Redwood is a kind of furniture material, and the wood of the genus Rosewood is prolific in Southeast Asia and Hainan, Guangdong, Yunnan and other places in China. The difference between the heartwood and the sapwood is obvious, the sapwood is narrow, grayish white; the heartwood is yellowish red to red, and it is purple-red when exposed to the air. The mahogany pattern is beautiful, the material is hard and durable, and it is used for valuable furniture and arts and crafts. Guangdong is commonly known as "sourwood". There are dozens of five types of redwoods, and the most widely known ones are Hainan huanghuali and sandalwood rosewood. The time for the construction of Hainan huanghuali is generally 500 years. Currently, it is almost rare in the market, and almost all of the furniture has entered the auction collection market. Because the available parts of the wood are generally only the heart, the Hainan huanghuali heart with a thick bowl may have only one chopstick thickness. This also makes it extraordinarily precious. Because of the beautiful lines, Hainan huanghuali is mostly used for furniture. In addition, Hainan huanghuali has a certain medicinal value, and it can be effectively worn for a long time. A set of new huanghuali-made southern official hat chairs on the market, the price is two or three million yuan. Sandalwood rosewood, also known as lobular rosewood, is a boutique of red sandalwood with a high density and is mainly produced in India. As the saying goes, "Ten Tan Nine", the largest rosewood is only about 20 cm in diameter, and its preciousness can be imagined. The ancient Chinese understanding and use of rosewood began in the late Eastern Han Dynasty. In the Jin Dynasty, Cui Bao’s "Ancient and Modern Notes" has a record, called "red sandalwood, out of Funan, color purple, also known as red sandalwood." The red sandalwood of the Ming Dynasty was valued by the royal family. The color of rosewood is deep purple. It has always been a special wood for royal aristocratic furniture. It is expensive and ranks first among all woods. It is called "the wood of the emperor." Due to the extremely low yield rate and the scarcity of resources, there is also the saying that “inch sandalwood is goldâ€. The new surface of the lobular rosewood is orange-yellow, which gradually turns into deep red, purple, and black after oxidation. Many people collect lobular rosewood furniture in order to enjoy the color change process, and its color is deep, dense, and looks very stable. The market has a set of new lobular rosewood material for the southern official hat chair, the price is four hundred and fifty thousand yuan. Buying a mahogany collection must not be painted. In order to save raw materials, some manufacturers fill the color of the meat near the heart, and draw the same texture as the concentric material. After painting, they can't see it completely. The collection value of such mahogany furniture is definitely greatly reduced. Therefore, the purchase of mahogany collection must not require lacquering, waxing, and whitening. After signing the contract, the upper layer of light wax can be used for better protection. When formulating a furniture contract, the scientific name of the wood must be clearly marked. Once the concept is enlarged, the value difference may be several million yuan. For example, there are many kinds of rose branches, the most expensive is the Sian rosewood. If there is no standard definition, some unscrupulous merchants will use the dimpled Dalbergia to pretend. There are many factors that affect the value of mahogany furniture. In addition to wood, imposition, coloring, and secondary filling are important indicators to measure their value. The quality of the process will directly affect its value.
small fan
DC Fan is through the input DC power, so that the DC motor rotates to drive the fan impeller rotation, in order to achieve DC to mechanical energy conversion process fan. The biggest feature of Dc Fan is the optional DC motor.
Introduction
At present, DC fans use more DC brushless motors. Brushless DC motors eliminate the need for slip rings and brushes for excitation and greatly simplify the structure. At the same time, it not only improves the processability of the motor, but also greatly enhances the mechanical reliability of the motor operation and increases the service life.
At the same time air gap flux density can be greatly improved, the motor indicator can achieve the best design, the direct effect of the motor is reduced in size and weight. Not only that, but also has very good control performance compared to other motors. This is because: First, the torque constant, moment of inertia ratio, power density and the like of the motor are greatly increased due to the high performance of permanent magnetic materials. Through rational design and can make the moment of inertia, electrical and mechanical time constants and other indicators greatly reduced, as a major indicator of servo control performance has been greatly improved. Second, the design of modern permanent magnetic circuit has been more perfect, coupled with the high coercivity of permanent magnetic materials, and thus permanent magnet motor anti-armature reaction and its anti-demagnetization greatly enhanced the control parameters of the motor with the external Disturbance effect greatly reduced. Thirdly, since the permanent magnet replaces the electrical excitation and the design of the field winding and the field magnetic field is reduced, the parameters of the field flux, the field winding inductance and the field current are reduced, thereby directly reducing the controllable variable or the parameter. Based on the above factors can be said that permanent magnet motor with excellent controllability.
At present, large-capacity fan air flow control has been a lot of frequency control methods, this type of inverter mainly rely on imports, expensive. Currently 1kw below the power level of fans, especially home air conditioners and other fans have permanent magnet brushless DC motor drive, and the use of speed control air volume method. 1 ~ 10kw power range of the huge amount of fan, the basic induction motor drive, and adjust the outlet opening to adjust the amount of wind. For fans in this power range, using permanent magnet brushless DC motor drives to replace the original induction motor drive has great advantages.
DC Fan Dc Fan,Dc Cooling Fan,Plastic Dc Fan Shenzhen Fu Sheng Electric Co., LTD. , http://www.fushengfan.com
Redwood material identification practical skills
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