A three-stage planetary gear reducer was designed for low-speed, heavy-load operating conditions, and a dynamic model was established after optimizing the load distribution through floating planet carriers. This model was used to study the nonlinear motion factors in the gear system, with a particular focus on the internal excitation caused by time-varying meshing stiffness. A mathematical analysis model of the mechanism was developed using MATLAB, and the time-varying meshing stiffness curves were derived. The analysis shows that the system exhibits periodic motion with changes in stiffness. Additionally, the load distribution of the system was analyzed based on stiffness variation, and the research indicates that as the stiffness increases, the transmission system experiences greater vibrations and impacts, leading to a decline in load distribution performance. Finally, a kinematic simulation model of the planetary gear system was established using ADAMS. Simulation results demonstrated that load distribution optimization for this transmission system is essential and provided the basis for this conclusion.
Between December 2020 and April 2023, the COVID-19 Scenario Modeling Hub (SMH) generated operational multi-month projections of COVID-19 burden in the US to guide pandemic planning and decision-making in the context of high uncertainty. This effort was born out of an attempt to coordinate, synthesize and effectively use the unprecedented amount of predictive modeling that emerged throughout the COVID-19 pandemic. Here we describe the history of this massive collective research effort, the process of convening and maintaining an open modeling hub active over multiple years, and attempt to provide a blueprint for future efforts. We detail the process of generating 17 rounds of scenarios and projections at different stages of the COVID-19 pandemic, and disseminating results to the public health community and lay public. We also highlight how SMH was expanded to generate influenza projections during the 2022-23 season. We identify key impacts of SMH results on public health and draw lessons to improve future collaborative modeling efforts, research on scenario projections, and the interface between models and policy.
An investigation was carried out on the charging voltage of deionized (DI) water during wafer cleaning at wafer sawing process, since it was supposed to be the root cause for EOS damages during semiconductor production. The charging voltage was measured using a non-contact electrostatic field meter. It was found that the positioning of the water filter influenced the amount of charging voltage of DI water.
The ESD protection program set up in the electronics manufacturing facilities especially in China region (evident but not limited to that area) appears to have common weaknesses. They have a lot of ESD protection in place but do not know whether this is the right method at the right place. Nevertheless they have enough backup solutions in place so that they can handle ESDS without big problems. With the future limitations expected for on-chip ESD protection, it is necessary to increase their knowledge and to enable them to assess the ESD risks of their production lines in the right way.
Although visual depictions of epidemiological data are not new in public health, the US public saw more of them during the COVID-19 pandemic than ever before. In this study, we considered visualizations of forecasts (i.e. predictions of how a disaster will unfold over time) formatted as line charts. We investigated how two choices scientists make when creating a forecast visual - the outcome of focus (cases or deaths) and the amount of data provided (more or less data) about the past or the potential future - shape behavioral intentions via risk-related appraisals (e.g. threat and efficacy). In an online experiment, participants (
Abstract Understanding the host range, patterns and consequences of parasite infection is essential for detecting and responding to parasite‐mediated insect declines. The debilitating protozoan Ophryocystis elektroscirrha ( OE ; Neogregarinorida: Ophryocystidae) was identified as a parasite of monarch ( Danaus plexippus ) and queen ( D. gilippus ) butterflies in the late 1960s in Florida, USA. Recently, similar parasites were documented in other Danaus species, but their occurrence among the diverse clade of milkweed butterflies (Nymphalidae: Danainae) remains unexplored. This study used museum collections to systematically investigate the host range and global occurrence of OE and similar Ophryocystis parasites in milkweed butterflies. We examined 2727 museum specimens from 86 countries/areas, spanning 61 milkweed butterfly species across 10 genera, to document parasitism. Our findings revealed that, among milkweed butterflies, Ophryocystis parasites were confined to hosts in the genus Danaus and were widespread across five continents. Positive specimens dated back to 1909. Lesser wanderers ( D. petilia ) exhibited the highest percentage of positive specimens (16%), followed by monarchs (12%), plain tigers ( D. chrysippus, 11%) and queens (4%). We also present the first documented infections in Jamaican monarchs ( D. cleophile , 4%). The patterns of parasite variation in size reflected the relatedness of their host species but not their size. Overall, this research underscores the value of museum collections for investigating geographic and temporal host–parasite associations and provides foundational ecological data on the relationships between Ophryocystis parasites and their milkweed butterfly hosts.
Electrical Overstress (EOS) is one of the major complaints from customers in the semiconductor industry. This paper will focus on the area of EOS which is power induced. Some real life examples of cases will be discussed. Practical approaches to identify the root cause in a large manufacturing environment are demonstrated. Long term preventive measures to avoid re-occurrence are proposed.
The demand for ESD control in the semiconductor industry has become more and more stringent especially from customers within the automotive industry segment. The requirement for an ESD capability analysis for the whole manufacturing process line is no longer an option. This paper provides an overview of an ESD capability/risk analysis in a semiconductor back end manufacturing process. The challenges encountered in the analysis and the solutions are provided.
To avoid contamination of wafers, ultra-clean, de-ionized (DI) water is used in the wafer sawing process as a cleaning media and lubricant. There are claims that the high resistivity of DI water creates static charges that cause damaging ESD voltages. Investigations are conducted, and results and conclusions are presented.
One of the major requirements for safe handling of IC?s is the grounding of personnel. The paper presents data about the effectiveness of using the floor/footwear system as primary means of grounding personnel in standing and sitting operation. It also discusses whether there is a contradiction with International Standards like IEC 61340-5-1 or ANSI/ESD S20.20.
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