Many of the traditional woods used for musical instruments have been selected not only for their natural beauty but for the high content of waxes and resins that help increase water repellency of the wood but have lit...Many of the traditional woods used for musical instruments have been selected not only for their natural beauty but for the high content of waxes and resins that help increase water repellency of the wood but have little or no effect on stabilizing dimensions or vibrational properties. Moisture changes have a great negative effect on both the musical quality of wooden musical instruments and limit the length of time they can be played without loss of musical quality. It is possible to stabilize both the wood and the vibrational properties by chemically modifying the wood. One technology that can do this is the reaction of wood with acetic anhydride. Acetylation of wood slightly increases density, and slightly （about 5%） reduces both sound velocity and sound absorption when compared to unreactedwood. Acetylation does not change the acoustic converting efficiency. Acetylation reduces the amount of moisture in the cell wall decreasing the effect of moisture on the viscose properties of wood. This allows a wooded musical instrument to be played longer without having to let it dry out. This gives an instrument made from acetylated wood a greater range of moisture conditions it can be played in without losing tone quality. Acetylation also greatly stabilizes the physical dimensions of the wood. The major effect of acetylation of wood, therefore, is to stabilize acoustic properties. The technology can be applied to almost any wood though more easily to permeable types so non-traditional wood species can be used. A violin, a piano soundboard, a guitar, a recorder, a bagpipe chanter, and trumpet and trombone mouthpieces have been made using acetylated wood with very positive results. Several more wooden instruments made from acetylated wood are presently being made for further testing and early market development.展开更多
针对普通硅胶吸水率不高、单一组分改性硅胶再生温度相对较高的缺陷,运用氯化钙和氯化镁复合改性硅胶,制备新型干燥剂。通过测定复合硅胶的差示扫描量热曲线(DSC)和热重分析(TG)曲线,考察复合硅胶的吸水性能、再生性能和对水的脱附活化...针对普通硅胶吸水率不高、单一组分改性硅胶再生温度相对较高的缺陷,运用氯化钙和氯化镁复合改性硅胶,制备新型干燥剂。通过测定复合硅胶的差示扫描量热曲线(DSC)和热重分析(TG)曲线,考察复合硅胶的吸水性能、再生性能和对水的脱附活化能的影响。研究表明:在室温饱和湿度下,用浓度均为0.25 mol L 1的氯化钙和氯化镁复合改性硅胶的吸水量约为未改性硅胶相应值的2倍,吸湿速率提高3.5倍以上。复合干燥剂的再生温度比改性前低了10℃,脱附活化能数值小,再生6次后再生率依然高达92%左右,且基本不再变化。展开更多
文摘Many of the traditional woods used for musical instruments have been selected not only for their natural beauty but for the high content of waxes and resins that help increase water repellency of the wood but have little or no effect on stabilizing dimensions or vibrational properties. Moisture changes have a great negative effect on both the musical quality of wooden musical instruments and limit the length of time they can be played without loss of musical quality. It is possible to stabilize both the wood and the vibrational properties by chemically modifying the wood. One technology that can do this is the reaction of wood with acetic anhydride. Acetylation of wood slightly increases density, and slightly （about 5%） reduces both sound velocity and sound absorption when compared to unreactedwood. Acetylation does not change the acoustic converting efficiency. Acetylation reduces the amount of moisture in the cell wall decreasing the effect of moisture on the viscose properties of wood. This allows a wooded musical instrument to be played longer without having to let it dry out. This gives an instrument made from acetylated wood a greater range of moisture conditions it can be played in without losing tone quality. Acetylation also greatly stabilizes the physical dimensions of the wood. The major effect of acetylation of wood, therefore, is to stabilize acoustic properties. The technology can be applied to almost any wood though more easily to permeable types so non-traditional wood species can be used. A violin, a piano soundboard, a guitar, a recorder, a bagpipe chanter, and trumpet and trombone mouthpieces have been made using acetylated wood with very positive results. Several more wooden instruments made from acetylated wood are presently being made for further testing and early market development.
文摘针对普通硅胶吸水率不高、单一组分改性硅胶再生温度相对较高的缺陷,运用氯化钙和氯化镁复合改性硅胶,制备新型干燥剂。通过测定复合硅胶的差示扫描量热曲线(DSC)和热重分析(TG)曲线,考察复合硅胶的吸水性能、再生性能和对水的脱附活化能的影响。研究表明:在室温饱和湿度下,用浓度均为0.25 mol L 1的氯化钙和氯化镁复合改性硅胶的吸水量约为未改性硅胶相应值的2倍,吸湿速率提高3.5倍以上。复合干燥剂的再生温度比改性前低了10℃,脱附活化能数值小,再生6次后再生率依然高达92%左右,且基本不再变化。
