As prestressed concrete(PC)structures age,long-termeffects,e.g.,creep,shrinkage,and prestress losses,compromise their structural performance.Strengthening these aged PC beams has become a crucial matter.One effective ...As prestressed concrete(PC)structures age,long-termeffects,e.g.,creep,shrinkage,and prestress losses,compromise their structural performance.Strengthening these aged PC beams has become a crucial matter.One effective solution is to use externally bonded fiber-reinforced polymer(FRP)sheets;however,limited research has been done on aged PC beams using the FRP,especially for beams with unbonded prestressing strands(UPC beams).Therefore,this research investigates the flexural strengthening efficacy of external FRP sheets on aged UPC beams with unbonded tendons.Aging minimally affected the failure modes of UPC beams,with nonstrengthened beams showing flexural failure via rebar yielding and concrete crushing,and FRP-strengthened beams failing due to FRP debonding and tensile reinforcement yielding,though tendons in the aged beams did not yield due to prestress losses,unlike the new beams.The U-wrap anchor curbed widespread debonding,leading to tensile reinforcement yielding and FRP rupture.Aging hastened crack growth and stiffness loss,increasing deflections and reducing load resistance,but FRP reinforcement mitigated these effects,enhancing cracking resistance by 14%over the unstrengthened aged beams and 7%over the new beams while boosting ultimate resistance by 9%above the non-strengthened new beams.Compared to the new FRP-strengthened beams,the aged counterparts had lower cracking resistance,stiffness and capacity—showing 20%higher deflections,7–9%lower serviceability loads,7%–17%reduced ultimate strength and 17%less deformability—due to prestress losses and premature FRP debonding.展开更多
Closing a single nozzle or multiple nozzles for a temporary casting operation(fewer strands casting)was common in a tundish due to insufficient molten steel or equipment failure.However,nozzle clogging usually happens...Closing a single nozzle or multiple nozzles for a temporary casting operation(fewer strands casting)was common in a tundish due to insufficient molten steel or equipment failure.However,nozzle clogging usually happens under the situation of fewer strands casting.Hence,a temperature deviation index was introduced to characterize the temperature stratification of molten steel for a large capacity tundish,and a new calculation method of residence time curve was used to describe the different flow types of molten steel at each outlet.Based on hydraulics experiment and numerical simulation,important parameters of present case and modified case were compared.Under the situation of fewer strands casting,the proportion of internal-recycle flow after modification decreased from 30.68%to 24.55%;the standard deviation of the response time reduced from 27.59 to 13.16,and the interquartile range of temperature deviation index changed from 0.89 to 0.27.展开更多
Harmonic thermoelastic waves in helical strands with Maxwell–Cattaneo heat conduction areinvestigated analytically and numerically. The corresponding dispersion relation is a sixth-orderalgebraic equation, governed b...Harmonic thermoelastic waves in helical strands with Maxwell–Cattaneo heat conduction areinvestigated analytically and numerically. The corresponding dispersion relation is a sixth-orderalgebraic equation, governed by six non-dimensional parameters: two thermoelastic couplingconstants, one chirality parameter, the ratio between extensional and torsional moduli, the Fouriernumber, and the dimensionless thermal relaxation. The behavior of the solutions is discussedfrom two perspectives with an asymptotic-numerical approach: (1) the effect of thermal relaxationon the elastic wave celerities, and (2) the effect of thermoelastic coupling on the thermal wavecelerities. With small wavenumbers, the adiabatic solution for Fourier helical strands is recovered.However, with large wavenumbers, the solutions behave differently depending on the thermalrelaxation and chirality. Due to thermoelastic coupling, the thermal wave celerity deviates from theclassical result of the speed of second sound.展开更多
Compact-siro spinning is a new kind of spinning technique which combines compact spinning and siro spinning,and widely put into practice. Based on the airflow data in the condensing zone,it builds the geometrical mode...Compact-siro spinning is a new kind of spinning technique which combines compact spinning and siro spinning,and widely put into practice. Based on the airflow data in the condensing zone,it builds the geometrical model of fiber strands,and then the trajectory of single fiber can be got. The difference of trajectory and compact effect of fibers strands is also analyzed in the condensing zone of three different suction slots. By comparing with the data of three different suction slots,it selects the compact-siro spinning suction device whose yarn has the best overall performance. The theory analysis gives foundation and explanation for experiment,and also provides theoretical basis for optimizing the properties of compactsiro yarn in production practice.展开更多
Ultrasonic guided wave inspection is an effective non-destructive testing method which can be used for stress level evaluation in steel strands.Unfortunately the propagation velocity of ultrasonic guided waves changes...Ultrasonic guided wave inspection is an effective non-destructive testing method which can be used for stress level evaluation in steel strands.Unfortunately the propagation velocity of ultrasonic guided waves changes due to temperature shift making the prestress measurement of steel strands inaccurate and even sometimes impossible.In the course of solving the problem,this paper reports on quantitative research on the temperature dependence of ultrasonic longitudinal guided wave propagation in long range steel strands.In order to achieve the generation and reception of a chosen longitudinal mode in a steel strand with a helical shaped surface,a new type of magnetostrictive transducer was developed,characterized by a group of thin clips and three identical permanent magnets.Excitation and reception of ultrasonic guided waves in a steel strand were performed experimentally.Experimental results shows that in the temperature range from-4 ℃ to 34 ℃,the propagation velocity of the L（0,1） mode at 160 kHz linearly decreased with increasing temperature and its temperature dependent coefficient was 0.90（m·s-1 ·（℃）-1） which is very close to the theoretical prediction.The effect of dimension deviation between the helical and center wires and the effect of the thermal expansion of the steel strand on ultrasonic longitudinal guided wave propagation were also analyzed.It was found that these effects could be ignored compared with the change in the material mechanical properties of the steel strands due to temperature shift.It was also observed that the longitudinal guided wave mode was somewhat more sensitive to temperature changes compared with conventional ultrasonic waves theoretically.Therefore,it is considered that the temperature effect on ultrasonic longitudinal guided wave propagation in order to improve the accuracy of stress measurement in prestressed steel strands.Quantitative research on the temperature dependence of ultrasonic guided wave propagation in steel strands provides an important basis for the compensation of temperature effects in stress measurement in steel strands by using ultrasonic guided wave inspection.展开更多
Herein,we report a new technique that consists of placing two 125 I seed strands and two stents in the right and left intrahepatic bile ducts for the treatment of hilar cholangiocarcinoma.A 75-year-old man presented w...Herein,we report a new technique that consists of placing two 125 I seed strands and two stents in the right and left intrahepatic bile ducts for the treatment of hilar cholangiocarcinoma.A 75-year-old man presented with jaundice and was diagnosed with Bismuth type Ⅳ Klatskin tumor.Abdominal computed tomography(CT) showed intrahepatic and extrahepatic bile ductdilatation and a soft tissue mass in the hepatic hilum.Because curative surgical resection was not possible,we placed 125 I seed strands and stents in the right and left intrahepatic bile ducts.Three months later,abdominal CT showed less intrahepatic and extrahepatic bile duct dilatation than before the procedure.This technique was feasible and could be considered for the treatment of patients with Bismuth type Ⅳ tumors.展开更多
Propagation characteristics of high order longitudinal modes of ultrasonic guided waves in seven-wire steel strands are investigated theoretically and experimentally. According to these analysis results, proper longit...Propagation characteristics of high order longitudinal modes of ultrasonic guided waves in seven-wire steel strands are investigated theoretically and experimentally. According to these analysis results, proper longitudinal modes are selected for defect detection in steel strands. Dispersion curves for helical and central wires in a 17.80 mm nominal diameter seven-wire steel strand are numerically obtained firstly, and propagation characteristics of high-order longitudinal modes, such as wave structures, attenuation and dispersion, are analyzed. In experiments, the signals of ultrasonic guided wave at different high frequencies are excited and received at one end of a steel strand by using the same single piezoelectric transducer. The identification of longitudinal modes in the received signals is achieved based on short time Fourier transform. Furthermore, appropriate L（0, 5） mode at 2.54 MHz is chosen for detecting an artificial defect in a helical wire of the steel strand. Results show that high order longitudinal modes in a high frequency range with low dispersion and attenuation whose energy propagates mainly in the center of the wires can be used for defect detection in long range steel strands.展开更多
Steel wire ropes have wide application in a variety of engineering fields such as ocean engineering and civil engineering.The stress calculation for steel wire ropes is of crucial importance when conducting strength a...Steel wire ropes have wide application in a variety of engineering fields such as ocean engineering and civil engineering.The stress calculation for steel wire ropes is of crucial importance when conducting strength and fatigue analyses.In this study,we performed a finite element analysis of single-strand steel wire ropes.For the geometric modeling,we used an analytic geometry of space method.We established helical line equations and used the coordinates of the contact points.The finite-element model was simplified using the periodic law.Periodic boundary conditions were used to simulate a wire strand of infinite length under tensile strain,for which we calculated the cross-sectional stresses and inner forces.The results showed that bending and torsion moments emerged when the wire strand was under tensile load.In some cases,the bending stress reached 18%of the tensile stress,and the torsion stress reached 29%of the tensile stress,which means that the total stress was higher than the nominal stress.Whereas in ear-lier studies,a conservative prediction of nominal stress was not possible,the results of our strength and fatigue analyses were more conservative.展开更多
A theoretical model is proposed to calculate the internal contact distributions and contact forces of a 3×4×4×4 twisted NbSn cable under applied axial strain.The critical current density reduction of th...A theoretical model is proposed to calculate the internal contact distributions and contact forces of a 3×4×4×4 twisted NbSn cable under applied axial strain.The critical current density reduction of the whole cable can be calculated.The thin rod theory is employed to analyze the mechanical behavior of each strand.According to the regular helical structure,the contact distribution of each strand is obtained,and the contact force in the cable is analyzed.At last,a prediction about the critical current density of the twisted cable is made.The results show that decreasing the pitch length can reduce the contact forces between strands.展开更多
This paper describes a general model for the mechanical behavior studying of general wire rope strand. An exact solution of the deformation characteristics was given when the strands is under tensile and torsional loa...This paper describes a general model for the mechanical behavior studying of general wire rope strand. An exact solution of the deformation characteristics was given when the strands is under tensile and torsional loads. The theoretical results are useful in evaluating the extensional and torsional moduli of rigidity for the strands. Finally, a simple design criterion is establised for the nonrotating ropes.展开更多
From the beginning of 1970’s,the research work onstrand current distribution in hydro-generator statorbars has been made marked progress in China.In order to know whythe generator bar insulations were broken down so ...From the beginning of 1970’s,the research work onstrand current distribution in hydro-generator statorbars has been made marked progress in China.In order to know whythe generator bar insulations were broken down so often both in op-eration and in testing after the generators being put into operation for8-10 years at Xinanjiang Hydropower Station.Investigations wereconducted and the results of field measurement showed that展开更多
Four sets of mono-element (ME) and two kinds of multifilament (MF) internal-Sn Nb3Sn superconducting strands were designed and fabricated through RRP method in which different compoment ratios, various composite confi...Four sets of mono-element (ME) and two kinds of multifilament (MF) internal-Sn Nb3Sn superconducting strands were designed and fabricated through RRP method in which different compoment ratios, various composite configurations and some third element alloying were arranged. All the strand samples underwent a 210°C/50 h + 340°C/25 h thermal duration for Cu-Sn alloying. After that A15 phase formation heat treatment (HT) was applied for which the ME samples were chosen at three reaction temperatures of 675°C, 700°C and 725°C for 100 h and 200 h while the MF samples at four temperatures of 650°C, 675°C, 700°C and 725°C for 128 h and 200 h. The heat-treated samples were examined for A15 phase composition distribution by X-ray EDS. SQUID magnetization measurement was used to determine critical temperature TC. The obtained results demonstrate that for fully-reacted internal-Sn Nb3Sn superconductors the A15 phase composition and the intrinsic property TC are determined by the diffusion and solid state reaction mechanism and are independent of the factors including HT temperature, strand composite component and configuration arrangement, and the third element addition within the experimental range.展开更多
Background and Aims:Hepatitis C virus(HCV)hepatotropism is associated with intra-peripheral blood mononuclear cell(PBMC)infection that causes post-treatment relapse in RNA seronegative patients.Our understanding of th...Background and Aims:Hepatitis C virus(HCV)hepatotropism is associated with intra-peripheral blood mononuclear cell(PBMC)infection that causes post-treatment relapse in RNA seronegative patients.Our understanding of the association of non-viremic hepatic fibrosis with positive anti-HCV IgG antibodies and active hepatocellular damage might be increased by PBMCs screening for intracellular infection.Thus,the goals of this study included evaluation of PBMCs PCR for diagnosing HCV infection,addressing PBMCs plus serum real-time(SRT)PCR benefits over SRT-PCR alone,studying intraPBMCs distribution of RNA sense and antisense strands,and identifying treatment feasibility in solitary intracellular infection.Methods:Enzyme-linked immunosorbent assay,SRT-PCR and PBMCs PCR were used to evaluate HCV infection in 401 subjects.The patients were classified into groups of negative controls(n=30),positive controls(n=63),non-viremia post-treatment(experienced;n=166)and na(i)ve(n=49)cases,and non-viremia positive PBMCs PCR na(i)ve(n=35)and experienced(n=58)patients.Results:The diagnosis of true positive and negative by PBMCs PCR and SRT-PCR had 100%and 96.7%compatibility respectively.PBMCs PCR detected intracellular HCV infection in 49 out of 215 non-viremia patients;among them,na(i)ve cirrhotics had significantly higher number of intracellular infection than the na(i)ve non-cirrhotic(P<0.001)and experienced patients(P<0.0001).Antisense and sense strands were respectively recognized in na(i)ve and experienced cases(P=0.01218).Intracellular HCV strands were detected in 18.02%of experienced patients.Recognition of intracellular RNA strands showed significant decline in experienced compared to na(i)ve patients(P<0.05).Conclusion:PBMCs PCR is a valid diagnostic test that can diagnose intracellular HCV when SRT-PCR is negative.Antisense and sense strands are respectively recognized more often in na(i)ve and experienced patients.The expected overall relapsing rate in our cohort was 18.02%.IntraPBMC infections are associated with liver cirrhosis in na(i)ve non-viremia patients.Eradication of intracellular strands is recommended to avoid RNA seroconversion.展开更多
For the development of high‐temperature superconducting(HTS)magnet systems of future fusion devices,a novel HTS round strand based on a stacking structure was designed and manufactured using second generation(2G)HTS ...For the development of high‐temperature superconducting(HTS)magnet systems of future fusion devices,a novel HTS round strand based on a stacking structure was designed and manufactured using second generation(2G)HTS tapes.Different mechanical loads during operation can result in irreversible degradation of the strand.The axial tension and fatigue loads need particular attention.Therefore,it is important to investigate the electromechanical behavior of the round strand under various axial tension and cyclic loads.In this paper,the axial tensile and fatigue tests were conducted at 77 K,self‐field.Taking 95%critical current(I_(c))retention as the criterion,the results of the tensile tests revealed that the average tensile stress and strain were as high as 344 MPa and 0.47%,respectively.Fatigue characteristics were also investigated as a function of axial tensile stress.No significant performance degradation was observed up to 100,000 loading cycles with stress amplitudes ranging from 20 MPa to 200 MPa.Ic degradation occurs after 16,000 loading cycles with 380 MPa as the maximum stress.Furthermore,the microscopic defects of the round strand samples due to fabrication imperfections and mechanical loading were investigated using metallographic microscope and scanning electron microscope.These results presented in this paper are useful for comprehending and improving the mechanical behaviors of the strand in high‐field and large‐scale fusion magnet systems.展开更多
T Parallel wire strands(PWSs),which are widely used in prestressed steel structures,are typically in highstress states.Under fire conditions,significant creep effects occur,reducing the prestress and influencing the m...T Parallel wire strands(PWSs),which are widely used in prestressed steel structures,are typically in highstress states.Under fire conditions,significant creep effects occur,reducing the prestress and influencing the mechanical behavior of PWSs.As there is no existing approach to analyze their creep behavior,this study experimentally investigated the elevated temperature creep model of PWSs.A charge-coupled camera system was incorporated to accurately obtain the deformation of the specimen during the elevated temperature creep test.It was concluded that the temperature level had a more significant effect on the creep strain than the stress level,and 450℃ was the key segment point where the creep rate varied significantly.By comparing the elevated temperature creep test results for PWSs and steel strands,it was found that the creep strain of PWSs was lower than that of steel strands at the same temperature and stress levels.The parameters in the general empirical formula,the Bailey–Norton model,and the composite timehardening model were fitted based on the experimental results.By evaluating the accuracy and form of the models,the composite time-hardening model,which can simultaneously consider temperature,stress,and time,is recommended for use in the fire-resistance design of pre-tensioned structures with PWSs.展开更多
Finless porpoises(FPs)serve as flagship species and key ecological indicators for assessing environmental quality.However,FPs are challenging to survey due to their elusive behavior and lack of distinctive features.St...Finless porpoises(FPs)serve as flagship species and key ecological indicators for assessing environmental quality.However,FPs are challenging to survey due to their elusive behavior and lack of distinctive features.Stranding and sighting events offer essential information on species diversity,distribution patterns,and potential threats.In this study,records from 1986 to 2023 were analyzed to assess the temporal and spatial distribution patterns of FP strandings and sightings in the Qiantang River Estuary,China.Results show an increase in the number of recorded events over time.Seasonal variations were evident,with a peak in strandings and sightings occurring in late winter.The frequency of records was higher during spring and moderate tides compared to neap tides,particularly in hydrologically normal years.Rapidly receding tides and sediment accumulation appear to restrict the activity space of FPs,thereby increasing the frequency of these events.Localized conditions associated with stranding and sighting events were classified into four categories:bifurcation zones,confluence zones,separation zones,and deep channels adjacent to concave banks.Deep channels,which are optimal for shipping,also elevate the risk of FP strandings.These findings offer valuable insights for the development and design of conservation strategies tailored to the needs of FPs in estuarine environments.展开更多
Crosstalk between the nervous system and cancer plays an important role in tumor metastasis yet is poorly understood.Recently,Padmanaban et al.demonstrated a novel mechanism for nerve-induced metastasis.Sensory nerve-...Crosstalk between the nervous system and cancer plays an important role in tumor metastasis yet is poorly understood.Recently,Padmanaban et al.demonstrated a novel mechanism for nerve-induced metastasis.Sensory nerve-derived substance P could induce apoptosis in breast cancer cells that overexpressed tachykinin receptors.Single-stranded RNAs(ssRNAs)leaking from dying cells subsequently interact with toll-like receptor 7(TLR7)on other cancer cells and finally promoted metastasis.This notable study displays a delicate loop between the nervous system and cancer and,more importantly,amplifies the conception of apoptosis-induced metastasis.Over the past years,a mass of breakthrough studies have proven the pivotal role of the nervous system in tumorigenesis and cancer progression thereby contributing to the creation of a new disciplinecancer neuroscience[1].Hanahan and Monje discussed in detail the interactions between the nervous system and tumors based on the theoretical framework of the cancer hallmarks,focused on nerve-mediated proliferation,angiogenesis,immune evasion,cell death resistance,and metastasis[2].展开更多
To tackle the issue of notch frequency and center frequency drift of the L(0,1)mode guided wave in ultra⁃sonic guided wave⁃based stress monitoring of prestressed steel strands,a method using higher⁃order mode plateau ...To tackle the issue of notch frequency and center frequency drift of the L(0,1)mode guided wave in ultra⁃sonic guided wave⁃based stress monitoring of prestressed steel strands,a method using higher⁃order mode plateau fre⁃quencies is adopted.First,the correlation between group velocity peaks and phase velocities at these plateau frequen⁃cies is analyzed.This analysis establishes a quantitative rela⁃tionship between phase velocity and stress in the steel strand,providing a theoretical foundation for stress monitor⁃ing.Then the two⁃dimensional Fourier transform is em⁃ployed to separate wave modes.Dynamic programming techniques are applied in the frequency⁃velocity domain to extract higher⁃order modes.By identifying the group veloc⁃ity peaks of these separated higher⁃order modes,the plateau frequencies of guided waves are determined,enabling indi⁃rect measurement of stress in the steel strand.To validate this method,finite element simulations are conducted under three scenarios.Results show that the higher⁃order modes of transient signals from three different positions can be ac⁃curately extracted,leading to successful cable stress moni⁃toring.This approach effectively circumvents the issue of guided wave frequency drift and improves stress monitoring accuracy.Consequently,it significantly improves the appli⁃cation of ultrasonic guided wave technology in structural health monitoring.展开更多
BACKGROUND Accurate preoperative T staging is essential for determining optimal treatment strategies in colorectal cancer(CRC).Low-keV virtual monoenergetic images(VMIs)have been shown to enhance lesion conspicuity.Th...BACKGROUND Accurate preoperative T staging is essential for determining optimal treatment strategies in colorectal cancer(CRC).Low-keV virtual monoenergetic images(VMIs)have been shown to enhance lesion conspicuity.This study aimed to assess the diagnostic value of dual-layer spectral computed tomography(CT)-derived VMIs,in combination with multiplanar reformation(MPR)and evaluation of peritumoral fat stranding(PFS),for improving the accuracy of T staging in CRC.AIM To assess the diagnostic performance of dual-layer spectral CT(DLSCT)VMIs,particularly at low energy levels,and their integration with personalized MPR for preoperative T staging of CRC.METHODS In this retrospective study,157 patients with pathologically confirmed CRC(mean age:63.5±12.1 years)underwent DLSCT within 1 week before surgery.VMIs ranging from 40 keV to 70 keV(at 10 keV intervals)and conventional polyenergetic images(PEIs)were reconstructed.Objective image quality parameters,including image noise,signal-to-noise ratio(SNR),and contrast-to-noise ratio(CNR),were quantified,alongside subjective image quality scores using a 5-point Likert scale.Interobserver agreement was evaluated usingκstatistics.Taking histopathology as the reference standard,the diagnostic accuracy of T staging(T1-2 vs T3-4)was compared across PEIs and VMIs,both with and without MPR and PFS.RESULTS Low-keV VMIs(40-70 keV)demonstrated significantly higher SNR and CNR than PEIs(all P<0.001).Notably,40-keV VMIs achieved noise levels comparable to PEIs(8.17±3.63 vs 8.53±2.90;P=0.673).Subjective image quality peaked at 40-50 keV VMIs(Likert scores 4.85-4.88 vs 3.97 for PEIs;P<0.001),supported by excellent interobserver agreement(κ=0.812-0.913).The combination of 40-50 keV VMIs with MPR yielded the highest T staging accuracy(94.27%)compared to axial PEIs(70.7%),with a sensitivity and specificity of 83.87%and 96.83%,respectively(Youden index=0.81;P<0.05).While PFS enhanced staging accuracy on PEIs(up to 77.07%with MPR),it provided no significant additional benefit for VMIs.CONCLUSION DLSCT VMIs at 40-50 keV significantly enhanced image quality and improved preoperative T staging accuracy of CRC when combined with MPR.These findings underscored the clinical value of low-keV spectral imaging in tailoring individualized treatment strategies.展开更多
基金support by the Ministry of Education and Training of Vietnam for this research,under grant no.B2023-MBS-02.
文摘As prestressed concrete(PC)structures age,long-termeffects,e.g.,creep,shrinkage,and prestress losses,compromise their structural performance.Strengthening these aged PC beams has become a crucial matter.One effective solution is to use externally bonded fiber-reinforced polymer(FRP)sheets;however,limited research has been done on aged PC beams using the FRP,especially for beams with unbonded prestressing strands(UPC beams).Therefore,this research investigates the flexural strengthening efficacy of external FRP sheets on aged UPC beams with unbonded tendons.Aging minimally affected the failure modes of UPC beams,with nonstrengthened beams showing flexural failure via rebar yielding and concrete crushing,and FRP-strengthened beams failing due to FRP debonding and tensile reinforcement yielding,though tendons in the aged beams did not yield due to prestress losses,unlike the new beams.The U-wrap anchor curbed widespread debonding,leading to tensile reinforcement yielding and FRP rupture.Aging hastened crack growth and stiffness loss,increasing deflections and reducing load resistance,but FRP reinforcement mitigated these effects,enhancing cracking resistance by 14%over the unstrengthened aged beams and 7%over the new beams while boosting ultimate resistance by 9%above the non-strengthened new beams.Compared to the new FRP-strengthened beams,the aged counterparts had lower cracking resistance,stiffness and capacity—showing 20%higher deflections,7–9%lower serviceability loads,7%–17%reduced ultimate strength and 17%less deformability—due to prestress losses and premature FRP debonding.
基金the National Natural Science Foundation of China(Grant No.51774031).
文摘Closing a single nozzle or multiple nozzles for a temporary casting operation(fewer strands casting)was common in a tundish due to insufficient molten steel or equipment failure.However,nozzle clogging usually happens under the situation of fewer strands casting.Hence,a temperature deviation index was introduced to characterize the temperature stratification of molten steel for a large capacity tundish,and a new calculation method of residence time curve was used to describe the different flow types of molten steel at each outlet.Based on hydraulics experiment and numerical simulation,important parameters of present case and modified case were compared.Under the situation of fewer strands casting,the proportion of internal-recycle flow after modification decreased from 30.68%to 24.55%;the standard deviation of the response time reduced from 27.59 to 13.16,and the interquartile range of temperature deviation index changed from 0.89 to 0.27.
基金supported by the National Science Foundation of United States (Grants IIP-1362146 and CMMI-1462749)
文摘Harmonic thermoelastic waves in helical strands with Maxwell–Cattaneo heat conduction areinvestigated analytically and numerically. The corresponding dispersion relation is a sixth-orderalgebraic equation, governed by six non-dimensional parameters: two thermoelastic couplingconstants, one chirality parameter, the ratio between extensional and torsional moduli, the Fouriernumber, and the dimensionless thermal relaxation. The behavior of the solutions is discussedfrom two perspectives with an asymptotic-numerical approach: (1) the effect of thermal relaxationon the elastic wave celerities, and (2) the effect of thermoelastic coupling on the thermal wavecelerities. With small wavenumbers, the adiabatic solution for Fourier helical strands is recovered.However, with large wavenumbers, the solutions behave differently depending on the thermalrelaxation and chirality. Due to thermoelastic coupling, the thermal wave celerity deviates from theclassical result of the speed of second sound.
基金Fundamental Research Funds for the Central Universities(Nos.CUSF-DH-D-2015002,2232014D3-01)Shanghai Natural Science Foundation,China(No13ZR1400900)Key Grant Project of Chinese M inistry of Education(No.113027A)
文摘Compact-siro spinning is a new kind of spinning technique which combines compact spinning and siro spinning,and widely put into practice. Based on the airflow data in the condensing zone,it builds the geometrical model of fiber strands,and then the trajectory of single fiber can be got. The difference of trajectory and compact effect of fibers strands is also analyzed in the condensing zone of three different suction slots. By comparing with the data of three different suction slots,it selects the compact-siro spinning suction device whose yarn has the best overall performance. The theory analysis gives foundation and explanation for experiment,and also provides theoretical basis for optimizing the properties of compactsiro yarn in production practice.
基金supported by National Natural Science Foundation of China (Grant No. 10602004,Grant No. 50975006)Beijing Municipal Natural Science Foundation of China (Grant No. 2072003)+1 种基金Beijing Municipal Talent Developing Project of China (Grant No.20081B0501500173)Beijing Municipal Nova Program of China(Grant No. 2008A015)
文摘Ultrasonic guided wave inspection is an effective non-destructive testing method which can be used for stress level evaluation in steel strands.Unfortunately the propagation velocity of ultrasonic guided waves changes due to temperature shift making the prestress measurement of steel strands inaccurate and even sometimes impossible.In the course of solving the problem,this paper reports on quantitative research on the temperature dependence of ultrasonic longitudinal guided wave propagation in long range steel strands.In order to achieve the generation and reception of a chosen longitudinal mode in a steel strand with a helical shaped surface,a new type of magnetostrictive transducer was developed,characterized by a group of thin clips and three identical permanent magnets.Excitation and reception of ultrasonic guided waves in a steel strand were performed experimentally.Experimental results shows that in the temperature range from-4 ℃ to 34 ℃,the propagation velocity of the L（0,1） mode at 160 kHz linearly decreased with increasing temperature and its temperature dependent coefficient was 0.90（m·s-1 ·（℃）-1） which is very close to the theoretical prediction.The effect of dimension deviation between the helical and center wires and the effect of the thermal expansion of the steel strand on ultrasonic longitudinal guided wave propagation were also analyzed.It was found that these effects could be ignored compared with the change in the material mechanical properties of the steel strands due to temperature shift.It was also observed that the longitudinal guided wave mode was somewhat more sensitive to temperature changes compared with conventional ultrasonic waves theoretically.Therefore,it is considered that the temperature effect on ultrasonic longitudinal guided wave propagation in order to improve the accuracy of stress measurement in prestressed steel strands.Quantitative research on the temperature dependence of ultrasonic guided wave propagation in steel strands provides an important basis for the compensation of temperature effects in stress measurement in steel strands by using ultrasonic guided wave inspection.
基金Supported by Peak of Six Personnel in Jiangsu Province,No.2013-WSN-038
文摘Herein,we report a new technique that consists of placing two 125 I seed strands and two stents in the right and left intrahepatic bile ducts for the treatment of hilar cholangiocarcinoma.A 75-year-old man presented with jaundice and was diagnosed with Bismuth type Ⅳ Klatskin tumor.Abdominal computed tomography(CT) showed intrahepatic and extrahepatic bile ductdilatation and a soft tissue mass in the hepatic hilum.Because curative surgical resection was not possible,we placed 125 I seed strands and stents in the right and left intrahepatic bile ducts.Three months later,abdominal CT showed less intrahepatic and extrahepatic bile duct dilatation than before the procedure.This technique was feasible and could be considered for the treatment of patients with Bismuth type Ⅳ tumors.
基金supported by the National Natural Science Foundation of China(No.10602004)Beijing Natural Science Foundation(No.2072003)Beijing Talent Developing Project(No.20081B0501500173).
文摘Propagation characteristics of high order longitudinal modes of ultrasonic guided waves in seven-wire steel strands are investigated theoretically and experimentally. According to these analysis results, proper longitudinal modes are selected for defect detection in steel strands. Dispersion curves for helical and central wires in a 17.80 mm nominal diameter seven-wire steel strand are numerically obtained firstly, and propagation characteristics of high-order longitudinal modes, such as wave structures, attenuation and dispersion, are analyzed. In experiments, the signals of ultrasonic guided wave at different high frequencies are excited and received at one end of a steel strand by using the same single piezoelectric transducer. The identification of longitudinal modes in the received signals is achieved based on short time Fourier transform. Furthermore, appropriate L（0, 5） mode at 2.54 MHz is chosen for detecting an artificial defect in a helical wire of the steel strand. Results show that high order longitudinal modes in a high frequency range with low dispersion and attenuation whose energy propagates mainly in the center of the wires can be used for defect detection in long range steel strands.
基金funded by the National Natural Science Foundation of China(No.51879188)the Key R&D Project of Hebei Province(No.1827350D).
文摘Steel wire ropes have wide application in a variety of engineering fields such as ocean engineering and civil engineering.The stress calculation for steel wire ropes is of crucial importance when conducting strength and fatigue analyses.In this study,we performed a finite element analysis of single-strand steel wire ropes.For the geometric modeling,we used an analytic geometry of space method.We established helical line equations and used the coordinates of the contact points.The finite-element model was simplified using the periodic law.Periodic boundary conditions were used to simulate a wire strand of infinite length under tensile strain,for which we calculated the cross-sectional stresses and inner forces.The results showed that bending and torsion moments emerged when the wire strand was under tensile load.In some cases,the bending stress reached 18%of the tensile stress,and the torsion stress reached 29%of the tensile stress,which means that the total stress was higher than the nominal stress.Whereas in ear-lier studies,a conservative prediction of nominal stress was not possible,the results of our strength and fatigue analyses were more conservative.
基金Project supported by the National Natural Science Foundation of China(Nos.11202087,11472120 and 11421062)the National Key Project of Magneto-Constrained Fusion Energy Development Program(No.2013GB110002)+1 种基金the National Key Project of Scientific Instrument and Equipment Development(No.11327802)New Century Excellent Talents in University of Ministry of Education of China(NCET-13-0266)
文摘A theoretical model is proposed to calculate the internal contact distributions and contact forces of a 3×4×4×4 twisted NbSn cable under applied axial strain.The critical current density reduction of the whole cable can be calculated.The thin rod theory is employed to analyze the mechanical behavior of each strand.According to the regular helical structure,the contact distribution of each strand is obtained,and the contact force in the cable is analyzed.At last,a prediction about the critical current density of the twisted cable is made.The results show that decreasing the pitch length can reduce the contact forces between strands.
文摘This paper describes a general model for the mechanical behavior studying of general wire rope strand. An exact solution of the deformation characteristics was given when the strands is under tensile and torsional loads. The theoretical results are useful in evaluating the extensional and torsional moduli of rigidity for the strands. Finally, a simple design criterion is establised for the nonrotating ropes.
文摘From the beginning of 1970’s,the research work onstrand current distribution in hydro-generator statorbars has been made marked progress in China.In order to know whythe generator bar insulations were broken down so often both in op-eration and in testing after the generators being put into operation for8-10 years at Xinanjiang Hydropower Station.Investigations wereconducted and the results of field measurement showed that
基金supported by the France-China Collaboration Research Contract: CNRS No722441the SUST doctoral foundation BJ07-07
文摘Four sets of mono-element (ME) and two kinds of multifilament (MF) internal-Sn Nb3Sn superconducting strands were designed and fabricated through RRP method in which different compoment ratios, various composite configurations and some third element alloying were arranged. All the strand samples underwent a 210°C/50 h + 340°C/25 h thermal duration for Cu-Sn alloying. After that A15 phase formation heat treatment (HT) was applied for which the ME samples were chosen at three reaction temperatures of 675°C, 700°C and 725°C for 100 h and 200 h while the MF samples at four temperatures of 650°C, 675°C, 700°C and 725°C for 128 h and 200 h. The heat-treated samples were examined for A15 phase composition distribution by X-ray EDS. SQUID magnetization measurement was used to determine critical temperature TC. The obtained results demonstrate that for fully-reacted internal-Sn Nb3Sn superconductors the A15 phase composition and the intrinsic property TC are determined by the diffusion and solid state reaction mechanism and are independent of the factors including HT temperature, strand composite component and configuration arrangement, and the third element addition within the experimental range.
基金Financial support for this study was provided by the Faculty of Medicine at Al-Azhar University,National Research Centerby the Academy of Scientific Research and Technology Development Fund(Grant 3365,to Mostafa K El Awady)
文摘Background and Aims:Hepatitis C virus(HCV)hepatotropism is associated with intra-peripheral blood mononuclear cell(PBMC)infection that causes post-treatment relapse in RNA seronegative patients.Our understanding of the association of non-viremic hepatic fibrosis with positive anti-HCV IgG antibodies and active hepatocellular damage might be increased by PBMCs screening for intracellular infection.Thus,the goals of this study included evaluation of PBMCs PCR for diagnosing HCV infection,addressing PBMCs plus serum real-time(SRT)PCR benefits over SRT-PCR alone,studying intraPBMCs distribution of RNA sense and antisense strands,and identifying treatment feasibility in solitary intracellular infection.Methods:Enzyme-linked immunosorbent assay,SRT-PCR and PBMCs PCR were used to evaluate HCV infection in 401 subjects.The patients were classified into groups of negative controls(n=30),positive controls(n=63),non-viremia post-treatment(experienced;n=166)and na(i)ve(n=49)cases,and non-viremia positive PBMCs PCR na(i)ve(n=35)and experienced(n=58)patients.Results:The diagnosis of true positive and negative by PBMCs PCR and SRT-PCR had 100%and 96.7%compatibility respectively.PBMCs PCR detected intracellular HCV infection in 49 out of 215 non-viremia patients;among them,na(i)ve cirrhotics had significantly higher number of intracellular infection than the na(i)ve non-cirrhotic(P<0.001)and experienced patients(P<0.0001).Antisense and sense strands were respectively recognized in na(i)ve and experienced cases(P=0.01218).Intracellular HCV strands were detected in 18.02%of experienced patients.Recognition of intracellular RNA strands showed significant decline in experienced compared to na(i)ve patients(P<0.05).Conclusion:PBMCs PCR is a valid diagnostic test that can diagnose intracellular HCV when SRT-PCR is negative.Antisense and sense strands are respectively recognized more often in na(i)ve and experienced patients.The expected overall relapsing rate in our cohort was 18.02%.IntraPBMC infections are associated with liver cirrhosis in na(i)ve non-viremia patients.Eradication of intracellular strands is recommended to avoid RNA seroconversion.
基金supported by the Southwestern Institute of Physics(SWIP)under project number 202101XWCXRZ001 and 2021XWCXRZ002.
文摘For the development of high‐temperature superconducting(HTS)magnet systems of future fusion devices,a novel HTS round strand based on a stacking structure was designed and manufactured using second generation(2G)HTS tapes.Different mechanical loads during operation can result in irreversible degradation of the strand.The axial tension and fatigue loads need particular attention.Therefore,it is important to investigate the electromechanical behavior of the round strand under various axial tension and cyclic loads.In this paper,the axial tensile and fatigue tests were conducted at 77 K,self‐field.Taking 95%critical current(I_(c))retention as the criterion,the results of the tensile tests revealed that the average tensile stress and strain were as high as 344 MPa and 0.47%,respectively.Fatigue characteristics were also investigated as a function of axial tensile stress.No significant performance degradation was observed up to 100,000 loading cycles with stress amplitudes ranging from 20 MPa to 200 MPa.Ic degradation occurs after 16,000 loading cycles with 380 MPa as the maximum stress.Furthermore,the microscopic defects of the round strand samples due to fabrication imperfections and mechanical loading were investigated using metallographic microscope and scanning electron microscope.These results presented in this paper are useful for comprehending and improving the mechanical behaviors of the strand in high‐field and large‐scale fusion magnet systems.
基金support provided by the National Natural Science Foundation of China(Grant No.51878348)the Shanghai Pujiang Program(No.22PJ1414000).
文摘T Parallel wire strands(PWSs),which are widely used in prestressed steel structures,are typically in highstress states.Under fire conditions,significant creep effects occur,reducing the prestress and influencing the mechanical behavior of PWSs.As there is no existing approach to analyze their creep behavior,this study experimentally investigated the elevated temperature creep model of PWSs.A charge-coupled camera system was incorporated to accurately obtain the deformation of the specimen during the elevated temperature creep test.It was concluded that the temperature level had a more significant effect on the creep strain than the stress level,and 450℃ was the key segment point where the creep rate varied significantly.By comparing the elevated temperature creep test results for PWSs and steel strands,it was found that the creep strain of PWSs was lower than that of steel strands at the same temperature and stress levels.The parameters in the general empirical formula,the Bailey–Norton model,and the composite timehardening model were fitted based on the experimental results.By evaluating the accuracy and form of the models,the composite time-hardening model,which can simultaneously consider temperature,stress,and time,is recommended for use in the fire-resistance design of pre-tensioned structures with PWSs.
基金The National Natural Science Foundation of China under contract Nos 42176214 and 42176170the Zhejiang Provincial Natural Science Foundation of China under contract Nos LZJWZ22E090002 and LZJWY22E090006the Key Program of the President of the Zhejiang Institute of Hydraulics and Estuaries under contract No.ZIHE21Z001.
文摘Finless porpoises(FPs)serve as flagship species and key ecological indicators for assessing environmental quality.However,FPs are challenging to survey due to their elusive behavior and lack of distinctive features.Stranding and sighting events offer essential information on species diversity,distribution patterns,and potential threats.In this study,records from 1986 to 2023 were analyzed to assess the temporal and spatial distribution patterns of FP strandings and sightings in the Qiantang River Estuary,China.Results show an increase in the number of recorded events over time.Seasonal variations were evident,with a peak in strandings and sightings occurring in late winter.The frequency of records was higher during spring and moderate tides compared to neap tides,particularly in hydrologically normal years.Rapidly receding tides and sediment accumulation appear to restrict the activity space of FPs,thereby increasing the frequency of these events.Localized conditions associated with stranding and sighting events were classified into four categories:bifurcation zones,confluence zones,separation zones,and deep channels adjacent to concave banks.Deep channels,which are optimal for shipping,also elevate the risk of FP strandings.These findings offer valuable insights for the development and design of conservation strategies tailored to the needs of FPs in estuarine environments.
文摘Crosstalk between the nervous system and cancer plays an important role in tumor metastasis yet is poorly understood.Recently,Padmanaban et al.demonstrated a novel mechanism for nerve-induced metastasis.Sensory nerve-derived substance P could induce apoptosis in breast cancer cells that overexpressed tachykinin receptors.Single-stranded RNAs(ssRNAs)leaking from dying cells subsequently interact with toll-like receptor 7(TLR7)on other cancer cells and finally promoted metastasis.This notable study displays a delicate loop between the nervous system and cancer and,more importantly,amplifies the conception of apoptosis-induced metastasis.Over the past years,a mass of breakthrough studies have proven the pivotal role of the nervous system in tumorigenesis and cancer progression thereby contributing to the creation of a new disciplinecancer neuroscience[1].Hanahan and Monje discussed in detail the interactions between the nervous system and tumors based on the theoretical framework of the cancer hallmarks,focused on nerve-mediated proliferation,angiogenesis,immune evasion,cell death resistance,and metastasis[2].
基金The National Natural Science Foundation of China(No.52278303).
文摘To tackle the issue of notch frequency and center frequency drift of the L(0,1)mode guided wave in ultra⁃sonic guided wave⁃based stress monitoring of prestressed steel strands,a method using higher⁃order mode plateau fre⁃quencies is adopted.First,the correlation between group velocity peaks and phase velocities at these plateau frequen⁃cies is analyzed.This analysis establishes a quantitative rela⁃tionship between phase velocity and stress in the steel strand,providing a theoretical foundation for stress monitor⁃ing.Then the two⁃dimensional Fourier transform is em⁃ployed to separate wave modes.Dynamic programming techniques are applied in the frequency⁃velocity domain to extract higher⁃order modes.By identifying the group veloc⁃ity peaks of these separated higher⁃order modes,the plateau frequencies of guided waves are determined,enabling indi⁃rect measurement of stress in the steel strand.To validate this method,finite element simulations are conducted under three scenarios.Results show that the higher⁃order modes of transient signals from three different positions can be ac⁃curately extracted,leading to successful cable stress moni⁃toring.This approach effectively circumvents the issue of guided wave frequency drift and improves stress monitoring accuracy.Consequently,it significantly improves the appli⁃cation of ultrasonic guided wave technology in structural health monitoring.
基金Supported by Jiangsu Province 333 Talent Key Industry Field Talent Project,No.[2022]21Key Scientific Research Program of Jiangsu Provincial Health Committee,No.ZD2021059+2 种基金Nantong Key Laboratory Project,No.[2020]163The Project of Nantong City Health Committee,No.MS2023027Young Medical Talents Fund of Health and Family Planning Commission of Nantong,No.QA2019006 and No.QNZ2023027.
文摘BACKGROUND Accurate preoperative T staging is essential for determining optimal treatment strategies in colorectal cancer(CRC).Low-keV virtual monoenergetic images(VMIs)have been shown to enhance lesion conspicuity.This study aimed to assess the diagnostic value of dual-layer spectral computed tomography(CT)-derived VMIs,in combination with multiplanar reformation(MPR)and evaluation of peritumoral fat stranding(PFS),for improving the accuracy of T staging in CRC.AIM To assess the diagnostic performance of dual-layer spectral CT(DLSCT)VMIs,particularly at low energy levels,and their integration with personalized MPR for preoperative T staging of CRC.METHODS In this retrospective study,157 patients with pathologically confirmed CRC(mean age:63.5±12.1 years)underwent DLSCT within 1 week before surgery.VMIs ranging from 40 keV to 70 keV(at 10 keV intervals)and conventional polyenergetic images(PEIs)were reconstructed.Objective image quality parameters,including image noise,signal-to-noise ratio(SNR),and contrast-to-noise ratio(CNR),were quantified,alongside subjective image quality scores using a 5-point Likert scale.Interobserver agreement was evaluated usingκstatistics.Taking histopathology as the reference standard,the diagnostic accuracy of T staging(T1-2 vs T3-4)was compared across PEIs and VMIs,both with and without MPR and PFS.RESULTS Low-keV VMIs(40-70 keV)demonstrated significantly higher SNR and CNR than PEIs(all P<0.001).Notably,40-keV VMIs achieved noise levels comparable to PEIs(8.17±3.63 vs 8.53±2.90;P=0.673).Subjective image quality peaked at 40-50 keV VMIs(Likert scores 4.85-4.88 vs 3.97 for PEIs;P<0.001),supported by excellent interobserver agreement(κ=0.812-0.913).The combination of 40-50 keV VMIs with MPR yielded the highest T staging accuracy(94.27%)compared to axial PEIs(70.7%),with a sensitivity and specificity of 83.87%and 96.83%,respectively(Youden index=0.81;P<0.05).While PFS enhanced staging accuracy on PEIs(up to 77.07%with MPR),it provided no significant additional benefit for VMIs.CONCLUSION DLSCT VMIs at 40-50 keV significantly enhanced image quality and improved preoperative T staging accuracy of CRC when combined with MPR.These findings underscored the clinical value of low-keV spectral imaging in tailoring individualized treatment strategies.
