With the continuous development of soilless cultivation techniques in recent years, the use of soilless facilities has become the focus of many people. Using environmental protection facilities, it is possible to control crops to the optimum extent according to the needs of crops, such as lighting, room temperature, wind speed, relative humidity, CO2 concentration and other above-ground environments, as well as the temperature of the substrate. Under the environmental conditions, achieve high yield, stability and high quality cultivation of crops. However, in fact, the impact of the external environment on crop growth and yield is comprehensive, not single factor. At the same time, the optimal environment for crop growth is not only different due to different varieties of vegetables, but also different cultivation seasons and different growth and development periods, which increases the difficulty and complexity of environmental regulation technology.
I. Regulation Principles and Objectives for Protecting the Environment of Facilities
Environmental protection facilities use nature to create nature and provide suitable environmental conditions for plant growth and development. Due to the barrier function of the facility cover, the greenhouse can produce a special environment different from the outside world, which can protect the crop from the disturbances and hazards of wind, rain, weeds, insects, diseases, etc., and can also make the producers unsuitable for the outside world. Production is carried out. The isolation of the greenhouse from the outside world makes it possible to warm up, apply CO2, and effectively use chemical and biological control techniques for plant protection. The high yield per unit area in the greenhouse allows growers to and will invest in advanced equipment such as soilless cultivation, fill light, insulation/cooling curtains, and movable bed cultivation to improve and simplify production. Therefore, greenhouse production is a fine, advanced form of crop production, often associated with the greenhouse industry, called greenhouse engineering, and the entire process emphasizes the role of technology. Due to the installation of advanced equipment, the environment of the greenhouse can be controlled. Greenhouse environmental control is a very important task in facility cultivation, which enables growers to control the production process without relying on the outside climate. For crop growth, production and product quality, the level of environmental control plays a decisive role to some extent. Therefore, in greenhouse environmental control, the most important goal is to reduce costs and increase income.
Specific indicators to achieve this goal can be summarized as follows: 1 increase production per unit area; 2 suitable listing period; 3 ideal product quality; 4 prevention of catastrophic climate or danger (windstorm, fire, snowstorm, man-made damage, etc.); 5 environmental protection; 6 cost management (such as CO2, energy, labor, etc.). On the basis of this goal, ideal crop growth conditions, at the same time, must consider greenhouse production is an economic behavior, so the principle of environmental regulation is to operate within the scope of the overall business framework, to conduct economic accounting. In this sense, environmental regulation is often considered to be associated with business objectives, achieving high quality and high yields of products within acceptable costs and acceptable risks. The cost of environmental regulation mainly comes from the energy consumption for heating, cooling, dehumidification or fill light. The application of CO2 also requires additional costs. The cost input must account for the additional economic benefits arising from the additional input costs. To this end, targeted regulation and improvement of the environment is the main way to improve the efficiency of greenhouse crop production.
Second, the lighting conditions and its regulation
(1) Lighting conditions of the protection facilities The lighting conditions in the protection facilities include light intensity, light quality, illumination time and light distribution, which respectively give different influences on the growth and development of greenhouse crops. The light conditions in the facility have the following characteristics compared with the open-light conditions: 1 the total radiation is low, which becomes the main limiting factor for the production of luminescent horticultural crops in winter; 2 the light quality changes are large; 3 the light is unevenly distributed in time and space. Especially in high-latitude regions, the intensity of light in winter facilities is short, and the illumination time is short, which seriously affects the growth and development of greenhouse crops. The main influencing factors affecting the light environmental conditions in the facility are the light transmission of the covering material and the shading of the greenhouse structural material. Therefore, we should start from these two aspects and study how to increase the indoor lighting capacity of the facility structure and corresponding management techniques to improve the lighting environment within the facility.
(2) Regulation of lighting conditions in the facility
Light is the basic condition for crop growth, which produces light, thermal and morphological effects on the growth and development of greenhouse crops. Therefore, we must strengthen the regulation of lighting conditions and take measures to meet the lighting conditions required for crop growth and development. To control the lighting conditions in the facility, the following measures can be taken: 1. The facility structure is constructed. The reasonable greenhouse adopts the azimuth design of the east and west extension of the north side; from the perspective of lighting, in addition to the modern temperature room, the single-span greenhouse is selected as much as possible; Dust-proof, drip-proof, anti-aging, high-transparent covering material, currently preferred vinyl acetate film (EVA), followed by polyethylene film (PE) and polyvinyl chloride film (PVC); choose the appropriate span of the greenhouse , height, angle of inclination; use thin and strong skeleton materials as much as possible to increase the amount of indoor lighting and reduce the shading of greenhouse structural materials. 2. Strengthen the facility management to clean and clean frequently, and maintain the high light transmittance of the roof transparent covering material; under the premise of maintaining the room temperature, the opaque inner and outer coverings of the facility (heating curtain, grasshopper, etc.) should be uncovered as early as possible to extend The light time increases the light transmittance; in the northern area, a 2 to 2.5 m high polyester aluminized mirror reflective screen is hung on the inner wall of the greenhouse wall to increase the light intensity. 3. Strengthen cultivation management to strengthen the rational close planting of crops, pay attention to the direction (usually north-south direction is good), expand the line spacing, reduce the plant spacing, remove the side branches and old leaves of the seedlings, and increase the light transmittance of the group. 4. Timely fill light In the case of concentrated seedlings, adjustment of flowering period, and guaranteed on-time listing, supplemental lighting is necessary. Fill light lamps generally use high-pressure mercury lamps, halogen lamps and bio-lights. Due to conditions, ordinary fluorescent lamps and energy-saving lamps should also be installed. The fill light is placed on the underside of the inner insulation layer, and a reflective film is often used around the greenhouse to enhance the fill light effect. The fill light intensity varies from crop to crop. Because the light supplement is not only expensive, it consumes a lot of electricity, and the operating cost is high. It is only used for flowers with high economic value or strong seasonal seedling production. 5. According to the need to shading or blackening the summer light is too strong, will cause room temperature is too high, transpiration is intensified, plants are prone to wilting, need to reduce indoor light intensity, production generally according to the light conditions use 25% ~ 85% of the shade net. The glass greenhouse can also use special reflective materials such as lime sprayed on the top of the greenhouse to reduce the light intensity and wash it off after the summer. Keep the facility dark and choose a black PE film, black braid or braid.
Third, temperature conditions and their regulation
(1) Characteristics of temperature changes in the facility The source of temperature in the greenhouse is mainly heated by the sun's radiation, causing a greenhouse effect. The temperature change characteristics of the greenhouse are as follows: 1. It changes with the external sunlight radiation and temperature, seasonal changes and daily changes, and the temperature difference between day and night is large, and the local temperature difference is obvious in the northern region. There are obvious seasonal changes in the protection facilities. According to the relevant regulations of meteorology, the number of winter days in the solar greenhouse is shortened by 3 to 5 months compared with the open field, and can be extended by 2 to 3 months in the summer and 20 to 30 days in the spring and autumn. Therefore, south of the latitude 410 to the north of the 330 The high-efficiency energy-saving solar greenhouse (the indoor and outdoor temperature difference is maintained at around 30 °C) can produce warm fruits and vegetables in all seasons. In the greenhouse, the winter is only about 50d shorter than the open field. The spring and autumn only increase by about 20d than the open field, and the summer is rarely increased. Therefore, the fruit and vegetables can only be advanced in spring, and then cultivated in autumn. Only under multiple coverage, it is possible to produce fruit and vegetables in winter and spring. . The highest and lowest temperatures in the northern winter and spring unheated greenhouses appear slightly later than the open fields, but the indoor temperature difference is much larger than the open field. In the northern energy-saving solar greenhouse, due to the good lighting and heat preservation, the daily temperature difference in winter is as high as 15~30°C, and the temperature and fruit vegetables can be produced without heating in the area around 400 latitude or basically without heating. 2. There is “inverse temperature†phenomenon in the facility. However, in plastic arch sheds or glass greenhouses without multiple coverage, the cooling rate after sunset is often faster than that of open land, such as cold air intrusion, especially after the northerly wind On a sunny breezy night, the indoor temperature in the greenhouse and the greenhouse often appears to be lower than the outdoor temperature of 1-2 °C. From October to March of the next year, it is possible to appear, especially in the case of spring inversion. 3. The temperature distribution in the greenhouse is uneven. Generally, the upper part of the room temperature is higher than the lower part, and the middle part is higher than the surrounding area. The north side of the northern solar greenhouse is higher than the south side. The smaller the area of ​​the protection facilities is, the larger the proportion of the low temperature area is, and the more uneven the distribution. The change in ground temperature, regardless of seasonal and daily changes, is less than temperature changes.
(2) The temperature regulation of the temperature conditions in the facility is the primary environmental condition for the cultivation of horticultural crop facilities. The growth and life-sustaining activities of any crop require a certain temperature range, that is, the “three basic points†of temperature. The temperature is related to the growth stage of the crop, flower bud differentiation and flowering, and the temperature of day and night affects the shape of the plant and the yield and quality of the product. Therefore, producers use temperature as the primary means of controlling the growth of greenhouse crops. Considering various factors, it is clear that the optimum temperature for crop growth is different from the optimum temperature for economic production, and the determined management temperature is to make the crop production suitable for market demand and to obtain the maximum benefit. The stable temperature environment is an important guarantee for stable crop growth and long-term production. The size, orientation, interception of light energy, wind speed and temperature of the building will affect the stability of the greenhouse temperature. The regulation of the temperature environment in the facility is generally carried out by means of heat preservation, heating, and cooling.
Insulation
The solar greenhouse can be provided with an insulation wall; the rear slope is reinforced, and the polystyrene foam board is used for heat insulation on the back slope; the straw cover, the paper quilt, the heat preservation quilt, the quilt, etc. are covered on the transparent cover to perform external heat preservation; In the greenhouse or plastic greenhouse, the arch shed is set up, and the second layer curtain is set; the cold-proof ditch with a depth of 60-70cm and a width of 50cm is dug around the greenhouse; try to keep the relative closure, reduce ventilation and other measures to enhance the insulation effect. Large-scale greenhouse insulation mainly adopts transparent roofing with double-layer inflatable film or double-layer polyethylene plate and two-layer insulation screen and vertical curtain which can be moved in parallel indoors for heat preservation.
2. Heating
When the temperature of the facility is low and the crop grows slowly, it can be properly warmed. Warming is divided into air heating, matrix heating, and nutrient solution heating.
(1) Air heating air heating method includes hot water heating, steam heating, fire channel heating, hot air furnace heating and so on. Hot water warming room temperature is relatively stable, it is a common heating method; steam, hot air heating effect is fast, but temperature stability is poor; rice road heating construction cost and operating cost is low, is a form often used in solar greenhouses, but the thermal efficiency is low.
(2) Heating of the ground In winter, the rhizosphere temperature is low, and the crop grows slowly, which becomes a growth limiting factor. Therefore, the rhizosphere heating has obvious effects on the crop. In order to increase the rhizosphere temperature, a plastic pipe having an outer diameter of 15 to 50 cm is usually buried in a cultivation substrate of 20 to 50 cm, and hot water is passed through, and the temperature of the substrate can be increased by this method. Some places use the method of brewing heat to increase the ground temperature, that is, digging a trench of 40cm in width and 50-60cm in depth in the greenhouse, filling the straw or chopped corn stover, and letting it slowly ferment and release heat. The heating line can also be used to increase the rhizosphere temperature when the area is small.
(3) The cultivation bed heating system is not cultivated. After the ground is hardened, the concrete floor is often heated. When heating the concrete floor, some pipes are buried in the concrete. Compared with the soil, the conductivity of the concrete material is often better, so the temperature difference between the pipe and the surface is smaller; the substrate layer of the elevated bed cultivation system is thinner. The temperature has a large influence. When the planting bed is heated, the heating pipe is laid at the bed near the bed. In the NFT cultivation, the winter is usually heated in the liquid storage tank. In order to ensure the stability of the nutrient solution temperature, the liquid supply pipeline needs to be insulated, that is, the aluminum foil wool or the like is used to coat the pipeline. In addition to the above heating method, the use of geothermal heat, plant waste heat, underground latent heat, urban waste heat, solar energy and other heating methods can also be used to warm the facility, sometimes using temporary heating, such as burning charcoal, sawdust, fumigation, etc. .
3. Cool down
The way to cool down is to reduce heat ingress and increase heat dissipation, such as sunshade sunshade, transparent roof spray coating (lime) and ventilation, spray (dissipated as vaporized heat), wet curtains, etc.
(1) Ventilation and ventilation is an important means of cooling. The principle of natural ventilation is to ventilate small, medium, re-top and final bottom. The order of closing the vents is reversed. The principle of forced ventilation is that the air should be far away from the plants. Reduce the impact of airflow on plants, and many small vents are better than a few large vents. In the winter, exhaust fans are used to dissipate heat to prevent cold air from blowing plants, frostbite crops, and perforated pipes in summer. The cold air is evenly sent to the vicinity of the plant.
(2) Shading Summer glare High temperature is a limiting factor for crop growth. It can be cooled by shading net, which can generally reduce the temperature by 5 to 7 °C. There are two kinds of internal shading and external shading.
(3) Water curtain, wet curtain and spray cooling the top of the greenhouse to spray water, forming a water curtain, the shading rate is up to 25%, and it can absorb heat and cool down. In high temperature and dry areas, wet curtains can be set to cool down. The wet curtain cooling system consists of a fan, a cooling plate (wet belt) and a pump and piping system that transfers moisture to the top of the wet curtain. The wet curtain is usually made of a 15 to 30 mm thick cross-woven fiber material, which is mounted on a wall facing the prevailing wind, and the fan is mounted on a mountain wall opposite to the wall with the wet curtain. Through the wet and cold air of the wet curtain, the greenhouse is cooled down through the greenhouse and left the greenhouse by a fan. The disadvantage of the wet curtain cooling system is that it will produce dirt and breed algae on the wet curtain, and will cause a certain temperature difference and humidity difference in the greenhouse, and the cooling effect will be significantly reduced in the area with high humidity. Spray equipment can also be designed to cool down in the greenhouse. If the size of the water droplets is less than 10um, they will be floated in the air and evaporated, while avoiding water droplets falling on the crop. Spray cooling is better than the cooling effect of the wet curtain system, especially for some foliage plants, because many types of foliage plants are "burned out" in the environment of high temperature airflow generated by fans.
Fourth, CO2 and its regulation
CO2 is an important raw material for crop photosynthesis. In a closed greenhouse condition, the CO2 concentration during the day is often lower than that of the outdoor. Even after ventilation, the CO2 concentration will rise, but it is still not as high as the CO2 concentration in the outside atmosphere. Therefore, regardless of the lighting conditions, the application of CO2 during the day has a positive effect on the growth of the crop. Due to the limited space and containment of the greenhouse, the application of CO2 (gas fertilization) is made possible. In northern China, the winter is tightly closed, the ventilation is less, and the indoor CO2 deficiency is serious. At present, the CO2 fertilization technology is promoted, and the effect is very remarkable. Generally, cucumber, tomato, pepper and other fruits and vegetables CO2 fertilization yields an average yield increase of 20% to 30%, and can improve quality. Fresh cut flowers with CO2 can increase flowering, increase and increase the quality of the flowers, and improve the quality of the flowers. CO2 application can not only increase the yield per unit area, but also improve facility utilization, energy efficiency and light energy utilization.
1. CO2 application concentration For general horticultural crops, the economically significant CO2 concentration is 5 times the atmospheric concentration. The optimum concentration of CO2 fertilization is related to crop characteristics and environmental conditions. The amount of CO2 is closely related to light intensity, temperature, humidity, ventilation, and the like. Japanese scholars have suggested that the concentration of greenhouse CO2 should be 0.01%, but the application rate in the greenhouse production in the Netherlands is mostly maintained between 0.0045% and 0.005%, so as to avoid excessive concentration inside and outside during ventilation, too much fugitiveness, and economically not. Cost effective. Generally, the CO2 concentration should be increased correspondingly with the increase of light intensity. The application of CO2 on cloudy days can increase the utilization of scattered light by plants; the application of CO2 during light supplementation has a significant synergistic effect.
2. CO2 source CO2 is derived from CO2 produced by burning coal, coke, natural gas, biogas, etc. during heating. It can also specifically burn white kerosene to produce CO2, and also use liquid CO2 or solid CO2 (dry ice) or CO2 particulate gas in the matrix. The fertilizer or a strong acid (sulfuric acid, hydrochloric acid) and carbonate (calcium carbonate, carbonic acid plating, ammonium hydrogencarbonate) react to produce CO2 and the like. At present, there are many CO2 generators for burning petroleum liquefied gas. Organic fertilizers such as greenhouse straw can ferment and release a large amount of CO2. The method is simple, economical and effective, and organic fertilizer is applied in greenhouse substrate culture production, which has significant effects on alleviating CO2 deficiency and increasing yield. The edible fungus is simultaneously produced under the cultivation bed, and the indoor CO2 can be maintained at 800-980 umol/mol.
3. CO2 application time Theoretically, CO2 fertilization should be carried out during the most vigorous period of photosynthesis in the crop and the best time in the day. CO2 fertilization in seedling stage should be carried out as early as possible. The time of CO2 fertilization after planting depends on the crop type, cultivation season, facility status and type of fertilizer source. Fruit and vegetable vegetables are generally not fertilized after planting until flowering, and fertilization is started after flowering and fruit setting, mainly to prevent excessive growth of nutrients and long plants; leafy vegetables are fertilized immediately after planting. In the Netherlands, using boiler gas, CO2 fertilization often runs through the entire growth period of the crop. During the day, the CO2 fertilization time should be based on the variation of CO2 in the facility and the photosynthetic characteristics of the plants. In Japan and China, CQ fertilization starts from 0.5~lh after sunrise or sunrise, and ends before ventilation and ventilation; when it is not ventilated during cold season or cloudy day, it can stop fertilization at noon. In the Nordic countries, the Netherlands and other countries, CO2 fertilizer application is carried out throughout the day, and the noon ventilation window automatically stops when it reaches a certain size. The application of CO2 should be noted: 1 The photosynthesis CO2 saturation point of crops is very high, and it is changed due to environmental factors. The application concentration is for economic production. The high CO2 concentration not only increases the cost, but also causes premature senescence of crops. Morphological change. 2 Use CO2 produced after combustion, pay attention to the incomplete combustion or impurity gases in the fuel, such as ethylene, propylene, hydrogen sulfide, carbon monoxide (CO), sulfur dioxide (SO2) and other damage to crops. 3 The chemical reaction to produce SO2 is only used as a temporary supplement. There are almost no chemical reactions in the greenhouses that are operated on a large scale in the world, because high costs, post-treatment of residues, pollution to the environment, and safety are all to be studied.
Five, air humidity
1. Characteristics of air humidity change in the facility Because the environmental protection facility is a closed or semi-closed system, the space is relatively small and the airflow is relatively stable, so that the air humidity in the facility has different characteristics from the open ground. The characteristics of air humidity changes in the facility are mainly:
(1) Humidity The relative humidity and absolute humidity in the facility are higher than those in the open field. The average relative humidity is generally around 90%, especially at night. Especially in the solar greenhouse and medium and small arch sheds, due to the relatively small space inside the facility, the winter and spring seasons are insulated, and there is little ventilation and ventilation, and the air humidity often reaches 100%.
(2) Seasonal changes and daily changes. Seasonal changes in the facility are generally high in relative humidity in low temperature seasons and low in relative humidity in high temperature seasons; day and night changes to high humidity at night, low humidity during the day, and lowest humidity during noon during the day. The smaller the facility space, the more obvious this change.
(3) Uneven distribution of humidity Due to the difference in temperature distribution within the facility, the relative humidity distribution also differs. Under normal circumstances, the lower temperature part has higher relative humidity, and often causes condensation at local low temperature parts, which adversely affects the installation environment and plant growth and development.
2. Adjustment of air humidity in the facility The air humidity mainly affects the stomatal opening and closing and leaf transpiration of horticultural crops; directly affects the growth and development of crops. If the air humidity is too low, the leaves of the plants will be too small, too thick, mechanical tissue will increase, and flowering will occur. Poor fruit setting, fruit swelling speed; high humidity, it is easy to cause crops to grow too strong stems and leaves, flowering and fruiting worse, physiological function is weak, resistance is not strong, there is deficiency, causing yield and quality are affected . Under normal circumstances, most vegetable crops have a suitable air growth temperature range of 50 to 85%. In addition, the occurrence of many diseases is closely related to air humidity. Most diseases require high humidity conditions. Under high humidity and low temperature conditions, the condensation on the surface of the plant and the condensation of the covering material on the plant will aggravate the occurrence and spread of the disease. Some diseases are prone to occur under low humidity conditions, especially under high temperature and drought conditions. Therefore, from the perspective of creating suitable conditions for plant growth and development, controlling disease occurrence, saving energy, increasing yield and quality, and increasing economic benefits, air humidity should be controlled at 70-90%. The main methods of humidity regulation are: controlling the source of water, temperature, ventilation, and using a hygroscopic agent.
1. Increasing the humidity Under the high temperature and strong light in summer, the humidity of the air is too dry, which is unfavorable to the growth of the crop. In severe cases, it will cause the plants to wilted or die. Especially when cultivating flowers and vegetables that require high humidity, the relative humidity is generally less than 40%. Need to increase the humidity. Common methods are spray or ground sprinkler, such as 103 type three-phase electric spray humidifier, air scrubber, centrifugal sprayer, ultrasonic sprayer, etc. The wet curtain cooling system can also increase the humidity of the air. In addition, the relative humidity or the transpiration intensity can be increased by lowering the room temperature or reducing the light intensity. Air humidity is also increased by increasing the number of waterings, the amount of watering, and reducing ventilation.
2. Reducing air humidity Soilless greenhouses often harden the ground or cover it with a film, which can effectively reduce evaporation and reduce air humidity. Natural ventilation dehumidification and cooling is a common method. By opening the ventilation window, uncovering the film, quilting and other ventilation methods, the purpose of reducing the humidity inside the facility is achieved. Film mulching reduces evaporation, which can reduce air humidity from 95% to 100% to 75% to 80%; increase temperature (heating, etc.) to reduce relative humidity; use moisture absorbing materials, such as two-layer curtain non-woven fabric, ground Laying straw, quicklime, oxidized silica gel, chlorination, etc.; strengthen ventilation and discharge humid air; set dehumidification membrane, use drip film and cooling tube to let water vapor dew and then discharge outside; spray anti-transpiration agent to reduce Absolute humidity. It is also possible to reduce the relative humidity by reducing the number of irrigations, the amount of irrigation, and changing the irrigation method.
Sixth, the comprehensive control technology of the environment
The comprehensive environmental management of the greenhouse is not only the comprehensive environmental regulation, but also the real-time monitoring of the environmental conditions and the operation status of various devices, and the configuration of various data and data records, storage, output and alarms of abnormal conditions. It is also necessary to proceed from the overall situation of greenhouse management, consider various input and output costs of production materials, market price changes of output products, labor and management operations and funds, and conduct effective comprehensive environmental regulation according to benefit analysis. The impact of greenhouse environmental factors on crops is the result of a comprehensive effect, and there is a close relationship between environmental factors, with a linkage effect. Therefore, although we can control the change of a certain factor within one day through sensors and equipment, such as using a hygrometer to link with the spray equipment to maintain the minimum air humidity, or use the temperature controller to control the temperature change with the time controller. Although the above is easy to implement automatic control, it seems to be somewhat mechanical or uneconomical. The development and application of computers enable complex computational analysis to be carried out quickly, creating conditions for the comprehensive regulation of greenhouse environmental factors, from static management to dynamic management. The computer is connected to indoor and outdoor weather stations and indoor environmental element control equipment (blackout curtain, second floor curtain, ventilation window, ventilation fan, spray equipment, CO2 generator, EC, pH control equipment, heating system, water pump, etc.). Generally, according to the amount of solar radiation and the type of cultivated crops, reasonable parameters such as temperature, CO2, and air humidity in greenhouse management are determined, and intelligent control equipment is started to achieve these goals. Automatically observe and record changes in indoor and outdoor environmental meteorological elements and equipment operation at any time.
Through the comparison of output and quality, the original design procedure is adjusted, and the control methods are changed to achieve economic production. In recent years, through the advancement of comprehensive control technology, the Netherlands has increased the tomato production from 40 kg/m2 to 54 kg/m2, while the production costs such as energy consumption and labor have been significantly reduced, which has greatly improved the economic benefits of greenhouse production.
Not only that, the computer system can also be equipped with an early warning device, which can process, prompt, and record in time when environmental elements are significantly changed. For example, when the wind speed is too large, the windward sunroof can be closed in time; when the measuring instrument stops working, it can prompt the location of the instrument to be processed in time; when there is power outage, water stop, insufficient pump power, motor failure, the alarm can be timely and recorded. To provide a basis for future adjustment and improvement. The development and application of computer control systems for greenhouse environments have made complex greenhouse management simple, standardized and scientific.
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