Cross-shaped Unit Research Articles

Development of Polarization-Insensitive THz-to-IR Converters for Low-IR-Signature Target Detection and Imaging.

A THz-to-IR converter can be an effective solution for the detection of low-IR-signature targets by combining the advantages of mature IR detection mechanisms with high atmospheric transmittance in the THz region. A metallic metasurface (MS)-based absorber with linear polarization dependence based on a split-ring resonator (SRR) unit cell has been previously studied as a preliminary example of a THz-to-IR converter structure in the literature. In this simulation-based study, a new cross-shaped unit cell-based metallic MS absorber structure sensitive to dual polarization is designed to eliminate linear polarization dependency, thereby allowing for incoherent detection of THz radiation. A model is developed to calculate the temperature difference and the response time for this new cross-shaped absorber structure, and its performance is compared to the SRR structure for both coherent and incoherent illumination. This model allows for understanding the efficiency of these structures by considering all loss mechanisms which previously had not been considered. It is found that both structures show similar performance under linearly polarized coherent illumination. However, under incoherent illumination, the IR emittance efficiency as gauged by the temperature difference for the cross-shaped structure is found to be twice as high as compared to the SRR structure. The results also imply that calculated temperature differences for both structures under coherent and incoherent illumination are well above the limit of the minimum resolvable temperature difference of the state-of-the-art IR cameras. Therefore, dual-polarized or multi-polarization-sensitive MS absorber structures can be crucial for developing cost-effective THz-to-IR converters and be implemented in THz imaging solutions.

High-Scanning-Rate and Wide-Scanning-Angle Leaky-Wave Antenna Based on Double-Layer Slow-Wave Structure

In this letter, a leaky-wave antenna (LWA) based on double-layer (DL) slow-wave structure, possessing high scanning rate and wide scanning angle features is investigated. The DL unit structure consists of a top layer structure with cross-shaped unit and a bottom layer structure with slot-shaped unit. The DL units realize the property of controlling the cut-off frequency and slope of dispersion curves independently by independently changing the unit slow-wave property of top and bottom layers. The radiation of LWA is achieved by triangularly modulating the cross-shaped units of top layer. Due to the existence of the slot-shaped units of bottom layer, strong slow-wave property is introduced to increase the growth rate of period phase shift, thus achieving high scanning rate. Meanwhile, the n = −2 space harmonic (SH) of the LWA is separated from the fast-wave region of n = −1 SH, thus enlarging scanning angle in forward quadrant. A prototype of the proposed LWA is fabricated and measured. The LWA can achieve a wide scanning angle from −68 ° to +74 ° in a narrow frequency band of 9 to 10.75 GHz.

Development of directed energy deposition strategy for a mechanically interlocked pure Ti and Al alloy component with cross-shaped internal pure Ti lattice

Directed energy deposition (DED) using multi-metal materials typically employs a metallurgical bonding approach. The components using titanium (Ti) and aluminum (Al) alloys have attracted significant interest in aerospace and automotive industries due to their ability to decrease fuel consumption through lightweight construction. However, DED using Ti and Al alloys that are difficult to fusion-bond is plagued by the formation of brittle intermetallic compounds. In particular, the deposition of a Ti alloy layer on that of Al alloy decreases the mechanical property of the entire component. This study developed a DED strategy using wire and arc discharge for the mechanical interlocking of pure Ti ERTi-2 and Al alloy ER5356. First, the effects of heat input, fabrication paths, and arc locations on the interface and composition of the adjacent beads were clarified. A fabrication strategy was developed to achieve the desired fusion state and avoid collision between welding torch-fabricated component. A mechanical interlocked component with an internal ERTi-2 cross-shaped lattice and planar ERTi-2 surface layers was successfully fabricated. In addition, these results demonstrate that the developed fabrication strategy can be applied to the other metal combinations that are difficult to fusion-bond. Subsequently, X-ray computed tomography clarified that the internal ERTi-2 lattice was fabricated in the target geometry. Tensile tests were carried out using the mechanical interlocked components with an internal cross-shaped unit lattice. The yield and ultimate tensile strength were 45.1 ± 3.4 MPa and 55.5 ± 4.6 MPa, respectively. These values and the fracture positions were in good agreement with the predictions from the mechanical properties of the used materials and the lattice geometry. Hence, this study underscores the potential of mechanical interlocking to improve the mechanical properties of the multi-metal components that pose challenges for fusion-bonding.

High-performance cross-sandwich Huygens’ metasurface excited by congener quadrupole

Huygens’ metasurface (HMS) can realize high-efficient real-time control of electromagnetic waves through impedance matching,which is specialty of multipoles. Previous designs of HMS mostly focus on realizing 2π phase coverage by combining different poles, while ignoring the limitation on transmittance caused by different attributes between poles. In this paper, we propose a new design of HMS, which can fulfill​ the excitation of the pure magnetic quadrupole (MQ) on target wavelength. Combined with the theory of multipole scattering, we strip off the interference of electric quadrupole by adding glass layers to the cross-shaped units. By optimizing the parameters of the unit after adding glass, we get an HMS element with extremely high transmittance and phase distribution covering full 2π. We found that the peak of MQ will be simultaneously affected by the thickness and position of glass, while the peak position will only be affected by the former. We also characterize the wavefront manipulation performance of the element by designing and simulating typical applications such as beam deflection, focusing and hologram reconstruction. This efficient wavefront modification indicates that multipole analysis is an effective way of dielectric Huygens’ metasurface parameter optimization and can be applied to computer-generated holograms, structured color display devices.

Polarization independent dielectric metasurface for infrared beam steering applications

Over the past years, metasurfaces have been of great interest due to their ability manipulate optical wavefront by introducing a phase gradient across the transverse directions of the wave. This phase gradient was usually realized using plasmonic resonators which had high intrinsic losses. Here, we demonstrate, numerically, a proof of principle of an all-dielectric silicon based metasurface at the infrared (IR) range that manipulates the wave front and achieves beam steering with significantly high transmission. The proposed cross-shaped unit cell design shows high transmission with the ability to fully control the phase of the transmitted wave from 0 to 2π. The metasurface is made of silicon cross resonators, arranged to have a linear phase gradient, on SiO2 substrate which makes the device compatible with most standard semiconductor fabrication techniques.

Preparation of a capillary isoelectric focusing column with monolithic immobilized pH gradient and its application on protein separation based on an online capillary isoelectric focusing platform

In the presence of methanol and n-decanol as porogens, a partially filled capillary monolithic column was prepared by in situ reaction of glycidyl methacrylate and poly (ethylene glycol) diacrylate. Then, Pharmalyte 3-10 was immobilized on this column in order to obtain a capillary isoelectric focusing (cIEF) column with monolithic immobilized pH gradient (M-IPG). In addition, an online self-built platform for protein separation was established on account of the introduction of a cross-shaped unit and two short-off valves. In this platform, a cross-shaped unit was not only used to join the M-IPG column and a six-way injection valve (1.5 μL sample loop), but also to supply a volume pool of anode buffer so that the process of injection, focusing and mobilization of samples could be sequentially performed. The short-off valve in the tee unit or cross-shaped unit could be used to control the direction of the fluid flow. Using this online cIEF platform and under the optimized conditions, 7-proteins mixture could be separated and a good linear correlation between pI values and migration times was obtained by the M-IPG column. Meanwhile, based on the online cIEF platform, human serum proteins and a mixture of Hb A and Hb A1c have been successfully resolved with the newly developed M-IPG column.

The effect of cross-shaped line width on the absorbance performance of terahertz metamaterial based on paper as spacer

Many researchers have paid attention to metamaterial based on paper as a recyclable material In this work, we studied the effect of cross-shaped line width on the absorbance performance of terahertz metamaterial. Cross-shaped unit cell was designed on paper with 100 μm thickness. Ground metal plate was placed on the other side of the paper. The maximum and minimum of the absorbance peak reached around 96 % with 20 μm line width and 50 % with 5 μm line width, respectively. The high absorbance was caused by multiple reflection phenomena on spacer. The numerical and analytical calculation show good agreement.

Preparation of capillary isoelectric focusing with monolithic immobilized pH gradient and its application in determination of isoelectric point of proteins

A partially filled monolith was prepared by in situ polymerization, and then carrier ampholytes (CAs, pH 3-10) were immobilized on its surface. For effective utilization of capillary isoelectric focusing (cIEF) with the monolithic immobilized pH gradient (M-IPG), a new online platform was established by the introducing of an eight-way injection valve, a three-way valve and a cross-shaped unit. Besides, a capillary coated with hydroxypropyl cellulose (HPC capillary) was prepared and used to determine the isoelectric points (pI) of trastuzumab and etanercept. In parallel, using the newly built capillary isoelectric focusing platform, the pI values of trastuzumab and etanercept were measured with the M-IPG column, and compared with the results obtained using the HPC capillary. It was found that these two cIEF columns can be effectively used to separate proteins and determine the pI values of monoclonal antibodies and fusion proteins in protein drugs. Moreover, the measured pI values were consistent with those estimated using the HPC capillary.

Nursing Unit Design, Nursing Staff Communication Networks, and Patient Falls: Are They Related?

Purpose:The purpose of this research is to (1) investigate the impact of nursing unit design on nursing staff communication patterns and, ultimately, on patient falls in acute care nursing units; and (2) evaluate whether differences in fall rates, if found, were associated with the nursing unit physical structure (shape) or size.Background:Nursing staff communication and nursing unit design are frequently linked to patient safety outcomes, yet little is known about the impact of specific nursing unit designs on nursing communication patterns that might affect patient falls.Method:An exploratory longitudinal correlational design was used to measure nursing unit communication structures using social network analysis techniques. Data were collected 4 times over a 7-month period. Floor plans were used to determine nursing unit design. Fall rates were provided by hospital coordinators.Results:An analysis of covariance controlling for hospitals resulted in a statistically significant interaction of unit shape and size (number of beds). The interaction occurred when medium- and large-sized racetrack-shaped units intersected with medium- and large-sized cross-shaped units.Conclusion:The results suggest that nursing unit design shape impacts nursing communication patterns, and the interaction of shape and size may impact patient falls. How those communication patterns affect patient falls should be considered when planning hospital construction of nursing care units.

Phase gradient metasurface with broadband anomalous reflection based on cross-shaped units

It has been pointed out by many documents that a phase gradient metasurface with wideband characteristics can be designed by the unit with a low-quality factor (Q value). In this paper, a cross-shaped unit with a low-quality factor Q is proposed. By changing the variable parameters of the unit, it is found that the reflection phase of the unit can achieve a stable distribution of phase gradient in the frequency range of 8.0–20.0 GHz. we analyze variation of the electromagnetic field distribution on the unit with frequency and find that the size along electrical field polarization of electromagnetic field distribution area changes with frequency. Based on our design, effective size of electromagnetic field distribution area keeps meeting the subwavelength condition, thus stable phase distribution is gained across broadened bandwidth. It is found by the analysis of the phase gradient metasurface composed of seven units that the metasurface can exhibit anomalous reflection in the wide frequency band of 8.0–20.0 GHz, and the efficiency of abnormal reflection is higher in the range of 10.0–18.0 GHz. The error between the simulation results of abnormal reflection angle and the theoretical result is only − 1.5° to 0.5° after the work of comparison. Therefore, the metasurface designed by the new cross-shaped unit has a good control on the deflection direction of the reflected wave, and shows obvious advantages in widening the bandwidth.

Periodic aperture imaging

We studied periodic aperture imaging with various subaperture configurations in terms of their point spread functions, optical transfer functions, and imaging quality. A circular-shaped unit cell provides the best performance compared to square- and cross-shaped unit cells when the total aperture size and collection area are kept the same. Moreover, decreasing the separation among the unit cells or the number of subapertures also improve the imaging performance. Results have potential applications in optical periodic aperture telescopes, diffraction masks, and coded aperture imaging.

The frequency response characteristics of planar frequency selective fabrics (FSFs) with cross-shaped units

In this paper, a computer-based carving experiment was conducted to make frequency selective fabrics (FSFs) with cross-shaped units. Different samples with varying frequency selective fabric types, structure parameters, conductive layers, base fabrics and unit shapes were prepared and the transmission characteristics were tested using the Shielding Room Method. The reflection characteristics under different electromagnetic (EM) wave incidence angles were also tested to study the angle stability. Experimental results showed that in the given frequency range of 4–14 GHz, two types of frequency selective fabrics had good complementary transmission characteristics, with ideal bandwidths and resonance peaks, and the aperture frequency selective fabrics showed certain stability to small electromagnetic wave incidence angles. Structure parameters played a very important role in determining frequency response characteristics and base fabrics with different effective dielectric constant could also exert a great influence. However, the change of electrical conductivity within a certain extent would not affect the transmission characteristics and related work should be continued to explore the effect rule. Through rational control of the unit shape to increase or decrease the conductive material mass, broad-spectrum shielding or passing-through properties could be obtained. In the paper, the experimental results were discussed and analyzed in detail aiming at different parameters, and internal causes were further investigated, which could provide reference values for the relevant design and product development process.

The novel frequency selective fabric and application research

There have been various efforts on frequency selective surface in recent years, and of course, some research progress has been made, especially in numerical calculation and simulation field. However, it seems that less work is done on the processing and forming methods. Soft fabrics are periodic and have advantages over the rigid materials in lightweight, softness, low bending rigidity, which make it possible and meaningful to study their filtering property as the medium in electromagnetic field. In this paper, a kind of electromagnetic functional textile based on frequency selective surface was proposed specifically for 10 GHz, dominant frequency of X-band radar. The full-wave simulation software, HFSS v14, was used for theoretical simulation and optimization, and two complementary cross-shaped unit cells with optimum size were obtained. Then, the frequency selective fabrics were manufactured through silk-screen-printing technology and measured using transmission method. It showed that the measured and simulated results had good consistency, and the fabricated frequency selective fabrics had ideal band-stop or band-pass performance. Finally, according to the analysis of S21 curve and transmission line equivalent circuit modal, the filtering mechanism was explained and the great potential in practical application of frequency selective fabrics was further illustrated.

Structure formation in adsorbed overlayers comprising functional cross-shaped molecules: A Monte Carlo study

Abstract Surface confined self-assembly of functional star-shaped organic molecules is a promising method to create nanoporous networks with tailorable structure and functions. In this work we use the Monte Carlo simulation method to demonstrate how the morphology of these supramolecular assemblies can be tuned by manipulating intrinsic parameters of the building blocks and modified by the presence of co-adsorbed metal atoms. To that purpose we study the 2D self-assembly of planar cruciform molecules modeled as collections of interconnected segments, some of which were activated to represent discrete interaction centers. We consider a few exemplary adsorbed systems in which the molecules with different size, aspect ratio and intramolecular distribution of active centers form superstructures stabilized by short-range segment–segment interactions or by metal–segment interactions. These two situations correspond to supramolecular assemblies sustained by, for example, hydrogen bonding and metal–organic ligand coordination, respectively. The simulated results show that proper encoding of intramolecular interactions into the cruciform building bricks allows for directing the self-assembly towards largely diversified structures ranging from nanoclusters to porous grids. The obtained findings can facilitate designing and optimization of molecular networks comprising cross-shaped units including functionalized porphyrins and phthalocyanines and they can be helpful in preliminary selection of these building blocks.