The Influence of the Sun and Moon on the Observation of Very High Energy Gamma-ray Sources Using EAS Arrays

With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.

Inelastic Scattering of Dark Matter with Heavy Cosmic Rays

We investigate the impact of inelastic collisions between dark matter(DM)and heavy cosmic ray(CR)nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections,allowing us to assess how these collisions affect the spectra of CR boron and carbon.We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species.In a specific example with a coupling strength of b_(χ)=0.1 and a DM mass of m_(χ)=0.1 GeV,considering a simplified scenario where DM interacts exclusively with oxygen,a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed.Particularly,the peak within the spectrum,spanning from 0.1 to 10 GeV,experiences an enhancement of approximately 1.5 times.However,in a more realistic scenario where DM particles interact with all CRs,this peak can be amplified to twice its original value.Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio,we estimate a 95%upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass.Our findings reveal that at m_(χ)?2 MeV,the effective inelastic cross-section between DM and protons must be less than O(10^(-32))cm^(2).

Study on the Performance of the GRANDProto300 Particle Detector Array by Simulation

The Giant Radio Array for Neutrino Detection(GRAND)is a proposed large-scale observatory designed to detect cosmic rays,gamma-rays,and neutrinos with energies exceeding 100 Pe V.The GRANDProto300 experiment is proposed as the early stage of the GRAND project,consisting of a hybrid array of radio antennas and scintillator detectors.The latter,as a mature and traditional detector,is used to cross-check the nature of the candidate events selected from radio observations.In this study,we developed a simulation software called G4GRANDProto300,based on the Geant4 software package,to optimize the spacing of the scintillator detector array and to investigate its effective area.The analysis was conducted at various zenith angles under different detector spacings,including 300,500,600,700,and 900 m.Our results indicate that,for large zenith angles used to search for cosmic-ray in the GRAND project,the optimized effective area is with a detector spacing of 500 m.The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.

中山大学物理学学科百年发展史(1924—2024)

中山大学物理学学科与中山大学同龄,至今已历一个世纪,期间涌现出一大批杰出的教育家、科学家,以及周誉侃、高兆兰、李华钟、郭硕鸿、莫党、张纯祥、张进修、余振新、罗蔚茵等一批物理学家及教学名师。经历了民国初期的以科学化人为核心的创系阶段、高校内迁的艰辛跋涉阶段、院系调整后面向国家专业人才培养分立学科发展阶段,建立了相对完整的物理学学科布局。拥有超快速激光光谱学国家重点实验室、国家首批物理学博士点等。21世纪以来,物理学发展壮大,孵化出中法核工程与技术学院、微电子学院、材料科学与工程学院等。2015年后,逐步形成物理学科三校区同质办学错位发展布局。中山大学物理学和光电信息科学与工程专业均为国家一流专业,成为国家重要的拔尖创新人才培养基地。中山大学天琴中心、广东省基础学科研究中心等专业研究机构和高能直接几何非弹性中子散射飞行时间谱仪等大型设备共同支撑中山大学物理学科在理论物理、凝聚态物理、光学、等离子体物理、天文学等学科方向为我国科学事业发展贡献力量。

中山大学化学学科百年发展史(1924—2024)

中山大学化学学科由原中山大学化学学科和岭南大学化学学科合并而成,已走过百年征程。在陈宗南、富伦、龙康侯、林尚安、曾汉民、计亮年、陈小明等院系负责人和科学家的努力下,克服艰难险阻,学科建设取得显著成绩,高分子化学与物理、无机化学成为国家重点学科,化学成为一级学科博士学位授权点,培养出梁栋材、黄维垣、江元生、苏锵、姜中宏、黄翠芬院士等一批学界翘楚。化学学科在建设与发展上,始终以国家需求为导向,搭平台,聚人才,重交叉,促进学产研用结合,每个发展阶段都有大批科研成果走向应用,为国家进步和社会发展作出了重要贡献。2017年,化学成为“双一流”建设学科,进入学科建设国家梯队。

Recent progress of solar physics research in China

Owing to the largely improved facilities and working conditions, solar physics research in China has recently shown marked development. This paper reports on the recent progress of solar physics research in China's Mainland, mainly focusing on several hot issues, including instrumentations, magnetic field observations and research, solar flares, filaments and their eruptions, coronal mass ejections and related processes, as well as active regions and the corona, small-scale phenomena, solar activity and its predictions. A vision of the future is also described.

Secret Codes of Scale Distribution of Different Matter Stratums from Planck Scale to the Sun-Scale, Proof of Anthropic Principle and Different Stratum Sciences

This paper discovers the secret codes of the scale distribution from Planck scale to the Sun-scale by using Planck length derived from three fundamental physics constants, i.e., gravitation constant G, light speed c and Plank constant, and starting from the global consideration of treating the whole universe as a well unified entity in all scales. According to this symmetric scale distribution law of different scale regions: (a) we naturally give a possibility overcoming the difficulty of the desert effect between the grand unification scale and electroweak unification scale relevant to quarks and leptons, and it is really surprising to discover that the scales of quarks & electrons, protons & neutrons and atoms again all sequentially locate at the predicted points of the scale space;(b) we closely uncover the scale of the cells, which is the basic unit constructing the human bodies;(c) even the average height of human being is naturally deduced;(d) further, it is very surprising that the scales of the celestial bodies tightly related to us human beings, including the earth and the sun, also exactly fall at the predicted points in scale space in order. Therefore, all these scales with 105n cm order (n = 0, 1, 2, …, 9) above just give a proof of very key anthropic principle for whole mankind (which just makes the anthropic principle be reduced as anthropic theorem), i.e., matter stratums (a) and (b) are inorganic and organic bases of constructing human being respectively;matter stratum (c) is just human being;matter stratums (d) are the living environments of human being. Namely, everything is for or relevant to the existence of human being. Consequently, the experimentally checked scale ladder of well-known matter levels just coincides with the scale ladder predicted by the deduced distribution law. From Planck scale to the Sun scale, people may systematically build up the exact scientific theories corresponding ten matter stratums, may set up the different sciences among the different cross stratums, further, can systematically understand all the different sciences and their relations in the deepest way up to now.

基于暗物质粒子探测卫星的宇宙线直接探测研究

高能宇宙线的起源、加速和传播是重大的前沿科学问题,回答该问题需要对宇宙线的能谱、各向异性以及各类高能天体电磁辐射进行精确观测.通过空间粒子探测器对宇宙线各成分能谱的直接测量是研究宇宙线物理问题的重要手段.中国于2015年底发射并持续运行至今的暗物质粒子探测卫星以其大接受度、高能量分辨率等特点,在宇宙线直接探测方面取得了系列重要成果,揭示出质子、氦核、硼碳和硼氧比例等宇宙线能谱的新结构,为理解宇宙线起源等科学问题提供了新的依据.介绍了暗物质粒子探测卫星的仪器设置、运行状况、科学成果及其物理意义.

勃莱特为何选择回到杰克身边?——《太阳照常升起》中的身体创伤及其隐喻

受主客观因素的影响,勃莱特在离开罗梅罗后,本不应该选择再回到有身体创伤的杰克身边,但她却这样做了,只因她承受着越界后的自我性别身份确认的焦虑,而有身体创伤的杰克可以给她带来安全感。杰克的身体创伤不仅属于个人的生理病症,还属于时代文化转型期的中产阶级白人男性的群体状态。杰克的个人悲剧,在本质上则成为那个时代白人青年男性的西西弗式的现代悲剧。虽然悲剧具有不可逆的时代必然性,但我们仍应该透过悲剧看到希望和幸福。

Injection Spectra of Different Species of Cosmic Rays from AMS-02, ACE-CRIS and Voyager-1

Precise measurements of energy spectra of different cosmic ray(CR) species have been obtained in recent years, by particularly the AMS-02 experiment on the International Space Station. It has been shown that apparent differences exist in different groups of the primary CRs. However, it is not straightforward to conclude that the source spectra of different particle groups are different since they will experience different propagation processes(e.g., energy losses and fragmentations) either. In this work, we study the injection spectra of different nuclear species using the measurements from Voyager-1 outside the solar system, and ACR-CRIS and AMS-02 on the top of atmosphere, in a physical framework of CR transportation. Two types of injection spectra are assumed, the broken power-law(BPL) form and the non-parametric spline interpolation form. The non-parametric form fits the data better than the BPL form, implying that potential structures beyond the constrained spectral shape of BPL may exist. For different nuclei the injection spectra are overall similar in shape but do show some differences among each other. For the non-parametric spectral form, the helium injection spectrum is the softest at low energies and the hardest at high energies. For both spectral shapes, the low-energy injection spectrum of neon is the hardest among all these species, and the carbon and oxygen spectra have more prominent bumps in 1–10 GV in the R2 d N dRpresentation.Such differences suggest the existence of differences in the sources or acceleration processes of various nuclei of CRs.

Matter-Antimatter Asymmetry from Preon Condensation Prior to the Hadron Epoch

A universe consisting of protons, neutrons, and electrons with electrical neutrality is consistent with an equal number of c and preons, assuming the rishon preon theory of Shupe and Harari. Similarly, a universe consisting of antiprotons, antineutrons, and positrons with electrical neutrality is consistent with an equal number of c and preons. Hence, any combination of such matter-antimatter compositions is also consistent with an equal number of c and preons and overall electrical neutrality. It is proposed that the difference observed in baryon-antibaryon number density relative to photon number density, ~5 × 10-10, is due to allocation of preons between matter and antimatter during preon condensation into normal matter. Three approaches of increasing rigor and complexity are considered: 1) an allocation at times corresponding to the Planck temperature due to fluctuations, 2) an allocation at times corresponding to quark formation due to preon bonding, and 3) an allocation at times corresponding to the electroweak scale. All approaches can give the correct order of magnitude of the asymmetry assuming out-of-equili-brium freeze-out and a slight and allowed charge (C) asymmetry in preon condensation in a self-consistent quantum field theory. Sakharov’s baryon non-conservation condition is evidently circumvented with these approaches, because they assume another level of matter (preons) which is present before quark formation. Thus, preons can provide an elementary explanation of primordial matter-antimatter asymmetry. A relationship between Higgs boson states and preons is proposed.

纳米技术与纳米材料(V)——防晒化妆品中的纳米二氧化钛

介绍了纳米二氧化钛屏蔽紫外线的原理;阐述了防晒化妆品中纳米二氧化钛应具备的特点和功能;详细讨论了国内外防晒领域的纳米二氧化钛的产品种类、发展趋势和研究方向。另外,就国内纳米二氧化钛规模化生产状况和应用现状论述了作者的观点。

调制过程中晒黄烟的物理变化和化学变化

研究了改进晒制法和传统晒制法调制过程中晒黄烟烟叶的物理变化和化学变化。结果表明,烟叶含水率和叶绿素含量随调制进程的推进而逐渐下降,在凋萎变黄期间烟叶中淀粉、蛋白质含量逐渐减少,总糖和游离氨基酸含量增加。总氮含量变化不大,烟碱含量则稍有下降。两种调制方法相比,改进法凋萎变黄期间烟叶的失水速率降低,有利于烟叶中叶绿素、淀粉和蛋白质的降解,使调制后烟叶杂气减轻,香气量提高,品质得到明显改善。

太阳宁静区的高分辨率像复原

本文介绍在怀柔６０ｃｍ多通道太阳望远镜上运用斑点干涉像复原方法所取得的一些初步结果。对用短曝光方法（曝光时间不大于１０毫秒）获得的一系列“冻结”大气后的目标像用斑点干涉像复原方法进行处理，即可获得消除了地球大气影响的目标复原像，斑点掩模法（Ｓｐｅｃｋｌｅ－Ｍａｓｋｉｎｇ）即为斑点干涉像复原方法的一种，我们用它对日面中心的宁静区米粒进行处理，复原出了分辨率不劣于０．″５的白光米粒像。

湖北地方晒晾烟物理性状与其他质量评价指标的典型相关分析

以湖北恩施、宜昌、十堰、襄阳4个产区普查晾晒烟样本为材料,对烟叶外观质量指标和评吸指标进行量化鉴定,对烟叶物理性状和化学成分进行测定。通过使用典型相关分析方法分析烟叶物理性状与烟叶外观质量、化学成分和评吸指标间的典型相关性。结果表明,烟叶的物理性状与外观质量、化学成分和评吸指标之间均存在显著典型相关关系,烟叶物理性状与外观质量关系最密切;在烟叶评价质量组间关联上起主要作用的物理性状评价指标是单叶重、叶长及平衡含水率。

不同晒烟和烤烟理化特性与中性致香物质的对比分析

【目的】系统了解国内规模化种植晒烟与烤烟的理化特性和香气特点,为卷烟企业开发研制具有独特品牌风格及低焦油中式卷烟提供参考依据。【方法】以湖南宁乡、云南保山、广西贺州等地规模化种植的晒烟与云南昆明烤烟、美国烤烟为材料,对比分析不同产地及类型烟草中部烟叶样品的填充值、化学成分、香韵特征及中性致香物质等。【结果】晒烟的填充值普遍高于烤烟,以云南保山晒烟肯那的填充值最高,为5.88 cm3/g,云南昆明烤烟的最低,为2.99cm3/g。不同产地晒烟与烤烟的化学成分差异较大,从而造成其感官品质差异较大。湖南宁乡晒烟的焦香、木香香韵较突出,云南保山晒烟的甜香香韵较突出,广西贺州晒烟的树脂香、坚果香香韵较突出,美国烤烟的干草香、焦香香韵较突出,云南昆明烤烟的清香、甜香香韵较突出。6个烟叶样品中共检出40种中性致香成分,其中酮类物质比例最高,有23种,其次为醛类,有7种;多重比较分析结果表明,有36种中性致香成分的含量差异达显著水平(P<0.05)。【结论】不同晒烟和烤烟的理化特性和中性致香物质含量差异较大,且各具特点,卷烟企业可根据自己的需求,通过合理配比获得适合中式卷烟开发与生产的原材料。其中,湖南宁乡晒烟适合添加应用于高品质卷烟;云南保山晒烟在低焦油、低危害卷烟开发研究中有很好的应用价值;广西贺州晒烟既可在混合型卷烟中使用,又可在烤烟叶组配方中适当应用。

对日定向半物理试验台的加载有效性验证

提出了一种基于扭振系统的半物理试验系统加载有效性验证方案,对扭振系统进行了设计,建立了扭振系统的动力学模型,通过仿真分析验证了方案的合理性,并最终通过实物验证来对比动力学模型产生的加载力矩曲线与实物产生的力矩曲线的一致性,实现了对空间站对日定向半物理试验系统加载有效性的考核。实验结果表明,半物理试验系统具有较高的加载精度,满足测试要求。通过特性清晰已知等效模型的考核,对提高试验系统的直观性及可信度具有重要意义,此方法对其它半物理试验设备的性能测试具有一定的借鉴意义。

空间站对日定向装置试验台的控制器设计与精度考核

针对太阳电池帆板大挠性、大惯量等特性,导致对对日定向装置施加的大幅值、高频响的变负载力矩难以模拟和模拟精度不足的问题,设计了以电动负载模拟器为核心装置的地面半物理仿真试验台。首先建立了电动负载模拟器(加载单元)模型,采用递推最小二乘法对加载单元各参数进行辨识,并分析各参数对加载单元响应特性的影响。提出一种超前校正与模糊自适应PID相结合的复合控制算法,该方法有效地拓宽了加载单元带宽、改善了力矩跟随性能和抑制了力矩误差。用不同信号对试验台响应速度、加载带宽和加载精度进行分析和考核。实验结果表明:该复合控制算法使加载力矩较好地复现了太阳电池帆板模型的期望输出力矩,为对日定向装置对太阳电池帆板的驱动性能考核实验模拟出较为精确的期望模型的负载(测试)力矩。

对阳光体育运动落到实处的理论思考

阳光体育运动要真正落到实处,离不开国家、学校、师生等利益相关者的共同努力。国家政策的保证是前提;基层、学校的执行力是关键;教师、学生、家长"三位一体"形成合力是保证。

太阳Ⅲ型暴与反向Langmuir波的产生

一般认为,Langmuir波(LW)转换为电磁波是太阳Ⅲ型射电暴的产生机制.由电子束流不稳定性可以很容易地激发LW,正向LW和反向LW的相互作用被认为是产生Ⅲ型暴二次谐波的原因,但反向LW的色散方程和产生机制尚未得到充分研究.对含有温度的双流不稳定性的方程进行了解析求解,发现温度和束流速度分别对反向和正向LW色散关系具有显著影响,并采用粒子模拟(PIC)方法部分证实了解析推导的结果.通过PIC模拟研究了反向LW的产生机制,发现反向LW不能由电子束流直接激发,其能量基本上都是由正向LW散射得到的.然而,电子束流对正向LW的二次谐波有直接放大作用.