Energy-absorbing origami structure for crashworthiness design

This paper presents experimental and numerical investigations on the origami-patterned tube which is acknowledged as a promising energy-absorption device. Its buckling mode leads to high performances in terms of specific energy absorption (SEA) and crush force efficiency (CFE). The polygonal tube is prefolded by following an origami pattern, which is designed to act as geometric imperfection and mode inducer. First, a series of quasi-static crushing tests are performed on origami tubes with different materials and geometrical features. Specimens in SUS316L and AlSi10Mg are produced through Additive Manufacturing (AM). It allows to conveniently produce few samples with a complex shape. Finite Element Analysis (FEA) and Direct Image Correlation (DIC) are employed for a better insight into the complex crushing behaviour. The Aluminum tube shows a brittle behaviour while SUS316L tubes have extremely promising performance until local crack happens. Limits stemming from the employment of AM are explored and a new geometry is designed to avoid cracking. Second, a numerical design exploration study is carried out to assess the sensitivity of origami pattern features over the energy-absorption performance. ANSYS Autodyn is utilized as FE solver and DesignXplorer for correlation and optimization. The benefits of new patterns are investigated through geometrical optimization, and an improved geometry is proposed. The pattern stiffness is tuned to account for the external boundary conditions, resulting in a more uniform crushing behaviour. A similar force trend is maintained with a SEA increment of 51.7% due to a drastic weight reduction in areas with lower influence on post-buckling stiffnes

Sex-specific associations of γ-glutamyltransferase to HDL-cholesterol ratio and the incident risk of cardiovascular disease: three Korean longitudinal cohorts from different regions

BackgroundThe combination of gamma-glutamyl transferase (GGT) and high-density lipoprotein cholesterol (HDL-C) (GGT/HDL-C) is a novel noninsulin-based marker for assessing the risk of nonalcoholic fatty liver disease and type 2 diabetes mellitus. However, whether the GGT/HDL-C ratio is related to the risk of incident cardiovascular disease (CVD) risk is not well known. Therefore, we aimed to investigate the longitudinal effect of GGT/HDL-C ratio on incident CVD risk in three large cohorts of Korean men and women.MethodsData were assessed from 27,643 participants without CVD from the Korean Genome and Epidemiology Study (KoGES), Health Risk Assessment Study (HERAS), and Korea Health Insurance Review and Assessment (HIRA) (HERAS-HIRA) datasets. The participants were divided into four groups according to the GGT/HDL-C quartiles. We prospectively assessed hazard ratios (HRs) with 95% confidence intervals (CIs) for CVD using multivariate Cox proportional-hazard regression models over a 50-month period following the baseline survey.ResultsDuring the follow-up period, 949 patients (3.4%; 529 men and 420 women) developed CVD. The HRs of CVD for GGT/HDL-C quartiles 2-4 were 1.36 (95% CI, 0.91–2.02), 1.54 (95% CI, 1.05–2.26), and 1.66 (95% CI, 1.12–2.47) after adjusting for metabolic parameters in women, but GGT/HDL-C did not show a trend toward increases in incident CVD in men. Regional discrepancies were evident in the results; the increase in HR in the metropolitan hospital cohort was more pronounced than that in the urban cohort, and the risk was not increased in the rural cohort.ConclusionGGT/HDL-C ratio may be a useful predictive marker for CVD in women. Furthermore, the prevalence of CVD was strongly correlated with the GGT/HDL-C ratio in metropolitan areas, and this correlation was more significant than that observed with GGT or HDL-C in isolation

One-step fabrication of surface-decorated inorganic nanowires via single-nozzle electrospinning

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2017R1A6A3A03004416) and (NRF-2015M1A2A2056833).One-dimensional heterostructured nanomaterials represent key building blocks for nanotechnologies due to a large number of applications such as electronics, catalysis, drug delivery, and energy storage and conversion devices. Electrospinning has been considered a straightforward and versatile method to prepare inorganic nanowires, but the heterostructured nanowires have been only fabricated by using dual-nozzle or by introducing additional encapsulating step. Here we report one-step fabrication of surface-decorated inorganic nanowires via single-nozzle electrospinning. Although the electrospinning precursor uses one mixed solution containing nickel salt, ceria nanoparticles, and polyvinylpyrrolidine (PVP), the nanowires show a core/shell-like shape. The surface-decorated nanowires consist of nickel shell and ceria core, which exhibits 95.52% of methane conversion at 600 °C whereas conventional particle-type catalysts have only 60% at the same temperature in steam reforming.PostprintPeer reviewe

Successful management of heterotopic cornual pregnancy with laparoscopic cornual resection

AbstractObjectiveTo examine the feasibility of laparoscopic cornual resection for the treatment of heterotopic cornual pregnancy.Study designWomen who underwent laparoscopic cornual resection for heterotopic cornual pregnancy at our hospital between January 2003 and March 2015 were retrospectively analyzed. We evaluated significant parameters such as operative complications and postoperative pregnancy outcomes of concomitant pregnancy.ResultsThirteen patients with heterotopic cornual pregnancy were included in the study. All were pregnant through assisted reproductive technology, and the diagnosis was made at a median of 6+6 weeks (range 5+4–10+0). They were successfully treated with laparoscopic cornual resection and admitted for a median of 4 days (range, 2–7) postoperatively. The median operative time was 65min (range, 35–145min) and estimated blood loss was 200mL (range, 10–3000mL). There was a spontaneous abortion at 7+6 gestational weeks in a patient who received bilateral cornual resection. Seven patients delivered babies at term and 3 at preterm. All 10 women delivered without any maternal or neonatal complications. Two were lost to follow-up.ConclusionsLaparoscopic cornual resection is a feasible primary approach for the management of heterotopic cornual pregnancy

Corn-cob like nanofibres as cathode catalysts for an effective microstructure design in solid oxide fuel cells

This research was supported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) with a financial resource from the Ministry of Trade, Industry & Energy (No. 20133030011320).An efficient cathode for solid oxide fuel cell (SOFC) is mainly determined by the oxygen reduction reaction (ORR) activity of the mixed materials. We demonstrate a new microstructure design through a nanofibrous electrode based on an unique corn-cob structure. One-step process to produce a corn-cob ceramic nanofiber of La0.8Sr0.2MnO3 (LSM) and Y2O3-stabilized ZrO2 (YSZ) is introduced by an electrospinning equipped with a coaxial nozzel. From the microscope analysis, perfect corn-cob nanofibers are finely produced with the diameter of 350 nm for a core and nanoparticles (30-40 nm) stacked on the surface like as a core-shell structure. The cathode fabricated by nanofibers with LSM outside and YSZ inside (YSZ@LSM) shows the best maximum power density of 1.15 Wcm-2 at 800 oC with low polarization resistance, which is higher than the reverse core and shell positions (LSM@YSZ) and even the commercial LSM-YSZ. This better outcome is more obvious at the elevated temperature due to the accelerated catalytic activity. Therefore, we could find the insight into the key factors enhancing the ORR activity and single cell performance in terms of not only the nanofibrous core@shell structure but also more reaction active sites from the optimum catalyst position at the designed corn-cob nanofibers based cathodes.PreprintPostprintPeer reviewe