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Converging/Diverging Self-Similar Shock Waves:From Collapse to Reflection
Get PDFWe solve the continuation problem for the nonisentropic Euler equations following the collapse of an imploding shock wave. More precisely, we prove that the self-similar Güderley imploding shock solutions for a perfect gas with adiabatic exponent γ ∊ (1, 3] admit a self-similar extension consisting of two regions of smooth flow separated by an outgoing spherically symmetric shock wave of finite strength. In addition, for γ ∊ (1, 5 3 ], we show that there is a unique choice of shock wave that gives rise to a globally defined self-similar flow with physical state at the spatial origin.</p
Influence of Strain Rate and Temperature on the Multiaxial Failure Stress Locus of a Polyamide Syntactic Foam
Get PDFThis study introduces a comprehensive experimental methodology allowing for the direct measurement of the rate dependent multiaxial response of polymer syntactic foams under combined direct-shear loading. The combined tension-torsion behaviour of a syntactic foam and its rate dependence are investigated for the first time.Dynamic tension-torsion experiments were conducted using a newly developed Tension-Torsion Hopkinson Bar (TTHB) enabling the measurement of the combined tensile-shear response of engineering materials at high rates of strain.The response and multiaxial failure envelope of a polyamide syntactic foam were experimentally measured and analysed to determine the combined influences of stress state, strain rate, and temperature. The multiaxial failure stress locus was defined in both the normal versus shear stress space and the principal stress space, providing a comprehensive characterisation of the behaviour of the material under various loading and environmental conditions.The suitability of existing pressure dependent failure criteria to represent the measured experimental data was also assessed. The Drucker-Prager pressure dependent criterion proved to be effective in capturing the measured quasi-static and dynamic multi-axial stress loci at different temperatures.The effects of temperature, loading rate and stress state on the deformation and failure modes were analysed by means of SEM micrographs of the tested samples
SceneExplorer:An Interactive System for Expanding, Scheduling, and Organizing Transformable Layouts
Get PDFNowadays, 3D scenes are not merely static arrangements of objects. With the development of transformable modules, furniture objects can be translated, rotated, and even reshaped to achieve scenes with different functions (e.g., from a bedroom to a living room). Transformable domestic space, therefore, studies how a layout can change its function by reshaping and rearranging transformable modules, resulting in various transformable layouts. In practice, a rearrangement is dynamically conducted by reshaping/translating/rotating furniture objects with proper schedules, which can consume more time for designers than static scene design. Due to changes in objects’ functions, potential transformable layouts may also be extensive, making it hard to explore desired layouts. We present a system for exploring transformable layouts. Given a single input scene consisting of transformable modules, our system first attempts to derive more layouts by reshaping and rearranging the modules. The derived scenes are organized into a graph-like hierarchy according to their functions, where edges represent functional evolutions (e.g., a living room can be reshaped to a bedroom), and nodes represent layouts that are dynamically transformable through translating/rotating/reshaping modules. The resulting hierarchy lets scene designers interactively explore possible scene variants and preview the animated rearrangement process. Experiments show that our system is efficient for generating transformable layouts, sensible for organizing functional hierarchies, and inspiring for providing ideas during interactions
Control of Shroud Leakage Loss and Windage Torque in a Low-Pressure Turbine Stage
Get PDFAs new aeroengine architectures move to larger diameter fans and rotors, the associated increase in weight will need to be counterbalanced by lighter, more compact, and more efficient low-pressure turbines (LPT). Efficiency gains in LPTs can be achieved by reducing the losses associated with the shroud leakage flows. Flow control studies on the topic have traditionally focused on reducing the mixing loss, which constitutes a considerable proportion of the total loss. Nonetheless, increasing engine speeds are driving additional gains obtained by also targeting the reduction of windage losses. Developing a flow control solution with the dual objective of reducing over-tip cavity mixing and windage losses has not previously been attempted. This is a challenge due to conflicting flow control requirements and geometric constraints. Reducing windage loss generally requires increasing the swirl ratio of the leakage flow, while reducing mixing loss requires reducing this ratio to match that of the main gas path. The current work proposes a novel flow control solution to successfully achieve this purpose through the emerging technology of additive manufacturing. The successful flow control concept (FCC) was developed through numerical simulation, printed using an additive manufacturing process, and validated in a purpose-built rig. Experiments and computations were consistent with a cumulative reduction in cavity windage of 16%. The FCC is estimated to increase the mechanical efficiency of the turbine stage in isolation by 1%
Ultrahigh piezocatalytic performance based on the micron-scale BaTiO<sub>3</sub> single crystal sheets with {111} highly exposed polar facets
Get PDFPiezocatalytic two-electron oxygen reduction to produce hydrogen peroxide (H2O2) is an emerging and green synthesis method. However, the low H2O2 yield of current piezocatalysts that results from their low piezocatalytic activity has been a long-standing challenge. Here, we have developed “capacitor-like” BaTiO3 single-crystal microsheets with {111} highly exposed polar facets, which are distinctively different from previously reported BaTiO3 piezocatalysts. The pure single-crystal microsheets exhibit a significantly improved H2O2 yield of 521 μmol g−1 h−1 compared to conventional BaTiO3 piezocatalysts. Remarkably, the yield significantly increases to 1088 μmol g−1 h−1 after photodeposition of Ag quantum dots onto the microsheets, which also exhibit a high degradation rate (k) of 0.259 min−1 for Rhodamine B (RhB), surpassing that of existed ABO3-type piezocatalysts reported to date for the same conditions. The excellent piezocatalytic activity is due to the high piezoelectric response of {111} single-crystal microsheets and the ability of Ag quantum dots to provide a high carrier activity under a double electric field, thereby promoting O2 adsorption for efficient 2e− reduction for H2O2 production. This work provides a novel design strategy to enhance the H2O2 yield of piezocatalysts, and develops a new understanding of piezoelectric-driven catalytic mechanisms for energy and environmental applications.</p
Effects of Exercise or Diet or Combined Interventions on Treatment Efficacy of Chemotherapy for Cancer:A Systematic Review
Get PDFPurpose of Review: While exercise and dietary interventions in patients with cancer undergoing chemotherapy have been demonstrated to be safe and feasible and improve patient-reported outcomes, the effects on treatment efficacy have not been widely examined and remain unclear. This review aimed to examine the effects of exercise, dietary, and combined interventions on tumour response and time-to-event outcomes in patients with cancer undergoing chemotherapy. Recent Findings: A systematic review of intervention studies was conducted based on PRISMA guidelines Databases searched were PubMed, Medline, CINAHL, Embase, and Web of Science. Methodological quality and risk of bias were assessed using the RoB2 and ROBINS-I tools. A total of 21 studies, involving 1,384 cancer patients, were included. Exercise interventions were studied in 13 studies, nine of which were controlled. Two studies reported improvements in tumour response, although none demonstrated a significant impact on survival outcomes. Dietary interventions were investigated in seven studies, all of which used either ketogenic diets or fasting-mimicking diets; three of these studies were controlled and recruited patients with breast cancer. Among all studies, three showed significant increases in tumour response and survival outcomes. Finally, only one study evaluated the combined effects of exercise and diet, reporting a significant increase in pathological complete response rates in the intervention group. Summary: Exercise and dietary interventions, particularly ketogenic and fasting-mimicking diets, may enhance tumour response and survival during chemotherapy in some cases. However, the current evidence is limited and inconsistent. Well-designed randomized controlled trials are needed to better establish the efficacy of these interventions as adjuncts to chemotherapy.</p
From Paralysis to Publicization:How Victims of the UK Post Office Horizon Scandal Experienced and Confronted Organizational Harm
Get PDFThe publicization of organizational harm is critical for enabling accountability and justice. While existing research offers valuable insights into how audiences label and sanction harm as misconduct, we know comparatively little about the early stages of such publicization – how knowledge of harm first moves from the private sphere to broader outsider awareness. In this study, we address this undertheorized phase in the misconduct literature by examining the UK Post Office Horizon IT scandal, in which over 4,000 subpostmasters were wrongly accused of theft and false accounting over many years due to faults in an IT system. Our analysis reveals how a series of organizational moves produced a state of response paralysis among victims, leaving them unable or unwilling to speak out, thereby stalling publicization. We then show how this paralysis was gradually broken down, enabling victims to take the first steps toward making their experiences public. By foregrounding these early dynamics in the process of publicization, our study offers a more complete understanding of publicization and the broader lifecycle of organizational misconduct. Overall, the study enables scholars to better understand why some organizational harm remains hidden for years, or never comes to light at all
Exploring good death in China:A qualitative study from the perspectives of family members
Get PDFChina's emerging palliative care services are heavily influenced by Western models of palliative medicine, which emphasize dignity, autonomy and individuality. How palliative care is designed and provided, however, within the distinctively non-Western context of Chinese society has yet to be fully explored. To examine palliative care as a socio-cultural construct, this qualitative study investigates what a good death means in China from the perspective of bereaved family members. Thirty-one semi-structured interviews were conducted, followed by an inductive thematic analysis. Four main themes were identified: (1) Negotiating Autonomy in Family Contexts; (2) Familial Obligations and Cultural Practices; (3) Security and Resource Stability; (4) Meaning and Legacy at the End of Life. We found that, for family members, a good death is primarily mediated by the objectives of family harmony and continuity, often overriding the dying person's individual wishes. This emphasis on the family can act as a double-edged sword, both supporting and complicating the experience of death in China. Based on our findings, we propose a social support system that balances individual and family interests, to inform more culturally informed end-of-life care within practical and policy paradigms.</p
A quantitative Robbins-Siegmund theorem
Get PDFThe Robbins-Siegmund theorem is one of the most important results in stochastic optimization, where it is widely used to prove the convergence of stochastic algorithms. We provide a quantitative version of the theorem, establishing a bound on how far one needs to look in order to locate a region of \emph{metastability} in the sense of Tao. Our proof involves a metastable analogue of Doob's theorem for L1-supermartingales along with a series of technical lemmas that make precise how quantitative information propagates through sums and products of stochastic processes. In this way, our paper establishes a general methodology for finding metastable bounds for stochastic processes that can be reduced to supermartingales, and therefore for obtaining quantitative convergence information across a broad class of stochastic algorithms whose convergence proof relies on some variation of the Robbins-Siegmund theorem. We conclude by discussing how our general quantitative result might be used in practice
Exploring the nexus of variables in English Medium Instruction research:a comprehensive global meta-analysis
Get PDFThe primary objective of this study is to conduct a comprehensive meta-analysis of English-medium instruction (EMI) literature, addressing the significant gap in quantitative evaluations within existing research. By analysing 47 empirical studies employing statistical methods, this research aims to uncover broader trends and correlations within EMI data. Specifically, the study investigates correlations for various factors, such as measurement outcomes and academic subjects. It also examines the influence of different research methodologies on reported correlation coefficients, assessing how methodological choices shape observed relationships in EMI studies. Key findings reveal that perceived academic performance and perceived English language proficiency exhibit the highest effect sizes, underscoring the importance of students' perceptions in EMI success. Conversely, actual academic performance, actual English language proficiency, motivation, and affective factors show small correlations, highlighting areas for pedagogical improvement. Self-efficacy demonstrates a medium correlation, indicating its significant role. Computer Science stands out with the highest effect size, suggesting discipline-specific variations in EMI effectiveness. Different measurement tools, including questionnaires and standardised tests, generally show small correlations, indicating a need for more refined assessment instruments in future EMI research. This meta-analysis provides crucial insights for enhancing EMI implementation and assessment, contributing to the broader discourse on educational strategies in multilingual settings.</p
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