Human activities have considerably increased nitrogen intake into waterways, resulting in the deterioration of water quality. The state of surface water requires special consideration in light of the water crisis caused by nitrogen pollution. In this study, the natural abundance of the nitrogen stable isotope (δ15N) is measured and sampled in sediments and compared with the total dissolved nitrogen (DN) in four main Chinese tributaries of Hun River upper reach, including the Dasuhe, Beisanjia, Beikouqian, and Nanzamu tributaries. Results show that for the Dasuhe and Nankouqian tributaries, the δ15N values of sediment samples in 2016 are all significantly higher than previous values in 2011. In the Dasuhe tributary, this change is attributed to the promotion of organic agricultural production under which chemical fertilizers are replaced by organic fertilizers. For the δ15N values of the sediment in the Nankouqian tributary, the construction of the municipal sewer system and wastewater treatment facilities are the causes of this rising trend. The δ15N values of nitrate released by facilities could be raised by microbial denitrification that is employed in the tertiary treatment process. Most of the δ15N values of the sediments are distributed between soil and manure, indicating that nitrogen in the river water mainly comes from agriculture. All the surveyed tributaries except Dasuhe show a significant increase in DN. In addition, a significant positive correlation between the change ratio of the farmland area and DN in river water is observed, suggesting that the increase in nitrogen in river water from 2011 to 2016 is due to agriculture. Based on the abovementioned data, this study provides a basis for local governments to formulate management measures.

Magnetic coupling resonance wireless power transfer can efficiently provide energy to intracranial implants under safety constraints, and is the main way to power fully implantable brain–computer interface systems. However, the existing maximum efficiency tracking wireless power transfer system is aimed at optimizing the overall system efficiency, but the efficiency of the secondary side is not optimized. Moreover, the parameters of the transmitter and the receiver change nonlinearly in the power control process, and the efficiency tracking mainly depends on wireless communication. The heat dissipation caused by the unoptimized receiver efficiency and the wireless communication delay in power control will inevitably affect neural activity and even cause damage, thus affecting the results of neuroscience research. Here, a linear-power-regulated wireless power transfer method is proposed to realize the linear change of the received power regulation and optimize the receiver efficiency, and a miniaturized linear-power-regulated wireless power transfer system is developed. With the received power control, the efficiency of the receiver is increased to more than 80%, which can significantly reduce the heating of fully implantable microsystems. The linear change of the received power regulation makes the reflected impedance in the transmitter change linearly, which will help to reduce the dependence on wireless communication and improve biological safety in received power control applications.

Autoclaved aerated concrete block (AACB) is a new kind of green, environmental protection and economical wall material. Its production process can absorb a large amount of industrial waste residue, and the ratio of raw materials can reach more than 70%. However, in the actual construction situation, crack problems such as wall cracking and plaster layer falling off, as well as quality problems such as insufficient strength and easy cracking occur from time to time in the masonry which using AACB. In this paper, the common faults and causes of AACB masonry are summarized and analyzed, moreover, the related prevention and solving measures are put forward for reference in the masonry engineering. This paper can provide reference for the construction specification and quality acceptance of masonry engineering.