Jung-Dal Lee

Dynamic Response Topology Optimization in the Time Domain using Equivalent Static Loads

Most topology optimization techniques find the optimal layout of a structure under static loads. Some studies are focused on dynamic response topology optimization because the dynamic forces act in the real world. Dynamic response topology optimization is solved in the time or frequency domain. A method for dynamic response topology optimization in the time domain is proposed using equivalent static loads. Equivalent static loads are static loads that generate the same displacement field as dynamic loads at each time step. The equivalent static loads are made by multiplying the linear stiffness matrix and the displacement field from dynamic analysis and used as multiple loading conditions for linear static topology optimization. The results of topology optimization are utilized in dynamic analysis again and a cyclic process is utilized until the convergence criterion is satisfied. The paradigm of the method was originally developed for size and shape optimizations. A new objective function is defined to minimize the peaks of the compliance in the time domain and a convergence criterion is newly defined considering that there are many design variables in topology optimization. The developed method is verified by solving some examples and the results are discussed.

Multiobjective design optimization of brushless permanent magnet motor using 3D equivalent magnetic circuit network method

In this paper, we discuss multiobjective design optimization of brushless permanent magnet motor (BLPMM) solved by genetic algorithm (GA) and 3D equivalent magnetic circuit network (EMCN) method. In the multiobjective optimization (MO) problem, we choose the decrease of cogging torque and the increase of torque as objectives. The airgap length, teeth width and magnetization angle of permanent magnet (PM) are also selected for the design variables respectively. From the results, our approach method enabled us to efficiently obtain diverse Pareto optimal (PO) solutions from the practical point of view. The experimental results are shown to confirm the validity of the optimization results.

Continuous measurement of systolic blood pressure using the PTT and other parameters

In this paper, we proposed the regression model which could estimate unspecified peoples systolic blood pressure (SBP) conveniently and continuously and checked its accuracy through clinical experiments. The method for estimating each individual SBP by using only pulse transit time (PTT) has been studied, but it is difficult to estimate unspecified peoples SBP with the method using only PTT. Thus we researched several physical characteristic parameters which might affect blood pressure (BP) with the standard that we can measure them easily and conveniently, chose valid physical characteristic parameters through a clinical testing and correlation analysis, and made the regression model using PTT and valid physical characteristic parameters for estimating unspecified peoples SBP. Comparing the result of the proposed method with American National Standards Institute of the Association of the Advancement of Medical Instrument (ANSI/AAMI), we know that the proposed regression model gives an acceptable result

Clinical importance of inflammatory facet joints of the spine in ankylosing spondylitis: a magnetic resonance imaging study

Objectives: The aims of this study were to assess the reliability of a novel magnetic resonance imaging (MRI) scoring system for inflammatory lesions of facet joints and to clarify the clinical significance of facet joint inflammation in ankylosing spondylitis (AS). Method: A total of 53 AS patients (45 males, 84.9%) were assessed for active inflammatory lesions involving the facet joints, as indicated by bone marrow oedema, at 23 discovertebral units (DVUs) between C2 and S1 using a novel scale, the AS Activity of the Facet joint (ASAFacet). The reliability of the ASAFacet was evaluated using intraclass correlation coefficients (ICCs) and Bland–Altman plots. Results: ICC values for the ASAFacet scores were 0.857 [95% confidence interval (CI) 0.741–0.919] for inter-observer and 0.941 (95% CI 0.873–0.969) for intra-observer reliability. Inflammatory activity scores in facet joints were evenly distributed at all spine levels (p = 0.294 for ASAFacet), whereas vertebral body inflammation was more prominent in the thoracic spine than in the cervical and lumbar spine [p < 0.001 for the AS spine MRI activity (ASspiMRI-a) score, p = 0.002 for the Berlin method, and p < 0.001 for the Spondyloarthritis Research Consortium of Canada (SPARCC) MRI index]. ASAFacet scores were closely associated with erythrocyte sediment rate (ESR) and C-reactive protein (CRP) levels (p < 0.05, respectively). Patients with peripheral arthritis had fewer lesions involving the vertebral bodies or facet joints than patients without peripheral arthritis (p < 0.001 for the four different MRI activity indexes). Conclusions: This study suggests that recognition of facet joint inflammation has the potential to contribute to our understanding of clinical outcomes in AS.

Comparison of Inner Ear Contrast Enhancement among Patients with Unilateral Inner Ear Symptoms in MR Images Obtained 10 Minutes and 4 Hours after Gadolinium Injection

BACKGROUND AND PURPOSE: Recently 4-hour delayed-enhanced 3D-FLAIR MR imaging has been used in pathophysiologic analysis of the inner ear in many auditory diseases, including sudden sensorineural hearing loss, but comparison among different time points is not clear in patients with unilateral inner ear symptoms. We compared the signal-intensity ratios of the inner ears in patients with unilateral inner ear symptoms on 10-minute delayed-enhanced and 4-hour delayed-enhanced 3D-FLAIR MR images after IV gadolinium injection. MATERIALS AND METHODS: The 10-minute delayed-enhanced and 4-hour delayed-enhanced 3D-FLAIR MR images were retrospectively analyzed. Signal-intensity ratios between the cerebellum and inner ear structures, such as the cochleae, vestibules, and vestibulocochlear nerve were assessed. Multiple comparisons were performed. RESULTS: Signal-intensity ratios of the affected cochleae, vestibules, and vestibulocochlear nerve were higher than those of unaffected sides in both 10-minute delayed-enhanced and 4-hour delayed-enhanced images. At the affected side, signal-intensity ratios of the vestibulocochlear nerve were higher in patients with nonsudden sensorineural hearing loss than in those with sudden sensorineural hearing loss on both 10-minute delayed-enhanced and 4-hour delayed-enhanced images. The signal-intensity ratios of some affected inner ear structures were higher than those of the unaffected sides in a group of 30 patients with sudden sensorineural hearing loss and 20 patients with nonsudden sensorineural hearing loss on 10-minute delayed-enhanced and 4-hour delayed-enhanced images. CONCLUSIONS: Signal-intensity ratios of the inner ear show statistically significant increases in many diseases, especially neuritis, in 10-minute delayed-enhanced and 4-hour delayed-enhanced images. The 4-hour delayed-enhanced images may be superior in neural inflammatory–dominant conditions, while 10-minute delayed-enhanced images may be superior in neural noninflammatory–dominant conditions.