Transplantation of human placental chorionic plate-derived mesenchymal stem cells for repair of neurological damage in neonatal hypoxic-ischemic encephalopathy

Neonatal hypoxic-ischemic encephalopathy is often associated with permanent cerebral palsy,neurosensory impairments,and cognitive deficits,and there is no effective treatment for complications related to hypoxic-ischemic encephalopathy.The therapeutic potential of human placental chorionic plate-derived mesenchymal stem cells for various diseases has been explored.However,the potential use of human placental chorionic plate-derived mesenchymal stem cells for the treatment of neonatal hypoxic-ischemic encephalopathy has not yet been investigated.In this study,we injected human placental chorionic plate-derived mesenchymal stem cells into the lateral ventricle of a neonatal hypoxic-ischemic encephalopathy rat model and observed significant improvements in both cognitive and motor function.Protein chip analysis showed that interleukin-3 expression was significantly elevated in neonatal hypoxic-ischemic encephalopathy model rats.Following transplantation of human placental chorionic plate-derived mesenchymal stem cells,interleukin-3 expression was downregulated.To further investigate the role of interleukin-3 in neonatal hypoxic-ischemic encephalopathy,we established an in vitro SH-SY5Y cell model of hypoxic-ischemic injury through oxygen-glucose deprivation and silenced interleukin-3 expression using small interfering RNA.We found that the activity and proliferation of SH-SY5Y cells subjected to oxygen-glucose deprivation were further suppressed by interleukin-3 knockdown.Furthermore,interleukin-3 knockout exacerbated neuronal damage and cognitive and motor function impairment in rat models of hypoxic-ischemic encephalopathy.The findings suggest that transplantation of hpcMSCs ameliorated behavioral impairments in a rat model of hypoxic-ischemic encephalopathy,and this effect was mediated by interleukin-3-dependent neurological function.

Functional Roux-en-Y Gastric Bypass (F-RYGB), with Preservation of Duodenal Access: Report of Two Revisional Cases of Sleeve Gastrectomy

Objective: This case report aimed to demonstrate a possible neuromuscular effect of Latarjet nerves transection or truncal vagotomy, in association with sleeve gastrectomy plus antrojejunostomy, in order to reproduce a Roux-en-Y gastric bypass (RYGB) mechanistic principles, in patients with previous Sleeve Gastrectomy (SG) who had had weight regain, with or without concomitant gastroesophageal reflux disease (GERD). Background: Sleeve gastrectomy (SG) is one of the most frequently performed bariatric operations worldwide. Nevertheless, weight regain and gastroesophageal reflux disease (GERD) have been consistently demonstrated, in association with this technique, which may require a revisional procedure. RYGB is an option in such a situation but, implies in gastrointestinal exclusions, which represents a shortcoming of this revision. Surpassing this inconvenient would be of great value for the patients. Methods: We describe herein two cases of SG revision for weight regain and GERD, with a follow-up of one year. Gastroesophageal reflux disease was evaluated by validated questionnaire, upper endoscopy, seriography, high resolution manometry (HRM) and impedance pHmetry (I-pHmetry), in the pre and postoperative periods. A re-Sleeve Gastrectomy with antrojejunal anastomosis was done in both cases, after informed consents. The Latarjet nerves were transected in one case, due to a bleeding in the left gastric vessels and a truncal vagotomy was required in the other, to appropriately treat an associated hiatal hernia. Results: In the postoperative evaluation it was observed a pyloric spasm in both cases, during seriography and endoscopy, kept until the one-year follow-up. There was unidirectional contrast flow to the gastrointestinal anastomosis, filling the jejunal limb, in radiologic contrast study. No contrast passed through the pylorus. Nonetheless, the duodenum was kept endoscopically accessible. In the one-year evaluation, weight loss was adequate and GERD resolution was obtained in both cases, confirmed by endoscopic and functional esophageal assessment, together with symptoms questionnaire. Conclusion: The association of Latarjet nerves sectioning or truncal vagotomy with re-sleeve gastrectomy plus gastrointestinal anastomosis (antrojejunal), in a revision for a failed sleeve, can represent a technical approach, to reproduce RYGB results, without exclusions and with duodenum endoscopic accessibility maintenance. It maybe could be applied for primary surgeries. Additional studies are necessary to confirm this hypothesis.

Laser-optimized Pt-Y alloy nanoparticles embedded in Pt-Y oxide matrix for high stability and ORR electrocatalytic activity

The development of active yet stable catalysts for oxygen reduction reaction(ORR)is still a major issue for the extensive permeation of fuel cells into everyday technology.While nanostructured Pt catalysts are to date the best available systems in terms of activity,the same is not true for stability,particularly under operating conditions.In this work,Pt_(Х)Y alloy nanoparticles are proposed as active and durable electrocatalysts for ORR.Pt_(Х)Y nanoalloys are synthesized and further optimized by laser ablation in liquid followed by laser fragmentation in liquid.The novel integrated laser-assisted methodology succeeded in producing Pt_(Х)Y nanoparticles with the ideal size(<10 nm)of commercial Pt catalysts,yet resulting remarkably more active with E_(1/2)=0.943 V vs.RHE,specific activity=1095μA cm^(-2) and mass activity>1000 A g^(-1).At the same time,the nanoalloys are embedded in a fine Pt oxide matrix,which allows a greater stability of the catalyst than the commercial Pt reference,as directly verified on a gas diffusion electrode.

Effect of Humidity on Formaldehyde Oxidation over Ce_(0.8)Zr_(0.2)O_(y)Catalyst

In the preparation of a series of Ce_(0.8)Zr_(0.2)O_(y)catalysts catalyzing the removal of formaldehyde,BET,H2-TPR,IR,SEM,XPS,and XRD were used to characterize the catalyst,and the influence of humidity on the catalyst activity was studied by adjusting the humidity during the process.The experimental results showed that the formaldehyde removal rate increased with the increase of humidity.When the humidity was higher than 50%,the formaldehyde removal rate decreased by 3%over that when the humidity was 50%.The characterization results showed that humidity facilitated the activation of oxygen and the formation of hydroxyl groups,which both promoted the formation and oxidative decomposition of intermediates and prevented the deposition of intermediates that clogged the pores,allowing more formaldehyde to be adsorbed and oxidized,which increased the activity of the catalyst.This provides new mechanistic evidence for the oxidation of formaldehyde and helps in the development of relatively low-cost materials for formaldehyde purification.

Effects of Inoculation with Phosphate Solubilizing Bacteria on the Physiology,Biochemistry,and Expression of Genes Related to the Protective Enzyme System of Fritillaria taipaiensis P.Y.Li

Fritillaria taipaiensis P.Y.Li is a widely used medicinal herb in treating pulmonary diseases.In recent years,its wild resources have become scarce,and the demand for efficient artificial cultivation has significantly increased.This article is the first to apply phosphate solubilizing bacteria isolated from the rhizosphere soil of F.taipaiensis P.Y.Li to the cultivation process of F.taipaiensis P.Y.Li.The aim is to identify suitable reference strains for the artificial cultivation and industrial development of F.taipaiensis P.Y.Li by examining the effects of various phosphate solubilizing bacteria and their combinations on photosynthesis,physiological and biochemical properties,and gene expression related to the protective enzyme system in F.taipaiensis P.Y.Li.The experiment,conducted in pots at room temperature,included a control group(CK)and groups inoculated with inorganic phosphorussolubilizing bacteria:W1(Bacillus cereus),W2(Serratia plymuthica),W12(Bacillus cereus and Serratia plymuthica),and groups inoculated with organophosphorus-solubilizing bacteria:Y1(Bacillus cereus),Y2(Bacillus cereus),Y12(Bacillus cereus and Bacillus cereus),totaling seven groups.Compared to CK,most growth indices in the bacterial addition groups showed significant differences,with W12 achieving the highest values in all indices except the leaf area index.The content of photosynthetic pigments,photosynthetic parameters,and osmoregulatory substances increased variably in each bacterial treatment group.W12 exhibited the highest content of chlorophyll a and soluble protein,while W1 had the highest free proline content.The activities of peroxidase(POD),superoxide dismutase(SOD),and catalase(CAT)in all inoculated groups were higher than in CK,with significant changes in SOD and CAT activities.The malondialdehyde(MDA)content in all inoculated groups was lower than in CK,with Y12 being the lowest,at approximately 30%of CK.Gene expression corresponding to these three enzymes also increased variably,with POD expression in Y2 being the highest at 2.73 times that of CK.SOD and CAT expression in Y12 were the highest,at 1.84 and 4.39 times that of CK,respectively.These results indicate that inoculating phosphate solubilizing bacteria can enhance the growth of F.taipaiensis P.Y.Li,with the mixed inoculation groups W12 and Y12 demonstrating superior effects.This lays a theoretical foundation for selecting bacterial fertilizers in the cultivation process of F.taipaiensis P.Y.Li.

Pyloric Sympathectomy: A Novel Way to Get Pylorus Relaxation? Report of Two Bariatric Cases

Objective: This case report aimed to demonstrate a possible neuromuscular effect of pyloric sympathectomy on the pylorus motility, leading to its permanent relaxation, observed in two bariatric surgical cases, one primary and the other, revisional. Background: Pyloric sphincter is a physiological barrier to free gastric emptying. In sleeve gastrectomy and in Roux-en-Y gastric bypass revisions, that put the remnant stomach in transit, the pylorus can contribute to generate a high intragastric pressure, which could lead to acute gastric fistulas and/or chronic gastroesophageal reflux disease. The possibility of functionally relaxing the pylorus, promoting intragastric pressure reduction, could represent a protective maneuver against these complications. Methods: We describe herein a surgical maneuver applied in two cases of bariatric surgeries, with the intention of facilitating antrum-duodenal region exposure, in a sleeve gastrectomy and in a Roux-en-Y gastric bypass conversion to SADI-S. For this, a ligation of terminal peripyloric vessels was done, allowing a passage of a tape, which surrounded the pylorus, for its traction. In both cases, 30-day and 1-year endoscopic evaluations were done, to assess esophagitis signs, anastomosis healing and anatomical pouch aspect. A clinical evaluation was also done, to assess gastroesophageal symptoms (validated questionnaire). Results: In the postoperative endoscopic evaluations, no esophagitis were observed in any case and the gastric pouches had normal aspect, with the expected anatomical findings, compatible with the surgeries performed. The anastomosis healed without problems, in the revisional case. Interestingly, in both cases, it was observed a complete pyloric sphincter relaxation, which lasted until 1-year endoscopic evaluation. There were no fistulas, nor esophagitis in any of these cases. Clinically, there were no symptoms of gastroesophageal reflux disease (validated questionnaire). Conclusion: The observation of a pyloric durable atomy, that followed peripyloric dissection and vessels ligation (arterial branches), with its concomitant sympathectomy, can represent a new way of decompressing gastric chamber, either in primary or revisional bariatric surgeries. This maneuver can be protective against acute fistulas and gastroesophageal disease. Additional studies are necessary to confirm this hypothesis.

Coercivity mechanism of La-Nd-Fe-B films with Y spacer layer

The effect of the Y spacer layer on the phase composition,coercivity,and magnetization reversal processes of La-Nd-Fe-B films has been investigated.The addition of a 10 nm Y spacer layer increases the coercivity of the film to 1.36 T at 300 K and remains 0.938 T at 380 K.As the thickness of the Y spacer layer increases,Y participates in the formation of the main phase in the film,and further regulates the formation of La-B phases.The results of the first-order reversal curve(FORC)and micromagnetic fitting show that the coercivity of all the films is dominated by nucleation mechanism.The c-axis preferred orientation,good magnetic microstructure parameters and the largest dipole interaction enhance the coercivity.Therefore,the introduction of the Y spacer layer can be an effective way to improve the coercivity of La-Nd-Fe-B film over a wide temperature range of 150 K-380 K.

Anticancer therapeutic strategies for targeting mutant p53-Y220C

The tumor suppressor p53 is a transcription factor with a powerful antitumor activity that is controlled by its negative regulator murine double minute 2(MDM2,also termed HDM2 in humans)through a feedback mechanism.At the same time,TP53 is the most frequently mutated gene in human cancers.Mutant p53 proteins lose wild-type p53 tumor suppression functions but acquire new oncogenic properties,among which are deregulating cell proliferation,increasing chemoresistance,disrupting tissue architecture,and promoting migration,invasion and metastasis as well as several other pro-oncogenic activities.The oncogenic p53 mutation Y220C creates an extended surface crevice in the DNA-binding domain destabilizing p53 and causing its denaturation and aggregation.This cavity accommodates stabilizing small molecules that have therapeutic values.The development of suitable small-molecule stabilizers is one of the therapeutic strategies for reactivating the Y220C mutant protein.In this review,we summarize approaches that target p53-Y220C,including reactivating this mutation with small molecules that bind Y220C to the hydrophobic pocket and developing immunotherapies as the goal for the near future,which target tumor cells that express the p53-Y220C neoantigen.

Hierarchical FeO_(χ)H_(y)@Ni_(3)B hybrid for efficient alkaline oxygen evolution at high current density

Electrocatalysts with high activity and long-term durability are vital toward large-scale hydrogen pro-duction from electrocatalytic water splitting.Here,the self-supported electrode(FeO_(χ)H_(y)@Ni_(3)B/NF)with hierarchical heterostructure was simply prepared by using Ni_(3)B chunks grown on nickel foam as sub-strate to in situ form vertical FeO_(χ)H_(y)nanosheets.Such hybrid shows efficient oxygen evolution reaction activity with overpotentials as low as 267 and 249 mV at 100 mA cm^(-2)in 1 M KOH solution and 30 wt%KOH solution,respectively.Meanwhile,it also exhibits excellent catalytic stability,sustaining catalysis at 500 mA cm^(-2)in 1 M KOH solution for 200 h,and even for 200 h at 1000 mA cm^(-2)in 30 wt%KOH solution.Further experimental results reveal that the FeO_(χ)H_(y)@Ni_(3)B/NF is endowed with superhydrophilic and superaerophobic surface properties,which not only provide more mass transport channels,as well as facilitated the diffusion of reaction intermediates and gas bubbles.Also,it holds faster reaction kinetics,more accessible active sites and accelerated electron transfer rates due to strong synergistic interactions attheheterogeneous interface.

不同预时效挤压态Mg−Gd−Y−Zn−Zr合金的再结晶行为和强化机制

通过控制预时效时间制备3种不同状态的试样,研究不同预时效状态对挤压态Mg−9.5Gd−4Y−2.2Zn−0.5Zr(质量分数,%)合金的动态再结晶行为(DRX)和性能的影响。结果表明,欠时效挤压(UAE)样品的细晶体积分数为17.4%,而峰时效挤压(PAE)和过时效挤压(OAE)样品的细晶体积分数分别达到89.7%和50.4%。在晶粒内部和晶界处分布的致密、细小的β颗粒相通过粒子激发形核机制显著提高了形核位点和位错密度。然而,致密针状γ'相抑制位错滑移,延迟DRX形核。PEA和OAE样品中细小晶粒的差异归因于原始颗粒相的数量和尺寸的不同,而其拉伸性能的差异归因于不同的显微组织。由于晶界强化和析出强化机制的贡献更大,PAE样品具有更优异的拉伸性能。

一种Y型延迟荧光分子及其蓝光和绿光OLED应用

以噻吨酮作为受体、3,6-(二咔唑基)三咔唑作为给体设计合成了一种具有延迟荧光特性的Y型分子(TX-TCz)。模拟计算表明化合物HOMO和LUMO能级完全分离且在苯环上存在较小的重叠,有助于获得小的S1和T1的能级差ΔEST。随着溶剂极性的增加,化合物发射峰发生明显的红移且由于电荷转移态和局域激发态的共存产生了双峰发射。在纯膜中TX-TCz的发射峰位于513 nm,量子产率为11.5%。基于低温下荧光和磷光发射峰,计算得到化合物的ΔEST为0.03 eV,并且检测到µs级的寿命,说明化合物具有延迟荧光发射。与此同时,化合物展示了良好的热稳定性能和电化学性能,有助于制备高性能OLED器件。其在掺杂浓度为5%(wt)的器件中展示了良好的蓝光性能,发射峰位于463 nm,最大外量子效率为1.53%;在非掺杂器件中展示了良好的绿光发射(522 nm),最大外量子效率达到1.81%。

基于Y-SNP和Y-STR揭示汉族人群父系遗传关系

汉族是中国人口最多的民族,现有研究多集中于汉族人群的起源、迁徙、融合等遗传历史,以及局部地区汉族人群的父系遗传关系,鲜有全局视角下的汉族人群父系遗传结构研究。本研究检测了362份青海、四川和辽宁的汉族无关男性样本,整合已发表文献相关数据,最终获得了国内15个省份16个汉族人群1830人份样本,覆盖89个Y-SNP、16个Y-STR的数据。通过统计Y-SNP单倍群频率、Y-STR单倍型多样性,使用主成分分析(principal component analysis,PCA)、系统发育树、单倍型网络等分析,综合Y-SNP和Y-STR两个反映不同时间尺度的遗传标记,研究不同地区汉族人群之间的遗传分化、汉族人群与其周边少数民族的遗传关系。单倍群频率统计结果显示单倍群O-M175是汉族人群主体单倍群(青海汉族60.53%~广东汉族92.7%),其下游亚单倍群呈现地域差异化分布。单倍群O2-M122高频分布于各地汉族,总体分布趋势北高南低;单倍群O1b-M268分布频率由南向北递减,尤其在岭南地区汉族人群中分布显著;单倍群O1a-M119在中部汉族人群中分布频率较高。汉族人群遗传结构研究表明,其主要分为北部、中部及南部三个聚类簇,其中青海汉族与其他地区汉族存在一定的遗传分化。在合并少数民族的遗传关系研究中,汉族人群彼此之间遗传关系更紧密,但北部汉族与回族遗传关系更近,而南部汉族则与仡佬族、黎族遗传关系更近。总之,本文基于89个Y-SNP和16个Y-STR,系统地研究了中国不同地域的汉族人群的单倍群分布、遗传亚结构及其与周边少数民族的遗传关系,为群体遗传学、法医遗传学补充理论依据,为Y染色体的法医学应用提供数据支撑。Y-SNP单倍群结合Y-STR单倍型对于分析汉族人群遗传亚结构以及法医学应用具有重要作用。

等臂双着丝粒Y染色体胎儿的产前诊断、遗传咨询与随访

目的分析5例等臂双着丝粒Y染色体[idic(Y)]胎儿的产前诊断、遗传咨询与随访结果,为idic(Y)胎儿的临床处理提供参考依据。方法选择2018年1月至2022年8月7347例有产前诊断指征的孕妇,采用常规G显带核型及染色体微阵列分析(CMA)技术检测胎儿羊水,并用荧光原位杂交(FISH)技术验证,亲代染色体核型溯源检测。遗传咨询后跟踪随访妊娠结局。结果共诊断新发的idic(Y)胎儿5例,其中例1胎儿为单纯的idic(Yq),例2~5均为idic(Yq)与X单体的嵌合体。产前超声提示5例胎儿均为男性,除例1胎儿伴双侧马蹄内翻足可能外,其余4例均未见明显结构畸形。结合超声结果并予以个性化咨询后,例1~2选择继续妊娠,例3~5均终止妊娠。随访例1患儿至4周岁,足内翻手术效果良好,轻度发育迟缓经康复训练后好转;随访例2患儿至2周岁,暂未见异常表型;例3已再次受孕并分娩1名健康女婴;例4~5仍在备孕中。结论细胞与分子遗传学技术的联合应用有助于产前诊断idic(Y)胎儿,合理的遗传咨询及长期随访可为其后续的临床诊疗提供重要依据。

NiW/介孔Y型分子筛催化剂上菲加氢裂化过程研究

为了实现对煤焦油中副产物多环芳烃菲的有效利用,采用等体积浸渍法制备了介孔Y型分子筛负载金属Ni、W催化剂,利用XRD、H2-TPR、BET、SEM-EDS对制备的催化剂进行表征分析,并在固定床反应器中考察催化剂上菲加氢裂化性能,探讨了反应过程中空速、气液比、温度、压力对催化剂积碳率、菲的转化率、液体收率及产物分布的影响.研究表明,增加空速和气液比会降低催化剂的积碳率,过高的反应温度会导致催化剂快速地积碳失活.通过定时采样对裂解产物分析得到菲在催化剂上的裂解率变化情况,同时也能反映出催化剂的稳定性.对反应过程条件优化得到的最优条件为:空速6 h^(-1),气液比750,温度400℃,压力6.5 MPa.此时,菲的裂解率可以稳定在99%以上,同时催化剂保持较高的稳定性,在4 h内未出现活性降低.

NPY-Y1信号通路调控嗜酸粒细胞性慢性鼻窦炎大鼠鼻黏膜嗜酸粒细胞性炎症的机制研究

目的探究NPY-Y1信号通路调控嗜酸粒细胞性慢性鼻窦炎(eosinophilic chronic rhinosinusitis,ECRS)大鼠鼻黏膜嗜酸粒细胞性炎症的机制。方法72只大鼠按照体重随机分组法分为6组,每组各12只,包括对照组、ECRS组、空载组、神经肽Y(NPY)干扰组、低拮抗剂组和高拮抗剂组。除对照组外,其余5组采用卵清蛋白致敏+细菌毒素法构建ECRS大鼠模型,空载组和NPY干扰组分别尾静脉注射siNC和NPY siRNA质粒进行干预,低拮抗剂组和高拮抗剂组分别腹腔注射20、50μg的BIBO 3304干预。末次刺激结束后处死大鼠,取鼻腔黏膜组织,进行HE染色和嗜酸粒细胞(Eos)计数;RT-PCT法检测鼻黏膜中NPY、IL-4、IL-5、IL-13 mRNA表达情况,Western blot法检测核因子κB p65(NF-κB p65)、NF-κB p50蛋白表达情况,免疫组织化学法检测NPY、NPY1受体(Y1R)表达情况。结果HE染色结果显示,对照组鼻黏膜组织结构完整有序,ECRS组、空载组细胞排列紊乱,出现大量炎性细胞浸润,低拮抗剂组中细胞结构得到改善,炎性细胞浸润减少,相对于低拮抗剂组,NPY干扰组、高拮抗剂组中细胞结构及炎性细胞浸润改善情况更显著。与对照组比较,ECRS组和空载组鼻黏膜Eos计数,NPY、IL-4、IL-5、IL-13 mRNA,NF-κB p65、NF-κB p50蛋白及NPY、Y1R细胞染色相对强度值均明显升高(P均<0.05);与ECRS组和空载组比较,NPY干扰组、低拮抗剂组、高拮抗剂组上述指标均降低,且NPY干扰组和高拮抗剂组低于低拮抗剂组(P均<0.05);ECRS组与空载组、NPY干扰组和高拮抗剂组上述指标比较差异无统计学意义(P均>0.05)。结论ECRS大鼠存在鼻黏膜Eos异常浸润炎症反应,其机制可能与NPY-Y1信号通路通过激活NF-κB信号通路及效应蛋白表达有关。

Y型管式油水分离结构分离特性仿真分析

管式油水分离技术具有占地面积小、分离效率高、成本低等优点,基于管式油水分离原理,设计一种Y型管式油水分离结构,利用Fluent数值模拟软件,采用标准k-ε湍流模型和Mixture多相流模型,对Y型管内部流场特性以及外部参数对分离效率的影响进行了研究。结果表明,Y型管对流体扰动小,内部流场特性稳定不易产生涡流,能够实现油水分离,支管与主管交汇处存在油水分离现象;油水分离效率随着油滴粒径的增大而逐渐提高,油滴粒径越大越利于油相上浮聚集在Y型管上层,能有效提高油水分离效率;入口速度对油水分离效果的影响很大,速度越大,油相上浮时间越短,Y型管的分离效率越低;分离效率随支管分流比的增大而增大,当入口速度为0.5 m/s时,分流比超过0.4后,分离效率不再增加。研究结果为油水分离提供了新思路,可为Y型管的设计提供理论参考。

Ru、Y对铸造高温合金与陶瓷界面反应的影响

在定向凝固炉中,采用相同的硅基陶瓷型芯,刚玉陶瓷型壳,熔炼工艺和定向凝固工艺制备了四种不同Ru、Y含量的单晶高温合金叶片,研究了组织稳定性提升元素Ru、抗氧化性增强元素Y对合金与陶瓷材料界面反应的影响。研究结果表明,合金中不含Ru、Y时,合金与型壳发生的界面反应主要为物理粘砂作用,未见合金元素与型壳发生明显的化学反应,合金与型芯发生轻微的界面反应,除了物理作用,还发生了Al与SiO2的化学反应。合金中添加Ru,对合金与型壳或型芯的界面反应无影响。合金中添加0.01%Y后,合金与陶瓷型壳或型芯的界面反应稍有增加,但由于其添加量较少,故影响较小。

基于Y-MMC的柔性低频输电控制策略

采用传统矢量控制的Y型模块化多电平换流器(Y-MMC),存在控制结构复杂、参数整定困难等缺点。针对上述问题,采用模型预测控制方法对Y-MMC进行控制器设计,提出一种适用于柔性低频输电的分层协调控制策略。建立各桥臂开关状态组合下的预测模型,实现内环电流控制和电容电压均衡控制。采用分层优化思想建立直流电容电压跟踪、交流电流跟踪和开关频率优化的逐级评估系统。结合稳态逆模型和比例积分控制实现了功率换流站的功率控制和电压频率换流站的低频电压控制。通过MATLAB/Simulink对双端低频输电系统进行仿真,结果验证了所提控制方案在多种工况下的正确性和有效性。相较于传统的矢量控制,该策略简化了控制器设计,加快了响应速度。

Y型沟谷桥址区风特性的数值模拟研究

复杂山区的风场特性不同于平原地区,风场十分复杂,没有较为统一的规律,对大跨度桥梁的结构振动影响较大。为了研究复杂山区地形对桥址区风场特性的影响规律,以某座位于多条沟谷交汇谷口的斜拉桥桥址区为工程背景,基于ALOS数字高程地形模型,通过CFD数值模拟的方法,计算了不同风向来流下桥位处的风场特性。分析了桥址区主要的几条沟谷和桥位处局部地形对沿主梁横桥向平均风速、风攻角、风偏角及桥梁跨中竖向风剖面等风特性的影响。研究了横桥向平均风速大小和风攻角之间的关系,定性讨论了存在风速放大效应的来流工况和桥址区地形特点之间的关系。结果表明:Y型沟谷桥址区风特性不同于一般的山区桥址区,当来流沿着几条比较顺直的沟谷时桥位处平均风速较大,其他风向桥位处风速较小;沟谷的弯曲致使沿着沟谷的来流产生回流和改向,这时桥位处的风攻角较大,沿着主梁的风偏角变化范围较大,水平风速较小,不存在风速峡谷放大效应;桥位处交汇的沟谷局部地形对桥梁跨中竖向风剖面影响较大。研究结果为桥梁设计风速的确定提供了依据,可为定性判断Y型沟谷口桥位处风特性提供指导。

挤压Mg-Y-Ni-Co合金的显微组织、加工性能及塑性变形行为

本工作通过光学显微镜(OM)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和万能实验机对挤压Mg-2Y-0.5Ni-0.5Co(%,原子分数)合金的显微组织、加工性能和塑性变形行为进行了研究。挤压合金的显微组织主要由α-Mg、沿挤压方向分布的片层状和细小块状18R-LPSO相、MgY(Co,Ni)_(4)相以及晶粒内细条纹状的14H-LPSO相组成。拉伸测试结果显示,挤压合金具有良好的室温塑性,断裂延伸率均高于15%。随着温度的升高和应变速率的降低,合金的拉伸强度降低,而塑性增强。合金在300℃、1×10^(-3)s^(-1)和1×10^(-4)s^(-1)应变速率下断裂延伸率分别为117.87%和143.9%,具有准超塑性。通过构建的热加工图谱,优化出合金的稳定加工区间为温度275~300℃、应变速率10^(-4)~10^(-3)s^(-1)。挤压合金的变形行为随温度和应变速率的变化而改变,在低温(室温(RT)到200℃)和不同应变速率下,合金的变形机制以位错滑移为主;在高温(300℃)和低应变速率(1×10^(-4)s^(-1)和1×10^(-3)s^(-1))下,合金的变形机制为晶界滑移协调的位错滑移。