Engineering topics
Chen, Qi
Publications and source records attributed to Chen, Qi.
Modeling of underexpanded hydrogen jets through square and rectangular slot nozzles
The development and revision of safety codes and standards for hydrogen infrastructure requires a solid scientific basis, including studies of unignited releases from high pressure systems for various scenarios. Most hydrogen releases are modeled as axisymmetric jets, but real leaks are more likely to be non-axisymmetric jets issuing from high aspect ratio cracks or slots. In the present study, underexpanded hydrogen jets from square and rectangular nozzles with aspect ratios of 1 to 16 were numerically modeled for stagnation pressures up to 20 MPa. The near and far flow fields were modeled separately using two sequential computational domains to accurately and efficiently capture the flow characteristics. The numerical models were first validated with experimental data from a previous experimental study and literature data. The mass fraction and velocity distributions show that the centerline decay rates increase as the nozzle aspect ratio increases, but this increase is dependent on the pressure. This means that the canonical decay law of round turbulent jets and plumes no longer applies to the slot nozzle jets for high pressures. The radial profiles collapse onto a Gaussian curve in the minor axis plane, but neither collapse, nor are they Gaussian in the major axis plane with peaks away from the jet centerline. Different shock patterns were identified along the major and minor axes and the axis switching phenomenon seen in the literature was also reproduced. The axis switching resulted in significantly wider flattened concentration distributions compared with the axisymmetric jet which may require consideration during safety analyses for non-circular nozzles. A scaling factor taking both the nozzle shape and pressure effects into account SAND2018-12056J This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. was then devleoped to better scale the centerline decay rates for jets from both the square and rectangular nozzles. The present study demonstrates that the nozzle shape effects on the jet spreading should not be overlooked and proper scaling factors are required to collapse the data and calculate decay rates.
Simulation on falling film absorption based on lattice Boltzmann method at moderate Reynolds number
Not Available
Structural Basis for ( S )-3,4-Dicarboxyphenylglycine (DCPG) As a Potent and Subtype Selective Agonist of the mGlu 8 Receptor
(S)-3,4-Dicarboxyphenylglycine (DCPG) was first reported in 2001 as a potent orthosteric agonist with high subtype selectivity for the mGlu8 receptor, but the structural basis for its high selectivity is not well understood. Herein, we have solved a cocrystal structure of recombinant human mGlu8 amino terminal domain (ATD) protein bound to (S)-DCPG, which possesses the largest lobe opening angle observed to date among known agonist-bound mGlu ATD crystal structures. The binding conformation of (S)-DCPG observed in the crystal structure is significantly different from that in the homology model built from an L-glutamate-bound rat mGlu1 ATD crystal structure, which has a smaller lobe opening angle. This highlights the importance of considering various lobe opening angles when modeling mGlu ATD–ligand complex. New homology models of other mGlu receptors based on the (S)-DCPG-bound mGlu8 ATD crystal structure were explored to rationalize (S)-DCPG’s high mGlu8 receptor subtype selectivity.
Hypoxia is involved in the reduction of HtrA3 in patients with endometrial hyperplasia and cancer
Endometrial cancer (EC) has recently become a major gynecological cancer and endometrial hyperplasia increases the risk for developing EC. Previous studies have reported that human high temperature requirement factor A3 (HtrA3), a member of ATP independent serine proteases family, is involved in endometrial carcinogenesis. However, the underlying mechanism of HtrA3 function is unclear in endometrial hyperplasia and cancer. In this study, we investigated that HtrA3 expression was reduced in endometrial hyperplasia as well as EC. The circulating levels of HtrA3 were also significantly reduced in both atypical hyperplasia and EC. Whether hypoxia is involved in the reduction of HtrA3 in EC was further investigated. Immunohistochemistry (IHC) scores of Glut1 and HtrA3 in type 1 and type 2 EC tissues showed the inverse correlation. And hypoxic condition reduced the expression of HtrA3. Furthermore, silencing HtrA3 promoted EC cell migration. Our study demonstrated the reduced levels of HtrA3 in endometrial hyperplasia including atypical hyperplasia which is a premalignant condition; and as the degree of hypoxia increases in EC, HtrA3 eventually loses its expression. Hypoxia is responsible for the reduction of HtrA3 which in turn promotes EC progression. These findings suggested that HtrA3 is an important adaptor in hypoxic regions that drives endometrial cancer development.
Energy Transfer Dynamics in Triplet–Triplet Annihilation Upconversion Using a Bichromophoric Heavy-Atom-Free Sensitizer
A heavy-atom-free triplet sensitizer suitable for triplet-triplet annihilation-based photon upconversion was developed from the thermally activated delayed fluorescence (TADF) molecule 4CzPN by covalently tethering a pyrene derivative (DBP) as a triplet acceptor. The triplet exciton produced by 4CzPN is captured by the intramolecular pyrenyl acceptor and subsequently transferred via intermolecular triplet–triplet energy transfer (TTET) to freely diffusing pyrenyl acceptors in toluene. Transient absorption and time-resolved photoluminescence spectroscopy were employed to examine the dynamics of both the intra- and intermolecular TTET processes, and the results show that the intramolecular energy transfer from 4CzPN to DBP is swift, quantitative, and nearly irreversible. The reverse intersystem crossing is suppressed while intersystem crossing remains efficient, attaining high triplet yield and long triplet lifetime at the same time. The ultra-long excited state lifetime characteristic of the DBP triplet was shown to be crucial for enhancing the intermolecular TTET efficiency and the subsequent triplet–triplet annihilation photochemistry. It was further demonstrated that with the long triplet lifetime of the tethered DBP, TTET was enabled under low free acceptor concentrations and/or with sluggish molecular diffusion in polymer matrices.
A Flexible Framework and Model Library for Process Simulation, Optimization and Control
Presented by NETL at Process Systems Engineering 2018, 07/18
A Comparative Study between GDP and NLP Formulations for Conceptual Design of Distillation Columns
Presented by NETL at Process Systems Engineering Conference, 07/18
Fluoroalkyl-substituted fullerene/perovskite heterojunction for efficient and ambient stable perovskite solar cells
In this study, we investigate the feasibility of using a fluoroalkyl-substituted fullerene/perovskite heterojunction (f-FPHJ) to realize efficient and ambient stable perovskite solar cells (PVSCs). The hybrid fluoroalkyl-substituted fullerene, DF-C 60 , is proven to effectively passivate the defects and grain boundaries in the perovskite film to facilitate charge transport/collection in the derived PVSC. Consequently, the f-FPHJ device yielded an enhanced PCE of 18.11%, outperforming that of the pristine CH 3 NH 3 PbI 3 device (15.67%). More interestingly, the f-FPHJ PVSC showed a decent PCE of 15.14% (under reverse scan) with small hysteresis even without employing a discrete PCBM electron-transporting layer (ETL), in contrast to the pristine PVSC showing a lower PCE of 14.78% (under reverse scan) accompanied with severe hysteresis. This might arise from the preferential distribution of DF-C 60 nearby the surface region of the f-FPHJ film due to its low surface energy, which serves the similar function of the PCBM ETL in device to reduce hysteresis. More importantly, benefitting from the hydrophobic nature of DF-C 60 , the f-FPHJ PVSC shows respectable ambient stability without encapsulation, which can maintain 83% of its initial PCE after being stored in ambient (with a relative humidity of 60 ± 5%) for 1 month.
Defect Passivation of Organic–Inorganic Hybrid Perovskites by Diammonium Iodide toward High-Performance Photovoltaic Devices
The polycrystalline feature of solutionprocessed perovskite film and its ionic nature inevitably incur substantial crystallographic defects, especially at the film surface and the grain boundaries (GBs). Here, a simple defect passivation method was exploited by post-treating CH 3 NH 3 PbI 3 (MAPbI 3 ) film with a rationally selected diammonium iodide. The molecular structure of the used diammonium iodide was discovered to play a critical role in affecting the phase purity of treated MAPbI 3 . Both NH 3 I(CH 2 ) 4 NH 3 I and NH 3 I(CH 2 ) 2 O(CH 2 ) 2 NH 3 I (EDBE) induce three-dimensional (3D) to two-dimensional (2D) perovskite phase transformation during the treatment while only NH 3 I(CH 2 ) 8 NH 3 I (C 8 ) successfully passivates perovskite surface and GBs without forming 2D perovskite because of the elevated activation energy arising from its unique anti-gauche isomerization. In conclusion, defect passivation of MAPbI 3 was clearly confirmed by scanning Kelvin probe microscopy (SKPM) and time-resolved photoluminescence (TRPL) studies, which results in the reduced recombination loss in derived devices. Consequently, the perovskite solar cell with C 8 passivation showed a much improved power conversion efficiency (PCE) of 17.60% compared to the control device PCE of 14.64%.
INPP4B reverses docetaxel resistance and epithelial-to-mesenchymal transition via the PI3K/Akt signaling pathway in prostate cancer
Docetaxel efficiency in the therapy of prostate cancer (PCa) patients is limited due to the development of chemoresistance. Recent studies have implied a role of INPP4B in tumor chemoresistance, while the effects of INPP4B on docetaxel resistance in PCa have not been elucidated. In the present study, the docetaxel-resistant human PCa cell lines PC3-DR and DU-145-DR were established from the parental cell lines PC3 and DU-145, and the expression and role of INPP4B in docetaxel-resistant PCa cells were investigated. The results demonstrated that INPP4B expression was significantly downregulated in docetaxel-resistant cells. Overexpression of INPP4B increased the sensitivity to docetaxel and promoted cell apoptosis in PC3-DR and DU-145-DR cells. In addition, INPP4B overexpression downregulated the expression of the mesenchymal markers fibronectin, N-cadherin, and vimentin, and upregulated the expression level of the epithelial maker E-cadherin. Furthermore, INPP4B overexpression markedly inhibited the PI3K/Akt pathway. We also found that IGF-1, the inhibitor of PI3K/Akt, markedly blocked the change in EMT markers induced by overexpression of INPP4B, and reversed the resistance of PC3-DR and DU-145-DR cells to docetaxel, which is sensitized by Flag-INPP4B. In summary, the presented data indicate that INPP4B is crucial for docetaxel-resistant PCa cell survival, potentially by regulating EMT through the PI3K/Akt signaling pathway. - Highlights: • INPP4B is downregulated in docetaxel-resistant PCa cells. • INPP4B inhibits cell proliferation. • INPP4B induces cell apoptosis. • INPP4B inhibits PCa cell EMT.
Motion Estimation System Utilizing Point Cloud Registration
A system and method of estimation motion of a machine is disclosed. The method may include determining a first point cloud and a second point cloud corresponding to an environment in a vicinity of the machine. The method may further include generating a first extended gaussian image (EGI) for the first point cloud and a second EGI for the second point cloud. The method may further include determining a first EGI segment based on the first EGI and a second EGI segment based on the second EGI. The method may further include determining a first two dimensional distribution for points in the first EGI segment and a second two dimensional distribution for points in the second EGI segment. The method may further include estimating motion of the machine based on the first and second two dimensional distributions.
Motion Estimation Utilizing Range Detection-Enhanced Visual Odometry
A motion determination system is disclosed. The system may receive a first and a second camera image from a camera, the first camera image received earlier than the second camera image. The system may identify corresponding features in the first and second camera images. The system may receive range data comprising at least one of a first and a second range data from a range detection unit, corresponding to the first and second camera images, respectively. The system may determine first positions and the second positions of the corresponding features using the first camera image and the second camera image. The first positions or the second positions may be determined by also using the range data. The system may determine a change in position of the machine based on differences between the first and second positions, and a VO-based velocity of the machine based on the determined change in position.
Independently tunable dual-band perfect absorber based on graphene at mid-infrared frequencies
We design a dual-band absorber formed by combining two cross-shaped metallic resonators of different sizes within a super-unit-cell arranged in mirror symmetry. Simulations indicate that absorption efficiencies greater than 99% can be achieved at two different frequencies under normal incidence. We also employ a design scheme with graphene integration, which allows independent tuning of individual absorption frequencies by electrostatically changing the Fermi energy of the graphene layer. High absorbance is maintained over a wide incident angle range up to 50 degrees for both TE and TM polarizations. Thus, it enables a promising way to design electrically tunable absorbers, which may contribute toward the realization of frequency selective detectors for sensing applications.
Rational design of a carboxylic esterase Rh Est1 based on computational analysis of substrate binding
A new carboxylic esterase RhEst1 which catalyzes the hydrolysis of (S)-(+)-2,2-dimethylcyclopropanecarboxylate (S-DmCpCe), the key chiral building block of cilastatin, was identified and subsequently crystallized in our previous work. Mutant Rh Est 1A147I/V148F/G254A was found to show a 5-fold increase in the catalytic activity. In this work, molecular dynamic simulations were performed to elucidate the molecular determinant of the enzyme activity. Our simulations show that the substrate binds much more strongly in the A147I/V148F/G254A mutant than in wild type, with more hydrogen bonds formed between the substrate and the catalytic triad and the oxyanion hole. The OH group of the catalytic residue Ser101 in the mutant is better positioned to initiate the nucleophilic attack on S-DmCpCe. Interestingly, the "170-179" loop which is involved in shaping the catalytic sites and facilitating the product release shows remarkable dynamic differences in the two systems. Based on the simulation results, six residues were identified as potential "hot-spots" for further experimental testing. Consequently, the G126S and R133L mutants show higher catalytic efficiency as compared with the wild type. In conclusion, this work provides molecular-level insights into the substrate binding mechanism of carboxylic esterase Rh Est1, facilitating future experimental efforts toward developing more efficient Rh Est1 variants for industrial applications.