). The fractal dimension of the fragments and the proportion of fine-grained fragments continuously increased throughout the entire movement process, once again confirming the fragmentation and disintegration phenomena during the entire process of failure and accumulation. The research findings provide a theoretical basis for revealing the dynamic fragmentation mechanism of the Zongling rock avalanche, and provide scientific guidance for the prevention and control of rock avalanche disasters in the mountainous areas of southwest China. [ABSTRACT FROM AUTHOR]

Gold and copper from a refractory copper-bearing gold ore in the transitional zone of a mine in Central Asia were comprehensively recovered by the process of flotation-flotation concentrate sale-direct CIL cyanide leaching of flotation tailings. The ore contained 3.52 g/t gold, 11.20 g/t silver, 0.54% copper, 0.40% arsenic and 1.54% sulfur, in which the content of copper oxide was 0.22%, accounting for 40.74% of the total copper content. The dissemination of gold and copper in the ore was fine and the dissemination relationship was complex, which belonged to the complex refractory gold ore containing copper oxide. According to the characteristics of copper oxide ore, the collector system of copper oxide ore was introduced, the cleaning stage was increased, the gold and copper flotation recovery was carried out according to the bulk flotation process of copper sulfides and copper oxides, and the gold was recovered by direct CIL cyanide leaching of copper flotation tailings. Finally, a flotation concentrate with a yield of 3.92%, a gold content of 48.50 g/t and a copper content of 8.45% was obtained, which can be sold directly. The flotation tailings contained 0.21% of copper and 0.12% of cyanide-leachable copper. The direct CIL of the tailings consumed 3.1 kg/t of sodium cyanide and the leaching rate of gold reached 74.71%. The comprehensive recovery of gold was 88. 26% and the recovery of copper was 62.16%. Compared with the process of flotation - floatation concentrate sale-floatation tailings copper inhibition leaching gold - ammonia-cyanide tailings pulp CIL, the flotation concentrate yield was close, the concentrate grade of gold and copper was better, the comprehensive recovery of gold was increased by 6.02 percentage points, and the recovery of copper was increased by 9.24 percentage points. The research results can be used as the basis for field technical renovation. [ABSTRACT FROM AUTHOR]

Parabolic trough solar collector (PTC) is one of the most mature technologies in the medium and high temperature solar thermal utilization field, and PTC is the key component which transforms solar radiation into heat. PTC performance directly affects the performance of solar energy heat utilization system. In order to improve the thermal efficiency and provide the theoretical basis for PTC design, this paper analyzes the heat transfer characteristics of PTC. One-dimensional heat transfer mathematical model of PTC is established, and using this model, heat transfer characteristics for PTR70 2008 type PTC are analyzed. The result shows solar radiation heat absorbed by PTC is significantly affected by the solar incident angle. Heat absorbed by PTC is calculated by direct normal irradiance data in September 21st and October 25th, and the mean direct solar radiation data of October 25th is higher than the data in September 21st by 37.5894 W/m2, solar radiation heat absorbed by PTC in September 21st is higher than the data in October 25th by 196.644 W/m. The heat transferred from the outer absorber surface to the inner absorber surface increases with the increase of temperature difference of the outer and inner absorber surface, decreases with the increase of the ratio of outer absorber diameter to inner absorber diameter. When the ratio of outer absorber diameter to inner absorber diameter is greater than 1.05, the thermal resistance increases to 0.00046-0.00047 K/(Wom). Convection and radiation heat transfer occur between the absorber and the glass envelope. The heat transferred across the evacuated annulus from the outer absorber surface to the inner glass surface through radiation increases with the increase of the temperature of the outer absorber surface. The convection heat transfer between the absorber and glass envelope is very small and plays a negligible role. The heat is associated with annulus gas type, and heat transfer of annulus hydrogen is greater than annulus air and heat transfer of annulus air is greater than annulus argon. The heat transfers from the glass envelope to the atmosphere by convection and radiation. The convection will either be forced or natural, depending on whether there is wind. Radiation heat loss occurs due to the temperature difference between the glass envelope and the sky. Radiation heat loss increases by 105 W when ambient temperature drops by 10°C. The convection heat increases by 116 W when wind speed increases from 0.5 to 6 m/s under the glass envelope outer surface temperature of 50°C. The value reaches 340 W when the glass envelope outer surface temperature is 80°C. The transient thermal efficiency of PTC is significantly affected by heat transfer fluid (HTF) temperature. The transient thermal efficiency decreases with the increase of the temperature of HTF, and increases with the increase of the direct solar radiation. PTC thermal efficiency is calculated by using the mathematical model established in this paper, and compared with the experimental data of the national renewable energy laboratory (NREL) in America, and the results show that the maximum deviation is about 3%. It shows that the mathematical model can reflect the heat transfer law of PTC. The characteristics of heat transfer mathematical model can provide theoretical basis for PTC design and system operation. [ABSTRACT FROM AUTHOR]

Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Heat transfer fluid is heated by sun rays through the solar concentrator, then used as a heat source for a conventional power plant. A wide range of concentrating technologies has existed; the most developed are parabolic trough collector (PTC), linear fresnel reflector system (LF), power tower, and dish/engine system (DE). Parabolic trough collector is considered as one of the most mature applications of solar energy in these four technologies, which makes it worth developing. Sun-tracking system plays an important role in the development of solar energy applications, especially for the high solar concentration systems that directly convert the solar energy into thermal or electrical energy. High accuracy of sun-tracking is required to ensure that the solar collector is capable of harnessing the maximum solar energy throughout the day. Compared to fixed systems, power output of single-axis and dual-axis tracking systems can increase by 25% and 41% respectively under the same condition. It is clear that an accurate sun-tracking control system can make solar collectors receive more solar radiation energy to improve the solar energy utilization. A good sun-tracking system must be reliable and able to track the sun at the right angle even in the periods of cloud cover. Although the tracking system is more complex and costs higher than the fixed system, increasing the annual output power can reduce cost effectively. As for photoelectric tracking mode, a sun position sensor is used to provide feedback signals to judge where the sun is, but they don't work on cloudy days because of the lower sensitivity. The stability of the solar tracking system is a key factor to obtain the maximum sunlight from parabolic trough collector. In order to improve tracking stability and accuracy of the parabolic trough collector sun-tracking control system, this paper chose the more reliable hydraulic drive mechanism to match the system and mainly focused on the design of sun-tracking control system and analysis of operational data from the parabolic trough collector sun-tracking system. Based on the existed working platform of parabolic trough collector system with a length of 50 meters, this paper developed a sun-tracking control system for parabolic trough solar collector. Based on programmable logic controller (PLC), active control mode on the trajectory of the sun was adopted, which could calculate the rotation angle of the parabolic trough solar collector and control commands to drive the hydraulic cylinder to achieve real-time tracking of the sun. The system's basic operating principle, design of sun-tracking, rotation angle algorithm of parabolic trough solar collector and PLC's programs have been analyzed. Experiments were conducted in the 4 typical dates (March 20, June 21, September 23, and December 22, in 2013). The analytical result showed that sun-tracking errors of parabolic trough solar collector were nearly 0.5°. Compared to more accurate SPA (solar position algorithm) algorithm, calculation error of algorithm to calculate the position of the sun was within 0.12°. The maximum error of intermittent operation tracking mode was within 0.398°. The maximum operating speed of parabolic trough collector in the year appeared at noon on the winter solstice, the maximum operating speed was 0.398°/min, and transmission error of an angle sensor was at 0.044° or less. This study may provide the theoretical basis for mechanical transmission design of parabolic trough collector. [ABSTRACT FROM AUTHOR]

Objective: To explore an method and the effectiveness of surgical treatment of thoracic and lumbar tuberculosis complicated with severe kyphotic deformity (Cobb angle ≥ 55°) and paraplegia., Methods: Between January 2009 and January 2013, 13 cases of thoracic and lumbar tuberculosis complicated with severe kyphotic deformity and paraplegia were treated by one-stage posterior vertebral column resection (PVCR), debridement, bone grafting, and instrumentation fixation. Of 13 patients, 7 were male and 6 were female with an average age of 23.5 years (range, 14-49 years). The disease duration was 13-38 months (mean, 19 months). The Cobb angle of kyphosis was (65.23 ± 7.95)°. The visual analogue scale score (VAS) was 7.38 ± 0.31. In 13 patients with incomplete paraplegia, 1 case was classified as Frankel grade B, 7 cases as grade C, and 5 cases as grade D. The lesion involved 2 vertebrae bodies in 7 cases (T8, 9 in 1 case, T11, 12 in 2 cases, and T12, L1 in 4 cases), 3 vertebrae bodies in 4 cases (T10-12 in 2 cases, T9-11 in 1 case, and T11-L1 in 1 case), and 4 vertebrae bodies in 2 cases (T4-7 in 1 case and T6-9 in 1 case). Imaging examination showed paravertebral abscess in 10 cases., Results: Healing of incision by first intention was obtained in all patients. The neurological injury and pulmonary infection occurred in 3 cases and 2 cases respectively, which were cured after symptomatic treatment. Thirteen patients were followed up 12-48 months (mean, 17 months). The erythrocyte sedimentation rate restored to normal level in all cases at 3-7 months after operation. All the patients achieved bony fusion at 10-20 months (mean, 14 months) after operation. No fixation loosening, displacement, or fracture occurred during follow-up. Common toxic symptom of tuberculosis disappeared, and there was no recurrence of local tuberculosis. The Cobb angle of kyphosis was corrected to (22.38 ± 1.76)° at 1 week and (22.15 ± 1.83)° at last follow-up, showing significant difference when compared with preoperative one (P < 0.05). There was no significant difference in Cobb angle of kyphosis between at 1 week after operation and at last follow-up (P > 0.05). The Frankel grading was grade B in 1 case, grade C in 10 cases, and grade D in 2 cases at 1 week after operation; and it was grade D in 1 case and grade E in 12 cases at last follow-up; significant differences were found between at pre- and post-operation (P < 0.05), and between at 1 week after operation and at last follow-up (P < 0.05). The VAS score was 4.08 ± 0.76 at 1 week and 0.62 ± 0.14 at last follow-up, showing significant differences between at pre- and post-operation (P < 0.05) and between at 1 week after operation and at last follow-up (P < 0.05)., Conclusion: One-stage PVCR, debridement, bone grafting, and instrumentation fixation is proved to be successful in treating thoracic and lumbar tuberculosis complicated with severe kyphotic deformity and paraplegia.