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Ultrasonic impact treatment (UIT) is a kind of mechanical assistive technology that can reduce the residual stress of the as-deposited metal parts. Up to now, the mechanism of ultrasonic characteristics affecting the residual stress has not been revealed distinctly. In this work, the 1Cr12Ni3MoVN deposition layer was treated by UIT with multiple ultrasonic characteristics. The results show that UIT transforms the residual tensile stress of the LMD deposition layer into compressive stress. As the amplitude increases from 20 to 30 μm, the maximum and depth of transverse residual stress observed in the vertical direction increased from 354 to 381 MPa and from 0.364 to 0.523 mm. The maximum and depth of longitudinal residual stress increased from 258 to 318 MPa and from 0.482 to 0.785 mm. As the frequency increases from 15 to 25 kHz, the maximum and depth of transverse residual stress observed in the vertical direction increased from 207 to 406 MPa and 0.301 to 0.395 mm. The maximum and depth of longitudinal residual stress increased from 240 to 326 MPa and from 0.341 to 0.517 mm. The influence of ultrasonic frequency is not as prominent as ultrasonic amplitude. The maximum impact velocity of the pin is the major factor determining the residual compressive stress field. The acceleration of the pin is positively correlated with the downward velocity of the horn. Increasing the ultrasonic amplitude can effectively increase the velocity of the horn. Once the impact energy is large enough, the σmax is basically unchanged, but the increase of impact energy can still increase the d. This work is of guiding significance for the elimination and control of residual stress in parts manufactured by LMD and other additive manufacturing methods. [ABSTRACT FROM AUTHOR]

Objective: To investigate the influence of different puncture needle types and ultrasonic characteristics of thyroid nodules on the sampling satisfaction rate of ultrasound⁃guided fine needle biopsy specimen. Methods: A total of 185 patients with thyroid nodules (185 nodules) who underwent fine⁃needle aspiration biopsy in Nanjing Tongren Hospital between August 2020 and August 2022 were included. All nodules received 23 G and 25 G ultrasound guided fine⁃needle aspiration biopsy. According to nodular ultrasonic characteristics (nodule size. coarse calcification. blood supply. echo) . puncture specimens were classified into satisfactory and unsatisfactory categories according to the Bethesda system for reporting thyroid cytopathology . The influence of puncture needle types and nodular ultrasonic characteristics on the sampling satisfaction rate were evaluated. Results: There was no statistical difference in the overall sampling satisfaction rate between the 23 G group and the 25 G group (85.4% vs. 88.1% . P=0.443) . According to the maximum diameter. the nodules were divided into three groups. The satisfactory rate of specimen collection in the group ≤ 0.5 cm was lower than those in the group 0.5⁃1.0 cm and group≥ 1.0 cm (P < 0.05) . According to nodule calcification. the patients were divided into coarse calcification group and other groups. The satisfaction rate of 23 G fine needle in the coarse calcification group was higher than that of 25 G fine needle (76.5% vs. 52.9%. P < 0.05) . There was no statistical difference in the satisfaction rate of the two kinds of fine needle in other groups. According to the blood supply. the nodules were divided into the blood supply rich group and the blood supply deficient group. The satisfaction rate of 25 G fine needle in the blood supply rich group was higher than that of 23 G fine needle (83.3% vs. 61.9% . P < 0.05) . There was no statistical difference in the sample collection satisfaction rate between 23 G and 25 G fine needles in the blood supply deficient group. The nodules were divided into hypoechoic. isoechoic and hyperechoic groups according to their echo. There was no statistical difference in sampling satisfaction rate between 23 G and 25 G fine needles in different echo groups (P ≥ 0.05) . Conclusion: Small thyroid nodule (maximum diameter≤ 0.5 cm) . accompanied by coarse calcification or rich blood supply will affect the sampling satisfaction rate. [ABSTRACT FROM AUTHOR]

Objective: Intravenous leiomyomatosis (IVL) is a rare and aggressive tumor type that has the potential to extend into the inferior vena cava (IVC) and is susceptible to be misdiagnosed and neglected. Despite its clinical significance, there is a paucity of research that has focused on the specific manifestations of IVL on ultrasonography. Therefore, this study aims to systematically analyze the specific ultrasound features of IVL and augment its diagnostic accuracy. Materials and method: Prospective inclusion was granted to patients admitted to our hospital between December 2016 and March 2021 for an IVC-occupying lesion. Multi-modal ultrasonography, encompassing gray-scale and color Doppler, was conducted. Lesions were categorized as IVL or non-IVL based on pathological or follow-up data. Two ultrasound sonographers with over 5 years of experience read and recorded ultrasound data for all lesions, which were subsequently comparatively analyzed to identify specific signs of IVL. Results: A total of 284 patients diagnosed with IVC-occupying lesions were included in the study. The lesion types comprised of IVL (n=67, 23.6%), IVC thrombus (n=135, 47.5%), tumor thrombus of renal carcinoma involving the IVC (n=35, 12.4%), tumor thrombus of liver carcinoma involving the IVC (n=24, 8.5%), leiomyosarcoma of the IVC (n=14, 4.9%), and tumor thrombus of adrenocortical adenocarcinoma (n=9, 4.1%). The presence of "sieve hole" and "multi-track" signs was observed in 20 IVL lesions under the grey-scale modality, while both signs were absent in the non-IVL group (P<0.01). The study found no statistically significant differences in the presentation of "sieve hole" and "multi-track" signs under the grey-scale and color Doppler modalities in cases of intravascular lithotripsy (IVL) (P>0.05). Using these two signs as diagnostic criteria for IVL, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), miss rate, misdiagnosis rate, and accuracy were determined to be 29.9%, 100%, 100%, 82.2%, 70.1%, 0, and 83.5%, respectively (AUC ROC=0.649; 95%CI: 0.537-0.761). Conclusion: IVL exhibits distinct ultrasound presentations, including "sieve hole" and "multi-track" signs, which demonstrate high specificity and accuracy as diagnostic indicators. Furthermore, these signs are corroborated by pathological evidence and effectively distinguish IVL from other lesions occupying the IVC. [ABSTRACT FROM AUTHOR]

Objective: Intravenous leiomyomatosis (IVL) is a rare disease, and few studies have focused on the diagnostic value of contrast-enhanced ultrasound (CEUS) in this condition. This study aimed to investigate the diagnostic value of CEUS in IVL and summarize the specific CEUS characteristics of IVL. Materials and Method: FromDecember2016toMarch2021,93patients admitted to our hospital with inferior vena cava (IVC) occupying lesions were prospectively enrolledandunderwentdetailedultrasoundmulti-modalityexaminations, including conventional and contrast-enhanced ultrasound scans. The diagnostic value of CEUS and conventional ultrasound (CU) in IVL was compared, and the specific IVL signswere summarized. Results: Amongthe 93 patients with inferiorvenacavamass, 67 were IVL while 26 were non-IVL. The inter-observer agreement of the two senior doctors was good, with Kappa coefficient = 0.71 (95% CI: 0.572-0.885). The area under the ROC curve of CU for IVL diagnosis was 0.652 (95% CI: 0.528-0.776), and its sensitivity, specificity, accuracy, positive predictive value, negative predictive value, missed diagnosis rate, and misdiagnosis rate were 61.1%, 69.2%, 63.4%, 83.7%, 40.9%, 38.8%, and 30.8%, respectively. The area under curve (AUC) for IVL diagnosis by CEUSwas 0.807 (95% CI: 0.701-0.911), and the sensitivity, specificity, accuracy, positive predictive value, negative predictivevalue, misseddiagnosis rate, andmisdiagnosis ratewere82.0%,84.6%,82.8%, 93.2%,64.7%, 15.4%, and17.9%, respectively. InCEUSmode, "sieveholesign" and "multitrack sign" were detected in 57 lesions, andthedetected ratewashigher thanthatofCU (https://loop.frontiersin.org/people/1014187<0.01). Conclusion: CEUScanbettershowthefinebloodflowinsidetheIVL, whichisimportant for IVL differential diagnosis. Moreover, CEUS can obtain more information about IVL diagnosis than CU, compensating for the shortcomings of CU in detectingmore blood flowwithin the lesion. Thus, this technique has great significance for IVL diagnosis. [ABSTRACT FROM AUTHOR]

• Clarified the structural failure patterns and mechanisms of plain concrete linings under different loading paths. • Revealed the three-dimensional ultrasonic characteristics of lining structures in various damage states. • Developed a predictive method for bearing capacity across different crack propagation stages. The state of tunnel lining structures plays a crucial role in determining safety and service quality throughout their serving life. Therefore, establishing a quantitative method for evaluating the bearing capacity of linings is crucial. Understanding the process and status of crack propagation is key to ensuring structural safety. The three-dimensional development of lining damage cracks is closely related to structural safety. Unveiling the spatial growth of these cracks and the evolution of structural performance is vital for an accurate assessment of lining safety. Key factors in crack propagation, along with non-destructive detection methods, serve as primary approaches for evaluating the safety condition. This paper explores the evolution law and evaluation model of the bearing capacity of plain concrete linings under different loading paths. The distribution of structural stiffness changes significantly under different boundary settings. Therefore, full-scale loading tests of lining components were conducted, designing two types of linings: one intact and the other with initial defects, to simulate the failure of plain concrete linings under diverse loading conditions. The results show that: (1) The damage development of linings exhibits clear staged evolution characteristics; (2) The spatial development of lining cracks can be divided into three stages; (3) There are significant differences in ultrasonic parameters at different stages. Consequently, a method for evaluating the local bearing capacity state of linings based on the coupling of crack characteristics and ultrasonic parameters is proposed; (4) This method is also applicable to linings with initial damage, where damage evolution follows similar stages. The findings provide theoretical guidance for predicting and preventing crack propagation in operational tunnel linings. [ABSTRACT FROM AUTHOR]

ObjectiveIntravenous leiomyomatosis (IVL) is a rare disease, and few studies have focused on the diagnostic value of contrast-enhanced ultrasound (CEUS) in this condition. This study aimed to investigate the diagnostic value of CEUS in IVL and summarize the specific CEUS characteristics of IVL.Materials and MethodFrom December 2016 to March 2021, 93 patients admitted to our hospital with inferior vena cava (IVC) occupying lesions were prospectively enrolled and underwent detailed ultrasound multi-modality examinations, including conventional and contrast-enhanced ultrasound scans. The diagnostic value of CEUS and conventional ultrasound (CU) in IVL was compared, and the specific IVL signs were summarized.ResultsAmong the 93 patients with inferior vena cava mass, 67 were IVL while 26 were non-IVL. The inter-observer agreement of the two senior doctors was good, with Kappa coefficient = 0.71 (95% CI: 0.572–0.885). The area under the ROC curve of CU for IVL diagnosis was 0.652 (95% CI: 0.528–0.776), and its sensitivity, specificity, accuracy, positive predictive value, negative predictive value, missed diagnosis rate, and misdiagnosis rate were 61.1%, 69.2%, 63.4%, 83.7%, 40.9%, 38.8%, and 30.8%, respectively. The area under curve (AUC) for IVL diagnosis by CEUS was 0.807 (95% CI: 0.701–0.911), and the sensitivity, specificity, accuracy, positive predictive value, negative predictive value, missed diagnosis rate, and misdiagnosis rate were 82.0%, 84.6%, 82.8%, 93.2%, 64.7%, 15.4%, and 17.9%, respectively. In CEUS mode, “sieve hole sign” and “multi-track sign” were detected in 57 lesions, and the detected rate was higher than that of CU (https://loop.frontiersin.org/people/1014187 < 0.01).ConclusionCEUS can better show the fine blood flow inside the IVL, which is important for IVL differential diagnosis. Moreover, CEUS can obtain more information about IVL diagnosis than CU, compensating for the shortcomings of CU in detecting more blood flow within the lesion. Thus, this technique has great significance for IVL diagnosis.

Background: Prediction of central lymph node metastasis (CLNM) is vital for clinical decision-making processes in clinically N0 (cN0) unifocal papillary thyroid carcinoma (PTC), but the sensitivity of preoperative detection of CLNM is limited. The aim of the present study was to determine whether there are ultrasonic (US) characteristics associated with CLNM. Methods: In total, 1657 PTC patients (514 men and 1143 women) were enrolled in the present study between January 2018 and May 2021. The patients met the following inclusion criteria based on preoperative detection: suspected nodule confirmed as PTC by biopsy; the nodule was unifocal and less than 4 cm in diameter; no prior neck radiation exposure; no extrathyroidal extension; and no CLNM or distant metastases on imaging. All the enrolled patients underwent total thyroidectomy with prophylactic central lymph node dissection (CLND). A postoperative pathological diagnosis was made. Results: CLNM was found in 58.4% of male patients and 36.9% of female patients. In univariate analysis, size, adjacent anterior capsule, distance to the lower pole and color Doppler flow imaging (CDFI) were considered risk factors for the male and female groups (p < 0.05). In multivariate analyses, size, adjacent anterior capsule, distance to the lower pole and CDFI were independent risk factors for male patients. For females, the independent risk factors included size, adjacent anterior capsule, distance to the lower pole and CDFI. Conclusion: In the present cohort, US imaging characteristics, including size, adjacent anterior capsule, distance to the lower pole and CDFI, were identified to be potentially beneficial in preoperative clinical decision-making processes for cN0 unifocal PTC patients. [ABSTRACT FROM AUTHOR]

Objective: To investigate the ultrasonic characteristics of gouty arthritis（GA） in acute stage and remission stage and its correlation with the levels of serum interleukin（IL）-22 and IL-37. Methods: From July 2019 to March 2021, 64 patients diagnosed with GA in our hospital were selected as the gout group, and 32 healthy volunteers in our hospital during the same period as the normal control group. After ultrasonic examination and serum sample test, the ultrasonic characteristics of GA patients were observed and the levels of serum IL-22 and IL-37 were compared. Spearman test was used to analyze the correlation between the levels of serum IL-22 and IL-37 and the ultrasonic characteristics of GA patients.To compare the diagnostic value of ultrasonographic features combined with levels of IL-22 and IL-37 single or combined in acute and remission stages of gout arthritis. Results: The level of IL-22 in acute stage of gout group was significantly higher than that in remission stage and normal control group（P<0.05）. The level of IL-37 in gout group in acute phase and remission phase was significantly higher than that in normal control group, and the level of IL-37 in remission phase was higher than that in acute phase（P<0.05）. 29 of the 64 GA patients had tophi. 60 patients had joint effusion in the acute phase, and 22patients had joint effusion absorbed to normal levels in the remission phase. Synovial hyperplasia occurred in 52 patients in the acute phase and resolved in 14 patients in remission. There were 29 cases with dual-track syndrome, and only 1 case disappeared in remission. Bone erosion occurred in 14 cases, and no significant improvement was observed during remission. The thickness of effusion and synovium in remission phase were significantly less than that in acute phases（P<0.05）. There was a significant positive correlation between IL-22 level and the degree of joint effusion in both acute and remission phase（P<0.05）. The sensitivity and specificity of ultrasonography combined with serum levels of IL-22 and IL-37 were the highest in both acute and remission phase. Conclusion: The level of IL-22 was positively correlated with the joint effusion under ultrasound in both acute and remission phases. Serum levels of IL-22and IL-37 combined with ultrasonography can improve the diagnostic performance of GA in acute and remission phases. [ABSTRACT FROM AUTHOR]

BackgroundPrediction of central lymph node metastasis (CLNM) is vital for clinical decision-making processes in clinically N0 (cN0) unifocal papillary thyroid carcinoma (PTC), but the sensitivity of preoperative detection of CLNM is limited. The aim of the present study was to determine whether there are ultrasonic (US) characteristics associated with CLNM.MethodsIn total, 1657 PTC patients (514 men and 1143 women) were enrolled in the present study between January 2018 and May 2021. The patients met the following inclusion criteria based on preoperative detection: suspected nodule confirmed as PTC by biopsy; the nodule was unifocal and less than 4 cm in diameter; no prior neck radiation exposure; no extrathyroidal extension; and no CLNM or distant metastases on imaging. All the enrolled patients underwent total thyroidectomy with prophylactic central lymph node dissection (CLND). A postoperative pathological diagnosis was made.ResultsCLNM was found in 58.4% of male patients and 36.9% of female patients. In univariate analysis, size, adjacent anterior capsule, distance to the lower pole and color Doppler flow imaging (CDFI) were considered risk factors for the male and female groups (p < 0.05). In multivariate analyses, size, adjacent anterior capsule, distance to the lower pole and CDFI were independent risk factors for male patients. For females, the independent risk factors included size, adjacent anterior capsule, distance to the lower pole and CDFI.ConclusionIn the present cohort, US imaging characteristics, including size, adjacent anterior capsule, distance to the lower pole and CDFI, were identified to be potentially beneficial in preoperative clinical decision-making processes for cN0 unifocal PTC patients.

Liquid nitrogen is proposed as a new fracturing fluid to develop enhanced geothermal systems based on the thermal stimulation method. The large temperature difference between cryogenic liquid nitrogen and hot dry rock reservoirs induces high thermal stress, which quenches the reservoir and improves the heat transfer efficiency. Ultrasonic detection is a common non-destructive method for evaluating rock damage, but current analysis procedures mainly focus on wave velocities. This paper thus proposes a comprehensive ultrasonic characterization method. Granite cores were treated by cyclic heating at temperatures of 200–600 °C for 0–5 liquid nitrogen cooling cycles. The damage process was evaluated quantitatively by testing and analyzing the ultrasonic waves transmitted in the rock samples, and the effects of heating temperature and cold-shock times were compared. The results indicated that the velocity, amplitude, and dominant frequency of ultrasonic waves all attenuated with increasing rock damage, among which the velocity attenuated the most strongly, with maximum decrease of 85.01%. In the time domain, pores and fractures distorted the ultrasonic waveform and partially or completely reduced the amplitude. In the frequency domain, the dominant frequency shifted toward lower frequency and the intensity decreased. The fractured cores reduced the proportion of high-frequency energy and increased the proportion of low-frequency energy. The dynamic mechanical properties (elastic modulus, bulk modulus, shear modulus, and Poisson's ratio) were calculated, among which the bulk modulus was the most sensitive to rock damage, with maximum reduction of 15.86 GPa. The calculated damage variables showed an initially rapid and then slower increasing trend with cooling time and a linear increase with heating temperature. The damage variable values after five cold shocks ranged from 0.44 to 0.96. The cores generally experienced stages of micro-fracturing, single fracturing, and fracture networking, and both the heating temperature and liquid nitrogen cold-shock times had a significant effect on the extent of rock damage. [ABSTRACT FROM AUTHOR]

Objective: To examine the ultrasonic changes in postmenopausal endometrial polyps and analyze factors related to their malignant transformation., Methods: This retrospective study analyzed clinical data from 200 postmenopausal patients with endometrial polyps treated at Jinan Maternity and Child Care Hospital and Pingyin Hospital of Traditional Chinese Medicine from December 2020 to December 2023. All patients underwent pathological biopsies to diagnose the nature of the endometrial polyps. This study compared the clinical and ultrasonic imaging features of these patients and analyzed factors influencing the malignant transformation of postmenopausal endometrial polyps., Results: Pathological findings classified 160 patients (80.00%) into the benign group and 40 patients (20.00%) into the malignant group. Significant differences were noted in endometrial thickness, polyp diameter, heterogeneity of lesion echogenicity, and vascularization between the groups (all P<0.05). The malignant group exhibited notably higher blood flow (Grade II+III constituted 70.00% compared to 29.38% in the benign group, P<0.05). The time average velocity (TAV), pulse index (PI), and resistance index (RI) were significantly lower in the malignant group (all P<0.05). The area under curve (AUC) values for TAV, PI, and RI in diagnosing malignant endometrial polyps were 0.754, 0.713, and 0.771, respectively. Increased body mass index (BMI), irregular premenopausal menstruation, and ≥2 occurrences of postmenopausal bleeding were identified as risk factors for malignant transformation (all P<0.05). These six indicators were used to create a predictive model for malignant transformation, achieving an AUC of 0.942., Conclusion: Malignancy in postmenopausal endometrial polyps is uncommon, yet distinct differences exist in the transvaginal color Doppler ultrasound characteristics between benign and malignant cases. Factors such as increased BMI, irregular premenopausal menstruation, and ≥2 occurrences of postmenopausal bleeding significantly contribute to the risk of malignant transformation. These findings, combined with ultrasound features, provide a robust basis for screening and monitoring these patients., Competing Interests: None., (AJTR Copyright © 2024.)

Objective: Intravenous leiomyomatosis (IVL) is a rare and aggressive tumor type that has the potential to extend into the inferior vena cava (IVC) and is susceptible to be misdiagnosed and neglected. Despite its clinical significance, there is a paucity of research that has focused on the specific manifestations of IVL on ultrasonography. Therefore, this study aims to systematically analyze the specific ultrasound features of IVL and augment its diagnostic accuracy., Materials and Method: Prospective inclusion was granted to patients admitted to our hospital between December 2016 and March 2021 for an IVC-occupying lesion. Multi-modal ultrasonography, encompassing gray-scale and color Doppler, was conducted. Lesions were categorized as IVL or non-IVL based on pathological or follow-up data. Two ultrasound sonographers with over 5 years of experience read and recorded ultrasound data for all lesions, which were subsequently comparatively analyzed to identify specific signs of IVL., Results: A total of 284 patients diagnosed with IVC-occupying lesions were included in the study. The lesion types comprised of IVL (n=67, 23.6%), IVC thrombus (n=135, 47.5%), tumor thrombus of renal carcinoma involving the IVC (n=35, 12.4%), tumor thrombus of liver carcinoma involving the IVC (n=24, 8.5%), leiomyosarcoma of the IVC (n=14, 4.9%), and tumor thrombus of adrenocortical adenocarcinoma (n=9, 4.1%). The presence of "sieve hole" and "multi-track" signs was observed in 20 IVL lesions under the grey-scale modality, while both signs were absent in the non-IVL group ( P <0.01). The study found no statistically significant differences in the presentation of "sieve hole" and "multi-track" signs under the grey-scale and color Doppler modalities in cases of intravascular lithotripsy (IVL) ( P >0.05). Using these two signs as diagnostic criteria for IVL, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), miss rate, misdiagnosis rate, and accuracy were determined to be 29.9%, 100%, 100%, 82.2%, 70.1%, 0, and 83.5%, respectively (AUC ROC=0.649; 95%CI: 0.537-0.761)., Conclusion: IVL exhibits distinct ultrasound presentations, including "sieve hole" and "multi-track" signs, which demonstrate high specificity and accuracy as diagnostic indicators. Furthermore, these signs are corroborated by pathological evidence and effectively distinguish IVL from other lesions occupying the IVC., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Ge, Wang, Wang, Li, Yang, Li and Wang.)

Objective: Intravenous leiomyomatosis (IVL) is a rare disease, and few studies have focused on the diagnostic value of contrast-enhanced ultrasound (CEUS) in this condition. This study aimed to investigate the diagnostic value of CEUS in IVL and summarize the specific CEUS characteristics of IVL., Materials and Method: From December 2016 to March 2021, 93 patients admitted to our hospital with inferior vena cava (IVC) occupying lesions were prospectively enrolled and underwent detailed ultrasound multi-modality examinations, including conventional and contrast-enhanced ultrasound scans. The diagnostic value of CEUS and conventional ultrasound (CU) in IVL was compared, and the specific IVL signs were summarized., Results: Among the 93 patients with inferior vena cava mass, 67 were IVL while 26 were non-IVL. The inter-observer agreement of the two senior doctors was good, with Kappa coefficient = 0.71 (95% CI: 0.572-0.885). The area under the ROC curve of CU for IVL diagnosis was 0.652 (95% CI: 0.528-0.776), and its sensitivity, specificity, accuracy, positive predictive value, negative predictive value, missed diagnosis rate, and misdiagnosis rate were 61.1%, 69.2%, 63.4%, 83.7%, 40.9%, 38.8%, and 30.8%, respectively. The area under curve (AUC) for IVL diagnosis by CEUS was 0.807 (95% CI: 0.701-0.911), and the sensitivity, specificity, accuracy, positive predictive value, negative predictive value, missed diagnosis rate, and misdiagnosis rate were 82.0%, 84.6%, 82.8%, 93.2%, 64.7%, 15.4%, and 17.9%, respectively. In CEUS mode, "sieve hole sign" and "multi-track sign" were detected in 57 lesions, and the detected rate was higher than that of CU ( https://loop.frontiersin.org/people/1014187 < 0.01)., Conclusion: CEUS can better show the fine blood flow inside the IVL, which is important for IVL differential diagnosis. Moreover, CEUS can obtain more information about IVL diagnosis than CU, compensating for the shortcomings of CU in detecting more blood flow within the lesion. Thus, this technique has great significance for IVL diagnosis., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Ge, Wang, Wang, Fang, Wang and Li.)

Coal and gas outbursts are a mechanical dislocation process of a gas-logged and porous medium. The existence of the disturbed coal is a precondition of the outbursts. The study showed that the disturbed coal and normal coal are greatly different in mechanical and physical properties which decided the speeds of ultrasonic wave travelling in them. This paper presents a set of experimental measuring system and method. The results of measurements conducted in 60 min areas revealed quite different ultrasonic characteristics in different types of coal mass textures. Measuring the disturbed coal is a new way for predicting the outbursts. [ABSTRACT FROM AUTHOR]

• The influence of the optimal detection position of partial discharge and the number of optical fiber sensing probes on the sensitivity of the optical fiber sensing system is studied. • The ultrasonic spectrum range of the partial discharge detection system is verified through experiments, and the characteristic frequency of partial discharge is obtained. • It is verified based on the ultrasonic location detection of partial discharge in 15 km HVDC cable system, and the positioning deviations is less than 80 m. To improve the safety and efficiency performance of partial discharge detection in a high-voltage direct current (HVDC) cable system, an optical fiber ultrasonic detection system for partial discharge is carried out in the long-distance HVDC operating environment. The correlation model between partial discharge ultrasonic wave and discharge quantity is established by analyzing the partial discharge mechanism and ultrasonic characteristics of DC cable. The partial discharge repetition rate and discharge magnitude of several common insulation defects are obtained experimentally, and the ultrasonic characteristic Sagnac fiber detection system is accomplished based on the data above. Then, the standard ultrasonic time-domain signal detection and fiber optic sensing probe directional experiment are fulfilled, and the ultrasonic wave is measured based on fiber-optic probe and can perform multi-point detection. The influence of different length fiber sensing probes on the sensitivity of partial discharge signals is investigated based on the frequency distribution characteristics of partial discharge. The effectiveness of the optical fiber sensing system is verified based on the zero-frequency point localization method with ultrasonic location detection of partial discharge in a 15 km HVDC cable system. The measurement results obtained show the deviations of determining the location of the partial discharge point is less than ±80 m. The reliability of the proposed PD optical fiber detection system for intrinsic safety and detection efficiency of partial discharge position in the HVDC cable system is verified. [ABSTRACT FROM AUTHOR]