Based on the mechanism of heat generation at the welding interface, welding methods for thermoplastics can be classified as external and internal heating methods, as shown in Fig 1. Fig. 1. Classification of welding methods for semi-finished polymeric materials.
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Ritalin: A Controlled Substance. Ritalin Â® (methylphenidate hydrochloride) is a prescription medication that is classified as a controlled substance. Longer-acting forms of the drug (Ritalin SR Â® and Ritalin LA Â®) are also available (and are also controlled substances). Controlled substances are medications or drugs that are habit-forming and, therefore, likely to be abused. Certain prescription medications and most illegal street drugs are controlled substances.