92 research outputs found
Study on genetic engineering of Acremonium chrysogenum, the cephalosporin C producer
AbstractAcremonium chrysogenum is an important filamentous fungus which produces cephalosporin C in industry. This review summarized the study on genetic engineering of Acremonium chrysogenum, including biosynthesis and regulation for fermentation of cephalosporin C, molecular techniques, molecular breeding and transcriptomics of Acremonium chrysogenum. We believe with all the techniques available and full genomic sequence, the industrial strain of Acremonium chrysogenum can be genetically modified to better serve the pharmaceutical industry
Multi-objective optimization of active suspension predictive control based on improved PSO algorithm
The design and control for active suspension is of great significance for improving the vehicle performance, which requires considering simultaneously three indexes including ride comfort, packaging requirements and road adaptability. To find optimal suspension parameters and provide a better tradeoff among these three performances, this paper presents a novel multi-objective particle swarm optimization (MPSO) algorithm for the suspension design. The mathematical model of quarter-car suspension is first established, and it integrates the hydraulic servo actuator model. Further a model predictive controller is designed for the suspension by using the control strategies of multi-step forecast, rolling optimization and online correction of predictive control theory. To use vehicle body acceleration, tire deflection and suspension stroke to represent the above three performances respectively, a multi-objective optimization model is constructed to optimize the suspension stiffness and damping coefficients. The MPSO algorithm includes extra crossover operations, which are applied to find the Pareto optimal set. The rule to update the Pareto pool is that the newly selected solutions must have two better performances compared with at least one already existed in the Pareto pool, which ensures that each solution is non-dominated within the Pareto set. Finally, numerical simulations on a vehicle-type example are done under B-level road surface excitation. Simulation results show that the optimized suspension can effectively reduce the vertical vibrations and improve the road adaptability. The model predictive controller also shows high robustness with vehicle under null load, half load and full load. Therefore, the proposed MPSO algorithm provides a new valuable reference for the multi-objective optimization of active suspension control
Measurement of the vertical atmospheric density profile from the X-ray Earth occultation of the Crab Nebula with Insight-HXMT
In this paper, the X-ray Earth occultation (XEO) of the Crab Nebula is
investigated by using the Hard X-ray Modulation Telescope (Insight-HXMT). The
pointing observation data on the 30th September, 2018 recorded by the Low
Energy X-ray telescope (LE) of Insight-HXMT are selected and analyzed. The
extinction lightcurves and spectra during the X-ray Earth occultation process
are extracted. A forward model for the XEO lightcurve is established and the
theoretical observational signal for lightcurve is predicted. The atmospheric
density model is built with a scale factor to the commonly used MSIS density
profile within a certain altitude range. A Bayesian data analysis method is
developed for the XEO lightcurve modeling and the atmospheric density
retrieval. The posterior probability distribution of the model parameters is
derived through the Markov Chain Monte Carlo (MCMC) algorithm with the
NRLMSISE-00 model and the NRLMSIS 2.0 model as basis functions and the best-fit
density profiles are retrieved respectively. It is found that in the altitude
range of 105--200 km, the retrieved density profile is 88.8% of the density of
NRLMSISE-00 and 109.7% of the density of NRLMSIS 2.0 by fitting the lightcurve
in the energy range of 1.0--2.5 keV based on XEOS method. In the altitude range
of 95--125 km, the retrieved density profile is 81.0% of the density of
NRLMSISE-00 and 92.3% of the density of NRLMSIS 2.0 by fitting the lightcurve
in the energy range of 2.5--6.0 keV based on XEOS method. In the altitude range
of 85--110 km, the retrieved density profile is 87.7% of the density of
NRLMSISE-00 and 101.4% of the density of NRLMSIS 2.0 by fitting the lightcurve
in the energy range of 6.0--10.0 keV based on XEOS method. This study
demonstrates that the XEOS from the X-ray astronomical satellite Insight-HXMT
can provide an approach for the study of the upper atmosphere.Comment: 31 pages, 15 figures, 5 tables, accepted for publication in
Atmospheric Measurement Technique
CHES: a space-borne astrometric mission for the detection of habitable planets of the nearby solar-type stars
The Closeby Habitable Exoplanet Survey (CHES) mission is proposed to discover
habitable-zone Earth-like planets of the nearby solar-type stars ( away from our solar system) via micro-arcsecond relative
astrometry. The major scientific objectives of CHES are: to search for Earth
Twins or terrestrial planets in habitable zones orbiting 100 FGK nearby stars;
further to conduct a comprehensive survey and extensively characterize the
nearby planetary systems. The primary payload is a high-quality,
low-distortion, high-stability telescope. The optical subsystem is a coaxial
three-mirror anastigmat (TMA) with a -aperture, field of view and
working waveband. The camera focal plane is composed of 81 MOSAIC scientific
CMOS detectors each with pixels. The
heterodyne laser interferometric calibration technology is employed to ensure
micro-arcsecond level (1 as) relative astrometry precision to meet the
requirements for detection of Earth-like planets. CHES satellite operates at
the Sun-Earth L2 point and observes the entire target stars for 5 years. CHES
will offer the first direct measurements of true masses and inclinations of
Earth Twins and super-Earths orbiting our neighbor stars based on
micro-arcsecond astrometry from space. This will definitely enhance our
understanding of the formation of diverse nearby planetary systems and the
emergence of other worlds for solar-type stars, and finally to reflect the
evolution of our own solar system.Comment: 39 pages, 37 figures, Invited Review, accepted to Research in
Astronomy and Astrophysic
Buddleja jinsixiaensis (Scrophulariaceae), a new species from Shaanxi, China
www.mapress.com/phytotaxa
Deformation Monitoring of Geomechanical Model Test and Its Application in Overall Stability Analysis of a High Arch Dam
Geomechanical model testing is an important method for studying the overall stability of high arch dams. The main task of a geomechanical model test is deformation monitoring. Currently, many types of deformation instruments are used for deformation monitoring of dam models, which provide valuable information on the deformation characteristics of the prototype dams. However, further investigation is required for assessing the overall stability of high arch dams through analyzing deformation monitoring data. First, a relationship for assessing the stability of dams is established based on the comprehensive model test method. Second, a stability evaluation system is presented based on the deformation monitoring data, together with the relationships between the deformation and overloading coefficient. Finally, the comprehensive model test method is applied to study the overall stability of the Jinping-I high arch dam. A three-dimensional destructive test of the geomechanical model dam is conducted under reinforced foundation conditions. The deformation characteristics and failure mechanisms of the dam abutments and foundation were investigated. The test results indicate that the stability safety factors of the dam abutments and foundation range from 5.2 to 6.0. These research results provide an important scientific insight into the design, construction, and operation stages of this project
Energy Savings Potential of Semitransparent Photovoltaic Skylights under Different Climate Conditions in China
Due to the limited available envelope area, height-constrained buildings integrated with photovoltaics require that more attention be given to the effective use of roofs. Thus, it is crucial to study the energy savings potential of previously neglected semitransparent photovoltaic (STPV) skylights. In this paper, the net energy consumption (NEC) of a room with STPV skylights and energy superiority compared to a reference window were investigated. The energy savings potential was then calculated for five representative cases located in different climate zones and daylight zones, according to the mandatory codes to be implemented in April 2022. Through a global sensitivity analysis, the extent to which each component of the NEC affects the energy savings potential was evaluated. The results indicate that STPV skylights exhibit promising energy savings potential in China. In temperate zones with excellent daylight conditions, an energy savings potential of 0.21 to 2.55 can be achieved, while the maximum energy savings rate (ESR) for the other four cases ranges from 0.52 to 1.1. The effect of electricity power generation (EPG) on the energy savings potential is most pronounced, except for that of STPV skylights on sloped roofs in hot summer and cold winter zones with poor daylight
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