翻訳と辞書 Words near each other ・ Self-executing right ・ Self-executing rule ・ Self-existing Perfection ・ Self-expandable metallic stent ・ Self-expansion model ・ Self-experimentation ・ Self-experimentation in medicine ・ Self-explanatory ・ Self-expression values ・ Self-extracting archive ・ Self-fabric ・ Self-fashioning ・ Self-financing portfolio ・ Self-flagellation ・ Self-focusing ・ Self-focusing transducers ・ Self-framing metal buildings ・ Self-fulfilling crisis ・ Self-fulfilling prophecy ・ Self-fulfillment ・ Self-funded health care ・ Self-governance ・ Self-governance of Singapore ・ Self-governing colony ・ Self-Government Army ・ Self-Government Guiding Board ・ Self-gravitation ・ Self-guided tour ・ Self-handicapping ・ Self-harm Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Self-focusing transducers ： ウィキペディア英語版 Self-focusing transducers Acoustic waves emitted by ultrasonics transducer crystals exhibit a property known as self-focusing (or ''natural focusing''). Note that this is distinct from the electronically controlled focusing employed in diagnostic ultrasound devices which employ arrays of transducers. The self-focusing effect exists even for a single crystal. Self-focusing refers to the narrowing of the ultrasonic beam in the near-field. The effect occurs because, if the ultrasound wave generated by the crystal is coherent, the edges of the emitting surface generate wavelets that constructively interfere with the plane wave that is generated. The volume near the transducer which exhibits this phenomenon is called the near field, as opposed to the far field where wave intensity decays approximately exponentially. The near-field size is usually approximated by $D\; =\; \backslash frac$ where $d\; =$crystal diameter and $\backslash lambda\; =$wavelength of the emitted wave. At the edge of the near-field, where the focusing reaches its maximum, the beam width reaches $\backslash frac$. However, there exist techniques, such as apodization that may be used to reduce the near field size. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Self-focusing transducers」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.