Feature Preserving Parameterization for Quadrilateral Mesh Generation Based on Ricci Flow and Cross Field

We propose a newmethod to generate surface quadrilateralmesh by calculating a globally defined parameterization with feature constraints.In the field of quadrilateral generation with features,the cross field methods are wellknown because of their superior performance in feature preservation.The methods based on metrics are popular due to their sound theoretical basis,especially the Ricci flow algorithm.The cross field methods’major part,the Poisson equation,is challenging to solve in three dimensions directly.When it comes to cases with a large number of elements,the computational costs are expensive while the methods based on metrics are on the contrary.In addition,an appropriate initial value plays a positive role in the solution of the Poisson equation,and this initial value can be obtained from the Ricci flow algorithm.So we combine the methods based on metric with the cross field methods.We use the discrete dynamic Ricci flow algorithm to generate an initial value for the Poisson equation,which speeds up the solution of the equation and ensures the convergence of the computation.Numerical experiments show that our method is effective in generating a quadrilateral mesh for models with features,and the quality of the quadrilateral mesh is reliable.

Experimental study on the effect of H2S and SO2 on high temperature corrosion of 12Cr1MoV

Aiming at the high temperature corrosion in a coal-fired boiler,the effect of H2S and SO2 on the corrosion of 12 CrlMoV under the water wall condition has been investigated by experiments.The results indicate that H2 S can promote the corrosion significantly,and the coarse porous oxide film formed cannot stop the progress of corrosion.While SO2 presents little effect on the corrosion.The main composition of the surface of 12 CrlMoV corrosion products is Fe2 O3.With H2S in the atmosphere,the corrosion gradually develops into deeper layers by forming FeS,FeO and Fe2 O3 alternately.The corrosion rate is doubled for every 50℃ inerease in temperature at 400-500℃.

National guidelines for diagnosis and treatment of thyroid cancer 2022 in China(English version)

Contents 1. Overview 2. Diagnosis and management 2.1 Screening for high-risk group 2.2 Clinical manifestations 2.2.1 Symptoms 2.2.2 Signs 2.2.3 Invasion and metastasis 2.3 Laboratory examination 2.3.1 Routine examination 2.3.2 Special examination 2.4 Imaging 2.4.1 Ultrasonography 2.4.2 Computed tomography (CT)2.4.3 Magnetic resonance imaging (MRI)2.4.4 Positron emission tomography (PET)-CT。

Comments on National guidelines for diagnosis and treatment of thyroid cancer 2022 in China (English version)

Thyroid cancer (TC) is the most common endocrine system cancer, of note, the overall survival of TC in China is suboptimal when comparing with the developed countries such as US (84.3%vs.98.3%), posing a great challenge among professionals involved in this field.Standardization of its diagnosis and treatment not only provides the basis for all the care givers to promote the entire level of TC management, but also is helpful in shortening the distance between China and other developed countries. A multidisciplinary team (MDT)should be involved in the comprehensive clinical management of TC, particularly for those advanced or refractory TC, which needs cooperation among members from ultrasonography, radiology, pathology, surgery.

Terahertz Imaging and Spectroscopy in Cancer Diagnostics:A Technical Review

Terahertz(THz)waves are electromagnetic waves with frequency in the range from 0.1 to 10 THz.THz waves have great potential in the biomedical field,especially in cancer diagnosis,because they exhibit low ionization energy and can be used to discern most biomolecules based on their spectral fingerprints.In this paper,we review the recent progress in two applications of THz waves in cancer diagnosis:imaging and spectroscopy.THz imaging is expected to help researchers and doctors attain a direct intuitive understanding of a cancerous area.THz spectroscopy is an efficient tool for component analysis of tissue samples to identify cancer biomarkers.Additionally,the advantages and disadvantages of the developed technologies for cancer diagnosis are discussed.Furthermore,auxiliary techniques that have been used to enhance the spectral signal-to-noise ratio(SNR)are also reviewed.

Temperature dependent terahertz giant anisotropy and cycloidal spin wave modes in BiFeO3 single crystal

THz time-domain spectroscopy(THz-TDS)is used to study the THz-optical properties of a single crystal bismuth ferrite BiFeO3(BFO).It can be found that the anisotropy of BiFeO3 is strongly dependent on the temperature.A giant birefringence up to around 3.6 is observed at 1 THz.The presence of a spatially modulated cycloidal antiferromagnetic structure leads to spin cycloid resonances(SCR)ψandΦ,corresponding to the out-of-plane and in-plane modes of the spin cycloid,respectively.We distinguish the SCR with respect to their response to orthogonal polarizations of the electric fields of the incident THz beam.In addition,we observe a resonance appearing below 140 K,which might be interpreted as an electromagnon mode and related to a spin reorientation transition.Our present observations present that the temperature and polarization,as the external control parameters,can be used to modulate the THz optical properties of BFO single crystal.

Review on the terahertz metasensor:from featureless refractive index sensing to molecular identification

The terahertz(THz)wave is at the intersection between photonics and electronics in the electromagnetic spectrum.Since the vibration mode of many biomedical molecules and the weak interaction mode inside the molecules fall in the THz regime,utilizing THz radiation as a signal source to operate substance information sensing has its unique advantages.Recently,the metamaterial sensor(metasensor)has greatly enhanced the interaction between signal and substances and spectral selectivity on the subwavelength scale.However,most past review articles have demonstrated the THz metasensor in terms of their structures,applications,or materials.Until recently,with the rapid development of metasensing technologies,the molecular information has paid much more attention to the platform of THz metasensors.In this review,we comprehensively introduce the THz metasensor for detecting not only the featureless refractive index but also the vibrational/chiral molecular information of analytes.The objectives of this review are to improve metasensing specificity either by chemical material-assisted analyte capture or by physical molecular information.Later,to boost THz absorption features in a certain frequency,the resonant responses of metasensors can be tuned to the molecular vibrational modes of target molecules,while frequency multiplexing techniques are reviewed to enhance broadband THz spectroscopic fingerprints.The chiral metasensors are also summarized to specific identification chiral molecules.Finally,the potential prospects of next generation THz metasensors are discussed.Compared to featureless refractive index metasensing,the specific metasensor platforms accelerated by material modification and molecular information will lead to greater impact in the advancement of trace detection of conformational dynamics of biomolecules in practical applications.

Bio-inspired Design and Inverse Kinematics Solution of an Omnidirectional Humanoid Robotic Arm with Geometric and Load Capacity Constraints

Inspired by the driving muscles of the human arm,a 4-Degree of Freedom(DOF)concentrated driving humanoid robotic arm is proposed based on a spatial double parallel four-bar mechanism.The four-bar mechanism design reduces the inertia of the elbow-driving unit and the torque by 76.65%and 57.81%,respectively.Mimicking the human pose regulation strategy that the human arm picks up a heavy object by adjusting its posture naturally without complicated control,the robotic arm features an integrated position-level closed-form inverse solution method considering both geometric and load capacity limitations.This method consists of a geometric constraint model incorporating the arm angle(φ)and the Global Configuration(GC)to avoid joint limits and singularities,and a load capacity model to constrain the feasible domain of the arm angle.Further,trajectory tracking simulations and experiments are conducted to validate the feasibility of the proposed inverse solution method.The simulated maximum output torque,maximum output power and total energy consumption of the robotic arm are reduced by up to 2.0%,13.3%,and 33.3%,respectively.The experimental results demonstrate that the robotic arm can bear heavy loads in a human-like posture,effectively reducing the maximum output torque and energy consumption of the robotic arm by 1.83%and 5.03%,respectively,while avoiding joints beyond geometric and load capacity limitations.The proposed design provides a high payload–weight ratio and an efficient pose control solution for robotic arms,which can potentially broaden the application spectrum of humanoid robots.

Metasurfaces designed by a bidirectional deep neural network and iterative algorithm for generating quantitative field distributions

Metasurfaces,which are the two-dimensional counterparts of metamaterials,have demonstrated unprecedented capabilities to manipulate the wavefront of electromagnetic waves in a single flat device.Despite various advances in this field,the unique functionalities achieved by metasurfaces have come at the cost of the structural complexity,resulting in a time-consuming parameter sweep for the conventional metasurface design.Although artificial neural networks provide a flexible platform for significantly improving the design process,the current metasurface designs are restricted to generating qualitative field distributions.In this study,we demonstrate that by combining a tandem neural network and an iterative algorithm,the previous restriction of the design of metasurfaces can be overcome with quantitative field distributions.As proof-of-principle examples,metalenses predicted via the designed network architecture that possess multiple focal points with identical/orthogonal polarisation states,as well as accurate intensity ratios(quantitative field distributions),were numerically calculated and experimentally demonstrated.The unique and robust approach for the metasurface design will enable the acceleration of the development of devices with high-accuracy functionalities,which can be applied in imaging,detecting,and sensing.

Intermittent F-actin Perturbations by Magnetic Fields Inhibit Breast Cancer Metastasis

F-actin(filamentous actin)has been shown to be sensitive to mechanical stimuli and play critical roles in cell attachment,migration,and cancer metastasis,but there are very limited ways to perturb F-actin dynamics with low cell toxicity.Magnetic field is a noninvasive and reversible physical tool that can easily penetrate cells and human bodies.Here,we show that 0.1/0.4-T 4.2-Hz moderate-intensity low-frequency rotating magnetic field-induced electric field could directly decrease F-actin formation in vitro and in vivo,which results in decreased breast cancer cell migration,invasion,and attachment.Moreover,lowfrequency rotating magnetic fields generated significantly different effects on F-actin in breast cancer vs.noncancerous cells,including F-actin number and their recovery after magnetic field retrieval.Using an intermittent treatment modality,low-frequency rotating magnetic fields could significantly reduce mouse breast cancer metastasis,prolong mouse survival by 31.5 to 46.0%(P<0.0001),and improve their overall physical condition.Therefore,our work demonstrates that low-frequency rotating magnetic fields not only can be used as a research tool to perturb F-actin but also can inhibit breast cancer metastasis through F-actin modulation while having minimum effects on normal cells,which reveals their potential to be developed as temporal-controlled,noninvasive,and high-penetration physical treatments for metastatic cancer.

Design and Experiments of a Human-Leg-Inspired Omnidirectional Robotic Leg

Bionic-based robotic legs enable the legged robots with elegant and agile mobility in multi-terrain environment,just like natural living beings.And the smart design could efficiently improve the performance of a robotic leg.Inspired by the simplified human leg structure,we present a 3-DOF robotic leg—OmniLeg,that is capable of making omnidirectional legged locomotion while keeping constant posture of the foot.Additionally,the concentrated drive mode,in which all the motor actuators are installed in the torso and do not move with the leg,minimizes the inertia of the robotic leg.In this paper,the modular design,the kinematics model,the structural analysis,the workspace,and the performance evaluation of the OmniLeg are discussed.Furthermore,we build a prototype based on the proposed design,and the precision of it is verified by the error calibration experiment which is conducted by tracking the trajectory of the prototype’s endpoint.Then,we present an OmniLeg-based single legged mobile robot.The capability of omnidirectional legged locomotion of the OmniLeg is demonstrated by the experiments.

Integrated terahertz vortex beam emitter for rotating target detection

We propose a terahertz(THz)vortex emitter that utilizes a high-resistance silicon resonator to generate vortex beams with various topological charges.Addressing the challenge of double circular polarization superposition resulting from the high refractive index contrast,we regulate the transverse spin state through a newly designed second-order grating partially etched on the waveguide’s top side.The reflected wave can be received directly by a linearly polarized antenna,simplifying the process.Benefiting from the tuning feature,a joint detection method involving positive and negative topological charges identifies and detects rotational Doppler effects amid robust micro-Doppler interference signals.This emitter can be used for the rotational velocity measurement of an on-axis spinning object,achieving an impressive maximum speed error rate of∼2%.This approach holds promise for the future development of THz vortex beam applications in radar target detection and countermeasure systems,given its low cost and potential for mass production.

磁场与血管生成研究进展

血管生成参与了多种生理和病理过程,是器官生长和修复的关键,在外科中起着至关重要的作用.目前已有大量关于磁场对血管生成影响的研究报道.本文对现有数据进行总结、分析和比较,包括不同磁场类型、磁场参数、处理方式、处理对象和磁场处理导致的血管生成变化等.由于针对不同磁场参数的系统性研究相对缺乏,目前细胞水平上的研究结果尚无确切的规律.然而动物水平上的研究结果显示,肿瘤组织的血管生成可以被多种磁场所抑制,而长时间或者较高磁场强度的稳态磁场处理非肿瘤组织似乎有促进血管生成的趋势,对此人们还需要进行更系统的研究来进一步确认.此外,本文还讨论了磁场与化疗等其他治疗方法联合使用对血管生成的影响,并总结分析磁场影响血管生成的潜在机制.这不仅有助于人们进一步了解磁场生物学效应,为磁外科技术的安全应用提供实验基础,而且可能为未来将磁场在医学领域的其他潜在应用奠定基础.

Mode splitting transmission effect of surface wave excitation through a metal hole array

The resonant frequencies of the excited surface waves on a metal hole array with respect to the incident angle were studied in the terahertz region.The experimental and theoretical results demonstrate that the resonant peak of surface wave excitation splits into two when transmitted through a metal hole array off-normally.The high-order mode with resonant frequency above the cutoff frequency fc(plasma frequency effect)has a shorter attenuation length than that of the low-order mode whose resonant frequency is below fc.The reason is that the high-order mode is a coupled mode consisting of surface wave and hole modes,while the low-order mode is just an excited surface wave(which can be considered as the spoof surface plasmons).Our investigation may open a door to distinguish the spoof surface plasmons and the coupled modes of surface waves and hole modes.

Terahertz wave generation from liquid nitrogen

We present the results of research carried out for the first time, to the best of our knowledge, on the generation of terahertz radiation under the action of "single-color" and "dual-color" high-power femtosecond laser pulses on liquefied gas–liquid nitrogen. Our experimental results supported by careful theoretical interpretation showed clearly that under femtosecond laser radiation, liquid and air emit terahertz waves in a very different way. We assumed that the mobility of ions and electrons in liquid can play an essential role, forming a quasi-static electric field by means of ambipolar diffusion mechanism.

Clue to a thorough understanding of terahertz pulse generation by femtosecond laser filamentation

In this work, it has been demonstrated that in order to fully understand the terahertz(THz) pulse generation process during femtosecond laser filamentation, the interaction between THz wave and air plasma has to be taken into account. This interaction is mainly associated with the spatial confinement of the THz pulse by the plasma column, which could be described by the one-dimensional negative dielectric(1DND) waveguide model. By combining the 1 DND model with the conventional four-wave mixing(4WM) and photocurrent(PC) models,the variation of THz spectral amplitude and width obtained in experiments could be better understood. Finally, a three-step procedure, with 1DND bridging 4WM and PC processes, has been established for the first time to describe the underlying mechanism of THz radiation from plasma sources.

Photoinduced large polaron transport and dynamics in organic-inorganic hybrid lead halide perovskite with terahertz probes

Organic-inorganic hybrid metal halide perovskites(MHPs)have attracted tremendous attention for optoelectronic applications.The long photocarrier lifetime and moderate carrier mobility have been proposed as results of the large polaron formation in MHPs.However,it is challenging to measure the effective mass and carrier scattering parameters of the photogenerated large polarons in the ultrafast carrier recombination dynamics.Here,we show,in a one-step spectroscopic method,that the optical-pump and terahertz-electromagnetic probe(OPTP)technique allows us to access the nature of interplay of photoexcited unbound charge carriers and optical phonons in polycrystalline CH_(3)NH_(3)PbI_(3)(MAPbI_(3))of about 10μm grain size.Firstly,we demonstrate a direct spectral evidence of the large polarons in polycrystalline MAPbI_(3).Using the Drude-Smith-Lorentz model along with the Frӧhlich-type electron-phonon(e-ph)coupling,we determine the effective mass and scattering parameters of photogenerated polaronic carriers.We discover that the resulting moderate polaronic carrier mobility is mainly influenced by the enhanced carrier scattering,rather than the polaron mass enhancement.While,the formation of large polarons in MAPbI_(3)polycrystalline grains results in a long charge carrier lifetime at room temperature.Our results provide crucial information about the photo-physics of MAPbI3 and are indispensable for optoelectronic device development with better performance.

Terahertz spatial sampling with subwavelength accuracy

A simple terahertz(THz)spatial sampling method offers kilohertz(kHz)level sampling rates and greatly preserves the energy of a THz pulse,which enables THz imaging detection with a high signal-to-noise ratio,micron-grade accuracy,and subwavelength resolution.

Dual-layered metasurfaces for asymmetric focusing

Asymmetric transmission,defined as the difference between the forward and backward transmission,enables a plethora of applications for on-chip integration and telecommunications.However,the traditional method for asymmetric transmission is to control the propagation direction of the waves,hindering further applications.Metasurfaces,a kind of two-dimensional metamaterials,have shown an unprecedented ability to manipulate the propagation direction,phase,and polarization of electromagnetic waves.Here we propose and experimentally demonstrate a metasurface-based directional device consisting of a geometric metasurface with spatially rotated microrods and metallic gratings,which can simultaneously control the phase,polarization,and propagation direction of waves,resulting in asymmetric focusing in the terahertz region.These dual-layered metasurfaces for asymmetric focusing can work in a wide bandwidth ranging from 0.6 to 1.1 THz.The flexible and robust approach for designing broadband asymmetric focusing may open a new avenue for compact devices with potential applications in encryption,information processing,and communication.

Thickness properties hexagonal and temperature dependent electrical of ZrS2 thin films directly grown on boron nitride

Two-dimensional ZrS2 materials have potential for applications in nanoelectronics because of their theoretically predicted high mobility and sheet current density. Herein, we report the thickness and temperature dependent transport properties of ZrS2 multilayers that were directly deposited on hexagonal boron nitride （h-BN） by chemical vapor deposition. Hysteresis-free gate sweeping, metal- insulator transition, and T-γ （γ- 0.82-1.26） temperature dependent mobility were observed in the ZrS2 films.