Changes of the Flowering Time of Trees in Spring by Climate Change in Seoul, South Korea

Flowering onset has attracted much attention in ecological research as an important indicator of climate change.Generally,warmer temperatures advance flowering onset.The effect of climate warming on flowering onset is more pronounced in spring because the difference between atmospheric and water temperatures creates more rapid convection than in other seasons.We analyzed the correlation between 73 species of spring woody plants in Hongneung Arboretum in Seoul,South Korea and the spring minimum temperature and average precipitation over the past 50 years(1968–2018).The spring minimum temperature and average precipitation have increased over the past 50 years,resulting in the advance of the first flowing date(FFD)in all 73 species by 8.5 days on average.A comparison of FFD changes over time by dividing the survey period into three time periods confirmed the advance of the FFD in 50 species(68%of investigated species)by 11.1 days on average in both Period 2(1999–2008)and Period 3(2009–2018)relative to Period 1(1968–1975).Additionally,a delay of the FFD by 3.2 days on average was observed in 8 species.The FFD of Lonicera chrysantha(Caprifoliaceae)advanced by over 40 days and was highly correlated with the increased spring minimum temperature.Analysis of the sensitivity of plant responses to climate change revealed that a temperature rise of 1℃ was associated with an FFD advance of 1.2 days in all species.The species that was most sensitive to temperature change was Spiraea pubescens for.leiocarpa(Rosaceae),whose FFD advanced by 4.7 days per 1℃ temperature rise.Each increase in precipitation by 1 mm was found to result in a 0.1-day advance of the FFD of all species.Prunus tomentosa(Rosa-ceae)was the most sensitive species,that advanced by 2.6 days for each 1 mm increase in precipitation.Thus,for all species,the FFD was more sensitive to the change in temperature than in precipitation.Assuming that the current greenhouse gas(GHGs)emission levels or atmospheric CO_(2) concentration is maintained,Seoul’s spring minimum temperature is projected to rise by 2.7℃ over the next 50 years.Accordingly,considering only the global temperature change,the mean FFD of the study’s 73 species is projected to advance by an additional 3.4 days.

Supersonically sprayed self-aligne d rGO nanosheets and ZnO/ZnMn_(2)O_(4)nanowires for high-energy and high-power-density supercapacitors

Core-shell-type bimetallic oxide and carbon composites comprising zinc oxide(ZnO)nanospheres and zinc manganese oxide(ZnMn_(2)O_(4))nanowires were produced by a hydrothermal method,and supersoni-cally sprayed together with reduced graphene oxide(rGO)nanosheets onto Ni foil to fabricate flexible su-percapacitors.The supersonic impact facilitated the exfoliation of the rGO nanosheets,thereby increasing the surface area and adhesion of the composite particles to the substrate.The rGO nanosheets were vertically aligned during the supersonic impact and formed localized zones,enabling optimal accommodation of the ZnO/ZnMn_(2)O_(4)particles.This localization,with the addition of rGO,reduced the agglomeration of ZnO/ZnMn_(2)O_(4)particles.The molar concentration of MnSO_(4)used in the synthesis of ZnO/ZnMn_(2)O_(4)was varied from 0.05 to 0.15 mol/L to determine the optimal MnSO_(4)concentration that would result in the highest energy storage capacitance.The unique nanostructure of ZnO/ZnMn_(2)O_(4)and the self-alignment of rGO sheets facilitated a favorable environment for high energy storage capability with a specific capaci-tance of 276.3 mF·cm^(−2)at a current density of 0.5 mA·cm^(−2)and an energy density of 98.2μWh·cm^(−2)at a power density of 1600μW·cm^(−2).The width of the potential window was increased to 1.2 V,imply-ing a significant increase in the energy storage capability of the supercapacitor.Capacitance retention of 88%was achieved after 10,000 charge/discharge cycles for the supercapacitor fabricated using an optimal MnSO_(4)concentration(0.10 mol/L)during the composite synthesis.

Wearable heater composites comprising traditional Hanji cellulose fibers coated with graphene,silver nanowires,and PEDOT:PSS via scalable supersonic spraying

Traditional Korean Hanji paper and cotton fabric were introduced as flexible substrates in the fabrication of graphene-coated heaters.Silver nanowires and PEDOT:PSS were added to increase the electrical conductivity of the heaters,thereby enhancing their heating performance.The optimal concentrations of silver nanowires and PEDOT:PSS with respect to that of graphene were identified.These active materials were deposited on flexible Hanji/cotton and non-flexible alumina substrates using supersonic spraying.The proposed Hanji-and cotton-based heaters were light,wearable,stretchable,skin-friendly,and biodegradable.The unyielding alumina-based heater exhibited the highest heating temperature of 275°C at 13 V.Wearable heater bendability and stretchability were tested considering multiple bending and stretching cycles.Moreover,water boiling and fabric drying were successfully performed using the alumina-based heater.The supersonic spraying deposition technique was used to produce writable and patternable heaters.

Wearable sensors and supercapacitors using electroplated-Ni/ZnO antibacterial fabric

Herein,nickel nanocones and zinc oxide nanosheets were electroplated onto a fabric to produce multifunctional(wearable,stretchable,washable,hydrophobic,and antibacterial)materials with sensing,heating,and supercapacitive properties.All these functionalities are integrated into a one-layered fabric that can be used as a portable intelligent electronic textile for potential application in healthcare monitoring,smart sportswear,and energy storage.Electroplated nickel enhances the electrical conductivity and thus increases the electron charge transfer for supercapacitor applications.The integration of ZnO with the Ni-plated fabric provides pseudocapacitance via redox reactions with the electrolyte.The resistance of the Ni/ZnO fabric changes in response to external stimuli such as temperature and strain.When voltage is applied,the fabric generates heat through Joule heating,demonstrating its potential application as winter sportswear.The superior mechanical durability of the fabric was confirmed through bending and stretching tests.The hydrophobic surface prevents viruses contained in liquid droplets from infiltrating the fabric.In addition,bacterial growth is inhibited because of the antibacterial properties of the Ni/ZnO fabric and because of Joule heating.The one-layered fabric integrated with such multiple functionalities is expected to be applicable in the development of next-generation portable and wearable electronic textiles in various industries.

Reusable and durable electrostatic air filter based on hybrid metallized microfibers decorated with metal–organic–framework nanocrystals

As global air pollution becomes increasingly severe,various types of fibrous filters have been developed to improve air filter performance.However,fibrous filters have limitations such as high packing density that generally causes high-pressure drop and ultimately deterioration in the filtration efficiency.High-pressure particulate matter precipitators are limited in terms of scope for commercialization because they require high voltage supplies and ozone generators.In this study,we develop fibrous filters with enhanced durability and improved performance using metallized microfibers decorated with metal-organic-framework(MOF)nanocrystals.Not only does the efficiency of the developed filters remain at or above 97%for 0.50-1.5μm PMs but the durability also significantly increases.In addition,using the water purification ability of the MOF,we explore the dye degradation effect of the hybrid microfibers by immersing them into Rhodamine B aqueous solution.In such an experiment the Rhodamine B aqueous solution is completely purified by the presence of the hybrid microfibers under the UV irradiation.