Mechanism of V-Shaped Pits on Promoting Hole Injection in the InGaN MQWs: First-Principles Investigation.

In the InGaN multiple quantum wells (MQWs), V-shaped pits play a crucial role in carrier transport, which directly affects emitting efficiency. First-principles calculations are applied to investigate the formation of the V-shaped pits, and the results indicate that they are inclined to form in the N-rich environment. Meanwhile, we calculate the interfacial electronic properties of the sidewalls of the V-shaped pits with varying indium (In) and magnesium (Mg) compositions. The calculated valence band offset (VBO) of the In0.3Ga0.7N/Ga0.94Mg0.06N (0001) is 0.498 eV, while that of the In0.07Ga0.93N/Ga0.94Mg0.06N (101̅1) is 0.340 eV. The band alignment results show that the valence band edges in the Ga1-yMgyN layer are in higher energy than in the InxGa1-xN layer. These are in good agreement with the values reported in the previous numerical simulation. Moreover, the calculation of the projected density of states (PDOS) of interfaces discloses that the strong hybridization between the N 2p orbital and the Mg 2p orbital exerts a vital influence on the upward shifts of the valence band edges in the superlattices (SLs). All these results reveal that holes are easier to inject into the quantum wells (QWs) via the sidewall of V-shaped pits rather than the c-plane QWs, providing a theoretical basis for the growth of InGaN MQWs samples containing V-shaped pits.

Efficiency enhancement mechanism of piezoelectric effect in long wavelength InGaN-based LED.

Improving the luminescence efficiency of InGaN-based long wavelength LEDs for use in micro-LED full-colour displays remains a huge challenge. The strain-induced piezoelectric effect is an effective measure for modulating the carrier redistribution at the InGaN/GaN heterointerfaces. Our theoretical results reveal that the hole injection is significantly improved by the diminution of the valence band offset (VBO) of the InGaN/GaN heterointerfaces along the [0001] direction, and inversely, the VBO increases along the [0001] direction. The energy band structures showed that the tensile strain of the GaN film grown on a silicon (Si) substrate could weaken the internal electric field of the InGaN well layer leading to a flattening of the energy band, which increases the overlap of electron and hole wave functions. In addition, the strain-induced piezoelectric polarisation of the InGaN layer on the Si substrate generates opposite sheet-bound charges at the heterointerfaces, which causes a reduction in the depletion region of the InGaN/GaN quantum wells (QWs). A systematic analysis illustrates that the control of the piezoelectric polarisation of the InGaN QW layer is available improve the internal quantum efficiency of the InGaN-based LEDs.

Numerical Simulation of Temperature Field Optimization to Enhance Nitrogen Transfer in GaN Crystal Growth by the Na-Flux Method.

Improved nitrogen transport is crucial for enhancing the growth rate of GaN crystals using the Na-flux method. This study investigates the nitrogen transport mechanism during the growth of GaN crystals by the Na-flux method using a combination of numerical simulations and experiments. The results indicate that the temperature field affects the effect of nitrogen transfer, and we propose a novel bottom ring heating approach to optimize the temperature field and enhance nitrogen transfer during the growth of GaN crystals. The simulation results demonstrate that optimizing the temperature field improves nitrogen transfer by causing convection within the melt to float up from the crucible wall and sink at the crucible center. This enhancement improves the nitrogen transfer from the gas-liquid interface to the GaN crystal growth surface, thereby accelerating the growth rate of GaN crystals. Additionally, the simulation results indicate that the optimized temperature field substantially reduces polycrystalline generation at the crucible wall. These findings are also a realistic guide to the growth of other crystals in the liquid phase method.

Effects of multifaceted optimization management for chronic heart failure: a multicentre, randomized controlled study.

AIMS: In recent years, we have developed the concept of 'clinical pathway based on integrated traditional Chinese and western medicine for the management of Chronic heart failure (CHF)'. The purpose of this study was to assess the implementation effects of multifaceted optimization management of chronic heart failure. METHODS: A total of nine physicians in optimization group from nine research sites received multifaceted intervention (a 1-day training session on how to implement the optimization programme, a written optimization programme for CHF management, supervision from daily quality coordinator, and 1-monthly monitoring and feedback of performance measure) with respect to the management of CHF, comparing to nine physicians in control group who did not receive the aforementioned multifaceted intervention and diagnosed and treated CHF patients with conventional programme (usual care). After that, a total of 256 patients with CHF were enrolled and randomly assigned to receive optimization programme [integration of usual care and traditional Chinese medicine (TCM) treatment] or conventional programme (usual care) for the treatment of CHF. The primary outcome was the change in New York Heart Association (NYHA) functional classification during 24 weeks of treatment. RESULTS: When compared with usual care, multifaceted optimization management resulted in superior improvements in NYHA functional classification at the 12-week visit (P = 0.023), the 16-week, 20-week, and 24-week visits (P < 0.001). It also demonstrated superior performance in comparison with the conventional programme with respect to readmission rate for major adverse cardiovascular events (MACEs), readmission rate for worsening heart failure, plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) level, left ventricular ejection fraction (LVEF), patient TCM syndrome scores, quality of life, and patients with heart failure with reduced ejection fraction (HFrEF) in optimization group more likely received beta-blockers and ACE inhibitors or ARBs than those in control group (P = 0.038 and P = 0.013, respectively). CONCLUSIONS: It is likely that the multifaceted optimization programme used in this study is feasible would benefit patients with CHF in NYHA functional classification, readmission for worsening heart failure, plasma NT-proBNP level, LVEF, patient TCM syndrome scores, and quality of life. Additionally, it would improve hospital personnel adherence to evidence-based performance measures for HFrEF.

Significantly suppressed thermal transport by doping In and Al atoms in gallium nitride.

Thermal transport plays a key role in the working stability of gallium nitride (GaN) based optoelectronic devices, where doping has been widely employed for practical applications. However, it remains unclear how doping affects thermal transport. In this study, based on first-principles calculations, we studied the doping effect on the thermal transport properties of GaN by substituting Ga with In/Al atoms. The thermal conductivities at 300 K along the in-plane(out-of-plane) directions of In- and Al-doped GaN are calculated to be 7.3(8.62) and 12.45(11.80) W m-1 K-1, respectively, which are more than one order of magnitude lower compared to that of GaN [242(239) W m-1 K-1]. From the analysis of phonon transport properties, we find that the low phonon group velocity and small phonon relaxation time dominate the degenerated thermal conductivity, which originated from the strong phonon anharmonicity of In/Al-doped GaN. Furthermore, by examining the crystal structure and electronic properties, the lowered thermal conductivity is revealed lying in the strong polarization of In-N and Al-N bonds, which is due to the large difference in electronegativity of In/Al and N atoms. The results achieved in this study have guiding significance to the thermal transport design of GaN-based optoelectronic devices.

Shear Performance Assessment of Sand-Coated GFRP Perforated Connectors Embedded in Concrete.

In order to evaluate the shear performance of sand-coated glass fiber-reinforced polymer (GFRP) perforated connectors (SCGPC) embedded in concrete, 8 pull-out tests were conducted. Finite element (FE) analysis considering GFRP failure and cohesion between GFRP and concrete of SCGPC were conducted for parametric analysis. Effects of surface treatment, hole's radius, embedment length, and multi holes were examined. The test and theoretical analysis revealed that the strength of SCGPC is considerably larger than GFRP Perforated Connector (GPC). The stiffness of SCGPC is determined by the adhesion between concrete and GFRP. When GFRP plate's thickness is less than the critical thickness, the embedment length plays a major role in the strength of SCGPC. When embedment length is less than the effective bond length, the shear strength of SCGPC is governed by both the adhesion and GPC's shear capacity; otherwise, the strength of SCGPC is governed by the adhesion strength. Furthermore, an empirical equation was suggested to predict the shear strength of SCGPC. The equation involves the failure mechanism of both bond and GPC and deals the strength of SCGPC into two ranges according to the embedment length. Good agreement was achieved between the strength prediction by the suggested equation and the parametric analysis result.

Chemical functionalization of the ZnO monolayer: structural and electronic properties.

Two-dimensional zinc oxide (ZnO) materials have been extensively investigated both experimentally and theoretically due to their novel properties and promising applications in optoelectronic and spintronic devices; however, how to tune the electronic property of the ZnO monolayer is still a challenge. Herein, employing the first-principles calculations, we explored the effect of chemical functionalization on the structural and electronic properties of the ZnO monolayer. The results demonstrated that the hydrogenated-, fluorinated- or Janus-functionalized ZnO monolayers were thermodynamically and mechanically stable except for the fully hydrogenated ZnO monolayer. The band gap of the ZnO monolayer could be effectively modulated by hydrogenation or fluorination, which varied from 0 to 2.948 eV, as obtained by the PBE functional, and from 0 to 5.114 eV, as obtained by the HSE06 functional. In addition, a nonmagnetic metal → nonmagnetic semiconductor transition was achieved after hydrogenation, whereas a transition from a magnetic half-metal to nonmagnetic semiconductor occurred after fluorination of the ZnO monolayer. These results demonstrate that tunability of the electronic properties of the ZnO monolayer can be realized by chemical functionalization for future nanoelectronic device applications.

Orbitally driven low thermal conductivity of monolayer gallium nitride (GaN) with planar honeycomb structure: a comparative study.

Two-dimensional (2D) materials with graphene as a representative have been intensively studied for a long time. Recently, monolayer gallium nitride (ML GaN) with honeycomb structure was successfully fabricated in experiments, generating enormous research interest for its promising applications in nano- and opto-electronics. Considering all these applications are inevitably involved with thermal transport, systematic investigation of the phonon transport properties of 2D GaN is in demand. In this paper, by solving the Boltzmann transport equation (BTE) based on first-principles calculations, we performed a comprehensive study of the phonon transport properties of ML GaN, with detailed comparison to bulk GaN, 2D graphene, silicene and ML BN with similar honeycomb structure. Considering the similar planar structure of ML GaN to graphene, it is quite intriguing to find that the thermal conductivity (κ) of ML GaN (14.93 W mK-1) is more than two orders of magnitude lower than that of graphene and is even lower than that of silicene with a buckled structure. Systematic analysis is performed based on the study of the contribution from phonon branches, comparison among the mode level phonon group velocity and lifetime, the detailed process and channels of phonon-phonon scattering, and phonon anharmonicity with potential energy well. We found that, different from graphene and ML BN, the phonon-phonon scattering selection rule in 2D GaN is slightly broken by the lowered symmetry due to the large difference in the atomic radius and mass between Ga and N atoms. Further deep insight is gained from the electronic structure. Resulting from the special sp orbital hybridization mediated by the Ga-d orbital in ML GaN, the strongly polarized Ga-N bond, localized charge density, and its inhomogeneous distribution induce large phonon anharmonicity and lead to the intrinsic low κ of ML GaN. The orbitally driven low κ of ML GaN unraveled in this work would make 2D GaN prospective for applications in energy conversion such as thermoelectrics. Our study offers fundamental understanding of phonon transport in ML GaN within the framework of BTE and further electronic structure, which will enrich the studies of nanoscale phonon transport in 2D materials and shed light on further studies.

[Non-Invasive Detection of Blood Glucose Concentration Based on Photoacoustic Spectroscopy Combined with Principle Component Regression Method].

This paper presents a photoacoustic noninvasive setup of detecting blood glucose based on the tunable pulsed laser coupled with the confocal ultrasonic transducer and the forward detection model. To validate the reliability of the setup, in the experiments, the different concentrations of glucose aqueous solution are excitated by the Q-switched 532 nm pumped Nd∶YAG pulsed laser to generate the time-resolved photoacoustic signals. And the glucose aqueous solutions are scanned by the tunable pulsed laser in the infrared waveband from 1 300 to 2 300 nm with the interval of 10nm and the photoacoustic peak-to-peak values are gotten. The difference spectral method is used to get the characteristic wavelengths of glucose, and the principle component regression algorithm is used to determine three optimal wavelengths and establish the correction mathematical model between the photoacoustic peak-to-peak values and the concentrations. The experimental results demonstrate that the mechanism of the photoacoustic signal is agreement with the cylindrical model, and the predicted results of the correction and prediction samples based on the established correction model demonstrate that the root-mean-square error of correction and prediction are all less than 10 mg·dl-1, the correlation coefficient reaches 0.993 6.

Raman Spectra of Bredigite at High Temperature and High Pressure.

Bredigite was synthesized by using the Piston-Cylinder in 1.2 GPa and 1 473 K. With external heating device and diamond anvil cell, high temperature and high pressure Raman spectra of bredigite were collected at temperatures 298, 353, 463, 543, 663, 773 and 873 K and with pressure from 1 atm up to 14.36 GPa (room temperature). The SEM image showed that the sample consisted of one crystalline phase with grain size ranging from 10～20 µm. The EPMA data suggest a chemical formula of Ca7.03(2)Mg0.98(2)Si3.94(2)O16 which was identical to the theoretical component of bredigite. The Raman spectroscopic results indicate there were 29 vibration bands of bredigite at high temperature. Some bands were merging, weakening and disappearing increasingly with the temperature, which was obvious in the range of 800~1 200 cm-1. The vibration bands of 909, 927 and 950 cm-1 disappeared at 873, 773 and 873 K, respectively. The results primarily indicated that the structure of bredigite was stable under experimental condition. In addition, isobaric mode-Grüneisen parameters and isothermal mode-Grüneisen parameters were calculated, yielding 1.47(2) and 0.45(3) as their mean values, respectively. Anharmonic coefficients were estimated based on the high temperature and high pressure Raman experiments, showing that the contributions to anharmonic-effect induced with the Si­O vibration modes were smaller than other modes.

A novel high level canonical piecewise linear model based on the simplicial partition and its application.

The piecewise linear (PWL) model has attracted more and more attention in recent research because it can handle complex nonlinearity while maintaining linearity in local regions. A large number of compact representations for PWL modeling have been introduced, such as hinging hyperplanes and its generalized version. However, the existing methods usually give rise to many and complex subregions, which is an issue known as "curse of partitions", and hampered practical applications of PWL models. In this paper, a novel high level canonical PWL model is presented to tackle the curse of partitions. In more detail, an improved simplicial partition strategy with alterable intervals is proposed to improve the model representation capability. The proposed PWL model guarantees an unchangeable topology during training and thus a limited number of subregions after training. Several numerical experiments, and a simulated chemical process, are used to demonstrate the effectiveness of the proposed model.

Simultaneous UPLC analysis of three major flavonoids in granule decoctions of Fructus aurantii-type formulae.

A simple, rapid, and sensitive liquid chromatographic method has been established for the simultaneous analysis of three compounds (narirutin, hesperidin and naringin), in granule decoctions of Fructus Aurantii-type formulae. The compounds were separated in less than 10 min using a C18 column with gradient elution using (A) acetonitrile, (B) water, and (C) acetic acid at a flow rate of 0.3 mL/min, and with a PDA detector. The method was validated for specificity, accuracy, precision, and limits of detection. Good linear regression data (r2 > 0.9980) were obtained for all the calibration plots within the ranges tested. The method is an attractive alternative for quality control and clinical monitor of granule decoctions of Fructus Aurantii-type formulae.

[Study on infrared spectra characteristics of fault particles of the sulfide deposit].

Predecessors researched emphatically the mineralization and the movement of ore body in space in fault movement. Study on particles that were formed from sulfide ore and wall rock in fault movement has been always ignored. The present paper studies the fault particles of the sulfide deposit using the FTIR spectroscopic spectra and scanning electron microscope. The results show that the samples consist of hydrous calcium sulphate, hydrous sulfur calcium carbonate, quartz, sericite, and organic matter. This shows that S(2-) in sulfide minerals is oxidized and transformed into S(6+) in fault movement. Sulfide minerals formed hydrous calcium sulphate and sulfide minerals and carbonate minerals formed hydrous sulfur calcium carbonate. Hydrous sulfur calcium carbonate is a mineral newly discovered in our study. The research results not only can be applied in the prospect and the exploration of this ore deposit type but also is important for ore utilization. In addition, this paper discussed identification characteristics of infrared spectrum of hydrous calcium sulphate and hydrous sulfur calcium carbonate and pointed out that infrared spectral analysis is suitable for analysis of hydrous calcium sulphate and hydrous sulfur calcium carbonate particles formed in fault movement.

On-line estimation of concentration parameters in fermentation processes.

It has long been thought that bioprocess, with their inherent measurement difficulties and complex dynamics, posed almost insurmountable problems to engineers. A novel software sensor is proposed to make more effective use of those measurements that are already available, which enable improvement in fermentation process control. The proposed method is based on mixtures of Gaussian processes (GP) with expectation maximization (EM) algorithm employed for parameter estimation of mixture of models. The mixture model can alleviate computational complexity of GP and also accord with changes of operating condition in fermentation processes, i.e., it would certainly be able to examine what types of process-knowledge would be most relevant for local models' specific operating points of the process and then combine them into a global one. Demonstrated by on-line estimate of yeast concentration in fermentation industry as an example, it is shown that soft sensor based state estimation is a powerful technique for both enhancing automatic control performance of biological systems and implementing on-line monitoring and optimization.