Rectangular Strip Research Articles

Compact high isolation wideband 4G and 5G multi‐input multi‐output antenna system for handheld and internet of things applications

This article presents a compact wideband multi-input multi-output (MIMO) antenna with a high port-to-port isolation, having a height h = 3.5 mm for 4G, 5G, and Internet of things (IoT) applications. Two identical planar inverted-F antennas (PIFA) are used in this antenna system. For achieving wideband characteristics, closed-ended and open-ended rectangular slots are etched out on top plate of each PIFA, whereas a slot is etched in ground plane under the top plate of each PIFA. For achieving high isolation, a rectangular slot is etched out in the center of ground plane between two PIFAs. For further reduction in mutual coupling, a small rectangular strip is connected between the top plates of two PIFAs that introduce an antiresonance for enhancing isolation between two PIFA elements. The minimum isolation obtained between the ports of the two PIFAs is about −20 dB. The minimum impedance bandwidth obtained by the two PIFAs is from 2 to around 3.6 GHz, thus become a wide band antenna covering WLAN band (2.45GHz), 4G-LTE bands, WiMAX bands (IMT-2.1 GHz, IMT-2.3 GHz, and IMT-E 2.6 GHz), and a sub-6 GHz 5G band (3.4-3.6 GHz). The simulated results are compared with the measured ones that are generally found in good agreement. Being low profile and compact, this antenna can be used for advanced 5G communication systems and IoT devices.

An open space based heuristic for the 2D strip packing problem with unloading constraints

This paper studies the two-dimensional strip packing problem with unloading constraints. Given a set of items (represented by rectangles) belonging to different customers and a rectangular strip with fixed width and open length, the objective is to pack all the items into the strip such that the used length is minimized. In addition, the resulting packing must satisfy the unloading constraints. Based on the characteristics of this problem, this paper employs the open space to represent the candidate position. An open space based first-fit heuristic is proposed to generate a packing pattern for a given sequence of items. An implementation using the segment tree is provided. Finally, a randomized local search without any parameter is used to improve the solution by trying different sequences. The computational results on well-known instances show that the proposed approach outperforms existing approaches in the literature. In additional, we test our approach on the two-dimensional orthogonal packing problem with unloading constraints, the results show that our approach is capable of finding feasible solutions for 283 open instances.

A comparative study for the performance of encased granular columns

This paper describes a three-dimensional (3D) numerical analysis of a test embankment on geotextile-encased columns (GECs), in comparison with two-dimensional (2D) axisymmetric and plane strain analyses. The 3D numerical analysis was performed considering a rectangular strip under the embankment centerline. The 2D analysis was also carried out using axisymmetric unit cell and plane strain approaches. Numerical results indicated that the adopted 3D strip model represented well the measured deformations and pore pressure evolution during embankment construction and post-contraction periods. Unlike the unit cell model, both plane strain and 3D analyses could properly determine the settlement profile along the embankment base as well as the profile of the horizontal soil deformation beneath the embankment toes. The plane strain analysis, however, was not able to compute the geotextile ring force which might be simply calculated using the axisymmetric unit cell approach. The paper also showed that, due to horizontal boundary fixities applied to the embankment borders, the unit cell model clearly underestimated the tension developed in the basal geogrid.

Effect of Strain Rate on the Tensile Performance of Nonwoven EVA/Aramid Composite Fabrics

The present research work investigates the effect of strain rate on the tensile response of rectangular strips made of nonwoven ethylene-vinyl acetate (EVA)/aramid composite fabrics. The strips were manufactured in four layers with stacking sequence of different fiber angles, sandwiched between two EVA films. The performance of these composite fabrics was studied by means of tensile testing conducted at various loading speeds and different positioning angles of 0° and 45° to determine the effect of strain rate in real-life operating conditions. The fabrics demonstrate strain rate sensitivity in positioning angle 0° has decreasing performance with increasing test speed due to a progressively growing triggering mechanism affecting the material stretching. On the other hand, the fabrics exhibit consistency in their performance in positioning angle 45 due to their nonwoven nature which allows for frictionless yarn-to-yarn rotation.

Diffraction of electromagnetic waves on the resonance graphene metasurfaces

By using three independent numerical approaches to solve the 3D diffraction boundary problems the reflection, transmittance coefficients and losses of metasurfaces of graphene strip elements, depending on the frequency and values of the chemical potential were calculated in the terahertz frequency range. The results of numerical simulation of performances of tuned by the external bias electric field THz absorbers and THz polarizers based on the resonance metasurfaces of single square and two connected rectangular graphene strips in the unit cell placed on the dielectric or multilayer graphene-dielectric substrates were obtained.

Comparison of bond strength of two porcelains and two base metal alloys in metal-ceramic restorations

The purpose of this study was to evaluate the bond strength between two porcelains (VITA VMK Master and VITA VM13) and two types of base metal alloys (Ceramill Sintron and Verabond). In an experimental study, 20 rectangular strips (25 mm × 4 mm × 0.5 mm) of each base metal alloy (Ceramill Sintron and Verabond) were fabricated according to the manufacturer's instructions. After sandblasting and polishing, the samples were placed in an ultrasonic device to remove surface contaminants. A surface of 8 mm × 4 mm × 1 mm of samples was veneered with Vita VM13 and VITA VMK Master. The samples were divided into four groups (n = 10 each group; VM13/Ceramill, VMK Master/Ceramill, VM13/Verabond, and VMK Master/Verabond), and bond strength was evaluated by three-point bending test with a universal testing machine. Two-way ANOVA was used for comparison in each group, post hoc Scheffe's test was used for analyzing data between groups, and the Kolmogorov-Smirnov test was used for the normality (P < 0.05). The maximum bond strength was related to Verabond/VM13 (44.35 ± 7.9 MPa) and then the Ceramill Sintron/VM13 (39.33 ± 4.43 MPa), and the lowest was related to the Ceramill Sintron/VMK Master (29.75 ± 3.2 MPa). There was no significant difference between bond strength of VM13 with the two alloy groups (P > 0.05), and bond strength of VMK Master to Ceramill Sintron CAD/CAM alloy was less than the conventional Verabond alloy (P < 0.05); however, bond strength of all the groups was above the standard threshold (25 MPa). Based on the results of this study, the bond strength of the porcelain to Verabond was better, but the bond strength of the porcelain to Ceramill Sintron also was not less than the standard threshold; thus, this new CAD/CAM alloy can be an alternative to the conventional base metal alloys in the metal-ceramic restorations.

Compact wideband MIMO antenna for 4G WI-MAX, WLAN and UWB applications

This article proposes a compact wideband MIMO antenna. The antenna comprises of two identical modified P shaped monopole radiators, spatially oriented at 180° to each other with side to side spacing of 0.075λo, where λo is the wavelength corresponding to the lowest operating frequency. To design a compact antenna, a semicircular monopole with a rectangular strip is designed instead of a circular monopole. This P shaped monopole antenna offers same impedance bandwidth with 50% size reduction. To enhance the impedance bandwidth of the antenna, the effective current path length is increased by introducing two semi-circular slots in P shaped monopole antenna. To achieve the desired impedance bandwidth of 2.5–12 GHz, the rectangular strip is corrugated on both sides in the slotted P shaped monopole. Triangular slots and meshed metal strip are introduced in the ground plane to achieve high mutual coupling over wideband. The triangular slots act as variable length capacitance and exhibits wide band notch characteristics. A meshed metal strip acts as decoupling structure for the surface current emerging from the surface waves and also act as reflector for space waves. Those bands which are not rejected by triangular slots, are notched by meshed metal strips. Thus by employing both triangular slots and meshed metal strip, isolation >20 dB is achieved over 2.5–12 GHz. The proposed antenna is a novel design which has smaller dimensions and still offers isolation >20 dB over a wider impedance bandwidth of 2.5 GHz to 12 GHz as compared to state of art antenna structures reported in literature. The band stop characteristics of proposed isolation techniques are analyzed by suspended stripline method. Mutual coupling reduction is also analyzed with the help of vector surface current density and magnetic field distribution. The proposed structure has compact dimensions of 0.25 λ0 × 0.241 λ0. The fabricated prototype antenna exhibits envelope correlation coefficient (ECC) >0.02, diversity gain >9.5 dB and stable radiation patterns. The antenna is suitable for 4G WI-MAX, WLAN and UWB applications.

Parametric Study of Heat Transfer and Pressure Drop Characteristics of a Rectangular Offset Strip Fin Compact Heat Exchanger

Compact heat exchangers are of great topics of interest while we are dealing with the enhancement of heat transfer rate. In this study, a rectangular offset strip fin compact heat exchanger is taken into consideration. The purpose of this study is to develop a numerical model to study the heat transfer characteristics as well as the pressure drop characteristics. The parametric study was done in FLUENT with a three dimensional computational domain in which air is selected as working fluid. The analysis was confined to the flow in laminar region and so the Reynolds number was limited to 1000. The variation of friction factor and Colburn factor with Reynolds number is also analysed. The results obtained were analysed and were also compared with an existing correlation. The findings of this study may serve as a helping tool to develop a correlation for fluid flow in offset strip fin geometry.

A Broadband Circularly Polarized Wide-Slot Antenna With a Miniaturized Footprint

This letter presents a novel and simple feeding technique for exciting orthogonal components in a wide-slot antenna. In this technique, a rectangular bracket-shape parasitic strip is placed at the open end of the straight microstrip line to excite the fundamental horizontal and vertical components of the circular polarization (CP). The proposed technique—when employed in conjunction with the asymmetrical geometry of coplanar waveguide and a protruded stub from the ground plane—permits for maintaining axial ratio (AR) below 3 dB within a wide range in the C-band as well as a compact footprint of the antenna. All geometry parameters of the antenna are adjusted through rigorous EM-driven optimization to obtain the best performance in terms of footprint, impedance matching, and AR bandwidth (ARBW). The size of the proposed antenna is only 27 mm × 28.8 mm. The structure features a 62% impedance bandwidth (3.6–6.85 GHz) and ARBW of approximately 49% (3.6–5.93 GHz) with the average realized gain of 3.3 dB within the CP operating band. Numerical results are validated experimentally. A close agreement between simulation and measurement results has been observed.

Balanced approach for the two-dimensional rectangular guillotine cutting stock problem with setup cost

The main optimization objective of two-dimensional rectangular guillotine cutting stock problem (2DRGCSP) is minimizing stock cost. However, setup cost is also needed to be considered as an important factor in the real manufacturing process. A sequential pattern generation algorithm with rectangular homogenous strips (SPGA-RHSs) is presented to generate a cutting plan based on each single stock. A better cutting pattern considering both stock cost and setup cost is obtained with the cost balance utilization (CBU). The balanced approach combining SPGA-RHSs and CBU is used to achieve a current optimal cutting plan for 2DRGCSP with the minimum sum of stock and setup cost. The computational results prove that the proposed balanced approach has good optimization performance for 2DRGCSP with setup cost.

Investigation of wave processes in a rectangular region with discontinuous boundary conditions

In the work in linear formulation the problem of propagation of nonstationary stress waves in an elastic single-supported construction, which is a rectangular strip, is solved. Formulated in terms of stresses and velocities the mixed problem is modeled numerically by means of an explicit difference scheme through counting, based on the method of spatial characteristics. The wave process is caused by applying of an external dynamic load on the front boundary of the rectangular region, and the lateral boundaries of the region are stress-free. At the lower boundary of the rectangular region, inhomogeneous boundary conditions are given, where the middle part of the boundary is rigidly fixed, and its lateral sections are free of stresses. Namely at the points of their conjugation, where the boundary conditions change jump-like, the method is proposed for obtaining resolving equations for finding required functions. The concentration of dynamic stresses in the neighborhood of discontinuity of boundary conditions is investigated. The results of the study are brought to numerical solution.DOI: http://dx.doi.org/10.5755/j01.mech.24.5.20102

Mechanical Properties of Contact Lens Materials.

To evaluate the mechanical properties of commonly available soft contact lens materials and compare results using custom-built MicroTensometer. The Young modulus, parameters for stress relaxation, and toughness of 18 types of single vision soft contact lenses were measured using custom-built MicroTensometer. Five lenses of each type were soaked in standard phosphate buffered saline and measured at a temperature of 35°C. Each lens was flattened and sliced into a rectangular strip sample using two parallel blades. The Acuvue Moist 1-Day and SofLens Daily lenses measured lowest moduli, whereas Air Optix Night & Day Aqua and Premio measured the highest. The measured moduli for silicone hydrogel materials were generally higher compared with the hydrogels except for Dailies AquaComfort Plus. The exponential curve fitted over the decay in stress showed a consistent time constant of approximately 10 sec for most lens types measured. However, the amplitude constant varied from 2.84% for SofLens Daily to 22.39% for Acuvue TruEye 1-Day. The toughness results showed that Dailies AquaComfort Plus is strong but not necessarily tough. The mechanical properties of commonly prescribed soft contact lens materials were measured using a dedicated instrument. Its reliability was demonstrated, and modulus results were compared against published data from manufacturers and other research groups. Agreement was generally good, with only a few exceptions exceeding 15% difference. The more recently released silicone hydrogel lens types have reduced modulus, approaching that of medium or high water content hydrogel materials.

Hydrokinetic energy harvesting from flow-induced vibration of a circular cylinder with two symmetrical fin-shaped strips

A circular cylinder with a pair of fin-shaped strips symmetrically mounted on its surface is proposed to harness the hydrokinetic energy of ocean currents. The flow induced vibration of a single converter is numerically investigated using a fluid-structure interaction (FSI) approach in Reynolds number range of 30480 ≤ Re ≤ 152400, falling in the TrSL3 flow regime (transition of shear layer 3). The numerical model is validated with the reported data for a cylinder with rectangular strips. By placing a pair of fin-shaped strips on the front surface of the cylinder, the VIV and galloping occur back-to-back. A recirculation region is generated behind the strips, resulting in a disturbance to the flow around the cylinder. The noncircular geometric shape contributes to the hydrodynamic instability, which is enhanced as the flow speed increases. The responses for the cylinder with fins at 20° and 45° fall in hard galloping zone 1, while the responses for fins placed at 0° and 60° belong to hard galloping zone 2. The maximum power of more than 60 W/m is harnessed at uin = 1.5 m/s (a typical ocean current speed). Nevertheless, the power efficiency decreases in galloping as the incoming fluid power increases with the response amplitude. Thus the maximum power efficiency occurs at the VIV upper branch or the onset of galloping. When the strips move to 90°, galloping is disappeared and the vibration is suppressed as the strips further move to 120°. By arranging the converters in a staggered configuration, the maximum power density could reach 441.11 W/m3.

Cost-effective fabrication of ionic polymer based artificial muscles for catheter-guidewire maneuvering application

In this paper, we have designed and developed an ionic polymer metal composite (IPMC)-based artificial muscles by physical vapor deposition based fabrication technique. This process was used to avoid other costly and time-consuming fabrication methods. In the present study, gold electrode-based IPMC actuator chosen for its attractive properties, such as biocompatibility, low voltage-based actuation, and lightweight. A 17 × 1 mm2 rectangular strip of IPMC actuator used as a prototype for an active catheter-guidewire maneuvering application. Performance of the IPMC-based actuator examined through experimental and simulation results.

Electrode Design to Overcome Substrate Transparency Limitations for Highly Efficient 1 cm2 Mesoscopic Perovskite Solar Cells

Summary Fluorine-doped tin oxide glass substrate is typically used for state-of-the-art perovskite solar cells (PSCs). However, indium-doped tin oxide (ITO) is better due to higher transparency for a given conductivity, although it has lower tolerance to high-temperature processes required for the compact and mesoporous TiO2 layers. Here we overcome this challenge by developing and utilizing a new electrode design. We successfully demonstrate high-efficiency mesoscopic PSCs on annealed ITO substrates showing improved photocurrent without sacrificing fill factor. After further optimizations of cell geometry and substrate conductivity guided by simulation, a certified 19.63% efficiency is achieved on 1 cm2 for ITO-based mesoscopic PSC, which is the highest among PSCs prepared by gas quenching. This work is useful for providing design principles and methods for optimizing cell geometry, metal electrode design, and substrate conductivity requirements for large-area PSCs.

Low-loss terahertz polarization splitter based on an asymmetric dual-suspended-core fiber

A relatively simple design of a terahertz (THz) polarization splitter based on an asymmetric dual-suspended-core fiber is proposed. One core is formed by two intersecting rectangular dielectric strips with dissimilar thickness, whereas the other is a round solid core suspended by crossed dielectric strips with the same thickness. The distance between the cores can be adjusted to ensure a short splitting length and low transmission loss. A THz polarization splitter with a length of 1.27 cm is realized with a low transmission loss of 0.53 and 0.67 dB for the x- and y-polarization modes, respectively. An extinction ratio of about −20 dB and a broad bandwidth of 0.046 THz are demonstrated.

Effective Demagnetizing Factors of Diamagnetic Samples of Various Shapes

Effective demagnetizing factors that connect the sample magnetic moment with the applied magnetic field are calculated numerically for perfectly diamagnetic samples of various non-ellipsoidal shapes. The procedure is based on calculating total magnetic moment by integrating the magnetic induction obtained from a full three dimensional solution of the Maxwell equations using adaptive mesh. The results are relevant for superconductors (and conductors in AC fields) when the London penetration depth (or the skin depth) is much smaller than the sample size. Simple but reasonably accurate approximate formulas are given for practical shapes including rectangular cuboids, finite cylinders in axial and transverse field as well as infinite rectangular and elliptical cross-section strips.

Thermal-aware SoC Test Scheduling with Voltage/Frequency Scaling and Test Partition

With increasing power density in modern integrated circuits, thermal issues are becoming a critical problem in System-on-a-Chip (SoC) testing. In this paper, we develop the thermal-aware test scheduling methods using Voltage/Frequency Scaling (VFS) and Test Partition (TP) to reduce the expensive Test Application Time (TAT). First, we develop a quick temperature estimation method in test scheduling to ensure the test temperature within the given range. Second, we propose a thermal-aware test scheduling method based on the mixed-integer linear programming model (MILP) (called STP-M) that applies VFS and TP to search the optimum scheduling and further reduce the TAT. Third, we develop a heuristic method based on Rectangular Strip Packing (called H-RSP) to quickly access the quasi-optimal scheduling. The experimental results on ITC’02 benchmarks showed that the STP-M obtains the most optimized result for every benchmark and saved 15.5% and 8.0% TAT on average compared with the existing works, while H-RSP takes less than 10 seconds to access the quasi-optimal scheduling that is close to that of STP-M.

An EDA for the 2D knapsack problem with guillotine constraint

In this paper we present an evolutionary heuristic for the 2D knapsack problem with guillotine constraint. In this problem we have a set of rectangles and there is a profit for each rectangle. The goal is to cut a subset of rectangles without overlap from a rectangular strip of width W and height H, so that the total profit of the rectangles from the subset is maximal. The sides of the rectangles are parallel to the strip sides and every cutting is restricted by orthogonal guillotine-cuts. A guillotine-cut is parallel to the horizontal or vertical side of the strip and cuts the strip into two separated rectangular strips. Our algorithm is an estimation of distribution algorithm (EDA), where recombination and mutation evolutionary operators are replaced by probability estimation and sampling techniques. Our EDA works with two probability models. It improves the quality of the solutions with local search procedures. The algorithm was tested on well-known benchmark instances from the literature.

Mixed boundary-value problem for an orthotropic rectangular strip with variable coefficients of elasticity

A dynamical problem for a rectangular strip with variable coefficients of elasticity is solved by an asymptotic method. It is assumed that the strip is orthotropic, the elasticity coefficients are exponential functions of y, and mixed boundary conditions are posed. The solution of the inner problem is obtained using Bessel functions.