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wanghaiju

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[求助] 高分子論文翻譯求助

The transmission losses of the as-received and oxidized woven fabrics are plotted in Fig. 6a and b, respectively, as a function of frequency. The decreasing fraction of the transmitted wave through the material corresponds to the weakening of the transmission loss (higher negative dB). The lowest transmission losses were seen in the ZE8 fabric in both as-received and heat-treated conditions. Similar to its reflection loss, the PN fabric recorded the largest difference in transmission loss between its as-received and heat-treated states. Moreover, as a general tendency, it was observed that woven fabrics that have a higher reflectivity of electromagnetic waves also recorded lower transmission(higher reflection loss corresponds to lower transmission loss).
In line with the principle of energy conservation, incident electromagnetic radiation energy is either reflected,transmitted, or absorbed (dissipated and converted into heat) by a material. Accordingly, the absorption percentages of the woven fabrics were calculated using Eq. 3,where %R and %T represent the reflected and transmitted portion of the electromagnetic wave, respectively. Table 3 shows the calculated absorption percentages (%) of the ceramic woven fabrics at various frequencies. The absorption percentages of single-layer SiC-based ceramic woven fabrics were \40%, which made them highly unsuitable as electromagnetic absorbing materials in commercial applications.
In order to achieve a better electromagnetic wave absorption potential, several double-layer combinations of the as-received and heat-treated ceramic woven fabrics were constructed. In the first case, combinations of as-received woven fabrics were measured, among which combinations of S8 woven fabrics recorded good absorption characteristics, with both reduced reflection and transmission loss. Figure 7 shows the absorption potentials of double-layer combinations containing S8-type woven fabrics as one of the layers. A low-conductivity layer(S8 woven fabric) reduced the reflection loss at the air/low-
conductivity layer interface, while most of the electromagnetic wave transmitted through the woven fabric was reflected from the surface of the second layer. The low-conductivity first layer behaved as an absorbing layer, whereas the high-conductivity second layer behaved as a reflective layer, binding electromagnetic energy within the material system. In the low→ high electrical conductivity layer combinations higher absorption potentials were
achieved. In this respect, the highest conductivity mismatch between the S8 and ZE8 fabrics resulted in the maximum absorption potential. Additionally, the ordering of the layers also affected the absorption potential of a given combination; for example, the absorption potential of the S8–ZE8 combination was different to that of the ZE8–S8 combination, although both combinations contained identical woven fabric layers. In the case of the S8–ZE8 combination, the electromagnetic wave was first confronted with the low-conductivity S8 woven layer,before passing through the ZE8 woven layer; whereas inthe ZE8–S8 combination, the ZE8 layer was the first layer to act upon the electromagnetic wave, followed by the S8 layer. Due to the high reflection loss of the ZE8 fabric,
the absorption potential was weaker in the ZE8–S8 combination.

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wanghaiju: 金幣+37, 翻譯EPI+1 2014-06-12 18:11:01

收貨狀態(tài)和氧化后織物關(guān)于頻率的傳輸損失如圖6a、6b所示。發(fā)射波穿過材料的減弱部分對(duì)應(yīng)傳輸損失的弱化（較高的負(fù)dB）。ZE8織物的收貨狀態(tài)和熱處理狀態(tài)都展現(xiàn)出最低的傳輸損失。與反射損失相似，PN織物的收貨狀態(tài)和熱處理狀態(tài)之間的傳輸損失區(qū)別最大。此外觀察到一個(gè)普遍趨勢(shì)，較高電磁波反射率的織物同時(shí)也具有較低的傳輸率（高反射損失對(duì)應(yīng)低傳輸損失）。
按照能量轉(zhuǎn)化原理，發(fā)射電磁輻射能量被材料反射、傳輸或吸收（耗散或轉(zhuǎn)化為熱）。相應(yīng)地，織物的吸收百分比用公式3計(jì)算，%R和%T分別代表電磁波的反射和傳輸部分。表3所示為陶瓷織物在不同頻率上計(jì)算得到的吸收百分比（%）。單層基于SiC的陶瓷織物的吸收百分比是\40%，導(dǎo)致它們不適合用作商業(yè)應(yīng)用中的電磁波吸收材料。
為了獲得更好的電磁波吸收能力，用收貨狀態(tài)和熱處理后的陶瓷織物制作了幾種雙層組合。第1例中測(cè)量了收貨狀態(tài)的織物組合，S8織物組合的反射和傳輸損失均減小，顯示出良好的吸收特性。圖7所示為含有一層S8型織物的雙層組合的吸收特性。低電導(dǎo)率層（S8織物）減小空氣/低電導(dǎo)率層界面的反射損失，大部分穿過織物的電磁波被第2層表面反射。低電導(dǎo)率的第1層作為吸收層，高電導(dǎo)率的第2層作為反射層，將電磁能量約束在材料系統(tǒng)內(nèi)部。低→高電導(dǎo)率層的組合實(shí)現(xiàn)了較高的吸收能力。據(jù)此，S8和ZE8織物間的最高電導(dǎo)率差導(dǎo)致最大化的吸收能力。此外，層的順序也影響組合的吸收能力；例如S8-ZE8組合的吸收能力不同于ZE8-S8，盡管2種組合含有相同的織物層。對(duì)于S8-ZE8的組合，電磁波在穿過ZE8織物層之前先接觸低電導(dǎo)率的S8織物層；而對(duì)于ZE8-S8組合，ZE8層先和電磁波發(fā)生作用，然后是S8層。由于ZE8織物的高反射損失，其吸收能力弱于ZE8-S8組合。

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2樓2014-06-12 13:42:38