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【多选题】
根据混凝土的密度不同，可将耐火混凝土分为（）。
A．普通耐火混凝土
B．硅酸盐水泥耐火混凝土
C．铝酸盐水泥耐火混凝土
D．磷酸盐耐火混凝土
E．轻质耐火混凝土
A.
南方某工业厂房于2008年7月2日进行一项机电安装工程。工程中有一项对基础要求严格的设备，此外，工程对电工线材、管材以及一些非金属材料也有十分严格的要求。机电安装公司根据设备需求合理利用材料，安装完毕经调试，无质量安全问题。该工程设备于2008年7月25日交付使用。
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参考答案：
举一反三
【多选题】铝酸盐水泥具有的特性包括( )
A.
长期强度有降低的趋势，强度降低可能是由于晶体转化造成的，因此高铝水泥不宜用于长期承重的结构及处在高温高湿环境的工程中，在一般的混凝土工程中应禁止使用
B.
早期强度增长快，1天的强度可达最高强度的80％以上，故宜用于紧急抢修工程及要求早期强度高的特殊工程
C.
水化热大，且放热速度快，一天内即可放出水化热总量的70％～80％'因此高铝水泥适用于冬季施工的混凝土工程，不宜用于大体积混凝土工程
D.
抗冻性、抗炭化性与耐磨性较差，抗碱性好、但耐酸性极差。
E.
耐热性较高
【单选题】Organic FoodOrganic farming was among the fastest growing segments of U.S. agriculture during the 1990s. The value of retail. sales of organic food was estimated to be $16 billion in 2004. According t...
A.
As you can imagine, organic agricultural practices are quite distinct from those of "conventional" fanning.
B.
Organic farmers:
C.
feed soil and build soil matter with natural fertilizer to grow their crops use insect predators, mating disruption, traps and barriers to protect crops from pests and disease make use of crop rotation, mechanical tillage and hand-weeding, as well as cover crops, mulches, flame weeding and other management methods to control weed growth.As a last resort, organic farmers may apply certain botanical or other non-synthetic pesticides. Conventional farmers:,
D.
apply chemical fertilizers to the soil to grow their crops spray with insecticides to protect crops from pests and disease use synthetic herbicides to control weed growth.
E.
How Do I Know if a Food is Organic
F.
Look for the word "organic" on vegetables or pieces of fruit, or on the sign above the organic produce display. The word "organic" may also appear on packages of meat, cartons of milk or eggs, cheese and other single-ingredient foods. Foods labeled "100 percent organic" must contain only organic ingredients. Products containing at least 70 percent organic content can be labeled "made with organic ingredients". Those foods labeled simply "organic" must have at least 95 percent organic ingredients, by weight or fluid volume, excluding water and salt. Anyone who knowingly sells or labels a product "organic" that is not produced and handled in accordance with these regulations can face a civil penalty of up to $10,000.
G.
Foods grown and processed according to the federal standards will in most cases bear the seal "USDA Organic". As its use is voluntary, companies may choose not to display the seal.
H.
Why Should I Care if a Food is Organic According to the USDA, organic food production allows farmers to lower input costs, decrease reliance on nonrenewable resources, capture high-value markets and premium prices, and boost farm income. Organic agriculture also has many important environmental, benefits:
I.
It promotes sustainability by establishing an ecological balance to prevent soil fertility or pest problems. In the long run, organic farms tend to conserve energy and protect the environment by maintaining ecological harmony.
J.
It enhances biodiversity, or the presence of multiple plant and animal species. Having a highly diverse genetic pool becomes useful in the future when beneficial characteristics can be tapped.
.
Because organic agriculture utilizes practices such as crop rotations, inter-cropping, symbiotic associations, cover crops and minimum tillage, the length of time that the soil is exposed to erosive forces is decreased, which minimizes nutrient losses and boosts soil productivity. By not using synthetic fertilizers and pesticides, organic agriculture-reduces pollution of groundwater.
K.
Organic agriculture helps to minimize the greenhouse effect and global warming through its ability to keep carbon in the soil.
L.
Why is Organic Food So Expensive
M.
Prices tend to be higher for organic titan conventional products. As stated on the Web site of the Food and Agriculture Organization (FAO) of the United Nations (UN), certified organic products are generally, more expensive than their conventional counterparts because:
N.
The organic food supply is limited as compared to demand. Production costs for organic foods are typically higher because of greater labor input and because farmers don’t produce enough of a single product to lower the overall cost.
.
Post-harvest handling of relatively small quantities of organic foods results in higher costs because organic and conventional 0roduce must be separated for processing and transportation.
.
Marketing and the distribution chain for organic products are relatively inefficient, and costs are higher because of relatively small volumes.
.
The FAO also notes that as the demand for organic food and products increases, technological innovations and economies of scale should reduce costs of production, processing, distribution and marketing for organic produce.
.
Is Organic Food Better than Conventional Food
.
Organic and conventional food must meet the same quality and safety standards. Organic food differs from conventionally produced food simply in the way it is grown, handled, and processed. There is no scientific evidence to suggest that it is more nutritious or safer than conventional food. A recently published report indicates that organic food is less likely to contain pesticide residues than conventional food. Yet, according to the National Research Council, the traces of pesticides left on conventionally grown products are unlikely to cause an increased cancer risk. Also, if fruits and vegetables are properly washed, most of the chemicals can be removed. As for taste, that’s up to you to decide what you like best. In general, people tend to find that the fresher a food is, the better it tastes, regardless of how it was produced.
【多选题】铝酸盐水泥具有的特性______。
A.
长期强度有降低的趋势，强度降低可能是由于晶体转化造成，因此，高铝水泥不宜用于长期承重的结构及处在高温高湿环境的工程中，在一般的混凝土工程中应禁止使用
B.
早期强度增长快，一天的强度可达最高强度的80%以上，故宜用于紧急抢修工程及要求早期强度高的特殊工程
C.
水化热大，且放热速度快，一天内即可放出水化热总量的70%～80%，因此，高铝水泥适用于冬季施工的混凝土工程，不宜用于大体积混凝土工程
D.
耐热性较高
E.
抗冻性、抗炭化性与耐磨性较差，抗碱性好，但耐酸性极差
相关题目：
【多选题】铝酸盐水泥具有的特性包括( )
A.
长期强度有降低的趋势，强度降低可能是由于晶体转化造成的，因此高铝水泥不宜用于长期承重的结构及处在高温高湿环境的工程中，在一般的混凝土工程中应禁止使用
B.
早期强度增长快，1天的强度可达最高强度的80％以上，故宜用于紧急抢修工程及要求早期强度高的特殊工程
C.
水化热大，且放热速度快，一天内即可放出水化热总量的70％～80％'因此高铝水泥适用于冬季施工的混凝土工程，不宜用于大体积混凝土工程
D.
抗冻性、抗炭化性与耐磨性较差，抗碱性好、但耐酸性极差。
E.
耐热性较高
【单选题】Organic FoodOrganic farming was among the fastest growing segments of U.S. agriculture during the 1990s. The value of retail. sales of organic food was estimated to be $16 billion in 2004. According t...
A.
As you can imagine, organic agricultural practices are quite distinct from those of "conventional" fanning.
B.
Organic farmers:
C.
feed soil and build soil matter with natural fertilizer to grow their crops use insect predators, mating disruption, traps and barriers to protect crops from pests and disease make use of crop rotation, mechanical tillage and hand-weeding, as well as cover crops, mulches, flame weeding and other management methods to control weed growth.As a last resort, organic farmers may apply certain botanical or other non-synthetic pesticides. Conventional farmers:,
D.
apply chemical fertilizers to the soil to grow their crops spray with insecticides to protect crops from pests and disease use synthetic herbicides to control weed growth.
E.
How Do I Know if a Food is Organic
F.
Look for the word "organic" on vegetables or pieces of fruit, or on the sign above the organic produce display. The word "organic" may also appear on packages of meat, cartons of milk or eggs, cheese and other single-ingredient foods. Foods labeled "100 percent organic" must contain only organic ingredients. Products containing at least 70 percent organic content can be labeled "made with organic ingredients". Those foods labeled simply "organic" must have at least 95 percent organic ingredients, by weight or fluid volume, excluding water and salt. Anyone who knowingly sells or labels a product "organic" that is not produced and handled in accordance with these regulations can face a civil penalty of up to $10,000.
G.
Foods grown and processed according to the federal standards will in most cases bear the seal "USDA Organic". As its use is voluntary, companies may choose not to display the seal.
H.
Why Should I Care if a Food is Organic According to the USDA, organic food production allows farmers to lower input costs, decrease reliance on nonrenewable resources, capture high-value markets and premium prices, and boost farm income. Organic agriculture also has many important environmental, benefits:
I.
It promotes sustainability by establishing an ecological balance to prevent soil fertility or pest problems. In the long run, organic farms tend to conserve energy and protect the environment by maintaining ecological harmony.
J.
It enhances biodiversity, or the presence of multiple plant and animal species. Having a highly diverse genetic pool becomes useful in the future when beneficial characteristics can be tapped.
.
Because organic agriculture utilizes practices such as crop rotations, inter-cropping, symbiotic associations, cover crops and minimum tillage, the length of time that the soil is exposed to erosive forces is decreased, which minimizes nutrient losses and boosts soil productivity. By not using synthetic fertilizers and pesticides, organic agriculture-reduces pollution of groundwater.
K.
Organic agriculture helps to minimize the greenhouse effect and global warming through its ability to keep carbon in the soil.
L.
Why is Organic Food So Expensive
M.
Prices tend to be higher for organic titan conventional products. As stated on the Web site of the Food and Agriculture Organization (FAO) of the United Nations (UN), certified organic products are generally, more expensive than their conventional counterparts because:
N.
The organic food supply is limited as compared to demand. Production costs for organic foods are typically higher because of greater labor input and because farmers don’t produce enough of a single product to lower the overall cost.
.
Post-harvest handling of relatively small quantities of organic foods results in higher costs because organic and conventional 0roduce must be separated for processing and transportation.
.
Marketing and the distribution chain for organic products are relatively inefficient, and costs are higher because of relatively small volumes.
.
The FAO also notes that as the demand for organic food and products increases, technological innovations and economies of scale should reduce costs of production, processing, distribution and marketing for organic produce.
.
Is Organic Food Better than Conventional Food
.
Organic and conventional food must meet the same quality and safety standards. Organic food differs from conventionally produced food simply in the way it is grown, handled, and processed. There is no scientific evidence to suggest that it is more nutritious or safer than conventional food. A recently published report indicates that organic food is less likely to contain pesticide residues than conventional food. Yet, according to the National Research Council, the traces of pesticides left on conventionally grown products are unlikely to cause an increased cancer risk. Also, if fruits and vegetables are properly washed, most of the chemicals can be removed. As for taste, that’s up to you to decide what you like best. In general, people tend to find that the fresher a food is, the better it tastes, regardless of how it was produced.
【多选题】铝酸盐水泥具有的特性______。
A.
长期强度有降低的趋势，强度降低可能是由于晶体转化造成，因此，高铝水泥不宜用于长期承重的结构及处在高温高湿环境的工程中，在一般的混凝土工程中应禁止使用
B.
早期强度增长快，一天的强度可达最高强度的80%以上，故宜用于紧急抢修工程及要求早期强度高的特殊工程
C.
水化热大，且放热速度快，一天内即可放出水化热总量的70%～80%，因此，高铝水泥适用于冬季施工的混凝土工程，不宜用于大体积混凝土工程
D.
耐热性较高
E.
抗冻性、抗炭化性与耐磨性较差，抗碱性好，但耐酸性极差
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