In the sufficiently sparse case, we find the probability that a uniformly random bipartite graph with given degree sequence contains no edge from a specified set of edges. This enables us to enumerate loop-free digraphs and oriented graphs with given in-degree and out-degree sequences, and obtain subgraph probabilities. Our theorems are not restricted to the near-regular case. As an application, we determine the expected permanent of sparse or very dense random matrices with given row and column sums; in the regular case, our formula holds over all densities. We also draw conclusions about the degrees of a random orientation of a random undirected graph with given degrees, including its number of Eulerian orientations.
Introduction The Korean Wave, or Hallyu, refers to the global proliferation of South Korean cultural products, which commenced in the late 1990s and gained considerable momentum throughout the 2000s propelled by the international success of television dramas, such as Winter Sonata and Jewel in the Palace. Over time, Hallyu has evolved into a major cultural phenomenon, transcending geographical boundaries and shaping cultural consumption patterns among youth across Asia, Africa, and the Middle East. Iran has not remained untouched by this trend. The broadcast of Korean television dramas on national television introduced many Iranian adolescents and young adults to Korean popular culture, thereby contributing to its rising popularity within the country. Among the various dimensions of Hallyu, K-pop—a hybrid musical genre blending pop, hip-hop, rock, and dance—has emerged as particularly influential. As K-pop gained traction in Iran, it gave rise to a distinct fan subculture. Given that a substantial portion of fan activities—including music streaming, online content creation, and hashtag promotion—occurs on social media platforms, the present study sought to examine how participation in K-pop fandom had shaped the identity formation of young Iranian fans. Materials & Methods This study adopted a qualitative approach, employing digital ethnography as its primary research method. Data were collected through online participant observation and unstructured interviews. Fieldwork was conducted from March to September 2025, involving systematic observation of Telegram channels, Instagram pages, blogs, and websites dedicated to K‑pop fandom. Field notes extended beyond the textual content of online posts and messages to document fans’ daily interactions, content‑sharing patterns, likes and comments, stories, profile images, decoration of personal spaces (e.g., rooms), clothing and accessories, arrangement of fandom‑related objects, dance practices, food‑related experiences, and various other aspects of everyday life. In addition to these observations, 12 unstructured interviews were carried out with male and female K‑pop fans. The data were analyzed using thematic analysis in MAXQDA 2024. To ensure credibility of the findings, methodological triangulation was achieved by cross‑validating field observations with interview data. Credibility was further strengthened through member checking, during which interview transcripts and observational summaries were shared with participants to obtain their feedback and confirm the accuracy of the interpretations. Moreover, the researcher’s prolonged engagement in the field, alongside a transparent account of field entry and the data collection process, contributed to the overall trustworthiness of the study. Ethical principles were rigorously observed throughout the research process. Prior to data collection, the researcher introduced herself, explained the purpose of the study, and provided clear information about the interview process and how the data would be used—including transcription, coding, and analysis. Participants were assured that their identities would remain confidential and that pseudonyms would be employed in all research reports and publications. Discussion of Results & Conclusion The findings revealed that K‑pop fandom identity among young Iranians constituted a dynamic and multi‑stage process, encompassing 4 distinct phases: pre‑fandom stage, the turning point of encountering K‑pop, fandom transition stage, and emergence of a balanced fandom identity. During the pre‑fandom stage, participants had no prior engagement with K‑pop. During the phase of becoming acquainted with K-pop, several salient themes also emerged, including the redefinition of masculinity, the desire for distinction, cleanliness as a valued practice, and the influence of messages promoting self-respect, future orientation, and self-confidence. In the fandom transition stage, participants actively negotiated between local cultural norms and emerging global influences by incorporating elements, such as music, fashion, language, and food into their daily lives. They also demonstrated creative agency through activities, including learning the Korean language, translating and redistributing fan‑produced content, and engaging actively in online fan communities. Finally, the balanced fandom identity reflected the development of a multilayered, selective, and reflexive identity, wherein participants maintained their attachment to K‑pop while simultaneously preserving and renegotiating their cultural values within the Iranian context. Overall, the findings suggested that K‑pop fandom extended beyond mere cultural consumption and functioned as a significant site for negotiating, reconstructing, and reflexively shaping identity within the broader context of cultural globalization. Acknowledgments The authors thank everyone who contributed to this article. Conflicts of Interest There is no conflict of interest. Funding The authors received no financial support for the research, authorship, and/or publication of this article. Statement on the Use of AI Artificial intelligence (AI), specifically ChatGPT (version GPT-6), was used to improve the writing and editing of the literature review and findings sections of this article. The authors reviewed and edited the AI-generated content and take full responsibility for the final content of the article.
Flexible, polymer-based nanocomposite dosimeters have attracted growing interest for radiation monitoring in diagnostic radiology because of their mechanical conformability and potential for low-cost, large-area fabrication. While silicone-based detectors loaded with heavier metal oxides have previously been explored, the dosimetric behavior of room-temperature-vulcanizing (RTV-2) silicone elastomer reinforced with copper oxide nanoparticles — which differs from these systems in both filler chemistry and cure mechanism — has not been systematically characterized. In this work, a flexible silicone/copper oxide nanocomposite was fabricated and evaluated, for the first time, as a current-mode X-ray dosimeter. Copper oxide nanoparticles were synthesized by a simple precipitation method and incorporated into the silicone matrix at weight fractions ranging from 0 to 36.4 wt percent. Structural and chemical characterization confirmed the formation of phase-pure, monoclinic copper oxide nanoparticles with an average crystallite size of 27–29 nm, dispersed within the amorphous silicone network as submicron aggregates (mean Feret diameter 253 ± 86 nm within the composite, from 121 measured particles). Under 60 kV diagnostic X-ray irradiation, the nanocomposite exhibited a stable, nearly linear photocurrent response over a dose-rate range of 2.8–12 mGy/min. Among the compositions evaluated, the sample containing approximately 27.6 wt percent copper oxide showed the best overall dosimetric performance, with a sensitivity of 0.102 ± 0.014 nA/(mGy/min) and a noise-limited detection threshold of 0.25 mGy/min; given that the composition-dependent variation in photocurrent (∼11%) is comparable to the measurement uncertainty, this composition is best regarded as a favorable rather than a definitively optimized formulation. The enhanced sensitivity relative to the unfilled matrix is attributed primarily to the higher photon-interaction probability associated with the increased effective atomic number introduced by the copper oxide phase. The devices showed good short-term repeatability, with a relative standard deviation of 1.01% over repeated irradiation cycles, and a signal-to-noise ratio exceeding 90 at an applied bias of 400 V. These results indicate that silicone/copper oxide nanocomposites constitute a cost-effective, mechanically flexible platform for low-energy X-ray dosimetry, with performance comparable to other polymer–metal oxide systems reported in the literature.
Perovskite solar cells are limited by charge-recombination losses associated with trap-rich electron transport layers. However, the concentration-dependent role of waste-derived asphaltene in modifying interfacial structure and charge transport in mesoporous TiO₂ remains unresolved. Here we establish asphaltene as a functional modifier of mesoporous TiO₂ for improved perovskite photovoltaic performance. Perovskite solar cells incorporating mesoporous TiO₂ modified with 0–5 vol% asphaltene were fabricated and evaluated using structural, optical, charge-transfer, and photovoltaic measurements. Asphaltene produced denser perovskite films with larger grains, increasing the mean grain size from 0.554 μm for the reference to 1.49 μm at 2 vol%. The optimized 2 vol% device achieved a power conversion efficiency of 14.68%, compared with 10.60% for the reference, with a short-circuit current density of 23.01 mA cm⁻² and fill factor of 67.2%. After 800 h, the 2 vol% devices retained approximately 73% of their initial efficiency, compared with approximately 42% for the reference. These results demonstrate that asphaltene-mediated modification of mesoporous TiO₂ improves perovskite film formation, charge extraction, and photovoltaic performance. The approach opens the door to using an industrial hydrocarbon residue as a functional electron-transport-layer additive for lower-cost perovskite photovoltaics.
آلودگی صوتی یکی از چالشهای مهم محیط زیست است که میتواند سلامت انسان و پایداری اکوسیستم را تهدید کند. استفاده از نانوساختارهای کربنی بهدلیل استحکام مکانیکی بالا و ویژگیهای منحصربهفرد هندسی، رویکردی نوین برای جذب صوت در مقیاس نانو متر بهشمار میآید. در این پژوهش، انتشار و جذب امواج صوتی در محیط گازی آرگون با بهرهگیری از شبیهسازی دینامیک مولکولی بررسی شد. مدل ابتدا در غیاب جاذب اعتبارسنجی گردید و سپس اثر قطر، تعداد، آرایش و فرکانس بر پارامترهای آکوستیکی شامل ضریب میرایی، عدد موج و ضریب جذب تحلیل شد. نتایج نشان داد افزایش قطر نانولولهها سطح تماس مؤثر را گسترش داده و افزایش تعداد آنها با کاهش مسیر آزاد مؤثر مولکولها، کارایی جذب را بهبود میدهد. آرایش مثلثی با محدودسازی فضا و افزایش برخوردهای گاز– دیواره، بالاترین ضریب جذب را ایجاد کرد. همچنین بررسی وابستگی فرکانس نشان داد میان فرکانس، ضریب میرایی و ضریب جذب همبستگی مستقیم برقرار است که تطابق آن با مطالعات پیشین، اعتبار شبیهسازی حاضر را تأیید میکند. محدودیت اصلی مطالعه، تمرکز بر محیط گازی آرگون و استفاده از نانولولههای تکجداره با ابعاد محدود است. با این وجود، یافتهها بر اهمیت بهینهسازی هندسه و پارامترهای ساختاری نانوجاذبها برای طراحی سامانههای کارآمد کنترل نویز در فرکانسهای بالا تأکید دارند.
