Strain of infrapatellar fat pad extensively occurs in people aged over 30 years, who often walk up hills or squat while working. The clinical manifestations are aching and weakness in the knee joints, aggravated when ...Strain of infrapatellar fat pad extensively occurs in people aged over 30 years, who often walk up hills or squat while working. The clinical manifestations are aching and weakness in the knee joints, aggravated when the knee joints are totally extended. Discomfort occurs in mild cases only when walking for long or going up and down the stairs. There is aching feeling in moderate cases when the patients are quiet. The pain is aggravated during exercises when the knee joints are half flexed and the patient can not stand up when squatting for prolonged periods of time. There are aching and weak feelings in the severe cases.展开更多
A method of accuracy assignment based on value analysis method （VAM） in tank fire control system （TFCS） is proposed. From the analysis of primary error sources and their error transfer relationships, the mathemati...A method of accuracy assignment based on value analysis method （VAM） in tank fire control system （TFCS） is proposed. From the analysis of primary error sources and their error transfer relationships, the mathematical model is built on the basis of VAM to solve the accuracy assignment problem. Simulation results show the validation and feasibility of the proposed method. It can help designer of tank fire control system work out an optimal system more efficiently and more economically.展开更多
Finite element method is employed to calculate the temperature fields for two kinds of steel concrete composite slabs: composite slab with profiled steel sheeting and LJMB composite slab. The calculated results are in...Finite element method is employed to calculate the temperature fields for two kinds of steel concrete composite slabs: composite slab with profiled steel sheeting and LJMB composite slab. The calculated results are in good agreement with those of tests. Fire resistance of the two kinds of composite slabs is calculated by using a numeric method. The results show that: due to heat absorbing of concrete, the performance of composite slabs under fire is better than that of unprotected steel structure, and fire resistance of composite slabs mentioned in this paper is at least 30 min subjected to standard fire. Parameters related to the fire resistance are discussed. It was found that with increasing of concrete strength and thickness of slab, fire resistance increases, and with increasing of steel strength and steel ratio, fire resistance decreases. Also thickness of fire proof is calculated by a numeric method. The results obtained in this paper may be referenced for practical engineering.展开更多
Fire effects can be one of the most harmful conditions that any building may experience throughout its service life. Developing practical protection methods and concepts against potential fire disasters in buildings h...Fire effects can be one of the most harmful conditions that any building may experience throughout its service life. Developing practical protection methods and concepts against potential fire disasters in buildings has been an important consideration in design of buildings in recent decades. Rapid developments in technology have heightened the demand for new and innovative fire protection systems in comparison with conventional and traditional methods. Such a need for new technologies is in particular of greater importance when it comes to existing buildings. Retrofitting an existing building for fire safety is a greater challenge compared with designing a new building using materials and components that have more desirable and superior fire rating to begin with. Furthermore, strategies to design a new building that includes state-of-the-art fire safety features are also different from solutions that may be more suitable for retrofitting an existing building. This paper presents a review of the literature concerning conventional and new or innovative retrofitting methods for fire safety of buildings. Advantages and disadvantages of different fire protection devices and methods as available and understood from the literature are mentioned. Study of fire safety systems shows that each has its drawbacks. Comparison of the results shows that disadvantages of a solitary system for retrofitting against fire can be improved by using a combination of several fire safety concepts or methods simultaneously.展开更多
The microstructural characteristics, elemental distribution law and microscopic formation mechanism of the burning products of TA15 titanium alloy were investigated by friction oxygen concentration method, associated ...The microstructural characteristics, elemental distribution law and microscopic formation mechanism of the burning products of TA15 titanium alloy were investigated by friction oxygen concentration method, associated with in situ observation, X-ray diffraction(XRD),scanning electron microscopy(SEM) and energy-dispersive spectroscopy(EDS) analyses, providing the thoughts to improve fireproof property. The results show that, when the friction contact pressure(p) is 0.20 MPa and oxygen concentration of premixed air flow(c) is 60 vol%, TA15 titanium alloy produces violent sparks and presents dazzling white light during combustion. The generated products after burning are mainly TiOand small amount of AlOoxides. Four distinct zones form from the combustion surface to the alloy matrix, and they are in the sequence of combustion zone, fusion zone, heat-affected zone and transition zone. Further, combustion zone is composed of TiOand A1203 compounds, containing obvious cracks. In the fusion zone, discontinuous oxygenrich Al-based solid solution forms, and the elemental distribution has strong volatility. In the heat-affected zone,there are abundant of Ti-based solid solution and small amount of Al-and Mo-based solid solution. Transition zone is made of lamellar structure. Two technical approaches are given to prevent oxygen diffusion inside the reaction zone and reaction-affected zone. On the one hand,the content of Al is designed as the upper limit of alloy composition; on the other hand, fireproof coatings are deposited on the surface of the alloy.展开更多
Forest fires are influenced by several factors,including forest location,species type,age and density,date of fire occurrence,temperatures,and wind speeds,among others.This study investigates the quantitative effects ...Forest fires are influenced by several factors,including forest location,species type,age and density,date of fire occurrence,temperatures,and wind speeds,among others.This study investigates the quantitative effects of these factors on the degree of forest fire disaster using nonparametric statistical methods to provide a theoretical basis and data support for forest fire management.Data on forest fire damage from 1969 to 2013 was analyzed.The results indicate that different forest locations and types,fire occurrence dates,temperatures,and wind speeds were statistically significant.The eastern regions of the study area experienced the highest fire occurrence,accounting for 85.0%of the total number of fires as well as the largest average forested area burned.April,May,and October had more frequent fires than other months,accounting for 78.9%,while September had the most extensive forested area burned(63.08 ha)and burnt area(106.34 ha).Hardwood mixed forest and oak forest had more frequent fires,accounting for 31.9%and 26.0%,respectively.Hardwood-conifer mixed forest had the most forested area burned(50.18 ha)and burnt area(65.09 ha).Temperatures,wind speeds,and their interaction had significant impacts on forested area burned and area burnt.展开更多
文摘Strain of infrapatellar fat pad extensively occurs in people aged over 30 years, who often walk up hills or squat while working. The clinical manifestations are aching and weakness in the knee joints, aggravated when the knee joints are totally extended. Discomfort occurs in mild cases only when walking for long or going up and down the stairs. There is aching feeling in moderate cases when the patients are quiet. The pain is aggravated during exercises when the knee joints are half flexed and the patient can not stand up when squatting for prolonged periods of time. There are aching and weak feelings in the severe cases.
文摘A method of accuracy assignment based on value analysis method （VAM） in tank fire control system （TFCS） is proposed. From the analysis of primary error sources and their error transfer relationships, the mathematical model is built on the basis of VAM to solve the accuracy assignment problem. Simulation results show the validation and feasibility of the proposed method. It can help designer of tank fire control system work out an optimal system more efficiently and more economically.
文摘Finite element method is employed to calculate the temperature fields for two kinds of steel concrete composite slabs: composite slab with profiled steel sheeting and LJMB composite slab. The calculated results are in good agreement with those of tests. Fire resistance of the two kinds of composite slabs is calculated by using a numeric method. The results show that: due to heat absorbing of concrete, the performance of composite slabs under fire is better than that of unprotected steel structure, and fire resistance of composite slabs mentioned in this paper is at least 30 min subjected to standard fire. Parameters related to the fire resistance are discussed. It was found that with increasing of concrete strength and thickness of slab, fire resistance increases, and with increasing of steel strength and steel ratio, fire resistance decreases. Also thickness of fire proof is calculated by a numeric method. The results obtained in this paper may be referenced for practical engineering.
文摘Fire effects can be one of the most harmful conditions that any building may experience throughout its service life. Developing practical protection methods and concepts against potential fire disasters in buildings has been an important consideration in design of buildings in recent decades. Rapid developments in technology have heightened the demand for new and innovative fire protection systems in comparison with conventional and traditional methods. Such a need for new technologies is in particular of greater importance when it comes to existing buildings. Retrofitting an existing building for fire safety is a greater challenge compared with designing a new building using materials and components that have more desirable and superior fire rating to begin with. Furthermore, strategies to design a new building that includes state-of-the-art fire safety features are also different from solutions that may be more suitable for retrofitting an existing building. This paper presents a review of the literature concerning conventional and new or innovative retrofitting methods for fire safety of buildings. Advantages and disadvantages of different fire protection devices and methods as available and understood from the literature are mentioned. Study of fire safety systems shows that each has its drawbacks. Comparison of the results shows that disadvantages of a solitary system for retrofitting against fire can be improved by using a combination of several fire safety concepts or methods simultaneously.
基金financially supported by the National Natural Science Foundation of China (No.51471155)the Aviation Science Foundation of China(No.2014E62149R)
文摘The microstructural characteristics, elemental distribution law and microscopic formation mechanism of the burning products of TA15 titanium alloy were investigated by friction oxygen concentration method, associated with in situ observation, X-ray diffraction(XRD),scanning electron microscopy(SEM) and energy-dispersive spectroscopy(EDS) analyses, providing the thoughts to improve fireproof property. The results show that, when the friction contact pressure(p) is 0.20 MPa and oxygen concentration of premixed air flow(c) is 60 vol%, TA15 titanium alloy produces violent sparks and presents dazzling white light during combustion. The generated products after burning are mainly TiOand small amount of AlOoxides. Four distinct zones form from the combustion surface to the alloy matrix, and they are in the sequence of combustion zone, fusion zone, heat-affected zone and transition zone. Further, combustion zone is composed of TiOand A1203 compounds, containing obvious cracks. In the fusion zone, discontinuous oxygenrich Al-based solid solution forms, and the elemental distribution has strong volatility. In the heat-affected zone,there are abundant of Ti-based solid solution and small amount of Al-and Mo-based solid solution. Transition zone is made of lamellar structure. Two technical approaches are given to prevent oxygen diffusion inside the reaction zone and reaction-affected zone. On the one hand,the content of Al is designed as the upper limit of alloy composition; on the other hand, fireproof coatings are deposited on the surface of the alloy.
基金supported financially by the National Key Research and Development Plan(2018YFD0600205)China’s National Foundation of Natural Sciences(31470497)the Project of Jilin Province Department of Education(JJKH20180347KJ)
文摘Forest fires are influenced by several factors,including forest location,species type,age and density,date of fire occurrence,temperatures,and wind speeds,among others.This study investigates the quantitative effects of these factors on the degree of forest fire disaster using nonparametric statistical methods to provide a theoretical basis and data support for forest fire management.Data on forest fire damage from 1969 to 2013 was analyzed.The results indicate that different forest locations and types,fire occurrence dates,temperatures,and wind speeds were statistically significant.The eastern regions of the study area experienced the highest fire occurrence,accounting for 85.0%of the total number of fires as well as the largest average forested area burned.April,May,and October had more frequent fires than other months,accounting for 78.9%,while September had the most extensive forested area burned(63.08 ha)and burnt area(106.34 ha).Hardwood mixed forest and oak forest had more frequent fires,accounting for 31.9%and 26.0%,respectively.Hardwood-conifer mixed forest had the most forested area burned(50.18 ha)and burnt area(65.09 ha).Temperatures,wind speeds,and their interaction had significant impacts on forested area burned and area burnt.
