In recent years, enhanced thermal conductive properties of polymer composites filled with reduced graphene oxide (rGO) have been studied for diverse applications. However, rGO fillers tend to form aggregates, making it difficult to reach the maximum enhancement through the use of rGO. Experiments have shown that the hydrogen bond between rGO and montmorillonite (MMT) can lead to a stable dispersion of rGO with the result of improving the effective thermal conductivity (ETC) of the composite. However, the mechanisms of this phenomenon are not yet well known. In this work, a micromechanics-based method is proposed to provide an analytical expression of the ETC of rGO/MMT/polymer composites. The predictions are in good agreement with the experimental data, demonstrating the effectiveness of the proposed framework. Also, the effect of the orientation of the fillers is investigated, which useful to determine the optimal orientation and filling ratio to meet various requirements in the material performance design and preparation of rGO/MMT/polymer composites.
Greenhouse gas mitigation and utilization attract huge attentions in energy and environment domains worldwide while few technologies enable to satisfy the both concurrently. In this study, a new greenhouse gas utilization technology, foamy emulsions, is initially developed and evaluated. Foamy emulsions usually have low production gas–liquid ratio but capable to facilitate the energy recovery. However, little researches have focused on the formation mechanism and flow property of foamy emulsions under greenhouse gas injection and the use of additives, which results in the relevant mechanism remains unclear. To address this problem, the formation process of foamy emulsions and the influence of the gas type, temperature and amount of viscosity reducer on the flow of foamy emulsions in the process of unconventional fossil fluids are investigated through a series of microscopic visualization experiments. According to the experimental results, the process of foamy emulsions formation can be divided into four stages, namely, the initial, early, middle and late stages. The middle stage corresponds to the period of steady flow of the foamy oil, with the largest number of bubbles and highest velocity. Moreover, the foamy emulsions formed using CO2 as the dissolved gas is the most effective, corresponding to an energy recovery factor of 40%. The effect of N2 is the most inferior, with the corresponding oil recovery factor being only 18%. Although the velocity of the bubbles increases with the increase in the temperature and amount of viscosity reducer, the stability of the bubbles degrades. The optimal effect of the foamy emulsions occurs at 80 °C with the amount of viscosity reducer being 1–3 wt%. This study will support the foundation of more general application pertaining to greenhouse gases mitigation and utilization in energy and environmental practices.
Prior mineral scaling investigations mainly studied the effects of membrane surface properties rather than on the mineral properties and their impact on membrane permeability. In our study, mass, crystal growth orientation, and crystallinity of mineral precipitates on membranes, as well as their effects on membrane permeability have been investigated. Gypsum scaling tests on bare and bovine serum albumin (BSA)-conditioned membranes were conducted under different saturation indices. Results show that a longer scaling period was required for BSA-conditioned membranes to reach the same membrane permeate flux decline as bare membranes. Though the final reduced permeability was the same for both two membranes, the masses of the mineral precipitates on BSA-conditioned membranes were around two times more than those on bare membranes. Further mineral characterizations confirmed that different permeability decay rates of both types of the membrane were attributed to the differences in growth orientations rather than amounts of gypsum precipitates. Moreover, BSA-conditioned layers with high carboxylic density and specific molecular structure could stabilize bassanite and disrupt the oriented growth to inhibit the formation of needle-like gypsum crystals as observed on bare membranes, thus resulting in lower surface coverage with scales on membranes and alleviating the detrimental scaling effect on membrane permeability.
Ammonia (NH3) emissions, mainly from agricultural sources, generate substantial health damage due to the adverse effects on air quality. NH3 emission reduction strategies are still far from being effective. In particular, a growing trade network in this era of globalization offers untapped emission mitigation potential that has been overlooked. Here we show that about one-fourth of global agricultural NH3 emissions in 2012 are trade-related. Globally they induce 61 thousand PM2.5-related premature mortalities, with 25 thousand deaths associated with crop cultivation and 36 thousand deaths with livestock production. The trade-related health damage network is regionally integrated and can be characterized by three trading communities. Thus, effective cooperation within trade-dependent communities will achieve considerable NH3 emission reductions allowed by technological advancements and trade structure adjustments. Identification of regional communities from network analysis offers a new perspective on addressing NH3 emissions and is also applicable to agricultural greenhouse gas emissions mitigation.
System efficient electrostatic discharge (ESD) design is an effective method for simulating the ESD behaviors of a system. Based on this simulation method, this article mainly investigates the transient behaviors of a system-level ESD protection circuit with and without a 2.5 V power supply. During power-ON state, latch-up levels of a feedback power clamp protected by off-chip elements are predicted and mainly analyzed under machine model stress. During power-OFF state, the physical failure of a hybrid-triggered power clamp under surge stress is investigated. In addition to the utilization of transmission line pulsing (TLP) I-V curves, transient TLP waveforms are also used for building the component modelsin the system-level ESD protection circuit. Moreover, the relevant measurements for the power-ON state and power-OFF state areincluded in this article for verifying the simulation results. For ESD designers, this article provides a complete modeling and analysisprocess of co-design protection circuit to investigate the electrical behaviors.
