DC active power filter based on model predictive control for DC bus overvoltage suppression of accelerator grid power supply

The China Fusion Engineering Test Reactor plans to build a 200 k V/25 A acceleration grid power supply(AGPS)for the negative-ion-based neutral beam injector prototype system.The AGPS uses a rectifier-inverter-isolated step-up structure.There is a DC bus between the rectifier and the inverter.In order to limit DC bus voltage ripple and transient fluctuations,a large number of capacitors are used,which degrades the reliability of the power supply and occupies a large amount of space.This work finds that due to the difference in the turn-off time of the rectifier and the inverter,the capacitance mainly depends on the rectifier current when the inverter is turned off.On this basis,an active power filter(APF)scheme is proposed to absorb the current.To enhance the dynamic response ability of the APF,model predictive control is adopted.In this paper,the circuit structure of the APF is introduced,the prediction model is deduced,the corresponding control strategy and signal detection method are proposed,and the simulation and experimental results show that APF can track the transient current of the DC bus and reduce the voltage fluctuation significantly.

重型燃气轮机用La2(Zr0.7Ce0.3)2O7/YSZ双层热障涂层热循环性能研究

重型发电燃气轮机低排放、高效率的发展目标,要求燃气轮机透平的进气温度不断提高。热障涂层作为保护金属热端部件的重要手段,是实现这一目标的关键技术之一。目前世界上最先进的J级燃气轮机的透平进口温度已经达到1600℃,热端部件表面温度超过1250℃,传统的YSZ热障涂层已经不能满足这一发展需求,因此迫切需要开发温度更高、热导率更低的新型热障涂层。本文对La2(Zr0.7Ce0.3)2O7(以下简称LZ7C3)热障涂层在重型发电燃气轮机中的应用进行了初步验证。结果表明,LZ7C3涂层具有比常规YSZ热障涂层更低的热导率(0.79~0.48Wm^-1K^-1,相对传统YSZ涂层下降30%以上),且在1250℃的高温火焰台架试验中表现出优良的热循环寿命(>7370次),具有良好的应用前景。

Terahertz Band: Lighting up Next-Generation Wireless Communications

With the explosion of wireless data rates,the terahertz(THz)band(0.1–10 THz)is envisioned as a promising candidate to break the existing bandwidth bottleneck and satisfy the ever-increasing capacity demand.The THz wireless communications feature a number of attractive properties,such as potential terabit-per-second capacity and high energy efficiency.In this paper,an overview on the state-of-the-art THz communications is studied,with a special focus on key technologies of THz transceivers and THz communication systems.The recent progress on both electronic and photonic THz transmitters are presented,and then the THz receivers operating in direct-and heterodyne reception modes are individually surveyed.Based on the THz transceiver schemes,three kinds of THz wireless communication systems are reviewed,including solid-state electronic systems,photonics-assisted systems and all-photonics systems.The prospective key enabling technologies,corresponding challenges and research directions for lighting up high-speed THz communication systems are discussed as well.

Quantum Key Distribution Network： Optimal Secret- Key- Aware Routing Method for Trust Relaying

Since the QKD network can overcome the distance limitation and expand the point-to-point QKD system to a multi-user key distribution system, some testing QKD networks have been built. However, all of this previous research seldom focused on the routing mechanism of QKD network in detail. Therefore, this paper focuses on the routing issue in trust relaying QKD network, builds a model of the trust relaying QKD network and proposes a secret-key-aware routing method. In our method, a dynamic model for the residual local key is proposed to forecast the residual local key quantity of each QKD link more accurately, and the cost of QKD link and relaying path are defined by multiple affecting factors, e.g. the generation, consumption rate and the local key depletion index. The proposed method is implemented and evaluated in a simulation environment. The simulation results show that our routing method can increase the success rate of key exchange, make all the QKD links participate key exchange with almost equal opportunity to achieve load balance, and trade off the local key generation and consumption of each QKD link. Therefore, our proposed method can contribute to effectively improve the holistic performance of the trust relaying QKD network.

Moving target defense of routing randomization with deep reinforcement learning against eavesdropping attack

Eavesdropping attacks have become one of the most common attacks on networks because of their easy implementation. Eavesdropping attacks not only lead to transmission data leakage but also develop into other more harmful attacks. Routing randomization is a relevant research direction for moving target defense, which has been proven to be an effective method to resist eavesdropping attacks. To counter eavesdropping attacks, in this study, we analyzed the existing routing randomization methods and found that their security and usability need to be further improved. According to the characteristics of eavesdropping attacks, which are “latent and transferable”, a routing randomization defense method based on deep reinforcement learning is proposed. The proposed method realizes routing randomization on packet-level granularity using programmable switches. To improve the security and quality of service of legitimate services in networks, we use the deep deterministic policy gradient to generate random routing schemes with support from powerful network state awareness. In-band network telemetry provides real-time, accurate, and comprehensive network state awareness for the proposed method. Various experiments show that compared with other typical routing randomization defense methods, the proposed method has obvious advantages in security and usability against eavesdropping attacks.

Fusion power supply advances by the J-TEXT engineering team

To meet the stringent requirements of the fusion power supply for large-scale fusion devices,the J-TEXT engineering team has carried out key technology research and applications in several important directions of fusion power supply.This article presents the advances made by the J-TEXT engineering team in recent years in the following areas:(1) a high-voltage power supply for an auxiliary heating system;(2) a breakdown protection device for an auxiliary heating power supply;(3) magnetic field compatibility;(4) a high-voltage pulsed power supply for a fieldreversed configuration;(5) a large physics experimental facility control system.The research backgrounds,technical progress,test results,applications,summaries and prospects are described in detail in each part.These innovative research results and valuable engineering experience can promote the progress of fusion power supply technology,and also lay a foundation for the development of power supplies with higher parameters in the future.

Fault diagnosis algorithm for 3-phase passive rectifiers based on frequency-domain analysis for acceleration grid power supply in CFETR NBI system

The acceleration grid power supply(AGPS) is a crucial part of the Negative-ion Neutral Beam Injection system in the China Fusion Engineering Test Reactor,which includes a 3-phase passive(diode) rectifier.To diagnose and localize faults in the rectifier,this paper proposes a frequencydomain analysis-based fault diagnosis algorithm for the rectifier in AGPS.First,time-domain expressions and spectral characteristics of the output voltage of the TPTL-NPC inverter-based power supply are analyzed.Then,frequency-domain analysis-based fault diagnosis and frequency-domain analysis-based sub-fault diagnosis algorithms are proposed to diagnose open circuit(OC) faults of diode(s),which benefit from the analysis of harmonics magnitude and phase-angle of the output voltage.Only a fundamental period is needed to diagnose and localize exact faults,and a strong Variable-duration Fault Detection Method is proposed to identify acceptable ripple from OC faults.Detailed simulations and experimental results demonstrate the effectiveness,quickness,and robustness of the proposed algorithms,and the diagnosis algorithms proposed in this article provide a significant method for the fault diagnosis of other rectifiers and converters.

Pipeline Embolization Device for intracranial aneurysms presenting with mass effect:a large Chinese cohort

Background Unruptured intracranial aneurysm treatment aims to reduce the risk of aneurysm rupture and bleeding,relieves symptoms and improve the quality of life for patients.This study aimed to assess the safety and efficacy of Pipeline Embolization Device(PED,Covidien/Medtronic,Irvine,CA)treatment for intracranial aneurysms presenting with mass effect in real-world settings.Methods We selected patients from the PED in China Post-Market Multi-Center Registry Study with mass effect presentation.The study endpoints included postoperative mass effect deterioration and mass effect relief at follow-up(3–36 months).We conducted multivariate analysis to identify factors associated with mass effect relief.Subgroup analyses by aneurysm location,size and form were also performed.Results This study included 218 patients with a mean age of 54.3±11.8 years and a female predominance of 74.0%(162/218).The postoperative mass effect deterioration rate was 9.6%(21/218).During a median follow-up period of 8.4 months,the mass effect relief rate was 71.6%(156/218).Notably,immediate aneurysm occlusion following treatment was significantly associated with mass effect relief(OR 0.392,95%CI,0.170 to 0.907,p=0.029).Subgroup analysis demonstrated that adjunctive coiling contributed to mass effect relief in cavernous aneurysms,while dense embolism impeded symptom relief in aneurysms<10mm and saccular aneurysms.Conclusions Our data confirmed the efficacy of PED in relieving mass effect.The findings of this study provide support for endovascular treatment to alleviate mass effect in unruptured intracranial aneurysms.Trial registration number NCT03831672.

Clinical features, treatment strategies and outcomes of craniocervical junction arteriovenous fistulas: a cohort study of 193 patients

Background Craniocervical junction(CCJ)arteriovenous fistulas(AVFs)are rare.The current treatment strategies for AVFs with different angioarchitecture need to be clarified.The present study aimed to analyse the correlation between angioarchitecture and clinical characteristics,share our experience in treating this disease and identify risk factors associated with subarachnoid haemorrhage(SAH)and poor outcomes.Methods A total of 198 consecutive patients with CCJ AVFs from our neurosurgical centre were retrospectively reviewed.The patients were grouped according to their clinical manifestations,and their baseline clinical characteristics,angioarchitecture,treatment strategies and outcomes were summarised.Results The patients’median age was 56 years(IQR 47–62 years).The majority of patients were men with 166(83.8%)patients.The most common clinical manifestation was SAH(52.0%),followed by venous hypertensive myelopathy(VHM)(45.5%).The most common CCJ AVFs type was dural AVF,with 132(63.5%)fistulas.The most frequent fistula location was C-1(68.7%)and dural branch of vertebral artery(70.2%)was the most involved arterial feeders for fistulas.The most common direction of venous drainage was descending intradural drainage(40.9%),followed by ascending intradural drainage(36.5%).Microsurgery was the most common treatment strategy applied for 151(76.3%)patients,15(7.6%)patients were treated with interventional embolisation only,and 27(13.6%)received both interventional embolisation and microsurgical treatment.The learning curve for microsurgery only was analysed by cumulative summation method,and the turning point was the 70th case,and blood loss in post-group was lower than that in pre-group(p=0.034).At the last follow-up,there were 155(78.3%)patients with favourable outcomes(modified Rankin Scale(mRS)<3).Age≥56(OR 2.038,95%CI 1.039 to 3.998,p=0.038),VHM as the clinical manifestation(OR 4.102,95%CI 2.108 to 7.982,p<0.001)and pretreatment mRS≥3(OR 3.127,95%CI 1.617 to 6.047,p<0.001)were significantly associated with poor outcomes.Conclusion The arterial feeders and direction of the venous drainage were important factors in the clinical presentations.The location of fistula and drainage vein was essential for choosing different treatment strategies.Older age,VHM onset and poor pretreatment functional status predicted poor outcomes.

Impaired autophagy activity-induced abnormal differentiation of bone marrow stem cells is related to adolescent idiopathic scoliosis osteopenia

Background:Osteopenia has been well documented in adolescent idiopathic scoliosis(AIS).Bone marrow stem cells(BMSCs)are a crucial regulator of bone homeostasis.Our previous study revealed a decreased osteogenic ability of BMSCs in AIS-related osteopenia,but the underlying mechanism of this phenomenon remains unclear.Methods:A total of 22 AIS patients and 18 age-matched controls were recruited for this study.Anthropometry and bone mass were measured in all participants.Bone marrow blood was collected for BMSC isolation and culture.Osteogenic and adipogenic induction were performed to observe the differences in the differentiation of BMSCs between the AIS-related osteopenia group and the control group.Furthermore,a total RNA was extracted from isolated BMSCs to perform RNA sequencing and subsequent analysis.Results:A lower osteogenic capacity and increased adipogenic capacity of BMSCs in AIS-related osteopenia were revealed.Differences in mRNA expression levels between the AIS-related osteopenia group and the control group were identified,including differences in the expression of LRRC17,DCLK1,PCDH7,TSPAN5,NHSL2,and CPT1B.Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed several biological processes involved in the regulation of autophagy and mitophagy.The Western blotting results of autophagy markers in BMSCs suggested impaired autophagic activity in BMSCs in the AIS-related osteopenia group.Conclusion:Our study revealed that BMSCs from AIS-related osteopenia patients have lower autophagic activity,which may be related to the lower osteogenic capacity and higher adipogenic capacity of BMSCs and consequently lead to the lower bone mass in AIS patients.

Promotion effect of FGF23 on osteopenia in congenital scoliosis through FGFr3/TNAP/OPN pathway

Background:Congenital scoliosis(CS)is a complex spinal malformation of unknown etiology with abnormal bone metabolism.Fibroblast growth factor 23(FGF23),secreted by osteoblasts and osteocytes,can inhibit bone formation and mineralization.This research aims to investigate the relationship between CS and FGF23.Methods:We collected peripheral blood from two pairs of identical twins for methylation sequencing of the target region.FGF23 mRNA levels in the peripheral blood of CS patients and age-matched controls were measured.Receiver operator characteristic(ROC)curve analyses were conducted to evaluate the specificity and sensitivity of FGF23.The expression levels of FGF23 and its downstream factors fibroblast growth factor receptor 3(FGFr3)/tissue non-specific alkaline phosphatase(TNAP)/osteopontin(OPN)in primary osteoblasts from CS patients(CS-Ob)and controls(CT-Ob)were detected.In addition,the osteogenic abilities of FGF23-knockdown or FGF23-overexpressing Ob were examined.Results:DNA methylation of the FGF23 gene in CS patients was decreased compared to that of their identical twins,accompanied by increased mRNA levels.CS patients had increased peripheral blood FGF23 mRNA levels and decreased computed tomography(CT)values compared with controls.The FGF23 mRNA levels were negatively correlated with the CT value of the spine,and ROCs of FGF23 mRNA levels showed high sensitivity and specificity for CS.Additionally,significantly increased levels of FGF23,FGFr3,OPN,impaired osteogenic mineralization and lower TNAP levels were observed in CS-Ob.Moreover,FGF23 overexpression in CT-Ob increased FGFr3 and OPN levels and decreased TNAP levels,while FGF23 knockdown induced downregulation of FGFr3 and OPN but upregulation of TNAP in CS-Ob.Mineralization of CS-Ob was rescued after FGF23 knockdown.Conclusions:Our results suggested increased peripheral blood FGF23 levels,decreased bone mineral density in CS patients,and a good predictive ability of CS by peripheral blood FGF23 levels.FGF23 may contribute to osteopenia in CS patients through FGFr3/TNAP/OPN pathway.

Single-lane 200 Gbit/s photonic wireless transmission of multicarrier 64-QAM signals at 300 GHz over 30 m

Recently,wireless communication capacity has been witnessing unprecedented growth.Benefits from the optoelectronic components with large bandwidth,photonics-assisted terahertz(THz)communication links have been extensively developed to accommodate the upcoming wireless transmission with a high data rate.However,limited by the available signalto-noise ratio and THz component bandwidth,single-lane transmission of beyond 100 Gbit/s data rate using a single pair of THz transceivers is still very challenging.In this study,a multicarrier THz photonic wireless communication link in the 300 GHz band is proposed and experimentally demonstrated.Enabled by subcarrier multiplexing,spectrally efficient modulation format,well-tailored digital signal processing routine,and broadband THz transceivers,a line rate of 72 Gbit/s over a wireless distance of 30 m is successfully demonstrated,resulting in a total net transmission capacity of up to 202.5 Gbit/s.The single-lane transmission of beyond 200 Gbit/s overall data rate with a single pair of transceivers at 300 GHz is considered a significant step toward a viable photonics-assisted solution for the next-generation information and communication technology (ICT) infrastructure.

Roles of light transmission aggregometry and CYP2C19 genotype in predicting ischaemic complications during interventional therapy for intracranial aneurysms

Background and purpose Light transmission aggregometry(LTA)and CYP2C19 genotype analysis are commonly used to evaluate the antiplatelet effects of clopidogrel during the interventional treatment of intracranial aneurysms.The aim of this study was to determine which test can predict ischaemic events during these treatments.Methods Patient demographic information,imaging data,laboratory data and ischaemic complications were recorded.LTA and CYP2C19 genotype results were compared,and multiple linear regression was performed to examine factors related to platelet reactivity.Multivariate regression analysis was performed to determine whether LTA and CYP2C19 could predict ischaemic complications and to identify other clinical risk factors.Receiver operating characteristic curve analysis was conducted to calculate the cut-off value for predicting ischaemic complications.A subgroup analysis was also performed for different CYP2C19 genotype metabolisers,as well as for patients with flow diverters and traditional stents.Results A total of 379 patients were included,of which 22 developed ischaemic events.Maximum platelet aggregation induced by ADP(ADP-MPA)could predict ischaemic events(p<0.001;area under the curve,0.752(95%CI 0.663 to 0.842)),and its cut-off value was 41.5%.ADP-MPA(p=0.001)and hypertension duration>10 years(p=0.022)were independent risk factors for ischaemic events,while the CYP2C19 genotype was not associated with ischaemic events.In the subgroup analysis,ADP-MPA could predict ischaemic events in fast metabolisers(p=0.004)and intermediate metabolisers(p=0.003).The cut-off value for ischaemic events was lower in patients with flow diverters(ADP-MPA=36.4%)than in patients with traditional stents(ADP-MPA=42.9%).Conclusions ADP-MPA can predict ischaemic complications during endovascular treatment of intracranial aneurysms.Patients with flow diverters require stronger antiplatelet medication than patients with traditional stents.

Angioarchitecture and prognosis of pediatric intracranial pial arteriovenous fistula

Objective Pial arteriovenous fistulas(PAVFs)are rare and mostly observed in children.However,the overall angioarchitecture,clinical features,treatments and long-term prognosis for pediatric patients remain unclear.Methods Clinical data of consecutive 42 pediatric PAVFs were documented and analysed.According to the differences of age distribution and clinical features,they were split into a younger group(≤3 years old;20 cases)and an older group(3-14 years old;22 cases).Results Their mean age was 4.9±3.9 years,and the mean preoperative modified Rankin Scale(mRS)score was 1.64±1.57.Fourteen patients(33.3%)were asymptomatic,followed by epilepsy(21.4%),intracranial haemorrhage(16.7%),hydrocephalus(9.5%),developmental delay(7.1%),intermittent headache(7.1%)and congestive heart failure(4.8%).Annual bleeding rate and rebleeding rate before treatment reached 3.86%and 3.17%.Poor venous drainage including sinus dynamic obstruction(21 cases,50.0%)and sinus occlusion(17 cases,40.48%)were found with high frequency among these patients.Finally,33 cases were cured(78.57%),and 4 cases faced surgery-related complications(9.52%).During 24-140 months’follow-up,the mean mRS score reduced to 0.57±0.40.However,only 22 cases(52.38%)recovered to absolutely normal,and poor venous drainage was the risk factor for patients’incomplete recovery(p=0.028,Exp(B)=14.692,95%CI 1.346 to 160.392).Compared with the older group,younger group showed more chronic symptoms,more secondary pathological changes,more times treatment and worse prognosis(p=0.013,0.002,0.000 and 0.032,respectively).Conclusions Pediatric PAVF has different angioarchitectures,clinical features and prognoses in different age groups.Poor venous drainage is an important factor leading to poor prognosis,and it accounts for incomplete recovery in nearly half of patients.

From polarimetry to helicity: Studies of solar magnetic fields at the Huairou Solar Observing Station

In this paper, we briefly introduce the basic questions in the measurements of solar magnetic fields and the possible error sources due to the approximation of the theory of radiation transfer of spectral lines in the solar atmosphere. We introduce some basic research progress in magnetic field measurement at Huairou Solar Observing Station of National Astronomical Observatories,Chinese Academy of Sciences, especially concerning the non-potentiality in solar active regions, such as the magnetic shear,current and helicity. We also discuss some basic questions for the measurements of the magnetic fields and corresponding challenges for the future studies.

Comparison of the Pipeline embolisation device alone or combined with coiling for treatment of different sizes of intracranial aneurysms

Objectives The aim of this study was to compare complications and outcomes between intracranial aneurysms treated with the Pipeline embolisation device(PED)alone or with PED combined with coiling for different-sized aneurysms.Method Patients with aneurysms treated by PED were collected from the PED in China postmarket multicentre registry study.We performed a propensity match analysis to compare the efficacy and safety between PED alone and PED combined with coiling treatment,and then aneurysms were organised into three groups based on their size:small(≤7 mm),medium(≤15 mm to>7 mm)and large/giant(>15 mm).Complications and aneurysm occlusion rates in the aneurysm size groups were compared between PED alone and PED combined with coiling patients.Result A total of 1171 patients with 1322 aneurysms were included.All patients received clinical follow-up,while angiographic follow-up was available in 967 aneurysms.For small aneurysms,there was no difference in the aneurysm occlusion rate between two groups(79.1%vs 88.4%,respectively),while there was a significant increase in the ischaemic complication rate(8.3%vs 19.3%,respectively,p=0.0001).For medium and large/giant saccular aneurysms,PED combined with coiling significantly improved the occlusion rate(medium aneurysms:74.7%vs 88.8%,respectively,p<0.0001;large/giant saccular aneurysms:72.9%vs 86.9%,respectively,p=0.018),while there were no differences in the total complication rate.For large/giant non-saccular aneurysms,two groups showed no differences.Conclusion Use of the PED with adjunctive coils can significantly improve the occlusion rate of medium aneurysms,without increasing the total complication rate.

Diagnostic of spectral lines in magnetized solar atmosphere:Formation of the Hβ line in sunspots

Formation of the Hβλ4861.34Aline is an important topic related to the diagnosis of the basic configuration of magnetic fields in the solar and stellar chromospheres.Specifically,broadening of the Hβλ4861.34Aline occurs due to the magnetic and microelectric fields in the solar atmosphere.The formation of Hβin the model umbral atmosphere is presented based on the assumption of non-local thermodynamic equilibrium.It is found that the model umbral chromosphere is transparent to the Stokes parameters of the Hβline,which implies that the observed signals of magnetic fields at sunspot umbrae via the Hβline originate from the deep solar atmosphere,where lgτc≈-1(about 300 km in the photospheric layer for our calculations).This is in contrast to the observed Stokes signals from non-sunspot areas,which are thought to primarily form in the solar chromosphere.

Improvement in Sensing Accuracy of an OFDM-Based W-Band System

Orthogonal frequency division multiplexing (OFDM) waveform is promising to converge communications and sensing functionalities for future wireless applications. This paper presents a novel method to improve the OFDM-based sensing accuracy by estimating the delay/Doppler leakages in the channel matrix, which is constructed by the received and the transmitted OFDM symbols. Both simulation and proof-of-concept experiment validate the proposed method for sensing improvement.The experiment uses a heterodyne W-band system at 97 GHz to transmit and receive an OFDM waveform of bandwidth 3.9 GHz.We achieve an improvement in sensing accuracy by an order of magnitude which is significant for OFDM-based converged systems.

Spherical harmonic series solution of fields excited by vertical electric dipole in earth-ionosphere cavity

The spherical harmonic series expression of electromagnetic fields excited by ELF/SLF vertical electric dipole in the spherical earth-ionosphere cavity is derived when the earth and ionosphere are regarded as non-ideal conductors.A method of speeding numerical convergence has been presented.The electromagnetic fields in the cavity are calculated by this algorithm,and the results show that the electromagnetic fields between the earth and the ionosphere are the sum of two traveling waves in the SLF band.Moreover,the results are in complete agreement with that of the well-known spherical second-order approximation in the SLF band.The electromagnetic fields in the cavity are a type of standing wave in the ELF band and the variation of the amplitude versus frequency coincides with Schumann’s resonance.