Explore the vast range of titles available.

Fused deposition modeling (FDM) is a well-known technology that is capable of fabricating three-dimensional prototypes with very complex geometries. However, the physical model built with acrylonitrile butadiene styrene (ABS) filament using a low-cost FDM machine is not satisfactory for most general engineering purposes due to warpage. Thus, minimizing the warpage of the ABS prototypes built with a low-cost FDM machine is a promising research issue. In this study, a closed chamber was designed and constructed to maintain the chamber temperature and increase the modeling space. It was found that the modeling space was increased by approximately 2.75 times. The optimal process parameters for reducing the warpage of ABS prototypes were also investigated using the Taguchi method. The dominant factor affecting the warpage of ABS prototypes is the bed temperature, followed by chamber temperature. The optimal process parameters for reducing the warpage of ABS prototypes are nozzle temperature of 230 °C, bed temperature of 93 °C, print speed of 60 mm/s, and chamber temperature of 43 °C. The optimal process parameter was also evaluated via the verification test. The optimal process parameters were also examined experimentally by a verification test.

Baicalin purified from the root of Radix scutellariae is widely used in clinical practices. This study aimed to evaluate the effect of baicalin on the pharmacokinetics of nifedipine, a CYP3A probe substrate, in rats in vivo and in vitro. In a randomised, three-period crossover study, significant changes in the pharmacokinetics of nifedipine (2 mg/kg) were observed after treatment with a low (0.225 g/kg) or high (0.45 g/kg) dose of baicalin in rats. In the low- and high-dose groups of baicalin-treated rats, C max of total nifedipine decreased by 40%±14% (P<0.01) and 65%±14% (P<0.01), AUC0-∞ decreased by 41%±8% (P<0.01) and 63%±7% (P<0.01), Vd increased by 85%±43% (P<0.01) and 224%±231% (P<0.01), and CL increased by 97%±78% (P<0.01) and 242%±135% (P<0.01), respectively. Plasma protein binding experiments in vivo showed that C max of unbound nifedipine significantly increased by 25%±19% (P<0.01) and 44%±29% (P<0.01), respectively, and there was a good correlation between the unbound nifedipine (%) and baicalin concentrations (P<0.01). Furthermore, in vitro results revealed that baicalin was a competitive displacer of nifedipine from plasma proteins. In vitro incubation experiments demonstrated that baicalin could also competitively inhibit CYP3A activity in rat liver microsomes in a concentration-dependent manner. In conclusion, the pharmacokinetic changes of nifedipine may be modulated by the inhibitory effects of baicalin on plasma protein binding and CYP3A-mediated metabolism.

Buoyant unstable behavior in initially spherical lean hydrogen-air premixed flames within a center-ignited combustion vessel have been studied experimentally under a wide range of pressures (including reduced, normal, and elevated pressures). The experimental observations show that the flame front of lean hydrogen-air premixed flames will not give rise to the phenomenon of cellular instability when the equivalence ratio has been reduced to a certain value, which is totally different from the traditional understanding of the instability characteristics of lean hydrogen premixed flames. Accompanied by the smoothened flame front, the propagation mode of lean hydrogen premixed flames transitions from initially spherical outwardly towards upwardly when the flames expand to certain sizes. To quantitatively investigate such buoyant instability behaviors, two parameters, “float rate (ψ)” and “critical flame radius (Rcr)”, have been proposed in the present article. The quantitative results demonstrate that the influences of initial pressure (Pint) on buoyant unstable behaviors are different. Based on the effects of variation of density difference and stretch rate on the flame front, the mechanism of such buoyant unstable behaviors has been explained by the competition between the stretch force and the results of gravity and buoyancy, and lean hydrogen premixed flames will display buoyant unstable behavior when the stretch effects on the flame front are weaker than the effects of gravity and buoyancy.

In this study, the effect of flame intrinsic instability on the flame structural characteristics of hydrogen/air mixtures premixed at various equivalence ratios were experimentally investigated from the macroscopic and microscopic perspectives, respectively. The correlation degree and the relative deformation degree were defined to quantitatively study the global flame structural characteristics. Peak detection was used to capture the characteristic length of the flame and fast Fourier transform was adopted to study the components of the fluctuation of the flame front. The results show that with the development of flames, the wrinkles in the flame front increase and the correlation degree of the flame decreases. The relative deformation degree of the flame first decreases and then increases. When the equivalence ratio is 0.6, the average characteristic length initially exhibits an increasing trend, followed by a decreasing trend. The average characteristic length scale gradually increases, and the growth rate gradually decreases when the equivalence ratio ranges from 0.70 to 0.99. With the increase in the wavenumber, the amplitude of the corresponding disturbance exhibited an increasing trend followed by a decreasing one. With the development of the flame, the maximum amplitude of the disturbance shows a reverse trend, i.e., first decreasing and then increasing. The disturbances with smaller wavelengths could be further developed.

The atomization process of swirling sprays in gas turbine engines has been investigated using a LES-VOF model. With fine grid resolution, the ligament and droplet formation processes are captured in detail. The spray structure of fully developed sprays and the flow field are observed firstly. A central recirculation zone is generated inside the hollow cone section due to the entrainment of air by the liquid sheet and strong turbulent structures promote the breakup of ligaments. At the exit of injector nozzle, surface instability occurs due to disturbance factors. Axial and transverse mode instabilities produce a net-like structure ligament zone. Finally, the generation mechanism of the droplet is analyzed. It is found that the breakup mechanism of ligaments is located at the Raleigh capillary region. Axial symmetry oscillation occurs due to the surface tension force and the capillary waves pinch off from the neck of the ligaments. Secondary breakup and coalescence occur at the “droplet zone,” resulting in a wider distribution curve at the downstream area.

An experimental study of the intrinsic instabilities of H2/CO lean (φ = 0.4 to φ = 1.0) premixed flames at different hydrogen fractions ranging from 0% to 100% at elevated pressure and room temperature was performed in a constant volume vessel using a Schlieren system. The unstretched laminar burning velocities were compared with data from the previous literature and simulated results. The results indicate that excellent agreements are obtained. The cellular instabilities of syngas-air flames were discussed and critical flame radii were measured. When hydrogen fractions are above 50%, the flame tends to be more stable as the equivalence ratio increases; however, the instability increases for flames of lower hydrogen fractions. For the premixed syngas flame with hydrogen fractions greater than 50%, the decline in cellular instabilities induced by the increase in equivalence ratio can be attributed to a reduction of diffusive-thermal instabilities rather than increased hydrodynamic instabilities. For premixed syngas flames with hydrogen fractions lower than 50%, as the equivalence ratio increases, the cellular instabilities become more evident because the enhanced hydrodynamic instabilities become the dominant effect. For premixed syngas flames, the enhancement of cellular instabilities induced by the increase in hydrogen fraction is the result of both increasing diffusive-thermal and hydrodynamic instabilities.

Sodium (±)-5-bromo-2-(α-hydroxypentyl) benzoate (BZP) is a potential cardiovascular drug and exerts potent neuroprotective effect against transient and long-term ischemic stroke in rats. BZP could convert into 3-butyl-6-bromo-1(3H)-isobenzofuranone (Br-NBP) in vitro and in vivo. However, the pharmacokinetic profiles of BZP and Br-NBP still have not been evaluated. For the purpose of investigating the pharmacokinetic profiles, tissue distribution, and plasma protein binding of BZP and Br-NBP, a rapid, sensitive, and specific method based on liquid chromatography coupled to mass spectrometry (LC-MS/MS) has been developed for determination of BZP and Br-NBP in biological samples. The results indicated that BZP and Br-NBP showed a short elimination half-life, and pharmacokinetic profile in rats (3, 6, and 12 mg/kg; i.v.) and beagle dogs (1, 2, and 4 mg/kg; i.v.gtt) were obtained after single dosing of BZP. After multiple dosing of BZP, there was no significant accumulation of BZP and Br-NBP in the plasma of rats and beagle dogs. Following i.v. single dose (6 mg/kg) of BZP to rats, BZP and Br-NBP were distributed rapidly into all tissues examined, with the highest concentrations of BZP and Br-NBP in lung and kidney, respectively. The brain distribution of Br-NBP in middle cerebral artery occlusion (MCAO) rats was more than in normal rats (P < 0.05). The plasma protein binding degree of BZP at three concentrations (8000, 20,000, and 80,000 ng/mL) from rat, beagle dog, and human plasma were 98.1-98.7, 88.9-92.7, and 74.8-83.7% respectively. In conclusion, both BZP and Br-NBP showed short half-life, good dose-linear pharmacokinetic profile, wide tissue distribution, and different degree protein binding to various species plasma. This was the first preclinical pharmacokinetic investigation of BZP and Br-NBP in both rats and beagle dogs, which provided vital guidance for further preclinical research and the subsequent clinical trials.

Tongguan Liqiao acupuncture therapy has been shown to effectively treat dysphagia after stroke-based pseudobulbar paralysis. We presumed that this therapy would be effective for dysphagia after bulbar paralysis in patients with brainstem infarction. Sixty-four patients with dysphagia following brainstem infarction were recruited and divided into a medulla oblongata infarction group（n = 22）, a midbrain and pons infarction group（n = 16）, and a multiple cerebral infarction group（n = 26） according to their magnetic resonance imaging results. All patients received Tongguan Liqiao acupuncture for 28 days. The main acupoints were Neiguan（PC6）, Renzhong（DU26）, Sanyinjiao（SP6）, Fengchi（GB20）, Wangu（GB12）, and Yifeng（SJ17）. Furthermore, the posterior pharyngeal wall was pricked. Before and after treatment, patient swallowing functions were evaluated with the Kubota Water Test, Fujishima Ichiro Rating Scale, and the Standard Swallowing Assessment. The Barthel Index was also used to evaluate their quality of life. Results showed that after 28 days of treatment, scores on the Kubota Water Test and Standard Swallowing Assessment had decreased, but scores on the Fujishima Ichiro Rating Scale and Barthel Index had increased in each group. The total efficacy rate was 92.2% after treatment, and was most obvious in patients with medulla oblongata infarction（95.9%）. These findings suggest that Tongguan Liqiao acupuncture therapy can repair the connection of upper motor neurons to the medulla oblongata motor nucleus, promote the recovery of brainstem infarction, and improve patient＇s swallowing ability and quality of life.

Water pinch technology for the water system of enterprises is one of the focuses on water-saving and emission reduction research of enterprises in recent years. This technology is characterized by the design minimal fresh water consumption and waste water emissions minimum and aims to achieve economic benefit optimum process integration technology. The application of water pinch technology to integration and optimization of the water system was reviewed, and engineering application examples of water pinch technology were introduced. The water pinch technology is simple and intuitive. Besides, it could achieve optimal solution for a single impurity system. But for multiple contaminants system, this method will no longer apply. Taking into account its limitations, the possible optimization solutions to application of water pinch technology in combination with other types of analysis tools in enterprise water system were put forward.

As the most advanced fuel injection system, the common rail system can achieve the flexible control of injection pressure, injection timing and injection rate. Thus, the pressure control strategy of high-pressure common rail system (HPCRS) will be critical for the performance of the diesel engine, as it affects its injection characteristics. In this paper, model in loop (MIL) simulation studies were carried out, a high-precision common rail hydraulic model and analytical rail pressure control strategy based on flow continuity equation were established. The delay of the high-pressure pump was accounted for and included in the proposed strategy, making it more targeted for HPCRS. The delay can be extremely important for high-pressure common rail overshoot especially in variable working condition. Next, the proposed strategy was compared to the traditional PI-based control strategy in both the start-up and transient conditions. Results indicated that the proposed strategy performs better regarding the overshoot, notably improving the control effect (compared to traditional PI-based strategy). The advances of using the proposed strategy primarily include improvements in working conditions with the obvious change in cycle injection quantity and engine speed. Both the proposed control strategy and PI-based strategy can track pressure effectively in various working conditions.