Energy consumption of block-cutting machines represents a major cost item in the processing of travertines and other natural stones. Therefore, determining the optimum sawing conditions for a particular stone is of ma...Energy consumption of block-cutting machines represents a major cost item in the processing of travertines and other natural stones. Therefore, determining the optimum sawing conditions for a particular stone is of major importance in the natural stone-processing industry. An experimental study was carried out utilizing a fully instrumented block-cutter to investigate the sawing performances of five different types of travertine blocks during cutting with a circular diamond saw. The sawing tests were performed in the down-cutting mode. Performance measurements were determined by measuring the cutting speed and energy consumption. Then, specific energy was determined. The one main cutting parameter, cutting speed, was varied in the investigation of optimum cutting performance. Furthermore, some physico-mechanical properties of file travertine blocks were determined in the laboratory. As a result, it is found that the energy consumption （specific energy） of block cutting machines is highly affected by cutting speed. It is determined that specific energy value usually decreases when cutting speed increases. When the cutting speed is higher than the determined value, the diamond saw can become stuck in the travertine block; this situation can be a problem for the block-cutting machine. As a result, the optimum cutting speed obtained for the travertine mines examined is approximately 1.5-2.0 m/min.展开更多
Sustainable building design in dry tropical areas recommends reducing exposure of buildings to solar radiation and/or designing efficient enclosures with satisfactory thermal inertia.We propose in this paper a study o...Sustainable building design in dry tropical areas recommends reducing exposure of buildings to solar radiation and/or designing efficient enclosures with satisfactory thermal inertia.We propose in this paper a study of the influence of the infiltration rate in the building and the coefficient of thermal transfer by convection of the walls, on the thermal comfort using TRNSYS software. All the models carried out were validated by recognized scientific criteria, namely correlation （R） and determination （R2） coefficients on the one hand and NBME and CVRMSE coefficients defined by ASHARE, 2002 on the other hand. The results obtained indicate that the modulation of the air infiltration rate allows the simulations on TRNSYS to be compared to in-situ measurements, with an annual average relative difference of 2.86% on the temperature difference. Furthermore, depending on the parameterization of the heat transfer coefficients by convection of the internal and external walls of walls used in the STD, the average annual difference can be reduced by 1% to 4% between the predictions and the measurements.展开更多
The surrounding rock of the gob-side entry driving(GSED)is subjected to multiple high ground pressure effects in extra-thick coal seams,resulting in severe damage and significant control challenges.This study proposes...The surrounding rock of the gob-side entry driving(GSED)is subjected to multiple high ground pressure effects in extra-thick coal seams,resulting in severe damage and significant control challenges.This study proposes a novel technology of cutting periodically fractured key blocks(CPFKB)to relieve pressure on the surrounding rock.The mechanism of CPFKB in mitigating ground pressure is elucidated,and an analytical model is built.Meanwhile,a discrimination method is given for determining the scientific parameters of CPFKB and when and in which form they fall into a gob.The results indicate that severed blocks exhibit four instability modes:sliding instability,rotational instability,simultaneous rotational-sliding instability,and stable hinge.Cutting angle exerts a significant influence on interfacial stress of severed blocks.Low-inclination cutting angles tend to induce simultaneous rotational-sliding instability,while high-inclination cutting angles typically result in initial rotation followed by sliding instability.The probability of instability markedly increases during mid-to-late stages of rotation compared to early phases.The GSED with narrow coal pillars in extra-thick coal seams using longwall top-coal caving mining is conducive to the implementation of CPFKB.Furthermore,a hydraulic fracturing technique with 75°cutting angle for CPFKB is introduced,and it achieves good practical results.展开更多
文摘Energy consumption of block-cutting machines represents a major cost item in the processing of travertines and other natural stones. Therefore, determining the optimum sawing conditions for a particular stone is of major importance in the natural stone-processing industry. An experimental study was carried out utilizing a fully instrumented block-cutter to investigate the sawing performances of five different types of travertine blocks during cutting with a circular diamond saw. The sawing tests were performed in the down-cutting mode. Performance measurements were determined by measuring the cutting speed and energy consumption. Then, specific energy was determined. The one main cutting parameter, cutting speed, was varied in the investigation of optimum cutting performance. Furthermore, some physico-mechanical properties of file travertine blocks were determined in the laboratory. As a result, it is found that the energy consumption （specific energy） of block cutting machines is highly affected by cutting speed. It is determined that specific energy value usually decreases when cutting speed increases. When the cutting speed is higher than the determined value, the diamond saw can become stuck in the travertine block; this situation can be a problem for the block-cutting machine. As a result, the optimum cutting speed obtained for the travertine mines examined is approximately 1.5-2.0 m/min.
文摘Sustainable building design in dry tropical areas recommends reducing exposure of buildings to solar radiation and/or designing efficient enclosures with satisfactory thermal inertia.We propose in this paper a study of the influence of the infiltration rate in the building and the coefficient of thermal transfer by convection of the walls, on the thermal comfort using TRNSYS software. All the models carried out were validated by recognized scientific criteria, namely correlation （R） and determination （R2） coefficients on the one hand and NBME and CVRMSE coefficients defined by ASHARE, 2002 on the other hand. The results obtained indicate that the modulation of the air infiltration rate allows the simulations on TRNSYS to be compared to in-situ measurements, with an annual average relative difference of 2.86% on the temperature difference. Furthermore, depending on the parameterization of the heat transfer coefficients by convection of the internal and external walls of walls used in the STD, the average annual difference can be reduced by 1% to 4% between the predictions and the measurements.
基金Project(523374149)supported by the National Natural Science Foundation of ChinaProject(2024M763553)supported by the Postdoctoral Science Foundation of China+2 种基金Project(Y202352229)supported by the General Research of Zhijiang Education Department,ChinaProject(2024K266)supported by the Housing and Urban-Rural Development Department of Zhejiang,ChinaProject(2024AY40014)supported by the Youth Project of Jiaxing Science and Technology Program,China。
文摘The surrounding rock of the gob-side entry driving(GSED)is subjected to multiple high ground pressure effects in extra-thick coal seams,resulting in severe damage and significant control challenges.This study proposes a novel technology of cutting periodically fractured key blocks(CPFKB)to relieve pressure on the surrounding rock.The mechanism of CPFKB in mitigating ground pressure is elucidated,and an analytical model is built.Meanwhile,a discrimination method is given for determining the scientific parameters of CPFKB and when and in which form they fall into a gob.The results indicate that severed blocks exhibit four instability modes:sliding instability,rotational instability,simultaneous rotational-sliding instability,and stable hinge.Cutting angle exerts a significant influence on interfacial stress of severed blocks.Low-inclination cutting angles tend to induce simultaneous rotational-sliding instability,while high-inclination cutting angles typically result in initial rotation followed by sliding instability.The probability of instability markedly increases during mid-to-late stages of rotation compared to early phases.The GSED with narrow coal pillars in extra-thick coal seams using longwall top-coal caving mining is conducive to the implementation of CPFKB.Furthermore,a hydraulic fracturing technique with 75°cutting angle for CPFKB is introduced,and it achieves good practical results.
