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Effect of Single- versus Double-Layer Uterine Closure during Caesarean Section on Niche Formation and Menstrual Irregularity
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作者 Mohamed Samy Esraa Hussein Fouad Ghoneimy Walid Hitler 《Open Journal of Obstetrics and Gynecology》 2024年第1期57-68,共12页
Background: The myometrium at the location of the CS (caesarean section) scars, also known as residual myometrium thickness (RMT), is larger after a double-layer uterine closure procedure than following a single-layer... Background: The myometrium at the location of the CS (caesarean section) scars, also known as residual myometrium thickness (RMT), is larger after a double-layer uterine closure procedure than following a single-layer one. It may lessen the formation of a niche that is the myometrium’s disruption at the location of the scar of the uterus. Gynecological manifestations, obstetric problems in a future pregnancy and birth, and maybe subfertility are linked to thin RMT and a niche. Objective: To ascertain if double-layer unlocked closure of the uterus is better than single-layer one in terms of post-menstrual spotting and niche development following a first CS. Patients and Methods: In this randomized clinical study, 287 patients were evaluated for qualifying. Of all eligible individuals, 57 patients were excluded from the study based on the inclusion criteria. Results: The variation in ages, gestational age, body mass index (BMI), and cesarean section indications between the two assigned groups is statistically insignificant. However, postmenstrual spotting was statistically significantly more common in single-layer group compared to in double-group. The current study revealed ultrasound findings suggestive of niche formation was statistically significantly more common in single-layer group compared to in double-layer group. Conclusion: As evident from the current study, it demonstrates the advantages of double-layer unlocked closure of the uterus over single-layer one in terms of post-menstrual spotting and niche development following first-time cs. Thus, we deduced that fewer niches are formed, and fewer menstrual spotting occurs in the presence of double unlocked layers closure. To ascertain the impact of uterus closure method on post-operative niche development and the risk of obstetrics and gynaecological problems, further prospective trials with extended follow-up periods are required. 展开更多
关键词 single-layer Double Caesarean Section Residual Myometrium Thickness
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Lower Bounds of Decay Rates for Solution to the Single-Layer Quasi-Geostrophic Model
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作者 Haoyu Zhao 《Journal of Applied Mathematics and Physics》 2023年第8期2221-2230,共10页
In this paper, we study the long-time behavior of solutions of the single-layer quasi-geostrophic model arising from geophysical fluid dynamics. We obtain the lower bound of the decay estimate of the solution. Utilizi... In this paper, we study the long-time behavior of solutions of the single-layer quasi-geostrophic model arising from geophysical fluid dynamics. We obtain the lower bound of the decay estimate of the solution. Utilizing the Fourier splitting method, under suitable assumptions on the initial data, for any multi-index α, we show that the solution Ψ satisfies . 展开更多
关键词 single-layer Quasi-Geostrophic Model Lower Bounds Fourier Splitting Method
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VELOCITIES OF PRECURSOR SOLITON GENERATION IN SINGLE LAYER FLOW 被引量:3
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作者 徐肇廷 史峰岩 楼顺里 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 1997年第2期130-136,共7页
In this study, the moving velocitiy of precursor solitons, of the flow in depressed region, and of the zero-crossing of the trailing wavetrain relative to the moving disturbance for single-layer flow over topography w... In this study, the moving velocitiy of precursor solitons, of the flow in depressed region, and of the zero-crossing of the trailing wavetrain relative to the moving disturbance for single-layer flow over topography were theorecticaly determined in terms of the mass and energy conservation theorems, and were examined with numerical calculations showing good agreement with theoretical results. 展开更多
关键词 PRECURSOR SOLITON GENERATING velocity single layer flow fKdV equation
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Single atom catalyst by atomic layer deposition technique 被引量:13
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作者 Niancai Cheng Xueliang(Andy) Sun 《Chinese Journal of Catalysis》 CSCD 北大核心 2017年第9期1508-1514,共7页
Noble single‐atom catalysts have rapidly been attracting attention due to their unique catalytic properties and maximized utilization.Atomic layer deposition(ALD)is an emerging powerful technique for large‐scale syn... Noble single‐atom catalysts have rapidly been attracting attention due to their unique catalytic properties and maximized utilization.Atomic layer deposition(ALD)is an emerging powerful technique for large‐scale synthesis of stable single atom.In this review,we summarize recent developments of single atom synthesized by ALD as well as explore future research direction and trends. 展开更多
关键词 single‐atom Atomic layer deposition CATALYSIS Noble catalyst MECHANISM
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Laser Multi-layer Cladding Experiment on the DD3 Single Crystal Using FGH95 Powder: Investigation on the Microstructure of Single Crystal Cladding Layer 被引量:3
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作者 冯莉萍 黄卫东 +3 位作者 林鑫 杨海鸥 李延民 杨健 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2002年第2期121-127,共7页
Laser multi\|layer cladding experiments were performed on the substrate of DD3 single crystal with FGH95 powder as cladding material. The solidification microstructure in the sample was investigated. It was found th... Laser multi\|layer cladding experiments were performed on the substrate of DD3 single crystal with FGH95 powder as cladding material. The solidification microstructure in the sample was investigated. It was found that the solidification microstructure was greatly influenced by the crystallography orientation of the substrate and the local solidification conditions. When the angle between the preferred orientation of the single crystal and the direction of heat flow in the cladding layer is less than 30°, single crystal cladding layers were acquired. Otherwise the crystallography orientation of the cladding layer will deviate from the orientation of the substrate and the microstructure with polycrystalline appears. Meanwhile, even when the experiments were performed on the same preferred crystal surface, the solidification microstructures will be different distinctly resulting from the variation of the local solidification conditions. The secondary arms were degenerated and the primary arm spacing was about 10\|20 μm. Further investigation shows that the phases of the cladding layer are mainly made up of γ,γ′ , the flower\|like γ/γ′ eutectic and carbide. The morphology of γ′ was cubical and the size is less than 0.1μm. { 展开更多
关键词 laser metal forming directional solidification \} laser multi\|layer cladding single crystal MICROSTRUCTURE composition segregation
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Experimental Study on a Single Layer Two-Way Grid Shell with Tension Members 被引量:3
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作者 Zhonghao Zhang Masumi Fujimoto +1 位作者 Atsuo Takino Katsuhiko Imai 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2015年第4期10-19,共10页
Single layer two-way grid shell with in-plane and out-of-plane tension members is a new type of single-layer latticed shell roofs. Compared with traditional single-layer latticed shells,this new type has a unique mesh... Single layer two-way grid shell with in-plane and out-of-plane tension members is a new type of single-layer latticed shell roofs. Compared with traditional single-layer latticed shells,this new type has a unique mesh form and excellent rigidity. In order to further understand the buckling behaviors of single layer two-way grid cylindrical shell roof with tension members,the buckling experiments have been undertaken to investigate the effect of tension members,in either out-of-plane or in-plane placement. A single layer two-way grid cylindrical shell roof with out-of-plane tension members has been tested under symmetric and asymmetric loading. The tension member placement,the introducing initial axial force to tension members and the load patterns are considered to investigate the buckling behavior. Experimental results indicate that four long out-ofplane tension members work well under symmetrical loading,but only two long out-of-plane tension members work under asymmetrical loading. It can be concluded that the PC bar members used as tension members for this study are useful in the construction of a single layer two-way grid cylindrical shell roof with structural members intersecting at small angles. 展开更多
关键词 single layer two-way grid shell tension members out-of-plane placement buckling behavior truss system
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An efficient source wavefield reconstruction scheme using single boundary layer values for the spectral element method 被引量:3
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作者 YouShan Liu Tao Xu +3 位作者 YangHua Wang JiWen Teng José Badal HaiQiang Lan 《Earth and Planetary Physics》 CSCD 2019年第4期342-357,共16页
In the adjoint-state method, the forward-propagated source wavefield and the backward-propagated receiver wavefield must be available simultaneously either for seismic imaging in migration or for gradient calculation ... In the adjoint-state method, the forward-propagated source wavefield and the backward-propagated receiver wavefield must be available simultaneously either for seismic imaging in migration or for gradient calculation in inversion. A feasible way to avoid the excessive storage demand is to reconstruct the source wavefield backward in time by storing the entire history of the wavefield in perfectly matched layers. In this paper, we make full use of the elementwise global property of the Laplace operator of the spectral element method (SEM) and propose an efficient source wavefield reconstruction method at the cost of storing the wavefield history only at single boundary layer nodes. Numerical experiments indicate that the accuracy of the proposed method is identical to that of the conventional method and is independent of the order of the Lagrange polynomials, the element type, and the temporal discretization method. In contrast, the memory-saving ratios of the conventional method versus our method is at least N when using either quadrilateral or hexahedron elements, respectively, where N is the order of the Lagrange polynomials used in the SEM. A higher memorysaving ratio is achieved with triangular elements versus quadrilaterals. The new method is applied to reverse time migration by considering the Marmousi model as a benchmark. Numerical results demonstrate that the method is able to provide the same result as the conventional method but with about 1/25 times lower storage demand. With the proposed wavefield reconstruction method, the storage demand is dramatically reduced;therefore, in-core memory storage is feasible even for large-scale three-dimensional adjoint inversion problems. 展开更多
关键词 spectral element METHOD SOURCE wavefield reconstruction single boundary layer memory-saving ratio ADJOINT METHOD reverse time migration
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Domain Decomposition for Wavelet Single Layer on Geometries with Patches 被引量:3
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作者 Maharavo Randrianarivony 《Applied Mathematics》 2016年第15期1798-1823,共27页
We focus on the single layer formulation which provides an integral equation of the first kind that is very badly conditioned. The condition number of the unpreconditioned system increases exponentially with the multi... We focus on the single layer formulation which provides an integral equation of the first kind that is very badly conditioned. The condition number of the unpreconditioned system increases exponentially with the multiscale levels. A remedy utilizing overlapping domain decompositions applied to the Boundary Element Method by means of wavelets is examined. The width of the overlapping of the subdomains plays an important role in the estimation of the eigenvalues as well as the condition number of the additive domain decomposition operator. We examine the convergence analysis of the domain decomposition method which depends on the wavelet levels and on the size of the subdomain overlaps. Our theoretical results related to the additive Schwarz method are corroborated by numerical outputs. 展开更多
关键词 WAVELET single layer PATCH Domain Decomposition Convergence Graph Partitioning Condition Number
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Study on electrical defects level in single layer two-dimensional Ta2O5 被引量:1
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作者 李大海 宋雄飞 +5 位作者 胡林峰 王子仪 张荣君 陈良尧 张卫 周鹏 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第4期339-343,共5页
Two-dimensional atomic-layered material is a recent research focus, and single layer Ta205 used as gate dielectric in field-effect transistors is obtained via assemblies of Ta205 nanosheets. However, the electrical pe... Two-dimensional atomic-layered material is a recent research focus, and single layer Ta205 used as gate dielectric in field-effect transistors is obtained via assemblies of Ta205 nanosheets. However, the electrical performance is seriously affected by electronic defects existing in Ta2Os. Therefore, spectroscopic ellipsometry is used to calculate the transition energies and corresponding probabilities for two different charged oxygen vacancies, whose existence is revealed by x-ray photoelectron spectroscopy analysis. Spectroscopic ellipsometry fitting also calculates the thickness of single layer Ta2Os, exhibiting good agreement with atomic force microscopy measurement. Nondestructive and noncontact spectroscopic ellipsometry is appropriate for detecting the electrical defects level of single layer Ta2O5. 展开更多
关键词 single layer electronic defects spectroscopic ellipsometry
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The exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses 被引量:1
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作者 胡晓龙 张江勇 +2 位作者 尚景智 刘文杰 张保平 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第11期653-657,共5页
This paper studies the exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses by low temperature photoluminescence (PL) measurements. With increasing cap la... This paper studies the exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses by low temperature photoluminescence (PL) measurements. With increasing cap layer thickness, the PL peak energy shifts to lower energy and the coupling strength between the exciton and longitudinal- optical (LO) phonon, described by Huang-Rhys factor, increases remarkably due to an enhancement of the internal electric field. With increasing excitation intensity, the zero-phonon peak shows a blueshift and the Huang-Rhys factor decreases. These results reveal that there is a large built-in electric field in the well layer and the exciton-LO-phonon coupling is strongly affected by the thickness of the cap layer. 展开更多
关键词 exciton longitudinal-optical-phonon InGaN/GaN single quantum well GaN cap layer Huang-Rhys factor
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Stability of Low Crested and Submerged Breakwaters with Single Layer Armouring 被引量:4
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作者 Markus Muttray Erik ten Oever Bas Reedijk 《Journal of Shipping and Ocean Engineering》 2012年第3期140-152,共13页
The stability of single layer armour units on low crested and submerged breakwaters has been investigated in 2D hydraulic model tests. Armour unit movements including settlements, rocking and displacements have been d... The stability of single layer armour units on low crested and submerged breakwaters has been investigated in 2D hydraulic model tests. Armour unit movements including settlements, rocking and displacements have been determined. The effect of freeboard, packing density and wave steepness on the armour layer stability on crest, front and rear slope has been investigated. Armour units were mostly displaced in the most upper part of the seaward slope and at the seaward side of the crest. Damage on the crest was progressing towards the rear slope. About 40% to 50% larger armour units are required on the seaward slope and crest of low crested structures (as compared to conventional high crested breakwaters). About 35% larger armour units are required on the rear slope. Larger armour units are not required on submerged breakwaters if the water depth on the crest exceeds 40% of design wave height. 展开更多
关键词 Rubble mound breakwater low crested breakwater armour layer stability single layer armour units Xbloc.
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Steady thermocapillary-buoyant convection in a shallow annular pool. Part 1:Single layer fluid 被引量:1
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作者 You-Rong Li Shuang-Cheng Wang Chuan-Mei Wu 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2011年第3期360-370,共11页
This paper examines the steady thermocapillarybuoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow... This paper examines the steady thermocapillarybuoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow and thermal fields in the case of small aspect ratios,which is defined as the ratio of the layer thickness to the gap width. The flow domain is divided into the core region away from the cylinder walls and two end regions near each cylinder wall. Asymptotic solutions are obtained in the core region by solving the core and end flows separately and then joining them through matched asymptotic expansions. For the system of silicon melt,the asymptotic solutions are compared with the results of numerical simulations. It is found that the two kinds of solutions have a good agreement in the core region for a small aspect ratio. With the increase of aspect ratio,the applicability of the present asymptotic solutions decreases gradually. 展开更多
关键词 Thermocapillary-buoyant flow. Annular shallow pool. single layer fluid. Asymptotic solution
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Vertical two-dimensional non-hydrostatic pressure model with single layer
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作者 康玲 郭晓明 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2013年第6期721-730,共10页
The vertical two-dimensional non-hydrostatic pressure models with multiple layers can make prediction more accurate than those obtained by the hydrostatic pres- sure assumption. However, they are time-consuming and un... The vertical two-dimensional non-hydrostatic pressure models with multiple layers can make prediction more accurate than those obtained by the hydrostatic pres- sure assumption. However, they are time-consuming and unstable, which makes them unsuitable for wider application. In this study, an efficient model with a single layer is developed. Decomposing the pressure into the hydrostatic and dynamic components and integrating the x-momentum equation from the bottom to the free surface can yield a horizontal momentum equation, in which the terms relevant to the dynamic pressure are discretized semi-implicitly. The convective terms in the vertical momentum equation are ignored, and the rest of the equation is approximated with the Keller-box scheme. The velocities expressed as the unknown dynamic pressure are substituted into the continuity equation, resulting in a tri-diagonal linear system solved by the Thomas algorithm. The validation of solitary and sinusoidal waves indicates that the present model can provide comparable results to the models with multiple layers but at much lower computation cost. 展开更多
关键词 vertical two-dimensional model non-hydrostatic pressure single layer Thomas algorithm WAVE
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Calculating single layer production contribution of heavy oil commingled wells by analysis of aromatic parameters in whole-oil GC-MS
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作者 Xu Yaohui Ma Li +3 位作者 Li Linxiang Cui Wenfu Cheng Xiaowei Wang Xiaoping 《Petroleum Science》 SCIE CAS CSCD 2014年第1期89-96,共8页
Traditional fluid production profile logging is not usually suitable for heavy-viscous crude oil wells.Biodegradation of heavy oil can lead to the loss of n-alkanes,and the use of chromatogram fingerprint techniques i... Traditional fluid production profile logging is not usually suitable for heavy-viscous crude oil wells.Biodegradation of heavy oil can lead to the loss of n-alkanes,and the use of chromatogram fingerprint techniques in studying the production contributions of single layers in heavy oil commingled wells has limitations.However,aromatic compounds are relatively well preserved.We took the heavy oil commingled wells of small layers NG55 and NG61 in the ninth area of the Gudong oil field as examples.Based on the principle of chromatography,the whole-oil GC-MS was used,and the aromatic parameters which have a strongly linear relationship with the ratio of mixed two end member oils were verified and selected in laboratory.Studies showed that the ratio of (1,4,6-+ 2,3,6-trimethylnaphthalene) to 1,2,5-trimethylnaphthalene has a strongly linear relationship with the ratio of the mixed two end member oils (R2=0.992).The oil contributions from single layers NG55 and NG61 in six commingled heavy oil wells were calculated using established charts and this relationship.The calculated results are consistent with the results of long period dynamic monitoring and logging interpretation in the study area and can provide a scientific basis for monitoring production performance and hierarchical management of reservoirs.The study provides a new geochemical method for calculation of the contributions of single layers in heavy oil commingled wells when conventional fluid production profile logging is not suitable. 展开更多
关键词 Whole-oil GC-MS aromatic parameters commingled producing wells single layer production the ninth area of the Gudong oilfield
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Ultra-thin circularly polarized lens antenna based on single-layered transparent metasurface 被引量:1
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作者 Kaiyue Liu Guangming Wang +3 位作者 Tong Cai Wenlong Guo Yaqiang Zhuang Gang Liu 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第8期235-241,共7页
Circularly polarized (CP) lens antenna has been applied to numerous wireless communication systems based on its unique advantages such as high antenna gain, low manufacturing cost, especially stable data transmissio... Circularly polarized (CP) lens antenna has been applied to numerous wireless communication systems based on its unique advantages such as high antenna gain, low manufacturing cost, especially stable data transmission between the transmitter and the receiver. Unfortunately, current available CP lens antennas mostly suffer from high profile, low aperture efficiency as well as complex design. In this paper, we propose an ultra-thin CP lens antenna based on the designed single- layered Pancharatnam-Berry (PB) transparent metasurface with focusing property. The PB metasurface exhibits a high transmissivity, which ensures a high efficiency of the focusing property. Launched the metasurface with a CP patch antenna at its focal point, a low-profile lens antenna is simulated and measured. The experimental results show that our lens antenna exhibits a series of advantages including high radiation gain of 20.7 dB, aperture efficiency better than 41.3%, and also narrow half power beam width (HPBW) of 13°at about 14GHz. Our finding opens a door to realize ultra-thin transparent metasurface with other functionalities or at other working frequencies. 展开更多
关键词 lens antenna ULTRA-THIN transparent Pancharatnam-Berry (PB) metasurface single-layered
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Ionospheric time delay corrections based on the extended single layer model over low latitude region
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作者 Sahithi Karanam D.Venkata Ratnam J.R.K.Kumar Dabbakuti 《Geodesy and Geodynamics》 2019年第3期235-240,共6页
Ionospheric delay error is considered to be one of the most prominent factors impacting the Global Navigation Satellite Systems(GNSS) positioning and navigation accuracies. Due to dispersive nature and anisotropic of ... Ionospheric delay error is considered to be one of the most prominent factors impacting the Global Navigation Satellite Systems(GNSS) positioning and navigation accuracies. Due to dispersive nature and anisotropic of the ionosphere above certain regions, the positioning accuracy is seriously affected when using a precision-limited model. In this paper, an attempt has been taken to estimate ionosphere-delays based on Planar Fit(PF) and Spherical Harmonic Function(SHF) models by applying the commonly used single layer Model(SLM) and an extended single layer model(ESLM) which has been explored sparsely over the region. The results show that ESLM of PF and SHF techniques performed better in estimating ionospheric delay compared to the existing SLM model. Although the performance of the ESLM approach is almost comparable to the SLM results during the quiet ionospheric conditions, the ESLM-PF and ESLMSHF models led to respective improvements of 4.66% and 7.14% over the classically used SLM model under the disturbed ionospheric conditions. In view of the uneven variability of equatorial/low latitude ionosphere above the Indian subcontinental region, the suitability of ESLM-PF and ESLM-SHF models has been emphasized and suggested for assessing its completeness and reliableness across other parts of the globe. The output of this work may be useful for high precession GNSS positioning through mitigating the ionospheric delays under quiet as well as varied ionospheric conditions across the low/equatorial latitude regions. 展开更多
关键词 Global Navigation Satellite Systems(GNSS) Planar fit(PF) Spherical Harmonic Function(SHF) EXTENDED single layer model(ESLM)
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Practical Universal Method for Designing Single-Layer Electromagnetic Wave Absorbers
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作者 Benjamin Jacard Alvaro Valenzuela Manuel Gonzalez 《Open Journal of Antennas and Propagation》 2018年第4期84-92,共9页
A simple design method for electromagnetic wave absorbers under normal incidence is presented. For the fabrication of the microwave absorbing material a novel design chart is used, including curves of constant ?ratio ... A simple design method for electromagnetic wave absorbers under normal incidence is presented. For the fabrication of the microwave absorbing material a novel design chart is used, including curves of constant ?ratio in a? plane. The practical use of the chart is explained and, as example, a microwave absorber fabricated with magnetite-impregnated plastisol is designed and tested at X-band frequencies. 展开更多
关键词 PERMITTIVITY PERMEABILITY single layer Microwave Absorption REFLECTION LOSS
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Nanoscale mass sensing based on vibration of single-layered graphene sheet in thermal environments 被引量:2
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作者 S.Ahmad Fazelzadeh Esmaeal Ghavanloo 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2014年第1期84-91,共8页
Based on vibration analysis, single-layered graphene sheet (SLGS) with multiple attached nanoparticles is developed as nanoscale mass sensor in thermal environments. Graphene sensors are assumed to be in simplysuppo... Based on vibration analysis, single-layered graphene sheet (SLGS) with multiple attached nanoparticles is developed as nanoscale mass sensor in thermal environments. Graphene sensors are assumed to be in simplysupported configuration. Based on the nonlocal plate the- ory which incorporates size effects into the classical theory, closed-form expressions lot the frequencies and relative fre- quency shills of SLGS-based mass sensor are derived using the Galerkin method. The suggested model is justified by a good agreement between the results given by the present model and available data in literature. The effects of tem- perature difference, nonlocal parameter, the location of the nanoparticle and the number of nanoparticles on the relative frequency shift of the mass sensor are also elucidated. The obtained results show that the sensitivity of the SLGS- based mass sensor increases with increasing temperature difference. 展开更多
关键词 Vibration - single-layered graphene sheet. Ther- mal environment - Nonlocal elasticity theory Relative frequency shift
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Gap opening and tuning in single-layer graphene with combined electric and magnetic field modulation 被引量:1
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作者 林鑫 王海龙 +1 位作者 潘晖 许怀哲 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第4期446-455,共10页
The energy band structure of single-layer graphene under one-dimensional electric and magnetic field modulation is theoretically investigated. The criterion for bandgap opening at the Dirac point is analytically deriv... The energy band structure of single-layer graphene under one-dimensional electric and magnetic field modulation is theoretically investigated. The criterion for bandgap opening at the Dirac point is analytically derived with a two-fold degeneracy second-order perturbation method. It is shown that a direct or an indirect bandgap semiconductor could be realized in a single-layer graphene under some specific configurations of the electric and magnetic field arrangement. Due to the bandgap generated in the single-layer graphene, the Klein tunneling observed in pristine graphene is completely suppressed. 展开更多
关键词 gap opening at Dirac point single-layer graphene electric and magnetic superlattice second-order perturbation
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Pseudohalide induced tunable electronic and excitonic properties in two-dimensional single-layer perovskite for photovoltaics and photoelectronic applications 被引量:1
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作者 Zhuo Xu Ming Chen Shengzhong(Frank)Liu 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2019年第9期106-113,共8页
Two-dimensional(2D) layered organic-inorganic hybrid perovskites have attracted much more attention for some applications than their three-dimensional(3D) perovskite counterparts due to their promising thermal and moi... Two-dimensional(2D) layered organic-inorganic hybrid perovskites have attracted much more attention for some applications than their three-dimensional(3D) perovskite counterparts due to their promising thermal and moisture stabilities.In particular, the 2D perovskite devices have shown better promise for optoelectronic applications.However, tunability of optoelectronic properties is often demanded to improve the device performance.Herein, we adopt a newly method to tune the electronic properties of 2D perovskite by introducing pseudohalide into the structure.In this work, we designed a pseudohalidesubstituted 2D perovskite by substituting the out-of-plane halide with pseudohalide and studied the electronic and excitonic properties of 2D-BA2MX4 and 2D-BA2MX2Ps2(M=Ge^(2+), Sn^(2+), and Pb^(2+);X=I;Ps=NCO, NCS, OCN, SCN, Se CN).We revealed the dependence of electronic properties including band gaps, composition of band edges, bonding characteristics, work functions, effective masses, and exciton binding energies on different pseudohalides substituted in 2D perovskite.Our results indicate that the substitution of pseudohalide in 2D perovskites is energetically favorable and can significantly affect the bonding characteristics as well as the CBM and VBM that often play major role in determining their performance in optoelectronic devices.It is expected that the pseudohalide substitution will be helpful in developing more advanced optoelectronic device based on 2D perovskite by optimizing band alignment and promoting charge extraction. 展开更多
关键词 Two-dimensional perovskites Pseudohalides Density functional theory Electronic and excitonic properties
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