{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,7]],"date-time":"2026-02-07T11:22:33Z","timestamp":1770463353586,"version":"3.49.0"},"reference-count":49,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2023,7,9]],"date-time":"2023-07-09T00:00:00Z","timestamp":1688860800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Guangxi Natural Science Foundation Program","award":["2018GXNSFAA294056"],"award-info":[{"award-number":["2018GXNSFAA294056"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>Within the scope of concrete internal defect detection via laser Doppler vibrometry (LDV), the acquired signals frequently suffer from low signal-to-noise ratios (SNR) due to the heterogeneity of the concrete\u2019s material properties and its rough surface structure. Consequently, these factors make the defect signal characteristics challenging to discern precisely. In response to this challenge, we propose an internal defect detection algorithm that incorporates local mean decomposition-singular value decomposition (LMD-SVD) and weighted spatial-spectral entropy (WSSE). Initially, the LDV vibration signal undergoes denoising via LMD and the SVD algorithms to reduce noise interference. Subsequently, the distribution of each frequency in the scan plane is analyzed utilizing the WSSE algorithm. Since the vibrational energy of the frequencies caused by the defect resonance is concentrated in the defect region, its energy distribution in the scan plane is non-uniform, resulting in a significant difference between the defect resonance frequencies\u2019 SSE values and the other frequencies\u2019 SSE values. This feature is used to estimate the resonant frequencies of internal defects. Ultimately, the defects are characterized based on the modal vibration patterns of the defect resonant frequencies. Tests were performed on two concrete blocks with simulated cavity defects, using an ultrasonic transducer as the excitation device to generate ultrasonic vibrations directly from the back of the blocks and applying an LDV as the acquisition device to collect vibration signals from their front sides. The results demonstrate the algorithm\u2019s capacity to effectively pinpoint the information on the location and shape of shallow defects within the concrete, underscoring its practical significance for concrete internal defect detection in practical engineering scenarios.<\/jats:p>","DOI":"10.3390\/e25071034","type":"journal-article","created":{"date-parts":[[2023,7,10]],"date-time":"2023-07-10T00:35:21Z","timestamp":1688949321000},"page":"1034","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["An Internal Defect Detection Algorithm for Concrete Blocks Based on Local Mean Decomposition-Singular Value Decomposition and Weighted Spatial-Spectral Entropy"],"prefix":"10.3390","volume":"25","author":[{"given":"Xu","family":"Tian","sequence":"first","affiliation":[{"name":"Research Institute of Optical Communication, School of Information and Communication, Guilin University of Electronic Technology, Guilin 541004, China"}]},{"given":"Jun","family":"Ao","sequence":"additional","affiliation":[{"name":"Research Institute of Optical Communication, School of Information and Communication, Guilin University of Electronic Technology, Guilin 541004, China"}]},{"given":"Zizhu","family":"Ma","sequence":"additional","affiliation":[{"name":"Pengcheng Laboratory, Shenzhen 518000, China"}]},{"given":"Chunbo","family":"Ma","sequence":"additional","affiliation":[{"name":"Research Institute of Optical Communication, School of Information and Communication, Guilin University of Electronic Technology, Guilin 541004, China"}]},{"given":"Junjie","family":"Shi","sequence":"additional","affiliation":[{"name":"Research Institute of Optical Communication, School of Information and Communication, Guilin University of Electronic Technology, Guilin 541004, China"}]}],"member":"1968","published-online":{"date-parts":[[2023,7,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1114","DOI":"10.4028\/www.scientific.net\/AMM.577.1114","article-title":"Detecting the Defects in Concrete Components with Impact-echo Method","volume":"577","author":"Liu","year":"2014","journal-title":"Appl. Mech. Mater."},{"key":"ref_2","first-page":"150","article-title":"Study on quantitative detection of defects of concrete members by impact-echo method","volume":"11","author":"Geng","year":"2021","journal-title":"Concrete"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"012036","DOI":"10.1088\/1742-6596\/842\/1\/012036","article-title":"Identification of Delamination in Concrete Slabs by SIBIE Procedure","volume":"842","author":"Yamada","year":"2017","journal-title":"J. Phys. Conf. Ser."},{"key":"ref_4","first-page":"367","article-title":"A Linear Prediction and Support Vector Regression-Based Debonding Detection Method Using Step-Frequency Ground Penetrating Radar","volume":"16","author":"Pan","year":"2018","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1016\/j.ndteint.2014.03.006","article-title":"Investigation of concrete mix variations and environmental conditions on defect detection ability using GPR","volume":"65","author":"Yehia","year":"2014","journal-title":"NDT E Int."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"107839","DOI":"10.1016\/j.measurement.2020.107839","article-title":"Identifying concrete structure defects in GPR image","volume":"160","author":"Jiao","year":"2020","journal-title":"Measurement"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"117474","DOI":"10.1016\/j.conbuildmat.2019.117474","article-title":"The influence of defects at the steel\/concrete interface for chloride-induced pitting corrosion of naturally-deteriorated 20-years-old specimens studied through X-ray Computed Tomography","volume":"235","author":"Rossi","year":"2022","journal-title":"Constr. Build. Mater."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"730","DOI":"10.3151\/jact.19.730","article-title":"Advancing Concrete Durability Research through X-ray Computed Tomography","volume":"19","author":"Sugiyama","year":"2021","journal-title":"J. Adv. Concr. Technol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"573","DOI":"10.3846\/13923730.2016.1210220","article-title":"The methodology for defect quantification in concrete using IR thermography","volume":"23","author":"Banjad","year":"2017","journal-title":"J. Civ. Eng. Manag."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"62","DOI":"10.1016\/j.proeng.2017.05.308","article-title":"Use of Infrared Thermography to Detect Defects on Concrete Bridges","volume":"190","year":"2017","journal-title":"Procedia Eng."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Concu, G., and Trulli, N. (2019). Concrete Defects Sizing by Means of Ultrasonic Velocity Maps. Buildings, 8.","DOI":"10.3390\/buildings8120176"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Sun, Y.S., Wang, G.H., and Li, Y.X. (2022). Study on Ultrasonic Nondestructive Testing of Self-Compacting Concrete under Uniaxial Compression Test. Materials, 15.","DOI":"10.3390\/ma15134412"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"6294603","DOI":"10.1155\/2019\/6294603","article-title":"Time-Domain Topological Energy Imaging Method of Concrete Cavity Defect by Lamb Wave","volume":"2019","author":"Zhu","year":"2019","journal-title":"Shock Vib."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Rhim, H.C., Kim, D.Y., Cho, C.S., and Kim, D.H. (2020). Effect of Steel Plates on Estimation of the Compressive Strength of Concrete via Ultrasonic Testing. Materials, 13.","DOI":"10.3390\/ma13040887"},{"key":"ref_15","first-page":"47","article-title":"Detection of concrete defects in steel tube lining by impact echo method","volume":"43","author":"Liu","year":"2021","journal-title":"Nondestruct. Test."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"e2555","DOI":"10.1002\/stc.2555","article-title":"Imaging techniques for defect detection of fiber reinforced polymer-bonded civil infrastructures","volume":"27","author":"Qiu","year":"2020","journal-title":"Struct. Control Health Monit."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"6","DOI":"10.3846\/jcem.2018.6186","article-title":"Infrared thermography for detecting defects in concrete structures","volume":"24","author":"Sirca","year":"2018","journal-title":"J. Civ. Eng. Manag."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1016\/j.conbuildmat.2019.03.110","article-title":"Review on microwave nondestructive testing techniques and its applications in concrete technology","volume":"209","author":"Abdul","year":"2019","journal-title":"Constr. Build. Mater."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"154","DOI":"10.1016\/j.conbuildmat.2016.10.061","article-title":"Experimental studies on void detection in concrete-filled steel tubes using ultrasound","volume":"128","author":"Dong","year":"2016","journal-title":"Constr. Build. Mater."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1016\/j.ndteint.2014.08.009","article-title":"Laser ultrasonic characterisation of branched surface-breaking defects","volume":"68","author":"Dutton","year":"2014","journal-title":"NDT E Int."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1016\/j.optlastec.2015.04.026","article-title":"Application of laser ultrasonic technique for non-contact detection of structural surface-breaking cracks","volume":"73","author":"Zhou","year":"2015","journal-title":"Opt. Laser Technol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1016\/j.biosystemseng.2020.04.001","article-title":"Non-destructive discrimination of avocado fruit ripeness using laser Doppler vibrometry","volume":"194","author":"Landahl","year":"2020","journal-title":"Biosyst. Eng."},{"key":"ref_23","first-page":"97","article-title":"Application of 3-D Scanning Vibrometry Technique in Liquid Rocket Engine Modal Test","volume":"38","author":"Yan","year":"2017","journal-title":"J. Astronaut."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Kumar, D., Agrawal, A.K., Cao, R., Zhan, L.H., and Wei, J. (2022, January 4\u20137). Damage Detection in Concrete Slab Using Smart Sounding. Proceedings of the 10th European Workshop on Structural Health Monitoring (EWSHM), Palermo, Italy.","DOI":"10.1007\/978-3-031-07258-1_11"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"107039","DOI":"10.1016\/j.ijmecsci.2021.107039","article-title":"Defect detection of concrete in infrastructure based on Rayleigh wave propagation generated by laser-induced plasma shock waves","volume":"218","author":"Wakata","year":"2022","journal-title":"Int. J. Mech. Sci."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Hashimoto, K., Shiotani, T., and Ohtsu, M. (2020). Application of Impact-Echo Method to 3D SIBIE Procedure for Damage Detection in Concrete. Appl. Sci., 10.","DOI":"10.3390\/app10082729"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"155014771988959","DOI":"10.1177\/1550147719889590","article-title":"Experimental study of grout defect identification in precast column based on wavelet packet analysis","volume":"15","author":"Zhang","year":"2019","journal-title":"Int. J. Distrib. Sens. Netw."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"S\u0142o\u0144ski, M., Schabowicz, K., and Krawczyk, E. (2020). Detection of Flaws in Concrete Using Ultrasonic Tomography and Convolutional Neural Networks. Materials, 13.","DOI":"10.3390\/ma13071557"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Tian, X., Ao, J., Ma, Z.Z., Jian, B.J., and Ma, C.B. (2022). Concrete Multi-Type DefectClassification Algorithm Based on MSSMA-SVM. Sensors, 22.","DOI":"10.3390\/s22239145"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1016\/j.ndteint.2018.04.012","article-title":"Ultrasonic imaging of multi-layer concrete structures","volume":"98","author":"Lin","year":"2018","journal-title":"NDT E Int."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Zhu, W.F., Chen, X.J., Li, Z.W., Meng, X.Z., Fan, G.P., Shao, W., and Zhang, H.Y. (2019). A SAFT Method for the Detection of Void Defect inside a Ballastless Track Structure Using Ultrasonic Array Sensors. Sensors, 19.","DOI":"10.3390\/s19214677"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Knak, M., Wojtczak, E., and Rucka, M. (2021). Non-Destructive Diagnostics of Concrete Beams Strengthened with Steel Plates Using Modal Analysis and Wavelet Transform. Materials, 14.","DOI":"10.3390\/ma14113014"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"8889277","DOI":"10.1155\/2020\/8889277","article-title":"Vibration-Based Damage Detection of a Steel-Concrete Composite Slab Using Non-Model-Based and Model-Based Methods","volume":"2020","author":"Fang","year":"2020","journal-title":"Adv. Civ. Eng."},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Buka-Vaivade, K., Gaile, L., Serdjuks, D., Tatarinovs, A., and Pakrastins, L. (2022). Non-Destructive Quality Control of the Adhesive Rigid Timber-to-Concrete Connection in TCC Structures. Buildings, 12.","DOI":"10.3390\/buildings12122151"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"2826","DOI":"10.1109\/TMECH.2021.3077496","article-title":"Weakly Supervised Acoustic Defect Detection in Concrete Structures Using Clustering-Based Augmentation","volume":"26","author":"Kasahara","year":"2021","journal-title":"IEEE\/ASME Trans. Mech."},{"key":"ref_36","first-page":"136","article-title":"Research on synthetic aperture focusing ultrasonic imaging based on phase coherence in frequency domain","volume":"41","author":"Mao","year":"2020","journal-title":"Chin. J. Sci. Instrum."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"103460","DOI":"10.1016\/j.tust.2020.103460","article-title":"Detection and characteristics estimation of defects in concrete structures using laser ablation-induced vibration","volume":"103","author":"Yasuda","year":"2020","journal-title":"Tunn. Undergr. Space Technol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1002\/ecj.12168","article-title":"Development of Laser-based Remote Sensing Technique for Detecting Defects of Concrete Lining","volume":"102","author":"Shimada","year":"2019","journal-title":"Electron. Commun. Jpn."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"103977","DOI":"10.1016\/j.tust.2021.103977","article-title":"Applicability of non-contact inspection using laser ablation-induced vibration in a reinforced concrete tunnel lining","volume":"113","author":"Yasuda","year":"2021","journal-title":"Tunn. Undergr. Space Technol."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"07LC13","DOI":"10.7567\/JJAP.57.07LC13","article-title":"Detection of internal defects of concrete structures based on statistical evaluation of healthy part of concrete by the noncontact acoustic inspection method","volume":"57","author":"Sugimoto","year":"2018","journal-title":"Jpn. J. Appl. Phys."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"SGGB15","DOI":"10.7567\/1347-4065\/ab1a2f","article-title":"Detection of resonance frequency of both the internal defects of concrete and the laser head of a laser Doppler vibrometer by spatial spectral entropy for noncontact acoustic inspection","volume":"58","author":"Sugimoto","year":"2019","journal-title":"Jpn. J. Appl. Phys."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Sugimoto, K., and Sugimoto, T. (2022). Detection of Internal Defects in Concrete and Evaluation of a Healthy Part of Concrete by Noncontact Acoustic Inspection Using Normalized Spectral Entropy and Normalized SSE. Entropy, 24.","DOI":"10.3390\/e24020142"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"553","DOI":"10.1016\/j.conbuildmat.2017.03.024","article-title":"A novel approach for near-surface defect detection in FRP-bonded concrete systems using laser reflection and acoustic-laser techniques","volume":"141","author":"Qiu","year":"2017","journal-title":"Constr. Build. Mater."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"4852","DOI":"10.21595\/jve.2016.16745","article-title":"Noise subspaces subtraction in SVD based on the difference of variance values","volume":"18","author":"Zhang","year":"2016","journal-title":"J. Vibroeng."},{"key":"ref_45","first-page":"10","article-title":"Fault Diagnosis Method of Planetary Gearboxes Based on LMD Permutation Entropy and BP Neural Network","volume":"46","author":"Gao","year":"2022","journal-title":"J. Mech. Transm."},{"key":"ref_46","first-page":"7962828","article-title":"Wavelet Denoising of Vehicle Platform Vibration Signal Based on Threshold Neural Network","volume":"2017","author":"Li","year":"2017","journal-title":"Shock Vib."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Wang, Q., Wang, L., Yu, H., Wang, D., and Nandi, A.K. (2022). Utilizing SVD and VMD for Denoising Non-Stationary Signals of Roller Bearings. Sensors, 22.","DOI":"10.3390\/s22010195"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"15022","DOI":"10.3390\/s140815022","article-title":"Fault Detection of a Roller-Bearing System through the EMD of a Wavelet Denoised Signal","volume":"14","author":"Ahn","year":"2014","journal-title":"Sensors"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"443","DOI":"10.1098\/rsif.2005.0058","article-title":"The local mean decomposition and its application to EEG perception data","volume":"2","author":"Smith","year":"2005","journal-title":"J. R. Soc. Interface"}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/25\/7\/1034\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T20:09:24Z","timestamp":1760126964000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/25\/7\/1034"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,7,9]]},"references-count":49,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2023,7]]}},"alternative-id":["e25071034"],"URL":"https:\/\/doi.org\/10.3390\/e25071034","relation":{},"ISSN":["1099-4300"],"issn-type":[{"value":"1099-4300","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,7,9]]}}}