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Waterproof and Wear-Resistant Surface Treatment on Printed Parts of Polyamide 12 (PA12) by Selective Laser Sintering Using a Large Pulsed Electron Beam
No full textPorosity is an unavoidable problem of products in powder bed fusion-based additive manufacturing. This hinders underwater applications of printed products due to water absorption by capillary force. This study reports the surface treatment of polyamide 12 (PA12) manufactured by selective laser sintering using large pulsed electron beam (LPEB) irradiations as an ecofriendly postprocessing technique. With the optimal conditions of LPEB, the surface roughness and porosity were reduced after the melting and resolidification of unmelted particles and pores without generating any dusts and using any chemicals. The surface roughness reduction increased static contact angle (CA) on the surface. From a chemical wettability investigation, the reduction of hydrophilicity after the LPEB irradiation was obtained and attributed to the elimination of hydrophilic functional groups on the surface. Due to the harmonic effects of roughness and hydrophilicity reduction, the CA on LPEB-treated surfaces was achieved around 95 degrees. The pore-closing effect of LPEB irradiation and hydrophobic transition of PA12 protected the surface from water absorption, eliminating the capillary effect. The waterproof performance on the surface was demonstrated by releasing droplets on the surface and immersing them in ink-dispersed distilled water. The result showed potential applications of rapidly sintered PA12 in underwater
Theoretical study on enhancement of heat transfer of nanofluids with functionalized graphene flakes in confined nanopipe system
No full textIn order to find a suitable type of nanoparticles to improve the heat transfer of nanofluids, the role of nanoparticles should be elucidated. The nanoparticles are known to affect the heat transfer, and here we investigated the role of nanoparticles using a nanopipe model system. Specifically, the heat transfer phenomena of nanofluids containing hydrophobic (i.e., hydrogenated) and hydrophilic (i.e., carboxylated) functionalized graphene flakes (GFs) were compared. Confined nanopipe (i.e., 325 K) with a diameter of 400 ?? system were adopted for the heat transfer and coarse-grained molecular dynamics (CGMD) simulations were performed. In the nanofluids, GF-concentrated layer was formed near the pipe wall, which induced the high HTC value of nanofluids. We found that after the thermal change of fluid became constant (i.e., thermally fully developed region), the thermal boundary layer was maintained for 100 ?? due the GF-concentrated layer. The thermal boundary layer and HTC was thicker and higher when using carboxylated GF, which was more soluble in the coolant
Dopamine-assisted wet spinning and mechanical reinforcement of graphene oxide fibers
No full textBioinspired polydopamine coatings have been widely used for the surface modification of various materials because of their strong adhesion, facile application method, and functionalization ability. However, dopamine has not been previously utilized as a coagulation agent for graphene oxide fibers (GOFs). In this study, we performed the wet spinning of GOFs using dopamine as a coagulation agent (denoted as DA-GOFs) and successive polymerization of dopamine inside the fibers. The polymerized DA-GOFs (pDA-GOFs) exhibited enhanced mechanical properties with a 97% higher tensile strength than that of the fibers coagulated with CaCl2. The described dopamine-assisted wet spinning and polymerization process were simple but effective method for preparing mechanically strong fibers, which can be potentially employed in flexible and wearable electronic applications
PCNB exposure during early embryogenic development induces developmental delay and teratogenicity by altering the gene expression in Xenopus laevis
No full textPentachloronitrobenzene (PCNB) is an organochlorine fungicide commonly used to treat seeds against seedling infections and controlling snow mold on golf courses. PCNB has been demonstrated to be toxic to living organisms, including fish and several terrestrial organisms. However, only phenotypical deformities have been studied, and the effects of PCNB on early embryogenesis, where primary organogenesis occurs, have not been completely studied. In the current study, the developmental toxicity and teratogenicity of PCNB is evaluated by using frog embryo teratogenesis assay Xenopus (FETAX). Our results confirmed the teratogenic potential of PCNB revealing the teratogenic index of 1.29 during early embryogenesis. Morphological studies revealed tiny head, bent axis, reduced inter ocular distance, hyperpigmentation, and reduced total body lengths. Whole mount in situ hybridization and reverse transcriptase polymerase chain reaction were used to identify PCNB teratogenic effects at the gene level. The gene expression analyses revealed that PCNB was embryotoxic to the liver and heart of developing embryos. Additionally, to determine the most sensitive developmental stages to PCNB, embryos were exposed to the compound at various developmental stages, demonstrating that the most sensitive developmental stage to PCNB is primary organogenesis. Taken together, we infer that PCNB's teratogenic potential affects not just the phenotype of developing embryos but also the associated genes and involving the oxidative stress as a possible mechanism of toxicity, posing a hazard to normal embryonic growth. However, the mechanisms of teratogenesis require additional extensive investigation to be defined completely
High-performance and self-calibrating multi-gas sensor interface to trace multiple gas species with sub-ppm level
No full textDeveloping a better understanding of gas-metal oxide interactions as well as improving the output performance with the aging of the gas sensing array represents a critical challenge. In this work, we have designed a surface-functionalized metal-oxide sensors array containing six units for detecting NO2, SO2, H2S, and CO hazardous gases. The responses of the sensor array to four target gases are enhanced by various catalytic effects on the surface, and they show distinctive responses to each gas. For improved selectivity, a pattern recognition algorithm is implemented under an edge computing-based environment to relieve the overload of a monitoring server. Moreover, a self-calibration method for long-term stability is designed to indirectly calibrate gas responses with aging. With its edge-computing device prototype, which includes a sensor array and its readout integrated circuit, four target gases are distinguished by an artificial neural network algorithm with 97% accuracy. The present work describes the effective platforms for emerging next-generation gas sensors with improved communication and monitoring systems
Nanozyme Based on Porphyrinic Metal-Organic Framework for Electrocatalytic CO2 Reduction
Get PDFMimicry of natural enzyme systems is an important approach for catalyst design. To create an enzyme-inspired catalyst, it is essential to mimic both the active center and the second coordination sphere. Metal-organic frameworks (MOFs), an emerging class of porous materials, are ideal candidates for heterogeneous catalysts because their versatile building blocks confer a high level of structural tunability, and the chemical environment surrounding the active center can be controlled at the molecular level. Herein, a new 2D porphyrinic MOF, PPF-100, constructed from a nonplanar saddle-distorted porphyrin linker and a Cu paddle-wheel metal node is reported. The strategic introduction of ethyl substituents allows not only to mimic the active center and second coordination sphere but also to increase the catalytic selectivity while completely inhibiting H-2 generation in the CO2 reduction reaction
Composition and phase engineering of metal chalcogenides and phosphorous chalcogenides
No full textTwo-dimensional (2D) materials with multiphase, multielement crystals such as transition metal chalcogenides (TMCs) (based on V, Cr, Mn, Fe, Cd, Pt and Pd) and transition metal phosphorous chalcogenides (TMPCs) offer a unique platform to explore novel physical phenomena. However, the synthesis of a single-phase/single-composition crystal of these 2D materials via chemical vapour deposition is still challenging. Here we unravel a competitive-chemical-reaction-based growth mechanism to manipulate the nucleation and growth rate. Based on the growth mechanism, 67 types of TMCs and TMPCs with a defined phase, controllable structure and tunable component can be realized. The ferromagnetism and superconductivity in FeXy can be tuned by the y value, such as superconductivity observed in FeX and ferromagnetism in FeS2 monolayers, demonstrating the high quality of as-grown 2D materials. This work paves the way for the multidisciplinary exploration of 2D TMPCs and TMCs with unique properties. A competitive-chemical-reaction-based growth mechanism by controlling the kinetic parameters can easily realize the growth of transition metal chalcogenides and transition metal phosphorous chalcogenides with different compositions and phases
Identifying household finance heterogeneity via deep clustering
Get PDFHouseholds are becoming increasingly heterogeneous. While previous studies have revealed many important insights (e.g., wealth effect, income effect), they could only incorporate two or three variables at a time. However, in order to have a more detailed understanding of complex household heterogeneity, more variables should be considered simultaneously. In this study, we argue that advanced clustering techniques can be useful for investigating high-dimensional household heterogeneity. A deep learning-based clustering method is used to effectively handle the high-dimensional balance sheet data of approximately 50,000 households. The employment of appropriate dimension-reduction techniques is the key to incorporate the full joint distribution of high-dimensional data in the clustering step. Our study suggests that various variables should be used together to explain household heterogeneity. Asset variables are found to be crucial for understanding heterogeneity within wealthy households, while debt variables are more important for those households that are not wealthy. In addition, relationships with sociodemographic variables (e.g., age, education, and family size) were further analyzed. Although clusters are found only based on financial variables, they are shown to be closely related to most sociodemographic variables
A Pixel Circuit with Leakage Current Compensation Using PWM-based Data Cycling for AMLED Displays
No full textThis brief presents a leakage current compensation scheme by using a data cycling function to a pixel driver circuitry of the active-matrix light emitting diode (AMLED) displays. The proposed function cycles the stored dimming data to repeat pulse width modulation (PWM) multiple times at a given frame time. It compensates for a decay of the LED driving current due to leakage by repeatedly charging the target dimming data across a storage capacitor in the current driver. The proposed circuit has been fabricated using a 0.18-??m CMOS process. The test chip includes a 2??16 pixel circuit array with a control system. The functional operation has been verified at a prototype using an 8 ?? 16 LED array system
Infinite families of class groups of quadratic fields with 3-rank at least one: quantitative bounds
No full textWe improve an effective lower bound on the number of imaginary quadratic fields whose absolute discriminants are less than or equal to X and whose ideal class groups have 3-rank at least one, which is >> X 17/18. We also obtain a better bound on the number of imaginary quadratic fields with 3-rank at least two, which is >> X 2/3; the best-known lower bound so far is X 1/3. For finding these effective lower bounds, we use the Scholz criteria and the parametric families of quadratic fields K-1 and K-2 (defined as follows) with escalatory case. We find new infinite families of quadratic fields K-1 = Q(root a(1)(2) - a(1)b(1)(3)) and K-2 = Q(root a(2)(2) - b(2)(3)), where a(i) and b(i) are integers subject to certain conditions for i = 1, 2. More specifically, we find a complete criterion for the 3-rank difference between K-1 and its associated quadratic field <(K)over tilde(1) to be one; this is the escalatory case. We also obtain a sufficient condition for the family K-2 and its associated family <(K)over tilde(2) to have escalatory case. We illustrate some selective implementation results on the 3-class group ranks of K-i and (K) over tilde (i) for i = 1, 2