Circular Units Research Articles

Assessing the Effects of POGIL-Based Instruction versus Lecture-Based Instruction on Grade 12 Self-Efficacy and Performance in Circular Motion Unit

This study investigates the impact of lecture-based instruction and process-oriented guided inquiry learning (POGIL)-based instruction on the self-efficacy and performance of Grade 12 students. The researchers used a quasi-experimental, pretest-posttest design to compare the effects of POGIL-based instruction to lecture-based instruction, as measured by three cognitive outcomes: knowing, applying, and reasoning (KAR)." self-efficacy as measured by physics learning variables", "understanding of physics", and "willingness to learn". The study included 110 participants (54 in the treatment group and 56 in the control group) and was conducted in two government high schools in Alain, one for boys and one for girls. POGIL-based instruction was used to teach a circular motion unit in physics to the treatment group, while lecture-based instruction was used for the control group. The findings show that POGIL-based instruction had a statistically significant positive impact on science performance and self-efficacy when compared to lecture-based instruction. Furthermore, after the intervention, there was a positive correlation between participants' KAR test performance and their self-efficacy toward scientific inquiry. The study recommends a shift toward POGIL-based instruction to improve students' performance and self-efficacy and suggests that future research should include a broader range of schools, teachers, and advisors.

In-Plane Compression Properties of Continuous Carbon-Fiber-Reinforced Composite Hybrid Lattice Structures by Additive Manufacturing.

Continuous-fiber-reinforced composite lattice structures (CFRCLSs) have garnered attention due to their lightweight and high-strength characteristics. Over the past two decades, many different topological structures including triangular, square, hexagonal, and circular units were investigated, and the basic mechanical responses of honeycomb structures under various load conditions, including tension, compression, buckling, shear, and fatigue were studied. To further improve the performance of the honeycombs, appropriate optimizations were also carried out. However, the mechanical properties of a single lattice often struggle to exceed the upper limit of its structure. This paper investigates the effect of permutation and hybrid mode on the mechanical properties of CFRCLSs by comparing five structures: rhomboid (R-type), octagon orthogonal array (OOA-type), octagon hypotenuse array (OHA-type), octagon nested array (ONA-type), and rhomboid circle (RC-type), with the conventional hexagonal structure (H-type). CFRCLS samples are fabricated using fused filament fabrication (FFF), with carbon-fiber-reinforced polylactic acid (PLA) as the matrix. The in-plane compression properties, energy absorption characteristics, and deformation behaviors of the hybrid structures were studied by experimental tests. The results demonstrate that different permutation and hybrid modes alter the deformation behaviors and mechanical properties of the structures. Taking elastic modulus as an example, the values of H-type, R-type, OOA-type, OHA-type, ONA-type, and RC-type are, respectively, 6.08 MPa, 5.76 MPa, 19.0 MPa, 10.3 MPa, 31.7 MPa, and 73.2 MPa, while the ratio of their masses is 1:1:1.10:1.52:1.66. Furthermore, hybrid lattice structures exhibit significantly improved mechanical properties compared to single lattice structures. Compared to the single structure R-type, the RC-type increases elastic modulus, yield strength, and energy absorption, respectively, by 12.7 times, 5.4 times, and 4.4 times.

Analysis of BUMDes Circular Economy-based Business Unit Development (Case Study in Sanankerto Village, Malang Regency)

Analysis of BUMDes Circular Economy-based Business Unit Development (Case Study in Sanankerto Village, Malang Regency)

Enhancing the energy absorption capability of auxetic metamaterials through auxetic cells within re-entrant circular units

Re-entrant circular (REC) auxetic metamaterials have garnered significant attention in structural engineering due to their enhanced energy absorption capability and reduced stress concentration compared to traditional re-entrant auxetic configurations. However, there is considerable potential for further enhancing their design to achieve even greater energy absorption capabilities. This study introduces three novel REC auxetic structures (REC-S, REC-Star and REC-Flower) specifically designed to enhance energy absorption capabilities compared to traditional REC configurations. These structures are formed by deploying an S-shaped, a star, and a newly designed auxetic unit-cell (UC) named Flower into the REC framework and fabricated through 3D printing by using fused deposition modeling (FDM) techniques. Their deformation behavior and mechanical performance are assessed through quasi-static compressive experimental tests and finite element analysis (FEA), with good agreement obtained between the two sets of results. Based on the validated FEA, the effects of the geometrical parameters of the structures on specific stiffness (Es), specific energy absorption (SEA), and Poisson's ratio are further investigated. The results show that the newly designed structures outperform the traditional REC structure with equivalent relative densities (∆ρ) and the REC-Flower has the highest SEA for all relative densities, positioning it as a promising candidate for the next generation of REC structures.

Exploring the Influence of POGIL-Based Instruction on Grade 12 Achievement in the Circular Motion Unit

This research aimed to explore the comparative impact of Process Oriented Guided Inquiry Learning (POGIL)-based instruction and traditional lecture-based instruction on the academic performance of Grade 12 students in the context of the circular motion unit. Employing a quasi-experimental pretest-posttest design, the study assessed students' cognitive outcomes in terms of Knowing, Applying, and Reasoning (KAR). A total of 110 participants were involved, with 54 assigned to the treatment group (25 girls and 29 boys) and 56 to the control group (27 girls and 29 boys). The treatment group received instruction on circular motion through POGIL, while the control group underwent lecture-based instruction. The results revealed statistically significant differences in circular motion performance between the control and treatment groups, with the latter exhibiting superior outcomes. This suggests that POGIL-based instruction positively influences students' understanding of circular motion, emphasizing its efficacy in enhancing learning outcomes in comparison to traditional lecture-based methods.

Optimization of an architected composite with tailored graded properties

The aim of the present study is to design a solid material with specific and tailored mechanical properties through a suitably defined design framework and to evaluate the effectiveness of different microstructure geometries in an engineering perspective. To these ends, topology optimization algorithms are applied on a 2D homogenized equivalent model of a periodic structure. The design framework, developed in a previous work for 2D lattices made of regular hexagons, is here expanded and validated also in the cases of circular and square unit cells. The proposed approach involves optimizing porosity distribution of a homogenized equivalent solid, obtained through a Bloch–Floquet-based analysis, within a 2D lattice of regular unit cells forming the core element of a sandwich panel. Finite-element analyses on homogenized and fine structural models are carried out in order to validate the procedure, beyond the particular choice of the unit cell geometry and to detect its effectiveness and limits.

Chromosomal integration and plasmid fusion occurring in ST20 carbapenem-resistant Klebsiella pneumoniae isolates coharboring bla NDM-1 and bla IMP-4 induce resistance transmission and fitness variation

ABSTRACT To investigate the epidemiology of ST20 carbapenem-resistant Klebsiella pneumoniae (CRKP) in China, and further explore the genomic characteristics of bla IMP-4 and bla NDM-1 coharboring isolates and plasmid contributions to resistance and fitness. Seven ST20 CRKP isolates were collected nationwide, and antimicrobial susceptibility testing was performed. Antimicrobial resistance genes, virulence genes, and plasmid replicons were identified via whole-genome sequencing, and clonality assessed via core-genome multilocus sequence typing. Furthermore, we found four dual-metallo-β-lactamases (MBL)-harbouring isolates, the gene location was detected by Southern blotting, and plasmid location analysis showed that bla IMP-4 was located on a separate plasmid, a self-conjugative fusion plasmid, or the bacterial chromosome. These isolates were subjected to long-read sequencing, the presence of bla IMP-4 in different locations was identified by genomic comparison, and transposon units were detected via inverse PCR. We subsequently found that bla IMP-4 on the fusion plasmid and bacterial chromosome was formed via intact plasmid recombination by the IS26 and ltrA, respectively, and the circular transposon unit was related to cointegration, however, bla IMP-4 in different locations did not affect the gene stability. The bla NDM-1-harbouring plasmid contributed to the increased resistance to β-lactams and shortened survival lag time which was revealed in plasmid cured isolates. In summary, the K. pneumoniae ST20 clone is a high-risk resistant clone. With the use of ceftazidime/avibactam, MBL-positive isolates, especially dual-MBL-harbouring isolates, should be given additional attention.

Manufacturability and deformation studies on a novel metallic lattice structure fabricated by Selective Laser Melting

Additive Manufacturing of metallic lattice structures has been well-researched and adopted in the biomedical and aerospace sectors. The reason is that these structures with tailored mechanical properties are worthy candidates for applications requiring lightweighting and energy absorption characteristics. In this paper, we propose a new unit cell that, by repetition in three directions, forms a lattice that can reduce the stress concentrations between the struts and enable smoother deformations compared to conventional structures and circular unit cell-based lattices. The designs were fabricated by Selective Laser Melting of the commercial Ti–6Al–4V alloy. It was found that the manufacturability of the novel cells was excellent, and the structure was found to perform better in terms of compressive yield strength and have almost similar energy absorption characteristics to the BCC lattices.

Full-field characterizations of additively manufactured composite cellular structures

Honeycomb structures possess unique mechanical and structural behaviors, including high specific strength, superior energy absorption, and potential for multifunctionality. The advantages of such structures are bolstered by their realization through additive manufacturing, enabling cellular geometries beyond traditionally fabricated hexagons and facilitating a pathway for hybridization using composite materials to tune the response. This research synthesized photocurable, particulate-reinforced resins using mechanically compliant matrix and glass microballoons reinforcement. The modified resins were used to additively manufacture lattice structures with circular and hexagonal unit cell geometries at different glass microballoons reinforcement weight ratios, ranging from neat to 20 wt.%. The 3D printed structures were tested under quasi-static and impact loading scenarios to elucidate the interrelationships between the cell geometry, induced deformations, and strain rates. The mechanical testing was coupled with digital image correlation (DIC) to reveal the deformation-geometry interrelationship on the global (macroscale) and local (mesoscale) levels. The multiscale analyses allowed for extensive characterization of the effect of cell geometry and increased weight reinforcement on the mechanical response at a global, sub-cellular, and cellular level, i.e., elucidating the hierarchical dependency. The novelty leading to the current study stems from probing and revealing the deformation state of cellular structures subjected to two loading scenarios using DIC. This study intended to provide mechanistic insights for engineering lattice structures for impact mitigation applications by offering a viable approach to additive manufacturing composite materials.

Comparison of a Circular Patch Unit Cell Performance for Reflector Applications between Using FR4 and F4BMX220 Substrates at 3.5 GHz Frequency

This paper presents a performance comparison of the circular patch unit cell as a unit cell for reflector application at 3.5 GHz frequency using a dielectric substrate between FR4 and F4BMX220 substrates. A circular patch is chosen as the unit cell of a reflector because it is commonly used, fabricated, and has a wider bandwidth compared to other structures. A performance comparison of the circular patch on both dielectric substrates is presented in a graph of S-parameters, reflection phase, and operating bandwidth, as well as in the table of dimensions, where the result is performed by simulation using CST software. Based on the simulated results, the F4BMX220 has a better performance compared to the FR4 in terms of the reflection value, operating bandwidth, and dielectric substrate thickness. However, a circular patch diameter when using the F4BMX220 is bigger than when using the FR4 substrate because the FR4 substrate has a higher dielectric constant than the F4BMX220, which is twice the F4BMX220 dielectric constant. Also, the F4BMX220 substrate has a narrower bandwidth compared to the FR4 substrate, which is a difference of around 0.1 GHz. The circular patch when using the F4BMX220 substrate has 0.96 of a reflection value, 0.007 of an absorption value, -6.77° of the reflection phase, and 0.24 GHz of the operating bandwidth at the normal incident wave angle (0°). Also, it can be properly worked if the incident wave angle is moving until 60°. The F4BMX220 substrate has the best performance compared to the FR4 substrate because the reflection value is much better value, even at the incident wave angle of 60°.

Acoustic Modeling and Analysis of Automotive Air-Filters

Air filters are placed upstream of internal combustion engines to remove dust particles in the suction air. In this article, we examine the acoustic characterization of an air-filtering unit in the absence of mean flow. For this purpose, a circular air-filtering unit with an axial inlet and side outlet widely used in the automobile industry is considered. The air-filter element is modeled as an equivalent acoustic fluid with finite flow resistivity. The flow resistivity of the region is estimated from the permeability of the filter paper and the geometrical arrangement of the paper folds (pleats) inside the air-filter element using an electrical analogy. A numerical model based on the finite element method (FEM) and an analytical model using classical one-dimensional plane wave analysis (1-D PWA) was developed. Experiments were carried out using an impedance tube to estimate transmission loss. A good correlation is observed between the FEM model and the experiments. The results obtained from the 1-D PWA are in reasonable agreement with those obtained from the other two methods.

Circularly polarized metalens antenna design for 5G NR sub-6 GHz communication systems

5G NR (new radio) FR1 range refers to as Sub-6 GHz band (410–7125 MHz and 3.4–6 GHz). In this paper, the frequency range of interest is from 3.4 to 6 GHz, as many cellular companies are focusing on this Sub-6 GHz band. A wideband circularly polarized (CP) antenna radiator is designed with diamond shape patches, fed by a microstrip line at the bottom through a rectangular shape wide slot on a ground plane. The proposed CP antenna covering a −10 dB bandwidth of 21.52 % (5.0–6.3 GHz) with 3-dB axial ratio (AR) bandwidth of 12.48 % (5.1–5.8 GHz). Furthermore, a metasurface-based lens (metalens) is designed for gain enhancement and fed by 3 × 1 array of the proposed CP antennas for multibeam operation. The lightweight dual-layer metasurface structure consisting of circular shape unit cell elements are used to implement the lens. For the proof-of-concept, the array of radiating elements is implemented and experimentally validated, which gives a ±18° beam scanning range with a maximum gain of 13dBic at 5.6 GHz.

Super-compact equal/unequal half-mode substrate integrated waveguide filtering power dividers using complementary G-shaped resonator

ABSTRACT In this paper, three super-compact equal/unequal filtering power dividers (FPDs) by combining the half-mode substrate integrated waveguide (HMSIW) platform and the metamaterial unit cell are proposed. To miniaturized the total dimension of the proposed equal/unequal FPDs, the evanescent mode technique, the half-mode technique, and the stepped-impedance resonator (SIR) technique have been utilized, simultaneously. In the modified metamaterial unit cell, which is called the complementary G-shaped resonator (CGR) unit cell, the quasi stepped-impedance slot line is replaced instead of the conventional slot line in the circular complementary split-ring resonator (CSRR) unit cell. Accordingly, the electrical size of the modified CGR unit cell is smaller than the conventional circular CSRR unit cell with the same physical sizes. Employing the introduced CGR unit cell and HMSIW structure, three equal/unequal FPDs with arbitrary power-dividing ratios have been designed and simulated. To illustration the performance of the proposed components, three HMSIW FPDs with different power division ratios of 1:1, 1:4, and 1:8 have been fabricated and measured. A reasonable agreement between simulated and measured results has been achieved. The results demonstrate that a miniaturization factor of about 0.64 is achieved.

The Chevalley–Herbrand formula and the real abelian Main Conjecture (New criterion using capitulation of the class group)

Analytic theory of real abelian fields K says (in the cyclic semi-simple case) that the order of the p-class group HK is equal to the p-index of cyclotomic units (EK:FK). We develop, in this article, new promising links between: (i) the Chevalley–Herbrand formula giving the number of “ambiguous classes” in p-extensions L/K, L⊂K(μℓ) for auxiliary prime numbers ℓ≡1(mod2pN) inert in K; (ii) the phenomenon of capitulation of HK in L; (iii) the Main Theorem for the isotypic components using the irreducible p-adic characters φ of K, that we had conjectured (1977). We prove that this real Main Theorem is trivially fulfilled as soon as HK capitulates in L (Theorem 1.2). Computations with PARI programs support this new philosophy of the Main Theorem and the very frequent phenomenon of capitulation suggests Conjecture 1.1.

Tailoring the refractive index of single layer touching circular metamaterial by adjusting the dielectric thickness

Metamaterials have unusual properties which are not readily available in nature. Multilayer metamaterial has been considered for tailoring the material properties. The critical challenge of the multilayer metamaterial is the alignment of each layer. This study aims to determine the performance of the negative refractive index using a touching circular unit cell of the single-layer metamaterial. This study's dielectric thickness varies from 1 mm to 4 mm. The simulation and experimental results are presented. The spectrum in this study is 2.7 – 3.8 GHz. The results showed that the negative refractive index value occurred for each dielectric thickness variation in single-layer metamaterials. The negative refractive index value peaks have shifted by the varied dielectric thickness. There are disparities between simulation and experimental results due to imperfect fabrication samples; however, the trend simulation result has similar to the experimental result.

Experimental Development of the Horizontal Drain Water Heat Recovery Unit

The increase in energy demand, the scarcity of resources, as well as the adverse environmental impact of burning fossil fuels make it necessary to diversify the energy sources used. This also applies to the residential sector, which accounts for a significant proportion of global energy consumption. Particular attention should be paid to water heating, as the importance of this process in the energy balance of buildings is steadily increasing. One of the methods used to decrease energy consumption for heating water is to recover heat from greywater. However, commercially available horizontal drain water heat recovery (DWHR) units are characterized by low effectiveness, which creates a need for further research to improve it. The aim of the paper was to evaluate the possibility of improving the effectiveness of a circular horizontal DWHR unit through the use of baffles. Six different baffle models for installation in the greywater section of the heat exchanger were analyzed. The tests were conducted under the assumption of the installation of the DWHR unit on the horizontal shower waste pipe. They showed that the effectiveness of the unit equipped with baffles was higher by several to as much as 40% compared to the DWHR unit without baffles. This is tantamount to an increase in annual financial savings resulting from greywater heat recovery, as well as a reduction in CO2 emissions into the atmosphere. However, it was not possible to clearly identify the optimum baffle model. In any case, the selection should consider the hydraulic conditions in the heat exchanger before installing the baffles. The results can provide guidance for companies interested in bringing new equipment and technologies to the market.

A Dual Resonance Frequency-Selective Surface Temperature Sensor With Linear Frequency–Temperature Behavior

Metamaterial temperature sensors are receiving increasing attention due to the wireless and passive operation. Unfortunately, the frequency response of most metamaterials sensors to temperature is nonlinear, which increases the complexity of signal processing. A dual resonance frequency selective surface (FSS) temperature sensor with linear frequency-temperature characteristic is proposed in this work. The dual frequency resonance of the sensor is realized by introducing the circular slot unit cell into the substrate integrated waveguide (SIW) structure. The linear relationship between the temperature and the difference in the two resonance frequencies can be achieved at specific condition. The proposed sensor was fabricated and measured from room temperature to 120 °C. Measured resonance frequency of the sensor decreases from 12.658 GHz to 12.57 GHz in SIW cavity resonance mode and from 13.787 GHz to 13.727 GHz in circular slot resonance mode. The experiment result shows that wireless temperature sensing is feasible and that the difference in resonance frequency has a good linear relationship with temperature. The sensitivity of the sensor is 0.309 MHz/°C. This design method can be extended to a wider temperature range and the sensor can be potentially applied in temperature sensing in industrial systems.

Biomimetic 4D printing of dome-shaped dynamic mechanical metamaterials

The dome shaped structures of natural organisms can provide design inspiration for impact resistant structural materials. Most of the existing biomimetic dome shaped impact resistant materials are directly formed using 3D printing technology, and the samples cannot dynamically adjust the impact resistance properties in the various applications. Herein, 4D printing of fused filament fabrication is employed to form flat structures with different structural patterns via programming the printing process parameters, which can be deformed into biomimetic dome structures with dynamic thermal stimulation treatment. The thermal stimulation treatment can drive the dynamic transformation of 2D planar structures into 3D structures, and the higher the thermal stimulation temperature, the greater the degree of eminence and the denser the structure under the same experimental conditions. The thermal stimulation temperature and the mechanical properties of the structural samples show a certain positive correlation. In addition, different design structural patterns have different compressive mechanical properties. The more the number of circular units, the more obvious the energy absorption characteristics. The impact-resistant biomimetic structures can be applied to the surface strengthening and cushioning of various weapons, vehicles, heavy equipment, and launch structure.

High-Gain Transmissive Array Antenna with Broadband Cross-Polarisation Isolation

A transmissive metal unit working in the range of 18 GHz-29 GHz is designed in this paper. This is a three-layer metal circular slit unit with promising cross-polarization isolation properties. A planar lens antenna with a center operating frequency of 28 GHz is designed based on the unit utilizing a phase compensation algorithm. The numerical simulation results show that the antenna can improve the gain of the horn antenna from 22.9 dB to 25.6 dB, which can effectively advance the development of 5G communication technology.

An experimental and numerical investigation on the performance of novel hybrid bio-inspired 3D printed lattice structures for stiffness and energy absorption applications

The modern additive manufacturing process enables the fabrication of innovative structural designs of lattice structures with enhanced mechanical properties. Characterizing the designability of lattice geometries and the corresponding mechanical performance, particularly the compressive strength is vital to commercializing lattice structures for lightweight components. In this paper, a Novel hybrid type of lattice structure was developed inspired by the overlapping pattern of scales on dermal layers of the species like fish and circular patterns observed from the bamboo tree structure. This research designed the lattice cell with 20%,30%,40%, and 50% overlapping areas based on the proposed circular area. The unit cell wall thickness varies between 0.4 mm and 0.6 mm. The designed structures with a constant volume of 40x40x40 mm, varied circular diameters, overlapping areas, and unit wall thickness are modeled in Fusion 360 software. 3D-printed lattice structures were fabricated using the vat polymerization type three-dimensional printing machine using the principle of stereolithography (SLA) technique. Then, the 3D-printed specimens are tested for quasi-static compressive response in a universal testing machine (UTM) by following ASTM standards. The test results are evaluated and compared with the simulation results. Finally, the best lattice structure is selected for energy absorption application in the aerospace and defense sectors.