Spatial Field Distribution Research Articles

Collective Coupling of 3D Confined Optical Modes in Monolithic Twin Microtube Cavities Formed by Nanomembrane Origami.

We report the monolithic fabrication of twin microtube cavities by a nanomembrane origami method for achieving collective coupling of 3D confined optical modes. Owing to the well-aligned twin geometries, two sets of 3D confined optical modes in twin microtubes are spectrally and spatially matched, by which both the fundamental and higher-order axial modes are respectively coupled with each other. Multiple groups of the coupling modes provide multiple effective channels for energy exchange between coupled microcavities illustrated by the measured spatial optical field distributions. The spectral anticrossing and changing-over features of each group of coupled modes are revealed in experiments and calculations, indicating the occurrence of strong coupling. In addition, the simulated 3D mode profiles of twin microcavities confirm the collective strong coupling behavior, which shows good agreement with experiments. The collective coupling of 3D confined resonant modes promises broad applications in multichannel optical signal processing, nanophotonics, and 3D non-Hermitian systems.

Computational modeling of capillary perfusion and gas exchange in alveolar tissue

Gas exchange is an essential function of the respiratory system that couples fundamentally with perfusion in respiratory alveoli. Current mathematical formulations and computational models of these two phenomena rely on one-dimensional approximations that neglect the intricate volumetric microstructure of alveolar structures. In this work, we introduce a coupled three-dimensional computational model of pulmonary capillary perfusion and gas exchange that conforms to alveolar morphology. To this end, we derive non-linear partial differential equations and boundary conditions from physical principles that govern the behavior of blood and gases in arbitrary alveolar domains. We numerically solve the resulting formulation by proposing and implementing a non-linear finite-element scheme. Further, we carry out several numerical experiments to validate our model against one-dimensional simulations and demonstrate its applicability to morphologically-inspired geometries. Numerical simulations show that our model predicts blood pressure drops and blood velocities expected in the pulmonary capillaries. Moreover, we replicate partial pressure dynamics of oxygen and carbon dioxide reported in previous studies. This overall behavior is also observed in three-dimensional alveolar geometries, providing more detail associated with the spatial distribution of fields of interest and the influence of the shape of the domain. We envision that this model opens the door for enhanced in silico studies of gas exchange and perfusion on realistic geometries, coupled models of respiratory mechanics and gas exchange, and multi-scale analysis of lung function; furthering our understanding of lung physiology and pathology. Codes are available at https://github.com/comp-medicine-uc/num-model-alv-perfusion-gas-exchange.

Phase-field approach to evolution and interaction of twins in single crystal magnesium

Crack initiation and propagation as well as abrupt occurrence of twinning are challenging fracture problems where the transient phase-field approach is proven to be useful. Early-stage twinning growth and interactions are in focus herein for a magnesium single crystal at the nanometer length-scale. We demonstrate a basic methodology in order to determine the mobility parameter that steers the kinetics of phase-field propagation. The concept is to use already existing molecular dynamics simulations and analytical solutions in order to set the mobility parameter correctly. In this way, we exercise the model for gaining new insights into growth of twin morphologies, temporally-evolving spatial distribution of the shear stress field in the vicinity of the nanotwin, multi-twin, and twin-defect interactions. Overall, this research addresses gaps in our fundamental understanding of twin growth, while providing motivation for future discoveries in twin evolution and their effect on next-generation material performance and design.

The Distribution of UV Radiation Field in the Molecular Clouds of Gould Belt

The distribution of ultraviolet (UV) radiation field provides critical constraints on the physical environments of molecular clouds. Within 1 kpc of our solar system and fostering protostars of different masses, the giant molecular clouds in the Gould Belt present an excellent opportunity to resolve the UV field structure in star-forming regions. We performed spectral energy distribution (SED) fitting of the archival data from the Herschel Gould Belt Survey (HGBS). Dust radiative transfer analysis with the DUSTY code was applied to 23 regions in 14 molecular complexes of the Gould Belt, resulting in the spatial distribution of the radiation field in these regions. For 10 of 15 regions with independent measurements of star formation rate, their star formation rate and UV radiation intensity largely conform to a linear correlation found in previous studies.

SuperScreen: An open-source package for simulating the magnetic response of two-dimensional superconducting devices

Quantitative understanding of the spatial distribution of magnetic fields and Meissner screening currents in two-dimensional (2D) superconductors and mesoscopic thin film superconducting devices is critical to interpreting the results of magnetic measurements of such systems. Here, we introduce SuperScreen, an open-source Python package for simulating the response of 2D superconductors to trapped flux and applied time-independent or quasi-DC magnetic fields for any value of the effective magnetic penetration depth, Λ. Given an applied magnetic field, SuperScreen solves the 2D London equation using an efficient matrix inversion method [1,2] to obtain the Meissner currents and magnetic fields in and around structures composed of one or more superconducting thin films of arbitrary geometry. SuperScreen can be used to model screening effects and calculate self- and mutual-inductance in thin film superconducting devices. Program summaryProgram title: SuperScreenCPC Library link to program files:https://doi.org/10.17632/bds57s4c83.1Developer's repository link:http://www.github.com/loganbvh/superscreenCode Ocean capsule:https://codeocean.com/capsule/5305996Licensing provisions: MIT licenseProgramming language: PythonNature of problem:SuperScreen solves for Meissner screening currents in structures composed of 2D or thin film superconductors in the presence of an applied magnetic field, pinned vortices, and trapped flux.Solution method: This package solves the 2D London equation for superconducting thin films using a matrix inversion method [1,2].

Ship path planning based on safety potential field in inland rivers

With the growth of the shipping trade, inland water traffic is getting more prosperous than ever. Meanwhile, the shipping risk in inland rivers increases gradually. In this paper, a path planning model based on the safety potential field theory is proposed for inland ships from the perspective of navigation risk. Firstly, different navigation risks for inland ships are defined based on the safety potential field theory for three types of obstacles including static obstacles, dynamic obstacles and waterway bank walls. Secondly, different potential fields are used to quantify the different navigation risks. Then, the superposition field is formulated by summing the above three potential fields, and the spatial distribution of the safety potential field is obtained. Finally, the minimum navigation risk points on each cross section, which is perpendicular to the navigation direction, are selected to formulate the optimal path. In addition, a case study of overtaking scenario is conducted using the proposed model. The simulation results show that the model can effectively describe the navigation risk, which could be used to generate the optimal path for ships in inland rivers. This research is of great importance for ship navigation in inland rivers.

Non-Contact And Non-Steady Rheo-Optical Measurement Of Hydrodynamic Stress Fields Inside A Cylindrical Tube

For measuring non-contact and non-steady rheo-optical measurement of hydrodynamic stress fields, we utilize a high-speed polarization camera that captures an unsteady phase-retardation field. It is known that the retardation has a proportional relationship to secondary principal stress difference. A solution of sodium iodide including crystal polymers (CNCs, cellulose nano crystals) was used as the working fluid. We have successfully measured the retardation induced by flow birefringence of CNCs without compromising the Newtonian fluid properties of the solution. In this paper, we propose a visualization technique for the retardation field of fluid in a cylindrical glass tube that incorporates index matching and discuss its comparison with the spatial intensity distribution of theoretical hydrodynamic stress field. Experimental results show that the retardation increases with an increase in flow rate. In addition, by utilizing the orientation angle data measured with the high-speed polarization camera, the vector field of principal stress difference is visualized, which is suggested to be useful for confirming the effects of direction of stresses. To investigate whether the measured retardation filed agrees with the theoretical secondary principal stress difference, the spatial intensity distribution of the two was compared. The overall trend agrees well while the retardation at the center of the tube is different, possibly owing to the effect of structure-induced retardation due to self-assembly of CNCs. The structure-induced retardation data were obtained by a combined measurement of a rotational rheometer and the high-speed polarization camera. As a result, the theoretical secondary principal stress difference distribution with considering structure-induced retardation showed better agreement with the retardation field than the case without considering it.

How the Number and Distance of Electrodes Change the Induced Electric Field in the Cortex during Multichannel tDCS.

Multichannel transcranial direct current stimulation (tDCS) is a promising approach to target neuromodulation of neural networks by making use of variable number of electrodes and distances to facilitate/inhibit specific connectivity patterns. Optimization of the electric field (EF) spatial distribution through computational models can provide a more accurate definition of the stimulation settings that are more effective. In this study, we investigate the effect of increasing the number of cathodes around a central anode placed over the target. We demonstrate that anode-cathode distance has the largest influence in the EF and using more than 3 cathodes did not result in considerable changes in the EF magnitude and direction. This could be relevant for simultaneous tDCS-electroencephalography (EEG) applications, by saving electrode positions for EEG acquisition. Clinical Relevance- This study demonstrates that distance between electrodes is more relevant than electrode number in determining the electric field distribution, and that a highly-focused stimulation can be equally effective with fewer electrodes.

Development of Self-Discharge Point Visualization Technique inside Lithium-Ion Battery

With the rapid spread of electric vehicles and hybrid vehicles in recent years, the energy density of lithium-ion batteries, which are the power sources of them, tends to increase.This means that the risk of ignition is further increased as represented by some fire accident case of an EV vehicle that had taken long time to extinguish, and thus eventually makes the requirement of safety management in the battery manufacturing process be expected stricter.To prevent ignition due to internal short circuit of battery, and eliminate a short-life battery product, we have been developing a technology to non-destructively visualize the self-discharged part inside the storage battery. In this technology, on the first, electric current is applied to the battery from external power source, and the leakage magnetic field that generated due to the internal electric current in the battery is sensed on outside of the battery. Next, the electric current density distribution inside the battery can be reconstructed and visualized three-dimensionally by using the spatial distribution of the measured magnetic field as the boundary condition and solving the inverse problem analytically.To measure leakage magnetic field with high sensitivity, it is necessary to take steps against disturbances as like DC magnetic field derived from magnetism or magnetic materials (often Ni is used for the collector foil), and AC magnetic fields generated from external circuits. In this method, two steps are used in combination for detection sensitivity of the pico-tesla order;(1) An AC current is applied to the battery, and the AC magnetic field generated in synchronization is phase-detected.(2) Install a small coil near the sensor and generate a DC cancel magnetic field by feedback control.By this method, it is possible to detect only the AC magnetic field corresponding to the applied current with high sensitivity in the linear operating region of the magnetic sensor. In actual detection of the leakage magnetic field, a DC voltage that balances with the output voltage of the battery is applied to the AC output of the AC current source connected to the battery so that the SOC of the storage battery is kept constant voltage. In addition to the above, the frequency of the AC output is usually set to 10 Hz or less to avoid the shielding effects of electrodes and the metallic package of the battery.By these steps and scanning two-dimensional of magnetic sensors or using a sensor array in which magnetic sensors are arranged two-dimensionally, the spatial distribution of the two-dimensional magnetic field outside the storage battery can be obtained. Since the sensor detects only one direction component of magnetic field, changing the direction of the sensor by 90 ° is needed.On data processing, some realistic structural assumptions are required to solve the inverse problem.(1) Defining that the plane parallel to the storage battery electrode plane is the XY plane, the Z component of the magnetic field vector is zero around the battery, and only X component and Y component remains as magnetic field vector components generated from internal current of the battery.(2) The thickness of the battery is sufficiently smaller than the size of the battery in the plane direction, that is, the three-dimensional current in the battery is confined in the thin two-dimensional plane.In the first step of the reconstruction, under the fact of (1), Laplace's equation is analytically solved in the "free space from the measurement surface to just above the electrode surface in the battery, without a magnetic source", and derive the two-dimensional magnetic field distribution directly above the electrode surface. In the next step, it is possible to obtain a three-dimensional current distribution inside the battery by analytically solving the Poisson-type equation and the electric current continuity equation under the realistic structural assumption of (2) with first calculation result as the boundary condition.In the presentation, we will introduce in detail the experiment and data processing for identifying the self-discharge point with this technology, including examples of visualizing the magnetic field distribution and current density distribution inside a battery after aging test.

Asymmetric propagation mechanism of hydraulic fracture networks in continental reservoirs

AbstractHydraulic fracturing technology is relatively mature in North America, but under complex geological conditions, such as those in China, the application of this technology still faces great challenges. At present, techniques for the numerical simulation of hydraulic fracture networks are mainly based on the prediction of the fracture half-height and half-length, which cannot capture the heterogeneity of continental low-permeability sandstone reservoirs in China and the distribution of the asymmetric hydraulic fracture network present in them. Therefore, determining the asymmetric propagation mechanism of hydraulic fracture networks is very important for improving the recovery rates of continental reservoirs. In this paper, taking the Ordos Basin in China as an example, the spatial distribution of the stress field of a heterogeneous continental reservoir is precisely predicted by reservoir mechanical heterogeneity modeling. By using a microseismic monitoring method, the 3-D morphology of the hydraulic fracture network is determined. Through the coupling of multisource data, the frequency distributions of the determined in situ stress magnitudes in different hydraulic fracturing stages are obtained. The propagation direction of the hydraulic fracture network changes under the control of the horizontal stress difference (Δσ) and the presence of natural fractures. The smaller Δσ is, the greater the deflection of the hydraulic fracture propagation direction. The asymmetric propagation of these fractures is related to the frequency distribution of Δσ. As the frequency of Δσ approaches a normal distribution, the two wings of the hydraulic fracture network become basically equal in length, and as Δσ deviates more from a normal distribution, the difference between the two wings of the hydraulic fracture network increases. These research results will provide new insight for modeling, exploring, and developing continental reservoirs.

3D Corona Discharge Model and Its Use in the Presence of Wind During a Thunderstorm

In this study, the authors developed a three-dimensional (3D) numerical model for the diffusion of positive corona charges based on a 2D model with a uniform grid to explore the characteristics of corona discharge at a building tip during a thunderstorm in the presence of wind. The variable-grid meshing method is used to solve the problems of implementing a large simulation domain for thunder clouds (kilometer-scale) and the minute calculations of corona discharge at the tip (centimeter scale) in the 3D numerical simulation. The proposed model has advantages in terms of the acquisition of the parameters of corona charges and the spatial distribution of the electric field (E-field) in the environment. We used positive corona discharge at the tip of a building under a negative thunderstorm, along with three wind fields (horizontal wind, updraft, and downdraft with wind speeds of 10 m/s) as an example. The presence of the wind increased the density of corona charges at the tip, where the horizontal wind was the most beneficial for its occurrence. Moreover, the characteristics of distortion of the electric field around the tip were significantly different, owing to the different directions of the wind. Downdraft led to the maximum enhancement in the E-field above the tip, and updraft prompted the minimum increase in it, by only 1.19 times. However, the opposite results were obtained for the enhancement in the spatial range of the charges: The updraft led to the greatest increase in it, and the downdraft caused the smallest. Corona charges had an apparent shielding effect on the E-field below the tip and can even change the polarity of the E-field in a small area close to it. The strongest shielding effect on the ground E-field occurred in the case of the downdraft, which decreased the E-field to 0.36 times compared with that without the corona charges. On the contrary, corona discharge had the weakest shielding ability on the ground when it met the updraft. The horizontal wind had the largest range of shielding on the ground, of up to 14,699.36 m2, while the updraft had the lowest, at only 6,170.91 m2.

Research on a Monte Carlo Simulation Method of Neutron Coded-Aperture Imaging

Pinhole imaging is an important test technique to obtain information on the spatial distribution of the radiation field in the target region and has been widely used in nuclear physics and inertial confinement fusion (ICF). Coded-aperture, able to maintain good resolution as well as enhancing signal strength, has become a more frequently used method than pinhole imaging in experimental studies. Thus, implementing Monte Carlo simulations of coded-aperture imaging will improve coded-aperture design, image reconstruction, and other related works. However, the current international mainstream Monte Carlo transport simulation programs do not possess the ability to directly simulate coded-aperture imaging. This paper develops a relatively complete coded-aperture imaging simulation function on the Neutron Photon Transport System code based on the next-event estimation method. With the application of Monte Carlo simulation techniques, such as variance reduction and rejection sampling, it is capable of simulating coded-aperture accurately, flexibly, and efficiently, including problems of multiple shapes and even irregular geometry. The results are consistent with combined pinhole imaging, and the computational efficiency has been improved significantly.

Synergistic enhancement of spin–phonon interaction in a hybrid system

An investigation to significantly enhance coupling to nitrogen−vacancy (NV) centers at a single-quanta level is of great interest to further explore its applications in quantum information processing (QIP). This study explores a joint scheme to further enhance NV–phonon coherent coupling with two methods working together in hybrid optomechanical systems. Both methods are mechanics-induced mode field coupling (MFC) that lead, respectively, to the modification of the spatial distribution of the optical field and the mechanical parametric amplification (MPA) realized by modulating the mechanical spring constant in time. With the joint assistance of MFC and MPA, the coherent coupling between the NV spin and one supermode of the mechanical resonators (MRs) can be further significantly enhanced with the rate ∝ n ¯ cav e r . Several potential applications are also discussed in this work. With the ultimate goal to enhance the coupling to NV spin at a single-quanta level, this attempt may provide a promising spin–phonon platform to implement more active control.

An electrical vortex air-assisted spraying system for improving droplet deposition on rice.

To improve droplet deposition rates at the base of rice, an electrical vortex air-assisted spraying system for small- and medium-sized high-clearance boom sprayers was developed. This system uses vortex airflows to guide droplets to the base of rice and the back of leaves, as well as to increase leaf perturbation and droplet penetration and deposition. The spatial distribution of the airflow field generated by this system and the effects of the canopy on the airflow field were described. An orthogonal experiment was performed in a rice field based on fan speed, auxiliary airflow angle, and spray height as the experimental factors. It was discovered that a fan speed of 4000 rpm, auxiliary airflow angle of 0°, and spray height of 30 cm were optimal for droplet deposition at the base of the canopy. These settings resulted in droplet coverage of 54.5% and 35.9% on the front and back of the leaves, respectively, which are 48% and 104% higher than that on the front and back sides of leaves without an auxiliary airflow, respectively. Compared with the traditional application method, vortex air-assisted application significantly improved the rate of droplet coverage in rice canopy of different area. Hence, vortex air-assisted application enables new approaches and methods for rice crop protection. © 2022 Society of Chemical Industry.

The MONARCH high-resolution reanalysis of desert dust aerosol over Northern Africa, the Middle East and Europe (2007–2016)

Abstract. One of the challenges in studying desert dust aerosol along with its numerous interactions and impacts is the paucity of direct in situ measurements, particularly in the areas most affected by dust storms. Satellites typically provide column-integrated aerosol measurements, but observationally constrained continuous 3D dust fields are needed to assess dust variability, climate effects and impacts upon a variety of socio-economic sectors. Here, we present a high-resolution regional reanalysis data set of desert dust aerosols that covers Northern Africa, the Middle East and Europe along with the Mediterranean Sea and parts of central Asia and the Atlantic and Indian oceans between 2007 and 2016. The horizontal resolution is 0.1∘ latitude × 0.1∘ longitude in a rotated grid, and the temporal resolution is 3 h. The reanalysis was produced using local ensemble transform Kalman filter (LETKF) data assimilation in the Multiscale Online Nonhydrostatic AtmospheRe CHemistry model (MONARCH) developed at the Barcelona Supercomputing Center (BSC). The assimilated data are coarse-mode dust optical depth retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue Level 2 products. The reanalysis data set consists of upper-air variables (dust mass concentrations and the extinction coefficient), surface variables (dust deposition and solar irradiance fields among them) and total column variables (e.g. dust optical depth and load). Some dust variables, such as concentrations and wet and dry deposition, are expressed for a binned size distribution that ranges from 0.2 to 20 µm in particle diameter. Both analysis and first-guess (analysis-initialized simulation) fields are available for the variables that are diagnosed from the state vector. A set of ensemble statistics is archived for each output variable, namely the ensemble mean, standard deviation, maximum and median. The spatial and temporal distribution of the dust fields follows well-known dust cycle features controlled by seasonal changes in meteorology and vegetation cover. The analysis is statistically closer to the assimilated retrievals than the first guess, which proves the consistency of the data assimilation method. Independent evaluation using Aerosol Robotic Network (AERONET) dust-filtered optical depth retrievals indicates that the reanalysis data set is highly accurate (mean bias = −0.05, RMSE = 0.12 and r = 0.81 when compared to retrievals from the spectral de-convolution algorithm on a 3-hourly basis). Verification statistics are broadly homogeneous in space and time with regional differences that can be partly attributed to model limitations (e.g. poor representation of small-scale emission processes), the presence of aerosols other than dust in the observations used in the evaluation and differences in the number of observations among seasons. Such a reliable high-resolution historical record of atmospheric desert dust will allow a better quantification of dust impacts upon key sectors of society and economy, including health, solar energy production and transportation. The reanalysis data set (Di Tomaso et al., 2021) is distributed via Thematic Real-time Environmental Distributed Data Services (THREDDS) at BSC and is freely available at http://hdl.handle.net/21.12146/c6d4a608-5de3-47f6-a004-67cb1d498d98 (last access: 10 June 2022).

Through-Wall Wireless Communication Enabled by a Metalens

Getting wireless signals around obstacles or passing them through walls is proven to be challenging for electromagnetic waves with a short wavelength and some energy-efficient buildings due to thick insulating materials. Here, we propose a scheme of through-wall wireless communication by applying purposely designed passive metalenses for an asymmetric background medium of the wall. An ultrathin metalens consisting of three layers of metallic patterns is applied to focus the incoming waves to the other side of the wall with high efficiency. The focusing effect is verified by scanning the spatial distribution of electric fields. Due to the focusing effect, the wireless signal strength is significantly enhanced while propagating through the wall. To validate its use in the 5-GHz Wi-Fi environment, we demonstrate that the metalens can reconnect a network channel that is otherwise broken due to weak signal strength, and thus, significantly increase the data transmission rate. Our work opens an unobstructive and retrofitting approach for sustaining wireless communication in future eco-friendly buildings beyond 5G and 6G.

Long-range stray field mapping of statically magnetized nanoparticles using magnetoresistive sensor

Analyzing the spatial distribution of stray field from magnetic nanoparticles is a crucial step to design and optimize the magnetometric system for a clinical magnetic particle imaging (MPI) scanner. Here, we used a magnetoresistive (MR) sensor to probe the stray field directly from a commercial magnetic nanoparticle suspension conditioned under a static field. For a given 20 mT by a small permanent magnet, the stray field of a liquid sample with a 0.7 mgFe iron mass is in nanotesla order measured by the MR sensor at 50 mm apart from the sample, while the magnetization is comparable to several microtesla. This field decay demands picotesla sensitivity of the sensing system to record the stray field for a further distance or a smaller excitation field. Moreover, from a two-dimensional trajectory of sample and magnet movements relative to the sensor position, we confirmed that the spatial distribution of the stray field appeared to correlate with sample geometry. The distribution became broadening for low iron mass concentration of the sample. From this observation, an MR sensor proves its potential for locating the magnetic nanoparticles under a quasistatic field, which can be extensively implemented for a single-sided MPI scanner.

Superconducting magnetic flux transformation amplifier for the superconductor/magnetoresistance mixed magnetic sensor: Finite element simulation method and experimental verification study

The superconductor/magnetoresistance (MR) mixed magnetic sensor, which is composed of a superconducting magnetic flux transformation amplifier (SMFTA) and a MR sensitive element, has extremely great development potential in weak magnetic field detection because of its excellent sensitivity, simple structure and small size. However, it still lacks an effective method to study the spatial distribution of the magnetic field produced by SMFTA. Here, a finite element simulation method was proposed to study the magnetic field amplification effect of the SMFTA. Several factors affecting the magnetic field amplification were studied via this simulation method. Furthermore, mixed magnetic sensors with three typical sizes were successfully fabricated, and the experimentally measured magnifications of the three sensors were basically consistent with the simulation values, demonstrating the reliability of this simulation method. Our works are expected to pave a meaningful way for the SMFTA design and promote the development of superconductor/MR mixed magnetic sensors.

The Influence of Inter-Element Phase Difference on the Beamforming and Spatial Electromagnetic Field Distribution of a Quad Microstrip Patch Antenna Array in the X Band

Abstract A simple model of 1x4 linear array of microstrip antennas was used to analyse the influence of phase difference between antenna elements on the performance of beamforming at 8.9 GHz. Simulations with full wave CST Studio were performed over a number of phase sets. Among them we identified the most constructive and the most destructive cases based on the maximum gain, the total efficiency and the polarization. It resulted that [0;0;0;0] phase case provided 10.6 dB higher gain, 46.5% higher efficiency and much more spatial uniformity of polarization along the propagation path than the [0;180;0;180] case. Field strength computations and vector representations proved the complexity of beamforming when one also takes into account the mutual coupling of the elements.

Design, modeling and experiments of a novel biaxial-pendulum vibration energy harvester

Pendulum-based vibration energy harvesting is a promising technology to supply energy for floating buoys and small ocean vehicles. However, the energy harvester with a uniaxial pendulum requires a specific direction of vibration excitation generated by wave. This paper develops a novel biaxial-pendulum vibration energy harvester, where a hemispherical pendulum can rotate around two axes simultaneously to adapt the direction of vibration excitation. Moreover, magnets and coils are distributed on the surfaces of the pendulum and the shell respectively to achieve a compact structure. The dynamics of the energy harvester are described based on Lagrangian approach. Electromagnetic analysis in three dimensions is carried out by using finite element method to obtain the spatial magnetic field distribution of the energy harvester. The relationship between the vibration excitation and the output voltage is modeled by taking dynamics and electromagnetic analysis into account together. A small-scale prototype of the proposed energy harvester is fabricated and tested through a six degree-of-freedom motion platform. It is found that the prototype can generate electricity with peak voltage and power of 14.25 V and 2.03 W when the excitation acceleration is 0.18 g. The analytical results and the experimental results are also in good agreement with each other.