Reducing Voltage Volatility with Step Voltage Regulators: A Life-Cycle Cost Analysis of Korean Solar Photovoltaic Distributed Generation

To meet the United Nation’s sustainable development energy goal, the Korean Ministry of Commerce announced they would increase renewable energy generation to 5.3% by 2029. These energy sources are often produced in small-scale power plants located close to the end users, known as distributed generation (DG). The use of DG is an excellent way to reduce greenhouse gases but has also been found to reduce power quality and safety reliability through an increase in voltage volatility. This paper performs a life-cycle cost analysis on the use of step voltage regulators (SVR) to reduce said volatility, simulating the impact they have on existing Korean solar photovoltaic (PV) DG. From the data collected on a Korean Electrical Power Corporation 30 km/8.2 megawatts (MW) feeder system, SVRs were found to increase earnings by one million USD. SVR volatile voltage mitigation increased expected earnings by increasing the estimated allowable PV power generation by 2.7 MW. While this study is based on Korean PV power generation, its findings are applicable to any DG sources worldwide.11Nsciescopu

Three-dimensional CT angiography of the canine hepatic vasculature

Eight Beagle dogs were anesthetized and were imaged using a single channel helical CT scanner. The contrast medium used in this study was iohexol (300 mg I/ml) and doses were 0.5 ml/kg for a cine scan, 3 ml/kg for an enhanced scan. The flow rate for contrast material administration was 2 ml/sec for all scans. This study was divided into three steps, with unenhanced, cine and enhanced scans. The enhanced scan was subdivided into the arterial phase and the venous phase. All of the enhanced scans were reconstructed in 1 mm intervals and the scans were interpreted by the use of reformatted images, a cross sectional histogram, maximum intensity projection and shaded surface display. For the cine scans, optimal times were a 9-sec delay time post IV injection in the arterial phase, and an 18-sec delay time post IV injection in the venous phase. A nine-sec delay time was acceptable for the imaging of the canine hepatic arteries by CT angiography. After completion of arterial phase scanning, venous structures of the liver were well visualized as seen on the venous phase

From Korean to northeast Asian endemicity: on the occurrence of Pelophylax chosenicus along the Eastern Coastal Yellow Sea

Understanding the distribution of species is a primary requirement to understand their behaviour, conservation, and phylogeography. Over the last decades, the number of species described on the Korean Peninsula has significantly increased, but surveys around the boundaries of the Peninsula are still needed to refine the range of these species. Further surveys, supported by ecological niche models, are especially needed in areas where the environment is similar and connected. We conducted surveys in the continuous landscapes of the Republic of Korea, the Democratic People’s Republic of Korea, and the People’s Republic of China to determine the distribution of the gold-spotted pond frog, Pelophylax chosenicus (Okada, 1931). The surveys were conducted between 2015 and 2021 through the use of visual and call encounters. We supported our surveys with molecular analyses by sequencing the mitochondrial 16S rRNA, 12S rRNA, and Cytb gene fragments to confirm the species identity of the northernmost population in China. As a result, we found the species to be widespread in low-elevation wetlands along the eastern coast of the Yellow Sea, with two isolated populations in the southeast of the Korean Peninsula, and the northernmost population in the vicinity of Dandong in the People’s Republic of China. We then determined the importance of landscape types for the species, especially rice paddies, and used ecological niche models to define suitable habitats across the region. As this species is listed as threatened in the Republic of Korea, knowing its exact distribution will be important for conservation practices