Small rootballs are usually wrapped with hessian and ropes , or enclosed in a timber box . large rootballs have to be secured in a steel box reinforced with steel beams 细小的根团需以麻布及绳封绑，或放进木盒内；庞大的根团则须放进钢箱，再用方钢柱稳固。
And its production lines are the most advanced ones in the steel industry of china , which have adopted 12 step continuous rolling technology , and it is best for producing all kinds of flat bars , square bars , angle bars and round bards 该生产线采用十道连轧，两道立轧工艺，专业轧制各种规格的扁钢、方钢角钢及圆钢，为目前国内生产同类产品中最先进的生产线。
The general situation and progress of magnetic dipole theoryresearch during recent twenty years in china were introduced briefly including magnetic dipole ; linear and strip magnetic dipoles of finite lengths ; magnetic force on a magnetic particle ; the effect of magnetizing field orientation on the revelation of defect by magnetic particles ; longitudinal magnetization of rod , tube and cuboid steel ; the relationship between the slot depth in a workpiece and magnetic leakage field ; the cause of stray magnetic pattern along base apex edges of a workpiece magnetized circumferentially ; the analytic expression for the magnetic leakage fields inside and outside the slot on the cylindrical surface of a disc ; and the effect of a needle - like magnetic medium on the magnetic force between two point magnetic charges 简述20年来中国无损检测中磁偶板子理论研究的概况和进展，主要介绍磁偶极子，有限长磁偶极线和极带，磁粉颗粒的受力，磁化场方向对磁粉显现缺陷的影响，棒料、管材和方钢的纵向磁化，工件表面沟槽深度对其引起漏磁场的影响，周向磁化时工件底棱上的杂乱显示成因，圆盘边缘柱面上沟槽内外漏磁场的解析表达式和针状磁介质对两个点磁荷间磁力的影响等。
Abstract : the general situation and progress of magnetic dipole theoryresearch during recent twenty years in china were introduced briefly including magnetic dipole ; linear and strip magnetic dipoles of finite lengths ; magnetic force on a magnetic particle ; the effect of magnetizing field orientation on the revelation of defect by magnetic particles ; longitudinal magnetization of rod , tube and cuboid steel ; the relationship between the slot depth in a workpiece and magnetic leakage field ; the cause of stray magnetic pattern along base apex edges of a workpiece magnetized circumferentially ; the analytic expression for the magnetic leakage fields inside and outside the slot on the cylindrical surface of a disc ; and the effect of a needle - like magnetic medium on the magnetic force between two point magnetic charges 文摘:简述20年来中国无损检测中磁偶板子理论研究的概况和进展，主要介绍磁偶极子，有限长磁偶极线和极带，磁粉颗粒的受力，磁化场方向对磁粉显现缺陷的影响，棒料、管材和方钢的纵向磁化，工件表面沟槽深度对其引起漏磁场的影响，周向磁化时工件底棱上的杂乱显示成因，圆盘边缘柱面上沟槽内外漏磁场的解析表达式和针状磁介质对两个点磁荷间磁力的影响等。
