Circular Part Research Articles

Design of cold formed C section beams with elongated circular openings based on tests

A design method to determine the shear resistance of elongated web openings in cold formed C sections is presented, that is based on Vierendeel bending in the web-flange Tee sections. The results of 6 tests on pairs of C section beams with stiffened and unstiffened openings of 155 mm depth and 220 mm length are presented. The tests also included a beam with closely spaced elongated openings and a comparative test on a plain C section. The tests showed that the bending resistance of the beam with stiffened openings was close to that of the plain C section.The design method is based on a derived formula for the normal stresses acting on radial planes around the circular part of the elongated opening. The results are compared to the stresses at an equivalent rectangular opening. It is proposed that in Vierendeel bending, buckling at the unstiffened openings may be represented as an equivalent ‘strut’ with an effective length of 0.3 x opening depth. The post-buckling resistance may take account of the redistribution of moments around the elongated openings. It was also found that for the tested beams, the additional shear and bending deflection due to each elongated opening was approximately 3 % of the plain beam deflection.

Experimental and numerical investigations on formation mechanisms of hollow structures in overflow water‐assisted injection‐molded parts of short‐glass‐fiber‐reinforced polypropylene

AbstractIn water‐assisted injection molding processes, it is crucial to understand the mechanisms governing the formation of hollow structures and identify the key factors influencing their morphology and dimensional accuracy. This work combined experimental analysis and numerical simulation to investigate the influence of different mold cavities and main processing parameters on hollow structures in overflow water‐assisted injection molded parts of short‐glass‐fiber‐reinforced polypropylene, that is, hollow shape and hollow ratio. The results show that the hollow shape and hollow ratio depended not only on the cross‐sectional location but also on the cross‐sectional shape of the mold cavity. For the circular parts, the hollow shape resembled the cross‐sectional shape of the mold cavity, with a relatively small and uniform hollow ratio across cross‐sectional locations. For the noncircular parts, the hollow shape varied considerably with increasing distance from the water inlet. Moreover, the results also show that except for the influence of water‐injection delay time on the uniformity of the hollow ratio, higher melt temperature (250°C), shorter water‐injection delay time (0 s), and higher water pressure (10 MPa) contributed to the hollow shape being closer to the cross‐sectional shape of mold cavities and made hollow ratios relatively larger and more uniform.

Experimental and numerical study of combined impinging jets at low nozzle-plate distance for confined and unconfined impingement plate

This study investigates the heat transfer and flow dynamics of combined impinging jets at low nozzle-plate distances. The combined jets comprise (i) circular and quadruple helical jets and (ii) circular and double helical jets. A conventional jet is generated from the only circular part of the combined jet. Experiments are conducted with a constant total flow rate (Qt = 85 LPM) and low nozzle-plate distances (H/D = 0.1, 0.2, 0.3, 0.4) for confined and unconfined jet cases. Flow rate ratios (Q*=0.176, 0.235, 0.352, 0.588, 0.823) are used for different swirl intensities. A numerical study was performed using ANSYS Fluent software. The results show that the numerical analysis is consistent with the experimental research. The combined impingement jet shows a potential to improve the low heat transfer occurring at the stagnation zone at low nozzle-plate distance in the swirl jet, leading to non-uniform heat transfer. The confined jet case at the low nozzle-plate distance reduces the heat transfer at the stagnation point and over the entire plate as regards the unconfined jet case. Increasing the H/D distance in the combined impinging jet improves the heat transfer in the confined jet case but reduces it in the unconfined case. Correlations are given for heat transfer prediction depending on H/D and Q* for unconfined and confined cases of the combined jet. Increasing the flow rate ratio and the nozzle-plate distance increases the heat transfer uniformity for the confined and unconfined jet cases. In contrast, the unconfined jet case is better regarding heat transfer uniformity. The confinement plate creates a negative pressure on the impingement plate in all conditions. In contrast, the unconfined jet case is precisely the opposite.

ANALYSIS OF CORRECTIVE MAINTENANCE MONITOR CCA TOOL DVOR SELEX TYPE-1150A

In the aviation industry, navigation has a crucial role in supporting the smooth running of flight routes to maintain the safety and security of air transportation. Perum LPPNPI Pekanbaru branch provides communication, Navigation, Surveillance, and Data Processing facilities to ensure flight safety, regularity, and comfort. One of the navigation facilities available at Perum LPPNPI Pekanbaru branch is the Doppler VHF-Omnidirectional Range (DVOR), an air navigation system control tool that can guide aircraft to land precisely at the destination airport by providing information in the form of azimuth or artificial bearing. This research aimed to analyze the care and maintenance system for DVOR equipment, and identify several potential problems that have arisen during the operation of DVOR equipment at Perum LPPNPI Pekanbaru branch. In this research, evaluations and observations were carried out to assess the level of DVOR maintenance in accordance with Advisory Circular CASR Part 171-12. This research focused on evaluating Corrective Maintenance Monitor (CMM) analysis on DVOR Selex Type-1150A equipment at Perum LPPNPI Pekanbaru Branch. DVOR is a critical air navigation system that requires effective corrective maintenance. The method used in the research is procedural analysis of equipment maintenance as in research conducted by Widasari Mutiara, this research also focused on CMM evaluation, identification of potential problems, and performance analysis to improve maintenance efficiency. Research adopted a qualitative research method with a descriptive approach, because the data collected is textual in nature. This research method involved CMM system inspection, equipment maintenance analysis, and interviews with engineering personnel. The research results provide insights for improving corrective maintenance procedures, and increasing the availability and reliability of the DVOR system. The implications of these findings support safe and reliable flight operations at Perum LPPNPI Pekanbaru Branch.

Experimental and model investigation of spreading characteristics of the liquid sheet formed by jet impinging on a circular plane

The focus of this paper is on the spreading characteristics of the liquid sheet formed by jet impinging on a circular plane. The liquid sheet is studied in two parts: the liquid film that spreads radially on the circular plane, and the free liquid sheet after leaving the circular plane, the former determines the initial thickness and velocity of the latter. Experimental results show that, for the liquid film on the circular plane part, as the jet velocity increases, the liquid film thickness increases due to the film velocity loss caused by the inelastic collision. The liquid film thickness is positively correlated with the jet radius and negatively correlated with the circular plane radius. Liquid viscosity slows the spreading of liquid film, forms the boundary layer, and thickens the liquid film. The surface tension inhibits the velocity loss due to the inelastic collision. For the free liquid sheet part, surface tension and gravity promote the bending of the liquid sheet. The larger the initial momentum of the liquid sheet leaving the circular plane, the larger the maximum spreading range of free liquid sheet reaching the equator. As for the theoretical model, a film velocity correction coefficient reflecting collision loss is introduced to improve the radial spreading theory of the liquid film on a solid surface, and a streamline function is assumed to solve the momentum integral equation of free liquid sheet. The predicted streamline agrees well with the experimental data.

Semi Automated Welding Machine Using PLC

Abstract: In this project, we will be doing Design,Analysis & Manufacturing automation for circular parts welding with uniform weld structure usingPLC. We will be designing & manufacturing the turntable, which will be rotating at specific requiredspeed depending upon the requirement of fillet material to be added. Further, the electrode nozzle iskept stationary, which will be in contact with the surface of components to be welded. Therefore, thisproject proposed a detailed design for the conversionof the conventional MIG welding machine (ARC) into an automated machine for welding round components. Together with this main modification, the existing MIG welding machine – (a stationary, downward-facing ARG – HEAD, which has provisions for horizontal and upward movements) isto be modified into portable robotic weldingmachine.

Zeros of modular forms and Faber polynomials

AbstractWe study the zeros of cusp forms of large weight for the modular group, which have a very large order of vanishing at infinity, so that they have a fixed number of finite zeros in the fundamental domain. We show that for large weight the zeros of these forms cluster near vertical lines, with the zeros of a weight form lying at height approximately . This is in contrast to previously known cases, such as Eisenstein series, where the zeros lie on the circular part of the boundary of the fundamental domain, or the case of cuspidal Hecke eigenforms where the zeros are uniformly distributed in the fundamental domain. Our method uses the Faber polynomials. We show that for our class of cusp forms, the associated Faber polynomials, suitably renormalized, converge to the truncated exponential polynomial of degree .

Cylindrical Models Motivated through Extended Sine-Skewed Circular Distributions

A class of cylindrical distributions, which include the Weibull-von Mises distribution as a special case, is considered. This distribution is obtained by combining the extended sine-skewed wrapped Cauchy distribution (marginal circular part) with the Weibull distribution (conditional linear part). This family of proposed distributions is shown to have simple normalizing constants, easy random number generation methods, explicit moment expressions, and identifiability in parameters. In particular, the marginal distribution of the circular random variable, and its conditional distribution given a linear random variable give relatively stronger skewness than those of existing cylindrical models. Some Monte Carlo simulations and real data analysis are performed to investigate the feasibility and tractability of the proposed models.

Torque Teno Virus load is associated with CDC stage and CD4+ cell count in people living with HIV but unrelated to AIDS-defining events and Human Pegivirus load.

Torque Teno Virus (TTV) is a non-enveloped, circular single-strand DNA virus and part of the human virome. The replication of TTV was related to the immune status in patients treated with immunosuppressive drugs after organ transplantation. We hypothesize that TTV load could be an additional marker for immune function in people living with HIV (PLWH). In this analysis serum samples of PLWH from the RESINA multicenter cohort were reanalysed for TTV. Investigated clinical and epidemiological parameters included Pegivirus (HPgV) load, age, sex, HIV load, CD4+ cell count (CDC 1, 2, 3) and CDC clinical stages (1993 CDC classification system, A, B, C) before initiation of antiretroviral treatment. Regression analysis was used to detect possible associations among parameters. Our analysis confirmed TTV as a strong predictor of CD4+ cell count and CDC class 3. This relationship was used to propose a first classification of TTV load in regard to clinical stage. We found no association with clinical CDC stages A, B and C. HPgV load was inversely correlated with HIV load but not TTV load. TTV load was associated with immunodeficiency in PLWH. Neither TTV- nor HIV load were predictive for the clinical categories of HIV infection.

Reducing heat gain from sheet metal‐clad walls by utilizing industrially wasted materials (experimental study)

AbstractBuildings' walls are covered to reduce environmental impact and esthetics, and cladding materials vary based on public preference and financial capacity. Metal sheets with glossy surfaces are commonly used, but researchers propose using aluminum sheets and filling gaps with commercial waste materials, like, fabric roll sticks or circular plastic hollow parts. A test room with internal dimensions of 1 × 1 × 2 m used in Baghdad (latitude 33.2° N) was used to study thermal behavior, with a window‐type air conditioner providing standard thermal conditions. The air gap attached to the top of the test wall was either left open or closed during the day. Results showed that double‐layer bamboo packing preserved 52.1% with a closed‐air gap and 49.5% with an open‐air gap, but no discernible difference was observed between the two situations.

Unveiling the spatiotemporal evolution of liquid-lens coalescence: Self-similarity, vortex quadrupoles, and turbulence in a three-phase fluid system

The coalescence of liquid lenses represents a fundamental challenge within the domains of fluid dynamics and statistical physics, particularly in the context of complex multi-phase flows. We demonstrate that the three-phase Cahn–Hilliard–Navier–Stokes (CHNS3) system provides a natural theoretical framework for studying liquid-lens coalescence, which has been investigated in recent experiments. Our extensive direct numerical simulations of lens coalescence, in the two and three dimensional (2D and 3D) CHNS3, uncover the rich spatiotemporal evolution of the fluid velocity u and vorticity ω, the concentration fields c1, c2, and c3 of the three liquids, and an excess pressure PℓG, which we define in terms of these concentrations via a Poisson equation. We find, in agreement with experiments, that as the lenses coalesce, their neck height h(t)∼tαv, with αv≃1 in the viscous regime, and h(t)∼tαi, with αi≃2/3 in the inertial regime. We obtain the crossover from the viscous to the inertial regimes as a function of the Ohnesorge number Oh, a dimensionless combination of viscous stresses and inertial and surface tension forces. We show that a vortex quadrupole, which straddles the neck of the merging lenses, and PℓG play crucial roles in distinguishing between the viscous- and inertial-regime growths of the merging lenses. In the inertial regime, we find signatures of turbulence, which we quantify via kinetic-energy and concentration spectra. Finally, we examine the merger of asymmetric lenses, in which the initial stages of coalescence occur along the circular parts of the lens interfaces; in this case, we obtain power-law forms for the h(t) with inertial-regime exponents that lie between their droplet-coalescence and lens-merger counterparts.

Manufacturer’s service relationships as a gateway to circular supply chains: merging insights from two literature fields

Many manufacturers now have established service businesses to support the use of their products (created through servitization) and are now facing new pressures of sustainability and circularity. This research explores how relationships with supply chain actors may change for servitized manufacturers when implementing circular economy. Based on a structured literature review of two literature streams – servitization and circular economy – this paper provides an overview of existing concepts regarding the relationship dynamics in these settings. A framework is proposed detailing the relationships necessary for recovery, processing, and commercialization of circular products, parts or components when creating circular servitized supply chains. Specific directions for future work and wider avenues for future research are provided for creating circular servitized supply chains. The contributions of this research stem from the combining and contextualization of key insights from two literature streams and proposed conceptual framework for creating circular servitized supply chains.

The Role of Independent Repair in a Circular and Regenerative Economy

AbstractThe focus on the transition to a circular economy has contributed to a growing research interest in repair. This paper investigates the role of independent repair, which consists of individuals, organisations, or businesses engaged in the repair of products without formal authorisation of the brand owners of these products. Repair—and independent repair in particular—is critical in achieving a paradigm shift that is anchored in regenerative sustainability. Especially in the electrical and electronics equipment sector, independent repair is challenged by difficult or expensive access to spare parts and repair information. This paper focuses on the independent electronics repair sector in Oslo. We implemented twenty-five semi-structured interviews with repairers working in commercial independent repair shops, focusing on challenges and opportunities in independent repair. They repaired a wide variety of products: mobile phones, desktop computers, laptops, tablets, cameras, printers, e-mobility batteries, remote-controlled cars, drones, and white goods. The thematic analysis of the interviews revealed three main findings. The independent repair sector employs different business models and strategies to tackle the challenges related to accessing affordable and quality spare parts. Secondly, independent repair fills the gap between expensive authorised repair, mostly covered by warranty or insurance, and discarding a broken product. Thirdly, independent repair has contributed to a circular spare part economy, both locally and on a global level. In the discussion, we address how repair can be understood as a regenerative practice, as well as how policy and regulation of repair, both on an EU and national level, supports or undermines independent repair.

Electromagnetic-mechanical coupling analysis of high-temperature superconducting racetrack coil

The second-generation high-temperature superconducting (HTS) coated conductor has been recognized as one of the most promising materialsfor high field magnets due to its superior electromagnetic and mechanical performances. HTS racetrack coils wound with the coated conductors are an extensively used configuration in engineering applications, such as HTS machines and high-speed maglevs. In this paper, in order to analyze the electromagnetic and mechanical behaviors of HTS racetrack coils, a 3D coupled electromagnetic-mechanical model is used to consider the effect of coil deformation and the strain dependence of critical current. The effectiveness of the coupled model is validated by comparing the numerical results with experimental data in the literature. A numerical simulation of a 3D HTS racetrack coil subjected to an external electromagnetic field is carried out using coupled and uncoupled models. The results indicate that the structure deformation can reduce the penetration depth of the screening current, and the hoop stress and strain are mainly concentrated on the circular part of the racetrack coil. Afterwards, the influences of various parameters on the electromagnetic and mechanical responses of the HTS racetrack coil are also investigated.

Shape distortion in composites: sources, characterization, and remedies

This paper reviews the shape distortions in a polymer composite, its sources, characterization techniques, and remedies. The shape distortion may include warpage, spring-in, or change in enclosed diameter for flat, angled, and circular parts. Residual stresses are considered to be the major source of shape distortion (dimensional instability) in laminated composites. These stresses are the result of the difference in thermal expansion behavior of the different plies or between matrix and reinforcement. Additionally, fiber buckling, transversal cracking, and delamination are also produced in the composite, affecting its mechanical properties like tensile, flexural, and compression. The produced residual stresses are determined through different techniques like layer removal of symmetrical laminates, first ply failure, and x-ray diffraction. The common remedies for shape distortion reported in the literature include nanoparticle addition and variable thickness at the base or flanges.

Rectangular Busbar With Circular Sensing Part for Wideband Current Measurement

Rectangular Busbar With Circular Sensing Part for Wideband Current Measurement

Heat transfer and entropy analysis for nanofluid flow in a semi-circular open cavity under mixed convection

This paper presents a numerical simulation of nanofluid flowing in an open cavity under mixed convection by considering various heat transfer zones. To enhance the heat transfer, water was augmented with copper nanoparticles at different ϕ (volume fraction of nanoparticles) values. The present paper aims to determine the optimal position which maximizes the heat transfer in a circular open cavity. Also, in this research the investigation of combined convection flow in a specific geometry, taking into account the changes in the flow parameters, is an attempt to model the temperature field and heat transfer. For this purpose, the nanofluid flow for Reynolds numbers of Re =10, 50 and 100 is investigated. On the other hand, the hot areas in the curved part of the open cavity are separated in various cases. The results show that due to the low velocity of the fluid in the circular part of the cavity, especially in the hot wall area, most of the fluid exchange is due to natural convection due to density difference and the hot areas are strengthen the flow circulation. The exchange is also improved by increasing Re (Reynolds number) or the momentum term, and the distribution of T (temperature) in the cavity becomes more uniform. Hot spots with low heat transfer coefficient were attenuated at higher Re. The most suitable temperature distributions were achieved for W4 and W2. By increasing ϕ, the friction factor decreases for pure water, especially in W2 and W3. However, due to fluid-surface impact at Re = 100 in W2 and W3, the friction factor does not change significantly by altering ϕ. Using a higher Re and the dominance of the fluid momentum in comparison with the viscous force, the effect of nanoparticle concentration decreases. In general, the best heat transfer occurs at higher volume fraction of nanoparticles. Finally, at all Reynolds numbers, the heat transfer increases by 8–19%. This is because nanoparticles are added to pure water (working fluid).

Prediction of machining deformation induced by turning residual stress in thin circular parts using ritz method

Workpiece deformation induced by surface residual stress during turning is a serious concern in the manufacturing of thin-walled parts. Prediction of machining deformations caused by residual stress is essential to explain deformation mechanism and design machining strategies. Although many studies have been focused on calculating those deformations using the finite element method (FEM), it is time-consuming and redundant. Based on energy equations considering residual stress fields developed by the three-dimensional elastic theory and the principle of minimum potential energy, a new analytic model was established to predict machining deformation of the thin circular parts. In this model, the modified Rayleigh-Ritz method and pseudo inverse method were used to solve energy equations under various machining conditions to obtain machining deformation. Corresponding experiments and existing methods were considered to validate the accuracy and efficiency of the proposed model. Based on the quantitative results of the proposed model, the effects of machining conditions on machining deformation were discussed comprehensively, which provides guidance for machining strategies. • The energy equations of the thin circular plates considering residual stress distributions in all directions is developed. • The improved Rayleigh–Ritz method associated with the pseudo inverse method are used to solve the machining deformation . • The influence factors of machining deformation induced by residual stresses are comprehensively analyzed.

Mode-locking threshold decrease in a fiber laser by heterochromic optical pulse injection

A Yb-doped fiber laser mode locked by a nonlinear amplifying loop mirror (NALM) with a figure-9 configuration is experimentally realized. By coupling heterochromic 1580-nm optical pulses into the circular part of the Yb-doped laser oscillator, a new injection-induced Q-switched mode-locking (Q-ML) like transition state is found for the first time to the best of our knowledge. We have investigated the envelope interval and duration of this Q-switched envelope by changing the pump power, injection power, and cavity length detuning. Experimental results have shown the injected pulses serve as a complementary source for establishing mode-locking (ML). As a result, the self-starting ML threshold of the Yb-doped fiber laser is significantly reduced from 355 to 171 mW, which is only half that in the non-injection case. This optical pulse injection assisted ML process is observed with a real-time oscilloscope, revealing stable and consistent buildup dynamics. Our finding may provide a new approach for understanding the buildup dynamics and building mode-locked fiber lasers with low threshold and high consistency.

First Report of Paraphoma chrysanthemicola Causing Crown and Leaf Rot of Atractylodes lancea in China.

Atractylodes lancea is an important traditional Chinese medicinal plant whose rhizome is used for treating complaints such as rheumatic diseases, digestive disorders, night blindness and influenza. Jiangsu Province is the optimal cultivation location for high-quality A. lancea rhizome. Since June 2019, symptoms of crown rot and leaf rot were observed in about 10-20% of the A. lancea in a plantation (31° 36' 1" N, 119° 6' 40" W) in Lishui, Jiangsu, China. Lesions occurred on the stem near the soil line and on the leaves (Fig. 1A). Disease incidence reached approximately 80-90% by September, 2021 (Fig. 1B) and resulted in severe loss of rhizome and seed yields. For pathogen isolation, ten samples of symptomatic stem segments and ten diseased leaves were collected, surface-sterilized using 5% NaClO solution, rinsed with sterile water, cut into 0.5-2 cm segments, and plated to potato dextrose agar (PDA), and then incubated at 30°C in darkness. Pure cultures of four isolates showing morphological characteristics of Paraphoma spp. were obtained, identified as a single P. chrysanthemicola strain, and named LSL3f2. Newly formed colonies initially consisted of white mycelia; the five-day-old colonies developed a layer of whitish grey mycelia with a grey underside. 20-day-old colonies had white mycelium along the margin and with a faint yellow inner circular part with irregular radial furrows, and the reverse side looking caramel and russet (Fig. 1C). Pycnidia were subglobose (diameter: 5 to 15 μm; Fig. 1D). Unicellular, bicellular or strings of globose or subglobose chlamydospores developed from hyphal cells (Fig. 1E and 1F). The internal transcribed spacer (ITS) region and large subulin-28S of LSL3f2 were cloned using primers ITS1/ITS4 and LR0R/LR7 (Aveskamp et al. 2010, Li et al. 2013), and deposited in GenBank (OK559658 and OK598973, respectively). BLASTn search and phylogenetic analysis showed the highest identity between LSL3f2 and P. chrysanthemicola sequences (Fig. 1G) and confirmed LSL3f2 as P. chrysanthemicola. Koch's postulates were completed using one-month-old vegetatively propagated A. lancea plantlets growing on autoclaved vermiculite/peat mixture at 26°C with a light/dark cycle of 12/12 hours. Each plantlet was inoculated with 5 ml of conidial suspension in water (1 × 108 cfu/ml) by applying to soil close to the plantlet, with sterile water used as a mock control (n = 10). By 20 days post-inoculation, inoculated plantlets showed a range of disease symptoms consistent to those observed in infested fields (Fig. 1H). Pathogenicity was additionally confirmed using detached leaves inoculated with a colonized agar plug of LSL3f2 or an uninoculated control comparison (diameter = 5 mm) and incubated at 26℃ in the dark. Five to seven days post-inoculation, detached leaves showed leaf rot symptoms including lesions, yellowing and withering consistent with those in infested fields, while control leaves remained healthy (n = 10, Fig. 1I). The pathogen was reisolated from the diseased plantlets and detached leaves, in both cases demonstrating the micromorphological characteristics of LSL3f2. P. chrysanthemicola has been reported to cause leaf and crown rot on other plants such as Tanacetum cinerariifolium (Moslemi et al. 2018), and leaf spot on A. japonicain (Ge et al. 2016). However, this is the first report of P. chrysanthemicola causing crown and leaf rot on A. lancea in China.