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• A viscoelastic approach into structural damage detection and diagnosis is proposed. • The present method exploits amplitude and frequency of vibration signals and determines their relation with mechanical parameters in detecting structural changes. • Two new parameters namely elastic module (E) and viscous coefficient (C 0) are suggested. This article addresses a novel approach to diagnose a structure's damage based on changes in the mechanical parameters of materials. Firstly, we integrate a viscoelastic model into structural damage detection and diagnosis. Accordingly, this model defines materials' mechanical characteristics via two parameters namely elastic module (E) and viscous coefficient (C 0). While Hooke's model is linear, the viscoelastic is non-linear, and therefore, it reflects real situation more precisely. Secondly, we exploit amplitude and frequency of vibration signals and determines their relation with mechanical parameters in detecting structural changes. Based on theoretical analysis and experimental results, our study reveals more effective and general than previous ones. The simultaneous monitoring of structural change using different parameters allow the research to collect more appropriate data compared to previous studies. The results derived from this research were adopted in monitoring health of Saigon bridge over the period of 15 years. Via more than 100 sensors permanently attached to the bridge, the measured signals enabled the evaluation of the structure's operation status. This experimental result shows suitability among the proposed theoretical approaches, and thereby forms a basis to forecast damages of complex structures. [ABSTRACT FROM AUTHOR]

The epidemiology of corneal ulcers in Vietnam has not been well characterized. In this report, we reviewed retrospectively the microbiological data of patients with a clinical diagnosis of corneal ulcer at the microbiology laboratory of Vietnam National Eye Hospital from January 1, 2010 to March 31, 2023. We observed a seasonal pattern for fungal and microsporidial keratitis, with an annual peak in November, and an inverse relationship between fungal keratitis and inclement weather. The November peak coincided with one of the major harvesting seasons in Vietnam. We also observed increasing numbers of microsporidial and Acanthamoeba keratitis cases in recent years. Knowledge of these trends are helpful in guiding empirical treatment of corneal infections and preventing corneal blindness.

Objective: To identify the mechanisms of angle closure in the fellow eyes of Vietnamese subjects with unilateral primary angle-closure glaucoma (PACG) using ultrasound biomicroscopy (UBM) before and after prophylactic laser peripheral iridotomy (LPI)., Design: This is a prospective observational study., Participants: Patients diagnosed with PACG in one eye and primary angle-closure suspect (PACS) in the other eye were included in this study, conducted from January 2014 to October 2014 at Vietnam National Institute of Ophthalmology., Materials and Methods: A total of 112 PACS fellow eyes of 112 patients presenting with unilateral PACG were evaluated. All subjects underwent standard ophthalmic clinical examination and UBM imaging a week before and after LPI. On the basis of UBM images, the angle-closure mechanism was defined according to the classification of Svend Vedel Kessing and John Thygesen as pupillary block (PB), plateau iris (PI), and mixed pattern., Results: The proportion of PACS subjects who showed PB was 86.6%, while 13.4% showed a PI configuration before LPI. After LPI the pre-LPI PB group was reclassified, with 55.4% showing pure PB, and 31.3% showing mixed mechanisms (PB and PI). The proportion of patients with PI remained unchanged (13.4%) even after LPI. After the LPI, the angle opening significantly increased in the PB subgroup (14.01±2.43 degrees, P<0.01) and reclassified mixed group (6.34±1.71 degrees, P<0.01) but remained almost unchanged in the PI group (1.81±0.98 degrees, P>0.05)., Conclusion: On the basis of the UBM criteria, PI was found in 13.4% of PACS fellow eyes of Vietnamese subjects with PACG. The clinical and UBM features of patients showing PI before LPI remained almost unchanged after the procedure. The proportion of patients showing PB pre-LPI reduced from 86.6% to 55.4% showing the important role of mixed mechanisms in PACG.