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The demand for non-toxic and biodegradable shale inhibitors is growing in the drilling industry. In this paper, the effect of notoginsenoside (NS) as a new, environmentally friendly inhibitor of shale hydration is systematically studied for the first time. The inhibition performance of NS was evaluated via inhibition evaluation tests, including mud ball immersion tests, linear expansion tests, shale rolling recovery tests, and compressive strength tests. The inhibition mechanism of NS was analyzed using Fourier transform infrared spectroscopy (FTIR), contact angle measurements, particle size distribution determination, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The experimental results demonstrate that NS is able to adhere to the clay surface, forming a hydrophobic film that prevents the entry of water molecules and inhibiting the hydration dispersion of the clay. Because of this, NS can maintain the original state of bentonite pellets in water, which can effectively reduce the swelling rate of bentonite, increase the recovery rate of shale drill cuttings, maintain the strength of the shale, and therefore maintain the stability of the borehole wall during drilling. In addition, NS is non-toxic, degradable, and compatible with water-based drilling fluids. The above advantages make NS a promising candidate for use as an environmentally friendly shale inhibitor.

Drilling fluids face failure during drilling deep reservoir with high temperature and high salt. The experimental results show that high temperature and salinity reduce the negative charge on the surface of bentonite in the drilling fluid and cause the coalescence of bentonite particles. As a result, the particles coalesce, the grid structure is destroyed, and the rheological properties, rock-carrying capacity and filtration properties are lost. To resolve the foregoing, in this study, 0.05-wt% carbon nanotubes are introduced into a 4% bentonite drilling fluid under conditions where the temperature and concentration of added NaCl reach 180 °C and 10 wt%, respectively. The carbon nanotubes adsorb on the bentonite surface and increase the space among bentonite particles. The steric hindrance prevents the coalescence of bentonite in high temperature and high salt environment. Thus bentonite maintains the small size distribution of bentonite and supports the bentonite grid structure in the drilling fluid. As a result, the rock-carrying capacity of the drilling fluid increases by 85.1%. Moreover, the mud cake formed by the accumulation of small-sized bentonite particles is dense; consequently, the filtration of bentonite drilling fluid reduced by 30.2%.

The introduction of oxygen-defects has been a versatile strategy to enhance photocatalysis efficiency. In this work, a 2D/3D Bi/BiO2-x/Bi2WO6 heterojunction photocatalyst with rich oxygen-defective was in sequence prepared through a facile solvothermal method, which displays favorable photocatalytic activity towards organic contaminants under visible-NIR light irradiation. The enhancement in photocatalytic performance can be attributed to the synergistic effect between oxygen-vacancy-rich heterojunction and the localized surface plasmon resonance induced by metallic Bi. The functional group interaction, surface morphology, crystal structure, element composition, and tuned bandgap were investigated by FT-IR, SEM, Raman shift, ICP-MS, and XPS technique. The spectrum response performance of the photocatalyst was verified by UV-visible DRS analysis. Results of photodegradation experiments toward organic contaminants showed that the prepared photocatalyst can degrade 90% of phenol in 20 mins under visible-NIR light irradiation, both Z-scheme heterojunction and the introduction of Bi metal contribute to the enhancement in the photocatalytic activity. The results of the DFT calculation suggest that the valence band-edge hybridization within BiO2-x and Bi2WO6 can effectively enhance the photocatalytic performance by increasing the migration efficiencies of electron-hole pairs. Moreover, a possible mechanism was proposed on the results of EIS, ESR and GC-MS tests. This work offers a novel insight for synthesizing efficient visible-NIR light photocatalysis by activating the semiconductors with Bi metal.

Hofbauer cycle machine is one promising technology for heating. It has many advantages compared to conventional Vuilleumier machines due to its non-continuous motions. However, its non-continuous motions also bring challenges for control. In this work, a simplified dynamic model is proposed to predict the free stroke for control. Based on assumption of a mass-spring system for the displacers, a simplified solution is deduced. The simplified solution is based on constant position of pressure balance points and a linear change of gas mass in the working chamber. Experiments on a prototype machine were carried out to validate the model. Motions of displacers are analyzed and causes for abnormal motions are revealed. Then, the predicted free stroke is obtained based on the simplified model and compared with the measured results. The relative error is in the range of -2.45% ∼ +3.02%. Thus, the simplified model could provide a reference for quick control in Hofbauer cycle machines.

Chronic wounds remain a worldwide clinical challenge, and bioactive materials that can promote skin regeneration are required. Self-assembling peptide (SAP) hydrogels have shown great potential in tissue repair, but their regenerative efficacy and possible mechanism in chronic wound healing are unclear. Here, we report an SAP (KGH) that enhances extracellular matrix (ECM) remodeling and angiogenesis, thereby promoting chronic wound healing in diabetic mice. In vivo, the KGH hydrogel was retained in wounds up to 7 days after injection, and it was effective in speeding up wound closure by ∼20% compared to the control groups and enhancing angiogenesis (e.g., VEGFA, CD31+ capillaries), cell proliferation (e.g., PCNA+ cells), formation of granulation tissue (e.g., α-SMA), and ECM deposition/remodeling (e.g., collagen I, fibronectin). In vitro, the KGH hydrogel created a 3D microenvironment for skin cells, maintained the sustained growth of cell spheroids, and increased the secretion of ECM proteins (e.g., laminin) and growth factors (e.g., PDGFB, VEGFA, and TGF-β) in skin keratinocytes compared to the conventional 2D culture. Mechanistically, the KGH hydrogel might promote wound tissue regeneration by activating the Rho/ROCK and TGF-β/MEK/MAPK pathways. As a type of designed material, SAP can be further re-engineered with biological motifs, therapeutic reagents, or stem cells to enhance skin regeneration. This study highlights that SAP hydrogels are a promising material platform for advanced chronic wound healing and might have translational potential in future clinical applications. Statement of significance Chronic wounds are a common and serious health issue worldwide, and bioactive dressing materials are required to address this issue. SAP hydrogels have shown certain tissue repair potential, but their regenerative efficacy and underlying mechanism in chronic wound healing remain elusive. Herein, we report that SAP hydrogels create a native 3D microenvironment that can remarkably stimulate angiogenesis and ECM remodeling in diabetic wounds. Mechanistically, the SAP hydrogel promoted ECM proteins and GFs secretion in skin cells through the activation of the Rho/ROCK and TGF-s/MEK/MAPK pathways. Additionally, SAP can be readily engineered with various bioactive motifs or therapeutic drugs/cells. This work highlights SAP hydrogels as a promising biomaterial platform for chronic wound healing and the regeneration of many other tissues.

An updated H2/O2 kinetic mechanism was proposed by incorporating carefully selected reaction rate coefficient and great progress in radical chain mechanisms, in which the uncertainties of rate coefficient were discussed. The performance of the current mechanism was compared to other H2 mechanism and validated against a wide range kinetic targets, including oxidation, decomposition in shock waves, ignition, flame speed and flame structure. Results show that the current mechanism obtains an overall improvement of performance, especially for the flame speed. By using the updated binary diffusion coefficient from ab initio calculations and the chemically termolecular reactions, the current mechanism presents better agreement with the new experimental flame speed at atmospheric pressure and obtains the improved performance with respect to the negative pressure dependence of high-pressure H2 flame. Furthermore, the flame speed predictions are strongly sensitive to the H2O third body efficiency in the H2 mechanism, affecting the water-contained H2 flame. The modeling results of rapid compression machine ignition show that present mechanism can more accurately predicts the ignition delay under engine-like conditions. However, all three mechanisms cannot accurately reproduce the negative pressure dependence behavior of mass burning rate in high-pressure H2 flame, which may be attributed to the fact that the important reaction O + OH(+M) = HO2(+M) that significantly affects lean high-pressure H2 flame is not included in current mechanism. Consequently, continuous works should be emphasized on the reactions that are important but neglected in H2 mechanism. All these not only develop an improved H2 reaction mechanism for high-pressure combustion, but also point out the direction for refining the H2 mechanism.

The respective performances of hypothetical Stirling engine and Stirling cooler in Vuilleumier machines are usually unclear. In this paper, a method of alternate combination of adiabatic sub-model with considering the losses and isothermal sub-model without considering the losses was proposed. The engine's work output is obtained by combining adiabatic engine and isothermal cooler, while the cooler's work input is obtained by combining adiabatic cooler and isothermal engine. Then, engine's thermal efficiency and cooler's coefficient of performance (COP) were obtained. The relative Carnot efficiency of hypothetical engine was 45%–57% at conditions of 550 °C hot temperature and 50 °C–70 °C warm temperature. The relative Carnot efficiency of hypothetical cooler was 44%–51% at conditions of −20 °C~10 °C cold temperature and 50 °C~70 °C warm temperature. In addition, a comparison of Vuilleumier machines’ COP based on a complete adiabatic model and the hybrid model was made. The ratio of COPV,hybrid over COPV,adia was in the range of 0.9~0.94. It indicated that the respective thermal efficiency and COPcooler in the hybrid model could approach to those in a complete adiabatic model.

The methane oxy-fuel combustion highly diluted by CO2 at supercritical region has the best potential for its near-zero emission characteristics and high thermal efficiency, while its auto-ignition characteristic is still not clear. In current investigation, a model with detailed chemical kinetic mechanism was introduced to research its ignition delay times (IDs). Results showed that the fold points in low-temperature and high-pressure region is due to CH3O2 which only involved in Aramco-Mech 1.3. When temperature increases, the inhibition of the termination reactions plays a dominate role at low pressure, while the promotion of the branching reactions contributes more to the acceleration of ignition at high pressure. Five dominant pathways and their variations were clarified to depict the inhibition effect of the ratio of CO2/O2. Based on the newly proposed combustion mode, it was found that temperature dependence of the nonnegligible CO2 collision effect is opposite under low and high pressure with full-oxy combustion mode. This investigation extended the research region to higher pressure and comprehensively studied the relevant factors on the auto-ignition which not only provides theoretical reference for the chemical kinetics study of methane, but also contributes to the further researches of EGR, SCF and near-zero emissions technologies.

Water direct injection into the cylinder is one of effective ways to suppress the combustion rate and knocking combustion in turbocharged SI engine. In this study, a detailed one-dimensional model coupled with the water direct injection was built by using the GT-Power according to the real tested hydrogen-enriched lean-burn natural gas (NG) SI engine, and validated against the experimental data. Then, a series of cases with various water injection quantity and injection timing were comprehensively investigated on the thermodynamics, combustion and emissions characteristics of the NGSI engine. The impact of the thermo-physical of the water were discussed in detailed by sweeping various water injection quantity and water injection timing. The results indicated that peak combustion pressure and peak heat release rate decreased with the increasing the water injection quantity. In addition, the 50% combustion location and peak combustion pressure location were retarded with the increasing the water injection quantity. As for the water injection timing, the peak combustion pressure and peak combustion temperature were slightly decreased with retarding the water injection timing. Apart from that, the indicated thermal efficiency decreased 4.03% and the equivalent fuel consumption increased 3.56% with injecting 60 mg water into the cylinder compared the case without water injection. Furthermore, the indicated thermal efficiency decreased 4.68% and the equivalent fuel consumption increased 4.66% by sweeping the water injection timing from the 150 CA to 50 CA before top dead center. However, the volumetric efficiency slightly ascended with increasing the water injection quantity and retarding the water injection timing. Finally, the NOx emissions declined with increasing the water injection quantity and retarding the water injection timing. However, CO emission and unburned HC emissions increased with increasing the water injection quantity and retarding the water injection timing. The main aim of this paper is expected to provide a comprehensively assessment of the thermo-physical of water on the thermodynamics, combustion, and emissions of the hydrogen enriched NGSI engine.

In this paper, three recently updated mechanisms were compared with experimental data, and FFCM 1.0 mechanism was chosen to perform chemical kinetic investigation of laminar burning velocity (LBV) for CH4/H2 mixtures. Results show that increasing hydrogen and pressure, LBV presents opposite results, which depends on the competition between promotion and inhibition effect at different hydrogen fractions and pressures. Based on growth rate of LBV, it is possible to determine three regimes for CH4/H2 mixtures at high pressures. When hydrogen fraction is less than 60%, the LBV of CH4/H2 mixtures at high pressures is not very sensitive to hydrogen, showing complex variation. Flame structure and radical concentration imply that the enhanced LBV by adding hydrogen, which is a combined result of chemical and thermal effects, is realized by improving the active radical production. Then, quantitative analysis of contribution value found that reaction OH+H2=H+H2O plays an important role in H production with increasing hydrogen fraction at high pressure. Through this work, it not only studied the interactive effect between CH4/H2 combustion system and varied conditions (such as pressure and hydrogen fraction), but also the influence mechanism was revealed in depth. All these have provided useful suggestions on fuel design for power machines.

The Coefficient of Performance of Vuilleumier cycle with ideal reversible changes is much higher than those obtained in practical machines. In this paper, an analytical model based on Hofbauer's Vuilleumier cycle (HVC) had been developed. The expansion and compression processes in the model were adiabatic. The expansion volume ratios for HVC were defined and formulas for determination of expansion volume ratios were derived. As the HVC is essentially consisted of hypothetical Stirling engine cycle and Stirling cooler cycle, the respective analytical models for Stirling engine cycle and Stirling cooler cycle were investigated firstly. The effects of regenerator effectiveness and expansion volume ratio were obtained. Then, the expansion volume ratios in the HVC were investigated and obtained at various ratios of dead volumes and temperatures. Then, the performance of HVC at various expansion volume ratios were obtained. Furthermore, the expansion volume ratios in a practical HVC machine was investigated. It was in the range of 1.045–1.068 for Stirling engine cycle and 1.091–1.095 for Stirling cooler cycle. The results showed that the performance could be improved by lifting the expansion volume ratios.

Ischemia-reperfusion (I/R)-induced organ injury is a serious health problem worldwide, and poor recovery of acute phase injury leads to chronic fibrosis and further organ dysfunction. Thus, a more precise approach to enhance tissue repair is needed. By using a renal I/R model, we aimed to evaluate the role of a hydrogel-based dual-drug delivery platform on promoting tissue repair. An injectable, self-assembling peptide/heparin (SAP/Hep) hydrogel was used to co-deliver TNF-α neutralizing antibody (anti-TNF-α) and hepatocyte growth factor (HGF). The microstructure and controlled release properties of KLD2R/Hep hydrogel were analyzed. The effects of the drug-loaded hydrogel (SAP-drug) on renal injury were evaluated in mice with I/R injury. In vitro, the SAP/Hep hydrogel allowed for a faster release of anti-TNF-α with a sustained release of HGF, and both drugs maintained their bioactivities after release. In vivo, combined anti-TNF-α/HGF showed better renal protective potential than anti-TNF-α or HGF alone. SAP-drug (anti-TNF-α/HGF in SAP hydrogel) treatment reduced the level of serum creatinine (Scr), blood urea nitrogen (BUN), tubular apoptosis, renal inflammatory factors, and macrophage infiltration compared to Free-drug (anti-TNF-α/HGF in solution) or SAP alone. Moreover, the SAP-drug group had better efficacy on promoting tubular cell proliferation and dedifferentiation than SAP or Free-drug alone, and thus reduced chronic renal fibrosis in I/R mice. This study highlighted that SAP could sequentially deliver the two drugs to achieve anti-inflammatory and pro-proliferative effects with one injection and thus is a promising delivery platform for tissue repair. STATEMENT OF SIGNIFICANCE: Ischemia-reperfusion (I/R)-induced organ injury is a serious health issue, and delayed tissue repair leads to chronic fibrosis and organ failure. Systemic administration of anti-inflammatory agents or growth factors have shown some benefits on I/R injury, but their therapeutic efficacy was limited by side effects, poor bioavailability, and absent key signals of tissue repair. To address these issues, a hydrogel-based drug co-delivery platform was used to treat I/R injury. This platform could achieve sequential release kinetics with faster rate of anti-TNF-ɑ and slower rate of HGF, and effectively promoted tissue repair by targeting inflammation and proliferation in mice with renal I/R. This nanoscale delivery platform represents a promising strategy for solid organs (heart, liver and kidney) regeneration after I/R.

In this research, a newly proposed method combining Chemkin with CONVERGE was used to study the transient in-cylinder chemical reaction process in NG-diesel dual fuel engine. The selected mechanism was verified by comparing the results of CONVERGE with experimental data, and then the calibrated model of CONVERGE was used to provide boundary conditions for Chemkin. On this basis, the detailed combustion process was simulated at different natural gas substitution ratio (NGSR). The results show that, the chain branching reaction, long-chain to short-chain reaction, and reactions associated with OH radicals have significant impacts on temperature. It can also be found that the combustion of fuel shows a distinct two-stage reaction process. During the low temperature stage, both the CO and NO emissions are little. While at the high temperature stage, the CO emissions first rapidly increase and then decrease due to the consumption reaction, and the NO emissions also have a quick increase. When the NGSR is reduced, a new path for CO generation occurs at low temperature stage, resulting in minor increase (up to 0.0019 mol fraction) of CO concentration. Meanwhile, the ignition delay is reduced significantly (by 88.5%), but the increase of diesel species does not alter the formation mechanism of emissions. All these provide guidance for improving combustion and emission performance of NG-diesel dual fuel engine.

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have shown great potential for tissue repair, but their therapeutic capacity is limited by rapid clearance and short half-life. Herein, we purposed a hydrogel-based slow release strategy to enhance the therapeutic potency of EVs. A matrix metalloproteinase-2 (MMP2) sensitive self-assembling peptide (KMP2) hydrogel was used for the local delivery of MSC-EVs. The structure and controlled release properties of the KMP2 hydrogel were analyzed. The effects of the EV-loaded KMP2 hydrogel (KMP2-EVs) on cell apoptosis, inflammation and angiogenesis were evaluated in mice with renal ischemia-reperfusion (I/R) injury. In vitro, KMP2 formed a cross-linked nanofiber hydrogel to encapsulate MSC-EVs. KMP2 showed greater degradation and EV release in response to MMP2. The released EVs had similar structures and bioactivities as fresh, isolated EVs. In vivo, I/R mice treated with KMP2-EVs showed improved renal function by reducing tubular cell apoptosis, pro-inflammatory cytokine expression, and macrophage infiltration than mice receiving either EVs or KMP2. Moreover, KMP2-EVs showed better efficacy on promoting endothelial cell proliferation and angiogenesis than KMP2 or EVs alone, which subsequently decreased chronic renal fibrosis in I/R mice. This study highlighted that the EV-released KMP2 hydrogel is a promising cell-free therapy for tissue repair.

In this study, a detailed 1D simulation model of the hydrogen-enriched natural gas SI engine was built according to realistic engine layout in the lab with practical boundary conditions, and validated against the experimental data. Four different types of EGR systems were comprehensively investigated, including a low-pressure (LP) EGR, a high-pressure (HP) EGR, their combinations, and an internal EGR, using the validated 1D simulation model of the hydrogen-enriched natural gas SI engine for their combustion, performance, and emissions characteristics. The results indicated that the peak combustion pressure of the in-cylinder pressure decreased with increase in EGR ratio either using the HP, LP, or combined HP-LP systems. The NOx emissions with the HP EGR were observed to be lowest of all types of EGR systems. Combined the 10% HP EGR ratio with the 5% LP EGR ratio (total 15% EGR ratio) was predicted to achieve the highest indicated thermal efficiency compared with other EGR strategies. As for the internal EGR, the peak combustion pressure and the heat release rate slightly increased with decrease in the valve overlap. Moreover, the indicated thermal efficiency firstly increased with decrease in overlap and then slightly declined. The internal EGR was mainly determined by the timing of the exhaust valve closing; However, it was not the only influence factor. The positive and negative waves in the intake and exhaust systems also played a crucial role in the gas exchange process and volumetric efficiency.

Vuilleumier heat pumps can reduce the consumption of fossil combustion and thus have huge potential for applications in heating systems. However, it receives less attentions. In this paper, a Vuilleumier heat pumps with alternate move-and-stop motions (Hofbauer–Vuilleumier heat pump) was studied. A theoretical adiabatic model and a simple adiabatic model were derived. Both models were compared to the numerical adiabatic model and isothermal model. The results of theoretical adiabatic model agreed well with that of the numerical adiabatic model in terms of Qh, Qc, COP, pressure and temperature. The accuracy of the simple adiabatic model was relatively worse than the theoretical adiabatic model but much higher than the isothermal model. Furthermore, the effects of hot, warm and cold temperatures, initial pressure, dead volumes and various heat losses (regenerators’ heat losses, displacers’ shuttle losses, pumping losses and axial conduction losses) on the performance were investigated.