Enhanced properties of stone coal-based composite phase change materials for thermal energy storage

Phase change materials (PCMs) can be incorporated with low-cost minerals to synthesize composites for thermal energy storage in building applications.Stone coal (SC) after vanadium extraction treatment shows potential for secondary utilization in composite preparation.We prepared SC-based composite PCMs with SC as a matrix,stearic acid (SA) as a PCM,and expanded graphite (EG) as an additive.The combined roasting and acid leaching treatment of raw SC was conducted to understand the effect of vanadium extraction on promoting loading capacity.Results showed that the combined treatment of roasting at 900℃ and leaching increased the SC loading of the composite by 6.2%by improving the specific surface area.The loading capacity and thermal conductivity of the composite obviously increased by 127%and 48.19%,respectively,due to the contribution of 3wt% EG.These data were supported by the high load of 66.69%and thermal conductivity of 0.59 W·m^(-1)·K-1of the designed composite.The obtained composite exhibited a phase change temperature of 52.17℃,melting latent heat of 121.5 J·g^(-1),and good chemical compatibility.The SC-based composite has prospects in building applications exploiting the secondary utilization of minerals.

Visualizing the electronic structure of kagome magnet LuMn6Sn6 by angle-resolved photoemission spectroscopy

Searching for the dispersionless flat band(FB)in quantum materials,especially in topological systems,becomes an interesting topic.The kagome lattice is an ideal platform for such exploration because the FB can be naturally induced by the underlying destructive interference.Nevertheless,the magnetic kagome system that hosts the FB close to the Fermi level(EF)is exceptionally rare.Here,we study the electronic structure of a kagome magnet LuMn6Sn6 by combining angleresolved photoemission spectroscopy and density functional theory calculations.The observed Fermi-surface topology and overall band dispersions are similar to previous studies of the XMn6Sn6(X=Dy,Tb,Gd,Y)family of compounds.We clearly observe two kagome-derived FBs extending through the entire Brillouin zone,and one of them is located just below EF.The photon-energy-dependent measurements reveal that these FBs are nearly dispersionless along the kz direction as well,supporting the quasi-two-dimensional character of such FBs.Our results complement the XMn6Sn6 family and demonstrate the robustness of the FB features across this family.

Neural metabolic activity in idiopathic tinnitus patients after repetitive transcranial magnetic stimulation

BACKGROUND The central mechanism of idiopathic tinnitus is related to hyperactivity of cortical and subcortical auditory and non-auditory areas.Repetitive transcranial magnetic stimulation(rTMS)is a well-tolerated,non-invasive potential treatment option for tinnitus.AIM To investigate the changes of neural metabolic activity after rTMS in chronic idiopathic tinnitus(IT)patients.ME THODS Eleven patients underwent rTMS(1 Hz,90%motor threshold,1000 stimuli/day for consecutive 10 d)on the left temporoparietal region cortex.Tinnitus handicap inventory(THI)and visual analogue score(VAS)were assessed at baseline and posttreatment.All patients underwent 18 F-fluorodeoxyglucose(FDG)positron emission tomography to evaluate the neural metabolic activity.Data were preprocessed using statistical parametric mapping and Gretna software to extract the regions of interest(ROls).The correlation between brain areas involved and THI scores was analyzed.RESULTS Baseline and posttreatment parameters showed no significant difference regarding THI score(t=1.019,P=0.342>0.05)and VAS(t=0.00,P=1.0>0.05).Regions with the highest FDG uptake were the right inferior temporal gyrus(ITG),right parahippocampa gyrus(PHG),right hippocampus,rectus gyrus,left middle frontal gyrus,and right inferior frontal gyrus in IT patients.After rTMS treatment,IT patients showed increased activities in the right PHG,right superior temporal gyrus,right superior frontal gyrus,anterior insula,left inferior parietal lobule,and left precentral gyrus,and decreased activities in the left postcentral gyrus and left ITG.The ROIs in the right parahippocampa gyrus and right superior frontal gyrus were positively correlated with THI scores(r=0.737,P=0.037<0.05;r=0.735,P=0.038<0.05).CONCLUSION Our study showed that 1-Hz rTMS directed to the left temporo-parietal junction resulted no statistically significant symptom alleviation.After treatment,brain areas of the limbic and prefrontal system showed high neutral metabolic activity The auditory and non-auditory systems together will be the target for rTMS treatment.

Circadian misalignment on submarines and other non-24-h environments – from research to application

Circadian clocks have important physiological and behavioral functions in humans and other organisms, which enable organisms to anticipate and respond to periodic environmental changes. Disturbances in circadian rhythms impair sleep, metabolism, and behavior. People with jet lag, night workers and shift workers are vulnerable to circadian misalignment. In addition, non-24-h cycles influence circadian rhythms and cause misalignment and disorders in different species, since these periods are beyond the entrainment ranges. In certain special conditions, e.g., on submarines and commercial ships, non-24-h watch schedules are often employed, which have also been demonstrated to be deleterious to circadian rhythms. Personnel working under such conditions suffer from circadian misalignment with their on-watch hours, leading to increased health risks and decreased cognitive performance. In this review, we summarize the research progress and knowledge concerning circadian rhythms on submarines and other environments in which non-24-h watch schedules are employed.

Analysis of retinal vasculature changes in indirect traumatic optic neuropathy using optic coherence tomography angiography

AIM:To assess the retinal vasculature alterations in indirect traumatic optic neuropathy(ITON)patients following craniofacial trauma by optic coherence tomography angiography(OCTA).METHODS:Patients diagnosed of monocular ITON were recruited from August 2016 to May 2020.OCTA was performed using the Angio Vue OCT-A system for two cube scans centered at the optic nerve head and fovea.OCTA data included thicknesses of peripapillary retinal nerve fiber layer(RNFL)and macular ganglion cell complex(GCC),as well as proportion of capillary perfusion and data were analyzed for correlation with post-injury timepoints:within 7,8-30,31-90,and 91-365d.RESULTS:A total of 73 ITON patients were studied.Significant thinning of RNFL and GCC layers and attenuation of microvascular perfusion were observed in ITON eyes as compared to contralateral unaffected eyes(for most of the analyzed sectors and quadrants,P<0.05).Without respect to surgical intervention and vision recovery,the decrease in retinal layer thicknesses and microvascular perfusion was time-dependent,and most significant within three months(P<0.001).CONCLUSION:ITON presents with time-dependent thinning of retinal layers and attenuation of microvasculature,indicating possible degeneration of retinal ganglion cells due to reduced retinal blood supply.

A Review on the Protection Mechanism of Trehalose on Plant Tissues and Animal Cells

Trehalose is a non-reducing disaccharide composed of glucose molecules connected byα-glycosidic bond.This soluble substance plays an important role of protecting green algae and other lower plants from stress.It can help plants cope with extreme environments such as severe cold,drought and high salinity,regulate the stomatal conductance and water utilization rate of plants,and participate in the growth and metabolism regulation of plants as a signal molecule.As an impermeable cryoprotectant,trehalose is widely used in the refrigeration protection of various animal cells and tissues due to its non-toxicity and high efficiency.According to the research results at home and abroad in recent years,the protection,regulation and mechanism of trehalose on plant tissues and animal cells were summarized,so as to provide a theoretical basis for the further development and utilization of trehalose.

Two-Dimensional Magnetotelluric Forward Research for the Vertical Anisotropy

When we study and process magnetotelluric data, the earth's interior structure is usually equated with isotropic medium in the existing approaches. When the underground structure is complex, there is serious resistivity anisotropy in macroscopic view, and then the traditional processing and interpretation methods often produce wrong results. For that we must establish the study method based on the anisotropy in order to explain the measured data exactly. In this paper, by considering the change of resistivity in three electrical spindle directions, we deduce two-dimensional magnetotelluric variational equation for vertical anisotropy. The study region is divided into many rectangular units, and it is dealt with linear interpolation in each of them. By comparing with former achievements including the results of the isotropic and anisotropic models, it demonstrates the validity of the program. The pseudosection map of vertical anisotropic body shows that we can’t ignore the anisotropy effect and provides a solid foundation for the further inversion study.

High-resolution angle-resolved photoemission study of large magnetoresistance topological semimetal CaAl4

Extremely large magnetoresistance(XMR)has been explored in many nonmagnetic topologically nontrivial/trivial semimetals,while it is experimentally ambiguous which mechanism should be responsible in a specific material due to the complex electronic structures.In this paper,the magnetoresistance origin of single crystal CaAl4 with C2/m structure at low temperature is investigated,exhibiting unsaturated magnetoresistance of~3000%at 2.5 K and 14 T as the fingerprints of XMR materials.By the combination of ARPES and the first-principles calculations,we elaborate multiband features and anisotropic Fermi surfaces,which can explain the mismatch of isotropic two-band model.Although the structural phase transition from I4/mmm to C2/m has been recognized,the subtle impact on electronic structure is revealed by our ARPES measurements.Considering that both charge compensation and potential topologically nontrivial band structure exist in CaAl4,our findings report CaAl4 as a new reference material for exploring the XMR phenomena.

Coexistence of Dirac and Weyl points in non-centrosymmetric semimetal NbIrTe_(4)

Using angle-resolved photoemission spectroscopy and density functional theory calculations methods,we investigate the electronic structures and topological properties of ternary tellurides NbIrTe_(4),a candidate for type-II Weyl semimetal.We demonstrate the presence of several Fermi arcs connecting their corresponding Weyl points on both termination surfaces of the topological material.Our analysis reveals the existence of Dirac points,in addition to Weyl points,giving both theoretical and experimental evidences of the coexistence of Dirac and Weyl points in a single material.These findings not only confirm NbIrTe_(4) as a unique topological semimetal but also open avenues for exploring novel electronic devices based on its coexisting Dirac and Weyl fermions.

Angle-resolved photoemission study of NbGeSb with non-symmorphic symmetry

We investigate the electronic structure of NbGeSb with non-symmorphic symmetry.We employ angle-resolved photoemission spectroscopy(ARPES)to observe and identify the bulk and surface states over the Brillouin zone.By utilizing high-energy photons,we identify the bulk Fermi surface and bulk nodal line along the direction X–R,while the Fermi surface of the surface state is observed by using low-energy photons.We observe the splitting of surface bands away from the high-symmetry point X.The density functional theory calculations on bulk and 1 to 5-layer slab models,as well as spin textures of NbGeSb,verify that the band splitting could be attributed to the Rashba-like spin–orbit coupling caused by space-inversion-symmetry breaking at the surface.These splitted surface bands cross with each other,forming two-dimensional Weyl-like crossings that are protected by mirror symmetry.Our findings provide insights into the two-dimensional topological and symmetry-protected band inversion of surface states.

Wearable multilead ECG sensing systems using on-skin stretchable and breathable dry adhesives

Electrocardiogram(ECG)monitoring is used to diagnose cardiovascular diseases,for which wearable electronics have attracted much attention due to their lightweight,comfort,and long-term use.This study developed a wearablemultilead ECG sensing system with on-skin stretchable and conductive silver(Ag)-coated fiber/silicone(AgCF-S)dry adhesives.Tangential and normal adhesion to pigskin(0.43 and 0.20 N/cm2,respectively)was optimized by the active control of fiber density and mixing ratio,resulting in close contact in the electrode–skin interface.The breathableAgCF-S dry electrodewas nonallergenic after continuous fit for 24 h and can be reused/cleaned(>100 times)without loss of adhesion.The AgCF encapsulated inside silicone elastomers was overlapped to construct a dynamic network under repeated stretching(10%strain)and bending(90°)deformations,enabling small intrinsic impedance(0.3,0.1 Hz)and contact impedance variation(0.7 k)in high-frequency vibration(70 Hz).All hard/soft modules of the multilead ECG system were integrated into lightweight clothing and equipped with wireless transmission for signal visualization.By synchronous acquisition of I–III,aVR,aVL,aVF,and V4 lead data,the multilead ECG sensing system was suitable for various scenarios,such as exercise,rest,and sleep,with extremely high signal-to-noise ratios.

Multi-Lever EarlyWarning forWind and Photovoltaic Power Ramp Events Based on Neural Network and Fuzzy Logic

With the increasing penetration of renewable energy in power system,renewable energy power ramp events(REPREs),dominated by wind power and photovoltaic power,pose significant threats to the secure and stable operation of power systems.This paper presents an early warning method for REPREs based on long short-term memory(LSTM)network and fuzzy logic.First,the warning levels of REPREs are defined by assessing the control costs of various power control measures.Then,the next 4-h power support capability of external grid is estimated by a tie line power predictionmodel,which is constructed based on the LSTMnetwork.Finally,considering the risk attitudes of dispatchers,fuzzy rules are employed to address the boundary value attribution of the early warning interval,improving the rationality of power ramp event early warning.Simulation results demonstrate that the proposed method can generate reasonable early warning levels for REPREs,guiding decision-making for control strategy.

急性结肠憩室炎132例临床特点分析

目的探讨急性结肠憩室炎的临床特点.方法回顾性分析2007年1月-2017年12月该院收治的资料完整且经腹部CT、结肠镜和/或手术确诊的急性结肠憩室炎132例患者的临床资料.结果男89例,女43例,男女比例为2.1:1.0,发病年龄(51.8±13.1)岁;急性单纯性结肠憩室炎119例(90.2%),急性复杂性结肠憩室炎13例(9.8%);发病部位:盲肠升结肠82例(62.1%),乙状结肠23例(17.4%),降结肠16例(12.1%),横结肠8例(6.1%),同时累及两个部位者3例(2.3%);主要症状:腹痛132例(100.0%),发热117例(88.6%),腹部压痛132例(100.0%);外周血白细胞计数(WBC)升高者103例(78.0%),WBC计数(15.8±5.1)×109/L,C反应蛋白(CRP)升高者124例(93.9%),CRP数值(34.1±15.3)mg/L;所有患者均行腹部CT检查,有结肠壁增厚表现者124例(93.9%),结肠周围脂肪组织密度增高者78例(59.1%);119例急性单纯性憩室炎患者均经静脉输注抗生素后好转,13例急性复杂性憩室炎患者中,3例经单纯静脉输注抗生素后好转,5例单纯腹腔脓肿和2例腹腔脓肿伴腹腔积液者静脉输注抗生素,同时行腹腔引流管引流后好转,2例腹腔游离气体及1例腹腔脓肿并瘘管形成、腹腔积液患者行开腹手术治疗后好转,在院期间无死亡病例.结论急性结肠憩室炎好发于中老年男性,常见临床表现为腹痛、发热、腹部压痛,腹部增强CT在其诊断及病情评估中起重要作用,大部分患者无并发症,预后良好.

基于MRI与病理对照的骨肉瘤动态增强MRI定量参数与肿瘤微循环及乏氧性表达的相关性研究

目的:基于MRI与病理对照,探讨动态增强MRI(dynamic contrast-enhanced MRI,DCE-MRI)定量参数与骨肉瘤微循环和乏氧性表达的相关性。方法:分析云南省肿瘤医院2019年1月至2020年6月收治的原发于膝关节周围的骨肉瘤患者,手术前行MRI检查。术后取瘤段正中矢状面组织切片,并分割为1 cm×1 cm组织块。检测每个组织块肿瘤坏死率(tumor necrosis rate,TNR)、微血管密度(microvessel density,MVD)、血管内皮生长因子(vascular endothelial growth factor,VEGF)、乏氧诱导因子-1α(hypoxia inducible factor-1α,HIF-1α),并按照Huvos分级标准划分为反应良好组(TNR≥90%)和反应差组(TNR<90%)。在对应位置的DCE-MRI图像上,定位划分与病理样本等感兴趣区,并测量定量参数(Ktrans、Kep、Ve、Vp)。探讨各定量参数与MVD、VEGF、HIF-1α的关系并绘制ROC曲线。结果:入组10例骨肉瘤患者,共取得460个肿瘤病理组织块,其中反应良好组59个(12.8%),反应差组401个(87.2%);VEGF阳性311个(67.6%),阴性149个(32.4%);HIF-1α阳性68个(14.8%),阴性392个(85.2%)。反应良好组Ktrans、Kep、Ve、Vp、MVD计数、VEGF阳性率均高于反应差组,而HIF-1α阳性率低于反应差组(P<0.05)。Ktrans、Kep、Ve与MVD具有相关性,回归系数分别为-0.652、0.525、0.418(P<0.01)。Ve预测VEGF、Kep预测HIF-1α阳性表达的阈值、曲线下面积、敏感性、特异性分别为0.634、0.609、63.7%、60.0%和0.115/min、0.614、42.2%、83.3%。结论:DCEMRI定量参数对骨肉瘤化疗后肿瘤微循环及乏氧性具有一定的评估价值,或可为新辅助化疗疗效评估提供依据。

基于MRI-病理对照的动态增强磁共振成像定量参数评估骨肉瘤新辅助化疗肿瘤坏死率的价值

目的:基于MRI-病理对照,探讨动态增强磁共振成像(dynamic contrast-enhanced magnetic resonance imaging,DCE-MRI)定量参数评估骨肉瘤新辅助化疗(neoadjuvant chemotherapy,NAC)肿瘤坏死率的价值。方法:收集2019年1月至2020年6月于昆明医科大学第三附属医院收治的膝关节周围骨肉瘤患者11例,于NAC前、后行常规MRI及矢状位DCE-MRI检查。NAC疗程结束后两周内经外科手术获取完整肿瘤瘤段,沿正中矢状面剖开,取厚度为5 mm病理切片并分割成大小为1 cm×1 cm的若干组织块,编号后作为与影像对照的病理样本。依靠解剖标志,确定与病理切片对应的DCE-MRI影像层面,将病灶划分为1 cm×1 cm大小感兴趣区(region of interest,ROI),并进行化疗前、后影像ROI与病理样本匹配。采用Omni Kinetics软件测量化疗前定量参数-pre-K^(trans)、pre-K_(ep)、pre-Ve、pre-Vp和化疗后参数-post-K^(trans)、post-K_(ep)、post-V_(e)、post-V_(p),并计算化疗前-后各参数差值∆K^(trans)、∆K_(ep)、∆V_(e)、∆V_(p)。采用Huvos分级标准检测每个病理样本肿瘤坏死率(tumor necrosis rate,TNR),并划分为缓解组(TNR≥90%)和未缓解组(TNR<90%)。采用Mann-Whitney U检验,比较两组病理样本NAC前、后各定量参数是否存在差异。采用ROC曲线,比较NAC后DCE-MRI定量参数及治疗前后的差值预测NAC后TNR的效能。结果:入组骨肉瘤11例,共取得304个病理样本,其中缓解组59个(19.4%),未缓解组245个(80.6%)。两组化疗后K^(trans)、V_(e)、V_(p)均明显降低,且未缓解组参数值明显低于缓解组(P<0.05);化疗后缓解组K_(ep)明显升高(P<0.05),但未缓解组K_(ep)无差异(P>0.05)。两组化疗前后参数差值ΔK^(trans)、ΔV_(e)、ΔV_(p)差异无统计学意义(P>0.05),但缓解组ΔK_(ep)明显低于未缓解组(P<0.05)。ROC曲线分析结果,化疗后定量参数诊断TNR缓解效能优于化疗前-后差值,其中post-K^(trans)诊断效能最高,诊断阈值为0.663/min、AUC为0.745、灵敏度为89.83%、特异性为52.24%。结论:DCE-MRI定量参数在评估骨肉瘤新辅助化疗TNR有一定的应用价值,具有即时、无创反映NAC疗效的应用潜力。

内镜下套扎术治疗内痔54例前瞻性研究

目的研究微创治疗内痔新方法内镜下套扎术治疗内痔的疗效及安全性。方法收集2017年2月-2018年2月于该院行内镜下套扎术治疗的54例Ⅱ至Ⅲ期内痔患者,随访1、6和12个月,观察患者症状改善情况、并发症发生及复发情况,应用疼痛评分、出血评分、生活质量评分和脱出程度评分来评估内镜下套扎术的疗效及安全性。结果术后随访12个月,47例治疗有效,治疗有效率87.0%,均未出现严重并发症,进行疼痛视觉模拟评分(VAS)、出血评分、生活质量及脱出程度评分,对比治疗前后,各个指标均有明显下降,VAS评分由(3.9±2.1)分降至(1.9±1.1)分(P=0.012),出血评分由(5.5±2.4)分降至(2.3±1.5)分(P=0.000),生活质量评分由(2.6±0.7)分降至(1.2±0.6)分(P=0.039),脱出程度评分由(2.4±0.5)分降至(1.6±0.6)分(P=0.002),2例(3.7%)患者出现复发,分别发生于10和11个月。结论内镜下套扎术治疗内痔临床疗效确切,是一种安全有效的治疗方法。

右美托咪定联合帕瑞昔布钠对鼻内镜手术苏醒期躁动及术后早期镇痛的影响

目的探讨帕瑞昔布钠联合右美托咪定(DEX)对鼻内镜手术苏醒期躁动的影响。方法选择2020年1月-2021年2月该院择期行全身麻醉下鼻内镜手术的患者104例。采用随机数表法分为实验组(DEX+帕瑞昔布钠组,DP组)和对照组(DEX,D组),各52例。两组患者麻醉诱导前,分别给予静脉输注DEX 0.5μg/kg,输注10 min,然后持续泵注0.4μg/(kg·h),手术结束前30 min停药。DP组DEX停药后立即给予帕瑞昔布钠40 mg静注。采用Ricker镇静-躁动评分(RSAS)评估两组患者拔管时及拔管后5 min躁动评分,视觉模拟评分法(VAS)评估患者术后2、4、8、12和24 h疼痛情况。比较两组患者苏醒期RSAS评分、术后VAS评分、恶心呕吐、鼻出血和胃肠道不适的发生率。结果与D组比较,DP组苏醒期RSAS明显降低[(3.6±0.7)和(4.0±0.8)分,(3.8±0.4)和(4.0±0.2)分,P<0.05],术后2、4和8 h VAS明显降低(P<0.05)。两组患者术后恶心、呕吐、鼻出血和胃肠道不适等并发症发生率比较,差异均无统计学意义(P>0.05)。结论帕瑞昔布钠联合DEX用于鼻内镜手术可以降低苏醒期RSAS评分,在术后早期具有良好的镇痛效果。

Effects of artificially cultivated biological soil crusts on soil nutrients and biological activities in the Loess Plateau

Biological soil crusts （BSCs） play an important role in the early succession of vegetation restoration in the Loess Plateau, China. To evaluate the effects of artificially cultivated BSCs on the soil surface micro-envir- onment, we obtained natural moss crusts and moss-lichen crusts from the Loess Plateau of Shaanxi province, and subsequently inoculated and cultivated on horizontal and sloping surfaces of loess soil in a greenhouse. The chemical and biological properties of the subsoil under cultivated BSCs were determined after 10 weeks of cul- tivation. The results indicated that BSCs coverage was more than 65% after 10 weeks of cultivation. Moss crust coverage reached 40% after 5 weeks of cultivation. Compared with the control, soil organic matter and available nitrogen contents in moss crust with the horizontal treatments increased by 100.87% and 48.23%, respectively; increased by 67.56% and 52.17% with the sloping treatments, respectively; they also increased in moss-lichen crust with horizontal and sloping treatments, but there was no significant difference. Available phosphorus in cultivated BSCs was reduced, soil pH was lower and cationic exchange capacity was higher in cultivated BSCs than in the control. Alkaline phosphatase, urease and invertase activities were increased in artificially cultivated BSCs, and alkaline phosphatase activity in all cultivated BSCs was obviously higher than that in the control. Numbers of soil bacteria, fungi and actinomycetes were increased in the formation process of cultivated BSCs. These results indicate that BSCs could be formed rapidly in short-term cultivation and improve the mi- cro-environment of soil surface, which provides a scientific reference for vegetation restoration and ecological reconstruction in the Loess Plateau. China.

Soil water response to precipitation in different microtopographies on the semi-arid Loess Plateau,China

Soil water is an important factor restricting afforestation on the semi-arid Loess Plateau.The microtopography of the loess slope has changed the distribution pattern of soil water on the slope.To improve water utilization efficiency and optimize afforestation configuration patterns,the relationship between soil water and precipitation at micro-topographic scale must be studied.We used time series analysis to study the temporal variation of soil water and its response to precipitation in four kinds of micro-topographies and undisturbed slope on loess slopes.Micro-topographies significantly influenced soil water distribution and dynamics on the slopes.Soil water stored in the platform,sinkhole,and ephemeral gully influenced subsequent soil water for 4 weeks,whereas soil water stored in the scarp and undisturbed slope could influence soil water for 2 weeks.It took 12 weeks,10 weeks,18 weeks,6 weeks,and 12 weeks for precipitation to reach the deeper soil layer in the platform,sinkhole,scarp,ephemeral gully,and undisturbed slope,respectively.These soil water characteristics in different micro-topographies are vital factors that should be taken into consideration when undertaking afforestation on the Loess Plateau.

Steady-state voltage-control method considering large-scale wind-power transmission using half-wavelength transmission lines

Half-wavelength transmission can transmit large-scale renewable energy over very long distances.This paper proposes an improved steady-state voltage-control method for half-wavelength transmission systems considering largescale wind-power transmission.First,the unique voltage characteristics of half-wavelength lines are deduced based on the distributed parameter model.In the secondary voltage-control level,reactive power-transmission limits of half-wavelength lines are introduced as another control objective except for tracing the pilot bus voltage reference.Considering the uncertainty and fluctuation of wind power,the overvoltage risk-assessment method of half-wavelength lines is presented to determine specific voltage-control strategies.Simulation results demonstrate that the proposed voltage-control method delivers superior tracking performance according to a voltage reference value and prevents the overvoltage risk of halfwavelength lines effectively in different wind-power penetrations.