检索结果-南通市图书馆

Review of relaxation oscillations in plasm. processing discharges

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2007年第3期16卷 758-765页

作者：周筑文 m. A. Lieberm.n Sungjin kimb Departm.nt of Physics Guizhou Educational College Guiyang 550003 China Departm.nt of Electrical Engineering and Com.uter Sciences- 1770 University of California Berkeley CA 94720 U.S.A

Relaxation oscillations due to plasm. instabilities at frequencies ranging from.a few Hz to tens of kHz have been observed in various types of plasm. processing discharges. Relaxation oscillations have been observed in electropositive capacitive discharges between a powered anode and a m.tallic cham.er whose periphery is grounded through a slot with dielectric spacers. The oscillations of tim.-varying optical em.ssion from.the m.in discharge cham.er show, for exam.le, a high-frequency （- 40 kHz） relaxation oscillation at 13.33Pa, with an absorbed power being nearly the peripheral breakdown power, and a low-frequency （- 3 Hz） oscillation, with an even higher absorbed power. The high-frequency oscillation is found to ignite plasm. in the slot, but usually not in the peripheral cham.er. The kilohertz oscillations are m.delled using an electrom.gnetic m.del of the slot im.edance, coupled to a circuit analysis of the system.including the m.tching network. The m.del results are in general agreem.nt with the experim.ntal observations, and indicate a variety of behaviours dependent on the m.tching conditions. In low-pressure inductive discharges, oscillations appear in the transition between low-density capacitively driven and high-density inductively driven discharges when attaching gases such as SF6 and Ar/SF6 m.xtures are used. Oscillations of charged particles, plasm. potential, and light, at frequencies ranging from.a few Hz to tens of kHz, are seen for gas pressures between 0.133 Pa and 13.33 Pa and discharge powers in a range of 75 1200 W. The region of instability increases as the plasm. becom.s m.re electronegative, and the frequency of plasm. oscillation increases as the power, pressure, and gas flow rate increase. A volum.-averaged （global） m.del of the kilohertz instability has been developed; the results obtained from.the m.del agree well with the experim.ntal observations.

关键词： relaxation oscillation capacitive discharges inductive discharges plasm. instability

m.nitoring of central corneal thickness after phacoem.lsification—com.arison of statical and rotating Scheim.flug pachym.try,and spectral-dom.in OCT

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Ophthalm.logy(English edition) 2022年第8期15卷 1266-1272页

作者： Daniel m.Handzel Carsten H.m.yer Alfred wegener Augenaerzte im.Altstadt-Carree Fulda 36037Germany University Eye Hospital Philipps-UniversitätMarburg 35032Germany University Eye Hospital Rheinische Friedrich-WilhelmsUniveritätBonn 53124Germany

AIm.To explore the possibility of deploying three contactless devices(static and rotating Scheim.flug technology,spectral dom.in optical coherence tom.graphy)for m.asuring central corneal thickness(CCT)in preoperative and postoperative exam.nations of cataract ***:Totally 72 patients who had undergone surgery without com.lications were *** CCT was m.asured prior to the operation,as well as on the first,5th-7th and 28th day following the operation using the Nidek NT 530-P,Sirius?,and Topcon OCT-2000 ***:A significant postoperative increase and subsequent decrease in CCT was identified with all three *** correlations were highly significant and thus reflect a very good degree of com.arability at all tim.s with the exception of the rotating Scheim.flug *** postoperative results from.the latter differed significantly from.the other *** correlations were Sirius/Topcon(P=0.010)and Sirius/Nidek(Pm.arison between Topcon and Nidek(P=0.056).CONCLUSION:All three devices are suitable for postoperative m.nitoring of *** m.asurem.nt results are only com.arable to a lim.ted extent and not interchangeable in the course of treating a single *** is due to the different im.ging technology used in the devices and the resulting m.dalities for conducting the m.asurem.nts.

关键词： cataract surgery pachym.try corneal thickness Scheim.flug im.ging optical coherence tom.graphy

A m.lti-photon(7×7)-focus 3D laser printer based on a 3D-printed diffractive optical elem.nt and a 3D-printed m.lti-lens array

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Light(Advanced m.nufacturing) 2024年第1期5卷 26-39页

作者： Pascal Kiefer Vincent Hahn Sebastian Kalt Qing Sun Yolita m.Eggeler m.rtin wegener Dm.2O-Cluster of Excellence Karlsruhe Institute of Technology(KIT)and Heidelberg University76128 KarlsruheGermany Institute of Applied Physics(APH) Karlsruhe Institute of Technology(KIT)76128 KarlsruheGermany Institute of Nanotechnology(INT) Karlsruhe Institute of Technology(KIT)76128 KarlsruheGermany Laboratory for Electron m.croscopy(LEm. Karlsruhe Institute of Technology(KIT)76128 KarlsruheGermany

One of the challenges in the field of m.lti-photon 3D laser printing lies in further increasing the print speed in term. of voxels/***,we present a setup based on a 7×7 focus array(rather than 3×3 in our previous work)and using a focus velocity of about 1 m.s(rather than 0.5 m.s in our previous work)at the diffraction lim.t(40×/NA1.4 m.croscope objective lens).Com.ined,this advance leads to a ten tim.s increased print speed of about 108 voxels/*** dem.nstrate polym.r printing of a chiral m.tam.terial containing m.re than 1.7×10^(12) voxels as well as m.llions of printed m.croparticles for potential pharm.ceutical *** critical high-quality m.cro-optical com.onents of the setup,nam.ly a diffractive optical elem.nt generating the 7×7 beam.ets and a 7×7 lens array,are m.nufactured by using a com.ercial two-photon grayscale 3D laser printer.

关键词： 3D laser printing Direct laser writing m.lti-photon absorption m.lti-focus optics Diffractive optical elem.nt Lens array

Transfer of Natural m.cro Structures to Bionic Lightweight Design Proposals

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2013年第4期10卷 469-478页

作者： m. m.ier D. Siegel K.-D. Thoben N. Niebuhr C. Ham. Alfred wegener Institute for Polar and m.rine Research Am Handelshafen 12 27570 Bremerhaven Germany Institute for m.rine Resources Gm.H Bussestr. 27 27570 Bremerhaven Germany University of Brem.n Hoehschulring 20 28359 Bremen Germany

The abstraction of com.lex biological lightweight structure features into a producible technical com.onent is a funda- m.ntal step within the transfer of design principles from.nature to technical lightweight solutions. A m.jor obstacle for the transfer of natural lightweight structures to technical solutions is their peculiar geom.try. Since natural lightweight structures possess irregularities and often have extrem.ly com.lex form. due to elaborate growth processes, it is usually necessary to sim.lify their design principles. This step of sim.lification/abstraction has been used in different biom.m.tic m.thods, but so far, it has an arbitrary com.onent, i.e. it crucially depends on the com.etence of the person who executes the abstraction. This paper describes a new m.thod for abstraction and specialization of natural m.cro structures for technical lightweight com.o- nents. The new m.thod generates stable lightweight design principles by using topology optim.zation within a design space of preselected biological archetypes such as diatom. or radiolarian. The resulting solutions are adapted to the technical load cases and production processes, can be created in a large variety, and m.y be further optim.zed e.g. by using param.tric optim.zation.

关键词： biom.m.tic finite elem.nts design space design principle topology optim.zation param.tric optim.zation dia- tom. radiolarian

m.ss budgets of the Lam.ert, m.llor and Fisher Glaciers and basal fluxes beneath their flowbands on Am.ry Ice Shelf

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2007年第11期50卷 1693-1706页

作者： Kenneth C. JEZEK Beata m. CSATHó Ute C. HERZFELD Katy L. FARNESS Philippe HUYBRECHTS Byrd Polar Research Center The Ohio State University Columbus OH 43210 USA CIRES/NSIDC University of Colorado Boulder Boulder CO 80309-0449 USA Departem.nt Geografie Vrije Universiteit Brussel Pleinlaan 2 B-1050 Brussels Belgium Alfred-Wegener-Institut für Polar-und Meeresforschung Postfach 120161 D-27515 Bremerhaven Germany

We used in situ m.asurem.nts and rem.te-sensing data sets to evaluate the m.ss budgets of the Lam.ert, m.llor and Fisher Glaciers and the basal m.lting and freezing rates beneath their flowbands on the Am.ry Ice Shelf. Our findings show the Lam.ert and m.llor Glaciers upstream.of the ANARE Lam.ert Glacier Basin (LGB) traverse m.y have positive im.alances of 3.9±2.1 Gt a-1 and 2.1±2.4 Gt a-1, respectively, while the Fisher Glacier is approxim.tely in balance. The upstream.region as a whole has a positive im.alance of 5.9±4.9 Gt a-1. The three sam. glaciers downstream.of the ANARE LGB traverse line are in negative im.alance, where the whole downstream.region has a negative im.alance of -8.5±5.8 Gt a-1. Overall the m.ss budgets of the Lam.ert, m.llor, and Fisher Glaciers are close to bal-ance, and the collective three-glacier system.is also nearly in balance with a m.ss budget of -2.6±6.5 Gt a-1. The significant positive im.alances for the interior basin upstream.of the ice-m.vem.nt stations established in the early 1970s (GL line) reported previously are possibly due to an overestim.te of the total accum.lation and an underestim.te of the ice flux through the GL line. The m.an m.lting rate is -23.0±3.5 m.ice a-1 near the southern grounding line, which decreases rapidly downstream. and transitions to refreezing at around 300 km.from.the southern extrem.ty of the Am.ry Ice Shelf. Freezing rates along the flowbands are around 0.5±0.1 to 1.5±0.2 m.ice a-1. The per-centage of ice lost from.the interior by basal m.lting beneath the flowbands is about 80%±5%. The total basal m.lting and refreezing beneath the three flowbands is 50.3±7.5 Gt ice a-1 and 7.0±1.1 Gt ice a-1, respectively. We find a m.ch larger total basal m.lting and net m.lting than the results for the whole Am.ry Ice Shelf derived from.previous m.deling and oceanographic m.asurem.nts.

关键词： m.ss budget basal m.lting and freezing Lam.ert Glacier Basin Am.ry Ice Shelf East Antarctica

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

干法纺丝工艺模拟

国际纺织导报 2021年第4期49卷 8-10页

作者： W.Arne R.wegener m.Wieland 李婷(译) 于俊荣(校) Fraunhofer工业数学研究所德国不详

干法纺丝是一种重要的化学纤维工业化生产工艺,用于仅能借助于溶剂进行纺丝的聚合物。在其常用工艺中,聚合物溶液通过由数百个毛细管组成的纺丝组件挤出到气室中,经溶剂蒸发而固化成纤维。纺丝工艺对于得到高质量且性能均匀的纤维至关... 详细信息

干法纺丝是一种重要的化学纤维工业化生产工艺,用于仅能借助于溶剂进行纺丝的聚合物。在其常用工艺中,聚合物溶液通过由数百个毛细管组成的纺丝组件挤出到气室中,经溶剂蒸发而固化成纤维。纺丝工艺对于得到高质量且性能均匀的纤维至关重要。采用试错法进行工业化规模的干法纺丝工艺的试验设计通常很困难且成本昂贵。因此,Fraunhofer工业数学研究所(ITWm.开发了一种仿真框架用以模拟此类过程并进行虚拟设计。为了证明该概念的可行性,以醋酸纤维素丙酮混合物为例进行了研究。为了验证该模型和仿真框架,采用简化设置将单根纤维的计算结果与复杂的3维(3D)仿真结果进行了比较,结果表明它们有较好的一致性。

关键词：干法纺丝模拟建模

Evidence for Transition of m.tastable Ice to Hexagonal Ice in Bulk Solutions at Relatively High Tem.eratures

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

International Journal of Geosciences 2020年第8期11卷 493-500页

作者： P. W. Wilson C. m.rshall m. Bayer-Giraldi m. Agustin m.teo School of Environm.nt Science and Engineering Southern Cross University Lismore NSW Australia Biochem.stry Departm.nt School of Medical Sciences University of Otago Dunedin New Zealand Alfred wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) Bremerhaven Germany Physics Departm.nt Interdisciplinary Sciences Building University of South Florida Tampa FL USA

There have been m.ny reports that a m.tastable form.of ice can exist in the atm.sphere and that it transitions rapidly to stable, hexagonal ice at tem.eratures above about 200 K. Although this often-called cubic ice has also been created in laboratories over the years, we present here a m.thod for the sim.le form.tion of this m.tastable phase in the laboratory, at one atm.sphere, in relatively large volum.s and at higher tem.eratures than previously reported. Evidence for this phase is found during the m.nitoring of optical transm.ssion through bulk sam.les of quenched aqueous solutions. In our experim.nts, frozen sam.les were created by quenching 0.2 m. aqueous volum.s in glass tubes to 195 K which are then warm.d to and held at 267 K. Results show an unusual drop in optical transm.ssion occurring in the first few m.nutes. Such a change is best explained by the transition of a m.tastable phase to hexagonal ice, rather than by any freeze concentration effects. In the m.nutes following nucleation and freezing of the sam.le, the average size of the poly-crystals form.ng the frozen m.trix would be typically expected to increase due to recrystallization, causing lower side and back-scatter of the traversing light and so a subsequent increased optical transm.ssion. However, the drop in transm.ssion we see with sam.les nucleated at such a low tem.erature cannot be explained by recrystallisation but rather by a re-ordering of the ice, the grain boundaries, and the interstitial water.

关键词： Ice Hexagonal Cubic Stacking Disorder m.tastable

The role of diabetes m.llitus in localized and m.tastatic renal cell carcinom.

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Diabetes m.llitus 2011年第4期1卷 104-108页

作者： Sandra Steffens Christoph von Klot Hendrik Egggers Christoph Seidel Gerd wegener m.rk Schrader m.rkus A. Kuczyk Andres J. Schrader 不详

Introduction & Objectives: Until recently, the incidence of renal cell carcinom. (RCC) has been increasing worldwide, m.inly in western countries, at a rate between 2% and 4% per year. However, the reason for this dram.tic increase in num.er has not been fully understood. Diabetes m.llitus (Dm. is a known risk factor for RCC, but the im.act of Dm.on the prognosis of RCC is unclear. In the present study, we investigated the potential influence of Dm.on clinicopathological features of localized and m.tastatic RCC. m.terial & m.thods: We evaluated 863 patients with prim.ry RCC who had undergone renal surgery between 1991 and 2005 in the University Hospital Hannover;the m.an follow-up was 58 m.nths. To test the association of Dm.with survival end-points, Kaplan-m.ier m.thod and Cox m.ltivariable logistic regression m.dels were applied. Results: In total, we identified 123 diabetic patients who suffered from.RCC, 9 patients with diabetes type 1 and 114 with type 2. Patients with Dm.type 2 presented significantly m.re often with pT1a tum.urs at diagnosis (40.0 vs. 31.7%, p = 0.02), had less frequently high grade cancer (G3/4;10.3 vs. 16.2%, p = 0.03), were older (m.dian, 65.3 vs. 61.6 years;p m. at diagnosis (m.dian, 27.6 vs. 25.8, p m.hatic and distant m.tastasis. In addition, there was no discrepancy in 5-year cancer specific survival between both groups (62.2 vs. 64.9% for patients without and with Dm.type 2, respectively). Applying m.ltivariable analysis, unlike age, tum.ur stage, grade and N/m.status, diabetes was not identified as a significant independent prognostic factor. Conclusions: To our knowledge this is the first study to show that even though diabetes is a risk factor for RCC it does not seem.to influence its prognoses even though it m.ght be diagnosed earlier in diabetic patients.

关键词： Renal Cell Cancer Risk Factor Diabetes m.llitus Survival Prognosis

一个秃冻胀丘的热及水文动力学——关于其形成的暗示(英)

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

冰川冻土 2002年第5期24卷 538-543页

作者： Julia Boike~ 1,\ Alfred wegener~ 1 ,\ Olaf Ippisch~ 2 ,\ Kurt Roth~ 2 (1. Institute for Polar and m.rine Research, Potsdam. Germ.ny 2. Institute for Environm.ntal Physics, University of Heidelberg, Heidelberg, Germ.ny) Institute for Polar and m.rine Research 德国 Potsdam Institute for Environm.ntal Physics University of Heidelberg 德国 Heidelberg

m.d boils, classified as non-sorted circles, are a com.on patterned ground phenom.non of perm.frost areas. They typically consist of a bare circle center of cryoturbated soil and are surrounded by vegetation on m.re stable soil. The objectives are to exam.ne differences in seasonal hydrologic and therm.l dynam.c across this gradient of cryoturbation, i.e. the region below the organic border and the m.d center. We installed instrum.nts in a m.d boil at a site close to Ny\|lesund, Spitsbergen, in Septem.er 1998. The bare soil circle center ranges about 1 m.in diam.ter and is surrounded by a vegetated border consisting of a m.xture of low vascular plants, m.sses and lichens. Fine soil (>95% clay and silt) in the lower part of the profile is overlain by coarser grained m.terial (silt and sand). The grain size distribution also suggests an upwelling of fine m.terial in the center of the circle. Tem.erature and m.isture sensors were installed over a vertical 1 m.1 m.profile and hourly data recording started in Septem.er 1998. Surface irregularities, as well as variations of grain size and m.isture, create a non\|uniform.therm.l and hydrologic dynam.c. We qualitatively analyze this dynam.c with respect to the m.d boils physical stability.

关键词：秃冻胀丘水文动力学热动力学温度湿度