Prevalence of pathogens in abnormal honey bees in South Korea, 2020-2023.

South Korea's beekeeping industry has been facing a major crisis due to colony collapse disorder (CCD), manifesting since the winter of 2021. CCD in South Korea is presumed to be caused by a combination of factors, including an abnormal climate, pesticide use, declining source plants, and increased honey bee diseases. We examined the prevalence of 12 major honey bee () pathogens by sampling 3,707 colonies with abnormal behavior and suspected pathogen infections from 1,378 apiaries nationwide between 2020 and 2023.

Investigation on the reduction in unburned ammonia and nitrogen oxide emissions from ammonia direct injection SI engine by using SCR after-treatment system.

Currently generated nitrogen oxides (NO) and unburned ammonia (NH) can be converted into nitrogen and moisture that are harmless to the human body and environment using selective catalytic reduction (SCR). The concentrations of NO and unburned NH emitted from the ammonia combustion engines are significantly higher than those emitted by engines using existing hydrocarbon fuels. In this study, ammonia, a representative carbon-free fuel, was used in spark ignition engines for existing passenger vehicles to identify the trends in exhaust gases emitted from engines and conduct experiments on after-treatment strategies to reduce NO and unburned NH.

Power characteristics with different types of turbochargers for lean boosted hydrogen direct injection engine in NOx-free operation.

Lean boosting is a low-temperature combustion technology that can contribute to the expansion of the operation range by reducing the pressure increase rate and the combustion temperature owing to the increase in the intake air amount, even though the amount of heat supplied is the same. By optimizing the boosting device of the direct-injection-type hydrogen engine, it was expected that the operating range could be expanded through the torque increase owing to the increase in the amount of heat supplied according to the increase in the intake air mass, and nitrogen oxides emission was expected to be suppressed owing to lean low-temperature combustion. In the present study, to examine the possible output limit of a hydrogen engine under high-lean boosting conditions by applying a boosting device with a different control method, the performance according to the engine speed was observed under the condition of minimizing nitrogen oxide emission.

3D-Printed Soft Structure of Polyurethane and Magnetorheological Fluid: A Proof-of-Concept Investigation of its Stiffness Tunability.

In this study, a soft structure with its stiffness tunable by an external field is proposed. The proposed soft beam structure consists of a skin structure with channels filled with a magnetorheological fluid (MRF). Two specimens of the soft structure are fabricated by three-dimensional printing and fused deposition modeling.