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Unification of General Relativity with Quantum Field Theory

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Chinese Physics Letters 2011年第11期28卷 24-27页

作者： ni jun Department of Physics Tsinghua UniversityBeijing 100084

In the frame of quantum field theory,instead of using the action principle,we deduce the Einstein equation from purely the general covariant principle and the homogeneity of *** Einstein equation is shown to be the gauge equation to guarantee the local symmetry of spacetime *** is an apparent force due to the curvature of spacetime resulted from the conservation of *** the action of quantum field theory,only electroweak-strong interactions should be considered with the curved spacetime metric determined by the Einstein equation.

关键词： equation Einstein equation

Solutions without a maximum mass limit of the general relativistic field equations for neutron stars

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Science China(Physics,Mechanics & Astronomy) 2011年第7期54卷 1304-1308页

作者： ni jun Department of Physics Tsinghua University Beijing 100084 China

We have investigated the general relativistic field equations for neutron *** find that there are solutions for the equilibriummass distribution without a maximum mass *** solutions correspond to stars with a void inside their *** thesesolutions,the mass density and pressure increase first from zero at the inner radius to a peak and then decrease to zero at the *** the change of the void boundary,the mass and particle number of the star can approach *** stars withlarge masses can remain stable and do not collapse into black holes.

关键词： neutron stars Tolman-Oppenheimer-Volkoff equations general relativistic field equations

RNF213 in moyamoya disease: Genotype-phenotype association and the underlying mechanism

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中华医学杂志(英文版) 2024年第21期137卷 2552页

作者： Fang Jianxun Yang Xinzhuang ni jun Department of Neurology Peking Union Medical College Hospital Peking Union Medical College and Chinese Academy of Medical Sciences Beijing China Medical Research Center Peking Union Medical College Hospital Peking Union Medical College and Chinese Academy of Medical Sciences Beijing China

Moyamoya disease (MMD) is a cerebrovascular disorder characterized by a steno-occlusive internal carotid artery and compensatory vascular network formation. Although the precise pathogenic mechanism remains elusive, genetic association studies have identifiedRNF213 as the principal susceptibility gene for MMD, with the single nucleotide polymorphism p.R4810K recognized as the founder variant predominantly in the Asian populations. Distinct genotype-phenotype correlations are observable inRNF213-related MMD. The clinical manifestations linked to p.R4810K bear commonalities within Asian cohort, including familial predisposition, earlier age of onset, ischemic episodes, and involvement of the posterior cerebral artery (PCA). However, despite these shared phenotypic characteristics, there is significant heterogeneity inRNF213-related MMD presentations. This diversity manifests as variations across ethnic groups, inconsistent clinical symptoms and prognosis, and occurrence of other vasculopathies involvingRNF213. This heterogeneity, in conjunction with the observed low disease penetrance ofRNF213 mutations, suggests that the presence of these mutations may not be sufficient to cause MMD, underscoring the potential influence of other genetic or environmental factors. Although the current research might not have fully identified these additional contributors, experimental evidence points toward the involvement ofRNF213 in angiogenesis, lipid metabolism, and the immune response. Future research is required to unveil the molecular mechanisms and identify the factors that synergize withRNF213 in the pathogenesis of MMD.

关键词： Moyamoya disease RNF213 Polymorphism p.R4810K

Effects of Rattling Behavior of K and Cd Atoms along Different Directions in Anisotropic KCdAs on Lattice Thermal Transport and Thermoelectric Properties

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Energy & Environmental Materials 2024年第6期7卷 388-398页

作者： Yue Wang Yinchang Zhao jun ni Zhenhong Dai Department of Physics Yantai UniversityYantai 264005China State Key Laboratory of Low-Dimensional Quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China

We employ advanced first principles methodology,merging self-consistent phonon theory and the Boltzmann transport equation,to comprehensively explore the thermal transport and thermoelectric properties of ***,the study accounts for the impact of quartic anharmonicity on phonon group velocities in the pursuit of lattice thermal conductivity and investigates 3ph and 4ph scattering processes on phonon *** various methodologies,including examining atomic vibrational modes and analyzing 3ph and 4ph scattering processes,the article unveils microphysical mechanisms contributing to the lowκL within *** features include significant anisotropy in Cd atoms,pronounced anharmonicity in K atoms,and relative vibrations in non-equivalent As atomic *** atoms,situated between As layers,exhibit rattling modes and strong lattice anharmonicity,contributing to the observed lowκ*** flat bands near the valence band maximum translate into high PF,aligning with ultralowκL for exceptional thermoelectric *** optimal temperature and carrier concentration doping,outstanding ZT values are achieved:4.25(a(b)-axis,p-type,3×10^(19)cm^(−3),500 K),0.90(c-axis,p-type,5×10^(20)cm^(−3),700 K),1.61(a(b)-axis,n-type,2×10^(18)cm^(−3),700 K),and 3.06(c-axis,n-type,9×10^(17)cm^(−3),700 K).

关键词： anharmonic lattice dynamics electron transport characteristics first principles calculation lattice thermal transport octahedron thermoelectric properties

Constant Speed Control of Four-stroke Micro Internal Combustion Swing Engine

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Chinese Journal of Mechanical Engineering 2015年第5期28卷 971-982页

作者： GAO Dedong LEI Yong ZHU Honghai ni jun State Key Laboratory of Fluid Power Transmission and Control Zhejiang University School of Mechanical Engineering Qinghai University Department of Mechanical Engineering University of Michigan

The increasing demands on safety, emission and fuel consumption require more accurate control models of micro internal combustion swing engine （MICSE）. The objective of this paper is to investigate the constant speed control models of four-stroke MICSE The operation principle of the four-stroke MICSE is presented based on the description of MICSE prototype. A two-level Petri net based hybrid mode/ is proposed to mode/ the four-stroke MICSE engine cycle. The Petri net subsystem at the upper level controls and synchronizes the four Petri net subsystems at the lower level. The continuous sub-models, including breathing dynamics of intake manifold, thermodynamics of the chamber and dynamics of the torque generation, are investigated and integrated with the discrete model in MATLAB Simulink. Through the comparison of experimental data and simulated DC voltage output, it is demonstrated that the hybrid model is valid for the four-stroke MICSE system. A nonlinear model is obtained from the cycle average data via the regression method, and it is linearized around a given nominal equilibrium point for the controller design. The feedback controller of the spark timing and valve duration timing is designed with a sequential loop closing design approach. The simulation of the sequential loop closure control design applied to the hybrid model is implemented in MATLAB. The simulation results show that the system is able to reach its desired operating point within 0.2 s, and the designed controller shows good MICSE engine performance with a constant speed. This paper presents the constant speed control models of four-stroke MICSE and carries out the simulation tests, the models and the simulation results can be used for further study on the precision control of four-stroke MICSE.

关键词： MICSE constant speed control hybrid model spark timing valve duration

Oscillatory Phase Behaviour as a Function of Film Thickness due to Confinement in fcc (100) A_(3)B Alloy Thin Films

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Chinese Physics Letters 2001年第11期18卷 1504-1506页

作者： ni jun LIU Hua GU Bing-Lin Department of Physics Tsinghua UniversityBeijing 100084

The order-disorder phase transitions in fcc thin films are investigated by using the mean field method. The result shows that there is a significant difference in the phase transitions and surface segregation between the films of even-number and odd-number layers. There are various types of phase transitions involving several ordered phases with spatial variation for the film of even-number layers, while there is only one phase transition for the film of odd-number layers.

关键词： transitions phase film

Adaptive guidance law design based on characteristic model for reentry vehicles

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Science in China(Series F) 2008年第12期51卷 2005-2021页

作者： YANG junChun HU jun ni MaoLin National Laboratory of Space Intelligent Control Beijing Institute of Control Engineering Beijing 100080 China

In this paper an adaptive guidance law based on the characteristic model is designed to track a reference drag acceleration for reentry vehicles like the Shuttle. The characteristic modeling method of linear constant systems is extended for single-input and single-output （SlSO） linear time-varying systems so that the characteristic model can be established for reentry vehicles. A new nonlinear differential golden-section adaptive control law is presented. When the coefficients belong to a bounded closed convex set and their rate of change meets some constraints, the uniformly asymptotic stability of the nonlinear differential golden-section adaptive control system is proved. The tracking control law, the nonlinear differential golden-section control law, and the revised logical integral control law are integrated to design an adaptive guidance law based on the characteristic model. This guidance law overcomes the disadvantage of the feedback linearization method which needs the precise model. Simulation results show that the proposed method has better performance of tracking the reference drag acceleration than the feedback linearizaUon one.

关键词： characteristic model nonlinear differential golden-section control law logical integral control law adaptiveguidance asymptotic stability reentry vehicles

Analysis of Causes Leading to High Bromine Number of C_8^+ Aromatics and Short Clay Service Life and Countermeasures Proposed

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China Petroleum Processing & Petrochemical Technology 2007年第2期9卷 23-28页

作者： Li Yousong ni Xiaoliang Yah jun SINOPEC Zhenhai Refining and Chemical Branch Company Ningbo 315207

After comparing the operating status of other catalytic reforming units and evaluation of the side-cut stream tests, the refinery investigated the influence of the feedstock property, clay types, and operating regime of the clay tower and catalytic reforming unit on the service life of the clay. Test results had revealed that the low potential aromatic content of the reformer feed and high operating severity were the critical causes leading to high bromine number of the C8^＋ aromatics feed for the PX unit and the shortened service life of clay. This article also puts forward the corresponding remedial measures.

关键词： C8^+ aromatic feedstock bromine number clay catalytic reforming unit

Nonlinear Magnetic Response of Superconducting Flux Arrays with Random Pinning

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Chinese Physics Letters 1997年第3期14卷 217-220页

作者： ni jun GU Bing-lin Shuichi Iwata Department of Physics Tsinghua UniversityBeijing 100084 Research into Artifacts Center for EngineeringThe University of TokyoKamaba 4-6-1Meguro-kuTokyo 153Japan

The static nonlinear magnetic response of randomly pinned flux-line lattice in a type-Ⅱ super-conductor has been investigated using variational replica-symmetry-broken method.A peak in the curve of susceptibility as a function of external magnetic field is *** the magnetic field is low,there is a softening in the susceptibility as an effect of pinning potential with nonzero correlation *** some critical magnetic field,the softening changes into *** reaching the maximum in hardening,the susceptibility decreases to its value of piire states with the increase of magnetic field.

关键词： method. field. susceptibility