Outbreak of Rice Panicle Blast in Jeonbuk Province of Korea in 2021.

Rice panicle blast is one of the most serious diseases threatening stable rice production by causing severe damage to rice yields and quality. The disease is easy to occur under low air temperature and frequent heavy rainfall during the heading season of rice. In 2021, a rice panicle blast severely occurred in the Jeonbuk province of Korea. The incidence area of panicle blast accounted for 27.7% of the rice cultivation area of Jeonbuk province in 2021, which was 13.7-times higher than in 2019 and 2.6-times higher than in 2020. This study evaluated the incidence areas of rice panicle blast in each region of Jeonbuk province in 2021. The weather conditions during the heading season of rice, mainly cultivated rice cultivars, and the race diversity of the Jeonbuk isolates were also investigated. It will provide important information for the effective control of the rice panicle blast.

Effect of fiber entanglement in chopped glass fiber reinforced composite manufactured via long fiber spray-up molding.

Long Fiber Spray-up Molding (LFSM) deviates from the conventional approach in liquid composite molding (LCM) processes by utilizing extremely long chopped strands of fibers as the primary reinforcement material in its fabrication process. In LFSM, chopped fibers are impregnated with resin that is sprayed vertically downwards before reaching the mold surface. The spraying mechanism is mounted on an actuator, which is capable of spraying freely in any specified pattern or direction. Under LFSM, it is extremely difficult to fabricate a composite part with uniformly distributed fiber content throughout its volume. The consequences of the non-uniform fiber volume distribution arise from the fiber entanglement as the length of the fiber reaches up to 100 mm in LFSM. In this study, the effect of fiber entanglement during LFSM was analyzed through various approaches. This included measuring the coefficient of friction between fibers in contact and examining the correlation between fiber lengths and the number of intersections. Furthermore, the viscoelastic properties of the uncured composite part were assessed by experimenting with the influence of viscosity on fiber length during compression molding. The results were then computed, modeled, and visualized in MATLAB, considering variations in viscosity and fiber length, both before and after compression molding.

Analysis of the Binding of Analyte-Receptor in a Micro-Fluidic Channel for a Biosensor based on Brownian Motion.

This study experimentally analyses the binding characteristics of analytes mixed in liquid samples flowing along a micro-channel to the receptor fixed on the wall of the micro-channel to provide design tools and data for a microfluidic-based biosensor. The binding or detection characteristics are analyzed experimentally by counting the number of analytes bound to the receptor, with sample analyte concentration, sample flow rate, and the position of the receptor along the micro-channel length as the main variables. A mathematical model is also proposed to predict the number of analytes transported and bound to the receptor based on a probability density function for Brownian motion. The coefficient in the mathematical model is obtained by using a dimensionless mathematical model and the experimental results. The coefficient remains valid for all different conditions of the sample analyte concentration, flow rate, and the position of the receptor, which implies the possibility of deriving a generalized model. Based on the mathematical model derived from mathematical and experimental analysis on the detection characteristics of the microfluidic-based biosensor depending on previously mentioned variables and the height of the micro-channel, this study suggests a design for a microfluidic-based biosensor by predicting the binding efficiency according to the channel height. The results show the binding efficiency increases as the flow rate decreases and as the receptor is placed closer to the sample-injecting inlet, but is unaffected by sample concentration.

Effect of Temperature on the Mechanical Properties and Polymerization Kinetics of Polyamide-6 Composites.

This work reports the preparation of carbon fiber reinforced thermoplastic composites via the in situ anionic ring opening polymerization of ε-caprolactam. Vacuum assisted resin transfer molding was used to fabricate polyamide-6/carbon fiber composites at different molding temperatures. As a result, the higher polymerization of ε-caprolactam was observed with the condition at 140 °C for satisfactory impregnation. Regarding molding temperature, the physical properties of polyamide-6/carbon fiber were observed that the bending and impact strengths at 140 °C were higher than those to at other molding temperatures. The polymerization kinetics of polyamide-6 was analyzed using differential scanning calorimetry by experimentally acquiring kinetic parameters according to model fitting approaches. Polymerization and crystallization, which occur simultaneously throughout the whole process, were separated using Gaussian and Maxwell-Boltzmann distributions to study polymerization kinetics. The result of the developed model was in good agreement with the experimental data for the presented first order autocatalytic reaction model.

Analysis of Cryogenic Impact Properties for a Glass-Fiber-Reinforced Dicyclopentadiene with a Different Amount of Decelerator Solution.

Composites using dicyclopentadiene (DCPD) as a matrix have gained significant popularity owing to their excellent impact and chemical corrosion resistance. In the present study, experiments addressing the impact behavior of glass-fiber-reinforced DCPD were conducted to quantitatively evaluate its impact properties. The glass-fiber-reinforced polydicyclopentadiene composite utilized in impact tests was manufactured using structural reaction injection molding (S-RIM) because of its fast curing characteristics and low viscosity. The impact properties of the glass-fiber-reinforced DCPD (GF/DCPD) were quantitatively evaluated by varying its fiber content and decelerator solution. The impact properties of neat DCPD and GF/DCPD composites were examined with different amounts of decelerator solution under various temperatures from room temperature to cryogenic temperature to observe the ductile-to-brittle transition temperature (DBTT). With an increase in the fiber weight fraction of the GF/DCPD composite, the effect of the DBTT significantly decreased. However, the decreasing rate retarded as the weight fraction of the GF increased. The decreased DBTT with the addition of GF in the GF/DCPD can be attributed to the differences in the thermal expansion ratio and the interfacial force between neat DCPD and the fiber. A fractograph analysis demonstrates that the effect of the brittle (smooth) surface resulted in a lower impact absorbed energy when the temperature decreased, along with the increased amount of the decelerator.

Self-organized anisotropic wrinkling of molecularly aligned liquid crystalline polymer.

Anisotropic wrinkling which utilizes the anisotropic nature of liquid crystalline polymer (LCP) is demonstrated as a means of physical self-assembly to produce periodic microstructures. Through the plasma treatment on the molecularly aligned LCP film surface, one-dimensionally ordered wrinkle pattern was spontaneously formed on glass substrates without employing external thin-film deposition or prestrain control of the system. Experimental results indicate that the directionality of the wrinkle pattern can be tailored by the structural ordering of LCP molecules in the bilayer system of a hard skin layer on a soft substrate. Studies on process variables, such as the plasma treatment time and the film thickness, were conducted to figure out the effect on the wrinkling morphology. Due to its spatial periodicity over a large area and undemanding requirement of the process, this approach can be a candidate for the microfabrication in various applications.

Measurement of pull-off force on imprinted nanopatterns in an inert liquid.

We report on the measurement of the pull-off force on nanoscale patterns that are formed by thermal nanoimprint lithography (t-NIL). Various patterns with feature sizes in the range of 50-900 nm were fabricated on silicon substrates using a rigiflex polymeric mold of ultraviolet curable polyurethane acrylate (PUA, Young's modulus approximately 1 GPa) or perfluoropolyether (PFPE, Young's modulus approximately 10.5 MPa) and a resist layer of polystyrene (PS) of three different molecular weights (M(w) = 18,100, 211,600 and 2043,000). The pull-off force was measured in non-polar, non-reactive perfluorodecalin (PFD) solvent between a sharp atomic force microscopy (AFM) tip and an imprinted pattern. Our experimental data demonstrated that the measured pull-off forces were in good agreement with a simple adhesion model based on Lifshitz theory. Also, the force on the pressed region (valley) is higher than that on the cavity region (hill), with the ratio (hill/valley) decreasing with the decrease of pattern size and the increase of molecular weight. The confinement effects were more pronounced for smaller patterns (<300 nm) and higher molecular weights (M(w) = 211,600 and 2043,000) presumably due to sluggish movement of polymer chains into nano-cavities. Finally, the experimental observations were compared with molecular dynamic simulations based on a simplified amorphous polyethylene model.