Recently, researchers set an ambitious goal of conducting speaker recognition in unconstrained conditions where the variations on ambient, channel and emotion could be arbitrary. However, most publicly available datasets are collected under constrained environments, i.e., with little noise and limited channel variation. These datasets tend to deliver over optimistic performance and do not meet the request of research on speaker recognition in unconstrained conditions.In this paper, we present CN-Celeb, a large-scale speaker recognition dataset collected 'in the wild'. This dataset contains more than 130, 000 utterances from 1, 000 Chinese celebrities, and covers 11 different genres in real world. Experiments conducted with two state-of-the-art speaker recognition approaches (i-vector and x-vector) show that the performance on CN-Celeb is far inferior to the one obtained on VoxCeleb, a widely used speaker recognition dataset. This result demonstrates that in real-life conditions, the performance of existing techniques might be much worse than it was thought. Our database is free for researchers and can be downloaded from http://project.cslt.org.

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Soil electrical resistivity is an important parameter in grounding system design. In this study, laboratory measurements of soil electrical resistivity are carried out using a soil box. Two measurement methods are used and compared: a two-electrode method and a four-electrode method. The measurements indicate that the results reported by the two-electrode method are affected by the contact resistance between the electrodes and the soil, which increases as the soil water content increases. Moreover, the soil electrical resistivity was observed to decrease as the test signal frequency increases. Using the four-electrode method and a 50-Hz AC signal, the effects of soil water content, soil porosity, pore fluid composition, and temperature on the soil electrical resistivity are then investigated. The results show that increasing the soil saturation level results in a power-function decrease in the soil electrical resistivity. Also, for a given gravimetric water content, as the soil porosity decreases, the resistivity decreases. In addition, owing to the mobility of the ions, different electrolytes in the pore fluid contribute differently to the soil electrical resistivity. Finally, the dependence of soil electrical resistivity on soil temperature is found to be divided into three stages: above 0 degrees Celsius, around 0 degrees Celsius, and below 0 degrees Celsius. An abrupt change in the soil electrical resistivity is observed at around 0 degrees Celsius.

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