This work applies stress tensors inversions and quantification of fracture patterns along the Mesa de Los Santos, in the Eastern Cordillera of Colombia, to better understand the potential fluid flow. It thus contributes to the conceptual hydrogeological model. The area was subdivided into three blocks, separated by the NW Potreros and the Los Santos faults, having minor inner faults of different orientations. This separation facilitates the analysis of the fractures measured in the field, which in general show high dip angles and a conjugate geometry in the northern block, tension fractures(Mode I) in the central block, and a random distribution in the southwestern block. WinTensor treatment of slickensides yielded a maximum horizontal stress(SHmax) of 111o, which coincides with the WNW-ESE tensor observed from the conjugate and tension joints. We then used Frac Pa Q to generate interpolation maps of fracture intensity and density. The maps show the highest values in the central block and the lowest in the northern block,where the precipitation is higher, causing intensive rock weathering and homogenization of the fracture planes. Although the highest values of connectivity by line are found to the south of the mesa, we suggest the possibility of greater flow from the recharge zone(NE) along bedding planes and open NW-SE fractures.
GARCÍA-ARIAS SergioVELANDIA FranciscoALVAREZ AngélicaSANABRIA-GÓMEZ JoséDTARAZONA YesseniaVARGAS María Camila
瞬态电压抑制器(Transient Voltage Suppressor,TVS)作为常用的防护型器件具有吸收功率高、响应速度快等特点。目前,雪崩型SiC-TVS器件尚缺乏合理的终端设计,以常用N型衬底为基础的外延P+N-N+/Mesa结构SiC-TVS器件在反偏P+/N-结边缘处易形成负斜角边缘结构,导致器件因边缘电场集中而提前击穿,严重影响器件的工作可靠性。本文基于Sentaurus TCAD数值仿真,研究了一种雪崩型SiC-TVS器件结构,该结构采用离子注入形成大曲率半径的U型平面PN结,并将其边缘与Mesa沟槽终端顶点在器件上表面以距离x进行耦合设计,使器件表面形成正斜角终端,有效地避免了边缘电场集中效应。同时x的选取具有一定余量,在工艺上较易实现。最后利用该结构仿真得到了响应时间约5.3ns、钳位因子达到1.01的雪崩型SiC-TVS器件,仿真结果表明新型耦合结构器件对异常瞬态浪涌信号表现出良好的抑制效果。
A low hole injection efficiency for InGaN/GaN micro-light-emitting diodes(μLEDs) has become one of the main bottlenecks affecting the improvement of the external quantum efficiency(EQE) and the optical power. In this work, we propose and fabricate a polarization mismatched p-GaN/p-Al_(0.25)Ga_(0.75)N/p-GaN structure for 445 nm GaN-based μLEDs with the size of 40 × 40 μm^(2), which serves as the hole injection layer. The polarization-induced electric field in the p-GaN/p-Al_(0.25)Ga_(0.75)N/p-GaN structure provides holes with more energy and can facilitate the non-equilibrium holes to transport into the active region for radiative recombination. Meanwhile, a secondary etched mesa for μLEDs is also designed, which can effectively keep the holes apart from the defected region of the mesa sidewalls, and the surface nonradiative recombination can be suppressed. Therefore, the proposed μLED with the secondary etched mesa and the p-GaN/p-Al_(0.25)Ga_(0.75)N/p-GaN structure has the enhanced EQE and the improved optical power density when compared with the μLED without such designs.
