Lateral Alignment Research Articles

The effect of magnetic field induced aggregates on ultrasound propagation in aqueous magnetic fluid

Ultrasonic wave propagation in the aqueous magnetic fluid is investigated for different particle concentrations. The sound velocity decreases while acoustic impedance increases with increasing concentrations. The velocity anisotropy is observed upon application of magnetic field. The velocity anisotropy fits with Tarapov’s theory suggests the presence of aggregates in the system. We report that these aggregates are thermodynamically unstable and the length of aggregate changes continuously with increasing concentration and, or magnetic field and resulted in a decrease in effective magnetic moment. The Taketomi's theory fits well with the experimental data suggesting that the particle clusters are aligned in the direction of the magnetic field. The radius of cluster found to increase with increasing concentration, and then decreases whereas the elastic force constant increases and then becomes constant. The increase in cluster radius indicates elongation of aggregate length due to tip-to-tip interaction of aggregates whereas for higher concentration, the lateral alignment is more favorable than tip-to-tip alignment of aggregates which reduces the cluster radius making elastic force constant to raise. Optical images show that the chains are fluctuating and confirming the lateral alignment of chains at higher fields.

Exploring the Possibilities for Improving the Performance of the Adapters used for Launching Multiple Small Space Vehicles on a Single Launch Vehicle

Background/Objectives: The research is aimed at determining the ways to improve the effectiveness of reconfigurable and extendable multipurpose adapters for multiple launch of small space vehicles by a launch vehicle. Methods: The structural design method is selected for studying design and constructive shape of the SSV adapters. The structural approach was used to define the principle for optimization of adapters of various constructive schemes, excluding modifications of launch vehicle used for multiple launches and enabling to extend and reduce adapter configuration with respect to a universal basic structure used for all tasks for SSV launch to be solved. Findings: To obtain quasi-optimal design and engineering parameters for the entire target set of tasks solved by the adapter, based on the structural approach we have considered design schemes of multi-purpose adapters for multiple and concurrent launching of SSVs of rod, shell, beam and platform types with side and end attachment configuration, the schemes with shock absorbers mounted in the places of adapters and MCAs installation, and scheme configuration combining adapter + small upper stage. The base and extension structures have been determined to form multi-purpose adapter with flexible and extensible design. As a result of the proposed technical solutions, weight of the adapter is reduced by 30%, configuration density is increased by 30-40 %, the number of the launched SSVs is increased, the fairing length and weight is reduced by 50%, root-mean-square amplitudes of accidental vibration decreased by 2.5-3 times, level of shock loads during SSV separation decreases by 6-10 dB, provision is made for shockless separation of SSV required lateral alignment of LV, cost reduction for ground and flight tests. Application/Improvements: Further improvement of the multi-purpose adapters is connected with the co-design of “Adapter + SSV” system, taking into account the mutual influence of design and engineering parameters of the SSV, adapter and LV used to launch them.

Wideband monopole antenna tightly aligned to the ground plate

The authors propose a wideband monopole antenna that is tightly aligned to one edge of its ground plate. Wideband impedance matching with fractional bandwidth of ∼93% is attained by varying stepwise the lateral alignment of the monopole and the ground plate so that the feed side of monopole partially overlaps the ground plate. The tight alignment and overlap concentrates a part of the electric field such as a travelling wave. The step structure rotates the electric field so that the concentrated electric field in the feed side orients roughly the same direction with the electric field in the tip side which is converted into radiation. The basic antenna characteristics are examined by simulation, and verified in experiments.

Coprecipitation of Aluminum Goethite and Amorphous Al-Hydroxy-Sulfate Using Urea and Characterization of the Thermal Decomposition Products

AbstractAluminum substitution is a common phenomenon in environmental iron oxides and oxyhydroxides, affecting the color, magnetic character, surface features, etc. Several methods for preparing Al-substituted iron oxyhydroxides can be found in the literature, resulting in samples with particular properties. In the present study, the synthesis of aluminum-substituted goethites, AlxFe1-xOOH with 0 ⩽ x ⩽ 0.15, by homogeneous precipitation and the transformation to aluminum-substituted hematites, (AlxFe1-x)O3, are presented. The goethite samples were produced at 90°C from solutions of urea and iron and aluminum nitrates in the presence of ammonium sulfate (GU series). Although attempts were made to incorporate up to 33 mole% of Al into the goethite, only ~15 mole% was found to be within the structure, due to the final pH, ~7, of the synthesis. Another feature of these goethites was a lateral alignment of the tabular particles. By heating batches of the GU samples at 400°C and 800°C, two series of Al-hematites were obtained, denoted here as the HX400 and HX800 samples, respectively. X-ray diffraction, thermal analysis, Karl-Fischer titration, transmission electron microscopy, and Mössbauer spectroscopy were used to characterize the samples. The X-ray patterns showed the samples to be pure iron phases, with particle sizes of ~10 nm for the GU and HX400 samples, and of ~70 nm for the HX800 samples. An inversion in the intensities of the (104) and (110) diffraction peaks of hematite was observed to be dependent on the aluminum substitution and was explained by small particle sizes, shape anisotropy, and the presence of nanopores. The cell parameters of both GU and HX samples showed a small decrease with increasing aluminum substitution up to x ≈ 0.15. The amount of adsorbed sulfate, presumably as an aluminum hydroxy sulfate gel, increased with aluminum substitution in all GU and HX samples, reaching a maximum of ~6.5 wt.% for the highest substitution. Heating at 100°C did not remove all of the adsorbed water, and significantly higher temperatures were required to achieve complete removal. Mossbauer spectra at 295 K and 80 K are typical for small-particle goethite and hematite, and revealed that Al-for-Fe substitution in all samples seems to be limited to ~15 mol.%.

Microtube Laser Forming for Precision Component Alignment

A micro-actuator for precision alignment, using laser forming of a tube, is presented. Such an actuator can be used to align components after assembly. The positioning of an optical fiber with respect to a waveguide chip is used as a test case, where a submicron lateral alignment accuracy is required. A stainless steel tube with an outer diameter of 635 μm was used as a simple and compact actuator, where the fiber is mounted concentrically in the tube. An experimental setup has been developed to measure the fiber displacement in real time with a resolution better than 0.1 μm. In addition, this setup allows the axial and radial positioning of the laser spot over the surface of the tube. Several tube samples were (de)formed to move a fiber to a predefined position, using a laser with a wavelength of 1080 nm, a pulse length of 200 ms, and a power between 4 W and 10 W. On average of 18 laser pulses were required to reach the targeted position of the fiber with an accuracy of 0.1 μm. It has been found that increasing the laser power not only results in a larger bending angle but also in a larger uncertainty of this angle. The opposite is true for the radial bending direction, where the uncertainty decreases with increasing laser power.

Cortical Bone Thickness of the Distal Part of the Tibia Predicts Bone Mineral Density.

Poor bone density may affect surgical planning, treatment outcome, and postoperative protocols. Many patients with foot and ankle problems have not undergone a dual x-ray absorptiometry (DXA) scan, which is currently the gold standard for determining bone density. The purpose of this study was to determine if the cortical bone thickness (CBT) of the distal part of the tibia measured on radiographs correlated with bone mineral density. After exclusion criteria were applied, 167 consecutive adult patients (mean age and standard deviation [SD], 62 ± 11.62 years) who had had standardized ankle radiographs and a DXA scan within 6 months of each other were included in this retrospective study. The CBT was measured with both the gauge and the average method on standardized anteroposterior, lateral, and hindfoot alignment radiographs. The relationship between CBT in the distal part of the tibia and DXA findings in the hip, proximal part of the femur, and lumbar spine was assessed with Pearson correlations. The interrater and intrarater reliability of CBT measurements was assessed with intraclass correlation coefficients. Subgroup analysis was performed to determine the ability of CBT thresholds to predict osteoporosis. Average CBT measurements on the anteroposterior, lateral, and hindfoot alignment views strongly correlated with DXA findings in the proximal part of the femur (r = 0.70, 0.64, and 0.55, respectively; p < 0.0001), the hip (r = 0.74, 0.67, and 0.53; p < 0.0001), and the lumbar spine (r = 0.61, 0.60, and 0.47; p < 0.0001). The interrater and intrarater reliability of the CBT measurements was excellent. Use of a 3.5-mm average CBT of the distal part of the tibia on the anteroposterior view as the threshold value for predicting osteoporosis (T score less than -2.5) had a sensitivity of 100%, a specificity of 25%, an accuracy of 33%, a positive predictive value of 19%, and a negative predictive value of 100%. Measurement of the average CBT of the distal part of the tibia is a quick and reliable method for obtaining information on bone quality. CBT measured on standard ankle radiographs correlated strongly with DXA results and may prove to be a useful screening tool for osteoporosis. Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Long-range forces affecting equilibrium inertial focusing behavior in straight high aspect ratio microfluidic channels.

The controlled and directed focusing of particles within flowing fluids is a problem of fundamental and technological significance. Microfluidic inertial focusing provides passive and precise lateral and longitudinal alignment of small particles without the need for external actuation or sheath fluid. The benefits of inertial focusing have quickly enabled the development of miniaturized flow cytometers, size-selective sorting devices, and other high-throughput particle screening tools. Straight channel inertial focusing device design requires knowledge of fluid properties and particle-channel size ratio. Equilibrium behavior of inertially focused particles has been extensively characterized and the constitutive phenomena described by scaling relationships for straight channels of square and rectangular cross section. In concentrated particle suspensions, however, long-range hydrodynamic repulsions give rise to complex particle ordering that, while interesting and potentially useful, can also dramatically diminish the technique's effectiveness for high-throughput particle handling applications. We have empirically investigated particle focusing behavior within channels of increasing aspect ratio and have identified three scaling regimes that produce varying degrees of geometrical ordering between focused particles. To explore the limits of inertial particle focusing and identify the origins of these long-range interparticle forces, we have explored equilibrium focusing behavior as a function of channel geometry and particle concentration. Experimental results for highly concentrated particle solutions identify equilibrium thresholds for focusing that scale weakly with concentration and strongly with channel geometry. Balancing geometry mediated inertial forces with estimates for interparticle repulsive forces now provide a complete picture of pattern formation among concentrated inertially focused particles and enhance our understanding of the fundamental limits of inertial focusing for technological applications.

Fully passive-alignment pluggable compact parallel optical interconnection modules based on a direct-butt-coupling structure for fiber-optic applications

A low-cost packaging method utilizing a fully passive optical alignment and surface-mounting method is demonstrated for pluggable compact and slim multichannel optical interconnection modules using a VCSEL/PIN-PD chip array. The modules are based on a nonplanar bent right-angle electrical signal path on a silicon platform and direct-butt-optical coupling without a bulky and expensive microlens array. The measured optical direct-butt-coupling efficiencies of each channel without any bulky optics are as high as 33% and 95% for the transmitter and receiver, respectively. Excellent lateral optical alignment tolerance of larger than 60 μm for both the transmitter and receiver module significantly reduces the manufacturing and material costs as well as the packaging time. The clear eye diagrams, extinction ratios higher than 8 dB at 10.3 Gbps for the transmitter module, and receiver sensitivity of better than −13.1 dBm at 10.3 Gbps and a bit error rate of 10−12 for all channels are demonstrated. Considering that the optical output power of the transmitter is greater than 0 dBm, the module has a sufficient power margin of about 13 dB for 10.3 Gbps operations for all channels.

Analyzing thermal integrity profiling data for drilled shaft evaluation

Thermal integrity profiling (TIP) is the most recent non-destructive test method to gain widespread popularity in post-construction evaluation of drilled shafts. The allure lies in its ability to detect anomalies across the entire cross-section of a shaft as well as provide a measure of lateral cage alignment. Similarly remarkable, early developments showed that the shape of a temperature profile (with depth) matched closely with the shape of the shaft, thus allowing for a fairly straightforward interpretation of data. Immediately apparent however, was that the relationship between shape and temperature was with two major exceptions: (1) near the ends of the shaft where heat can escape both radially and longitudinally and (2) where drastic changes in the surroundings are encountered (e.g. soil to water, soil to air). Today, methods for analyzing these portions of data exist, but can often involve tedious levels of parameter iterations and trial-and-error thermal modeling. This is particularly true when th...

Fiber-Based, Injection-Molded Optofluidic Systems: Improvements in Assembly and Applications

We present a method to fabricate polymer optofluidic systems by means of injection molding that allow the insertion of standard optical fibers. The chip fabrication and assembly methods produce large numbers of robust optofluidic systems that can be easily assembled and disposed of, yet allow precise optical alignment and improve delivery of optical power. Using a multi-level chip fabrication process, complex channel designs with extremely vertical sidewalls, and dimensions that range from few tens of nanometers to hundreds of microns can be obtained. The technology has been used to align optical fibers in a quick and precise manner, with a lateral alignment accuracy of 2.7 ± 1.8 μm. We report the production, assembly methods, and the characterization of the resulting injection-molded chips for Lab-on-Chip (LoC) applications. We demonstrate the versatility of this technology by carrying out two types of experiments that benefit from the improved optical system: optical stretching of red blood cells (RBCs) and Raman spectroscopy of a solution loaded into a hollow core fiber. The advantages offered by the presented technology are intended to encourage the use of LoC technology for commercialization and educational purposes.

XPS, AFM, and electrochemical investigation on the inner composition of insulating poly(o‐aminophenol), PoAP, deposited on platinum by CV, as a function of the number of cycles

The finite electrosynthesis, requiring 20 voltammetric cycles at neutral pH, of insulating poly(o‐aminophenol) (PoAP)and its polymerization mechanism and chemical structure up to the outermost surface were reported in previous work. By reducing the number of voltammetric cycles, XPS, atomic force microscopy, and electrochemical experiments were here confined to partially grown PoAP to better understand the role of the platinum surface on the initial adhesion mechanism and polymer growth. XPS results from reduced number and conventional 20 cycles show that PoAP composition is the same at any cycle. The main differences imaged by atomic force microscopy between 1, 5, and 20 cycles are on the amount of ‘small‐sized particles’ adsorbed on platinum prone to ‘fill’ the empty sites. The progressive filling of the platinum sites with cycles was also proved by electrochemical test with potassium‐ferricyanide. These new results add valuable information, which sustain previous hypotheses on the growth process of PoAP chains, their composition, and lateral alignment. Some questions, concerning the identification of PoAP anchoring bonds on platinum, lateral H‐bonds with water, and inter‐chains interactions, still remain unanswered and will be further addressed by the employment of new advanced means of investigation already in progress. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Alignment Tolerant Couplers for Silicon Photonics

Laser integration, optical coupling, and assembly are challenging problems that need to be further addressed to reduce the manufacturing costs of silicon photonic-based products. In this paper, we propose novel coupling devices that facilitate the passive assembly of silicon photonics chips with laser diodes and optical fibers by means of pick-and-place tools by relaxing the stringent alignment tolerances required for maintaining a high coupling efficiency. In these devices, a lateral misalignment of the laser or fiber relative to the chip is accommodated by a varying phase difference between two on-chip single-mode SOI waveguides to which the light is coupled with minimal insertion loss penalty and a balanced power splitting. This device concept is successfully applied to the fabrication of in-plane laser couplers based on inverse taper arrays and out-of-plane fiber couplers with diffraction gratings. Furthermore, we experimentally demonstrate the suitability of the proposed devices for fiber array assembly in Mach–Zehnder interferometer configuration. The best devices exhibit a three-fold improvement relative to the lateral alignment tolerances of conventional couplers.

An analytical design approach for self-powered active lateral secondary suspensions for railway vehicles

In this paper, an analytical design approach for the development of self-powered active suspensions is investigated and is applied to optimise the control system design for an active lateral secondary suspension for railway vehicles. The conditions for energy balance are analysed and the relationship between the ride quality improvement and energy consumption is discussed in detail. The modal skyhook control is applied to analyse the energy consumption of this suspension by separating its dynamics into the lateral and yaw modes, and based on a simplified model, the average power consumption of actuators is computed in frequency domain by using the power spectral density of lateral alignment of track irregularities. Then the impact of control gains and actuators’ key parameters on the performance for both vibration suppressing and energy recovery/storage is analysed. Computer simulation is used to verify the obtained energy balance condition and to demonstrate that the improved ride comfort is achieved by this self-powered active suspension without any external power supply.

EyeSelfie

Eye alignment to the optical system is very critical in many modern devices, such as for biometrics, gaze tracking, head mounted displays, and health. We show alignment in the context of the most difficult challenge: retinal imaging. Alignment in retinal imaging, even conducted by a physician, is very challenging due to precise alignment requirements and lack of direct user eye gaze control. Self-imaging of the retina is nearly impossible. We frame this problem as a user-interface (UI) challenge. We can create a better UI by controlling the eye box of a projected cue. Our key concept is to exploit the reciprocity, "If you see me, I see you", to develop near eye alignment displays. Two technical aspects are critical: a) tightness of the eye box and (b) the eye box discovery comfort. We demonstrate that previous pupil forming display architectures are not adequate to address alignment in depth. We then analyze two ray-based designs to determine efficacious fixation patterns. These ray based displays and a sequence of user steps allow lateral (x, y) and depth (z) wise alignment to deal with image centering and focus. We show a highly portable prototype and demonstrate the effectiveness through a user study.

Lateral alignments – engineering and the politics of race

Lateral alignments – engineering and the politics of race

Characterization of ZnO thin film grown on c-plane substrates by MO-CVD: Effect of substrate annealing temperature, vicinal-cut angle and miscut direction

The annealing effects of c-plane sapphire (α-Al2O3) substrate with a nominally vicinal-cut angle α (α<0.1°, α=0.25° toward the m-plane (101¯0) and α=0.25° toward the a-plane (112¯0)) on the quality of epitaxial ZnO films grown by metal organic chemical vapor deposition (MO-CVD) were studied. The atomic steps formed on sapphire substrate surface by annealing at high temperature were analyzed by atomic force microscopy (AFM). The annealing and the miscut direction of sapphire substrate on the microstructural and optical properties for ZnO films were examined by high resolution X-ray diffraction (HR-XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and photoluminescence spectroscopy (PL). Experimental results indicate that the film quality is strongly affected by annealing treatment and miscut direction of the sapphire substrate. X-ray diffraction study revealed that all films exhibit a wurtzite phase and have a c-axis orientation. ZnO films deposited on sapphire substrate (α<0.1° and α=0.25° toward the m-plane (101¯0), annealed substrate at 1100°C), exhibit a low quantity of defects and a quite good vertical and lateral alignment compared to other disorientation plane (α=0.25° toward the a-plane (112¯0), annealed substrate at 1100°C). The Lattice parameters a and c slightly decreases for ZnO layer deposited on annealed sapphire substrate with increase the annealing substrate temperature for all samples. AFM image show significant differences between morphologies of samples depending on annealing treatment and miscut direction of substrates but no significant differences on surface roughness have been found. Sapphire annealing at 1100°C with a nominally vicinal-cut angle α=0.25° toward the m-plane (101¯0), provides the best optical quality of ZnO film.

Surface-Order Mediated Assembly of π-Conjugated Molecules on Self-Assembled Monolayers with Controlled Grain Structures

This study systematically demonstrates the effects of the grain structure of crystalline self-assembled monolayers (SAMs) on the growth of organic semiconductor thin films on such monolayers, as well as the electrical characteristics of the resulting semiconductor films. The grain structure of the octadecyltrichlorosilane (OTS) monolayers could be tailored by constructing the monolayers at three different temperatures: −30 °C (−30 °C OTS), −5 °C (−5 °C OTS), and 20 °C (20 °C OTS). Among the three layers, −30 °C OTS exhibited the largest crystalline grains and longest-range homogeneity of alkyl chain arrays. We found that pentacene films deposited on −30 °C OTS monolayers show larger crystalline grains with higher degrees of crystallinity and lateral alignment compared to that of films deposited on −5 °C OTS or 20 °C OTS monolayers, following the surface characteristics of the underlying OTS monolayers. Furthermore, pentacene field-effect transistors fabricated with −30 °C OTS monolayers showed lower charg...

Lower limb alignment control: Is it more challenging in lateral compared to medial unicondylar knee arthroplasty?

IntroductionLimb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on outcomes. The literature lacks lateral UKA alignment studies, making our understanding of this issue based on medial UKA. MethodsWe evaluated limb alignment in 241 patients who underwent medial (229 knees) or lateral (37 knees) UKA. Alignment was measured pre and postoperatively in radiographs and intra-operatively using a navigation system. We compared the percentage of over-correction and the difference between post-operative alignment and navigation measurement. ResultsPercentage of overcorrection was significantly higher in the lateral UKAs (11%) compared to the medial UKAs (4%). In medial UKAs, the mean difference between the intraoperative alignment and the post-operative was 1.33°. This was significantly lower than the mean 1.86° difference in the lateral UKAs. ConclusionsOur data demonstrated an increased risk of “overcorrection,” and greater difficulty in predicting postoperative alignment using computer navigation, when performing lateral UKAs compared to medial UKAs.

Self-assembly of amphiphilic peptides: Effects of the single-chain-to-gemini structural transition and the side chain groups

Abstract By designing cysteine-containing single-chain peptides and then linking two such molecules with disulfide bond under oxidation, a series of amphiphilic gemini peptides were successfully synthesized. The gemini geometry introduced not only additional constraints in molecular conformations but also the differentiated intra- and intermolecular hydrogen bonding. These aspects result in specific transition of the self-assembly behavior. The single-chain peptides tended to form spherical aggregates, while the gemini molecules all self-assembled into fiber-like structures, especially that I3C–CI3 could form short thin fibers with highly ordered lateral alignments that are rarely found. Moreover, the self-assembly of both the single-chain and the gemini peptides showed great dependence on the side chain groups. With increasing the size of the side chain alkyl groups, the molecules gave decreased critical aggregation concentration (CAC) and were more ready to arrange into ordered assemblies. This should be ascribed to the enhanced hydrophobic interaction and the subsequent force balance shifts.

Top‐Coat Dewetting for the Highly Ordered Lateral Alignment of Block Copolymer Microdomains in Thin Films

Extremely straight and laterally aligned cylindrical microdomains of block copolymer (BCP) films have been prepared by simply covering the BCP films with a top coat and dewetting the latter via thermal annealing to generate shear flow in the BCP underlayer. The polystyrene‐block‐polydimethylsiloxane microdomains are perfectly aligned with sunburst direction along the polyvinyl alcohol top‐coat dewetting front from the nucleation point to the end of the dewetting front. This alignment is at least 150 μm long and the aspect ratio is higher than 15 000:1. Studying the morphologies obtained as a function of top‐coat and BCP film thickness at various annealing temperatures, highly ordered BCP patterns are obtained for a wide range of shear rates, while higher (but not the highest) temperatures and thicker BCP films lead to more ordered microdomain patterns, because of increased polymer mobility and a reduced surface/interface effect. An imprinting process is also introduced to pattern top coats, which then provide selective control of the dewetting direction so that unidirectionally aligned BCP patterns can be created in specific areas.