Phase field method simulation of faceted dendrite growth with arbitrary symmetries

A numerical simulation based on a regularized phase field model is developed to describe faceted dendrite growth morphology. The effects of mesh grid, anisotropy, supersaturation and fold symmetry on dendrite growth morphology were investigated, respectively. These results indicate that the nucleus grows into a hexagonal symmetry faceted dendrite. When the mesh grid is above 640×640, the size has no much effect on the shape. With the increase in the anisotropy value, the tip velocities of faceted dendrite increase and reach a balance value, and then decrease gradually. With the increase in the supersaturation value, crystal evolves from circle to the developed faceted dendrite morphology. Based on the Wulff theory and faceted symmetry morphology diagram, the proposed model was proved to be effective, and it can be generalized to arbitrary crystal symmetries.

Simulation of faceted dendrite growth of non-isothermal alloy in forced flow by phase field method

Numerical simulation based on a new regularized phase field model was presented to simulate the dendritic shape of a non-isothermal alloy with strong anisotropy in a forced flow. The simulation results show that a crystal nucleus grows into a symmetric dendrite in a free flow and into an asymmetry dendrite in a forced flow. As the forced flow velocity is increased, both of the promoting effect on the upstream arm and the inhibiting effects on the downstream and perpendicular arms are intensified, and the perpendicular arm tilts to the upstream direction. With increasing the anisotropy value to 0.14, all of the dendrite arms tip velocities are gradually stabilized and finally reach their relative saturation values. In addition, the effects of an undercooling parameter and a forced compound flow on the faceted dendrite growth were also investigated.

High-Index Faceted Nanocrystals as Highly Efficient Bifunctional Electrocatalysts for High-Performance Lithium-Sulfur Batteries

Precisely regulating of the surface structure of crystalline materials to improve their catalytic activity for lithium polysulfides is urgently needed for high-performance lithium-sulfur(Li-S)batteries.Herein,high-index faceted iron oxide(Fe_(2)O_(3))nanocrystals anchored on reduced graphene oxide are developed as highly efficient bifunctional electrocatalysts,effectively improving the electrochemical performance of Li-S batteries.The theoretical and experimental results all indicate that high-index Fe_(2)O_(3)crystal facets with abundant unsaturated coordinated Fe sites not only have strong adsorption capacity to anchor polysulfides but also have high catalytic activity to facilitate the redox transformation of polysulfides and reduce the decomposition energy barrier of Li_(2)S.The Li-S batteries with these bifunctional electrocatalysts exhibit high initial capacity of 1521 mAh g^(-1)at 0.1 C and excellent cycling performance with a low capacity fading of 0.025%per cycle during 1600 cycles at 2 C.Even with a high sulfur loading of 9.41 mg cm^(-2),a remarkable areal capacity of 7.61 mAh cm^(-2)was maintained after 85 cycles.This work provides a new strategy to improve the catalytic activity of nanocrystals through the crystal facet engineering,deepening the comprehending of facet-dependent activity of catalysts in Li-S chemistry,affording a novel perspective for the design of advanced sulfur electrodes.

Computer Aided Design Technology for Convex Faceted Gem Cuts Based on the Half-Edge Data Structure

Aiming to increase the efficiency of gem design and manufacturing, a new method in computer-aided-design (CAD) of convex faceted gem cuts (CFGC) based on Half-edge data structure (HDS), including the algorithms for the implementation is presented in this work. By using object-oriented methods, geometrical elements of CFGC are classified and responding geometrical feature classes are established. Each class is implemented and embedded based on the gem process. Matrix arithmetic and analytical geometry are used to derive the affine transformation and the cutting algorithm. Based on the demand for a diversity of gem cuts, CAD functions both for free-style faceted cuts and parametric designs of typical cuts and visualization and human-computer interactions of the CAD system including two-dimensional and three-dimensional interactions have been realized which enhances the flexibility and universality of the CAD system. Furthermore, data in this CAD system can also be used directly by the gem CAM module, which will promote the gem CAD/CAM integration.

Phase-field modeling of faceted growth in solidification of alloys

A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys.Predicted results show that the value of δ can only affect the region near the tip,and the convergence with respect to δ can be achieved with the decrease of δ near the tip.It can be found that the steady growth velocity is not a mo no tonic function of the cusp amplitude,and the maximum value is approximately at ε=0.8 when the supersaturation is fixed.Moreover,the growth velocity is an increasing function of supersaturation with the morphological transition from facet to dendrite.

Lithium storage performance of {010}-faceted and [111]-faceted anatase TiO2 nanocrystals

As a popular anode material for lithium-ion batteries,anatase TiO2 nanoparticles with exposed{001}facets usually exhibit exceptional lithium storage performance owing to more accessible sites and fast migration of lithium ions along the good crystalline channels.However,there are few researches on the lithium storage capability of TiO2 nanocrystals with other high-energy facets owing to lack of effective synthesis method for controlling crystal facets.Herein,anatase TiO2 nanocrystals with exposed{010}-and[111]-facets are successfully prepared by using the delaminated tetratitanate nanoribbons as precursors.The electrochemical properties of these TiO2 nanocrystals with high-energy surfaces and the comparison with commercial TiO2 nanoparticles(P25)are studied.It is found that the cycle and rate performance of TiO2 nanocrystals is highly improved by reducing the particle size of nanocrystals.Moreover,TiO2 nanocrystals with exposed{010}-and[111]-facets exhibit better lithium storage capacities in comparison with P25 without a specific facet though P25 has smaller particle size than these TiO2 nanocrystals,indicating that the exposed facets of TiO2 nanocrystals have an important impact on their lithium storage capacity.Therefore,the synthesis design of high-performance TiO2 materials applied in the next-generation secondary batteries should both consider the particle size and the exposed facets of nanocrystals.

High-index faceted noble metal nanostructures drive renewable energy electrocatalysis

Noble metallic nanocrystals are used in a wide variety of applications,such as catalysis,batteries,and bio-and chemical sensors.Most of the previous studies focus on the preparation of thermodynamically stable nanocrystals enclosed by low-index facets and discuss their corresponding catalytic properties.Recently,researchers have found that the nanocrystals with high-index facets(HIFs)are of more interest for electrocatalysis.Herein,we review recent key progress in the synthesis of noble metallic nanoparticles enclosed with HIFs and their facetdependent electrocatalytic behaviors.First,we introduce the concept of HIFs,and establish the correlation between their surface structure and catalytic activity.Then,we discuss various synthetic approaches for controlling the shapes and composition of the nanocrystals enclosed by HIFs.Afterwards,we showcase the enhanced electrocatalytic performance realized by HIF-based nanostructures.Finally,we provide guidance on how to improve the electrocatalysis by engineering HIFs on noble metallic nanocrystals.

Multifaceted control of focal points along an arbitrary 3D curved trajectory

Metalenses can integrate the functionalities of multiple optical components thanks to the unprecedented capability of optical metasurfaces in light control.With the rapid development of optical metasurfaces,metalenses continue to evolve.Polarization and color play a very important role in understanding optics and serve as valuable tools for gaining insights into our world.Benefiting from the design flexibility of metasurfaces,we propose and experimentally demonstrate a super metalens that can realize multifaceted control of focal points along any 3D curved trajectory.The wavelengths and polarization states of all focal points are engineered in a desirable manner.The super metalens can simultaneously realize customized 3D positioning,polarization states,and wavelengths of focal points,which are experimentally demonstrated with incident wavelengths ranging from 501 to 700 nm.We further showcase the application of the developed super metalenses in 3D optical distance measurement.The compact nature of metasurfaces and unique properties of the proposed super metalenses hold promise to dramatically miniaturize and simplify the optical architecture for applications in optical metrology,imaging,detection,and security.

A review of energy and environment electrocatalysis based on high-index faceted nanocrystals

Today,nanocrystals enclosed by high-index facets(HIFs)are attracting widely attentions of researchers due to their tremendous potential in the field of catalysis,especially in electrocatalysis,such as electro-oxidation of small organic molecule(such as formic acid,methanol,and ethanol),oxygen reduction reaction(ORR),hydrogen evolution reaction(HER),as well as the oxygen evolution reaction(OER).However,the practical applications of nanocrystals enclosed by HIFs still face many limitations in preparations of advanced electrocatalysts,including preparation strategy,limited life-time and stability.The development of advanced electrocatalysts enclosed with HIFs is crucial for solving these problems if the large-scale application of them is to be realized.Herein,we firstly detailedly demonstrate the identification methods of nanocrystals enclosed by HIFs,and then preparation strategies are elaborated in detail in this review.Current advanced nanocrystals enclosed by HIFs in electrocatalytic application are also summarized and we present representative achievements to further reveal the relationship of excellent electrocatalytic performance and nanocrystals with HIFs.Finally,we predict the remaining challenges and present our perspectives with regards of design strategies of improving electrocatalytic performance of Ptbased catalysts in the future.

Meaningful comparison of photocatalytic properties of {001} and {101} faceted anatase TiO2 nanocrystals

The facet-dependent photocatalytic performance of TiO_2 nanocrystals has been extensively investigated due to their promising applications in renewable energy and environmental fields. However, the intrinsic distinction in the photocatalytic oxidation activities between the {001}and {101} facets of anatase TiO_2 nanocrystals is still unclear and under debate. In this work, a simple photoelectrochemical method was employed to meaningfully quantify the intrinsic photocatalytic activities of {001} and{101} faceted TiO_2 nanocrystal photoanodes. The effective surface areas of photoanodes with different facets were measured based on the monolayer adsorption of phthalic acid on TiO_2 photoanode surface by an ex situ photoelectrochemical method, which were used to normalize the photocurrents obtained from different faceted photoanodes for meaningful comparison of their photocatalytic activities. The results demonstrated that the {001} facets of anatase TiO_2 nanocrystals exhibited much better photocatalytic activity than that of {101} facets of anatase TiO_2 nanocrystals toward photocatalytic oxidation of water and organic compounds with different functional groups(e.g.,–OH, –CHO, –COOH). Furthermore, the instantaneous kinetic constants of photocatalytic oxidation of pre-adsorbates on {001} faceted anatase TiO_2 photoanode are obviously greater than those obtained at {101} faceted anatase TiO_2 photoanode, further verifying the higher photocatalytic activity of {001} facets of anatase TiO_2.This work provided a facile photoelectrochemical method to quantitatively determine the photocatalytic oxidation activity of specific exposed crystal facets of a photocatalyst, which would be helpful to uncover and meaningfully compare the intrinsic photocatalytic activities of different exposed crystal facets of a photocatalyst.

基于FACET滤波加权局部对比度的红外小目标检测

针对低空复杂背景下红外图像中目标与背景对比度低、边缘高亮的问题,提出一种基于FACET滤波加权局部对比度的红外小目标检测算法。首先,通过FACET滤波运算获取目标候选像素;然后,利用目标区域和背景区域灰度差异的比率计算局部对比度,同时基于目标和背景的异质性设计了一种加权函数,用来增强目标显著性和抑制背景;最后,通过自适应阈值分割提取真实的目标。在5组真实红外小目标图像数据集上与不同的算法进行性能比较分析,实验结果表明,提出的算法在不同低空复杂场景中具有较好的检测性能。

回注泵液力端承压能力提升研究

钻屑回注泵液力端存在易疲劳开裂的现象,维护成本极高。在高泵注压力条件下,钻屑回注泵液力端内应力峰值较大,排出孔相贯口处易开裂,导致钻屑回注泵使用寿命较短。为此,利用ANSYS软件对液力端进行静力学分析,分析发现,在排出工况下液力端相贯区域为应力集中区域,最大应力值为725MPa,利用FACET修型技术优化之后,最大应力值降为636MPa。

Optical facet coatings for high-performance LWIR quantum cascade lasers atλ∼8.5μm

We report on the performance improvement of long-wave infrared quantum cascade lasers(LWIR QCLs)by studying and optimizing the anti-reflection(AR)optical facet coating.Compared to the Al2O3 AR coat⁃ing,the Y_(2)O_(3)AR coating exhibits higher catastrophic optical mirror damage(COMD)level,and the optical facet coatings of both material systems have no beam steering effect.A 3-mm-long,9.5-μm-wide buried-heterostruc⁃ture(BH)LWIR QCL ofλ~8.5μm with Y_(2)O_(3)metallic high-reflection(HR)and AR of~0.2%reflectivity coating demonstrates a maximum pulsed peak power of 2.19 W at 298 K,which is 149%higher than that of the uncoated device.For continuous-wave(CW)operation,by optimizing the reflectivity of the Y_(2)O_(3)AR coating,the maximum output power reaches 0.73 W,which is 91%higher than that of the uncoated device.

F-doped orthorhombic Nb_(2)O_(5) exposed with 97% (100) facet for fast reversible Liþ-Intercalation

Orthorhombic Nb_(2)O_(5)(T-Nb_(2)O_(5))is attractive for fast-charging Li-ion batteries,but it is still hard to realize rapid charge transfer kinetics for Li-ion storage.Herein,F-doped T-Nb_(2)O_(5) microflowers(F-Nb_(2)O_(5))are rationally synthesized through topotactic conversion.Specifically,F-Nb_(2)O_(5) are assembled by single-crystal nanoflakes with nearly 97%exposed(100)facet,which maximizes the exposure of the feasible Li^(+)transport pathways along loosely packed 4g atomic layers to the electrolytes,thus effectively enhancing the Li^(+)-intercalation performance.Besides,the band gap of F-Nb_(2)O_(5) is reduced to 2.87 eV due to the doping of F atoms,leading to enhanced electrical conductivity.The synergetic effects between tailored exposed crystal facets,F-doping,and ultrathin building blocks,speed up the Li^(+)/electron transfer kinetics and improve the pseudocapacitive properties of F-Nb_(2)O_(5).Therefore,F-Nb_(2)O_(5) exhibit superior rate capability(210.8 and 164.9 mAh g^(-1) at 1 and 10 C,respectively)and good long-term 10 C cycling performance(132.7 mAh g^(-1) after 1500 cycles).

Surface deterioration dependent on the crystal facets of spinel LiNi_(0.5)Mn_(1.5)O_(4) cathode active material

The spinel LiNi_(0.5)Mn_(1.5)O_(4)(LNMO)cathode active materials(CAMs)are considered a promising alternative to commercially available cathodes such as layered and polyanion oxide cathodes,primarily due to their notable safety and high energy density,particularly in their single-crystal type.Nevertheless,the industrial application of the LNMO CAMs is severely inhibited due to the interfacial deterioration and corrosion under proton-rich and high-voltage conditions.This study successfully designed and synthesized two typical types of crystal facets-exposed single-crystal LNMO CAMs.By tracking the electrochemical deterioration and chemical corrosion evolution,this study elucidates the surface degradation mechanisms and intrinsic instability of the LNMO,contingent upon their crystal facets.The(111)facet,due to its elevated surface energy,is found to be more susceptible to external attack compared to the(100)and(110)facets.Our study highlights the electrochemical corrosion stability of crystal plane engineering for spinel LNMO CAMs.

Facet effects on bimetallic ZnSn hydroxide microcrystals for selective electrochemical CO_(2)reduction

Employing crystal facets to regulate the catalytic properties in electrocatalytic carbon dioxide reduction reaction(eCO_(2)RR)has been well demonstrated on electrocatalysts containing single metals but rarely explored for bimetallic systems.Here,we synthesize ZnSn(OH)_(6)(ZSO)microcrystals(MCs)with distinct facets and investigate the facet effects in eCO_(2)RR.Electrochemical studies and in situ Fourier Transform Infrared Spectroscopy(in situ-FTIR)reveal that ZSO MCs produce mainly C1 products of HCOOH and CO.The{111}facet of the ZSO MCS exhibits higher selectivity and faradaic efficiency(FE)than that of the{100}facet over a wide range of potentials(-0.9 V∼-1.3 V versus RHE).Density Functional Theory(DFT)calculations elucidate that the{111}facet is favorable to the adsorption/activation of CO_(2)molecules,the formation of intermediate in the rate-determining step,and the desorption of C1 products of CO and HCOOH molecules.

Kiran Nandivada’s Stuck Blade in a Grinder Jar Degenerative Cascade by LSTV at L5-S1

Background: Mario Bertolotti, (1917) described LSTV-Lumbar spinal transitional vertebra as Bertolotti Syndrome a century ago and associated low back pain with it. Yet, it needs to be given significance in general orthopaedic practice even now, and radiologists underreport it. LSTV is a congenital anatomical anomaly that Castellvi classified into four varying types. Purpose: I titled this phenomenon “Kiran Nandivada’s stuck blade in a grinder jar degenerative cascade by LSTV at L5-S1” to clearly explain how an abnormal mega-transverse apophysis with its various variations affects the weight-bearing mechanics as the L5-S1 which is a vital junction where the maximum body weight is directed into both the sacroiliac joints and if a transitional vertebra occurs it becomes detrimental and abnormally redirects the load-bearing forces and leads to a progressive degenerative cascade both proximally and distally. As the L5 vertebral rotations and other movements of flexion, extensions, lateral flexion are stuck like a bent grinder blade, the other areas of the region are damaged progressively as the pelvis, just like the grinder motor tries to move it, resulting in overheating and maybe even a burnout results in the form of facet arthritis, disc degeneration in the normal disc above, the transitional disc at L5-S1, foraminal osteophytes causing radiculopathy, sacroiliac joint arthritis. Material and Methods: Around 200 X-rays of children and adults with this congenital anomaly have been studied between 2020 and 2023. This is a retrospective study. Results: 1) Our study showed an Increased incidence of LSTV at 15%. 2) Patients ranged from asymptomatic, atypical lumbago to classical lumbago with sciatica and claudication. Findings supported facet and sacroiliac joint arthritis and the pain, relieved with physiotherapy, posture corrections, weight reduction, and lifestyle precautions, negating the need for local steroid injections, radiofrequency ablation or surgical excision as per our experience. Conclusion: Other dysplastic congenital manifestations like associated scoliosis, facet tropism and nerve root, and sacroiliac joint anomalies can co-exist. These radiological findings must be clearly explained to the patient so that the inherently progressive nature of this phenomenon is well understood and the patient can take the required precautions to slow them and suitable conservative treatment can be planned. In rare cases, radiofrequency ablation or even rarely a surgical resection could be beneficial, but the surgical approach could be complex as normal anatomy is changed. Hence, prior anaesthesia blocks and even scintigraphy are essential steps to clearly define and confirm the LSTV to be the actual cause of the pain.

Determinants of Satisfaction at Work and Its Reflections on Performance

This study examines the relationship between job satisfaction and performance,investigating personality traits and satisfaction aspects among employees of a Federal Higher Education Institution.A questionnaire was administered to 658 participants,using structural equation modeling for analysis.Results highlighted that challenging work,neuroticism,and self-esteem significantly influenced overall workplace satisfaction,while general satisfaction,self-efficacy,and lack of attention were key determinants of work performance.This emphasizes the importance for managers to prioritize factors enhancing employee satisfaction,as it positively correlates with job performance.

一种改进的基于Facet模型的亚体素表面检测算法

在基于CT的工业应用中,常常需要从CT切片序列获得实体的3D高精度表面信息。介绍了一种基于Facet模型的亚体素表面检测算法,并针对其计算效率低的问题,给出了一种3DFacet模型的加速算法。该改进算法将Facet模型的三维卷积核分解为3个一维卷积核,使算法复杂度从O(m3)降低到O(3m),并采用增量算法解决了由此产生的存储空间问题。通过对仿真图像的实验,验证了该算法的效率和精度,表明该算法在保持原始算法精度的同时,处理速度提高了约两倍。

基于3-D Facet模型的亚体素边缘检测算法研究

在产品的虚拟测量中,需要获得产品内外表面的3D高精度轮廓信息。本文首先介绍了一种直接从CT切片序列获得表面点的方法,通过3DFacet模型计算方向导数并根据沿梯度方向的二阶导数零点获得边缘点的亚体级精确位置。该方法可以检测到法向垂直于切片的表面,并且由于考虑了待检测切片相邻层的信息,与仅考虑单层信息的2D亚像素边缘检测方法相比,它抗噪能力更强、精度更高。其次,本文提出了一种改进方法,通过缩减候选像素的预处理,在很大程度上提高了原始算法的处理速度。最后将改进算法应用到航空发动机叶片仿真模型的检测中,结果表明本算法检测精度可达0.1个像素左右,速度较原始算法提高约10倍。