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BL Lacertae: Hard Optical Spectrum and GeV γ-ray Emission

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Chinese Journal of Astronomy and Astrophysics 2004年第3期4卷 231-246页

作者： shan-jieqian xi-zhenzhang T.P.Krichbaum NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012 Max-Planck-InstitutfürRadioastronomie AufdemHügel6953121BonnGermany

The spectral energy distribution (SED) of the γ-ray flare observed inJuly 1997 in BL Lacertae is re-considered. It is pointed out that the optical observa-tions made by Webb et al. showed the associated optical flare has a hard spectrum(the average spectral index αopt～ 0.48, F_v∝v^(-α)), and the ASCA observationsmade by Tanihata et al. showed very steep spectra in the soft X-ray band (0.7-1.5 keV) (α_x～3-4). We find that the flux densities and spectral indices in both theoptical and soft X-ray bands are closely consistent with a ‘canonical' synchrotronspectrum emitted by relativistic electrons of a power-law energy distribution witha high energy cutoff, and thus the peak of the SED of the synchrotron radiation (inrepresentation of vF_v) is located in the EUV -- soft X-ray bands. Therefore, theGeV γ-ray emission observed in the July 1997 outburst may be mainly due to thesynchrotron self-Compton (SSC) process, contrasting with the current explanationsin terms of external radiation Compton (ERC) process, in which the seed photonsare mostly taken to be the UV emission from the clouds of the broad emission lineregion. We argue that the hard optical spectra observed during the γ-ray outburstmay be an important signature for the acceleration of high energy electrons (γ_e～10~4)in the γ-ray emitting region.

关键词： galaxies:compact gamma rays:observations quasars:individual:BL Lacertae

Periodic Variations of the Jet Flow Lorentz Factor in 3C 273

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Chinese Journal of Astronomy and Astrophysics 2001年第3期1卷 236-244页

作者： shan－jieqian xi－zhenzhang 等 Max－Planck－InstitutfuerRadioastronomie AufdemHuegel69D－53121BonnGermany BeijingAstronomicalObservat

C 273 has been observed with VLBI for more than 30 years. The entire data have shown that the position angle of the superluminal knots ejected from the core varies periodically with a period of ~15 years. Moreover, their apparent velocity observed during the period 1963 -- 1997 has systematically decreased by a factor of 2. These remarkable properties are explained in terms of a precessing jet model, in which the ejection Lorentz factor of the superluminal knots has been decreasing during the last thirty years and has superposed on it a short-term (~5 year) oscillation. The periodic variations derived by the model-fitting are compared with the variations in the optical flux density. Binary black hole models are briefly discussed to show possible relations of the observed periods to the periods involved in a binary system (orbital motion, spin of black hole, accretion-disk rotation and Newtonian-driven precession etc.).

关键词： Galaxies: jets - quasars: individual: 3C273 - Galaxies: nuclei - Radio Continuum: galaxies - Radiation mechanisms: nonthermal

The gut microbiome promotes locomotion of Drosophila larvae via octopamine signaling

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Insect Science 2025年第1期32卷 277-289页

作者： Juncheng Hu Ran Bi Yuxuan Luo Kaihong Wu shan Jin Zhihua Liu Yicong Jia Chuan-xi Mao State Key Laboratory of Biocatalysis and Enzyme Engineering School of Life SciencesHubei UniversityWuhanChina

The gut microbiome is a key partner of animals,influencing various aspects of their physiology and *** the diverse behaviors regulated by the gut microbiome,locomotion is vital for survival and reproduction,although the underlying mechanisms remain ***,we reveal that the gut microbiome modulates the locomotor behavior of Drosophila larvae via a specific neuronal type in the *** crawling speed of germ-free(GF)larvae was significantly reduced compared to the conventionally reared larvae,while feeding and excretion behaviors were *** with Acetobacter and Lactobacillus can fully and partially rescue the locomotor defects in GF larvae,respectively,probably due to the highest abundance of Acetobacter as a symbiotic bacterium in the larval gut,followed by ***,the gut microbiome promoted larval locomotion,not by nutrition,but rather by enhancing the brain levels of tyrosine decarboxylase 2(Tdc2),which is an enzyme that synthesizes octopamine(OA).Overexpression of Tdc2 rescued locomotion ability in GF *** findings together demonstrate that the gut microbiome specifically modulates larval locomotor behavior through the OA signaling pathway,revealing a new mechanism underlying larval locomotion regulated by the gut microbiome.

关键词： Drosophila melanogaster larval locomotion microbiome octopamine signaling

Interstellar Refractive Scintillation and Intraday Polarization Angle Swings

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Chinese Journal of Astronomy and Astrophysics 2005年第1期5卷 27-40页

作者： shan-jieqian xi-zhenzhang A.Kraus NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012 Max-Planck-InstitutfiirRadioastronomie aufdemHiigel6953121BonnGermany

Intraday polarization angle swings of ～180° observed in two sources (QSO0917+624 and QSO 1150+812) are discussed in the framework of refractive interstellar scintillationby a continuous interstellar medium. Model-fits to the I-, Q- and U- light curves were made for bothsources. It is shown that for the case of 0917+624 both the intraday intensity variations and thepolarization angle swing of ～180° could be explained consistently in terms of a four-componentmodel, which comprises one steady and two scintillating polarized components and one furthernon-polarized scintillating component. The polarization angle swing of ～180° observed in 1150+812,which occurred when the polarized flux density was almost constant, could not be explained in termsof refractive scintillation by a continuous medium and might be due to other mechanisms (e.g.,scintillation by interstellar clouds).

关键词： radio continuum galaxies polarization intraday variability scattering refractive scintillation quasars individual: QSO 0917+624 and 1150+812

Spectral Reversal and Stratification of the Jet in 3C 273

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Chinese Journal of Astronomy and Astrophysics 2001年第4期1卷 296-304页

作者： shan－jieqian xi－ZhengZhang 等 Max－Planck－InstitutfuerRadioastronomie AufdemHuegel69D－53121BonnGermany NationalAstronomicalObserva

Quasi-simultaneous VLBI observations at 15-86 GHz have shown that in the classical superluminal radio source 3C273, the spectral index a (Sv ∝ vα) has a systematic variation along the jet. For epoch 1995.15, a spectral reversal was observed at core distance - 1.5 mas, where the superluminal knot C12 located. Similarly, for epoch 1997.18, two spectral reversals were observed at core distances of -1.8 mas and -4.2 mas, where superluminal knots C11 and C14 werel respectively. These spectral reversals are associated with local maxim of the jet width. We suggest that this phenomenon may be related to a stratification of the jet structure, i.e., its physical parameters (flow velocity, Doppler factor, electron density and energy, magnetic field strength, etc.) are substantially dependent on the distance from the jet axis. These properties may be naturally formed through gasdynamic processes when the jet expands into a lower pressure ambient medium.

关键词： galaxies: active - galaxies: compact - quasars: individual: 3C 273- galaxies: jets - radio continuum: galaxies - radiation mechanisms: non-thermal

考虑两个短路点的配电网不对称短路分析与通用计算方法

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电网技术 2025年第2期49卷 807-814页

作者：杨杉喻希张晓彤罗朝旭湖南工业大学电气与信息工程学院湖南省株洲市412007 西安交通大学电力设备电气绝缘国家重点实验室陕西省西安市710049

针对换流器型分布式电源(inverter based distributed generation,IBDG)广泛应用的新型配电网,解决目前不对称短路电流计算方法主要以计算单个短路点为主,且新增短路点后将面临计算通用性问题,该文研究一种新颖的配电网不对称短路电流... 详细信息

针对换流器型分布式电源(inverter based distributed generation,IBDG)广泛应用的新型配电网,解决目前不对称短路电流计算方法主要以计算单个短路点为主,且新增短路点后将面临计算通用性问题,该文研究一种新颖的配电网不对称短路电流计算方法。该方法将2个短路点的情况考虑在内,进一步对不对称短路进行分类,并形成结合IBDG短路等效电路的配电网不对称短路通用等效电路。接着分别建立1个和2个短路点情况下的计算方程和边界方程,提出一种能计及2个不对称短路点的,对配电网普遍适用的不对称短路电流通用计算方法。最后,在一个配电网算例中对所提计算方法进行验证,结果验证了所提方法的正确性和有效性。

关键词：新型配电网不对称短路电流换流器型分布式电源通用计算 2个短路点

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Design and implementation of reconfigurable CNN accelerator architecture based on elastic storage

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The Journal of China Universities of Posts and Telecommunications 2025年

作者： shan Rui Xu Jianing Huo Ziqing College of Electronic Engineering， xi'an University of Post and Telecommunications

With the rapid iteration of neural network algorithms， higher requirements was placed on the computational performance and memory access bandwidth of neural network accelerators. Simply increasing bandwidth cannot improve energy efficiency， so improving data reuse rate is a hot research topic. From the perspective of supporting data reuse， a reconfigurable convolutional neural networks (CNN) accelerator based on elastic storage was designed in this paper. By supporting elastic memory access and flexible data flow， it reduces data movement between the processor and memory， eases the bandwidth pressure and enhances CNN acceleration performance. The experimental results indicate that conducting 1×1 convolution and 3×3 convolution when performing convolution calculations， the execution speed increased by 25.00% and 61.61%， respectively. The 3×3 maximum pooling speed was increased by 76.04%.

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Radio Observations at 232 MHz and Multifrequency Spectral Studies of the SNR HB21

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Chinese Journal of Astronomy and Astrophysics 2001年第5期1卷 443-452页

作者： xi－zhenzhang L.A.Higgs 等 NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012 DominionRadioAstrophysicalOb

Radio observational results at 232 MHz and multifrequency studies of the supernova remnant (SNR) HB21 are presented. Its integrated flux density at 232 MHz is about 390 + 30 Jy. Both the integrated spectral index and the spatial variations of spectral index of the remnant were calculated by combining the new map at 232 MHz with previously published maps made at 408, 1420, 2695, and 4750 MHz. The SNR has an integrated spectral index of about a = -0.43 (Sv Vα) between 232 and 4750 MHz. In general the spectral index varies from -0.5 in southeast and west regions of the remnant to -0.3 in the central region and near the northwest edge. The new data of 232 MHz reveal that there is interaction between the remnant and the surrounding gas along the east edge of the remnant which causes the spectrum flattening at low frequency, while the very good agreement between the structure of X-ray emission and the central flat spectrum area suggests that the existence of thermal emission is the reason of spectrum flattening in the area.

关键词： ISM: supernova remnants - ISM: structure

On the Spectral Index-Flux Density Relation for Large Samples of Radio Sources

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Chinese Journal of Astronomy and Astrophysics 2003年第4期3卷 347-358页

作者： xi-zhenzhang W.Reich P.Reich R.Wielebinski NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012 Max-Planck-InstitutfuerRadioastronomie AufdemHuegel69D-53121BonnGermany

We present new statistical results on the spectral index-flux density relation for large samples of radio sources using archival data of the most sensitive surveys, such as 6C, Miyun, WENSS, B3, NVSS, GB87. Instrumental selection effects and the completeness of the catalogs are discussed. Based on the spectral indices calculated for about 200 000 sources from the WENSS (327 MHz) and NVSS (1.4 GHz) catalogs, we obtained (1) The median spectral index increases from amed --0.9 toαmed --0.8 (Svαvα), while S327 flux densities decrease from 0.1 Jy down to 25mJy. The median spectral indices nearly show no variation within the error bars when the flux density is larger than 0.1 Jy. (2) A dependence of the fraction of ultra-steep spectrum sources (USS, -1.5 <α<-1.0), steep spectrum sources (SSS, -1.0 <α< -0.5) and flat spectrum sources (FSS, -0.5≤α≤0.0) is partly responsible for the spectral flattening. Another contribution to the spectral flattening comes from the variation of αmed of steep spectrum sources (α<-0.5) themselves which increases with decreasing flux densities. (3) The spectral flattening for faint sources (down to S327- 20mJy) with steep spectra (α< -0.5) suggests that amed is correlated with luminosity rather than redshift according to the Condon' model. (4) A strong spectral selection effect occurs when spectral indices are calculated from samples with a large frequency separation.

关键词： radio continuum: general-methods: statistical - cosmology