When disturbed, the interaction between power grid and wind farm may cause serious sub/super-synchronous oscillation (SSO), affecting the security and stability of the system. It is therefore important to detect the t...When disturbed, the interaction between power grid and wind farm may cause serious sub/super-synchronous oscillation (SSO), affecting the security and stability of the system. It is therefore important to detect the time-varying amplitude and frequency of SSO to provide information for its control. The matching synchroextracting wavelet transform (MSEWT) is a new method proposed in this paper to serve this purpose. Based on the original synchrosqueezing wavelet transform, MSEWT uses a synchronous extraction operator to calculate the time-frequency coefficients and a chirp-rate estimation to modify the instantaneous frequency estimation. Thus, MSEWT can improve the concentration degree and reconstruction accuracy of the signal's time-frequency representation without iterative calculation, and can achieve superior noise robustness. After the time-frequency analysis and modal decomposition of the SSO by MSEWT, the amplitudes and frequencies of each oscillation component can be obtained by Hilbert transform (HT). The simulation studies demonstrate that the proposed scheme can accurately identify the modal parameters of SSO even in the case of noise interference, providing a reliable reference for stable operation of power system time-frequency.展开更多
Correction to:Nano-Micro Letters(2025)17:123 https://doi.org/10.1007/s40820-025-01654-y Following publication of the original article[1],the authors reported that Dr.Mohamed Bououdina’s affiliation needed to be corre...Correction to:Nano-Micro Letters(2025)17:123 https://doi.org/10.1007/s40820-025-01654-y Following publication of the original article[1],the authors reported that Dr.Mohamed Bououdina’s affiliation needed to be corrected from 1 to 2.The correct author affiliation has been provided in this Correction and the original article[1]has been corrected.展开更多
Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large v...Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large volumetric cooling capacity and reduced working temperatures far below 1K remains a challenge.Here,through ultra-low temperature magnetism and thermodynamic characterizations,we unveil the large magnetocaloric effect(MCE)realized at sub-Kelvin temperatures in the frustrated Kagome antiferromagnet Gd_(3)BWO_(9) with T_(N)∼1.0 K.The isothermal magnetization curves indicate the existence of field(B)induced anisotropic magnetic phase diagrams,where four distinct magnetic phases for B‖c-axis and five magnetic phases for B‖ab-plane are identified at T<T_(N).The analysis of magnetic entropy S(B,T)data and direct adiabatic demagnetization tests reveal remarkable cooling performance at sub-Kelvin temperatures featured by a large volumetric entropy density of 502.2 mJ/K/cm^(3)and a low attainable minimal temperature T_(min)∼168mK from the initial cooling condition of 2K and 6 T,surpassing most Gd-based refrigerants previously documented in temperature ranges of 0.25–4 K.The realized T_(min)∼168mK far below T_(N)∼1.0K in Gd_(3)BWO_(9) is related to the combined effects of magnetic frustration and criticality-enhanced MCE,which together leave substantial magnetic entropy at reduced temperatures by enhancing spin fluctuations.展开更多
High-performance, large-area optical gratings for applications like chirped pulse amplification, gravitational wave astronomy, and X-ray optics require sub-nanometer line placement control over several cm^(2). Electro...High-performance, large-area optical gratings for applications like chirped pulse amplification, gravitational wave astronomy, and X-ray optics require sub-nanometer line placement control over several cm^(2). Electron beam lithography with a variable shaped beam(VSB) is well suited but limited by tool-dependent address grid discretization. We adapted address grid interpolation to the VSB method, reducing the effective placement grid to 25 pm, as confirmed by stray light measurements.展开更多
Introduction: Family planning is one of the pillars of the Safe Motherhood Initiative which is aimed at reducing unwanted pregnancy and maternal death. Objective: To evaluate the uptake, efficacy, and safety profile o...Introduction: Family planning is one of the pillars of the Safe Motherhood Initiative which is aimed at reducing unwanted pregnancy and maternal death. Objective: To evaluate the uptake, efficacy, and safety profile of 68 mg etonogestrel subdermal implant in Alex Ekwueme Federal University Teaching Hospital Abakaliki (AEFUTHA), Ebonyi State. Materials and Methods: A 5-year retrospective descriptive analysis was carried out on 68 mg etonogestrel subdermal implant uptake among family planning attendees in AEFUTHA. The medical records of the clients that had 68 mg etonogestrel subdermal implant insertion were studied. Socio-demographic characteristics, side effects, discontinuation, and reasons for discontinuation were extracted and analyzed. Analysis was done with SPSS version 20. Data obtained were represented using frequency tables and pie chart. Results: During the study period, 2538 women accepted various methods of contraception, 14.3% (364) of the women used Implanon. The mean age of 68 mg etonogestrel subdermal implant users was 30.7 ± 13.4 years with a range of 20 - 44. Multiparous clients constituted 54.5%. The majority (55.2%) had secondary education as their highest level of education. Less than 20% of the acceptors had side effects, the commonest 24 (42.9%) being prolonged menstrual flow and followed by irregular menstrual flow 18 (32.1%). Discontinuation rate was 17.9%;desire to conceive. 40 (61.5%) was the commonest reason for discontinuation. Only one (0.3%) acceptor reported serious itching at the site of insertion. None of the women reported pregnancy during the period of use (Pearl Index = 0). Conclusion: The acceptance rate of 68 mg etonogestrel subdermal implant among the women is low, however, it is found be effective with good continuation rate in the center. Efforts should be made to increase its uptake so as to prevent unwanted pregnancy and associated sequelae.展开更多
Background: Unsafe abortion (USA) is defined as the termination of a non-desired pregnancy, performed by an unqualified person or in an environment without minimum medical standards, or both. It can impact negatively ...Background: Unsafe abortion (USA) is defined as the termination of a non-desired pregnancy, performed by an unqualified person or in an environment without minimum medical standards, or both. It can impact negatively the fertility in the future by tubo-peritoneal lesions. The current study aimed to highlight the infertility factors associated with USA. Material and Methods: From January 1st 2000 to December 31st 2021, a total of 3876 patients that sought care for infertility in the University Clinic of Kinshasa and the Edith Medical Center were enrolled. The socio-demographic, clinical and paraclinical variables were recorded and analyzed in relation to USA history. Results: The patients’ average age was 33.4 ± 5.7 years. Half of them were housewives;about sixty percent of the patients were nulliparous (59.31%). Seventy percent had a secondary infertility with 43.33% having a history of unsafe abortion. The main diagnosis was genital infections and uterus myoma. The chronic endometritis, bilateral tubal occlusion and Uterine synechiae were more associated with USA group. The spermogram anomalies and other partners’ lesions seemed of infectious origin. Conclusion: The USA remains a more frequent phenomenon in our setting. The chronic endometritis, bilateral tubal occlusion, uterine synechiae and indirectly uterus myoma were the infertility factors related to USA. The genital infection of any origin seems to be the main denominator underlying the female and the male infertility in our setting.展开更多
On the basis of introducing the fundamental theory and the basic analysis steps of the sub model method, the strength of the new engine complex assembly structure was analyzed according to the properties of the engin...On the basis of introducing the fundamental theory and the basic analysis steps of the sub model method, the strength of the new engine complex assembly structure was analyzed according to the properties of the engine structures, some of the key parts of the engine were analyzed with refined mesh by sub model method and the error of the FEM solution was estimated by the extrapolation method. The example showed that the sub model can not only analyze the comlex structures without the restriction of the software and hardware of the computers, but get the more precise analysis result also. This method is more suitable for the strength analysis of the complex assembly structure.展开更多
基金supported by National Natural Science Foundation of China(No.52077081)Guangdong Basic and Applied Basic Research Foundation(No.2022A1515011608).
文摘When disturbed, the interaction between power grid and wind farm may cause serious sub/super-synchronous oscillation (SSO), affecting the security and stability of the system. It is therefore important to detect the time-varying amplitude and frequency of SSO to provide information for its control. The matching synchroextracting wavelet transform (MSEWT) is a new method proposed in this paper to serve this purpose. Based on the original synchrosqueezing wavelet transform, MSEWT uses a synchronous extraction operator to calculate the time-frequency coefficients and a chirp-rate estimation to modify the instantaneous frequency estimation. Thus, MSEWT can improve the concentration degree and reconstruction accuracy of the signal's time-frequency representation without iterative calculation, and can achieve superior noise robustness. After the time-frequency analysis and modal decomposition of the SSO by MSEWT, the amplitudes and frequencies of each oscillation component can be obtained by Hilbert transform (HT). The simulation studies demonstrate that the proposed scheme can accurately identify the modal parameters of SSO even in the case of noise interference, providing a reliable reference for stable operation of power system time-frequency.
文摘Correction to:Nano-Micro Letters(2025)17:123 https://doi.org/10.1007/s40820-025-01654-y Following publication of the original article[1],the authors reported that Dr.Mohamed Bououdina’s affiliation needed to be corrected from 1 to 2.The correct author affiliation has been provided in this Correction and the original article[1]has been corrected.
基金supported by the National Key Research and Development Program(Grant Nos.2024YFA1611200 and 2023YFA1406500)the National Natural Science Foundation of China(Grant Nos.12141002 and 52088101)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB1270000)。
文摘Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large volumetric cooling capacity and reduced working temperatures far below 1K remains a challenge.Here,through ultra-low temperature magnetism and thermodynamic characterizations,we unveil the large magnetocaloric effect(MCE)realized at sub-Kelvin temperatures in the frustrated Kagome antiferromagnet Gd_(3)BWO_(9) with T_(N)∼1.0 K.The isothermal magnetization curves indicate the existence of field(B)induced anisotropic magnetic phase diagrams,where four distinct magnetic phases for B‖c-axis and five magnetic phases for B‖ab-plane are identified at T<T_(N).The analysis of magnetic entropy S(B,T)data and direct adiabatic demagnetization tests reveal remarkable cooling performance at sub-Kelvin temperatures featured by a large volumetric entropy density of 502.2 mJ/K/cm^(3)and a low attainable minimal temperature T_(min)∼168mK from the initial cooling condition of 2K and 6 T,surpassing most Gd-based refrigerants previously documented in temperature ranges of 0.25–4 K.The realized T_(min)∼168mK far below T_(N)∼1.0K in Gd_(3)BWO_(9) is related to the combined effects of magnetic frustration and criticality-enhanced MCE,which together leave substantial magnetic entropy at reduced temperatures by enhancing spin fluctuations.
基金Bundesministerium für Bildung und Forschung(03Z1H534, 13N16028)Deutsche Forschungsgemeinschaft(448663633, 455425131)。
文摘High-performance, large-area optical gratings for applications like chirped pulse amplification, gravitational wave astronomy, and X-ray optics require sub-nanometer line placement control over several cm^(2). Electron beam lithography with a variable shaped beam(VSB) is well suited but limited by tool-dependent address grid discretization. We adapted address grid interpolation to the VSB method, reducing the effective placement grid to 25 pm, as confirmed by stray light measurements.
文摘Introduction: Family planning is one of the pillars of the Safe Motherhood Initiative which is aimed at reducing unwanted pregnancy and maternal death. Objective: To evaluate the uptake, efficacy, and safety profile of 68 mg etonogestrel subdermal implant in Alex Ekwueme Federal University Teaching Hospital Abakaliki (AEFUTHA), Ebonyi State. Materials and Methods: A 5-year retrospective descriptive analysis was carried out on 68 mg etonogestrel subdermal implant uptake among family planning attendees in AEFUTHA. The medical records of the clients that had 68 mg etonogestrel subdermal implant insertion were studied. Socio-demographic characteristics, side effects, discontinuation, and reasons for discontinuation were extracted and analyzed. Analysis was done with SPSS version 20. Data obtained were represented using frequency tables and pie chart. Results: During the study period, 2538 women accepted various methods of contraception, 14.3% (364) of the women used Implanon. The mean age of 68 mg etonogestrel subdermal implant users was 30.7 ± 13.4 years with a range of 20 - 44. Multiparous clients constituted 54.5%. The majority (55.2%) had secondary education as their highest level of education. Less than 20% of the acceptors had side effects, the commonest 24 (42.9%) being prolonged menstrual flow and followed by irregular menstrual flow 18 (32.1%). Discontinuation rate was 17.9%;desire to conceive. 40 (61.5%) was the commonest reason for discontinuation. Only one (0.3%) acceptor reported serious itching at the site of insertion. None of the women reported pregnancy during the period of use (Pearl Index = 0). Conclusion: The acceptance rate of 68 mg etonogestrel subdermal implant among the women is low, however, it is found be effective with good continuation rate in the center. Efforts should be made to increase its uptake so as to prevent unwanted pregnancy and associated sequelae.
文摘Background: Unsafe abortion (USA) is defined as the termination of a non-desired pregnancy, performed by an unqualified person or in an environment without minimum medical standards, or both. It can impact negatively the fertility in the future by tubo-peritoneal lesions. The current study aimed to highlight the infertility factors associated with USA. Material and Methods: From January 1st 2000 to December 31st 2021, a total of 3876 patients that sought care for infertility in the University Clinic of Kinshasa and the Edith Medical Center were enrolled. The socio-demographic, clinical and paraclinical variables were recorded and analyzed in relation to USA history. Results: The patients’ average age was 33.4 ± 5.7 years. Half of them were housewives;about sixty percent of the patients were nulliparous (59.31%). Seventy percent had a secondary infertility with 43.33% having a history of unsafe abortion. The main diagnosis was genital infections and uterus myoma. The chronic endometritis, bilateral tubal occlusion and Uterine synechiae were more associated with USA group. The spermogram anomalies and other partners’ lesions seemed of infectious origin. Conclusion: The USA remains a more frequent phenomenon in our setting. The chronic endometritis, bilateral tubal occlusion, uterine synechiae and indirectly uterus myoma were the infertility factors related to USA. The genital infection of any origin seems to be the main denominator underlying the female and the male infertility in our setting.
文摘On the basis of introducing the fundamental theory and the basic analysis steps of the sub model method, the strength of the new engine complex assembly structure was analyzed according to the properties of the engine structures, some of the key parts of the engine were analyzed with refined mesh by sub model method and the error of the FEM solution was estimated by the extrapolation method. The example showed that the sub model can not only analyze the comlex structures without the restriction of the software and hardware of the computers, but get the more precise analysis result also. This method is more suitable for the strength analysis of the complex assembly structure.
