Step Structure Research Articles

Double-Sided Microwells with a Stepped Through-Hole Membrane for High-Throughput Microbial Assays.

To improve the throughput of microwell arrays for identifying immense cellular diversities even at a single-bacteria level, further miniaturization or densification of the microwells has been an obvious breakthrough. However, controlling millions of nanoliter samples or more at the microscale remains technologically difficult and has been spatially restricted to a single open side of the microwells. Here we employed a stepped through-hole membrane to utilize the bottom as well as top side of a high-density nanoliter microwell array, thus improving spatial efficiency. The stepped structure shows additional effectiveness for handling several millions of nanoliter bacterial samples in the overall perspectives of controllability, throughput, simplicity, versatility, and automation by using novel methods for three representative procedures in bacterial assays: partitioning cells, manipulating the chemical environment, and extracting selected cells. As a potential application, we show proof-of-concept isolation of rare cells in a mixed ratio of 1 to around 106 using a single chip. Our device can be further applied to various biological studies pertaining to synthetic biology, drug screening, mutagenesis, and single-cell heterogeneity.

Numerical analysis of shipping water impacting a step structure

Shipping water, the flow washing over and impacting the upper decks of ships and offshore structures, occurs frequently during their service life and often causes structural problems. For engineers to design safe floating structures subjected to shipping water it is essential to gain an in-depth understanding of its depth and flow field, and the resulting impact forces. In this work, Computational Fluid Dynamics (CFD) is applied to understand the physics of shipping water washing over a stepped platform. We find that the most accurate solutions are obtained with the k−ε turbulence closure. The hydrodynamic load generated by the shipping water is found to strongly depends on the kinematic energy of the water hitting the step. It is shown that with smaller values of the freeboard a more dynamic flow ensues, with a stronger vortex and larger velocity gradient resulting in deeper shipping water and a larger impact force.

Thermal shock behaviours of atmospheric plasma sprayed NiCrAlY/Al2O3–20%TiO2 gradient coating on Cu–Be alloy

ABSTRACT NiCrAlY/Al2O3–20 wt-%TiO2 gradient coating on Cu–Be substrate was fabricated by atmospheric plasma spraying method. Effect of the phase composition and the microstructure of gradient coating on thermal shock behaviours were investigated by using the X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry. The gradient coating shows a typical lamellar structure with a uniform thickness and good interface. The microhardness of gradient coating was 875 HV compared to the substrate of 199 HV. The thermal shock failure of gradient coating took place after 467 and 37 cycles at 400 and 600°C, respectively. The spallation boundaries of gradient coating with a step structure could be divided into three regions: coating spallation region (I), oxidation region (II) and coating region (III). The mechanism of thermal shock failure was discussed.

A modified proposed capacitance model for step structure capacitive RF MEMS switch by incorporating fringing field effects

ABSTRACT This paper presents a new expression for the capacitance model based on ligament efficiency. The parallel plate capacitance is the first component derived based on the percentage of ligament efficiency and the second component which is fringing field capacitance is the combination of both existing Yang’s fringing field developed by the perforations and Meji’s capacitance model developed for fringing field due to sidewalls of parallel plates. The proposed model is the combination of three components and enhances accuracy to estimate the total capacitance. The proposed model contributes up to 10% and 2% of the fringing field in upstate capacitance and downstate conditions. The proposed capacitance model is validated by designing in FEM tool to obtain the deviation between the results and respective deviation is expressed as the percentage of error which results from 0.013% to 2.10% in up and downstate conditions. The error percentages are analysed for different ligament efficiencies to obtain the optimum value to enhance the performance of the switch.

(Invited) Intercalation Anodes Based on Titanium Oxides for Sodium-Ion Batteriesmmd

Possible supply security issues associated with lithium-ion batteries have recently prompted further research into sodium-ion analogs, which can be used as drop-in replacements. Sodium ion batteries have reached a fairly advanced level of development and are probably the closest of all the “Beyond Lithium Ion” systems to commercialization. At present, hard carbons are the most commonly used anode materials for sodium-ion batteries, but these materials have some drawbacks, such as potential safety issues due to the very low insertion potentials. While several alloy systems such as Na/Sn or Na/P have been suggested as alternatives, the large volume changes are difficult to manage and have a negative impact on energy density. We have recently described several types of intercalation anodes based on sodium titanates with low potentials and high capacities. These materials are denser than carbon and have smaller volume changes than the alloys. One of these is “sodium nonatitanate” (NaTi3O6(OH)·2H2O), a stepped layered structure made hydrothermally and dried to remove interlayer water. Capacities are somewhat dependent upon drying temperature, with a maximum close to 200 mAh/g achieved for the material treated at 500°C. These anodes show excellent reversibility, which may be a consequence of their structure, which appears to have some tunnel-like features. Lepidocrocite-type (corrugated structure) titanates are another attractive group of materials with similar electrochemical properties, including good reversibility and high capacities. These materials will be discussed in more detail for this presentation.

ANALYSIS ON CONSTRUCTION DEFORMATION AND SUPPORTING STRUCTURE OF TWO-STEP AND THREESECTION EXCAVATION METHOD FOR SUPER LARGER SPAN HIGHWAY TUNNEL

The super larger span tunnel is a common form of highway reconstruction and expansionprojects in recent years. In order to determine the stability of tunnel structure of the two-step andthree-section excavation method of the III-level surrounding rock mass of the super larger spanhighway, the field test method was adopted. Relying on the Laohushan Tunnel in Jinan, Shandong,China, the deformation and the structure performance of the super larger span tunnel in III-levelsurrounding rock mass are analyzed, and the safety of the tunnel and the support structure isevaluated on this basis. The results show that the maximum settlement of the arch section of theGrade III surrounding rock section is 12.5mm, and the maximum clearance convergence is 5.8mm.Both of them are much smaller than the design reserved deformation of 80mm. The maximumpressure of the surrounding rock is 0.091MPa, showing that the force acting on the supportingstructure by surrounding rock mass is small. The inner and outer arched parts of the steel frameare subject to large stresses, and most of them are tensile stresses. The maximum stress of thesteel frame is 283 MPa, and occurs at the inner side of right arch waist. Although the local stressexceeds the yield strength of the steel (235 MPa), it does not exceed its ultimate compressivestrength of 400 MPa, and the tensile and compressive stress values of the other inner and outerparts do not exceed the yield strength. Mainly, the maximum stress appears on the left side wall,reaching 4.83 MPa, which is far less than the ultimate compressive strength of sprayed concrete(11.9 MPa). For super larger span highway tunnels, located in III-level surrounding rock mass,constructed by two-step and three-section excavation method, the initial support effectivelycontrolled the tunnel deformation, the supporting structures were fully protected and the tunnelstructure was stable. The super larger span tunnel is a common form in the road reconstructionand expansion project in recent years. In order to determine the stability of tunnel structure of thetwo steps and three excavation method of the III-level surrounding rock mass of the super largerspan highway, the field test method was adopted. Relying on the Laohushan Tunnel, thedeformation and the structure performance of the super larger span tunnel in III-level surroundingrock mass were analyzed. The results show that the maximum settlement of arch of the III-levelsurrounding rock mass is 12.5mm in super larger span highway tunnel, and the maximumclearance convergence is 5.8mm. Both of them are smaller than the design reserved deformationof 80mm. The maximum surrounding rock mass pressure is 0.091MPa, the force acting on thesupporting structure by surrounding rock mass are small. The inner and outer arched parts of the steel frame bear larger stress, and are mostly tensile stress. The maximum stress on inner side ofthe steel frame is 283 MPa, and occurs at the right arch waist. The maximum stress on the outerside of the steel frame is184 MPa, and occurs at the vault. The steel frame plays an important rolein the initial support, however the force does not reach the yield strength of the steel. The shotcreteis subjected to pressure, the maximum stress appears on the left side wall is 4.83 MPa, which ismuch smaller than the ultimate compressive strength of shotcrete of 25 MPa. So for super largerspan highway tunnels, located in III-level surrounding rock mass, constructed by two-step andthree-excavation method, the whole structure is stable.

Development of a low stress RF MEMS double-cantilever shunt capacitive switch

In this paper, a novel RF MEMS shunt capacitive switch with application in the Ka frequency band is proposed. The spring design and the step structure added to the beam succeeded in improving the performance of the switch and reducing the stress which results in extended life-time of the switch. Also, by optimally reducing the gap between the dielectric and the beam (without problems such as self-actuation), the actuation voltage of the switch is significantly reduced. Electromechanical and scattering parameters analysis have been done by using COMSOL Multiphysics and HFSS software, respectively. The actuation voltage of the proposed device is 9.2 V. Since the aluminum has a lower mass compared to gold, an aluminum beam has been used in the switch. Desirable scattering parameters at the resonance frequency of 33.5 GHz have been obtained which include insertion loss of − 0.3 dB and return loss of − 18 dB. The high isolation of − 57 dB verifies the improved performance of the switch. Finally, as another innovation in this paper, the effect of inductor and capacitor presence in the input of transmission line is investigated. This analysis has been done by using ADS. Results of the circuit analysis presented in this paper, help the MEMS switch designers to understand the realistic switch behavior before fabrication which considerably saves cost and time.

Modeling and nonlinear analysis of stepped beam energy harvesting from galloping vibrations

This paper presents a nonlinear distributed-parameter model for harvesting energy from galloping oscillation. The stepped beam structure is beneficial to increase the stress and strain of the piezoelectric elements, thereby enhancing the power generation. The finite element analysis is used to verify the feasibility and effectiveness of the developed harvester. A nonlinear distributed-parameter model for the piezoelectric energy harvester with a stepped beam is developed. The instantaneous fluid force in the transverse direction is analyzed. Based on Euler-Bernoulli beam theory, a distributed-parameter model for undamped free vibration is derived, which can be used for the modal analysis. The electromechanical coupling model is established by using the piezoelectric effect theory. The forced vibration subjected to the galloping excitation load is analyzed by using the mode superposition method. The state vector and the fourth order Runge-Kutta algorithm are used to seek the numerical solution. The effects of the electrical load resistance, length, width and thickness of the piezoelectric beam, exposure area and mass of the bluff body on the output power are investigated. In order to find the optimal design of the energy harvester, optimization design is performed based on the established theoretical model. The particle swarm optimization algorithm is employed to search the optimal solution in multidimensional space. Finally, experimental work was carried out, the electrical output characteristics of the energy harvester prototypes were measured. The simulation results are validated with the experimental data. It is demonstrated that the optimal configuration of the energy harvester can improve the output power from galloping phenomenon effectively.

Optimization design of the in-place-machining tool beam for FRPs bonded repair

Inward-bonded Patch technology is a common method for repairing defects and damage of (Fiber Reinforce Plastics) FRP parts. In the project, there is an urgent need for an in-situ machining machine with a concave step structure in the method. Such thin-walled, weakly rigid parts are easily deformed under pressure. Therefore, the machine beam is lightly designed to reduce the influence of compression deformation on the machining quality. In this paper, the annular (basalt fiber polymer composite) BFPC beam of a certain type of in-situ machining machine prototype is taken as the research object. Firstly, based on the analysis of the prototype working conditions, the comprehensive performance index of the beam is clarified. Using the topology optimization technology, the beam topology of the optimal topology is obtained. Finally, the establishment is established. The multi-objective optimization function with regular structural parameters as variables and minimum beam quality and deformation as the target has obtained the optimal topology and optimal performance of the beam structure.

Performance enhancement of AlGaN-based deep ultraviolet light-emitting diodes by using stepped and super-lattice n-type confinement layer

Abstract In this paper, a new n-type confinement layer that uses the stepped and super-lattice structure to replace conventional n-type AlGaN layer of deep ultraviolet light-emitting diode (DUV LED) is investigated. The simulation results indicate that the new structure significantly enhances the light output power (LOP) and internal quantum efficiency (IQE) of DUV LED. This is because the capability of carrier confinement in the quantum wells (QWs) is enhanced; the carrier concentrations and the radiative recombination rate in the active region of DUV LED are improved.

Dispersion-tunable chalcogenide tri-cladding fiber based on novel continuous two-stage extrusion

A novel robust tri-cladding stepped fiber structure has been proposed for the dispersion tuning, and a systematic simulation has been given for the fibers with different sizes of claddings and cores. The results show that double zero-dispersion wavelength (ZDW) points can be obtained, and the first ZDW is shorter at 3.3 µm and the second ZDW at 9.9 µm. Based on the simulation of the structural optimization, we have prepared a well-structured tri-cladding fiber with a minimum loss of 1.55 dB/m at 6.77 µm by a novel continuous two-stage extrusion method. Moreover, a flattened supercontinuum extending from 1.3 to 12.9 µm pumping at anomalous dispersion wavelength of 5 µm between the two ZDWs can be achieved, which fits well with the simulated results. After all, the optimized fiber consisting of As2Se3, Ge10As22Se68, As2S3 exhibits excellent properties that demonstrate the potential for a simple way to prepare high quality fiber with a tri-cladding structure.

Broadband near-perfect terahertz absorber in single-layered and non-structured graphene loaded with dielectrics.

In this work, we have done an extensive study on broadband near-perfect absorbers consisting of single-layered and non-structured graphene loaded with periodical arrays of dielectric bricks, including square and elliptical bricks. We also propose and investigate circular cylinder, rectangular brick, and racecourse dielectric structure. Moreover, the calculated ${z}$z component of the electric field enables us to understand the physical mechanism of resonance absorption. Furthermore, we also studied and proposed a new absorber with periodical arrays of stepped rectangle dielectric structure. We could achieve a broadband absorption from 1.6 to 4.2 THz, with a bandwidth of 2.6 THz and absorption over 90%. The proposed absorber is also tunable; the tunability of the terahertz (THz) broadband absorber is achieved via changing the external gate voltage to modify the Fermi energy of graphene. Also, we compared the results and absorption spectra of different dielectric structures. This THz metamaterial structure can be used in different THz applications such as cloaking, sensing, detection, and imaging.

Radio Emission Reveals Inner Meter-Scale Structure of Negative Lightning Leader Steps.

We use the Low Frequency Array (LOFAR) to probe the dynamics of the stepping process of negatively charged plasma channels (negative leaders) in a lightning discharge. We observe that at each step of a leader, multiple pulses of vhf (30-80MHz) radiation are emitted in short-duration bursts (<10 μs). This is evidence for streamer formation during corona flashes that occur with each leader step, which has not been observed before in natural lightning and it could help explain x-ray emission from lightning leaders, as x rays from laboratory leaders tend to be associated with corona flashes. Surprisingly, we find that the stepping length is very similar to what was observed near the ground, however with a stepping time that is considerably larger, which as yet is not understood. These results will help to improve lightning propagation models, and eventually lightning protection models.

Steps and Ge epitaxy on vicinal Si (111) surfaces: An STM study

Using high-resolution scanning tunneling microscopy, we investigate the periodicity of mixed arrays of single and triple steps and the atomic structure of triple steps on three vicinal Si(111) samples with off-angles 1.5 ∘ ≤ θ ≤ 9.45 ∘ towards the [1¯1¯2] direction. The comparison between the (556) and (557) triple-step structure demonstrates that only the number of 7x7 terraces is affected by miscut. At variance with the singular Si(111) case, Ge epitaxy is strongly correlated to step morphology, resulting, at the critical coverage and small misorientation, in the nucleation of holed nanoislands from step-edge protrusions. During step-flow growth, stress-driven bunching of atomic steps (ripples) is observed on the (557) surface, indicating that this mechanism of stress relief of Si(001) vicinal surfaces works also on Si(111) surfaces.

Structural-fingerprinting of polysaccharides to discern Panax species by means of gas-liquid chromatography and mass spectrometry

In this paper, a sequential gas-liquid chromatography and mass spectrometry route was proposed for characterization of polysaccharides in Panax ginseng (PG), P. notoginseng (PN), and P. quinquefolius (PQ). Due to the reflection of stepped structure parameters, the resulting integrative profiles were tentatively defined as structural-fingerprinting of polysaccharides (SFP) with monosaccharide compositional fingerprinting (MCF), Smith degradation and non-degradation fingerprinting (SDF and SNF), and oligosaccharide compositional fingerprinting (OCF). The MCF, OCF and SDF did not allow for visual discrimination of the three species due to the high interspecific similarity of PG and PQ, whereas SNF could intuitively distinguish PG, PN, and PQ by the presence or absence of Rha and the peak area ratio of Glc/Gal. Similarity analysis, heatmap analysis and principal component analysis were further performed to discern three Panax species based on SNF data sets. The linear →4)-Hexp-(1 → structures were clearly identified as the common structural backbones in side chains or smooth regions of the main chain in PPG, PPN, and PPQ using HILIC-UHPLC-ESI−-MS/MS for characterization of partial acid hydrolyzates. The experimental results displayed that the established SFP approach possesses high comprehensibility as well as satisfactory generalization capability for analysis of plant polysaccharides.

Atomic scale step structure and orientation of a curved surface ZnO single crystal

We have investigated the surface structure of a curved ZnO-crystal, going from the (0001)-facet at 0° miscut to the (101¯4)-facet at a miscut of 24.8° using scanning tunneling microscopy and low energy electron diffraction. We find that the surface separates locally into (0001)-terraces and (101¯4)-facets, where the ratio between the facets depends on the miscut angle. In X-ray photoemission spectroscopy (XPS) the intensity of an O 1s component scaling with the step density of the surface is observed. No other facets were observed and the surface maintains a high degree of order over all angles. Such a curved ZnO crystal can be used for systematic studies relating the step density to the chemical reactivity using XPS to probe the curved surface at different positions.

Knoevenagel condensation versus Michael addition reaction in ionic-liquid-catalyzed synthesis of hexahydroquinoline: a SMD–DFT study

Knoevenagel condensation and Michael addition reaction are two different mechanisms for C–C bond formation. In this work, M06-2X method is used to compare activation free energies of Knoevenagel condensation and Michael addition reaction in the gas and ionic liquid phases. The role of 2-ethyl imidazolium hydrogen sulfate in the synthesis of hexahydroquinolines is investigated. To model ionic liquid phase, SMD continuum universal solvation model is used. Data show that Knoevenagel condensation and Michael addition have activation free energies of 45 and 13 kcal mol−1 in the gas phase and + 24 and + 12 kcal mol−1 in the ionic solution phase, respectively. The final cyclization process has zero barrier energy. Analyzing TS structures by the quantum theory of atoms in molecules (QTAIM) show that the TS structure of Knoevenagel step is similar to the product, while the TS structure of Michael addition step is similar to the reactants.

A Novel Multi-Stage Stacked Triggering Method to Induce Progressive Failure Behaviors of Composite Corrugated Plate

To better induce progressive collapse modes of composite corrugated plate, a novel multi-stage stacked structure is proposed. The multi-stage stacked triggering consists of stepped structures and sawtooth cutout that guides the progressive crushing load and failure mode. The different triggering configurations including non-sawtooth, partial sawtooth, overall evenly sawtooth and overall uneven sawtooth are discussed and compared. To better predict the progressive failure process, the material failure is initiated by the maximum-stress failure criterion and a stiffness degradation method. The traction-separation model is adopted to simulate inter-layer delamination failure. Under the validated model, the influences of geometrical parameters on the crushing responses are performed. Numerical simulation results show that a good agreement is exhibited between simulated and experimental results. The progressive failure behavior could be obtained by the stepped structures and sawtooth cutout. The initial loading responses highly depend on the gradient stacking methods. The initial peak load of proposed novel multi-stage stacked concepts is about 30% lower than that of traditional structure.

Performance analysis of printed antenna on different novel substrates to enhance V2V communication in future

In recent years, advancement in wireless technologies, communication in automotive vehicles has witnessed a tremendous growth in the market. All the sophisticated wireless services offered depends on the type of antenna used in it. The researchers in antenna community are trying very hard to improve the performance of the systems by making smaller antenna devices; however they face both scientific and technical limits. Other alternative approach is to use of novel materials for patch and substrate to adhere higher performance and better functionality. In this paper rectangular patch antenna with stepped ground structure is proposed and its radiation characteristics are analyzed for different dielectric substrates like Si3N4, Al2O3, BN, Quartz and Silica. This study will facilitate researchers to get a clear idea on the patch and substrate material that can be used for V2V applications. The proposed CNT patch antenna on Si3N4 substrate resonates at 5.9 GHz is designed and simulated results show that the minimum return loss of -37 dB is achieved with maximum gain of 6.87. In Addition, the proposed antenna also achieves an omni-directional radiation pattern with maximum radiation efficiency of 89%.

New Investigations on “The Square-Plan Building” at Dascyleum

During excavations in Dascyleum in 2011, a structure was discovered and was identified as a tower located on the slope east of an area called Hisartepe in Ergili, located in the Bandırma District of Balıkesir Province. The excavations revealed that this square-plan structure was constructed over four building phases. During the first phase, a wall at the bottom northeastern corner of the structure was constructed. The second phase added a support wall (glacis) with a stepped structure that is built on the first building phase, but on a different axis to fit on top of the walls built during the first phase. In the third phase, the area in the eastern part of the glacis was filled with soil and a square structure was built on top of it. In the fourth phase, a pavement-like architectural element was constructed to the east of the building, parallel to the eastern wall of the building. The present study includes the dating of the buildings’ remains and presents the initial conclusions as to the function of the square-plan structure.&nbsp;