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  Concave-convex lens is an important and error-prone knowledge point in junior high school physical optical imaging. Because there are many imaging laws involved in the two, students often confuse them. In this article, we will sort out the structure and imaging of concave and convex lenses. And the difference in use, etc., to help students learn better. 【 Definition of convex lens 】 Convex lenses are made according to the principle of refraction of light. A convex lens is a lens that is thicker in the center and thinner at the edges. Convex lenses are divided into biconvex, plano-convex and concave-convex (or positive meniscus) forms. Convex lenses have the function of converging light, so they are also called converging lenses. Thicker convex lenses have functions such as telescopic and converging, which are related to the thickness of the lens. . 【 Definition of  Concave Lens 】 A concave lens is also called a negative spherical lens. The middle of the lens is thin and the edge is t

  High-speed rotary union is a type of rotary joint. High-speed rotary joints are used for high-speed interface transmission media. High-speed rotary joints are different from ordinary rotary joints, so you must pay special attention to them during normal use. Now let's take a look at the daily maintenance of high-speed rotary joints. High Speed Rotary Union   Maintenance Methods 1. Sealing surface Check the wear condition and thickness change of the sealing surface (generally, the normal wear is 5-10mm); observe the friction track of the sealing surface to see if there are three-point discontinuity or scratches. If these problems occur, don't hesitate to replace the rotary joint immediately. 2. Clean regularly Special attention should be paid to the inside of  the rotary joint  drum and pipeline, and a filter should be added when necessary. This is because many foreign objects will cause strong wear on the rotary joint, and frequent cleaning can effectively extend the service

  PET bottles have long penetrated into every part of people's lives - whether it is food, beverages, or cosmetics, or even the medicines we use, you can see it in them. But how are these PET bottles with different shapes and functions produced? The answer lies in the fully automatic production of PET blow molding machines. This article gives a detailed description of the production principle, application scenarios and production advantages of the PET bottle blowing machine, so as to help you get a preliminary understanding of the PET bottle blowing machine and gain some inspiration. What is a PET blow molding machine? The definition of a  PET blow molding machine   is a production machine used to make bottles of different shapes and sizes. How it works is not complicated: relying on the applied air pressure, the blower blows air into the heated preform and sets it with a specific mold that wraps it. In detail, the overall production process of the blow molding machine is as follow

    Malleable steel pipe fittings are pipe fittings made of malleable steel. Malleable steel is actually not steel, but malleable cast iron. The pipe fittings of this material can be machined, and have high mechanical properties, good plasticity and toughness, so they are widely used. The production process of malleable steel pipe fittings is very simple. It is first poured into white iron castings, and then can be treated by forge annealing. The annealing process technology is an important production process. Let's take a look at the material of malleable steel pipe fittings and the production process of malleable steel pipe fittings. 1. What are Malleable Steel Pipe Fittings There are many  types of pipe fittings , malleable steel pipe fittings are one of them, malleable iron is commonly known as malleable iron, the so-called malleable steel pipe fittings are pipe fittings made of malleable iron. 2. What is the material of the malleable steel pipe fittings? The material of  malle

A rectifier is a rectifying device, which in simple terms is a device that converts alternating current (AC) into direct current (DC). It has two main functions: first, to convert alternating current (AC) into direct current (DC), which is filtered and supplied to the load, or to the inverter; second, to provide charging voltage to the battery. Therefore, it also acts as a charger at the same time. The alternating current generated by the automobile generator is converted into direct current after being rectified by the rectifier, but its waveform still has irregular fluctuations, which directly affects the accuracy of vehicle ignition; the output voltage cannot be kept relatively constant, resulting in the energy difference of each spark plug ignition, which is easy to The engine of the vehicle is shaken, the gear shift is stuttered, the acceleration is slow and weak, the idle speed is unstable, and the efficiency of the vehicle air conditioner is low. As a result, the performance and

Teeth whitening strips  are flexible gel-based film strips for teeth whitening. They are easy to use, effective, and whiten teeth quickly. How do teeth whitening strips work? What are the characteristics of the different types of teeth whitening strips? Take a look below! How Do Teeth Whitening Strips Work? Teeth whitening strips are made of a soft plastic material covered with a thin layer of whitening gel, usually containing hydrogen peroxide or carbamide peroxide. When you place the strips on your teeth, the gel makes contact with the tooth surfaces and penetrates them to begin the whitening process.  Dead Sea Salt Teeth Whitening Strips Different Types of Teeth Whitening Strips Yellow teeth are a worry for many people. Healthy teeth are not very white. A color that matches your skin tone is the healthiest. However, some people overly pursue white teeth and use whitening products indiscriminately, which affects their health. I believe some people have used teeth whitening strips, so

  Plug gauges are available in several different types. These include: Go plug gauges No-go plug gauges Combination go/no-go plug gauges Go plug gauges and no-go plug gauges are called single-ended gauges and consist of a handle into which a precisely machined pin or shaft has been inserted (sometimes called a member) and which is used to verify an aspect of the dimensional tolerances of the hole. For single-ended gauges, they are usually offered in pairs with one go gauge and one no-gauge gauge. In its use, a go plug gauge is designed to test the minimum dimensional limit of the hole (i.e. the lower tolerance of the hole ’ s diameter) which represents the maximum amount of remaining material on the part or workpiece. For an acceptance condition, the go plug gauge should fit in the hole. If the go plug gauge will not fit into the hole in the workpiece, then that is an indication that the hole ’ s diameter is too small (an insufficient amount of material has been removed from the workpi

    The effective solution to the yellowing of elastomers is to add  antioxidants   and ultraviolet absorbers, which can effectively prevent and delay the yellowing. However, there are many kinds of antioxidants, and the selection of suitable products requires certain technical support and experience accumulation. The main culprit of oxidative yellowing of elastomers is ultraviolet rays, which are mainly from sunlight. Therefore, especially in the face of customers whose products need to be used outdoors, we will recommend adding a certain amount of ultraviolet absorbers to the products. , Can effectively absorb ultraviolet rays and delay yellowing. Moreover, the use of ultraviolet rays and antioxidants together can play a synergistic effect, and the effect of 1 plus 1 is greater than 2. 2. What are the different classifications and mechanisms of antioxidants? The classification of antioxidants, one is the main antioxidant: capture peroxidative free radicals, mainly hindered phenol ant

Construction projects require a great amount of detail and can take months or years to complete. An important part of the construction process is ensuring you choose the right structure design and materials.For example   spc floor , vinyl flooring , manhole cover , thread bar , aluminum building materials , plywood , vanities   and so on. You must consider the foundation and various natural elements before incorporating certain additional items into the building.   When building multi-story buildings, you should think about how people are going to access each floor. Stairs are a natural choice, but it is also wise to install an elevator   because it ’ s faster, more convenient, and it considers people with disabilities and mobility limitations.   What is an Elevator? An elevator is a platform that could either be open or closed and is used for lifting or lowering both people and goods to upper and lower floors. In the past, it was not mandatory for story buildings to have elevators. As