bluuebunny/crossref_metadata_2025 huggingface dataset:
The content of Cd and Pb in undeveloped and shallow soils and plant material in the area of national park Tara
Authors: Novaković Angelina , Miletić Stefan , Beloica Jelena , Belanović-Simić Snežana , Obratov-Petković Dragica
Published: January 2022

Ultramafic (serpenites) are a group of igneous or metamorphic rocks, which are characterized by high concentrations of Mg, Fe, Ni, Cr, and Co, along with low concentrations of Ca, P, and K, contain less than 45% silicon (SiO2). Tara Mountain is natural good of western Serbia where areas under serpentinites occupy 28%. Researchers agree that the flora of serpentine areas is unique and botanically very important. The specificity of the flora and the development of vegetation on serpentinites are characterized by special mechanisms of plant species adaptation to increased concentrations of some heavy metals in the soil with low content of essential elements (nutrients). This paper examines the influence of serpentinite geological substrate on the occurrence of certain plant species in the initial stages of plant community development. The soil was mainly sampled in rock crevices in the early phases of soil development (Lithosols) where the influence and origin of the metals from the rock can be considered the most obvious. Content of cadmium (Cd) and lead (Pb) in geological substratum, soil and plants biomass is analysed in order to differentiate levels and extents of natural and anthropogenic pollution and also deposition data from the EMEP program (European Monitoring and Evaluation Programme). Results show that the content of lead and cadmium in the soil and plant samples are higher than the content in the corresponding rock sample, except for two soil samples, in which the content of Cd is lower. Thissuggest that the origin of the increased Pb and Cd content might be from anthropogenic sources. Deposition (data from EMEP program) of Cd and Pb, which was analysed for the period from 1990-2018, indicate significant cumulative effect. The values of cumulative deposition in research area have a value of 91,51 kg/km2 lead, while the value of cadmium is 1665 g/km2 , which classifies NP Tara in above-average polluted area in R. Serbia.
Freshwater Lubricated Hydrostatic Stern Tube and Strut Bearing Design
Authors: Prince Kevin , Dray James
Published: January 2022

This paper discusses the design of freshwater lubricated hydrostatic bearings for use as marine stern tube and strut bearings. The advantages of this type of bearing design over conventional hydrodynamic seawater and oil lubricated bearings are: elimination of bearing oil as a source of pollution, improved wear characteristics, reduced seal cost, elimination of shaft noise at low RPM and the potential reduction of tail shaft diameter and inspection interval. Presented in this paper is the development and comparison of two freshwater lubricated hydrostatic bearings designed for the direct replacement of an existing commercial oil lubricated and military seawater lubricated stern tube and strut system. Comparative analysis presents the difference in design and operating parameters, lubricant film thickness versus shaft speed and life cycle cost.
Estimate of the Propeller Oscillatory Loads Introduced in the Shaft and their Reduction Using Skew Angle
Authors: Sbragio Ricardo
Published: January 2022

This paper describes the determination of the oscillatory loads generated by a propeller operating in an irregular wakefield. The vibrations caused by these loads can damage the shaft and its bearings or cause undesirable noise. The method used in this determination is the two-dimensional unsteady method based on Sears function. The loads are corrected for the aspect ratio of the propeller blades. The results are compared with results from literature. The influences of the skew angle and number of blades in the reduction of shaft vibrations are also evaluated, qualitatively and quantitatively, for a single propeller ship model.
Numerical Analysis of Surface-Piercing Propellers
Authors: Young Yin Lu , Kinnas Spyros A.
Published: January 2022

A 3-D low-order boundary element method, PROPCAV, has been extended to predict unsteady hydrodynamic forces and ventilation patterns on a surface-piercing propeller. The negative image method is used to account for the effect of the free surface. The ventilated cavity patterns at every time step is determined iteratively by satisfying both the kinematic and the dynamic boundary conditions. The detachment locations of the ventilated cavities are determined iteratively by applying a condition similar to the Villat-Brillouin smooth detachment criterion. Finally, the coupling of boundary element method with a finite element method to include hydroelastic effects is presented.
Numerical Analysis of Podded and Steering Systems Using a Velocity Based Source Boundary Element Method with Modified Trailing Edge
Authors: Achkinadze Alexander S. , Berg Aage , Krasilnikov Vladimir I. , Stepanov Ivan E.
Published: January 2022

This paper describes an improved velocity based source boundary element method (HEM) as applied to modeling of podded propellers and propeller/rudder systems. The distinctive feature of the present method consists in the direct satisfaction of the Kutta-Joukowski condition on the additional Kutta panel constructed behind the realistic blade trailing edge when defining the unknown doublet strength. This Modified Trailing Edge (MTE) is also used as a tool for the approximate accounting for viscous and related effects on circulation. The integrated propulsive/steering system is simulated within the potential frameworks using the velocity field iterations method and quasi-steady approach, which assumes the simulation of a propeller in a spatially varying flow field while pod and strut(/rudder) are considered in a circumferentially averaged flow field The developed method is applied for calculation of rudder behind the operating propeller and podded units of different arrangement tested at MARINTEK (Norwegian Marine Technology Research Institute). The results of the measurements and theory/experiment comparisons are discussed.
U.S. Navy Waterborne Bearing Problems
Authors: Vath Frederick
Published: January 2022

The U.S. Navy currently uses a rubber stave and bearing shell configuration for most main, intermediate, and stem tube strut bearing configurations. The rubber stave consists of two parts, the soft wear rubber and a harder non-metallic backing. The main and intermediate strut bearings are lubricated by means of seawater flow, as a result of ship movement through the bearing channels between the staves. The stem tube bearings are lubricated by pressurized seawater from the ship's firemain system.

Beginning in December 1999, increased oversight focused on problems associated with staves that resulted in unscheduled replacements and disruptions to several ships' schedule. A government investigation team, consisting of representatives from various commands, was formed to identify the problem, determine the root cause, and develop corrective action. Bearing staves from various ships of different classes were identified for examination and testing. The results indicated: a lack of bond adhesion between the wear rubber and its backing, leading edge (LE) debonding, delamination, bubbles, dimples, installation damage, cracking or bulging of the stave ends; and damage caused by obstructed water channels. Discussions with various shipyards and other organizations indicated that this was not a new problem but rather an existing problem that was detected during bearing removal. It was remedied simply by replacing the staves with new ones, therefore, no corrective action or concerns were raised.

During the investigation, several problems associated with the waterborne bearing military specification were noted. These problems included: areas of unclear guidance or requirements, allowance for variation within the manufacturing process, and inconsistent sampling size requirements.

In addition to problems noted above, the dry-docking and subsequent maintenance philosophy are beginning to change that will adversely affect the life of a stave and increase the demand for performance. Past practice has been to dry-dock the ship every 5 years; pull the shafting every 10 years, at which time, the staves are replaced. Dry-dockings are beginning to be extended for between 10 to 16 years, which will increase the in-service time for staves. The current practice is switching from a time-based to a condition-based maintenance philosophy. This will probably entail periodic measurement of stave wear to determine replacement. This approach will only be successful with an increase in stave durability.

The results of the investigation team were changes to the waterborne bearing military specification to clarify requirements and guidance, modification of the sampling requirements, as appropriate, to match the manufacturing process, and verification that stave material requirements are being met in order to better survive increased in-service life expectancy. Additional guidance to shipyards and the fleet was issued to provide better instructions for stave and bearing installation and direction for "zero" thrust controllable pitch propeller (CPP) ship operation.
Hydrodynamic Analysis of Podded Propellers
Authors: Kinnas Spyros A. , Lee Hanseong , Mishra Bikash , He Lei , Rhee Shin-Hyung , Sasunapuri Balasubramanyam
Published: January 2022

This paper presents computational techniques which couple a lifting surface method (MPUF-3A) for the unsteady cavitating flow analysis of propellers with an Euler solver (GBFLOW) and a Reynolds-Averaged Navier Stokes Solver (FLUENT) to predict the flow and the performance of various types of podded propellers such as pull, push and twin types. The time-averaged propeller force distributions are considered as source terms in the momentum equations of GBFLOW or FLUENT. The effect of viscosity on the effective wake and on the performance of each propeller, as well as on the forces on the pod and strut are assessed, and the results of the involved methods are validated with those measured in experiments.
Predication of Hull Pressure Fluctuations Induced by Single and Twin Propellers
Authors: Hwang Yoonsik , Sun Hong , Kinnas Spyros A.
Published: January 2022

A previously developed method which solves for the diffraction potential on the hull subject to the presence of a single propeller (HULLFPP) is coupled with a Vortex Lattice Method (MPUF3A) which solves for the unsteady sheet cavitation on the propeller blades. Systematic studies on grid dependence of cavity solution, propeller forces and hull pressure fluctuations are performed in the case of single propellers. The effects of the presence of tunnel wall or free surface on the predicted pressure fluctuations on the hull are also investigated. The method is then extended to the case of twin propellers. Comparisons between the numerical results and those measured in existing experiments are presented.
CFD Simulation for Propeller Four-Quadrant Flows
Authors: Lee Sing-Kwan
Published: January 2022

A Reynolds-Averaged Navier-Stokes (RANS) method has been employed in conjunction with an overlapping moving grid approach to provide accurate resolution of four-quadrant propeller flows under both the design and off-design conditions. It is well known that some off-design propeller flow phenomena are dominated by viscous effects and cannot be accurately predicted by the potential flow methods. In order to properly account for viscous effects, it is necessary to employ accurate and robust numerical methods which can provide detailed resolution of the propeller boundary layer, turbulent wake, leading-edge separation, and unsteady ring vortices induced by propeller operations under off-design conditions. In this study, time-domain simulations are performed for the DTRC 4I18 propeller under ahead, bollard pull, crash-ahead, crash-astern, and backing conditions and compared with the available experimental data.
Fully Transient CFD Analysis of Waterjet Pumps
Authors: Bulten Norbert W.H. , van Esch Bart P.M.
Published: January 2022

This paper presents results of fully transient calculations of the flow-through waterjet pumps. The fully transient method is based on a moving mesh option to implement the rotation of the impeller. In this way, the time-dependent forces, acting on the impeller, can be determined. These forces can be divided into axial and radial forces, e.g. as a result of rotor-stator interaction. In waterjet applications, the non-uniform inflow velocity distribution creates additional steady transverse impeller force in the stationary frame (in the horizontal and vertical direction). CFD analyses are made of two Lips-Jets waterjet pumps equipped with 3 and 6 bladed impellers to investigate the rotor-stator interaction force for various flow rates. Calculations with a non-uniform inflow velocity distribution are made to determine the steady transverse forces. The strength of this steady force depends on the amplitude of the velocity variations and the flow rate through the pump.
Alternatives in Gearbox Seals for Main Drive Gearboxes
Authors: Roche Brian P.
Published: January 2022

A variety of sealing devices have been used to seal Marine Main Reduction Gears. One means of sealing Main Reduction Gears today is the labyrinth seal. While the labyrinth seal has been successfully employed in some applications, it has performed unsatisfactorily in others. This paper discusses mechanical seals as alternatives to labyrinth seals for use in Marine Main Reduction Gears. Along with a discussion a/Labyrinth Seals, various types of mechanical seals are considered, along with their respective advantages and disadvantages. Split Circumferential Seals are described in particular. Seal design features, as well as test results, are presented.
A Solution to Robust Shaft Alignment Design
Authors: Sverko Davor
Published: January 2022

The primary problem that shafting alignment designers are faced with today, is high sensitivity of the alignment to the hull girder deflections resulting from the changes in the loading condition of the vessel. Accordingly, the accuracy of the alignment procedure will depend on our ability to account for hull deflections in the alignment design.

The shafting alignment optimization approach, that ABS is proposing in this paper, provides a solution to the problem. So far ABS collected a sufficient amount of hull girder deflection data to generate an initial database, and enable alignment designers to estimate hull deflections with high confidence on new designed tankers and bulk carriers.

Establishing the hull deflection database is an essential part in shafting alignment optimization, as we want to ensure the robust alignment design, with sufficient margin of safety to remain satisfactory under extreme hull deflections, thermal change in bearing offsets, as well as to absorb much of the possible unpredicted disturbances.

In this paper we will show how the hull deflections are utilized in the alignment design and optimization. We will indicate the advantages of undertaking this approach and discuss concerns and constraints the designer should be aware of when analyzing the alignment.
IDH-Mutated AML: Beyond Enasidenib and Ivosidenib Monotherapy: Highlights From SOHO 2021
Authors: C. Geppner, MLS, CTTS, PA-C Alexis
Published: January 2022

Alexis C. Geppner, MLS, CTTS, PA-C, of The University of Texas MD Anderson Cancer Center, distills information reviewed in the session on IDH-mutated acute myeloid leukemia presented by Courtney D. DiNardo, MD, MSCE, also of MD Anderson Cancer Center, at the 2021 SOHO Annual Meeting.
The Next Wave of Novel Agents in Aggressive B-Cell Lymphoma: Highlights From SOHO 2021
Authors: Valla, PharmD, BCOP Kelly
Published: January 2022

Kelly Valla, PharmD, BCOP, of Winship Cancer Institute of Emory University, describes the clinical implications of novel agents for aggressive B-cell lymphoma, which were described at a session presented by Gilles Salles, MD, PhD, of Memorial Sloan Kettering Cancer Center, at the 2021 SOHO Annual Meeting.
Taking a Diversity, Equity, Inclusion & Accessibility Lens to Engineering Librarian Job Postings: Recommendations from an Analysis of Postings from 2018 and 2019
Authors: Thielen Joanna , Marsolek Wanda
Published: January 2022

Objective: While diversity, equity, inclusion, and accessibility (DEIA) principles and practices have been incorporated into much of academic librarianship, there has been less focus on the job postings. Methods: In order to quantify ways in which DEIA is being integrated into job postings, we analyzed 48 job positions for engineering librarians posted in 2018 and 2019 via deductive thematic analysis, looking for trends in salary and qualifications related to education and academic or professional experience. Results: Of postings that listed a quantitative salary value, salary ranged from $45,000 to $81,606; the median was $60,750. However, only 33% (n = 16) of positions listed a quantitative salary value. For educational qualifications, we found that 98% of job postings (n = 47) listed a Master’s in Library and Information Science (MLIS) as a required qualification; however, 34% of these postings (n = 16) would accept an equivalent degree in lieu of the MLIS. Additionally, 73% (n = 35) of positions sought candidates with an MLIS and another degree; 91% of these positions (n = 32) wanted the additional degree to be in a science, technology, engineering, and mathematics discipline. For academic or professional experience, 56% of positions (n = 27) sought candidates with previous academic library experience. Conclusions: Using this data, we provide actionable recommendations on how to incorporate DEIA principles into any academic librarian job posting. Our study provides quantitative data and evidence-based recommendations that can be used to make DEIA an integral part of the job postings in academic librarianship.
A Meta-Review of Servant Leadership: Construct, Correlates, and the Process
Authors: Chaudhry Anjali , Cao Xiaoyun , Liden Robert C. , Point Sébastien , Vidyarthi Prajya R.
Published: January 2022

The goal of this article is to present qualitative and quantitative reviews of servant leadership literature since its formal inception in 1970. Summarizing previous studies, we theorized and explored issues concerning the conception and relevance of servant leadership, the merits of varied measurements, issues concerning construct dimensionality, and the potential effects of national culture on the relationship between servant leadership and its correlates. We developed theory to distinguish servant leadership from competing leadership theories of transformational leadership and leader-member exchange (LMX) theory and examined the direct and the incremental influence of servant leadership on individual and unit-level outcomes. To consolidate extant research and to guide future theory development we tested a mediational process model linking servant leadership to outcomes. Meta-analytic results supported distinctiveness of servant leadership, showed effects of servant leadership on individual-level and unit-level outcomes, and supported theorized mediating effects of trust and fairness perceptions in the relationship.
Jeunes au travail en France : en quête d’une place
Authors: Gaviria Sandra , Mélo David
Published: January 2022

It is often said, especially by those in management, that young people lack commitment to work. Based
on a recent study conducted in France involving interviews with 60 individuals under the age of 30 who
have obtained at least a secondary school diploma (baccalauréat) and who are neither “high fliers” nor
particularly vulnerable, this article sets out to assess the truth of such claims. Drawing and building on
already published research, the analysis pushes beyond conventional ideas to provide a more
comprehensive view of youth attitudes towards work. It therefore aims to gain a deeper understanding
of young people’s concrete relationships with work by examining their work experiences and career
strategies. The interview data show that young people are prepared to work within a hierarchical
management structure and, on occasion, to tolerate difficult working conditions and unfavourable terms
of employment. All things considered, they appear interested in finding a place in the professional world,
especially insofar as work is commonly seen as a pathway to autonomy.
Exposition à la violence conjugale : regards de jeunes adultes sur leur parcours de vie
Authors: Dumont Annie , Lessard Geneviève
Published: January 2022

Population surveys involving North American youth suggest that between 14% and 19% of young people
are likely to have been exposed to intimate partner violence during childhood. Such violence and its
aftermath can have a significant impact on the life course trajectories of young adults, although this
impact can also be tempered or aggravated by other life experiences. Based on semi-structured
interviews with 35 young adults between the ages of 18 and 25 who were exposed to intimate partner
violence in childhood or adolescence, this qualitative study aims to learn more about the connections
between such exposure and other life course experiences. An adapted Life History Calendar was used
during data collection. In addition to highlighting the superposition of study participants’ life course
trajectories, analysis of the data also demonstrates the importance of agency in determining how these
trajectories influence each other. Studies on exposure to intimate partner violence therefore need to
consider not only the life contexts of the young people involved, but also the meaning these individuals
ascribe to their experiences and to the actions they decide to take.
“French element” in the Russian art culture of the mid XVIII century
Authors: Nikulina Viktoriya Vladimirovna
Published: January 2022

The subject of this research is the reflection of Russian realities of the mid XVIII century in cultural sphere. The article touches upon the problem of cross-cultural communication between Russia and France in the XVIII century: the theme of “French presence” in the Russian art and theater culture of the first half and the middle of the XVIII century. The acquired results elucidate the characteristic features of the relations between French and Russian people during this period. The research was conducted with consideration of the unity of internal and external, subjective and objective factors within the framework of the cultural-historical process. The conclusions were made leaning on the analysis of the entire range of sources use and existing research traditions. The article reveals the contribution of the French representatives of art and culture while their stay in Russia, as well as describes the forms and manifestations of their activity that in prospect affected the image of Russia. The author believes that working at the Russian Court, the French representatives imposed the vision of their country on Russia, transforming the Russian images in the French spirit. The presented materials are valuable for the study of cross-cultural communication between Russia and France in the XVIII century. This article is important and relevant in the conditions of constantly developing cultural dialogue and determination of the new vectors of cooperation between the countries.
Isolated attosecond pulse generation from helium atom irradiated by a three-color laser pulse
Authors: Chen Gao ,   School of Physics, Changchun University of Science and Technology, Changchun 130022, China
Published: January 2022

Isolated attosecond pulses enables the studying and controlling of ultrafast electron processes in atoms and molecules. High-order harmonic generation (HHG) is the most promising way to generate such pulses, benefiting from the broad plateau structure of the typical HHG spectrum. We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom in a three-color laser field, which is synthesized by 16 fs/1600 nm, 15 fs/1100 nm and 5 fs/800 nm pulse laser. Compared with harmonic spectrum generated by a two-color laser field synthesized by 16 fs/1600 nm and 15 fs/1100 nm, the harmonic spectrum generated from the synthesized three-color field exhibits high conversion efficiency and broadband supercontinuum characteristics. The continuous spectrum range covers from 230th to 690th harmonics, and the generation of 128 attosecond isolated short pulses with higher intensity is realized after Fourier transform. This result is attributable to the fact that the synthesized three-color electric field exhibits high-intensity and few-cycle mid-infrared femtosecond pulse laser characteristics, which can effectively control atomic ionization and recombination occurring within an effective optical period of the mid-infrared femtosecond pulse. This scheme solves the problems faced by the current femtosecond pulse laser technology, i.e. the few-cycle mid-infrared femtosecond pulse laser cannot have both carrier envelope phase stability and high power output.
Theoretical calculation of fiber cavity coupling silicon carbide membrance
Authors: Zhou Ji-Yang , Li Qiang , Xu Jin-Shi , Li Chuan-Feng , Guo Guang-Can ,   CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China,   CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China,   State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
Published: January 2022

Single spin color centers in solid materials are one of the promising candidates for quantum information processing, and attract a great deal of interest. Nowadays, single spin color centers in silicon carbide, such as divacancies and silicon vacancies have been developed rapidly, because they not only have similar properties of the NV centers in diamond, but also possess infrared fluorescence that is more favorable for transmission in optical fiber. However, these centers possess week fluorescence with broad spectrum, which prevents some key technologies from being put into practical application, such as quantum key distribution, photon-spin entanglement, spin-spin entanglement and quantum sensing. Therefore, optical resonator is very suitable for coupling centers to filter their spectrum and enhance the fluorescence by Purcell effect. It is very advantageous to use the fiber end face as cavity mirrors, thereby the fiber can provide small cavity volume corresponding to a large enhancement in spin color centers, and collect the fluorescence in cavity simultaneously, which has no extra loss in comparison with other collection methods. In this work, the properties and performance of fiber Fabry-Perot cavity coupling silicon carbide membrane are mainly studied through theoretical calculation. Firstly, some parameters are optimized such as membrane roughness and mirror reflection by calculating the mode of the fiber cavity and enhancing the color centers coupling into the cavity, then analyzing the properties of different modes in cavity, the enhancement effect on cavity coupling color centers, and other relevant factors affecting the cavity coupling color centers. Next, the influences of dominated factor and vibration on the properties of the cavity, the enhancement and outcoupling of centers coupled into the cavity are investigated, and finally the optimal outcoupling efficiency corresponding to different vibration intensities is obtained. These results give direct guidance for the further experimental design and direction for optimization of the fiber cavity coupling color centers.
Wave propagation characteristics in porous medium containing a solid in pores
Authors: Liu Lin , Zhang Xiu-Mei , Wang Xiu-Ming ,   State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China,   University of Chinese Academy of Sciences, Beijing 100149, China,   Beijing Engineering Research Center of Sea Deep Drilling and Exploration, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China
Published: January 2022

Aiming at the propagation characteristics of acoustic waves in a porous medium containing a solid in pores, the equations of motion and constitutive relation are deducted in the case of two-solid porous media. The frequency dispersion and attenuation characteristics of wave modes are analyzed by a plane wave analysis. In addition, based on the first-order velocity-stress equations, the time-splitting high-order staggered-grid finite-difference algorithm is proposed and constructed for understanding wave propagation mechanisms in such a medium, where the time-splitting method is used to solve the stiffness problem in the first-order velocity-stress equations. The generation mechanisms and energy distributions of different kinds of waves are investigated in detail. In particular, the influences of the friction coefficient between solid grains and pore solid as well as frequency on wave propagation are analyzed. It can be known from the results of plane wave analysis that there are two compression waves (P1 and P2) and two shear waves (S1 and S2) in a porous medium containing a solid in pores. The attenuations of P2 wave and S2 wave are much larger than those of P1 wave and S1 wave. This is due to the friction between the solid grains and the pore solid. The results show that our proposed numerical simulation algorithm can effectively solve the problem of stiffness in the velocity-stress equations, with high accuracy. The excitation mechanisms of the four wave modes are clearly revealed by the simulation results. The P1 wave and S1 wave propagate primarily in the solid grain frame, while P2 wave and S2 wave are concentrated mainly in the pore solid, which are caused by the relative motion between the solid grains and the pore solid. Besides, it should be pointed out that the wave diffusions of the P2 wave and S2 wave are influenced by the friction coefficient between solid grains and pore solid. The existence of friction coefficient between two solids makes P2 wave and S2 wave attenuate to a certain extent at high frequency, but the attenuation is much smaller than that at low frequency. This is the reason why it is difficult to observe the slow waves in practice. However, because the slow waves also carry some energy, it may not be ignored in the studying of the energy attenuation of acoustic waves in porous media.
Optimization of distribution of permanent magnetrings for Faraday rotation spectroscopy
Authors: Jia Feng-Ming , Mei Jiao-Xu , Wang Rui-Feng , Cheng Gang , Liu Kun , Gao Xiao-Ming ,   Anhui Institute of Optics and Fine Mechanics, Hefei Institute of Physical Science, Chinese Academy of Sciences, Hefei 230031, China,   University of Science and Technology of China, Hefei 230026, China,   State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science and Technology, Huainan 232001, China
Published: January 2022

Faraday rotation spectroscopy (FRS) is generally used to detect the concentrations of various paramagnetic trace gases because of its high detection sensitivity, zero background noise and the ability to get rid of the interference of diamagnetic materials effectively. In most of FRS technologies, the used electromagnetic fields are produced by coils, thereby triggering off some problems such as high energy consumption and excessive heat generation. Thus the modeling and the simulation study of spatial magnetic field distribution based on the combined ring permanent magnets are carried out to establish an axially distributed homogeneous magnetic field and provide a permanent magnet-based homogeneous magnetic field along the optical axis for FRS measurement. In this simulation, the method of finite element mesh division is adopted based on basic electromagnetic relationship in Maxwell equations. By the simulation study of the magnetic field distribution of the actual Nd-Fe-B permanent magnet magnetic ring array, the physical model proves to be reliable. Basically, three methods of optimizing the permanent magnetic ring arrays. i.e. single ideal value optimization method, the multi-part single objective optimization method, and the gradient optimization method, are proposed. The single ideal value optimization method and the multiple ideal value optimization method are used to realize the optimization of magnets. However, by analyzing the two methods, it is clear that compared with the single ideal value optimization method, the multiple ideal value optimization method in which the whole region is divided into several small parts can achieve good uniformity of permanent magnet array. In this way, the third method, i.e. the gradient optimization method is used to realize the construction of a homogeneous magnetic field with a uniform central axis magnetic flux density distribution used for FRS. Finally, the standard magnetic field uniformity for measuring the quality of magnet field is suggested, and through the calculation and evaluation of the magnetic field uniformity, the optimization effects of different optimization methods are analyzed and compared with each other. And the final results about realizing a homogeneous magnetic field provide a reference for developing the FRS equipment based on permanent magnets.
Absolute distance measurement using cross correlation interferometer with a repetition rate multiplication frequency comb
Authors: Liang Xu , Lin Jia-Rui , Wu Teng-Fei , Zhao Hui , Zhu Ji-Gui ,   State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China
Published: January 2022

In this paper, the Fabry-Perot etalon is used to multiply the repetition rate of the fiber optical frequency comb. The repetition rate is amplified from 250 MHz to 10 GHz, and the corresponding pulse interval is reduced from 1200 mm to 30 mm. For the pulse cross correlation ranging method, the repetition rate multiplication can greatly reduce the length requirement of the scanning reference arm. We analyze in detail the principle of cross correlation interferometry based on repetition rate multiplication frequency comb. A numerical mode of the function is comprehensively established. The basic parameters of optical source and Fabry-Perot cavity for the influence of filtered optical spectrum and cross correlation fringe are analyzed through the numerical simulation. The multiplied frequency comb is utilized for absolute ranging with the help of a pulse cross correlation method. By comparison, our result differs from the result obtained by a conventional counting interferometer only by 4 μm for distances up to 210 mm.
Wavelet transform based method of measuring multi-frequency electrostatic force microscopy dynamic process
Authors: Wang Jian-Hai , Qian Jian-Qiang , Dou Zhi-Peng , Lin Rui , Xu Ze-Yu , Cheng Peng , Wang Cheng , Li Lei , Li Ying-Zi ,   School of Physics, Beihang University, Beijing 100191, China
Published: January 2022

Electrostatic force microscopy (EFM) has high sensitivity and lateral resolution, and it is widely used to measure the electrostatic properties of new energy materials. The time-resolved electrostatic force microscope technology is used to measure the dynamic electrical properties of materials, pump detection method commonly used in this technology has problems such as complex equipment, high cost, and uncertainty in the measurement. In this work the method of directly measuring the time domain is adopted. This method reduces the complexity of measurement. By using the multi-frequency or high-frequency excitation method, the simultaneous measurement of multiple EFM parameters and the improvement of time resolution can be achieved, reaching a time resolution of microseconds, and by applying wavelet transform to the tip signal obtained by the measurement the dynamic electrical properties of the materials can be extracted. Applying this technology to simulation experiments, it is possible to measure the dynamic potential changes and the characteristic time parameter of ion movement in the microsecond-level electrical dynamic process of the simulated battery materials.
Interaction-modulated tunneling dynamics of a mixture of Bose-Fermi superfluid
Authors: Xu Hong-Ping , He Zhen-Zhen , Yu Zi-Fa , Gao Ji-Ming ,   College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China
Published: January 2022

In this paper, we study the interaction-modulated tunneling dynamics of a Bose-Fermi superfluid mixture, where a Bose-Einstein condensate (BEC) with weak repulsive interaction is confined in a symmetric deep double-well potential and an equally populated two-component Fermi gas in a harmonic potential symmetrically is positioned in the center of the double-well potential. The tunneling between the two wells is modulated by fermions trapped in a harmonic potential. When the temperature is adequately low and the bosonic particle number is adequately large, we can employ the mean-field theory to describe the evolution of the BEC in the double-well potential through the time-dependent Gross-Pitaevskii equation. For the Fermi gas in the harmonic potential trap, we consider the case where the inter-fermion interaction is tuned on the deep Bose-Einstein condensate of the inter-fermion Feshbach resonance, where two fermions of spin-up and spin-down form a two-body bound state. Within the regime, the Fermi gas is well described by a condensate of these fermionic dimers, and hence can be simulated as well by a Gross-Pitaevskii equation of dimers. The inter-species interactions couple the dynamics of the two species, which results in interesting features in the tunneling oscillations. The dynamic equations of the BEC in the double-well potential is described by a two-mode approximation. Coupling it with time-dependent Gross-Pitaevskii equation of the harmonically potential trapped molecular BEC, we numerically investigate the dynamical evolution of the Boson-Fermi hybrid system under different initial conditions. It is found that the interaction among fermions in a harmonic potential leads to strong non-linearity in the oscillations of the bosons in the double-well potential and enriches the tunneling dynamics of the bosons. Especially, it strengthens macroscopic quantum self-trapping. And the macroscopic quantum self-trapping can be expressed in three forms: the phase tends to be negative and monotonically decreases with time, the phase evolves with time, and the phase tends to be positive and increases monotonically with time. This means that it is possible the tunneling dynamics of the BEC in double-well potential is adjustable. Our results can be verified experimentally in a Bose-Fermi superfluid mixture by varying different interaction parameters via Feshbach resonance and confinement-induced resonance.
Analysis and optimization of few-mode fibers with low differential mode group delay by variational method
Authors: Wang Jian , Wu Chong-Qing ,   Institute of Optical Information, Key Laboratory of Luminescence and Optical Information, Ministry of Education, Beijing Jiaotong University, Beijing 100044, China
Published: January 2022

Mode-division multiplexing (MDM) technology based on few-mode fibers (FMFs) is the current research hotspot of optical fiber communication system because of its ability to increase the transmission capacity several times. When the number of multiplexed modes is large, the crosstalk between modes can be removed by multiple input multiple output digital signal processing algorithm at the receiving end. The larger the differential mode group delay (DMGD, \begin{document}$ \tau_{\rm DMGD} $\end{document}), the more complex the algorithm is. Therefore, in order to reduce the complexity of the receiver, it is necessary to use FMFs with low DMGD. The variational method is proposed to analyze any FMFs with higher refractive index of core than that of cladding. The analytical formula of the fundamental mode size, the normalized propagation constant for each of all guided modes, and DMGD relative to the fundamental mode are derived. Moreover, their relationship with the normalized frequency and other fiber manufacturing parameters are given. On this basis, the graded-index FMFs are studied, and the fiber parameters are optimized. The optimization parameters are the difference between the maximum core refractive index and cladding refractive index n1 – n2 = 0.01, the core radius a = 14 μm, and the paramenter of refractive index distribution α = 1.975. In the optimized FMF, 6 LP modes can be guided and |\begin{document}$ \tau_{\rm DMGD} $\end{document}| is less than 15 ps/km within the C band and L band. In the end, the effects of the fiber manufacturing errors on DMGD are discussed.
Preparation of CsPbBr3 perovskite nanocrystals with controllable morphology and in-situ photoluminescence of formation kinetics
Authors: Chen Xue-Lian , Ju Bo , Jiao Hu-Po , Li Yan , Zhong Yu-Jie ,   School of Materials Science and Engineering, Xi’an Shiyou University, Xi’an 710065, China
Published: January 2022

Cesium-lead halide perovskite nanocrystals (CsPbX3 (X = Br, Cl, I) PNCs) have become ideal luminescent materials for wide color gamut display devices, white LED lighting and high-efficiency solar cells, due to adjustable energy band gap, high fluorescence quantum yield, narrow fluorescence emission peak, and ultra-high defect tolerance. The preparation of CsPbX3 PNCs with controllable size and morphology is a prerequisite for obtaining efficient and stable photovoltaic/photovoltaic devices. In this report, the CsPbBr3 PNCs with different shapes are prepared by adding different concentrations of dodecanedioic acid (DDDA) ligands at room temperature through using ligand-assisted reprecipitation method. Utilizing the X-ray diffractometer, transmission electron microscopy, ultraviolet spectrophotometer, fluorescence spectrometers (PL), the phase structure, microstructure and optical properties of the nanocrystals are investigated. The results show that the presence of DDDA ligands have no influence on the phase structure of nanocrystal products, they all present a cubic phase structure. Surprisingly, the morphology of the nanocrystals gradually transforms from nanocubes into nanoplatelets with ～5 layers in thickness as the concentration of DDDA increases. In addition, the PL spectrum shows a significant blue shift from 509 nm to 478 nm. By using the in-situ homemade PL device with ultra-high time resolution (～100 ms), the real-time monitoring PL spectra of nanocrystals in the formation process are measured. The results demonstrate that nanocrystals undergo rapid nucleation and focusing of size distribution growth to generate nanocubes in the absence of DDDA ligand. When the DDDA ligand is present, nanocrystals are mainly nanoplatelets in the early growth stage due to the decelerated reaction. As the reaction proceeds, nanocubes can emerge and grow gradually while the nanoplatelets disappear when the concentrations of DDDA ligands are 25% and 50%. As the concentration is further increased to 75%, almost nanoplatelets could be formed after the nucleation stage and growth stage. Unexpectedly, preformed nanoplatelets are unstable for the prolonged reaction time as a result of the high surface energy, and they will eventually transform into isotropic nanocubes through dissolution-recrystallization pathway, indicating that the process in the later stage is controlled mainly by thermodynamics. Our findings offer an efficient strategy to synthesize the perovskite nanocrystals with controllable size and morphology.
“Quantum memory” quantum computers and noiseless phton echoes
Authors: Zhou Zong-Quan ,   CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China
Published: January 2022

One of the most important applications of quantum computing is to crack classical cryptosystem. Previous studies showed that the number of qubits required to crack the widely used 2048-bit RSA cipher is about 20 million, which is far beyond the current technology for quantum computing. Recently, É. Gouzien and N. Sangouard of the French Alternative Energies and Atomic Energy Commission proposed a quantum computing architecture based on a two-dimensional grid of superconducting qubits and a three-dimensional multimode quantum memory. They showed that only 13k qubits are required to crack a 2048-bit RSA integer with the help of a long-lived quantum memory with 28 million spatial modes and 45 temporal modes. Their results clearly demonstrate the values of quantum memories in quantum computing and provide an alternative approach for building practically useful quantum computers. Quantum computers require quantum memories to work at microwave band, which remains an outstanding challenge. Based on a detailed analysis of atomic radiations during the quantum storage process, we recently proposed a noiseless-photon-echo protocol which can successfully eliminate the spontaneous emission noise in photon echoes. This protocol is expected to further enable microwave quantum storage and the construction of “quantum memory” quantum computers.
Entanglement robustness of continuous variable Einstein-Podolsky-Rosen-entangled state distributed over optical fiber channel
Authors: Zhao Hao , Feng Jin-Xia , Sun Jing-Ke , Li Yuan-Ji , Zhang Kuan-Shou ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China,   Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
Published: January 2022

Einstein-Podolsky-Rosen (EPR)-entangled state light field at a telecommunication wavelength of 1.5 μm is an important quantum source for realizing the continuous variable quantum information processing and some quantum protocols over optical fiber channel. When the EPR-entangled state light field is distributed over the optical fiber channel, the disentanglement is always present because the the EPR entangled state interacts with the fiber channel. It affects the performance of quantum information processing. In this paper, we theoretically calculate the positive partial transposition (PPT) of the entangled state distributed over the optical fiber channel in the single-channel and dual-channel distribution scheme, respectively. Three types of initial entangled light field are considered and analyzed, they being an initial EPR entangled state, an EPR entangled state with asymmetric quadratures, and an EPR entangled state with asymmetric modes. Furthermore, the influence of the extra noise in the optical fiber on the transmission distance of EPR entangled state over the optical fiber channel is investigated. In the single-channel scheme or dual-channel scheme, the extra noise in the optical fiber channel leads the entangled state light field to be disentangled, and the transmission distance of EPR entangled state over the optical fiber channel to decrease rapidly with the increase of the extra noise. For maintaining the robustness of EPR entangled states in lossy optical fiber channels, the dual-channel scheme has more stringent requirements for the correlation quadrature symmetry and purity of the initial entangled state than the single-channel scheme. In the single fiber noise channel scheme, the maximum transmission distance and the robustness of the EPR entangled states with asymmetric modes are not sensitive to the asymmetry between modes. The change of asymmetry between modes does not lead to being disentangled. The maximum transmission distance does not change either. However, the decrease of asymmetry between modes results in the disentanglement in the double fiber noise channels’ scheme. The maximum transmission distance is reduced and the sudden death occurs to the entanglement. The present results will lay a foundation for continuous variables quantum information processing based on optical fiber, such as realizing continuous variables quantum communication over optical fiber and constructing metropolitan quantum network over optical fiber.