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Heuristic Optimization Method for Cellular Structure Design of Light Weight Components
Jason Nguyen,박상인,David Rosen 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.
Additive manufacturing can be used to produce structures which would be impossible to manufacture using traditional manufacturing processes. One application of this technology is for fabrication of customized, light-weight material called mesoscale lattice structure (MSLS), which is a type of cellular structure with dimensions in the range of 0.1 to 10 mm. The problem to be addressed in this paper is how to efficiently synthesize MSLS with thousands of struts and, hence, thousands of design variables. A heuristic optimization method is presented for efficiently synthesizing large MSLS on complex shaped parts that reduces the multivariate optimization problem to a problem of only two variables. The heuristic is based on the observation that the stress distribution in a MSLS will be similar to the stress distribution in a solid body of the same overall shape. Based on local stress states, unit cells from a predefined unit-cell library are selected and sized to support those stress states. In this paper, the method is applied to design a strong, stiff, and light-weight Micro Air Vehicle fuselage. Weight savings are demonstrated as a result.
Material feature representation and identification with composite surfacelets
Huang, Wei,Wang, Yan,Rosen, David W. Society for Computational Design and Engineering 2016 Journal of computational design and engineering Vol.3 No.4
Computer-aided materials design requires new modeling approaches to characterize and represent fine-grained geometric structures and material compositions at multiple scales. Recently, a dual-Rep approach was developed to model materials microstructures based on a new basis function, called surfacelet. As a combination of implicit surface and wavelets, surfacelets can efficiently identify and represent planar, cylindrical, and ellipsoidal geometries in material microstructures and describe the distribution of compositions and properties. In this paper, these primitive surfacelets are extended and composite surfacelets are proposed to model more complex geometries. Composite surfacelets are constructed by Boolean operations on the primitives. The surfacelet transform is applied to match geometric features in three-dimensional images. The composition of the material near the identified features can then be modeled. A cubic surfacelet and a v-joint surfacelet are developed to demonstrate the reverse engineering process of retrieving material compositions from material images.
Multidisciplinary design optimization in design for additive manufacturing
Guang Liu,Yi Xiong,David W. Rosen 한국CDE학회 2022 Journal of computational design and engineering Vol.9 No.1
Design for additive manufacturing (AM) involves decision making in various design domains, including product design, material selection, and process planning. In practice, engineers typically adopt a sequential design process to optimize these design domains in consecutive order. However, coupling factors, e.g. shared variables, related constraints, and conflicting objectives, are not sufficiently considered within the sequential design process, resulting in an inefficient workflow and suboptimal design solutions. To address the above issues, this paper proposes a multidisciplinary design optimization framework to simultaneously optimize different domains, which enables rapid exploration and complete exploitation of the AM design space under complex constraints. More specifically, the proposed framework is based on the concurrent optimization method, which coordinates the optimization of different design domains by allowing an automated exchange of design information. Also, the framework utilizes the surrogate modeling approach to approximate high-fidelity simulations for facilitating the iterative process. The effectiveness of the proposed framework is validated with two examples, a plate with a hole design and a hook design, which involve multiple design objectives from both process and structure domains, i.e. the print time, print area, strain energy, and maximum von Mises stress.
Procedural training models among emergency medicine residency programs
Leslie Bilello,Andrew Ketterer,Shaked Yarza,David Chiu,Carlo Rosen 대한응급의학회 2021 Clinical and Experimental Emergency Medicine Vol.8 No.1
Objective Optimal training methods remain controversial for rarely performed emergency procedures. Previous research has failed to demonstrate the superiority or inferiority of live anesthetized animal models (LAA) as compared to other modalities. Most of the data on LAA use comes from military contexts; less information is available for civilian emergency medicine (EM) training. We sought to characterize the prevalence of LAA use among civilian EM residency programs and reasons for its use or discontinuation. Methods Survey study of program directors of EM residency programs accredited by the Accreditation Council for Graduate Medical Education. A 16-item questionnaire was electronically delivered to program directors, including program region, current and historical use of LAA, and attitudes regarding the optimal procedural training modalities. Results Of 179 survey recipients, 83 completed the survey (46.4%). Twelve programs (14.3%) currently use LAA, and 17 programs (20.5%) report previous LAA use. Reasons for discontinuing LAA use included ethical concerns, financial and logistical limitations, political pressures, and feeling that there were superior or equivalent alternative models available. Programs that currently use LAA were more likely to rank LAA as being the most preferable training modality while programs that do not currently use LAA were more likely to rank human cadavers as the most preferable modality. Conclusion Despite a lack of data showing educational outcomes-driven differences between LAA and alternative training models, LAA use is declining among civilian EM residencies. Despite this, disagreement exists among programs that do and do not use LAA regarding the most optimal procedural training.
Role of matrix metalloproteinases in delayed cortical responses after stroke
Zhao, Bing-Qiao,Wang, Sophia,Kim, Hahn-Young,Storrie, Hannah,Rosen, Bruce R,Mooney, David J,Wang, Xiaoying,Lo, Eng H Nature Publishing Group 2006 Nature medicine Vol.12 No.4
Matrix metalloproteinases (MMPs) are zinc-endopeptidases with multifactorial actions in central nervous system (CNS) physiology and pathology. Accumulating data suggest that MMPs have a deleterious role in stroke. By degrading neurovascular matrix, MMPs promote injury of the blood-brain barrier, edema and hemorrhage. By disrupting cell-matrix signaling and homeostasis, MMPs trigger brain cell death. Hence, there is a movement toward the development of MMP inhibitors for acute stroke therapy. But MMPs may have a different role during delayed phases after stroke. Because MMPs modulate brain matrix, they may mediate beneficial plasticity and remodeling during stroke recovery. Here, we show that MMPs participate in delayed cortical responses after focal cerebral ischemia in rats. MMP-9 is upregulated in peri-infarct cortex at 7–14 days after stroke and is colocalized with markers of neurovascular remodeling. Treatment with MMP inhibitors at 7 days after stroke suppresses neurovascular remodeling, increases ischemic brain injury and impairs functional recovery at 14 days. MMP processing of bioavailable VEGF may be involved because inhibition of MMPs reduces endogenous VEGF signals, whereas additional treatment with exogenous VEGF prevents MMP inhibitor–induced worsening of infarction. These data suggest that, contrary to MMP inhibitor therapies for acute stroke, strategies that modulate MMPs may be needed for promoting stroke recovery.
Leslie A Bilello1,Céline Pascheles,Kiersten Gurley,Douglas Rappaport,David T Chiu,Shamai A. Grossman,Carlo L Rosen 대한응급의학회 2020 Clinical and Experimental Emergency Medicine Vol.7 No.3
Objective Electrocardiogram (ECG) interpretation skills are of critical importance for diagnostic accuracy and patient safety. In our emergency department (ED), senior third-year emergency medicine residents (EM3s) are the initial interpreters of all ED ECGs. While this is an integral part of emergency medicine education, the accuracy of ECG interpretation is unknown. We aimed to review the adverse quality assurance (QA) events associated with ECG interpretation by EM3s. Methods We conducted a retrospective study of all ED ECGs performed between October 2015 and October 2018, which were read primarily by EM3s, at an urban tertiary care medical center treating 56,000 patients per year. All cases referred to the ED QA committee during this time were reviewed. Cases involving a perceived error were referred to a 20-member committee of ED leadership staff, attendings, residents, and nurses for further consensus review. Ninety-five percent confidence intervals (CIs) were calculated. Results EM3s read 92,928 ECGs during the study period. Of the 3,983 total ED QA cases reviewed, errors were identified in 268 (6.7%; 95% CI, 6.0%–7.6%). Four of the 268 errors involved ECG misinterpretation or failure to act on an ECG abnormality by a resident (1.5%; 95% CI, 0.0%–2.9%). Conclusion A small percentage of the cases referred to the QA committee were a result of EM3 misinterpretation of ECGs. The majority of emergency medicine residencies do not include the senior resident as a primary interpreter of ECGs. These findings support the use of EM3s as initial ED ECG interpreters to increase their clinical exposure.
Amina El Ayadi,Ron C. Helderman,Celeste C. Finnerty,David N. Herndon,Clifford J. Rosen,Gordon L. Klein 대한골다공증학회 2019 Osteoporosis and Sarcopenia Vol.5 No.3
Objectives: The objective of the study was to determine whether postburn reduction of bone formation occurred earlier than 2e3 weeks after burn injury and whether that reduction was inversely related to marrow adiposity. Methods: Using a rat model of burn injury with sacrifice at 3 days postburn, we measured serum osteocalcin, a biomarker of bone formation, as well as a regulator of glucose metabolism, and counted tibial marrow adipocytes. Results: Serum osteocalcin was reduced as early as 3 days postburn, coinciding with a trend toward decline in marrow adipocyte number rather than demonstrating an inverse relationship with adipocyte count. Conclusions: Factors that may be responsible for the dissociation include lack of circulating sclerostin, previously reported, increased energy demands following burn injury, increased sympathetic tone and perhaps oxidative stress. The relationship between bone formation and marrow adiposity is complex and subject to a variety of influences.