[Objectives]miRNAs play an important role in the proliferation and differentiation of different myoblasts.This study was conducted to elucidate the complex genetic mechanisms that affect the meat production performanc...[Objectives]miRNAs play an important role in the proliferation and differentiation of different myoblasts.This study was conducted to elucidate the complex genetic mechanisms that affect the meat production performance of Sichuan white rabbits and reveal the regulatory role of miRNAs in their muscle growth and meat quality formation.[Methods]Three constructed skeletal muscle libraries of Sichuan white rabbits aged six months were sequenced by the solexa technology to identify known miRNAs,predict new miRNAs and construct an expression profile of muscle miRNAs.[Results]A total of 511 known miRNAs and 42 miRNAs were detected in 34089472 pure sequences,and the proportion of miRNAs with a length of 22 nt was the highest.The number of known miRNA sequences accounted for 71.38%of pure sequences,which was much higher than the proportion of other types of RNAs.The proportion of sequences from exons was 0.38%,indicating a low degree of mRNA degradation in the samples.Base U had the highest proportion at the first position,and the bases with the highest proportions at positions 8 and 10 were U and A,respectively.Muscle-specific miRNAs(miR-1,miR-133,and miR-206)ranked in the top 10 in terms of expression level.The number and expression levels of new miRNAs were lower than those of known miRNAs.The length distribution,base bias at different positions and expression profile characteristics of miRNAs might be related to the biological function of miRNAs in regulating muscle proliferation and differentiation and the action mechanisms with target genes.[Conclusions]The identification and expression of miRNAs in muscle tissues of Sichuan white rabbits will help to understand the complex molecular mechanisms of meat production performance and provide a theoretical basis for the functional research of miRNAs in meat rabbits.展开更多
<strong>Background:</strong> Henoch Schonlein Purpura (HSP) is a common immune-related allergic disease in children. It is very important to understand the clinical features of this disease for doctors. &l...<strong>Background:</strong> Henoch Schonlein Purpura (HSP) is a common immune-related allergic disease in children. It is very important to understand the clinical features of this disease for doctors. <strong>Objective:</strong> To explore the clinical efficacy of glucocorticoids in the treatment of HSP in Tibetan children at high altitude, and to analyze the possible causes of HSP in children at high altitude. The risk factors of the disease provide a reference for the treatment of HSP in children in high altitude areas. <strong>Methods:</strong> Selecting January 2015 to November 2020, 88 children diagnosed with Henoch-Schonlein Purpura in the outpatient and inpatient departments of the People’s Hospital of Bomi County, Tibet Autonomous Region were the subjects of the study. Its gender, age of onset, season of onset, predisposing factors, allergy history, first symptoms, clinical manifestations, laboratory examinations, etc., perform retrospective analysis. <strong>Results: </strong>Among 88 children with allergic purpura, 55 were boys, accounting for 62.5%, and 33 were girls, accounting for 37.5%. Men have more cases than women. All have clinical manifestations of purpura of the skin, among which 35 cases have obvious triggers, of which the above there were 26 cases of respiratory infections, 6 cases of dietary factors, and 3 cases of contact with allergic substances. Simple skin type: 18 cases, accounting for 20.45%;Abdominal type: 6 cases, accounting for 6.82%;2 male cases, accounting for 33.33%;4 female cases, accounting for 66.67%;Articular type: 8 cases, accounting for 33.33%;Renal type: 2 cases, accounting for 2.27%;54 cases of mixed type, accounting for 61.36%. After glucocorticoids, the rashes disappeared, no any adverse reactions. <strong>Conclusion:</strong> Allergic purpura in children is more common in school-age children, and upper respiratory tract infection is the main predisposing factor. Skin purpura is the main clinical manifestation, often associated with lower extremity joint swelling and pain. There is no significant difference in the efficacy and course of the disease between intravenous and oral treatment. Therefore, clinicians should strictly grasp the indications of glucocorticoids to reduce the occurrence of complications.展开更多
近年来,在医药卫生领域,利用真实世界数据生成真实世界证据的研究方法在药品研发、审批、适应证拓展等领域取得广泛的关注和认可,开展真实可信、高质量的真实世界研究证据(real world evidence,RWE),已成为循证医学的一个重要发展方向...近年来,在医药卫生领域,利用真实世界数据生成真实世界证据的研究方法在药品研发、审批、适应证拓展等领域取得广泛的关注和认可,开展真实可信、高质量的真实世界研究证据(real world evidence,RWE),已成为循证医学的一个重要发展方向。本文介绍了近年来国内外关于结直肠癌真实世界研究的现状,将真实世界研究(real world research/study,RWS)与相应的随机对照研究(randomized controlled trial,RCT)的meta分析结果进行对比和评价,以阐述RWS的特征、研究方法、相对于传统RCT研究的优势,并归纳其在肠癌领域的应用现状。在此基础上,对RWS在结直肠癌临床研究中的价值和前景进行总结,为后续研究提供新的思路。展开更多
The track association problem of radar and electronic support measure (ESM) has been considered in the literature for several years.This problem is crucial for radar-to-ESM track fusion and is complicated by the prese...The track association problem of radar and electronic support measure (ESM) has been considered in the literature for several years.This problem is crucial for radar-to-ESM track fusion and is complicated by the presence of individual systematic errors and measurement errors.In order to improve the track association of radar and ESM sensors,a pseudo-linear filtering algorithm is proposed to estimate the target states and improve the stability of the filter.It is found that,however,the correct probability of radar-to-ESM track association decreases as the radar measurement error decreases,when the pseudo-linear filter is used for ESM sensor filtering.In view of the strange phenomenon,this paper analyzes the reason for it by using the statistic theory and further performs Monte Carlo simulation to verify the analysis.展开更多
Phytohormones are key factors in plant responsiveness to abiotic and biotic stresses,and maintaining hormone homeostasis is critically important during stress responses.Cut rose(Rosa hybrida)flowers experience dehydra...Phytohormones are key factors in plant responsiveness to abiotic and biotic stresses,and maintaining hormone homeostasis is critically important during stress responses.Cut rose(Rosa hybrida)flowers experience dehydration stress during postharvest handling,and jasmonic acid(JA)levels change as a result of this stress.However,how JA is involved in dehydration tolerance remains unclear.We investigated the functions of the JA-and dehydration-induced RhHB1 gene,which encodes a homeodomain-leucine zipper Iγ-clade transcription factor,in rose flowers.Silencing RhHB1 decreased petal dehydration tolerance and resulted in a persistent increase in JA-Ile content and reduced dehydration tolerance.An elevated JA-Ile level had a detrimental effect on rose petal dehydration tolerance.RhHB1 was shown to lower the transient induction of JA-Ile accumulation in response to dehydration.In addition to transcriptomic data,we obtained evidence that RhHB1 suppresses the expression of the lipoxygenase 4(RhLOX4)gene by directly binding to its promoter both in vivo and in vitro.We propose that increased JA-Ile levels weaken the capacity for osmotic adjustment in petal cells,resulting in reduced dehydration tolerance.In conclusion,a JA feedback loop mediated by an RhHB1/RhLOX4 regulatory module provides dehydration tolerance by fine-tuning bioactive JA levels in dehydrated flowers.展开更多
From the lifecycle of schistosome, the phenomenon of time delay is widespread. In this paper, a two-dimensional system is studied that incorporates two time delays which are the incubation period of human and snail, r...From the lifecycle of schistosome, the phenomenon of time delay is widespread. In this paper, a two-dimensional system is studied that incorporates two time delays which are the incubation period of human and snail, respectively. Our purpose is to demonstrate that the time delays are harmless for stability of equilibria of the system. Further, sufficient conditions of stability of equilibria are obtained.展开更多
Copper ion conducting solid electrolyte Rb_(4)Cu_(16)I_(6.5)Cl_(13.5)was prepared by means of mechano-chemical method.The structure and morphology of the powder was investigated by x-ray diffraction and scanning elect...Copper ion conducting solid electrolyte Rb_(4)Cu_(16)I_(6.5)Cl_(13.5)was prepared by means of mechano-chemical method.The structure and morphology of the powder was investigated by x-ray diffraction and scanning electron microscopy.The grain size was estimated to be 0.2-0.9μm and the ionic conductivity at room temperature was approximately 0.206 S/cm.The solid electrolyte Rb_(4)Cu_(16)I_(6.5)Cl_(13.5)was exploited for copper ion beam generation.The copper ion emission current of several nA was successfully obtained at acceleration voltages of 15 kV and temperature of 197℃in vacuum of 2.1×10^(-4)Pa.A good linear correlation between the logarithmic ion current(logI)and the square root of the acceleration voltage(U_(acc))at high voltage range was obtained,suggesting the Schottky emission mechanism in the process of copper ion beam generation.展开更多
In this study,using Liangshan semi-fine wool sheep as an experimental material,full-length CDS sequence of IGFBP-1 gene was cloned with RT-PCR method and analyzed with bioinformatics methods. The results showed that t...In this study,using Liangshan semi-fine wool sheep as an experimental material,full-length CDS sequence of IGFBP-1 gene was cloned with RT-PCR method and analyzed with bioinformatics methods. The results showed that the full-length CDS sequence of IGFBP-1 gene in Liangshan semi-fine wool sheep was792 bp in length,encoding 263 amino acids. The CDS sequence shared 97%,76% and 74% homology with bovine,human and rat,respectively; the amino acid sequence shared 97%,69% and 71%,respectively. The Gen Bank accession number was FJ589639. 1. The amino acid molecular weight of IGFBP-1 was 27. 8k D,and the theoretical isoelectric point( p I) was 5. 99. The result of phylogenetic analysis showed that IGFBP-1 gene in Liangshan semi-fine wool sheep exhibited close phylogenetic relationships with bovine,goat and other mammals,and distant phylogenetic relationships with chicken and fish. IGFBP-1 gene had obvious hydrophobic and hydrophilic regions,harboring one signal peptide,one transmembrane region,16 phosphorylation sites,six N-glycosylation sites and eight O-glycosylation sites. The result of secondary structure analysis showed that the random coil,α-helix and β-sheet regions accounted for 61. 98%,24. 33% and 13. 69%,respectively. The result of tertiary structure analysis showed that IGFBP-1 harbors an IGFBP_N domain and a thyroglobulin type-I domain. This study laid a solid foundation for further investigating the function of IGFBP-1 gene in sheep.展开更多
In this study,full-length CDS sequence of IGFBP-7 gene was cloned from Liangshan semi-fine wool sheep with RT-PCR method and analyzed with bioinformatics methods. The results showed that the full-length CDS sequence o...In this study,full-length CDS sequence of IGFBP-7 gene was cloned from Liangshan semi-fine wool sheep with RT-PCR method and analyzed with bioinformatics methods. The results showed that the full-length CDS sequence of IGFBP-7 gene in Liangshan semi-fine wool sheep was 846 bp in length,encoding282 amino acids. The CDS sequence shared 99%,95% and 90% homology with bovine,human and rat,respectively; the amino acid sequence shared 98%,93%and 89%,respectively. The GenB ank accession number was FJ589640. 1. The amino acid molecular weight of IGFBP-7 was 29. 0 kD,and the theoretical isoelectric point( pI) was 8. 25. The result of phylogenetic analysis showed that IGFBP-7 gene in Liangshan semi-fine wool sheep exhibited close phylogenetic relationships with bovine,goat and other mammals,and distant phylogenetic relationships with Danio rerio and Haliotis diversicolor. IGFBP-7 gene had uniformly distributed hydrophobic and hydrophilic regions,harboring one signal peptide,two transmembrane regions,16 phosphorylation sites,four N-glycosylation sites and one O-glycosylation site. The result of secondary structure analysis showed that the random coil,α-helix and β-sheet regions accounted for 64. 89%,19. 86% and 15. 25%,respectively. The result of tertiary structure analysis showed that IGFBP-7 harbors an IGFBP_N domain and an Ig-like domain. This study provided scientific basis for further investigating the function of IGFBP-7 gene in sheep.展开更多
We report the discovery of KMT-2020-BLG-0414 Lb,with a planet-to-host mass ratio q2=0.9-1.2×10-5=3-4 q⊕at 1σ,which is the lowest mass-ratio microlensing planet to date.Together with two other recent discoveries...We report the discovery of KMT-2020-BLG-0414 Lb,with a planet-to-host mass ratio q2=0.9-1.2×10-5=3-4 q⊕at 1σ,which is the lowest mass-ratio microlensing planet to date.Together with two other recent discoveries(4?q/q⊕?6),it fills out the previous empty sector at the bottom of the triangular(log s,log q)diagram,where s is the planet-host separation in units of the angular Einstein radiusθE.Hence,these discoveries call into question the existence,or at least the strength,of the break in the mass-ratio function that was previously suggested to account for the paucity of very low-q planets.Due to the extreme magnification of the event,Amax~1450 for the underlying single-lens event,its light curve revealed a second companion with q3~0.05 and|log s3|~1,i.e.,a factor~10 closer to or farther from the host in projection.The measurements of the microlens parallaxπE and the angular Einstein radiusθE allow estimates of the host,planet and second companion masses,(M1,M2,M3)~(0.3 M⊙,1.0 M⊕,17 MJ),the planet and second companion projected separations,(a⊥,2,a⊥,3)~(1.5,0.15 or 15)au,and system distance DL~1 kpc.The lens could account for most or all of the blended light(I~19.3)and so can be studied immediately with high-resolution photometric and spectroscopic observations that can further clarify the nature of the system.The planet was found as part of a new program of high-cadence follow-up observations of high-magnification events.The detection of this planet,despite the considerable difficulties imposed by COVID-19(two KMT sites and OGLE were shut down),illustrates the potential utility of this program.展开更多
Objective:Lianhua Qingwen combined with Western medicine(LHQW+WM)has been proposed as a viable treatment for coronavirus disease 2019(COVID-19).Interestingly,umbrella reviews of systematic reviews(SRs),which provide t...Objective:Lianhua Qingwen combined with Western medicine(LHQW+WM)has been proposed as a viable treatment for coronavirus disease 2019(COVID-19).Interestingly,umbrella reviews of systematic reviews(SRs),which provide the most comprehensive evidence,are the best evidence in evidence-based medicine.Therefore,an umbrella review of SRs that summarizes and evaluates the efficacy of LHQW+WM for COVID-19 is urgently required.Methods:Overall,6 databases were used to conduct a comprehensive literature search from inception to January 22,2022.The corrected covered area(CCA)was used to analyze the overlapping between SRs.Meta-analysis was conducted when that of the included SRs was inappropriate.A MeaSurement Tool to Assess Systematic Reviews(AMSTAR-2)was also employed to assess the quality of the included SRs.Results:In total,12 SRs were identified,which included 12 unique primary studies.The included SRs ranged in quality from moderate to critically low and had an extremely high CCA(36.4%).Compared to conventional treatment,LHQW+WM showed efficacy concerning fatigue recovery[risk ratio(RR)=1.69,95%confidence interval(CI):1.04-2.73,n=2,I2=0%],cough recovery(RR=1.65,95%CI:1.09-2.51,n=3,I2=39.1%),and overall effective rates(RR=1.17,95%CI:1.07-1.28,n=3,I2=17.5%).Conclusion:LHQW+WM may improve the clinical symptoms of patients with COVID-19;however,the results should be interpreted cautiously because of the rigorous processes in the included SRs.展开更多
In this work,hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide(3D-rGO)skeleton and lamellar boron nitride(BN)/silicon carbide(SiC)coatings are prepared by chemical vapor infi...In this work,hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide(3D-rGO)skeleton and lamellar boron nitride(BN)/silicon carbide(SiC)coatings are prepared by chemical vapor infiltration(CVI)process.The graphene framework prepared by 3D printing and frozen self-assembly exhibits a lightweight structure and a perforated conductive network,which extends the transmission path of incident microwaves.The introduced ceramic coatings can effectively tune the impedance matching degree and supply a lossy phase,and the hierarchical structure of the composites enhances the multiple scattering of the incident microwaves.As expected,the 3D-rGO/BN/SiC composites possess an excellent absorbing performance with a minimum reflection loss value of–37.8 dB,and the widest effective absorbing bandwidth(RL<–10 dB)of 5.90 GHz is obtained.The controllable fabrication of composites can provide a guideline for rational design and fabrication of high-performance electromagnetic waves absorbing materials in practical applications.展开更多
Background:Immune checkpoint inhibitors(ICIs)are increasingly used as first-line therapy for patients with advanced non-small cell lung cancer(NSCLC)harboring no actionable mutations;however,data on their efficacy amo...Background:Immune checkpoint inhibitors(ICIs)are increasingly used as first-line therapy for patients with advanced non-small cell lung cancer(NSCLC)harboring no actionable mutations;however,data on their efficacy among patients presenting with intracranial lesions are limited.This study aimed to explore the efficacy and safety of ICIs combined with chemotherapy in advanced NSCLC patients with measurable brain metastasis at initial diagnosis.Methods:Our study retrospectively analyzed clinical data of a total of 211 patients diagnosed with driver gene mutation-negative advanced NSCLC with measurable,asymptomatic brain metastasis at baseline from Hunan Cancer Hospital between January 1,2019 and September 30,2021.The patients were stratified into two groups according to the first-line treatment regimen received:ICI combined with chemotherapy(n=102)or chemotherapy(n=109).Systemic and intracranial objective response rates(ORRs)and progression-free survival(PFS)were analyzed.Adverse events were also compared between the groups.Results:Compared with the chemotherapy-based regimen,the ICI-containing regimen was associated with a significantly higher intracranial(44.1%[45/102]vs.28.4%[31/109],χ^(2)=5.620,P=0.013)and systemic(49.0%[50/102]vs.33.9%[37/109],χ^(2)=4.942,P=0.019)ORRs and longer intracranial(11.0 months vs.7.0 months,P<0.001)and systemic(9.0 months vs.5.0 months,P<0.001)PFS.Multivariable analysis consistently revealed an independent association between receiving ICI plus platinum-based chemotherapy as a first-line regimen and prolonged intracranial PFS(hazard ratio[HR]=0.52,95%confidence interval[CI]:0.37-0.73,P<0.001)and systemic PFS(HR=0.48,95%CI:0.35-0.66,P<0.001).No unexpected serious adverse effects were observed.Conclusion:Our study provides real-world clinical evidence that ICI combined with chemotherapy is a promising first-line treatment option for driver gene mutation-negative advanced NSCLC patients who present with brain metastasis at initial diagnosis.Clinical trial registration:https://www.clinicaltrials.gov/,OMESIA,NCT05129202.展开更多
As a promising option to provide gaseous NH_(3) for SCR system,catalytic urea hydrolysis has aroused great attention,and improving surface area and activity of catalysis are the crucial issues to be solved for efficie...As a promising option to provide gaseous NH_(3) for SCR system,catalytic urea hydrolysis has aroused great attention,and improving surface area and activity of catalysis are the crucial issues to be solved for efficient urea hydrolysis.Therefore,a composite metal oxide(TiO_(2)@Al_(2)O_(3))catalyst was prepared by a simple hydrothermal method,with mesoporous alumina(γ-Al_(2)O_(3))as substrate.The results verify the mesoporous structure and submicron cluster of TiO_(2)@Al_(2)O_(3),with exposed crystal faces of(101)and(400)for TiO_(2)andγ-Al_(2)O_(3),respectively.The electronegativity difference of Ti4+and Al3+changes the charge distribution scheme around the interface,which provides abundant acid/base sites to boost the urea hydrolysis.Consequently,for an optimal proportioning with nano TiO_(2)content at 10 wt.%,the hydrolysis efficiency can reach up to 35.2%at 100℃ in 2 h,increasing by~7.1%than that of the blank experiment.^(13)C NMR spectrum measurements provide the impossible intermediate species during urea hydrolysis.Theoretical calculations are performed to clarify the efficient H_(2)O decomposition at the interface of TiO_(2)@Al_(2)O_(3).The result offers a favorable technology for energy-efficiency urea hydrolysis.展开更多
DC short-circuit faults pose a hazard to the operation of a modular multilevel converter(MMC)-based high voltage direct current(HVDC)system,necessitating reliable fault clearing solutions with rapid reaction.However,b...DC short-circuit faults pose a hazard to the operation of a modular multilevel converter(MMC)-based high voltage direct current(HVDC)system,necessitating reliable fault clearing solutions with rapid reaction.However,because the parasitic capacitances of the main equipment oscillate with the lumped inductances of the HVDC system,strong electromagnetic oscillations with multiple frequencies occur during clearance transients.These oscillations will disturb the HVDC system’s protection and control systems.Therefore,this paper focuses on the modeling of these oscillations.First,an equivalent circuit for the MMC-based HVDC system is proposed,taking into account the parasitic capacitances of the system’s major components,such as DC reactors,connecting cables,and DC circuit breakers(DCCBs).Second,four distinct oscillation stages are postulated based on action coordination of MMCs and DCCBs,and the associated analytical equations for the oscillation frequencies are derived.Third,a 200 kV MMC-based DC converter station is subjected to an 6ms/6kA pole-to-pole(PTP)short-circuit test.Electromagnetic oscillations have a frequency range of several kHz to several hundreds of kHz.The measured waveforms correspond well with simulated results,including the parasitic characteristics.Additionally,the relative errors between the simulated and measured frequencies are less than 5%.展开更多
The surface topography of implants plays a major role in osteogenesis and immunomodulation.In this study,three types of TiO_(2) nanoarrays including nanorod arrays with a diameter of 45 nm(TiO_(2)-N),nanorod arrays wi...The surface topography of implants plays a major role in osteogenesis and immunomodulation.In this study,three types of TiO_(2) nanoarrays including nanorod arrays with a diameter of 45 nm(TiO_(2)-N),nanorod arrays with a diameter of 60 nm(TiO_(2)-N N),and nanocone arrays(TiO_(2)-NW)are prepared on titanium and the behavior of bone marrow stromal cells(BMSCs)and polarization of macrophages are studied.Compared to the planar titanium control,TiO_(2) nanoarrays facilitate osteogenesis of BMSCs and stimulate the pro-healing M2 phenotype.However,adhesion,spreading,proliferation,and osteogenic differentiation of BMSCs are more pronounced on TiO_(2)-N N than both TiO_(2)-N and TiO_(2)-NW.TiO_(2)-NN also produces the best immune microenvironment,while TiO_(2)-NW is more favorable than TiO_(2)-NN from the viewpoint of cell adhesion and spreading of osteoblasts.展开更多
C_(f)/Ta_(x)Hf_(1−x)C–SiC composites are ideal thermal structural materials for service under extreme conditions of hypersonic vehicles.However,how to synthesize TaxHf1-xC powders and efficiently fabricate C_(f)/Ta_(...C_(f)/Ta_(x)Hf_(1−x)C–SiC composites are ideal thermal structural materials for service under extreme conditions of hypersonic vehicles.However,how to synthesize TaxHf1-xC powders and efficiently fabricate C_(f)/Ta_(x)Hf_(1−x)C–SiC composites still faces some challenges.Furthermore,mechanical properties and thermophysical properties of Ta_(x)Hf_(1−x)C vary with the composition,but not monotonically.In-depth analysis of mechanical behaviors of the C_(f)/Ta_(x)Hf_(1−x)C–SiC composites is extremely important for their development and applications.In this study,the Ta_(x)Hf_(1−x)C powders(x=0.2,0.5,0.8)were successfully synthesized via solid solution of TaC and HfC at a relatively low temperature of 1800℃,with a small amount of Si as an additive.Subsequently,the efficient fabrication of 2D-C_(f)/Ta_(x)Hf_(1−x)C–SiC composites was achieved by slurry impregnation and lamination(SIL)combined with precursor infiltration and pyrolysis(PIP).In addition,the mechanical behavior of the composites was investigated systematically.It is demonstrated that the composites present remarkable non-brittle fractures,including a large number of fiber pull out and interphase debonding.Also,the fracture failure involves a complex process of microcrack generation and propagation,matrix cracking,and layer fracture.Moreover,the interfacial bonding between the fibers and the matrix is enhanced as the Ta∶Hf ratio decreases from 4∶1 to 1∶4.As a result,C_(f)/Ta_(0.2)Hf_(0.8)C–SiC composites exhibit exceptional flexural strength of 437±19 MPa,improved by 46%compared with C_(f)/Ta_(0.8)Hf_(0.2)C–SiC(299±19 MPa).This study provides a new perception of design and fabrication of ultra-high-temperature ceramic(UHTC)matrix composites with high performance.展开更多
Machine learning control(MLC)is a highly flexible and adaptable method that enables the design,modeling,tuning,and maintenance of building controllers to be more accurate,automated,flexible,and adaptable.The research ...Machine learning control(MLC)is a highly flexible and adaptable method that enables the design,modeling,tuning,and maintenance of building controllers to be more accurate,automated,flexible,and adaptable.The research topic of MLC in building energy systems is developing rapidly,but to our knowledge,no review has been published that specifically and systematically focuses on MLC for building energy systems.This paper provides a systematic review of MLC in building energy systems.We review technical papers in two major categories of applications of machine learning in building control:(1)building system and component modeling for control,and(2)control process learning.We identify MLC topics that have been well-studied and those that need further research in the field of building operation control.We also identify the gaps between the present and future application of MLC and predict future trends and opportunities.展开更多
In traditional hybrid DC circuit breakers(HCBs)schemes,complex equipment is usually required to ensure current commutation from mechanical to semiconductor switches,which cause not only additional construction costs a...In traditional hybrid DC circuit breakers(HCBs)schemes,complex equipment is usually required to ensure current commutation from mechanical to semiconductor switches,which cause not only additional construction costs and volume but also additional losses and maintenance work.Different from this condition,a low-loss and compact HCB scheme that does not use separate current commutation equipment is proposed in this study.By rationally using the charge and discharge of the snubber capacitor,the self-commutated semiconductor switch(SCS)module can integrate both the current commutation and shutdown functions,thereby greatly reducing cost and volume.The working process is discussed and analyzed in detail,and then a 10-kA prototype is developed and tested,which verifies the feasibility and effectiveness of the proposed scheme.Index Terms-HVDC circuit breakers,hybrid DC circuit breakers(HCBs),self-commutated semiconductor switch(SCS).展开更多
基金Supported by Science and Technology Achievement Transformation Project of Scientific Research Institutions(2021JDZH0019)National Modern Agricultural Industry Technology System of the Ministry of Agriculture(CARS-43-D-1)+4 种基金Sichuan Provincial Breeding Research(2021YFYZ0033)Special Fund for Basic Scientific Research Business of Sichuan Animal Science Academy(SASA202105SASA202305)Natural Science Foundation of Sichuan Province(2023NSFSC0171)Basic Research for Application of Sichuan Provincial Science and Technology Planning Project(2021YJ0267)。
文摘[Objectives]miRNAs play an important role in the proliferation and differentiation of different myoblasts.This study was conducted to elucidate the complex genetic mechanisms that affect the meat production performance of Sichuan white rabbits and reveal the regulatory role of miRNAs in their muscle growth and meat quality formation.[Methods]Three constructed skeletal muscle libraries of Sichuan white rabbits aged six months were sequenced by the solexa technology to identify known miRNAs,predict new miRNAs and construct an expression profile of muscle miRNAs.[Results]A total of 511 known miRNAs and 42 miRNAs were detected in 34089472 pure sequences,and the proportion of miRNAs with a length of 22 nt was the highest.The number of known miRNA sequences accounted for 71.38%of pure sequences,which was much higher than the proportion of other types of RNAs.The proportion of sequences from exons was 0.38%,indicating a low degree of mRNA degradation in the samples.Base U had the highest proportion at the first position,and the bases with the highest proportions at positions 8 and 10 were U and A,respectively.Muscle-specific miRNAs(miR-1,miR-133,and miR-206)ranked in the top 10 in terms of expression level.The number and expression levels of new miRNAs were lower than those of known miRNAs.The length distribution,base bias at different positions and expression profile characteristics of miRNAs might be related to the biological function of miRNAs in regulating muscle proliferation and differentiation and the action mechanisms with target genes.[Conclusions]The identification and expression of miRNAs in muscle tissues of Sichuan white rabbits will help to understand the complex molecular mechanisms of meat production performance and provide a theoretical basis for the functional research of miRNAs in meat rabbits.
文摘<strong>Background:</strong> Henoch Schonlein Purpura (HSP) is a common immune-related allergic disease in children. It is very important to understand the clinical features of this disease for doctors. <strong>Objective:</strong> To explore the clinical efficacy of glucocorticoids in the treatment of HSP in Tibetan children at high altitude, and to analyze the possible causes of HSP in children at high altitude. The risk factors of the disease provide a reference for the treatment of HSP in children in high altitude areas. <strong>Methods:</strong> Selecting January 2015 to November 2020, 88 children diagnosed with Henoch-Schonlein Purpura in the outpatient and inpatient departments of the People’s Hospital of Bomi County, Tibet Autonomous Region were the subjects of the study. Its gender, age of onset, season of onset, predisposing factors, allergy history, first symptoms, clinical manifestations, laboratory examinations, etc., perform retrospective analysis. <strong>Results: </strong>Among 88 children with allergic purpura, 55 were boys, accounting for 62.5%, and 33 were girls, accounting for 37.5%. Men have more cases than women. All have clinical manifestations of purpura of the skin, among which 35 cases have obvious triggers, of which the above there were 26 cases of respiratory infections, 6 cases of dietary factors, and 3 cases of contact with allergic substances. Simple skin type: 18 cases, accounting for 20.45%;Abdominal type: 6 cases, accounting for 6.82%;2 male cases, accounting for 33.33%;4 female cases, accounting for 66.67%;Articular type: 8 cases, accounting for 33.33%;Renal type: 2 cases, accounting for 2.27%;54 cases of mixed type, accounting for 61.36%. After glucocorticoids, the rashes disappeared, no any adverse reactions. <strong>Conclusion:</strong> Allergic purpura in children is more common in school-age children, and upper respiratory tract infection is the main predisposing factor. Skin purpura is the main clinical manifestation, often associated with lower extremity joint swelling and pain. There is no significant difference in the efficacy and course of the disease between intravenous and oral treatment. Therefore, clinicians should strictly grasp the indications of glucocorticoids to reduce the occurrence of complications.
文摘近年来,在医药卫生领域,利用真实世界数据生成真实世界证据的研究方法在药品研发、审批、适应证拓展等领域取得广泛的关注和认可,开展真实可信、高质量的真实世界研究证据(real world evidence,RWE),已成为循证医学的一个重要发展方向。本文介绍了近年来国内外关于结直肠癌真实世界研究的现状,将真实世界研究(real world research/study,RWS)与相应的随机对照研究(randomized controlled trial,RCT)的meta分析结果进行对比和评价,以阐述RWS的特征、研究方法、相对于传统RCT研究的优势,并归纳其在肠癌领域的应用现状。在此基础上,对RWS在结直肠癌临床研究中的价值和前景进行总结,为后续研究提供新的思路。
基金supported by the National Natural Science Foundation of China (609721596103200161002006)
文摘The track association problem of radar and electronic support measure (ESM) has been considered in the literature for several years.This problem is crucial for radar-to-ESM track fusion and is complicated by the presence of individual systematic errors and measurement errors.In order to improve the track association of radar and ESM sensors,a pseudo-linear filtering algorithm is proposed to estimate the target states and improve the stability of the filter.It is found that,however,the correct probability of radar-to-ESM track association decreases as the radar measurement error decreases,when the pseudo-linear filter is used for ESM sensor filtering.In view of the strange phenomenon,this paper analyzes the reason for it by using the statistic theory and further performs Monte Carlo simulation to verify the analysis.
基金funded by the National Key R&D Program of China(2018YFD1000407)the Construction of Beijing Science and Technology Innovation and Service Capacity in Top Subjects(CEFFPXM2019_014207_000032).
文摘Phytohormones are key factors in plant responsiveness to abiotic and biotic stresses,and maintaining hormone homeostasis is critically important during stress responses.Cut rose(Rosa hybrida)flowers experience dehydration stress during postharvest handling,and jasmonic acid(JA)levels change as a result of this stress.However,how JA is involved in dehydration tolerance remains unclear.We investigated the functions of the JA-and dehydration-induced RhHB1 gene,which encodes a homeodomain-leucine zipper Iγ-clade transcription factor,in rose flowers.Silencing RhHB1 decreased petal dehydration tolerance and resulted in a persistent increase in JA-Ile content and reduced dehydration tolerance.An elevated JA-Ile level had a detrimental effect on rose petal dehydration tolerance.RhHB1 was shown to lower the transient induction of JA-Ile accumulation in response to dehydration.In addition to transcriptomic data,we obtained evidence that RhHB1 suppresses the expression of the lipoxygenase 4(RhLOX4)gene by directly binding to its promoter both in vivo and in vitro.We propose that increased JA-Ile levels weaken the capacity for osmotic adjustment in petal cells,resulting in reduced dehydration tolerance.In conclusion,a JA feedback loop mediated by an RhHB1/RhLOX4 regulatory module provides dehydration tolerance by fine-tuning bioactive JA levels in dehydrated flowers.
文摘From the lifecycle of schistosome, the phenomenon of time delay is widespread. In this paper, a two-dimensional system is studied that incorporates two time delays which are the incubation period of human and snail, respectively. Our purpose is to demonstrate that the time delays are harmless for stability of equilibria of the system. Further, sufficient conditions of stability of equilibria are obtained.
基金supported by Shenzhen Municipal Science and Technology Innovation Commission(Grant Nos.JCYJ20170818112901473 and GJHZ20200731095604015)the Department of Science and Technology of Guangdong Province,China(Grant Nos.2020A0505100059,2020A1515011531,and 2020A1515011451)by the Ministry of Education and Science of the Russian Federation in the frame of the state assignment(Grant No.FSSN-2020-0003)。
文摘Copper ion conducting solid electrolyte Rb_(4)Cu_(16)I_(6.5)Cl_(13.5)was prepared by means of mechano-chemical method.The structure and morphology of the powder was investigated by x-ray diffraction and scanning electron microscopy.The grain size was estimated to be 0.2-0.9μm and the ionic conductivity at room temperature was approximately 0.206 S/cm.The solid electrolyte Rb_(4)Cu_(16)I_(6.5)Cl_(13.5)was exploited for copper ion beam generation.The copper ion emission current of several nA was successfully obtained at acceleration voltages of 15 kV and temperature of 197℃in vacuum of 2.1×10^(-4)Pa.A good linear correlation between the logarithmic ion current(logI)and the square root of the acceleration voltage(U_(acc))at high voltage range was obtained,suggesting the Schottky emission mechanism in the process of copper ion beam generation.
基金Supported by Special Fund for Agro-scientific Research in the Public Interest from the Ministry of Agriculture(201003061)Key Project of Livestock and Poultry Breeding of Sichuan Province(01NG029-18)
文摘In this study,using Liangshan semi-fine wool sheep as an experimental material,full-length CDS sequence of IGFBP-1 gene was cloned with RT-PCR method and analyzed with bioinformatics methods. The results showed that the full-length CDS sequence of IGFBP-1 gene in Liangshan semi-fine wool sheep was792 bp in length,encoding 263 amino acids. The CDS sequence shared 97%,76% and 74% homology with bovine,human and rat,respectively; the amino acid sequence shared 97%,69% and 71%,respectively. The Gen Bank accession number was FJ589639. 1. The amino acid molecular weight of IGFBP-1 was 27. 8k D,and the theoretical isoelectric point( p I) was 5. 99. The result of phylogenetic analysis showed that IGFBP-1 gene in Liangshan semi-fine wool sheep exhibited close phylogenetic relationships with bovine,goat and other mammals,and distant phylogenetic relationships with chicken and fish. IGFBP-1 gene had obvious hydrophobic and hydrophilic regions,harboring one signal peptide,one transmembrane region,16 phosphorylation sites,six N-glycosylation sites and eight O-glycosylation sites. The result of secondary structure analysis showed that the random coil,α-helix and β-sheet regions accounted for 61. 98%,24. 33% and 13. 69%,respectively. The result of tertiary structure analysis showed that IGFBP-1 harbors an IGFBP_N domain and a thyroglobulin type-I domain. This study laid a solid foundation for further investigating the function of IGFBP-1 gene in sheep.
基金Supported by Special Fund for Agro-scientific Research in the Public Interest from the Ministry of Agriculture(201003061)Key Project of Livestock and Poultry Breeding of Sichuan Province(01NG029-18)
文摘In this study,full-length CDS sequence of IGFBP-7 gene was cloned from Liangshan semi-fine wool sheep with RT-PCR method and analyzed with bioinformatics methods. The results showed that the full-length CDS sequence of IGFBP-7 gene in Liangshan semi-fine wool sheep was 846 bp in length,encoding282 amino acids. The CDS sequence shared 99%,95% and 90% homology with bovine,human and rat,respectively; the amino acid sequence shared 98%,93%and 89%,respectively. The GenB ank accession number was FJ589640. 1. The amino acid molecular weight of IGFBP-7 was 29. 0 kD,and the theoretical isoelectric point( pI) was 8. 25. The result of phylogenetic analysis showed that IGFBP-7 gene in Liangshan semi-fine wool sheep exhibited close phylogenetic relationships with bovine,goat and other mammals,and distant phylogenetic relationships with Danio rerio and Haliotis diversicolor. IGFBP-7 gene had uniformly distributed hydrophobic and hydrophilic regions,harboring one signal peptide,two transmembrane regions,16 phosphorylation sites,four N-glycosylation sites and one O-glycosylation site. The result of secondary structure analysis showed that the random coil,α-helix and β-sheet regions accounted for 64. 89%,19. 86% and 15. 25%,respectively. The result of tertiary structure analysis showed that IGFBP-7 harbors an IGFBP_N domain and an Ig-like domain. This study provided scientific basis for further investigating the function of IGFBP-7 gene in sheep.
基金support by the National Natural Science Foundation of China(Grant Nos.11821303 and 11761131004)supported by grants from the National Research Foundation of Korea(2019R1A2C2085965 and 2020R1A4A2002885)+3 种基金supported by JPL grant 1571564supported by JSPS KAK-ENHI(Grant Nos.JSPS24253004,JSPS26247023,JSPS23340064,JSPS15H00781,JP16H06287,JP17H02871 and JP19KK0082)supported by Tsinghua University Initiative Scientific Research Program(Program ID 2019Z07L02017)supported by the Natural Sciences and Engineering Research Council of Canada(NSERC)under the funding(reference#CITA 490888-16)。
文摘We report the discovery of KMT-2020-BLG-0414 Lb,with a planet-to-host mass ratio q2=0.9-1.2×10-5=3-4 q⊕at 1σ,which is the lowest mass-ratio microlensing planet to date.Together with two other recent discoveries(4?q/q⊕?6),it fills out the previous empty sector at the bottom of the triangular(log s,log q)diagram,where s is the planet-host separation in units of the angular Einstein radiusθE.Hence,these discoveries call into question the existence,or at least the strength,of the break in the mass-ratio function that was previously suggested to account for the paucity of very low-q planets.Due to the extreme magnification of the event,Amax~1450 for the underlying single-lens event,its light curve revealed a second companion with q3~0.05 and|log s3|~1,i.e.,a factor~10 closer to or farther from the host in projection.The measurements of the microlens parallaxπE and the angular Einstein radiusθE allow estimates of the host,planet and second companion masses,(M1,M2,M3)~(0.3 M⊙,1.0 M⊕,17 MJ),the planet and second companion projected separations,(a⊥,2,a⊥,3)~(1.5,0.15 or 15)au,and system distance DL~1 kpc.The lens could account for most or all of the blended light(I~19.3)and so can be studied immediately with high-resolution photometric and spectroscopic observations that can further clarify the nature of the system.The planet was found as part of a new program of high-cadence follow-up observations of high-magnification events.The detection of this planet,despite the considerable difficulties imposed by COVID-19(two KMT sites and OGLE were shut down),illustrates the potential utility of this program.
文摘Objective:Lianhua Qingwen combined with Western medicine(LHQW+WM)has been proposed as a viable treatment for coronavirus disease 2019(COVID-19).Interestingly,umbrella reviews of systematic reviews(SRs),which provide the most comprehensive evidence,are the best evidence in evidence-based medicine.Therefore,an umbrella review of SRs that summarizes and evaluates the efficacy of LHQW+WM for COVID-19 is urgently required.Methods:Overall,6 databases were used to conduct a comprehensive literature search from inception to January 22,2022.The corrected covered area(CCA)was used to analyze the overlapping between SRs.Meta-analysis was conducted when that of the included SRs was inappropriate.A MeaSurement Tool to Assess Systematic Reviews(AMSTAR-2)was also employed to assess the quality of the included SRs.Results:In total,12 SRs were identified,which included 12 unique primary studies.The included SRs ranged in quality from moderate to critically low and had an extremely high CCA(36.4%).Compared to conventional treatment,LHQW+WM showed efficacy concerning fatigue recovery[risk ratio(RR)=1.69,95%confidence interval(CI):1.04-2.73,n=2,I2=0%],cough recovery(RR=1.65,95%CI:1.09-2.51,n=3,I2=39.1%),and overall effective rates(RR=1.17,95%CI:1.07-1.28,n=3,I2=17.5%).Conclusion:LHQW+WM may improve the clinical symptoms of patients with COVID-19;however,the results should be interpreted cautiously because of the rigorous processes in the included SRs.
基金supported by the National Natural Science Foundation of China(No.51772310)National Natural Science Foundation of China(No.52222202)+3 种基金Chinese Academy of Sciences Key Research Program of Frontier Sciences(No.QYZDYSSWJSC031)Key Deployment Projects of the Chinese Academy of Sciences(No.ZDRW-CN2019-01)Shanghai Sailing Program(No.21YF1454600)Outstanding Chinese and Foreign Youth Exchange Program of China Association of Science and Technology.
文摘In this work,hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide(3D-rGO)skeleton and lamellar boron nitride(BN)/silicon carbide(SiC)coatings are prepared by chemical vapor infiltration(CVI)process.The graphene framework prepared by 3D printing and frozen self-assembly exhibits a lightweight structure and a perforated conductive network,which extends the transmission path of incident microwaves.The introduced ceramic coatings can effectively tune the impedance matching degree and supply a lossy phase,and the hierarchical structure of the composites enhances the multiple scattering of the incident microwaves.As expected,the 3D-rGO/BN/SiC composites possess an excellent absorbing performance with a minimum reflection loss value of–37.8 dB,and the widest effective absorbing bandwidth(RL<–10 dB)of 5.90 GHz is obtained.The controllable fabrication of composites can provide a guideline for rational design and fabrication of high-performance electromagnetic waves absorbing materials in practical applications.
基金support from the National Natural Science Foundation of China(Nos.82003206 and 82173338)Natural Science Foundation of Hunan Province(Nos.2020SK2031,2020SK2030,2021RC4040,and 2020JJ3025).
文摘Background:Immune checkpoint inhibitors(ICIs)are increasingly used as first-line therapy for patients with advanced non-small cell lung cancer(NSCLC)harboring no actionable mutations;however,data on their efficacy among patients presenting with intracranial lesions are limited.This study aimed to explore the efficacy and safety of ICIs combined with chemotherapy in advanced NSCLC patients with measurable brain metastasis at initial diagnosis.Methods:Our study retrospectively analyzed clinical data of a total of 211 patients diagnosed with driver gene mutation-negative advanced NSCLC with measurable,asymptomatic brain metastasis at baseline from Hunan Cancer Hospital between January 1,2019 and September 30,2021.The patients were stratified into two groups according to the first-line treatment regimen received:ICI combined with chemotherapy(n=102)or chemotherapy(n=109).Systemic and intracranial objective response rates(ORRs)and progression-free survival(PFS)were analyzed.Adverse events were also compared between the groups.Results:Compared with the chemotherapy-based regimen,the ICI-containing regimen was associated with a significantly higher intracranial(44.1%[45/102]vs.28.4%[31/109],χ^(2)=5.620,P=0.013)and systemic(49.0%[50/102]vs.33.9%[37/109],χ^(2)=4.942,P=0.019)ORRs and longer intracranial(11.0 months vs.7.0 months,P<0.001)and systemic(9.0 months vs.5.0 months,P<0.001)PFS.Multivariable analysis consistently revealed an independent association between receiving ICI plus platinum-based chemotherapy as a first-line regimen and prolonged intracranial PFS(hazard ratio[HR]=0.52,95%confidence interval[CI]:0.37-0.73,P<0.001)and systemic PFS(HR=0.48,95%CI:0.35-0.66,P<0.001).No unexpected serious adverse effects were observed.Conclusion:Our study provides real-world clinical evidence that ICI combined with chemotherapy is a promising first-line treatment option for driver gene mutation-negative advanced NSCLC patients who present with brain metastasis at initial diagnosis.Clinical trial registration:https://www.clinicaltrials.gov/,OMESIA,NCT05129202.
基金supported by the Science and Technology Projects of China Huaneng Group Co.,Ltd.(No.HNKJ21-H15)the National Natural Science Foundation of China(No.22106084)the Special Projects of China Postdoctoral Science Foundation(No.2022T150350).
文摘As a promising option to provide gaseous NH_(3) for SCR system,catalytic urea hydrolysis has aroused great attention,and improving surface area and activity of catalysis are the crucial issues to be solved for efficient urea hydrolysis.Therefore,a composite metal oxide(TiO_(2)@Al_(2)O_(3))catalyst was prepared by a simple hydrothermal method,with mesoporous alumina(γ-Al_(2)O_(3))as substrate.The results verify the mesoporous structure and submicron cluster of TiO_(2)@Al_(2)O_(3),with exposed crystal faces of(101)and(400)for TiO_(2)andγ-Al_(2)O_(3),respectively.The electronegativity difference of Ti4+and Al3+changes the charge distribution scheme around the interface,which provides abundant acid/base sites to boost the urea hydrolysis.Consequently,for an optimal proportioning with nano TiO_(2)content at 10 wt.%,the hydrolysis efficiency can reach up to 35.2%at 100℃ in 2 h,increasing by~7.1%than that of the blank experiment.^(13)C NMR spectrum measurements provide the impossible intermediate species during urea hydrolysis.Theoretical calculations are performed to clarify the efficient H_(2)O decomposition at the interface of TiO_(2)@Al_(2)O_(3).The result offers a favorable technology for energy-efficiency urea hydrolysis.
基金supported by the National Key Research and Development Program of China(2021YFB2400602)。
文摘DC short-circuit faults pose a hazard to the operation of a modular multilevel converter(MMC)-based high voltage direct current(HVDC)system,necessitating reliable fault clearing solutions with rapid reaction.However,because the parasitic capacitances of the main equipment oscillate with the lumped inductances of the HVDC system,strong electromagnetic oscillations with multiple frequencies occur during clearance transients.These oscillations will disturb the HVDC system’s protection and control systems.Therefore,this paper focuses on the modeling of these oscillations.First,an equivalent circuit for the MMC-based HVDC system is proposed,taking into account the parasitic capacitances of the system’s major components,such as DC reactors,connecting cables,and DC circuit breakers(DCCBs).Second,four distinct oscillation stages are postulated based on action coordination of MMCs and DCCBs,and the associated analytical equations for the oscillation frequencies are derived.Third,a 200 kV MMC-based DC converter station is subjected to an 6ms/6kA pole-to-pole(PTP)short-circuit test.Electromagnetic oscillations have a frequency range of several kHz to several hundreds of kHz.The measured waveforms correspond well with simulated results,including the parasitic characteristics.Additionally,the relative errors between the simulated and measured frequencies are less than 5%.
基金supported by the National Natural Science Foundation of China (No.52171240)the Postdoctoral Science Foundation of China (No.2021M691992)+3 种基金the Major Projects in Research and Development of Shanxi (Projects of International Cooperation,No.201803D421090)the City University of Hong Kong Donation Research Grant (No.DON-RMG 9229021)the Hong Kong PDFS-RGC Postdoctoral Fellowship Scheme (Nos.PDFS2122-1S08 and CityU 9061014)the Hong Kong HMRF (Health and Medical Research Fund) (Nos.2120972 and CityU 9211320).
文摘The surface topography of implants plays a major role in osteogenesis and immunomodulation.In this study,three types of TiO_(2) nanoarrays including nanorod arrays with a diameter of 45 nm(TiO_(2)-N),nanorod arrays with a diameter of 60 nm(TiO_(2)-N N),and nanocone arrays(TiO_(2)-NW)are prepared on titanium and the behavior of bone marrow stromal cells(BMSCs)and polarization of macrophages are studied.Compared to the planar titanium control,TiO_(2) nanoarrays facilitate osteogenesis of BMSCs and stimulate the pro-healing M2 phenotype.However,adhesion,spreading,proliferation,and osteogenic differentiation of BMSCs are more pronounced on TiO_(2)-N N than both TiO_(2)-N and TiO_(2)-NW.TiO_(2)-NN also produces the best immune microenvironment,while TiO_(2)-NW is more favorable than TiO_(2)-NN from the viewpoint of cell adhesion and spreading of osteoblasts.
基金support from the National Key R&D Program of China(No.2022YFB3707700)Program of Shanghai Academic/Technology Research Leader(No.23XD1424300)the National Natural Science Foundation of China(No.52332003)are greatly acknowledged.
文摘C_(f)/Ta_(x)Hf_(1−x)C–SiC composites are ideal thermal structural materials for service under extreme conditions of hypersonic vehicles.However,how to synthesize TaxHf1-xC powders and efficiently fabricate C_(f)/Ta_(x)Hf_(1−x)C–SiC composites still faces some challenges.Furthermore,mechanical properties and thermophysical properties of Ta_(x)Hf_(1−x)C vary with the composition,but not monotonically.In-depth analysis of mechanical behaviors of the C_(f)/Ta_(x)Hf_(1−x)C–SiC composites is extremely important for their development and applications.In this study,the Ta_(x)Hf_(1−x)C powders(x=0.2,0.5,0.8)were successfully synthesized via solid solution of TaC and HfC at a relatively low temperature of 1800℃,with a small amount of Si as an additive.Subsequently,the efficient fabrication of 2D-C_(f)/Ta_(x)Hf_(1−x)C–SiC composites was achieved by slurry impregnation and lamination(SIL)combined with precursor infiltration and pyrolysis(PIP).In addition,the mechanical behavior of the composites was investigated systematically.It is demonstrated that the composites present remarkable non-brittle fractures,including a large number of fiber pull out and interphase debonding.Also,the fracture failure involves a complex process of microcrack generation and propagation,matrix cracking,and layer fracture.Moreover,the interfacial bonding between the fibers and the matrix is enhanced as the Ta∶Hf ratio decreases from 4∶1 to 1∶4.As a result,C_(f)/Ta_(0.2)Hf_(0.8)C–SiC composites exhibit exceptional flexural strength of 437±19 MPa,improved by 46%compared with C_(f)/Ta_(0.8)Hf_(0.2)C–SiC(299±19 MPa).This study provides a new perception of design and fabrication of ultra-high-temperature ceramic(UHTC)matrix composites with high performance.
文摘Machine learning control(MLC)is a highly flexible and adaptable method that enables the design,modeling,tuning,and maintenance of building controllers to be more accurate,automated,flexible,and adaptable.The research topic of MLC in building energy systems is developing rapidly,but to our knowledge,no review has been published that specifically and systematically focuses on MLC for building energy systems.This paper provides a systematic review of MLC in building energy systems.We review technical papers in two major categories of applications of machine learning in building control:(1)building system and component modeling for control,and(2)control process learning.We identify MLC topics that have been well-studied and those that need further research in the field of building operation control.We also identify the gaps between the present and future application of MLC and predict future trends and opportunities.
基金supported by the National Natural Science Foundation of China(No.52107004)the China Postdoctoral Science Foundation(No.2020M680484 and No.2021T140201)the Fundamental Research Funds for the Central Universities(No.2021MS003)。
文摘In traditional hybrid DC circuit breakers(HCBs)schemes,complex equipment is usually required to ensure current commutation from mechanical to semiconductor switches,which cause not only additional construction costs and volume but also additional losses and maintenance work.Different from this condition,a low-loss and compact HCB scheme that does not use separate current commutation equipment is proposed in this study.By rationally using the charge and discharge of the snubber capacitor,the self-commutated semiconductor switch(SCS)module can integrate both the current commutation and shutdown functions,thereby greatly reducing cost and volume.The working process is discussed and analyzed in detail,and then a 10-kA prototype is developed and tested,which verifies the feasibility and effectiveness of the proposed scheme.Index Terms-HVDC circuit breakers,hybrid DC circuit breakers(HCBs),self-commutated semiconductor switch(SCS).
