Brazilian Journal of Physics最新文献_第10页

Techniques for Searching for Anisotropy in the Arrival Directions of Ultra-High Energy Cosmic Rays 搜索超高能量宇宙射线到达方向各向异性的技术

IF 1.5 4区物理与天体物理

Brazilian Journal of Physics Pub Date : 2024-11-08 DOI: 10.1007/s13538-024-01640-6

Diego C. dos Santos, Rogerio M. de Almeida, João R. T. de Mello Neto, Bruno L. Lago

{"title":"Techniques for Searching for Anisotropy in the Arrival Directions of Ultra-High Energy Cosmic Rays","authors":"Diego C. dos Santos, Rogerio M. de Almeida, João R. T. de Mello Neto, Bruno L. Lago","doi":"10.1007/s13538-024-01640-6","DOIUrl":"10.1007/s13538-024-01640-6","url":null,"abstract":"<div><p>Understanding the origin and distribution of ultra-high-energy cosmic rays (UHECRs) remains a cornerstone challenge in astrophysics. These cosmic rays, with energies exceeding 8 EeV, provide insights into the most energetic phenomena in the universe. In this paper, we review and apply various statistical and analytical techniques to a simulated dataset to investigate the anisotropy in the arrival directions of UHECRs with energies exceeding 8 EeV. We simulate cosmic-ray events based on the distribution of local matter from the 2MASS Redshift Survey, supplemented with an isotropic background component, to create a robust dataset for analysis. Our methods include blind searches for excesses over the sky, Rayleigh analysis in right ascension, reconstruction of dipole and quadrupole moments using spherical harmonics, and the angular power spectrum technique — a method extensively utilized in cosmic microwave background studies — to assess anisotropies across multiple angular scales. The results underscore the potential of these methodologies to reveal significant anisotropies and contribute to our understanding of the possible extragalactic sources and propagation mechanisms of UHECRs.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142595947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Dynamics of Soliton Collision in DNA Double Helix DNA 双螺旋中的孤子碰撞动力学

IF 1.5 4区物理与天体物理

Brazilian Journal of Physics Pub Date : 2024-11-07 DOI: 10.1007/s13538-024-01632-6

Christy Maria Joy, L. Kavitha

引用次数: 0

Synergistic Investigation of Binary Hydrogen Bond Liquid Crystal Complex: Experimental and Theoretical (DFT) Perspectives of Smectic Molecular Ordering via Molecular Dynamics 二元氢键液晶复合物的协同研究：通过分子动力学研究 Smectic 分子排序的实验和理论（DFT）视角

IF 1.5 4区物理与天体物理

Brazilian Journal of Physics Pub Date : 2024-11-04 DOI: 10.1007/s13538-024-01643-3

V. Balasubramanian, Ginson P. Joseph, S. Sundaram, Sujay Chakravarty, V. N. Vijayakumar

{"title":"Synergistic Investigation of Binary Hydrogen Bond Liquid Crystal Complex: Experimental and Theoretical (DFT) Perspectives of Smectic Molecular Ordering via Molecular Dynamics","authors":"V. Balasubramanian, Ginson P. Joseph, S. Sundaram, Sujay Chakravarty, V. N. Vijayakumar","doi":"10.1007/s13538-024-01643-3","DOIUrl":"10.1007/s13538-024-01643-3","url":null,"abstract":"<div><p>Binary hydrogen bond liquid crystal (HBLC) complex is isolated from the combination of cholesteryl stearate (CHS) and 4-methoxycinnamic acid (4MCA) mesogenic compounds. Induced chiral smectic phases are observed and characterized using a polarizing optical microscope (POM). Enthalpy values and transition temperatures of liquid crystal (LC) phases and their thermal stability are reported using differential scanning calorimetry (DSC), and the same has been supported by the density functional theory (DFT) method. Observation of a strong peak at 3580 cm<sup>−1</sup> from the FTIR spectrum confirms the hydrogen bond (H-bond) between chiral (CHS) and non-chiral (4MCA) mesogenic compounds. Further, DFT calculation explores the molecular mechanism of the complexation (CHS + 4MCA). The calculated global reactivity parameters (GRP) values (DFT calculations) justify the stability of the synthesized binary HBLC complex (CHS + 4MCA). In addition, topological analysis of DFT confirms the intermolecular interaction in the title binary HBLC complex. Donor and acceptor interaction in the binary HBLC complex (CHS + 4MCA) is reported using molecular electrostatic potential (MEP) analysis. Further, the impact of increased H-bond length and bond angle on induced chiral smectic ordering has been discussed in the present communication. Quantum theory of atoms-in-molecules (QTAIM) study endorses the existence of linear H-bonding of O–H···O in the binary HBLC complex. In addition, the enhanced mesomorphic behaviour along with non-linear optical properties (NLO) is reported.</p><h3>Graphical Abstract</h3>\u0000<div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Next Generation Terahertz Biosensor Based Broadband Photonic Crystal Fiber for High Sensitivity Precision Kerosene Admixture Simultaneous Detection 基于宽带光子晶体光纤的下一代太赫兹生物传感器用于高灵敏度精确煤油混合物同步检测

IF 1.5 4区物理与天体物理

Brazilian Journal of Physics Pub Date : 2024-11-01 DOI: 10.1007/s13538-024-01644-2

A. H. M. Iftekharul Ferdous, Zonaki Khaton, Dilip Kumar Sarker, Khalid Sifulla Noor, Jeneetha Jebanazer, Kannan Krishnan, Ganekanti Naresh, Ramachandran Thandaiah Prabu, Ahmed Nabih Zaki Rashed

{"title":"Next Generation Terahertz Biosensor Based Broadband Photonic Crystal Fiber for High Sensitivity Precision Kerosene Admixture Simultaneous Detection","authors":"A. H. M. Iftekharul Ferdous, Zonaki Khaton, Dilip Kumar Sarker, Khalid Sifulla Noor, Jeneetha Jebanazer, Kannan Krishnan, Ganekanti Naresh, Ramachandran Thandaiah Prabu, Ahmed Nabih Zaki Rashed","doi":"10.1007/s13538-024-01644-2","DOIUrl":"10.1007/s13538-024-01644-2","url":null,"abstract":"<div><p>A unique PCF detector is suggested that contains octagonal cladding and hexagonal core which is used for kerosene adulteration detection. The sensor performance was numerically investigated between the frequencies of 1.0 and 2.8 THz. The central hole has been full with kerosene. The strut size is adjusted to investigate This research as well as the detector’s functionality be carried out at THz frequencies. At 2.2 THz, the photonic crystal fiber sensor has a relative sensitivity of roughly 94.25%, EML 0.01106, and a confinement loss of 1.77 × 10<sup>−13</sup> of the order of 10<sup>14</sup>. This suggested detector can play a fine role in detecting kerosene admixture since it has high sensitivity and remarkable precision. This will be helpful for consumer to consume high-grade petroleum fuel without admixture of kerosene. Technologies related to extrude and 3D print might be utilized for the photonic crystal fiber detector.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142565955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

On the Oblique Propagation of Large Amplitude Dust-Acoustic Solitary Waves in Anisotropic Polarized Magnetoplasma 论各向异性极化磁等离子体中大振幅尘声孤波的斜向传播

IF 1.5 4区物理与天体物理

Brazilian Journal of Physics Pub Date : 2024-10-30 DOI: 10.1007/s13538-024-01635-3

Weaam Alhejaili, Almas, Ata-ur-Rahman, S. A. El-Tantawy

{"title":"On the Oblique Propagation of Large Amplitude Dust-Acoustic Solitary Waves in Anisotropic Polarized Magnetoplasma","authors":"Weaam Alhejaili,  Almas,  Ata-ur-Rahman, S. A. El-Tantawy","doi":"10.1007/s13538-024-01635-3","DOIUrl":"10.1007/s13538-024-01635-3","url":null,"abstract":"<div><p>This study comprehensively investigates the oblique propagation of arbitrary dust-acoustic solitary waves (DASWs) in an anisotropic polarized complex magnetoplasma. The model consists of Maxwellian electrons and ions as well as inertial hot dust fluid. The hot dust is presumed to exhibit adiabatic behavior, distinguished by anisotropic thermal pressure. The linear dispersion relation (LDR) for both dust-cyclotron waves (DCWs) and dust-acoustic waves (DAWs) is obtained and investigated numerically using the plane wave approximation. The analysis applies Sagdeev’s pseudopotential theory to the fluid equations of the plasma model and simplifies them into the energy equation. Various factors, including polarization force, ions-to-electron temperature ratio, dust concentration, and dust pressure anisotropy, are considered to explore their influence on solitary waves’ existence and propagation characteristics (amplitude, width). The results reveal the presence of only rarefactive DASWs. This study provides valuable insights into wave phenomena in polarized magnetized plasmas and holds potential applications in space-dusty plasma environments like Saturn’s F rings.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142555248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of SnO2 Coating on the Structural, Optical, and Electrical Properties of TiO2 Nanowires Fabricated by a Two-Step Deposition Method 二氧化锡涂层对两步沉积法制备的二氧化钛纳米线的结构、光学和电学特性的影响

IF 1.5 4区物理与天体物理

Brazilian Journal of Physics Pub Date : 2024-10-28 DOI: 10.1007/s13538-024-01639-z

Hasan Tayfun Ay, Mehmet Fahri Sarac, Tuba Solakyildirim

{"title":"Effect of SnO2 Coating on the Structural, Optical, and Electrical Properties of TiO2 Nanowires Fabricated by a Two-Step Deposition Method","authors":"Hasan Tayfun Ay, Mehmet Fahri Sarac, Tuba Solakyildirim","doi":"10.1007/s13538-024-01639-z","DOIUrl":"10.1007/s13538-024-01639-z","url":null,"abstract":"<div><p>The photosensing properties of SnO<sub>2</sub>-coated TiO<sub>2</sub> NWs have been fabricated by a two-step sequential deposition method; a thermal oxidation method followed by a hydrolysis method. Pure TiO<sub>2</sub> NWs show vertically aligned and uniformly distributed NW arrays on Ti foil. It was observed that the SnO<sub>2</sub> coating accumulated on the TiO<sub>2</sub> NW surfaces with increasing Sn concentration. It filled the spaces between the NWs and finally covered the entire surface of the 100 mM SnO<sub>2</sub> concentrated sample. The presence of increased Sn concentration on the surface was qualitatively determined by EDS and XPS measurements. The PL intensity decreases as the SnO<sub>2</sub> coating increases, indicating recombination retardation. Coating thickness also decreases the band gap since electron excitation requires less energy. Since electrons are easily excited by the conduction band of TiO<sub>2</sub>, SnO<sub>2</sub> coatings can form an energy level within the band gap. The highest photosensitivity was 142.05% with 100-mM SnO<sub>2</sub>-coated TiO<sub>2</sub> NW arrays. An alternative approach to photosensitive UV devices can be made with 100-mM SnO<sub>2</sub>-coated TiO<sub>2</sub> NW arrays due to their excellent light absorption properties and efficient charge carrier generation.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142524501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Hybrid Optimization Framework for MIMO Antenna Design in Wearable IoT Applications Using Deep Learning and Bayesian Method 利用深度学习和贝叶斯方法为可穿戴物联网应用设计 MIMO 天线的混合优化框架

IF 1.5 4区物理与天体物理

Brazilian Journal of Physics Pub Date : 2024-10-26 DOI: 10.1007/s13538-024-01634-4

Pradanya A. Gajbhiye, Satya P. Singh, Madan K. Sharma

{"title":"Hybrid Optimization Framework for MIMO Antenna Design in Wearable IoT Applications Using Deep Learning and Bayesian Method","authors":"Pradanya A. Gajbhiye, Satya P. Singh, Madan K. Sharma","doi":"10.1007/s13538-024-01634-4","DOIUrl":"10.1007/s13538-024-01634-4","url":null,"abstract":"<div><p>The growing adoption of wearable Internet of Things (IoT) devices requires efficient wireless communication systems for applications like healthcare and fitness. Multiple-input multiple-output (MIMO) technology improves signal quality by using multiple antennas but presents challenges in compactness and low power consumption and offers minimal mutual coupling while interacting with the human body. Ensuring compliance with specific absorption rate (SAR) limits is also crucial. In this paper, we present a hybrid optimization framework for designing MIMO antennas for such wearable devices. We integrate deep learning with Bayesian optimization. We use artificial neural networks (ANNs) to model antenna performance and Bayesian optimization to explore the design space efficiently. The final optimized MIMO antenna has an overall size of 122.44 mm <span>(times )</span> 58.32 mm. The proposed MIMO antenna achieved minimized mutual coupling in free space, on hand, and leg with values of <<span>(-)</span>75.77 dB, <<span>(-)</span>46 dB, and <<span>(-)</span>37 dB, respectively. In every scenario, the antenna has a stable resonance at a 2.45 GHz frequency and maintains a SAR within the 1.6 W/kg safety limit. Additionally, our optimization reduced computational effort by about 30% compared to traditional methods. These results show the effectiveness of combining ANNs and Bayesian optimization in designing high-performance MIMO antennas, advancing wireless communication for wearable IoT devices.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142518955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

On the Fermi Gas, the Sommerfeld Fine Structure Constant, and the Electron–Electron Scattering in Conductors 关于导体中的费米气体、索默费尔德精细结构常数和电子-电子散射

IF 1.5 4区物理与天体物理

Brazilian Journal of Physics Pub Date : 2024-10-25 DOI: 10.1007/s13538-024-01611-x

C. A. M. dos Santos, M. S. da Luz, F. S. Oliveira, L. M. S. Alves

{"title":"On the Fermi Gas, the Sommerfeld Fine Structure Constant, and the Electron–Electron Scattering in Conductors","authors":"C. A. M. dos Santos, M. S. da Luz, F. S. Oliveira, L. M. S. Alves","doi":"10.1007/s13538-024-01611-x","DOIUrl":"10.1007/s13538-024-01611-x","url":null,"abstract":"<div><p>Electrical energy is revisited as a fundamental parameter for inclusion in Fermi gas theory, in addition to thermal energy. It is argued that electrical energy can move some electrons to above the Fermi level, providing free charges to carry the electrical current, even at absolute zero temperature. The Drude model, Ohm’s law, quantum resistance, and the electrical resistivity due to electron–electron scattering appear naturally as a consequence of the theoretical description, which is based on the quantization of the angular momentum and the Fermi–Dirac distribution, considering total energy as <span>(epsilon ={k}_{B}T+{Phi }_{0}I)</span>. The electrical and magnetic forces acting on an electron are related to the ratio between the Fermi velocity and the speed of light and show that the electron motion is due to helical paths. Considering the center of mass description for the Bohr atom, it was possible to show that the magnetic force is related to the electrical force as <span>({F}_{M}=(alpha /pi ){F}_{E})</span>, which demonstrates that the electrons move in helical paths along the orbit. The helical motion naturally provides for quantization of the magnetic flux, the spin of the electron, and the first correction term of the anomalous magnetic moment. Applying the model to describe the electron–electron scattering allows prediction of the behavior of the electrical resistivity of many metals at low temperatures, which is in excellent agreement with empirical observations.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"55 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142518723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

An Exploration of Anisotropic Acoustic Wave Attenuation in Quartz Crystals 石英晶体中各向异性声波衰减的探索

IF 1.5 4区物理与天体物理

Brazilian Journal of Physics Pub Date : 2024-10-24 DOI: 10.1007/s13538-024-01638-0

Temur Mustafayev, Farkhad Akhmedjanov, Jurabek Abdiev, Shakhboz Khasanov

引用次数: 0

Synthesis and Characterization of Cadmium Tin Oxide for MEMS Substrates and Its Comparative Computational Study with Silicon and Silicon Carbide 用于微机电系统（MEMS）基板的氧化镉锡的合成与表征及其与硅和碳化硅的比较计算研究

IF 1.5 4区物理与天体物理

Brazilian Journal of Physics Pub Date : 2024-10-22 DOI: 10.1007/s13538-024-01624-6

Nicholas Ongwen

{"title":"Synthesis and Characterization of Cadmium Tin Oxide for MEMS Substrates and Its Comparative Computational Study with Silicon and Silicon Carbide","authors":"Nicholas Ongwen","doi":"10.1007/s13538-024-01624-6","DOIUrl":"10.1007/s13538-024-01624-6","url":null,"abstract":"<div><p>The rising demand for semiconductor substrates for printing electronic circuits has been sparked by recent breakthroughs in electronics. The most popular substrate for printing these devices is silicon (Si), which is chosen over other substrates like silicon nitride because it is more widely accessible, and has better electrical and electronic properties. Despite the benefits above, Si has a number of disadvantages, including being brittle and only occasionally existing as a pure element. This study synthesized and characterized cadmium tin oxide (CTO) as potential substrates for MEMS manufacturing. A comparative computational study of the structural and mechanical properties with Si and silicon carbide (SiC) was also made. The experiments involved structural characterization of the synthesized samples at varied concentrations of cadmium, while the computations involved use of density functional theory within the generalized gradient approximation to investigate the structural and mechanical properties of the three materials. SiC was found to have better mechanical properties than both Si and CTO, but its brittleness prevents it from being used in the production of flexible MEMS. The manufacturing of flexible MEMS, including microbolometers and biomedical MEMS, can be made possible due to the soft and ductile character of CTO, especially the CTO 3, which was the most ductile.</p></div>","PeriodicalId":499,"journal":{"name":"Brazilian Journal of Physics","volume":"54 6","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142453132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0