Search

Anion exchange membrane (AEM) water electrolyzers are expected to be novel devices for hydrogen (H2) production that achieve high performance at low capital cost. The effect of catalyst distribution in anode porous transport electrodes (PTEs) on the performance of AEM water electrolysis is experimentally examined. Based on the analysis of the correlation between the PTE structure and the electrolysis performance, it was revealed that the surface catalyst coverage is related to the activation overpotential, and that the location and compactness of the catalyst layer (CL) affects the concentration overpotential. This suggests that the water diffusion through the membrane is related to the concentration overpotential, and that denser CLs can promote water diffusion and thus mitigate the concentration overpotential. Based on the electrolysis data with PTEs of different thickness, it was also revealed that decreasing the thickness of the anode PTE enables good performance with low catalyst loading.

The Lean Blowout (LBO) limit is crucial for the aircraft engines. The semi-empirical (such as Lefebvre’s LBO model and Flame Volume (FV) model), numerical and hybrid methods are widely utilized for the LBO limit quick prediction. An innovative hybrid method based on the FV concept is proposed. This method can be classified as a semi-empirical/physical based hybrid prediction method. In this hybrid method, it is assumed that the flame volume varies nearly linearly with the fuel/air ratio near the LBO. The flame volume is obtained directly by the numerical simulation using the threshold value of the visible flame boundary as 900 K. Then the final LBO limits is determined by the FV model. On the premise of keeping the good generality of prediction, the hybrid method based on the FV concept can further improve the prediction accuracy. The comparison with the prediction of the existing available methods on fifteen combustors shows that the hybrid method based on the FV concept achieves better prediction accuracy. The prediction uncertainties between the experimental results and the predicted values by the hybrid method based on the FV concept are within about ±10%.

In this work, the Mg-doped ZnO (ZMO)/Lead sulfide (PbS) quantum dot (QD) heterojunction solar cells are fabricated via layer-by-layer spin-coating method. The quantum dot solar cells (QDSCs) with structure of FTO/ZMO/PbS-EMII/PbS-EDT/Au and relatively larger area of 0.372 cm2 are prepared in ambient atmosphere. The effect of PbS active layer thickness on the photovoltaic performance of PbS QDSCs is investigated under room temperature of 293 K. It is concluded that seven spin-coating cycles of PbS active layers is the best choice for the device, and the cell with that achieves a power conversion efficiency (PCE) of 9.46%. Furthermore, the temperature dependent characteristics of PbS QDSCs are studied. It is exhibited that the power efficiency improves as the device temperature increases first then shows a decreasing trend as the temperature substantially rises. As a result, a highest PCE of 12% is shown at the working temperature of 273 K due to higher VOC and FF. Moreover, it is demonstrated the PbS QDSCs possess noticeably stability for over 30 days of storage in air.

In this work, the effect of Mg doping on the performance of PbS quantum dot (QD) solar cells (QDSCs) is investigated. To elucidate that, PbS QDSCs with pristine ZnO and Mg-doped ZnO (ZMO) as electron transporting layers (ETLs) are fabricated, respectively. The current density-voltage (J-V) measurements are performed. The results show that the cell efficiency of the device with ZMO as an ETL is 9.46%, which increases about 75% compared to that of the pristine ZnO based device (5.41%). Enhanced short current density (Jsc) and fill factor (FF) are observed. It is demonstrated that Mg doping could passivate the surface defects and suppress the carrier recombination in ZnO ETL, thus resulting in larger bandgap and higher Fermi level (EF). The strategy of Mg-doped ZnO ETL provides a promising way for pushing solar cell performance to a high level.

Metal and nitrogen-doped carbon (M-N-C) materials have been considered as the most promising non-precious metal oxygen reduction (ORR) catalysts to replace expensive Pt catalysts. Due to high Fenton catalytic activity of Fe element and the resulting instability, Co-based N–C (Co–N–C) catalysts without Fenton catalytic activity should be a worthier ORR catalyst being explored. Although the high ORR activity of Co–N–C catalyst has been demonstrated in aqueous half-cell tests, their performance under PEMFC working condition is still far away from that of state-of-the-art Fe–N–C catalysts. In this study, a high-performance Co–N–C catalyst was synthesized by one-step pyrolyzing Co-doped ZIF-8 (zeolitic imidazolate framework-8) particles in-situ grown on the high-surface-area KJ600 carbon black with high electronic conductivity. The resulting Co–N–C catalyst exhibited high intrinsic ORR activity, fast mass transfer rate and high electronic conductivity, and thus yielded a remarkable peak power density of 0.92 W cm-2 in H2–O2 PEMFC, which is comparable to state-of-the-art Fe–N–C catalyst. This strategy is helpful to synthesize highly active M-N-C ORR catalysts with improved mass transfer and electric conductivity.

In this work, the effect of adding sodium chloride (NaCl) in zinc oxide (ZnO) electron transport layer (ETL) on the photovoltaic performance of lead sulfide (PbS) quantum dot (QD) solar cells is investigated. To elucidate that, PbS QD solar cells with pristine ZnO and NaCl passivated ZnO (ZnO–NaCl) as ETLs are fabricated, respectively. The current density–voltage (J–V)​ measurements are performed. The results show a considerable improvement in the current density of the device with ZnO–NaClas ETL, thus boosting the power conversion efficiency (PCE) from 7.278% to 9.149%. It is demonstrated that NaCl treatment benefits surface defects and series resistance ( R s ) reduction in ZnO ETL, enhancing the carrier transport performance of the device. The strategy of adding NaCl in ZnO ETL provides a promising way for pushing solar cell performance to a high level.

Direct carbon solid oxide fuel cells (DC-SOFCs) are promising for generating electricity cleanly and efficiently from solid carbon fuel. Biochar from Camellia oleifera shells is used in a tubular electrolyte-supported 2-cell DC-SOFC stack with a yttrium-stabilized zirconia (YSZ) electrolyte and silver–gadolinium-doped ceria (Ag-GDC) as symmetrical electrodes. The DC-SOFC exhibits comparable electrical performance to the same cell operated on hydrogen fuel and can cogenerate CO and electricity when fueled by biochar. The gas–electricity cogeneration performance of the DC-SOFC is tested under constant-current discharge in terms of electrical power output, CO output rate and purity, electrical conversion efficiency, and gas–electrical cogeneration conversion efficiency. The purity of the output CO can reach more than 80%. Considering the chemical energy of CO a part of the output power, the energy conversion efficiency of >70% is attained. Furthermore, the gas–electricity cogeneration performance is relatively stable before the biochar fuel is exhausted.

As a radioactive heavy metal element with a long half-life, uranium causes environmental pollution when it enters the surrounding soil. This study analyzed the changes about soil enzyme activity, non-targeted metabolomics, microbial community structure and function microbial community structure and function to assess the differences in the effects of uranium stress on rhizosphere and non-rhizosphere soil. Results showed that uranium stress significantly inhibited the activities of urease and sucrase in rhizosphere and non-rhizosphere, which had less effect on rhizosphere. Compare to the non-rhizosphere soil, the uranium stress induced the production of gibberellin A1, to promoted several metabolic pathways, such as nitrogen and PTS (Phosphotransferase system) metabolic in rhizosphere soil. The species and abundance of Aspergillus, Acidobacter, and Synechococcus in both rhizosphere and non-rhizosphere soil were decreased by uranium stress. However, the microorganisms in rhizosphere soil were less inhibited according to the soil metabolism and microbial network map analysis. Furthermore, the Chujaibacter in rhizosphere soil under uranium stress was found significantly positively correlated with lipid and organic oxygen compounds. Overall, the results indicated that ryegrass roots significantly alleviated the effects of uranium stress on soil microbial activity and population abundances, thus playing a protective role. The study also provided a theoretical basis for in-depth understanding of the biological effects, prevention and control mechanisms of uranium-contaminated soil.

A planner heterojunction quantum dot solar cells (QDSCs) structure of FTO/TiO2/PbS-EMII/PbS-EDT/Au is fabricated via layer-by-layer spin coating method, and then the temperature dependent photovoltaic performance of QDSCs is studied. The results indicate that the environment temperature has great influence on the current density-voltage (J-V) characteristics of quantum dot solar cell. The short-circuit photocurrent density (JSC), open-circuit voltage (VOC) and fill factor (FF) are all increased when the temperature decreases from 353 K to 253 K. A top value of power conversation efficiency (PCE, 9.78%) is obtained for the QDSCs when the environment temperature is lowered to 253 K, with a VOC of 0.63 V, JSC of 33.1 mA/cm2 and FF of 0.47, which is 33% above the PCE at room temperature (7.34%). In conclusion, it is necessary to cool the device for keeping the high efficiency operation of solar cell.

The applications in high-power fields of white light-emitting diodes (WLEDs) are restricted due to their poor thermal stability. Transparent Y3Al5O12:Ce3+ phosphor-in-glass (YAG-PiG) provides an efficient way to resolve this problem. In this work, novel transparent Te/Pb-free YAG-PiGs are successfully prepared via a facile screen-printing route. It is revealed that 5 mol% Eu2O3 optimizes the concentration in substrate glass. Slight erosion of YAG particles occurs in the as-prepared samples. With increasing YAG concentration and film thickness, the intensities of photoluminescence spectra of YAG-PiGs increase. The energy transfer from Eu3+ to Ce3+ is greatly suppressed. Superior thermal stability and high quantum efficiency are obtained. The optimal optical performance values in terms of a luminous efficiency of 117.2 lm/W, a correlated color temperature of 5859 K and a color rendering index of 77.2 are achieved in YAG-PiGs. All of the results reveal that the as-prepared YAG-PiGs are promising candidates for high-power WLEDs.

Working fluid is an important influencing factor for the heat transfer performance of a pulsating heat pipe (PHP). In this study, zeotropic immiscible working fluid was proposed based on the difficult start and easy dry-out with large heat flux of PHP. Deionized water mixed with HFE-7100 was used as the working fluid. The volume mixing ratios used were 4:1, 2:1, 1:1, 1:2, and 1:4, and the heating power ranged from 20 W to 250 W with inclination angles of 30°, 45°, 60°, 75°, and 90°. The filling ratio was 50%. Result shows that at a high heating power (210 W, 250 W), the PHP with mixtures could quickly start and achieve a stable one-way pulsation cycle with low thermal resistance. Meanwhile, the dry-out phenomenon of the working fluid with high boiling point had been inhibited because of the working fluid with low boiling point and high saturation vapor pressure, thereby raising the heat transfer limit of the PHP. During operation, the two working fluids were pulped and stirred to form an emulsion, which promoted the heat transfer between them. When the mixing ratio was 1:1, the two working fluids could be uniformly mixed, the contact surface between them was large, and the heat transfer property performed well. The lowest thermal resistance achieved with mixing ratio of 1:2 was 0.1634 °C/W due to some of the HFE-7100 would exist in gaseous form when the heating power was high (250 W, with an inclination angle of 90°).

The lean blowout (LBO) limit is a crucial performance for aircraft engine combustors. It is essential to obtain the LBO limit during the design stage of the aircraft engine combustors. The semi-empirical correlation is an important tool for quick prediction of the LBO limits. Among all the semi-empirical correlations for the prediction of the LBO limits, Lefebvre's LBO model is widely used for the swirl stabilized combustors. The Flame Volume (FV) model was proposed based on Lefebvre's LBO model to accommodate the effects of the geometry of the flame tube on the LBO. Meanwhile, the multi-point lean direct injection (MPLDI) combustor whose geometry of the dome is different from the traditional combustors is a promising low NOx emission combustor. Up to now, there are few existing semi-empirical correlations to predict the LBO limit for the MPLDI combustors although the prediction of the LBO limit is critical for them. Based on the FV concept and new physics-based analysis, the FV-MP (Flame Volume for the Multi-Point) model is derived to predict the LBO limits for the MPLDI combustors. The FV-MP model could accommodate the effects of the fuel staging and recessed pilot stage, in addition to the operating conditions, on the LBO limits of the MPLDI combustors and achieve better prediction accuracy than both the FV and Lefebvre's LBO models within the range of corresponding validation experiments. Compared with Lefebvre's LBO model, the FV model could double the prediction accuracy. Compared with the FV model, the FV-MP model could further double the prediction accuracy.

Selenium is a trace element that has been shown to inhibit the growth of various cancer cell types. However, its role in cervical cancer and its underlying mechanisms remains largely unknown. Herein, we explored the anti-cervical cancer effect of selenium and its potential mechanisms through xenograft and in vitro experiments. HeLa cell xenografts in female nude mice showed tumor growth retardation, with no obvious liver and kidney toxicity, after being intraperitoneally injected with 3 mg/kg sodium selenite (SS) for 14 days. Compared to the control group, selenium levels in the tumor tissue increased significantly after SS treatment. In vitro experiments, SS inhibited the viability of HeLa and SiHa cells, blocked the cell cycle at the S phase, and enhanced apoptosis. RNA-sequencing, Kyoto encyclopedia of genes and genomes pathway analysis showed that forkhead box protein O (FOXO) was a key regulatory signaling pathway for SS to exhibit anticancer effects. Gene Ontology analysis filtered multiple terms associated with apoptosis, anti-proliferation, and cell cycle arrest. Further research revealed that SS increased intracellular reactive oxygen species (ROS) and impaired mitochondrial function, which activated adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) via phosphorylation at Thr172, resulting in activation of FOXO3a and its downstream growth arrest and DNA damage-inducible alpha (GADD45a). In summary, SS exhibited anti-cervical cancer effects, and their mechanisms may be that SS is involved in inducing cell cycle arrest and potentiating cell apoptosis caused by ROS-dependent activation of the AMPK/FOXO3a/GADD45a axis.

We propose a novel consumption measure that has a daily frequency and is based on real-time shopping data. Our measure explains the joint equity-premium–risk-free-rate puzzle with a risk aversion coefficient much lower than any other consumption measures. It encompasses other consumption measures in explaining the cross-sectional variation of expected returns on various portfolio and is the only consumption measure that passes Kleibergen and Zhan (Journal of Finance, 2020) robust tests. Our model decomposes consumption shocks into different frequency of volatility and shows that ignoring short-term dynamics and intra-annual fluctuations explains the much higher risk aversion from low-frequency consumption measures.

Using founder imprinting literature, we theorize the innovation performance of founder versus agent CEOs. While founder imprinting is a unique mechanism that is exclusively available to founder CEOs, few studies have explored this phenomenon with corporate innovation performance. Previous studies addressing founder imprinting are in smaller context such as family firms. The role of founder imprinting in large publicly traded companies and its mechanisms that impact innovation performance are underexplored. To address this gap in literature, we created a large longitudinal dataset of 2,716 publicly traded companies from 1992 to 2010. We identify hiring board members with technological backgrounds as an initial imprinting condition and long tenured founder CEO with co-working boards as imprinting institutionalizing conditions that enable successful innovation performance of public firms. Our findings have theoretical and practical implications for how founder CEOs can imprint conditions that enhance the innovation performance of large publicly traded organizations.

Prenatal ethanol exposure (PE) causes many cognitive and behavioral deficits including increased drug addiction risk, demonstrated by enhanced ethanol intake and behavioral phenotypes associated with addiction risk. Additionally, preclinical studies show that PE persistently changes the function of dopaminergic neurons in the ventral tegmental area, a major neural substrate for addiction, and alters these neurons’ responses to psychostimulants. Accordingly, PE could also lead to increased risk of addiction to drugs of abuse, other than ethanol. In the present study, addiction risk was examined utilizing paradigms of amphetamine conditioned place preference (CPP) and intravenous self-administration. Ethanol was administered to pregnant dams via intragastric gavage (6 g/kg, during gestational days 8–20). Behavioral tests were conducted in adult male offspring. Amphetamine at a low dose (0.3 mg/kg, i.p.) induced CPP in PE but not control rats, whereas at a higher dose (0.6 mg/kg, i.p.) both groups acquired CPP. There was no group difference in amphetamine-induced CPP reinstatement. Furthermore, PE rats self-administered more amphetamine at a low dose (0.02 mg/kg/infusion) than controls, while no group differences were observed at a higher dose (0.1 mg/kg/infusion). Rats with PE also exhibited greater reactivity to contextual drug cues after extended abstinence and amphetamine-induced reinstatement of drug seeking. These results support that PE persistently leads to increased psychostimulant addiction risk later in life, manifested in many elements of addictive behavior following limited psychostimulant exposure. The observations provide insights into prevention strategies for drug addiction in individuals with fetal alcohol spectrum disorders.

In this work, the thermal performance of pulsating heat pipe (PHP) using surfactant aqueous solution as working fluid was experimentally investigated. The cetyl trimethyl ammonium bromide (CTAB) was applied for preparation of surfactant solution in the concentration range of 0.025–0.25 wt%. It is found that the adding of CTAB can significantly reduce the surface tension and improve the wettability, thus enhance heat transfer between the tube wall and working fluid due to the increase in the liquid film area. The thermal performance of CTAB solution PHP depends greatly on the input power, filling ratio and surfactant concentration. Experimental results indicate that the heat transfer enhancement of PHP with CTAB solution is apparent at higher input power when the concentration is very high. Comparing to the water PHP, the thermal resistance of 0.25 wt% CTAB solution is decreased by 48.5% at the input power of 100 W when filling ratio is kept as 50%.

Compound parabolic concentrators (CPC) have immense potential for middle-and-low temperature heat collection of solar energy. In this study, the propagation process of solar radiation rays in a CPC–tubular solar collector was simulated using an in-house MATLAB code by the Monte Carlo ray tracing (MCRT) method. The effects of ray incidence angle, CPC concentration ratio, and truncation residual ratio on the heat flux distribution on the tubular heat receiver were analyzed. Moreover, the effects of CPC deformations on concentration characteristics were analyzed, involving the rotation and translation of the reflective surface, the truncation of the involute starting point, and the position offset of the heat receiver. The heat flux distribution exhibited two evident peaks on the heat receiver external surface due to the concentration effect of the CPC. A small internal rotation, a small internal or external translation of the reflective surface, and the truncation of the involute starting point had mere effect on the heat flux distribution on the heat receiver. Therefore, the reflective surface can be allowed to have certain translation and internal rotation when machining a CPC. The downward, rightward, and leftward offsets of heat receivers should be avoided in the assembly of heat receivers and CPCs.