Separate Fronts Research Articles

Ranking-based multi/many-objective evolutionary optimization with hierarchical evaluation rules and its application in water distribution network

To solve multi/many-objective optimization problems characterized by complex Pareto fronts, we propose a two-phase ranking-based multi-objective evolutionary algorithm with hybrid convergence rules. Firstly, we introduce a novel hybrid convergence criterion by integrating Pareto dominance, localized pruning power (LPP), and distance-based measure. Secondly, we design a two-phase ranking-based selection strategy. Specifically, we employ the acute angle between objective vector and reference vector to divide the current population into multiple sub-populations. In the first-phase ranking, the solutions within each subpopulation are sorted according to the hybrid convergence rule. The best solutions are chosen based on the angle-based diversity criterion into separate fronts. In the second-phase selection, a specific number of solutions with best diversity are further selected to the next generation based upon their front-level assignments. To obtain better diversity of selected solutions, we employ the maximum angle between solutions and the sum of normalized objectives of solutions to assist the selecting process. The experimental results, which encompass benchmark problems involving up to 10 objectives as well as two real-world application instances, validating our proposed algorithm’s competitiveness and effectiveness.

Spanwise unsteadiness in the sidewall-confined shock-wave/boundary-layer interaction

Three-dimensional effects of sidewalls on the low-frequency unsteadiness of the shock-wave/boundary-layer interaction (SBLI) are of academic and practical importance but not yet well understood. Considerable attention has been paid to the viscous effect of sidewalls, whereas the potential inviscid confinement effect of sidewalls has received little attention. The present work provides experimental evidence of multiscale spanwise travelling waves crossing the separation front under the confinement of sidewalls. Global pressure measurements were made for a sidewall-confined 24 $^\circ$ compression ramp interaction in Mach-2.83 flow using fast-responding pressure-sensitive paint. The unsteady pressure in a statistically two-dimensional intermittent region suggests that in addition to the canonical streamwise oscillation, the separation front exhibits significant low-frequency, multiscale spanwise distortion. Modal analysis further reveals that multiscale spanwise unsteadiness has higher intensity and frequency than the streamwise oscillation. Such strong spanwise unsteadiness calls attention to the low-frequency unsteadiness in previous sidewall-confined SBLI experiments and encourages further study on the mechanism of the confinement effect.

Interacting density fronts in saturated brines cooled from above

When a saturated brine layer is cooled from above, both a convective temperature front as well as a front of sedimenting salt crystals can form. We employ direct numerical simulations to investigate the evolution and interaction of these two density fronts. Depending on the ratio of the temperature front velocity and the crystal settling velocity, which is governed by a dimensionless parameter in the form of a Rayleigh number, we find that either two separate fronts exist for all times, two initially separate fronts combine into a single front after some time or a single front exists at all times. We furthermore propose approximate scaling laws for the propagation of the thermal and crystal fronts in each regime and compare them with the simulation data, with generally good agreement.

In-depth size and charge variants characterization of monoclonal antibody with native mass spectrometry

Although the reversed-phase liquid chromatography (RPLC) is the most used separation front for mass spectrometry, many other separation modes are critical for enabling characterization of the protein therapeutics. Specifically, chromatographic separations under native conditions, such as those based on size exclusion chromatography (SEC) and ion-exchange chromatography (IEX), are used for characterizing important biophysical properties of protein variants in drug substance and drug product. Because most native state separation modes use non-volatile buffers with high salt concentration, optical detection has been traditionally used. However, there is an increasing need to understand and identify the optical underlying peaks by mass spectrometry for structure elucidation. For size variant separation by SEC, the native MS helps to understand the nature of the high molecular weight species, as well as clipping sites for low molecular weight fragments. For charge variant separation by IEX, native MS can reveal the post-translational modifications or other important factors contributing to charge heterogeneity at the intact level. Here, we demonstrate the power of native MS by direct coupling of SEC and IEX eluent to a time-of-flight mass spectrometer to characterize bevacizumab and NISTmAb. Our studies exemplify the effectiveness of native SEC-MS for characterizing bevacizumab's high molecular weight species at less than 0.3% (based on SEC/UV peak area%) and analyzing the fragment pathway with single amino acid difference for its low molecular weight species at less than 0.05%. Good IEX charge variant separation was obtained with consistent UV and MS profiles. The identity of separated acidic and basic variants were elucidated by native MS at intact level. We successfully differentiated several charge variants including glycoform variants that have not been reported before. In addition, native MS allowed identification of higher molecular weight species as late eluted variants. Overall, the SEC and IEX separation combined with high resolution and high sensitivity native MS, which is significantly different from the traditional RPLC-MS workflows, can be an effective tool that offers valuable insights for us to understand protein therapeutics at native state.

Level-Set Mass-Conservative Front-Tracking Technique for Multistep Simulations of In-Flight Ice Accretion

This paper presents a novel level-set-based approach to model evolving boundary problems for in-flight ice accretion. No partial differential equations are solved as in the standard level-set formulation, but simple geometrical quantities are employed to provide an implicit discretization of the updated boundary. This method avoids mesh entanglements and grid intersections typical of algebraic and mesh deforming techniques, making it suitable for generating a body-fitted discretization of arbitrarily complex geometries as in-flight ice shapes, including the collision of separate ice fronts. Moreover, this paper presents a local ice thickness correction, which accounts for the body’s curvature, to conserve the prescribed iced mass locally. The verification includes ice accretion over an ellipse and a manufactured example to show the proposed strategy’s advantages and robustness compared to standard algebraic methods. Finally, the method is applied to ice accretion problems. A temporal and grid convergence study is presented for automatic multistep in-flight simulations over a NACA0012 airfoil in rime, glaze, and mixed ice conditions.

Propagation dynamics in periodic predator-prey systems with nonlocal dispersal

In this paper, we study the propagation dynamics of a time-periodic predator-prey system with nonlocal dispersal. We first establish the existence and nonexistence of periodic traveling waves and then investigate the spreading properties of solutions starting from compactly supported initial conditions. Roughly speaking, we show that if predators disperse faster than the prey, then both species spread simultaneously; whereas if the prey disperses faster than predators, then there exist two separate invasion fronts, one front occurs as the prey invades open habitats, and the other front appears when predators catch up the prey. We emphasize that one needs to find some new techniques to treat nonlocal predator-prey systems due to the presence of the time dependence of nonlinearity, the lack of compactness of the nonlocal dispersal operators and the lack of the comparison principle for predator-prey systems.

Comparative-legal analysis of the structure of external functions of Ukraine and Hungary: implementation of experience (part 2)

Now a new military battle has begun for Ukraine and Ukrainians, and each component of the function is own separate front of confrontation today. The Ministry of Foreign Affairs of Ukraine is considered as a PR manager of the international level of a specific state. Based on the experience of Hungary and the legislative tasks of the Ministry of Foreign Affairs of Ukraine, which are quite extensive with a wide range of tasks, it is proposed to systematize its competences into six logical groups. The first is to promote the interests of Ukraine and support security and territorial integrity. The second is investments and information space. The third is maintaining ties with legal and physical Ukrainians. The fourth is image formation. The fifth is the EU and NATO. And considering the foreign policy strategy, as a sixth separate group we can highlight the expansion of relations with Africa and Asia, because this is not only a new breath for the renewal of relations, but also a new stage of investment and trade, which is mutually beneficial for both sides. The structure of external functions is the same for most states, the main differences between them are contained in the approaches to their implementation. For Ukraine, which until February 24 was on the verge of a full-scale military invasion and conducted its activities in an almost basic mode, today must not only review its stereotypical tasks, but must create them in a new way. The group's data are priorities for the coming years, and each of these realized directions will help not only in rebuilding the destroyed, but also in creating a new one, otherwise, we can predict that Ukraine will be thrown back decades. Under each of the proposed systematic groups, a specific component of the external function is considered, as a way of realizing the function itself and the goal of the selected group. In this part of the scientific article, we consider issues within the framework of the following components of external functions: establishing international cultural ties (humanitarian), countering international terrorism and international organized crime, nature protection or Ecological (participation in international environmental protection) function.

Comparative legal analysis of external functions of Ukraine and Hungary: implementation of experience (Part 1)

The structure of external functions is the same for most states, the main differences between them are contained in the approaches to their implementation. For Ukraine, which until February 24 was on the verge of a full-scale military invasion and conducted its activities in an almost basic mode, today must not only review its stereotypical tasks, but must create them in a new way. Now a new military battle has begun for Ukraine and Ukrainians, and each component of the function is own separate front of confrontation today. The Ministry of Foreign Affairs of Ukraine is considered as a PR manager of the international level of a specific state. Based on the experience of Hungary and the legislative tasks of the Ministry of Foreign Affairs of Ukraine, which are quite extensive with a wide range of tasks, it is proposed to systematize its competences into six logical groups. The first is to promote the interests of Ukraine and support security and territorial integrity. The second is investments and information space. The third is maintaining ties with legal and physical Ukrainians. The fourth is image formation. The fifth is the EU and NATO. And considering the foreign policy strategy, as a sixth separate group we can highlight the expansion of relations with Africa and Asia, because this is not only a new breath for the renewal of relations, but also a new stage of investment and trade, which is mutually beneficial for both sides. The group's data are priorities for the coming years, and each of these realized directions will help not only in rebuilding the destroyed, but also in creating a new one, otherwise, we can predict that Ukraine will be thrown back decades. Under each of the proposed systematic groups, a specific component of the external function is considered, as a way of realizing the function itself and the goal of the selected group. These components of the external function in this scientific article of the first part are considered foreign-political (diplomatic), foreign-economic and foreign-informational as a comparative analysis with the experience of Hungary. A significant difference is the levels from which they operate. It is not surprising that the de jure level of a European state with all its privileges and disadvantages makes Hungary more stable and protected from external influences, Ukraine is, on the contrary, more vulnerable, because behind Hungary stands the Alliance with the latest weapons developments, behind Ukraine - Ukrainians.

Experimental and Numerical Methods for the Evaluation of Sound Radiated by Vibrating Panels Excited by Electromagnetic Shakers in Automotive Applications

Numerical simulations are increasingly employed in the automotive industry to optimize the design stage, reduce prototype testing, and shorten the time to market. The aim of the presented research is the development of a fast and reliable method for the prediction of the sound field generated outside a vehicle by vibrating panels under electromagnetic shaker excitation. Despite that multi-physics numerical simulation software already link mechanical vibrations to their acoustic effect, they show a drawback when calculating the exterior sound field produced by a vibrating panel: the presence of a car model to separate front and rear radiations avoiding the acoustic short circuit, and an air volume surrounding it are required, thus increasing the model complexity and calculation time. Both problems can be overcome with the presented methodology: only the mechanical vibration of the panel is solved numerically, and the radiated sound field is then calculated postprocessing, relying on Rayleigh’s integral. At first, the method’s validation is presented through laboratory experiments; then, a real vehicle panel is analyzed. Comparisons between the finite element method (FEM) simulations and experimental measurements showed very good agreement while keeping the calculation time low for both the laboratory and on-vehicle tests.

Episodic Venting of a Submarine Gas Seep on Geological Time Scales: Formosa Ridge, Northern South China Sea

AbstractThe Formosa Ridge cold seep is among the first documented active seeps on the northern South China Sea passive margin slope. Although this system has been the focus of scientific studies for decades, the geological factors controlling gas release are not well understood due to a lack of constraints of the subsurface structure and seepage history. Here, we use high‐resolution 3D seismic data to image stratigraphic and structural relationships associated with fluid expulsion, which provide spatio‐temporal constraints on the gas hydrate system at depth and methane seepage at modern and paleo seafloors. Gas has accumulated beneath the base of gas hydrate stability to a critical thickness, causing hydraulic fracturing, propagation of a vertical gas conduit, and morphological features (mounds) at paleo‐seafloor horizons. These mounds record multiple distinct gas migration episodes between 300,000 and 127,000 years ago, separated by periods of dormancy. Episodic seepage still seems to occur at the present day, as evidenced by two separate fronts of ascending gas imaged within the conduit. We propose that episodic seepage is associated with enhanced seafloor sedimentation. The increasing overburden leads to an increase in effective horizontal stress that exceeds the gas pressure at the top of the gas reservoir. As a result, the conduit closes off until the gas reservoir is replenished to a new (greater) critical thickness to reopen hydraulic fractures. Our results provide intricate detail of long‐term methane flux through sub‐seabed seep systems, which is important for assessing its impact on seafloor and ocean biogeochemistry.

Impingement Atomization of Carbopol Gels

Experiments were performed on the atomization of Carbopol–water gels of compositions in the range 0.10–0.30 gellant wt.% on a like-on-like jet impingement configuration. Analysis indicates two primary modes of sheet breakup: perforation driven and wave driven. While perforation-driven breakup is not seen for the lowest gellant concentration case, 0.10 wt.%, the wave-driven breakup is present in all cases within the range of investigated jet velocities. Based on the observations, a mechanism involving feedback between the impingement point and the sheet vertex, and a separation front initiated in between the impingement point and the sheet vertex are proposed for the wave-driven breakup.

A Skid-Steering Method for Path-Following Control of Distributed-Drive Articulated Heavy Vehicles

Distributed-drive articulated heavy vehicles (DAHVs) have separate front and rear sections and require a complex hydraulic steering system to achieve the steering process, which poses considerable challenges in obtaining better steering characteristics and achieving path-following control. In this paper, the distributed-drive characteristic of DAHVs is used to develop a novel skid-steering method (SSM) in which the hydraulic steering method (HSM) is replaced with a system that differentially controls the driving wheels to improve vehicle steering performance and path following control accuracy. Three main contributions are made: 1) The novel SSM with direct yaw moment that is used to be the sole power source during steering process of DAHVs is designed to replace the conventional HSM. 2) The idea of SSM by yaw rate control of one vehicle section to achieve the steering process for DAHVs is proposed firstly, which can solve the complex problem of requiring multiple control parameters due to the separate vehicle sections of DAHVs. 3) A layered control method is implemented to improve the robustness of the control system, which is composed of an upper path following controller and a lower skid steering controller combined with a double sliding mode control technique. The system’s stability and robustness are proven by the Lyapunov approach. A co-simulation model verified by field tests is used to demonstrate the feasibility and effectiveness of the proposed control method. The results of this study provide a new way to improve the intelligence of DAHVs.

Loss Characterization of Advanced VIGV Configurations With Adjustable Blade Geometry

Abstract Variable inlet guide vanes (VIGV) are the main control element to adjust the flow rate of industrial centrifugal compressors by customized pre-swirl in the inlet plane of the impeller. The efficient working range of VIGVs is however restricted due to open flow separation occurring at critical stagger angles. In order to overcome the narrow limitations of current blade geometries and to enhance the operating range of the compressor, split blades consisting of a separate front and tail blade segment proved to be particularly promising in previous linear-cascade measurements. Each blade segment is thereby individually staggered. This enables a gradual flow deflection along the chord length. Secondary flow losses, however, were not considered in the previous investigations with linear cascades. To highlight the potential of the split blade concept under more application-oriented conditions including all relevant flow effects, highly resolved field measurements were conducted in the wake of annular VIGVs. Four different blade configurations, a customary reference case and three variations of the split blade with full, partial and missing sealing in the gap between the segments were assessed using five-hole probe measurements. By investigating a wide range of stagger angles, the coverage of the full low-loss working range of the VIGV could be ensured. Especially, the fully sealed split blade configuration proved its capacity to extend the efficient operational range significantly.

기산 풍속화의 항라직기 복원에 관한 연구

The purpose of this study is to restore the Hang-ra loom of late Joseon Dynasty that had appared in the painting “A weaving Hang-ra(亢羅: leno weave type)”, painted by Gisan Kim Jun-geun. The intention of this study is to identify a traditional Hang-ra loom within the history of Hang-ra in 1888, when the genre painting was purchased. The methods of this study are threefold, consisting of a historical investigation of Hang-ra and Hang-ra looms through the literature, a comparative analysis of the loom and its parts done by pictures and artifact materials, and test weaving of the restored Hang-ra loom. Gisan’s Hang-ra loom has a “separated front leg” structure and highly sloped poles as the traditional looms in Gisan’s other genre painting. Therefore, it is assumed that the Hang-ra loom is the traditional Korean Hang-ra loom with local characteristics of Wonsan. However, the prototype of the restored Hang-ra loom, which was built based on the Gisan’s Hang-ra loom, was unsuccessful in weaving Hang-ra. It is assumed that the Gisan had misdescribed or omitted several details, because of their insufficient understanding of its weaving mechanism, as many other painters of genre painting. In the following process of correcting the restored Hang-ra loom, the position of the “Nullimdae” which had interfered with the movement of warp thread has been changed. Also, to recover the insufficient movement of heddle, a traditional tool called “Bigeomi” has been added, opening the warp upward. This study restores the traditional backstrap treadle Hang-ra loom that had disappeared from the folklore history, finds several complementary points, and demonstrates that the restored Hang-ra loom has succeeded in weaving Hang-ra. It is meaningful that the range of traditional fabrics could be expanded, as Hang-ra has been examined.

Effect of Throttling on Dual-Bell Sneak-Transition Side Loads

An experimental investigation has been conducted on a subscale dual-bell nozzle to study the effect of throttle settings on sneak-transition side loads. The results are from a cold-gas test campaign conducted in a high-altitude simulation chamber for three throttle settings of 1, 2, and . An analysis is carried out by correlating the simultaneously acquired side-load measurements and real-time wall pressure data from transducers mounted in the vicinity of the wall inflection. The study reveals that the longer is the time duration of separation front in the region of wall inflection, the higher is the amplitude of overall sneak-transition side loads. Increasing the throttle settings from 1 to significantly reduces not only the overall sneak-transition duration but also the amplitude of flow unsteadiness in the region of wall inflection during the intermittent flow condition of the sneak transition and, hence, the associated side loads. It is further observed that even though the total transition time decreases with an increase in throttle settings, the actual transition side-load peak amplitude remains more or less similar irrespective of throttle setting.

Periodic forcing of a large turbulent separation bubble

Abstract

Impact of Underlying RANS Turbulence Models in Zonal Detached Eddy Simulation: Application to a Compressor Rotor

The present study focuses on the impact of the underlying RANS turbulence model in the Zonal Detached Eddy Simulation (ZDES) method when used for secondary flow prediction. This is carried out in light of three issues commonly investigated for hybrid RANS/LES methods (detection and protection of attached boundary layer, emergence, and growth of resolved turbulent fluctuations and accurate prediction of separation front due to progressive adverse pressure gradient). The studied configuration is the first rotor of a high pressure compressor. Three different turbulence modelings (Spalart and Allmaras model (SA), Menter model with (SST) and without (BSL) shear stress correction) are assessed as ZDES underlying turbulence model and also as turbulence model of unsteady RANS simulations. Whatever the underlying turbulence model, the ZDES behaves well with respect to the first two issues as the boundary layers appear effectively shielded and the RANS-to-LES switch is close downstream of trailing edges and separation fronts leading to a quick LES treatment of wakes and shear layers. Both tip leakage and corner flows are strongly influenced by the Navier–Stokes resolution approach (unsteady RANS vs. ZDES) but the underlying turbulence modelling (SA vs. SST vs. BSL) impacts mainly the junction flow near the hub for both approaches. ZDES underlying turbulence model choice appear essential since it leads to quite different corner flow separation topologies and so to inversion of the downstream stagnation pressure radial gradient.

Conceptual design analysis of a variable swept half-span wing of a supersonic business jet

Supersonic business jets have a huge market potential, but face strict economic and environmental requirements. To guarantee the viability of the project, it must balance aerodynamic efficiency and low sonic boom intensity when operating in supersonic cruise. This paper describes the concept of an aircraft with one fixed low-swept half-span wing and one variably-swept half-span wing. Its aerodynamics will be studied in subsonic and supersonic regimes by both analytical methods, and numerical methods developed by the authors. The volumetric wave drag is evaluated numerically, through a method based on the linearized supersonic area rule, properly implemented in a VBA routine, coupled with a cone-based area extraction routine, implemented in a three-dimensional CAD environment. The study is divided in three separate fronts: first, the behavior of the wave drag with respect to the angle of sweep of the variable half-span wing; second, the influence of the tail configuration in both subsonic and supersonic parasite drag; and third, a comparison between different wing configurations. Results show that the proposed half-span variably-swept wing configuration is a promising alternative to operations flown in low supersonic Mach numbers over land, presenting a good aerodynamic efficiency, simultaneously with low-boom intensity.

(Invited) Electrochemical Liquid-Liquid-Solid Deposition of Microwires, Nanowires, and Nanoparticles

This presentation will describe our group's latest efforts to advance the concept of electrochemical liquid-liquid-solid (ec-LLS) deposition of inorganic nanomaterials. A brief historical overview of the concept and relevant precedents in the literature will be presented, followed by advances on two separate fronts. First, in-situ TEM studies of nanowire and nanoparticle growth will be detailed. These measurements describe the initial stages of the ec-LLS process. The cumulative data suggest that ec-LLS nanowire growths are typically performed under conditions of extreme supersaturation and this has a large influence on the resultant crystal quality. Second, the prospects for using ec-LLS to synthesize intermetallic nanoparticles and films will be documented for the first time. An important aspect of this work is describing the fate of initial electrodeposited adsorbates at the liquid metal/liquid electrolyte interface.

Performance of cylindrical and planar meso­scale combustor with double narrow slit flame holder for micropower generator

This research compared the performance of a cylindrical mesoscale combustor against two planar mesoscale combustors, which include the shape of the flame front, temperature of the combustor axis and the combustor wall, and the resulting flammability limit. The combustor used has a circular, square and rectangular cross-section. All three combustors have the same cross-section area and combustion chamber volume. The flame holder used is a double narrow slit. The fuel used is liquefied petroleum gas with a pure oxygen oxidizer. The experiment results showed that the cylindrical combustor produces a more even flame shape that fills the combustion chamber and there is no clear separation between the sides of the flame on each side of the narrow slit. A high ratio of the entrance to average velocity results in a large adverse pressure gradient which generates vortex and recirculation behind the flame holder which gives the mixture a longer chance in the combustion chamber (prolonged residence time). The flame front shape affects the temperature of the combustor axis. The flame front shape that fills the entire combustion chamber has a higher flame temperature than the separate flame front shape. The circular combustor has the highest average axis temperature, but it has the lowest combustor wall temperature. This fact shows that the circular combustor has the smallest heat loss from the flame to the combustor wall. Furthermore, a circular mesoscale combustor has the most extensive stability map. For the same volume, the circular combustor has a lower surface area to volume ratio, thus the heat loss is also low. The dead zone area also becomes narrower, only at a low reactant rate. Rectangular combustors have the largest surface area to volume ratio, thus the losses are also the biggest. Despite the narrowest flammability limits, rectangular combustors have the highest average wall temperatures