Circular Sector Research Articles

Isogeometric analysis of the Laplace eigenvalue problem on circular sectors: Regularity properties and graded meshes

The Laplace eigenvalue problem on circular sectors has eigenfunctions with corner singularities. Standard methods may produce suboptimal approximation results. To address this issue, a novel numerical algorithm that enhances standard isogeometric analysis is proposed in this paper by using a single-patch graded mesh refinement scheme. Numerical tests demonstrate optimal convergence rates for both the eigenvalues and eigenfunctions. Furthermore, the results show that smooth splines possess a superior approximation constant compared to their C0-continuous counterparts for the lower part of the Laplace spectrum. This is an extension of previous findings about excellent spectral approximation properties of smooth splines on rectangular domains to circular sectors. In addition, graded meshes prove to be particularly advantageous for an accurate approximation of a limited number of eigenvalues. Finally, a hierarchical mesh structure is presented to avoid anisotropic elements in the physical domain and to omit redundant degrees of freedom in the vicinity of the singularity. Numerical results validate the effectiveness of hierarchical mesh grading for simulating eigenfunctions of low and high regularity.

Digital twins for environmentally sustainable and circular manufacturing sector: visions from industry professionals

ABSTRACT Traditional make-use-dispose operations are no longer an option in the manufacturing sector – companies face mounting sustainability pressures and incentives to move towards circular economy (CE) operations. Accordingly, they must implement new technologies to maintain competitiveness in the transition. One potential tool in navigating the change is the digital twin (DT). Previous research on DTs has largely focused on technological prerequisites, devoting less attention to their business and sustainability aspects. To fill the gap, this qualitative research provides an overview of sustainability pressures in manufacturing sector and examines how DTs can promote environmentally sustainable business and circularity. The results indicate that external pressures, such as stakeholder expectations, competition, ongoing megatrends, and regulations, push companies towards better sustainability, accompanied by employee expectations and internal willingness. The results also reveal a vast potential for DTs with sustainability and CE, especially in product design, use, and operation and at the decommissioning and renewal stages.

Zooming Out: Circular Economy Development in the European Union and its Implications on the Economy and Society

The concept of the circular economy has emerged as a response to the challenges posed by resource constraints, waste accumulation, and pollution, threatening both social welfare and business profitability. The circular economy aims for sustainable development, encompassing environmental quality, economic prosperity, and social equity across current and future generations. Despite its recognition as a pivotal solution, there needs to be more comprehensive understanding regarding its development and its economic and social impacts. Therefore, the objective of this paper is to investigate the progress of circular economy sectors in the European Union to get an overview of the circular economy advancements and discuss geographical economic and social effects. The focus is on the indicators of gross value added, private investments, and full-time employment within recycling, repair, and reuse sectors because these sectors provide good proxies for the circular economy activities in the European economy. Results suggest a linear growth of circular economy sectors across the European Union, albeit with variations among member states. The paper discusses the implications of circular economy transition on the economy and society, particularly on the labour market, skill demands, and technology integration, emphasising the need for a critical academic discourse. It questions assumptions about job creation and local employment, especially considering technological advancements that may reduce manual labour in recycling plants. Future research is invited to focus on these macro-level implications and critically reflect on the societal implications of a circular economy transition to shape a more fair and socially inclusive economy.

Key Factors Influencing Consumer Choices in Wood-Based Recycled Products for Circular Construction Sector

This article explores the integration of wood recycling and reuse practices within construction and reconstruction processes, as highlighted in a wood products questionnaire. The aim of this study is to understand how the Romanian consumers perceive the circular economy in order to adopt responsible consumption models. The working instrument consisted of a questionnaire. The questionnaire was applied to 60.7% urban respondents and 39.3% rural ones and consisted of 23 items. The response rate was 68.5% for certain items (257 responses). In the first part, the integration of wood recycling and reuse practices within construction and reconstruction processes is examined. Emerging recycling techniques and demolition processes, particularly incorporating reused, reconditioned, and recycled wood in the construction industry, are evaluated. The economic and environmental implications of these practices are also examined, contributing to the discussion of eco-design policies, and construction waste management and standards. In the second part, insights are provided into how Romanian consumers’ knowledge of CE principles, information about product characteristics, and attitudes influence the demand for recycled wood products. The study concludes with recommendations for better promotion strategies of wood-based recycled products, aiming to increase awareness of its long-term environmental and socio-economic benefits. Additionally, it suggests the need for providing more information on the environmental benefits of wood-based recycled products, and for a more active engagement of stakeholders in the transition to a circular economy. The results serve as a basis for a better understanding of Romanian consumers’ adoption of sustainable consumption behavior in agreement with circular economy concepts and SDGs. While the majority of respondents generally shows openness to an eco-friendly product, mere promotion of these principles may not suffice to change entrenched behaviors and purchasing habits.

Toolpath and Tool Design Innovations in Deformation Machining for Superior AA-7075 T6 Fins

Abstract A hybrid manufacturing process, deformation machining (DM) combines subtractive manufacturing with incremental forming. Monolithic components with complex profiles are created through the hybridization of manufacturing technologies, which also reduces the wastage of raw materials. The properties of geometry and surface quality of the fin made from the aluminum alloy Al-7075 T6 using the DM process’s bending mode was examined in this research, as were the effects of various approaches, toolpath methods, and tool design. To achieve the desired shape for the machined fin, various combinations of arcuate and slanting fin toolpath techniques were explored utilizing both top-down and bottom-up methods. The bottom-up method and the arcuate toolpath strategy were used to investigate various tool profiles. Using the best combination of toolpath strategy and tool profile, named as the T3 tool profile, which has a 0.6 mm nose radius and a circular sector, bottom-to-top (BTT)technique, and arcuate toolpath method, components with better geometrical features and surface roughness (SR) were produced. The analysis of the forming force in the bending approach of the DM progression was further carried out using this optimal combination.

The circular balancing problem

We propose a balancing problem with a minmax objective in a circular setting. This balancing problem involves the arrangement of an even number of items with different weights on a circle while minimizing the maximum total weight of items arranged on any half circle. Due to its generic structure, it may have applications in fair resource allocation schemes. We show the NP-hardness of the problem and develop polynomial-time algorithms when the number of distinct weights is a fixed constant. We propose for the general case a tight 7/6-approximation algorithm and show that it performs better than two existing algorithms designed for an equivalent problem in the literature. The worst-case performance ratio is derived through a linear combination of valid inequalities that are obtained from the problem definition, the properties of the proposed algorithm, and the optimal circular permutation structure. Furthermore, we formulate a more general problem of minimizing the maximum total weight of items on equally divided circular sectors and present its computational complexity and a tight approximation algorithm.

Investigating the Impact of Circular Sector Pole Head Structure on the Performance of a Multipole Magnetorheological Brake

The magnetorheological brake (MRB) epitomized a revolutionary modification in the braking systems because of its extremely efficient and well-controlled performance. To increase the safety and controllability of automotive braking system, researchers have developed a different MRB structures. Although much research on magnetorheological brakes has shown positive results in terms of brake torque, braking time, thermal efficiency, etc., the ability to increase braking force by expanding the disc surface, through which the magnetic field operates in a compact structure, is restricted. To address this issue, a new multipole MRB configuration with a unique pole head design that maintains compactness. Initially, the conceptual design was achieved by leveraging the combined impact of the twin disc-type structure and multipole concept. The model was used in a dynamic simulation to show how the braking torque of a magnetorheological braking system varies with coil current. The effects of circular sector pole head shape on braking performance were investigated using COMSOL Multiphysics software (version 5.5). A three-dimensional electromagnetic model of the proposed MRB was developed to examine the magnetic flux intensity and the impact of magnetic field dispersion on the proposed pole head structure of a magnetorheological brake. Based on simulation results, the circular sector pole head configuration is capable of increasing the active chaining regions for the MR fluid on the rotor surface, allowing for a more effective use of magnetic flux throughout the whole surface of a rotating brake disc, thereby increasing the magnetic field usage rate. The acquired simulation results show an increase in braking torque while keeping a compact and practical design structure.

Industrial symbiosis and eco-industrial transformation opportunities for environmental protection in Nigeria

The establishment of industrial parks has functioned as a catalyst for sustained economic growth and industrial advancement in Nigeria, mirroring trends observed in industrialized countries globally. However, no attention has been given to the conversion of existing industrial parks to eco-industrial parks (EIPs) to address the environmental challenges caused by increased industrialization in the country. This paper presents an assessment of opportunities for environmental protection through eco-industrial transformation in Nigeria, specifically focusing on the case of Sharada Industrial Park (SIP). The study applies the international eco-industrial park (EIP) framework to evaluate the current and intended performance of the park and identify opportunities for its conversion into an EIP, through an on-site tour of the park and interviews with the park managers. Similarly, questionnaires were used to assess the readiness of eco-industrial transformation in the country. The assessment of SIP's performance against the EIP framework reveals a concerning lack of compliance, with only 39 % of the performance indicators being met. This translates to several issues including resource inefficiency, increased pollution, higher operating costs and environmental non-compliance for the resident industries in SIP. Key opportunities for the transformation of SIP into an EIP were identified, including the diversity of industries in the park, existing infrastructure and renewable energy integration. These opportunities represent the potential for the establishment of sustainable industrial ecosystems in Nigeria. Tailored strategies for compliance, including policy reforms and stakeholder engagement, are recommended to drive eco-industrial transformation and foster a sustainable and circular manufacturing sector in Nigeria. It is also recommended that future research should investigate the drivers and barriers of industrial symbiosis (IS) and circular economy practices within industrial parks, alongside material flow analysis to determine synergy opportunities.

Mapping Circular Economy Performance: EU Member States Analysis and Insights

Abstract The concept of the circular economy was created around the desire to extend the life of products and, implicitly, their use in an economy. The waste reduction process is founded on the basis of the three R's - reduce, reuse, recycle, which aims to conserve natural resources. In order to determine the contribution made by the European Union (EU) states regarding the circular economy sector, a descriptive analysis was carried out at the level of the member countries, followed by the identification of their ranking regarding the performances recorded in accordance with the analyzed indicators, a final step being the realization of a cluster analysis through which to determine the similarities and differences between them. Among the results obtained, it was found that the countries in the center of the EU have among the highest values in terms of private investment related to circular economy sectors, but also for resource productivity, although they have among the lowest percentages of people employed in this field, but and among the largest greenhouse gas emissions from production activities.

VO2 based multi-functional ultra-wideband terahertz meta-absorber for EMI shielding application

ABSTRACT This paper presents a multifunctional tuneable wideband metasurface absorber based on phase-changing Vanadium dioxide (VO2). The ‘quad isotropic VO2 circular sectors’ are constructed on amorphous silicon dioxide (SiO2), backed with 0.2 µm-thick gold layer to design the proposed absorber. This novel wideband tunable structure can independently be used as a reflector and absorber as an EMI shield; hence, this multi-functionality in a single structure proves novel and unique in the terahertz frequency range. This unit cell offers a bandwidth of 3.5 THz with more than 90% of absorptivity under normal wave incidence. The equivalent circuit model, surface currents, and field distributions are further investigated to provide a better understanding of structural evolution. Moreover, a wideband absorption has been observed up to the 60° incident angle for both the transverse modes, showing a polarization-insensitive behavior due to the symmetricity in the structure. The parametric study explores, optimizes, and demonstrates various other main characteristics and parameters of the proposed absorber. The novel structure offers shielding effectiveness (SE) higher than 40 dB throughout the frequency band under both normal and oblique incidence. This outstanding performance makes it a strong contender for EMI-EMC applications. Furthermore, it shows great potential in the field of terahertz technology, such as terahertz imagers, detectors, sensors, and other wideband applications.

Towards a Circular Solar Power Sector: Experience with a Support Framework for Business Model Innovation

The rapid expansion of the global solar photovoltaic (PV) market as part of the transition to a low-carbon energy future will increase both demand for raw materials used in PV product manufacturing as well as future PV panel waste volumes. There is an urgent need for solar industry businesses to adopt circular business models, and to support this process through targeted tools and methods that can facilitate the innovation process of such models. This paper employs an action-oriented case study methodology, drawing on insights garnered from five demonstrator cases that have applied and validated a Circular Business Model Innovation (CBMI) framework within the PV sector. Results show how this framework was applied in practice during the ideation, design, experimentation, and scaling phases of the innovation process. Specifically, results show how an experimental and iterative approach was found critical to assess viability, desirability, and feasibility of circular business strategies. The study’s empirical testing of tools with the context of a Circular Economy complements earlier theoretical conceptualizations of business model innovation processes. It illustrates how using multiple tools can provide firms with complementary insights in each stage of ideation, design, testing, and scaling of business models. It is recommended that policy makers and business leaders endorse such co-creative and experimental approaches to foster learning and business model innovation, thereby catalysing the transformation of an entire renewable energy industry sector towards Circular Economy.

Assessing the Circular Economy Funds: Performance, Fees, Risks, and Sustainability

We studied various fund investing options in the circular economy sector. We found that most circular economy mutual funds and exchange-traded funds charge higher fees and take higher risks than their benchmarks. However, they appear to have underperformed their benchmarks during their short existence so far. Most of these funds are rated as sustainable and low-carbon funds. Investors keen on circular economy startups may consider private equity/venture capital funds, but most of these funds are exclusive to institutional and accredited investors.

Using Natural Language Processing to monitor circular activities and employment

In Europe, NACE codes are used for the official classification of sectors, however, the circular economy is not sufficiently captured in this classification. Therefore, this paper improves previous attempts for defining circular activities and jobs by web scraping techniques applied to each company in Belgium. We analyze their first, second, and third official NACE codes and compare these to the NACE codes they should have been allocated to according to the web scraping data. Subsequently, we calculate circularity scores for every sector to construct an indicator for the number of circular companies and jobs. The results show that the number of circular companies is lower than the baseline from official statistics when we only consider the companies' first and main NACE code. The estimates are higher than the baseline when we also take the second and third NACE codes into account and the estimated number of circular jobs is far higher than the baseline. This research upgrades previous classifications of circular sectors and demonstrates how web scraping and novel data might improve our understanding and capacity to build data. Based on the results in this paper, we recommend a uniform data collection such as reporting standards, and an inclusion of all circular strategies in sectoral classifications.

Design Approach to Azimuthal Null Frequency Scanning Circular Sector Patch Antenna Under Triple-Mode Resonance

Design Approach to Azimuthal Null Frequency Scanning Circular Sector Patch Antenna Under Triple-Mode Resonance

Transforming polypropylene waste into transparent anti-corrosion weather-resistant and anti-bacterial superhydrophobic films

The global pollution crisis arising from the accumulation of plastic in landfills and the environment necessitates addressing plastic waste issues. Notably, polypropylene (PP) waste accounts for 20% of total plastic waste and holds promise for hydrophobic applications in the realm of recycling. Herein, the transparent and non-transparent superhydrophobic films made from waste PP are reported. A hierarchical structure with protrusions is induced through spin-casting and thermally induced phase separation. The films had a water contact angle of 159° and could vary in thickness, strength, roughness, and hydrophobicity depending on end-user requirements. The Bode plot indicated enhanced corrosion resistance in the superhydrophobic films. Antibacterial trials with Escherichia coli and Staphylococcus aureus microbial solutions showed that the superhydrophobic film had a significantly lower rate of colony-forming units compared to both the transparent surface and the control blank sample. Moreover, a life cycle assessment revealed that the film production resulted in a 62% lower embodied energy and 34% lower carbon footprint compared to virgin PP pellets sourced from petroleum. These films exhibit distinctiveness with their dual functionality as coatings and freestanding films. Unlike conventional coatings that require chemical application onto the substrate, these films can be mechanically applied using adhesive tapes on a variety of surfaces. Overall, the effective recycling of waste PP into versatile superhydrophobic films not only reduces environmental impact but also paves the way for a more sustainable and eco-friendly future.

Mass moments of functionally graded 2D domains and axisymmetric solids

We present a general methodology to evaluate the mass moments of two-dimensional domains and axisymmetric solids made of functionally graded materials. The approach developed in the paper is based on the sequence of two steps. First, the original domain integrals are converted to integrals extended to the relevant boundary by exploiting Gauss theorem. Second, for domains having a polygonal or circular shape, the boundary integrals are evaluated analytically by providing algebraic expressions that depend upon the parameters defining the density distribution, the position vectors of the vertices of the polygonal domain or the initial and ending points of an arbitrary circular sector, respectively. While the first step refers to moments of arbitrary order, the second step is limited to the most useful quantities for engineering applications, i.e. generalised mass, static moment and inertia tensor. The formulas derived in the paper are validated by means of examples retrieved from the specialised literature for which analytical results are available or have been specifically derived by the authors. Finally, in order to ascertain the computational savings entailed by the use of the proposed analytical formulas with respect to numerical techniques, the mass moments of a longitudinal section of a human femure, made of a functionally graded material and characterised by a linear density distribution, have been computed.

Usefulness of the Ordinal Logistic Biplot: Analysis of the Path Taken towards a Circular Primary Sector in Spain

Population growth and greater global interconnection require a profound transformation in how we produce, consume, and manage natural resources. In this sense, the circular transition of the agricultural and livestock sectors is vital to guarantee adequate production without compromising the availability of resources for future generations. In this work, we analyze the level of circular development of the primary sector in Spain using a sample of the 84 largest companies. We utilize the biplot analysis, multivariate graphic models that represent the joint distribution of four scores (constructed with sixteen ecological initiatives), and three financial and geographic variables. These techniques allow for visualization of the status and the relationships between all of them. We evidence an important degree of progress in initiatives associated with the use of non-polluting energy, eco-design, eco-innovation, management, and care of ecosystems. We also observe that the current transition towards a circular primary sector is strongly associated with firms’ capital investments and long-term innovations. On the other hand, the actions aimed at protecting water resources are in an intermediate state of progress, being necessary to invest in additional friendly water initiatives. In this vein, it is advisable to promote public policies focused on promoting the ecological transition of this sector and the research that advances efficient water management.

Accessibility of osteochondral lesion at the capitellum during elbow arthroscopy: an anatomical study.

Osteochondrosis dissecans (OCD) at the capitellum is a common pathology in young patients. Although arthroscopic interventions are commonly used, there is a lack of information about the accessibility of the defects during elbow arthroscopy by using standard portals. An elbow arthroscopy using the standard portals was performed in seven fresh frozen specimens. At the capitellum, the most posterior and anterior cartilage surface reachable was marked with K-wires. Using a newly described measuring method, we constructed a circular sector around the rotational center of the capitellum. The intersection of K-wire "A" and "B" with the circular sector was marked, and the angles between the K-wires and the Rogers line, alpha angle for K-Wire "A" and beta angle for K-wire "B", and the corridor not accessible during arthroscopy was digitally measured. On average, we found an alpha angle of 53° and a beta angle of 104°. Leaving a sector of 51° which was not accessible via the standard portals during elbow arthroscopy. Non-accessible capitellar lesions during elbow arthroscopy should be considered preoperatively, and the informed consent discussion should always include the possibility of open procedures or the use of flexible instruments.

Design and analysis of X-band metamaterial absorber

This study introduces a novel metamaterial absorber operating in X-band frequency range, characterized by two resonating peaks. The proposed structure consist of four circular sectors connected by two cross resonators enclosed by a circular strip with the dielectric between them. FR4 is used as a substrate backed by a copper ground plane. Simulation results reveal that the reflection co-efficient remains consistently below -10dB across the entire X-band, ensuring effective absorption of incident electromagnetic waves. Moreover, the absorber achieves 100% absorptivity with the gain of -25dB under normal incidence. The validity of absorber performance is confirmed through impedance plot and Voltage Stand Waving Ration (VSWR) analysis, verifying the accuracy of S11 parameter. Furthermore, the proposed structure has a compact size of 0.1666 λ. The absorber’s robust performance validated through numerical analysis, positions it as a compelling candidate for various X-band applications, including radar systems, communication devices, and stealth technology. This research establishes the proposed metamaterial absorber as a promising solution for X-band electromagnetic wave attenuation needs, offering both superior performance and compact design.

북한의 SDGs 달성을 위한 입법과 정책의 변화

North Korea is actively utilizing the SDGs as a means to emphasize the unfairness and contradictions of the U.S. and other U.N. sanctions, saying that they are hindering peace-making and global partnerships, including the promotion of the SDGs and development cooperation, and to inform the international community that they are threatening North Korea's survival in non-political areas such as energy, food, water and sanitation, and the climate crisis. Furthermore, by actively embracing the UN SDGs, the DPRK is emphasizing its image as a ‘normal country’ and a ‘moderate country’ by accepting universal norms and values of the international community, including the United Nations, and cooperating with the international community, and recognizing the SDGs as a key means to attract development cooperation from the international community. In other words, the DPRK is establishing an implementation system by linking the UN SDGs to the Kim Jong-un regime's mid- and long-term national development plans, including the National Development Strategy and National Plan. Analyzing the specifics of the linkages and understanding the implications of the North Korean regime's policies can have important implications for advancing inter-Korean relations in the future. North Korea's legislative and policy responses to the implementation of the SDGs, particularly in the area of climate and environment, have so far fallen far short of the 30-year target. Nevertheless, North Korea's diplomatic diversification strategy to actively deal with the prolonged sanctions and diplomatic isolation is centered on the United Nations. North Korea's internal development strategy is also seeking a new direction, and the five-year plan for national economic development established at the 8th Party Congress in January 2021 and the new third UNSF (2022-2026) are also clarifying its intention to implement the SDGs with the international community. Among them, the renewable energy and circular economy sectors are being promoted by North Korea with a very active and urgent will to fulfill the SDGs, which is seen as a way to overcome the internal and external economic difficulties faced by North Korea. In addition, the disaster response field due to the climate crisis is being promoted by the North Korean regime with all its might. Given the need for the United Nations to include integrated SDGs on the Korean Peninsula in the new third UNSF (2022-2026), it is time for North and South Korea to work together with the United Nations to implement the SDGs, and we believe that cooperative projects in the field of climate and environment will be a key driver.