Characterization of investment shell thermal properties

Thermal properties of investment casting shells have a great influence on the solidification of metal and thus control the properties of the cast product. Computational simulation requires accurate thermal properties to better represent the real process. Due to the porosity and meta-stable materials used in the investment shells, it is difficult to determine the real time thermal properties as a function of components and thermal processing history. Previous studies measured the thermal properties using a variety of methods, but very few results can be directly used in simulations due to lack of accuracy. This research developed a new methodology that combines the laser flash thermal diffusivity measurement technology and inverse method. This methodology was used to accurately characterize the thermal properties of the investment shells within the temperature range from 200 ºC to 1200 ºC. Tests were performed on the shells over a wide component range and different thermal processing histories (prefiring at 600 ºC, 850 ºC, 1000 ºC). It was also found that at under 1000ºC, a higher prefiring temperature reduces the reactivity of amorphous silica toward devitrification during the casting process, thus a lower thermal conductivity shell can be achieved. Cenosphere particles were applied in the investment shells to engineer the investment shell thermal properties. Compared to introducing porosity by sacrificed phases, the use of cenospheres was found effective to lower the thermal diffusivity by up to 70% but retain a favorable thermal diffusivity/mechanical strength ratio. Moreover, metal/mold interactions were analyzed for several prime coat materials, and some suggestions for zircon substitution were made. --Abstract, page iii

Trade Shocks and Firms Hiring Decisions::Evidence from Vacancy Postings of Chinese Firms in the Trade War

This paper studies adjustments in labor demand of firms exposed to the recent China-US trade war. Our analysis leverages information from a Chinese online job board and a firm-level measure of tariff exposure obtained from customs transactions data. Firms that are more exposed to US tariffs on Chinese goods responded by posting fewer job vacancies and offering lower wages. The latter is partly balanced out by increased non-wage compensation. We also find a negative relationship between US-tariff exposure and the educational background required in firms’ job ads. China’s retaliatory tariffs against the US does not appear to have a statistically significant systematic impact on hiring. The paper also reports heterogeneous adjustment patterns across firms of different size, ownership and product mix. Overall, the trade war reveals to have negative impact on firms and job-seekers in China

Trade Shocks and Firms Hiring Decisions::Evidence from Vacancy Postings of Chinese Firms in the Trade War

This paper studies adjustments in labor demand of firms exposed to the recent China-US trade war. Our analysis leverages information from a Chinese online job board and a firm-level measure of tariff exposure obtained from customs transactions data. Firms that are more exposed to US tariffs on Chinese goods responded by posting fewer job vacancies and offering lower wages. The latter is partly balanced out by increased non-wage compensation. We also find a negative relationship between US-tariff exposure and the educational background required in firms’ job ads. China’s retaliatory tariffs against the US does not appear to have a statistically significant systematic impact on hiring. The paper also reports heterogeneous adjustment patterns across firms of different size, ownership and product mix. Overall, the trade war reveals to have negative impact on firms and job-seekers in China

Efficiency of Solid Inclusion Removal from the Steel Melt by Ceramic Foam Filter: Design and Experimental Validation

An investigation was performed to measure the efficiency of solid alumina inclusion removal by filtration during casting. A mold design was developed using modeling software to produce two castings that fill simultaneously, one with a filter and the other without a filter. The design avoided vortex formation and thus air entrainment, which helped to avoid reoxidation inside the mold cavity. Samples from these castings were analyzed utilizing an SEM/EDS system with automated feature analysis (AFA) to measure the efficiency of inclusion removal using a 20 ppi zirconia foam filter. This study also documents the occurrence of inclusion flotation and agglomeration in the ladle which, in turn, affects the removal efficiency of these inclusions by filtration in the mold

Factors Affecting the Evolution of Inclusion Populations during Steelmaking and Casting Processes

Investigations into the evolution of inclusion populations during ladle processing and continuous casting are reviewed. Details of the steelmaking practices employed in BOP and EAF steelmaking have been observed to have a strong influence on the size distribution, quantity, composition, phases and morphology of the final inclusion population delivered to the caster. Examples of the effects of different processing paths on the evolution of inclusion populations are presented. The importance of preexisting inclusion populations on the formation and removal of new inclusion populations is also reviewed and discussed

Media framing and public support for China’s social credit system: An experimental study

Although China’s social credit system (SCS) is widely portrayed by Western media as repressive surveillance, recent studies show that it receives high levels of support among Chinese citizens. Previous research suggests that people support the SCS because they lack knowledge about the system. This study further examines the roles of media framing (Western vs Chinese framing) and monitored behaviors (financial vs social behaviors). The results from a survey experiment conducted in China (N = 1600) demonstrate that when exposed to Western framing, public support for the SCS is lower, but only when participants are informed that the SCS monitors social behavior. By contrast, when people are told that the SCS focuses on financial behavior, Western framing exposure is not associated with low levels of public support. The findings suggest that an expansion to social domains and exposure to Western media framing will likely result in decreased support for the system

Scene Summarization: Clustering Scene Videos into Spatially Diverse Frames

We propose scene summarization as a new video-based scene understanding task. It aims to summarize a long video walkthrough of a scene into a small set of frames that are spatially diverse in the scene, which has many impotant applications, such as in surveillance, real estate, and robotics. It stems from video summarization but focuses on long and continuous videos from moving cameras, instead of user-edited fragmented video clips that are more commonly studied in existing video summarization works. Our solution to this task is a two-stage self-supervised pipeline named SceneSum. Its first stage uses clustering to segment the video sequence. Our key idea is to combine visual place recognition (VPR) into this clustering process to promote spatial diversity. Its second stage needs to select a representative keyframe from each cluster as the summary while respecting resource constraints such as memory and disk space limits. Additionally, if the ground truth image trajectory is available, our method can be easily augmented with a supervised loss to enhance the clustering and keyframe selection. Extensive experiments on both real-world and simulated datasets show our method outperforms common video summarization baselines by 50

Influence of SiO2, Al2O3 and TiO2 nanoparticles on okra seed germination under PEG-6000 simulated water deficit stress

Abstract: A comparative study for evaluating the influence of metal oxide nanoparticles (MONPs) (Al2O3, TiO2, and SiO2) on seed germination and seedling growth in okra was implemented under water deficit stress stimulated by PEG-6000. The results revealed that additive of SiO2 nanoparticles (SNPs) and Al2O3 (ANPs) have significant positive effect on seeds germination, while a reduction of that were observed by using TiO2 nanoparticles (TNPs) at 50 mg.L-1 concentration under 5% PEG-6000 stimulated drought stress as compared to that without MONPs. Further, relative to non-MONPs treatment, all the tested MONPs dramatically enhanced the drought stress tolerance in okra seedlings due to the improvement of morphological growth despite a few traits were inhibited under certain water deficiency to some degree. Improvement of drought resistance induced by TNPs and ANPs were found to be higher than that by SNPs. Our finding provides a promising approach to cope with water scarcity, as application of metal oxide nanoparticles to be a potential option to protect okra plants against drought stress

Ladder-like energy-relaying exciplex enables 100% internal quantum efficiency of white TADF-based diodes in a single emissive layer.

Development of white organic light-emitting diodes based on purely thermally activated delayed fluorescence with a single-emissive-layer configuration has been a formidable challenge. Here, we report the rational design of a donor-acceptor energy-relaying exciplex and its utility in fabricating single-emissive-layer, thermally activated delayed fluorescence-based white organic light-emitting diodes that exhibit 100% internal quantum efficiency, 108.2 lm W-1 power efficiency, and 32.7% external quantum efficiency. This strategy enables thin-film fabrication of an 8 cm × 8 cm thermally activated delayed fluorescence white organic light-emitting diodes (10 inch2) prototype with 82.7 lm W-1 power efficiency and 25.0% external quantum efficiency. Introduction of a phosphine oxide-based acceptor with a steric group to the exciplex limits donor-acceptor triplet coupling, providing dual levels of high-lying and low-lying triplet energy. Transient spectroscopic characterizations confirm that a ladder-like energy relaying occurs from the high-lying triplet level of the exciplex to a blue emitter, then to the low-lying triplet level of the phosphine oxide acceptor, and ultimately to the yellow emitter. Our results demonstrate the broad applicability of energy relaying in multicomponent systems for exciton harvesting, providing opportunities for the development of third-generation white organic light-emitting diode light sources

Can Large Language Models Be Good Companions? An LLM-Based Eyewear System with Conversational Common Ground

Developing chatbots as personal companions has long been a goal of artificial intelligence researchers. Recent advances in Large Language Models (LLMs) have delivered a practical solution for endowing chatbots with anthropomorphic language capabilities. However, it takes more than LLMs to enable chatbots that can act as companions. Humans use their understanding of individual personalities to drive conversations. Chatbots also require this capability to enable human-like companionship. They should act based on personalized, real-time, and time-evolving knowledge of their owner. We define such essential knowledge as the \textit{common ground} between chatbots and their owners, and we propose to build a common-ground-aware dialogue system from an LLM-based module, named \textit{OS-1}, to enable chatbot companionship. Hosted by eyewear, OS-1 can sense the visual and audio signals the user receives and extract real-time contextual semantics. Those semantics are categorized and recorded to formulate historical contexts from which the user's profile is distilled and evolves over time, i.e., OS-1 gradually learns about its user. OS-1 combines knowledge from real-time semantics, historical contexts, and user-specific profiles to produce a common-ground-aware prompt input into the LLM module. The LLM's output is converted to audio, spoken to the wearer when appropriate.We conduct laboratory and in-field studies to assess OS-1's ability to build common ground between the chatbot and its user. The technical feasibility and capabilities of the system are also evaluated. OS-1, with its common-ground awareness, can significantly improve user satisfaction and potentially lead to downstream tasks such as personal emotional support and assistance.Comment: 36 pages, 25 figures, Under review at ACM IMWU