Large Changes In Geometry Research Articles

An integrated analysis of transport, oxidation, and creep during oxidation of interior pores in SiC

AbstractOxidation of SiC plays a critical role in the durability of ceramic matrix composites, as large changes in molar volume generate significant stresses that can drive cracking in adjacent features. The analysis of such phenomena requires coupling between descriptions of diffusion through the oxide, growth of the oxide domain (i.e., evolution of the oxide/SiC interface), and creep relaxation in the oxide at elevated temperatures. This paper presents a two‐dimensional finite element framework that uses a single finite element mesh to predict these behaviors; large changes in the oxide geometry are simulated by tracking the oxidation front as a discrete interface and periodically re‐meshing. The numerical performance of the framework is illustrated using an analytical description of oxidation of a flat surface and subsequent stress evolution. The framework is then used to analyze internal oxidation within a cylindrical cavity for a wide range of temperatures and water vapor concentrations pertinent to gas turbines. The results are used to discuss the roles of oxide growth rate, creep, and geometry with respect to the tensile stresses that develop in the adjacent SiC, and their implications for oxidation‐driven damage at high temperatures.

Tuning the hydraulic resistance by swelling-induced buckling of membranes in high-aspect-ratio microfluidic devices.

Controlling fluid flow in microfluidic devices and adapting it to varying conditions by selectively regulating hydrodynamic properties is of critical importance, as the field of microfluidics faces increasingly complex challenges in its wide range of applications. One way to manipulate flows in microfluidic devices is to introduce elastic elements that can be actively or passively deformed. In this work, we developed a membrane-based microfluidic device that allows us to study the deformation of swollen thin membranes as a function of the volume fractions in binary mixtures - here isopropanol and water. Furthermore, the membrane deformation can be used to control pressure-driven flows within the device. The device consists of two microfluidic channels separated by a thin membrane that deforms by a buckling-based mechanism, when the isopropanol volume fraction of the solvent flowing through it exceeds a certain volume fraction. The buckling membrane causes a sinusoidal height variation in both adjacent channels, resulting in a large increase in hydraulic resistance. We show that buckling-based deflections of elastic membranes can be used to amplify small changes in the degree of swelling to produce large changes in the microchannel geometry of the device, sufficient to manipulate the flow rate of pressure-driven flows in the microdevice.

Do Existing Theories Explain Seasonal to Multi‐Decadal Changes in Glacier Basal Sliding Speed?

AbstractTheoretical descriptions of ice‐bed friction beneath glaciers and ice sheets are key to predict changes in sea level. Applicability of these theories at the natural landscape scale and over long periods has however not been tested. Here we test hard bed friction laws by analyzing a unique data set of in‐situ basal sliding measurements collected over three decades under an Alpine glacier enduring large changes in geometry. We report many observational features that are in striking agreement with theoretical predictions. However, we also observe an undocumented behavior where the basal stress state stabilizes near Iken's limit under meltwater input, which suggests the basal effective pressure is primarily set by bed shear stress rather than by water input and drainage specifics as commonly thought. As a result, long‐term changes in year‐averaged sliding velocities follow a simple power law scaling with bed shear stress as opposed to more complex pressure‐dependent relationships.

Scaling of internal organs during Drosophila embryonic development

Many species show a diverse range of sizes; for example, domestic dogs have large variation in body mass. Yet, the internal structure of the organism remains similar, i.e., the system scales to organism size. Drosophila melanogaster has been a powerful model system for exploring scaling mechanisms. In the early embryo, gene expression boundaries scale very precisely to embryo length. Later in development, the adult wings grow with remarkable symmetry and scale well with animal size. Yet, our knowledge of whether internal organs initially scale to embryo size remains largely unknown. Here, we utilize artificially small Drosophila embryos to explore how three critical internal organs—the heart, hindgut, and ventral nerve cord (VNC)—adapt to changes in embryo morphology. We find that the heart scales precisely with embryo length. Intriguingly, reduction in cardiac cell length, rather than number, appears to be important in controlling heart length. The hindgut, which is the first chiral organ to form, displays scaling with embryo size under large-scale changes in the artificially smaller embryos but shows few hallmarks of scaling within wild-type size variation. Finally, the VNC only displays weak scaling behavior; even large changes in embryo geometry result in only small shifts in VNC length. This suggests that the VNC may have an intrinsic minimal length that is largely independent of embryo length. Overall, our work shows that internal organs can adapt to embryo size changes in Drosophila, but the extent to which they scale varies significantly between organs.

The Utrecht Finite Volume Ice-Sheet Model: UFEMISM (version 1.0)

Abstract. Improving our confidence in future projections of sea-level rise requires models that can simulate ice-sheet evolution both in the future and in the geological past. A physically accurate treatment of large changes in ice-sheet geometry requires a proper treatment of processes near the margin, like grounding line dynamics, which in turn requires a high spatial resolution in that specific region, so that small-scale topographical features are resolved. This leads to a demand for computationally efficient models, where such a high resolution can be feasibly applied in simulations of 105–107 years in duration. Here, we present and evaluate a new ice-sheet model that solves the hybrid SIA–SSA approximation of the stress balance, including a heuristic rule for the grounding-line flux. This is done on a dynamic adaptive mesh which is adapted to the modelled ice-sheet geometry during a simulation. Mesh resolution can be configured to be fine only at specified areas, such as the calving front or the grounding line, as well as specified point locations such as ice-core drill sites. This strongly reduces the number of grid points where the equations need to be solved, increasing the computational efficiency. A high resolution allows the model to resolve small geometrical features, such as outlet glaciers and sub-shelf pinning points, which can significantly affect large-scale ice-sheet dynamics. We show that the model reproduces the analytical solutions or model intercomparison benchmarks for a number of schematic ice-sheet configurations, indicating that the numerical approach is valid. Because of the unstructured triangular mesh, the number of vertices increases less rapidly with resolution than in a square-grid model, greatly reducing the required computation time for high resolutions. A simulation of all four continental ice sheets during an entire 120 kyr glacial cycle, with a 4 km resolution near the grounding line, is expected to take 100–200 wall clock hours on a 16-core system (1600–3200 core hours), implying that this model can be feasibly used for high-resolution palaeo-ice-sheet simulations.

Functional packaging of seeds.

SummaryThe encapsulation of seeds in hard coats and fruit walls (pericarp layers) fulfils protective and dispersal functions in many plant families. In angiosperms, packaging structures possess a remarkable range of different morphologies and functionalities, as illustrated by thermo and hygro‐responsive seed pods and appendages, as well as mechanically strong and water‐impermeable shells. Key to these different functionalities are characteristic structural arrangements and chemical modifications of the underlying sclerenchymatous tissues. Although many ecological aspects of hard seed encapsulation have been well documented, a detailed understanding of the relationship between tissue structure and function only recently started to emerge, especially in the context of environmentally driven fruit opening and seed dispersal (responsive encapsulations) and the outstanding durability of some seed coats and indehiscent fruits (static encapsulations). In this review, we focus on the tissue properties of these two systems, with particular consideration of water interactions, mechanical resistance, and force generation. Common principles, as well as unique adaptations, are discussed in different plant species. Understanding how plants integrate a broad range of functions and properties for seed protection during storage and dispersal plays a central role for seed conservation, population dynamics, and plant‐based material developments.

Tuning two-electron transfer in terpyridine-based platinum(ii) pincer complexes.

An important factor in obtaining reversible multi-electron transfer is overcoming large changes in coordination geometry. One strategy is to use ligands that can support the geometries favored before and after the electron transfer. Pip2NCN− pincer and terpyridine ligands are used to support square planar Pt(ii) and octahedral Pt(iv). For the Pt(ii) complexes, [Pt(Z-pip2NCN)(R-tpy)]+ (Z = NO2, MeO, H; R = H, tertyl butyl, tolyl), 1H NMR spectroscopy shows that the Z-pip2NCN− ligand is monodentate whereas the R-terpyridyl ligand is tridentate. The availability of flanking piperidyl groups of the monodentate pincer ligand is essential for the stabilization of the metal center upon oxidation. Pt(Z-pip2NCN)(R-tpy)+ complexes undergo two-electron platinum centered oxidation near 0.4 V and two Pt(tpy) centered reductions near −1.0 V and −1.5 V. An estimate of nox/nred = 1.8 is consistent with an oxidation that involves two-electron transfer per Pt center. Variation in the pincer-(Z) and terpyridine-(R) substituents allows for tuning of the oxidation process over a 260 mV range and the two reduction processes over ranges of 230 mV (first reduction) and 290 mV (second reduction step).

Deforming black holes in AdS

We investigate how changes in the boundary metric affect the shape of AdS black holes. Most of our work is analytic and based on the AdS C-metric. Both asymptotically hyperbolic and compact black holes are studied. It has recently been shown that the AdS C-metric contains configurations of highly deformed black holes, and we show that these deformations are usually the result of similar deformations of the boundary metric. However, quite surprisingly, we also find cases where the horizon is insensitive to certain large changes in the boundary geometry. This motivates the search for a new family of black hole solutions with the same boundary geometry in which the horizon does respond to the changes in the boundary. We numerically construct these solutions and we (numerically) explore how the horizon response to boundary deformations depends on temperature.

Association of stent-induced changes in coronary geometry with late stent failure: Insights from three-dimensional quantitative coronary angiographic analysis.

The relationship between vessel angulation and large changes in vessel geometry after stent implantation and the occurrence of stent failure still remains unclear. We sought to investigate the association of the change in the coronary bending angle after stenting and the risk for late stent failure by three-dimensional quantitative coronary angiography (3D QCA). The bending angle in coronary lesions that presented with late stent failure and those without stent failure was computed during the cardiac cycle, before and after stenting using a recently developed 3D QCA software. A total of 40 lesions with stent failure (cases) were successfully matched to 47 lesions without stent failure (controls).The mean duration to follow-up coronary angiography was 1,011 days in cases and 1,109 days in the control group (P = 0.14). In stent failure, the systolic bending angle after stenting was smaller (14.45° [12.18, 17.68] versus 18.20° [14.00, 20.30], P = 0.01), while the stent-induced change in systolic bending angle was significantly larger (4.15° [1.13, 7.20] versus 1.80° [-1.90, 4.40], P = 0.004). Multivariable logistic regression analysis suggested that systolic bending angle after stenting (odds ratio: 0.88; 95% CI: 0.79-0.99; P = 0.03), and decrease in systolic bending angle after stenting (odds ratio: 1.13; 95% CI: 1.02-1.26; P = 0.03) were predictors of stent failure. Our study suggests that a change in the natural tortuous course of the coronaries by stent implantation with the decrease in coronary bending angle is a potentially major contributor in stent failure.

Role of autochthonous versus detrital micrite in depositional geometries of Middle Triassic carbonate platform systems

Middle Triassic platforms (Formazione di Contrin, Upper Anisian) in the Italian Dolomites, southern Alps, record large changes in carbonate production and depositional geometry. The changes include variation in the abundance of detrital micrite, i.e., allochthonous calcareous mud, relative to the autochthonous micrite, which formed in situ and was syndepositionally lithified. Carbonate factory dynamics controlled the geometry of the clinostratified slope units and were probably associated with changes in oxygenation. Early Anisian low-relief platforms were followed by late Anisian, high-relief buildups, associated with basinal dysoxic-anoxic environments. The geometric evolution of the platform slopes records a progressive increase in the dip angle of clinostratifications, matched by a deepening evolution of the basinal environments. At the same time, the slope sediments record a gradual change from loose detrital micrite, characterizing the lower portion, to autochthonous micrite, dominating the upper part and recording massive syndepositional lithification. The development of the autochthonous micrite was associated with the preservation of significant amounts of organic matter. This sharp increase in automicrite formation was probably induced by a rapid change from oxic to suboxic conditions in the carbonate slope and margin environments, while anoxic conditions developed in the adjacent organic-rich basin (Moena Formation). The low oxygen level promoted the preservation of organic matter and the activity of sulfate-reducing bacteria, which in turn induced in situ deposition of autochthonous micrite through biomediated processes. This pervasive early cementation and lithification induced the development of steep platform slopes. The conceptual model distilled from this Middle Triassic case can support the interpretation of analogous buildups where the skeletal framework is subordinate to the micrite component.

Chemical Equilibrium Models for the S3 State of the Oxygen-Evolving Complex of Photosystem II.

We have performed hybrid density functional theory (DFT) calculations to investigate how chemical equilibria can be described in the S3 state of the oxygen-evolving complex in photosystem II. For a chosen 340-atom model, 1 stable and 11 metastable intermediates have been identified within the range of 13 kcal mol(-1) that differ in protonation, charge, spin, and conformational states. The results imply that reversible interconversion of these intermediates gives rise to dynamic equilibria that involve processes with relocations of protons and electrons residing in the Mn4CaO5 cluster, as well as bound water ligands, with concomitant large changes in the cluster geometry. Such proton tautomerism and redox isomerism are responsible for reversible activation/deactivation processes of substrate oxygen species, through which Mn-O and O-O bonds are transiently ruptured and formed. These results may allow for a tentative interpretation of kinetic data on substrate water exchange on the order of seconds at room temperature, as measured by time-resolved mass spectrometry. The reliability of the hybrid DFT method for the multielectron redox reaction in such an intricate system is also addressed.

Observational Tests of Magnetospheric Accretion Models in Young Stars

Magnetically controlled accretion of disk material onto the surface of Classical T Tauri stars is the dominant paradigm in our understanding of how these young stars interact with their surrounding disks. These stars provide a powerful test of magnetically controlled accretion models since all of the relevant parameters, including the magnetic field strength and geometry, are in principle measureable. Both the strength and the field geometry are key for understanding how these stars interact with their disks. This talk will focus on recent advances in magnetic field measurements on a large number of T Tauri stars, as well as very recent studies of the accretion rates onto a sample of young stars in NGC 2264 with known rotation periods. We discuss how these observations provide critical tests of magnetospheric accretion models which predict a rotational equilibrium is reached. We find good support for the model predictions once the complex geometry of the stellar magnetic field is taken into account. We will also explore how the observations of the accretion properties of the 2264 cluster stars can be used to test emerging ideas on how magnetic fields on young stars are generated and organized as a function of their internal structure (i.e. the presence of a radiative core). We do not find support for the hypothesis that large changes in the magentic field geometry occur when a radiative core appears in these young stars.

Boundary element model for electrochemical dissolution under externally applied low level stress

Abstract The effects of low levels of stress on the dissolution rate of type 304 stainless steel in seawater are determined, and these effects are incorporated into a boundary element method (BEM) code which was written to predict long-term changes in geometry, including those due to the stress-modified dissolution rates. Corrosion in the absence of stress effects is thoroughly documented, while the effects of micromechanical damage caused by strains in the plastic region are also well recognized. However, very little is known regarding the effects of low levels of stress (in the elastic region) on the behavior of dissolution rates of metals in general. To quantify this effect, a system consisting of stainless steel in seawater was chosen as the subject of this investigation. An initial set of controlled experiments using nearly pure copper with NHOH electrolyte was used to test the experimental methods developed for this study and to verify the functionality of the numerical code in predicting large changes in geometry due to long duration dissolution. The numerical code is based on the BEM to predict the electrochemical dissolution activity in 2D and in 3D-axisymmetric geometries with nonlinearities in the response to stress and the boundary conditions given by the highly non-linear polarization response of the specimen. A Newton–Raphson iterative procedure is used to solve for equilibrium at each solution step. In the BEM code, a nodal optimization routine dynamically modifies the number of nodes and their location on the boundary, which is required by the large changes in geometry experienced during long duration dissolution. New SE-elements are developed to model sections of the boundary where nodes are dynamically located, defined by a curvilinear fit using orthogonal Chebyshev polynomials through previous nodal locations. The code links stress and potential type corrosion formulations to generate geometrical changes due to stress and corrosion. Polarization curves were measured and input into the BEM code and recession profiles were predicted. Comparison between experiment and predictions reveal that, given the polarization curves measured in the lab, the BEM code predicts accurate recession profiles. Once the laboratory methods and computer program were verified, a second electrochemical system is adopted to study the effects of stress in the linear range upon recession rates. This system consists of type 304 stainless steel in simulated seawater subjected to compressive and tensile stresses up to 20% of yield. Comparison between numerical predictions using polarization curves determined by experiment for the copper/ammonium system reveals that the BEM code developed to model recession of corroding surfaces faithfully reproduces the recession fronts measured in the experiments. Furthermore, it is shown in a series of repeatable laboratory tests, in the stainless-steel/saline system, that stress in the linear range indeed affects the polarization curves for different levels of stress and, furthermore, it is found that the shift in the polarization curve depends on stress rate.

Modes of Operation and Optimum Design for Application of Source-Gated Transistors

We show that the source-gated transistor has two distinct modes of operation. In the low-field mode, the current from the reverse-biased source barrier is restricted by the depleted semiconductor at the drain end of the source. In the high-field mode, the current depends on field-dependent barrier lowering in the same region of the source. In practice, both these modes usually occur: the former at low VG, the latter at high VG. It is shown that this understanding enables us to design devices in which the current is insensitive to large changes in structure and geometry.

Interaction of fuel with ferrite-martensite steel fuel-element cladding under fast reactor conditions

The peripheral fuel elements of test fuel assemblies in the low- and high-enrichment zones were studied after operation to maximum burnup 7‐9% h.a. and maximum damaging dose 40‐74 dpa. The temperature of the sodium coolant was 380‐580°C. The maximum lineal power density of the fuel elements did not exceed 35 kW/m. Cladding Creep. EP-450 steel cladding curbs the deformation of the kernel in irradiated fuel elements at the end of an operating period. The linear thermal expansion coefficient of ferrite-martensite steel is 30% lower than that of austenitic steel and is comparable to that of sintered uranium dioxide [3]. EP-450 steel is not subject to radiation swelling in the damaging dose range studied. Thus, the technological fuel‐cladding gap vanishes at burnup above 4‐5% h.a. The fuel can exert a high mechanical pressure on the cladding and cladding can become deformed as a result of creep. To evaluate creep, profilograms of the outer diameter and material density of the cladding of the experimental fuel elements were studied. It was found that the deviation of the diameter and density of the steel from their initial values falls within the measurement error. This showed that for the burnup attained and operating temperature below 580°C there is no deformation of EP-450 by the mechanical action of a pelleted fuel kernel and pressure due to the gaseous fission products. This is because under irradiation uranium dioxide is in a plastic state. For this reason, prolonged stresses caused by contact between a kernel and unswelled cladding relax as a result of the contraction of the central cavity and the decrease in the porosity. The residual stresses do not reach the yield stress of EP-450 steel and cannot increase the rate of radiation creep appreciably even in concert with the gas pressure inside a fuel element. The short-time stresses arising at the periphery of uranium dioxide pellets during the transient regimes of BN-600 likewise do not exceed the macroscopic yield stress of irradiated EP-450 steel. Kernel Volume Change. Large changes in the initial geometry of a fuel-element kernel are due to the high temperature at the center of fuel elements, high swelling of uranium dioxide and thermal cracking of fuel pellets. An increase of the outer diameter of a fuel-element kernel and contraction of the residual gap increase heat transfer between the fuel and cladding, intensifying their mechanical interaction (see Table 1). EP-450 steel cladding impedes kernel swelling. The specific change of the kernel diameter in such fuel elements is 0.03‐0.3% per 1% burnup. The absolute change in the pellet shape is limited by the inner cladding diameter 6.1 mm and does not exceed 2.5% for burnup 9.2% h.a. Under the conditions of cladding-limited swelling uranium dioxide undergoes creep. Plastic flow of the central regions of the fuel pellets in fuel assemblies in the high-enrichment zone causes considerable (~0.7 mm) contraction of the central opening. The competing process of axial mass transfer, which enlarges the kernel cavity at the center of the active part, does not develop consistently. This is because the experimental fuel elements are located at the periphery, the lineal power density is low (<30 kW/m) and the fuel temperature is average. At higher lineal power density in the peripheral fuel elements in the fuel assemblies in the low-enrichment zone with maximum burnup 8.7% h.a. axial mass transfer stabilizes

On integrating experimental and theoretical models to determine physical mechanisms of morphogenesis

Researchers in developmental biology are increasingly recognizing the value of theoretical models in studies of morphogenesis. However, creating and testing realistic quantitative models for morphogenetic processes can be an extremely challenging task. The focus of this paper is on models for the mechanics of morphogenesis. Models for these problems often must include large changes in geometry, leading to highly nonlinear problems with the possibility of multiple solutions that must be sorted out using experimental data. Here, we illustrate our approach to these problems using the specific example of head fold formation in the early chick embryo. The interplay between experimental and theoretical results is emphasized throughout, as the model is gradually refined. Some of the limitations inherent in theoretical/computational modeling of biological systems are also discussed.

Risk of target lesion failure in relationship to vessel angiographic geometry and stent conformability using the second generation of drug-eluting stents

Vessel angulation and large changes in vessel geometry after stent implantation have been associated with an increased risk of target lesion failure (TLF) using bare-metal stents. Second-generation drug-eluting stents (DES)offer superior conformability and inhibition of neointima. The aim of the study is to investigate the relationship between pre and post-implant vessel geometry and the occurrence of TLF at 1 year after treatment with second-generation DES; and to compare the conformability of Resolute and Xience stents. The RESOLUTE All-Comers trial randomized 2292 patients (3366 lesions) to Resolute zotarolimus-DES (Medtronic CardioVascular) or Xience everolimus-DES (Abbott Vascular). At 1 year, 176 lesions (121 patients)presented with TLF; a composite of cardiac death, acute myocardial infarction (AMI) and target lesion revascularization (TLR). Lesions with TLF were matched with 176 lesions (168 patients) without TLF adjusting for clinical and procedural characteristics. The number of bends, vessel curvature and angulation were assessed with quantitative coronary angiography pre and post-implantation. The absolute difference post minus pre-implantation was used as a surrogate of stent conformability. At pre-implantation, lesions without and with TLF had similar numbers of bends/lesion (1.81 vs 1.74; P = .35), vessel curvature (0.295 cm(-1) vs 0.363 cm(-1); P = .13) and vessel angulation (46.3° vs 43.5°; P = .80), respectively. Lesions without and with TLR also had similar numbers of bends/lesion (1.39 vs 1.39; P = .83), vessel curvature (0.368 cm(-1) vs 0.325 cm(-1); P = .33) and angulation (40.2° vs 37.2°; P = .19). Lesions without and with in-hospital AMI also presented with similar number of bends/lesion (1.69 vs 1.81; P = .48), vessel curvature (0.349 cm(-1) vs 0.345 cm(-1); P = .91) and vessel angulation (43.53° vs 48.45°; P = .38). The absolute difference post- - pre-implantation was similar in lesions without and with TLF, TLR and In-hospital AMI. The absolute difference post- - pre-implantation was similar with both Resolute and Xience in vessel curvature (-0.046 cm(-1) vs -0.047 cm(-1); P = .66) and was smaller in number of bends/lesion (-0.08 vs -0.16; P = .13) and in vessel angulation (-6.0° vs -10.1°; P = .03) with the Resolute. Bended, curved, and angulated lesions and changes in the number of bends/lesion, vessel curvature, and angulation from pre to post-implantation have no relation with TLF and TLR at 1 year and have no relation with In-hospital AMI using second-generation of DES. Resolute appears to be more conformable than Xience.

Influence of ligand substituent on molecular architecture; very large changes in structural assembly and coordination geometry

Influence of ligand substituent on molecular architecture; very large changes in structural assembly and coordination geometry

Boundary element model of electrochemical dissolution with geometric non-linearities

Large scale changes in geometry due to corrosion of polycrystalline pure copper are modeled using the Boundary Element Method. Axisymmetric geometries are considered. A quasi-static analysis is performed and a nonlinear polarization curve is determined from experiments to impose third kind boundary conditions. Super-elements, based on a cubic spline fit interpolation, are introduced to model the motion of the boundaries. Faraday's law is used to relate boundary motion to the surface flux. An set of controlled experiments using nearly pure (99.99% and 99.9%) copper with aerated NH 4OH electrolyte was used to test the experimental methods developed for this study and to verify the functionality of the numerical code in predicting large changes in geometry due to long duration dissolution. Polarization curves were measured and input into the BEM code and recession profiles were predicted. Comparison between experiment and predictions reveal that, given the polarization curves measured in the lab, the BEM code predicts accurate recession profiles.

Aerodynamic Optimization Algorithm with Integrated Geometry Parameterization and Mesh Movement

An efficient gradient-based algorithm for aerodynamic shape optimization is presented. The algorithm consists of several components, including a novel integrated geometry parameterization and mesh movement, a parallel Newton―Krylov flow solver, and an adjoint-based gradient evaluation. To integrate geometry parameterization and mesh movement, generalized B-spline volumes are used to parameterize both the surface and volume mesh. The volume mesh of B-spline control points mimics a coarse mesh; a linear elasticity mesh-movement algorithm is applied directly to this coarse mesh and the fine mesh is regenerated algebraically. Using this approach, mesh-movement time is reduced by two to three orders of magnitude relative to a node-based movement. The mesh-adjoint system also becomes smaller and is thus amenable to complex-step derivative approximations. When solving the flow-adjoint equations using restarted Krylov-subspace methods, a nested-subspace strategy is shown to be more robust than truncating the entire subspace. Optimization is accomplished using a sequential-quadratic-programming algorithm. The effectiveness of the complete algorithm is demonstrated using a lift-constrained induced-drag minimization that involves large changes in geometry.