Negative net migration hasn’t definitively happened in the U.S. for almost a century, not since the Great Depression. The U.S. native-born population is also in free fall, well below the replacement rate needed to maintain population numbers in the long run. With fewer immigrant arrivals already dealing a blow to the workforce, the shrinkage of the American taxpayer base is set to further widen the country’s deficit and hurt its prospects for economic growth.
（三）后处理，是指对反应堆乏燃料进行处理，以分离其中的裂变产物，并回收可裂变物质的过程。
。爱思助手下载最新版本是该领域的重要参考
viewContainer.appendChild(renderer.domElement);
20+ curated newsletters