At present, China's urban construction is in a period of rapid growth. Each year, the area of ​​newly added urban residential buildings is approximately 500 million square meters. Land use in major and medium-sized cities has become increasingly tense. Green spaces have been replaced by high-rise buildings one after another, and the quality of human settlements has dropped significantly. With the limited urban land resources, how can the green coverage rate be improved and the environmental quality improved? At this time, the fifth facade of the building has begun to enter people's horizons. The greening of urban building roofs can not only improve the top-level buildings. Comfort, increase urban green space, beautify the urban environment, and can store 2/3 of rainwater, clear and hot weather can purify the air when rainwater evaporates, adjust the urban climate, and mitigate the heat island effect.In the hospitals, sanatoriums and other environmental quality requirements are higher In public places, the promotion of roof greening can alleviate the situation of crowded venues, and provide a new leisure space for doctors and patients and convalescence personnel. The greening of roofs in urban buildings involves professional knowledge such as botany, soil nutrition, building waterproofing technology, building energy-saving technology, and greening construction technology. Therefore, the greening of roofs in urban buildings requires targeted special design and construction in order to guarantee the desired results. In the process of promoting roof greening, Beijing, Shanghai, Hangzhou, Chengdu, Shenzhen and other places are at the forefront. Among them, Beijing Municipality has issued the "Code for Roof Greening" and imposed large-scale greening of roofs around main roads; the Hangzhou Municipal Government has issued a document to force new buildings to be roofed; Shanghai has actively promoted demonstration projects and created China's largest The roof gardens; other domestic cities have actively promoted roof greening projects, and roofing greening technology has gained unprecedented opportunities for development. According to the final status of the greening of the roof, the type of plant, and the load of the new generation, Guangzhou Hongguang Guangzhou Housing Development and Construction Co., Ltd., Guangzhou Green Building Energy Conservation and Environmental Protection Section, and the difficulty of construction, etc., can be used to green the roof. The system is divided into two types: one is a light green roof (see), which is characterized by greening methods such as ground cover type, canopy type, etc. There are few greening species, and the roof load is light and easy to construct. The other type is heavy green roofing (see below). It is designed and constructed by a professional company and has specific landscape structures. There are many species of greenery and the load is heavy. Generally, the roof is also provided with courtyards and leisure areas. Roofing greening technology mainly involves the following aspects: 1. Roofing structure; 2. Plant selection; 3. Cultivation quality selection; 4. Storage and drainage selection; 5. Root resistance waterproof layer selection; 6. Insulation layer selection type. Green roof structure should be reasonable, to meet the construction of waterproof and energy-saving standards, while the roof load should be light in order to facilitate the repair of leakage in the later period. Greening roofs prefer non-absorbent insulation materials. The insulation layer is placed under the waterproof layer and a slip layer is provided. The use of a waterproof blanket structure is preferred for the purpose of ensuring insulation and energy saving effects and leakage maintenance. The selection of plants in any area of ​​the plant requires certain conditions. The plants should be selected according to regional climate conditions. Take the south of Guangzhou as an example: Guangzhou is located at low latitudes, and the surface receives more solar radiation. At the same time, it is affected by the monsoon. In summer, it is affected by the ocean warming current to form a high-temperature, high-humidity, and rainy climate; in the winter, it is affected by the coldness of the northern mainland and forms low temperatures. , dry and drier climate. Therefore, roof greening should generally use relatively low, shallow roots, drought-tolerant, cold-tolerant and thin-tolerant plants. Mainly include: 1. Sedum is a genus, such as Buddha grass, Stipa grass, concave Ye Jingtian, golden leaf Sedum, etc.; 2. The local vines are categories, such as vine periwinkle, linseed ivy, etc.; 3. Perennial rattan flowers, such as Dianthus, thyme, big flower coreopsis, genus, purple genus, etc.; 4. Dwarf shrubs, such as dwarf crape myrtle, June snow, mallow, hibiscus, Euonymus fortunei, etc.; 5. shrubs small arbor , such as roses, spring, pomegranate, red maple, small lotus, Nandina, bamboo flowers and so on. In addition, it is also necessary to select suitable plants for planting based on the type of building and the surrounding environment. Cultivation quality selection cultivars should be selected according to the roof bearing capacity, plant growth characteristics and natural environment conditions. With the scarcity of natural soil resources and the popularity of roof greening, it is an inevitable trend to use artificial cultivation substrates as growth media. At present, Germany and Japan have high research and production levels. Our country is restricted by factors such as economy, technology, and degree of concern. Research and development of cultivation quality has only just begun. The performance of cultivating materials plays a key role in the long-term stability of the entire system. The cost accounts for 2030% of the total system cost. Therefore, the selection of cultivating materials must be adapted to local conditions and fully tap the local cheap and readily available raw material resources. Through the optimization of technological and technological innovations, the quality and production capacity of cultivation quality will be improved, and the application cost will be reduced, with a view to promoting the overall popularization of roof greening. The commonly used soil-less culture substrates include: rock wool, perlite, vermiculite, coal residue, sawdust zymogenic fermented soil, ion culture soil, vermicompost, coco peat, pond mud, mountain soil, carbonized chaff, volcanic ash, compost soil, Bark, straw, pottery, etc. At present, in the landscaping and clothing industry including roof greening, there is no uniform quality standard for the production of soilless cultures in China. Different manufacturers have very different product standards according to actual conditions. In order to promote the application of soilless culture materials, institutions such as the Shenxuanyuan Institute are working on the quality standards for the cultivation substrates for light roofing. The following table (see Table 1). Organic-inorganic composite cultivation matrix Product quality Partial physical and chemical standard items pH Organic matter porosity Density (Dry) Bulk Density (Wet) Conductivity Standard Table 2 Typical Green Roof Structure Project Typical Lightweight Green Roof Typical Structural Plan Heavy Green Roof Typical Structural Plan Structure 90 Thickness L†Roofing Greening System Greening Planting Layer 150g Non-woven Fabric> 300 Thickness Cultivation Material 1.2 Thickness T-99 Anti-Rolling Waterproof Blanket 150g Geotextile Water Filter Cloth 25 Thickness Cement Mortar Leveling Layer YK Storage Drainage Board Tenoning Board 150g Nonwoven 1.2 Thick T- 99 Anti-Rolling Blanket 15 Thick Extruded Polystyrene Board 15 Thick Cement Mortar Leveling Layer ç ¼Structure Board Description 1.The insulation layer can be replaced with 30 thick high-density polystyrene board (density >40kg/m3); 2.L†roof greening The system includes greening + cultivation quality + water filter cloth + heat preservation and anti-root storage drainage board 3. Cultivation quality is preferably soilless nutrient cultivation to ensure lightness and nutrition; 4. The above design of insulation layer has met the standards of summer hot and cold area "G" 75; 5. Roofing planting species should be selected based on the local climate conditions. Table 1) only. Roof plants have their own growth characteristics, drought-tolerant plants are more often afraid of earthworms. Therefore, in the greening of the roof, it is necessary to take into account the problem of water storage and drainage, and it is necessary to ensure that a small amount of rainwater can be retained, and surplus water can be drained immediately. There are mainly two ways to solve the problem of roof storage and drainage: The first type is achieved through the structure, such as YK storage and drainage board (egg shelf structure, see details), L" roof greening water tank (overflow hole box type structure), etc. Another species is achieved through cultivar quality. Water-retaining culture materials include: organic water-retaining agent (problems caused by soil in the later stage), inorganic sodium bentonite (through modification, the water absorption rate is up to 20 times, and can be used for a long time) Etc.; use of water-based cultivation of the quality of: vermiculite, fine ceramsite, expanded perlite, sepiolite, natural zeolite and so on. Of course, both methods can also be used in combination. The waterproof material for roofing shall meet the following requirements: 1. Good weather resistance, at least 30 years of weather resistance; 2. Resistance to puncture of roots of plants; waterproof material has strong root resistance; 3. Convenient construction and maintenance, load of waterproof system light. Plant roots have a strong puncture ability, especially roots, the longer the age, the deeper the bar, and secrete a strong corrosive juice, many waterproof materials can not withstand. At present, the anti-root type waterproof material used for roofing in China mainly includes: 1. Aluminum alloy coils; 2. High-density polyethylene geomembrane (HDPE); 3. Polyvinyl chloride P-type coils; 4. Polyether polyurethane waterproof blanket 5.T-99 anti-root coating. At present, because there is no waterproof root-resistance test method in China, the manufacturer of waterproof material can only adopt the German standard of DN4062 and send it to the German Bayer Laboratory for testing. However, the standard is to plant a certain amount of fan-shaped beans under certain environmental conditions for six months to see whether the material is punctured by the roots of the plants. Due to the longer planting time of heavy green roofing species and the stronger root puncture capacity, the German DN4062 standard is not suitable for the root-resistance test method of roof greening plants. Through series of experiments, it can be concluded that the root resistance of the material is mainly manifested in several aspects such as non-permeability (gas permeability test method), impact resistance, wear resistance, corrosion resistance and weather resistance. In the experiment of improving the survival rate of transplanting trees, the trees were planted in cylindrical plastic buckets with a small number of vent holes. The roots of the trees were all grown in the direction of the vent holes. It can be inferred that there should be a certain amount of root growth in the trees. The gas concentration, humidity, and other environments, the molecular permeability of the material, the molecular permeability of the water should be the main evaluation basis for the resistance to the root. At present, new buildings in China must implement energy-saving standards, and old buildings are gradually undergoing energy-saving reforms. Simple roof greening can not meet the requirements of energy-saving standards. Therefore, suitable roofing insulation should be set at the same time. Insulation materials should be preferred non-absorbent insulation materials, such as extruded polystyrene foam board, high-density polystyrene board (density> 40kg/m3), waterproof insulation polymer mortar and so on. The thickness of the insulation layer should be selected in accordance with the requirements of the energy-saving standard in the area where the building is located. The green roof in the hot summer and warm winter regions can be selected with 15 mm extruded polystyrene foam board. 3.7 Typical Green Roof Structure According to the building energy conservation standard in hot summer and warm winter areas, there are the following types of typical green roof structures (see Table 2). 3.8 Greening Roof of Old Buildings The transformation of the green roofs of old buildings should be carried out according to the following procedures: First, check whether there is any leakage on the roof, and check the method and durability of the waterproof layer of the engineering drawings, if there is leakage or durability of the waterproof layer. Poor, you can re-lay the T-99 anti-root waterproof blanket directly on the old roof, and then do the roof greening method as shown in Table 2. For non-human roofing, T-99 anti-root waterproof blanket has the characteristics of no need of leveling layer and protective layer, which is lighter and more convenient than conventional materials. When the roof waterproof layer has a certain degree of durability, considering only the greening of the roof, a 90-thick LJ roof green water tank can be laid directly on the old roof. Because the LJ roof green water tank can be moved, it is easy to maintain and the cost is low. The transformation of the old roof should be combined with the specific conditions of the original structure of the roof, light materials should be selected as much as possible, light green roofs should be used, and thermal insulation layers should be added when the top insulation effect is not good. After the development of roof greening technology in recent years, the technology has become more mature, but there are certain resistances to promotion throughout the country because (1) there are not many professional companies that can systematically design and construct roof greening; ( 2) The government requires special qualifications for greening and waterproofing construction units; (3) Non-specialized design and construction cannot be promoted in large and medium-sized cities; (4) Plant maintenance and leakage at the later stage of roof greening, resulting in green roofing Promotion is more difficult. Taking Guangzhou as an example, the old roofs have reached 40 million square meters, and the government and enterprises have completed less than 30,000 square meters of roof greening. According to the climate characteristics of Guangzhou, roof greening is the most economical and reasonable choice for thermal insulation and energy saving solutions. In the greening of 10,000 square meters of roofs, the new cost is 1.5 million yuan (including all the contents of insulation, waterproof, greening, etc.), while the greening of the ground is 10,000 square meters. The cost of land acquisition and demolition is huge. The greening of old roofs can be light-weighted, economically viable and easy to maintain. In the major garden-style hotels, key landscape areas, airport express, Inner Ring Road and other key areas complemented by heavy roof greening. Through continuous trials, research, promotion and summing up experiences, we believe that greening of roofs is a systematic project involving a wide range of plant greening, plant nutrition, building waterproofing, building energy-saving insulation, building construction, plant diseases and insect pests, Many aspects such as building maintenance and management need to be designed and constructed by a professional company. Otherwise, it may not be worth the candle, and maintenance and maintenance costs are high. Soilless cultures will directly affect the cost of green roofs and have a larger proportion. The permeability of water molecules and gas molecules is an important evaluation indicator for the root resistance of waterproof materials. Roof insulation shall be provided with additional insulation to ensure the insulation and energy saving effect of the roof. The scientific nature of the roof structure and effective storage and drainage measures are important links in reducing maintenance costs. Roofing greening is easy to form a large-scale roof garden, and large and medium-sized cities are the best time for promotion.
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