The aim of this study was to develop a new Al–Mg–Si–Zr alloy with a high magnesium content to achieve a wide range of mechanical properties using heat treatment and at a lower cost. Additive ...manufacturing was conducted using a powder bed fusion process with various scan speeds to change the volumetric energy density and establish optimal process conditions. In addition, mechanical properties were evaluated using heat treatment under various conditions. The characterization of the microstructure was conducted by scanning electron microscopy with electron backscatter diffraction and transmission electron microscopy. The mechanical properties were determined by tensile tests. The as-built specimen showed a yield strength of 447.9 ± 3.6 MPa, a tensile strength of 493.4 ± 6.7 MPa, and an elongation of 9.6 ± 1.1%. Moreover, the mechanical properties could be adjusted according to various heat treatment conditions. Specifically, under the HT1 (low-temperature artificial aging) condition, the ultimate tensile strength increased to 503.2 ± 1.1 MPa, and under the HT2 (high-temperature artificial aging) condition, the yield strength increased to 467 ± 1.3 MPa. It was confirmed that the maximum elongation (14.3 ± 0.8%) was exhibited with the HT3 (soft annealing) heat treatment.
In this study, Al joint systems without heat-affected zones (HAZ) were developed on Al/Fe alloy lap joints fabricated by resistance element welding (REW). The robustness of the joints with and ...without HAZs was quantitatively evaluated to consider another side effect in REW Al/Fe alloy systems. Compared to conventional REW, removing the Al HAZ not only alters the steel properties, but also reduces the work hardening of the Al alloy due to the difference in the distinct heat transfer paths. Furthermore, the presence of Al HAZ significantly influenced the hardness characteristics of the molten steel portion. In the cold wall configuration without Al HAZ, hardness values exceeding those of the hot wall by approximately 100 Hv or more were observed. At a welding current of 10.5 kA, the hot wall configuration demonstrated an approximate 30 % increase in tensile shear load and a 66 % increase in displacement compared to the cold wall configuration without HAZ. In the cold wall conditions, interfacial failure (IF) was not attributed to microstructural disparities but was linked to the formation of an inherent notch root when S20C melted due to the absence of Al HAZ. Contrary to previous reports, the presence of HAZ in Al alloys results the production of tough steel through REW.
To increase the efficiency of jumping-droplet condensation, this study proposes a hierarchical superhydrophobic surface that promotes coalescence-induced jumping. Inspired by the phenomenon in which ...a growing droplet moves spontaneously within a superhydrophobic V structure, we fabricated nanograssed zigzag structures on the surface to induce the spontaneous motion of condensed droplets. The direction of the motion was parallel to the surface, so the condensed droplets easily coalesced on it. Compared with a conventional nanograssed superhydrophobic surface, the proposed surface increased the frequency of coalescence-induced jumping by ≥17 times and increased the cumulative volume of jumping droplets by ∼1.8 times. The proposed surface has great potential to increase the efficiency of applications such as water- and energy-harvesting and cooling systems that exploit jumping-droplet condensation.
In recent years, neuroscientific knowledge has been applied to marketing as a novel and efficient means to comprehend the cognitive and behavioral aspects of consumers. A number of studies have ...attempted to evaluate media contents, especially TV commercials using various neuroimaging techniques such as electroencephalography (EEG). Yet neurophysiological examination of detailed cognitive and affective responses in viewers is still required to provide practical information to marketers. Here, this study develops a method to analyze temporal patterns of EEG data and extract affective and cognitive indices such as happiness, surprise, and attention for TV commercial evaluation.
Twenty participants participated in the study. We developed the neurophysiological indices for TV commercial evaluation using classification model. Specifically, these model-based indices were customized using individual EEG features. We used a video game for developing the index of attention and four video clips for developing indices of happiness and surprise. Statistical processes including one-way analyses of variance (ANOVA) and the cross validation scheme were used to select EEG features for each index. The EEG features were composed of the combinations of spectral power at selected channels from the cross validation for each individual. The Fisher's linear discriminant classifier (FLDA) was used to estimate each neurophysiological index during viewing four different TV commercials. Post hoc behavioral responses of preference, short-term memory, and recall were measured.
Behavioral results showed significant differences for all preference, short-term memory rates, and recall rates between commercials, leading to a 'high-ranked' commercial group and a 'low-ranked' group (P < 0.05). Neural estimation of happiness results revealed a significant difference between the high-ranked and the low-ranked commercials in happiness index (P < 0.01). The order of rankings based on happiness and attention matched well with the order of behavioral response rankings. In the elapsed-time analysis of the highest-ranked commercial, we could point to visual and auditory semantic structures of the commercial that induced increases in the happiness index.
Our results demonstrated that the neurophysiological indices developed in this study may provide a useful tool for evaluating TV commercials.
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