Detection Of Structural Changes Research Articles

B-Spline signature responses in structural change detection: method development

Damage detection is perhaps the most critical objective of structural health monitoring. Proper documentation of the progression of structural damage from onset to failure enables performance-based maintenance that mitigates risk and contains socioeconomic impact. Recently, damage detection methods that focus on change detection through analyses of the structural global response in the frequency or time domain have garnered attention due to their efficiency and accuracy. This work proposes a novel time-domain, nonparametric, data-driven change detection method. The time-domain B-Spline transfer function is defined as a signature time history response of the structure, referred to in this work as the B-Spline signature response (BSR). BSR may be computed directly through a physics-based simulation, or it be extracted in a discrete form from measurements of displacement, velocity, or acceleration time histories of structural response to any external excitation. The BSR is independent of loading, is a characteristic of the system, and captures the condition of the structure at the time of acquisition without the need for identifying structural properties. In this work, the fundamentals of the BSR concept are introduced first along with the process of extracting a BSR from structural responses to arbitrary excitations. Verification and validation studies are conducted based on computer simulations and laboratory testing and are discussed in detail. Subsequently, an approach is proposed to detect change through correlation of BSR signals acquired at different times during the monitoring period. Any changes in the intrinsic characteristics affecting the response cause BSR changes and correlation loss. The change detection methodology is demonstrated through computer simulations and experimental investigations. Initial parametric studies are conducted to investigate the suitability of the proposed approach to detect small structural changes. This article demonstrates the validity of the proposed method and establishes the framework for further development and case-specific applications.

Polyamidoamine-based photostabilizers for cotton fabrics

Four water-soluble α-amino acid-derived polyamidoamines (PAAs) obtained by reacting N,N’-methylenebisacrylamide with glycine, leucine, arginine and glutamic acid were studied as photostabilizers of cotton. Untreated and PAA-treated cotton strips with 10 % PAA add-on underwent accelerated photoaging by UV irradiation in air at temperature from 25 to 50°C and 30 % relative humidity. Irradiation was applied in consecutive 4 h cycles, after each of which samples were analyzed by different techniques. After 30 h irradiation, the whiteness index and colorimetric parameters indicated significant yellowing of cotton, which became slightly more intense after 100 h irradiation. On irradiation, PAA-treated samples showed only slow decrease in whiteness and increase in yellowing. After 100 h, yellowing achieved significantly lower levels than in untreated cotton. In no case did the infrared spectroscopy and electron microscopy reveal detectable structural and morphological alterations, even after 100 h of UV exposure. Thermogravimetric analysis showed only little changes of thermograms following photoaging. X-ray diffraction analysis revealed slight deformation of the cellulose crystalline structure following both PAA treatment and UV irradiation. Finally, the PAA coatings were extracted from the cotton strips and analyzed by 1H-NMR analysis. Only the glutamic acid-derived PAA showed detectable structural changes that did not involve the main chain. The FT-IR spectra and white indexes of the washed cotton strips did not differ from those of untreated cotton. Overall, it was proven that α-amino acid-derived PAAs protect cotton from photo-oxidation. Their performance was attributed to the radical scavenging ability of tert-amine groups present in their repeat units.

Testing for distributional structural change with unknown breaks: application to pricing crop insurance contracts

Abstract Agriculture in developed countries is produced under heavily subsidized insurance. The pricing of these insurance contracts, termed premium rates, directly influences farmers profits, their financial solvency, and indirectly, global food security. Changing climate and technology have likely caused significant shifting of mass in crop yield distributions and, if so, has rendered some of the historical yield data irrelevant for estimating premium rates. Insurance is primarily interested in lower tail probabilities and as such the detection of structural change in tail probabilities or higher moments is of great concern for the efficacy of crop insurance programs. We propose a test for structural change with an unknown break(s) which has power against structural change in any moment and can be tailored to a specific range of the underlying distribution. Simulations demonstrate better finite sample performance relative to existing methods and reasonable performance at identifying the break. The asymptotic distribution is shown to follow the Kolmogorov distribution. Our proposed test finds structural change in most major U.S. field crop yields leading to significant premium rate differences. Results of an out-of-sample premium rating game indicate that incorporating structural change in crop yields leads to more accurate premium rates.

Vibrational spectroscopic detection of radiation-induced structural changes in Chironomus hemoglobin

PurposeChironomus hemoglobin is known to exhibit higher gamma radiation resistance compared to human hemoglobin. In the present study, we have introduced a sensitive method to analyze radiation-induced alterations in Chironomus hemoglobin using Vibrational spectroscopy and further highlighting its potential for monitoring radiotoxicity in aquatic environments. Materials and methodsVibrational spectroscopic methods such as Raman and FT-IR spectroscopy were used to capture the distinctive chemical signature of Chironomus hemoglobin (ChHb) under both in vitro and in vivo conditions. Any radiation dose-dependent shifts could be analyzed Human hemoglobin (HuHb) as standard reference. ResultsDistinctive Raman peak detected at 930 cm-1 in (ChHb) was attributed to C–N stretching in the heterocyclic ring surrounding the iron atom, preventing heme degradation even after exposure to 2400 Gy dose. In contrast, for (HuHb), the transition from deoxy-hemoglobin to met-hemoglobin at 1210 cm-1 indicated a disruption in oxygen binding after exposure to 1200 Gy dose. Furthermore, while ChHb exhibited a consistent peak at 1652 cm-1 in FT-IR analysis, HuHb on the other hand, suffered damage after gamma irradiation. ConclusionThe findings suggest that vibrational spectroscopic methods hold significant potential as a sensitive tool for detecting radiation-induced molecular alterations and damages. Chironomus hemoglobin, with its robust interaction of the pyrrole ring with Fe, serves as a reliable bioindicator molecule to detect radiation damage using vibrational spectroscopic method.

Clinical predictors of Alzheimer's disease-like brain atrophy in individuals with memory complaints.

The definition and assessment methods for subjective cognitive decline (SCD) vary among studies. We aimed to investigate which features or assessment methods of SCD best predict Alzheimer's disease (AD)-related structural atrophy patterns. We assessed 104 individuals aged 55+ with memory complaints but normal cognitive screening. Our research questions were as follows: To improve the prediction of AD related morphological changes, (1) Would the use of a standardized cognitive screening scale be beneficial? (2) Is conducting a thorough neuropsychological evaluation necessary instead of relying solely on cognitive screening tests? (3) Should we apply SCD-plus research criteria, and if so, which criterion would be the most effective? (4) Is it necessary to consider medical and psychiatric comorbidities, vitamin deficiencies, vascular burden on MRI, and family history? We utilized Freesurfer to analyze cortical thickness and regional brain volume meta-scores linked to AD or predicting its development. We employed multiple linear regression models for each variable, with morphology as the dependent variable. AD-like morphology was associated with subjective complaints in males, individuals with advanced age, and higher education. Later age of onset for complaints, complaints specifically related to memory, excessive deep white matter vascular lesions, and using medications that have negative implications for cognitive health (according to the Beers criteria) were predictive of AD-related morphology. The subjective cognitive memory questionnaire scores were found to be a better predictor of reduced volumes than a single-question assessment. It is important to note that not all SCD-plus criteria were evaluated in this study, particularly the APOE genotype, amyloid, and tau status, due to resource limitations. The detection of AD-related structural changes is impacted by demographics and assessment methods. Standardizing SCD assessment methods can enhance predictive accuracy.

Expert recommendations for magnetic resonance imaging of muscle disorders

Magnetic resonance (MRI) imaging of the skeletal muscles (muscle MRI for short) is increasingly being used in clinical routine for diagnosis and longitudinal assessment of muscle disorders. However, cross-centre standards for measurement protocol and radiological assessment are still lacking. The aim of this expert recommendation is to present standards for the application and interpretation of muscle MRI in hereditary and inflammatory muscle disorders. This work was developed in collaboration between neurologists, neuroradiologists, radiologists, neuropaediatricians, neuroscientists and MR physicists from different university hospitals in Germany. The recommendations are based on expert knowledge and afocused literature search. The indications for muscle MRI are explained, including the detection and monitoring of structural tissue changes and oedema in the muscle, as well as the identification of asuitable biopsy site. Recommendations for the examination procedure and selection of appropriate MRI sequences are given. Finally, steps for astructured radiological assessment are presented. The present work provides concrete recommendations for the indication, implementation and interpretation of muscle MRI in muscle disorders. Furthermore, it provides apossible basis for the standardisation of the measurement protocols at all clinical centres in Germany.

Expert recommendations for magnetic resonance imaging of muscle disorders

Magnetic resonance (MRI) imaging of the skeletal muscles (muscle MRI for short) is increasingly being used in clinical routine for diagnosis and longitudinal assessment of muscle disorders. However, cross-centre standards for measurement protocol and radiological assessment are still lacking. The aim of this expert recommendation is to present standards for the application and interpretation of muscle MRI in hereditary and inflammatory muscle disorders. This work was developed in collaboration between neurologists, neuroradiologists, radiologists, neuropaediatricians, neuroscientists and MR physicists from different university hospitals in Germany. The recommendations are based on expert knowledge and afocused literature search. The indications for muscle MRI are explained, including the detection and monitoring of structural tissue changes and oedema in the muscle, as well as the identification of asuitable biopsy site. Recommendations for the examination procedure and selection of appropriate MRI sequences are given. Finally, steps for astructured radiological assessment are presented. The present work provides concrete recommendations for the indication, implementation and interpretation of muscle MRI in muscle disorders. Furthermore, it provides apossible basis for the standardisation of the measurement protocols at all clinical centres in Germany.

A Fluctuation Test for Structural Change Detection in Heterogeneous Panel Data Models

A Fluctuation Test for Structural Change Detection in Heterogeneous Panel Data Models

Mechanical activation and silver supplementation as determinants of the antibacterial activity of titanium dioxide nanoparticles

Metals and metal oxides have subpar antibacterial activities compared to those of small-molecule antibiotics, yet there are hopes that with proper compositional and structural adjustments this gap might be bridged. In this study, titanium dioxide (TiO2) nanoparticles were mechanically activated and combined with particulate silver through simple reduction process elicited by UV irradiation and assisted with the ultrasound. The resulting powders in various combinations (Ag vs. no Ag, activated vs. non-activated) were characterized using a range of experimental techniques and assessed for their antibacterial activities. The preparation procedure presented in this work prevails over the disadvantages of many chemical routes, most critically by avoiding the use of toxic substances. The mechanical activation did not reduce the particle size or crystallinity of TiO2 nor did it consistently alter the bandgap, yet it enabled the doubling of the amount of silver incorporable into the material. Further, while both mechanical activation and the addition of silver in the amount not exceeding 0.5 wt% produced barely detectable structural changes in the material, they both augmented its antibacterial activity. The precursor TiO2 powder produced no inhibition zone against any of the four bacterial species tested, while the mechanical activation of TiO2 led to the formation of distinct inhibition zones against each of the four bacterial species tested. The addition of silver to activated TiO2 further widened the inhibition zones and it also imparted the antibacterial activity to non-activated TiO2. The boost in the antibacterial activity achieved by the short mechanical activation was of a similar magnitude as the boost obtained after the addition of silver. The antibacterial activity was not different for different species when no silver was added to the system. However, with the addition of silver, species selectivity was obtained, as the composites were more effective against the two Gram-negative species (Escherichia coli and Klebsiella pneumoniae) than against the two Gram-positive ones (Staphylococcus aureus and Bacillus subtilis). The antibacterial activity increased with the addition of silver in the broth assay, but it was mediocre compared to that detected in the agar assay, attesting to the poor dispersability of the powders and their best performance when the bacterial cells migrate to the composite surface than vice versa. The findings of this study give hope that with appropriate microstructural or compositional alterations, the antibacterial activity of metal oxide powders and inorganic materials in general can be made comparable to that of small-molecule antibiotics.

Remote sensor measurement system for sub-centimeter structural change detection

This work presents an autonomous remote sensor measurement system to monitor structural change detection. We utilized a portable network analyzer as a core component of a ground-based synthetic aperture radar to achieve structural monitoring. First, we realized a 2-meter rail apparatus, where antennas and radio frequency components of the radar can move, to obtain a synthetic radar aperture. Then, we develop signal processing algorithms to obtain radar images and to perform change detection. Although the range resolution of our system is 15 cm due to the frequency bandwidth of the radar, we have successfully developed an interferometric change detection technique to achieve up to 440μm change detection of the monitored structure.

Degradation processes in polyolefins with phenolic stabilizers subjected to ionizing or non-ionizing radiation

We investigated degradation processes in polymer plaques made of polyolefin (HDPE or UHMWPE or COC) prepared by melt-mixing with or without phenolic stabilizer (natural α-tocopherol or synthetic Irganox®1010) and spin trapping agent (TTBNB; 2,4,6-Tri‑tert-butylnitrosobenzene). The degradation was initiated either by low-energy, non-ionizing radiation (wavelengths corresponding to terrestrial range of solar UV radiation) or high-energy, ionizing radiation (electrons accelerated at 1.5 MeV). The motivation for the study was our recent finding that some phenolic stabilizers exhibited a surprising pro-oxidant activity in polyolefins subjected to non-ionizing radiation. Consequently, we asked if the phenolic stabilizers in polyolefins behave in the same way during long-term, low-energy, non-ionizing UV irradiation and after short-term, high-energy, ionizing e-beam irradiation. All samples were characterized thoroughly by means of electron spin resonance (ESR; the information about radiation-induced radicals), infrared microspectroscopy (IR; the detection of oxidation products and structural changes), instrumented microindentation (MHI; local mechanical properties) and light and electron microscopy (LM and SEM; surface morphology). The results proved that (i) the degradation processes in polyolefins subjected to non-ionizing or ionizing radiation were different, (ii) the phenolic stabilizers exhibited mostly their expected antioxidant activity, while pro-oxidant activity was detected only for specific conditions and/or systems subjected to non-ionizing radiation, and (iii) the selected spin trapping agent, TTBNB, was stable enough to survive standard sample preparation by melt-mixing and catch short-living unstable radicals.

Non-covalent complexes of lutein/zeaxanthin and whey protein isolate formed at different pH levels: Binding interactions, storage stabilities, and bioaccessibilities

Lutein (Lut) and zeaxanthin (Zx) are promising healthy food ingredients; however, the low solubilities, stabilities, and bioavailabilities limit their applications in the food and beverage industries. A protein-based complex represents an efficient protective carrier for hydrophobic ligands, and its ligand-binding properties are influenced by the formulation conditions, particularly the pH level. This study explored the effects of various pH values (2.5–9.5) on the characteristics of whey protein isolate (WPI)–Lut/Zx complexes using multiple spectroscopic techniques, including ultraviolet–visible (UV–Vis), fluorescence, and Fourier transform infrared (FTIR) spectroscopies and dynamic light scattering (DLS). UV–Vis and DLS spectra revealed that Lut/Zx were present as H-aggregates in aqueous solutions, whereas WPI occurred as nanoparticles. The produced WPI–Lut/Zx complexes exhibited binding constants of 104–105 M−1, which gradually increased with increasing pH from 2.5 to 9.5. FTIR spectra demonstrated that pH variations and Lut/Zx addition caused detectable changes in the secondary WPI structure. Moreover, the WPI–Lut/Zx complexes effectively improved the physicochemical stabilities and antioxidant activities of Lut/Zx aggregates during long-term storage and achieved bioaccessibilities above 70% in a simulated gastrointestinal digestion process. The comprehensive data obtained in this study offer a basis for formulating strategies that can be potentially used in developing commercially available WPI complex-based xanthophyll-rich foods.

Protein painting for structural and binding site analysis via intracellular lysine reactivity profiling with o-phthalaldehyde.

The three-dimensional structure and the molecular interaction of proteins determine their roles in many cellular processes. Chemical protein painting with protein mass spectrometry can identify changes in structural conformations and molecular interactions of proteins including their binding sites. Nevertheless, most current protein painting techniques identify protein targets and binding sites of drugs in vitro using a cell lysate or purified protein. Here, we tested 11 membrane-permeable lysine-reactive chemical probes for intracellular covalent labeling of endogenous proteins, which reveals ortho-phthalaldehyde (OPA) as the most reactive probe in the intracellular environment. An MS workflow and a new data analysis strategy termed RAPID (Reactive Amino acid Profiling by Inverse Detection) was developed to enhance detection sensitivity. RAPID with OPA successfully identified structural changes induced by the allosteric drug TEPP-46 on its target protein PKM2 and was applied to profile the conformation change of the proteome occurring in cells during thermal denaturation. The application of RAPID-OPA on cells treated with geldanamycin, selumetinib, and staurosporine successfully revealed their binding sites on target proteins. Thus, RAPID-OPA for cellular protein painting enables the identification of ligand-binding sites and detection of protein structural changes occurring in cells.

Harnessing Liquid Crystal Sensors for High-Throughput Real-Time Detection of Structural Changes in Lysozyme during Refolding Processes.

Despite the rapid advances in process analytical technology, the assessment of protein refolding efficiency has largely relied on off-line protein-specific assays and/or chromatographic procedures such as reversed-phase high-performance liquid chromatography and size exclusion chromatography. Due to the inherent time gap pertaining to traditional methods, exploring optimum refolding conditions for many recombinant proteins, often expressed as insoluble inclusion bodies, has proven challenging. The present study describes a novel protein refolding sensor that utilizes liquid crystals (LCs) to discriminate varying protein structures during unfolding and refolding. An LC layer containing 4-cyano-4'-pentylbiphenyl (5CB) intercalated with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) is used as a sensing platform, and its proof-of-concept performance is demonstrated using lysozyme as a model protein. As proteins unfold or refold, a local charge fluctuation at their surfaces modulates their interaction with zwitterionic phospholipid DOPE. This alters the alignment of DOPE molecules at the aqueous/LC interface, affecting the orientational ordering of bulk LC (i.e., homeotropic to planar for refolding and planar to homeotropic for unfolding). Differential polarized optical microscope images of the LC layer are subsequently generated, whose brightness directly linked to conformational changes of lysozyme molecules is quantified by gray scale analysis. Importantly, our LC-based refolding sensor is compatible with diverse refolding milieus for real-time analysis of lysozyme refolding and thus likely to facilitate the refolding studies of many proteins, especially those lacking a method to determine structure-dependent biological activity.

Advancement of microfluidic modulation spectroscopy as a highly sensitive protein characterization technique for the detection of small structural changes

The higher order structure (HOS) of a protein is vital to its function and activity, making it a critical component in the development of protein-based therapeutics. Characterization of HOS can be performed using various biophysical techniques, but many of these methods have limitations such as low throughput, complicated workflow, narrow concentration range, and low sensitivity. Microfluidic Modulation Spectroscopy (MMS) is an emerging technology that addresses these limitations, offering high sensitivity and automated analysis for protein secondary structure. This study evaluates and compares the different well plate formats and scan modes of two MMS instruments. The newer Apollo system features a high throughput 96-well plate format and sweep scan mode that allows a 50% reduction in sample volume consumption and measurement time compared to the previous system. By measuring two proteins with drastically different secondary structures, the results demonstrated that the measurements were highly repeatable (>99% repeatability by area of overlap) regardless of the well plate formats or the scan modes. The limit of quantitation (LOQ) for determining structural impurity using the sweep scan mode was 3.2% and significantly better than that of FTIR at 23% from previous studies. This work highlighted the advancement of MMS as a highly sensitive technique to detect small changes of protein structures due to aggregation or misfolding.

Prevalence of Irritable Bowel Syndrome in Saudi Arabia: A Systematic Review and Meta-Analysis.

Irritable bowel syndrome (IBS) is a commonly found global functional pathology with no detectable structural changes. It affects the quality of life and often coexists with psychiatric and somatic issues. We reviewed all articles published between 1990 and April 2023. The databases used for the data search were Google Scholar, Web of Science, Cochrane Library, and PubMed/MEDLINE. Ovid search engine was also used to broaden the search strategy. Predefined keywords, including "Irritable bowel syndrome" (MeSH) OR "IBS" (all fields), along with "Saudi Arabia" and "Middle East," were used to avoid data loss and ambiguity. Any cross-sectional study that reported the prevalence of IBS in any gender, age, and group of the Saudi population was included. Data extraction was independently performed in duplicate to mitigate bias and data loss. Statistical analysis of proportion was conducted by using Miller (Freeman-Tukey double arcsine - exact inverse). Out of 350 records identified, only 38 studies were included in the quantitative synthesis. The total number of study participants was 26,567, on the basis of the predefined inclusion criteria of the study. StatsDirect software was used for the statistical analysis of the study parameters. Based on all 38 identified studies, the calculated pooled prevalence was 20.7% (95% confidence interval (CI) = 17.8% to 23.7% by applying random effects (DerSimonian-Laird method). IBS was identified in 21% (95% CI = 16.7% to 25.7%) of the general population, 22% (95% CI = 17.6% to 26.7%) of students, and 18.3% (95% CI = 13.3% to 23.9%) of healthcare workers. The pooled prevalence of IBS among the Saudi population was 20.7%. The pathophysiology of IBS is complexed and significantly affected by genetics, diet, cultural characteristics, age, anxiety, depression, stress, and sleep disorders. This study fills a gap in understanding IBS prevalence in Saudi Arabia, contributing valuable data to this region.

Interior structural change detection using a 3D model and LiDAR segmentation

Interior structural change detection using a 3D model and LiDAR segmentation

AB1542 APPLICATION OF THE OMERACT ULTRASOUND SCORING SYSTEM FOR SALIVARY GLANDS IN PATIENTS WITH SUSPECTED SJÖGREN’S SYNDROME

BackgroundPrimary Sjogren’s Syndrome (pSS) is a connective tissue disease characterized by the presence of sicca syndrome. Confirmation of pSS requires immunological test and biopsy of the accessory salivary glands[1].Salivary gland ultrasonography (SGUS) allows the detection of structural changes of salivary glands and is proposed as a reliable tool to assess involvement of major salivary glands in patients with pSS. Recently, a new semi- quantitative score have been validated by experts: The OMERACT US score to assess salivary gland involvement in pSS [2].ObjectivesThe aim of our study was to describe salivary gland involvement in patient with suspected of pSS according to the OMERACT ultrasound scoring system for pSS.MethodsAll patients referred for a suspicion of pSS during the last period june 2022-2023 were enrolled. All underwent measurement of salivary flow, minor salivary gland biopsy, SSA antibody. SGUS was performed for all included patients. Both parotid glands and submandibular glands were exanimated using the scoring system 0-3 (OMERACT). Exact Fischer test was used to compare qualitative variables. Sensitivity, specificity and cutoffs were determined by ROC curve analysis.ResultsWe enrolled 73 patients with a suspected pSS. Women represented 80 % of the cohort. Median age was 59 years [Q1 52-Q3 65]. Thirty-four patients were diagnosed with primary SS (pSS) and all fulfilled the 2016 American College of Rheumatology (ACR)/EULAR classification criteria. Thirty-one (91%) patients with pSS had a focus score > 1 in the biopsy of minor salivary gland. Twenty-one (62%) of patients with pSS had a positive SSA antibody.Of the 73 patients, 26 (35%) patients had at least one gland with an ultrasound score of 2 among them, 21 patients were diagnosed with pSS. More patients with pSS compared with non-pSS had score ≥2 in at least one gland (21 pSS vs 5 non pSS) in at least one gland. Among the 26 patients with an ultrasonographic score ≥ 2, 14 patients had positive SSA antibody (p= 0.001). When using ROC analysis, we found that an ultrasound score cutoff ≥2 in at least one gland was associated with a sensitivity at 67 % and specificity at 88%, air under the curve (AUC) was 0.83 [IC95% 0.732-0.93].ConclusionMore patients with pSS compared with non-pSS had score ≥2 in at least one gland (21 pSS vs 5 non pSS) in at least one gland. An ultrasound cutoff > 1 is associated with a sensitivity at 67 % and Specificity at 88%. Our data supports what have been previously reported in several studies. Fana et al [3] reported in a cohort of 143 patients with suspected pSS that the best ultrasound cutoff value was ≥ 1 gland with a score ≥2 was associated to sensitivity at 72 % and specificity of 91%.Our data supports the importance of use of ultrasound as tool for diagnosing pSS. SGUS should be integrated as a criterion in ACR/EULAR score.

Detecting and testing multiple change points in distributions of damage-sensitive feature data for data-driven structural condition assessment: A distributional time series change-point analytic approach

Structural change detection is a core component of structural health monitoring (SHM). One appealing aspect of SHM is that structural changes can be detected by detecting the changes in extracted damage-sensitive features (DSFs). The feature changes of the data are usually attributed to the changes of the underlying distributions; thus, developing reliable change-point detectors for automatically detecting and testing various potential changes in the distributions of DSF data are particularly beneficial for automatic structural health diagnosis. However, methodological researches devoted to detecting change points for probability distributions are rare either in statistics or engineering literature, and state-of-the-art approaches mainly focus on single change-point detection and have restrictive assumptions on the distributions or the types of change points. This motivates us to develop a more flexible multiple change-point detection method for the distributions of DSF data employed for data-driven structural condition assessment. To accommodate a large dataset, the DSF data are summarized by a distributional time series that consists of probability density functions (PDFs) estimated from blocks of DSF data. Then, detecting the distributional changes for the massive DSF data can be phrased as detecting the changes in the resulting distributional time series with much less data objects. To overcome the obstacle that the PDF-valued data are special functional data residing in nonlinear abstract spaces, this study employs two transformations to convert the PDFs into more tractable vector spaces. Then, by using the linear structures possessed by the vector spaces, a nonparametric multiple change-point detection method is presented for the distributional time series based on the techniques of functional principal component analysis and E-Divisive data segmentation. The proposed method possesses various nice features, such as being capable for multiple change-point detection, having fewer restrictive assumptions and scalability to large datasets. Moreover, it also shows superiority in revealing the modes of distributional variations. An application to distributional change detection involved in cable condition assessment for a long-span cable-stayed bridge demonstrates the applicability and versatility of our proposal, and some interesting results are also discovered.

ADGSC: video anomaly detection algorithm based on graph structure change detection in public places

ADGSC: video anomaly detection algorithm based on graph structure change detection in public places