Every year,the State of Qatar generates about 400,000 tons of steel slag and another 500,000 tons of gravel as a result of steel manufacturing and washing sand,respectively.The two materials(by-products)are not fully ...Every year,the State of Qatar generates about 400,000 tons of steel slag and another 500,000 tons of gravel as a result of steel manufacturing and washing sand,respectively.The two materials(by-products)are not fully utilized to their best market values.At the same time,infrastructural renewal will take place in Qatar over the next ten years,and there will be a greater demand for aggregates and other construction materials as the country suffers from the availability of good aggregates.This paper presents results obtained on the use of steel slag,gravel and gabbro(control)in HMAC(hot mix asphalt concrete)paving mixtures and road bases and sub-bases.Tests were conducted in accordance with QCS-2010(Qatar Construction Specifications)and results were compared with QCS requirements for aggregates used in these applications.Based on the data obtained in this work,steel slag and gravel aggregates have a promising potential to be used in HMAC paving mixtures on Qatar’s roads,whether in asphalt base and asphalt wearing courses or as unbound aggregates in the base and sub-base pavement structure.展开更多
Symptoms of dryness discomfort in soft contact lens wearers frequently lead to discontinuation from wear.The negative influence of pre-fitting tear dysfunctions appears likely to be exacerbated by the challenges to te...Symptoms of dryness discomfort in soft contact lens wearers frequently lead to discontinuation from wear.The negative influence of pre-fitting tear dysfunctions appears likely to be exacerbated by the challenges to tear homeostasis caused by contact lenses.The corneal mechanisms for symptoms in contact lens wearers are different to those for dry eye disease because the cornea is insulated by the lens from ambient conditions as well as from lid wiper friction during blinking.Symptoms of dryness discomfort might be the consequence of increased lid wiper friction during blinking when the lens front surface becomes soiled and dry and exhibits very rapid tear break up.It is possible that some cases of contact lens intolerance and discontinuation could be a function of lid wiper neuropathy.In relation to the possibility of corneal neuropathy,a stagnant post-lens tear pool with the possibility of increased concentrations of metabolic by-products,cellular debris,and bacterial exotoxins,might have the potential to disturb the corneal epithelial and sub-basal nerves.Contributions by contact lens-induced inflammation to any neuropathic changes may partly depend on the degree to which inflammatory mediators are concentrated in a stagnant post-lens tear pool.It does not appear to be known if corneal neuropathic changes could develop under these conditions.The chances of neuropathic involvement may be greater if discomfort develops after a significant period of successful wear and there is a history of comorbid pain conditions.Esthesiometry and in vivo confocal microscopy in discontinued contact lens wearers may support a diagnosis of contact lens-related corneal neuralgia.展开更多
The waste clay bricks from debris of buildings were evaluated through lab tests as environ- mental friendly materials for pavement sub-base in the research. Five sets of coarse aggregates which contained 0, 25%, 50%, ...The waste clay bricks from debris of buildings were evaluated through lab tests as environ- mental friendly materials for pavement sub-base in the research. Five sets of coarse aggregates which contained 0, 25%, 50%, 75% and 100% crushed bricks, respectively, were blended with sand and treated by 5 % cement. The test results indicated that cement treated aggregate which contains crushed clay brick aggregate had a lower maximum dry density （MDD） and a higher optimum moisture content （OMC）. Moreover, the unconfined compressive strength （UCS）, resilience modulus, splitting strength, and frost resistance performance of the specimens decreased with increase of the amount of crushed clay brick aggregate. On the other hand, it can be observed that the use of crushed clay brick in the mixture decreased the dry shrinkage strain of the specimens. Compared with the asphalt pave- ment design specifications of China, the results imply that the substitution rate of natural aggregate with crushed clay brick aggregate in the cement treated aggregate sub-base material should be less than 50% （5 % cement content in the mixture）. Furthermore, it needs to be noted that the cement treated aggre- gate which contains crushed clay bricks should be cautiously used in the cold region due to its insuffi- cient frost resistance performance.展开更多
文摘Every year,the State of Qatar generates about 400,000 tons of steel slag and another 500,000 tons of gravel as a result of steel manufacturing and washing sand,respectively.The two materials(by-products)are not fully utilized to their best market values.At the same time,infrastructural renewal will take place in Qatar over the next ten years,and there will be a greater demand for aggregates and other construction materials as the country suffers from the availability of good aggregates.This paper presents results obtained on the use of steel slag,gravel and gabbro(control)in HMAC(hot mix asphalt concrete)paving mixtures and road bases and sub-bases.Tests were conducted in accordance with QCS-2010(Qatar Construction Specifications)and results were compared with QCS requirements for aggregates used in these applications.Based on the data obtained in this work,steel slag and gravel aggregates have a promising potential to be used in HMAC paving mixtures on Qatar’s roads,whether in asphalt base and asphalt wearing courses or as unbound aggregates in the base and sub-base pavement structure.
文摘Symptoms of dryness discomfort in soft contact lens wearers frequently lead to discontinuation from wear.The negative influence of pre-fitting tear dysfunctions appears likely to be exacerbated by the challenges to tear homeostasis caused by contact lenses.The corneal mechanisms for symptoms in contact lens wearers are different to those for dry eye disease because the cornea is insulated by the lens from ambient conditions as well as from lid wiper friction during blinking.Symptoms of dryness discomfort might be the consequence of increased lid wiper friction during blinking when the lens front surface becomes soiled and dry and exhibits very rapid tear break up.It is possible that some cases of contact lens intolerance and discontinuation could be a function of lid wiper neuropathy.In relation to the possibility of corneal neuropathy,a stagnant post-lens tear pool with the possibility of increased concentrations of metabolic by-products,cellular debris,and bacterial exotoxins,might have the potential to disturb the corneal epithelial and sub-basal nerves.Contributions by contact lens-induced inflammation to any neuropathic changes may partly depend on the degree to which inflammatory mediators are concentrated in a stagnant post-lens tear pool.It does not appear to be known if corneal neuropathic changes could develop under these conditions.The chances of neuropathic involvement may be greater if discomfort develops after a significant period of successful wear and there is a history of comorbid pain conditions.Esthesiometry and in vivo confocal microscopy in discontinued contact lens wearers may support a diagnosis of contact lens-related corneal neuralgia.
基金supports from the program for New Century Excellent Talents in University,Ministry of Education of China (No.NCET -08-0748 )the Special Fund for Scientific Research of Central Colleges , Chang'an University ( No. CHD2011TD014 )Traffic Science and Technology Talents Training Plan , Ministry of Transport of China ( No . 2012-16 )
文摘The waste clay bricks from debris of buildings were evaluated through lab tests as environ- mental friendly materials for pavement sub-base in the research. Five sets of coarse aggregates which contained 0, 25%, 50%, 75% and 100% crushed bricks, respectively, were blended with sand and treated by 5 % cement. The test results indicated that cement treated aggregate which contains crushed clay brick aggregate had a lower maximum dry density （MDD） and a higher optimum moisture content （OMC）. Moreover, the unconfined compressive strength （UCS）, resilience modulus, splitting strength, and frost resistance performance of the specimens decreased with increase of the amount of crushed clay brick aggregate. On the other hand, it can be observed that the use of crushed clay brick in the mixture decreased the dry shrinkage strain of the specimens. Compared with the asphalt pave- ment design specifications of China, the results imply that the substitution rate of natural aggregate with crushed clay brick aggregate in the cement treated aggregate sub-base material should be less than 50% （5 % cement content in the mixture）. Furthermore, it needs to be noted that the cement treated aggre- gate which contains crushed clay bricks should be cautiously used in the cold region due to its insuffi- cient frost resistance performance.
