RESUMEN La altura de la columna del bosque de tierra es generalmente de 8 ~ 30 m en el condado de Yuanmou, provincia de Yunnan, que es mucho más alta que la altura autoportante de la columna de suelo general. El cemento ferruginoso es una razón importante para la formación del suelo columnar alto y erecto. Las pruebas físicas y mecânicas macroscópicas confirmaron que la resistencia del estrato que contiene cemento ferruginoso fue mucho mayor que la de la formación sin cemento ferruginoso. La microestructura y la morfologia del cemento ferruginoso fueron analizadas por SEM y EDS. Se encuentra que el cemento ferruginoso se compone principalmente de compuestos de hierro y minerales arcillosos, que solo existen en ciertos estratos. En el proceso de crecimiento, los compuestos de hierro se unen químicamente con minerales de arcilla durante el crecimiento para formar cementos ferruginosos, que primero forman una esfera única en la superfície de partículas o minerales de arcilla. Luego se agrupa y llena los espacios entre las partículas. Finalmente, las partículas dispersas se conectan entre sí para formar una estructura espacial laminar estable, que mejora en gran medida la resistencia del suelo. A través del estudio del cemento ferruginoso, se comprende el mecanismo de este agente de curado natural, que enriquece el contenido de la investigación en este campo.

ABSTRACT The column height of earth forest is generally 8~30m in Yuanmou county of Yunnan province, which is far higher than the self-supporting height of general soil column. Ferruginous cement is an important reason for formation of the tall and erect columnar soil. Macroscopic physical and mechanical tests confirmed that the strength of the stratum containing ferruginous cement was much higher than that of the formation without ferruginous cement. The microstructure and morphology of ferruginous cement were analyzed by SEM and EDS. It is found that ferruginous cement is mainly composed of iron compounds and clay minerals, which only exists in certain stratum. In the process of growth, Iron compounds chemically bond with clay minerals during growth to form ferruginous cements, which first form unique sphere on the surface of particles or clay minerals. It then clumps together and fills the spaces between the particles. Finally, the dispersed particles are connected together to form a stable lamellar spatial structure, which greatly improves the strength of the soil. Through the study of ferruginous cement, the mechanism of this natural curing agent is understood, which enriches the research content in this field.

Abstract In this paper, design of dual-band equal-split Wilkinson power divider (WPD) with two and three transmission line (TL) sections is tackled from the perspective of a new simplified mathematical approach as compared to the previously presented work. It is mathematically proven and experimentally verified that only even-mode circuit analysis suffices for outlining the design guidelines for such WPDs which greatly reduces the mathematical complexity. Owing to the cascaded nature of the TL sections and using even-mode analysis, firstly, design equations and design graph are drawn for the two TL sections WPD. The technique is then extended to the design of a three TL sections WPD with simplifications in the circuit, rendering the approach much simpler and mathematically less rigorous (as compared to the previous work). The comparisons of the proposed and previous design approach are drawn. To prove the efficacy of the presented simplified design approach, a two TL sections and a three TL sections WPD are designed at 1GHz and 2.4GHz and fabricated. The measured S-parameters show good conformance with the simulated results indicating practical viability of the presented simplified approach. For instance the insertion loss in the two and three TL section is better than 3.2dB. The return loss and isolation between the ports in two TL sections WPD come out to be better than 28dB and 29dB, and in three TL sections is better than 30dB and 29dB respectively at the two design frequencies.