Jaesung Kwon

The rust layer on carbon steel controls how the metal beneath it corrodes, but its state is usually assessed by destructive analysis. This work followed uncoated cold-rolled carbon steel through 30 cycles (240 h) of a modified ISO 14993 cyclic corrosion test in which ultrapure water replaced the NaCl spray. Two specimens were retrieved at each of nine intervals. Surface color and rust coverage were measured from photographs and compared with SEM/EDS, XRD, linear polarization resistance and confocal topography. Three stages were resolved. Rust coverage stayed below 6% up to cycle 5. Between cycles 10 and 15, coverage rose to about 50%, γ-FeOOH appeared and polarization resistance fell from 441.1 to 301.3 Ω∙cm². Coverage then leveled off near 63% while the instantaneous corrosion rate kept rising. Among the color coordinates, b* correlated most strongly with corrosion rate (Spearman ρ = 0.867, exact p = 0.005, 95% CI 0.46–0.97). These correlations rest on nine intervals under one condition, and they partly reflect exposure time. No predictive model was built or validated. Within these limits, surface color serves as a non-destructive indicator of rust-layer stage.

This study investigates the effects of n‐pentanol/diesel blends on the performance of a naturally aspirated, air‐cooled, single‐cylinder diesel engine under full load across 1400–2500 rpm. The engine was equipped with a mechanical direct injection system. Performance parameters were evaluated and compared for pure diesel (D100) and diesel blended with n‐pentanol at volume ratios of 10%, 30%, and 50% (designated as D90P10, D70P30, and D50P50, respectively). The results showed that brake torque and power increased with engine speed but plateaued above 2000 rpm due to intake and friction constraints. At low speeds (e.g., 1400 rpm), D50P50 showed a ~3.7% reduction in brake torque (11.58 vs. 12.02 Nm), ~14.9% lower brake thermal efficiency (BTE, 14.16% vs. 16.64%), and a ~17.5% increase in brake specific energy consumption (BSEC, 25.40 vs. 21.62 MJ/kWh) due to its lower energy density. In contrast, at high speeds (e.g., 2500 rpm), D50P50 exhibited improved BTE by ~1.3% (18.25% vs. 18.02%), with brake specific fuel consumption (BSFC) and BSEC gaps narrowed by oxygen‐assisted combustion. Exhaust gas temperature (EGT) was lower with higher n‐pentanol content at low speeds; however, it increased at high speeds due to n‐pentanol’s combustion characteristics and the cooling limitations of the air‐cooled engine. These findings fill a critical research gap by systematically evaluating high n‐pentanol/diesel blends under full‐load and variable‐speed conditions. The results provide novel insights for optimized engine control strategies, such as injection timing adjustments and intake enhancements.

Unmanned Aerial Vehicles (UAVs), commonly known as drones, have become widely used in many fields, ranging from agriculture to military operations, due to recent advances in technology and decreases in costs. Quadrotors are particularly important UAVs, but their complex, coupled dynamics and sensitivity to outside disturbances make them challenging to control. This paper introduces a new control method for quadrotors called Backstepping Sliding Mode Control (BSMC), which combines the strengths of two established techniques: Backstepping Control (BC) and Sliding Mode Control (SMC). Its primary goal is to improve trajectory tracking while also reducing chattering, a common problem with SMC that causes rapid, high-frequency oscillations. The BSMC method achieves this by integrating the SMC switching gain directly into the BC through a process of differential iteration. Herein, a Lyapunov stability analysis confirms the system’s asymptotic stability; a genetic algorithm is used to optimize controller parameters; and the proposed control strategy is evaluated under diverse payload conditions and dynamic wind disturbances. The simulation results demonstrated its capability to handle payload variations ranging from 0.5 kg to 18 kg in normal environments, and up to 12 kg during gusty wind scenarios. Furthermore, the BSMC effectively minimized chattering and achieved a superior performance in tracking accuracy and robustness compared to the traditional SMC and BC.

This work provides a systematic evaluation of the performance and regulated emissions of binary n-pentanol–diesel blends under steady-state conditions, thereby clarifying condition-dependent efficiency–emission trade-offs across multiple loads and speeds. A single-cylinder, air-cooled diesel engine was operated at two speeds (1700 and 2700 rpm) and four brake mean effective pressure (BMEP) levels (0.25–0.49 MPa) using commercial diesel (D100) and three n-pentanol–diesel blends at volume ratios of 10%, 30%, and 50% (designated D90P10, D70P30, and D50P50, respectively). Brake thermal efficiency (BTE), brake specific energy consumption (BSEC), and brake specific fuel consumption (BSFC) were measured alongside exhaust emissions of nitrogen oxides (NO_x), carbon monoxide (CO), hydrocarbon (HC), carbon dioxide (CO₂), and smoke opacity. The results show that due to a lower cetane number, high latent heat of vaporization, and reduced heating value, n-pentanol blends incur efficiency and fuel consumption penalties at light to moderate loads. However, these disadvantages diminish or reverse at high loads and speeds: D50P50 surpasses D100 in BTE and matches or improves BSEC and BSFC at 2700 rpm and 0.49 MPa. Emission data reveal that the blend’s fuel-bound oxygen and enhanced mixing provide up to 16% NO_x reduction; 35% and 45% reductions in CO and HC, respectively; and a 74% reduction in smoke opacity under demanding conditions, while CO₂ per unit work output aligns with or falls below D100 at high load. These findings demonstrate that optimized n-pentanol–diesel blends can simultaneously improve efficiency and mitigate emissions, offering a practical pathway for low-carbon diesel engines.

This study examined the effects of blending decanol, an oxygenated fuel, with diesel on diesel engine performance and emissions. Experiments were conducted on a single-cylinder engine at 1700 rpm and 2700 rpm, using diesel/decanol blends at 10%, 30%, and 50% by volume (D90de10, D70de30, D50de50). Results showed that brake thermal efficiency decreased with higher decanol ratios at low speeds. As a result, brake specific fuel consumption and brake specific energy consumption increased due to decanol’s lower calorific value. Regarding emissions, decanol blending reduced NO_x, CO, HC, and smoke. NO_x emissions were lowered by the cooling effect resulting from decanol’s higher latent heat of vaporization and lower calorific value, especially at low speeds. CO and HC emissions declined as decanol’s oxygen content promoted oxidation, reducing incomplete combustion. Smoke emissions were minimized in fuel-rich zones by preventing unburned carbon particle formation. This study highlights decanol’s potential as an eco-friendly diesel blending option. Future work should optimize blending ratios and injection settings to enhance diesel engine performance.

This study examined the effects of blending decanol, an oxygenated fuel, with diesel on diesel engine performance and emissions. Experiments were conducted on a single-cylinder engine at 1700 rpm and 2700 rpm, using diesel/decanol blends at 10%, 30%, and 50% by volume (D90de10, D70de30, D50de50). Results showed that brake thermal efficiency decreased with higher decanol ratios at low speeds. In contrast, brake specific fuel consumption and brake specific energy consumption increased due to decanol's lower calorific value. Regarding emissions, decanol blending reduced NOx, CO, HC, and smoke. NOx emissions were lowered by the cooling effect resulting from decanol's higher latent heat of vaporization and lower calorific value, especially at low speeds. CO and HC emissions declined as decanol's oxygen content promoted oxidation, reducing incomplete combustion. Smoke emissions were minimized in fuel-rich zones by preventing unburned carbon particle formation. This study highlights decanol's potential as an eco-friendly diesel blending option. Future work should optimize blending ratios and injection settings to enhance diesel engine performance.

This study evaluates the viability of n-octanol as an alternative fuel in a direct-injection diesel engine, aiming to enhance sustainability and efficiency. Experiments fueled by different blends of n-octanol with pure diesel were conducted to analyze their impacts on engine performance and emissions. The methodology involved testing each blend in a single-cylinder engine, measuring engine performance parameters such as brake torque and brake power under full-load conditions across a range of engine speeds. Comparative assessments of performance and emission characteristics at a constant engine speed were also conducted with varying loads. The results indicated that while n-octanol blends consistently improved brake thermal efficiency, they also increased brake-specific fuel consumption due to the lower energy content of n-octanol. Consequently, while all n-octanol blends reduced nitrogen oxide emissions compared to pure diesel, they also significantly decreased carbon monoxide, hydrocarbons, and smoke opacity, presenting a comprehensive reduction in harmful emissions. However, the benefits came with complex trade-offs: notably, higher concentrations of n-octanol led to a relative increase in nitrogen oxide emissions as the n-octanol ratio increased. The study concludes that n-octanol significantly improves engine efficiency and reduces diesel dependence, but optimizing the blend ratio is crucial to balance performance improvements with comprehensive emission reductions.