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APV systems producing both crops and electricity are becoming popular as an alternative way of producing renewable energy in many countries with land shortage issues (e.g., South Korea). This study aims at developing a hybrid performance model of an Agrophotovoltaic (APV) system that produces crops underneath the PV modules. In this study, the physical model used to estimate solar radiation is integrated with a polynomial regression approach to forecast the amount of electricity generation and crop production in the APV system. The model takes into account not only the environmental factors (i.e., daily temperature, precipitation, humidity, and wind speed) but also physical factors (i.e., shading ratio of the APV system) related to the performance of the APV system. For more accurate modelling, the proposed approach is validated based on field experiment data collected from the APV system at Jeollanam-do Agricultural Research and Extension Services in South Korea. As a result, the proposed approach can predict the electricity generation quantity in the APV system with an R2 of 80.4%. This will contribute to the distribution of the APV system, which will increase farmers' income as well as the sustainability of our society. [ABSTRACT FROM AUTHOR]

The Agrophtovoltaic (APV) system is an alternative for sustainable crop production, where solar power is generated via Photovoltaic (PV) modules. Since both crop production and solar power generation activities are heavily dependent on dynamic environmental conditions, it is challenging to design an APV system based on accurate estimation of its performance. To this end, this study aims to introduce an agent-based simulation (ABS) framework integrated with polynomial regression and ridge regression. In particular, two agent types are devised, as follow: (1) The photovoltaic agent calculates electricity produced via PV modules, and estimates its profits; and (2) the crop production agent calculates crop harvests underneath the PV modules, and estimates their profits. To validate the proposed framework, field experiment data with five types of crops (i.e., corn, sesame, soybean, mung bean, and red bean) at the APV system at Jeollanam-do Agricultural Research and Extension Services in South Korea with three different shading ratios of 21.3%, 25.6%, and 32.0% have been used. In addition, for the sustainable operation of an APV system in terms of electricity generation as well as crop production, three climate change scenarios based on the shared socioeconomic pathway (SSP) are considered. The proposed framework identifies that the agrophotovoltaic system with 32% sharing ratio increases up to 20% of the total profit of normal farmland. As a result, the proposed framework enables the performance of an APV system under dynamic climate conditions to be accurately estimated, so that APV system designers can utilize it to identify a profitable long-term APV system. • Crop and energy production activities were modelled via the hybrid framework. • An agent-based simulation (ABS) was integrated with machine learning algorithms. • The shared socioeconomic pathway (SSP) climate change scenarios were considered. • Validation result of the framework with a field study data was R2 of 83%. • The Agrophotovoltaic system increased up to 20% of the profit of normal farmland. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the characterization of the event mean concentration (EMC) of runoff during heavy precipitation events on highways. Highway runoff quality data were collected from the 7th highway, in South Korea during 2007–2009. The samples were analyzed for runoff quantity and quality parameters such as CODcr, TSS, TPHs, TKN, NO3, TP, PO4 and six heavy metals, e.g., As, Cu, Cd, Ni, Pb and Zn. Analysis of resulting hydrographs and pollutant graphs indicates that the peak of the pollutant concentrations in runoff occurs 20 min after the first rainfall runoff occurrence. The first flush effect depends on the preceding dry period and the rainfall intensity. The results of this study can be used as a reference for water quality management of urban highways. [Copyright &y& Elsevier]

Analyses and comparisons of generic models and a novel modeling method of line-commutated converter (LCC)-based high voltage direct current (HVDC) systems are presented for the power system simulator for engineering (PSS/E) simulation tool. The main purposes are to describe the dynamics of the DC voltage and current of HVDC system and to improve estimation of the maximum values using the generic and proposed HVDC models when AC line-to-ground faults are occurred. For the generic HVDC models, the characteristics and limitations as well as parameter investigations are conducted. Three modules are also are developed for the proposed HVDC model, which are composed of (a) AC/DC conversion; (b) controller selection; and (c) DC line model. Case studies were conducted considering the real-operated HVDC system in Korea under the PSS/E and power systems computer aided design (PSCAD) simulation environments. The simulation results were compared with measured data from the real-operated HVDC system and the results from the PSCAD HVDC models considering single- and three-phase line-to-ground faults. The case study results show that a specific generic HVDC model in PSS/E can simulate the dynamics of the DC voltage and current after the AC line-to-ground faults. The case studies also showed that the proposed modeling method is effectively improves the estimation of the maximum DC voltage and current values for the AC line-to-ground faults. [ABSTRACT FROM AUTHOR]

Sasa spp., monocarpic dwarf bamboos, are known to form recalcitrant understories, lower species diversity, and hinder forest development. Sasa borealis distributed throughout Korea showed a phenomenon of synchronized dieback after large-scale synchronized flowering nationwide around 2015. Therefore, we conducted this study to take advantage of the rare event and add prevailing activity of wild boars and culm removal to elucidate whether they promote the regeneration of a long-term suppressed forest. We set permanent plots in forests with different understory types, and tracked the vegetation change in 5 years with respect to species composition, tree regeneration, and S. borealis reestablishment. This study focused on comparison between plots established after mass flowering. In flowering stands, we found the species diversity increased significantly with increase in species evenness, but not with recruitment of new species. Furthermore, the seeds of mass-produced bamboo germinated, and the seedling abundance was found to increase considerably. In stands rooted by wild boar, species diversity increased through the recruitment of new species, including tree species. It increased the abundance of shrub and perennial herbs, while it suppressed the reestablishment of S. borealis. Although rooting effect was independently significant regardless of flowering, the synergistic effect of rooting and flowering on forest regeneration was outstanding. Wild boar seemed to function as a remover of dead culms and a breaker of remaining underground mats as well as a seed disperser. Consequently, the species composition became similar to the reference stands. However, culm cutting caused negative effects by facilitating S. borealis to re-occupy or resprout. Overall, as the wild boar population increases, the positive effect can be expected to enhance. At landscape scale, considering several factors such as flowering and non-flowering, and population size of wild boar, the long-term suppressed forests by S. borealis are projected to regenerate with mosaic forests. [ABSTRACT FROM AUTHOR]

Background: Genus Quercus is a successful group that has occupied the largest area of forest around the world including South Korea. The acorns are an important food source for both wild animals and humans. Although the reproductive characteristics of this genus are highly variable, it had been rarely studied in South Korea. Therefore, in Seoraksan and Odaesan National Parks (i) we measured the acorn production of Quercus mongolica, an overwhelmingly dominant species in South Korea, for 3 years (2017–2019), (ii) evaluated the spatial-temporal variation of acorn production, and (iii) analyzed the effects of oak- and site-related variables on the acorn production. Results: The annual acorn production of Q. mongolica increased 36 times from 1.2 g m−2 in 2017 to 43.2 g m−2 in 2018, and decreased to 16.7 g m−2 in 2019, resulting in an annual coefficient of variation of 104%. The coefficient of spatial variation was high and reached a maximum of 142%, and the tree size was the greatest influencing factor. That is, with an increase in tree size, acorn production increased significantly (2018 F = 16.3, p < 0.001; 2019 F = 8.2, p < 0.01). Elevation and slope also significantly affected the production in 2019. However, since elevation and tree size showed a positive correlation (r = 0.517, p < 0.001), the increase in acorn production with increasing elevation was possibly due to the effect of tree size. The acorn production of Odaesan for 3 years was 2.2 times greater than that of Seoraksan. This was presumed that there are more distribution of thick oak trees and more favorable site conditions such as deep soil A-layer depth, high organic matter, and slower slopes. Conclusion: As reported for other species of the genus Quercus, the acorn production of Q. mongolica showed large spatial and annual variations. The temporal variability was presumed to be a weather-influenced masting, while the spatial variability was mainly caused by oak tree size. [ABSTRACT FROM AUTHOR]

Background: Genus Sasa, dwarf bamboos, are considered to be species that lower biodiversity in the temperate forests of East Asia. Although they have a long interval, they, the monocarpic species, have a unique characteristic of large-scale synchronized flowering. Therefore, once they have flowered and then declined, it may be an opportunity for suppressed surrounding species. A previous study reported that Sasa borealis showed specialized flowering nationwide with a peak in 2015. However, this was based on data from a social network service and field survey at Mt. Jeombong. Therefore, we investigated S. borealis in the forests of five national parks in order to determine whether this rare synchronized flowering occurred nationwide, as well as its spatial distribution. Results: We found a total of 436 patches under the closed canopy of Quercus mongolica-dominated deciduous forests in the surveyed transects from the five national parks. Of these patches, 75% occupied a whole slope area, resulting in an enormous area. The patch area tended to be larger in the southern parks. Half (219 patches) of the patches flowered massively. Among them, 76% bloomed in 2015, which was consistent with the results of the previous report. The flowering rate varied from park to park with that of Mt. Seorak being the highest. The culms of the flowering patches were significantly taller (F = 93.640, p < 0.000) and thicker (F = 61.172, p < 0.000). Following the event, the culms of the flowering patches declined, providing a good opportunity for the suppressed plant species. The concurrent massive flowering of the mature patches was believed to be triggered by some stress such as a spring drought. Conclusion: We confirmed that the rare synchronized flowering of S. borealis occurred with a peak in 2015 nationwide. In addition, we explored that S. borealis not only monopolized an enormous area, but also dominated the floors of the late-successional Q. mongolica-dominated deciduous forests. This presents a major problem for Korean forests. As it declined simultaneously after flowering, there are both possibilities of forest regeneration or resettlement of S. borealis by massively produced seeds. [ABSTRACT FROM AUTHOR]